CA2625111C - A soft demodulating method for 16qam in communication system - Google Patents
A soft demodulating method for 16qam in communication system Download PDFInfo
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
- H04L27/3845—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier
- H04L27/3854—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
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Abstract
A soft demodulating method for 16-ary QAM (quadrature amplitude modulation) in a communication system can obtain average power of each constellation in 16QAM by estimating receiving power in traffic channels; and then said received intermediate frequency signal can be made carrier wave delamination, and in-phase symbol sequence information I and quadrature symbol sequence information Q can be obtained. Based on the constellation mapping relation between said input binary bits sequence I, Q branch, different decision segment and corresponding error probability decision curve can be determined; and in different decision segment, decision can be made for obtained in-phase symbol sequence information and quadrature symbol sequence information by using corresponding decision curve, in order to obtain real value soft information sequence.
Finally, resulting real value sequence should be input to decoder and made error correction decoding, reception bits sequence corresponding to transmission bits can be decoded.
Present invention can combine fully the advantage of hard decision and soft decision, the algorithm is simple, and it can be realized easily.
Finally, resulting real value sequence should be input to decoder and made error correction decoding, reception bits sequence corresponding to transmission bits can be decoded.
Present invention can combine fully the advantage of hard decision and soft decision, the algorithm is simple, and it can be realized easily.
Description
PCT/CN2005/001708 English Translation A Soft Demodulating Method for 16QAM in Communication System Technical Field The present invention relates to a soft demodulation method, more specifically, to a soft demodulation method for 16 Quadrature Amplitude Modulation (16QAM) in a communication system.
Technical Background Adaptive Modulation and Coding (AMC) is a link adaptation technique widely used in mobile communication system. It adaptively chooses link modulation and coding to adapt the fading in the link, thereby increasing the system capacity and improving the communication quality.
The modulation methods often applied in AMC strategy are Quadrature Phase Shift Keying (QPSK) and 16QAM. Compared with QPSK, 16QAM has higher bandwidth efficiency (twice as QPSK) but lower power efficiency, which means that in order to obtain the same Bit Error Rate (BER), Eb/No (the ratio of each bit power to noise power density) required by 16QAM is higher than that required by QPSK, in other words, 16QAM
is more difficult to be demodulated since the constellation points of 16QAM are denser than those of QPSK and the demodulation needs to estimate both phase and amplitude.
There are two methods for demodulation at the receiving end, i.e. hard decision demodulation and soft decision demodulation. The main idea of the former is to hard decide the bit information corresponding to the input of the modulator when performing demodulation, which means that what is input to the decoder is the binary bit information after hard decision, and the decoder uses a known codeword structure to decide the codeword at the input of the encoder. Since some valuable information may be lost by the demodulator during each hard decision, the hard decision is not a good solution. However, by combining the coding and modulation together, the demodulator will not send some errors to the decoder.
Technical Background Adaptive Modulation and Coding (AMC) is a link adaptation technique widely used in mobile communication system. It adaptively chooses link modulation and coding to adapt the fading in the link, thereby increasing the system capacity and improving the communication quality.
The modulation methods often applied in AMC strategy are Quadrature Phase Shift Keying (QPSK) and 16QAM. Compared with QPSK, 16QAM has higher bandwidth efficiency (twice as QPSK) but lower power efficiency, which means that in order to obtain the same Bit Error Rate (BER), Eb/No (the ratio of each bit power to noise power density) required by 16QAM is higher than that required by QPSK, in other words, 16QAM
is more difficult to be demodulated since the constellation points of 16QAM are denser than those of QPSK and the demodulation needs to estimate both phase and amplitude.
There are two methods for demodulation at the receiving end, i.e. hard decision demodulation and soft decision demodulation. The main idea of the former is to hard decide the bit information corresponding to the input of the modulator when performing demodulation, which means that what is input to the decoder is the binary bit information after hard decision, and the decoder uses a known codeword structure to decide the codeword at the input of the encoder. Since some valuable information may be lost by the demodulator during each hard decision, the hard decision is not a good solution. However, by combining the coding and modulation together, the demodulator will not send some errors to the decoder.
PCT/CN2005/001708 English Translation The term of "soft decision" usually means that the decoder only temporarily estimates various symbols, by which, some information valuable to the decoder will not be lost.
In general, for the Eb/No of the signal, soft decision gains 2dB more than hard decision, so most practical systems adopt the soft decision.
