We investigate the effects of quantized channel state information (CSI) on the performance of
resource allocation algorithms in wireless networks. The thesis starts with a brief overview
of a specific type of quantizer, referred to as a conservative quantizer where we propose the
optimality and sufficiency conditions as well as practical methods to find such quantizers. We
apply this theory to the quantization of transmitter CSI in point-to-point Gaussian channels
and transmission under short-term power constraints. Next, we show that in a multiple-node
decode-and-forward (DF) cooperative network, the same structure for quantizer is close to op-
timal for the sum-rate objective function. Based on a proposed upper bound on the rate loss in
such scenarios, we also argue that the quantizer should assign uneven numbers of quantization
bits to different links in the network. The simulation results show that given a target rate loss
level, through quantization and bit allocation, there is, on average, 0.5−1 bits per link savings
in CSI feedback requirements compared to the uniform and equal bit allocation approaches.
Given the many benefits in non-uniform allocation of CSI rate in the network, we formulate a
generalized bit allocation scheme which is extensible to arbitrary classes of network resource
allocation problems.
In the last part of this thesis, we focus on power control in an interference network and then,
investigate the effects of CSI imperfections on the performance of power control algorithms.
First, we propose an iterative power control algorithm based on a fixed-point iteration and prove
its local convergence. Then, we show that for a centralized implementation of the power control
algorithm, a uniform in dB (geometric) quantizer of channel power is efficient. Based on this
choice of channel quantizer, we propose a bound on rate loss in terms of the resolution of the
ii
deployed quantizer, where a 3 dB in quantization error is shown to contribute to a maximum of
1 bit rate loss at each user. Similarly to the previous scenario, the upper bound suggests that an
uneven assignment of numbers of quantization levels leads to smaller distortion. Based on this
bound, we develop the corresponding bit allocation laws. We also investigate the effects of CSI
errors on the performance of distributed power control algorithms and show that, compared to
the centralized case, the distributed algorithm could lead to a further SINR loss of up to 3
dB for one or more transmitters. This error is due to the fact that because of CSI errors, the
estimated interference level at each receiver is different from the induced interference wireless
transmitters expect.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/43612 |
| Date | 10 January 2014 |
| Creators | Karamad, Ehsan |
| Contributors | Adve, Raviraj |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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