CN101883063A - Iterative detecting method and device - Google Patents

Iterative detecting method and device Download PDF

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Publication number
CN101883063A
CN101883063A CN2009101382568A CN200910138256A CN101883063A CN 101883063 A CN101883063 A CN 101883063A CN 2009101382568 A CN2009101382568 A CN 2009101382568A CN 200910138256 A CN200910138256 A CN 200910138256A CN 101883063 A CN101883063 A CN 101883063A
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estimated value
modulation symbol
symbol estimated
code word
soft
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包国平
吴岩巍
徐俊
袁志锋
孙芝利
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ZTE Corp
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Abstract

The invention discloses iterative detecting method and device. The iterative detecting method comprises the following steps of: 1. obtaining a transmission modulating symbol estimated value; 2. calculating a bit log-likelihood ratio of the transmission modulating symbol estimated value by adopting M-QAM (M-ary Quadrature Amplitude Modulation) soft demodulation processing, wherein when M is equal to 4, 16 and 64, xk is the transmission modulating symbol estimated value, lk is the approximative log-likelihood ratio of the i bit of xk, M is a modulating order of M-QAM soft demodulation, and C1 and C2 are constants; 3. decoding the bit log-likelihood ratio and iteratively detecting whether the decoding is successful or not; and 4. carrying out following processing according to the condition that whether the decoding is successful or not.

Description

Iteration detection method and device
Technical field
The present invention relates to the communications field, in particular to a kind of iteration detection method and device.
Background technology
In wireless communication system, adopt channel coding technology usually, with reliability and the antijamming capability thereof that ensures that information data is transmitted in wireless channel.At present, low density parity check code (Low Density Parity Check Code, abbreviate LDPC as) be one of reasonable channel coding technology of error-correcting performance, it is at IEEE802.16 standard, China Mobile multimedia broadcasting (China Mobile Multimedia Broadcasting, abbreviate CMMB as) be able to be adopted and use in the standard, in the formulation process of future broadband wireless communication systems standard 4G, LDPC might substitute Turbo code, become the first-selected channel coding method of data service.
Multiple-input and multiple-output (Multi-Input Multi-Output, abbreviating MIMO as) technology can provide the gain of diversity gain and spatial reuse, under the constant prerequisite of bandwidth and transmitting power, utilize the MIMO diversity gain, can effectively improve the information data transmission reliability, utilize the gain of MIMO spatial reuse, can effectively improve message transmission rate.At present, the MIMO technology has inserted in (Wideband Code Division MultipleAccess abbreviates WCDMA as), the standard agreements such as IEEE802.16,3GPP LTE in Wideband Code Division Multiple Access (WCDMA) and has been widely adopted.
In the LDPC-MIMO communication system, detect performance in order to improve receiver, adopt " Turbo " iterative manner usually, that is, and iteration exchange external information between MIMO detector and decoder.Yet, when adopting the Turbo iterative manner, along with the increase of iterative detection number of times, the increase that also is directly proportional of receiver detection algorithm complexity.
Currently used iteration detection method is following realization: the data-signal that receives according to receiver and the modulation symbol of feedback are estimated, adopt the MIMO detection algorithm, obtain to send the estimated value of modulation symbol; Adopt the soft demodulating algorithm of M-QAM, calculate and send bit log-likelihood ratio; Adopt the soft input soft output decode algorithm that the bit log-likelihood ratio of soft demodulation output is deciphered; Judge whether decoding is successful; Upgrade current iteration and detect number of times; If successfully decoded, the decoding code word, Iterative detection algorithm finishes; If decoding failure, and current iteration detects number of times and does not reach default maximum iteration time as yet, and then output decoding is adopted soft mapping algorithm about sending the external information of bit, the external information that sends bit is mapped as the transmission modulation symbol estimates, feed back to the MIMO detector.If decoding failure, and current iteration is when detecting number of times and reaching default maximum iteration time, output decoding code word, and Iterative detection algorithm finishes.
The soft demodulating algorithm of M-QAM that adopts is as follows at present: for example, and 64-QAM,
Figure B2009101382568D0000021
Figure B2009101382568D0000022
Here,
Figure B2009101382568D0000023
Figure B2009101382568D0000024
Be emission modulation symbol estimated value,
Figure B2009101382568D0000025
For
Figure B2009101382568D0000026
The approximate log-likelihood ratio of i bit.
Figure B2009101382568D0000027
Figure B2009101382568D0000028
Figure B2009101382568D0000029
else
Figure B2009101382568D00000212
Figure B2009101382568D00000213
Figure B2009101382568D00000215
else
Figure B2009101382568D00000216
Above-mentioned M-QAM demodulating algorithm computation complexity is higher, therefore along with the increase of iterative detection number of times, and the increase that also is directly proportional of receiver detection algorithm complexity.How under the prerequisite of receiver control algorithm complex, further raising system detects performance, is the current problem that solves of needing.
Summary of the invention
The present invention aims to provide a kind of improved iterative detection scheme, to solve present iteration detection method complexity problem of higher.
