Transmit Power Minimization for MIMO Systems of Exponential Average BER with Fixed Outage Probability

This document is the Accepted Manuscript version of the following article: Dian-Wu Yue, and Yichuang Sun, ‘Transmit Power Minimization for MIMO Systems of Exponential Average BER with Fixed Outage Probability’, Wireless Personal Communications, Vol. 90 (4): 1951-1970, first available online on 20 June 2016. Under embargo. Embargo end date: 20 June 2017. The final publication is available at Springer via https://link.springer.com/article/10.1007%2Fs11277-016-3432-4This paper is concerned with a wireless multiple-antenna system operating in multiple-input multiple-output (MIMO) fading channels with channel state information being known at both transmitter and receiver. By spatiotemporal subchannel selection and power control, it aims to minimize the average transmit power (ATP) of the MIMO system while achieving an exponential type of average bit error rate (BER) for each data stream. Under the constraints on each subchannel that individual outage probability and average BER are given, based on a traditional upper bound and a dynamic upper bound of Q function, two closed-form ATP expressions are derived, respectively, which can result in two different power allocation schemes. Numerical results are provided to validate the theoretical analysis, and show that the power allocation scheme with the dynamic upper bound can achieve more power savings than the one with the traditional upper bound.Peer reviewe

NETWORK MIMO FOR DOWNLINK IN-BAND RELAY TRANSMISSIONS WITH RELAYING PHASES OF FIXED DURATION

ABSTRACT 1 A half-duplex relay station (RS)-based cellular system deployment is considered, where multiple base stations (BS) cooperate in the BS-RS in-band transmission for the downlink. The duration of the relay-receive and the relay-transmit phases are fixed beforehand, so that the interference induced by other cells is stationary during a transmission interval. With the optimization of the precoders and powers allocated to the wireless backhaul (relay-receive phase) and to the RS-MS access (relay-transmit phase), it is possible to exploit the benefits of network-MIMO (N-MIMO Index terms-Network-MIMO, Relay transmissions, QoS INTRODUCTION With the advent of new sophisticated terminals and bandwidthdemanding services, system designers are pushed towards the challenge of enhancing system spectral efficiency and providing homogeneous coverage for wireless networks. Next generation standards are already considering that conventional paradigms need to be rethought. In this respect, mature enabling technologies (like MIMO) are considered an integral part of the system, while other (like RS-based deployments and coordinated BS transmissions, or Network-MIMO) are part of ambitious study items. Leveraging on the advantages offered by the joint use of all these techniques is a challenge faced by IEEE 802.16m [1] and LTE-A. While implementation details of full-duplex RS are under investigation, relay-based enhancements in standards consider halfduplex relay operation, which incur a rate penalty as they require at least two timeslots to relay a message from source to destination It has been observed that N-MIMO based on zero-forcing (BD-ZF) performs closely to dirty-paper coding An additional way to improve the efficiency of relay transmissions is by optimizing the duration of the relay-receive and the relay-transmit phases SYSTEM ASSUMPTIONS Our system definition is based on the following practical assumptions: 1. The number of antennas at BS, RS and MS is n B , n R and n M respectively, so MIMO performance gains are captured