以灰預測-模糊決策法設計無線通訊交遞程序演算法

A Hybrid Handoff Algorithm for Wireless Communication Systems Using Grey Prediction and Fuzzy Decision Systems

游春傑(Chun-Jie Yu.)

指導教授 ： 李慶鴻

元智大學/工程學院/電機工程學系/碩士(2003年)

摘要

在無線通訊系統中，為了在有限頻寬同一時間下得以服務更多使用者，因此通道的重複使用率之提高，是必然之趨勢，其基地台間之交遞程序更顯重要。本論文探討無線通訊系統中之交遞程序(Handoff)問題，並提出以灰預測-模糊決策方法(Grey-Prediction and Fuzzy Decision, GPFD)設計交遞程序演算法，其方法可簡述如下：GPFD係以灰預測系統(Grey Prediction, GP)為基礎，並結合模糊邏輯系統(Fuzzy Logic System, FLS)做成模糊決策(Fuzzy Decision, FD)，本論文採用基地台間之接收信號強度指示(Received Signal Strength Indication, RSSI)做為GPFD之預測輸入，而後級決策條件是以基地台間之滯留區效應為基礎。GPFD法可利用預測得到RSSI之動態，配合後級之決策對於RSSI之驟降可以達到預先執行交遞程序，另外當本地基地台信號回復相較於遠端基地台有更大強度時，GPFD法亦快速地切回本地基地台以減少交遞延遲。
最後，本論文提出之GPFD法除了預測結果具有與輸入之高度近似及具備基地台間執行交遞程序即時性外，亦能確實地執行交遞程序切換，並且有效地減少不必要之交遞程序執行，還有減少交遞延遲，故GPFD確實不失為高效能之交遞程序演算法。

關鍵字

無線通訊系統 ； 模糊邏輯系統 ； 灰預測 ； 接收信號強度指示 ； 交遞程序

並列摘要

For wireless communication, due to finite bandwidth and obtaining an efficiently service, it is important to increase the channel reuse ratio (CRR), thus an available and efficient handoff algorithm should be developed. In this thesis, we proposed a hybrid handoff algorithm for wireless communication systems using Grey prediction and fuzzy decision system (GPFD). The GPFD method composed of grey prediction scheme and fuzzy decision system. The grey predictor is used to predict the RSSI (Received Signal Strength Indication) value for the inputs of fuzzy decision system. Thus, fuzzy decision system calculates the so-called handoff factor (HF) and compares with the handoff factor threshold (HFT) to make the decision. Our decision is based on effice of hysteresis and due to reduce delayed handoff. They are BS’s RSSI drop fastly and less than remote BS switch to remote BS, and local BS’s RSSI great than remote BS then come back. The GPFD has high prediction accuracy, on-line, and robustness of decision, which results good performance even the so-called Manhattan corner effect occur (causes the received signal level to drop). Several simulation results and comparisons show the effectiveness of GPFD method.

並列關鍵字

Wireless communication system ； fuzzy logic system ； grey prediction ； Received Signal Strength Indication ； handoff algorithm

參考文獻

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