When performing QPSK modulation, one symbol carries the information of two bits, which are mapped to I (in-phase) branch and Q (quadrature) branch respectively. Soft demodulation can be realized at the receiving end as long as the in-phase part of the received symbol after removing the carrier is mapped to I branch and the quadrature part is mapped to Q branch, I branch and Q branch correspond to a real value information of a binary bit respectively, and the real value information after soft demodulation is serial-parallel converted and sent to the decoder to realize soft decision decoding. However, the soft demodulation is more complex for 16QAM, since the 16QAM modulation maps four bits to one symbol, among which, two bits are mapped to I branch and the other two to Q; when the soft demodulation is performed at the receiving end, the in-phase part of the received symbol after removing the carrier corresponds to two-bits information and the quadrature part to the other two-bits information, and the constellation amplitudes corresponding to the symbols are different.
Figure 1 is a basic block diagram of the typical 16QAM modulation and coding/
demodulation and decoding, wherein after Cyclic Redundancy Check (CRC) bits are added in the transmitting block, the transmitting block is input to Turbo coding module for error correction encoding (step 101), then physical layer hybrid automatic repeat request HARQ
(step 102), 16QAM base band modulation (step 103) are performed, and sequently spectrum spread processing (step 104) is performed, including channelizing and scrambling, the base band signal modulates the carrier signal, and the modulated signal then is transmitted over the channel (step 105); after the signal is received by the UE, firstly, the carrier is removed to obtain the in-phase and quadrature phase signals which are then de-spreaded (step 106), the de-spreaded in-phase and quadrature phase symbols are sent to 16QAM soft decision PCT/CN2005/001708 English Translation demodulator for soft demodulation (step 107), and the real value soft information sequence llqll29z corresponding to the sent binary bit sequenceljgt'z92 is obtained, then the real value soft information sequence is sent to Turbo decoder (step 109) for error correction decoding after performing physical layer de-HARQ processing (step 108), and finally the received bit sequence corresponding to the sent bit sequence is obtained.
At present, in order to solve this problem, a soft decision demodulation method of calculating the input to Turbo decoder is often applied. The main idea of this method is to calculate the log likelihood ratio (LLR) of each bit corresponding to the in-phase and quadrature components of each constellation point, which means the information after soft demodulation is the LLR of the corresponding input bit of the modulator. When this method is applied, Carrier Signal to Interference (C/I) may need to be estimated for LLR
of some bits and the error of C/I may affect the performance of the soft demodulation; In addition, the calculation process of LLR is relatively complicated and the hardware is difficult to be realized.
Summary of the Invention The technical problem to be solved in the present invention is to provide a soft demodulation method for 16QAM in a communication system, so as to provide a simply realizable 16QAM soft demodulation method and conveniently achieve adaptive modulation and coding strategy.
In order to solve the above technical problem, the present invention provides the technical solution of:
estimating the receiving power of the traffic channel according to the pilot power and the power deviation between the traffic channel and pilot channel so as to obtain the average power Pa,,e of the 16QAM constellation;
removing the carrier from the received intermediate frequency signals to obtain in-phase symbol sequence information I and quadrature symbol sequence information Q;
In general, for the Eb/No of the signal, soft decision gains 2dB more than hard decision, so most practical systems adopt the soft decision.
When performing QPSK modulation, one symbol carries the information of two bits, which are mapped to I (in-phase) branch and Q (quadrature) branch respectively. Soft demodulation can be realized at the receiving end as long as the in-phase part of the received symbol after removing the carrier is mapped to I branch and the quadrature part is mapped to Q branch, I branch and Q branch correspond to a real value information of a binary bit respectively, and the real value information after soft demodulation is serial-parallel converted and sent to the decoder to realize soft decision decoding. However, the soft demodulation is more complex for 16QAM, since the 16QAM modulation maps four bits to one symbol, among which, two bits are mapped to I branch and the other two to Q; when the soft demodulation is performed at the receiving end, the in-phase part of the received symbol after removing the carrier corresponds to two-bits information and the quadrature part to the other two-bits information, and the constellation amplitudes corresponding to the symbols are different.
