An EM Algorithm-Based Channel Estimation for OFDM Amplify-And-Forward Relaying Systems

The issue of channel estimation is investigated for the orthogonal frequency-division multiplexing (OFDM) relaying system with amplify-and-forward (AF) operation mode. Channel estimation in the AF mode is unique in that both the source-to-relay and relay-to-destination channels are needed at the destination in order to perform optimum combining of the received signals from the direct (source-to-destination) and relay paths if a cooperative diversity transmission is employed. Until now, however, there have been only literatures to study the estimation of the composite channel of the relay path. In this work, an iterative expectation-maximization (EM) algorithm-based channel estimation is proposed for respective estimations of the source-to-relay and relay-to-destination links at the destination. Computer simulations show that the iterative channel estimator performs satisfactorily and converges rapidly.

[1]  G. McLachlan,et al.  The EM algorithm and extensions , 1996 .

[2]  Gregory W. Wornell,et al.  Distributed space-time-coded protocols for exploiting cooperative diversity in wireless networks , 2003, IEEE Trans. Inf. Theory.

[3]  Gregory W. Wornell,et al.  Cooperative diversity in wireless networks: Efficient protocols and outage behavior , 2004, IEEE Transactions on Information Theory.

[4]  Gerhard Fettweis,et al.  Relay-based deployment concepts for wireless and mobile broadband radio , 2004, IEEE Communications Magazine.

[5]  Patrick Mitran,et al.  Variable-Rate Two-Phase Collaborative Communication Protocols for Wireless Networks , 2006, IEEE Transactions on Information Theory.

[6]  Ozgur Oyman,et al.  Multihop Relaying for Broadband Wireless Mesh Networks: From Theory to Practice , 2007, IEEE Communications Magazine.

[7]  Gordon L. Stüber,et al.  Channel Estimation for Amplify and Forward Relay Based Cooperation Diversity Systems , 2007, IEEE Transactions on Wireless Communications.

[8]  Feifei Gao,et al.  On channel estimation and optimal training design for amplify and forward relay networks , 2008, IEEE Transactions on Wireless Communications.

[9]  A.A. Rontogiannis,et al.  Channel estimation techniques in amplify and forward relay networks , 2008, 2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications.

[10]  Fang Liu,et al.  Channel Estimation for Amplify and Forward Relay in OFDM System , 2008, 2008 4th International Conference on Wireless Communications, Networking and Mobile Computing.

[11]  Ahmed M. Eltawil,et al.  On Channel Estimation and Capacity for Amplify and Forward Relay Networks , 2008, IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference.

[12]  Haitao Liu,et al.  A Low-Complexity LMMSE Channel Estimation Method for OFDM-Based Cooperative Diversity Systems with Multiple Amplify-and-Forward Relays , 2008, EURASIP J. Wirel. Commun. Netw..