Effects of Carrier Frequency Offset, Timing Offset, and Channel Spread Factor on the Performance of Hexagonal Multicarri
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Research Article Effects of Carrier Frequency Offset, Timing Offset, and Channel Spread Factor on the Performance of Hexagonal Multicarrier Modulation Systems Kui Xu and Yuehong Shen Institute of Communications Engineering, PLA University of Science and Technology, No. 2 Biaoying Road, Yudao Street, Nanjing 210007, China Correspondence should be addressed to Kui Xu, xiancheng [email protected] Received 17 May 2008; Revised 6 October 2008; Accepted 31 January 2009 Recommended by Mounir Ghogho Hexagonal multicarrier modulation (HMM) system is the technique of choice to overcome the impact of time-frequency dispersive transmission channel. This paper examines the effects of insufficient synchronization (carrier frequency offset, timing offset) on the amplitude and phase of the demodulated symbol by using a projection receiver in hexagonal multicarrier modulation systems. Furthermore, effects of CFO, TO, and channel spread factor on the performance of signal-to-interference-plus-noise ratio (SINR) in hexagonal multicarrier modulation systems are further discussed. The exact SINR expression versus insufficient synchronization and channel spread factor is derived. Theoretical analysis shows that similar degradation on symbol amplitude and phase caused by insufficient synchronization is incurred as in traditional cyclic prefix orthogonal frequency-division multiplexing (CP-OFDM) transmission. Our theoretical analysis is confirmed by numerical simulations in a doubly dispersive (DD) channel with exponential delay power profile and U-shape Doppler power spectrum, showing that HMM systems outperform traditional CP-OFDM systems with respect to SINR against ISI/ICI caused by insufficient synchronization and doubly dispersive channel. Copyright © 2009 K. Xu and Y. Shen. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction Multicarrier modulation (MCM) is a popular transmission scheme in which the data stream is split into several substreams and transmitted, in parallel, on different subcarriers. We consider MCM over time-varying multipath propagation channels which spread the MCM signal simultaneously in both the time and frequency domains. This spreading induces both intersymbol interference (ISI) and intercarrier interference (ICI) which complicate data demodulation. We will refer to channels that are time dispersive and frequency dispersive as doubly dispersive (DD) channels. Orthogonal frequency-division multiplexing (OFDM) systems with guard time interval or cyclic prefix can prevent ISI, but do not combat ICI because they are based on rectangular-type pulses. In order to overcome the aforementioned drawbacks of OFDM systems, several pulse-shaping OFDM systems were proposed [1–15]. Most works on pulse design exclusively dealt with rectangular time-frequency
(TF) lattices. It is shown that transmission in rectangular lattices is suboptimal for doubly dispersive cha
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