HK1137889A - Power control method and apparatus for a channel with multiple formats in a communication system - Google Patents

Description

Method and apparatus for power control of channels with multiple formats in a communication system

The present application is a divisional application of the chinese patent application entitled "power control method and apparatus with channels of multiple formats in a communication system" of the invention having the application number of 02820166.3 on 8/20/2002.

Background

FIELD

The present invention relates generally to data communications, and more particularly to techniques for controlling transmit power for data transmissions using multiple formats (e.g., rates, transport formats) supported by a communication system that uses power control (e.g., W-CDMA).

Background

In a wireless communication system, a user with a terminal (e.g., a cellular phone) communicates with other users through transmissions on the downlink and uplink by one or more base stations. The downlink (i.e., forward link) refers to transmission from the base station to the terminal, and the uplink (i.e., reverse link) refers to transmission from the terminal to the base station. The downlink and uplink are typically allocated different frequencies.

In a Code Division Multiple Access (CDMA) system, the total transmit power available to a base station generally indicates the total downlink capacity of the base station, since data may be transmitted to multiple terminals on the same frequency band at the same time. A portion of the total available transmit power is allocated to each active terminal such that the aggregate transmit power for all active terminals is less than or equal to the total available transmit power.

To maximize downlink capacity, power control mechanisms are typically used to minimize power consumption and interference while maintaining a desired level of performance. Typically, the power control mechanism is implemented with two power control loops. The first power control loop, commonly referred to as the "inner" power control loop, or simply the inner loop, adjusts the transmit power to each terminal so that the signal quality of the transmission received at the terminal (e.g., as measured by the signal-to-noise-plus-interference ratio (SINR)) is maintained at a particular target SNIR. This target SNIR is generally referred to as the power control set point (or simply set point). The second power control loop (often referred to as the "outer" power control loop, or simply the outer loop) adjusts the target SNIR to maintain a desired level of performance (e.g., measured with a particular target block error rate (BLER), Frame Error Rate (FER), or bit rate (BER)). By minimizing transmit power while maintaining a target BLER, system capacity may be increased and latency of service to users may be reduced.

A W-CDMA system supports data transmission on one or more transport channels, and one or more transport channels, possibly using one or more transmission modes for each transport channel. Each transport format defines various processing parameters such as the Transmission Time Interval (TTI) for which the transport format applies, the size of each data transport block, the number of transport blocks within each TTI, the coding scheme used for the TTI, and so forth. The use of multiple transport formats allows different types or rates of data to be transmitted on a single transport channel.

The W-CDMA standard now allows a target BLER to be specified by the base station for each transport channel, regardless of the number of transport formats that may be selected for the transport channel. Each transport format may be associated with a different coded block length, which in turn requires a different target SNIR to achieve the target BLER. (for W-CDMA, the code block length is determined by the transport block size, which is specified by the transport format). In W-CDMA, one or more transport channels are multiplexed together within a single physical channel, the transmit power of which is adjusted by power control. Using conventional power control mechanisms, the inner power control loop adjusts the target SNIR based on the received transport block to achieve a target BLER or better BLER for each transport channel.

Since different transport formats may require different target SNIRs to achieve the target BLER, the average transmit power of the physical channel fluctuates depending on the particular sequence of transport formats (i.e., the relative frequencies of the transport formats and their ordering) selected for use in the constituent transport channels. And since the outer and inner loops take the same amount of time to converge, each time the transport format is changed, a transition occurs until the loop under the new transport format converges to the target SNIR. During this transition time, the actual BLER may be much larger or much smaller than the target BLER, which may result in degraded performance and lower system capacity.

There is therefore a need in the art for an improved power control mechanism for use in a communication system (e.g., W-CDMA) capable of transmitting data on one or more transport channels using multiple transport formats.

SUMMARY

Aspects of the present disclosure provide techniques for more efficiently controlling transmit power for data transmission on a power-controlled channel comprising one or more data channels, each data channel associated with one or more formats (e.g., rates, transport formats, etc., as defined in W-CDMA). As used herein, a data channel refers to any signaling channel (e.g., traffic or control) for information for which there are one or more associated data integrity specifications (e.g., BLER, FER, and/or BER specifications) for the information. The present invention recognizes that different formats for a given data channel (e.g., transport channels within W-CDMA) may require different target SNIRs to achieve a particular BLER. Various schemes are provided herein to efficiently process these different formats into "individual" transmissions with their own performance requirements while reducing the overall transmit power of the data transmission. For clarity of description, various aspects and embodiments are described for W-CDMA, in which multiple transport formats may be defined for each transport channel, and one or more physical transport channels are multiplexed on one physical channel. However, the techniques described herein are also potentially applicable to other systems in which multiple formats are defined for each data channel, and one or more data channels are multiplexed on a single power-controlled channel.

In an aspect, rather than defining one target BLER for all transport formats of each transport channel, it is possible to define a specific target BLER for each transport format of each transport channel used for data transmission. If N transport formats are available for a given transport channel, up to N target BLERs may be specified for the transport channel.

In another aspect, various power control schemes are provided to achieve different target SNIRs for different transport formats. These schemes may be used to achieve different target BLERs (i.e., different code block lengths) specified for different transport formats, which typically require different target SNIRs. These schemes may also be used if a single target BLER is fixed for all transport formats of a given transport channel, since different transport formats may require different target SNIRs to achieve the same target BLER.

In a first power control scheme for obtaining different target SNIRs for different transport formats, multiple single outer loops are maintained for multiple transport formats. For each transport format, its associated outer loop attempts to set the target SNIR to achieve the target BLER specified for that transport format. A plurality of individual outer loops will then form an overall outer loop which together with a (common) inner loop derives suitable power control commands for all transport formats.

In a second power control scheme to achieve different target SNIRs for different transport formats, multiple single outer loops are maintained for multiple transport formats, and the base station further applies different adjustments to the transmit power levels for the different transport formats. The base station is aware of the specific transport format used for the incoming Transmission Time Interval (TTI) and can participate in power control by adjusting the transmit power of the data transmission according to the actually selected transport format.

In an embodiment of the second scheme, the base station is provided with a table of power offsets for available transport formats, which may be calculated based on the relative difference in target SNIRs required for the transport formats to achieve their target BLERs. For each TTI, the base station selects one or more transport formats for the TTI, obtains a power offset for each selected transport format from the table, and transmits at a power level determined in part by the power offset for the selected transport format. The power adjustment (based on the transport format) of the base station may indicate that a portion of the transmitted frame is to be made while maintaining the transmit power of the remaining portion of the transmitted frame (i.e., not adjusted according to the transport format).

In another embodiment of the second scheme, the terminal assists in determining the power offset (which is updated via a third power control loop) and may provide an update of the power offset to the base station according to a particular update scheme (e.g., periodically, when needed, when one or more conditions are met, etc.)

Aspects and embodiments of the present invention may be applied to a communication system that uses multiple formats for a single power controlled channel. Multiple formats or rates are supported by using multiple transport formats within W-CDMA or other mechanisms within other CDMA standards. The techniques described herein may also be applied to the uplink and downlink.

The present invention also provides methods, power control mechanisms, apparatus, and other elements to implement various aspects, embodiments, and features of the present invention, as described in detail below.

Brief description of the drawings

The features, nature, and advantages 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 is a diagram of a wireless communication system that supports multiple users and is capable of implementing various aspects and embodiments of the present invention;

FIGS. 2A and 2B are diagrams of signal processing at a base station and a terminal, respectively, for downlink data transmission in accordance with the W-CDMA standard;

FIGS. 3A and 3B illustrate two different possible transport formats for two different transport channels;

fig. 4 is a frame format and a slot format of a downlink DPCH defined by the W-CDMA standard;

fig. 5 is an illustration of a downlink power control mechanism in which various aspects and embodiments of the present invention may be implemented;

fig. 6 illustrates a first power control mechanism in which multiple single outer loops are maintained to control transmit power for data transmissions using multiple transport formats;

fig. 7 is a flow diagram of an embodiment of a process implemented at a terminal to maintain multiple single outer loops for multiple transport formats according to a first power control mechanism;

fig. 8 illustrates a second power control scheme in which multiple single outer loops are maintained and transport format-based power adjustment is made at the base station;

FIG. 9 is a diagram illustrating a particular implementation of a second power control scheme;

fig. 10 is a diagram illustrating an embodiment of a third power control loop to maintain power offsets for multiple transport formats;

fig. 11 is a flowchart of an embodiment of a process implemented at a terminal to maintain multiple single outer loops for multiple transport formats according to a second power control scheme; and

fig. 12 and 13 are block diagrams of embodiments of a base station and a terminal, respectively.

Detailed Description

Fig. 1 is an illustration of a wireless communication system 100 that supports multiple users and is capable of implementing various aspects and embodiments of the present invention. The system 100 includes a plurality of base stations 104 that provide coverage for a plurality of geographic areas 102. A base station IS also known as a Base Transceiver System (BTS) (within IS-95), an access point (within IS-856), or a node B (within W-CDMA). A base station and/or its coverage area are also often referred to as a cell. System 100 may be designed to implement any combination of one or more CDMA standards, such as IS-95, CDMA2000, IS-856, W-CDMA, among others. These standards are well known in the art and are incorporated herein by reference.

As shown in fig. 1, various terminals 106 are dispersed throughout the system. A terminal IS also referred to as a mobile station, an access terminal (within IS-856), or a User Equipment (UE) (within W-CDMA). In an embodiment, each terminal 106 may communicate with one or more base stations 104 on the downlink and uplink at any time, depending on whether the terminal is active and whether it is in soft handoff. As shown in fig. 1, base station 104a communicates with terminals 106a, 106b, 106c, and 106d, and base station 106b communicates with terminals 106d, 106e, and 106 f. Terminal 106d is in soft handoff and is communicating with both base stations 104a and 104 b.

