CN103166903A - Soft demapping pretreatment method and soft demapping method for constellation map - Google Patents

Abstract

The invention discloses a soft demapping pretreatment method and a soft demapping method for a constellation map. By the soft demapping pretreatment method and the soft demapping method, the problems of large operand, large occupancy of system resources, high implementation cost of hardware and the like in the conventional Max-Log-MAP are solved. The constellation mapped soft demapping pretreatment method comprises the following steps of: dividing signal space containing M constellation points into N areas according to the constellation map; and constructing a table B, and recording a constellation point set Si for the calculation of a log-likelihood ratio in an area i in the table B, wherein i is a positive integer which is smaller than or equal to N, Si comprises a constellation point subset, the constellation point subset contains a constellation point of which the k bit position is 0 and which is closest to the distance of a preset point in the area i, a constellation point of which the k bit position is 1 and which is closest to the distance of the preset point in the area i, and k is a positive integer which is smaller than or equality log2M. The soft demapping method comprises the following steps of: receiving and judging the area i to which an information symbol belongs; and reading the table B, and performing the calculation of the log-likelihood ratio on the information symbol and the constellation points in the Si in a preset method.

Description

The soft solution preprocess method of constellation mapping and soft solution method

Technical field

The present invention relates to the digital information communications field, relate in particular to a kind of soft solution preprocess method and soft solution method of constellation mapping.

Background technology

The soft solution method of at present the most frequently used constellation mapping comprises the following steps:

Step 1: receive information symbol;

Step 2: according to each constellation point in each bit and signal space in information symbol, ask for log-likelihood ratio by formula (2), this method is called the Max-Log-MAP algorithm;

Log-likelihood ratio LLR(Log-Likelihood Ratio) be usually used in the soft information of each bit in the expressing information symbol;

For certain bit b, its log-likelihood ratio is defined as:

$\mathrm{LLR}\left(b\right)=\log \frac{P(b=1|y)}{P(b=0|y)}---\left(1\right)$

The symbology of the log-likelihood ratio that obtains the court verdict of this bit, the absolute value of the value of log-likelihood ratio is the confidence level of this result, obtains having completed after log-likelihood ratio soft solution mapping.

For example in additive white Gaussian noise AWGN (Additive White Gaussian Noise) channel model, the mapping exponent number is that M namely comprises in the planisphere of M constellation point:

$\mathrm{LLR}\left(b_{i,k}\right)=\frac{1}{2{\mathrm{\σ}}^2}(\underset{x\∈S_k^{\left(1\right)}}{\min }\left({|y_i-G_{i}x|}^2\right)-\underset{x\∈S_k^{\left(0\right)}}{\min }\left({|y_i-G_{i}x|}^2\right))---\left(2\right)$

G wherein _iFor the channel fading of separating i the information symbol that obtains before mapping is estimated (being channel condition information); For i receiving symbol yi; Represent that k bit is the set of 1 constellation symbols (being constellation point),

Represent that k bit is the set of 0 constellation symbols.

From the foregoing, ask for the log-likelihood ratio of each bit in information symbol if adopt the Max-Log-MAP method, need the computing of O (M) sub-addition, the inferior multiplying of O (M) and the inferior compare operation of O (MlogM), therefore as can be known when in planisphere, mapping exponent number M value is larger, amount of calculation is large, thereby the system resource that consumes is many, and hard-wired cost is large.

Summary of the invention

The technical problem that (one) will solve

The present invention aims to provide a kind of soft solution preprocess method and soft solution method that log-likelihood calculations amount, computing time and minimizing system resource took, reduced the constellation mapping of hardware implementation cost that reduce.

(2) technical scheme

For addressing the above problem, the soft solution preprocess method of constellation mapping of the present invention comprises the following steps:

The signal space that will include M constellation point according to the constellation mapping that adopts is divided into N zone;

Build table B, record the constellation point set S that is used for log-likelihood calculations in regional i in table B _iI is the integer that is not more than N;

Wherein,

Described S _iComprise the constellation point subset

And constellation point subset

Described

Comprise the k bit and be 0 and with regional i in the nearest constellation point in preset;

Described

Comprise the k bit and be 1 and with regional i in the nearest constellation point in preset;

Described k is for being not more than log ₂The positive integer of M.

