MXPA01002701A - Method and system for alternating transmission of codec mode information - Google Patents

Abstract

A communication system supports multiple source coding/channel coding schemes. A mode indicator can be transmitted with payload data to inform the receiver of the particular scheme currently being employed. Similarly, a mode request can be transmitted to inform the receiver of a particular scheme to be employed for information to be transmitted on the return radio link. The rate of change of the mode indications and mode requests can be decimated so that they need not both be transmitted in each frame to thereby reduce the overhead capacity consumption associated with the transmission of mode information. According to one exemplary embodiment, the mode indication and the mode request can be tramsmitted independently on alternating frames.

Description

METHOD AND SYSTEM FOR ALTERNATE TRANSMISSION OF MODERN INFORMATION CODEC BACKGROUND The present invention relates generally to the handling of mode in the field of communication systems and, more particularly, to the handling of information transmission associated with the request and identification of encoding modes in digital communication systems that support Multiple voice coding schemes / sending error correction. The growth of commercial communication systems and, in particular, the explosive growth of cell phone radio systems, have challenged system designers to look for ways to increase system capacity without reducing the quality of communication beyond the tolerance thresholds of the client. One technique to achieve objectives involved switching from systems where analog modulation was used to print data on a carrier wave, to systems where digital modulation was used to print the data on the carrier probes. In wireless digital communication systems, standardized air interferences specify most of the parameters of the system, including the type or types of voice coding, the burst format, the communication protocol, etc. For example, the European Telecommunication Standard Institute (ETSI) has specified a standard for a Global System for Mobile Communications (GSM) that uses multiple time division access (TDMA) to communicate control, voice and data information over physical channels of radio frequency (RF) or links using a Minimum Gaussian Displacement Modulation Scheme (GMSK) at a symbol rate of 271 ksps. In the United States, the Telecommunication Industry Association (TIA) has published a number of Interim standards, such as IS-54 and IS-136, which define several versions of mobile telephone service (D-AMPS), a TDMA system that uses a differential quadrature phase shift modulation scheme (DQPSK) for data communication on RF links. TDMA systems subdivide the available frequency into one or more RF channels. The RF channels are further divided into a number of physical channels corresponding to the time segments in the TDMA structures. The logical channels are formed from one or several physical channels where modulation and coding are specified. In such systems, mobile stations communicate with a plurality of dispersed base stations by transmitting and receiving bursts of digital information over uplink and downlink RF channels. The increasing number of mobile expressions in use today has generated the need for more voice and data channels within cellular telecommunication systems. As a result, the base stations have been separated less and less, with ^^^^^^^^^^ j ^ úM¡3li ^? Hr «an increase in the interference between mobile stations operating on the same frequency in cells closely or closely separated. In fact, some systems now use code division multiple access (CDMA), using a form of extended spectrum modulation where the signals share intensionally the same time and frequency. Although digital techniques provide a greater number of useful channels from a given frequency spectrum, there is still a need to maintain the interference at acceptable levels, or more specifically to monitor and control the carrier-to-signal resistance ratio. the interference (that is, the carrier to interference ratio (C / l)). Another factor that is increasingly important in providing various communication services is the user bit rate required / desired for the data to be transmitted over a particular connection. For example, for voice and / or data services, the user bit rate corresponds to the voice quality and / or the performance of the data, with a higher user bit rate that produces better voice quality and / or higher data throughput. In the total user bit rate is determined by a selected combination of techniques for voice coding, channel coding, modulation and resource allocation, for example, for a TDMA system, the latter technique may refer to the number of time segments assignable per connection, for each system - ^ Ra, ^ * as i. M mt¡i7 CDMA, this last parameter can refer to the number of assignable codes per connection. Voice coding (or more generally "source coding" to include techniques associated with data compression) is used to compress the input information into a format that uses an acceptable amount of bandwidth although from which it can reproduce an intelligible output signal. Many different types of voice coding algorithms exist, for example, residual excited linear predictive (RELP), regular pulse excitation (RPE), etc., the details of which are not particularly relevant to this invention. More importantly in this context is the fact that several voice coders have several bit rates of output and that, as might be expected, speech coders having a higher bit rate of output tend to provide greater acceptance of the speech. consumer of its reproduced voice quality than those that have a lower bit rate of output. As an example, consider more traditional wired telephone systems using 64 kbps PCM voice coding, while GSM systems employ an RPE voice coding scheme operating at 13 kbps. In addition to voice coding, digital communication systems also employ various techniques to handle information received in a wrong way. Generally speaking, these techniques include those that help a receiver to correct erroneously received information, for example, error correction techniques (FEC), and those that allow erroneously received information to be retransmitted to the receiver, for example, automatic retransmission request techniques (ARQ) FEC techniques include, for example, convolulsive or block coding (collectively referred to herein as "channel rating") of the data before modulation. Channel coding involves representing a certain number of data bits using certain number of bitcodes therefore, and as an example, it is common to refer to convolusional codes by their code rates, for example 1 and 1/3, where the lower code rates provide greater error protection although lower user bit rates for a bit rate of determined channel. Conventionally, each of the techniques that impact the user's bit rate were set for any given radio communication system, or at least for the duration of a connection established by a radio system communication. That is, each system established connections that operated with one type of voice coding, one type of channel coding, one type of modulation, and one resource allocation. However, more recently, the dynamic adaptation of these techniques has become a popular method to optimize the system performance against the numerous parameters that i '.' ^, ^ can vary rapidly over time, for example, the radio propagation characteristics of radio communication channels, the system load, the user's bit rate requirements, etc. For example, different modulations have been assigned dynamically to selectively take advantage of the resistances of the individual modulation schemes and to provide higher user bit rates and / or increased resistance to noise and interference. An example of a communication system employing multiple modulation schemes is found in the US Patent NO. 5,577,087. In the present, a technique for switching between 16QAM and QPSK is described. The decision to switch between the types of modulation is made based on quality measurements, although this system employs a constant user bit rate that represents a change in the modulation scheme that also requires a change in the channel bit rate, for example, the number of time slots used to support a transmission channel . It is contemplated that many different combinations of these processing techniques may be used selectively as between different connections supported by a radio telecommunication system and during the lifetime of an individual connection. However, it will be necessary for some type of "signal exchange" between the transmitting and receiving entities to form the receiving entity of a transmission mode that is employed and / or the receiving entity requests a particular mode of transmission from the transmitting entity. . For example, there are two general categories of techniques for receiving information about the processing techniques associated with a radio signal: (1) explicit information, that is, a message field within the transmitted information that has a value of which is indicative of the processing type (s) and (2) implicit information, which is sometimes referred to as "blind" decoding, whereby the receiver determines the processing executed by the transmitter by analyzing the received signal. This last technique is used in CDMA systems that operate in accordance with the TIA / EIA IS-95 standard. Explicit information is sometimes considered to be preferable because it reduces the processing delay in the receiver, although it comes at cost to the need for the transmitter to include additional general bits together with the user data. Of particular interest for the present invention are the indicators so as to reflect the combination of channel coding / speech coding currently employed by the transmitter and the requests so as to reflect the request of the receiver of a channel coding / coding mode of particular voice that will be used. For example, - when the channel conditions are adequate, the receiver can send a mode request in the uplink for a coding mode of channel / voice coding that provides a high bit rate of source coding and a relatively low degree of error protection. When the transmitter transmits the information using the requested mode, it will also include a corresponding mode indicator in its downlink transmissions. Alternatively, when channel conditions are scarce, then a coding mode in which a low bit rate speech coding technique coupled with a relatively high degree of error protection is provided may be requested by the receiver. The transmitter will then provide a corresponding indicator associated with this other mode in the return link. Systems can rapidly switch between these different coding nodes based on the varying changes in channel conditions, so that mode requests and / or indicators need to be transmitted relatively frequently. Therefore, the mode indicators and mode requests are communicated between the transmitting and receiving entities to allow the operation of the variable code mode. Typically, those mode indicators / requests may include only a few, for example two bits, which are transported along with the data fields. Therefore, it will be appreciated that it is particularly important for the receiver / transmitter to be able to decode accurately and quickly the indicator / request mode since otherwise a complete data frame may be T niMi j ^ jjj¡ ^ unrecoverable by the receiver on a sub-optimal transmission mode that can be used. This need for accurate and rapid reception of the indicator / request mode can lead designers to strongly protect the indicator / request mode with complicated channel coding. However, the use of complicated channel coding implies a greater redundancy, which means more bits to be transmitted for the mode indicator and / or the request field. That is, as explained above, undesirable since general bits should be minimized and not increased, Therefore, it would be desirable to provide techniques and systems to increase the likelihood that indicators and mode requests, such as the indicator and the encoding mode request is appropriately decoded, while at the same time minimizing the number of general bits that are transmitted with the payload data and reducing the delay associated with the processing mode information.