Figure 1 is a basic block diagram of the typical 16QAM modulation and coding/
demodulation and decoding, wherein after Cyclic Redundancy Check (CRC) bits are added in the transmitting block, the transmitting block is input to Turbo coding module for error correction encoding (step 101), then physical layer hybrid automatic repeat request HARQ
(step 102), 16QAM base band modulation (step 103) are performed, and sequently spectrum spread processing (step 104) is performed, including channelizing and scrambling, the base band signal modulates the carrier signal, and the modulated signal then is transmitted over the channel (step 105); after the signal is received by the UE, firstly, the carrier is removed to obtain the in-phase and quadrature phase signals which are then de-spreaded (step 106), the de-spreaded in-phase and quadrature phase symbols are sent to 16QAM soft decision PCT/CN2005/001708 English Translation demodulator for soft demodulation (step 107), and the real value soft information sequence llqll29z corresponding to the sent binary bit sequenceljgt'z92 is obtained, then the real value soft information sequence is sent to Turbo decoder (step 109) for error correction decoding after performing physical layer de-HARQ processing (step 108), and finally the received bit sequence corresponding to the sent bit sequence is obtained.
At present, in order to solve this problem, a soft decision demodulation method of calculating the input to Turbo decoder is often applied. The main idea of this method is to calculate the log likelihood ratio (LLR) of each bit corresponding to the in-phase and quadrature components of each constellation point, which means the information after soft demodulation is the LLR of the corresponding input bit of the modulator. When this method is applied, Carrier Signal to Interference (C/I) may need to be estimated for LLR
of some bits and the error of C/I may affect the performance of the soft demodulation; In addition, the calculation process of LLR is relatively complicated and the hardware is difficult to be realized.
Summary of the Invention The technical problem to be solved in the present invention is to provide a soft demodulation method for 16QAM in a communication system, so as to provide a simply realizable 16QAM soft demodulation method and conveniently achieve adaptive modulation and coding strategy.
In order to solve the above technical problem, the present invention provides the technical solution of:
estimating the receiving power of the traffic channel according to the pilot power and the power deviation between the traffic channel and pilot channel so as to obtain the average power Pa,,e of the 16QAM constellation;
removing the carrier from the received intermediate frequency signals to obtain in-phase symbol sequence information I and quadrature symbol sequence information Q;
PCT/CN2005/001708 English Translation determining the different decision segments and the corresponding error probability decision curves according to the 16QAM constellation mapping relationship between the input binary bit sequence tigI1292 and the constellation's position in I, Q
branches, and based on this, judging said obtained in-phase symbol sequence information and quadrature symbol sequence information in different decision segments by using the corresponding decision curves in order to obtain the real value soft information sequence i1q1i2q2 In the present invention, said obtained real value sequence 41rz9z can be further input into the decoder for error correction decoding to obtain the received bit sequence corresponding to the sent bits.
Said soft demodulation method for 16QAM of the present invention fully integrates the benefits of soft decision and hard decision, the algorithm is simple, and the method is easily to be realized.
Brief Description of the Drawings Figure 1 is a basic block diagram of the typical 16QAM modulation and coding/
demodulation and decoding;
Figure 2 is a diagram of constellation maps of QPSK and 16QAM;
Figure 3 is a diagram of the mapping principle of I branch and Q branch of 16QAM;
Figure 4 is a sectional diagram of 16QAM clipped soft decision segments;
Figure 5 is a diagram of the algorithm flow of 16QAM soft decision demodulation.
Preferred Embodiment of the Invention The basic idea of the present invention is to apply the Clipped Soft Decision (CSD) method combining hard decision and soft decision, fully utilize the advantage of soft decision against high uncertainty and the advantage of hard decision of preventing over-estimations so as to make the algorithm of CSD soft decision simple and easily realized and have good performance.
PCT/CN2005/001708 English Translation In the following, the present invention will be described in detail by taking the 16QAM
soft decision in High Speed Downlink Packet Access (HSDPA) as an example.
HSDPA is a new technique offered in R5 protocol by 3GPP to meet the needs for asymmetrical uplink/downlink data service. It solves the conflict between coverage and capacity of the system, increases the system capacity greatly and meets the needs for high speed services of users. Compared with R99, HSDPA adopts Adaptive Modulation and Coding (AMC) and Hybrid Automatic Repeat Request (HARQ) to perform link adaptation.
The core algorithm of 16QAM CSD soft decision is to apply segment proportional method similar to QPSK base band mapping to realize soft decision demodulation according to the feature of the four bits 'Iql1z92 at the input of 16QAM modulator corresponding to the constellation and the different error probability decision curves of the above four bits, namely to perform the soft decision respectively by dividing different decision segments corresponding to the above riqit292 (corresponding to the thought of hard decision) so as to obtain the four real value soft bit information sequence llql1z92 corresponding to the four bits at the input of the 16QAM modulator.
