CN104113393A - Superposition coded modulation method based on subcarrier index modulation (SIM)-orthogonal frequency division multiplexing (OFDM) - Google Patents

Abstract

The invention relates to the technical field of communication anti-jamming, in particular to a superposition coded modulation (SCM) technology communication system, subcarrier index modulation (SIM) and related time domain detecting technologies. According to an SCM method based on SIM-orthogonal frequency division multiplexing (OFDM), ideas of SIM-OFDM and spatial modulation (SM) are used as reference, a part of a string of bit data is used for transmission, the other part of the string of bit data is used as indexing bits, and the indexing bits are respectively coded. During transmission in an OFDM system, particular subcarrier is selected for transmitting data according to the bit data after coding of the indexing bits. A maximum likelihood method is used at a receiving end to obtain soft information of the indexing bits, and the indexing bits are decoded. Compared with prior SCM methods, the SCM method based on the SIM-OFDM has the advantages that the SCM superposition layers are reduced, the complexity is reduced, and error rate performances can be maintained or even improved to a certain degree. Meanwhile, the SCM is used for replacing quadrature amplitude modulation (QAM), and performances can be improved under the same transmission efficiency.

Description

A kind of supercomposed coding modulator approach based on SIM-OFDM

Technical field

The invention belongs to Communication Anti-Jamming Techniques field, relate in particular to supercomposed coding modulation technique (Superposition Coded Modulation) communication system, sub-carrier indices modulation (Subcarrier Index Modulation, SIM) and relevant time domain detection technique thereof.

Background technology

In noisy communication channel, coded modulation is transmitting efficiently, as early stage trellis coded modulation (TCM) and Multilevel Coded Modulation, when combining with binary coding multi-system signal, can obtain good performance gain.And Bit Interleave coded modulation (BICM) can obtain better performance by relatively simple method especially.And supercomposed coding modulation technique (SCM) can be seen as a kind of special circumstances of BICM.The detection complexity of BICM system doubly increases with index with transmitted bit number, and the complexity of SCM is existing increase along with the increase of the number of plies, and the obvious excellent and BICM of the performance of the SCM of multilayer.

Recently, the ofdm system based on sub-carrier indices modulation (Subcarrier Index Modulation, SIM) is suggested as new multi-carrier communication mode.SIM method is selected different carrier transmission data by index bit, makes SIM OFDM have better performance than traditional OFDM.But original SIM scheme may make the mistake, bit is propagated and is occurred in initiation Error Set, and when receiving terminal detects, is difficult to determine that a suitable thresholding carries out demodulation.For the problems referred to above, there is at present research to make improvement to SIM OFDM method, and proposed a kind of simple detection method.

In the middle of SCM, the number of plies of stack is more, power that every one deck distributes is lower, interference is between layers also more serious, receiving terminal is also more not easy to distinguish each layer signal, if can not distinguish each layer of information, just can not diversity merge, thus performance along with the increase of the stack number of plies, promote more and more not obvious.

Summary of the invention

The present invention uses for reference the thought of SIM-OFDM and the thought of spatial modulation SM, and by a part for a string Bit data, for transmission, another part is used as index bit, and encodes respectively.When transmitting in ofdm system, according to the Bit data after index bit coding, select specific subcarrier to transmit data.At receiving terminal, adopt the method for maximum likelihood, obtain the soft information of index bit, and then index bit is carried out to decoding.

A supercomposed coding modulator approach based on SIM-OFDM, specific as follows:

S1, by digitlization information source, produce M ₁+ M ₂* L position information bit, through a deserializer, front M ₁position as index bit, rear M ₂another deserializer, as data bit, is sent data bit in * L position;

S2, index bit are encoded and interweave: by M described in S1 ₁position bit is encoded, and the index bit after having encoded is interweaved, and obtains index data { u _j, wherein, coded system is Turbo code, encoder bit rate is R, and j=1,2 ..., M ₁/ R;

