HK1096210A - Multiplexing and transmission of multiple data streams in a wireless multi-carrier communication system - Google Patents

Description

Multiplexing and transmitting multiple data streams in a wireless multi-carrier communication system

The present application claims priority from U.S. provisional application No.60/499741 entitled "A Method for Multiple and Transmitting Multiple Multimedia Streams to Mobile terminals over Terrietary Radio" filed on 9/2 2003 and U.S. provisional application No.60/559,740 entitled "Multiple and Transmission of Multiple data Streams in a Wireless Multiple-Carrier Communication System" filed on 4/5 2004.

Technical Field

The present invention relates generally to communication, and more specifically to techniques for multiplexing and transmitting multiple data streams in a wireless multi-carrier communication system.

Technical Field

Multicarrier communication systems utilize multiple carriers for data transmission. These multiple carriers may be provided by Orthogonal Frequency Division Multiplexing (OFDM), other multi-carrier modulation techniques, or other concepts. OFDM effectively partitions the overall system bandwidth into multiple orthogonal subbands. These subbands are also referred to as audio bands (tones), carriers, subcarriers, bins (bins), and frequency channels. With OFDM, each subband is associated with a respective subcarrier, which may be modulated with data.

A base station in a multi-carrier system may transmit multiple data streams for broadcast, multicast, and/or unicast services simultaneously. A data stream is a stream of data that a wireless device is interested in receiving independently. A broadcast transmission is sent to all wireless devices within a specified coverage area, a multicast transmission is sent to a group of wireless devices, and a unicast transmission is sent to a particular wireless device. For example, a base station may broadcast multiple data streams of a multimedia (e.g., television) program over a terrestrial wireless link for reception by wireless devices. The system employs a conventional multiplexing and transmission scheme such as digital video broadcasting-terrestrial (DVB-T) or integrated services digital broadcasting-terrestrial (ISDB-T). This scheme first multiplexes all of the digital streams to be transmitted onto a high-rate composite stream, and then processes (e.g., encodes, modulates, and upconverts) the composite stream to generate a modulated signal for broadcast over the wireless link.

A wireless device within the coverage area of that base station may only be interested in receiving one or more particular ones of the multiple data streams carried by the composite stream. The wireless device needs to process (e.g., down convert, demodulate, and decode) the received signal to obtain a high-rate decoded data stream, and then demultiplex the stream to obtain one or more particular data streams of interest. This type of processing may not be a problem for receiver units that are always powered on, such as those used in the home. However, many wireless devices are portable and are powered by a built-in battery. Demodulating and decoding the high-rate composite stream just to recover the particular data stream or streams of interest consumes a significant amount of power. This may greatly shorten the "power on" time of the wireless device and is therefore undesirable.

There is therefore a need in the art for techniques to transmit multiple data streams in a multi-carrier system in order to facilitate their reception by wireless devices with minimal power consumption.

Disclosure of Invention

Techniques for multiplexing and transmitting multiple data streams are disclosed that facilitate power-efficient and robust reception of separate data streams by wireless devices. Each data stream is independently processed based on a coding and modulation scheme (e.g., outer code, inner code, and modulation scheme) selected for that data stream to generate a corresponding data symbol stream. In this way, these data streams can be recovered by the wireless device individually. Each data flow is also allocated a certain amount of resources to transmit the data flow. The allocated resources are represented by "transmission units" on a time-frequency plane, where each transmission unit corresponds to a subband within a symbol period and may be used to transmit a data symbol. The data symbols for each data stream are mapped directly onto the transmission units assigned to that stream. This enables the wireless device to recover each data stream independently without having to process other data streams transmitted simultaneously.

In one embodiment, the transmission of the multiple data streams occurs within "super frames," each having a predetermined duration (e.g., on the order of one or several seconds). Each superframe is further divided into a plurality (e.g., two, four, or other number) of frames. For each data stream, each data block is processed (e.g., outer coded) to generate a corresponding code block. Each code block is divided into a plurality of sub-blocks, and each sub-block is further processed (e.g., inner coded and modulated) to generate a corresponding sub-block of modulation symbols. Each code block is transmitted within one super-frame, and a plurality of sub-blocks of the code block are transmitted within a plurality of frames of the super-frame, one sub-block being transmitted within each frame. Each code block is divided into a plurality of sub-blocks, the sub-blocks are transmitted through a plurality of frames, and block coding is used for the sub-blocks of the code block, thereby providing robust reception performance in a slow time-varying fading channel.

Within each super-frame, each data stream may be "allocated" (allocated) a variable number of transmission units, depending on the load of the stream within the frame, the availability of transmission units within the frame, and other factors. The assignment scheme used, which also assigns (assign) each data stream a specific transmission unit within each superframe, attempts to: (1) packetizing the transmission units of all data streams as efficiently as possible, (2) reducing the transmission time of each data stream, (3) providing sufficient time diversity, (4) reducing the amount of signaling that is used to represent the particular data units allocated to each data stream. Overhead signaling of various parameters of the data streams (e.g., the coding and modulation schemes used for each data stream, the particular transmission units assigned to each data stream, etc.) may be sent prior to the respective super-frames or embedded in the data payload of the respective data streams. In this way, the wireless device is able to determine the time-frequency location of each expected data stream within the upcoming superframe. The wireless device can be powered on using embedded overhead signaling only when the desired data stream is transmitted, thereby reducing power consumption.

Various aspects and embodiments of the invention are described in further detail below.

Brief Description of Drawings

The features and nature of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:

fig. 1 shows a wireless multi-carrier system;

FIG. 2 illustrates an exemplary superframe structure;

FIGS. 3A and 3B illustrate the transmission of one data block and multiple data blocks, respectively, on a Physical Layer Channel (PLC) within a superframe;

fig. 4 shows a frame structure in the time-frequency plane;

fig. 5A shows a burst-type TDM (time division multiplexing) scheme;

FIG. 5B shows a cyclical TDM scheme;

FIG. 5C illustrates a burst-mode TDM/FDM (frequency division multiplexing) scheme;

FIG. 6 shows an interleaved subband structure;

FIG. 7A illustrates the assignment of time slots to PLCs in a histogram;

FIG. 7B illustrates assigning time slots to PLCs in a zig-zag pattern;

FIG. 7C illustrates the assignment of time slots to two joint PLCs in a histogram;

FIG. 8 illustrates encoding a data block using outer coding;

FIGS. 9A and 9B illustrate assigning time slots for one data block using one subband group and a maximum allowable number of subband groups, respectively;

FIG. 9C shows the slot assignments for six data blocks;

FIGS. 9D and 9E illustrate the assignment of time slots to two joined PLCs using horizontally and vertically stacked histograms, respectively;

FIG. 10 shows a process for broadcasting multiple data streams;

fig. 11 shows a block diagram of a base station;

FIG. 12 shows a block diagram of a wireless device;

FIG. 13 shows a block diagram of a Transmit (TX) data stream processor, channelizer, and OFDM modulator in a base station; and

fig. 14 shows a block diagram of a data stream processor for one data stream.

Detailed Description

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

The multiplexing and transmission techniques described herein may be used for various wireless multi-carrier communication systems. These techniques may also be used for broadcast, multicast, and unicast services. For clarity, the techniques are described in connection with an exemplary multi-carrier broadcast system.

Fig. 1 shows a wireless multi-carrier broadcast system 100. System 100 includes a plurality of base stations 110 distributed within the system. A base station is typically a fixed station and may also be referred to as an access point, a transmitter, or some other terminology. Neighboring base stations may broadcast the same or different content. The wireless device 120 is located within the coverage area of the system. A wireless device may be fixed or mobile and may also be referred to as a user terminal, a mobile station, a user equipment, or by other terminology. The wireless device may also be a portable unit such as a cellular telephone, a handheld device, a wireless module, a Personal Digital Assistant (PDA), or the like.

Each base station 110 may simultaneously broadcast multiple data streams to wireless devices within its coverage area. These data streams may be multimedia content such as video, audio, teletext, data, video/audio clips, etc. For example, a single multimedia (e.g., television) program may be transmitted in three separate data streams for video, audio, and data. A single multimedia program may also have multiple audio data streams, e.g., for different languages. For simplicity, each data stream is sent on a separate Physical Layer Channel (PLC). Thus, there is a one-to-one correspondence between data streams and PLCs. The PLC may also be referred to as a data channel, a traffic channel, or other terminology.

Fig. 2 illustrates the structure of an exemplary superframe that may be used in the broadcast system 100. The unit of occurrence of the data transmission is a superframe 210. Each superframe has a predetermined duration, which may be selected based on various factors, such as the expected statistical multiplexing of the data streams, the expected amount of time diversity, the acquisition time of the data streams, the buffering requirements of the wireless device, and so forth. A larger superframe size may provide greater time diversity and better statistical multiplexing of the transmitted data streams, thereby reducing the buffering required for each data stream in the base station. However, larger superframe sizes also result in longer acquisition times for new data streams (e.g., at power-up or when switching between data streams), require larger buffers in the wireless device, and longer decoding delays or delays. A superframe size of about 1 second may provide a good compromise between the above factors. However, other superframe sizes (e.g., one-quarter second, one-half second, two seconds, or four seconds) may also be used. Each superframe is further divided into a plurality of equally sized frames 220. For the embodiment shown in fig. 2, each superframe is divided into four frames.

The data streams for each PLC are encoded and modulated based on the coding and modulation scheme selected for that PLC. In general, the coding and modulation schemes include all of the different types of coding and modulation performed on the data streams. For example, the coding and modulation schemes may include a particular coding scheme and a particular modulation scheme. The coding scheme may include error detection coding (e.g., Cyclic Redundancy Check (CRC)), forward error correction coding, and the like, or combinations thereof. The coding scheme may also specify a particular code rate for the base code. In one embodiment described below, the data stream for each PLC is encoded with a concatenated code comprising an outer code and an inner code, and is also modulated based on a modulation scheme. The "mode" as used herein refers to a combination of an internal code rate and a modulation scheme.