Table 1 offers the base band modulation mapping of 16QAM in HSDPA. When 16QAM
modulation is applied, four sequential binary symbols hAiz9'2 are series-parallel connected to be 1112 on I branch and 9lq2 on Q branch, then the mapping is performed according to the mapping principle of Table 1. It should be noted that the average constellation power of the constellation mapped according to Table 1 is exactly 1.
Table 1 i 1 q l i2q2 I branch Q branch 0000 0.3162 0.3162 0001 0.3162 0.9487 0010 0.9487 0.3162 0011 0.9487 0.9487 PCT/CN2005/001708 English Translation 0100 0.3162 -0.3162 0101 0.3162 -0.9487 0110 0.9487 -0.3162 0111 0.9487 -0.9487 1000 -0.3162 0.3162 1001 -0.3162 0.9487 1010 -0.9487 0.3162 1011 -0.9487 0.9487 1100 -0.3162 -0.3162 1101 -0.3162 -0.9487 1110 -0.9487 -0.3162 1111 -0.9487 -0.9487 Figure 2 is the constellation maps of QPSK and 16QAM. From the constellation maps, it can be clearly figured out that constellation points of QPSK have the same magnitudes and different phases, while the constellation points of 16QAM may have different magnitudes and different phases, and the constellation points of 16QAM are denser than those of QPSK, therefore the demodulation, especially the soft decision demodulation of 16QAM
is more complicated.
Figure 3 concludes the mapping principle of Table 1. When Il or ql is binary 0, a positive real value signal is bound to be mapped, and when Il or ql is binary 1, a negative real value signal is bound to be mapped. The mapping of 12 and q2 is more complicated.
On the basis of Figure 3, Figure 4 further figuratively represents the principle of clipped soft demodulation algorithm. Since the mapping principles of 11 and ql are the same and the mapping principles of 12 and q2 are the same, the principle of the 16QAM
CSD soft decision demodulation will be illustrated by taking h, l2 as examples. From Figure 4, it can PCT/CN2005/001708 English Translation be seen that when the in-phase symbol information I is positive, the corresponding lt tends to be decided as 0, and the greater the I is, the higher the probability of right decision for 11 is; when I is negative, the corresponding Z, tends to be decided as 1, and the less the I is, the higher the probability of right decision for t1 is; similarly, when the quadrature symbol information Q is positive, the corresponding q1 tends to be decided as 0, and the greater the Q is, the probability of right decision for q1 is; when the Q is negative, the corresponding q, tends to be decided as 1, and the less the Q is, the higher the probability of right decision for q, is; Therefore, when segment proportional algorithm is applied to perform the soft decision, the above tendency can be reflected.
For i2, when the in-phase symbol information 1>0.9487 or 1<-0.9487, the corresponding t2 tends to be decided as 1; when -0.3162<1<0.3162, the corresponding t2 tends to be decided as 0; When -0.9487<I<-0.3162 or 0.3162<1<0.9487, whether the corresponding t2 tends to be decided as I or as 0 is decided by the value of I, the more the I
tends to be 0, the higher the probability of correctness of i2 being decided as 0 is, and the more the I tends to be I or -1, the higher the probability of correctness of 12 being decided as I
is; the same principle is suitable for q2, when the quadrature symbol information Q>0.9487 or Q<-0.9487, the correspondingqz tends to be decided as 1; when -0.3162<Q<0.3162, the correspondingq2 tends to be decided as 0; When -0.9487<Q<-0.3162 or 0.3162<Q<0.9487, whether the corresponding42 tends to be decided as 1 or as 0 is decided by the value of Q, the more the Q
tends to be 0, the higher the probability of correctness of q2 being decided as 0 is, and the more the Q tends to be I or -1, the higher the probability of correctness of q2 being decided as 1 is.
PCT/CN2005/001708 English Translation Therefore the algorithm of the present invention performs the soft decision corresponding to the proportional algorithm of the hard decision and exactly reflects the above-mentioned tendency. In soft decision, different soft demodulation equations are applied to demodulate the soft information i1q1i2q2 corresponding to ~I9l'2g2 for different segments.
But from analysis, it can be seen that the CSD demodulation equations can be combined to obtain the soft decision demodulation algorithm of Figure 5. In the corresponding soft decision demodulation equation of Figure 5, 0.7071 corresponds to the in-phase or quadrature component of QPSK base band modulation with average constellation power being 1.
