CN105227509A - Mixing decision method in quadrature amplitude modulation code demodulating system and receiving system thereof - Google Patents
Mixing decision method in quadrature amplitude modulation code demodulating system and receiving system thereof Download PDFInfo
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Abstract
The embodiment of the present invention provides a kind of and is used in mixed decision method in quadrature amplitude modulation code demodulating system and receiving system thereof.Mixing decision method is applicable to the receiving system of quadrature amplitude modulation code demodulation, and its step is as follows.One of them of K bit of the constellation point of selected pending quadrature amplitude modulation code demodulation separates bit as waiting.Rcv decoder calculate K of K position of constellation point and export likelihood ratio.To (K-1) individual bit remaining except waiting to separate bit, according to (K-1) individual output likelihood ratio of described (K-1) individual bit, select N number of bit and M bit, wherein, N+M=K-1.Hard decision is carried out, to determine the bit value of a described M bit to described M the bit selected.According to described M the bit value determined, for waiting that separating bit carries out soft-decision, to wait the bit value separating bit described in obtaining.
Description
Technical field
The present invention is a kind of employing quadrature amplitude modulation (QuadratureAmplitudeModulation, QAM) code demodulation (codeddemodulation) system, and the mixing decision method be used in particular in quadrature amplitude modulation code demodulating system and receiving system thereof.
Background technology
DVB-T2 is ETSI (EuropeanTelecommunicationsStandardsInstitute, ETSI) one of terrestrial digital visual radio (DigitalVideoBroadcasting-Terrestrial, DVB-T) transmission standard proposed.DVB-T2 utilizes advanced modulation and coding techniques to carry out digital terrestrial transmissions, realizes second generation terrestrial digital visual radio standard (2ndGenerationTerrestrial) of the efficient transmission of audio frequency, video and data, services.DVB-T2 technology can use 16-QAM, 64-QAM or 256-QAM to modulate and low-density parity check code (Low-densityparity-checkcode, LDPCcode) encoding and decoding technique, compared with 1st generation DVB-T standard, the transmission capacity of DVB-T2 increases by more than 50%.
Because low-density parity check code has higher coding gain in performance, and be proved to be its error correction capability and can approach very much the summer agriculture limit (ShannonLimit), and along with the technological evolvement of integrated circuit, the framework of low-density parity check code and easily carrying out gradually, thus low-density parity check code has been widely used in wireless communication system so far.In low-density parity check code decode procedure, log-likelihood ratio (the loglikelihoodratio of each coding bit need be calculated, LLR), therefore when low-density parity check code uses as internal code (innercode), if when considering that internal code is provided by soft-decision (softdecision), the computing of log-likelihood ratio can be made to become considerably complicated.For example, under the DVB-T2 standard of 256-QAM modulation, if the log-likelihood ratio of one of them bit after calculation code, then need altogether to list 256 constellation point in calculating.But, if consider, internal code changes when being provided by hard decision (harddecision), though under the DVB-T2 standard of 256-QAM modulation, the log-likelihood ratio calculating a coding bit only needs to list 2 constellation point in calculating, thus will speed up the process time of whole decoding, but compared with the low-density parity check code decoding performance of soft-decision, the low-density parity check code decoding performance of employing hard decision can be poor many.
Summary of the invention
The embodiment of the present invention provides a kind of and is used in mixed decision method in quadrature amplitude modulation code demodulating system and receiving system thereof, and described mixing decision method and receiving system thereof can in order to determine the bit value waiting to separate bit.Described mixing decision method and receiving system thereof be using all bits of constellation point one of them as wait separate bit, and except waiting to separate bit remaining except bit, the bit selecting out part uses hard decision to determine its bit value, and again for waiting that separating bit carries out soft-decision.Therefore the constellation point number participated in needed for computing can significantly be reduced, to reduce hardware cost and operation time further.
