103 research outputs found
A worst-case robust MMSE transceiver design for nonregenerative MIMO relaying
Transceiver designs have been a key issue in guaranteeing the performance of multiple-input multiple-output (MIMO) relay systems, which are, however, often subject to imperfect channel state information (CSI). In this paper, we aim to design a robust MIMO transceiver for nonregenerative MIMO relay systems against imperfect CSI from a worst-case robust perspective. Specifically, we formulate the robust transceiver design, under the minimum mean-squared error (MMSE) criterion, as a minimax problem. Then, by decomposing the minimax problem into two subproblems with respect to the relay precoder and destination equalizer, respectively, we show that the optimal solution to each subproblem has a favorable channel-diagonalizing structure under some mild conditions. Based on this finding, we transform the two complex-matrix subproblems into their equivalent scalar forms, both of which are proven to be convex and can be efficiently solved by our proposed methods. We further propose an alternating algorithm to jointly optimize the precoder and equalizer that only requires scalar operations. Finally, the effectiveness of the proposed robust design is verified by simulation results
Improving Bandwidth Efficiency in E-band Communication Systems
The allocation of a large amount of bandwidth by regulating bodies in the
70/80 GHz band, i.e., the E-band, has opened up new potentials and challenges
for providing affordable and reliable Gigabit per second wireless
point-to-point links. This article first reviews the available bandwidth and
licensing regulations in the E-band. Subsequently, different propagation
models, e.g., the ITU-R and Cane models, are compared against measurement
results and it is concluded that to meet specific availability requirements,
E-band wireless systems may need to be designed with larger fade margins
compared to microwave systems. A similar comparison is carried out between
measurements and models for oscillator phase noise. It is confirmed that phase
noise characteristics, that are neglected by the models used for narrowband
systems, need to be taken into account for the wideband systems deployed in the
E-band. Next, a new multi-input multi-output (MIMO) transceiver design, termed
continuous aperture phased (CAP)-MIMO, is presented. Simulations show that
CAP-MIMO enables E-band systems to achieve fiber-optic like throughputs.
Finally, it is argued that full-duplex relaying can be used to greatly enhance
the coverage of E-band systems without sacrificing throughput, thus,
facilitating their application in establishing the backhaul of heterogeneous
networks.Comment: 16 pages, 6 Figures, Journal paper. IEEE Communication Magazine 201
Robust Iterative Transceiver Beamforming For Multipair Two-Way Distributed Relay Networks
OAPA In this paper, the transceiver beamforming problem is studied for multipair two-way distributed relay networks, particularly with multi-antenna user nodes and in the presence of channel state errors. With multi-antenna setting on the user nodes, some of the usual signal processing tasks are shifted from the relay nodes to the user nodes with the proposed transceiver beamforming designs. The transmit beamforming vectors, distributed relay coefficients and the receive beamforming vectors are obtained by iteratively solving three sub-problems, each having a closed-form solution. The tasks of maximizing desired signal power, and reducing inter-pair interference (IPI) and noise are thus allocated to different iteration steps. By this arrangement, the transmit and receive beamformers of each user are responsible for improving its own performance and the distributed relay nodes with simple amplify-and-forward protocol aim at creating a comfortable communication environment for all user pairs. With respect to the channel uncertainty, two relay strategies are proposed considering two different requirements from the communication network: sum relay output power and individual relay output power. Our simulation demonstrates that the performance improvement can be very significant through cooperation of the three components, especially when the number of relay nodes is large
Joint source and relay optimization for interference MIMO relay networks
This paper considers multiple-input multiple-output (MIMO) relay communication in multi-cellular (interference)
systems in which MIMO source-destination pairs communicate simultaneously. It is assumed that due to severe
attenuation and/or shadowing effects, communication links can be established only with the aid of a relay node. The
aim is to minimize the maximal mean-square-error (MSE) among all the receiving nodes under constrained source
and relay transmit powers. Both one- and two-way amplify-and-forward (AF) relaying mechanisms are considered.
Since the exactly optimal solution for this practically appealing problem is intractable, we first propose optimizing the
source, relay, and receiver matrices in an alternating fashion. Then we contrive a simplified semidefinite programming
(SDP) solution based on the error covariance matrix decomposition technique, avoiding the high complexity of the
iterative process. Numerical results reveal the effectiveness of the proposed schemes
A Fast Eigen Solution for Homogeneous Quadratic Minimization with at most Three Constraints
We propose an eigenvalue based technique to solve the Homogeneous Quadratic
Constrained Quadratic Programming problem (HQCQP) with at most 3 constraints
which arise in many signal processing problems. Semi-Definite Relaxation (SDR)
is the only known approach and is computationally intensive. We study the
performance of the proposed fast eigen approach through simulations in the
context of MIMO relays and show that the solution converges to the solution
obtained using the SDR approach with significant reduction in complexity.Comment: 15 pages, The same content without appendices is accepted and is to
be published in IEEE Signal Processing Letter
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