Showing papers by "Andre Bourdoux published in 2003"

Non-reciprocal transceivers in OFDM/SDMA systems: impact and mitigation

Abstract: Channel reciprocity is needed in SDMA or MIMO downlink pre-filtering when the channel knowledge is acquired in the uplink. We first show analytically that the non-reciprocity of the base station analog hardware, which is part of the channel, introduces a very high level of multi-user interference and quantify the effect of the non-reciprocity by means of simulations. We then propose a novel calibration technique at the base station that enables to compensate for the non-reciprocity and reduce the MUI to a negligible value while having a low implementation cost.

A performance and complexity comparison of auto-correlation and cross-correlation for OFDM burst synchronization

Abstract: A symbol timing synchronization scheme is critical in the design of an OFDM receiver. Large timing errors can result in a loss of orthogonality between subcarriers, ISI and severe bit error degradation. To minimize this degradation, standards incorporate preambles suitable for two kinds of synchronization algorithms: auto-correlation and crosscorrelation. Unfortunately, the performance and complexity tradeoffs between these algorithms have not been well explored. To address this problem, we have built an FPGA implementation of a synchronization system using both autocorrelation and cross-correlation. Based on our results, in this paper we propose a novel cross-correlation synchronizer and hardware architecture. We then compare its performance and complexity to auto-correlation algorithms for HiperLAN/2 and IEEE 802.11a preambles.