The embodiment of the present invention provides a kind of mixing decision method.Described mixing decision method is applicable in the receiving system of quadrature amplitude modulation code demodulation, and has following steps.First, one of them of K bit of the constellation point of selected pending quadrature amplitude modulation code demodulation is as treating solution bit.Secondly, K that receives a described K bit exports likelihood ratio (likelihoodratio), and wherein, described K exports likelihood ratio and calculated respectively by the decoder in receiving system.Then, (K-1) individual bit remaining except waiting to separate bit, according to the respective output likelihood ratio of described (K-1) individual bit, selects N number of bit and M bit, wherein, and N+M=K-1.Moreover, hard decision is carried out, to determine the bit value of a described M bit to described M the bit selected.Finally, according to described M the bit value determined, for waiting that separating bit carries out soft-decision, to wait the bit value separating bit described in obtaining.
The embodiment of the present invention separately provides a kind of receiving system, and described receiving system comprises one or more circuit, becomes to wait to separate position choose module, decoder, firmly sentence module and softly sentence module in order to configuration.Wait to separate bit and choose module in order to one of them of K bit of the constellation point of selected pending quadrature amplitude modulation code demodulation as treating solution bit.Decoder exports likelihood ratio in order to K of calculating a described K bit.K that firmly sentences described K the bit that module calculates in order to Rcv decoder exports likelihood ratio, and according to (K-1) individual output likelihood ratio of (K-1) individual bit remaining except treating solution bit, select N number of bit and M bit, and hard decision is carried out to a described M bit, to determine the bit value of a described M bit, wherein, N+M=K-1.According to M the bit value firmly sentenced module and determine, softly sentence module for waiting that separating bit carries out soft-decision, to obtain the bit value waiting to separate bit.
In sum, one that the embodiment of the present invention provides mixing decision method and receiving system thereof carry out hard decision by the credible bit value of part, and then the constellation point of participation computing are reduced to only have 2
n+1individual.Described mixing decision method and receiving system significantly can reduce the constellation point number participated in needed for computing, to reduce operation time and operand.Therefore, adopt the receiving system of described mixing decision method can not need to adopt the hardware possessing high-speed computational capability, and its manufacturing cost is minimized.
Further understand feature of the present invention and technology contents for enable, please refer to hereafter detailed description for the present invention and accompanying drawing, but these illustrate with appended accompanying drawing only for illustration of the present invention, but not any restriction is done to interest field of the present invention.
Accompanying drawing explanation
Fig. 1 is the schematic flow sheet of the mixing decision method that the embodiment of the present invention provides.
Fig. 2 is the function block schematic diagram of the receiving system that the embodiment of the present invention provides.
Symbol description
S101 ~ S109: process step
2: receiving system
201: wait that separating bit chooses module
203: decoder
205: firmly sentence module
207: softly sentence module
Embodiment
Hereinafter, the present invention will be described in detail by graphic explanation various embodiment of the present invention.But concept of the present invention may embody in many different forms, and should not be construed as and be limited to set forth exemplary embodiments herein.In addition, same reference numbers can in order to element like representation class in the drawings.
When calculating one of them bit value until solution bit of all bits of quadrature amplitude modulation code demodulation constellation point, after the hybrid decision method that the embodiment of the present invention provides can carry out hard decision by part trusted bit unit value, then for waiting that separating bit carries out soft-decision.So, described hybrid decision method significantly can reduce the constellation point number participated in needed for computing, and then reaches reduction hardware cost and the effect of operation time.
The mixing decision method that the embodiment of the present invention provides is applicable in the receiving system of any quadrature amplitude modulation code demodulation.For example, described receiving system can be a DVB-T2 receiving system, but the present invention is not as limit.In addition, quadrature amplitude modulation refers to transmits two or more bit on a tilde, and described tilde can represent (such as, alpha+beta i) with the mathematical formulae of real number and imaginary number.The available planisphere that transmits of QAM represents easily, on planisphere each constellation point correspondence transmit in a signal, constellation point adopts level and the equally spaced square mesh configuration of vertical direction usually, generally the number of constellation point is the power of 2, therefore common quadrature amplitude modulation form has 16-QAM, 64-QAM, 256-QAM etc., and number of constellation points is more, represent the amount of information that each symbol can transmit larger.For example, the constellation point on 256-QAM is the signal indication formed with 8 bits, and that is a constellation point energy transmission information amount of 256-QAM is 8 bits.To this, the mixing judgement mode that the embodiment of the present invention provides can be applicable in any type of quadrature amplitude modulation code demodulating system, and the present invention is not as limit.
