In spatially distributed multiuser antenna systems, the received signalcontains multiple carrier-frequency offsets (CFOs) arising from mismatchbetween the oscillators of transmitters and receivers. This results in atime-varying rotation of the data constellation, which needs to be compensatedat the receiver before symbol recovery. In this paper, a new approach for blindCFO estimation and symbol recovery is proposed. The received base-band signalis over-sampled, and its polyphase components are used to formulate a virtualMultiple-Input Multiple-Output (MIMO) problem. By applying blind MIMO systemestimation techniques, the system response can be estimated and decoupledversions of the user symbols can be recovered, each one of which contains adistinct CFO. By applying a decision feedback Phase Lock Loop (PLL), the CFOcan be mitigated and the transmitted symbols can be recovered. The estimatedMIMO system response provides information about the CFOs that can be used toinitialize the PLL, speed up its convergence, and avoid ambiguities usuallylinked with PLL.
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