Two-ray Multipath Model Research Articles

A Mitigation of Multipath Ranging Error Using Non-linear Chirp Signal

While the chirp signal is extensively used in radar and sonar systems for target decision in wireless communication systems, it has not been widely used for positioning in indoor environments. Recently, the IEEE 802.15.4a standard has adopted the chirp spread spectrum (CSS) as an underlying technique for low-power and low-complexity precise localization. Chirp signal based ranging solutions have been established and deployed but their ranging performance has not been analyzed in multipath environments. This paper presents a ranging performance analysis of a chirp signal and suggests a method to suppress multipath error by using a type of non-linear chirp signal. Multipath ranging performance is evaluated using a conventional linear chirp signal and the proposed non-linear chirp signal. We verify the feasibility of both methods using two-ray multipath model simulation. Our results demonstrate that the proposed non-linear chirp signal can successfully suppress the multipath error.

Performance of optimum and suboptimum OFDM-CPM receivers over multipath fading channels

Summary A class of orthogonal frequency division multiplexing-continuous phase modulation (OFDM-CPM) signals is introduced in which binary data sequence is mapped to complex symbols using the concept of correlated phase states of a CPM signal. Canonical optimum and suboptimum multiple-symbol-observation OFDM-CPM receivers are derived. Multipath channel with AWGN is assumed. The receivers are analyzed for bit error rate (BER) performance in terms of high- and low-SNR bounds. These bounds are illustrated as a function of parameter h, time delay and attenuation level. It is shown that OFDM-CPM systems, with h ¼ 0:5; 0:25 and an observation interval length of two symbols, can outperform conventional OFDM-PSK system for a two-ray multipath model. Copyright # 2005 John Wiley & Sons, Ltd.