CN100518165C - Hard-decision method fitted for implementation of multilevel quadrature amplitude modulation - Google Patents

Abstract

The invention relates to one MQAM hard judgment method in hard judgment in the multiple level cross range modulation communication system, which comprises the following steps: storing each signal point relative hard judgment two bit in star pattern on sequence number into one data set; receive end processes the demodulated character information to get data set index value according to this invention method and steps and then gets the character hard judgment results according to the index value.

Description

A kind of multilevel quadrature amplitude modulation(PAM) hard decision method that is suitable for realizing

Technical field

The invention belongs to communication technical field, particularly relate to a kind of in adopting multilevel quadrature amplitude modulation(PAM) (16QAM) communication system, a kind of 16QAM hard decision method that be suitable for realize of receiving terminal when carrying out hard decision.

Background technology

Along with development of times, people comprise the requirement to communication quality and class of business etc. to the requirement of communication, and are also more and more higher.Along with development of Communication Technique, people are more and more higher for the rate requirement of message transmission.Under the background that is becoming tight frequency resource day now, in limited frequency band, transmit more information, a kind of common method adopts the high order modulation technology exactly.Current common digital high order modulation technology comprises: multistage phase shift keying (MPSK), multistage frequency shift keying (MFSK) and multilevel quadrature amplitude modulation(PAM) (MQAM) technology.Wherein orthogonal amplitude modulation technique is widely used in the wired and wireless communication system most, as the cable modem in wired communication system, WLAN (wireless local area network) IEEE802.11a system in the wireless communication system, 3-G (Generation Three mobile communication system), and high speed downlink packet inserts (HSDPA) system or the like.

In the Modern Communication System,, generally all adopted error correction coding for the reliability that guarantees to transmit.Common error correcting code comprises convolution code and Turbo code.These encoders generally all adopt soft information input in order to obtain preferable performance.But for other functional module, may use the hard decision result after the quadrature amplitude modulation demodulation, as adjudicate auxiliary channel estimation technique, received signal to noise ratio estimates, decision feedback equalization and based on frequency offset correction of decision-feedback or the like.

When quadrature amplitude modulation was carried out hard decision, conventional algorithm will consume a large amount of processing time of digital signal processor (DSP), and the processing time prolongs the anxiety that will cause whole receiver link sequential and causes the communication system instability.

Conventional hard decision method is (with 16QAM is example, and planisphere is as shown in Figure 1) as shown in Figure 2:

If $S_k=\left(\begin{array}{cccc}{v}_k^1& v_k^2& v_k^3& {\mathrm{<figure-callout\; id="4"\; label="v\; k"\; filenames="C20061015506100101.png,C20061015506100111.png"\; state="\{\{state\}\}">v</figure-callout>}}_k^{}\end{array}\right)$ Be a 16QAM symbol, $v_k^n\&Element;\left\{\mathrm{0,1}\right\}$ Be n the binary bits of k 16QAM.As seen from Figure 2, the hard decision result that obtain 16QAM needs 4 logic determines altogether, and each judgement all is based on former judged result for the basis, always has 16 logic branches.Be without loss of generality, this conclusion is generalized to multilevel quadrature amplitude modulation(PAM) (MQAM): carry out hard decision to a MQAM symbol, need carry out log ₂M logic determines, each judgement all are based on former judged result and are the basis, always total M logic branch.Modern Communication System often adopts 256QAM and 512QAM to improve the transfer rate of information, to have 256 and 512 logic branches this moment, the judgement of big like this logic branch, if realize to take a large amount of resource of processor, if realize to cause the bigger wasting of resources with field programmable gate array (FPGA) with digital signal processor (DSP).

Summary of the invention

Purpose of the present invention is exactly at the deficiencies in the prior art, propose a kind of multilevel quadrature amplitude modulation(PAM) hard decision method that is suitable for realizing, can realize low complex degree, obtains the function of the hard decision signal of 16QAM apace.

Basic thought of the present invention is that each symbol on the planisphere of 16QAM is distributed certain sequence number according to certain rules.In sequential storage to an array of hard decision binary value with each the signaling point correspondence on the planisphere according to sequence number.The symbolic information of receiving terminal after to demodulation handled, and the index value that method that provides according to the present invention and step obtain array is searched value in the corresponding array according to index value then, obtains the hard decision result of this symbol.

Earlier according to the positive and negative of 16QAM symbol real part the signaling point on 16 planispheres is divided into 2 1/2 group, each 1/2 group has 8 signaling points; Positive and negative according to each 1/2 group code imaginary part again is divided into 2 1/4 group again with each 1/2 group, and each 1/4 group has 4 signaling points; Absolute value according to the real part of each 1/4 group code deducts the positive and negative of average again, is divided into 2 1/8 group again with each 1/4 group, and each 1/8 group has 2 signaling points; And then deduct the positive and negative of average according to the absolute value of each 1/8 group code imaginary part, and being divided into 2 1/16 group again with each 1/8 group, each 1/16 group has 1 signaling point; This grouping is designated as S _m(1≤m≤16).Then to each grouping S _mBe marked with sequence number sequentially, again with each grouping S _mPairing hard decision binary result stores in the array by the size of sequence number.The work of grouping and mark was done in the hard decision method design phase, so can not influence the processing time of actual hard decision.

The actual hard decision method of carrying out comprises:

1. judge the positive and negative of 16QAM symbol real part, as canonical: Index=Index+16/n, n=2;

2. judge the positive and negative of the 16QAM imaginary part of symbol, as bearing then: Index=Index+16/n, n=4;

3. the absolute value of judging the symbol real part deducts the positive and negative of average, as bearing then: Index=Index+16/n, n=8;

4. the absolute value of judging the imaginary part of symbol deducts the positive and negative of average, as bearing then: Index=Index+16/n, n=16;

5. go to check hard decision value among the array Index that answers according to the Index value that calculates at last.

