MXPA99008514A - Method and apparatus for communicating a block of digital information between a sending and a receiving station - Google Patents

Abstract

Apparatus, and an associated method, facilitates the efficient utilization of a channel (16) extending between a sending (12) and a receiving (14) station of a digital communication system. A block of symbols to be transmitted by the sending to the receiving station is encoded (134) utilizing a parallel-concatenated encoding technique. Selected encoded versions, or portions thereof, are transmitted (136) by the sending station to the receiving station. The receiving station decodes the signals received thereat. If recovery of the informational content of the block of symbols cannot be effectuated, a request is made to transmit additional encoded versions (138), or portions thereof, of the block of symbols.

Description

METHOD AND APPARATUS FOR COMMUNICATION OF A DIGITAL INFORMATION BLOCK BETWEEN A STATION AND ONE RECEPTOR The present invention relates, in general, to the communication of a digital information block in coded form between a sending station and a receiving station in a digital communication system. More specifically, the present invention relates to the apparatus, and an associated method, by which a transmission apparatus is provided consisting of at least portions of at least one coded version concatenated in parallel, selected from the digital information block between the sending station and receiver. If the receiving station can not accurately retrieve the information content of the digital information from the transmission series transmitted to it, the successive, redundant transmission of the additional transmission series, consisting of additional portions of coded versions, is initiated, selected to the receiving station. When the conditions of the channel, of a channel that extends between the sending and receiving stations are of good quality, the performance of the information between the sending and receiving stations can be increased by sending only a small number of the transmission series to the station receiver And, when the channel conditions are deficient, the successive, redundant transmission to the receiving station of the additional transmission series better guarantees that the information content of the digital information can be recreated with greater precision. The feedback signals that return from the receiving station to the transmitter indicate to the sending station that it implements the successive, redundant transmission of the series of additional transmissions for the receiving station.

BACKGROUND OF THE INVENTION A communication system is formed, at a minimum, by a transmitter and a receiver interconnected by a communication channel. The transmitter forms at least a part of the sending station, and the receiver forms at least a part of a receiving station. The communication signals transmitted by the sending station are transmitted in the communication channel to be received by the receiving station. The information contained in the communication signals transmitted by the sending station is recovered once received at the receiving station. In a digital communication system, the information that is going to be communicated to the receiving station is digitized. The digitized information is then used to form the communication signal. In some conventional digital communication systems communication signals are transmitted in bursts. The digital information blocks are communicated by the sending station to a receiving station during the transmission of the bursts through the communication channel. In a non-ideal communication system, the communication signal is distorted during its transmission in the communication channel. Due to this distortion, when the communication signal is received at the receiving station, the received signal differs somewhat from the communication signal transmitted from the sending station. If the communication channel is of poor quality, and the amount of distortion is significant, the informational content of the communication signal can not be adequately recovered at the receiving station. In a digital radio communication system, for example, distortion of multiple routes and Rayleigh are sometimes introduced into the communication signal as it is transmitted on the communication channel from the sending station to the receiving station. Different schemes have been developed to ensure that the informational content of the communication signal transmitted on a non-ideal channel can be recovered at a receiving station. Some of these schemes use a feedback array in which the receiving station returns a report to the sending station if the informational content of the received signal can be adequately recovered. Some of these schemes have been instrumented in a digital communication system in which the blocks of information are communicated in bursts. The receiving station determines whether a burst of the information block received at the receiving station is of an acceptable quality level. The indications of the determinations that form the feedback information are returned to the sending station by means of a feedback channel. The indication can also be communicated back to the broadcasting station implicitly. That is to say, the lack of transmission of feedback information from the receiving station to the station may indicate successful recovery of the information content of the digital information block. Or, the feedback information may be provided to the sending station in a different way by means of a direct feedback channel extending directly to the sending station. Otherwise, the indication can be communicated back to the sending station indirectly. For example, the sending station can measure the conditions of the channel and decide that the probability that the receiving station will successfully decode the digital information block will be so low that the retransmission of the digital information block would be justifiable. More simply, the receiving station simply detects if the burst of the received signal is of an acceptable quality level. If the signal quality level of the received signal burst is not good enough to allow retrieval of the informational content thereof, the receiving station simply requests the sending station to retransmit the digital information block in a subsequent burst. This scheme is sometimes called an ARQ scheme (automatic request). The retransmission of the digital information block can be repeated in successive burst until the digital information block is received at the receiving station with at least a minimum quality level. The receiving station makes the determination of the quality of the block received from the digital information in response, for example, to the detection of an error detection code, the recognition of the communication channel in which the information block is transmitted or another suitable scheme. The digital information block can also be transmitted using an error-protection code, such as the hybrid ARQ (Automatic Repeat Request) scheme, type I, a general channel decoding technique. When the receiving station receives the digital information block, the received block is decoded by a decoder to extract the information content of the received signal. A determination is made if the information content of the digital information block can be recovered with at least an acceptable quality level. Due to the protection against errors, the digital information block can be recovered even better if it is transmitted in a communication channel of reduced quality. In addition, if the decoder has the possibility to exploit, not only the received symbol values, but also the reliability information in the symbols, called soft information, the operation will be substantially increased. The decoder circuits in the receiving station capable of using the soft information are known as a soft input decoder. In some other schemes, such as the hybrid ARQ (Automatic Repeat Request) scheme of type II and type III, the blocks of digital information determined by the receiving station as corrupted, that is, of poor quality, are simply discarded. Instead, corrupted blocks are combined with blocks of digital information transmitted later. The information contained in previously transmitted blocks accumulates and forms the accumulated recognition. This accumulated recognition can be used to facilitate the recovery of blocks subsequently transmitted. By this means the "accumulated recognition" decreases the number of times in which the blocks of digital information must otherwise be retransmitted. The advantages of using the cumulative recognition allowed by the combination of successive retransmissions of the digital information blocks occurs with increased amounts of information contained in the digital information blocks.

