CN101237434A - A Soft Decision Method for Gray Mapped M-PSK Modulation - Google Patents

Abstract

The invention provides a soft demodulation algorithm with low complexity for high price gray code mapping M-PSK demodulation, consisting of a balancing procedure, a channel estimation procedure, a balancing procedure on a received signal r, a hard decision procedure, a bit likelihood ratio calculation procedure and a coding procedure. The soft demodulation algorithm is characterized in that the method for calculating the bit likelihood ratio is easier to realize compared with the prior constellation search method and greatly decreases the calculated mount.

Description

Translated fromChinese

一种格雷映射M-PSK调制的软判决方法A Soft Decision Method for Gray Mapped M-PSK Modulation

技术领域technical field

该项发明属于无线通信的调制解调领域。The invention belongs to the field of modulation and demodulation of wireless communication.

背景技术Background technique

随着无线通信用户的快速增加，如何提高频谱利用率已成为设计无线通信系统的一个主要目标。With the rapid increase of wireless communication users, how to improve spectrum utilization has become a major goal in designing wireless communication systems.

格雷映射M-PSK(多进制相移键控)调制由于频谱利用率高而被广泛应用于无线数字通信系统中。其中，格雷映射代表所采用的调制星座图进行的是格雷编码，从而可以保证任意两个相邻星座点之间只有一位码元不同，从而能在与高效编译码结合的通信系统中有效提高系统性能。Gray-mapped M-PSK (Multiple Phase Shift Keying) modulation is widely used in wireless digital communication systems because of its high spectrum efficiency. Among them, Gray mapping means that the modulation constellation diagram used is Gray coded, so that it can ensure that only one bit of code element is different between any two adjacent constellation points, so that it can effectively improve the communication system combined with efficient coding and decoding. system performance.

在具有FEC(前向纠错)的无线系统中，软判决解调法相对硬判决解调法能提供较大的性能改善，见文献：F.Tosato and P.Bisaglia，”Simplifed soft-output demapper for binary interleavedCOFDM with application to HIPERLAN/2，”in proc.IEEE ICC’02，2002，pp，664-668。In a wireless system with FEC (Forward Error Correction), the soft-decision demodulation method can provide greater performance improvement than the hard-decision demodulation method, see the literature: F.Tosato and P.Bisaglia,"Simplifed soft-output demapper for binary interleaved COFDM with application to HIPERLAN/2," in proc. IEEE ICC'02, 2002, pp, 664-668.

综上所述，在无线通信系统的发射端使用格雷映射M-PSK调制，同时在接收端使用软判决解调的无线调制解调技术已被广泛的使用。To sum up, the wireless modulation and demodulation technology that uses Gray-mapped M-PSK modulation at the transmitting end of the wireless communication system and soft-decision demodulation at the receiving end has been widely used.

传统的软解调判决方法如下：接收信号r通常可以表示如式(1)所示。The traditional soft demodulation decision method is as follows: the received signal r can usually be expressed as shown in formula (1).

                       r＝ax+n                                  (1)r=ax+n

其中x是发射信号，其属于格雷映射M-PSK调制的星座点集合S＝{s₁，s₂，...s_M}，其中M代表调制的阶数，a为信道增益，n为均值为0，方差为σ²的加性白高斯噪声。每个星座点s_i代表k＝log₂ M个比特的信息，记为：b₀，b₁，...，b_k-1。where x is the transmitted signal, which belongs to the constellation point set S={s₁ , s₂ ,...s_M } of Gray map M-PSK modulation, where M represents the order of modulation, a is the channel gain, and n is the mean value is 0, additive white Gaussian noise with variance^σ2 . Each constellation point s_i represents k=log₂ M bits of information, denoted as: b₀ , b₁ , . . . , b_k-1 .

