Abstract
In this paper, we consider optimization of a two-way multiple-input multiple-output (MIMO) amplify-and-forward relay network which consists of a pair of transceivers and several relay nodes. Multiple antennas are equipped on the transceivers and relays. Multiple access broadcast scheme which finishes communication in two time slots is considered. In the first time slot, signals received by the relays are scaled by several beamforming matrices. In the second time slot, the relays transmit the scaled signals to the two transceivers. Upon receiving these signals, a MIMO equalizer is implemented at each transceiver to recover the desired signal. In this paper, zero forcing equalizers are used. Joint optimization of the beamforming matrices and the equalizers are realized using the following criteria: 1) the total relay transmission power is minimized subject to the minimal output signal-to-noise ratio (SNR) constraint at each transceiver, 2) the minimal output SNR of the two transceivers is maximized subject to total relay transmission power constraint, and 3) the minimal output SNR of the two transceivers is maximized subject to individual relay transmission power constraint. It is shown that the proposed optimization problems can be formulated as the second-order cone programming problems which can be solved efficiently. The validity of the proposed algorithm is verified by computer simulations.
Highlights
Relaying technique is capable of extending communication range and coverage by providing link to shadowed users via relay nodes, and it received extensive study in recent years
The network with a single pair of users and multiple relay nodes equipped with single antenna has been widely investigated [1-7]
In [2], similar optimization criterion was used in the case that only the second-order statistics of channel-state information (CSI) are available
Summary
Relaying technique is capable of extending communication range and coverage by providing link to shadowed users via relay nodes, and it received extensive study in recent years. The network with a single pair of users and multiple relay nodes equipped with single antenna has been widely investigated [1-7]. Zheng [1] assumed perfect knowledge of channel-state information (CSI) and proposed to optimize the beamforming vector by maximizing the destination signal-to-noise ratio (SNR) subject to total and local relay transmission power constraints. Quantizer at each relay and beamforming vectors at destination were optimized to minimize the uncoded bit error rate. In [5], Multiple relay nodes create a virtual multiple-input multiple-output (MIMO) environment at the relay layer
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