This is advantageous as the probability of correcting the decoding generally increases if accumulated recognition is used during decoding better than if only the last retransmitted block is used. The decoder circuits in the receiving station capable of using soft information are known as soft input decoders. In another scheme, a sequence formed of other symbols created from the same block of digital information is transmitted. For example, if the first sequence is formed from an original series of parity symbols (possibly including uncoded information symbols of the digital information block) and the retransmission is requested, additional parity symbol numbers are transmitted by the station station in a retransmitted sequence. The receiving station accumulates the symbols received from different transmissions and the symbols accumulated during the different transmissions are used together during a decoding process. It is possible to perform a conventional block or low convolutional rate coding process to form a coded signal. Then, the encoded signal is "perforated". That is, the selected symbols of the coded block are marked so that they are not transmitted. Only the symbols "not perforated" that is, the symbols that have not been marked are transmitted. Although the encoded signal is weakened by transmitting only some of the encoded symbols, a higher effective coding rate for a given encoder structure is possible. If the informational content of the digital information block can not be recovered with a desired quality level from the symbols first received at the receiving station, additional coded portions of the signal are requested by the receiving station to be transmitted thereto. Some of the symbols previously perforated and not yet sent are then transmitted by the sending station to the receiving station. The receiving station uses previously transmitted symbols and newly transmitted symbols. If additional retransmissions are requested, still additional symbols are subsequently transmitted to the receiving station. This scheme is known as a successive redundancy transmission scheme. A successive redundancy transmission scheme designed to cope with adverse channel conditions, however, requires a complex decoding process to recover the informational content of the digital information block. And, if the digital information block is encoded using a convolutional coding scheme, the decoding necessary in a receiving station to decode the information is complex regardless of the amount of code drilling. When a punctured convolutional code is used, a series of received redundant symbols which, by themselves would cause a decoding error, still cooperate in the same way to counteract any error correction attempts supported by the additional redundant bits. When the channel conditions of the communication channel that extends between the sending and receiving stations are of poor quality, the conventional codes of moderate complexity do not work well. The higher complexity codes, which work well in these conditions, however, add complexity not necessary when the channel conditions are of good quality. That is, although complex coding is necessary when the channel conditions are of poor quality levels, this channel coding is not necessary when the channel conditions are of good quality levels. Therefore, a way by which adaptively selecting the complexity of the coding of a digital information block to be transmitted between a sending station and a receiving station would be advantageous. When the channel conditions are of good quality, only limited portions of an encoded signal would have to be transmitted to a receiving station to allow the retrieval of the informational content thereof. And when the channel conditions are of poor quality, additional portions of the encoded signal could be transmitted, to ensure that the informational content of the digital information block can be retrieved at the receiving station. In light of this prior information related to the digital communication systems is that the improvements of the present invention have been developed.

SUMMARY OF THE INVENTION Accordingly, the present invention advantageously provides the apparatus, and an associated method, by which a transmission string is formed consisting of at least portions of at least one coded version, concatenated in parallel, selected from a block of digital information between a transmitting station and a receiving station. When it is received at the receiving station, a determination is made to know if the informational content of the digital information block from which the transmission series is formed can be adequately recovered. The distortion introduced in the transmission series transmitted to the receiving station could prevent the receiving station from adequately recovering the informational content of the digital information block. If so, the receiving station requests the transmitting station to transmit another transmission series consisting of at least portions of at least one of the encoded, concatenated parallel versions, selected from the digital information block to the receiving station. Redundant, successive transmission of the series of additional transmissions is made to the receiving station if the informational content of the digital information block can not yet be adequately recovered.

The number of series of transmissions that are transmitted by the sending station will depend on the quality of the channel conditions that extend between the sending and receiving stations. When the channel conditions are of good quality, it will be necessary to transmit a smaller number of series of transmissions to allow the receiving station to recover the informational content of the digital information block. And, when the channel conditions are of poor quality, a greater number of series of transmissions are transmitted to guarantee that the receiving station can recover the informational content of the digital information block. By this means, when the conditions of the channel are of good quality, the rates of information performance improve and, when the conditions of the channel are of poor quality, the transmission of series of additional transmissions formed of portions of codified versions of the block of digital information facilitate the recovery of the digital information block. By this means, the complexity of the coding and decoding in the sending and receiving stations, respectively, is controlled in an adaptive manner.