根据文献M.M.Wang，Weimin Xiao，and T.Brown，“Soft decision metric for QAM withchannel estimation error.”IEEE trans，Commun，vol.50.pp.1058-1061.July 2002。接收信号r中第i个比特b_i的比特似然比可以表示为：According to the literature MMWang, Weimin Xiao, and T. Brown, "Soft decision metric for QAM with channel estimation error." IEEE trans, Commun, vol.50.pp.1058-1061.July 2002. The bit likelihood ratio of the i-th bit_bi in the received signal r can be expressed as:

$\mathrm{<span><span>LLR</span>LLR</span>}<span><span>(</span>(</span>{\mathrm{<span><span>b</span>b</span>}}_{\mathrm{<span><span>i</span>i</span>}}<span><span>)</span>)</span><span><span>=</span>=</span>\frac{\mathrm{<span><span>1</span>1</span>}}{{\mathrm{<span><span>\&sigma;</span>\&sigma;</span>}}^{\mathrm{<span><span>2</span>2</span>}}}<span><span>(</span>(</span>{<span><span>|</span>|</span>\mathrm{<span><span>r</span>r</span>}<span><span>-</span>-</span>{\mathrm{<span><span>as</span>as</span>}}_{\mathrm{<span><span>i</span>i</span>}}^{<span><span>-</span>-</span>}<span><span>|</span>|</span>}^{\mathrm{<span><span>2</span>2</span>}}<span><span>-</span>-</span>{<span><span>|</span>|</span>\mathrm{<span><span>r</span>r</span>}<span><span>-</span>-</span>{\mathrm{<span><span>as</span>as</span>}}_{\mathrm{<span><span>i</span>i</span>}}^{<span><span>+</span>+</span>}<span><span>|</span>|</span>}^{\mathrm{<span><span>2</span>2</span>}}<span><span>)</span>)</span><span><span>,</span>,</span>\mathrm{<span><span>i</span>i</span>}<span><span>=</span>=</span>\mathrm{<span><span>0,1</span>0,1</span>}<span><span>.</span>.</span><span><span>.</span>.</span><span><span>.</span>.</span><span><span>,</span>,</span>\mathrm{<span><span>k</span>k</span>}<span><span>-</span>-</span>\mathrm{<span><span>1</span>1</span>}<span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>$

其中LLR(b_i)表示b_i的比特似然比，s_i^-表示第i个比特为0且离r/a最近的星座点，s_i⁺表示第i比特为1且离r/a最近的星座点，σ²是接收信号的噪声功率。Where LLR(_bi ) represents the bit likelihood ratio of_bi , s_i^- represents the constellation point whose i-th bit is 0 and is the closest to r/a, s_i⁺ represents the i-th bit is 1 and is the closest to r/a The constellation points of , σ² is the noise power of the received signal.

根据公式(2)，计算比特似然比LLR(b_i)要寻找的是s_i^-和s_i⁺。假设用s^*表示由硬判决确定的星座点，那么s^*是M-PSK星座图中距离r/a最近的星座点，显然，如果s^*的第i个比特为0，则$s_i^{-}=s^{*};$如果s^*的第i个比特为1，则$s_i^{*}=s^{*}.$这样，在传统的软解调方法中，s_i^-和s_i⁺其中一个可以通过硬判决获得，但另一个需要搜索星座图中的所有点才能获得，对于高阶调制来说，其计算量十分大。According to the formula (2), what is to be looked for in calculating the LLR(b_i ) is s_i⁻ and s_i⁺ . Assuming that s^* is used to represent the constellation point determined by the hard decision, then s^* is the constellation point closest to r/a in the M-PSK constellation diagram. Obviously, if the i-th bit of s^* is 0, then${\mathrm{the\; s}}_i^{-}={\mathrm{the\; s}}^{*};$ If the ith bit of s^* is 1, then${\mathrm{the\; s}}_i^{*}={\mathrm{the\; s}}^{*}.$ In this way, in the traditional soft demodulation method, one of s_i^- and s_i⁺ can be obtained by hard decision, but the other needs to search all the points in the constellation diagram to obtain it. For high-order modulation, the calculation amount very large.