S3, carry out SCM modulation: M described in S1 ₂* L position bit, after a deserializer, divides data on L layer and transmits, and the data of l layer are the frequency multiplier that is S through spread spectrum length, interweaves, and BPSK modulation, obtains each layer passes through respectively weighted value { ω ^(l), ω ⁽²⁾..., ω ^(L)be weighted, the data after weighting are superposeed, obtain send into SIM modulator, wait to be sent, wherein, m=1,2 ..., M ₂, j=1,2 ..., M ₂* S;

S4, carry out SIM modulation: S3 is obtained adopt subcarrier 2 to select 1 mode to carry out SIM modulation, i.e. S3 gained M ₂* S bit data is passed through M ₂* S * 2 subcarrier transmits;

S5, the M that S4 is obtained ₂* S * 2 bit data is carried out IFFT and is transformed to time domain to described add after Cyclic Prefix, cross channel plus noise, carry out FFT and transform to frequency domain, remove Cyclic Prefix and obtain wherein, N=2 * M ₂* S, K represents the actual sub-carrier number that has data, the channel parameter values of corresponding subcarrier, described in be unknown, need to try to achieve by the method for ML, represent the j bit of l layer constantly, n _jbe 0 average, variance is δ ²=N ₀/ 2 Gaussian noise;

S6, ML criterion detect index bit and obtain channel parameter, specific as follows:

S61, use with represent that j bit is 1 and when being 0, adopt the method for ML, calculate the likelihood ratio information of index bit $L\left(u_j\right)=\log \{\underset{x^{\′}\∈X}{\underset{u^{\′}=u_j^{\left(1\right)}}{\mathrm{\Σ}}}{e}^{\frac{{\left|\right|y-h_{u^{\′}}{x}^{\′}\left|\right|}^2}{-{\mathrm{\δ}}^2}}/\underset{x^{\′}\∈X}{\underset{u^{\′}=u_j^{\left(1\right)}}{\mathrm{\Σ}}}{e}^{\frac{{\left|\right|y-h_{u^{\′}}{x}^{\′}\left|\right|}^2}{-{\mathrm{\δ}}^2}}\},$ Wherein, X represents the set of all transmission symbols, h _u'the channel parameter that represents corresponding subcarrier, described h _u'according to index bit, u' determines;

S62, according to L (u described in S61 _j) obtain value, if L (u _j)>=0, described in 2j the channel parameter values on subcarrier, if L is (u _j) < 0, described in 2j-1 the channel parameter values on subcarrier;

S63, according to described in S62, obtain channel parameter H={h _j, wherein, j=M ₂* S;

S7, the channel parameter information H that S6 is obtained send into the detection decoding of SCM, by the likelihood ratio information L (u of index bit described in S61 _j) send into decoder for decoding after deinterleaving, after decoding completes, the index bit data that obtain having detected, wherein, decoded mode is corresponding to the encoder of transmitting terminal;

S8, SCM detect, specific as follows:

S81, in GA module, adopt Gaussian approximation to detect, weight coefficient is W={w ⁽¹⁾, w ⁽²⁾..., w ^(l), j reception information is constantly $r_j=h_j\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}{c}_j^{\left(l\right)}+n_j;$

S82, reception information is sent into GA module, described in S3 can obtain ${\mathrm{\&zeta;}}_j^{\left(l\right)}=r_j-h_j{w}^{\left(l\right)}{c}_j^{\left(l\right)},E\left(r_j\right)=h_j\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}E\left(c_j^{\left(l\right)}\right),\mathrm{Var}\left(r_j\right)=h_j\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}\mathrm{Var}\left(c_j^{\left(l\right)}\right)+{\mathrm{\&delta;}}^2,$ Wherein, expression for interference;

S83, initialization, obtain receiving signal r _javerage and variance;

S84, try to achieve average $E\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)=E\left(r_j\right)-h_j{w}^{\left(l\right)}E\left(c_j^{\left(l\right)}\right)$ And variance $\mathrm{Var}\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)=\mathrm{Var}\left(r_j\right)-\left(h_j{w}^{\left(l\right)}{c}_j^{\left(l\right)}\right);$