In one aspect of the present invention, the sending station includes a concatenated encoder in parallel to form a plurality of encoded versions of a digital information block. A transmitter is selectively coupled to be provided with series of transmissions formed from at least selected portions of at least the selected encoded versions of the digital information block. The transmitters are operable to transmit the series of transmissions to a receiving station. A selector controls the formation of the series of transmissions and when the series of transmissions are provided to the transmitter. The selection by the selector responds to the indications as to whether the receiving station can adequately recover the digital information block from the digital information from the one or more series of transmissions, previously transmitted to the receiving station. When the channel conditions are of poor quality, the selector selects the series of additional transmissions to be transmitted by the transmitter to the receiving station. In another aspect of the present invention, the receiving station includes a parallel concatenated decoder coupled to receive at least the indications of the series of transmissions from the portions of the encoded versions of the digital information block transmitted to the receiving station by the sending station. . The parallel concatenated decoder decodes the encoded signal received at the receiving station and forms a decoded signal in response thereto. A determiner determines whether the decoded signal formed by the parallel concatenated decoder allows the recovery of the digital information block with at least the selected precision level. The requestor requests the transmitting station to transmit another series of transmissions formed from a selected portion of another encoded version, selected from the digital information block. In one embodiment, the present invention is incorporated into a cellular communication system that uses digital communications, such as a GSM communication system (Global System For Mobile Communications). When installed in the base station and mobile terminals operable in the cellular communication system, the operation of one embodiment of the present invention facilitates communication, downlink and uplink transmissions, between the base station and the mobile terminals. When the channel conditions are of good quality, the amount of coded data communicated between the base station and the mobile terminal is minimized, thereby increasing the throughput rates. And when the channel conditions are of poor quality, increasing amounts of encoded data are communicated between the mobile station and the mobile terminal, thereby facilitating the retrieval of the informational content of the transmissions. In these and other aspects, therefore, an associated method and apparatus, in an iterative and selective manner, increases the redundancy of a block of digital information communicated by a sending station to at least one receiving station in a digital communications system. A block of digital information is encoded, concatenated in parallel to form a plurality of encoded versions of the digital information block. At least one first selected portion of at least one encoded version selected from the plurality of encoded versions of the digital information block is transmitted from the sending station to the at least one receiving station. The iterative transmission of at least one second selected portion of at least one encoded version selected from the plurality of encoded versions of the digital information block from the sending mobile station to the receiving station is initiated if the recovery of the digital information block in the receiving station is not possible with at least one selected accuracy level. The second selected portion has at least one part that is different with the first selected portion of the at least one encoded, selected version.

A more complete appreciation of the present invention and the scope thereof may be obtained from the accompanying drawings which are briefly summarized below, the following detailed description of the presently preferred embodiments of the invention and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 illustrates a functional block diagram of a communication system in which an embodiment of the present invention operates. FIGURE 2 illustrates another functional block diagram of the communications system shown in FIGURE 1. FIGURE 3 illustrates a functional, block diagram of a parallel concatenated encoder that forms a portion of a station issuing a mode of the present invention. FIGURE 4 illustrates another functional block diagram of the parallel concatenated encoder shown in FIGURE 3. FIGURE 5 illustrates a functional block diagram of the operation of the decoder circuits of a receiving station of an embodiment of the present invention. in which the received sequences of the reception signal are decoded iteratively.

FIGURE 6 illustrates a functional block diagram of a parallel concatenated decoder forming a portion of a receiving station of an embodiment of the present invention. FIGURE 7 illustrates a flow diagram of the method illustrating the steps of the method of one embodiment of the present invention.

