Abstract
In this paper, we propose a simple approach to reduce the sensitivity of OFDM system to the carrier frequency offset (CFO). The main idea is to choose a well-known channel code and to rotate each coordinate by a fixed phase shift such that the maximum inter-carrier interference (ICI) taken over all sub-carriers is minimized. This approach is based on a geometric interpretation of the peak interference to carrier ratio (PICR) of OFDM signals. Simulation results show that a reduction in PICR of 7 dB can be easily achieved. Furthermore, we addressed the fundamental limit of the proposed technique by providing both an exact and an approximate lower bound of PICR of phase-shifted binary codes. The bounds are applied to some codes: non-redundant binary code, BCH codes, and Reed-Muller codes. Simulation results demonstrated that phase-shift designs approach lower bounds and are resilient to CFO change.
Highlights
1.1 Motivations Orthogonal frequency-division multiplexing (OFDM) is a multicarrier modulation technique that has been implemented for many high-speed wireless and wireline applications
1.3 Our contributions The intend of this paper is to reduce the sensitivity of OFDM systems to carrier frequency offset (CFO) without reducing the transmission rate
The key departure of our research from prior works on CFO effect reduction is that (a) we provide a geometric interpretation of the peak interference to carrier ratio (PICR) of OFDM signals, (b) we propose a simple phaseshift approach to reduce the sensitivity of OFDM to fine frequency offset, (c) we analyze the fundamental limit of the proposed technique and obtain a lower bound of the PICR of phase-shifted binary codes which we evaluate for non-redundant binary code, BCH codes, and Reed-Muller codes, and (d) we numerically evaluate phase-shift designs and prove their resilience to CFO change
Summary
1.1 Motivations Orthogonal frequency-division multiplexing (OFDM) is a multicarrier modulation technique that has been implemented for many high-speed wireless and wireline applications. Self-cancellation: A simple and effective method— known as the ICI self-cancelation scheme—was proposed by Zhao and Haggman in [18] and later generalized in [15, 19], where polynomial coding in the frequency domain is used to mitigate the effect of frequency offset In this method, copies of the same data symbol are modulated on r adjacent sub-carriers using specific weights. The key departure of our research from prior works on CFO effect reduction is that (a) we provide a geometric interpretation of the peak interference to carrier ratio (PICR) of OFDM signals, (b) we propose a simple phaseshift approach to reduce the sensitivity of OFDM to fine frequency offset, (c) we analyze the fundamental limit of the proposed technique and obtain a lower bound of the PICR of phase-shifted binary codes which we evaluate for non-redundant binary code, BCH codes, and Reed-Muller codes, and (d) we numerically evaluate phase-shift designs and prove their resilience to CFO change
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