WO2005055435A1 - Linear approximation of the max* operation for log-map decoding - Google Patents
Linear approximation of the max* operation for log-map decoding Download PDFInfo
- Publication number
- WO2005055435A1 WO2005055435A1 PCT/IB2004/004420 IB2004004420W WO2005055435A1 WO 2005055435 A1 WO2005055435 A1 WO 2005055435A1 IB 2004004420 W IB2004004420 W IB 2004004420W WO 2005055435 A1 WO2005055435 A1 WO 2005055435A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- modf
- max
- modulo
- linear approximation
- threshold value
- Prior art date
Links
- 101100346151 Escherichia coli (strain K12) modF gene Proteins 0.000 claims abstract description 49
- 238000000034 method Methods 0.000 claims description 10
- URWAJWIAIPFPJE-YFMIWBNJSA-N sisomycin Chemical compound O1C[C@@](O)(C)[C@H](NC)[C@@H](O)[C@H]1O[C@@H]1[C@@H](O)[C@H](O[C@@H]2[C@@H](CC=C(CN)O2)N)[C@@H](N)C[C@H]1N URWAJWIAIPFPJE-YFMIWBNJSA-N 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
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
- H03M13/37—Decoding methods or techniques, not specific to the particular type of coding provided for in groups H03M13/03 - H03M13/35
- H03M13/39—Sequence estimation, i.e. using statistical methods for the reconstruction of the original codes
- H03M13/3905—Maximum a posteriori probability [MAP] decoding or approximations thereof based on trellis or lattice decoding, e.g. forward-backward algorithm, log-MAP decoding, max-log-MAP decoding
- H03M13/3911—Correction factor, e.g. approximations of the exp(1+x) function
-
- 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
-
- 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
- H03M13/65—Purpose and implementation aspects
- H03M13/6577—Representation or format of variables, register sizes or word-lengths and quantization
- H03M13/6583—Normalization other than scaling, e.g. by subtraction
- H03M13/6586—Modulo/modular normalization, e.g. 2's complement modulo implementations
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0055—MAP-decoding
Definitions
- the present invention relates to a decoder for a wireless communication device.
- Wireless communication systems are widely deployed to provide various types of communications such as voice and data.
- One such system is wideband code division multiple access WCDMA, which has been adopted in various competing wireless communication standards, for example 3 rd generation partnership project 3GPP and 3GPP2.
- the different wireless communication standards typically include some form of channel coding, where one common channel coding technique is turbo coding.
- Turbo coding involves the use of a turbo encoder for encoding a code segment (i.e. a data packet) and a turbo decoder for the decoding of the encoded code segment.
- a turbo encoder includes two convolutional encoders and an interleaver, where the interleaver shuffles (i.e. interleaves) the information bits in the packet in accordance with a specified interleaving scheme.
- the turbo encoder uses a first convolutional encoder to encode information bits within a packet to generate a first sequence of parity bits in parallel to the interleaver shuffling the information bits, where the shuffled information bits are encoded by a second encoder to generate a second sequence of parity bits.
- the information bits and the parity bits in the first and second sequence are then modulated and transmitted to a receiver.
- the information bits and the first and second sequence of parity bits are received by a receiver and decoded by a turbo decoder.
- the turbo decoder initially stores the received information bits and the parity bits in the first and second sequence in a buffer. Initially, the information bits and the first sequence of parity bits from the first convolutional encoder are retrieved from the buffer and decoded by a first soft input soft output SISO decoder to provide 'extrinsic' information indicative of adjustments in the confidence in the detected values for the information bits. Intermediate results that include the extrinsic information from the first SISO decoder are then stored in the buffer in an interleaved order matching the code interleaving used at the transmitter.
- the intermediate results, the information bits and the second sequence of parity bits from the second encoder are retrieved from the buffer and decoded by a second SISO decoder to provide extrinsic information indicative of further adjustments in the confidence in the detected values for the information bits.
- Intermediate results that comprise the extrinsic information from the second SISO decoder are then stored in the buffer in a deinterleaved order complementary to the code interleaving performed at the transmitter.
- the intermediate results are used in a next decoding iteration performed by the turbo decoder.
- the turbo decoder performs a predetermined number of decoding iterations before producing a decision on the value of the decoded information bit.
- the log MAP decoding algorithm is analogues to the MAP decoding algorithm but performed in the logarithmic domain.
- the MAP decoding algorithm uses forward state metrics, commonly referred to as alphas ⁇ , and backward state metrics, commonly referred to as betas ⁇ , to determine soft output results, where the forward state metrics ⁇ and backward state metrics ⁇ characterise a state in a trellis structure.