Refer to Fig. 1, Fig. 1 is the schematic flow sheet of the mixing decision method that the embodiment of the present invention provides.The mixing decision method of the embodiment of the present invention can be executed in the receiving system of quadrature amplitude modulation code demodulating system.First, in step S101, receiving system first can select K bit of a constellation point of pending quadrature amplitude modulation code demodulation one of them separate bit as waiting.Then, in step s 103, receiving system receive its built-in decoder calculate K of a described K bit and export likelihood ratio (likelihoodratio).Described decoder can be a low-density parity check code decoder, and above-mentioned K output likelihood ratio can be K and export log-likelihood ratio in addition, but the present invention is not all as limit.For example, decoder other types can export the decoder of likelihood ratio in order to produce, and the likelihood ratio exported must not represent with the form of logarithm, should be understood that, the likelihood ratio of output is in fact represent that corresponding bit value is the operation result of the probability size of 0 or 1.
In step S105, to remaining (K-1) the individual bit except treating solution bit, receiving system selects N number of bit and M bit, wherein N+M=K-1 according to described (K-1) individual output likelihood ratio from (K-1) individual bit.In step s 107, receiving system carries out hard decision to a described M bit, to determine the bit value of a described M bit.Then, in step S109, receiving system based on the bit value of described M bit determined, for waiting that separating bit carries out soft-decision, to obtain the bit value treating solution bit.
Subsidiary one carry be, when K output likelihood ratio of K bit is K output log-likelihood ratio, in above-mentioned steps S105, receiving system selectes out according to the absolute value of described (K-1) individual output likelihood ratio described M the bit that wish performs hard decision.In simple terms, determine part (such as, the M) bit that confidence level is higher by the absolute value of (K-1) individual output likelihood ratio, and directly can be decided the bit value of described part bit in order to subsequent step by hard decision.In fact, can sort according to the absolute value of (K-1) individual output likelihood ratio of described (K-1) individual bit, then select out M the bit of maximum absolute value of (K-1) individual output likelihood ratio.Also or, make comparisons for the absolute value of (K-1) individual output likelihood ratio of described (K-1) individual bit and a threshold value, the absolute value finding out (K-1) individual output likelihood ratio is greater than M bit of described threshold value.Generally speaking, the detailed implementation of the present invention not conditioning step S105.Specifically, by the way (such as, sequence or threshold value judge), the mixing decision method of the embodiment of the present invention can determine the bit that part confidence level is higher, therefore relatively can reduce the constellation point number participated in needed for computing.Note that those of ordinary skill in the art maybe should should be used for carrying out selecting according to actual demand the design of the higher bit of M confidence level at this, the detailed implementation of the present invention not conditioning step S105.
In addition, when K output likelihood ratio of K bit is K output log-likelihood ratio, in above-mentioned steps S107, the polarity that the hard decision module in receiving system mainly exports likelihood ratio according to M of a described M bit determines the bit value of a described M bit respectively.For example, if there is the output likelihood ratio of 5 bits (M=5) to be respectively [10, 3,-5.6,-1.4, 3.5], the hard decision module that then receiving system is built-in judges the bit value of its 5 bits respectively according to the polarity of the output likelihood ratio of 5 bits described in it, wherein, when the words that output likelihood ratio is greater than 0, determine that the bit value of described correspondence is 0, and work as the words exporting likelihood ratio and be less than 0, then determine that the bit value of described correspondence is 1, as example, therefore the bit value of 5 bits that above-mentioned 5 bits determine through the hard decision module that receiving system is built-in is respectively [0, 0, 1, 1, 0].Maybe should should be used for carrying out according to actual demand the design of hard decision at this those of ordinary skill that note that in the art, the detailed implementation of the present invention not conditioning step S107.