In the following, the detailed flow of 16QAM CSD soft decision demodulation algorithm of the present invention will be described according to figure 5.
step 501, estimating the receiving power of traffic channel by UE according to the pilot power and the power deviation between the traffic channel and the pilot channel in order to obtain the average power of each point in 16QAM constellation;
step 502, separating the symbol information of I branch and Q branch;
step 503, directly applying the equations i, =1 * 0 7071 /( PaVe * 0 3 162) and q, = Q* 0 7071 /(j.,.* 0 3162) to calculate for the soft decision of t1 and ql corresponding to the binary bit sequence tiqt12q2 input into the 16QAM modulator;
step 504, deciding whether I is positive or negative, if I>0, then turning to step 505; if 1<0, then turning to step 506;
~ *(1/ P,~)-03162 *
step 505, calculating ~2 by the equation t2 -~1-2 0 9487-0 3162 0 7071 1*
Z1+2*(1+03162 o step 506, calculating 12 by the equationl - 0 9487-0 3162 J 7o7t step 507, deciding whether Q is positive or negative, if Q>0, then turning to step 508; if Q<0, then turning to step 509;
A ( *(Q/ Pme)-03162 q2 -I'1-2 0 9487-0 3162 0 7071 q step 508, calculating 2 by the equation PCT/CN2005/001708 English Translation ~ gZ =(1+2* (Q~~' "')+0 3 q 162)*0 7071 step 509, calculating 2 by the equation l 0 9487-0 3162 step 510, incorporating q, and q2 after soft demodulation to be the real value ~ A A A
sequence 11q112q2 corresponding to bit sequence ilql 12q2 input into the 16QAM
modulator;
step 511, inputting the real value sequence into the decoder for error correction decoding to obtain the received bit sequence corresponding to the sent bits.
branches, and based on this, judging said obtained in-phase symbol sequence information and quadrature symbol sequence information in different decision segments by using the corresponding decision curves in order to obtain the real value soft information sequence i1q1i2q2 In the present invention, said obtained real value sequence 41rz9z can be further input into the decoder for error correction decoding to obtain the received bit sequence corresponding to the sent bits.
Said soft demodulation method for 16QAM of the present invention fully integrates the benefits of soft decision and hard decision, the algorithm is simple, and the method is easily to be realized.
Brief Description of the Drawings Figure 1 is a basic block diagram of the typical 16QAM modulation and coding/
demodulation and decoding;
Figure 2 is a diagram of constellation maps of QPSK and 16QAM;
Figure 3 is a diagram of the mapping principle of I branch and Q branch of 16QAM;
Figure 4 is a sectional diagram of 16QAM clipped soft decision segments;
Figure 5 is a diagram of the algorithm flow of 16QAM soft decision demodulation.
Preferred Embodiment of the Invention The basic idea of the present invention is to apply the Clipped Soft Decision (CSD) method combining hard decision and soft decision, fully utilize the advantage of soft decision against high uncertainty and the advantage of hard decision of preventing over-estimations so as to make the algorithm of CSD soft decision simple and easily realized and have good performance.
PCT/CN2005/001708 English Translation In the following, the present invention will be described in detail by taking the 16QAM
soft decision in High Speed Downlink Packet Access (HSDPA) as an example.
HSDPA is a new technique offered in R5 protocol by 3GPP to meet the needs for asymmetrical uplink/downlink data service. It solves the conflict between coverage and capacity of the system, increases the system capacity greatly and meets the needs for high speed services of users. Compared with R99, HSDPA adopts Adaptive Modulation and Coding (AMC) and Hybrid Automatic Repeat Request (HARQ) to perform link adaptation.
The core algorithm of 16QAM CSD soft decision is to apply segment proportional method similar to QPSK base band mapping to realize soft decision demodulation according to the feature of the four bits 'Iql1z92 at the input of 16QAM modulator corresponding to the constellation and the different error probability decision curves of the above four bits, namely to perform the soft decision respectively by dividing different decision segments corresponding to the above riqit292 (corresponding to the thought of hard decision) so as to obtain the four real value soft bit information sequence llql1z92 corresponding to the four bits at the input of the 16QAM modulator.
Table 1 offers the base band modulation mapping of 16QAM in HSDPA. When 16QAM
modulation is applied, four sequential binary symbols hAiz9'2 are series-parallel connected to be 1112 on I branch and 9lq2 on Q branch, then the mapping is performed according to the mapping principle of Table 1. It should be noted that the average constellation power of the constellation mapped according to Table 1 is exactly 1.