Fig. 3A illustrates transmission of a data block over a PLC within a superframe. The data stream to be transmitted on the PLC is processed in data blocks. Each data block contains a certain number of information bits and is first encoded with an outer code to obtain a corresponding code block. Each code block is divided into four sub-blocks, and the bits within each sub-block are further encoded using an inner code and then mapped to modulation symbols based on the mode selected for the PLC. The four sub-blocks of modulation symbols are then transmitted in four frames of a super-frame, one sub-block being transmitted in each frame. Each code block is transmitted within four frames, which may provide time diversity and robust reception performance in a slowly time-varying fading channel.

FIG. 3B shows a plurality (N)_bl) Transmission of data blocks over the PLC within a superframe. Pair the N with outer code_blEach of the data blocks is individually encoded to obtain a corresponding code block. Each code block is further divided into four sub-blocks, which are intra-coded and modulated based on the mode selected for the PLC, and then transmitted within the four frames of a super-frame. For each frame, these N_blOf one code blockN_blThe individual blocks are transmitted in a portion of the frame that has been allocated to the PLC.

Each data block may be coded and modulated in different ways. An exemplary concatenated coding scheme is described below. To simplify the allocation and assignment of resources to PLCs, each code block may be divided into four equally sized sub-blocks and then transmitted in the same portions or locations of four frames within a super-frame. In this case, assigning superframes to the PLCs is equivalent to assigning frames to PLCs. Thus, resources can be allocated to these PLCs once per superframe.

Each PLC may be transmitted continuously or discontinuously, depending on the characteristics of the data stream carried by the PLC. Thus, one PLC may or may not be transmitted within any given superframe. For each superframe, an "active" PLC is a PLC transmitted within the superframe. Each active PLC may carry one or more data blocks within the superframe.

Returning to fig. 2, each superframe 210 is preceded by a pilot and overhead segment 230. In one embodiment, the segment 230 includes: (1) one or more pilot OFDM symbols used by a wireless device for frame synchronization, frequency acquisition, opportunity acquisition, channel estimation, etc.; (2) one or more overhead OFDM symbols for carrying overhead signaling information associated with (e.g., immediately following) the superframe. For example, the overhead information indicates a specific PLC transmitted within the associated super-frame, a specific portion of the super-frame used to transmit the data block of each PLC, an external code rate and mode for each PLC, and the like. The overhead OFDM symbols carry overhead signaling for all PLCs sent within the superframe. The pilot and overhead information is sent in a Time Division Multiplexed (TDM) manner, which enables the wireless device to process the segment with a minimum power-on time. In addition, overhead information associated with each PLC transmission within the next superframe may be embedded within the transmit data block of one PLC within the current superframe. The embedded overhead information enables the wireless device to recover PLC transmissions within the next superframe without having to examine overhead OFDM symbols transmitted within the superframe. Thus, the wireless device may first determine the time-frequency location of each desired data stream using overhead OFDM symbols and then may power up only for the time that the desired data stream is transmitted using embedded overhead signaling. These signaling techniques can significantly reduce power consumption and enable the wireless device to receive content using a standard battery. Since the external code rate and mode used by each PLC typically does not change based on the superframe, the external code rate and mode can be transmitted on a separate control channel, rather than having to be transmitted within each superframe.

Fig. 2 shows a specific superframe structure. In general, a superframe may have any duration and may be divided into any number of frames. The pilot and overhead information may also be sent in a different manner than that shown in fig. 2. For example, overhead information may be sent on dedicated subbands using Frequency Division Multiplexing (FDM).

Fig. 4 shows the structure of one frame on the time-frequency plane. The horizontal axis represents time and the vertical axis represents frequency. Each frame has a predetermined duration in units of OFDM symbol periods (or simply, symbol periods). Each OFDM symbol period is the duration of one OFDM symbol to be transmitted (described below). Specific number of symbol periods (N) per frame_spf) Depending on the frame duration and the symbol period duration, which in turn depends on various parameters, such as the total system bandwidth, the total number of subbands (N)_tsb) And a cyclic prefix length (to be described below). In one embodiment, each frame is 297 symbol periods (N)_spf297). Each frame is also covered with labels 1 to N_tsbTotal of N_tsbAnd (4) sub-bands.

With OFDM, one modulation symbol may be transmitted on each subband (i.e., each transmission unit) in each symbol period. In this total N_tsbIn one sub-band, N_dsbThe subbands are used for data transmission and are referred to as "data" subbands, N_psbThe subbands may be used for pilot transmission and are referred to as "pilot" subbands, with the remaining N_gsbThe subbands may be used as "guard" subbands (i.e., not used for data or pilot)Frequency transmission) of which N_tsb＝N_dsb+N_psb+N_gsb. The number of "available" subbands equals the number of data and pilot subbands, i.e., N_usb＝N_dsb+N_psb. In one embodiment, the broadcast system 100 uses a total of 4096 sub-bands (N)_tsb4096), 3500 data subbands (N)_dsb3500), 500 pilot subbands (N)_psb500), 96 guard subbands (N)_gsb96). Other OFDM structures with different amounts of data, pilots, available and total subbands may also be used. In each OFDM symbol period, in N_dsbN may be transmitted on a subband_dsbData symbols at N_psbN may be transmitted on a subband_psbOne pilot symbol at N_gsbN may be transmitted on one subband_gsbA guard symbol. As used herein, a "data symbol" is a modulation symbol for data, a "pilot symbol" is a modulation symbol for pilot, and a "guard symbol" is a signal of zero value. The pilot symbols are known a priori by the wireless device. N within each OFDM symbol_dsbThe data symbols can be for one or more PLCs.

In general, any number of PLCs may be transmitted within each superframe. Each active PLC may carry one or more data blocks for a given superframe. In one embodiment, one specific pattern and one specific outer code rate are used for each active PLC, and all data blocks of the PLC are encoded and modulated according to the outer code rate and pattern, thereby generating corresponding code blocks and sub-blocks of modulation symbols, respectively. In another embodiment, each data block may be encoded and modulated according to a specific outer code rate and pattern to generate a corresponding code block and sub-block of modulation symbols, respectively. In any case, each code block contains a certain number of data symbols, depending on the mode used for the code block.

Each active PLC within a given superframe is allocated a certain amount of resources in order to transmit the PLC within the superframe. The amount of resources allocated to each active PLC depends on: (1) a number of code blocks transmitted on the PLC within the superframe; (2) the number of data symbols within each code block; (3) the number of code blocks transmitted on other PLCs, and the number of data symbols within each code block. The allocation of resources may take many forms. Two exemplary allocation schemes are described below.

Fig. 5A shows a burst-type TDM (time division multiplexing) scheme. For this scheme, each active PLC is assigned all N within one or more OFDM symbol periods_dsbA plurality of data subbands. In the example shown in fig. 5A, PLC1 is allocated all the data subbands in symbol periods 2 through 3, PLC 2 is allocated all the data subbands in symbol periods 4 and 5, and PLC 3 is allocated all the data subbands in symbol periods 6 through 9. For this scheme, each OFDM symbol contains data symbols for only 1 PLC. The OFDM symbol bursts for different PLCs are time division multiplexed within one frame.

Burst TDM may reduce the transmission time of the PLC if consecutive OFDM symbols are assigned to each active PLC. However, short transmission times for each PLC also reduce time diversity. Since the entire OFDM symbol is allocated to one PLC, the resource allocation granularity (i.e., the minimum unit allocatable to one PLC) of each frame is one OFDM symbol. The number of information bits that can be transmitted in one OFDM symbol depends on the mode used to process the information bits. For a burst TDM scheme, the allocation granularity depends on the mode. The granularity is also larger for higher order modes that can carry more information bits in each data symbol. In general, a larger granularity adversely affects "packetization" efficiency, which refers to the proportion of frames that are actually used to carry data. If the active PLC does not require the data carrying capability of the entire OFDM symbol, excess capability is wasted, reducing the sealing efficiency.

Fig. 5B shows a round robin TDM allocation scheme. For this scheme, the active PLCs within the superframe are arranged into L groups, where L > 1. A frame is also divided into L segments and each PLC group is assigned to a respective segment of the frame. For each group, cycling through the PLCs in the group, allocating each PLC for all of the PLCs in the assigned segment within one or more OFDM symbol periodsWith N_dsbA plurality of data subbands. For the example shown in fig. 5B, PLC1 is assigned all data subbands in symbol period 1, PLC 2 is assigned all data subbands in symbol period 2, PLC 3 is assigned all data subbands in symbol period 3, PLC1 is assigned all data subbands in symbol period 4, and so on. The round robin TDM scheme may improve time diversity, reduce receiver buffering requirements and peak decoding rates, but increase the power-on time for a receiver to receive a given PLC compared to burst TDM.

Fig. 5C shows a burst TDM/FDM (frequency division multiplexing) scheme. For this scheme, each active PLC is assigned one or more data subbands in one or more symbol periods. For the example shown in fig. 5C, PLC1 is assigned data subbands 1 through 3 for symbol periods 1 through 8, PLC 2 is assigned data subbands 4 and 5 for symbol periods 1 through 8, and PLC 3 is assigned data subbands 6 through 9 for symbol periods 1 through 8. For a burst TDM/FDM scheme, each OFDM symbol may contain data symbols for multiple PLCs. The data symbol bursts for different PLCs are time division multiplexed and frequency division multiplexed within a frame.

Since the load of each PLC can be distributed in time and frequency, the burst TDM/FDM scheme may increase the transmission time of the PLC. However, this also improves time diversity. By allocating more subbands to each PLC, the transmission time of the PLC may be reduced. For a burst TDM/FDM scheme, the granularity of resource allocation may be selected based on a tradeoff between packet efficiency and overhead signaling. Generally, the smaller the granularity, the more efficient the packetization, but also requires more overhead signaling to indicate the resources allocated to each PLC. For larger particle sizes, the opposite is generally true. The following description assumes the use of a burst TDM/FDM scheme.

In one embodiment, N_usbThe usable sub-bands are divided into N_grGroups the usable subbands. This N_grOne of the groups may contain pilot subbands. For the remaining groups, the number of data subbands in a group determines the granularity of resource allocation. This N can be put into different ways_usbSetting the number of usable subbands to N_grIn the group. In a sub-band grouping scheme, each group contains N_spgA number of successively usable sub-bands, of which N_usb＝N_gr·N_spg. In another subband grouping scheme, each group contains N_spgA usable sub-band pseudo-randomly distributed over the N_usbAmong the available subbands. In another sub-band grouping scheme, each group contains N_spgAvailable sub-bands at the N_usbEvenly spaced among the available subbands.