- the MAX* function is used within the log-MAP algorithm and is represented by MAX*(a(n),b(n)), where a(n) and b(n) are inputs to the MAX* function.
- the inputs a(n) and b(n) can be forward state metrics, backward state metrics or a combination of both.
- the MAX*(a(n),b(n)) function is equal to MAX(a(n),b(n)) plus a correction value where the correction value is equal to log(1+exp(-
- the MAX(a(n),b(n)) term of the equation is usually straight forward to calculate, however the correction value is relatively complicated to calculate and is usually approximated using either a linear approximation, a step approximation or a look-up table.
- the modulo function as illustrated in figure 1, can be regarded as a sawtooth function.
- modulo function An alternative implementation of the modulo function can be defined by:
- Figure 1 illustrates a graphical representation of a first modulo function
- Figure 2 illustrates a graphical representation of a second modulo function
- Figure 3 illustrates a graphical representation of the variation in the MAX* correction term versus ;
- Figure 4 illustrates a decoder according to an embodiment of the present invention.
- the curve A in figure 3 illustrates the correction term for the MAX*(a(n),b(n)) function (i.e. MAX*(a(n),b(n)-MAX(a(n),b(n)) as a function of ), where is the absolute value of the difference between a(n) and b(n)).
- an easy technique for approximating the correction term is the use of linear approximation, as illustrated by line B in figure 3.
- the linear approximation provides a close approximation for the correction term for low values .
- the intersection of the line B on the axis indicates th value above which the linear approximation correction term goes to zero. Consequently, using linear approximation, the intersection point determines a threshold value, designated C, for determining if a correction value is to be applied to , where the intersection point is defined by the linear approximation equation.
- the MAX* function can be written as: MAX(a(n),b(n)) + MAX(0, ' C ⁇ a ⁇ h ⁇ ⁇
- the modulo value F is preferable a value to the power of two.
- the modF of a(n) becomes a(n)modF.
- the modF of b(n) becomes b(n)modF.
- Equation xmodF is equivalent to where the J_CJ term is the floor of 'x'.
- This algorithm is easy to calculate in silicon as s involves only binary operations and F is chosen to be a power of two.
- a decoder 400 for implementing the above MAX* equation is shown in figure 4 and is arranged to output MAX(a(n)modF,b(n)modF) when is greater than the threshold value C and to output -b(n) ⁇ is less than the threshold value C. If equals C then either MAX(a(n)modF,b(n)modF) or .
- the decoder 400 includes a first substracting unit 401, a second substracting unit 402, a calculator 403 in the form of an adder unit and a selector 404 in the form of a multiplexer unit.
- the first substracting unit 401 , the second substracting unit 402 and the adder unit 403 are each arranged to receive a(n)modF, b(n)modF and the threshold value C.
- the first substracting unit 401 is arranged to generate the sign of
- the second substracting unit 402 is arranged to generate the sign of (a(n)modF-b(n)modF-C)modF.
- the adder unit 403 is , , , arranged to generate , where the division by two corresponds to a shift in bit position by one.
- the modF operation is performed by ignoring the overflow (i.e. the carry bit of the msb bit addition is ignored).
- the output from the first substracting unit 401, the second substracting unit 402 and the adding unit 403 i.e. the sign of (b(n)modF-a(n)modF-C)modF, the sign of (a(n)modF-b(n)modF-C)modF and
- the multiplexer 404 is arranged to output a MAX*(a(n)modF, b(n)modF) equal to a(n)modF when the sign of (a(n)modF-b(n)modF-C)modF is positive and the sign of (b(n)modF-a(n)modF-C)modF is negative.
- the multiplexer 404 is arranged to output a MAX*(a(n)modF, b(n)modF) equal to b(n)modF when the sign of (a(n)modF-b(n)modF-C)modF is negative and the sign of (b(n)modF-a(n)modF-C)modF is positive.
- the multiplexer 404 is arranged to output a MAX * (a(n)modF, b(n)modF) equal to the sign of (a(n)modF-b(n)modF-C)modF is negative and the sign of (b(n)modF- a(n)modF-C)modF is negative.
