Blind Identification of Distributed Antenna Systems with Multiple Carrier Frequency Offsets

TL;DR

This paper introduces a blind method for estimating multiple carrier frequency offsets in distributed multiuser antenna systems by formulating a virtual MIMO problem and applying blind estimation techniques, enabling effective CFO mitigation and symbol recovery.

Contribution

It presents a novel blind CFO estimation approach using polyphase components and MIMO system estimation, improving accuracy and convergence speed in distributed antenna systems.

Findings

Effective blind CFO estimation in distributed systems

Enhanced symbol recovery accuracy

Faster convergence of phase lock loop

Abstract

In spatially distributed multiuser antenna systems, the received signal contains multiple carrier-frequency offsets (CFOs) arising from mismatch between the oscillators of transmitters and receivers. This results in a time-varying rotation of the data constellation, which needs to be compensated at the receiver before symbol recovery. In this paper, a new approach for blind CFO estimation and symbol recovery is proposed. The received base-band signal is over-sampled, and its polyphase components are used to formulate a virtual Multiple-Input Multiple-Output (MIMO) problem. By applying blind MIMO system estimation techniques, the system response can be estimated and decoupled versions of the user symbols can be recovered, each one of which contains a distinct CFO. By applying a decision feedback Phase Lock Loop (PLL), the CFO can be mitigated and the transmitted symbols can be recovered. The estimated MIMO system response provides information about the CFOs that can be used to initialize the PLL, speed up its convergence, and avoid ambiguities usually linked with PLL.