The method that adopts the present invention to provide, the 16QAM symbol is carried out hard decision only needs 4 logic determines and a logic branch.Its thought is exactly: before deal with data, earlier the signaling point of 16QAM planisphere is divided into groups by rule, to sequence number of each packet allocation corresponding to the memory location in the array.In carrying out the hard decision process, remember former logic determines result by the index value that changes array, thereby saved a large amount of processing times and reduced size of code.

In addition, what need indicate is, the step of the 16QAM hard decision method that the present invention provides does not have inevitable sequence requirement, step 1 can be carried out simultaneously to step 4, this is more convenient for carrying out the application (realizing as FPGA) of concurrent operation, each step can be overlapping on the processing time, thereby further reduced the processing delay of 16QAM hard decision.

Description of drawings

The common 16QAM planisphere of Fig. 1;

The conventional 16QAM hard decision of Fig. 2 method flow diagram;

The hard decision method serial flow chart of Figure 31 6QAM;

The hard decision method of Figure 41 6QAM flow chart that walks abreast.

Embodiment

Below in conjunction with Fig. 3 a specific embodiment of the present invention is described, so that further understand summary of the invention of the present invention.

As shown in Figure 3, the program of the present invention is suitable for the multilevel quadrature amplitude modulation schemes (16QAM) that DSP realizes and comprises the steps:

Step 1, obtain after the demodulation 16QAM symbol S _k

Step 2 is judged formula Re (S _kWhether set up)＞0, as otherwise change step 4;

Step 3 is upgraded array indexing value Index=Index+8;

Step 4 is judged formula Im (S _kWhether set up)＜0, as otherwise change step 6;

Step 5 is upgraded array indexing value Index=Index+4;

Step 6, the judgement formula $\left|\mathrm{Re}\left(S_k\right)\right|-E\left(\frac{\mathrm{Re}\left(S\right)+\mathrm{Im}\left(S\right)}{2}\right)<0$ Whether set up, as otherwise change step 8;

Step 7 is upgraded array indexing value Index=Index+2;

Step 8, the judgement formula $\left|\mathrm{Im}\left(S_k\right)\right|-E\left(\frac{\mathrm{Re}\left(S\right)+\mathrm{Im}\left(S\right)}{2}\right)<0$ Whether set up, as otherwise change step 10;

Step 9 is upgraded array indexing value Index=Index+1;

Step 10 is checked the value of answering in the array according to the index value that calculates, and obtains the hard decision result;

Step 11 finishes.

Below in conjunction with Fig. 4 another specific embodiment of the present invention is described, so that further understand summary of the invention of the present invention.

As shown in Figure 4, the program of the present invention is suitable for the multilevel quadrature amplitude modulation schemes (16QAM) that FPGA realizes and comprises the steps:

Step 1, obtain after the demodulation 16QAM symbol S _k

Step 2.1 is judged formula Re (S _kWhether set up)＞0, as otherwise change step 4;

Step 3.1 is upgraded array indexing value Index=Index+8;

Step 2.2 is judged formula Im (S _kWhether set up)＜0, as otherwise change step 4;

Step 3.2 is upgraded array indexing value Index=Index+4;

Step 2.3, the judgement formula $\left|\mathrm{Re}\left(S_k\right)\right|-E\left(\frac{\mathrm{Re}\left(S\right)+\mathrm{Im}\left(S\right)}{2}\right)<0$ Whether set up, as otherwise change step 4;

Step 3.3 is upgraded array indexing value Index=Index+2;

Step 2.4, the judgement formula $\left|\mathrm{Im}\left(S_k\right)\right|-E\left(\frac{\mathrm{Re}\left(S\right)+\mathrm{Im}\left(S\right)}{2}\right)<0$ Whether set up, as otherwise change step 4;

Step 3.4 is upgraded array indexing value Index=Index+1;

Step 4 is checked the value of answering in the array according to the index value that calculates, and obtains the hard decision result;

Step 5 finishes.

Claims (1)

1, a kind of multilevel quadrature amplitude modulation(PAM) hard decision method that is suitable for realizing is characterized in that this method is divided into 2 1/2 group according to the positive and negative of 16QAM symbol real part with the signaling point on 16 planispheres earlier, and each 1/2 group has 8 signaling points; Positive and negative according to each 1/2 group code imaginary part again is divided into 2 1/4 group again with each 1/2 group, and each 1/4 group has 4 signaling points; Absolute value according to the real part of each 1/4 group code deducts the positive and negative of average again, is divided into 2 1/8 group again with each 1/4 group, and each 1/8 group has 2 signaling points; And then deduct the positive and negative of average according to the absolute value of each 1/8 group code imaginary part, and being divided into 2 1/16 group again with each 1/8 group, each 1/16 group has 1 signaling point; This grouping is designated as S _m, 1≤m≤16; Then to each grouping S _mBe marked with sequence number sequentially, again with each grouping S _mPairing hard decision binary result stores in the array by the size of sequence number; Concrete hard decision method comprises:

(1) judges the positive and negative of 16QAM symbol real part, as canonical: Index=Index+16/n, n=2;

(2) judge the positive and negative of the 16QAM imaginary part of symbol, as bearing then: Index=Index+16/n, n=4;

(3) absolute value of judgement symbol real part deducts the positive and negative of average, as bearing then: Index=Index+16/n, n=8;

(4) absolute value of the judgement imaginary part of symbol deducts the positive and negative of average, as bearing then: Index=Index+16/n, n=16;

(5) go to check hard decision value among the array Index that answers according to the Index value that calculates at last.

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