In the present embodiment, when K output likelihood ratio of K bit is K output log-likelihood ratio, in above-mentioned steps S109, receiving system is based on the bit value of described M bit determined, as follows for treating that solution bit carries out the output log-likelihood ratio equation that soft-decision adopts:
Wherein, P
r(b
i=1|I, Q) represent code demodulation after bit value be the probability of " 1 ", and P
r(b
i=0|I, Q) represent code demodulation after bit value be the probability of " 0 ".
But, due to P
r(b
i=1|I, Q) and P
r(b
i=0|I, Q) logarithm of ratio is too complicated, therefore aforesaid equation can be simplified by prior art, its derivation content simplified can please refer to DVB-T2 implementation guide (the ImplementationGuidelinesforasecondgenerationdigitalterre strialtelevisionbroadcastingsystem (DVB-T2) that DVB steering committee delivers in ETSI, ETSITS102831V1.2.1,2012-08), however the present invention not as limit.Equation after simplification is expressed as follows:
Wherein, ρ
i, ρ
qfor the amplitude fading factor,
be respectively the set that segmentation constellation point is formed, LLR
eXTb () is feedback log likelihood ratio.
Specifically, in above-mentioned steps S109, receiving system based on determine described M bit bit value for treat solution bit carry out in the process of soft-decision, receiving system be use N number of feedback log likelihood ratio of described N number of bit obtain described in wait to separate the bit value of bit, N number of output log-likelihood ratio that wherein said N number of feedback log likelihood ratio is respectively described N number of bit deducts N number of input log-likelihood ratio of described N number of bit.I.e. LLR
eXT(b)=LLR
oUT(b)-LLR
iN(b).Therefore, at receiving system for waiting that separating bit carries out in the process of soft-decision, because the bit value of an existing described M bit is determined by hard decision, therefore the constellation point of participation computing can reduce to and only has 2
n+1individual.
It should be noted that, according to above embodiment, can learn, within a work period, by using above-mentioned hybrid decision method, receiving system can select K bit of a constellation point of pending quadrature amplitude modulation code demodulation one of them separate bit as waiting, and described in can obtaining, wait the bit value separating bit.But on the planisphere of quadrature amplitude modulation code demodulation, on planisphere, each constellation point is actual is expressed as a corresponding transmitting symbol, and each launches symbol is then represented by K bit.Therefore, when receiving system goes out the bit value of all K bits of described constellation point for perfect restitution, receiving system must perform hybrid decision method of the present invention K the work period altogether.That is, each work period performs mixed once decision method, can obtain out the bit value of one of them bit in K bit, by that analogy.Subsequently, after K work period, receiving system just can go out K bit value of a described K bit by perfect restitution.Accordingly, receiving system complete decoding can go out all bits in described constellation point.But for the order of bit value of described K bit distinctly decoding constellation point, those of ordinary skill in the art maybe should should be used for designing according to actual demand, and the present invention is not as limit.
Carry out decoding for 8 bits of the constellation point of 256-QAM by using below and exports likelihood ratio for an example of output log-likelihood ratio and be described, but the present invention is not limited thereto.Please continue to refer to Fig. 1, on the planisphere of described 256-QAM, each constellation point all represents with 8 bits, and described 8 bits are expressed as (b
0, b
1, b
2, b
3, b
4, b
5, b
6, b
7).
First, the bit b of 8 bits of a constellation point of pending 256-QAM code demodulation selected by receiving system
0bit (step S101) is separated as waiting.Secondly, receiving system receive its built-in decoder calculate 8 of described 8 bits and export log-likelihood ratios, 8 of wherein said 8 bits export log-likelihood ratios and are respectively [0.15 ,-0.2,10,3 ,-5.6 ,-1.4,3.5 ,-0.6] (step S103).Receiving system separates bit b to except waiting
0outside remaining 7 bits, export log-likelihood ratios according to 7 of described 7 bits and select 2 bit (position b
1and position b
7) and 5 bit (position b
2~ position b
6), wherein 2+5=8-1 (i.e. N=2, M=5) (step S105).