Further, in the soft solution preprocess method of described constellation mapping, according to constellation mapping, zone division and performance requirement, one or more presets are set in regional i.

Further, described constellation point set S _iInterior constellation point is calculated by Monte Carlo algorithm or greedy algorithm and is asked for.

Further, described table B is stored in random access storage device, read-only memory or combinational logic circuit.

For addressing the above problem, the soft solution method of constellation mapping of the present invention after being used for preliminary treatment that the soft solution preprocess method of above-mentioned constellation mapping carries out, comprises the following steps:

Receive information symbol, the regional i under the determination information symbol;

Regional i from table B under the obtaining information symbol is used for the constellation point set S of log-likelihood calculations _i, and press presetting method to information symbol and S _iIn constellation point carry out log-likelihood calculations.

Preferably, described presetting method is for passing through formula

$\mathrm{LLR}\left(b_K\right)=\frac{1}{2{\mathrm{\σ}}^2}(\underset{x\∈S_{i,k}^{\left(1\right)}}{\min }\left({|y-G_{i}x|}^2\right)-\underset{x\∈S_{i,k}^{\left(0\right)}}{\min }\left({|y-G_{i}x|}^2\right))$ Calculate the log-likelihood ratio of each bit in described information symbol;

Wherein, LLR is log-likelihood ratio; b _kBe k bit of information symbol, and k is for being not more than log ₂The positive integer of M.

Preferably, the zone that belongs to by hard decision method determination information symbol.

Preferably, also comprise and utilize channel condition information to carry out normalized to described information symbol after receiving information symbol with before the zone of judging under described information symbol, thereby obtain the normalization information symbol.

(3) beneficial effect of the present invention

By repeatedly studying and verifying in the soft solution process of finding constellation mapping, be usually located at the information symbol of close positions in signal space, when carrying out the log-likelihood calculations of each bit, tagmeme same with it is some specific position that 0 or 1 the nearest point of constellation point middle distance concentrates on signal space, and in traditional Max-Log-MAP method, during the log-likelihood ratio computing of each bit in carrying out information symbol, what do not add screening carries out computing with all constellation point;

The soft solution preprocess method of constellation mapping of the present invention is to utilize above-mentioned rule, above-mentioned special point is screened, and the soft solution method of constellation mapping of the present invention, to utilize the result that the soft solution preprocess method of constellation mapping of the present invention solves to carry out the computing of log-likelihood ratio, thereby reduced widely operand, reduced taking of system resource, reduced hard-wired cost, especially for the large constellation mapping of mapping exponent number, soft solution effect is especially obvious.

Description of drawings

Fig. 1 is the described signal space schematic diagram of the embodiment of the present invention one;

Fig. 2 is the soft solution method flow diagram of the described constellation mapping of second embodiment of the invention;

Fig. 3 is the described signal space schematic diagram of fourth embodiment of the invention;

Fig. 4 is the schematic diagram after the described signal space of Fig. 3 is divided into a plurality of zones;

Fig. 5 is the soft solution method of the described constellation mapping of fourth embodiment of the invention and traditional Max-Log-MAP method performance comparison figure under awgn channel;

Fig. 6 is the soft solution method of the described constellation mapping of fourth embodiment of the invention and traditional Max-Log-MAP method performance comparison figure under the i.i.d.Rayleigh channel.

Embodiment

Below in conjunction with Figure of description and embodiment to the soft solution preprocess method of constellation mapping of the present invention to be described further.