S85, according to the log-likelihood ratio of trying to achieve l the bit that j transmits constantly described in S84, be $L\left(c_j^{\left(l\right)}\right)=\log \left(\frac{\mathrm{Pr}(c_j^{\left(l\right)}=+1|r_j)}{\mathrm{Pr}(c_j^{\left(l\right)}=-1|r_j)}\right)=\frac{2h_j(r_j-E\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)}{\mathrm{Var}\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)};$

S86, according to S85, try to achieve all user's of L layer likelihood ratio information L (c) corresponding to transmission data;

S9, the every one deck in SCM, carry out deinterleaving according to L described in S86 (c) and obtain L (a), uses i the bit that represents l layer, described in inciting somebody to action send into solution spread spectrum module and separate spread spectrum, obtain the log-likelihood ratio of the 1st bit of l layer wherein, S is the spread spectrum length in transmitter, for spread spectrum bit;

S10, obtain described in S9 deinterleaving after bit external information $\mathrm{Ext}\left(a_j^{\left(l\right)}\right)=s_j^{\left(l\right)}L\left(d_1^{\left(l\right)}\right)-L\left(a_j^{\left(l\right)}\right);$

S11, by bit external information described in S10 through interweaving, obtain described in inciting somebody to action again send into GA module, right average and variance upgrade: $E\left(c_j^{\left(l\right)}\right)=\tanh \left(\frac{\mathrm{Ext}\left(c_j^{\left(l\right)}\right)}{2}\right),\mathrm{Var}\left(c_j^{\left(l\right)}\right)=1-E\left(c_j^{\left(l\right)}\right);$

S12, the average that completes all data of L layer and the renewal of variance, average and variance substitution S8-S9 by the transmission data after upgrading, carry out iteration according to the iterations CH arranging, and while proceeding to the CH time according to iteration, obtains can be in the hope of wherein, represent the estimation of m bit of k layer;

S13, by described in S12 send into deserializer with the index bit data that detected described in S7, obtain finally exporting bit.

Further, described in S83, initialization is carried out in the time of iteration for the first time.

Further, iterations CH >=5 described in S12.

The invention has the beneficial effects as follows:

The invention provides a kind of SCM technology based on SIM-OFDM, this technology be take SCM technology as basis, in conjunction with the method for SIM, a part of data are carried out SIM modulation and are indexed, and a part is used as SCM transmission, as long as the context of detection at index adopts suitable method, obtain higher performance, the performance of so whole method is compared with previous SCM, and not only the stack number of plies due to SCM tails off, reduced complexity, can also keep even improving bit error rate performance to a certain extent.Meanwhile, with SCM modulation, replace QAM modulation, under identical efficiency of transmission, also can make performance be improved.And adopt the method for SIM-OFDM, can be so that the better effects if of its antagonism ICI, and in the time of the effective subcarrier number of change IFFT, spectrum efficiency also can flexible.

Accompanying drawing explanation

Fig. 1 is the flow chart of transmitter schemes proposed by the invention.

Fig. 2 is the reception overhaul flow chart that the present invention proposes.

Embodiment

The present invention is the combination with SIM-OFDM by supercomposed coding modulation, make the transmitting terminal of SCM can be according to certain rule, at each time slot, can choose certain subcarrier and send data, make receiving terminal to index bit, carry out decoding by certain method, find out effective subcarrier, find out corresponding channel parameter values.Therefore at the receiving terminal of SCM, only need to detect according to the method for Gaussian approximation.As long as the decoding of index bit is adopted to suitable method, can compare the combination of other modulation systems and SIM-OFDM so that SCM is combined with SIM-OFDM, can obtain better performance gain.Specific as follows:

S1, by digitlization information source, produce M ₁+ M ₂* L position information bit, through a deserializer, front M ₁position as index bit, rear M ₂another deserializer, as data bit, is sent data bit in * L position;

S2, index bit are encoded and interweave: by M described in S1 ₁position bit is encoded, and the index bit after having encoded is interweaved, and obtains index data { u _j, wherein, coded system is Turbo code, encoder bit rate is R, and j=1,2 ..., M ₁/ R;

