The algebraic eigenvalue problem
The algebraic eigenvalue problem
Convex Optimization
Fundamentals of wireless communication
Fundamentals of wireless communication
Network beamforming using relays with perfect channel information
IEEE Transactions on Information Theory
Bit and Power Loading for OFDM-Based Three-Node Relaying Communications
IEEE Transactions on Signal Processing - Part II
Linear Transceiver Design in Nonregenerative Relays With Channel State Information
IEEE Transactions on Signal Processing
MIMO-OFDM wireless systems: basics, perspectives, and challenges
IEEE Wireless Communications
Power Allocation Schemes for Amplify-and-Forward MIMO-OFDM Relay Links
IEEE Transactions on Wireless Communications
Fading relay channels: performance limits and space-time signal design
IEEE Journal on Selected Areas in Communications
Joint optimization of relay strategies and resource allocations in cooperative cellular networks
IEEE Journal on Selected Areas in Communications
An overview of limited feedback in wireless communication systems
IEEE Journal on Selected Areas in Communications
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In this paper, we propose frequency-domain (FD) and time-domain (TD) beamforming (BF) schemes for co-operative orthogonal frequency division multiplexing (OFDM) networks with multiple amplify-and-forward relays. Whereas for FD-BF the BF weights are applied in the FD, for TD-BF cyclic BF filters (C-BFFs) are used on the TD signal avoiding discrete-time Fourier transform operations at the relays and drastically reducing the required amount of feedback from the receiver to the relays. Adopting the average mutual information (AMI) per sub-carrier as optimality criterion, we show that the direction of the optimal FD-BF weights can be obtained in closed-form and that the optimal sub-carrier power allocation (PA) problem is convex. For solution of the PA problem an interior point method and a bisectional search dual method are provide. Furthermore, for solution of the C-BFF optimization problem an efficient gradient algorithm is proposed. Simulation results for IEEE 802.11n channels show that TD-BF with short C-BFFs closely approaches the performance of FD-BF and outperforms direct transmission without relaying.