Within system 100, a system controller 102 is coupled to a base station 104, and may further be coupled to a Public Switched Telephone Network (PSTN) and/or one or more Packet Data Serving Nodes (PDSNs). The system controller 102 provides coordination and control of the base stations coupled to it. The system controller 102 also controls the routing of calls (e.g., general telephone calls) between the terminals 106, between the terminals 106 and a PDSN or other subscriber coupled to the PSTN. System controller 102 is often referred to as a Base Station Controller (BSC) or a Radio Network Controller (RNC).

Fig. 2A is an illustration of signal processing for downlink data transmission at a base station according to the W-CDMA standard. Upper layer signaling for W-CDMA has supported data transmission to specific terminals on one or more transport channels, each of which can carry data for one or more services. These services may include voice, video, packet data, etc., which are collectively referred to herein as "data.

The data for each transport channel is processed according to one or more transport formats selected for that transport channel. Each transport format defines various processing parameters such as a Transmission Time Interval (TTI) over which the transport format is applied, the size of each data transport block, the number of transport blocks within each TTI, the coding scheme used for the TTI, etc. A TTI may be specified as 10 milliseconds, 20 milliseconds, 40 milliseconds, or 80 milliseconds. Each TTI can be used for transmission with N_BA transport block set of transport blocks of equal size, as specified by the transport format of the TTI. For each transport channel, the transport format changes dynamically as the TTI changes, and the set of transport formats that may be used for a transport channel is referred to as a transport format set.

As shown in fig. 2A, the data for each transport channel is provided to a corresponding transport channel processing portion 210 within one or more transport blocks per TTI. Within each processing section 210, each transport block is used to compute a set of Cyclic Redundancy Check (CRC) bits in block 212. The CRC bits are added to the transport block and used at the terminal for block error detection. The one or more CRC-encoded blocks for each TTI are then concatenated together in series within block 214. If the total number of bits is greater than the maximum size of the coded block after concatenation, the bits are segmented into a plurality of (equal-sized) coded blocks. The maximum code block size is determined by the coding scheme (e.g., convolutional, Turbo, or no coding) specifically chosen for the current TTI, as specified by the transport format. In block 216, each coded block is then encoded or not encoded with the selected coding scheme to generate coded bits.

The coded bits are then rate matched in block 218 according to rate matching attributes assigned by the higher signaling layer and specified by the transport format. On the uplink, bits are repeated or truncated (i.e., deleted) so that the number of bits to be transmitted matches the number of available bit positions. On the downlink, unused bit positions are padded with Discontinuous Transmission (DTX) bits, at block 220. The DTX bits indicate when transmission should cease and not actually be transmitted.

The rate-matched bits for each TTI are then interleaved according to a particular interleaving scheme to provide time diversity, at block 222. According to the W-CDMA standard, interleaving is implemented over a TTI, which may be chosen to be 10, 20, 40, or 80 milliseconds. When the selected TTI is longer than 10 milliseconds, the bits are segmented and mapped to successive transport channel frames within the TTI in block 224. Each transport channel corresponds to a portion of a TTI to be transmitted over a (10 ms) physical channel radio frame period (or simply "frame").

In W-CDMA, data to be transmitted to a particular terminal is processed at a higher signaling layer as one or more transport channels. The transport channels are then mapped into one or more physical channels allocated to the terminal for communication (e.g., a call). In W-CDMA, a downlink dedicated physical channel (downlink DPCH) is typically allocated to each terminal for the duration of the communication. The downlink DPCH is used to carry transport channel data as well as control data (e.g., pilot, power control information, etc.) in a time-division multiplexed manner. The downlink DPCH may thus be considered as a multiplex of a downlink Dedicated Physical Data Channel (DPDCH) and a downlink Dedicated Physical Control Channel (DPCCH), as described below. The transport channel data is mapped only to the DPDCH and the DPCCH includes physical layer signaling information.

In block 232, the transport channel frames from all active transport channel processing sections 210 are serially multiplexed into a coded composite transport channel (CCTrCH). In block 234, DTX bits may then be inserted into the multiplexed radio frame such that the number of bits to be transmitted matches the number of available bit positions on one or more "physical channels" for data transmission. If more than one physical channel is used, the bits are segmented within the physical channel in block 236. The bits within each frame of each physical channel are then further interleaved to provide additional time diversity in block 238.

The interleaved bits are then mapped to the data portion of their respective physical channels at block 240. The subsequent signal processing to generate a modulated signal suitable for transmission from a base station to a terminal is well known in the art and will not be described herein.

Fig. 2B is an illustration of signaling processing at a terminal according to the downlink of the W-CDMA standard. The signaling process shown in fig. 2B is complementary to that shown in fig. 2A. Initially, a modulated signal is received, conditioned, digitized, and processed to provide symbols for each physical channel used for data transmission. Each symbol has a particular resolution (e.g., 4 bits) and corresponds to the transmitted bits. In block 252, the symbols within each frame of each physical channel are deinterleaved. At block 254, the deinterleaved symbols from all physical channels are concatenated. The symbols are then demultiplexed into individual transport channels in block 258. The radio frame of each transport channel is then provided to the corresponding transport channel processing section 260.

Within each transport channel processing section 260, transport channel radio frames are concatenated into a transport block set in block 262. Each transport block set includes one or more transport channel radio frames of a respective TTI. The symbols in each set of transport blocks are deinterleaved in block 264 and the symbols not transmitted are removed in block 266. In block 268, inverse rate matching (or de-rate matching) is then performed to accumulate the repeated symbols and insert "erasures" for the truncated symbols. Each encoded module within the transport block set is then decoded in block 270, and the decoded modules are concatenated and segmented into one or more transport blocks in block 272. Each transport block is then error checked using the CRC bits added to the transport block in block 274. For each transport channel, one or more decoded transport blocks are provided for each TTI.

Fig. 3A and 3B illustrate two different possible transport formats for two different transport channels. As described above, each transport channel may be associated with a respective set of transport formats that includes one or more available transport formats that may be used for the transport channel. Each transport format defines, among other parameters, the size of the transport block and the number of transport blocks within a TTI.

Fig. 3A illustrates a transport format set in which one transport block is transmitted per TTI, the transport blocks having different sizes for different transport formats. For example, the transport format set may be used for speech services, where an adaptive multi-rate (AMR) speech coder may be used every 20 milliseconds to provide full-rate (FR), silence descriptor (SID), or no data (NULL or DTX) frames, depending on the speech content. The TTI may then be chosen to be 20 milliseconds. FR frames are provided during active speech periods, while SID frames are typically transmitted every 160 milliseconds during silence (i.e., pause) periods. In general, shorter transport blocks may be sent when there is no (or less) voice activity, and longer transport blocks may be sent when (longer) voice activity is possible. NULL frames are transmitted during the silence period when the SID is not transmitted.

Fig. 3B illustrates a transport format set in which one or more transport blocks are transmitted for each TTI, the transport blocks for different transport formats having different sizes. For example, the set of transport formats may be used to support multiple services on a given channel. For example, non-real time services (e.g., packet data) may be multiplexed with real time services (e.g., voice). In this case, additional transport blocks may be used to support non-real time services, if desired.

The W-CDMA standard defines a channel structure capable of supporting multiple users and is designed for efficient transmission of different types of data. As described above, according to the W-CDMA standard, data to be transmitted to each terminal is processed at a higher signaling layer as one or more transport channels, and the transport channel data is then mapped into one or more physical channels allocated to the terminal. The transport channels support the simultaneous transmission of different types of services (e.g., voice, video, packet data, etc.) for multiple users.

In a W-CDMA system, the downlink DPCH is typically allocated to each terminal for the duration of the communication. The downlink DPCH is used to carry one or more transmission channels, characterized in that: the possibility of fast data rate changes (e.g. every 10 ms), fast power control, intrinsically addressed to a specific terminal. The downlink DPCH is used to transmit user-specific data along with control data in a time-division multiplexed manner.

Fig. 4 is a diagram of a frame format and a slot format of a downlink DPCH, as defined by the W-CDMA standard. The data to be transmitted on the downlink DPCH is divided into radio frames, each radio frame being transmitted over a frame (10 milliseconds) comprising 15 slots, which are labeled as slot 0 through slot 14. Each slot is further divided into fields for carrying user-specific data, signaling, and pilot or a combination thereof.

As shown in fig. 4, for the downlink DPCH, each slot includes data fields 420a and 420b (data 1 and data 2), a Transmit Power Control (TPC) field 422, a Transport Format Combination Indicator (TFCI) field 424, and a pilot field 426. Data fields 420a and 420b are used to transmit user-specific data. The TPC field 422 is used to send power control information to direct the terminals to adjust their uplink transmit power up or down to achieve desired uplink performance while minimizing interference to other terminals. The TFCI field 424 is used to transmit information indicating the transport format of the downlink DPCH and, if any, the downlink shared channel DSCH assigned to the terminal. And a pilot field 426 for transmitting a dedicated pilot for the downlink.

On the downlink, the capacity of each base station is limited by its total available transmit power. To provide a desired level of performance and maximize system capacity, the transmit power of each data transmission from the base station is typically controlled such that it is as low as possible to reduce power consumption and interference, while maintaining the desired level of performance (e.g., a particular target BLER, FER, or BER). If the received signal quality, as measured by the received signal-to-noise-plus-interference ratio (SNIR), at the terminal is poor, the likelihood of correctly decoding the data transmission is reduced and performance is compromised (higher BLER). Conversely, if the received signal quality is too good, the transmit power level may be too high and excess transmit power may be unnecessarily used for data transmission, which may reduce system capacity and further create additional interference to transmissions from other base stations.

Fig. 5 is an illustration of a downlink power control mechanism 500 in which aspects and embodiments of the invention may be implemented. Power control mechanism 500 includes an inner power control loop 510 that operates in conjunction with an outer power control loop 520.