Embodiment one:

As shown in Figure 1, the soft solution preprocess method of the present embodiment constellation mapping comprises the following steps:

The signal space that will include 16 constellation point according to the constellation mapping that adopts is divided into 4 zones; Each zone is all distinguished with different shade, the digitized representation of each regional center regional numbering, wherein comprise 4 constellation point in each zone; Each information symbol comprises 4 bits;

Build table B; Record the constellation point set S that is used for log-likelihood calculations in regional i in table B _iI is that to be not more than 4 integer be that i is 1,2,3 or 4; Concrete zone as shown in Figure 11, zone 2, zone 3 and zone 4;

Wherein,

Described S _iComprise the constellation point subset

And constellation point subset

Described

Comprised the k bit and be 0 and with regional i in preset---the constellation point that some p is nearest;

Described

Comprised the k bit and be 1 and with regional i in preset---the constellation point that some p is nearest;

Described k is for being not more than log ₂The positive integer of M can be less than or equal to 4;

Build table B; Record the constellation point set that each zone is used for log-likelihood calculations in table B;

In zone 1, when the preset is one and during for zone 1 central point, the constellation point set has comprised that high-order the first bit is 0 constellation point subset

And high-order the first bit is 1 constellation point subset

Therefore in computational process, it is that 4 constellation point of 0 and 2 constellation point of high-order the first bit 1 are carried out computing that information symbol only needs with high-order the first bit, be that 8 constellation point of 0 and high-order the first bit are that 8 constellation point of 1 are carried out computing with respect to traditional Max-Log-MAP method and high-order the first bit, saved operand, reduced the consumption of system resource, hardware implementation cost is lower.

And in traditional Max-Log-MAP method, there is no the soft solution preprocessing process of constellation mapping, wherein to have included M/2 be 0 with information symbol with tagmeme or be that 1 constellation point is calculated in computing each time; And at first the soft solution preprocess method of the present embodiment constellation mapping is confirmed by preliminary treatment the nearest point that may occur not only to have reduced multiplication and add operation between information symbol and constellation point in follow-up log-likelihood calculations; Also reduce comparison operation, be applied in the soft solution process of constellation mapping of high-order effect of optimization especially obvious.

In concrete implementation process, described preset divides according to constellation mapping, zone and the requirement of performance is one or more, is distributed in the diverse location of regional i; Required precision is higher, and the value of preset should be more.In zone 1, comprise center and two marginal points in zone 1 when the preset, and one of described marginal point is positioned at the central point of the edge line that has a common boundary with zone 2, a central point that is positioned at the edge line that has a common boundary with zone 3; Described constellation point set has comprised that high-order the first bit is 0 constellation point subset

And high-order the first bit is 1 constellation point subset

As from the foregoing, the number of preset and position all are related to the composition of constellation point subset, be related to equally the accuracy of final operation result etc., therefore in concrete implementation process, the position of preset and number decide according to zone division, constellation mapping and performance requirement again, when the number of preset is 1, usually be chosen for the center of constellation point in the zone.

In concrete implementation process, the division in zone should be according to different types of constellation mapping, the required precision of solving result and the size of operand are divided, and the zone of dividing is unsuitable excessive.

Embodiment two:

On the basis of a upper embodiment, provide two kinds of methods of asking for the constellation point set at the soft solution preprocess method of the present embodiment constellation mapping,

Described constellation point set S _iInterior constellation point is asked for by Monte Carlo algorithm or greedy algorithm computing method.

Method one: the Monte Carlo algorithm is asked for:

Take statistics and probability as basic, through checking repeatedly, the described constellation point set that obtains;

Method two: greedy algorithm is asked for:

A: the point in definition information symbol signal space arrives the distance of regional i,

B: then calculate

And

N is the n bit of information symbol, and n is for being not more than log ₂In M (M is the mapping exponent number of planisphere), the distance of the regional i that has a few, get several the shortest conducts Be expressed as i zone, u is expressed as u bit of the information symbol of reception; W is 0 or 1; Wherein, the constellation point in signal space can have different definition modes to the distance of regional i.Especially, when having in regional i and a constellation point is only arranged, can will arrive the Euclidean distance of this point as the distance to regional i.

In the present embodiment, provide particularly two kinds to obtain the method that regional is used for finding the solution information symbol each bit log-likelihood ratio, had and realize advantage simply and easily.