DETAILED DESCRIPTION FIGURE 1 illustrates a communications system, generally shown at 10, in which one embodiment of the present invention operates. Although the following description should be described with respect to an exemplary embodiment in which the communication system 10 forms a cellular communication system, it should be understood that this description is only by way of example. The communication system 10 is in the same way representative of other types of communication systems, both non-wired and wired. The embodiments of the present invention in the same way are operable in other types of communication systems. And, the operation of the different embodiments of the present invention can in the same way be described with respect to these other types of communication systems. The communication systems 10 include a transmitting station 12 and a receiving station 14 coupled by means of a communication channel 16. The exemplary operation of the communication system 10 must be described with respect to the transmission of a downlink transmission transmitted by the transmitting station 12 forming a radio base station to the receiving station 14 forming a mobile terminal. The operation may likewise be described with respect to the transmission of an uplink signal by a transmitting station forming a mobile terminal to a receiving station forming a radio base station. In exemplary mode, the communication system forms a digital communication system in which digital information blocks are transmitted in bursts between the sending station 12 and the receiving station 14. The sending station 12 receives, or generates, an information signal , shown in the present is formed by an information source 22. An information signal formed by the information source 22 is encoded by a source encoder 24. The source encoder, in one embodiment, digitizes and formats the information signal applied to it An encoded signal in the source encoder, with a format, generated by the encoder 24 is applied to the encoder of the channel 26. The channel encoder 26 encodes in the channel the signal applied to it in ways that must be described in more detail later with respect to FIGURES 3 and 4. In the exemplary embodiment, the channel encoder forms a parallel concatenated encoder that forms a plurality of encoded versions of digital information blocks provided thereto by the source encoder 24. The selected portions of the encoded versions, selected formed by the channel encoder 26 form series of transmissions that are selectively applied to a modulator 28. The selection of which portions of whose encoded versions formed by the channel encoder 26 form the series of transmissions and are provided to the modulator 28 is it does so by a selector 30. The selector 30 is formed of, for example, a processing device. The selector 30 is operable in response to the indications of the feedback information reported back to the sending station 12 by the receiving station 14. This feedback information is here received by the receiving circuits 32 of the sending station 12. The modulator 28 modulates the series of transmissions provided thereto by the channel encoder to allow transmission of the transmission string in the communication channel 16. Channel 16 in this case is shown including multiple numbers of tracks forming a multi-way communication channel . The scattering is introduced into the signal transmitted in the multi-channel channel by the sending station 12. Such distortion causes the signal received by the receiving station 14 to differ from that which is transmitted by the sending station 12. The receiving station 14 includes a demodulator 36 for demodulating the downlink signal received at the receiving station 14. The demodulator 26 generates demodulated signals that are applied to the channel decoder 38 which decodes the demodulated signal applied to it in a generally reverse fashion to that used by the encoder of channel 26 of the sending station 12. Further details of the operation of the encoder 38 should be described with respect to the description of FIGURES 5 and 6 below. The channel decoder generates a decoded channel signal that is provided to a source decoder 42 and a determiner 44. The source decoder 42 functions for the source decoding of a signal applied to it and for providing a decoded signal to a data acceptor of information 46. The determiner 44 operates to determine whether the channel decoder 38 has been able to decode the signal applied to the channel decoder 38 with at least one selected precision level. If a determination is made by means of the determiner 44 that the channel decoder has been able to adequately decode the signal applied to it, a request is generated by means of the transmit circuits 48 of the receiving station 14 to return the transmission to the sending station. The request requests the transmitting station to transmit another series of transmission. This indication is received by the receiver circuits 32 of the sending station 12. The selector 30 of the transmitting station 12 is provided with indications of the request and causes the channel encoder 26 to provide another transmission series to the modulator 28. The iterative transmission , redundant, successive of the series of additional transmissions can be realized by means of the sending station 12 to the receiving station 14, if necessary, to ensure that the receiving station 14 can recover the informational content of the digital information block. When a series of additional transmission is to be selected by the selector 30 of the transmitting station 12 to be transmitted to the receiving station 14, the newly selected transmission series, selected by the selector, differs from at least one, but not necessarily all , the series of transmissions previously transmitted with the corresponding information block, in an exemplary embodiment, the same transmission series may be retransmitted but not until at least another series of dissimilar transmission has been previously transmitted. It is said that two series of transmissions differ when they are formed by taking a different series of code bits from coded versions, possibly different from the code concatenated in parallel. Viz, the values of the symbol actually transmitted, transmitted with two series of different transmissions may be the same, but the positions and, possibly, the codes that constitute them of which they are formed differ for at least a number of the series. For example, a second transmission series must differ from the first transmission series. The third series of transmission must differ from the first series of transmission or the second series of transmission, but not necessarily from both transmission series previously transmitted. And, usually, since the second series must differ from the first series, and the third series can not match the first and second series simultaneously, the third series automatically meets the restriction. And, in this way, no other constraint is necessary for the third series of transmission. The series of transmissions subsequently transmitted can be analyzed in the same way. Therefore, the restriction on the selection of the transmission series is simply that the transmission series transmitted in the second place must differ from the series transmitted in the first place. These series are known as the second and first series of transmissions, respectively. FIGURE 2 again illustrates the communication system 10 and illustrates the feedback arrangement by means of which the receiving station 14 again reports to the sending station 12 requests to transmit an additional transmission string formed from an additional portion of the encoded versions, selected of a digital information block. The transmitting station 12 operates to transmit in a forward channel portion 16-1 a transmission series formed of at least a selected portion of at least one encoded version, selected from the digital information block. The receiving station 14 receives the transmission series formed from the at least the portion of the at least one encoded version of the digital information block, once transmitted in the portion of the advance channel 16-1. The receiving station 14 reports again by means of an inverse channel, in this case the feedback channel 16-2, when the informational content of the signal transmitted to the receiving station 14 can not be recovered with the selected accuracy level. The iterative transmission of additional portions of encoded versions, selected from the digital information block can be effected, if necessary, better to ensure that the receiving station 14 can recover the informational content of the data transmitted thereto. On the contrary, when the advance channel 16-1 is of a good quality level and the receiving station 14 can recover the informational content of the signal transmitted thereto, it is not necessary to transmit to the receiving station iterative, repeated transmissions of portions of encoded versions of the digital information block. By this means the performance rates of the information transfer between the sending and receiving stations 12 and 14 are improved. FIGURE 3 illustrates the channel encoder 26 which forms a portion of the sending station 12, as shown in FIGURE 1 The channel encoder 26 forms a concatenated encoder in parallel to form, in parallel, the plurality of encoded versions of a block of information symbols. For purposes of explanation, the digital information block is formed of a length of K information symbols I. Each block of length K of I-symbols is applied to N branches, in this case the branches 62-1, 62-2, ..., and 62-N, of the channel encoder 26. Each branch permutes the block of information symbols provided thereto by a separate permutation. Each branch 62-1 to 62-N includes a permuter 64-1, 64-2, ..., 64-N to perform these permutations. In general, the exchangers permute the block of information symbols to form N separate permutations of the symbol block provided to the encoder 26. A permutation performed by one of the branches may, for example, form a trivial identity permutation. The permuted symbol blocks formed by the switches 64-1 to 64-N are provided in each respective branch to a separate encoder, in this case the encoders 66-1, 66-2, ..., and 66-N. The encoders encode the permuted symbol blocks provided thereto. In the exemplary embodiment, each of the coders adds parity symbols to the permuted block provided thereto. And in one modality, the coders of each of the branches form systematic, constituent coding elements. The parity bits added by the encoders of the different branches may substantially correspond to each other in one embodiment, or they may differ from each other in another embodiment. A functional switching element 67 selectively passes select portions of the encoded versions formed in the different branches. The switching element is controlled by the selector 30 (as shown in FIGURE 1). If all the information symbols and all the parity symbols formed by the channel encoder 26 are provided to the modulator 28 (as shown in FIGURE 1) and transmitted, the next effective code rate, CR, for each symbol block It is as follows: K CR = K + ni + + nN where K: is the length of the block of information symbols, i; and n is the number of parity symbols added by each of the N branches of the encoder 26. FIGURE 4 again illustrates the channel encoder 26 shown in FIGURE 3. In the illustration of FIGURE 4 the branches 62 are shown. -1, 62-2, ..., and 62-N of an exemplary instrumentation of channel encoder 26. In branch 62-1, a separate 64-1 switch (shown in FIGURE 3) is not illustrated in separated as a trivial identity permutation is provided to the encoder 66-1. The switches 64-2 and 64-N are, however, illustrated separately in branches 62-2 and 62-N, respectively. Each of the encoders 66-1 to 66-N includes delay units 68 and summation elements 72 to form signals encoded in forms as described above with respect to FIGURE 3. And, the encoded signals formed by the encoder 66- 1 to 66-N are selectively coupled by means of the switching element 67, to the modulator 28 (shown in FIGURE 1). The switch element 67 is again shown controlled by the selections made by the selector 30 (as shown in FIGURE 1). During operation of one embodiment of the present invention, any portion selected from any one of the one or more encoded versions, selected from the symbol block formed by any of branches 62-1 to 62-N forms a transmission string that is provided to the modulator. In one embodiment, a complete coded version, formed by a single branch, forms a transmission series that is provided to the modulator. In other embodiments, selected portions of an encoded version form a transmission string that is provided to the modulator, and in other embodiments, the transmission string is formed of selected portions taken from different encoded versions generated by the different branches of the encoder 26. control over the selection is done by the selector 30 (again as shown in FIGURE 1). By way of example, in an exemplary embodiment, a transmission string formed from a first encoded version generated by the first branch 62-1 is first transmitted to the receiving station 14. If the receiving station 14 can not retrieve the informational content of the block from the transmission series transmitted thereto on the communication channel 16, a request is made for the transmitting station 12 to transmit additional information. The selector 30 causes a second transmission series formed of an encoded version of the symbol block to be transmitted to the receiving station. This procedure can be repeated iteratively, if necessary, if the receiving station 14 can not retrieve the informational content of the symbol block. By this means, when the conditions of the channel are of good quality, the performance of the information transmitted between the sending and receiving stations 12 and 14 can be increased to the maximum according to only minimum portions of a coded signal, concatenated in parallel must be transmitted to the receiving station. And, when the channel conditions are of poor quality, the additional encoded versions of the parallel concatenated code formed by the channel encoder 26 are transmitted to the receiving station, better to guarantee that the informational content of the symbol block can be recovered in the same. FIGURE 5 illustrates the operation of the exemplary decoder of the channel decoder 38 of the receiving station 14 when at least portions of the selected encoded versions of the symbol block are received at the receiving station. For purposes of illustration, the operation of the channel decoder 38 must be described with respect to the above-described embodiment in which all the encoded versions, formed by separate branches 62-1 through 62-N of the channel encoder are transmitted by the station 12 to the receiving station 14. In other embodiments, the analogous operation of the channel decoder can be described instead.

