The ECMA-368 standard specifies multiband orthogonal frequency division multiplexing (MB-OFDM) as the definitive technology for high rate ultra-wideband (UWB) communications. Like other wireless systems, the performance of a correct data signals detection and decoding in MB-OFDM UWB is reduced by narrowband interference (NBI). A more specific problem of severity arises when interferences are present during the channel estimation process, since this eventually results to severe degradation in the performance of signal reconstruction in the whole packet layer convergence protocol (PLCP) and service data unit (PSDU). In this article, we propose an improved channel estimation technique for OFDM-based UWB systems in presence of NBI. Several steps have been carried out to achieve this purpose. First, the location of center frequency of NBI is found out through zero padded suffix (ZPS) aided subspace-based method. Secondly, we propose an adaptive band select and replace (ABSR) scheme to eliminate NBI based on frequency-domain redundancy (FR) property we introduce into preamble symbols during transmission. Thirdly, we perform least-square (LS) channel estimation on NBI-free received preamble symbols to get the estimated channel at each subcarrier. Fourthly, low rank least square minimum mean squared error (LMMSE) channel estimation is performed using this LS channel estimation. Lastly, Blackman windowing is applied on low rank LMMSE channel to reduce the spectral leakage and thus to increase the channel estimation accuracy. Link level simulation (LLS) urges that our proposed technique has improved performances.
Key words: Ultra-wideband (UWB), channel estimation, multiband orthogonal frequency division multiplexing (MB-OFDM), narrowband interference (NBI), ECMA-368, wireless personal area network (WPAN).
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