S3, carry out SCM modulation: M described in S1 ₂* L position bit, after a deserializer, divides data on L layer and transmits, and the data of l layer are the frequency multiplier that is S through spread spectrum length, interweaves, and BPSK modulation, obtains each layer passes through respectively weighted value { ω ^(l), ω ⁽²⁾..., ω ^(L)be weighted, the data after weighting are superposeed, obtain send into SIM modulator, wait to be sent, wherein, m=1,2 ..., M ₂, j=1,2 ..., M ₂* S;

S4, carry out SIM modulation: S3 is obtained adopt subcarrier 2 to select 1 mode to carry out SIM modulation, i.e. S3 gained M ₂* S bit data is passed through M ₂* S * 2 subcarrier transmits.Therefore the M, obtaining ₂* S bit data is by 2 * M ₂* S subcarrier transmits, every two data bits of subcarrier transmission that close on, and specifically which passes, according to index bit, determine, such as, first index bit u ₁be 0, x ₁be placed on the 1st subcarrier and pass, if u ₁be 1, x ₁being placed on the 2nd subcarrier passes; If the 2nd index bit u ₂be 1, the 2nd data are placed on the 4th subcarrier, by that analogy.As known from the above, described index bit { u _j, j=1,2 ..., M ₁/ R}, meets M ₁/ R=M ₂* S.

S5, the M that S4 is obtained ₂* S * 2 bit data is carried out IFFT and is transformed to time domain to described add after Cyclic Prefix, cross channel plus noise, carry out FFT and transform to frequency domain, remove Cyclic Prefix and obtain wherein, N=2 * M ₂* S, K represents the actual sub-carrier number that has data, the channel parameter values of corresponding subcarrier, described in be unknown, need to try to achieve by the method for ML, represent the j bit of l layer constantly, n _jbe 0 average, variance is δ ²=N ₀/ 2 Gaussian noise.

S6, ML criterion detect index bit and obtain channel parameter, specific as follows:

S61, use with represent that j bit is 1 and when being 0, adopt the method for ML, calculate the likelihood ratio information of index bit $L\left(u_j\right)=\log \{\underset{x^{\&prime;}\&Element;X}{\underset{u^{\&prime;}=u_j^{\left(1\right)}}{\mathrm{\&Sigma;}}}{e}^{\frac{{\left|\right|y-h_{u^{\&prime;}}{x}^{\&prime;}\left|\right|}^2}{-{\mathrm{\&delta;}}^2}}/\underset{x^{\&prime;}\&Element;X}{\underset{u^{\&prime;}=u_j^{\left(1\right)}}{\mathrm{\&Sigma;}}}{e}^{\frac{{\left|\right|y-h_{u^{\&prime;}}{x}^{\&prime;}\left|\right|}^2}{-{\mathrm{\&delta;}}^2}}\},$ Wherein, X represents the set of all transmission symbols, h _u'the channel parameter that represents corresponding subcarrier, described h _u'according to index bit, u' determines;

S62, according to L (u described in S61 _j) obtain value, if L (u _j)>=0, described in 2j the channel parameter values on subcarrier, if L is (u _j) < 0, described in 2j-1 the channel parameter values on subcarrier;

S63, according to described in S62, obtain channel parameter H={h _j, wherein, j=M ₂* S;

S7, the channel parameter information H that S6 is obtained send into the detection decoding of SCM, by the likelihood ratio information L (u of index bit described in S61 _j) send into decoder for decoding after deinterleaving, after decoding completes, the index bit data that obtain having detected, wherein, decoded mode is corresponding to the encoder of transmitting terminal;

S8, SCM detect, specific as follows:

S81, in GA module, adopt Gaussian approximation to detect, weight coefficient is W={w ⁽¹⁾, w ⁽²⁾..., w ^(l), j reception information is constantly $r_j=h_j\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}{c}_j^{\left(l\right)}+n_j;$

S82, will receive information and send into GA module, described in S3 can obtain ${\mathrm{\&zeta;}}_j^{\left(l\right)}=r_j-h_j{w}^{\left(l\right)}{c}_j^{\left(l\right)},E\left(r_j\right)=h_j\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}E\left(c_j^{\left(l\right)}\right),\mathrm{Var}\left(r_j\right)=h_j\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}\mathrm{Var}\left(c_j^{\left(l\right)}\right)+{\mathrm{\&delta;}}^2,$ Wherein, expression for interference;