BRIEF DESCRIPTION OF THE INVENTION This and other disadvantages and limitations of conventional methods and systems for communicating information are overcome in accordance with the present invention, wherein the mode-information transmission rate is reduced to one-tenth to reduce the use of bandwidth associated with it and / or to allow more complex channel coding of the > ** £ ** - & * - * & mode information. The mode information may comprise, for example, an indicator so as to inform a receiver of the voice coding / channel coding combination currently used to encode the payload data, a request so as to inform a transmitter in a way particular codee desired by a receiver to subsequently transmit blocks of information or structures and / or channel measurement information, which acts as an implicit request for a particular codee mode to be provided by the transmitter. In accordance with the illustrative embodiments of the present invention, the mode information exchange rate is restricted to be less than each structure. For example, mode indication and mode requests can be restricted by changing not more than once per structure. Under those circumstances, the transmission of mode indicators and mode requests can also be alternated to reduce the transmission capacity used by those indicators and to minimize the processing delays associated with the mode changes. In accordance with other illustrative embodiments of the present inventionWhen the links become inactive, for example, when a loudspeaker is silent, the transmission of the mode information can be further reduced or adjusted according to them. and íát á a ^ J & Í ^? «^? S? É? BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features and advantages of the present invention will become more apparent upon reading the following detailed description, taken in conjunction with the accompanying drawings, wherein: Figure 1 is a diagram of block of an illustrative GSM communication system that advantageously uses the present invention; Figure 2 (a) illustrates a codec mode used in a conventional GSM system; Figure 2 (b) illustrates a conventional bit mapping in a speech structure for unequal error protection coding; Figure 3 (a) is a block diagram illustrating multiple codeine modes, the individual ones that can be selected to process data to be transmitted and an indicator correspondingly according to the illustrative embodiment of the present invention; Figure 3 (b) is another block diagram illustrating another example technique for generating multiple codee modes; Figure 4 illustrates a block diagram of a receiver that includes a mode probability processor and a mode information model; Figure 5 is a block diagram of an illustrative transceiver according to the present invention; Y Figure 6 illustrates the alternate transmission of mode indicators and mode requests according to an illustrative embodiment of the present invention.

