Interference management in cooperative multi-cell networks

In multi-cell networks where resources are aggressively reused, eliminating<br/>interference is the key factor to reduce the system energy consumption.<br/>This thesis proposes interference management techniques based on beamforming<br/>with different levels of cooperation amongst base stations (BSs).<br/>First, a multi-cell beamforming (MBF) technique is introduced to design<br/>beamformers as if geographically distributed BSs were a single BS. The<br/>aim is to minimise the total transmit power across the network while maintaining<br/>the required signal-to-interference-plus-noise ratio (SINR) for every<br/>user. An iterative algorithm is proposed to solve the optimisation problem<br/>of MBF. Since the MBF scheme requires the circulation of all users’ data<br/>amongst coordinating BSs, a user position aware (UPA) algorithm is developed<br/>for MBF to reduce the backhaul overhead by allocating each user<br/>to nearby BSs only. To completely avoid user data circulation, a semi definite<br/>programming (SDP) algorithm, named as coordinated beamforming<br/>(CBF), is introduced to jointly calculate beamformers for all coordinating<br/>BSs in a manner that each BS transmits to its local users only. Taking<br/>into account errors in channel estimations, robust beamforming designs are<br/>developed for CBF. Next, fast wireless backhaul protocols, i.e., Star and<br/>Ring, are proposed using network coding to enable links amongst coordinating<br/>BSs. The maximum achievable throughput of each protocol is<br/>analysed. The power consumption of the Ring protocol is characterised<br/>and used to compare and evaluate the performance of the proposed beamforming<br/>schemes. The deployments of MBF, UPA-MBF and CBF schemes<br/>require a central unit for a group of coordinating BSs as well as backhaul<br/>links amongst them. In fact, a central unit may not always be available,<br/>e.g., in femtocell and self-organising networks, while backhaul links may<br/>be limited. Hence, distributed beamforming (DBF) is proposed to independently<br/>design beamformers for the local users of each BS. In DBF, the<br/>combination of each BS’s total transmit power and its resulting interference<br/>power toward other BSs’ users is minimised while the required SINRs for<br/>its local users are maintained. SDP and iterative algorithms are introduced<br/>to solve the optimisation problem of DBF.

Name dc:type.qualificationname

Doctor of Philosophy

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

King's College London

Year dc:date.issued

2012

Author dc:creator

• Le, Tuan

Advisors dc:contributor.advisor

• Nakhai, Mohammad Reza
• Friderikos, Vasilis

Language dc:language

eng

Identifier

oai:kclpure.kcl.ac.uk:studenttheses/276c8a4f-a152-4fab-8619-54f6bfbeaafc

OAI identifier oai:identifier

oai:kclpure.kcl.ac.uk:studenttheses/276c8a4f-a152-4fab-8619-54f6bfbeaafc