S83, initialization, obtain receiving signal r _javerage and variance;

S84, try to achieve average $E\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)=E\left(r_j\right)-h_j{w}^{\left(l\right)}E\left(c_j^{\left(l\right)}\right)$ And variance $\mathrm{Var}\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)=\mathrm{Var}\left(r_j\right)-\left(h_j{w}^{\left(l\right)}{c}_j^{\left(l\right)}\right);$

S85, according to the log-likelihood ratio of trying to achieve l the bit that j transmits constantly described in S84, be $L\left(c_j^{\left(l\right)}\right)=\log \left(\frac{\mathrm{Pr}(c_j^{\left(l\right)}=+1|r_j)}{\mathrm{Pr}(c_j^{\left(l\right)}=-1|r_j)}\right)=\frac{2h_j(r_j-E\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)}{\mathrm{Var}\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)};$

S86, according to S85, try to achieve all user's of L layer likelihood ratio information L (c) corresponding to transmission data;

S9, the every one deck in SCM, carry out deinterleaving according to L described in S86 (c) and obtain L (a), uses i the bit that represents l layer, described in inciting somebody to action send into solution spread spectrum module module and separate spread spectrum, obtain the log-likelihood ratio of the 1st bit of l layer wherein, S is the spread spectrum length in transmitter, for spread spectrum bit;

S10, obtain described in S9 deinterleaving after bit external information $\mathrm{Ext}\left(a_j^{\left(l\right)}\right)=s_j^{\left(l\right)}L\left(d_1^{\left(l\right)}\right)-L\left(a_j^{\left(l\right)}\right);$

S11, by bit external information described in S10 through interweaving, obtain described in inciting somebody to action again send into GA module, right average and variance upgrade: $E\left(c_j^{\left(l\right)}\right)=\tanh \left(\frac{\mathrm{Ext}\left(c_j^{\left(l\right)}\right)}{2}\right),\mathrm{Var}\left(c_j^{\left(l\right)}\right)=1-E\left(c_j^{\left(l\right)}\right);$

S12, the average that completes all data of L layer and the renewal of variance, average and variance substitution S8-S9 by the transmission data after upgrading, carry out iteration according to the iterations CH arranging, and while proceeding to the CH time according to iteration, obtains can be in the hope of wherein, represent the estimation of m bit of k layer, CH>=5.Described iterations is more, and decoding is more accurate, but complexity is also higher.

S13, by described in S12 send into deserializer with the index bit data that detected described in S7, obtain finally exporting bit.

Below in conjunction with embodiment and accompanying drawing, describe technical scheme of the present invention in detail.

The number of plies of supposing SCM is 4, so weight coefficient is 4, is W={w ₁, w ₂, w ₃, w ₄,, spread spectrum length is 4.

Step 1: suppose that the sequence sending is: { 1,1,0,1,0,0,1,1}.1101 of bits are above used as index bit, and index bit, through code interleaving, supposes that the index bit after code interleaving is { 1,1,0,1,0,0,1,1,1,1,0,1,0,0,1,1}.

Step 2: below 0011, through going here and there and change, be mapped in 4 layers of SCM and go, ground floor is 0, the second layer is 0, the three layer, and to be 1, the four layer be 1.After modulating by BPSK, suppose four layers frequency expansion sequence all one for 1,1 ,-1,1}, and the data of ground floor become 1 ,-1,1 ,-1}, the second layer be also 1 ,-1,1 ,-1}, the three or four layer is all { 1,1 ,-1,1}.After supposing to have interweaved 1 to 4 layer, the data of every one deck be respectively 1 ,-1 ,-1,1}, 1,1 ,-1 ,-1}, 1 ,-1,1 ,-1}, 1 ,-1,1,1}:.The 1st data that constantly send are x ₁=1w ₁+ 1w ₂+ 1w ₃-1w ₄.

Step 3: { 1,1,0,1,0,0,1,1,1,1,0,1,0,0,1,1}, according to the mode of corresponding alternative, because first bit is 1, by x according to front index bit ₁be placed on first subcarrier.By that analogy, according to index bit, data are placed on corresponding subcarrier.Then cross channel plus noise.