When a first transmission series is received at the receiving station 14, demodulated by the demodulator 36 and applied to the channel decoder 38, decoding of the first encoded version is performed, represented by the decoder in step 82. A determination is made , as indicated by the terminator 44 as to whether the retrieval of the informational content of the symbol block can be done in response to the first decoding step 82. If retrieval of the informational content of the symbol block can be performed properly, additional information pertaining to this block of symbols does not need to be transmitted by the sending station 12. However, if the retrieval of the informational content of the symbol block can not be effected successfully in response to the first decoding step 82, a request is made for the sending station transmit another series of transmission. A transmission series formed of a second encoded version of the symbol block is then transmitted to the receiving station 14, and the transmission series is decoded by a second decoding step, in this case the second coding step 86. The first and second decoding steps 82 and 86 are repeated Y number of times, as indicated by block 88. Then, determiner 44 again determines whether recovery of the informational content of the symbol block can be performed with a selected level of precision. If so, the transmission of the additional information belonging to this block of symbols does not need to be transmitted by the sending station. However, if the retrieval of the informational content of the symbol block can not be effected with the selected accuracy level, a request is made for the transmitting station 12 to transmit another transmission series formed from another encoded version of the symbol block. When this series of additional transmission is received at the receiving station 14 and demodulated by the demodulator 36, the third encoded version is decoded as indicated by the third decoding step 92. The three decoding steps 82, 86 and 92 can be repeated. a Z number of times, as indicated by block 94. Next, determiner 44 again makes a determination as to whether the informational content of the symbol block can be properly recovered. If so, the transmission of additional information is not needed. Otherwise, the transmission of additional encoded versions, without successive decoding steps of which the decoding step 96 is illustrative, are subsequently performed. When the conditions of the channel are of good quality and the recovery of the informational content of the block of symbols can be done by decoding only one or some series of transmissions, the processing necessary to recover the informational content of the block is reduced. And, when the channel conditions are of generally bad quality, series of additional transmissions are transmitted by the sending station to the receiving station, to ensure that the informational content of the symbol block can be recovered. FIGURE 6 illustrates the channel decoder 38 of one embodiment of the present invention. A block of received I 'symbols is provided to a first branch of the decoder 106-1. As illustrated, the channel decoder 38 includes a plurality of N decoder branches whose decoder branches 106-2 and 106-N are shown in the figure. Each of the branches of the decoder is coupled to receive the block of received systematic symbols. Again, the operation of the channel decoder must be described with respect to the mode in which all the encoded versions of the symbol block are transmitted between the sending and receiving stations. In other modalities, the analogous operation of the channel decoder 38 can be described in the same way. The block of received systematic symbols is provided to the first branch of the decoder 106-1. The received block is applied to a first switch 108-1. The switch 108-1 performs a process generally identical to that of the switch 64-1 shown in FIGURE 3. Next, the block of received, permuted, systematic symbols is provided to a decoder of the first branch 112-1. The decoder of the first branch 112-1 also receives indications of the parity bits that form at least part of the first coded vexsion of the symbol block formed by the channel coder 26, in this case indicated by the line 114-1. And, the decoder 112-1 also receives a-priori information that, initially, could have a zero confidence level associated with it. The decoder of the first branch operates to decode the block of received symbols corresponding to the first encoded version of the block of symbols transmitted thereto. When the decoding function has been terminated, a determination is made, in this case indicated by the successive query block 116. As to whether the decoding of the first modified version has allowed the retrieval of the informational content of the symbol block with when minus a selected accuracy level. If so, it is not necessary to transmit additional transmissions of coded versions added from the block of symbols. If the retrieval of the informational content of the symbol block can not be carried out satisfactorily, a request is made, as already indicated, for the transmitting station 12 to transmit another encoded version of the symbol block. If the transmission of the second coded version of the symbol block is necessary, the symbols of the second coded version are provided to the second branch of the decoder 106-2. The second branch of the decoder 106-2 also includes a switch, in this case 108-2 and a decoder of the second leg 112-2. These elements work in a similar way to their counterparts in the first branch of the decoder 106-1. The decoder of the second branch 112-2 is also coupled to receive indications of the parity bits that form at least part of the encoded version, in this case by means of the line 114-2 and to receive a-priori information generated by the decoder of the first branch 112-1. The decoders 112-1 and 112-2 alternately decode the first and second coded versions received from the symbol block, respectively, a selected number of times. Once the decoding functions have been completed in the decoder of the second branch 112-2, a determination is made, as indicated by the block 116 as to whether this decoding allows the retrieval of the informational content of the symbol block. If the informational content can be retrieved with at least one selected accuracy level, additional transmissions by the sending station to the receiving station of this symbol block are not necessary. Otherwise, another request is generated for the transmission of another encoded version of the symbol block. As illustrated, the channel decoder 38 includes N branches of the decoder that allow up to N number of encoded versions to be decoded. An Nth branch of decoder 106-N is also illustrated in the figure. The nth branch of the decoder also includes an umpteenth switch 108-N and the nth decoder 112-N. The decoder 112-N is further coupled to receive indications of the parity bits that form at least part of the nth coded version provided by the channel encoder 26. And, the decoder 112-N is also coupled to receive information a- priori generated in response to the preceding decoding steps. A determination is also made as to the success of the recovery of the informational content of the block of symbols transmitted by means of the determiner 116., as it can be by performing the decoding process a selected number of times. In this way, if the conditions of the channel are of good quality and the retrieval of the informational content of the symbol block can be recovered in response to the reception of one or some encoded versions of the symbol block, it is possible to maximize the performance of the information transferred between the sending and receiving stations. And, when the channel conditions are of poor quality, the informational content of the symbol block will most likely be