Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
  • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
  • H03M13/03—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words
  • H03M13/23—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using convolutional codes, e.g. unit memory codes
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
  • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
  • H03M13/29—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes combining two or more codes or code structures, e.g. product codes, generalised product codes, concatenated codes, inner and outer codes
  • H03M13/2957—Turbo codes and decoding
  • H03M13/2996—Tail biting

Definitions

• This invention pertains to convolutional coding, with particular but nonexclusive application to telecommunications.
• Detection of loss or inaccurate transmission of data over a channel is possible when certain additional information in the form of an error detection code is added to the data stream.
• an error detection code in the form of (for example) a check character(s) or check sum which is computed or otherwise derived from the block.
• the receiver can independently recompute or re-derive the error detection code (e.g., the receiver's version of the check character(s) or check sum). If the recomputed or re-derived error detection code (e.g., check sum) is the same as the error detection code included in the received block or frame, the receiver can confirm that the block or frame is correctly decoded.
• error correcting techniques are also known. For example, error correction codes (generated by polynominals that operate over a frame or block of user data) can also be added to the data stream. Upon reception of the complete frame or block, using the known error correction code/technique the receiver can locate and correct certain errors in the data stream.
• error correction codes generated by polynominals that operate over a frame or block of user data
• a convolutional code is a forward error-correction scheme, whereby the coded sequence is algorithmically achieved through the use of current data bits plus some of the previous data bits from the incoming stream.
• a convolutional code is a type of error-correcting code in which (a) each m-bit information symbol (each m-bit string) to be encoded is transformed into an w-bit symbol, where mln is the code rate (n > m) and (b) the transformation is a function of the last k information symbols, where k is the constraint length of the code.
• a trellis description of a convolutional encoder shows how each possible input to the encoder influences both the output and the state transitions of the encoder.
• a convolutional code is called tail-biting (or circular) if the beginning state of its encoding trellis is always equal to the ending state of its encoding trellis after encoding.
• Tail-biting convolutional codes are simple and powerful forward error correction (FEC) codes, as described, e.g., in H. H. Ma and J. K. Wolf, "On tail biting convolutional codes," IEEE Trans. Commun., vol. 34, pp. 104-1 1 1, Feb. 1986.
• Tail-biting convolutional codes are employed in many environments, including telecommunication networks having an air, radio, or "wireless" interface.
• Tail-biting convolutional codes have been adopted as the mandatory channel codes for the data channels and the overhead channels (like frame control header) in 802.16 WiMAX (Worldwide Interoperability for Microwave Access) system.
• 802.16 WiMAX is described, e.g., in IEEE Std 802.16-2004, "IEEE Standard for Local and Metropolitan Area Networks - Part 16: Air Interface for Fixed Broadband Wireless Access Systems", October, 2004; and IEEE Std P802.16e-2005, "IEEE Standard for Local and Metropolitan Area Networks - Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems", February, 2006, both of which are incorporated herein by reference. They have also been adopted as the channel codes for the header channel in the EDGE system and for the control channel in the IS-54 system. For a description of the EDGE system, see, e.g., M. Mzyece and J.
• LTE Long-Term Evolution
• E-UTRA Evolved Universal Terrestrial Radio Access
• Multiplexing and channel Coding (Release 8)", V8.0.0, 2007-09, e.g., which is incorporated herein by reference).
• tail biting convolutional codes comprise one class of error correction codes, which adds redundancy bits to the information bits (information bits and redundancy bits together is called one codeword) for error correction.
• Uj is the input bit at time i
• (Vj (0) ,..., ⁇ ⁇ n'l) ) are the n output bits at time i.
• G (go,...,g n -
• a convolutional code is called tail-biting (or circular) if the beginning state of its encoding trellis is always equal to the ending state of its encoding trellis after encoding.
• the beginning state is simply determined by the last v number of input bits, where v is the overall constraint length.
• the encoder structure has to comply with certain conditions so that the circular encoding is possible.
• the beginning state also called the circular state
• the beginning state of the encoding trellis is determined from the input information bit vector. That is, the beginning state is not always equal to the all-zero state and depends on the values of the input bits.
• ZTCC zero-tail convolutional codes
• the beginning state and the ending state are always equal to the all-zero state, and v number of redundant zero-tail bits are needed to return the encoder to the all-zero state.
• FIG. 2 An example encoder for the 802.16 Tail-biting convolutional codes (TBCC) is shown in Fig. 2.
• the adder A g0 for the first polynomial g 0 is connected to receive the bit values from the first through fourth positions and the seventh position of the shift register chain of Fig. 2
• the adder A g) for the second polynomial gi is connected to receive the bit values from the first, third, fourth, sixth, and seventh positions of the shift register chain of Fig. 2.
