Linear Precoders for Nonregenerative Asymmetric Two-Way Relaying in Cellular Systems

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 se...

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Bibliographic Details
Published in:IEEE transactions on wireless communications 2014-09, Vol.13 (9), p.5002-5014
Main Authors: Budhiraja, Rohit, Karthik, K. S., Ramamurthi, Bhaskar
Format: Article
Language:English
Subjects:
Allocations
Antennas
Asymmetry
Cellular
Channels
Interference
Maximization
MIMO
Receivers
Relay
Relaying
Relays
Spectra
Wireless communication
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Summary: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.
ISSN:1536-1276
1558-2248
DOI:10.1109/TWC.2014.2327962