recovered in response to the transmission of the additional encoded versions of the symbol block. The parallel concatenated encoder forming the channel encoder 26 can be considered for constructing a number of transmission series. Each transmission series consists of any selected number of information symbols and symbols from any number of parity settings Pp ±. Although not necessarily so, in one embodiment, the intersection between any two transmission settings forms an empty set. The dimension of a transmission setting is defined as the number of parity settings (or, equivalently, the number of constituent codes) that has contributed to the particular transmission settings. In an analogous way, the dimension of the union between any number of transmission settings is the number of parity settings (constituent code) that has contributed to the union of the transmission settings. The first transmission setting is transmitted by the sending station 12 to the receiving station 14. Once the transmission setting is received at the receiving station and provided to the decoder 38, decoding of the transmission setting is performed. The first transmission setting is decoded by the first decoding branch 106-1. The N number of branches of the decoder corresponds to the number of dimensions of the first transmission setting. Again, as shown in Figure 6, it is possible to use a-priori information. { aL (ü) 1e} , if available, to facilitate decoding in the decoder of the first branch 106-1. The iteration of the decoding of the first transmission adjustment is performed a selected number of times, in this case on the iteration variable, until some interruption criterion is met. The success of the decoding is then evaluated, as indicated in the Figure by block 116. In order to determine the success of the decoding, in the information set it is possible to use, for example, an embedded error detection code. Or, to perform such evaluation it is possible to estimate the number of decoded bit errors, expected, using the soft, inherent, currently available information. In another embodiment, the success of the decoding of the first transmission setting is not evaluated at this time. In contrast, the decoding of any external error correction code is performed before the evaluation is made. If it is determined that the resulting setting is reliable, additional transmissions are not necessary and other operations may be performed on the receiving apparatus. Otherwise, the receiving station 14 reports feedback information back to the sending station 12 that the decoding of the first transmission setting was not successful. If the decoding was not successful, the transmitting station 12 then transmits another transmission setting, the following one, to the receiving station 12. The channel decoder 38 decodes the additional transmission setting using any number of symbols from the junction of the two received, available transmission sets, where N is equal to the dimension of the total set of symbols used. The order of the decoding of the constituent codes, or even the basic structure of the decoding can differ between two decodings. In an embodiment of the present invention, the sending station 12 initiates a second transmission, or later, without explicit feedback information returned to the sending station by the receiving station. In contrast, the sending station 12 passes a decision to start the additional transmission on an independent criterion, for example, the availability of the channel bandwidth 16 or a stopwatch. If the availability of the bandwidth is the criterion, the transmitting station 12 automatically transmits a new transmission setting corresponding to the block of information symbols if there is a channel 16 available and no other transmission setting (or higher priority) awaits the transmission. transmission. If the expiration of a chronometer forms the criterion, the transmitting station 12 automatically transmits the new transmission setting if it has not received an acknowledgment, for example, due to the loss of feedback information, within a set period of time after sending. a pre-transmission setting corresponding to the block of information symbols. The iterative transmission and the decoding process continue until the block of information symbols has been successfully received or discontinued due to the inability of the receiving station to reach an acceptable result within, for example, a set period of time or a limit of retransmission account. In an implementation of one embodiment of the present invention, each transmission setting consists only of parity bit information taken from a specific constituent code, a different code for each transmission setting. By this means, the dimension for each of the transmission settings is a dimension of one. Also, at the receiving station 12, the received connection of the transmission settings has a dimension that increases by one for each transmission. In this way, the complexity of the decoder increases from transmission to transmission in the sense that exactly one more constituent decoder is needed each time a transmission adjustment has been received, producing a gradual increase in the complexity of the decoder. In another embodiment of one embodiment of the present invention, each transmission setting consists of symbols of all, e.g., N, constituent codes. The dimension of the transmission set therefore is equal to N. Therefore, the channel decoder 38 will always need N ramifications of constituent encoders, producing a higher, fixed decoder complexity in the sense of the number of constituent decoders. However, possibly fewer transmissions and / or fewer iterations of the decoding in the decoding structure may be necessary as the higher dimension code, supposedly resulting in better error correction capabilities than a smaller dimension code. FIGURE 7 illustrates a method, generally shown at 132, of one embodiment of the present invention. The method iteratively and selectively increases the redundancy of a digital information block communicated by a sending station to at least one receiving station in a digital communications system. First, as indicated in block 134, the digital information block is encoded, concatenated in parallel, to form a plurality of encoded versions of the digital information block. Then, as indicated in block 136, at least a selected portion of at least one first encoded version, selected from the plurality of encoded versions of the digital information block is transmitted from the sending station to the receiving station. And, as indicated in block 138, the transmission of at least a selected portion of at least one additional version of the plurality of encoded versions is initiated if the recovery of the digital information block in the receiving station is non-recoverable with at least a selected level of precision. By the operation of one embodiment of the present inventionWhen the channel conditions of a channel extending between the sending and receiving stations are of good quality, it is possible to maximize the performance of the information between the sending and receiving stations. And, when the channel conditions are of poor quality, redundant, successive transmission of additional portions of the encoded, selected versions guarantee that the informational content of the digital information can be accurately recreated. The feedback signals returning from the receiving station to the transmitter indicate to the sending station that it implements the redundant, successive transmission of additional portions of encoded versions, selected to the receiving station. The above descriptions are of the preferred examples for carrying out the invention, and the scope of the invention is not necessarily limited by this description. The scope of the present invention is defined by the following claims.