Table 1 i 1 q l i2q2 I branch Q branch 0000 0.3162 0.3162 0001 0.3162 0.9487 0010 0.9487 0.3162 0011 0.9487 0.9487 PCT/CN2005/001708 English Translation 0100 0.3162 -0.3162 0101 0.3162 -0.9487 0110 0.9487 -0.3162 0111 0.9487 -0.9487 1000 -0.3162 0.3162 1001 -0.3162 0.9487 1010 -0.9487 0.3162 1011 -0.9487 0.9487 1100 -0.3162 -0.3162 1101 -0.3162 -0.9487 1110 -0.9487 -0.3162 1111 -0.9487 -0.9487 Figure 2 is the constellation maps of QPSK and 16QAM. From the constellation maps, it can be clearly figured out that constellation points of QPSK have the same magnitudes and different phases, while the constellation points of 16QAM may have different magnitudes and different phases, and the constellation points of 16QAM are denser than those of QPSK, therefore the demodulation, especially the soft decision demodulation of 16QAM
is more complicated.
Figure 3 concludes the mapping principle of Table 1. When Il or ql is binary 0, a positive real value signal is bound to be mapped, and when Il or ql is binary 1, a negative real value signal is bound to be mapped. The mapping of 12 and q2 is more complicated.
On the basis of Figure 3, Figure 4 further figuratively represents the principle of clipped soft demodulation algorithm. Since the mapping principles of 11 and ql are the same and the mapping principles of 12 and q2 are the same, the principle of the 16QAM
CSD soft decision demodulation will be illustrated by taking h, l2 as examples. From Figure 4, it can PCT/CN2005/001708 English Translation be seen that when the in-phase symbol information I is positive, the corresponding lt tends to be decided as 0, and the greater the I is, the higher the probability of right decision for 11 is; when I is negative, the corresponding Z, tends to be decided as 1, and the less the I is, the higher the probability of right decision for t1 is; similarly, when the quadrature symbol information Q is positive, the corresponding q1 tends to be decided as 0, and the greater the Q is, the probability of right decision for q1 is; when the Q is negative, the corresponding q, tends to be decided as 1, and the less the Q is, the higher the probability of right decision for q, is; Therefore, when segment proportional algorithm is applied to perform the soft decision, the above tendency can be reflected.
For i2, when the in-phase symbol information 1>0.9487 or 1<-0.9487, the corresponding t2 tends to be decided as 1; when -0.3162<1<0.3162, the corresponding t2 tends to be decided as 0; When -0.9487<I<-0.3162 or 0.3162<1<0.9487, whether the corresponding t2 tends to be decided as I or as 0 is decided by the value of I, the more the I
tends to be 0, the higher the probability of correctness of i2 being decided as 0 is, and the more the I tends to be I or -1, the higher the probability of correctness of 12 being decided as I
is; the same principle is suitable for q2, when the quadrature symbol information Q>0.9487 or Q<-0.9487, the correspondingqz tends to be decided as 1; when -0.3162<Q<0.3162, the correspondingq2 tends to be decided as 0; When -0.9487<Q<-0.3162 or 0.3162<Q<0.9487, whether the corresponding42 tends to be decided as 1 or as 0 is decided by the value of Q, the more the Q
tends to be 0, the higher the probability of correctness of q2 being decided as 0 is, and the more the Q tends to be I or -1, the higher the probability of correctness of q2 being decided as 1 is.
PCT/CN2005/001708 English Translation Therefore the algorithm of the present invention performs the soft decision corresponding to the proportional algorithm of the hard decision and exactly reflects the above-mentioned tendency. In soft decision, different soft demodulation equations are applied to demodulate the soft information i1q1i2q2 corresponding to ~I9l'2g2 for different segments.
But from analysis, it can be seen that the CSD demodulation equations can be combined to obtain the soft decision demodulation algorithm of Figure 5. In the corresponding soft decision demodulation equation of Figure 5, 0.7071 corresponds to the in-phase or quadrature component of QPSK base band modulation with average constellation power being 1.
In the following, the detailed flow of 16QAM CSD soft decision demodulation algorithm of the present invention will be described according to figure 5.