FIG. 6 illustrates an interleaved subband structure 600 that may be used for a burst-based TDM/FDM scheme. N is a radical of_usbThe usable sub-bands are set at N_grOf disjoint groups, denoted subband groups 1 through N_gr. This N_grThe subband groups do not intersect because of N_usbEach of the available subbands belongs to only one group. Each subband group comprising N_spgOne usable subband, this N_spgThe usable sub-bands are uniformly distributed in the N_usbOf the available subbands, the interval of successive subbands in the group is therefore N_spAnd (4) sub-bands. In one embodiment, 4000 usable subbands (N)_usb4000) are arranged in 8 groups (N)_gr8), each group contains 500 usable subbands (N)_spg500), the available subband spacing for each group is 8 subbands (N)_sp8). Thus, the usable subbands in each group are compared to the other N_grThe usable subbands in 1 group are interleaved. Each subband group is also referred to as an "interlace".

The staggered subband structure provides many advantages. First, better frequency diversity is achieved because each group includes available subbands throughout the entire system bandwidth. Second, the wireless device may recover the data symbols transmitted on each subband group by performing a "partial" (e.g., 512-point) Fast Fourier Transform (FFT) rather than a full (e.g., 4096-point) FFT, which may reduce the power consumption of the wireless device. A technique for performing a partial FFT is described in commonly assigned U.S. patent application No.10/775,719 entitled "sub-band-based demodulator for an OFDM-based Communication System," filed on 9/2/2004. The following description assumes the use of the interleaved subband structure shown in fig. 6.

On a superframe basis, each PLC may be allocated resources on a superframe. The amount of resources allocated to each PLC within each super-frame depends on the load of that PLC in that super-frame. The PLC may carry a fixed rate data stream or a variable rate data stream. In one embodiment, each PLC uses the same pattern even if the data rate of the data stream carried by that PLC changes. This ensures that the coverage area of the data stream remains substantially constant regardless of the data rate, so that the reception performance is independent of the data rate. The variable rate nature of the data stream is handled by varying the amount of resources allocated to the PLC within each superframe.

Each active PLC is allocated resources from the time-frequency plane as shown in fig. 4. Each active PLC is assigned resources in units of "transmission slots" (or simply "slots"). One slot corresponds to a set of data subbands (e.g., 500), or equivalently, a set of modulation symbols in one symbol period. With N in each symbol period_grAn available time slot to which time slot designations 1 through N can be assigned_gr. Each slot index may be mapped to a group of subbands in each symbol period based on a slot-to-interlace mapping scheme. One FDM pilot may use one or more slot designations and the remaining slot designations may be used for the PLC. The slot-to-interlace mapping may be such that: the subband groups (or interlaces) for the FDM pilot have different distances to the subband groups for each slot index. In this way, all time slots for the PLC can achieve the same performance.

Each active PLC is allocated at least one time slot within a superframe. Each active PLC is also assigned a specific time slot within the superframe. The "allocation" process provides an amount of resources for each active PLC, while the "assignment" process provides specific resources within the superframe for each active PLC. For clarity, allocation and assignment may be considered as separate processes. In practice, allocation and assignment are typically performed together, since assignment affects allocation and vice versa. In any case, the assignment can be performed in a manner that achieves the following goals:

1. minimizing the transmission time of each PLC to reduce the power-on time and power consumption of the wireless device to restore the PLC;

2. maximizing the time diversity of each PLC to provide robust reception performance;

3. constraining each PLC to within a specified maximum bit rate; and

4. the buffering requirements of the wireless device are minimized.

The maximum bit rate represents the maximum number of information bits that can be transmitted by one PLC in each OFDM symbol. The maximum bit rate is typically set by the decoding and buffering capabilities of the wireless device. By limiting each PLC to within the maximum bit rate, it can be ensured that the PLC can be recovered by a wireless device having the prescribed decoding and buffering capabilities.

Some of the goals listed above are conflicting. For example, targets 1 and 2 conflict, and targets 1 and 4 conflict. The resource allocation/assignment scheme attempts to achieve a balance between conflicting goals and can flexibly set priorities.

Each active PLC within a superframe is assigned a specific number of time slots based on the load of the PLC. Different PLCs may be divided into different time slots. The particular time slot to be assigned to each active PLC may be determined in a variety of ways. Some exemplary slot assignment schemes are described below.

Fig. 7A illustrates the rectangular assignment of time slots to PLCs according to a first time slot assignment scheme. Each active PLC is assigned a time slot located in a two-dimensional (2-D) histogram. The size of the histogram depends on the number of time slots allocated to the PLC. The vertical dimension (or height) of the histogram depends on various factors, such as the maximum bit rate. The horizontal dimension (or width) of the histogram depends on the number of allocated slots and the vertical dimension.

To minimize transmission time, one active PLC may be assigned as many subband groups as possible while following a maximum bit rate. The maximum number of information bits that can be transmitted in one OFDM symbol can be coded and modulated with different modes to obtain different numbers of data symbols that require different numbers of data subbands to transmit. The maximum number of data subbands available to each PLC depends on the mode used by that PLC.

In one embodiment, the histogram for each active PLC includes adjacent groups of subbands (labeled adjacent) and adjacent symbol periods. This type of assignment reduces the amount of overhead signaling required to specify the histogram and also makes the slot assignments for these PLCs more compact, thereby simplifying the packing of the PLCs within a frame. The frequency dimension of the histogram may be represented by the starting subband group and the total number of subband groups for the histogram. The time dimension of the histogram may be represented by the starting symbol period and the total number of symbol periods of the histogram. Thus, the histogram for each PLC can be represented by four parameters.

For the example shown in FIG. 7A, PLC1 is assigned 8 time slots in 2 × 4 histogram 712, PLC 2 is assigned 12 time slots in 4 × 3 histogram 714, and PLC 3 is assigned 6 time slots in 1 × 6 histogram 716. The remaining time slots in the frame may be assigned to other active PLCs. As shown in fig. 7A, different active PLCs may use different rectangular graphs. To improve the efficiency of the packetization, the active PLCs may be assigned time slots within a frame, one PLC at a time, the order of which depends on the number of time slots allocated to each PLC. For example, a time slot within the frame may be assigned to a PLC having the largest number of allocated time slots, then to a PLC having the next largest number of allocated time slots, and so on, and finally to a PLC having the smallest number of allocated time slots. The time slots may also be assigned based on other factors, such as the priority of the PLCs, the relationship between the PLCs, and the like.

Figure 7B illustrates assigning timeslots to PLCs in a "sinusoidal" or "zig-zag" segment, according to a second timeslot assignment scheme. For this scheme, a frame is divided into N_stA strip. Each stripe covers at least one subband group and also spans a plurality of adjacent symbol periodsUp to a maximum number of symbol periods within a frame. This N_stThe "strips" may include the same or different number of subband groups. Mapping each of the active PLCs to the N based on a plurality of factors_stOne of the "bars". For example, to minimize transmission time, each active PLC may be mapped to a stripe having the maximum number of subbands allowed for that PLC.

The active PLC for each strip is assigned a time slot in that strip. The time slots may be assigned to the PLCs in a particular order, for example using a vertical zig-zag pattern. The zigzag pattern is indexed from low to high subband groups and from symbol period 1 to N_spfThe slot is selected, one symbol period at a time. For the example shown in fig. 7B, strip 1 includes subband groups 1 through 3. Segment 732 assigned for PLC1 includes 10 slots from subband group 1 in symbol period 1 to subband group 1 in symbol period 4. Segment 734 assigned for PLC 2 includes 4 slots from subband group 2 in symbol period 4 to subband group 2 in symbol period 5. Segment 736 assigned for PLC 3 comprises 6 slots from subband group 3 in symbol period 5 to subband group 2 in symbol period 7. The remaining time slots in bar 1 may be assigned to other active PLCs mapped to the bar.

The second slot assignment scheme effectively maps all slots in a two-dimensional (2-D) strip onto a one-dimensional (1-D) strip, and then performs 2-D slot assignment using one dimension. Each active PLC is assigned a segment within the bar. The assigned segment can be represented by two parameters: the start of the segment (represented by the starting subband and symbol period) and the length of the segment. The particular bar to which the PLC is mapped is represented by an additional parameter. In general, the segments assigned to each active PLC may include any number of time slots. However, if the segment size is limited to an integer number (e.g., 2 or 4) of slots, less overhead signaling is required to identify the assigned segment.

The second time slot assignment scheme can assign time slots to active PLCs very simply. In addition, each strip can achieve tight packing because the time slots within the strip can be assigned to the PLC consecutively. Can convert this N_stThe vertical dimension of the bar is defined to match theAn aggregate case (profile) of all active PLCs within a superframe such that: (1) transmitting as many PLCs as possible using a maximum number of data subbands allowed for the PLCs; (2) to make this N as complete as possible_stAnd (4) packaging the strips.

Fig. 7A and 7B illustrate two exemplary slot assignment schemes. Both schemes enable efficient packing of PLCs within each frame. Both of these schemes also reduce the amount of overhead signaling required to represent the particular time slot assigned to each active PLC. Other slot assignment schemes may be used, but fall within the scope of the present invention. For example, one slot assignment scheme may divide a frame into a plurality of bars, the active PLCs of the frame may be mapped to the available bars, and the PLCs of each bar may be assigned a histogram within the bar. The strips may have different heights (i.e., different numbers of groups of subbands). The histogram of PLCs assigned to each strip may have the same height as the strip, but a different width (i.e., a different number of symbol periods) depending on the number of time slots assigned to the PLCs.

For simplicity, fig. 7A and 7B illustrate assigning time slots to each PLC. For some services, a wireless device may decode multiple PLCs together, and thus these PLCs are referred to as "joint" PLCs. This is the case, for example, if multiple PLCs are used for the video and audio components of a multimedia program and they are decoded together to recover the program. The joint PLC may be allocated the same or different number of time slots within each super-frame, depending on their load. To reduce power-on time, the joint PLC may be assigned time slots within successive symbol periods so that the wireless device does not have to "wake up" multiple times within a frame to receive the PLCs.

