Robust Channel Estimation Methods for Spectrally Efficient FDM Systems

Abstract

This paper proposes and explores a novel channel estimation scheme for non-orthogonal multi-carrier signals and systems; spectrally efficient frequency division multiplexing (SEFDM), in which higher spectral efficiency is achieved by violating the orthogonality of its subcarriers. The proposed scheme is distinguished by its simplicity, low computational complexity, high accuracy and performance independent of the number of subcarriers and compression factor. The presented results demonstrate the efficacy of the proposed scheme by comparing its complexity and performance to other estimation schemes.

Experimental Demonstration of Spectrally Efficient Frequency Division Multiplexing Transmissions at E-Band

“…The demodulated symbolẑ n , at the n th subcarrier, affected by the channel and contaminated by interference resulting from ICI can be expressed as [31] 1 is the multipath CFR acting on the m th subcarrier of the SEFDM symbol, and (m, n) is the cross correlation between the subcarriers m and n given by [40] (m, n) = exp( j πα(m − n))sinc(α(m − n)) (4) where sinc(x) = sin(π x)/π x. The second summation term of (3) on the right-hand side represents the AWGN effect on the n th subcarrier.…”

“…Direct channel estimation using an SEFDM pilot is impractical due to the ill-conditioned matrix in (5). Recently, a new robust CFR estimation scheme for SEFDM signals was proposed in [31], where the pilot signals are sent over orthogonally spaced subcarriers as an OFDM symbol (i.e., in (5) is an identity matrix). The pilot symbol uses the same number of subcarriers and the same frequency spacing of SEFDM signals used to transmit data.…”

“…The nonorthogonality nature of SEFDM signals further complicates the channel estimation problem. Estimation of the system phase offset and channel response has been addressed using various methods, either in the time domain [29], [30] or in the frequency domain [31]. Recently, a new robust channel frequency response (CFR) estimation scheme for SEFDM signals was proposed in [31], and it will be experimentally demonstrated in this paper for the first time.…”

“…Estimation of the system phase offset and channel response has been addressed using various methods, either in the time domain [29], [30] or in the frequency domain [31]. Recently, a new robust channel frequency response (CFR) estimation scheme for SEFDM signals was proposed in [31], and it will be experimentally demonstrated in this paper for the first time. In this estimation scheme, the pilot symbol uses the same number of subcarriers and the same frequency spacing of SEFDM signals used to transmit data, while maintaining the orthogonality.…”

“…This paper, and for the first time, presents an experimental demonstration of SEFDM signal wireless transmission at a rate of 12 Gb/s over the E-band (81-86 GHz) frequency range. The powerful low-density parity-check (LDPC) FEC codes invented by Gallager [38] and adopted in future cellular 5G standards [39], and the CFR estimation scheme of [31] is used in this experimental demonstration. The experiment results show that the use of SEFDM signals enhances the system spectral efficiency by up to 50% compared to OFDM.…”