Furthermore, receiving system first sorts according to 7 absolute values exporting log-likelihood ratio [-0.2,10,3 ,-5.6 ,-1.4,3.5 ,-0.6] of remaining 7 bits, the descending ranking results of this absolute value is [10,5.6,3.5,3,1.4,0.6,0.2], therefore can learn, the descending order of 7 bits is respectively [b
2, b
4, b
6, b
3, b
5, b
7, b
1], judged by sequence or threshold value, receiving system determines 5 bits that in remaining 7 bits, confidence level is the highest and (is sequentially b
2, b
4, b
6, b
3, b
5) directly can perform hard decision (step S105).
Then, module is firmly sentenced for described 5 bit (b in receiving system
2, b
3, b
4, b
5, b
6) the polarity of output log-likelihood ratio carry out hard decision, to determine described 5 bit (b respectively
2, b
3, b
4, b
5, b
6) bit value, for example, when output likelihood ratio be greater than 0, judge that the bit value of described corresponding bit is as 0, and when export likelihood ratio be less than 0, then judge that the bit value of described corresponding bit is as 1.Therefore, through receiving system built-in firmly sentence described 5 bit (b that module determines
2, b
3, b
4, b
5, b
6) bit value be respectively [0,0,1,1,0] (step S107).
Receiving system is based on described 5 the bit (b determined
2, b
3, b
4, b
5, b
6) bit value [0,0,1,1,0], separate bit b for waiting
0carry out soft-decision, wait to separate bit b to obtain
0bit value (step S109).Therefore, receiving system is separating bit b for waiting
0carry out in the process of soft-decision, based on the bit (b that part confidence level is higher
2, b
3, b
4, b
5, b
6) decide its bit value by hard decision, and then make to need the constellation point participating in computing to reduce to only to have 2
2+1=8 (being respectively 00001100,01001100,00001101,01001101,10001100,11001100,10001101,11001101), to reduce hardware cost and operation time by this.
It should be noted that according to mentioned above, can learn, the bit b of 8 bits of the constellation point of 256-QAM code demodulation
0bit value can determine by mixed decision method.Subsequently, receiving system will change with the bit b of 8 of selected constellation point bits
1separate bit (step S101) as waiting, and repeat same steps flow process (step S101 ~ step S109), to obtain described bit b
1bit value.By that analogy, receiving system sequentially can obtain the bit value of all 8 bits of the described constellation point of 256-QAM code demodulation.
According to mentioned above, due on the receiving system of traditional employing quadrature amplitude modulation code demodulation techniques, if when considering that internal code is provided by soft-decision, the computing of LLR can be made to become considerably complicated.For example, under the standard of 256-QAM code modulation, if wherein one wait to separate the log-likelihood ratio of bit after calculation code, then need altogether to list 256 constellation point in calculating.But, if consider, internal code changes when being provided by hard decision, though under the standard of 256-QAM code modulation, calculate the log-likelihood ratio waiting to separate bit only to need to list 2 constellation point in calculating, thus the process time of whole decoding can be accelerated, but compared with the decoding performance of soft-decision, the decoding performance of employing hard decision can be poor many.On the contrary, the mixing decision method that the embodiment of the present invention provides mainly realizes in the mode of hard decision collocation soft-decision.Described mixing decision method part uses soft-decision, to possess preferably decoding performance, in addition according to carrying out hard decision by the bit that part confidence level is higher, constellation point number required when participating in computing significantly to reduce, to reduce hardware cost and operation time.
As mentioned before, the receiving system that decision method can be applicable to the demodulation of any quadrature amplitude modulation code is mixed.In order to illustrate further the running about mixing decision method, the embodiment of the present invention provides a kind of execution mode of receiving system further.Please refer to Fig. 2, Fig. 2 is the function block schematic diagram of the receiving system that the embodiment of the present invention provides.But following receiving system 2 is only wherein a kind of implementation of above-mentioned mixing decision method, and it is not intended to limiting the invention.