Fig. 7C shows the assignment of time slots to two joint PLCs 1 and 2 based on a first time slot assignment scheme. In a first embodiment, slots within a histogram that is stacked horizontally or side-by-side are assigned to a joint PLC. For the example shown in fig. 7C, PLC1 is assigned 8 time slots in 2 x 4 histogram 752, and PLC 2 is assigned 6 time slots in 2 x 3 histogram 754 located directly to the right of the histogram 752. This embodiment allows each PLC to be decoded as quickly as possible, thereby reducing the buffering requirements of the wireless device.

In a second embodiment, the joint PLC is assigned a time slot within a vertically stacked histogram. For the example shown in fig. 7C, PLC 3 is assigned 8 slots in 2 x 4 histogram 762, and PLC 4 is assigned 6 slots in 2 x 3 histogram 764, which is directly above the histogram 762. The total number of subband groups for joint PLC may be such that: these joint PLCs collectively comply with a maximum bit rate. For the second embodiment, the wireless device may store the received data symbols for the joint PLC in different buffers until they are ready for decoding. The second embodiment can reduce the power-on time of the joint PLC compared to the first embodiment.

In general, any number of PLCs can be decoded together. The histogram of the joint PLC may span the same or different number of subband groups, which is constrained by the maximum bit rate. The histogram may also span the same or a different number of symbol periods. Some of the histograms of the joined PLCs may be horizontally stacked, while other histograms of the joined PLCs may be vertically stacked.

The joint PLC may also be assigned zigzag segments. In one embodiment, multiple PLCs to be decoded together are assigned consecutive segments within the same strip. In another embodiment, multiple PLCs are assigned segments within different bars, and the segments overlap as much as possible in time, thereby reducing the power-on time to recover the PLCs.

In general, each data stream may be encoded in various ways. In one embodiment, each data stream is encoded using a concatenated code comprising an inner code and an outer code. The outer code may be a block code such as a reed-solomon (RS) code or other code. The inner code may be a Turbo code (e.g., Parallel Concatenated Convolutional Code (PCCC) or Serial Concatenated Convolutional Code (SCCC)), a convolutional code, a Low Density Parity Check (LDPC) code, or other code.

Fig. 8 shows an exemplary outer coding scheme employing reed-solomon codes. The data stream of the PLC is divided into a plurality of data packets. In one embodiment, each data packet contains a predetermined number (L) of information bits. As a specific example, each data packet may contain 976 information bits. Other packet sizes and formats may also be used. The data packets of the data stream are written into a plurality of rows of a memory, one packet per row. After writing K data packets into K rows, block encoding is performed column by column, one column at a time. In one embodiment, each column contains K bytes (one byte for each row) and is encoded with an (N, K) reed-solomon code, thereby generating a corresponding codeword containing N bytes. The first K bytes of the codeword are data bytes (also referred to as systematic bytes) and the next N-K bytes are parity bytes (which may be used by the wireless device for error detection). The reed-solomon encoding generates N-K parity bytes for each codeword and writes into rows K +1 to N stored after the K rows of data. One RS block contains K rows of data and N-K rows of parity. In one embodiment, N16, K is a configurable parameter, e.g., K e {12, 14, 16 }. When K is N, the reed-solomon code is not valid. The CRC value, e.g., 16 bits in length, is added to each data packet (or row) of the RS block, followed by (e.g., 8) zero (tail) bits, thereby resetting the inner encoder to a known state. The resulting longer (e.g., 1000 bit) packet is then encoded with an inner code to generate a corresponding inner encoded packet. For N rows of an RS block, a code block contains N outer encoded packets, where each outer encoded packet may be a data packet or a parity packet. The code block is divided into four sub-blocks, each containing four outer encoded packets if N-16.

In one embodiment, each data stream may be transmitted with or without layered coding, where the term "coding" refers herein to channel coding in the transmitter, rather than source coding. A data stream may comprise two sub-streams, referred to as a base stream and an enhancement stream. In one embodiment, the elementary stream may carry information that is sent to all wireless devices within the coverage area of the base station. The enhanced stream may carry additional information sent to wireless devices observing better channel conditions. The base stream is encoded and modulated in a first mode by layered coding to generate a first modulation symbol stream, and the enhancement stream is encoded and modulated in a second mode to generate a second modulation symbol stream. The first and second modes may be the same or different. The two modulation symbol streams are then combined to obtain one data symbol stream.

Table 1 shows an exemplary set of 8 modes that may be supported by the system. Let m represent a pattern, where m is 1, 2, …, 8. Each mode is associated with a particular modulation scheme (e.g., QPSK or 16-QAM) and a particular inner code rate R_in(m) (e.g., 1/3, 1/2, or 2/3). The first five modes are only used for "regular" coding of the base stream, and the last three modes are used for layered coding of the base stream and the enhancement stream. For simplicity, the base stream and enhancement stream use the same modulation scheme and inner code rate for each layered coding mode.

TABLE 1

Mode m	Modulation scheme	Internal code rate Rin(m)	Number of slots per packet Nspp(m)	Number of slots per sub-block Nsps(m)
					1	QPSK	1/3	3	12
2	QPSK	1/2	2	8

3	16-QAM	1/3	1.5	6
					4	16-QAM	1/2	1	4
5	16-QAM	2/3	0.75	3
					6	QPSK/QPSK	1/3	3	12
7	QPSK/QPSK	1/2	2	8
					8	QPSK/QPSK	2/3	1.5	6

Table 1 also shows various transmission parameters for each mode. The fourth column of table 1 indicates the number of slots required to transmit one packet for each mode, assuming a packet size of approximately 1000 information bits and 500 data subbands per slot. The fifth column indicates the number of slots required to transmit one subblock of four packets for each mode. The number of subband groups available to a PLC is different for all modes. Using more subband groups may shorten transmission time but provide less time diversity.

As an example of mode 1, one data block having K data packets may be encoded to generate 16 code packets. Each data packet contains 1000 information bits. Since mode 1 uses code rate R_in(1) 1/3, each coded packet contains 3000 code bits, so QPSK, which can carry two code bits within each data symbol, can be used to transmit on 1500 data subbands (or groups of three subbands). The 4 code packets per sub-block may be transmitted in 12-out time slots. Each sub-block may be transmitted in a rectangular map, e.g., of dimensions 4 x 3, 3 x 4, 2 x 6, or 1 x 12Where the first value P of the dimension P × Q is the number of subband groups and the second value Q is the number of symbol periods of the histogram.

Table 1 shows an exemplary design that gives various parameters that may affect subband allocation and assignment. In general, the system may support any number of modes, and each mode may correspond to a different coding and modulation scheme. For example, each mode may correspond to a different combination of modulation scheme and inner code rate. To simplify the design of a wireless device, a system may utilize a single inner code (e.g., a base code rate of 1/3 or 1/5), and different code rates may be achieved by puncturing or deleting some of the coded bits generated by the inner code. However, the system may also use multiple inner codes. The maximum allowed number of subband groups for each mode may be different and may be based on the maximum bit rate.

Typically, one or more data blocks may be transmitted on one active PLC per superframe. The number of data blocks transmitted within each superframe depends on the data rate of the data stream transmitted over the PLC. Number of time slots (N) to be allocated to PLCs per frame_slot) Equal to the number of data blocks (N) transmitted on the PLC within the super-frame_bl) Multiplied by the number of time slots required for a sub-block, i.e. N_slot＝N_bl·N_sps(m) wherein N_sps(m) depends on the mode used by the PLC. If the PLC carries a large number of data blocks (high rate data streams) within a super-frame, then to minimize the PLC transmission time, it is preferable to use as many subband groups as possible. For example, if the PLC is carrying 16 data blocks in a superframe, then with each frame transmission time of mode 1, one subband group is used, which is 192 · 12 symbol periods (which is 65% of the frame duration), four subband groups are used (which is 16.25% of the frame duration), and only 48 — 192/4 symbol periods. Therefore, the transmission time of the PLC can be significantly shortened by using more subband groups.

Fig. 9A shows the allocation of a time slot within a super-frame to a code block (N) using a subband group_bl1), which is equivalent to allocating a time slot within one frame to one sub-block. For the above embodiment, each sub-block contains four packets labeled 1, 2, 3, and 4 in fig. 9A. For modes 1 through 5 of table 1, each packet is transmitted in a different number of slots. Four packets 1 to 4 of one sub-block may be transmitted on one subband group: for mode 1, within 12 symbol periods; for mode 2, within 8 symbol periods; for mode 3, within 6 symbol periods; for mode 4, within 4 symbol periods; for mode 5, within 3 symbol periods. For mode 3 and mode 5, the two packets may share the same time slot. Once the entire packet is received, the packet can be decoded.

Fig. 9B shows the allocation of slots within a superframe to a code block (N) using 4, 3, 2 and 1 subband groups for modes 1, 2, 3, 4 and 5, respectively_bl1). Four packets within one sub-band may be sent: for mode 1, within a 4 × 3 histogram 932; for mode 2, within a 4 × 2 histogram 934; for mode 3, within a 3 × 2 histogram 936; for mode 4, within a 2 × 2 histogram 938; for mode 5, this is within a 1 × 4 histogram 940.

In one embodiment, four packets within a sub-block are transmitted in a vertical zig-zag 942 in a rectangular chart, as shown in FIG. 9B. This embodiment may reduce buffering requirements because each packet is transmitted in as few symbol periods as possible, and there is only one partial packet in any given symbol period. In another embodiment, four packets are transmitted in the horizontal zig-zag 944. This embodiment provides more time diversity because each packet is transmitted in as many symbol periods as possible. However, the maximum bit rate may limit the number of available subband groups or additional buffering may be required because, using a horizontal zigzag pattern, up to two packets may be received completely in the same symbol period.

FIG. 9C illustrates the use of fourThe subband groups allocate time slots within a superframe to six code blocks (N)_bl6). In this example, the PLC employs mode 2, with each packet being transmitted in two time slots, 24 packets being transmitted within each frame for these 6 code blocks, and the PLC being assigned 48 time slots in the 4 x 12 histogram 952 for each frame. In the histogram 952, the 24 packets may be sent in various ways.

