標題: MAI-free, MC-CDMA systems based on Hadamard-Walsh codes
作者: Tsai, Shang-Ho
Lin, Yuan-Pei
Kuo, C. -C. Jay
電控工程研究所
Institute of Electrical and Control Engineering
關鍵字: carrier frequency offset (CFO);Hadamard-Walsh code;interference free;large-area synchronized (LAS) code;multiaccess interference (MAI)-free;multicarrier code-division multiple-access (MC-CDMA);multiuser detection (MUD)
公開日期: 1-Aug-2006
摘要: It is known that multicarrier code-division multiple-access (MC-CDMA) systems suffer from multiaccess interference. (MAI) when the channel is frequency-selective fading. In this paper, we propose a Hadamard-Walsh code-based MC-CDMA system that achieves zero MAI over a frequency-selective fading channel. In particular, we will use appropriately chosen subsets of Hadamard-Walsh code as codewords. For a multipath channel of length L, we partition a Hadamard-Walsh code of size N into G subsets, where G is a power of two with G >= L. We will show that the N/G codewords in any of the G subsets yields an MAI-free system. That is, the number of MAI-free users for each codeword subset is N/G. Furthermore, the system has the additional advantage that it is robust to carrier frequency offset (CFO) in a multipath environment. It is also shown that the MAI-free property allows us to estimate the channel of each user separately and the system can perform channel estimation much more easily. Owing to the MAI-free property, every user can enjoy a channel diversity gain of order L to improve the bit error performance. Finally, we discuss a code priority scheme for a heavily loaded system. Simulation results are given to demonstrate the advantages of the proposed code and code priority schemes.
URI: http://dx.doi.org/10.1109/TSP.2006.875387
http://hdl.handle.net/11536/11938
ISSN: 1053-587X
DOI: 10.1109/TSP.2006.875387
期刊: IEEE TRANSACTIONS ON SIGNAL PROCESSING
Volume: 54
Issue: 8
起始頁: 3166
結束頁: 3179
Appears in Collections:Conferences Paper


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