上鏈無線通訊系統中分碼與分交錯器多重存取渦輪接收機之電腦模擬與效能評估

Abstract

分碼多重存取(CDMA)為第3代行動通訊的核心，是近二十年來各種多重存取技術中，能夠提供較多系統容量的一種技術。多重存取干擾(MAI)是影響CDMA系統容量與效能的重要因素。最近幾年分交錯器多重存取(interleave division multiple access, IDMA)被提出，此技術利用不同的交錯器來辨別用戶，也可以利用簡單的切片到切片(chip by chip, CBC)多用戶偵測的方法，藉由這個方法每個用戶計算的複雜度不會隨著用戶數增加。相較於CDMA需設計好的展頻碼，才能有較好的效能，IDMA用隨機產生的交錯器，即可達到不錯的效能。在本篇論文中，我們基於多路徑區塊瑞雷衰減通(block Rayleigh fading channel)及國際電信聯盟(ITU)所制定的Veh.A通道的假設，探討CDMA和IDMA在上鏈的傳輸系統中，使用不同多用戶偵測及渦輪式解碼方法的系統效能。從模擬結果中發現IDMA用CBC多用戶偵測之位元錯誤率效能比CDMA所採用的最小均方等化器-軟式平行干擾消除(MMSE-SPIC)及CBC二種多用戶偵測好。

Nowdays CDMA took the core of the 3rd generation of cellular mobile radio communication systems, and it is a multiple access technology that can provide more system capacity. Multiple access interference (MAI) is the major factor which limits the capacity and performance of a CDMA system. In recent years, interleave division multiple access (IDMA) was proposed. It uses different interleavers to distinguish users, and it employs simple chip by chip (CBC) multiuser detection method for which each user’s computation complexity does not increase with the number of users. In contract to CDMA which need many good spreading codes to provide good system performance, IDMA can achieve good system performance by using randomly generated interleavers. In this paper, assuming a predefined multipath block Rayleigh fading channel and the International Telecommunication Union (ITU) developed Veh.A channel, we explored the uplink transmission system performance of CDMA and IDMA, in which turbo decoder is used with different type of multiuser detection methods. From our simulation results, BER performance of IDMA use the CBC multiuser detection method are better than that of CDMA using MMSE-SPIC and CBC multiuser detection methods.