In the first embodiment, shown in fig. 9C, the packets are sent in a histogram cycling through six code blocks. For each cycle through the 6 code blocks, one packet is selected from each code block, and then six packets of the six code blocks are transmitted with a vertical zigzag pattern. Six packets 1 for these code blocks are sent in box 954a, six packets 2 for these code blocks are sent in box 954b, six packets 3 for these code blocks are sent in box 954c, and six packets 4 for these code blocks are sent in box 954 d. In fig. 9C, the jth packet of the ith code block is denoted as B_iP_j。

The first embodiment provides more time diversity within each code block because the four packets for that code block are transmitted in more symbol periods. A packet transmitted within one symbol period is likely to be affected by association deletion information (erasure). For example, deep fading within a symbol period may cause decoding errors for all packets transmitted within the symbol period. By transmitting packets from different code blocks in the same symbol period, the associated (packet) erasure information will be distributed over multiple code blocks. This enhances the block decoder's ability to correct for these erasure information. The first embodiment also spaces the four packets of each code block as far apart in time as possible, which improves the time diversity within the code block. For example, four packets for code block 1 are sent in symbol periods 1, 4, 7, 10, and separated by 3 symbol periods. The first embodiment also reduces buffering requirements because each packet is sent in as few symbol periods as possible.

In a second embodiment, not shown, the cycle is through N_blOne code block selects a packet, which is identical to the first oneThe examples are similar, however, for each cycle, N_blThe packets are sent using a horizontal zig-zag pattern within the box 954. This embodiment may provide more time diversity within each packet. In a third embodiment, four packets for one code block are sent first, then four packets for another code block, and so on. This embodiment enables early recovery of some code blocks. Thus, multiple code blocks may be transmitted on the PLC in different ways.

As described above, multiple PLCs may be decoded together. Each joint PLC may carry any number of code blocks within a super-frame depending on the data rate of the data stream being transmitted on the PLC. The total number of subband groups used by the joint PLC may be limited by the maximum bit rate.

Fig. 9D illustrates the allocation of timeslots of one superframe to two joint PLCs using horizontally stacked histograms. In this example, PLC1 carries two code blocks (e.g., for one video stream) using mode 4, and thus, 8 packets are transmitted in 8 slots per frame. PLC 2 uses mode 2 to carry one code block (e.g., for one audio stream), and thus, transmits 4 packets in 8 slots per frame. Cycling through the two code blocks and using a vertical zig-zag, 8 packets of PLC1 are transmitted in a 2 x 4 rectangular graph 962, as shown in fig. 9C. Four packets of PLC 2 are sent in a 2 x 4 rectangular graph 964 using a vertical zig-zag graph. The graphic 964 is stacked to the right of the image 962.

Fig. 9E shows the allocation of timeslots of one superframe to two joint PLCs using vertically stacked histograms. Cycling through the two code blocks and using the vertical zigzag pattern, 8 packets of PLC1 are sent in a 1 x 8 rectangular pattern 972, but using only one subband group. Four packets of PLC 2 are sent in a 2 x 4 rectangular graph 974 using a vertical zig-zag graph. The graphic 974 is stacked on top of the image 972. PLC1 uses a 1 x 8 histogram to ensure that only two packets are transmitted per symbol period, which may be a limitation imposed by the highest bit rate. PLC1 may use a 2 x 4 histogram if the maximum bit rate allows, thereby reducing the total transmission time of PLC1 and 2.

The examples shown in fig. 9D and 9E can be extended to cover any number of joint PLCs, any number of code blocks per PLC, and any pattern per PLC. Time slots can be assigned to the joint PLCs such that the total transmission time of the PLCs is minimized while the maximum bit rate is met.

For the outer coding scheme shown in fig. 8, the first K packets of each code block are data and the last N-K packets are parity bits. Because each packet includes a CRC value, the wireless device can determine whether each packet was decoded correctly or in error by recalculating the CRC value using the information bits of the received packet and comparing the recalculated CRC value to the received CRC value. For each code block, the wireless device does not have to process the next N-K packets if the first K packets are decoded correctly. For example, if N16, K12 and the last four packets of a code block were sent in the fourth frame, then the wireless device does not have to wake up in the last frame if the 12 data packets sent in the first three frames were decoded correctly. Furthermore, any combination of up to N-K incorrectly (intra) decoded packets can be corrected by a Reed-Solomon decoder.

For clarity, the above description is based on a concatenated coding scheme comprising an outer code and an inner code and is directed to the parameters given in fig. 1. Other coding schemes may be used in the system. Further, the system may use the same or different parameters. Subband allocation and assignment may be performed using the techniques described herein and depending on the particular coding scheme and parameters applicable to the system.

Fig. 10 is a flow diagram illustrating a process 1000 for broadcasting multiple data streams using the multiplexing and transmission techniques described herein. For each superframe, process 1000 may be performed.

First, the active PLC for the current superframe is identified (block 1012). For each active PLC, at least one data block is processed according to the outer code (and rate) selected for that PLC, thereby obtaining at least one code block, each data block corresponding to one code block (block 1014). A particular number of transmission units is allocated for each active PLC within the current superframe based on the load of the active PLC (block 1016). In general, transmission units within the current superframe may be allocated to active PLCs with any level of granularity. For example, transmission units may be assigned to active PLCs in time slots, each time slot containing 500 transmission units. A particular transmission unit within each frame of the current superframe is then assigned to each active PLC (block 1018). Block 1016 determines the amount of resources allocated to each active PLC. Block 1018 provides for each active PLC a particular resource allocation and may be performed based on an assignment scheme. For example, for block 1018, a scheme of assigning a rectangular chart or a scheme of assigning zigzag segments within a bar may be used. The allocation and assignment scheme for the transmission units may also be performed together, since the allocation may depend on the packet efficiency achieved by the assignment.

Each code block of each active PLC is divided into a plurality of sub-blocks, one sub-block within each frame (block 1020). Each packet within each sub-block is encoded by an inner code and mapped to modulation symbols (block 1022). The internal code rate and modulation scheme for each PLC is determined by the mode selected for that PLC. The multiple sub-blocks of each code block are then transmitted within multiple frames of the current superframe to achieve time diversity. For each frame of the current superframe, data symbols in the sub-block of each active PLC transmitted within the frame are mapped onto transmission units allocated to that PLC (block 1024). A composite symbol stream is then formed using (1) the multiplexed data symbols for all active PLCs and (2) the pilot, overhead and guard symbols (block 1026). The composite symbol stream is further processed (e.g., OFDM modulated and trimmed) and broadcast to wireless devices within the system.

The multiplexing and transmission techniques described herein enable multiple data streams transmitted within each superframe to be independently recovered by the wireless device. A given data stream of interest may be recovered by: (1) performing OFDM demodulation on all subbands or subbands used for the data stream; (2) demultiplexing the detected data symbols of the data stream; (3) the detected data symbols for the data stream are decoded. It is not necessary to decode all or part of the other data streams in order to receive the intended data stream. The wireless device may perform partial demodulation and/or partial decoding of another data stream in accordance with the selected allocation and assignment scheme to recover the data stream of interest. For example, if multiple data streams share the same OFDM symbol, demodulation of a selected data stream may result in partial demodulation of unselected data streams.

Fig. 11 shows a block diagram of a base station 110x, which base station 110x is one base station in the system 100. In base station 110x, a Transmit (TX) data processor 1110 receives multiple (N) data from one or more data sources 1108, e.g., multiple data sources for different services_plc) A data stream (denoted as d)₁} to { d_Nplc}), where each service may be carried in one or more PLCs. TX data processor 1110 processes the data streams based on the mode selected for each data stream to generate corresponding data symbol streams and combines N with N_plcA stream of data symbols (denoted as s)₁Is from { s } to { s }_Nplc}) is provided to a symbol multiplexer (Mux)/channelizer 1120. TX data processor 1110 also receives overhead data (denoted as d) from controller 1140_oH) processing the overhead data according to the mode used for the overhead data and representing an overhead symbol stream (denoted as s)_o}) to a Channelizer (Channelizer) 1120. The overhead symbols are modulation symbols for overhead data.

Channelizer 1120 passes the N_plcThe data symbols in the individual data symbol streams are multiplexed onto their assigned transmission units. Channelizer 1120 also provides pilot symbols on the pilot subbands and guard symbols on the guard subbands. The channelizer 1120 also multiplexes pilot symbols and overhead symbols in the pilot and overhead portion preceding each superframe (see fig. 2). The channelizer 1120 provides a composite symbol stream (denoted as s)_c}) that carry data, overhead, pilot, and guard symbols on the appropriate subbands and symbol periods. An OFDM modulator 1130 performs OFDM modulation on the composite symbol stream and provides an OFDM symbol stream to a transmitter unit (TMTR) 1132. Reflector unit1132, and conditioned (e.g., converted to analog, filtered, amplified, and upconverted) and generate a modulated signal, which is transmitted from an antenna 1134.

Fig. 12 shows a block diagram of a wireless device 120x, the wireless device 120x being one wireless device within the system 100. In wireless device 120x, an antenna 1212 receives the modulated signal transmitted by base station 110x and provides a received signal to a receiver unit (RCVR) 1214. Receiver unit 1214 conditions, digitizes, and processes the received signal and provides a stream of samples to an OFDM demodulator 1220. OFDM demodulator 1220 performs OFDM demodulation on the sample stream and provides (1) received pilot symbols to channel estimator 1222 and (2) received data symbols and received overhead symbols to detector 1230. Channel estimator 1222 obtains a channel response estimate for the wireless link between base station 110x and wireless device 120x based on the received pilot symbols. A detector 1230 detects (e.g., quantizes or match filters) the received data and overhead symbols using the channel response estimate. The detector 1230 provides "detected" data and overhead symbols, which are estimates of the transmitted data and overhead symbols, respectively, to a symbol demultiplexer (Demux)/de-channelizer 1240. The detection of the data/overhead symbols may be represented by log-likelihood ratios (LLRs) of the code bits used to form the data/overhead symbols, or by other representations. Channel estimator 1222 may also provide time and frequency information to OFDM demodulator 1220.

