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Interference Cancellation with DFE in Frequency Domain for OFDM Systems with Insufficient CP
Lan YANG Shixin CHENG
Publication
IEICE TRANSACTIONS on Communications
Vol.E88B
No.12
pp.46164624 Publication Date: 2005/12/01
Online ISSN:
DOI: 10.1093/ietcom/e88b.12.4616
Print ISSN: 09168516 Type of Manuscript: PAPER Category: Wireless Communication Technologies Keyword: Orthogonal Frequency Division Multiplexing, cyclic prefix, intersymbolinterference, intercarrier interference, decision feedback equalizer,
Full Text: PDF(632.8KB)>>
Summary:
In OFDM systems, employing a cyclic prefix (CP) as the guard interval is a simple way to combat the intersymbol interference (ISI) and the intercarrier interference (ICI), however it reduces the transmission efficiency of the system, especially for some channels with a very long delay spread. In this paper, we consider the OFDM system with insufficient CP, much more efficient than conventional OFDM systems. First, we present the system mathematical model and give the ISI and ICI analysis. Then the signaltointerference power ratio (SIR) performance is presented. To reduce the ISI and ICI due to the insufficient CP, we develop a minimummeansquareerror decision feedback equalizer (MMSE_DFE). Based on the MMSE criterion, the optimum feedforward and feedback filter coefficients are derived. For timevarying channel, to avoid brute force matrix inversion in conventional schemes, we propose an adaptive LMS based solution to update the filtering coefficients by tracing the channel variation. Since the high complexity of MMSE_DFE, a reduced complexity scheme, ordered successive partial interference cancellation DFE (OSPIC_DFE), is developed. From the performance comparison between the MMSE_DFE and the OSPIC_DFE, we see that the latter is very near to the former. Finally the simulation shows these proposed methods are highly effective in combating ISI and ICI with low complexity.

