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題名 | Parallel Interference Cancellation Multiuser Detection for CDMA Power Line Communication Systems=分碼多重進接電力線通訊系統之平行干擾消除多用戶檢測器 |
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作者姓名(中文) | 黃永發; 陳世寬; | 書刊名 | 中州學報 |
卷期 | 16 2002.12[民91.12] |
頁次 | 頁63-76 |
分類號 | 448.6 |
關鍵詞 | 電力線通訊系統; 序列分碼多重進接; 多用戶檢測器; 平行干擾消除; Power line communications; DS-CDMA; Multiuser detection; Partial parallel interference cancellation; |
語文 | 英文(English) |
中文摘要 | 本論文基於模糊推論機制,提出適用於電力線 (power line) 序列分碼多重進接 (direct-sequence code-division multiple-access, DS-CDMA) 系統的部份平行干擾清除檢測技街。序列分碼多重進接通訊技術具備甚高之系統容量 (system capacity) 潛力 (potentiality)。但用戶使用之非正交展頻碼 (spreading codes) 在上連 (uplink) 傳輸峙,均會有交互相關性 (cross-correlation),因此用戶在接收訊號時就產生了多重進接干擾 (multiple access interference, MAI),當用戶增加峙,MAI成為系統效能惡化 (degradation) 之主要因素,而多用戶檢測器 (multiuser detector) 則是可有放抑制或消除MAI的主要技術。應用電力線傳輸訊號,不但方便,又節省了傳輸線的成本;但由於在電力線通訊系統的傳輸通道具有多重路徑衰退 (mu1tipath fading) 現象,使得載波訊號之振幅、相位及時間延遲均具有隨機特性。此多重路徑進成之瑞雷衰退 (Rayleigh Fading) 會使性能嚴重惡化;在高速傳輸速率峙,電力線傳輸通道之同調頻寬 (coherent bandwidth) 不夠寬,而造成選頻衰退。因此,在本文中,我們於電力線通訊系統中之選頻通道環境中,用RAKE接收器件第一級之檢測後,應用棋糊推論機部分平行干擾清除 (FB-PPIC) 技術作多用戶檢測器,我們應用一個調整因子 (scaling factor, SF) 來調整模糊推論機之輸入模糊量,以適當反應出RAKE接收器之位元決策 (bit-decision) 之可靠度 (reliability) 提升;且當解析之路徑愈多時,調整因子則愈大。由電腦模擬結果知,當我們應用此調整因子分別將模糊推論機之輸入模糊量訊號雜訊比 (signal-to-noise ratio, SNR) 調高及有效用戶數 (effective number of users, Keff) 調低峙,可改善傳統平行干擾消除 (CPIC) 接收器之性能,並且比固定權重 (constant weight PPIC, CW-PPIC) 還要好:因此,應用模糊推論機部分平行干擾消除 (FB-PPIC) 多用戶檢測器作電力線通訊系統之CDMA訊號傳輸,確實可提升系統容量。 |
英文摘要 | In this paper, we investigate the performance of the multistage partial parallel interference cancellation (PPIC) multiuser detector for direct-sequence code-division multiple-access (DS-CDMA) communication systems over power line communication (PLC) channels. The PPIC, which tries to reduce the cancellation error in PIC due to the wrong interference estimations in the early stage, was proposed by Divsalar et al. to outperform the conventional PIC under the heavy load. However, the adequate partial cancellation weights (PCW) of individual user in a PPIC scheme over the frequency selective fading channels is adaptively related to the channel characteristics which is very dynamic with the power of users and the channel noise. Therefore, in this paper an adaptive fuzzy inference mechanism is proposed to generate the adequate PCWs for the PPIC detection scheme. By the measured SNR and signals' amplitudes, the proposed fuzzy logic system can infer much more adequate PCWs to reveal the reliability of received signals. Simulation results show that the proposed fuzzy-based PPIC (FB-PPIC) outperforms both the conventional PIC (CPIC) and constant weight PPIC (CW-PPIC) schemes. It should be emphasized that the proposed multistage FB-PPIC scheme achieves a high adaptation on the effect of high attenuations of lognormal distributions and frequency selective filtering in the power-line-based communication systems. |
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