The controller 1260 obtains an indication (e.g., a user selection) of one or more particular data streams/PLCs to be recovered. The controller 1260 then determines the resource allocation and assignment for each selected PLC. If wireless device 120x acquires the signal for the first time (e.g., initial acquisition), then signaling information is obtained from the overhead OFDM symbols decoded by Receive (RX) data processor 1250. If wireless device 120x successfully receives the data blocks within the super-frame, the signaling information may be obtained through embedded overhead signaling that is part of at least one data block transmitted within each super-frame. The embedded overhead signaling indicates the allocation and assignment of the corresponding data stream/PLC within the next superframe. Controller 1260 provides MUX _ RX control to de-channelizer (Dechannelizer) 1240. For each symbol period, the de-channelizer 1240 performs de-multiplexing of the detected data or overhead symbols based on MUX _ RX control and provides one or more streams of detected data symbols or one stream of detected overhead symbols, respectively, to the RX data processor 1250. For the case of overhead OFDM symbols, RX data processor 1250 processes the detected overhead symbol stream based on the mode used for overhead signaling and provides decoded overhead signaling to a controller 1260. For the case of data symbol streams, RX data processor 1250 processes the detected data symbol streams of interest based on the mode used for each detected data symbol stream and provides a corresponding decoded data stream to data receiving device 1252. In general, the processing in wireless device 120x is complementary to the processing in base station 110 x.

Controllers 1140 and 1260 manage the operation in base station 110x and wireless device 120x, respectively. Memory units 1142 and 1262 store program codes and data used by controllers 1140 and 1260, respectively. Controller 1140 and/or scheduler 1144 allocates resources for the active PLCs and further assigns transmission units to each active PLC.

Fig. 13 shows a block diagram of TX data processor 1110, channelizer 1120, and OFDM modulator 1130 in base station 110 x. TX data processor 1110 includes N_plcOne for N_plcTX data stream processors 1310a and 1310p for each data stream and a data stream processor 1310q for overhead data. Each TX data processor 1310 can process each data stream { d }_iIndependently encode, interleave, and modulate to generate a corresponding stream of data symbols s_i}。

Fig. 14 shows a block diagram of a TX data processor 1310i, which can be used for each TX data processor 1310 shown in fig. 13. TX data processor 1310i processes a data stream for a PLC. TX data processor 1310i includes a base stream processor 1410a, an enhanced stream processor 1410b, and a bit-to-symbol mapping unit 1430. Processor 1410a processes the base stream of the PLC and processor 1410b processes the enhancement stream (if any) of the PLC.

In the base stream processor 1410a, an outer encoder 1412a encodes the base stream data for each data block according to, for example, a reed-solomon code to generate RS code blocks. The RS code block includes N outer code packets. The encoder 1412a also attaches a CRC value to each outer encoded packet. This CRC value may be used by the wireless device for error detection (i.e., to determine whether the packet is decoded correctly or in error). Outer interleaver 1414a divides each code block into a plurality of sub-blocks, interleaves (i.e., reorders) packets in different sub-blocks transmitted within frames, and buffers sub-blocks transmitted within different frames of a super-frame. The inner encoder 1416a then encodes each outer encoded packet for a sub-block according to, for example, a Turbo code to generate an inner encoded packet. Inner bit interleaver 1418a interleaves the bits within each inner encoded packet to generate a corresponding interleaved packet. The encoding of the outer encoder 1412a and inner encoder 1416a provides transmission reliability for the elementary stream. The interleaving by outer interleaver 1414a and inner interleaver 1418a provides time and frequency diversity, respectively, for the transmission of the base stream. The scrambler 1420a scrambles bits in each of the encoded and bit-interleaved packets using the PN sequence and provides the scrambled bits to the mapping unit 1430.

The enhanced stream processor 1410b performs similar processing on the PLC's enhanced stream (if any). The inner code, outer code, and modulation scheme used by processor 1410b and processor 1410a may be the same, or different. Processor 1410b provides the scrambled bits for the enhancement stream to a mapping unit 1430.

Mapping section 1430 receives scrambled bits of base stream and enhancement stream, and gain G of base stream_bsAnd gain G of the enhancement stream_es. Gain G_bsAnd G_esThe amount of transmit power used for the base stream and the enhancement stream is determined separately. By transmitting these streams at different power levels, the base stream and enhancement stream can achieve different coverage areas. The mapping unit 1430 is based on the selected mapping scheme and the gain G_bsAnd G_esThe received scrambled bits are mapped to data symbols. Symbol mappingThe shooting can be realized by the following modes: (1) grouping sets of B scrambled bits to form a binary value of the B bits, wherein B > 1; (2) the binary value of each B-bit is mapped to a data symbol, which is a complex value of a point in a signal constellation (signal constellation) of the selected modulation scheme. If hierarchical coding is not used, each data symbol corresponds to a signal diagram (e.g., M-PSK or M-QAM, where M2^B) One point in (b). If hierarchical coding is used, each data symbol corresponds to a point in the complex signal diagram, which may or may not be formed by the superposition of two scaled signal diagrams. In the above embodiment, the base stream and the enhancement stream carry the same number of code blocks for each super frame. The code blocks for the base stream and the enhancement stream may be transmitted simultaneously, as shown in fig. 14, or using TDM and/or FDM.

Returning to FIG. 13, channelizer 1120 is implemented with multiplexer 1320, multiplexer 1320 receiving N_plcA stream of data symbols, a stream of overhead symbols, pilot symbols, and guard symbols. Multiplexer 1320 places the data symbols, overhead symbols, pilot symbols, and guard symbols on the appropriate subbands and symbol periods based on MUX _ TX control from controller 1140 and outputs a composite symbol stream s_c}. In assigning modulation symbols to groups of subbands, another level of (symbol) interleaving may be performed by assigning modulation symbols to subbands in each group of subbands in a pseudo-random manner. To simplify assignment of subbands, the PLCs can be assigned time slots, as described above. For example, slots may be mapped to different groups of subbands from one symbol period to another in a pseudo-random manner. The mapping of the slots to subband groups ensures that: the modulation symbols associated with a particular slot number have different distances from the pilot subbands for different symbol periods, which may improve performance.

OFDM modulator 1130 includes an inverse fourier transform (IFFT) unit 1330 and a cyclic prefix generator 1332. For each symbol period, the IFFT unit 1330 uses N_tsbPoint IFFT, sum of N_tsbN of sub-bands_tsbEach set of individual symbols is transformed into the time domain, thereby obtaining a packetContaining N_tsbA "transformed" symbol of time-domain chips. To combat inter-symbol interference (ISI) caused by frequency selective fading, cyclic prefix generator 1332 repeats a portion of each transformed symbol to form a corresponding OFDM symbol. The repeated portion is often referred to as a cyclic prefix or guard interval. Cyclic prefix generator 1332 for a composite symbol stream s_cProvides a stream of data chips (denoted as c).

The multiplexing and transmission techniques described herein may be implemented in a number of ways. For example, these techniques may be implemented in hardware, software, or a combination of hardware and software. For a hardware implementation, the processing units used to perform multiplexing and/or transmitting in the base station may be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. The processing units for performing the complementary processing in the wireless device may also be implemented in one or more ASICs, DSPs, and the like.

For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit (e.g., memory unit 1142 or 1262 in fig. 11) and executed by a processor (e.g., controller 1140 or 1260). The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (89)

1. A method for broadcasting and multicasting data in a wireless multi-carrier communication system, comprising:

processing the plurality of data streams to obtain a plurality of data symbol streams, one data symbol stream for each data stream;

allocating a transmission unit for each of the plurality of data streams, each transmission unit corresponding to a subband in a symbol period and being operable to transmit a data symbol;

mapping the data symbols in each data symbol stream to transmission units assigned to the respective data stream; and

forming a composite symbol stream using the data symbols of the plurality of data streams mapped to the allocated transmission units, wherein a receiver can independently recover the data streams based on the data symbols included in the composite symbol stream for each data stream.

2. The method of claim 1, further comprising:

multiplexing overhead symbols to the composite symbol stream, wherein the overhead symbols carry signaling indicating transmission units allocated to each of the plurality of data streams.

3. The method of claim 1, wherein each of the plurality of data symbol streams carries signaling indicating transmission units assigned to the data stream in a subsequent transmission interval.

4. The method of claim 1, wherein a total of T subbands are available for transmitting data symbols in each symbol period for broadcast and the T subbands are allocable to multiple data streams, where T > 1.

5. The method of claim 4, wherein different groups of subbands in each symbol period used for broadcast and multicast are assigned to multiple data streams.

6. The method of claim 5, wherein the subbands in each group are distributed across the T total subbands, and wherein the subbands in each group are interleaved with the subbands in the other groups in a same symbol period.

7. The method of claim 1, wherein the data streams are independently processed using coding and modulation schemes selected for each data stream to obtain a corresponding data symbol stream.

8. The method of claim 7, wherein the coding and modulation schemes are selected for each data stream based on an expected coverage for the data stream.

9. The method of claim 7, wherein the coding and modulation schemes are selected for the data streams based on a data rate for each data stream.

10. The method of claim 7, wherein the coding and modulation schemes used for each data stream are maintained even if an instantaneous information data rate of the data stream changes.

11. The method of claim 1, wherein each of the plurality of data streams is independently encoded with a base inner code and an inner code rate selected for the data stream.

12. The method of claim 1, wherein the plurality of data streams includes a first data stream for a multimedia program audio component and a second data stream for the multimedia program audio component, and wherein the first and second data streams are independently recoverable by the receiver.

13. The method of claim 12, wherein the plurality of data streams further includes a third data stream for the multimedia program data component.

14. The method of claim 12, wherein the first data stream is processed using a first coding and modulation scheme to obtain a first data symbol stream, and wherein the second data stream is processed using a second coding and modulation scheme to obtain a second data symbol stream.

15. The method of claim 1, wherein, among the plurality of data streams, each of at least one data stream comprises a base stream and an enhancement stream carrying different information for the data stream.

16. The method of claim 15, wherein the base stream and the enhancement stream for each of the at least one data stream have different coverage areas.

17. The method of claim 15, wherein the base stream and the enhancement stream for each of the at least one data stream are processed using coding and modulation schemes selected for the data stream and transmitted with different transmit power levels.

18. The method of claim 15, wherein the base stream and the enhancement stream for each of the at least one data stream are processed using coding and modulation schemes separately selected for the base stream and the enhancement stream.

19. The method of claim 1, wherein transmission units are allocated for each data stream based on an information data rate of the data stream.