Comprehensive as can be known above-mentioned, described constellation point concentrates the constellation point number of subsets that comprises to be at most 2*log ₂M。

Soft solution preprocess method in the present embodiment constellation mapping, two kinds of method for optimizing of finding the solution the constellation point set are provided, above two kinds of equal technology maturations of method, use easy, thereby the soft solution preprocess method of the described constellation mapping of the present embodiment have use simply, characteristics easily.

Particularly, described table B is stored in random access storage device, read-only memory or combinational logic circuit.The number of the constellation point that described constellation point is concentrated is according to the difference of the mode of the zone at place, constellation mapping and implementation and difference, and is common all much smaller than the mapping exponent number M of constellation mapping.

Below in conjunction with Figure of description and embodiment to the soft solution method of constellation mapping of the present invention to be described further.

The first embodiment:

The soft solution method of the present embodiment constellation mapping after being applied to preliminary treatment that the soft solution preprocess method of above-mentioned constellation mapping carries out, comprises the following steps particularly:

Receive information symbol, the regional i under the determination information symbol;

Regional i from table B under the obtaining information symbol is used for the constellation point set S of log-likelihood calculations _i, and press presetting method to information symbol and S _iIn constellation point carry out log-likelihood calculations.

In the soft solution method of the present embodiment constellation mapping, due to the table B that has obtained being used for log-likelihood calculations by the soft solution preprocess method as embodiment one or embodiment two described constellation mapping, and the number of the constellation point that records in table B, need to carry out the number of the constellation point of log-likelihood calculations much smaller than the Max-Log-MAP method, thereby reduced amount of calculation, reduce simultaneously taking of system resource, reduced hard-wired cost.The constellation mapping of high-order particularly, the bit number that information symbol carries is many, and the constellation point in information space is also many, yet concentrate on some specific position with the nearest point of arbitrfary point in regional i, when adopting traditional Max-Log-MAP method to go to calculate, carried out much obviously can not being conducive to the calculating of final result, and screened out these useless points by pretreated method in the present embodiment, thereby reached the purpose that reduces amount of calculation.

As the improvement further of the present embodiment, the soft solution method of the present embodiment constellation mapping has provided the method for solving of the log-likelihood ratio of each bit in the information symbol further, concrete passes through following formula

Described presetting method is for passing through formula

$\mathrm{LLR}\left(b_K\right)=\frac{1}{2{\mathrm{\σ}}^2}(\underset{x\∈S_{i,k}^{\left(1\right)}}{\min }\left({|y-G_{i}x|}^2\right)-\underset{x\∈S_{i,k}^{\left(0\right)}}{\min }\left({|y-G_{i}x|}^2\right))$

Calculate the log-likelihood ratio of each bit in described information symbol;

Wherein, LLR is log-likelihood ratio; b _kBe k bit of information symbol, and k is for being not more than log ₂The positive integer of M.

As the constellation mapping on 16 rank, each information symbol in signal space and constellation point form (as 0000,1111 etc.) by 4 bits.The constellation mapping on 256 rank, each information symbol in signal space and star chart point is by 8 bits compositions (as 00010010 etc.).

By above-mentioned formula, when soft solution constellation mapping, have advantages of directly easy, adopt the soft solution method of the described constellation mapping of the present embodiment ask for each bit of information symbol log-likelihood ratio find the solution convenient, fast, operand is little, it is few that system takies resource, realizes that cost is low in concrete hardware implementation procedure.

The second embodiment:

As shown in Figure 2, the soft solution method of the present embodiment constellation mapping comprises the following steps:

The pre-treatment step that realizes as the soft solution preprocess method of embodiment one or embodiment two described constellation mapping;

Step S1: receive information symbol;

Step S2: utilize channel condition information to carry out normalized to the information symbol of described reception, thereby obtain the normalization information symbol.When the state of channel changes, usually need to estimate the information symbol that receives is carried out normalized according to the decay of signal, thereby obtain equal strong and weak information symbol so that follow-up processing;

Step S3: judge the regional i that described information symbol is affiliated;

Step S4: obtaining information symbol area i is used for the constellation point set of log-likelihood calculations from table B, and by presetting method, information symbol and the concentrated constellation point of constellation point is carried out log-likelihood calculations.

