In this thesis, we consider a wireless network consisting of d source-destination pairs
and R relaying nodes. Each source wishes to communicate to its corresponding destination.
By exploiting the spatial multiplexing capability of the wireless medium, we
develop two cooperative beamforming schemes in order to establish wireless connections
between multiple source-destination pairs through a collaborative relay network.
Our first communication scheme consists of two steps. In the first step, all sources
transmit their signals simultaneously to the relay network. As a result, each relay receives
a noisy faded mixture of all source signals. In the second step, each relay transmits
an amplitude- and phase-adjusted version of its received signal, i.e., the relay
received signals are multiplied by a set of complex coefficients and are retransmitted.
Our goal is to obtain these complex coefficients (beamforming weights) through minimization
of the total relay transmit power while the signal-to-interference-plus-noise
ratio at the destinations are guaranteed to be above certain pre-defined thresholds.
Our second scheme is a distributed downlink beamforming technique which is
performed in d + 1 successive time slots. In the first d time slots, the d sources
transmit their data to the relay network successively. The relay nodes receive and
store the noisy faded versions of the source signals. In the (d + 1)th time slot, the
relays aim to collectively provide downlink connections to all d destinations. To do so, each relay transmits a linear combination of the stored signals received during the
first d time slots. Again, our goal is to determine the complex weights (used at the
relaying nodes to linearly combine the source signals) by minimizing the total relay
transmit power while satisfying certain quality of services at the destinations.
We use semi-definite relaxation to turn both problems into semi-definite programming
(SDP) problems. Therefore, they can be efficiently solved using interior point
methods. We showed that our proposed schemes significantly outperform orthogonal
multiplexing schemes, such as time-division multiple access schemes, in a large range
of network data rates. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2008-09-17 13:07:21.505
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/1442 |
| Date | 18 September 2008 |
| Creators | Fazeli Dehkordy, Siavash |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | 584283 bytes, application/pdf |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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