• the more compact octal notation is typically used herein to represent the generator polynomials.
• Tail-biting convolutional codes (TBCC) over the conventional zero-tail convolutional codes (ZTCC) and some block codes. Two example advantages are listed below:
• ZTCC zero-tail convolutional codes
• TBCC Tail- biting convolutional codes
• Performances of convolutional codes are determined by the generator polynomials and the resulting weight spectrum, and the constructions of convolutional codes (CC) with good weight spectrum are usually done by extensive computer searches (as described, e.g., in references [2]-[9], listed hereinafter).
• d f is the free distance (or the minimum distance d min )
• n d is the number of codewords with weight d
• b d is the total number of nonzero information bits associated with codewords with weight d.
• Each triple (d,n ⁇ j,b d ) is called a line in the weight spectrum. If a convolutional code (CC) does not have a weight-d
• CC convolutional code
• CC convolutional codes
• FER decoder frame error rate
• BER bit error rate
• CC convolutional codes
• MFD codes are useful when the E 1 JN 0 value is so large (i.e., over the very high SNR region) that only the d f term (the first line in the
• FER or BER (See, reference [4] , listed hereinafter)
• a Convolutional Code (CC) C is called ODS-FER code (or ODS-BER code) if it has a superior FER (or BER) distance spectrum than another code with the same code rate R and overall constraint length v.
• an ODS code is always an MFD code, but not vice versa.
• two MFD codes C and C with the same (d f ,n df ,b df ) may have quite different lines (d,n d ,b d ) for d>d f , and have different performances. Therefore, from the performance perspective, the ODS criterion should be used to find good convolutional codes (CC).
• ZTCC zero-tail convolutional codes
• Tail-biting convolutional codes are usually very different than those of zero-tail convolutional codes (ZTCC) with the same generator polynomials, especially for short and medium-length encoder packets.
• ZTCC zero-tail convolutional codes
• the optimum generator polynomials for either the MFD or the ODS criterion
• the optimization (or selection) of the Tail-biting convolutional codes (TBCC) generator polynomials needs to be done for each packet length.
• Tail-biting convolutional codes are used by major wireless systems like EDGE, WiMAX and LTE.
• the generator polynomials of TBCC used by these systems are taken from the MFD zero-tail convolutional codes (ZTCC) or ODS zero-tail convolutional codes (ZTCC) and are not the optimum ones for Tail- biting convolutional codes (TBCC). This is mainly due to the unavailability of Tail- biting convolutional codes (TBCC) search results at the time when the corresponding standards were written.
• the technology disclosed herein concerns a method of generating a set of generator polynomials for use as a tail biting convolution code to operate on data transmitted over a channel.
• the method comprises: (1) selecting valid combinations of generator polynomials to include in a pool of potential codes, each valid combination being a potential code; (2) determining first lines of a weight spectrum for each potential code in the pool and including potential codes of the pool having best first lines in a candidate set; (3) determining best codes of the candidate set based on the first L number of lines in the weight spectrum; (4) selecting an optimum code(s) from the best codes; and (5) configuring a shift register circuit(s) of a data transceiver to implement the optimum code(s).
• Optimum code(s) generated by the methods described herein can be expressed by a set of polynomials which are listed in Tables and/or stored in a memory.
• the method further comprises using a free distance parameter and a multiplicity parameter for selecting the optimum code(s) from the best codes.
• the method further comprises using a free distance parameter and a bit multiplicity parameter for selecting the optimum code(s) from the best codes.
• the technology disclosed herein concerns a node of a communications network which participates in data transmissions over a channel.
• the node comprises a transceiver for sending and receiving data over the channel and a shift register circuit configured to implement an optimum tail biting convolutional code for operating on the data transmitted over the channel.
• the optimum code can be expressed by a set of polynomials listed in Tables described herein and generated by acts of the afore-summarized method.
• the node further comprises plural shift register circuits and a code activator.
• Each of the plural shift register circuits is configured to implement a respective different one of plural optimum tail biting convolutional codes, each of the plural optimum tail biting convolutional codes being of a different rate and being expressed by a set of polynomials listed in any of several tables described herein.
• the code activator is configured to include one of the plural shift register circuits in a processing stream for a respective data transmission over the channel.
• the technology disclosed herein concerns a method of operating a node of a communications network.
• the method comprises configuring a shift register circuit of the node to implement an optimum tail biting convolutional code expressed by a set of polynomials listed in any one of certain tables described herein; and using the optimum tail biting convolutional code to operate on data transmitted over a channel of the communications network.
• the shift register circuit can be configured in accordance with the optimum code either to function as an encoder to append error correction information to data transmitted over the channel.
