On the Implementation of 5G LDPC Decoder
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54th Institute of CETC, Shijiazhuang 050080, China
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摘要: 該文介紹了5G標(biāo)準(zhǔn)中LDPC碼的特點(diǎn),比較分析了各種譯碼算法的性能,提出了譯碼器實(shí)現(xiàn)的總體架構(gòu):將譯碼器分為高速譯碼器和低信噪比譯碼器。高速譯碼器適用于碼率高、吞吐率要求高的情形,為譯碼器的主體;低信噪比譯碼器主要針對(duì)低碼率、低信噪比下的高性能譯碼,處理一些極限情形下的通信,對(duì)吞吐率要求不高。分別對(duì)高速譯碼器和低信噪比譯碼器進(jìn)行了設(shè)計(jì)實(shí)踐,給出了FPGA綜合結(jié)果和吞吐率分析結(jié)果。
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關(guān)鍵詞:
- 5G移動(dòng)通信 /
- 低密度奇偶校驗(yàn)碼 /
- 譯碼器 /
- FPGA
Abstract: This paper focuses on the Low-Density-Parity-Check (LDPC) decoder for 5G New Radio (NR) specification. After introducing the characteristics of the LDPC code in 5G NR, the performance of different decoding algorithms are compared, and then the overall architecture of the decoder is proposed. In the proposed architecture, the decoder is divided into high-speed decoder and high-performance decoder. The high-speed decoder is intended for high-rate and high throughput decoding, while the high-performance decoder is used for low-rate decoding under low Signal-to-Noise-Ratio (SNR) scenarios, which is for communications under extremely bad situations, and does not need a high throughput. The design is implemented on Field Programmable Gate Array (FPGA) and the results are shown.-
Key words:
- 5G Mobile Communications /
- LDPC /
- Decoder /
- Field Programmable Gate Array (FPGA)
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表 1 準(zhǔn)循換子碼塊長(zhǎng)度取值
集指數(shù) (${i_{\rm LS} }$) 子碼塊大小集合 ($Z$) 0 {2, 4, 8, 16, 32, 64, 128, 256} 1 {3, 6, 12, 24, 48, 96, 192, 384} 2 {5, 10, 20, 40, 80, 160, 320} 3 {7, 14, 28, 56, 112, 224} 4 {9, 18, 36, 72, 144, 288} 5 {11, 22, 44, 88, 176, 352} 6 {13, 26, 52, 104, 208} 7 {15, 30, 60, 120, 240} 下載: 導(dǎo)出CSV
表 2 譯碼算法
初始化$\forall i,j$,${L^0}\left( {{q_i}} \right) = 2{y_i}/{\sigma ^2}$,${L^0}\left( {{r_{ji}}} \right) = 0$; For 迭代次數(shù)$l$ For 每一個(gè)校驗(yàn)節(jié)點(diǎn)$j$ ${\rm{idx}}$= 與校驗(yàn)節(jié)點(diǎn)$j$相連的所有變量節(jié)點(diǎn)坐標(biāo); ${L_{{\rm{in}}}} = {L^{l - 1}}\left( {{q_{{\rm{idx}}}}} \right) - {L^{l - 1}}\left( {{r_{j,{\rm{idx}}}}} \right)$;//去掉自身產(chǎn)生的外信息 ${L_{ {\rm{out} } } } = A\lg \,{\rm orithm}\,\left( { {L_{ {\rm{in} } } }} \right)$;//變量節(jié)點(diǎn)對(duì)校驗(yàn)節(jié)點(diǎn)的更新 ${L^l}\left( {{q_{{\rm{idx}}}}} \right) = {L_{{\rm{in}}}} + {L_{{\rm{out}}}}$;//變量節(jié)點(diǎn)更新 ${L^l}\left( {{r_{j,{\rm{idx}}}}} \right) = {L_{{\rm{out}}}}$;//外信息更新 End $\forall i$, ${d_i} = {L^l}\left( { {q_i} } \right) > 0$; If $Hd = = 0$ Break; end end 下載: 導(dǎo)出CSV
表 3 變量節(jié)點(diǎn)對(duì)校驗(yàn)節(jié)點(diǎn)更新方式
序號(hào) 算法名稱(chēng) 更新方式 1 log-bp(BP) $L_{{\rm{out}}}^{{\rm{log - bp}}}\left( {{r_{ji}}} \right) = 2{\tanh ^{ - 1}}\left( {\prod\limits_{{i'} \in {V_j}\backslash i} {\tanh \left( {{L_{{\rm{in}}}}\left( {{q_{{i'}j}}} \right)/2} \right)} } \right)$ 2 MSA $L_{{\rm{out}}}^{{\rm{MSA}}}\left( {{r_{ji}}} \right) = \prod\limits_{{i'} \in {V_j}\backslash i} {{\rm{sgn}} \left( {{L_{{\rm{in}}}}\left( {{q_{{i'}j}}} \right)} \right)} \bullet \mathop {\min }\limits_{{i'} \in {V_j}\backslash i} \left( {\left| {{L_{{\rm{in}}}}\left( {{q_{{i'}j}}} \right)} \right|} \right)$ 3 Offset MSA(OMSA) $L_{{\rm{out}}}^{{\rm{Offset}}}\left( {{r_{ji}}} \right) = \prod\limits_{{i'} \in {V_j}\backslash i} {{\rm{sgn}} \left( {{L_{{\rm{in}}}}\left( {{q_{{i'}j}}} \right)} \right)} \bullet \max \left( {\mathop {\min }\limits_{{i'} \in {V_j}\backslash i} \left( {\left| {{L_{{\rm{in}}}}\left( {{q_{{i'}j}}} \right)} \right|} \right) - \beta ,0} \right)$ 4 Normalized MSA(NMSA) $L_{{\rm{out}}}^{{\rm{Norm}}}\left( {{r_{ji}}} \right) = \alpha \prod\limits_{{i'} \in {V_j}\backslash i} {{\rm{sgn}} \left( {{L_{{\rm{in}}}}\left( {{q_{{i'}j}}} \right)} \right)} \bullet \mathop {\min }\limits_{{i'} \in {V_j}\backslash i} \left( {\left| {{L_{{\rm{in}}}}\left( {{q_{{i'}j}}} \right)} \right|} \right)$ 下載: 導(dǎo)出CSV
表 4 通道實(shí)現(xiàn)復(fù)雜度
序號(hào) 算法 組合邏輯 寄存器 存儲(chǔ)器(bit) 1 log-bp 447 85 768 2 MSA, Offset MSA, Normalized MSA 222 58 0 下載: 導(dǎo)出CSV
表 5 譯碼器的FPGA實(shí)現(xiàn)結(jié)果
序號(hào) 模塊 組合邏輯 寄存器 存儲(chǔ)器(bit) 最大時(shí)鐘頻率(MHz) 資源占用比例(%) 1 高速譯碼加速器(含存儲(chǔ)器) 124457 50515 393216 112.74 74 2 log-bp譯碼加速器 10901 1937 18432 97.59 5 下載: 導(dǎo)出CSV
表 6 譯碼器吞吐率(Mbps)
序號(hào) 模塊\碼率 1/5 1/2 5/6 9/10 1 高速譯碼加速器(含存儲(chǔ)器) 29.94 119.74 598.69 1077.60 2 log-bp譯碼加速器 2.84 11.37 56.85 102.34 下載: 導(dǎo)出CSV
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