According to an aspect of the present invention, provide a kind of iteration detection method, this method comprises following processing:
Step 1 is obtained emission modulation symbol estimated value;
Step 2 adopts the soft demodulation process of M-QAM, calculates the bit log-likelihood ratio of emission modulation symbol estimated value;
When M=4, l k 1 = Re ( x ^ k ) , l k 2 = Im ( x ^ k ) ;
When M=16, l k 1 = Re ( x ^ k ) , l k 2 = Im ( x ^ k ) , l k 3 = C 1 - | l k 1 | , l k 4 = C 1 - | l k 2 | ,
When M=64, l k 1 = Re ( x ^ k ) , l k 2 = Im ( x ^ k ) , l k 3 = C 1 - | l k 1 | , l k 4 = C 1 - | l k 2 | , l k 5 = C 2 - | l k 3 | , l k 6 = C 2 - | l k 4 | ,
Wherein,
Figure B2009101382568D0000036
Be emission modulation symbol estimated value, For
Figure B2009101382568D0000038
The approximate log-likelihood ratio of i bit, M is the demodulation exponent number of the soft demodulation of M-QAM; C 1And C 2Be constant;
Step 3 is deciphered bit log-likelihood ratio, and whether iterative detection decoding is successful;
Step 4, whether successful according to decoding, carry out subsequent treatment.
Preferably, when M=16,
Figure B2009101382568D0000041
When M=64,
Figure B2009101382568D0000042
Preferably, if decoding failure, then subsequent treatment comprises:
Step 4-1 obtains the external information of the code word bits sequence of decoding output, and by soft mapping processing, the external information that sends code word bits is mapped as the first emission modulation symbol estimated value, turns back to step 1.
Preferably, determine the first emission modulation symbol estimated value according to following formula
Figure B2009101382568D0000043
When M=4,
Figure B2009101382568D0000044
When M=16,
Figure B2009101382568D0000045
When M=64,
Figure B2009101382568D0000046
Wherein, l e(c K, i) for sending the external information of code word bits; When code word bits is 0, C iBe 1, when code word bits is 1, C iBe-1.I=1,2 ... .M, wherein, M is an order of modulation, and is the integer greater than 1; K=1,2 ... ..N T, N TThe number of expression transmitting antenna;
Figure B2009101382568D0000048
Be complex signal.
Preferably, obtaining emission modulation symbol estimated value comprises: the data-signal that each antenna of receiver is received carries out the MIMO detection, obtains launching the modulation symbol estimated value; Perhaps the data-signal and the first emission modulation symbol estimated value that each antenna of receiver is received carried out the MIMO detection, obtains launching the modulation symbol estimated value.
Preferably, whether after the success, method also comprises at iterative detection decoding: add 1 and upgrade by current iteration being detected number of times, and judge that whether iterative detection number of times after upgrading is less than predetermined threshold value; In step 4, if decoding failure, and the iterative detection number of times after upgrading then proceeds to step 4-1 less than predetermined threshold value; If decoding failure, and the iterative detection number of times after upgrading is not less than predetermined threshold value, then proceeds to step 4-2: output decoding code word, detection of end.
Preferably, if successfully decoded, then subsequent treatment comprises: to follow-up information receiving unit output decoding code word, detection of end.
According to a further aspect in the invention, provide a kind of iteration detection method, this method comprises following processing:
Step 1 is obtained emission modulation symbol estimated value;
Step 2 adopts the soft demodulation process of M-QAM, calculates the bit log-likelihood ratio of emission modulation symbol estimated value;
Step 3 is deciphered bit log-likelihood ratio, obtains the external information sequence of binary message bit sequence and code word bits sequence, and whether iterative detection decoding is successful;
Step 4 if decoding failure is then handled by soft mapping, is mapped as emission modulation symbol estimated value with the external information that sends code word bits, turns back to step 1, wherein:
When M=4,
When M=16,
Figure B2009101382568D0000052
When M=64,
Wherein, l e(c K, i) for sending the external information of code word bits; When code word bits is 0, C iBe 1, when code word bits is 1, C iBe-1.I=1,2 ... .M, wherein, M is an order of modulation, and is the integer greater than 1; K=1,2 ... ..N T, N TThe number of expression transmitting antenna;
Figure B2009101382568D0000063
Be complex signal.
Preferably, this method also comprises following processing: step 5, if successfully decoded, then to follow-up information receiving unit output decoding code word, detection of end.
According to a further aspect in the invention, also provide a kind of iterative detection device, this device comprises as lower member:
Emission modulation symbol estimated value acquiring unit is used to obtain the modulation symbol estimated value;
Soft demodulator is used to obtain the modulation symbol estimated value of emission modulation symbol estimated value acquiring unit output, and calculates the bit log-likelihood ratio of launching the modulation symbol estimated value by the soft demodulation process of M-QAM, wherein, and when M=4,
Figure B2009101382568D0000064
When M=16,
Figure B2009101382568D0000065
When M=64,
Figure B2009101382568D0000066
Wherein,
Figure B2009101382568D0000067
Be emission modulation symbol estimated value, For
Figure B2009101382568D0000069
The approximate log-likelihood ratio of i bit, M is the demodulation exponent number of the soft demodulation of M-QAM; C 1And C 2Be constant;
Decoder is used for the bit log-likelihood ratio of soft demodulator output is deciphered, and obtains the external information sequence of binary message bit sequence and code word bits sequence, and decode results is carried out iterative detection.