The multiple advantages such as adopt the soft solution method of the described constellation mapping of the present embodiment, the log-likelihood ratio of finding the solution each bit of information symbol obtains final soft solution result, has amount of calculation few, and system resource is few, and operation time is few.

The 3rd embodiment:

The soft solution method of the present embodiment constellation mapping comprises the following steps:

Step S1: receive information symbol, the zone under described information symbol is judged in judgement; In concrete implementation process, can adopt the zone under hard decision (namely dividing the border with the zone compares) determination information symbol; Much more no longer hard decision is the decision method that is applied to decode of technology maturation, to do at this and give unnecessary details;

Step S2: the zone from table B under the obtaining information symbol is used for the constellation point set of log-likelihood calculations, and by presetting method, information symbol and the concentrated constellation point of constellation point is carried out log-likelihood calculations;

Wherein, table B is that soft solution preprocess method by constellation mapping obtains; The soft solution preprocess method of described constellation mapping comprises the following steps again:

S0.1 is divided into N zone according to the signal space that the constellation mapping that adopts will include M constellation point;

S0.2 builds table B; Record the constellation point set S that is used for log-likelihood calculations in regional i in table B _iI is the integer that is not more than N;

Preferred hard decision in the present embodiment, adopt the decision method of this technology maturation, guaranteed on the one hand the realizability of judgement, guaranteed simultaneously the simple and efficient property that realizes, adopt simultaneously the table B that generates in preprocessing process to carry out finding the solution of follow-up log-likelihood ratio, operand is little, and acquisition time is short as a result, system resource is few, and hardware implementation cost is low.

The 4th embodiment:

As Fig. 3-shown in Figure 6, the soft solution method of the present embodiment constellation mapping, applied environment is that constellation mapping is the Gray-APSK(Amplitude-Phase Shift Keying on 256 rank) Gray-Amplitude phase shift keying; Chnnel coding adopts LDPC code---the low density parity check code Low Density Parity Check Code in the DVB-S2 standard; The LDPC decoding algorithm adopts modified min-sum algorithm, and maximum iteration time is 50 times; Transmission channel is AWGN (Additive White Gaussian Noise) channel or i.i.d.Rayleigh channel---independent Rayleigh channel;

Wherein, shown signal space annular signal space as shown in Figure 3;

At first, the pretreated table B that arrives of the constellation mapping of carrying out, concrete operation is as follows:

The signal space that will include 256 constellation point according to the constellation mapping that adopts is divided into 256 zones, and the signal space after division as shown in Figure 4;

Build table B; Record the constellation point set S that is used for log-likelihood calculations in regional i in table B _iI is not more than 256 integer;

Wherein,

Described S _iComprise the constellation point subset And constellation point subset

Described

Comprised the k bit and be 0 and with regional i in the nearest constellation point in preset;

Described

Comprised the k bit and be 1 and with regional i in the nearest constellation point in preset; Wherein described preset is the point of constellation point position in each zone in the present embodiment;

Described k is for being not more than log ₂The positive integer of M

Receive information symbol and channel condition information;

Utilize channel condition information to carry out normalized to information symbol, the normalization information symbol after being processed;

Zone under judgement normalization information symbol;

Zone from table B under the obtaining information symbol is used for the constellation point set of log-likelihood calculations, and by presetting method, information symbol and the concentrated constellation point of constellation point is carried out log-likelihood calculations.

The soft solution method of the described constellation mapping of the present embodiment is applied in the communication that is provided with above-mentioned parameter the table that is compared as follows with the arithmetic speed of traditional Max-Log-MAP method and operand:

In addition, the performance of the soft solution method of the described constellation mapping of the present embodiment is also very little with respect to the traditional difference of Max-Log-MAP method on error rate of system, concrete as Fig. 5-shown in Figure 6:

Fig. 5 is when transmission channel is awgn channel (Additive White Gaussian Noise) channel, the soft solution method of the described constellation mapping of the present embodiment and the comparison diagram of Max-Log-MAP method.