DETAILED DESCRIPTION The following illustrative modalities are provided in the context of TDMA telecommunications radio systems. However, those skilled in the art will appreciate that this access methodology is used only for the purposes of illustrates and that the present invention is easily applicable to all types of access methodology including multiple access without division of frequency (FDMA), TDMA multiple access by division of code (CDMA) and hybrids thereof. In addition, the operation according to the systems of The GSM communication is described in the documents of the European Telecommunication Standard Institute (ETSI) ETS 300 573, ETS 300 574 and ETS 300 578, which are incorporated by reference herein. Therefore, the operation of the GSM system is described only herein to the extent necessary for understand the present invention. Although, the present invention is described in terms of illustrative embodiments in a GSM system, those skilled in the art will appreciate that the present invention can be used in a wide variety of other digital communication systems, such as those based on standards and PDC or D-AMPS improvements thereof. gÉggáát ^ i ^ Referring to Figure 1, a communication system 10 according to an illustrative embodiment of the present invention is described. The system 10 is designed as a hierarchical network with multiple levels for handling calls. Using a set of uplink and downlink frequencies, the mobile stations 12 operating within the system 10 participate in calls using time segments assigned to them over those frequencies. At a higher hierarchical level, a group of Mobile Switching Centers (MSCs) 14 are responsible for routing calls from a source to a destination. In particular, these entities are responsible for the establishment, control and termination of calls. One of the MSCs 14 known as the bridge MSC, handles communication with a Public Switched Telephone Network (PSTN) 18, or other public and private networks. At a lower hierarchical level, each of the MSCs 14 is connected to a group of base station controllers (BSCs) 16. Under the GSM standard, the BSCs 16 communicate with an MSC 14 under a standard interface known as the interface -A, which is based on the Mobile Application Part of the CCITT Signaling System NO. 7. At an even lower hierarchical level, each of the BSCs 16 controls a group of base transceiver stations (BTSs) 20. Each BTS 20 includes a number of TRXs (not shown) that use the uplink and uplink RF channels. downlink for serving a particular common geographic area, such as one or more communication cells 21. BTSs 20 primarily provide RF links for transmitting and receiving bursts of data to and from mobile stations 12 within the designated cell. In an exemplary embodiment, a number of BTSs 20 are incorporated into a radio base station (RBS) 22. The RBS 22 may be, for example, configured in accordance with an RBS-2000 product family, whose products are offered by Telefonaktiebolaget LM Ericsson, assignee of the present invention. For further details regarding the illustrative mobile station 12 and the RBS implementations 22, the reader interested in the reference to the US Patent Application Serial No. 08 / 921,319 entitled "A Link Adaptation Method for Links using Modulation Schemes That Have Different Symbol Rates ", for Magnus Frodingh et al., And filed on August 29, 1997, the description of which is expressly incorporated herein by reference. In accordance with the illustrative embodiments of the present invention, information transmitted between a BTS 20 and a mobile station 12 can be processed in accordance with the use of different codee modes. The phrase "code mode" as used herein is used in the combination of source coding (eg, voice coding) and channel coding, although the present invention is also applicable to the transmission and reception of other types of information. way and even more so 7 -. 7 - 'mmááiiiáifM? I generally transmit and receive other information about an air interface. For a more complete understanding of the illustrative modes for which the indicators, requests and information associated with them can be protected, transmitted and decoded, consider the illustrated GSM mode shown in Figures 2 (a) and 2 (b) . Figure 2 (a) illustrates a portion of a transmission signal processing path downstream of the A / D converter (not shown) that digitizes an audio signal of illustrative entry. A block of 160 samples is presented to a RPE speech encoder 30 which operates in accordance with well-known GSM specifications (eg GSM 06.53) to produce two categories of output bits, bits 1 of class 182 and bits 2 of class 78, for a total output bit rate of 13 kbps. As can be seen in Figure 2, the class 1 bits are further divided into the class 1a bits and the class 1b bits, both of which are input to a channel encoder 32, which executes a convolutional speed coding A. This results in an output of 378 bits from the channel 32 encoder, including 3 parity bits associated with the class 1a bits and four terminal bits associated with the class 1b bits. This composite process can be considered to make an example of an individual code mode. However, the Applicants contemplate future systems that provide a plurality of different codec modes. By ****** "* - ^ -m Éß j ki idbví *., A '? Í, example, as illustrated conceptually in Figure 3 (a), there are two different voice coders and two coders of different channels that can be used in those combinations for encoding bits before transmission A first voice coder 40 can operate to process digital samples and provide an output bit rate of X kbps, while a second speech coder 42 can process the digital input samples to provide an output bit rate of Y kbps, where X > Y. Similarly, two different channel encoders 44 and 46 (in this example convolutional encoders, although one or both can be encoders) block alternatively), provide different degrees of error protection by virtue of their different speeds 1 / A and 1 / B, respectively, where A >; B. Thus, it can be seen that using the mode control processor 48 in conjunction with the multiplexers O and 52 to select a path, i.e. a combination of speech coder and channel coder for this example, to process a particular block or structure of payload data, four different codee modes are available. Many other techniques, of course, are available to create multiple codec modes in a transmitter. Consider the example in Figure 3 (b), where a plurality of source (eg voice) encoders 60, 62, 64 and 66 are provided in selectable transmission signal processing paths. Each encoder has an output speed different (X > Y> ZA kbps) and is associated with a different one of the channel encoders 68, 70, 72 and 74. To provide a uniform output data rate of F kbps as between the different selectable paths (the which may be desirable for similar resource allocation / connection), the channel encoders may be designed so that the amount of redundancy added to the source encoded data stream is greater for the low bit rate source encoder and lower for the lower bit rate source encoder. encoders source of higher bit rate. As in the previous example, the