Preferably, this device also comprises: soft mapper is used to obtain the external information about the transmission code word bits of decoder output, and handles by soft mapping, the external information of code word bits sequence is mapped as the first emission modulation symbol estimated value, and exports emission modulation symbol estimated value acquiring unit to.
Preferably, emission modulation symbol estimated value acquiring unit comprises: the first input end mouth, be connected with the reception antenna of receiver, and be used to receive data-signal from reception antenna; And/or second input port is connected with soft mapper, is used for the first emission modulation symbol estimated value from soft mapper; The MIMO detecting unit is used for the data-signal and/or the first emission modulation symbol estimated value are carried out the MIMO detection, obtains emission modulation symbol estimated value.
According to a further aspect in the invention, also provide a kind of iterative detection device, this device comprises: emission modulation symbol estimated value acquiring unit is used to obtain the modulation symbol estimated value; Soft demodulator is used to obtain the modulation symbol estimated value of emission modulation symbol estimated value acquiring unit output, and calculates the bit log-likelihood ratio of emission modulation symbol estimated value by the soft demodulation process of M-QAM; Decoder is used for the bit log-likelihood ratio of soft demodulator output is deciphered, and obtains the external information sequence of binary message bit sequence and code word bits sequence, and decode results is carried out iterative detection; Soft mapper, be used to obtain decoder output about sending the external information of code word bits, and handle by soft mapping, the external information of code word bits sequence is mapped as the first emission modulation symbol estimated value, and exports to and launch modulation symbol estimated value acquiring unit;
Wherein:
When M=4,
Figure B2009101382568D0000071
When M=16,
Figure B2009101382568D0000072
When M=64,
Wherein,
Figure B2009101382568D0000082
l e(c K, i) for sending the external information of code word bits; When code word bits is 0, C iBe 1, when code word bits is 1, C iBe-1.I=1, ... .M, wherein, M is an order of modulation, and is the integer greater than 1; K=1,2 ... ..N T, N TThe number of expression transmitting antenna;
Figure B2009101382568D0000083
Be complex signal.
By above-mentioned at least one technical scheme of the present invention, in the iterative detection process, adopt the M-QAM algorithm of simplifying, perhaps adopt the M-QAM algorithm of simplification and the soft mapping algorithm of simplification, than present iterative detection scheme, the complexity of algorithm can be reduced, thereby receiver performance can be reduced.
Description of drawings
Accompanying drawing described herein is used to provide further understanding of the present invention, constitutes the application's a part, and illustrative examples of the present invention and explanation thereof are used to explain the present invention, do not constitute improper qualification of the present invention.In the accompanying drawings:
Fig. 1 is the structural representation according to the emission pusher side of the embodiment of the invention;
Fig. 2 is the structured flowchart according to the iterative detection device of the embodiment of the invention one;
Fig. 3 is the structural representation according to the iterative detection device of the embodiment of the invention one;
Fig. 4 is the structured flowchart according to the iterative detection device of the embodiment of the invention two;
Fig. 5 is the structural representation according to the iterative detection device of the embodiment of the invention two;
Fig. 6 is the flow chart according to the iteration detection method of the embodiment of the invention;
Fig. 7 is the detailed process flow chart according to the iteration detection method of the embodiment of the invention;
Fig. 8 is gray mappings M=4 (QPSK) modulation constellation and the bit mapping thereof according to the embodiment of the invention.
Fig. 9 is gray mappings M=16 (16QAM) modulation constellation and the bit mapping thereof according to the embodiment of the invention.
Figure 10 is gray mappings M=64 (64QAM) modulation constellation and the bit mapping thereof according to the embodiment of the invention.
Embodiment
In the technical scheme that the embodiment of the invention provides, based on gray mappings the LDPC-MIMO communication system is carried out multilevel quadrature amplitude modulation(PAM) (MultipleQuadrature Amplitude Modulation, abbreviate M-QAM as), adopt and simplify soft demodulating algorithm of M-QAM and soft mapping algorithm.Usually, the technical scheme that provides of the embodiment of the invention is applied to comprise in the following processing one or the multinomial process:---receiver received signal---MIMO detection---demodulation---decoding---iterative detection that transmitter transmits.Preferably, in the demodulating process, the soft demodulating algorithm of simplification M-QAM that can use the embodiment of the invention to provide.Preferably, in iterative detection, the soft mapping algorithm that can use the embodiment of the invention to provide.
Describe embodiments of the invention below with reference to accompanying drawing, if do not conflict, the feature among the embodiment of the invention and the embodiment can make up mutually.
