SST2000-15 / SAT2000-25 やり直し機構を含めた多段型干渉除去に関する一検討  [in Japanese] A Study on Multi-Stage CCI Cancellation Algorithm Incorporating Redoing  [in Japanese]

CDMAにおけるシステム容量は整合受信機を想定する上で, その限界が指摘されている.その原因は相互の系列間の相関に起因する局間干渉であるが, これに対抗する手段が広く検討されている.提案されている局間干渉除去方式は各段での判定の信頼性に干渉除去の性能が依存するが, 判定誤りはその後の判定で連鎖的な誤りを引き起こす.本稿では, 判定の信頼度を正確に求めるために, 相関器として直交化整合フィルタを用いて, 干渉除去を判定の信頼度の高いユーザから順に行う.その判定を評価するために検定を行い, 検定に合格しなかった判定に関しては干渉除去のやり直しを行う方法を提案する.まず, 尤度比に基づく統計量を用いた検定について検討を行ったが, 十分な検出力が得られなかった.そこで, 帰無仮説に基づいた検定を提案した.

It is well known that the system capacity of CDMA is limited by Co-Channel Interference so far as the receiver uses the single user matched filter. CCI is caused by the cross-corrlation berween the spreading sequences assigned to the simultaneous users. Many proposals for coping with the CCI have been made and investigated. Among them a typical scheme repeatedly eliminaes interference all together using replicas based on the single user decision for the simultaneous users. The performance of the method was found to deteriorate for the smaller signal dimension because of the error propagation. We already propose a cancellation scheme for CCI which eliminates in turn the replica of the user whose Orthogonal Matched Filter output looks the most reliable. In this report, we introduced the hypothesis testing schemes for detecting erroneous cancellation. We first tried using a statistic derived from the likelihood ratio. It was found, however, the detectability was insufficient. Therefore we proposed another scheme based on the null hypothesis testing.