Experimental results for low overhead frequency offset estimation in MANETs with concurrent transmission

Abstract

Mobile ad-hoc networks (MANET) are of particular importance in military communications. With the trend towards higher throughput requirements and spectrum congestion, researchers have looked at using multi-antenna techniques to enable concurrent transmissions within a one-hop MANET. However, the acquisition overhead has been shown to be a problem when dealing with concurrent transmission in MANET systems. Recently a novel time/resource efficient algorithm for frequency acquisition in concurrent MANETs has been proposed which uses simultaneous transmissions of Zadoff-Chu (ZC) sequence pairs. In this paper, we have prototyped this algorithm in hardware and have focused on validating its theoretically based claims and finding its performance limitations. We have been able to identify a series of hardware non idealities that affect the performance of the algorithm in practical schemes. We have performed indoor and outdoor experiments for Carrier Frequency Offset (CFO) estimation and shown that the algorithm is able to achieve reliable CFO estimation using off the shelf hardware, all while attaining better (smaller) acquisition overhead. Our results show that by choosing a proper length for the ZC sequences, we are able to estimate the CFO within ten Hertz of its real value. We have also identified scenarios under which the algorithm would be suboptimal.