Inner loop 510 is a (relatively) fast loop that attempts to maintain the signal quality of the data transmission received at the terminal as close as possible to the target SNIR (i.e., the set point). As shown in fig. 5, inner loop 510 operates between the base station and the terminal and generally maintains an inner loop for each data transmission to achieve independent power control thereof.

The inner loop adjustment for a particular data transmission is generally obtained by (1) measuring the signal quality of the data transmission at the terminal (block 512), (2) comparing the received signal quality (i.e., the received SNIR) to the target SNIR (block 514), and (3) sending power control information back to the base station. Signal quality measurements are typically made on pilots included in the data transmission. The power control information may be used by the base station to adjust its transmit power for data transmission, and may be in the form of an "up" instruction to request an increase in transmit power, or may be in the form of a "down" instruction to request a decrease in transmit power. Each time it receives the power control information, the base station may adjust the transmit power of the data transmission accordingly (block 516). For a W-CDMA system, the frequency of transmission of the power control information may be 1500 times per second (i.e., one power control command per slot), thereby providing a relatively fast response time for inner loop 510.

These typically change over time due to path loss and other factors within the communication channel (cloud 518), especially for mobile terminals where the received SNIR at the terminal continuously fluctuates. Inner loop 510 attempts to maintain the received SNIR at or near the target SNIR in the presence of a communication channel change.

Outer loop 520 is a (relatively) slow loop that continuously adjusts the target SNIR such that the desired level of performance is achieved for data transmission to the terminal. The desired performance level is typically specified as a particular target BLER, although some other performance criteria may also be used to adjust the target SNIR. The target SNIR necessary to maintain a particular target BLER may vary depending on the conditions of the communication channel. For example, a fast fading channel may have a different SNIR target than a slow fading channel to maintain the same BLER.

The adjustment of the SNIR target for the outer loop is generally accomplished by (1) receiving and processing the data transmission to recover the transmitted data chunks (or transport chunks), (2) determining the status of each received transport chunk (block 522) as correctly decoded (good) and erroneously received (erased), and (3) adjusting the target SNIR based on the transport chunk status (and possibly along with other information, as described below) (block 524). If the transport block is decoded correctly, the received SNIR at the terminal may be higher than necessary and the target SNIR may be adjusted slightly downward. Alternatively, if the transport block is received in error, the received SNIR at the terminal may be lower than necessary and the target SNIR may be adjusted slightly upward. In both cases, the inner loop 510 may attempt to maintain the received SNIR at the target SNIR provided by the outer loop.

By controlling the manner in which the target SNIR is adjusted, different power control characteristics and performance levels may be obtained. For example, the target BLER may be adjusted by: selecting an appropriate upward adjustment (Δ UP) for the target SNIR for the bad module; for good blocks, the appropriate down adjustment (Δ DN); the necessary elapsed time between two successive increases in the target SNIR, etc. The target BLER (i.e., long-term BLER) may be set to Δ DN/(Δ DN + Δ UP). The size of the Δ UP and Δ DN also determines the response of the power control mechanism to sudden changes in the communication channel.

For a W-CDMA system, the terminal may estimate the received SNIR (or more specifically the pilot on the DPCCH) for the transmission on the downlink DPCH. The terminal then compares the received SNIR to the target SNIR and generates a Transmit Power Control (TPC) command to increase (or decrease) transmit power if the received SNIR is less than (or greater than) the target SNIR. Based on the received TCP instructions, the base station may adjust the transmit power of the downlink DPCH.

In a W-CDMA system, for any given transport channel, the base station may specify a particular target BLER for the terminal. For data integrity, the actual BLER should not exceed the target BLER. At the same time, the actual BLER should not always be below the target BLER, since this means that excessive transmit power is used for data transmission, which reduces the capacity of the transmitting base station and may cause unnecessary interference to neighbouring cells.

The terminal and the base station attempt to obtain and maintain the target BLER specified for the transport channel by the power control mechanism described above. For transport channels with only one transport format (i.e. equal size transport blocks, which are translated into code blocks of the same length), a steady state condition of power control is reached when the outer and inner loops converge (under given channel conditions) on the required target SNIR, which provides the target BLER for the (one) transport format of the transport channel. A POWER control mechanism FOR maintaining a single outer loop FOR each transport channel is described in U.S. patent application serial No. 09/718316, entitled "METHOD and apparatus FOR POWER control A WIRELESS COMMUNICATION SYSTEM," filed on 21/11/2000, assigned to the assignee of the present invention and incorporated herein by reference.

However, in W-CDMA, data may be transmitted on a given transport channel using multiple possible transport formats. For example, on a transport channel, for a voice call, shorter transport blocks may be transmitted when there is no voice activity and longer transport blocks may be transmitted when there is voice activity. The SNIR required to achieve the target BLER may be very different for code blocks of different lengths and therefore the required SNIR may be different for different transport formats.

The W-CDMA standard currently allows a target BLER to be specified for each transport channel regardless of the number of transport formats that may be used for that transport channel. The W-CDMA specification is inaccurate because different transport formats may require different target SNIRs to meet the target BLER described above. The average transmit power may fluctuate depending on the relative frequency and/or the sequential order of the transport formats used for the transport channels.

If the outer loop converges to the target SNIR for a particular transport format, and if the transport format is then changed, the outer loop typically requires a transition time to reconverge to the new target SNIR for the new transport format. During this transition time, the actual BLER may be much larger or smaller than the target BLER. For data transmission using a mixed transmission format, the duty cycle and the duty cycle period of the transmission format may determine different values of the required target SNIR. For example, for the case where 10 TTIs for transport format 1(TF (1)) are then changed to 10 TTIs for TF (2), the outer loop may converge to a different set of required NSIRs than for the 20 TTIs for TF (1) and 10 TTIs for TF (2). If a conventional power control mechanism is used, it is possible that the target BLER may not achieve the same effective transmit power for all transport formats, or even not at all.

Furthermore, when using many transport formats for a given transport channel, the target BLER may not need to be the same for all transport formats. For example, for a voice call, a known transport format with insignificant voice content (e.g., background noise) may be able to allow a higher BLER than a transport format with voice content.

The present invention advantageously provides for more efficient and effective control of transmit power for data transmission using multiple transmission formats. The present invention recognizes that different transport formats for a given transport channel may require different target SNIRs to achieve a particular BLER. Various schemes are provided herein to effectively treat these transport formats as "single" transmissions with their own performance requirements, while at the same time reducing the overall transmit power of the data transmission.

In an aspect of the invention, rather than specifying a single target BLER for all transport formats of each transport channel, it is possible to specify a specific target BLER for each transport format of each transport channel used for data transmission. If N transport formats are available for a given transport channel, up to N target BLERs may be specified for that transport channel.

SNIR for each transport format TF (i) of a particular transport channel TrCH (k)_TCk，TFiIs to BLER_TCk，TFiReceived BLER required SNIR, BLER_TCk，TFiIs the target BLER for the transport format. If N transport formats are available, the target SNIR is required_TCk，TF1To target SNIR_TCk，TFNObtaining a target BLER for transport formats TF (1) to TF (N) accordingly_TCk，TF1To BLER_TCk，TFN. The power control mechanism may then be operated to use an appropriate set of target BLERs for each received transport format and provide appropriate power control instructions based on the target BLERs and the SNIR set. Some power control mechanisms that can achieve this are described in more detail below.

It is more efficient to specify multiple individual target BLERs for each transport channel, since different types of data may have different performance requirements. Some data may be more critical and so require a lower target BLER. Conversely, some other data may be less critical, so a higher target BLER may be tolerated. In an extreme case, a "don't care" target BLER may be specified for any BLER insignificant transport format, in which case the power control mechanism may be temporarily suspended when using these transport formats. The "don't care" target BLER may be explicitly specified (e.g., sent over the air) or implicitly specified (e.g., by not specifying any values), and may be used, for example, for NULL/DTX transport blocks.

Multiple individual target BLERs per transport channel enable the specification of a target BLER that is efficient and independent of the selected transport format combination, relative frequency of occurrence, and its sequential order. Current W-CDMA standards may be modified to support the specification of multiple target BLERs for multiple transport formats for each transport channel.

In another aspect of the invention, various power control schemes are provided to achieve different target SNIRs for different transport formats. These schemes may be used to obtain different target BLERs specified for different transport formats, which typically require different target SNIRs. Even if a single target BLER is specified for all transport formats of a given transport channel, it is possible to use these schemes, as in the current W-CDMA standard, since different transport formats may require different target SNIRs to achieve the same target BLER. Some such power control schemes are described below, and other schemes may be implemented and are within the scope of the invention.

In a first power control scheme to achieve different target SNIRs for different transport formats, a plurality of single outer loops are maintained for a plurality of transport formats. For each transport format, its associated outer loop attempts to set the target SNIR to achieve the target BLER specified for that transport format. A plurality of individual outer loops would then form an overall outer loop that operates with the (common) inner loop to derive the appropriate power control commands for all transport formats. Various embodiments of the power control scheme may be devised, some of which are described below.

Fig. 6 illustrates a particular embodiment of a first power control scheme in which multiple single outer loops are maintained to control transmit power for data transmissions using multiple transmission formats. In fig. 6, the horizontal axis represents time, and the unit thereof is TTI. The vertical axis is the SNIR target used for inner loop power control at the terminal.