• the technology disclosed herein concerns a code generator comprising a computer which executes a computer program comprising instructions stored on a computer-readable medium, and a method performed by the execution. Execution of the instructions of the program results in performance of the acts of: (1) selecting valid combinations of generator polynomials to include in a pool of potential codes, each valid combination being a potential code; (2) determining first lines of a weight spectrum for each potential code in the pool and including potential codes of the pool having best first lines in a candidate set; (3) determining best codes of the candidate set based on the first L number of lines in the weight spectrum; (4) selecting an optimum code(s) from the best codes; and (5) outputting an identification of the optimum code(s).
• the technology disclosed herein optimizes the performances of Tail-biting convolutional codes (TBCC) over short to medium-length encoder packets, codes with the best distance spectrum (ODS-FER codes or ODS-BER codes) being searched and tabulated.
• TBCC Tail-biting convolutional codes
• ODS-FER codes or ODS-BER codes codes with the best distance spectrum
• only the feedforward encoders are considered.
• the technology concerns ODS-FER and ODS-BER TBCC codes with short to medium-length encoder packets.
• Fig. 1 is a diagrammatic view of encoder structure of a rate 1/n feedforward convolutional code with constraint length v.
• TBCC Tail-biting convolutional codes
• Fig. 3 is a diagrammatic view of portions of a communication network including a base station and a wireless station which communicate data over a channel using an optimized tail biting convolutional code.
• Fig. 4 is a flow chart showing basic, representative acts or steps which comprise a method of code determination according to the technology disclosed herein.
• Fig. 5 is a flow chart showing basic, representative acts or steps which comprise a method of code determination and utililization according to the technology disclosed herein.
• Fig. 6 is a diagrammatic view of a portion of a wireless station including a wireless station coder according to an example embodiment.
• Fig. 7 is a diagrammatic view of a portion of a base station node including a base station coder according to an example embodiment.
• Fig. 8 is a diagrammatic view of a portion of a wireless station including a wireless station coder according to another example embodiment.
• Fig. 9 is a diagrammatic view of a portion of a base station node including a base station coder according to another example embodiment.
• processors may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software.
• the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared or distributed.
• explicit use of the term "processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may include, without limitation, digital signal processor (DSP) hardware, read only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage.
• DSP digital signal processor
• ROM read only memory
• RAM random access memory
• Fig. 3 shows portions of an example communications network, particularly a communications network portion which includes, as two of its nodes, base station 28 and wireless station 30.
• base station 28 and wireless station 30 communicate with each other over a channel which exists on or over a network interface, which interface happens in the example of Fig. 3 to be a radio or air interface 32.
• the channel can be provided over a network interface which is other than wireless, e.g., a wired interface, for example.
• at least some of the data which is transmitted over network interface 32 is encoded using an optimized tail biting convolutional code.
• the optimized tail biting convolutional code is generated by optimized tail biting convolutional code generator 40 using methods described herein with reference, for example, to Fig. 4.
• at least some of the data transmitted over network interface 32 on a downlink from base station 28 to wireless station 30 is encoded using the optimized tail biting convolutional code by base station 28, and therefore is decoded using the optimized tail biting convolutional code upon receipt by wireless station 30.
• at least some of the data transmitted over network interface 32 on an uplink from wireless station 30 to base station 28 is encoded using the optimized tail biting convolutional code by wireless station 30, and therefore is decoded using the optimized tail biting convolutional code upon receipt by base station 28.
• Fig. 3 further illustrates certain units or functionalities comprising base station 28.
• base station 28 On its downlink side, base station 28 comprises base station downlink data buffer 50, base station error correction encoder 52; an optional base station interleaver 56; base station modulator 58; and base station transceiver(s) 60.
• base station 28 On its uplink side, base station 28 comprises base station demodulator 62; an optional base station de- interleaver 64; base station error correction decoder 66; and base station uplink data buffer 68.
• the base station 28 further comprises base station node controller 70, which in turn comprises (among other functionalities or units) base station scheduler 72.
• the base station scheduler 72 includes, among other entities or functionalities, TBCC code selector 74.
• Fig. 3 also illustrates certain units or functionalities comprising wireless station 30.
• the wireless station 30 executes, via a controller or the like, certain applications (e.g., application programs 76).
• wireless station 30 On its uplink side, wireless station 30 comprises wireless station uplink data buffer 80, wireless station error correction encoder 82; an optional wireless station interleaver 84; wireless station modulator 86; and wireless station transceiver(s) 90.
• wireless station 30 On its downlink side, wireless station 30 comprises wireless station demodulator 92; an optional wireless station de-interleaver 94; wireless station error correction decoder 96; and wireless station uplink data buffer 98.