Described receiving system 2 is in order to any quadrature amplitude modulation code demodulating system, and for example, described receiving system 2 can be a DVB-T2 receiving system, but the present invention is not as limit.Receiving system 2 can comprise one or more circuit, becomes to wait to separate bit choose module 201, decoder 203, firmly sentence module 205 and softly sentence module 207 in order to configuration.Above-mentioned each element realizes by pure hardware circuit, or is realized by hardware circuit collocation firmware or software, and in a word, the present invention does not limit the specific implementation of receiving system 2.
Wait to separate bit choose module 201 in order to select out K bit of a constellation point of pending quadrature amplitude modulation code demodulation one of them as treating solution bit.In general, quadrature amplitude modulation form common are 16-QAM, 64-QAM, 256-QAM etc., and number of constellation points is more, represents the amount of information that each symbol can transmit larger.For example, the constellation point on 256-QAM is the signal indication formed with 8 bits, and the amount of information that is a constellation point of 256-QAM can be transmitted is 8 bits.To this, the receiving system 2 that the embodiment of the present invention provides can be applicable in any type of quadrature amplitude modulation code demodulation mode, and the present invention is not as limit.
Decoder 203 exports likelihood ratio in order to K of calculating described K bit of constellation point.Decoder 203 can be a low-density parity check code decoder, and above-mentioned K output likelihood ratio can be K and export log-likelihood ratio in addition, but the present invention is not all as limit.
Firmly sentence module 205 in order to receive decoder 203 calculate K of K bit of constellation point and export likelihood ratio, to remaining (K-1) the individual bit except treating solution bit, N number of bit and M bit is selected according to its (K-1) individual output likelihood ratio, and hard decision is carried out to a described M bit, to determine the bit value of a described M bit, wherein N+M=K-1.Softly sentence module 207 based on the bit value of described M bit determined, for waiting that separating bit carries out soft-decision, to obtain the bit value treating solution bit.
In the present embodiment, K exports likelihood ratio and can be K output log-likelihood ratio, firmly sentences module 205 and selectes out according to the absolute value of described (K-1) individual output likelihood ratio described M the bit that wish performs hard decision.In simple terms, determine part (such as, the M) bit that confidence level is higher by the absolute value of (K-1) individual output likelihood ratio, and firmly to sentence module 205 directly carry out hard decision for the bit that described part confidence level is higher.Note that those of ordinary skill in the art maybe should should be used for carrying out selecting according to actual demand the design of the higher bit of M confidence level at this, the present invention does not limit the detailed implementation firmly sentencing module 205.
In fact, can sort according to the absolute value of (K-1) individual output likelihood ratio of described (K-1) individual bit, then select out M the bit of maximum absolute value of (K-1) individual output likelihood ratio.Also or, make comparisons for the absolute value of (K-1) individual output likelihood ratio of described (K-1) individual bit and a threshold value, the absolute value finding out (K-1) individual output likelihood ratio is greater than M bit of described threshold value.Generally speaking, the present invention does not limit the detailed implementation firmly sentencing module 205.Specifically, according to aforesaid way (such as, sequence or threshold value judge), the receiving system 2 of the embodiment of the present invention can determine the position that part confidence level is higher, therefore relatively reduces the constellation point number participated in needed for computing.
In addition, when K export likelihood ratio can be K export log-likelihood ratio time, firmly sentence module 205 determines a described M bit respectively bit value according to the polarity of M of described M bit output likelihood ratio.For example, if there is the output likelihood ratio of 5 bits (M=5) to be respectively [10, 3,-5.6,-1.4, 3.5], the hard decision module that then receiving system is built-in judges the bit value of its 5 bits respectively according to the polarity of the output likelihood ratio of 5 bits described in it, wherein, when the words that output likelihood ratio is greater than 0, determine that the bit value of described correspondence is 0, and work as the words exporting likelihood ratio and be less than 0, then determine that the bit value of described correspondence is 1, as example, therefore the bit value of 5 bits that above-mentioned 5 bits determine through the hard decision module that receiving system is built-in is respectively [0, 0, 1, 1, 0].Those of ordinary skill in the art maybe should should be used for carrying out according to actual demand the design of hard decision, and the present invention does not limit the detailed implementation firmly sentencing module 205.