At time t_nPreviously, the base station had transmitted multiple DTX frames along with transmitting at a power level Δ above the power level of the "reference" portion of the frame (e.g., the pilot portion of the DPCCH shown in fig. 4)The data portion of the shot. This power offset Δ is typically unknown to the terminal. The inner and outer loops typically operate on the reference portion of the frame and the transmit power of the data portion is adjusted by controlling the transmit power of the reference portion (i.e., the difference between the transmit power levels of the data and reference portions is delta). Outer loop determines target SNIR required for data portion_DTXTo obtain a target BLER for DTX frames_DTX. Corresponding target SNIR (SNIR) of the reference part_ref) For TTI (n), provided by the outer loop to the inner loop, and thus SNIR_ref(n)＝SNIRD_DTX-Δ。

At time t_nThe base station switches to the new transport format and during tti (n) a Full Rate (FR) frame is transmitted, where the data portion of the frame is transmitted at a transmission level that differs by Δ from the transmission level of the reference portion of the frame. In the whole TTI (n), the terminal uses the reference part target SNIR for the inner loop_ref(n) of (a). The reference portion target SNIR_ref(n) is derived by the outer loop from frames received within TTI (n-1), which are DTX type frames, since it has not yet been determined that the transport format has changed within TTI (n). For W-CDMA, 15 power control commands are sent every 10 ms frame, and the duration of each TTI may be 1, 2, 4, or 8 frames.

In the particular embodiment shown in fig. 6, the terminal is not provided with transport format information in advance, and detects the transport format only after receiving and processing the entire FR frame. According to W-CDMA, the TFCI is transmitted every 10 ms, and the terminal can thus detect the transport format after the first 10 ms of the received frame (e.g., after the first half of a20 ms AMR (RF, SID or DTX) frame). If the transport format can be detected before the entire frame is received (e.g., only after half of the DTX/SID/FR frame), then only a portion of the frame may be received with the wrong target SNIR and the remainder of the frame may be received with the appropriate target SNIR. For simplicity of explanation, aspects and embodiments of the present invention are described in the context of an entire frame needing to be received before a transport format is determined. However, the techniques described herein may also be applied to the case where the transport format may be determined before the entire frame is received (e.g., by decoding the TFCI immediately after the first 10 milliseconds).

For the embodiment shown in FIG. 6, the SNIR over the reference portion of TTI (n) is derived as the SNIR_ref(n+1)＝SNIR_DTXΔ, and the data part will be at SNIR_DTX. The SNIR is smaller than the data portion of the FR frame to obtain BLER_FRRequired SNIR_FR. The first FR frame during tti (n) may thus be received in error due to the use of the target SNIR during tti (n)_DTXWhile a lower received SNIR (i.e., for FR frames) is obtained.

At the time t_n+1Thereafter, the terminal determines to use the FR transport format in TTI (n), and updates the reference part target SNIR of the inner loop accordingly_ref(n +1) from old (SNIR)_DTX- Δ) to become new (SNIR)_FR- Δ). The reference portion target SNIR_ref(n +1) is then used for the inner loop during reception of the frame within TTI (n + 1). The terminal also updates the target SNIR of the FR frame according to the status (e.g., good or erased) of the received FR frame_FRTo obtain a target BLER for FR frames_FR. During TTI (n +1), another FR frame is transmitted and the terminal uses (correctly) the reference part target SNIR of the inner loop_ref(n+1)。

At time t_n+2The base station switches to the new transport format and the SID frame is transmitted within TTI (n +2) at a transmission level Δ above the reference transmission level. The terminal uses the reference part target SNIR for the reference part of the SID frame of the inner loop for the entire TTI (n +2)_ref(n+2)＝SNIR_FRΔ, since it has not yet been determined that the transport format has changed within TTI (n + 2). At the time t_n+3Shortly thereafter, the terminal determines that the transport format of the previous TTI (n +2) has changed and switches to the outer loop for the SID frame. Then using the reference portion target SNIR_ref(n+3)＝SNIR_SID- Δ to derive an inner loop from the point until another outer loop is selected. The terminal also updates the target SNIR of the SID frame according to the state of the received SID frame_SIDTo obtain a target BLER for SID frames_SID。

At time t_n+3At this point, the base station switches to DTX transmission format and transmits DTX frames within TTI (n + 3). The terminal uses the reference part target SNIR for the inner loop for the entire TTI (n +3)_ref(n+3)＝SNIR_SIDΔ, since it has not yet been determined that the transport format has changed within TTI (n + 3). At the time t_n+4Shortly thereafter, the terminal determines that the transport format for the previous TTI (n +3) has changed and switches to the outer loop for the DTX frame. Then using the reference portion target SNIR_ref(n+4)＝SNIR_DTX- Δ to derive an inner loop from the point until another outer loop is selected. The terminal also updates the target SNIR of the DTX frame according to the state of the received DTX frame_DTXTo obtain a target BLER for DTX frames_SID。

In a first embodiment of the first power control scheme, as shown in fig. 6, the transport format of the current TTI is not known a priori, and the terminal uses the target SNIR for the transport format received by the inner loop just before the TTI.

If the terminal is provided with information indicating the particular transport format used for the current TTI before the entire frame has to be received, it can apply the appropriate outer loop and use the appropriate target SNIR for the inner loop during the TTI. The transport format information may be provided to the terminal by various mechanisms, such as a predetermined arrangement, a preamble at the beginning of each transmitted frame, signaling on other transport channels, and so forth.

If the terminal is not provided with transport format information in advance, there is some delay in the power control scheme. The amount of delay is determined by the amount of time required to process a received frame to determine the transport format for the received frame. If the entire transmitted frame needs to be received and processed before the transport format is determined, there may be a one frame delay (or possibly more) between the time the new transport format is used for data transmission at the base station and the time the appropriate target SNIR is used for power control at the terminal.

To reduce the negative effects of delays due to later detection of transport formats, the transport format of the current TTI may be predicted. The prediction may be based on any existing information of the data transmission. In this case, the predicted target SNIR for the transport format (and not the maximum target SNIR) may be used for the inner loop, which may improve efficiency and performance.

In a second embodiment of the first power control scheme, to ensure that sufficient transmit power is used at any given time for all transport formats that may be used within a particular TTI (i.e., "possible" transport formats), the target SNIRs for all possible transport formats are compared, and the largest target SNIR is selected. If only a subset of all available transport formats is used within a particular TTI, the maximum value may be chosen over a subset of possible transport formats, rather than over a set of all available transport formats.

As described above, if there is a delay in the power control mechanism due to "late" detection of a transport format, an inappropriate target SNIR may be used when the transport format is unknown during the delay period. The second embodiment thus ensures that sufficient transmit power is used regardless of the transport format selected. The one or more target SNIRs may be updated at the end of each TTI based on the status of the received transport blocks, the transport format used by the TTI, etc., as described below.

Fig. 7 is a flow diagram of an embodiment of a process 700 implemented at a terminal to maintain a single outer power control loop for multiple transport formats. Initially, the outer loop target SNIR is for all transport channels and all transport formats_TCk，TFi(n) is set to some specific (e.g., arbitrary) initial value. Corresponding overall target SNIR, SNIR_ref(n) is also set to the same value. In step 712, the terminal receives data of K transport channels (i.e., trch (K) during tti (n), where K is 1, 2.. K, and K may be any integer, one or greater). Each of the K transport channels is then processed, beginning with the first transport channel one at a time by setting K to 1 at step 714.

For the transport channel trch (k), all transport formats (i.e. TF) available for the transport channel(i) Wherein i ═ 1, 2.. N_kAnd N is_kWhich may be any integer, 1 or greater) is initially determined at step 716. It is then determined in step 718 whether transport blocks in any transport channel trch (k) are received in error for tti (n). This may be achieved, for example, by implementing a CRC parity check on each received transport block.

In an embodiment, any transport block within a transport channel trch (k) within a TTI is considered to be transmitted with insufficient transmit power if it is received in error within the TTI (n). Thus, if any transport block within the transport channel trch (k) within tti (n) is received in error, as determined in block 720, then at step 722 the target SNIR, SNIR for each transport format actually used within tti (n)_TCk，TFiIncreasing the upward adjustment of the transport format by Δ UP_TCk，TFi. The transport format actually used in tti (n) may be determined based on the TFCI sent on the downlink DPCH or by "blind detection" (e.g. as described in document No. 3GPP TS 25.212, incorporated herein by reference). The upward adjustment of the target SNIR for each transport format within tti (n) may be obtained as follows:

SNIR_TCk，TFi(n+1)＝SNIR_TCk，TFi(n)+ΔUP_TCk，TFi(dB) formula (1)

Step 722 is performed for all transport channels used in tti (n). (all available transport channels are assumed to be used in each TTI. if nothing is sent on a transport channel, the transport format for that transport channel is {0 module size, 0 module })

In one embodiment, if all transport blocks in the transport channel TrCH (k) in TTI (n) are correctly received with transport format TF (i), and if transport format TF (i) has a value equal to SNIR_ref(n) target SNIR, the SNIR target SNIR_TCk，TFi(n) reduction by Δ DN_TCk，TFiThe amount of step (2). The target SNIR of other transport channels is not reduced because they are lower than the SNIR_ref(n) and is not selected by the inner loopThe application is as follows. In general, the target SNIR adjustment achieved at the terminal should be complementary to the specific scheme used to select the inner loop.

For each transport format tf (i) actually used within tti (n), the target SNIR of the transport format is to be determined; at step 734, SNIR_TCk，TFi(n)＝SNIR_ref(n) of (a). If the answer is yes, then the target SNIR for the transport format is adjusted downward at step 738 as follows:

SNIR_TCk，TFi(n+1)＝SNIR_TCk，TFi(n)-ΔDN_TCk，TFi(dB) formula (2)

Otherwise, if the target SNIR of the transport format is not equal to the SNIR_ref(n), then its current value is maintained at step 736. Step 734 and either step 736 or step 738 are implemented for each transport format actually used within tti (n).

After all available transport formats for transport channels trch (K) have been updated (in steps 722, 736 and 738), a determination is made in step 740 as to whether all K transport channels have been processed. If the answer is no, the next transport channel is considered to be processed, k is incremented by 1 at step 742, and back to step 716. Otherwise, if all K transport channels have been processed, then the reference partial target SNIR for the next TTI (n +1) is determined in step 744_ref(n + 1). For the first embodiment in the first power control scheme, the reference portion target SNIR is as described in fig. 6_ref(n +1) may be determined as the maximum target SNIR for all transport formats actually used within tti (n). And for a second embodiment of the first power control scheme, the reference portion target SNIR_ref(n +1) may be determined as the maximum target SNIR for all transport formats available for all K transport channels. The reference portion target SNIR_ref(n +1) is then provided to the inner loop. The process then repeats for the next TTI (n +1) by adding 1 to n at step 746.