At first, with reference to accompanying drawing 1, the processing of transmitter is described.As shown in Figure 1, at the emission pusher side, generally to encode, planisphere modulation, string and conversion, launch at antenna then.Particularly, at first to sent binary message Bit data sequence i=[i 1, i 2..., i K] carry out the LDPC coding, the binary system LDPC code word bits sequence behind the coding is c=[c 1, c 2..., c N], the LDPC encoder bit rate is R=K/N; Afterwards, modulate according to the gray mappings M-QAM modulation system that system determines, modulation back symbol sebolic addressing is s=[s 1, s 2..., s L], L=N/M wherein.Modulation back symbol sebolic addressing s obtains X after string and conversion 1, X NTSend into a plurality of transmitting antennas (antenna 1... antenna N respectively T) launch.Fig. 8 is gray mappings M=4 (QPSK) modulation constellation and the bit mapping thereof according to the embodiment of the invention.Fig. 9 is gray mappings M=16 (16QAM) modulation constellation and the bit mapping thereof according to the embodiment of the invention.Figure 10 is gray mappings M=64 (64QAM) modulation constellation and the bit mapping thereof according to the embodiment of the invention.
Embodiment one
According to the embodiment of the invention, at first provide a kind of iterative detection device.As shown in Figure 2, the iterative detection device according to the embodiment of the invention has following structure: emission modulation symbol estimated value acquiring unit, soft demodulator, decoder, above-mentioned each parts are connected in series successively.
Fig. 3 has provided the schematic diagram of a kind of preferred structure of this device.As shown in Figure 3, emission modulation symbol estimated value acquiring unit can be realized by MIMO detector 1, is connected to antenna 1.... antenna N R, be used to obtain the modulation symbol estimated value.Particularly, MIMO detector 1 is by receiving data-signal Y from antenna 1... Y NR, the data-signal that receives is carried out MIMO detects and obtain the modulation symbol estimated value
Figure B2009101382568D0000101
Soft demodulator 3 is used to obtain the modulation symbol estimated value of MIMO detector 1 output, and calculates the bit log-likelihood ratio l of emission modulation symbol estimated value by the soft demodulation process of M-QAM.The concrete computational process of this soft demodulator is as follows: wherein, and when M=4,
Figure B2009101382568D0000102
Figure B2009101382568D0000103
When M=16, When M=64,
Figure B2009101382568D0000105
Figure B2009101382568D0000106
Wherein, Be emission modulation symbol estimated value,
Figure B2009101382568D0000108
For
Figure B2009101382568D0000109
The approximate log-likelihood ratio of i bit, M is the demodulation exponent number of the soft demodulation of M-QAM; C 1And C 2Be constant.Preferably, when M=16, When M=64,
Figure B2009101382568D00001011
Decoder preferably can use ldpc decoder 5 to realize, is used for the bit log-likelihood ratio of soft demodulator 3 outputs is deciphered, and obtains the external information sequence of binary message bit sequence and code word bits sequence, and decode results is carried out iterative detection.For example, when detecting successfully, can export the binary message bit sequence
Figure B2009101382568D0000111
To information source.The iterative detection process for here will be described in more detail below.
By the iterative detection device that this embodiment provides, because soft demodulator has used the M-QAM algorithm of simplifying, simplified the soft demodulating algorithm complexity of receiver, therefore the complexity of whole iterative detection process can be reduced, and performance can be kept detecting.
Embodiment two
According to the embodiment of the invention, also provide another kind of iterative detection device.As shown in Figure 4, the iterative detection device according to the embodiment of the invention has following structure: emission modulation symbol estimated value acquiring unit, soft demodulator, decoder, soft mapper.
Fig. 5 has provided the schematic diagram of a kind of preferred structure of this iterative detection device.As shown in Figure 5,
Emission modulation symbol estimated value acquiring unit can be realized by MIMO detector 2, is connected to antenna 1.... antenna N RWith soft mapper 8, be used to obtain the modulation symbol estimated value.Particularly, the MIMO detector receives the data-signal Y from antenna 1... Y NR, and might receive emission modulation symbol estimated value from soft mapper
Figure B2009101382568D0000112
Data-signal or data-signal and the emission modulation symbol estimated value that receives are carried out MIMO detect, obtain the emission modulation symbol estimated value of the soft demodulator of output valve
Figure B2009101382568D0000113
Soft demodulator 4 is used to obtain the modulation symbol estimated value of MIMO detector 2 outputs, and calculates the bit log-likelihood ratio l of emission modulation symbol estimated value by the soft demodulation process of M-QAM.
Decoder preferably can use ldpc decoder 6 to realize, is used for the bit log-likelihood ratio of soft demodulator 4 outputs is deciphered, and obtains the binary message bit sequence
Figure B2009101382568D0000121
External information sequence l with the code word bits sequence e, and decode results carried out iterative detection.The iterative detection process for here will be described in more detail below.Particularly, if the iterative detection decoding success, decoder will be exported the binary message bit, and iterative detection finishes.If the iterative detection failure, decoder outputs to soft mapper 8 with the external information sequence of code word bits sequence.