particular codec mode selected for any particular data block or structure is controllable by, for example, a mode control processor 76 and multiplexer 78. Regardless of the technique used on the transmission side to provide In different codeine modes, in order to be able to correctly decode the received data, a receiver will need to know the code mode used by the transmitter to process any given block or structure of received data. In accordance with the illustrative embodiments of the present invention, this can be achieved by transmitting a mode indicator from the transmitter to the receiver in conjunction with or before the block or data structure to which it relates. In the example of Figures 3 (a) and 3 (b), a two-bit mode indicator field would be sufficient to inform the receiver of the combination of the voice coder and the channel coder 'used to process the data before the broadcast. Additionally, the receiver may transmit a request for a particular code mode to the transmitter on the return radio link or the receiver may transmit the signal quality measures associated with the downlink channel (i.e. BTS to the link). mobile station) for the transmitter which uses the transmitter to identify an appropriate codee mode. In any of those three cases, some kind of mode information is exchanged between the transmitter and the receiver over the interface of air, whose phrase is used to include each of those three specific examples, as well as other types of mode information. In any case, since the mode information is also communicated on the air interface between the BTS 20 and the mobile station 12, it must also be protected against errors of channel as well as the data. However, adding complex channel coding, ie, with a large amount of redundancy, is undesirable since it is additionally added to general transmissions (ie, non-payload data) and reduces the effective bit rate of the user. It would also be desirable to maintain a low coding delay so that the codec modes can be changed quickly to account for the rapid changes in transmission channel conditions. According to the above identified patent application, those objectives can be achieved by coding the mode information with a relatively weak channel code (it is ffl ^: **** ^ - ^ ^ ¡t ^ - ^^ say, with a smaller amount of redundancy). In Figure 3 (a), which is exemplified by the channel coder 54 which employs a 1 / C speed convolutional code. In Figure 3 (b), this is exemplified by a block encoder 67 employing a block encoding (8.2). However, the present invention addresses the issue of capacity consumption associated with the transmission of mode information by reducing the rate of change of certain mode information as will be described below. On the receiver side, as exemplified by the block diagram of Figure 4, an antenna 100 of a receiving apparatus, for example, receives radio signals on a certain radio channel. The signals (ie, data / voice messages) transmitted over the channel can be strongly distorted, for example, due to fading, so that TDMA bursts give rise to a highly distorted speech structure. The demodulation takes place in the radio receiver 102 at a given radio frequency (in the GSM system of 865-935 MHz) in a known manner, to obtain a modulated baseband signal. The signal resistance level or levels of the radio signals arriving at the radio receiver 112 can measure and are referenced Sm in Figure 4. The baseband modulated signal is demodulated in the demodulator 104 within the IF range, this The demodulator also includes an equalizer to compensate for or correct the multipath propagation to which the input signal has been subjected during transmission in a known manner. For example, the well-known Viterbi equalizer can be used for this purpose. The so-called software information associated with the probability of any given symbol information is obtained from the Viterbi equalizer in the demodulator 104, this software information which is referred to as Sj in Figure 4. A deinterleaver 106 is connected downstream of the demodulator / equalizer 104 and recover the bursts divided by time allocated to the receiver, in a known manner. The receiver also includes a mode indication decoder 107 that operates to identify the code mode based on the received mode information. The mode indication decoder provides an output to the channel decoder 109 and the speech decoder 112, indicating the techniques used by the transmitter to process the received data block or structure before transmission. Illustrative techniques for implementing the mode indication decoder 107 can be found in the above-identified patent application and incorporated by reference and, consequently, is no longer further described herein. More generally, a transceiver (either on a remote device or on a side of the network) according to the present invention will include the functionality to transmit the mode indication information, transmit the mode request indication, receiving the mode indication information and receiving the request information in a manner as represented by the block diagram of Figure 5. Here, the RX_ data received by n transceiver 116 on a first link are separated in their first fields components and are provided to an appropriate decoding block or algorithm by demultiplexer 120. For simplicity in the description of the present invention, Figure 5 refers only to the mode and payload information, although those skilled in the art will appreciate that other types of information can be received by the transceiver. If the received structure includes mode indication information, then that information is provided to the mode indication decoder 122, which determines the code mode used to encode the received payload data. The decoded mode indication information is provided to the multiple mode decoder 124 so that properly decoded payload data, eg, voice, can be issued, if, on the other hand, the received structure includes request information so , then the information is disproportionate to the mode request decoder 126. The mode request decoder determines whether the code mode requested by the other transceiver (not shown), whose information is sent to the transmitter side of that transceiver. On the transmission side, the requested mode is presented to the mode control unit 128 which selects a e ".» iwBH »Sfe appropriate code mode for processing the input payload, for example voice information. This mode information is passed to a multi-mode encoder 130, which, for example, encodes the speech and encodes the error correction of the input speech structures. The mode information is also passed to the mode encoder 132 which creates an indication so that it is to be transmitted to the other transceiver (not shown) on a second (return) link which identifies the mode used by the mode encoder. Additionally, the transmit side of the transceiver 116 includes a code mode 134 measurement or request function which, based on the quality measured on the first link, provides a mode request or measurement information that will be transmitted on the second link. The mode request, the payload information and the mode indication are