发明内容Contents of the invention

针对在传统软解调方法中计算比特似然比LLR(b_i)时，由于s_i^-或s_i⁺需要搜索星座图中的所有点才能获得，由此对于高阶调制来说，其计算量十分大的问题，本发明提供了一种高阶格雷码映射M-PSK调制的低复杂度软解调算法，包括发射端处理过程和接收端处理过程。When calculating the bit likelihood ratio LLR(bi₎ in the traditional soft demodulation method, since s_i^- or s_i⁺ needs to search all points in the constellation diagram to obtain, so for high-order modulation, its calculation To solve the problem of very large volume, the present invention provides a low-complexity soft demodulation algorithm for high-order Gray code mapping M-PSK modulation, including the processing process at the transmitting end and the processing process at the receiving end.

发射端处理过程如下列步骤完成：The processing at the transmitting end is completed in the following steps:

步骤1：对输入的二进制数据进行编码，以降低其在传输过程可能出现的随机和突发错误。Step 1: Encode the input binary data to reduce random and burst errors that may occur during transmission.

步骤2：对编码后的数据进行格雷映射M-PSK调制得到发送信号x∈S。Step 2: Perform Gray mapping M-PSK modulation on the coded data to obtain the transmitted signal x∈S.

接收端对接收信号的处理过程如下步骤完成：The receiving end processes the received signal in the following steps:

步骤3：信道估计。根据某种估计准则，从接收信号中进行信道估计，为下一步均衡提供条件。Step 3: Channel estimation. According to some estimation criterion, from the received signal The channel estimation is carried out in order to provide conditions for the next step of equalization.

步骤4：信道均衡消除干扰。根据步骤3得到的估计信道对接收信号r进行均衡，以期消除信道对发送信号x所造成的干扰，得到均衡后的信号

Step 4: Channel equalization eliminates interference. Equalize the received signal r according to the estimated channel obtained in step 3, in order to eliminate the interference caused by the channel to the transmitted signal x, and obtain the equalized signal

步骤5：硬判决。对

进行硬判决，获得硬判星座点$s^{*}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},b_i^{*},b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}).$其中b_i^*(i＝0，1，2...k-1)表示s^*的第i个比特。Step 5: Hard Judgment. right

Make a hard judgment and get a hard judgment constellation point${\mathrm{the\; s}}^{*}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},b_i^{*},b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}).$ Wherein b_i^* (i=0, 1, 2...k-1) represents the ith bit of s^* .

步骤6：计算接收信号的第0比特b₀的比特似然比LLR(b₀)，具体步骤如下：Step 6: Calculate the Received Signal The bit likelihood ratio LLR(b₀ ) of the 0th bit b₀ of , the specific steps are as follows:

子步骤1：判断所述的比特b₀^*，Sub-step 1: judging the bit b₀^* ,

●如果$b_0^{*}=0,$则令$s_0^{-}=s^{*}=(0,b_1^{*},...,b_{i-1}^{*},b_i^{*},b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$而令星座点s₀⁺的第0个比特取1，s₀⁺的第1个比特与硬判星座点s^*的第1个比特相同，s₀⁺的其余比特全为0，即$s_0^{+}=(1,b_1^{*},\mathrm{0,0},...,\mathrm{0,0,0},...,\mathrm{0,0});$●If$b_0^{*}=0,$ order${\mathrm{the\; s}}_0^{-}={\mathrm{the\; s}}^{*}=(0,b_1^{*},...,b_{i-1}^{*},b_i^{*},b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$ And let the 0th bit of the constellation point s₀₊ be 1,^the 1st bit of^s₀₊ is the same as the 1st bit of the hard-judged constellation point s^* , and the^remaining bits of s₀₊ are all 0, that is${\mathrm{the<figure-callout\; label="s"\; filenames="S2008100449138E00011.png"\; state="\{\{state\}\}">s</figure-callout>}}_0^{+}=(1,b_1^{*},\mathrm{0,0},...,\mathrm{0,0,0},...,\mathrm{0,0});$

