Blind and Semiblind Channel and Carrier Frequency-Offset Estimation in Orthogonally Space-Time Block Coded MIMO Systems (original) (raw)
2008, IEEE Transactions on Signal Processing
In this paper, the problem of joint channel and carrier frequency offset (CFO) estimation is studied in the context of multiple-input multiple-output (MIMO) communications based on orthogonal space-time-block codes (OSTBCs). A new blind approach is proposed to jointly estimate the channel matrix and the CFO parameters using a relaxed maximum likelihood (ML) estimator that, for the sake of simplicity, ignores the finite alphabet constraint. Although the proposed technique can be applied to the majority of OSTBCs, there are, however, a few codes that suffer from an intrinsic ambiguity in the joint channel, CFO, and symbol estimates. For such specific OSTBCs, a semiblind modification of the proposed approach is developed that resolves the aforementioned estimation ambiguity. Our simulation results demonstrate that although the finite alphabet constraint is relaxed, the performance of the proposed techniques approaches that of the informed (fully frequency-synchronized and coherent) receiver, provided that a sufficient number of data blocks is available for each channel realization. Index Terms-Blind channel and carrier frequency offset estimation, multiple-input multiple-output (MIMO) communications, orthogonal space-time block codes. I. INTRODUCTION S PACE-TIME coding has recently gained much interest because of its ability to combat fading by means of exploiting spatial diversity provided by multiple-input multiple-output (MIMO) communication channels [1]-[3]. Among different space-time coding techniques proposed so far, orthogonal space-time codes (OSTBCs) are of great interest as they collect full diversity at low decoding complexity. The optimal ML decoder for OSTBCs amounts to a simple linear matched filter (MF) receiver followed by a symbol-by-symbol decoder. It has recently been shown in the literature that for the majority of OSTBCs, the MIMO channel is blindly identifiable Manuscript
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