The first power control scheme described above may be applied when the TTIs of all transport channels multiplexed on the same downlink DPCH are the same. When TTIs of all transport channels are different from each otherThen the outer loop may be modified as follows. The TTI index n no longer increases every TTI, but every 10 ms frame. Target SNIR for TF (i) of TrCH (k) if frame n corresponds to the last frame in TTI of TrCH (k)_TCk，TFi(n) will only be updated. This is because the entire TTI of the transport channel needs to be received to determine whether a block error has occurred within one transport block. Also, a determination is made for each 10 ms frame as to whether the target SNIR is equal to the target SNIR_refAnd the target SNIR may drop all the time as long as the transport format is the one that restricts the outer loop within any one 10 ms frame.

In a second power control scheme for obtaining different target SNIRs for different transport formats, multiple single outer loops are maintained for multiple transport formats, and the base station further applies different adjustments to transmit power levels for the different transport formats. As mentioned above, if there is a delay in the power control mechanism, the maximum target SNIR of all available transport formats may be used in the inner loop to ensure that the proper transmit power is used for data transmission. Since the particular transport format to be used is unknown, using the maximum target SNIR for the inner loop may result in unnecessary waste of power if there is a large difference between the maximum SNIR and the SNIR of the transmitted transport format. However, since the base station knows the specific transport format used for the incoming TTI, it can participate in power control by adjusting the transmit power of its data transmission based on the actual transport format combination chosen, ideally such that all transport formats require the same reference SNIR.

In an embodiment, the base station is provided with a table of relative differences within the target SNIR required to achieve the target BLER for each transport format. For each TTI, the base station selects one or more transport formats for the TTI, obtains a relative target SNIR difference for each selected transport format from a table, and transmits at a power level determined in part by the relative target SNIR difference for the selected transport formats.

As a specific example, a specific target BLER (e.g., 1%) may be required for FR, SID and DTX transmission formats. This may require FR frames to be transmitted +2.5dB above a particular reference power level, SID frames to be transmitted +2.0dB above a particular reference power level, and DTX frames to be transmitted +0.8dB above a particular reference power level. The base station may transmit a long DTX frame burst +0.8dB above a particular reference power level and suddenly switch to a SID transmission format. The base station would then automatically adjust the transmit power of the SID frame from +0.8dB to +2dB at the reference power level, as derived from its look-up table, without waiting until the terminal informs to do so through power control.

For this second power control scheme, if the inner loop of the terminal is driven by the data portion of the received frame, or if the base station applies the above-described power offset to the entire frame (i.e., the data and reference portions), the terminal may assume that the channel conditions have changed and may attempt to reverse the power adjustment (depending on the transport format) made by the base station. This oppositional action occurs because the inner loop of the terminal detects that the received power is suddenly changed without the terminal sending any corresponding power control command. Moreover, this oppositional action by the terminal only occurs if the terminal needs to process the entire received frame to determine the transport format of the received frame, and by then it is not known that the change in received power level is due to a new transport format, and not to a change in channel conditions. Therefore, the base station may apply the above-described power offset to only the data portion of the frame, and the inner loop of the terminal may drive only the reference portion of the received frame. If only the transmit power of the data part is adjusted according to the transmission format, the inner loop of the terminal does not detect any change in the received power in the reference part.

As described above, power adjustment by the base station (depending on the transport format) may be performed only for the data portion of the transmitted frame, while maintaining (i.e., not adjusting according to the transport format) the transmit power level for the remainder of the transmitted frame, which is used by the terminal to implement inner loop power control. Returning to fig. 4, for downlink transmission in W-CDMA, it is possible for the power adjustment to be applied by the nodeb only to the DPDCH (which carries the data portion), while it is possible to maintain the power level of the DPCCH (which carries the control or reference portion of the frame) and make it independent of the transport format.

The transmit power of the DPDCH may thus vary from the transmit power of the DPCCH according to a "power offset" that depends on the transport format. The transmit power of the DPCCH (and thus the DPDCH) is adjusted in the normal manner according to power control commands derived from the inner loop.

As shown in fig. 4, the DPCCH includes pilot, TFCI and TPC fields. If only the pilot is used for power control by the inner loop and since the DPCCH is not adjusted according to the transport format, the terminal does not attempt to control a sudden change in the power level of the DPDCH. The transmit power of the DPCCH is then used as a reference power level, and the transmit power of the DPDCH may be adjusted relative to the reference power level of the DPCCH according to the particular transport format used by the DPDCH. At the terminal, the inner loop may be used to maintain the DPCCH at a (reference part) target SNIR provided by the overall outer loop, as described below.

Once the terminal determines that the current transport format is tf (i), the corresponding target SNIR is adjusted by the outer loop and the target SNIR for that transport format (and possibly other transport formats) is used to derive the reference portion target SNIR, which is then used to derive the inner loop for the next TTI. This then reduces (or possibly removes) the time and excess transmit power required for the outer loop to re-converge to the reference portion target SNIR when a change in transport format occurs.

Fig. 8 illustrates an embodiment of a second power control scheme with multiple single outer loops and transport formats depending on power adjustment at the base station. It is assumed that the base station knows the terminal needs to obtain the corresponding target BLER_FR、BLER_SIDAnd BLER_DTXTarget SNIR of (1)_FR、SNIR_SIDAnd SNIR_DTX. These SNIR_FR、SNIR_SIDAnd SNIR_DTXIs generally channel dependent and may further change over time. The techniques described herein are thus applied to time-varying target SNIRs. For simplicity, for target SNIR_FR、SNIR_SIDAnd SNIR_DTXUsing constantsThe value is obtained. Techniques for deriving and providing these target SNIRs are described in further detail below.

At time t_nPreviously, multiple DTX frames were sent by the base station along with the data portion at a transmit power Δ above the power level of the reference portion of the frame_DTXThe adjusted power level of (a). The outer loop determines the BLER required by the data portion to obtain a DTX frame_DTXTarget SNIR of (1)_DTX. Since the inner loop generally operates on the reference portion of the frame, the overall outer loop provides the target SNIR for the reference portion of the frame_refIs SNIR_ref＝SNIR_DTX，ref＝SNIR_DTX-Δ_DTXAnd the target SNIR_refFor deriving the inner loop.

At time t_nThe base station switches to the new transport format and the FR frames are sent in tti (n), the data portion of the frame being transmitted at an adjusted power level Δ above the reference portion of the frame_FRTo (3). The terminal uses the reference partial target SNIR derived from the TTI (n-1) of the inner loop for the whole TTI (n)_refThis is the DTX frame type. Thus, the SNIR on the reference part of TTI (n) is changed to SNIR_DTX，ref＝SNIR_DTX-Δ_DTX+ Δ UP or Δ DN, and the SNIR of the data portion would be the SNIR_DTX-Δ_DTX+Δ_FR+ Δ UP or Δ DN. The data part SNIR may or may not be equal to the requirement on the data part to obtain BLER_FRSNIR of (1)_FR. However, since it is assumed that the base station knows the SNIR exactly_FRAnd SNIR_DTX(especially their differences), the base station may compare the difference (Δ)_FR-Δ_DTX) Is set to be more accurately (SNIR)_FR-SNIR_DTX). In this case, the data part of TTI (n) is changed to SNIR_FRThis is due to when Δ_FR-Δ_DTX＝SNIR_FR-SNIR_DTXWhen (i) is in contact with the surface of the substrate_DTX-Δ_DTX+Δ_FR＝SNIR_FR。

At the time t_n+1Shortly thereafter, the terminal determines that TTI (n) uses the FR transport format and routes the inner loop accordinglyLabel (SNIR)_DTX-Δ_DTX) Update to a new target (SNIR)_FR-Δ_FR) For reception during TTI (n +1), based on the status of the received FR frame (e.g., good or erased) to obtain the target BLER_FR. During TTI (n +1), another FR frame is transmitted and the terminal continues to use the reference portion target SNIR_ref. In FIG. 8, (SNIR)_DTX-Δ_DTX) Shown as (SNIR)_FR-Δ_FR) Same level, which comes from the assumption that the base station sets Δ_FR-Δ_DTX＝SNIR_FR-SNIR_DTX。

At time t_n+2The base station switches to the new transport format and transmits during TTI (n +2) -SID frames at an adjusted power level Δ above the reference power level_SIDThe level of (d). At time t_n+3Shortly thereafter, the terminal determines that TTI (n +2) uses the SID transmission format, and accordingly updates the target SNIR of the SID frame according to the state of the received SID frame_SIDTo obtain a target BLER_SID. Reference part target SNIR_refAnd then updated again.

At time t_n+3The base station switches to DTX transmission format and transmits a DTX frame at TTI (n +3) at an adjusted power level Δ above the reference power level_DTXThe level of (d). At time t_n+4Shortly thereafter, the terminal determines that TTI (n +3) uses the DTX transport format and updates the target SNIR for the DTX frame accordingly based on the status of the received DTX frame_DTXTo obtain a target BLER_DTX. Reference part target SNIR_refAnd then updated.

Fig. 9 is an embodiment illustrating a particular implementation of the second power control scheme. At the base station 104, a table 910 is maintained that lists all transport channels used for data transmission to the terminal 106 and all available transport formats for each transport channel. For each transport format, table 910 also lists the particular power offset Δ if that transport format is selected for use_TCk，TFiTo be applied to the data part (e.g. DPDCH).