Soft mapper 8 is used to receive the external information sequence l from the code word bits sequence of decoder 6 e, generate emission modulation symbol estimated value by soft mapping algorithm
Figure B2009101382568D0000122
And feed back to the MIMO detector, according to this
Figure B2009101382568D0000123
The MIMO detector can obtain
Figure B2009101382568D0000124
As can be seen, in this embodiment, different with embodiment one.The MIMO detector not only will receive the input from antenna, also will accept the input from soft mapper 7, and preferably, the MIMO detector has two ports that are connected respectively to antenna and soft mapper, and further, the MIMO detector can be according to Y 1... Y NRObtain
Figure B2009101382568D0000125
Also can be according to Y 1... Y NRAnd Obtain
Figure B2009101382568D0000127
In this embodiment, preferably, the following formula that passes through of soft mapper 8 generates emission modulation symbol estimated value:
When M=4,
When M=16,
Figure B2009101382568D0000129
When M=64,
Figure B2009101382568D0000131
Wherein,
Figure B2009101382568D0000132
l e(c K, i) for sending the external information of code word bits.
When code word bits is 0, C iBe 1, when the sign indicating number bit is 1, C iBe-1.I=1,2 ... .M, wherein M represents order of modulation.Modulation system is QPSK, 16QAM, and during 64QAM, M is respectively 2,4, and 6.K=1,2 ... ..N T, N wherein TThe number of expression transmitting antenna.Here
Figure B2009101382568D0000133
Be complex signal.
By the iterative detection device that this embodiment provides, be provided with the soft mapper that uses soft mapping method, can reduce the complexity of whole iterative detection process.
Preferably, the soft demodulator 3 that uses among soft demodulator 4 in this embodiment and the embodiment has identical functions,, can move the soft demodulating algorithm of simplification M-QAM that the embodiment of the invention provides that is.By this optimized technical scheme, provide a kind of and can move the iterative detection device of simplifying soft demodulating algorithm of M-QAM and soft mapping algorithm, simplify the soft demodulation of receiver, soft mapping algorithm complexity, thereby made the complexity of " Turbo " iteration detection method can adapt to practical application request.
Embodiment three
In this embodiment, provide a kind of iteration detection method.This iteration detection method can use any above-mentioned iterative detection device to realize.Fig. 6 has provided the general implementation procedure of this method, hereinafter, for convenience of description, has introduced step number, and this does not constitute any limitation of the invention, according to the needs of implementing, also can carry out with the order that is different from herein.
Usually, as shown in Figure 6, handle according to the iterative detection of the embodiment of the invention and to comprise following process:
S602 obtains emission modulation symbol estimated value; This step can use above-mentioned emission modulation symbol estimated value acquiring unit to carry out;
S604 adopts the soft demodulation process of M-QAM, calculates the bit log-likelihood ratio of emission modulation symbol estimated value; This step can use above-mentioned soft demodulator to carry out;
S606 deciphers bit log-likelihood ratio, and whether iterative detection decoding is successful; This step can use above-mentioned decoder to carry out;
S608, whether successful according to decoding, carry out subsequent treatment.This step can be carried out by above-mentioned decoder according to whether successfully decoded, also can be carried out by decoder and soft mapper.
Preferably, as shown in Figure 7, in S608,, then can proceed to S608-1 if successfully decoded: decoder output decoding code word, finishing iteration detects; If decoding failure then can proceed to S608-2: carry out soft mapping and handle, obtain the first emission modulation symbol estimated value, and turn back to S602.
The following specifically describes each details of above step.
(1) S602
In this step, for obtaining of emission modulation symbol estimated value, preferably, can detect by MIMO and realize, and, can realize by following dual mode at least:
Mode one: receive data-signal from reception antenna, data-signal is carried out MIMO detect, obtain emission modulation symbol estimated value; This mode is used when successfully decoded in iterative detection and/or last iteration testing process first usually, this be because, when iterative detection and/or last iteration detect successfully first, the feedback of 608-2 in steps not.
Mode two: receive data-signal from reception antenna, and the first emission modulation symbol estimated value of receiving step 608-2 feedback, the data-signal and the first emission modulation symbol estimated value are carried out the MIMO detection, obtain launching the modulation symbol estimated value.This mode is used in the pilot process of iterative detection usually, particularly, uses during decoding failure in the last iteration testing process.
Preferably, the MIMO that uses in this step detects and adopts minimum mean-square error soft interference eliminated (MMSE-SIC) detection algorithm, but the MIMO detection algorithm among the present invention is not limited thereto.
For example, establishing number of transmit antennas is N T, the reception antenna number is N RIn certain moment, the emitting side transmitting antenna sends symbolic vector
Figure B2009101382568D0000151
The mimo channel matrix The transmission modulation symbol of step 608-2 feedback is estimated Minimum mean-square error soft interference eliminated detected symbol x then jEstimated value For:
Figure B2009101382568D0000155
Wherein, w is the least mean-square error filter factor, (j=1 ... N T).It should be noted that as mentioned above when iterative detection first, the transmission modulation symbol of feedback is estimated
Figure B2009101382568D0000156
(2) S604
In this step, preferably,, adopt and simplify the soft demodulating algorithm of M-QAM based on gray mappings M-QAM modulation.Wherein, M represents planisphere modulation symbol number, that is, and and order of modulation.Particularly, establishing the emission modulation symbol estimated value that MIMO detects output is
Figure B2009101382568D0000157
Figure B2009101382568D0000158
Be the modulation symbol estimated value
Figure B2009101382568D0000159
The approximate log-likelihood ratio of i bit.