presented to the multiplexer 136 for selective transmission using well known techniques, eg, upconversion modulation, etc. In accordance with the illustrative embodiments of the present invention, the voltage between the protection of the mode information against the transmission errors and the providing a low delay, on the one hand, and reducing the amount of bandwidth consumed by the transmission of the mode information, on the other hand, is solved by reducing by one tenth the permissible change rate associated with the mode information and by alternating the transmissions of the mode indicators and the transmissions of the mode requests (or measurement information ). This can be achieved in a number of different ways according to the illustrative embodiments of the present invention. For example, the code mode changes in the transmission entity that may be restricted to present only 5 in each n-th structure. As a result of this restriction, code-mode indications will change only at a reduced rate to one tenth of a time for n structures, where, for example, n may be equal to 2 or a multiple thereof. Similarly, codec mode requests generated by the 0 receiver can be sub-sampled with a tenth reduction factor of n, the result being those code mode requests that can only change at a maximum rate of one time per each n structure . These restrictions on the ability to change syndications and requests 5 so can, in turn be used to toggle the transmission of mode indications and mode requests so that the total bandwidth consumed by the mode transmission can be reduced by a factor of \ / n. Consider the example illustrated in Figure 6 with 0 regarding the communication between a GSM mobile station 150 and the base station 152. Here, the mobile station 150 transmits information to the base station 152 on the uplink and receives the information transmitted by the base station over the downlink. For the purposes of this example, the alternate transmission characteristic of the information of iffiíiiii] ** rr? tt * -fflm i ^ =? ^ .f ^ ffftfSfeMi »^^ mode received by for example, transceiver 116, according to the present invention is illustrated in the downlink. In the present, the information contained in several consecutive channel structures (after deinterleaving to simplify the illustration, are shown). In particular, in the structure n, the mobile station 150 receives a mode request (MR) from the base station 150 indicating the code mode with which the mobile station must transmit to the base station over the uplink. Since no mode indication is transmitted in the structure n, the mobile station continues to decode the information by using the codee mode indicated in structure n-1 (not shown). Analogically, since mode request information is not transmitted in the n + 1 structure, the mode request from the n structure remains valid for the structure r? +1. In structure n + 1, however, base station 152 transmits a mode indication (Ml) instead of mode request. Therefore, the mobile station uses this mode information to switch the code data (if a new code mode is indicated) to decode the payload information found in this structure (and / or a subsequent one). Then, in the n + 2 structure, this link again contains a request so that it is decoded by the mobile station 150 and used on its transmit side which it processes as described above with respect to Figure 5. As indicated in the Figure 6, each structure can also include other general information that includes, for example, synchronization information. Those skilled in the art will appreciate that, although not explicitly described herein, the mobile station 150 can similarly alternate the 5 mode request transmissions and mode indications to the base station 152 on the uplink . Furthermore, although it is not illustrated explicitly in Figure 6, note that the mode information Ml and MR can occupy the same bit positions within each structure. 10 In an even more specific example, although purely illustrative, the mode information in the previous example can comprise eight bits totale4s (full speed, four total bits of average speed) and the reduction factor to the tenth part n is equal to two . Mode requests are transmitted in even structures and mode indications in odd structures. After the diagonal collation, the total bits belonging to each codeword are distributed individually in separate bursts, thus providing an optimal interleaving gain for the speech channels. frequency jump. By transmitting mode indications and mode requests only in every third structure, for example, the bandwidth to transmit those general changes is reduced by a factor of two, regardless of the amount of aggregate redundancy by virtue of the correction coding of error. The particular way used to select the alternate pattern can, of course, be varied. For example, consecutive codec mode requests can be transmitted using structures (1 ... n / 2) + k * n, where k is an integer value. Then, the codec mode indications would be transmitted using structures (n / 2 + 1 ... n) + k * n. Alternatively, codec mode requests can only be sent using odd-numbered structures, while mode indications can only be sent using odd-numbered structures, although only the latter solution can increase the transmission delay. Since those illustrative embodiments of the present invention provide alternation of mode indication transmission and mode request, it is important that some form of synchronization of the transmission / decoding mode is provided so that the receiving entity knows when it is receiving a mode indication and when you are receiving a mode request. Otherwise, the wrong decoding of the mode information can be presented. One way to provide synchronization for the mode information is to align the transmission of the mode information to the time segment structure of the radio communication system. For example, in the GSM system the mode information can be aligned with the SACCH (Slow Associated Control Channel) so that, for example, the mode indications are sent in even structures relative to the SACCH while the mode requests are sent using odd structures. Alternatively, when both links are active, it could be understood that the first transmission will always be a specified one of the mode request or the mode indication. In accordance with other aspects of the present invention, the use of discontinuous transmission, (DTX) or voice operated transmissions (VOX) in some radio communication systems may be explained in conjunction with the transmission of mode information. DTX and VOX are mechanisms to transmit structures of information only during the speech periods while the transmitter is deactivated during voice inactivity to reduce power consumption and interference. In two-way communication systems that use DTX, situations can therefore arise where both links are active (for example, example, when the speaker is active during conversation changes), an active link / an inactive link, or both inactive links. Transmitters that have inactive links commonly transmit some information, commonly referred to as noise descriptor structures (SID) or noise information.