Step 4: the detection to the soft information of index bit, the method for employing maximum likelihood, $L\left(u_1\right)=\log \{\underset{x^{\&prime;}\&Element;X}{\underset{u^{\&prime;}=1}{\mathrm{\&Sigma;}}}{e}^{\frac{{\left|\right|y-h_{u^{\&prime;}}{x}^{\&prime;}\left|\right|}^2}{-{\mathrm{\&delta;}}^2}}/\underset{x^{\&prime;}\&Element;X}{\underset{u^{\&prime;}=0}{\mathrm{\&Sigma;}}}{e}^{\frac{{\left|\right|y-h_{u^{\&prime;}}{x}^{\&prime;}\left|\right|}^2}{-{\mathrm{\&delta;}}^2}}\}.$ If w ₁, w ₂, w ₃, w ₄different, X has 2 ⁴=16 elements.If L is (u ₁)>=0, h ₁get the channel parameter values of second subcarrier, otherwise get the channel parameter values of first subcarrier, can obtain channel parameter information H={h thus _j, j=M ₂* S}.

Step 5: by H={h _j, j=M ₂* S} brings in the middle of the bit-detection of SCM.First time slot, the signal obtaining receiving is: $r_1=h_1\underset{l=1}{\overset{4}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}{c}_1^{\left(l\right)}+n_1,r_1=h_1{w}^{\left(1\right)}{c}_1^{\left(1\right)}+{\mathrm{\&zeta;}}_1^{\left(1\right)},$ Wherein, expression for interference.

${\mathrm{\&zeta;}}_1^{\left(1\right)}=r_1-h_1{w}_1^{\left(1\right)}{c}_1^{\left(1\right)}.$

$E\left(r_1\right)=h_1\underset{l=1}{\overset{4}{\mathrm{\&Sigma;}}}{w}_1^{\left(l\right)}E\left(c_1^{\left(l\right)}\right)$

$\mathrm{Var}\left(r_1\right)=h_1\underset{l=1}{\overset{4}{\mathrm{\&Sigma;}}}{w}_1^{\left(l\right)}\mathrm{Var}\left(c_1^{\left(l\right)}\right)+{\mathrm{\&delta;}}^2$

When iterating for the first time, can carry out initialization: therefore can be in the hope of receiving signal r ₁average and variance, with this, try to achieve average $E\left({\mathrm{\&zeta;}}_1^{\left(1\right)}\right)=E\left(r_1\right)-h_1{w}_1^{\left(1\right)}E\left(c_1^{\left(1\right)}\right)$ And variance $\mathrm{Var}\left({\mathrm{\&zeta;}}_1^{\left(1\right)}\right)=\mathrm{Var}\left(r_1\right)-\left(h_1{w}_1^{\left(1\right)}{c}_1^{\left(1\right)}\right).$

By above derivation, can be in the hope of the log-likelihood ratio of the 1st bit of ground floor just $L\left(c_1^{\left(1\right)}\right)=\log \left(\frac{\mathrm{Pr}(c_1^{\left(1\right)}=+1|r_1)}{\mathrm{Pr}(c_1^{\left(1\right)}=-1|r_1)}\right)=\frac{2h_1(r_1-E\left({\mathrm{\&zeta;}}_1^{\left(1\right)}\right)}{\mathrm{Var}\left({\mathrm{\&zeta;}}_1^{\left(1\right)}\right)}$

With the method, can calculate log-likelihood ratio, in like manner can try to achieve first time slot, the bit log-likelihood ratio of other layers.Due to H={h _j, j=M ₂* S}, according to the channel parameter of different time-gap, but in like manner can try to achieve the soft information of the every one deck of each time slot.

Step 6: then likelihood ratio information is carried out to deinterleaving and obtain separate spread spectrum: wherein, 4 is the spread spectrum length in transmitter, it is the spread spectrum bit of i of l layer correspondence.Obtain the external information of the bit after deinterleaving $\mathrm{Ext}\left(b_j^{\left(l\right)}\right)=s_j^{\left(l\right)}L\left(d_1^{\left(l\right)}\right)-L\left(b_j^{\left(l\right)}\right),$ Wherein, represent j bit of l layer.