Then preferably, when M=4,
Figure B2009101382568D00001510
When M=16,
Figure B2009101382568D00001511
When M=64,
Figure B2009101382568D00001512
Figure B2009101382568D00001513
Wherein,
Figure B2009101382568D00001514
Be emission modulation symbol estimated value,
Figure B2009101382568D0000161
For
Figure B2009101382568D0000162
The approximate log-likelihood ratio of i bit, M is the demodulation exponent number of the soft demodulation of M-QAM; C 1And C 2Be constant.
Preferably, coefficient C 1, C 2Relevant with M, for M=16,
Figure B2009101382568D0000163
For M=64,
Figure B2009101382568D0000164
Coefficient
Figure B2009101382568D0000165
For above C 1, C 2: value only be exemplary, the needs according to implementing can adopt other values.
For example, if adopt if adopt the 64QAM gray mappings, then each modulation symbol need be formed by 6 bit mappings,
Figure B2009101382568D0000166
The expression estimate symbol
Figure B2009101382568D0000167
In the log-likelihood ratio of i bit.At this moment,
Figure B2009101382568D0000168
Figure B2009101382568D0000169
Wherein,
Figure B2009101382568D00001610
Certainly, in this step, also can adopt other M-QAM demodulating algorithm.
(3) S606 and S608
S606 can realize by following operation:
Bit log-likelihood ratio for S604 calculates at first, adopts soft inputting and soft output (Soft Input Soft Output abbreviates SISO as) LDPC decoding algorithm to decipher, and produces hard decision binary message bit sequence
Figure B2009101382568D00001611
With external information about the code word bits sequence.Next whether, it is successful to utilize the judgement of LDPC check matrix to decipher, and establishes LDPC decoding back binary message bit sequence to be
Figure B2009101382568D00001612
The binary code word bit sequence is The LDPC check matrix that adopts is H LDPC, its dimension is (N-K) * N.Then work as
Figure B2009101382568D00001614
The time, LDPC is successfully decoded in expression; When The time, expression LDPC decoding failure.As mentioned above,, then proceed to S608-1, to the binary message bit sequence of follow-up information receiving unit output LDPC decoding if successfully decoded
Figure B2009101382568D0000171
The receiver Iterative detection algorithm finishes, otherwise, proceed to S608-2.
Preferably, in a kind of optimal way of the embodiment of the invention, in the iterative detection process, cause detection efficiency to descend for fear of too much iteration, can set in advance a greatest iteration and detect frequency threshold value, surpass this threshold value, then no longer continue to detect if current iteration detects number of times.Relate to the renewal that current iteration detects number of times in this case.For example, detecting number of times in the hypothesis current iteration is I Cur, during first iteration, I Cur=0, upgrade being operating as I Cur=I Cur+ 1, that is, after detection is finished, current iteration is detected number of times add 1.
The setting of threshold value also can be influential for the subsequent operation step of the embodiment of the invention.For example, if the LDPC decoding failure needs then further to judge that current iteration detects number of times and whether reaches preset threshold value I MaxIf current iteration detects number of times I Cur＜I Max, then output sends the external information sequence of code word bits sequence, and changes S608-2 over to; If current iteration detects number of times I Cur〉=I Max, then can change S608-3 over to, to the binary message bit sequence of follow-up information receiving unit output LDPC decoding
Figure B2009101382568D0000172
The receiver Iterative detection algorithm finishes.By the setting of this preferred implementation, can further improve the iterative detection number of times of receiver.
(4) S608
The processing of this step can comprise above-mentioned S608-1 and S608-2.Preferably,, then can also comprise above-mentioned S608-3, specifically can need to prove that the frame of broken lines representative among Fig. 7 is optional with reference to Fig. 7 if this iterative detection process is provided with threshold value.
Particularly, in S608-2, can determine the first emission modulation symbol estimated value by following processing:
When M=4,
Figure B2009101382568D0000173
When M=16,
Figure B2009101382568D0000181
When M=64
Figure B2009101382568D0000182
Wherein,
Figure B2009101382568D0000183
l e(c K, i) for sending the external information of code word bits.
When code word bits is 0, C iBe 1, when code word bits is 1, C iBe-1.I=1,2 ... .M, wherein M represents order of modulation.Modulation system is QPSK, 16QAM, and during 64QAM, M is respectively 2,4, and 6.K=1,2 ... N T, N wherein TThe number of expression transmitting antenna.Here
Figure B2009101382568D0000184
Be complex signal.
Simplify the M-QAM demodulating algorithm if adopt in S604, it is constant to keep detecting performance, the soft demodulating algorithm complexity of simplified receiver; Simplify the M-QAM demodulating algorithm if in S604, adopt, and in S608-2, adopt and simplify soft mapping algorithm, can the soft demodulation of simplified receiver, soft mapping algorithm complexity, thereby make the complexity of " Turbo " iteration detection method can adapt to practical application request.
