Joint estimation of the channel and I/Q imbalance for two-way relay networks

In this work, we consider amplify-and-forward two-way relay networks operating under the imperfect conditions of in-phase and quadrature-phase (I/Q) imbalance. We propose novel, efficient solutions for the problem of joint channel and I/Q imbalance estimation and the related problem of optimal pilot...

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Bibliographic Details
Published inTelecommunication systems Vol. 78; no. 3; pp. 449 - 462
Main Authors Abdallah, Saeed, Salameh, Ahmed I., Saad, Mohamed, El-Moursy, Ali A.
Format Journal Article
LanguageEnglish
Published New York Springer US 01.11.2021
Springer Nature B.V
Subjects
Algorithms
Artificial Intelligence
Business and Management
Computer Communication Networks
IT in Business
Maximum likelihood estimators
Optimization
Probability Theory and Stochastic Processes
Quadratures
Relay networks
Telecommunications systems
Expectation maximization
Two-way relay network
Cramer–Rao bound
Maximum likelihood
I/Q imbalance
Channel estimation
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Summary:In this work, we consider amplify-and-forward two-way relay networks operating under the imperfect conditions of in-phase and quadrature-phase (I/Q) imbalance. We propose novel, efficient solutions for the problem of joint channel and I/Q imbalance estimation and the related problem of optimal pilot design. Three different estimation algorithms are developed. The first is the pilot-based maximum-likelihood (ML) estimator. The second is a semi-blind estimator that employs the expectation–maximization (EM) strategy. The third is the semi-blind decision-directed (DD) estimator. As benchmarks on estimation performance, we obtain the analytical expressions for the Cramer–Rao bound (CRB) for pilot-based estimation, and the modified-CRB for semi-blind estimation. In addition to the estimation algorithms, we propose an optimal pilot design that minimizes the mean-squared estimation error. Using simulations, we show that both the pilot-based ML and the semi-blind EM converge to their respective exact CRBs. Importantly, it is shown that both the EM and the DD estimators offer substantially higher estimation accuracy than pilot-based estimation, as well as improved symbol-error-rate (by up to 1.8 dB), which is achieved at a low computational cost.
ISSN:1018-4864
1572-9451
DOI:10.1007/s11235-021-00825-7