In the present embodiment, soft sentence module 207 based on determine described M bit bit value for treat solution bit carry out in the process of soft-decision, determine because the bit value of an existing described M bit passes through firmly to sentence module 205, therefore softly sentence the constellation point participating in computing in module 207 and can reduce to and only have 2
n+1individual.
Subsidiary one carry be, according to above embodiment, can learn, within a work period, receiving system chooses module 201 using one of them of K bit of a constellation point of selected pending QAM code demodulation as treating solution bit by waiting to separate bit, and sentence module 207 for waiting that separating bit carries out soft-decision, to obtain the bit value waiting to separate bit by soft.But on the planisphere of QAM code demodulation, on planisphere, each constellation point is actual is expressed as a corresponding transmitting symbol, and each launches symbol is then represented by K bit.Therefore, when receiving system goes out the bit value of all K bits of described constellation point for perfect restitution, treat that solution bit is chosen module 201 and must sequentially be selected by each bit in turn as waiting to separate bit, and sentence module 207 and distinctly obtain by soft the bit value that each waits to separate bit, by that analogy, receiving system just complete decoding can go out all bits in described constellation point.But wait that separating bit chooses the order of one of them that module 201 selectes out K bit of constellation point, those of ordinary skill in the art maybe should should be used for designing according to actual demand, and the present invention is not as limit.
According to mentioned above, due on the receiving system of traditional employing quadrature amplitude modulation code demodulation techniques, if when considering that internal code is provided by soft-decision, the computing of log-likelihood ratio can be made to become considerably complicated.For example, under the standard of 256QAM code modulation, if one of them after calculation code waits the output likelihood ratio of separating bit, then need altogether to list 256 constellation point in calculating.But, if consider, internal code changes when being provided by hard decision, though under the standard of 256QAM code modulation, calculate one and wait that the LLR separating bit only needs to list 2 constellation point in calculating, thus the process time of whole decoding can be accelerated, but compared with the decoding performance of soft-decision, the decoding performance of employing hard decision can be poor many.On the contrary, mainly firmly to sentence, module collocation is soft sentences module to the receiving system that provides of the embodiment of the present invention.Softly sentence module for waiting that separating bit carries out soft-decision, possess preferably decoding performance, the part bit that confidence level is higher in addition then directly carries out hard decision, to determine the bit value of described part bit by firmly sentencing module.Therefore, the receiving system of the embodiment of the present invention significantly can reduce and participates in soft constellation point number required when sentencing module arithmetic, to reduce hardware cost and operation time.
In sum, one that embodiment of the present invention provides mixing decision method and receiving system thereof carry out hard decision by the credible bit value of part, and then the constellation point of participation computing are reduced to only have 2
n+1individual.Described mixing decision method and receiving system significantly can reduce the constellation point number participated in needed for computing, to reduce operation time and operand.Therefore, adopt the receiving system of described mixing decision method can not need to adopt the hardware possessing high-speed computational capability, and its manufacturing cost is minimized.
Mentioned abovely be only embodiments of the invention, it is also not used to limit to the scope of the claims of the present invention.
Claims (18)
1. mix a decision method, be applicable in a receiving system of a quadrature amplitude modulation code demodulation, it is characterized in that, described mixing decision method comprises:
One of them of K bit of one constellation point of selected pending described quadrature amplitude modulation code demodulation is waited to separate bit as one;
Receive a decoder of described receiving system calculate K of described K bit of corresponding described constellation point and export likelihood ratio;
To except described remaining (K-1) individual bit waiting to separate except bit, described (K-1) the individual output likelihood ratio according to described (K-1) individual bit selects N number of bit and M bit, wherein, and N+M=K-1;
Hard decision is carried out to a described M bit, to determine the bit value of a described M bit; And
Based on the bit value of described M bit determined, wait that separating bit carries out soft-decision for described, to treat the bit value of solution bit described in obtaining.
2. mixing decision method according to claim 1, it is characterized in that, described K exports likelihood ratio is K output log-likelihood ratio, and selects a described M bit according to the absolute value of described (K-1) individual output log-likelihood ratio of described (K-1) individual bit.