20. The method of claim 1, wherein the plurality of data streams are allocated transmission units within each super-frame having a predetermined duration.

21. The method of claim 1, wherein the multi-carrier communication system utilizes Orthogonal Frequency Division Multiplexing (OFDM).

22. An apparatus in a wireless multi-carrier broadcast communication system, comprising:

a data processor for processing the plurality of data streams to obtain a plurality of data symbol streams, one data symbol stream for each data stream;

a controller configured to assign a transmission unit to each of the plurality of data streams, each transmission unit corresponding to a subband in a symbol period and being operable to transmit a data symbol; and

a multiplexer for mapping data symbols in each data symbol stream to the transmission units allocated to the respective data stream, and forming a composite symbol stream using the data symbols of the data streams mapped to the allocated transmission units, wherein the receiver can independently recover the data streams based on the data symbols included in the composite symbol stream of each data stream.

23. The apparatus of claim 22, wherein a total of T subbands are available for transmitting data symbols in each symbol period used for broadcast and are allocable to multiple data streams, where T > 1.

24. The apparatus of claim 23, wherein different groups of subbands are assigned to the multiple data streams in each symbol period used for broadcast, wherein the subbands in each group are distributed among the T total subbands, and wherein the subbands in each group are interleaved with the subbands in other groups in the same symbol period.

25. An apparatus in a wireless multi-carrier broadcast communication system, comprising:

a processing module for processing the plurality of data streams to obtain a plurality of data symbol streams, one data symbol stream for each data stream;

an allocation module, configured to allocate a transmission unit for each data stream of the multiple data streams, where each transmission unit corresponds to a subband in a symbol period and is used to transmit a data symbol;

a mapping module for mapping the data symbols in each data symbol stream to transmission units allocated to the respective data stream; and

a forming module for forming a composite symbol stream using the data symbols of the plurality of data streams mapped onto the allocated transmission units, wherein a receiver can independently recover the data streams based on the data symbols included in the composite symbol stream for each data stream.

26. The apparatus of claim 25, wherein a total of T subbands are available for transmitting data symbols in each symbol period used for broadcast and are allocable to multiple data streams, where T > 1.

27. The apparatus of claim 26, wherein different subband groups are assigned to multiple data streams in each symbol period used for broadcast.

28. The apparatus of claim 27, wherein the subbands in each group are distributed across the T total subbands, and wherein the subbands in each group are interleaved with the subbands in other groups in a same symbol period.

29. A method for transmitting multiple data streams in a wireless multi-carrier communication system, comprising:

for each super-frame having a predetermined duration,

identifying a plurality of data streams to be transmitted within the superframe;

processing at least one data block of each of the plurality of data streams to obtain at least one code block of the data stream, one code block for each data block, each code block comprising a plurality of data symbols;

assigning transmission units within the superframe to each of the plurality of data streams, each transmission unit corresponding to a subband within a symbol period and being operable to transmit a data symbol;

mapping data symbols in at least one code block of each data stream onto transmission units allocated to the data stream; and

forming a composite symbol stream using the data symbols of the plurality of data streams mapped to the allocated transmission units.

30. The method of claim 29, wherein a receiver can independently recover the data streams based on data symbols included in the composite symbol stream for each data stream.

31. The method of claim 29, further comprising:

multiplexing overhead symbols onto the composite symbol stream for each super-frame, wherein the overhead symbols carry signaling that indicates transmission units in the super-frame that are assigned to each of the plurality of data streams.

32. The method of claim 29, wherein at least one code block of each data stream within a current super-frame carries signaling indicating transmission units allocated to the data stream within a subsequent super-frame.

33. The method of claim 29, wherein each superframe spans a predetermined number of symbol periods and includes a plurality of subbands for each of the predetermined number of symbol periods, and wherein the plurality of subbands is allocable to ones of the plurality of data streams for each symbol period.

34. The method of claim 29, further comprising:

assigning at least one uninterrupted symbol period within the superframe to each of the plurality of data streams to be transmitted within each superframe, and wherein a transmission unit of each data stream is for the at least one symbol period assigned to the data stream.

35. The method of claim 29, further comprising:

for each super-frame it is possible to,

assigning at least one symbol period within the superframe to each of the plurality of data streams to be transmitted within the superframe; and

cycling through the plurality of data streams and assigning one symbol period within the superframe to each data stream until the at least one symbol period allocated to the data stream has been assigned.

36. The method of claim 29, wherein transmission units within the super-frame are allocated to each data stream based on a number of data symbols to be transmitted within the super-frame for the data stream.

37. The method of claim 29, wherein each superframe comprises a plurality of frames, each frame having a particular duration.

38. The method of claim 37, further comprising:

for each of the frames of the video stream,

each code block of each data stream is divided into a plurality of sub-blocks, and wherein the plurality of sub-blocks of each code block are transmitted within a plurality of frames of the super-frame, one sub-block being transmitted within each frame.

39. The method of claim 37, further comprising:

for each super-frame it is possible to,

dividing each code block of each data stream into a plurality of sub-blocks, one sub-block for each frame;

forming a plurality of sets of sub-blocks for each data stream, each frame corresponding to a set of sub-blocks, each set of sub-blocks comprising one sub-block of each of the at least one code block of the data stream; and

for each of the frames of the super-frame,

assigning transmission units within the frame to each of the plurality of data streams; and

multiplexing data symbols in the set of sub-blocks for each data stream within the frame onto transmission units within the frame that have been allocated to the data stream.

40. The method of claim 39, wherein the plurality of sets of sub-blocks for each data stream comprise an equal number of sub-blocks, and wherein an equal number of transmission units are allocated for each data stream for each of the plurality of frames.

41. The method of claim 29, wherein each superframe spans a predetermined number of symbol periods and is divided into a plurality of transmission slots, each transmission slot corresponding to a predetermined number of subbands in one symbol period, and wherein the plurality of data streams are allocated transmission slots within the superframe.

42. The method of claim 41, wherein each superframe comprises S transmission slots for each of the predetermined number of symbol periods, wherein S > 1, and wherein the S transmission slots within each symbol period are individually allocable to the plurality of data streams.

43. The method of claim 42, wherein the S transmission slots correspond to different groups of subbands in different symbol periods.

44. The method of claim 41, wherein the subbands for each transmission slot are distributed across a total of T subbands usable for data transmission in the system, where T > 1.

45. The method of claim 41, wherein the subbands for each transmission slot are interleaved with the subbands for other transmission slots in the same symbol period.

46. The method of claim 39, further comprising:

for each of the frames within the super-frame,

assigning a particular transmission unit within the frame to each data stream, wherein data symbols in a set of sub-blocks of each data stream within the frame are multiplexed onto the particular transmission unit assigned to the data stream.

47. The method of claim 46, wherein the plurality of data streams are assigned specific transmission units in order based on a number of transmission units allocated to the data streams.

48. The method of claim 46, wherein transmission units arranged in a rectangular pattern on a time-frequency plane of the frame are assigned to the data streams.

49. The method of claim 48, wherein for the plurality of frames of the superframe, transmission units of a same histogram are assigned for each data stream.

50. The method of claim 48, wherein the histogram for each data stream has a frequency dimension that is less than or equal to a maximum number of subbands allowed by a coding and modulation scheme used for the data stream.

51. The method of claim 46, wherein assigning a particular transmission unit within the frame to each data stream comprises:

dividing the frame into a plurality of two-dimensional (2-D) slices, each 2-D slice comprising a different set of subbands and spanning a plurality of symbol periods within the frame;

mapping each of the plurality of data streams onto one of the plurality of 2-D stripes; and

the transmission units in each 2-D strip are assigned to the data streams mapped onto the 2-D strips.

52. The method of claim 51, wherein the transmission units in each 2-D strip are mapped onto one-dimensional (1-D) strip, and wherein each data stream mapped onto the 2-D strip is assigned one uninterrupted segment of transmission units in the respective 1-D strip.

53. The method of claim 52, wherein the transmission units in each 2-D bar are mapped onto the corresponding 1-D bar using a vertical zigzag pattern that selects the transmission units in the 2-D bar: for one symbol period at a time, the selection is made sequentially across subbands, and for the frame, the selection is made sequentially across symbol periods.

54. The method of claim 46, wherein the plurality of data streams comprises a number of data streams adapted to be received together, and wherein the number of data streams are assigned transmission units that are close in time.

55. The method of claim 54, wherein each of the number of data streams is assigned transmission units arranged in a histogram on a time-frequency plane of the frame.

56. The method of claim 55, wherein a number of histograms for the number of data streams are vertically stacked in a time-frequency plane of the frame.

57. The method of claim 55, wherein a number of histograms for the number of data streams are stacked horizontally in a time-frequency plane of the frame.

58. The method of claim 54, wherein the plurality of data streams represent a single multimedia program.

59. The method of claim 51, wherein transmission units that are adjacent within a single 2-D strip are assigned to several data streams that are adapted to be received together.

60. The method of claim 39, wherein each data block of each data stream is processed with a concatenated code comprising an outer code and an inner code to obtain a corresponding code block.

61. The method of claim 60, wherein the outer code is selectively activated for each data stream.

62. The method of claim 60, wherein each data block comprises a plurality of data packets, and wherein processing at least one data block of each of the plurality of data streams comprises:

encoding a plurality of data packets for each data block using the outer code to obtain at least one parity packet for the data block; and

the plurality of data packets and the at least one parity packet of the data block are individually encoded with the inner code to obtain a plurality of encoded packets for a respective code block.

63. The method of claim 60, wherein the outer code is a block code and the inner code is a Turbo code.

64. The method of claim 62, wherein each super-frame comprises a plurality of frames of equal duration, wherein each code block of each data stream is divided into a plurality of sub-blocks of equal number of encoded packets, and wherein the plurality of sub-blocks of each code block are transmitted within the plurality of frames of the super-frame, one sub-block being transmitted within each frame.

65. The method of claim 64, wherein each encoded packet in each sub-block of each data stream is transmitted in as few symbol periods as possible based on transmission units allocated to the data stream in order to reduce buffering requirements.

66. The method of claim 64, wherein each code packet in each sub-block of each data stream is transmitted in as many symbol periods as possible based on transmission units allocated to the data stream in order to improve time diversity.