Claims (24)

1. A method for iteratively and selectively increasing the redundancy of a digital information block communicated by a sending station to at least one receiving station in a digital communications system, the method comprises the steps of: coding the information block concatenated in parallel digital to form a plurality of encoded versions of the digital information block; transmitting at least one selected first portion of at least one encoded version, selected from the plurality of encoded versions of the encoded digital information block during the encoding step from the sending station to the receiving station; and initiating the transmission of a second selected portion of at least one encoded version, selected from the plurality of encoded versions of the digital information block from the sending station to the receiving station if the digital information block in the receiving station is not retrievable with at least one selected precision level, the second portion having at least one part being selected that is different with the first selected portion transmitted during the transmission step. The method of claim 1, wherein the step of initiating transmission consists in sending a request from the receiving station to the transmission station to transmit the at least one additional version of the digital information block. The method of claim 1, wherein the at least one selected portion of the selected, at least one, encoded version transmitted during the transmission step comprises the entire selected, coded version. The method of claim 1, wherein the at least selected portion of the at least selected first encoded version transmitted during the transmission step contains a selected portion of the first encoded version, selected and a selected portion of at least a second encoded version, selected from the plurality of encoded versions. The method of claim 1, comprising the additional step, subsequent to the transmission step, of: determining whether the recovery of the digital information block in the receiving station with at least one selected accuracy level that is possible. The method of claim 5, wherein the step of determining comprises the iterative decoding of at least the selected portion of the at least selected first encoded version transmitted during the transmission step. The method of claim 6, wherein the iterative decoding step comprises the concatenated decoding in parallel of the at least the selected portion of the at least the first encoded version, selected from the digital information block. The method of claim 6, wherein the iterative decoding step comprises the iterative decoding of the at least the selected portion of the at least the first encoded version, selected, a selected number of times. The method of claim 8, wherein the selected number of times during which the least selected portion of the at least first coded, selected version is iteratively decoded, is selected to allow convergence of the decoding within a range selected of allowable values. The method of claim 1, wherein the plurality of encoded versions in which the digital information block is encoded during the parallel concatenated coding step consists of an N number of encoded versions. The method of claim 10, wherein the coding step concatenated in parallel to form the N number of encoded versions comprises permutation of the digital information block at an N number of permutations to form the N permutations. 1