Step 7: the external information obtaining, through interweaving, can be obtained again send into GA module, right average and variance upgrade:

$E\left(c_j^{\left(l\right)}\right)=\tanh \left(\frac{\mathrm{Ext}\left(c_j^{\left(l\right)}\right)}{2}\right)$

$\mathrm{Var}\left(c_j^{\left(l\right)}\right)=1-E\left(c_j^{\left(l\right)}\right).$

With the method, complete the average of all data of L layer and the renewal of variance.Again by the data feedback after upgrading to GA module, repeat step 5 and 6.

Step 8: by { L (u _j), j=1,2 ..., M ₁/ R}, after the deinterleaver of index bit, sends into decoder for decoding, can obtain the value of all initial index.

Step 9: index bit and SCM decoding gained bit are gone here and there and changed, just obtained original data.

Claims (3)

1. the supercomposed coding modulator approach based on SIM-OFDM, is characterized in that, comprises the following steps:

S1, by digitlization information source, produce M ₁+ M ₂* L position information bit, through a deserializer, front M ₁position as index bit, rear M ₂another deserializer, as data bit, is sent data bit in * L position;

S2, index bit are encoded and interweave: by M described in S1 ₁position bit is encoded, and the index bit after having encoded is interweaved, and obtains index data { u _j, wherein, coded system is Turbo code, encoder bit rate is R, and j=1,2 ..., M ₁/ R;

S3, carry out SCM modulation: M described in S1 ₂* L position bit, after a deserializer, divides data on L layer and transmits, and the data of l layer are the frequency multiplier that is S through spread spectrum length, interweaves, and BPSK modulation, obtains each layer passes through respectively weighted value { ω ^(l), ω ⁽²⁾..., ω ^(L)be weighted, the data after weighting are superposeed, obtain send into SIM modulator, wait to be sent, wherein, m=1,2 ..., M ₂, j=1,2 ..., M ₂* S;

S4, carry out SIM modulation: S3 is obtained adopt subcarrier 2 to select 1 mode to carry out SIM modulation, i.e. S3 gained M ₂* S bit data is passed through M ₂* S * 2 subcarrier transmits;

S5, the M that S4 is obtained ₂* S * 2 bit data is carried out IFFT and is transformed to time domain to described add after Cyclic Prefix, cross channel plus noise, carry out FFT and transform to frequency domain, remove Cyclic Prefix and obtain wherein, N=2 * M ₂* S, K represents the actual sub-carrier number that has data, the channel parameter values of corresponding subcarrier, described in be unknown, need to try to achieve by the method for ML, represent the j bit of l layer constantly, n _jbe 0 average, variance is δ ²=N ₀/ 2 Gaussian noise;

S6, ML criterion detect index bit and obtain channel parameter, specific as follows:

S61, use with represent that j bit is 1 and when being 0, adopt the method for ML, calculate the likelihood ratio information of index bit $L\left(u_j\right)=\log \{\underset{x^{\&prime;}\&Element;X}{\underset{u^{\&prime;}=u_j^{\left(1\right)}}{\mathrm{\&Sigma;}}}{e}^{\frac{{\left|\right|y-h_{u^{\&prime;}}{x}^{\&prime;}\left|\right|}^2}{-{\mathrm{\&delta;}}^2}}/\underset{x^{\&prime;}\&Element;X}{\underset{u^{\&prime;}=u_j^{\left(1\right)}}{\mathrm{\&Sigma;}}}{e}^{\frac{{\left|\right|y-h_{u^{\&prime;}}{x}^{\&prime;}\left|\right|}^2}{-{\mathrm{\&delta;}}^2}}\},$ Wherein, X represents the set of all transmission symbols, h _u'the channel parameter that represents corresponding subcarrier, described h _u'according to index bit, u' determines;

S62, according to L (u described in S61 _j) obtain value, if L (u _j)>=0, described in 2j the channel parameter values on subcarrier, if L is (u _j) < 0, described in 2j-1 the channel parameter values on subcarrier;

