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
  • H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
  • H03M13/13—Linear codes
  • H03M13/15—Cyclic codes, i.e. cyclic shifts of codewords produce other codewords, e.g. codes defined by a generator polynomial, Bose-Chaudhuri-Hocquenghem [BCH] 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
  • H03M13/37—Decoding methods or techniques, not specific to the particular type of coding provided for in groups H03M13/03 - H03M13/35
  • H03M13/45—Soft decoding, i.e. using symbol reliability information
• • 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
  • H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
  • H03M13/13—Linear codes
  • H03M13/136—Reed-Muller [RM] codes

Definitions

• This invention relates to coding, i.e. ' encoding and decoding.
• the invention relates to decoding using a Hadamard transform.
• a binary word can be encoded using the first-order Reed-Muller code.
• the word to be encoded comprises 5 bits, al to a5, then the code comprises a code line for each bit, as follows: a2 0101 0101 0101 0101 a3 0011 0011 0011 0011 a4 0000 mi 0000 nil a5 0000 0000 nil nil
• the code for a particular word is created by combining the code lines corresponding to the non zero bits of the word to be encoded.
• This word becomes encoded as 1100 0011 1100 0011 by combining the al , a3 and a4 code lines. Words encoded in this manner are decoded at a receiver using a Fast Hadamard Transform, FHT.
• FHT Fast Hadamard Transform
• An aim of the invention is to enhance the decoding of words using a Hadamard transform.
• the invention provides a method of producing a second binary codeword from a first binary codeword destined for decoding using a Hadamard transform, the method comprising selecting soft decisions from the first codeword into one or more groups, and combining the soft decisions within each group to produce a number of resultant soft decisions forming the second codeword.
• the invention also provides apparatus for producing a second binary codeword from a first binary codeword destined for decoding using a Hadamard transform, the apparatus comprising selecting means for selecting soft decisions from the first codeword into one or more groups, and combining means for combining the soft decisions of each group to produce a number of resultant soft decisions forming the second codeword.
• a second codeword is produced which can be decoded optimally in terms of error recovery even where the dataword encoded as the first codeword has a number of unused bits at one end.
• TFCI decoding in third generation mobile telecommunications is TFCI decoding in third generation mobile telecommunications (UMTS).
• UMTS third generation mobile telecommunications
• the TFCI is a 10 bit dataword encoded into a 32 bit codeword.
• the first 6 bits of the TFCI word are encoded using the first order Reed-Muller code.
• Many channels use less than 6 bits for the TFCI and the invention can be used to gain improved error recoveiy in such cases.
• the soft decisions selected for each group are a group of soft decisions that would appear consecutively in the first codeword if it were permuted by, for each soft decision in the first codeword, taking the position of said soft decision in the first codeword as a decimal number and converting said decimal number into binary number, bit reversing the binary number, and converting the reversed binary number into a decimal number giving the position of said soft decision in the permuted codeword.
• the first codeword is permuted by, for each soft decision in the first codeword, moving said soft decision by a process of, or equivalent to, taking the position of the soft decision in the first codeword as a decimal number and converting said decimal number into binary number, bit reversing the binary number, and converting the reversed binary number into a decimal number giving the position of said soft decision in the permuted codeword, and thereafter the soft decisions of the permuted codeword are grouped by selecting groups of consecutive soft decisions from the permuted codeword.
• the combining operation comprises generating each soft decision of the second codeword from a group of soft decisions by summing the soft decisions of the group.
• the size of the groups may depend upon the number of unused bits at one end of a dataword encoded as the first codeword.
• the first codeword may be produced by encoding a dataword using the first order Reed-Muller code.
• the invention also extends to using a Hadamard transform to decode the manipulated codeword.
• receiver 10 receives a stream of soft decisions 12.
• the soft decisions 12 originate from the transmission by a transmitter (e.g. a base station in a wireless telephony system) of a series of 5 bit datawords, each of which has been encoded by the first-order Reed-Muller code to produce a corresponding 16 bit codeword.
• the stream of soft decisions therefore comprises a series of codewords, each 16 soft decisions long.
• the receiver 10 decodes the codewords in the soft decision stream 12 using a Hadamard transform, thereby recovering the datawords.
• a standard, 16-point FHT decodes the codewords optimally, in terms of error recoverability.
• the 16-point FHT will not be optimal in cases where the encoded dataword is known to use only a portion at the least significant end of the dataword (e.g., the most significant bit is not used). .
• the decoding process is performed using a decoder 14 operating a 16-point FHT algorithm.
• the codeword is decoded in a different way, by first passing the codeword to permuting unit 16.
• the permuting unit 16 permutes the soft decisions (SDs) of a codeword in the following way.
• SDs soft decisions
• a codeword contains 16 SDs in positions numbered from 0 to 15 in decimal notation.
• the SDs are permuted within the codeword in the manner indicated by the following table. The top row of the table indicates the positions of the SDs in the codeword as received by the permuting unit 16, and the bottom row indicates the order of those SDs in the permuted codeword.
• the decimal number of each position is converted to a binary number, which is subsequently reversed and converted back to a decimal number which is the position of the SD in the permuted codeword.
• the effect of the permutation can be considered the same as taking the codelines used to produce the codewords, other than that for the most significant bit of the dataword, and reversing their order.
• the combiner 18 divides up the permuted codeword into groups of SDs.
• the number of groups depends on the number of non-used bits at the most significant end of the dataword represented by the codeword. Where only the 4 least significant bits are used in the dataword, then the codeword is divided into 8 groups of 2 SDs. Where only the 3 least significant bits are used in the dataword, then the codeword is divided into 4 groups of 4 SDs. Where only the 2 least significant bits are used in the dataword, then the codeword is divided into 2 groups of 8 SDs. Where the least significant bit only is used in the dataword, then the codeword is treated as a single group of 16 SDs. Each group contains consecutive SDs from the permuted codeword.
• the combiner 18 performs majority polling on the SDs in each group.
• Each SD is represented by a word comprising a sign (positive or negative - indicating that the bit appears to be a zero or a one, respectively) and a magnitude (indicating the confidence in the decision that the bit is correctly designated a one or a zero).
• the majority polling comprises summing the soft decisions of a group to produce an overall soft decision representing the group. Taken together, these resultant SDs constitute a resultant codeword which is then decoded using a FHT in decoder 20.
• the resultant codeword supplied to decoder 20 has fewer SDs than the initial codeword, it can be handled using a lower order FHT than the FHT applicable to the initial codeword. Error correction performance is improved by performing the permuting/majority polling on codewords corresponding to datawords having unused bits.
• the described embodiment permutes the first codeword and then selects consecutive soft decisions for each group, it will be apparent that soft decisions may be selected directly into the groups to give the effect of the permutation followed by selection of consecutive soft decisions, but without having to use the intermediate step of having to explicitly permute the first codeword.