2. The method of claim 11, wherein the coding step concatenated in parallel consists of block coding of each of the N permutations of the digital information block. The method of claim 12, wherein each of the N permutations of the digital information block encoded during the parallel concatenated coding step are encoded by a systematic, constituent encoder. The method of claim 1, wherein the at least selected portion of the at least one version of the plurality of encoded versions of which the transmission thereof is initiated during the initiation step of the transmission comprises all of the at least one version of the plurality of encoded versions of the digital information block. The method of claim 1, wherein the at least the selected portion of the at least one version of the plurality of encoded versions, of which the transmission thereof is initiated during the initiation step of the transmission comprises a selected portion of a first version of the plurality of versions and a selected portion of at least one second encoded version, selected from the plurality of encoded versions. 16. The method of claim 1, wherein the digital communication system comprises a digital multiple access communication system. The method of claim 16, wherein the digital, multi-access communication system uses time division as part of a multiple access protocol. The method of claim 16, wherein the digital, multi-access communication system uses code division as part of a multiple access protocol. The method of claim 16, wherein the digital multiple access communication system uses frequency division as part of a multiple access protocol. The method of claim 1, wherein the digital communication system comprises a digital radio communication system. The method of claim 20, wherein the digital radio communication system is a digital cellular radio communication system. 22. The method of claim 20, wherein the digital radio communication system constitutes the radius of a radio in the local circuit system. The method of claim 20, wherein the digital radio communication system comprises a microwave radio link. The method of claim 20, wherein the digital radio communication system comprises a digital radio communication satellite system. The method of claim 1, wherein the digital communication system includes a digital control channel in an analog communication system. 26. The method of claim 1, wherein the parallel concatenated coding step comprises the convolutional coding of the digital information block. The method of claim 26, wherein the convolutional coding step is performed by convolutional encoders concatenated in parallel, at least two of the convolutional encoders concatenated in parallel using polynomials generating virtually identical values. 28. The method of claim 26, wherein the parallel concatenated coding step uses a "turbo" code. 29. The method of claim 1, wherein the parallel concatenated coding step comprises the block coding of the digital information block. 30. The method of claim 1, wherein at least two of the encoded versions of the digital information block are formed using practically identical codes. 31. A method for communication of a bit sequence between a sending station and a receiving station, the method comprising the steps of: encoding, in the sending station, the bit sequence according to a coding technique concatenated in parallel to forming a plurality of concatenated code portions in parallel; transmitting at least one selected part of at least one first portion of code concatenated in parallel, selected to the receiving station; decoding, according to a concatenated decoding technique in parallel, the at least the selected part of the at least the first coded portion concatenated in parallel after reception of the at least the selected part of the at least the first coded portion concatenated in parallel to the receiving station; determining whether the bit sequence is recoverable with a precision level selected from at least the selected part of the at least the first portion of code concatenated in parallel, selected after decoding it during the coding step; transmitting at least one selected part of at least one coded portion concatenated in parallel, additional to the receiving station if it is determined that the bit sequence, during the determination step, will not be recoverable with the selected accuracy level; and if it is transmitted, then decoding, according to a concatenated decoding technique in parallel, the at least selected part of at least one coded portion, concatenated in parallel, additional after receiving it at the receiving station. 32. The method of claim 31, wherein the coding technique concatenated in parallel forms N number of code portions concatenated in parallel. The method of claim 32, wherein the coding step of the bit sequence to form the N number of code portions concatenated in parallel consists of permutation of the bit sequence into an N number of permutations to form N permutations. 34. The method of claim 33, wherein the coding step comprises block coding of each of the N permutations of the bit sequence. 35. The method of claim 34, wherein each of the N permutations of the block of the coded bit sequence during the block coding step are dissimilar. 36. The method of claim 35, wherein each of the N permutations of the block of the bit sequences encoded during the block coding step is coded en bloc by a systematic, constituent encoder. 37. The method of claim 31, wherein the decoding step of the at least the selected part of the at least the first code portion concatenated in parallel comprises the iterative decoding of the at least the selected part of the at least first portion of code concatenated in parallel a selected number of times, using each iteration of the decoding a-posteriori information obtained during the iteration of the preceding decoding. 38. In a digital communication system having a sending station for sending a block of digital information to at least one receiving station, a combination with the sending station of the apparatus for iteratively and selectively increasing the redundancy of the digital information block, the apparatus consists of: a parallel concatenated encoder coupled to receive the digital information block, the concatenated encoder in parallel to encode the digital information block to form a plurality of encoded versions of the digital information block; a transmitter selectively coupled to receive the at least selected portions of the plurality of encoded versions of the digital information block encoded by the parallel concatenated encoder, the transmitter for transmitting the at least selected portions of the least selected ones of the plurality of encoded versions and provided to it; a selector coupled to control which of the at least selected portions of the least selected ones of the plurality of encoded versions are provided to the transmitter, the selector to select a portion of at least one first encoded version, selected from the digital information block to be provided to the transmitter and then to select at least the selected portions of at least one additional encoded version of the digital information recovery block of the Information block in the receiving station is indicated to be non-recoverable with at least one selected accuracy level [sic]. 39. In a digital communication system having a receiving station for receiving a block of digital information transmitted thereto by a transmitting station in coded form and formed from at least a selected portion of at least one encoded version, selected from the block of digital information, a combination with the receiving station of the apparatus for recreating the digital information block, the apparatus consists of: a parallel concatenated decoder coupled to receive at least indications of the block of digital information transmitted to the receiving station in the encoded form , and to form a second signal in response to it; a determinator operable in response to the decoded signal formed by the parallel concatenated decoder, the determiner for determining whether the decoded signal formed by the parallel concatenated decoder allows the recreation of the digital information block with at least one selected precision level; and a requestor operable at least in response to the determinations by the determiner that the decoded signal formed by the parallel concatenated decoder does not allow the recreation of the digital information block with the at least selected accuracy level, the requestor to request the sending station for transmitting a selected portion of another encoded version, selected from the digital information block. 40. A method for communicating a sequence of symbols between a sending station and a receiving station, the method comprising the steps of: encoding concatenated in parallel of the sequence at the sending station to form a plurality of coded portions in parallel, each coded portion in parallel with a selected number of code symbols; forming a selected number of transmission sets, each transmission set having at least a selected number of selected code symbols from at least one of the parallel coded portions formed during the parallel concatenated coding step, at least one of the sets of transmission of a dissimilar value to the values of other transmission sets; transmitting a first transmission assembly of the transmission sets formed during the training step to the receiving station; and selectively transmitting at least one additional transmission assembly of the transmission assemblies formed during the formation step, the at least one additional transmission assembly including the at least one additional transmission assembly of a value dissimilar to the value of the first transmission assembly transmitted. 41. The method of claim 40, comprises the additional step of detecting, at the sender station, indications by means of the receiving station of the acceptable recovery of the symbol sequence in response to reception at the receiving station of at least the first transmission set, and wherein the at least one additional transmission set is transmitted during the step of selectively transmitting absent detection for at least one period selected during the step of detecting the indications for acceptable recovery of the symbol sequence.