To sum up, pass through the embodiment of the invention, to simplify soft demodulation/soft mapping algorithm and iteration LDPC-MIMO detection algorithm organically combines, can simplify the high complexity that soft demodulation in traditional iterative detection and feedback modulation symbol are estimated, thereby can reduce LDPC-MIMO Iterative detection algorithm complexity, improve receiver performance.
Obviously, those skilled in the art should be understood that, above-mentioned each module of the present invention or each step can realize with the general calculation device, they can concentrate on the single calculation element, perhaps be distributed on the network that a plurality of calculation element forms, alternatively, they can be realized with the executable program code of calculation element.The present invention is not restricted to any specific hardware and software combination.
The above is the preferred embodiments of the present invention only, is not limited to the present invention, and for a person skilled in the art, the present invention can have various changes and variation.Within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (12)

1. an iteration detection method is characterized in that, comprising:
Step 1 is obtained emission modulation symbol estimated value;
Step 2 adopts the soft demodulation process of M-QAM, calculates described emission modulation symbol
The bit log-likelihood ratio of number estimated value;
When M=4, l k 1 = Re ( x ^ k ) , l k 2 = Im ( x ^ k ) ;
When M=16, l k 1 = Re ( x ^ k ) , l k 2 = Im ( x ^ k ) , l k 3 = C 1 - | l k 1 | , l k 4 = C 1 - | l k 2 | ,
When M=64, l k 1 = Re ( x ^ k ) , l k 2 = Im ( x ^ k ) , l k 3 = C 1 - | l k 1 | , l k 4 = C 1 - | l k 2 | , l k 5 = C 2 - | l k 3 | , l k 6 = C 2 - | l k 4 | ,
Wherein,
Figure F2009101382568C0000015
Be described emission modulation symbol estimated value,
Figure F2009101382568C0000016
For The approximate log-likelihood ratio of i bit, M is the demodulation exponent number of the soft demodulation of M-QAM; C 1And C 2Be constant;
Step 3 is deciphered described bit log-likelihood ratio, and whether iterative detection decoding is successful;
Step 4, whether successful according to decoding, carry out subsequent treatment.
Method according to claim 1 is characterized in that, when M=16,
Figure F2009101382568C0000018
When M=64,
Figure F2009101382568C0000019
3. method according to claim 1 is characterized in that, if decoding failure, then
Described subsequent treatment comprises:
Step 4-1 obtains the external information of the code word bits sequence of decoding output, and handles by soft mapping, the external information of described transmission code word bits is mapped as first launches the modulation symbol estimated value, turns back to described step 1.
4. method according to claim 3 is characterized in that, determines according to following formula
The described first emission modulation symbol estimated value
Figure F2009101382568C0000021
When M=4,
When M=16,
Figure F2009101382568C0000023
When M=64,
Figure F2009101382568C0000024
Wherein,
Figure F2009101382568C0000025
l e(c K, i) be the external information of described transmission code word bits; When code word bits is 0, C iBe 1, when code word bits is 1, C iBe-1.I=1,2 ... .M, wherein, M is an order of modulation, and is the integer greater than 1; K=1,2 ... ..N T, N TThe number of expression transmitting antenna;
Figure F2009101382568C0000026
Be multiple mark.
5. method according to claim 3 is characterized in that, the described emission modulation symbol estimated value of obtaining comprises:
The data-signal that each antenna of receiver is received carries out the MIMO detection, obtains described emission modulation symbol estimated value; Perhaps
Data-signal and the described first emission modulation symbol estimated value that each antenna of receiver receives are carried out the MIMO detection, obtain described emission modulation symbol estimated value.
6. method according to claim 3 is characterized in that,
Whether after the success, described method also comprises at iterative detection decoding: add 1 and upgrade by current iteration being detected number of times, and judge that whether iterative detection number of times after upgrading is less than predetermined threshold value;
In described step 4, if decoding failure, and the iterative detection number of times after upgrading then proceeds to described step 4-1 less than predetermined threshold value; If decoding failure, and the iterative detection number of times after upgrading is not less than predetermined threshold value, then proceeds to step 4-2: output decoding code word, detection of end.
7. method according to claim 1 is characterized in that, if successfully decoded, then described subsequent treatment comprises:
To follow-up information receiving unit output decoding code word, detection of end.
8. an iteration detection method is characterized in that, comprising:
Step 1 is obtained emission modulation symbol estimated value;
Step 2 adopts the soft demodulation process of M-QAM, calculates the bit log-likelihood ratio of described emission modulation symbol estimated value;
Step 3 is deciphered described bit log-likelihood ratio, obtains the external information sequence of binary message bit sequence and code word bits sequence, and whether iterative detection decoding is successful;
Step 4 if decoding failure is then handled by soft mapping, is mapped as emission modulation symbol estimated value with the external information of described transmission code word bits, turns back to described step 1, wherein:
When M=4,
Figure F2009101382568C0000031
When M=16,
Figure F2009101382568C0000032
When M=64,
Figure F2009101382568C0000041
Wherein, l e(c K, i) be the external information of described transmission code word bits; When code word bits is 0, C iBe 1, when code word bits is 1, C iBe-1.I=1,2 ... .M, wherein, M is an order of modulation, and is the integer greater than 1; K=1,2 ... ..N T, N TThe number of expression transmitting antenna;
Figure F2009101382568C0000043
Be complex signal.