Fig. 6 for when transmission channel be the i.i.d.Rayleigh channel---during independent Rayleigh channel, the soft solution method of the described constellation mapping of the present embodiment and the comparison diagram of Max-Log-MAP method.

Comprehensive as can be known above-mentioned, the soft solution method of the described constellation mapping of the present embodiment, under the condition that almost there is no performance loss, reduced greatly the operand of log-likelihood ratio of each bit of information symbol, especially the constellation mapping of high-order as the constellation mapping on 256 rank in effect especially obvious, thereby reduced the system resource that takies when adjudicating in soft solution process, also reduced hard-wired cost.

Above execution mode only is used for explanation the present invention; and be not limitation of the present invention; the those of ordinary skill in relevant technologies field; without departing from the spirit and scope of the present invention; can also make a variety of changes and modification; therefore all technical schemes that are equal to also belong to category of the present invention, and scope of patent protection of the present invention should be defined by the claims.

Claims (8)

1. the soft solution preprocess method of a constellation mapping, is characterized in that, the soft solution preprocess method of constellation mapping comprises the following steps:

The signal space that will include M constellation point according to the constellation mapping that adopts is divided into N zone;

Build table B, record the constellation point set S that is used for log-likelihood calculations in regional i in table B _iI is the integer that is not more than N;

Wherein,

Described S _iComprise the constellation point subset And constellation point subset

Described

Comprised the k bit and be 0 and with regional i in the nearest constellation point in preset;

Described

Comprised the k bit and be 1 and with regional i in the nearest constellation point in preset;

Described k is for being not more than log ₂The positive integer of M.

2. the soft solution preprocess method of constellation mapping according to claim 1, is characterized in that, in the soft solution preprocess method of described constellation mapping, according to constellation mapping, zone division and performance requirement, one or more presets is set in regional i.

3. the soft solution preprocess method of constellation mapping according to claim 1 and 2, is characterized in that, described constellation point set S _iInterior constellation point is calculated by Monte Carlo algorithm or greedy algorithm and is asked for.

4. the soft solution preprocess method of constellation mapping according to claim 1 and 2, is characterized in that, described table B is stored in random access storage device, read-only memory or combinational logic circuit.

5. the soft solution method of a constellation mapping after being used for preliminary treatment that the soft solution preprocess method of the arbitrary described constellation mapping of claim 1-4 carries out, is characterized in that, the soft solution method of described constellation mapping comprises the following steps:

Receive information symbol,

Regional i under the determination information symbol;

The constellation point set S that is used for log-likelihood calculations in regional i from table B under the obtaining information symbol _i, and utilize S by presetting method _iIn constellation point carry out log-likelihood calculations.

6. the soft solution method of constellation mapping according to claim 5, is characterized in that, described presetting method is for passing through formula

$\mathrm{LLR}\left(b_k\right)=\frac{1}{2{\mathrm{\σ}}^2}(\underset{x\∈S_{i,k}^{\left(1\right)}}{\min }\left({|y-G_{i}x|}^2\right)-\underset{x\∈S_{i,k}^{\left(0\right)}}{\min }\left({|y-G_{i}x|}^2\right))$

Calculate the log-likelihood ratio of each bit in described information symbol;

Wherein, LLR is log-likelihood ratio; b _kK the bit that carries for information symbol, and k is for being not more than log ₂The positive integer of M.

7. the soft solution method of according to claim 5 or 6 described constellation mapping, is characterized in that, the zone that belongs to by hard decision method determination information symbol.

8. the soft solution method of according to claim 5 or 6 described constellation mapping, it is characterized in that, also comprise and utilize channel condition information to carry out normalized to described information symbol after receiving information symbol with before the zone of judging under described information symbol, thereby obtain the normalization information symbol.

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