• the air interface 32 further comprises wireless station controller 100, which in turn comprises (among other functionalities or units) TBCC code requestor 104.
• Fig. 3 shows by arrow 106 the loading of the optimized tail biting convolutional code into base station error correction encoder 52 and base station error correction decoder 66.
• Fig. 3 also shows by arrow 108 the loading of the optimized tail biting convolutional code into wireless station error correction encoder 82 and wireless station error correction decoder 96.
• the same optimized tail biting convolutional code is loaded into the encoders and decoders of both base station 28 and wireless station 30.
• the "loading" of the optimized tail biting convolutional code into an encoder can involve the configuring of shift register circuit(s) which comprise the encoder(s).
• the technology disclosed herein concerns a method of generating a set of generator polynomials for use as a tail biting convolution code to operate on data transmitted over a channel.
• the technology disclosed herein comprises an efficient method for computing a weight spectrum of Tail-biting convolutional codes (TBCC).
• TBCC Tail-biting convolutional codes
• the method of the technology disclosed herein is a modified version of an approach for computing a turbo code weight spectrum (See, reference [7], listed hereinafter).
• the method of generating an optimized tail biting convolutional code can be performed by a unit such as the optimized tail biting convolutional code generator 40 shown in Fig. 3.
• the optimized tail biting convolutional code generator 40 can be realized by (e.g., implemented using) a computer or processor which executes a computer program comprising instructions stored on a computer-readable medium.
• the basic, representative acts or steps for finding the ODS-FER TBCC codes and ODS- BER TBCC codes are illustrated in Fig. 4 and described as follows: [0061]
• Act 4-1 comprises selecting valid combinations of generator polynomials to include in a pool of potential codes, each valid combination being a potential code.
• Act 4-2 comprises an initial search for best first lines of weight spectrum for building of a candidate set.
• act 4-2 comprises determining first lines of a weight spectrum for each potential code in the pool, and including potential codes of the pool having best first lines in a candidate set.
• the first line of the weight spectrum (the first line being the minimum distance terms (d r ,n df ,b d r)) for each valid combination (e.g., valid set) of polynomials from act 4-1 is computed, and the best ones (e.g., the best first lines) in terms of MFD-FER (or MFD- BER) are put into a set know as the candidate set.
• the Tail-biting convolutional codes (TBCC) codes in the candidate set are actually MFD-FER TBCC (or MFD-BER TBCC).
• Act 4-3 comprises a detailed search to find the best codes of the candidate set based on the first L number of lines of the weight spectrum.
• the first L number of lines of the weight spectrum, ⁇ (d,n d ,b d ): d ranges from the first L codeword weights beginning from d f ⁇ , are computed for all codes in the candidate set obtained from act 4-2.
• the best codes in terms of ODS-FER (or ODS-BER) are selected, and the resulting sets are ODS-FER TBCC (or ODS-BER TBCC).
• the code (or the set of generator polynomials) with the largest free distance d f will be selected.
• Condition 1 If a new set of valid generator polynomials (whose weight spectrum is to be computed) G 1 is equivalent to an existing set of generator polynomials G2 in the candidate set in the sense of weight spectrum, then the computation for the weight spectrum of Gl can be skipped. This condition can be detected by checking if the generator matrix of Gl can be obtained from the generator matrix of G2 by column permutation operations and/or row permutation operations (See, e.g., reference [9], listed hereinafter). The same rule can be applied to act 2-3.
• Condition 2 During the computation of the weight spectrum for a new set of valid generator polynomials Gl , if Gl has inferior FER (or BER) distance spectrum than that of any existing set of generator polynomials G2 in the candidate set, then the computation can be stopped early and Gl will not be included in the candidate set. The same rule can be applied to act 2-3.
• G 1 can refer to a valid set of polynomials that survive act 4-1 and G2 can refer to one set of generator polynomials in the candidate set (who survive act 4-2).
• condition 1 Gl needs to be compared with all sets of polynomials in the candidate set to see if Gl is equivalent to any of them.
• condition 2 Gl needs to be compared with one set of polynomials (since all sets of polynomials in the candidate set have the same first line weight spectrum) in the candidate set to see if Gl is inferior to any of them in terms of FER (or BER). Note that if Gl has better first line weight spectrum than that of the candidate set, the candidate set will be updated to Gl ; if Gl has the same first line weight spectrum as that of the candidate set, G 1 will be added to the candidate set.
• Gl refers to a set of polynomials from the candidate set (who survive act 4-2), and G2 refers to one set of generator polynomials in the final set (who survive act 4-3).
• G l needs to be compared with all sets of polynomials in the final set to see if Gl is equivalent to any of them.