Landscapes
- Physics & Mathematics (AREA)
- Probability & Statistics with Applications (AREA)
- Engineering & Computer Science (AREA)
- Theoretical Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Error Detection And Correction (AREA)
- Electroluminescent Light Sources (AREA)
- Steroid Compounds (AREA)
- Compression, Expansion, Code Conversion, And Decoders (AREA)
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP04816632A EP1692770B1 (en) | 2003-12-05 | 2004-12-03 | Linear approximation of the max* operation for log-map decoding |
JP2006542056A JP2007514347A (en) | 2003-12-05 | 2004-12-03 | Linear approximation of MAX * operation for LOG-MAP decoding |
DE602004013186T DE602004013186T2 (en) | 2003-12-05 | 2004-12-03 | LINEAR APPROXIMATION OF MAX * OPERATION FOR LOG MAP DECODING |
US10/596,205 US7634703B2 (en) | 2003-12-05 | 2004-12-03 | Linear approximation of the max* operation for log-map decoding |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0328322A GB2408901B (en) | 2003-12-05 | 2003-12-05 | A decoder for a wireless communication device |
GB0328322.3 | 2003-12-05 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2005055435A1 true WO2005055435A1 (en) | 2005-06-16 |
WO2005055435B1 WO2005055435B1 (en) | 2005-09-29 |
Family
ID=29764713
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2004/004420 WO2005055435A1 (en) | 2003-12-05 | 2004-12-03 | Linear approximation of the max* operation for log-map decoding |
Country Status (7)
Country | Link |
---|---|
US (1) | US7634703B2 (en) |
EP (1) | EP1692770B1 (en) |
JP (1) | JP2007514347A (en) |
AT (1) | ATE392745T1 (en) |
DE (1) | DE602004013186T2 (en) |
GB (1) | GB2408901B (en) |
WO (1) | WO2005055435A1 (en) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9380292B2 (en) | 2009-07-31 | 2016-06-28 | 3Dmedia Corporation | Methods, systems, and computer-readable storage media for generating three-dimensional (3D) images of a scene |
US20110025830A1 (en) | 2009-07-31 | 2011-02-03 | 3Dmedia Corporation | Methods, systems, and computer-readable storage media for generating stereoscopic content via depth map creation |
WO2011014419A1 (en) * | 2009-07-31 | 2011-02-03 | 3Dmedia Corporation | Methods, systems, and computer-readable storage media for creating three-dimensional (3d) images of a scene |
US9185388B2 (en) | 2010-11-03 | 2015-11-10 | 3Dmedia Corporation | Methods, systems, and computer program products for creating three-dimensional video sequences |
WO2012092246A2 (en) | 2010-12-27 | 2012-07-05 | 3Dmedia Corporation | Methods, systems, and computer-readable storage media for identifying a rough depth map in a scene and for determining a stereo-base distance for three-dimensional (3d) content creation |
US8274552B2 (en) | 2010-12-27 | 2012-09-25 | 3Dmedia Corporation | Primary and auxiliary image capture devices for image processing and related methods |
US10200671B2 (en) | 2010-12-27 | 2019-02-05 | 3Dmedia Corporation | Primary and auxiliary image capture devices for image processing and related methods |
KR101749096B1 (en) * | 2011-05-12 | 2017-06-21 | 한국전자통신연구원 | Method and apparatus for ldpc code decoding |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20020018533A1 (en) * | 2000-08-04 | 2002-02-14 | Noam Sivan | Apparatus and method for implementing a linearly approximated log map algorithm |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2001352258A (en) * | 2000-06-08 | 2001-12-21 | Sony Corp | Decoder and decoding method |
US6865711B2 (en) * | 2000-12-15 | 2005-03-08 | Conexant Systems, Inc. | System of and method for decoding trellis codes |
JP4269520B2 (en) * | 2001-01-23 | 2009-05-27 | 株式会社デンソー | Approximation calculation device and MAP decoding device |
US6993098B2 (en) * | 2001-07-12 | 2006-01-31 | Koninklijke Philips Electronics N.V. | Method and apparatus for efficient calculating distance metric |
KR100487183B1 (en) * | 2002-07-19 | 2005-05-03 | 삼성전자주식회사 | Decoding apparatus and method of turbo code |
-
2003
- 2003-12-05 GB GB0328322A patent/GB2408901B/en not_active Expired - Lifetime
-
2004
- 2004-12-03 US US10/596,205 patent/US7634703B2/en not_active Expired - Fee Related
- 2004-12-03 AT AT04816632T patent/ATE392745T1/en not_active IP Right Cessation
- 2004-12-03 EP EP04816632A patent/EP1692770B1/en not_active Not-in-force
- 2004-12-03 DE DE602004013186T patent/DE602004013186T2/en active Active