This allows the receiver to generate an appropriate background noise output instead of the listener experiencing dry noises and creaks associated with a complete absence of reproduced sound. However, these SID structures are transmitted with a reduced structure transmission speed in relation to the active voice structures.

^^? ^ In addition to the SID structures in the types of systems described above, the mode information also needs to be transmitted. However, instead of alternating the information as described above, the presence of inactive links can be recognized and used by the system to further reduce the transmission of the mode information. For example, the mode indications do not need to be transmitted for idle links since the encoded speech structures are not included with them. Consider the case when a mobile station is not transmitting to a base station on the uplink, but is receiving voice structures (and other data) on the downlink. Then, the mobile station does not need to send mode indications on the uplink and can, instead, only send the mode requests associated with the transmissions to do so by the base station on the currently active downlink. Analogously, on requests for active link code mode for transmissions on the inactive link does not need to be sent until the inactive link becomes active again. Having eliminated the need to transmit the mode indications on the idle link and the mode requests on the active link, the released bandwidth can therefore be used in several different ways. For example, the mode requests can be repeated, for example, in each structure sent, on the inventive link and the mode indications can be repeated on the active link, IÉÉa »» Atieia ^ a ^ afeA > ja8Aja »^ which leads to an improved channel error protection. Alternatively, some other general information may be transmitted during the omitted information fields. In the situation where both links are inactive, the transmission of all mode information can be temporarily suspended waiting for the reactivation of one or both links. The corresponding transmission capacity is then released for other uses, for example the transmission of other general information. Alternatively, mode requests may continue to be transmitted over idle links as indicators of the current quality of the channel. Then, when the inventive link becomes active, those mode requests can be used to select an appropriate code mode to encode the next information structure to be transmitted. If the mode requests associated with the inactive links are not limited to the use of the transmission capacity for other purposes. , then, when an inactive link becomes active again, some other technique must be used to determine which mode to use initially until the receiving entity begins to return the mode requests on the other link. There are several possibilities, for example, the transmitting entity can use a stronger n-th default codec mode, where n = .1 implies a codec mode that has a higher level of error correction protection. If this solution is used, then it is not necessary to transmit mode indication with this initial structure or structures of the information since the receiving activity will know a prior! which modes are being used for transmission after inactivity. Another alternative for post-idle selection in a code mode that is to use the same code mode that is currently being used for the active link. For example, if a mobile station is inactive on the uplink and active on the uplink, once another structure is prepared for transmission on the uplink, you can select the codec mode that is currently being used to decode the structures received on the uplink. the downlink from the base station. This solution is based on the recognition that there is a certain correlation between the characteristics and the uplink channel and the downlink channel in a double pair. As in the previous illustrative embodiment, the receiving entity knows the codec mode applied according to this is the same mode that it is using to transmit information structures in the other link. A variation on this solution is to use, instead of the same way that is being used in the active link, a mode that is n more resistant modes than the mode that is being used on the active link, for example, the following more resistant mode , assuming that there is a more resistant mode. Taking the illustrative modes shown in Figure 3 (b), if the active link is currently using a code mode defined by the combination of the source encoder 62 and the speed C-channel encoder 70, then (for n = 1) the link previously inactive will use the following stronger codec mode provided by the source encoder 64 and the channel encoder 72 to transmit its first information structure. Another alterative to select a code mode after a period of transmission inactivity is to select the mode used to transmit on that link before inactivity. This solution can be particularly useful in situations where the radio channel conditions do not change rapidly. As in the above illustrative embodiment, this technique can be varied, using, instead of the same codec mode used previously, a code mode that is n more resistant modes, for example, the following more resistant mode. Although the invention has been described in detail with reference to only a few illustrative embodiments, those skilled in the art will appreciate that various modifications can be made without departing from the invention. For example, although the previously described illustrative embodiments of the present invention alternate mode information transmissions after reducing the rate of change to one tenth, other transmission patterns may be selected. Therefore, the present invention can be implemented by sending a portion of the mode request information and the mode indication information in each structure. Accordingly, the invention is defined only by the claims following that are intended to cover all equivalents thereof.

