A novel multiple-input multiple-output (MIMO) channel-diagonalization design is proposed for non-simultaneous two-way relaying (NS-TWR). Unlike conventional TWR, the base station in NS-TWR serves two different users - a transmit-only user and a receive-only user. The receive-only user experiences back-propagating interference (BI). The proposed design, which uses linear receivers, cancels the BI and diagonalizes the end-to-end MIMO channels. The diagonalized NS-TWR overcomes the restrictive antenna configurations of existing designs and yields substantial sum-rate improvement over them. © 2014 IEEE.

Bhaskar Ramamurthi

Department of Electrical Engineering

Cellular arrays

Cellular telephone systems

Communication channels (information theory)

MIMO systems

Mobile security

Mobile telecommunication systems

Wireless telecommunication systems

Antenna configurations

Cellular system

DIAGONALIZATIONS

DIAGONALIZED CHANNEL

LINEAR RECEIVER

MULTIPLE-INPUT MULTIPLE-OUTPUT CHANNELS

NON-SIMULTANEOUS

TWO-WAY RELAYING

signal processing

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IIT Madras

Diagonalized two-way MIMO AF relaying for non-simultaneous traffic in cellular systems

IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC

In conventional two-way relaying (TWR), it is assumed that a user has data to send and receive simultaneously from the base station (BS) via a relay. In cellular systems, data flow between the BS and a user is usually not simultaneous, e.g., a transmit-only user (say, TUE) may have uplink data to send in the multiple access (MAC) phase, but may not have downlink data to receive in the broadcast (BC) phase. Such one-way data flow will reduce TWR to spectrally inefficient one-way relaying. The multiple-input-multiple-output (MIMO) asymmetric TWR (ATWR) protocol considered here restores the two-way data flow via a relay. In ATWR, the BC phase following the MAC phase of a TUE is used to send downlink data to a receive-only user (say, RUE). However, the RUE will not be able to cancel the back-propagating interference. We design a structured precoder at the relay to cancel this interference. The proposed precoder also triangularizes the end-to-end MIMO channels. The channel triangularization reduces the weighted sum-rate maximization and relay power minimization problems to power allocation problems, which are then cast as geometric programs. Simulation results illustrate the effectiveness of the proposed precoder when compared with conventional solutions. © 2014 IEEE.

Fulltext

IEEE Transactions on Wireless Communications

Linear precoders for nonregenerative asymmetric two-way relaying in cellular systems

Two-way relaying reduces the loss in spectral efficiency caused in a conventional half-duplex relay due to two channel uses per data unit transmitted to the destination. Two-way relaying is possible when two nodes exchange data simultaneously through a relay. In the case of cellular systems, data exchange between base station (BS) and users (UE) is usually not symmetric, e.g., a user (UE1) might have uplink data to transmit during multiple access (MAC) phase, but might not have downlink data to receive during broadcast (BC) phase. This asymmetry in data exchange will reduce the gains of two-way relaying. In the case of infrastructure relays, where there are multiple users communicating through a relay, we propose that the BC phase following the MAC phase of UE 1 be used by the relay to transmit downlink data to a second user (UE2). Conventional two-way relaying with symmetric MAC and BC phases must now be modified to asymmetric MAC (BS → RS ← UE1) and BC phases (BS ← RS → UE2), respectively. This will result in UE2 not being able to cancel the back-propagating interference in the usual way. We design precoders using conventional zero-forcing and linear minimum-mean-square-error criteria to mitigate the back-propagating interference at UE2 for an amplify-and-forward (AF) relay. We also propose a novel precoder appropriate for the asymmetric two-way relaying. The sum-rate performance of the proposed precoder is shown to be better than the conventional precoders. © 2013 IEEE.

IEEE International Conference on Communications

Precoder design for asymmetric multi-user two-way AF relaying in cellular systems

IEEE Transactions on Signal Processing

Sum-Rate Maximization With Minimum Power Consumption for MIMO DF Two-Way Relaying— Part I: Relay Optimization

IEEE Communications Letters

Cell-Edge Multi-User Relaying with Overhearing

IEEE Transactions on Communications

A New Physical-Layer Network Coding Scheme with Eigen-Direction Alignment Precoding for MIMO Two-Way Relaying

Journal	Data powered by TypesetIEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC
Publisher	Data powered by TypesetInstitute of Electrical and Electronics Engineers Inc.
Open Access	No