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• Physics & Mathematics (AREA)
• Probability & Statistics with Applications (AREA)
• Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Algebra (AREA)
• General Physics & Mathematics (AREA)
• Mathematical Physics (AREA)
• Pure & Applied Mathematics (AREA)
• Error Detection And Correction (AREA)
• Detection And Correction Of Errors (AREA)
• Detection And Prevention Of Errors In Transmission (AREA)
• Dc Digital Transmission (AREA)
• Reduction Or Emphasis Of Bandwidth Of Signals (AREA)
• Lubricants (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Mobile Radio Communication Systems (AREA)

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• 2000
  • 2000-12-21 GB GB0031358A patent/GB2370472B/en not_active Revoked
• 2001
  • 2001-12-04 AU AU2002220889A patent/AU2002220889A1/en not_active Abandoned
  • 2001-12-04 US US10/451,538 patent/US7379610B2/en not_active Expired - Lifetime
  • 2001-12-04 AT AT01271696T patent/ATE282262T1/de not_active IP Right Cessation
  • 2001-12-04 DE DE60107118T patent/DE60107118T2/de not_active Expired - Lifetime
  • 2001-12-04 CN CNA018223222A patent/CN1488196A/zh active Pending
  • 2001-12-04 EP EP01271696A patent/EP1350326B1/en not_active Expired - Lifetime
  • 2001-12-04 KR KR10-2003-7008380A patent/KR100528139B1/ko not_active Expired - Fee Related
  • 2001-12-04 WO PCT/GB2001/005371 patent/WO2002051014A1/en not_active Ceased
  • 2001-12-04 JP JP2002552197A patent/JP2004527149A/ja active Pending

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