Claims (56)

1. CLAIMS 1. A method for transmitting information about a first link and receiving information about a second link in a communication system comprising the steps of: 5 providing at least two different codee modes for processing said information in the system; transmitting, in at least one first structure on the first link, so as to identify one of at least two different codee modes that have been used to process the first data structure; and transmitting, in at least a second structure of the first link different from the first structure, a request so that it identifies one of at least two different codee modes to be used in order to process the information that is going to
2. 15 transmit on the second link. The method according to claim 1, characterized in that at least two codeine modes identify a source identification technique and a channel coding technique. The method according to claim 1, characterized in that the mode request is channel measurement information that can be used by a transceiver to determine an appropriate one of at least two different codee modes for information processing that is going to to transmit
3. 25 on the second link.
4. 4. The method according to claim 1, characterized in that at least one of the first and second structures are consecutively transmitted.
5. The method according to claim 1, characterized in that the first transmission stage comprises the step of: transmitting the mode indication in at least one structure including the structures (n / 2 + 1 ... n) + k / n, where k is an incremental structure number and n is an integer.
6. The method according to claim 5, characterized in that the second transmission stage further comprises the step of: transmitting the request information so in at least a second structure including the structures (n / 2 + 1 .. .n) + k / n, where k is an increasing structure number and n is an integer.
7. The method according to claim 1, characterized in that at least one of the first and second structures are even and odd structures.
8. The method according to claim 7, characterized in that at least one first structure comprises two consecutive even-numbered structures.
9. 9. The method according to claim 7, characterized in that at least one second structure comprises two consecutive odd numbered structures.
10. 10. The method according to claim 1, characterized in that it further comprises the step of: synchronizing the first and second transmission stages to a time segment structure of other information transmitted by the communication system.
11. The method according to claim 10, characterized in that the time segment structure is a slow associated control channel structure (SACCH).
12. 12. A system for transmitting information on a first link and receiving information on a second link in a communication system comprising the steps of: means for providing at least two different codee modes for processing the information in the system; means for transmitting, in at least a first structure on the first link, an indication so as to identify one of at least two different codee modes that have been used to process the first data structure; and means for transmitting, in at least one second structure on first link different from the first structure, a request so that it identifies one of at least two different codee modes that will be used to process the information to be transmitted on the second link. The system according to claim 12, characterized in that each of at least two codeine modes identifies a source identification technique and a technique of
13. f1 & i ^ ^^ Í ^ f ^^ a. É ^^ a ^ S.? channel coding. The system according to claim 12, characterized in that the mode request is channel measurement information that can be used by a transceiver for
14. 5 to determine an appropriate one of at least two different codee modes to process information that is to be transmitted on the second link.
15. 15. The system according to claim 12, characterized in that at least one first and second

    10 structures are transmitted consecutively.
16. 16. The system according to claim 12, characterized in that the first means for transmitting further comprises: means for transmitting the mode indication in at least one first structure including structures (n / 2 + 1 ... n) + k / n, where k is an increasing structure number and n is an integer.
17. 17. The system according to claim 16, characterized in that the second means for transmission

    20 further comprise: means for transmitting request information so in at least a second structure including the structures (n / 2 + 1 ... n) + k / n, where k is an increasing structure number and n is a whole.
18. 18. The system according to claim 12,

    j? = iaffi ^^^^^^^^^^ «^« jadaa ^ characterized in that said first and second structures are even and odd structures.
19. 19. The system according to claim 18, characterized in that at least one first structure comprises two consecutive even-numbered structures.
20. 20. The system according to claim 18, characterized in that at least one second structure comprises two consecutive odd numbered structures.
21. The system according to claim 12, characterized in that it further comprises: means for synchronizing the first and second transmission means to a time segment structure of other information transmitted by the communication system.
22. 22. The system according to claim 21, characterized in that the time segment structure is a slow associated control channel structure (SACCH).
23. 23. A communication station comprising: a processor for processing payload information and mode indication and request information; and a transmitter for receiving the payload information, the mode indication information and the mode request information from said processor and for selectively transmitting one of the mode indication information and the mode request information in each structure further. of the payload information on the first communication link.
24. The communication station according to claim 23, further comprising a receiver for receiving the mode indication information, the mode request information and the payload information on a second radio link. 5 communication, wherein the mode indication information is used by the processor to decode the payload information and request training so it is used to determine a decoding mode for the payload information transmitted to the transmitter.
25. 25. The communication station according to claim 23, characterized in that the processor selectively adapts to the transmission of the mode indication information based on the input payload information.
26. 26. The method according to claim 1, further comprising the steps of: determining that a data source associated with the first link is inactive; and stopping the transmission of the mode indications in at least one first structure during a period when the data source 20 is inactive. The method according to claim 26, further comprising the step of: transmitting mode requests during at least a first and second structure during the period of inactivity. 28. The method according to claim 26,