• Gl needs to be compared with one set of polynomials (since all sets of polynomials in the final set have the same first L lines weight spectrum) in the final set to see if Gl is inferior to any of them in terms of FER (or BER). Note that if Gl has better first L lines weight spectrum than that of the final set, the final set will be updated to Gl ; if G l has the same first L lines weight spectrum as that of the final set, Gl will be added to the final set.
• MFD-FER or MFD-BER can be arbitrary as long as the choice (MFD-FER or MFD-BER) remains consistent for act 4-2 and act 4-3. IfFER is to be minimized, then MFD-FER criterion should be used and codes marked with ODS-FER from the appropriate Table below should be used. Otherwise, if BER is to be minimized, then MFD-BER criterion should be used and codes marked with ODS-BER from the appropriate Table below should be used.
• Act 4-4 comprises outputting an identification of the optimized tail biting convolutional code(s).
• the identification can be output in any suitable manner, such as displaying on a screen, printing or recording or affixing on/to any tangible medium, or storing in a memory, just to name a few examples.
• the identification can comprise an indication of the generator polynomials which comprise the optimized tail biting convolutional code.
• the description or indication for a generator polynomial of the optimized tail biting convolutional code can be expressed in the octal notation previously described herein.
• One form of outputting the identification of the optimized tail biting convolutional code can include listing of the search results for generated optimized tail biting convolutional code in a table, the table providing optimized tail biting convolutional codes grouped by code rate and constraint length.
• the table can be stored in a memory or the like, such as a memory or a processor, a semiconductor memory, a non- volatile memory, for example.
• Table 2 - Table 21 show example new ODS feedforward Tail-biting convolutional codes (TBCC) of various rates and constraint lengths.
• Table 1 serves an index by which to reference Table 2 - Table 21. That is, from Table 1 it can be determined which other Table to consult for a given rate and constraint length.
• columns 2 - 4 correspond to the rates of 1/4, 1/3, and 1/2, respectively; while rows 2 - 8 correspond to constraint lengths of 2 - 8, respectively.
• TBCC ODS feedforward Tail- biting convolutional codes
• Table 2 - Table 21 list only search results (e.g., sets of generator polynomials) which are believed not to have been previously reported in the literature.
• TBCC Tail-biting convolutional codes
• Table 2 - Table 21 are subject to the following comments and conditions, each of which is herein referred to as a "Table Note":
• Table Note 1 In each of Table 2 - Table 21 , the letter "K" in the first column represents the number of payload bits; that is, the number of information bits to be encoded.
• ODS-FER TBCC do not have the same weight spectrum WS(C)
• ODS-FER denotes that the TBCC in the corresponding row have ODS-FER
• ODS-BER denotes that the TBCC in the corresponding row have ODS-BER
• ODS-FER/BER denotes that the TBCC in the corresponding row have both ODS-FER and ODS-BER.
• Table Note 3 For given payload size (K), coding rate (R) and constraint length (v), usually there are more than one sets of generator polynomials which generate the optimum distance spectrum (ODS) TBCC under the FER or BER criterion (see category 2 in page 3).
• ODS-FER or ODS-BER
• all sets of generator polynomials which generate the ODS-FER (or ODS-BER) codes are permutation equivalent; that is, the codes generated by these sets of generator polynomials are equivalent if permutation of codeword bits are allowed.
• 2 sets of generator polynomials can be used by both the base station 28 and the wireless station.
• (16,46,56) is used by the base station 28, then it also needs to be used by the wireless station; or if (26,52,56) is used by the base station, then it also needs to be used by the wireless station 30.
• the letter "G" in the second column of the tables is the set of generator polynomials. Usually more than one set of generator polynomials exist for each row.
• each codeword is permuted (a,b,c,d,e,f) in Cl by a fixed permutation pattern to generate a permutated codeword, say (b,c,a,e,d,f)
• a permutated codeword say (b,c,a,e,d,f)
• the new set of permuted codewords C2 is permutation equivalent to Cl .
• the codewords in Cl and C2 are actually the same but with different orderings of the codeword bits. As stated above, for sets of generator polynomials are permutation equivalent, only one such set is listed in the Tables below.
• Table Note 4 The term "WS" in the third column of the tables stands for weight spectrum. Under this column only the first line of the weight spectrum (d f ,n d r,b df ) is listed.
• L is chosen to be 20 for the search of act 4-3.
• ODS codes by definition all lines of the weight spectrum need to be computed at act 4-3. Most of the codes considered herein have less than 20 lines of the weight spectrum. Therefore, L can be chosen to be 20 to cover most of the cases.
• act 4-3 if some code has more than 20 lines of the weight spectrum (for example, when the payload size K is very large), then only the first 20 lines are computed and are used in act 4-3 to see if the code is ODF-FER (or ODS-BER).
