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: | 1-八月-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 |
顯示於類別: | 會議論文 |