    ^ Bfc -.A further comprising the step of: using a more resilient n-th mode of at least two different codec modes to process the information for transmission on the first link after the period of inactivity has ended. 29. The method according to claim 26, further comprising the step of: using a codec mode that was used before the period of inactivity to process the information for transmission on the link after the period of inactivity has ended. 30. The method according to claim 26, further comprising the step of: using a codec mode which is n modes more robust than a codee mode used immediately before the period of inactivity to process the information for transmission after it has finished the period of inactivity. The system according to claim 12, further comprising the steps of: means for determining that a data source associated with the first link is inactive; and means for stopping the transmission of the mode indications in at least one first structure during a period when the data source is inactive. 32. The system according to claim 31, further comprising:

    3, ar ^ a ^? »,. * K - .ÉiáÉÉI mß & ®? Éffl m means for transmitting the request so during at least one first and second structure during the period of inactivity. The system according to claim 31, 5 comprising: means for using a more robust n-th mode predetermined by at least two different codec modes to process the information for transmission on the first link after the end of the period of inactivity. The system according to claim 31, further comprising: means for using a codec mode that was used before the period of inactivity to process the information for transmission on the link after the period of inactivity 15 has ended. 35. The system according to claim 31, further comprising: means for using a codec mode which is n modes more robust than a codee mode used immediately before the inactivity period to process the information for transmission after it has finished the period of inactivity. 36. A method for receiving information about a first link in a communication system comprising the steps of: providing at least two different codee modes 25 for processing the information in the system;

    iV-MJñllií? iíifíiiiii '^ sS & ^ s ^^ S SÉS ^^^^^^^^^^ receive, in at least a first structure on the first link, an indication so that it identifies one of at least two different codec modes that have been used to process the payload dataf and receive, in at least one second structure on the first link different from the first structure, a request so that it identifies one of at least two different codec modes for be used to process the information that is going to be transmitted on a second link. 37. The method according to claim 36, characterized in that each of at least two code mode modes identifies a source coding technique and a channel coding technique. 38. The method according to claim 36, characterized in that the payload data is contained in the same received structure as mode indication. 39. The method according to claim 36, characterized in that the payload data is contained in a subsequent received structure different from at least one structure including the mode indication. 40. The method according to claim 36, characterized in that it comprises the steps of: processing the payload data based on the received mode indication; and during at least a second structure, continue the process of the additional payload data on a previously received mode indication. 41. The method according to claim 1, characterized in that the first transmission stage further comprises the step of: transmitting the mode indication in at least a first structure including structures (1 ... n / 2) * 2 + k * n, where k is an incremental structure number and n is an integer. 42. The method according to claim 41, characterized in that the second transmission stage further comprises the step of: transmitting the request information so in at least a second structure including structures 2 * (1 ... p / 2) -1 + / * n, where k is an incremental structure number and n is an integer. 43. The system according to claim 12, characterized in that the first means for transmission further comprise the step of: means for transmitting the mode indication in at least a first structure including the structures (1 ... n / 2) ) * 2 + k * n, where k is an incremental structure number and n is an integer. 44. The system according to claim 1, characterized in that the second means for transmitting further comprise: means for transmitting the request information so in at least a second structure including the structures 2 * C \ ... nl2) - + k * n, where k is an incremental structure number and n is an integer. 45. The method according to claim 36, further comprising the steps of: determining that a data source associated with the first link is inactive; and stop the transmission of mode requests on the second link during a period when the data source is inactive. 46. The method according to claim 45, further comprising: transmitting the mode indications on the second link during at least a first and second structure during the period of inactivity. 47. The method according to claim 26, further comprising the step of: using a code mode that is n modes more robust than a codee mode used on the second link to process the information for transmission after the period has ended of inactivity. 48. The system according to claim 26, further comprising means for receiving the mode indications in each structure on the second link during the period

    iHz? V & a? tiauíM? inactivity in the first link. 49. The system according to claim 31, further comprising: means for using a code mode which is n modes more robust than a codee mode used on the second link to process the information for transmission after the period of inactivity. 50. The method according to claim 36, comprising the steps of: transmitting information about the second link, whose information is processed in accordance with the received mode requests; and during at least one first structure, continue the processing of the information to be transmitted on the second link based on a request previously received. 51. The method according to claim 1, characterized in that said at least one of the first and second structures are time structures associated with a multiple time division access structure (TDMA). 52. The system according to claim 12, characterized in that said at least one of the first and second structures are time structures associated with a time division multiple access structure (TDMA). 53. The method according to claim 26,

    which further comprises the step of: using a code mode which is the same as a user code mode on the second link to process the information for transmission after the period of inactivity has ended. 54. The system according to claim 31, further comprising: means for using a code mode which is the same as a code mode used on the second link to process the transmission information after the period of inactivity has ended. 55. The method according to claim 1, characterized in that at least one of the first and second structures are time structures associated with the time segment structure of the source employed and the channel coding processing. 56. The system according to claim 12, characterized in that at least one of the first and second time structures are time structures associated with a time structure of the source employed and the channel coding processing.