- 2004-12-03 JP JP2006542056A patent/JP2007514347A/en active Pending
- 2004-12-03 WO PCT/IB2004/004420 patent/WO2005055435A1/en active IP Right Grant
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20020018533A1 (en) * | 2000-08-04 | 2002-02-14 | Noam Sivan | Apparatus and method for implementing a linearly approximated log map algorithm |
Non-Patent Citations (3)
Title |
---|
CHENG J-F ET AL: "LINEARLY APPROXIMATED LOG-MAP ALGORITHMS FOR TURBO DECODING", PROC. IEEE 51ST VEHICULAR TECHNOLOGY CONFERENCE, TOKYO, JAPAN, vol. VOL. 3 OF 3. CONF. 51, 15 May 2000 (2000-05-15), pages 2252 - 2256, XP000968405, ISBN: 0-7803-5719-1 * |
ERICSSON INC: "Simplified log-MAP algorithm (Ericsson Inc)", RESEARCH DISCLOSURE, KENNETH MASON PUBLICATIONS, HAMPSHIRE, GB, vol. 421, no. 33, May 1999 (1999-05-01), XP007124292, ISSN: 0374-4353 * |
WU Y ET AL: "INTERNAL DATA WIDTH IN SISO DECODING MODULE WITH MODULAR RENORMALIZATION", PROC. IEEE 51ST VEHICULAR TECHNOLOGY CONFERENCE,TOKYO, JAPAN, vol. VOL. 1 OF 3. CONF. 51, 15 May 2000 (2000-05-15), pages 675 - 679, XP000970706, ISBN: 0-7803-5719-1 * |
Also Published As
Publication number | Publication date |
---|---|
DE602004013186T2 (en) | 2010-04-15 |
DE602004013186D1 (en) | 2008-05-29 |
US7634703B2 (en) | 2009-12-15 |
GB2408901B (en) | 2006-07-12 |
GB2408901A (en) | 2005-06-08 |
EP1692770A1 (en) | 2006-08-23 |
JP2007514347A (en) | 2007-05-31 |
ATE392745T1 (en) | 2008-05-15 |
US20070168820A1 (en) | 2007-07-19 |
GB0328322D0 (en) | 2004-01-07 |
EP1692770B1 (en) | 2008-04-16 |
WO2005055435B1 (en) | 2005-09-29 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP1383246B1 (en) | Modified Max-LOG-MAP Decoder for Turbo Decoding | |
KR100941346B1 (en) | Turbo decoder with multiple scale selections | |
US8443265B2 (en) | Method and apparatus for map decoding and turbo decoder using the same | |
JP4101653B2 (en) | Scaling demodulated data in interleaver memory | |
EP1170870A1 (en) | Turbo decoder | |
JP2008099048A (en) | Decoding device and decoding method | |
WO2005006564A1 (en) | Decoding device and decoding method | |
EP1821415B1 (en) | Hybrid decoding using multiple turbo decoders in parallel | |
US7634703B2 (en) | Linear approximation of the max* operation for log-map decoding | |
JP2004147329A (en) | Method of decoding turbo code | |
US20030018941A1 (en) | Method and apparatus for demodulation | |
US7770092B2 (en) | Method for iterative decoding in a digital system and apparatus implementing the method | |
WO2005055433A1 (en) | Decoder apparatus and decoding method | |
KR100625242B1 (en) | Apparatus and method for turbo decoder | |
GB2418109A (en) | Approximation of the logarithm of the sum of exponentials correction term in log-MAP decoding using Padé approximants or continued fractions | |
Kim et al. | A Memory‐Efficient Block‐wise MAP Decoder Architecture | |
JP2002198829A (en) | Decoder and decoding method | |
KR20110071932A (en) | Turbo decoding apparatus | |
KR20060100716A (en) | Approximation method for logmap of turbo decoder |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AK | Designated states |
Kind code of ref document: A1 Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BW BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE EG ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NA NI NO NZ OM PG PH PL PT RO RU SC SD SE SG SK SL SY TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW |
|
AL | Designated countries for regional patents |
Kind code of ref document: A1 Designated state(s): BW GH GM KE LS MW MZ NA SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LT LU MC NL PL PT RO SE SI SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
B | Later publication of amended claims |
Effective date: 20050523 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2004816632 Country of ref document: EP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2006542056 Country of ref document: JP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2007168820 Country of ref document: US Ref document number: 10596205 Country of ref document: US |
|
WWP | Wipo information: published in national office |
Ref document number: 2004816632 Country of ref document: EP |
|
WWP | Wipo information: published in national office |
Ref document number: 10596205 Country of ref document: US |
|
WWG | Wipo information: grant in national office |
Ref document number: 2004816632 Country of ref document: EP |