On pilot-symbol aided channel estimation in FBMC-OQAM

Filter bank multicarrier modulation is considered as a possible candidate for 5G. In this paper, we consider pilot-symbol aided channel estimation and address the problem of canceling the imaginary interference at the pilot positions. We develop a matrix formulation for the transmission system which allows us to formulate general conditions on the auxiliary pilot symbols, capturing also the interde-pendency of closely spaced pilots and an arbitrary number of auxiliary pilot symbols. By using two auxiliary symbols per pilot instead of one, we are able to improve the peak-to-average power ratio as well as the achievable capacity for small to medium signal-to-noise ratios. The achievable capacity can further be increased by interference cancellation based on linear precoding for which we propose an algorithm to find the coding matrix required. Finally, we compare auxiliary pilot symbols and linear precoding in terms of complexity and performance.

1. Introduction

Multicarrier modulation [1] offers many advantages such as simple equalization and adaptive modulation and coding techniques, with Orthogonal Frequency Division Multiplexing (OFDM) being the most prominent scheme, currently employed in many wireless communication standards such as LTE and IEEE 802.11. However, OFDM is based on rectangular pulses which perform poorly in the frequency domain, causing some disadvantages [2]. Recently, Filter Bank MultiCarrier (FBMC) has been identified by many authors [3], [4], [5], [6] as a possible candidate to replace OFDM in the next generation of wireless communications systems (5G). The basic idea of FBMC dates back to the 1960s [7], [8] and was reformulated, for example, in [9], [10], [11]. Note that throughout literature, different names, such as cosine-modulated multitone, staggered multitone, discrete wavelet multitone and OFDM/Offset Quadrature Amplitude Modulation (OQAM), have been used to describe, essentially, the same concept that we will refer to here as FBMC.