10,085 research outputs found
Joint Source and Relay Precoding Designs for MIMO Two-Way Relaying Based on MSE Criterion
Properly designed precoders can significantly improve the spectral efficiency
of multiple-input multiple-output (MIMO) relay systems. In this paper, we
investigate joint source and relay precoding design based on the
mean-square-error (MSE) criterion in MIMO two-way relay systems, where two
multi-antenna source nodes exchange information via a multi-antenna
amplify-and-forward relay node. This problem is non-convex and its optimal
solution remains unsolved. Aiming to find an efficient way to solve the
problem, we first decouple the primal problem into three tractable
sub-problems, and then propose an iterative precoding design algorithm based on
alternating optimization. The solution to each sub-problem is optimal and
unique, thus the convergence of the iterative algorithm is guaranteed.
Secondly, we propose a structured precoding design to lower the computational
complexity. The proposed precoding structure is able to parallelize the
channels in the multiple access (MAC) phase and broadcast (BC) phase. It thus
reduces the precoding design to a simple power allocation problem. Lastly, for
the special case where only a single data stream is transmitted from each
source node, we present a source-antenna-selection (SAS) based precoding design
algorithm. This algorithm selects only one antenna for transmission from each
source and thus requires lower signalling overhead. Comprehensive simulation is
conducted to evaluate the effectiveness of all the proposed precoding designs.Comment: 32 pages, 10 figure
Interference driven antenna selection for Massive Multi-User MIMO
Low-complexity linear precoders are known to be close-to-optimal for massive multi-input multi-output (M-MIMO) systems. However, the large number of antennas at the transmitter imposes high computational burdens and high hardware overloads. In line with the above, in this paper we propose a low complexity antenna selection (AS) scheme which selects the antennas that maximize constructive interference between the users. Our analyses show that the proposed AS algorithm, in combination with a simple matched filter (MF) precoder at the transmitter, is able to achieve better performances than systems equipped with a more complex channel inversion (CI) precoder and computationally expensive AS techniques. First, we give an analytical definition of constructive and destructive interference, based on the phase of the received signals from phase-shifted-keying (PSK) modulated transmissions. Then, we introduce the proposed antenna selection algorithm, which identifies the antenna subset with the highest constructive interference, maximizing the power received by the user. In our studies, we derive the computational burden of the proposed technique with a rigorous and thorough analysis and we identify a closed form expression of the upper bound received power at the user side. In addition, we evaluate in detail the power benefits of the proposed transmission scheme by defining an efficiency metric based on the achieved throughput. The results presented in this paper prove that antenna selection and green radio concepts can be jointly used for power efficient M-MIMO, as they lead to significant power savings and complexity reductions
Sum-rate Maximizing in Downlink Massive MIMO Systems with Circuit Power Consumption
The downlink of a single cell base station (BS) equipped with large-scale
multiple-input multiple-output (MIMO) system is investigated in this paper. As
the number of antennas at the base station becomes large, the power consumed at
the RF chains cannot be anymore neglected. So, a circuit power consumption
model is introduced in this work. It involves that the maximal sum-rate is not
obtained when activating all the available RF chains. Hence, the aim of this
work is to find the optimal number of activated RF chains that maximizes the
sum-rate. Computing the optimal number of activated RF chains must be
accompanied by an adequate antenna selection strategy. First, we derive
analytically the optimal number of RF chains to be activated so that the
average sum-rate is maximized under received equal power. Then, we propose an
efficient greedy algorithm to select the sub-optimal set of RF chains to be
activated with regards to the system sum-rate. It allows finding the balance
between the power consumed at the RF chains and the transmitted power. The
performance of the proposed algorithm is compared with the optimal performance
given by brute force search (BFS) antenna selection. Simulations allow to
compare the performance given by greedy, optimal and random antenna selection
algorithms.Comment: IEEE International Conference on Wireless and Mobile Computing,
Networking and Communications (WiMob 2015
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