In W-CDMA, one or more transport channels may be multiplexed onto a coded composite transport channel (CCTrCH) and then transmitted using a single power control mechanism. To ensure that the proper transmit power level is used for the transport formats transmitted on all transport channels multiplexed within a data transmission, a power offset may be maintained for each transport format for each transport channel. For any given TTI, the maximum value of the power offsets for all transport formats selected for that TTI is determined, and the maximum power offset may be used for power adjustment for data transmission for that TTI. This ensures that each transport format within a TTI is transmitted with sufficient power to maintain its specific target BLER.

For each TTI, the base station determines a set of amounts by which to adjust the transmit power for the data transmission (step 912). These amounts include, for example:

1) power offset for transport formats selected for each transport channel in a particular TTI (e.g., power offset Δ for transport channels A and B, respectively, in the example shown in FIG. 9_TCAAnd Δ_TCB)。

2) Maximum power offset (e.g., Δ) for all transport channels_max＝max{Δ_TCA，Δ_TCB}) and

3) transmit power for the DPDCH based on transmit power of the DPCCH and the maximum power offset (i.e., P)_DPDCH＝P_DPCCH+Δ_max)

The transmit power of the DPCCH is adjusted according to power control commands received from the terminal, which are generated by the inner loop. DPCCH of the TTI with a transmit power P_DPCCHTransmitting and the DPDCH of the TTI with the transmission power P_DPDCHAnd transmitting (step 914).

At the terminal 106, a table 930 is maintained that lists all transport channels used for data transmission, the available transport formats for each transport channel, and the target SNIRs for the reference portion of the frame for each transport format. Each reference portion target SNIR within table 930 is associated with a respective single outer loop maintained by the terminal for the corresponding transport format. The overall outer loop may be considered to comprise a single outer loop for all transport formats. The reference portion target SNIRs listed in table 930 are used to derive the inner loop set point for the reference portion (e.g., DPCCH) of the received frame.

For each TTI, the transport format of each transport channel for the received frame is determined, and the status of each received transport block (e.g., good or erased) is also determined. For each transport format actually used during TTI (n), the reference part target SNIR of the transport format_{TCk，TFi，ref}Updated (i.e., adjusted up or down, or maintained at a current level) according to a particular outer loop power control scheme, which may take into account whether module errors were previously received and/or the actual transmit power used on the data portion during the most recent TTI.

The total outer loop provides a single reference portion target SNIR (SNIR) for the inner loop_ref) And the reference portion target SNIR may be updated in each frame because transport channels multiplexed together may have different TTIs. For each frame, after determining the transport formats of all the transport channels used in the current frame, a single outer loop implements the necessary adjustments to those transport channels that have just completed the full TTI reception in the last frame and updates the target SNIR for the DPCCH accordingly. Table 930 lists possible reference part target SNIRs for DPCCH. Target SNIR (SNIR) of a reference portion of a frame for each transport format of each transport channel_{TCk，TFi，ref}) Target SNIR (SNIR) with data portion of frame_{TCk，TFi，data}) The correlation is as follows:

SNIR_{TCk，TFi，ref}＝SNIR_{TCk，TFi，data}-Δ_TCk，TFi(dB), formula (3)

Wherein Δ_TCk，TFiIs the power offset used at the base station for the transport format tf (i) of the transport channel trch (k).

In effect, a single outer loop adjusts the target of the reference portion of the frameSNIR_{TCk，TFi，ref}To obtain a target BLER for the data portion, and thus not directly obtain a target SNIR for the data portion_{TCk，TFi，data})。

Since the transport format of the incoming TTI is not known a priori, the target SNIR used by the inner loop for the DPCCH may be chosen as the maximum of all reference partial target SNIRs for all available transport formats (if there is no available information about the specific transport format used in the incoming TTI). For the example shown in FIG. 9, the inner loop reference portion target SNIR (SNIR)_ref) It may be calculated as:

SNIR_ref＝max{SNIR_{TCA，TF1，ref}，SNIR_{TCA，TF2，ref}，

SNIR_{TCA，TF3，ref}，SNIR_{TCB，TF1，ref}equation (4)

If the transport format of any part of the TTI is known (e.g., after decoding the first 10 ms frame), then the reference part target SNIR for that transport format may be used as the SNIR for the successive part of the TTI_ref)。SNIR_refThese instructions are then provided to the base station (step 934) for use in the inner loop to derive power control instructions. The base station may then adjust the transmit power (up or down) of the DPCCH according to the received power control commands. The transmit power of the DPDCH is adjusted accordingly as well, since it facilitates the power offset a applied to the transmit power of the DPCCH_max。

The power offsets for different transport formats may be derived and maintained in a variety of ways. As described above, the goal is to set Δ_TCk，TFiAnd Δ_{TCk′，TFi′}The values (for two different transmission channels k and k ' with different formats i and i ') are such that at the receiver (Δ & ' is_TCk，TFi-Δ_{TCk′，TFi′}) Is equal to (SNIR)_TCk，TFi-SNIR_{TCk′，TFi′}). In an embodiment, a fixed power offset may be used for the duration of time that the base station is in communication with the terminal. Can be measured empirically (in a laboratory or field), and can be calculated by computerSimulations, etc. determine the value of the power offset. In another embodiment, the power offset is determined at the terminal and provided to the base station.

Fig. 10 is a diagram illustrating a particular embodiment of a third power control loop to derive power offsets for multiple transport formats for data transmission. In this embodiment, the terminal maintains a single outer loop for each transport format, and the overall outer loop includes these single outer loops, as described above. The terminal also helps to determine the relative difference between the reference part target SNIR and the base SNIR for these transport formats, which can be selected as the reference part target SNIR for one transport format. These relative differences include updates to the power offset and are provided from the terminal to the base station. The power offset update may be sent periodically or only when it is determined that a change in channel conditions is sufficient to warrant transmission.

At the base station 104, a table 910 is maintained that lists all transport channels used for data transmission, each transport format available for each transport format, and the power offset for each transport format. For each frame, the base station determines the transmit power P of the DPCCH_DPCCHAnd further calculates the transmission power P for DPDCH based on the DPCCH transmission power, the transport formats used for TTI and the power offsets associated with these transport formats_DPDCH(step 912). The base station then transmits at a transmission power P_DPCCHTransmitting DPCCH with transmission power P_DPDCHThe DPDCH is transmitted (step 914), steps 912 and 914 are described above.

At the terminal 106, the transmitted frames are received and used to adjust the reference portion target SNIRs for the various transport formats, as described above. The update of the power offset may also be derived based on the reference portion target SNIR for the transport format and the base SNIR, which may be the reference portion target SNIR for one transport format (step 942). Updated power offset delta for each transport format_TCk，TFiCan be calculated as:

δ_TCk，TFi＝SNIR_{TCk，TFi，ref}-SNIR_base(dB) formula (5)

For the example shown in FIG. 10, the basic SNIR is selected as the SNIR_{TCA，TF1，ref}And the power offset updates δ_TCk，TFiCan be calculated as:

δ_TCA，TF1＝SNIR_{TCA，TF1，ref}-SNIR_{TCA，TF1，ref}，

δ_TCA，TF2＝SNIR_{TCA，TF2，ref}-SNIR_{TCA，TF1，ref}，

δ_TCA，TF3＝SNIR_{TCA，TF3，ref}-SNIR_{TCA，TF1，ref}，

δ_TCB，TF1＝SNIR_{TCB，TF1，ref}-SNIR_{TCA，TF1，ref}.

the power offset update attempts to minimize the difference between the reference portion target SNIRs for all transport formats so that they can be approximately equal. Thus, the changes applied in the reference portion target SNIR of the inner loop are small regardless of the transport format chosen.

Although not shown in equation (5), the power offset update for each transport format may be filtered according to a particular (low-pass) filter response to obtain an average. The time constant of the filter for the power offset should generally be longer than the time constant of the outer loop.

Based on various update schemes, power offset updates may be provided from the terminal to the base station (step 944). In a first update scheme, all power offset updates are performed at a predetermined time interval t_updateIs periodically provided to the base station. In a second update scheme, power offset updates for each transport channel are provided to the base station periodically (e.g., at predetermined times selected for the transport channel) and/or when necessary. For this scheme, power offset updates for different transport channels may be at different times and/or different time intervals t_TCk，updateIs provided to the base station. In a third update scheme, power offset updates for each transport format are provided to the base station periodically (e.g., at predetermined times of selection for a transport format)Time) and/or if necessary. Likewise, power offset updates for various transport formats may be at different times and/or different time intervals t_{TCk，TFi，update}Is provided to the base station.

In a fourth update scheme, a power offset update is provided to the base station when certain conditions are met. For example, if the maximum power offset update exceeds a certain threshold Th, a power offset update is provided. This can be expressed, for example, as shown in fig. 10:

max{|δ_TCA，TF1|，|δ_TCA，TF2|，|δ_TCA，TF3|，|δ_TCB，TF1|}＞Th

in a fifth update scheme, power offset updates for each transport format are provided to the base station when certain conditions are met, e.g., if the power offset updates for the transport formats exceed a certain threshold Th_TFiThe threshold is specific to the transmission format. This can be expressed as

|δ_TCk，TFi|＞Th_TFi.

Various other update schemes may also be implemented and are within the scope of the invention.

The base station receives the power offset update from the terminal and updates its table of power offsets. The power offset per transport format for each transport channel may be updated as follows:

Δ_TCk，TFi(n+1)＝Δ_TCk，TFi(n)+δ_TCk，TFi(n) formula (6)

The base station then uses the updated power offset to adjust the transmit power of the DPDCH, as described above.

Accordingly, for each transport format of each transport channel actually used in a given TTI, the terminal may update a reference portion target SNIR (SNIR) for that transport format_{TCk，TFi，ref}). The terminal also derives a reference portion target SNIR for the inner loop based on the updated reference portion target SNIR_refThe target SNIR may be, for example, etcEquation (4) is calculated based on the reference partial target SNIR for one or more transport formats (e.g., all available transport formats, only the transport formats used in the previous TTI, or some other set of transport formats).