●如果$b_0^{*}=1,$则$s_0^{+}=s^{*}=(1,b_1^{*},...,b_{i-1}^{*},b_i^{*},b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$星座点s₀^-的第0个比特取0，s₀^-的第1个比特与硬判符号s^*第1个比特相同，s₀^-的其余比特全为0，即●if$b_0^{*}=1,$ but${\mathrm{the<figure-callout\; label="s"\; filenames="S2008100449138E00011.png"\; state="\{\{state\}\}">s</figure-callout>}}_0^{+}={\mathrm{the\; s}}^{*}=(1,b_1^{*},...,b_{i-1}^{*},b_i^{*},b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$ The 0th bit of the constellation point s₀^- is 0, the 1st bit of s₀^- is the same as the 1st bit of the hard judgment symbol s^* , and the remaining bits of s₀^- are all 0, that is

${\mathrm{<span><span>s</span>the\; s</span>}}_{\mathrm{<span><span>0</span>0</span>}}^{<span><span>-</span>-</span>}<span><span>=</span>=</span><span><span>(</span>(</span>\mathrm{<span><span>0</span>0</span>}<span><span>,</span>,</span>{\mathrm{<span><span>b</span>b</span>}}_{\mathrm{<span><span>1</span>1</span>}}^{<span><span>*</span>*</span>}<span><span>,</span>,</span>\mathrm{<span><span>0,0</span>0,0</span>}<span><span>,</span>,</span><span><span>.</span>.</span><span><span>.</span>.</span><span><span>.</span>.</span>\mathrm{<span><span>0,0,0</span>0,0,0</span>}<span><span>,</span>,</span><span><span>.</span>.</span><span><span>.</span>.</span><span><span>.</span>.</span><span><span>,</span>,</span>\mathrm{<span><span>0,0</span>0,0</span>}<span><span>)</span>)</span><span><span>;</span>;</span>$

子步骤2：将子步骤1所得到的s₀^-与s₀⁺代入公式(3)计算接收信号的第0比特的似然比：Sub-step 2: Substitute s₀^- and s₀⁺ obtained insub-step 1 into formula (3) to calculate the received signal The likelihood ratio of the 0th bit of :

$\mathrm{<span><span>LLR</span>LLR</span>}<span><span>(</span>(</span>{\mathrm{<span><span>b</span>b</span>}}_{\mathrm{<span><span>0</span>0</span>}}<span><span>)</span>)</span><span><span>=</span>=</span>\frac{\mathrm{<span><span>1</span>1</span>}}{{\mathrm{<span><span>\&sigma;</span>\&sigma;</span>}}^{\mathrm{<span><span>2</span>2</span>}}}<span><span>(</span>(</span>{<span><span>|</span>|</span>\stackrel{<span><span>^</span>^</span>}{\mathrm{<span><span>r</span>r</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>s</span>the\; s</span>}}_{\mathrm{<span><span>0</span>0</span>}}^{<span><span>-</span>-</span>}<span><span>|</span>|</span>}^{\mathrm{<span><span>2</span>2</span>}}<span><span>-</span>-</span>{<span><span>|</span>|</span>\stackrel{<span><span>^</span>^</span>}{\mathrm{<span><span>r</span>r</span>}}{<span><span>-</span>-</span>\mathrm{<span><span>s</span>the<figure-callout\; label="s"\; filenames="S2008100449138E00011.png"\; state="\{\{state\}\}">s</figure-callout></span>}}_{\mathrm{<span><span>0</span>0</span>}}^{<span><span>+</span>+</span>}<span><span>|</span>|</span>}^{\mathrm{<span><span>2</span>2</span>}}<span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>3</span>3</span>}<span><span>)</span>)</span>$

步骤7：计算接收信号的其余比特b_i(i＝1，2...，k-1)的似然比LLR(b_i)方法为：Step 7: Calculate the received signal The likelihood ratio LLR(b_i ) method of the remaining bits b_i (i=1, 2...,k-1) is:

子步骤1：判决步骤5中计算所得的b_i^*，Sub-step 1: The b_i^* calculated in the decision step 5,

●如果$b_i^{*}=0,$则令$s_i^{-}=s^{*}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},0,b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$而令星座点s_i⁺的第0至i-1个比特与硬判符号s^*的第0至i-1个比特相等，第i个比特为1，第i+1个比特为1，其余比特全为0，即$s_i^{+}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},\mathrm{1,1,0,0},...,0);$●if$b_i^{*}=0,$ order${\mathrm{the\; s}}_i^{-}={\mathrm{the\; s}}^{*}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},0,b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$ And let the 0th to i-1 bits of the constellation point s_i⁺ be equal to the 0th to i-1 bits of the hard judgment symbol s^* , the i-th bit is 1, the i+1-th bit is 1, and the rest The bits are all 0, that is${\mathrm{the\; s}}_i^{+}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},\mathrm{1,1,0,0},...,0);$

●如果$b_i^{*}=1,$则令$s_i^{+}=s^{*}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},1,b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$而令星座点s_i^-的第0至i-1个比特与硬判符号s^*的第0至i-1个比特相等，第i个比特为0，第i+1个比特为1，其余比特全为0，即$s_i^{-}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},\mathrm{0,1,0,0},...,0);$●if$b_i^{*}=1,$ order${\mathrm{the\; s}}_i^{+}={\mathrm{the\; s}}^{*}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},1,b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$ And let the 0th to i-1 bits of the constellation point s_i^- be equal to the 0th to i-1 bits of the hard judgment symbol s^* , the i-th bit is 0, the i+1-th bit is 1, and the rest The bits are all 0, that is${\mathrm{the\; s}}_i^{-}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},\mathrm{0,1,0,0},...,0);$

子步骤2：将s_i^-与s_i⁺代入公式(4)计算得到

中第i个比特b_i的比特似然比：Sub-step 2: Substituting s_i^- and s_i⁺ into formula (4) to calculate

The bit-likelihood ratio of the i-th bit_bi in :

$\mathrm{<span><span>LLR</span>LLR</span>}<span><span>(</span>(</span>{\mathrm{<span><span>b</span>b</span>}}_{\mathrm{<span><span>i</span>i</span>}}<span><span>)</span>)</span><span><span>=</span>=</span>\frac{\mathrm{<span><span>1</span>1</span>}}{{\mathrm{<span><span>\&sigma;</span>\&sigma;</span>}}^{\mathrm{<span><span>2</span>2</span>}}}<span><span>(</span>(</span>{<span><span>|</span>|</span>\stackrel{<span><span>^</span>^</span>}{\mathrm{<span><span>r</span>r</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>s</span>the\; s</span>}}_{\mathrm{<span><span>i</span>i</span>}}^{<span><span>-</span>-</span>}<span><span>|</span>|</span>}^{\mathrm{<span><span>2</span>2</span>}}<span><span>-</span>-</span>{<span><span>|</span>|</span>\stackrel{<span><span>^</span>^</span>}{\mathrm{<span><span>r</span>r</span>}}{<span><span>-</span>-</span>\mathrm{<span><span>s</span>the\; s</span>}}_{\mathrm{<span><span>i</span>i</span>}}^{<span><span>+</span>+</span>}<span><span>|</span>|</span>}^{\mathrm{<span><span>2</span>2</span>}}<span><span>)</span>)</span><span><span>,</span>,</span>\mathrm{<span><span>i</span>i</span>}<span><span>=</span>=</span>\mathrm{<span><span>1,2</span>1,2</span>}<span><span>.</span>.</span><span><span>.</span>.</span><span><span>.</span>.</span>\mathrm{<span><span>k</span>k</span>}<span><span>-</span>-</span>\mathrm{<span><span>1</span>1</span>}<span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>4</span>4</span>}<span><span>)</span>)</span>$

步骤8：利用步骤6和步骤7计算得到的每个比特的似然比，进行译码，然后输出译码后的数据。Step 8: Use the likelihood ratio of each bit calculated in Step 6 and Step 7 to decode, and then output the decoded data.