S63, according to described in S62, obtain channel parameter H={h _j, wherein, j=M ₂* S;

S7, the channel parameter information H that S6 is obtained send into the detection decoding of SCM, by the likelihood ratio information L (u of index bit described in S61 _j) send into decoder for decoding after deinterleaving, after decoding completes, the index bit data that obtain having detected, wherein, decoded mode is corresponding to the encoder of transmitting terminal;

S8, SCM detect, specific as follows:

S81, in GA module, adopt Gaussian approximation to detect, weight coefficient is W={w ⁽¹⁾, w ⁽²⁾..., w ^(l), j reception information is constantly $r_j=h_j\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}{c}_j^{\left(l\right)}+n_j;$

S82, reception information is sent into GA module, described in S3 can obtain ${\mathrm{\&zeta;}}_j^{\left(l\right)}=r_j-h_j{w}^{\left(l\right)}{c}_j^{\left(l\right)},E\left(r_j\right)=h_j\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}E\left(c_j^{\left(l\right)}\right),\mathrm{Var}\left(r_j\right)=h_j\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{w}^{\left(l\right)}\mathrm{Var}\left(c_j^{\left(l\right)}\right)+{\mathrm{\&delta;}}^2,$ Wherein, expression for interference;

S83, initialization, obtain receiving signal r _javerage and variance;

S84, try to achieve average $E\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)=E\left(r_j\right)-h_j{w}^{\left(l\right)}E\left(c_j^{\left(l\right)}\right)$ And variance $\mathrm{Var}\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)=\mathrm{Var}\left(r_j\right)-\left(h_j{w}^{\left(l\right)}{c}_j^{\left(l\right)}\right);$

S85, according to the log-likelihood ratio of trying to achieve l the bit that j transmits constantly described in S84, be $L\left(c_j^{\left(l\right)}\right)=\log \left(\frac{\mathrm{Pr}(c_j^{\left(l\right)}=+1|r_j)}{\mathrm{Pr}(c_j^{\left(l\right)}=-1|r_j)}\right)=\frac{2h_j(r_j-E\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)}{\mathrm{Var}\left({\mathrm{\&zeta;}}_j^{\left(l\right)}\right)};$

S86, according to S85, try to achieve all user's of L layer likelihood ratio information L (c) corresponding to transmission data;

S9, the every one deck in SCM, carry out deinterleaving according to L described in S86 (c) and obtain L (a), uses i the bit that represents l layer, described in inciting somebody to action send into solution spread spectrum module and separate spread spectrum, obtain the log-likelihood ratio of the 1st bit of l layer wherein, S is the spread spectrum length in transmitter, for spread spectrum bit;

S10, obtain described in S9 deinterleaving after bit external information $\mathrm{Ext}\left(a_j^{\left(l\right)}\right)=s_j^{\left(l\right)}L\left(d_1^{\left(l\right)}\right)-L\left(a_j^{\left(l\right)}\right);$

S11, by bit external information described in S10 through interweaving, obtain described in inciting somebody to action again send into GA module, right average and variance upgrade: $E\left(c_j^{\left(l\right)}\right)=\tanh \left(\frac{\mathrm{Ext}\left(c_j^{\left(l\right)}\right)}{2}\right),\mathrm{Var}\left(c_j^{\left(l\right)}\right)=1-E\left(c_j^{\left(l\right)}\right);$

S12, the average that completes all data of L layer and the renewal of variance, average and variance substitution S8-S9 by the transmission data after upgrading, carry out iteration according to the iterations CH arranging, and while proceeding to the CH time according to iteration, obtains can be in the hope of wherein, represent the estimation of m bit of k layer;

S13, by described in S12 send into deserializer with the index bit data that detected described in S7, obtain finally exporting bit.

2. a kind of supercomposed coding modulator approach based on SIM-OFDM according to claim 1, is characterized in that: described in S83, initialization is carried out in the time of iteration for the first time.

3. a kind of supercomposed coding modulator approach based on SIM-OFDM according to claim 1, is characterized in that: iterations CH >=5 described in S12.