• the function Q(x), described previously, is a monotonically decreasing function, which means that Q(x)>Q(y) if y>x.
• Q(x)>Q(y) if y>x For large Eb/NO values (high SNR region), only the first few lines of the weight spectrum (with smaller values of d) will have significant contributions to P F, UB and PB.U B - For the extremely large Eb/N0 value, only the first line of the weight spectrum will have significant contributions to P F UB and
• the MFD-FER (or MFD-BER) codes may not have the smallest value of P F , UB (or P B , UB )-
• the low error rate transmission that is, over the high SNR region
• ODS-FER TBCC have the optimum weight spectrum for achieving lower FER
• ODS-BER TBCC have the optimum weight spectrum for achieving lower BER
• Fig. 5 shows a variation of the general method of Fig. 4, wherein acts 5-1 through 5-4 are essentially the same as acts 4-1 through 4-4, respectively, of Fig. 4.
• Fig. 5 differs from Fig. 4 by showing that, in one example method implementation, act 4-5 of Fig. 4 (the act of outputting the optimized tail biting convolutional code(s)) can comprise configuring a shift register circuit(s) of a data transceiver to implement the optimum code(s).
• the shift register circuit which is configured to implement the optimized tail biting convolutional code can comprise, for example, one or more of base station error correction encoder 52 and base station error correction decoder 66 of base station 28 and wireless station error correction encoder 82 and wireless station error correction decoder 96 of wireless station 30. Since the mapping from one set of generator polynomials to the shift register encoder is illustrated in Fig. 1 and Fig. 2, and taking Fig.
• a first act comprises take the set of optimum generator polynomials from the Tables 2 - 21, such as the optimized tail biting convolutional code (744,554), for example.
• gO is for connections from the upper part of the shift registers to output Vi(O), and (from left to right) there are four connections followed by two "no connections" then ended by one connection.
• Fig. 6 illustrates portions of an example wireless station 30, and particularly portions of a wireless station coder 1 10 which operates in conjunction with wireless station controller 100.
• the wireless station coder 110 can comprise a portion of a baseband application specific integrated circuit (ASIC) which hosts, in addition to coding, other baseband processing functionalities.
• ASIC application specific integrated circuit
• wireless station controller 100 comprises not only TBCC code requestor 104, but also TBCC code table 112.
• the wireless station coder of Fig. 6 serves to illustrate the wireless station error correction encoder 82.
• wireless station coder 110 comprises plural shift register circuits 12O 1 - 12O n and code activator 122.
• - 12O n is configured to implement a respective different one of plural optimum tail biting convolutional codes.
• - 12O n is of a different rate and is expressed by a set of polynomials listed in any of Table 2 - Table 21.
• Fig. 6 shows by arrow 108 that the configuration of the respective shift register circuits 12O 1 - 12O n is based upon identification of different ones of the optimized tail biting convolutional codes generated by optimized tail biting convolutional code generator 40.
• the code activator 122 is configured to include one of the plural shift register circuits 120( - 12O n in a processing stream for a respective data transmission over the channel.
• the code activator 122 includes an appropriate one of the plural shift register circuits 120
• Fig. 7 illustrates portions of an example base station 28, and particularly portions of a base station coder 130 and base station node controller 70.
• Base station node controller 70 comprises base station scheduler 72, which in turn comprises TBCC code selector 74 and TBCC code table 132.
• the base station coder 130 can, at any one time, serve plural channels or even plural wireless stations by engaging in separately encodable connections, frames, or sessions with the plural wireless stations over network interface 32.
• base station 28 may transmit multiple signals, like one control channel and one data channel, to a first wireless station at the same time, and the TBCCs (or other error correction code) in these channels may be different.
• the base station 28 may use different tail biting convolutional codes (or different error correction codes) to protect the data of different wireless stations, as different wireless stations may have different applications or requirements.
• a first wireless station may ask the base station to use a rate 1/2 TBCC with pay load size 12 bits, while a second wireless station may ask the base station 28 to use a rate 1/4 TBCC with pay load size 24 bits.
• a first wireless station may ask the base station to use a rate 1/2 TBCC with pay load size 12 bits to transmit the short control channel, and the second wireless station may ask the base station to use a more powerful error correction codes (like turbo code) to transmit the long data channel with 5000 payload bits.
• a base station 28 may also use different tail biting convolutional codes (or different error correction codes) for different applications executed at the same wireless station.
• each wireless station 30 has one ASIC to do the baseband processing including channel encoder/decoder.
• the wireless station 30 may transmit multiple signals, like one control channel and one data channel, to base station 28.