需要说明的是：It should be noted:

1)步骤2中的格雷映射M-PSK调制方法必须采用3GPP在TR 25.848 V4.0.0标准中规定的规则，如图4所示；详情见TR 25.848 V4.0.0；1) The gray mapping M-PSK modulation method in step 2 must adopt the rules stipulated by 3GPP in the TR 25.848 V4.0.0 standard, as shown in Figure 4; see TR 25.848 V4.0.0 for details;

2)步骤5中格雷映射M-PSK调制下接收信号对应的简化硬判算法见文献：“C.K，Yuen，A fast analog to gray code converter，”in Proceedings of the IEEE，vol.65，pp.1510-1511，Oct.1977，利用该算法能够有效地降低格雷映射M-PSK调制的硬判决复杂度。2) For the simplified hard judgment algorithm corresponding to the received signal under Gray mapping M-PSK modulation in step 5, see the literature: "C.K, Yuen, A fast analog to gray code converter," in Proceedings of the IEEE, vol.65, pp.1510 -1511, Oct.1977, using this algorithm can effectively reduce the hard decision complexity of Gray mapping M-PSK modulation.

本发明的实质与效果：Essence and effect of the present invention:

本发明的实质是：用硬判决法确定s_i^-与s_i⁺符号中的其中一个后，就可以根据s_i^-与s_i⁺之间的内在关系直接确定s_i^-与s_i⁺中的另外一个符号，然后计算得到接收信号每个比特的似然比LLR(b_i)，从而避免了复杂星座图搜索过程。因此，该算法能够有效地降低软解调的复杂度，便于硬件实现，同时降低硬件成本，使之能在未来高速移动通信系统中得到广泛应用。The essence of the present invention is: after using the hard decision method to determine one of the s_i^- and s_i⁺ symbols, the s_i^- and s_i⁺ can be directly determined according to the internal relationship between_s i^- and s_i⁺ Then calculate the likelihood ratio LLR(bi₎ of each bit of the received signal, thus avoiding the complex constellation search process. Therefore, this algorithm can effectively reduce the complexity of soft demodulation, facilitate hardware implementation, and reduce hardware cost, so that it can be widely used in future high-speed mobile communication systems.

附图说明Description of drawings

图1为本发明LLR(b_i)计算的实现流程。Fig. 1 is the implementation process of LLR(_bi ) calculation in the present invention.

图2为3GPP规定的16-PSK格雷映射星座图。FIG. 2 is a 16-PSK Gray mapping constellation diagram specified by 3GPP.

实施例：Example:

下面给出一个具体的本专利的实施方法，需要说明的是：下例中的参数并不影响本专利的一般性。A specific implementation method of this patent is given below, and it should be noted that the parameters in the following examples do not affect the generality of this patent.

发端originate

输入信号进行码长为300，码率为1/2的LDPC编码后，进行格雷映射，然后进行16-PSK调制，再将调制后的信号功率归一化后经过无线信道。The input signal is encoded by LDPC with a code length of 300 and a code rate of 1/2, then Gray mapped, then 16-PSK modulated, and then the modulated signal power is normalized and passed through the wireless channel.

如图2所示，这里M＝16，k＝4。As shown in Figure 2, here M=16, k=4.

收端receiving end

对接收信号依次进行信道估计、均衡，得到经均衡后的信号

对

进行硬判获得硬判符号s^*根据发明内容中步骤7和步骤8的方法计算接收

的每个比特的比特似然比。最后将接收信号的比特似然比送到译码模块译码后，得到判决输出。Perform channel estimation and equalization on the received signal in sequence to obtain the equalized signal

right

Carry out hard judgment to obtain hard judgment symbol s^* Calculate and receive according to the method of step 7 and step 8 in the summary of the invention

The bit-likelihood ratio for each bit of . Finally, the bit likelihood ratio of the received signal is sent to the decoding module for decoding to obtain a decision output.

