Frequency Offset Compensation Scheme Using Interference Cancellation in Reverse Link of OFDM/SDMA Systems

Naoto EGASHIRA  Takahiko SABA  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E89-A   No.10   pp.2543-2548
Publication Date: 2006/10/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e89-a.10.2543
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Information Theory and Its Applications)
Category: Coding Theory
Keyword: 
OFDM,  SDMA,  frequency offset compensation,  interference cancellation,  

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Summary: 
In the reverse link of orthogonal frequency division multiplexing (OFDM)/ space division multiple access (SDMA) systems, each receive antenna of a base station receives a multiplexed version of signals transmitted from users, where the transmitted signals have individual amounts of frequency offset. Therefore, a frequency offset compensation scheme which is different from those used in general OFDM systems is required. For this requirement, frequency offset compensation schemes using the feedback transmission from the base station to user terminals have been proposed for multiuser OFDM systems. These schemes work with good precision when the feedback information is correct and is transmitted without errors. However, when the offset information is incorrectly received at user terminals, the frequency offset is not accurately compensated for. In OFDM/SDMA systems, one user is enough for causing inter-carrier interference to all users. Therefore, a frequency offset compensation scheme without feedback transmission is sometimes preferable. In this paper, we propose a frequency offset compensation scheme without feedback transmission. To compensate for frequency offset in every transmitted signal, the multiplexed received signals must be separated into each user's component before the offset compensation. Thus, we adopt the principle of the parallel interference cancellation (PIC). By employing PIC, the received signals can be separated before the offset compensation. Thus, the frequency offset of every user's signal can be compensated for. Simulation results show the bit error rate performance of the proposed scheme attains almost the same as that of the conventional scheme using the feedback transmission without errors.