step 501, estimating the receiving power of traffic channel by UE according to the pilot power and the power deviation between the traffic channel and the pilot channel in order to obtain the average power of each point in 16QAM constellation;
step 502, separating the symbol information of I branch and Q branch;
step 503, directly applying the equations i, =1 * 0 7071 /( PaVe * 0 3 162) and q, = Q* 0 7071 /(j.,.* 0 3162) to calculate for the soft decision of t1 and ql corresponding to the binary bit sequence tiqt12q2 input into the 16QAM modulator;
step 504, deciding whether I is positive or negative, if I>0, then turning to step 505; if 1<0, then turning to step 506;
~ *(1/ P,~)-03162 *
step 505, calculating ~2 by the equation t2 -~1-2 0 9487-0 3162 0 7071 1*
Z1+2*(1+03162 o step 506, calculating 12 by the equationl - 0 9487-0 3162 J 7o7t step 507, deciding whether Q is positive or negative, if Q>0, then turning to step 508; if Q<0, then turning to step 509;
A ( *(Q/ Pme)-03162 q2 -I'1-2 0 9487-0 3162 0 7071 q step 508, calculating 2 by the equation PCT/CN2005/001708 English Translation ~ gZ =(1+2* (Q~~' "')+0 3 q 162)*0 7071 step 509, calculating 2 by the equation l 0 9487-0 3162 step 510, incorporating q, and q2 after soft demodulation to be the real value ~ A A A
sequence 11q112q2 corresponding to bit sequence ilql 12q2 input into the 16QAM
modulator;
step 511, inputting the real value sequence into the decoder for error correction decoding to obtain the received bit sequence corresponding to the sent bits.
Claims (5)
1. A soft demodulation method of 16 Quadrature Amplitude Modulation (16QAM), performing soft decision demodulation for binary bit sequence processed at sending end with 16QAM to get corresponding real value soft information sequence , including the following steps of:
estimating receiving power of traffic channel according to pilot power and power deviation between the traffic channel and pilot channel to obtain an average power P ave of 16QAM constellation;
removing carrier from intermediate frequency signals received in order to obtain in-phase symbol sequence information I and quadrature symbol sequence information Q;
determining different decision segments and their corresponding error probability decision curves according to constellation mapping relationship between the binary bit sequence input during said 16QAM and I, Q branches, and based on this, judging said obtained in-phase symbol sequence information and quadrature symbol sequence information in the different decision segments by using the corresponding decision curves in order to obtain real value soft information sequence .
estimating receiving power of traffic channel according to pilot power and power deviation between the traffic channel and pilot channel to obtain an average power P ave of 16QAM constellation;
removing carrier from intermediate frequency signals received in order to obtain in-phase symbol sequence information I and quadrature symbol sequence information Q;
determining different decision segments and their corresponding error probability decision curves according to constellation mapping relationship between the binary bit sequence input during said 16QAM and I, Q branches, and based on this, judging said obtained in-phase symbol sequence information and quadrature symbol sequence information in the different decision segments by using the corresponding decision curves in order to obtain real value soft information sequence .
2. The method according to claim 1, further including:
inputting said obtained real value sequence into a decoder for error correction decoding to obtain a received bits sequence corresponding to sent bits.
inputting said obtained real value sequence into a decoder for error correction decoding to obtain a received bits sequence corresponding to sent bits.
3. The method according to claim 1, wherein said 16QAM is a 16QAM in a High Speed Downlink Packet Access system; said step of determining the different decision segments and their corresponding error probability decision curves according to the mapping relationship is:
when the in-phase symbol information I is positive, the corresponding ~ tends to be decided as 0, the greater the I is, the higher a probability of right decision for ~ is; when the I is negative, the corresponding ~ tends to be decided as 1, and the less the I is, the higher the probability of right decision for ~ is;
when the quadrature symbol information Q is positive, the corresponding ~
tends to be decided as 0, and the greater the Q is, the higher the probability of right decision for ~ is;
when the Q is negative, the corresponding ~ tends to be decided as 1, and the less the Q is, the higher the probability of right decision for ~ is;
when the in-phase symbol information I is greater than 0.9487 or less than -0.9487, the corresponding ~ tends to be decided as 1; when the I is greater than -0.3162 and less than 0.3162, the corresponding ~ tends to be decided as 0; When the I is greater than -0.9487 and less than -0.3162 or the I is greater than 0.3162 and less than 0.9487, whether the corresponding ~ tends to be decided as 0 or as 1 is decided by a value of the I, the more the I
tends to be 0, the higher the probability of correctness of ~ being decided as 0 is, and the more the I tends to be I or -1, the higher the probability of correctness of ~
being decided as 1 is;
when the quadrature symbol information Q is greater than 0.9487 or less than -0.9487, the corresponding ~ tends to be decided as 1; when Q is greater than -0.3162 and less than 0.3162, the corresponding ~ tends to be decided as 0; when Q is greater than -0.9487 and less than -0.3162 or Q is greater than 0.3162 and less than 0.9487, whether the corresponding ~
tends to be decided as 0 or as I is decided by the value of the Q, the more the Q tends to be 0, the higher the probability of correctness of ~ being decided as 0 is, and the more the Q tends to be 1 or -1, the higher the probability of correctness of ~ being decided as 1 is.
