Channel parameter acquisition in MIMO LOS systems for high capacity microwave links

Abstract

Due to the increased traffic load, next generation wireless communication standards require to increase the capacity of current point-to-point (PtP) wireless backhaul links in the microwave frequency bands. Multiple-input, multiple-output (MIMO) systems are essential to multiply the link capacity, and such solutions have been already presented in the recent literature as a promising technology to increase the data rate, for line-of-sight (LOS) wireless PtP connections. In this paper, we focus on the initial acquisition scheme of a MIMO 2x2 architecture for microwave M-ary quadrature amplitude modulation (M-QAM) transceivers, based on two completely independent radio frequency (RF) chains which use different local oscillators (LOs). During the acquisition phase, a 4-QAM training preamble is considered with a joint algorithm for estimating both the MIMO gains for the interference cancellation and the timing error for initializing the clock recovery loop. A phase recovery closed loop scheme is jointly used during the acquisition phase, and the same algorithm may be used for phase error correction when the receiver switches to the tracking mode. Simulations prove the effectiveness of the proposed solutions, by considering both qualitative and quantitative results.