• base station coder 130 is shown as comprising plural coder sections 134
• Each coder section can comprise a portion of a baseband application specific integrated circuit (ASIC) which hosts, in addition to coding, other baseband processing functionalities.
• ASIC application specific integrated circuit
• through 134 j represents the base station error correction encoder 52 of Fig. 3.
• base station coder 130 serves plural channels or wireless stations
• data in a data stream involving a first channel or wireless station can be applied to a first coder section 134j as indicated by arrow 136], be processed by a selected shift register circuit 140 of coder section 134
• data in a data stream involving a second channel or second wireless station can be applied to a second coder section 134 2 as indicated by arrow 136 2 , be processed by a selected shift register circuit 140 of coder section 134 2 , and output from the selected shift register circuit 140 of coder section 134 2 as indicated by arrow 138 2 , and so forth for each of the plural coder sections 134.
• Each of the plural coder sections 134 of base station coder 130 comprise plural shift register circuits 140 and a TBCC code activator 142.
• coder section 134 1 is shown in Fig. 7 as comprising shift register circuits 14Oi - 14O n .
• each of the plural optimum tail biting convolutional codes implemented by the respective shift register circuits 140 ⁇ — 14O n is of a different rate and is expressed by a set of polynomials listed in any of Table 2 - Table 21.
• the configuration of the respective shift register circuits 140j — 14O n is based upon identification of different ones of the optimized tail biting convolutional codes generated by optimized tail biting convolutional code generator 40.
• the code activator 142 is configured to include one of the plural shift register circuits 140 ⁇ — 14O n in a processing stream for a respective data transmission over the channel.
• the code activator 142 includes an appropriate one of the plural shift register circuits 14Oi - 14O n in the processing stream by operating AND gates so that an input signal to base station coder 130 is applied only to the one activated shift register circuits 140, and so that an output signal from the base station coder 130 is taken only from the activated shift register circuits 140.
• tail biting convolutional codes each have different rates, for example a first TBCC having a rate 1/5 (which is denoted by a rate value "00"); a second example TBCC having a rate 1/4 (denoted by a rate value "01 "); a third example TBCC having a rate 1/3 (denoted by a rate value of " 10"); and a fourth example TBCC having a rate 1/2 (denoted by a rate value of "1 1 ").
• Each of these TBCCs is an optimized tail biting convolutional codes and is obtained by the method of Fig. 3 and/or Fig. 4 and is expressed by a set of polynomials listed in any of Table 2 - Table 21. It is assumed for simplicity these 4 TBCC have the same payload size and constraint length.
• the coder section 120 ⁇ is configured to implement the first TBCC having a rate 1/5
• the coder section 120 2 is configured to implement the second example TBCC having a rate 1 A
• a coder section 12O 3 is configured to implement the third example TBCC having a rate 1/3
• a coder section 12O 4 is configured to implement the fourth example TBCC having a rate Vi.
• base station coder 130 an appropriate one of the coder sections 134 for the involved wireless station is configured to implement the four TBCCs of different rates.
• the coder section 140i is configured to implement the first TBCC having a rate 1/5
• the coder section 14O 2 is configured to implement the second example TBCC having a rate 1 A
• a coder section MO 3 is configured to implement the third example TBCC having a rate 1/3
• a coder section 14O 4 is configured to implement the fourth example TBCC having a rate Vi.
• wireless station 30 typically measures the strength of the signal it receives from base station 28, for example the symbol energy to noise power spectral density ratio Es/N0. Then the measurement (e.g. Es/N0) will be further processed by the wireless station 30 to decide which TBCC the wireless station 30 thinks should be used between base station 28 and wireless station 30.
• Es/N0 the symbol energy to noise power spectral density ratio
• wireless station 30 gets a very strong measurement (Es/N0 is larger than a threshold, meaning that the channel quality is very good and the weakest code is good enough for error protection)
• the TBCC with rate 1/2 (the higher the rate, the weaker the code) is selected by TBCC code requestor 104 , and a rate value of " 1 1 " is sent from the 104 of wireless station 30 to base station 28 through an appropriate message or channel, e.g., on the Channel Quality Indicator (CQI) channel.
• CQI Channel Quality Indicator
• wireless station 30 obtains a very weak measurement (Es/N0 is smaller than a threshold, meaning that the channel quality is very bad and the strongest code is needed for error protection), then the TBCC with the rate 1/5 is selected by TBCC code requestor 104 of wireless station 30, and a rate value of "00" is sent from wireless station 30 to base station 28 (e.g., through the CQI channel).
• Es/N0 is smaller than a threshold, meaning that the channel quality is very bad and the strongest code is needed for error protection
• a message such as the CQI message may and like does also include other suggestions in addition to TBCC preference, such as (for example) the modulation order (2 for QPSK, 4 for 16QAM, 6 for 64-QAM, etc).