67. The method of claim 64, wherein for a first data stream of a current superframe, B code blocks are obtained, wherein B > 1, and the first data stream is one of the plurality of data streams, wherein each of the B code blocks is divided into F sub-blocks of F frames for a current superframe, wherein F > 1, wherein each sub-block includes P coded packets, wherein P > 1, and wherein PxB coded packets in B sub-blocks are transmitted within frames of the current superframe for the first data stream.

68. The method of claim 67, wherein P code packets in each of the B sub-blocks of the first data stream to be transmitted within the frame are distributed within transmission units allocated to the frame of the first data stream for each frame of the super-frame to achieve time diversity.

69. The method of claim 67, wherein for each frame of a current superframe, the B sub-blocks of the first data stream to be transmitted within the frame are cycled through, and for each cycle, a coded packet is sequentially selected from the B sub-blocks and multiplexed onto the transmission units assigned to the frame of the first data stream.

70. The method of claim 29, further comprising:

and sending the composite symbol stream carrying the plurality of data streams to a receiver in the system.

71. The method of claim 29, wherein the predetermined duration of the superframe is 1 second.

72. The method of claim 29, wherein the multi-carrier communication system utilizes Orthogonal Frequency Division Multiplexing (OFDM).

73. An apparatus in a wireless multi-carrier communication system, comprising:

a controller that identifies a plurality of data streams to be transmitted within each super-frame having a predetermined duration and allocates a transmission unit within the super-frame for each of the plurality of data streams, each transmission unit corresponding to a subband within a symbol period and being usable to transmit a data symbol;

a data processor that processes, for each super-frame, at least one data block of each data stream to be transmitted within the super-frame to obtain at least one code block of the data stream, wherein, for each data block, one code block is obtained and each code block comprises a plurality of data symbols; and

a multiplexer for mapping, for each super-frame, data symbols in at least one code block of each data stream to be transmitted within the super-frame onto transmission units of the super-frame allocated to the data stream, and forming a composite symbol stream using the data symbols of the plurality of data streams mapped onto the allocated transmission units.

74. The apparatus of claim 73, wherein the data processor is further operative to divide each code block of each data stream into a plurality of sub-blocks for each frame, and wherein the plurality of sub-blocks for each code block are transmitted within a plurality of frames of the super-frame, one sub-block being transmitted within each frame.

75. The apparatus of claim 74, wherein for each super-frame, the controller is further to assign a particular transmission unit within each frame of the super-frame to each of the plurality of data streams to be transmitted within the super-frame, and wherein sub-blocks of each data stream to be transmitted within each frame are multiplexed onto the particular transmission unit of the frame assigned to the data stream.

76. An apparatus in a wireless multi-carrier communication system, comprising:

an identification module that identifies a plurality of data streams to be transmitted within each superframe having a predetermined duration;

an allocation module configured to allocate a transmission unit in each super frame for each of the plurality of data streams, each transmission unit corresponding to a subband in a symbol period and being capable of transmitting a data symbol;

a processing module that, for each super-frame, processes at least one data block of each data stream to be transmitted within the super-frame to obtain at least one code block of the data stream of the super-frame, wherein, for each data block, one code block is obtained and each code block comprises a plurality of data symbols; and

a mapping module that maps, for each superframe, data symbols in at least one code block of each data stream to be transmitted within the superframe onto transmission units of the superframe assigned to the data stream; and

a forming module for forming a composite symbol stream using the data symbols of the plurality of data streams transmitted in each super-frame mapped to the allocated transmission unit.

77. The apparatus of claim 76, further comprising:

a dividing module to divide each code block of each data stream into a plurality of sub-blocks, and wherein the plurality of sub-blocks of each code block are transmitted within a plurality of frames of the super-frame, one sub-block being transmitted within each frame.

78. The apparatus of claim 77, further comprising:

an assignment module that assigns, for each super-frame, a particular transmission unit within each frame of the super-frame to each of the plurality of data streams to be transmitted within the super-frame, wherein sub-blocks to be transmitted within each frame in each data stream are multiplexed onto the particular transmission unit assigned to the data stream in the frame.

79. A method of receiving data in a wireless multi-carrier communication system, comprising:

selecting at least one data stream to be recovered from a plurality of data streams broadcast by a transmitter in the system;

determining a transmission unit for each selected data stream, each transmission unit corresponding to a subband in a symbol period and operable to transmit a data symbol, wherein the data symbols for each data stream are mapped onto the transmission units assigned to the data stream prior to transmission, and wherein each data stream is independently recoverable based on the data symbols for the data stream;

obtaining detected data symbols for each selected data stream, each detected data symbol being an estimate of a corresponding data symbol broadcast by the transmitter;

demultiplexing detected data symbols from a transmission unit for each selected data stream onto a detected data symbol stream of said selected data stream, wherein for said at least one data stream selected for recovery at least one detected data symbol stream is obtained; and

each of the at least one detected data symbol stream is processed to obtain a corresponding decoded data stream.

80. The method of claim 79, further comprising:

overhead information is obtained indicating the transmission units assigned to each selected data stream, and wherein the demultiplexing is based on the overhead information.

81. The method of claim 79, wherein the plurality of data streams comprises a plurality of data streams adapted to be received together, and wherein the plurality of data streams are assigned transmission units that are close in time.

82. An apparatus in a wireless multi-carrier communication system, comprising:

a controller that selects at least one data stream to be recovered from a plurality of data streams broadcast by a transmitter in the system, and determines a transmission unit for each selected data stream, each transmission unit corresponding to a subband within a symbol period and operable to transmit a data symbol, wherein the data symbols for each data stream are mapped onto the transmission units assigned to the data stream prior to transmission, and wherein each data stream is independently recoverable based on the data symbols for the data stream;

a detector to obtain detected data symbols for each selected data stream, each detected data symbol being an estimate of a corresponding data symbol broadcast by the transmitter;

a demultiplexer demultiplexing detected data symbols from transmission units for respective selected data streams onto detected data symbol streams of said selected data streams, wherein for said at least one data stream selected for recovery at least one detected data symbol stream is obtained; and

a data processor processes each of the at least one detected data symbol stream to obtain a corresponding decoded data stream.

83. An apparatus in a wireless multi-carrier communication system, comprising:

a selection module that selects at least one data stream to be recovered from a plurality of data streams broadcast by a transmitter in the system;

a determining module that determines a transmission unit for each selected data stream, each transmission unit corresponding to a subband in a symbol period and operable to transmit a data symbol, wherein the data symbols for each data stream are mapped onto the transmission units assigned to the data stream prior to transmission, and wherein each data stream is independently recoverable based on the data symbols for the data stream;

an acquisition module that acquires detected data symbols for each selected data stream, each detected data symbol being an estimate of a corresponding data symbol broadcast by the transmitter;

a demultiplexing module that demultiplexes detected data symbols from transmission units for each selected data stream onto detected data symbol streams of the selected data stream, wherein at least one detected data symbol stream is obtained for the at least one data stream selected for recovery; and

a processing module that processes each of the at least one detected data symbol stream to obtain a corresponding decoded data stream.

84. A method for receiving data in a wireless multi-carrier communication system, comprising:

selecting at least one data stream to be recovered from a plurality of data streams transmitted by a transmitter within the system; and

for each super-frame having a predetermined duration,

determining transmission units for each selected data stream within the superframe, each transmission unit corresponding to a subband within a symbol period and being usable for transmitting one data symbol, wherein the transmission units within the superframe are allocated to each of the plurality of data streams, and wherein at least one code block of each of the plurality of data streams is transmitted on the transmission units allocated to the data stream, each code block being generated from a respective data block;

obtaining at least one received code block for each selected data stream from the transmission units for the selected data stream, each code block transmitted for the selected data stream corresponding to one received code block, an

Each received code block for each selected data stream is processed to obtain a corresponding decoded block, which is an estimate of the data block transmitted for the selected data stream.

85. The method of claim 84, wherein each code block for each selected data stream is transmitted on a set of subbands, and wherein each received code block for each selected data stream is obtained by performing a Fast Fourier Transform (FFT) on the set of subbands used to transmit the corresponding code block.

86. The method of claim 84, wherein each super-frame comprises a plurality of frames, wherein each code block of each of the plurality of data streams is divided into a plurality of sub-blocks, and wherein the plurality of sub-blocks of each code block are transmitted within the plurality of frames of the super-frame, one sub-block being transmitted within each frame.

87. The method of claim 86, further comprising:

for each super-frame it is possible to,

determining transmission units for each selected data stream within each frame of the superframe,

for each frame of the super frame, obtaining at least one receiving sub-block of each selected data stream from a transmission unit for the selected data stream; and

a plurality of received sub-blocks of each received code block are processed to obtain a corresponding decoded block.

88. An apparatus in a wireless multi-carrier communication system, comprising:

a controller that selects at least one data stream to be recovered from a plurality of data streams transmitted by a transmitter in the system, and determines transmission units for each selected data stream within each super-frame having a predetermined duration, each transmission unit corresponding to a subband within a symbol period and being usable to transmit a data symbol, wherein the transmission units within each super-frame are selectively assigned to each selected data stream, and wherein code blocks for each selected data stream are transmitted on the transmission units assigned to the selected data stream;

a detector for obtaining at least one received code block for each selected data stream from the transmission unit used for the selected data stream, each code block transmitted for the selected data stream corresponding to one received code block; and

a data processor processes each received code block for each selected data stream to obtain a corresponding decoded block, which is an estimate of the data block transmitted for the selected data stream.

89. An apparatus in a wireless multi-carrier communication system, comprising:

a selection module that selects at least one data stream to be recovered from a plurality of data streams transmitted by a transmitter within the system;

a determining module that determines transmission units for respective selected data streams within each superframe having a predetermined duration, each transmission unit corresponding to a subband within a symbol period and being operable to transmit a data symbol, wherein the transmission units within the respective superframe are selectively allocated for the respective selected data streams, and wherein code blocks for each selected data stream are transmitted on the transmission units allocated to the selected data stream;

an obtaining module, configured to obtain a received code block of each selected data stream from a transmission unit for the selected data stream, where each code block transmitted for the selected data stream corresponds to one received code block; and

a processing module that processes each received code block of each selected data stream to obtain a corresponding decoded block that is an estimate of the data block transmitted for the selected data stream.