交織多重接取系統之通道估測及時序偏移估測之共同設計

Abstract

交織多重接取系統是近年來一項類似分碼多重接取系統的嶄新的多重接取技術，顧名思義每位使用者使用不同的交織器來區分彼此；相對於分碼多重接取系統在多用戶偵測器的高複雜度，交織多重接取系統使用Chip-by-chip演算法具有線性的低複雜度；且交織多重接取系統使用疊代解碼演算法，每位使用者在解碼的同時也會幫助彼此使效能更加精確；在本篇論文中，我們結合了通道估測及時序偏移估測使系統在同一次疊代中進行通道估測及時序偏移估測。 時序偏移估測可以分成粗調及微調；在通道估測跟時序微調的實作中我們借助了嵌入式領航訊號來使系統更快收斂且不會浪費多餘的頻寬，我們同樣使用Chip-by-chip演算法來做這兩項估測，使得它們同樣具有低複雜度的性質；在時序微調中我們使用鎖相迴路來抓到正確的時序偏移，而在時序粗調中使用了類似分碼多重接取系統的相關器來使用者的交織器可以跟使用者的訊號同步；共同設計時，因為三種估測是彼此獨立運作的，因此保有了各自的優缺點及演算法。

Interleave Division Multiple Access system, IDMA, proposed in recently year is a multiple access technique similar to CDMA. As its names, It uses user-specific interleave to distinguish one user’s signal from others. Comparing with the high complexity when CDMA do multi-user detection, IDMA system applies Chip-by-chip algorithm and thus has the linearly complexity. Moreover IDMA system uses iterative decoding algorithm, which makes each user can help each other become more accurate and more reliable when decoding. In this thesis, we combine channel estimation and timing estimation into one system, such that during each iteration, the system can do both channel estimation and timing estimation. Timing estimation can be subdivided into course estimation, Acquisition and fine estimation, Tracking. In the realization of channel estimation and timing tracking, we employ embedded pilot signal to make the system become convergence more quickly and don’t waste another bandwidth. We apply chip-by-chip algorithm to do these two estimation which makes them have the property of the same low-complexity. In timing tracking, delayed-locked loop is used to catch the true timing drift, whereas in timing acquisition, we uses correlator method similar to CDMA to make the user’s interleaver can be synchronous with user’s data. When joint design, they remain their own advantage, disadvantage and algorithm because these three estimation is operating independently to each other.