Claims (1)

1, the soft decision method of a kind of gray mappings M-PSK modulation by equilibrium, channel estimating, r carries out equilibrium, hard decision, calculating bit likelihood ratio, decode procedure and forms to received signal, is characterized in that: obtain constellation point at hard decision$s^{*}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},b_i^{*},b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*})$Afterwards, the method for calculating bit likelihood ratio is:

Step 1: calculate received signal

The 0th bit b₀Bit likelihood ratio LLR (b₀), concrete steps are as follows:

Substep 1: judge described bit b₀^*,

If ●$b_0^{*}=0,$Then order$s_0^{-}=s^{*}=(0,b_1^{*},...,b_{i-1}^{*},b_i^{*},b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$And make constellation point s₀⁺The 0th bit get 1, s₀⁺The 1st bit with declare constellation point s firmly^*The 1st bit identical, s₀⁺All the other bits be 0 entirely, promptly$s_0^{+}=(1,b_1^{*},\mathrm{0,0},...,\mathrm{0,0,0},...,\mathrm{0,0});$

If ●$b_0^{*}=1,$Then$s_0^{+}=s^{*}=(1,b_1^{*},...,b_{i-1}^{*},b_i^{*},b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$Constellation point s₀^-The 0th bit get 0, s₀^-The 1st bit with declare symbol s firmly^*The 1st bit is identical, s₀^-All the other bits be 0 entirely, promptly$s_0^{-}=(0,b_1^{*},\mathrm{0,0},...,\mathrm{0,0,0},...,\mathrm{0,0});$

Substep 2: with substep 1 resulting s₀^-With s₀⁺Substitution formula (1) calculates received signalThe likelihood ratio of the 0th bit:

$\mathrm{LLR}\left(b_0\right)=\frac{1}{{\mathrm{\&sigma;}}^2}({|\hat{r}-s_0^{-}|}^2-{|\hat{r}-s_0^{+}|}^2)---\left(3\right)$

Step 2: calculate received signal

All the other bit b_i(i=1,2..., likelihood ratio LLR (b k-1)_i) method is:

Substep 1: the b that calculates gained in the decision steps 5_i^*,

If ●$b_i^{*}=0,$Then order$s_i^{-}=s^{*}={(b}_0^{*},b_1^{*},...,b_{i-1}^{*},0,b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$And make constellation point s_i⁺The the 0th to i-1 bit with declare symbol s firmly^*The the 0th to i-1 bit equate that i bit is that 1, an i+1 bit is 1, all the other bits are 0 entirely, promptly

$s_i^{+}={(b}_0^{*},b_1^{*},...,b_{i-1}^{*},\mathrm{1,1,0,0},...,0);$

If ●$b_i^{*}=1,$Then order$s_i^{+}=s^{*}={(b}_0^{*},b_1^{*},...,b_{i-1}^{*},1,b_{i+1}^{*},...,b_{k-2}^{*},b_{k-1}^{*}),$And make constellation point s_i^-The the 0th to i-1 bit with declare symbol s firmly^*The the 0th to i-1 bit equate that i bit is that 0, an i+1 bit is 1, all the other bits are 0 entirely, promptly$s_i^{-}=(b_0^{*},b_1^{*},...,b_{i-1}^{*},\mathrm{0,1,0,0},...,0);$

Substep 2: with s_i^-With s_i⁺Substitution formula (2) calculates

In i bit b_iThe bit likelihood ratio:

$\mathrm{LLR}\left(b_i\right)=\frac{1}{{\mathrm{\&sigma;}}^2}({|\hat{r}-s_i^{-}|}^2-{|\hat{r}-s_i^{+}|}^2),i=\mathrm{1,2}...k-1---\left(2\right)$

Step 3: utilize the likelihood ratio of each bit that step 1 and step 2 calculate, decipher, then the data after the output decoding.

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