when the in-phase symbol information I is positive, the corresponding ~ tends to be decided as 0, the greater the I is, the higher a probability of right decision for ~ is; when the I is negative, the corresponding ~ tends to be decided as 1, and the less the I is, the higher the probability of right decision for ~ is;
when the quadrature symbol information Q is positive, the corresponding ~
tends to be decided as 0, and the greater the Q is, the higher the probability of right decision for ~ is;
when the Q is negative, the corresponding ~ tends to be decided as 1, and the less the Q is, the higher the probability of right decision for ~ is;
when the in-phase symbol information I is greater than 0.9487 or less than -0.9487, the corresponding ~ tends to be decided as 1; when the I is greater than -0.3162 and less than 0.3162, the corresponding ~ tends to be decided as 0; When the I is greater than -0.9487 and less than -0.3162 or the I is greater than 0.3162 and less than 0.9487, whether the corresponding ~ tends to be decided as 0 or as 1 is decided by a value of the I, the more the I
tends to be 0, the higher the probability of correctness of ~ being decided as 0 is, and the more the I tends to be I or -1, the higher the probability of correctness of ~
being decided as 1 is;
when the quadrature symbol information Q is greater than 0.9487 or less than -0.9487, the corresponding ~ tends to be decided as 1; when Q is greater than -0.3162 and less than 0.3162, the corresponding ~ tends to be decided as 0; when Q is greater than -0.9487 and less than -0.3162 or Q is greater than 0.3162 and less than 0.9487, whether the corresponding ~
tends to be decided as 0 or as I is decided by the value of the Q, the more the Q tends to be 0, the higher the probability of correctness of ~ being decided as 0 is, and the more the Q tends to be 1 or -1, the higher the probability of correctness of ~ being decided as 1 is.
4. The method according to claim 1, wherein said 16QAM is a 16QAM in a High Speed Downlink Packet Access system; said step of deciding the different decision segments and their corresponding error probability decision curves according to the mapping relationship is:
whatever the value of the I is, the error probability decision curve of ~should meet the equation: ;
whatever the value of the Q is, the error probability decision curve of ~should meet the equation: .
when the I is greater than or equal to 0, the error probability decision curve of ~ should meet the equation:
when the I is less than 0, the error probability decision curve of ~ should meet the equation:
when the Q is greater than or equal to 0, the error probability decision curve of ~should meet the equation:
when the Q is less than 0, the error probability decision curve of ~should meet the equation:
whatever the value of the I is, the error probability decision curve of ~should meet the equation: ;
whatever the value of the Q is, the error probability decision curve of ~should meet the equation: .
when the I is greater than or equal to 0, the error probability decision curve of ~ should meet the equation:
when the I is less than 0, the error probability decision curve of ~ should meet the equation:
when the Q is greater than or equal to 0, the error probability decision curve of ~should meet the equation:
when the Q is less than 0, the error probability decision curve of ~should meet the equation:
5. The method according to claim 4, wherein said value of 0.7071 corresponds to an in-phase or quadrature component of Quadrature Phase Shift Keying base band modulation with average constellation power being 1.
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| PCT/CN2005/001708 WO2007045122A1 (en) | 2005-10-18 | 2005-10-18 | A soft demodulating method for 16qam in communication system |
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| JP5145766B2 (en) * | 2007-05-21 | 2013-02-20 | 株式会社Ｊｖｃケンウッド | Soft decision device and soft decision method |
| CN103378921B (en) | 2012-04-17 | 2016-08-03 | 华为技术有限公司 | Signal demodulating method and device |
| RU2713206C1 (en) * | 2019-03-29 | 2020-02-04 | Акционерное Общество Научно- Производственный Концерн "Барл" | Signal demodulation method and device |
| CN111953446B (en) * | 2019-05-14 | 2023-05-16 | 中兴通讯股份有限公司 | Soft information hard decision configuration method, device, equipment and readable storage medium |
| CN111131107B (en) * | 2019-12-04 | 2022-03-11 | 重庆邮电大学 | Self-adaptive soft demodulation method based on 5G downlink shared channel state |
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| US7580480B2 (en) * | 2003-06-23 | 2009-08-25 | Hong-seok Seo | Demodulation method using soft decision for quadrature amplitude modulation and apparatus thereof |
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| CN101176325B (en) | 2011-02-02 |
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