Hopping pilot pattern for interference mitigation in OFDM

Abstract

In an OFDM system, known symbols referred to as pilot are transmitted across the time-frequency plane for the receiving device to estimate the channelpsilas time-frequency response in order to perform coherent demodulation of data symbols. The placement of these pilot symbols largely falls into two categories, namely, the regular and irregular patterns. Inspired by synchronization techniques used in radars, derived a time-frequency hoping pattern, called Costas Array which provides a better frequency offset estimation and accommodates substantially higher number of unique patterns that can be used for Base Stations (BSs) and/or antenna identifications. In this paper, we investigate the link and system performance of both pilot designs. From a link perspective we examine if there is a need to boost the pilot signals in order to achieve an adequate Signal to Noise Ratio (SNR). From the radio network perspective we analyze the impact of power pilot boosting. Further we explore an alternative method to reduce the interference perceived by the pilot signals, by introducing a data frequency reuse at interfering BSs. Our results show that a pilot boosting of 9 dB is required and data frequency reuse yields minor SINR improvement for the pilot signals. Furthermore the Costas Array, in addition to having lower peak power, yields substantially better SINR statistics compared to the regular pilot patterns.