Referring to fig. 5, a third loop may be implemented between the terminal and the base station. At the terminal, the base SNIR and reference part target SNIR (SNIR) of the transport format_{TCk，TFi，ref}) For deriving an update of the power offset (block 526). It is also possible to implement other processing (e.g., filtering) on the power offset update in block 526. The power offset update is then provided to the base station according to a particular update scheme and used by the base station to implement the power adjustment dependent transport format (block 516).

Fig. 11 is a flow diagram of an embodiment of a process 1100 implemented at a terminal to maintain multiple single outer loops for multiple transport formats and to use a transport format that is dependent on power adjustment at a base station. Initially, in step 1110, the terminal receives data of K transport channels (i.e., trch (K), where K is 1, 2, … K) in tti (n). The terminal then determines a target SNIR to be used on the reference portion within frame n_ref(n), which may be determined with any knowledge of the transport format combination of frame n. At step 1114, each of the K transport channels is processed, one at a time, starting with the first transport channel by setting K to 1.

For transport channel trch (k), all transport formats (i.e., tf (i), where i ═ 1, 2, … N) available for the transport channel are determined beginning at step 1116. It is then determined whether any transmissions in the block transport channel trch (k) are received in error for tti (n) in step 1118. This may be accomplished by implementing a CRC parity check on each received transport block.

In an embodiment, if any transport block in the transport channel trch (k) is received in error in TTI (n), the entire transmission (i.e. all transport formats) in TTI is considered not to be sent with sufficient transmit power. Thus, if any transport block in the transport channel TrCH (k) in TTI (n) is received in error, as in block 1120Determined, then in step 1122, the reference portion target SNIR (SNIR) for each transport format actually used in tti (n)_{TCk，TFi，ref}) UP adjustment of added transport format by Δ UP_TCk，TFi. The upward adjustment of the target SNIR for each transport format within tti (n) may be obtained as follows:

SNIR_{TCk，TFi，ref}(n+1)＝SNIR_{TCk，TFi，ref}(n)+ΔUP_TCk，TFi(dB) equation (7)

In one embodiment, if all transport blocks in a transport channel TrCH (k) in TTI (n) are correctly received, only the target SNIR equal to the received frame is present_ref(n) the reference portion target SNIR is adjusted downward by Δ DN_TCk，TFi. If the base station determines the transmit power of the data transmission during TTI (n) based on the maximum power offset of all transport formats actually used in the TTI, as depicted in fig. 9, only the maximum reference partial target SNIR of all transport formats actually used for all transport channels in TTI (n) is reduced, while the reference partial target SNIRs of all other transport formats are maintained at their current levels. In general, the target SNIR adjustment implemented at the terminal should be complementary to the transmit power adjustment implemented at the base station.

Thus, if all transport blocks in the transport channel trch (k) are correctly received in tti (n), as determined in block 1120, then for each transport format used in tti (n), a reference power level SNIR for that transport format is then determined in step 1134_{TCk，TFi，ref}Whether or not equal to SNIR_ref(n) of (a). If the answer is in the affirmative, then the target SNIR for that transport format is adjusted downward at step 1138 as follows:

SNIR_{TCk，TFi，ref}(n+1)＝SNIR_{TCk，TFi，ref}(n)-ΔDN_TCk，TFi(dB) formula (8)

Otherwise, if the reference power level of the transport format is not equal to the SNIR_ref(n), then its current value is maintained at step 1136. Step 1134 and/or step are performed for each transport format actually used in tti (n)1136 or step 1138.

After all the applied transport formats have been updated (in steps 1122, 1136 and 1138), it is determined in step 1140 whether to process all K transport channels. If the answer is negative, the next transport channel is considered for processing by incrementing k in step 1142 and returning to step 1116. Otherwise, if all K transport channels have been processed, then in step 1144 the maximum reference portion target SNIR for all transport formats available for all K transport channels is determined and selected as the reference portion target SNIR provided to the inner loop_ref(n + 1). The process then repeats at step 1146 for the next TTI (n +1) by incrementing n.

For the embodiment described in fig. 11, the maximum of all possible transport formats on the transport channel is used to determine the SNIR_ref(n + 1). This differs from the embodiment shown in fig. 8, where a radio frame carries only one transport channel and only the current transport format received in frame n is used to determine the SNIR_ref(n + 1). These and other embodiments are within the scope of the present invention.

Power adjustment by the base station based on the power offset of the selected transport format (depending on the transport format) may also be achieved independently, i.e., without operating on multiple individual outer loops of the transport format. The power adjustment may be made for the data portion (e.g., DPDCH) of each transmitted frame and may maintain the reference portion (e.g., DPCCH or pilot) of the transmitted frame. A single (or conventional) outer loop may be maintained to adjust the transmit power of the reference portion, which correspondingly adjusts the transmit power of the data portion.

Another aspect of the present invention provides a mechanism to report the actual BLER more accurately. In an embodiment, the measured BLER that the terminal uses to set the outer loop usage should be calculated as (the number of received transport blocks over CRC, excluding zero block transport format) divided by (the total number of received transport blocks, excluding zero block CRC). This is also the BLER that could be reported to the base station if the base station requires a measurement of the actual BLER. The BLER may be incorrectly calculated if the Transport Format Combination Indicator (TFCI) is incorrectly received, or if the Blind Transport Format Detection (BTFD) performed by the terminal is erroneous.

In some examples, the terminal is required to report the measured BLER to the base station. Instead of the terminal reporting the BLER calculated by the terminal to the base station, the terminal only reports the number of correctly received frames (or data blocks) to the base station, and the base station may then determine the BLER itself. Since the base station knows which transport format is used, it can use this knowledge to accurately calculate the BLER.

Fig. 12 is a block diagram of an embodiment of a base station 104 that is capable of implementing aspects and embodiments of the present invention. On the downlink, data for a particular terminal and indicating a transmission channel on one or more downlink DPCHs is received and processed (e.g., formatted, encoded) by a Transmit (TX) data processor 1212. The processing of the downlink DPCH may be as described above in fig. 2A, and the processing (e.g., encoding) of each transport channel may be different from the processing of the other transport channels. The processed data is then provided to a Modulator (MOD)1214 and further processed (e.g., channelized (or spread, in terms of W-CDMA) and further spread (or scrambled, in terms of W-CDMA).

Fig. 13 is a block diagram of an embodiment of a terminal 106. The downlink modulated signals are received by antennas 1312 and routed through duplexer 1314 and provided to an RF receiver unit 1322. RF receiver unit 1322 conditions (e.g., filters, amplifies, frequency downconverts, and digitizes) the received signal and provides samples. A demodulator 1324 receives and processes (e.g., descrambles, channelizes, and pilot demodulates) the symbols to provide recovered symbols. Demodulator 1324 may implement a rake receiver that processes multiple signal instances within the received signal and generates combined recovered symbols. A Receive (RX) data processor 1325 then decodes the recovered symbols for each transport channel and checks each received transport block and provides output data and decodes the status (e.g., good or erased) of each received transport block. A demodulator 1324 and an RX data processor 1326 may be used to process received data transmissions for multiple transmission channels using multiple transmission formats. The processing by demodulator 1324 and RX data processor 1326 may be described in fig. 2B.

For downlink power control, the samples from the RF receiver unit 1322 may also be provided to an RX signal quality measurement unit 1328, which estimates the received SNIR of the data transmission on the downlink DPCH. The SNIR may be estimated from the pilots included in the DPCCH and using various techniques, such as those described in U.S. patent nos. 6097972, 5903554, 5056109, and 5265119.

The received SNIR estimate for the downlink DPCH is provided to a power control processor 1330, which compares the received SNIR to a target SNIR and generates appropriate power control information (which may be in the form of TPC commands). The power control information for the downlink DPCH is then sent back to the base station.

Power control processor 1330 also receives the status of the transport blocks (e.g., from RX data processor 1326) and one or more other metrics. For example, power control processor 1330 may receive a target BLER, Δ UP, and Δ DN for each transport format, etc. Power control processor 1330 then updates the target SNIR for the transport format based on the received state of the transport block and its target BLER, and calculates a reference portion target SNIR for inner loop use for the incoming TTI_ref. Depending on the particular power control scheme being implemented, power control processor 1330 may further maintain a third power control loop that derives power offset updates for the transport formats. Memory 1332 may be used to store various types of power control information, such as target SNIRs for transport formats and power offset updates.

On the uplink, data is processed by a Transmit (TX) data processor 1342, further processed (e.g., channelized, scrambled) by a Modulator (MOD)1344, and conditioned (e.g., converted to analog signals, amplified, filtered, and quadrature modulated) by an RF TX unit 1346 to generate an uplink modulated signal. Power control information (e.g., TPC commands, power offset updates, etc.) from power control processor 1330 may be multiplexed with the processed data in modulator 1344. The uplink modulated signal is routed through duplexer 1314 and transmitted via antenna 1312 to one or more base stations 104.

Referring to fig. 12, at the base station, the uplink modulated signal is received by antenna 1224, routed through duplexer 1222, and provided to an RF receiver unit 1228. RF receiver unit 1228 conditions (e.g., downconverts, filters, and amplifies) the received signal and provides a conditioned signal for each terminal being received. A channel processor 1230 receives and processes the conditioned signal for one terminal to recover the transmitted data and power control information. Power control processor 1240 receives power control information (e.g., TPC commands, power offset updates, etc., or a combination thereof) and adjusts the power of the downlink DPCH. Power control processor 1240 may further update the power offset for the transport format based on the received power offset. Memory 1242 may be used to store various types of power control information, such as power offsets to be used for various transmission formats.

In fig. 12 and 13, power control processors 1240 and 1330 implement portions of the inner and outer loops (and possibly the third loop) described above. For the inner loop, power control processor 1330 is provided with the estimated received SNR and sends information (e.g., TPC commands) back to the base station. A power control processor 1240 at the base station receives the TPC commands and adjusts the transmit power of the data transmission on the downlink DPCH accordingly. For the outer loop, power control processor 1330 receives the transport block status from RX data processor 1326 and adjusts the target SNIR for the appropriate transport format.

