講演抄録/キーワード |
講演名 |
2020-03-05 14:50
無線通信におけるPolar符号の符号化と逐次除去復号の検討 ○荒木駿生・張 裕淵・府川和彦(東工大) RCS2019-369 |
抄録 |
(和) |
Polar符号は,第5世代移動通信方式(5G)の制御チャネルの誤り訂正符号として採用されており,誤り易いビットを凍結ビットとして送受信間で既知とすることで誤りを抑制し,シャノン限界に迫る通信路容量を達成できる.
本報告では,Polar符号を無線通信へ適用する際,その復号法として逐次除去(SC: Successive Cancellation)に注目し,その特性改善を目指す.
具体的には,SC復号器の入力となる尤度比(LR: Likelihood Ratio)の精度を高めるため,符号化ビットの対数尤度比(LLR: Logarithm LR)にSP(Sum-Product)アルゴリズムを用いてLRを更新し,ビット誤り率(BER)特性とパケット誤り率(PER)特性の改善を図る.
まず,生成行列の行重みに基づき凍結ビットを設定し,これに伴いSPアルゴリズムに必要なパリティチェック行列を求める.
凍結ビットを考慮した生成行列を情報ビットに乗算して符号化ビットを求め,さらにパリティチェック行列に応じてビットを付加し送信する.
受信機では,受信信号から求めた受信LLRにSPアルゴリズムを適用してLRの信頼度を高める.
周波数選択性フェージング条件におけるOFDM(Orthogonal Frequency-Division Multiplexing)伝送の計算機シミュレーションを行い,提案方式の平均BER特性と平均PER特性の改善効果を明らかにする. |
(英) |
Polar codes have been adopted as an error correction code for the control channel of the 5th generation mobile communication system (5G).
To alleviate bit errors, the polar code assigns coded bits that are likely to cause bits errors, into frozen bits and makes the frozen bits known to both the transmitter and receiver sides, which can approach the channel capacity of the Shannon limit.
This report considers applications of the polar code into wireless communications, focuses on successive cancellation (SC) as a decoding scheme for the polar code, and aims to improve the performance of SC.
For the improvement, we update likelihood ratios (LRs) of the encoded bits by applying the sum-product (SP) algorithm into the logarithm LRs (LLRs), which is expected to improve the bit error rate (BER) and packet error rate (PER) performances.
First, the frozen bits are determined according to row weights of the generator matrix, and then the parity check matrix, which is necessary for the SP algorithm, is obtained from the generator matrix.
Next, the generator matrix is updated considering the frozen bits, and multiplying the information bit sequence by the updated generator matrix yields the encoded bit sequence.
Furthermore, additional bits are determined according to the parity check matrix and are inserted into the tail of the encoded bit sequence.
On the receiver side, LLRs of the encoded bits are obtained from received signals, and then the SP algorithm is applied into the LLRs, which can improve the reliability of the corresponding LRs.
Computer simulations of orthogonal frequency-division multiplexing (OFDM) transmission over frequency selective fading channels are conducted, and show the improvement of average BER and average PER performances of the SC decoding due to the application of the SP algorithm. |
キーワード |
(和) |
無線通信 / Polar符号 / 凍結ビット / 逐次除去復号 / Sum-Productアルゴリズム / パリティチェック行列 / / |
(英) |
Wireless communications / polar codes / frozen bits / successive cancellation decoding / sum-product algorithm / parity check matrix / / |
文献情報 |
信学技報, vol. 119, no. 448, RCS2019-369, pp. 251-256, 2020年3月. |
資料番号 |
RCS2019-369 |
発行日 |
2020-02-26 (RCS) |
ISSN |
Online edition: ISSN 2432-6380 |
著作権に ついて |
技術研究報告に掲載された論文の著作権は電子情報通信学会に帰属します.(許諾番号:10GA0019/12GB0052/13GB0056/17GB0034/18GB0034) |
PDFダウンロード |
RCS2019-369 |
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