Novel Pilot Position Selection and Signal Reconstruction Methods for Frequency-Domain Pilot Multiplexing Techniques of SC-FDE

The frequency-domain pilot multiplexing technique (FDPMT) has recently emerged as an appealing technique for channel estimation in single-carrier frequency-domain equalization (SC-FDE) systems due to the high spectral efficiency it promises. However, the performance of the FDPMT system is significantly affected by the signal distortion level, which depends on the pilot position selection (PPS) strategy at the transmitter and the signal reconstruction (SR) ability of the receiver. In this paper, the relationship between the interference pattern and the loss of equally spaced tones is discovered. By exploiting this relationship, we propose a novel PPS method and a novel SR method. The proposed PPS method, which is based on the minimization of the most severe intersymbol interference (ISI) experienced by those subblocks decimated from the transmitted signal block, dispenses with a priori knowledge of the channel statistics and imposes very low computational cost to the transmitter. The proposed SR method, which is based on the maximum-likelihood criterion, can be carried out subblock by subblock in parallel and sample by sample within each subblock, saving the computational complexity and time consumption of the receiver. Simulation results in terms of bit error rate (BER) corroborate the superiority of both proposed methods over their existing counterparts in various channels of interest.

I. Introduction

Single-CARRIER frequency-domain equalization (SC-FDE), which has been widely accepted as an alternative to orthogonal frequency-division multiplexing (OFDM), e.g., in IEEE 802.11ad and 802.15.3c, is favorable for uplink communications as it promises a much lower peak-to-average power ratio than OFDM [1]– [3]. In SC-FDE, pilots for channel estimation can be multiplexed in either the time domain or the frequency domain. Traditionally, pilots are time multiplexed within or in between data blocks, which, however, requires an extra time slot [3], [4]. Multiplexing pilot in the frequency domain circumvents this problem [2], [3], [5]– [8]. So far, three frequency-domain multiplexed pilot insertion techniques, namely, the frequency expanding technique (FET), the frequency-domain superimposed pilot technique (FDSPT), and the frequency-domain pilot multiplexing technique (FDPMT), are available in the literature [8]– [10]. Compared with the other two techniques, the FDPMT has attracted much more attention since it prevents losing the spectral efficiency, which happens in the FET, and degrading the bit error rate (BER) performance, which happens in the FDSPT [8].