9. method according to claim 8 is characterized in that, described method also comprises:
Step 5, if successfully decoded, then to follow-up information receiving unit output decoding code word, detection of end.
10. an iterative detection device is characterized in that, comprising:
Emission modulation symbol estimated value acquiring unit is used to obtain the modulation symbol estimated value;
Soft demodulator is used to obtain the described modulation symbol estimated value of described emission modulation symbol estimated value acquiring unit output, and calculates the bit log-likelihood ratio of described emission modulation symbol estimated value by the soft demodulation process of M-QAM, wherein, and when M=4,
Figure F2009101382568C0000044
When M=16,
Figure F2009101382568C0000046
When M=64,
Figure F2009101382568C0000047
Wherein,
Figure F2009101382568C0000049
Be described emission modulation symbol estimated value,
Figure F2009101382568C00000410
For
Figure F2009101382568C00000411
The approximate log-likelihood ratio of i bit, M is the demodulation exponent number of the soft demodulation of M-QAM; C 1And C 2Be constant;
Decoder is used for the bit log-likelihood ratio of described soft demodulator output is deciphered, and obtains the external information sequence of binary message bit sequence and code word bits sequence, and decode results is carried out iterative detection.
11. device according to claim 10, it is characterized in that, described device also comprises: soft mapper, be used to obtain the external information about the transmission code word bits of described decoder output, and by soft mapping processing, the external information of described code word bits sequence is mapped as the first emission modulation symbol estimated value, and exports described emission modulation symbol estimated value acquiring unit to.
12. device according to claim 10 is characterized in that, described emission modulation symbol estimated value acquiring unit comprise following one of at least:
The first input end mouth is connected with the reception antenna of receiver, is used to receive the data-signal from reception antenna;
Second input port is connected with described soft mapper, is used for the described first emission modulation symbol estimated value from described soft mapper;
The MIMO detecting unit is used for described data-signal and/or the described first emission modulation symbol estimated value are carried out the MIMO detection, obtains described emission modulation symbol estimated value.
13. an iterative detection device is characterized in that, comprising:
Emission modulation symbol estimated value acquiring unit is used to obtain the modulation symbol estimated value;
Soft demodulator is used to obtain the described modulation symbol estimated value of described emission modulation symbol estimated value acquiring unit output, and calculates the bit log-likelihood ratio of described emission modulation symbol estimated value by the soft demodulation process of M-QAM;
Decoder is used for the bit log-likelihood ratio of described soft demodulator output is deciphered, and obtains the external information sequence of binary message bit sequence and code word bits sequence, and decode results is carried out iterative detection;
Soft mapper, be used to obtain the external information about the transmission code word bits of described decoder output, and handle by soft mapping, the external information of described code word bits sequence is mapped as the first emission modulation symbol estimated value, and exports described emission modulation symbol estimated value acquiring unit to;
Wherein:
When M=4,
When M=16,
Figure F2009101382568C0000062
When M=64,
Wherein,
Figure F2009101382568C0000064
l e(c K, i) be the external information of described transmission code word bits; When code word bits is 0, C iBe 1, when code word bits is 1, C iBe-1.I=1,2 ... .M, wherein, M is an order of modulation, and is the integer greater than 1; K=1,2.....N T, N TThe number of expression transmitting antenna; Be complex signal.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102208964A (en) * 2011-05-25 2011-10-05 中兴通讯股份有限公司 System and method for realizing log likelihood ratio in digital system
CN104660370A (en) * 2013-11-25 2015-05-27 华为技术有限公司 Sequence processing method and equipment
CN105337653A (en) * 2014-08-12 2016-02-17 电信科学技术研究院 Signal receiving method in MIMO (Multiple-Input Multiple-Output) system, device and system
WO2018113677A1 (en) * 2016-12-19 2018-06-28 Huawei Technologies Co., Ltd. Hardware virtualization for mean and variance estimations of qam symbols

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102208964A (en) * 2011-05-25 2011-10-05 中兴通讯股份有限公司 System and method for realizing log likelihood ratio in digital system
CN104660370A (en) * 2013-11-25 2015-05-27 华为技术有限公司 Sequence processing method and equipment
CN104660370B (en) * 2013-11-25 2018-09-07 华为技术有限公司 The processing method and equipment of sequence
CN105337653A (en) * 2014-08-12 2016-02-17 电信科学技术研究院 Signal receiving method in MIMO (Multiple-Input Multiple-Output) system, device and system
CN105337653B (en) * 2014-08-12 2019-02-01 电信科学技术研究院 Signal acceptance method, apparatus and system in a kind of mimo system
WO2018113677A1 (en) * 2016-12-19 2018-06-28 Huawei Technologies Co., Ltd. Hardware virtualization for mean and variance estimations of qam symbols
US10270625B2 (en) 2016-12-19 2019-04-23 Futurewei Technologies, Inc. Hardware virtualization for mean and variance estimations of QAM symbols

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