• the rate value carried from TBCC code requestor 104 of wireless station 30 to base station 28 in a message is just a suggestion from the TBCC code requestor 104 to the base station 28 about which TBCC the TBCC code requestor 104 of the wireless station 30 thinks should be used.
• the base station 28 Upon receipt of the suggestion from wireless station 30, and possibly in conjunction with CQI messages received from all wireless stations, the base station 28 makes its final decisions about which TBCC is to be used for each/which wireless station 30.
• the TBCC choice decided by the base station 28 may be different from the suggestion of the wireless station 30 as expressed in the CQI message.
• the TBCC code selector 74 of the base station 28 makes the decisions according to such factors as the available resources, the Quality of Service (QoS) requirements of different UEs, etc.
• QoS Quality of Service
• the TBCC code selector 74 is able to make an intelligent decision regarding which particular TBCCs are possible at a particular wireless station in view of the fact that the base station scheduler 72 comprises TBCC code table 132.
• the TBCC code table 132 includes a listing of the wireless stations served by the base station 28, as well as an identification of the optimized tail biting convolutional codes available at (implemented or implementable in the shift register circuit(s)) the
• the base station 28 will first try to meet the request (CQI) from the first wireless station.
• CQI request
• the TBCC code selector 74 directs the TBCC code activator 142 for the appropriate coder section 134 to activate the one of the shift register circuits 140 which corresponds to the selected tail biting convolutional code for that wireless station 30.
• the decision of which TBCC to be used for each wireless station 30 is sent from the base station 28 to the wireless station through an appropriate message, such as the Media Access Control (MAC) management message in the UL- Media Access Protocol (MAP) channel (in WiMAX system).
• MAC Media Access Control
• MAP UL- Media Access Protocol
• the wireless station 30 of Fig. 6 and the base station 28 of Fig. 7 comprise coder sections which include plural dedicated shift register circuits (with each shift register circuit being configured in essentially dedicated manner to implement a specific optimized tail biting convolutional code)
• the wireless station 30' partially shown in Fig. 8 and base station 28' partially shown in Fig. 9 comprise coder sections which include a programmable shift register circuit that is changed for implementing different optimized tail biting convolutional codes at different times.
• the wireless station coder 1 10' comprises programmable shift register circuit 120' and TBCC programmer 122'.
• each coder section 134' of base station coder 130' of Fig. 9 comprises programmable shift register circuit 140' and TBCC programmer 142'.
• the programmable shift register circuit 120' of the wireless station coder 1 10' of Fig. 8 and the programmable shift register circuit 140' of base station coder 130' of Fig. 9 can be reprogrammed essentially on the fly by the respective programmers 122' and 142' to implement a specific optimized tail biting convolutional code which, at any given moment, the coder section needs to utilize.
• optimized tail biting convolutional code generator 40 can be applied (e.g., stored) in TBCC code table 1 12 and TBCC code table 132, so that the respective controllers 100 and 70 can interact with the programmers 122' and 142' for implementing in the programmable shift register circuits the specific optimized tail biting convolutional code which is necessary at any given time.
• controllers and coders of both the base stations and wireless stations have been illustrated and described as being structurally distinct, it should be realized that functionalities may be shared.
• the code tables and code requestor(s)/selector(s) mentioned herein can, instead of being separate from the coders, actually comprise ASICs or other circuitry that embody the shift resister circuit-hosting coders.
• FCH frame control header
• Different control channels can send different messages for controlling different functionalities.
• the technology disclosed herein can be applied to channels whose payload sizes are not too big (less than about 40 bits), as TBCC are more efficient when payload size is small. So the technology disclosed herein can be applied to control channels and to the specific frame control headers, with there being essentially no difference in considerations or acts/steps performed.
• TABLE 1 SUMMARY OF TABLES FOR THE ODS FEEDFORWARD TAIL-BITING CONVOLUTIONAL CODES (TBCC)
• Table 21 below sets forth new ODS feedforward TBCC with rate 2/5 and various constraint lengths.
• Each puncturing pattern is a 3-by-2 matrix and 0 means puncturing and 1 means no puncturing.
• the number of columns of puncturing patterns is 3 since there are 3 output bits for each input bit for the rate 1/3 code.
• the number of rows of puncturing patterns is 2 and is the periodity of the puncturing pattern. For example, if pi is used, then the third output bit from the input bit at odd time instant (assuming the time instants for input bits are 0, 1 , ..., k-1) is punctured and is not transmitted.
• Table 21 NEW ODS FEEDFORWARD TBCC WITH RATE 2/5 AND VARIOUS CONSTRAINT LENGTHS.

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