Abstract
We consider signal transmission with the aid of multiple half-duplex single-antenna relay nodes using the amplify-and-forward (AF) strategy for a multiuser wireless machine-to-machine (M2M) communication system. In such a scenario, relay beamforming has been proved to be an effective way to improve system performance by employing spatial diversity gains. Early works have mostly focused on various centralized relay beamforming schemes based on global channel state information (CSI). Since global CSI is often unavailable due to geometric locations, power limitation, or other constraints of the relay nodes in M2M networks, our work aims to develop distributed algorithms that each relay node individually learns its own beamforming weights with local CSI. We propose two suboptimal relay beamforming schemes that only require local CSI to minimize mean square error (MSE) for all the users with nonorthogonal channels. For multiuser systems with orthogonal channels, we divide the optimization problem into multiple single user problems which then can be solved by each relay independently. Numerical simulations for the proposed algorithms are presented showing the performance of the proposed schemes is close to that of the optimal scheme with global CSI in terms of bit error rate (BER) criterion.
Highlights
With the ability to provide reliable transmission and improve the coverage and capacity of wireless networks, cooperative communication using relay beamforming has attracted considerable attention [1]
In [9], optimal relay beamforming weights for a nonorthogonal multiuser system are found to meet a given set of target signal-to-interference-plus-noise ratio (SINR) at the destinations while minimizing transmission power at the relays. These relay schemes aiming to maximum SNR (MSNR) or target SINR assume that all the relay nodes can communicate with each other and each relay has global channel state information (CSI), that is, channel coefficients of all the relay nodes
We study the bit error rate (BER) performance under different circumstances
Summary
With the ability to provide reliable transmission and improve the coverage and capacity of wireless networks, cooperative communication using relay beamforming has attracted considerable attention [1]. In [9], optimal relay beamforming weights for a nonorthogonal multiuser system are found to meet a given set of target SINR at the destinations while minimizing transmission power at the relays These relay schemes aiming to MSNR or target SINR assume that all the relay nodes can communicate with each other and each relay has global channel state information (CSI), that is, channel coefficients of all the relay nodes. We aim at developing efficient distributed relay beamforming algorithms with local CSI that minimize the sum MSE of all users for a multiuser wireless M2M network using the AF strategy. The notation x ∼ CN (m, σ2) means that x is a complex Gaussian random variable with mean m and variance σ2
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