The power control techniques described herein may be implemented by various means. For example, the power control mechanism may be implemented in hardware, software, and combinations thereof. For a hardware implementation, the elements for power control are implemented on: one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.

For a software implementation, the elements used for power control 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 memory units (e.g., memories 1242 and 1332) and executed by processors (e.g., power control processors 1240 and 1330). 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.

For simplicity of explanation, various aspects, embodiments and features of the power control techniques are specifically described for downlink power control within W-CDMA. The techniques described herein may also be used in other communication systems (e.g., other CDMA-based systems or power-controlled systems) where certain attributes of the data transmission (e.g., rate of format, transport format) on a particular "logical channel" may result in different characteristics of the power control mechanism (e.g., different target SNIRs). The techniques described herein may thus be used for power control of different attribute values (e.g., different rates, formats, or transport formats) of a data channel (e.g., a transport channel) transmitted on a power controlled physical channel (e.g., a downlink DPCH). The techniques described herein may also be used for downlink power control.

The previous description of the preferred 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 the use of the inventive faculty. 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 (29)

1. A data communication method in a communication system using a feedback power control scheme, comprising:

transmitting a first data frame in a first transmission format and a first power level ratio corresponding to the first transmission format;

determining that a conversion of a transmission format from the first format to a second transmission format is required; and

transmitting a second data frame at the second transmission format and a second power level ratio corresponding to the second transmission format prior to receiving power control feedback from a receiving destination associated with a transmit power level of the second data frame;

wherein each said power level ratio is a power level ratio between a power level set for the data portion of said data frame and a reference power level, and wherein the transmission of said second data frame occurs within a time frame subsequent to the time frame of the transmission of said first data frame.

2. The method of claim 1, further comprising:

determining that the SNIR required for the data portion of the second data frame is different from the SNIR required for the data portion of the first data frame, thereby triggering a need to transition from the first transmission format to the second transmission format; and

determining the second power level ratio based on the different SNIR while maintaining a reference power level the same as a reference power level used for the first power level ratio.

3. A data communication apparatus in a communication system using a feedback power control scheme, the apparatus comprising:

a transmitter for transmitting a first data frame in a first transmission format and a first power level ratio corresponding to the first transmission format; and

a controller for determining that a conversion of a transmission format from the first format to a second transmission format is required;

wherein the transmitter transmits a second data frame at the second transmission format and a second power level ratio corresponding to the second transmission format prior to receiving power control feedback from a receiving destination associated with a transmit power level of the second data frame;

wherein each said power level ratio is a power level ratio between a power level set for the data portion of said data frame and a reference power level, and wherein the transmission of said second data frame occurs within a time frame subsequent to the time frame of the transmission of said first data frame.

4. The apparatus of claim 3, wherein:

the controller also determines that the SNIR required for the data portion of the second data frame is different from the SNIR required for the data portion of the first data frame, thereby triggering a need to transition from the first transmission format to the second transmission format, and determines the second power level ratio based on the different SNIR while maintaining the reference power level the same as the reference power level for the first power level ratio.

5. An apparatus for wireless communication, comprising:

means for transmitting a first data frame in a first transmission format and a first power level ratio corresponding to the first transmission format;

means for determining that a conversion of a transmission format from the first format to a second transmission format is required; and

wherein the means for transmitting transmits a second data frame at the second transmission format and a second power level ratio corresponding to the second transmission format prior to receiving power control feedback from a receiving destination associated with the transmit power level of the second data frame;

wherein each said power level ratio is a power level ratio between a power level set for the data portion of said data frame and a reference power level, and wherein the transmission of said second data frame occurs within a time frame subsequent to the time frame of the transmission of said first data frame.

6. The apparatus of claim 5, further comprising:

means for determining that the SNIR required for the data portion of the second data frame is different from the SNIR required for the data portion of the first data frame, thereby triggering a need to transition from the first transmission format to the second transmission format; and

means for determining the second power level ratio based on the different SNIR while maintaining a reference power level the same as a reference power level used for the first power level ratio.

7. A base station, comprising:

an antenna;

a transmitter for transmitting a first data frame over the antenna in a first transmission format and a first power level ratio corresponding to the first transmission format; and

a controller for determining that a conversion of a transmission format from the first format to a second transmission format is required;

wherein the transmitter transmits a second data frame at the second transmission format and a second power level ratio corresponding to the second transmission format prior to receiving power control feedback from a receiving destination associated with a transmit power level of the second data frame;

wherein each said power level ratio is a power level ratio between a power level set for the data portion of said data frame and a reference power level, and wherein the transmission of said second data frame occurs within a time frame subsequent to the time frame of the transmission of said first data frame.

8. The base station of claim 7, wherein:

the controller also determines that the SNIR required for the data portion of the second data frame is different from the SNIR required for the data portion of the first data frame, thereby triggering a need to transition from the first transmission format to the second transmission format, and determines the second power level ratio based on the different SNIR while maintaining the reference power level the same as the reference power level for the first power level ratio.

9. A processor-readable medium for wireless communication, the processor-readable medium comprising code for:

transmitting a first data frame in a first transmission format and a first power level ratio corresponding to the first transmission format;

determining that a conversion of a transmission format from the first format to a second transmission format is required; and

transmitting a second data frame at the second transmission format and a second power level ratio corresponding to the second transmission format prior to receiving power control feedback from a receiving destination associated with a transmit power level of the second data frame;

wherein each said power level ratio is a power level ratio between a power level set for the data portion of said data frame and a reference power level, and wherein the transmission of said second data frame occurs within a time frame subsequent to the time frame of the transmission of said first data frame.

10. The processor-readable medium of claim 9, wherein the code is further executable to:

determining that the SNIR required for the data portion of the second data frame is different from the SNIR required for the data portion of the first data frame, thereby triggering a need to transition from the first transmission format to the second transmission format; and

determining the second power level ratio based on the different SNIR while maintaining a reference power level the same as a reference power level used for the first power level ratio.

11. A method for data communication, comprising:

transmitting a first data frame in a first transmission format and a first power level corresponding to the first transmission format;

converting a transmission format from the first format to a second transmission format;

transmitting a second data frame in the second transmission format and a second power level corresponding to the second transmission format prior to receiving feedback from a receiving destination related to the transmit power level of the second data frame;

wherein the transmission of the second data frame occurs within a time frame subsequent to the time frame of the first data frame transmission.

12. The method of claim 11, wherein the feedback comprises power control feedback.

13. The method of claim 11, further comprising:

determining a second power level of the data portion of the second data frame to be higher than the first power level of the data portion of the first data frame.

14. The method of claim 11, further comprising:

determining a second power level of the reference portion of the second data frame to be the same as the first power level of the reference portion of the first data frame.

15. The method of claim 11, further comprising:

determining that the SNIR required for the data portion of the second data frame is different from the SNIR required for the data portion of the first data frame, thereby triggering a transition from the first transmission format to the second transmission format.

16. The method of claim 15, further comprising:

determining the second power level based on the different SNIR.

17. An apparatus for data communication, comprising:

a transmitter configured to transmit a first data frame in a first transmission format and a first power level corresponding to the first transmission format;

a controller configured to convert a transmission format from the first format to a second transmission format;

the transmitter is further configured to: transmitting a second data frame in the second transmission format and a second power level corresponding to the second transmission format prior to receiving feedback from a receiving destination related to the transmit power level of the second data frame;

wherein the transmission of the second data frame occurs within a time frame subsequent to the time frame of the first data frame transmission.

18. The apparatus of claim 17, wherein the feedback comprises power control feedback.

19. The apparatus of claim 17, the controller further configured to: determining a second power level of the data portion of the second data frame to be higher than the first power level of the data portion of the first data frame.

20. The apparatus of claim 17, the controller further configured to: determining a second power level of the reference portion of the second data frame to be the same as the first power level of the reference portion of the first data frame.

21. The apparatus of claim 17, the controller further configured to: determining that the SNIR required for the data portion of the second data frame is different from the SNIR required for the data portion of the first data frame, thereby triggering a transition from the first transmission format to the second transmission format.

22. The apparatus of claim 21, the controller further configured to: determining the second power level based on the different SNIR.

23. An apparatus for data communication, comprising:

means for transmitting a first data frame in a first transmission format and a first power level corresponding to the first transmission format; and

means for converting a transmission format from the first format to a second transmission format;

wherein the means for transmitting transmits a second data frame in the second transmission format and a second power level corresponding to the second transmission format prior to receiving feedback from a receiving destination related to the transmit power level of the second data frame;

wherein the transmission of the second data frame occurs within a time frame subsequent to the time frame of the first data frame transmission.

24. The apparatus of claim 23, wherein the feedback comprises power control feedback.

25. The apparatus of claim 23, further comprising:

means for determining a second power level of the data portion of the second data frame to be higher than a first power level of the data portion of the first data frame.

26. The apparatus of claim 23, further comprising:

means for determining a second power level of the reference portion of the second data frame to be the same as the first power level of the reference portion of the first data frame.

27. The apparatus of claim 23, further comprising:

means for determining that the SNIR required for the data portion of the second data frame is different from the SNIR required for the data portion of the first data frame, thereby triggering a transition from the first transmission format to the second transmission format.

28. The apparatus of claim 27, the second power level is determined from the different SNIRs.

29. A processor-readable medium for wireless communication, the processor-readable medium comprising code for:

transmitting a first data frame in a first transmission format and a first power level corresponding to the first transmission format;

converting a transmission format from the first format to a second transmission format;

transmitting a second data frame in the second transmission format and a second power level corresponding to the second transmission format prior to receiving feedback from a receiving destination related to the transmit power level of the second data frame;

wherein the transmission of the second data frame occurs within a time frame subsequent to the time frame of the first data frame transmission.