3. mixing decision method according to claim 2, is characterized in that, is carrying out in hard decision to a described M bit, and the polarity according to described M output log-likelihood ratio of a described M bit determines the bit value of a described M bit respectively.
4. mixing decision method according to claim 2, it is characterized in that, absolute value according to described (K-1) individual output log-likelihood ratio of described (K-1) individual bit sorts, with described M the bit that the absolute value selecting described M output log-likelihood ratio is larger.
5. mixing decision method according to claim 2, is characterized in that, described M the absolute value exporting log-likelihood ratio of a described M bit is greater than a threshold value.
6. mixing decision method according to claim 2, is characterized in that, waits that separating bit carries out, in the step of soft-decision, having 2 at the bit value based on described M the bit determined for described
n+1individual constellation point must carry out computing.
7. mixing decision method according to claim 1, is characterized in that, described receiving system is a DVB-T2 receiving system.
8. mixing decision method according to claim 1, is characterized in that, described decoder is a low-density parity check code decoder.
9. mixing decision method according to claim 2, it is characterized in that, wait that separating bit carries out in the step of soft-decision at the bit value based on described M the bit determined for described, use N number of feedback log likelihood ratio of described N number of bit obtain described in wait to separate the bit value of bit, wherein, described N number of output log-likelihood ratio that described N number of feedback log likelihood ratio is respectively described N number of bit deducts N number of input log-likelihood ratio of described N number of bit.
10. a receiving system, is characterized in that, described receiving system comprises:
One or more circuit, described one or more circuit is used for configuration and becomes:
One waits that separating bit chooses module, described in wait to separate bit and choose module and treat solution bit for one of them of K bit of a constellation point of a selected pending quadrature amplitude modulation code demodulation as one;
One decoder, described decoder exports likelihood ratio for K of calculating described K bit of corresponding described constellation point;
One sentences module firmly, described firmly sentence module for receive described decoder calculate described K of described K bit of corresponding described constellation point and export likelihood ratio, to except described remaining (K-1) individual bit waiting to separate except bit, described (K-1) individual output likelihood ratio according to described (K-1) individual bit selects N number of bit and M bit, and hard decision is carried out to a described M bit, to determine the bit value of a described M bit, wherein, N+M=K-1; And
One softly sentences module, describedly softly sentences the bit value of module based on described M the bit determined, waits that separating bit carries out soft-decision for described, to treat the bit value of solution bit described in obtaining.
11. receiving systems according to claim 10, it is characterized in that, described K exports likelihood ratio is K output log-likelihood ratio, and describedly firmly sentences module and select a described M bit according to the absolute value of described (K-1) individual output log-likelihood ratio of described (K-1) individual bit.
12. receiving systems according to claim 11, is characterized in that, are carrying out in hard decision to a described M bit, describedly firmly sentence module determines a described M bit respectively bit value according to the polarity that described M of a described M bit exports log-likelihood ratio.
13. receiving systems according to claim 11, it is characterized in that, describedly firmly sentence module and sort according to the absolute value of described (K-1) individual output log-likelihood ratio of described (K-1) individual bit, to select described M larger bit of described M the absolute value exporting log-likelihood ratio.
14. receiving systems according to claim 11, is characterized in that, described M the absolute value exporting log-likelihood ratio of a described M bit is greater than a threshold value.
15. receiving systems according to claim 11, is characterized in that, described soft sentence module based on determine described M bit bit value for described until solution bit carry out soft-decision time, have 2
n+1individual constellation point must carry out computing.
16. receiving systems according to claim 10, is characterized in that, described receiving system is a DVB-T2 receiving system.
17. receiving systems according to claim 10, is characterized in that, described decoder is a low-density parity check code decoder.
18. receiving systems according to claim 11, it is characterized in that, described soft sentence module based on determine described M bit bit value for described until solution bit carry out soft-decision time, wait to separate the bit value of bit described in the described soft N number of feedback log likelihood ratio sentencing the described N number of bit of module use obtains, wherein, described N number of output log-likelihood ratio that described N number of feedback log likelihood ratio is respectively described N number of bit deducts N number of input log-likelihood ratio of described N number of bit.
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