Electrical and Electronic Engineering - Theses
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ItemTopics in resource optimization in wireless networks with limited feedback( 2011)This thesis focuses on the design of various optimal resource allocation algorithms for wireless communication networks with imperfect channel state information (CSI) available at the transmitter obtained via a finite-rate feedback channel from the receiver (the so-called limited feedback technique). We first look at an M parallel block-Nakagami-fading channels where we seek to design an optimal power allocation scheme that minimize the outage probability under a long term average transmit power (ATP) constraint with quantized CSI. A simultaneous perturbation stochastic approximation algorithm (SPSA) based simulation-optimization method is applied to obtain a locally optimal power codebook. As this method is computationally intensive and time-consuming, we then derive a number of reduced-complexitysuboptimal finite-rate power codebook design algorithms. For the large number of parallel channels case, a Gaussian approximation based low-complexity power allocation strategy is provided. We then consider a secondary user (SU) transmit power control problem in a spectrum sharing cognitive radio networks scenario with quantized channel feedback for optimizing relevant performance measures such as secondary ergodic capacity or outage probability under interference power constraints (which can be restricted either by an average (AIP) or a peak (PIP) constraint) at primary user (PU) receivers to protect the PU, and an average transmit power (ATP) constraint on SU. Firstly, we study the problem of ergodic capacity maximization over M parallel channels (each of which is licensed to a distinct PU) of SU subject to an ATP constraint at SU and M individual AIP constraints on each PU with quantized feedback of the joint channel space of SU transmitter to SU receiver and SU transmitter to PU receivers. We develop a “modified generalized Lloyds-type algorithm (GLA)” for finding a locally optimal quantized power codebook. An approximate but computationally efficient quantized power allocation algorithm is then derived for the case of large number of feedback bits. It is seen that only 3-4 bits of feedback per channel band achieves SU ergodic capacity close to the full CSI based performance. We also extend these results to the noisy limited feedback case. We then consider the problem of throughput maximization of SU with a finite rate power codebook under an ATP constraint at SU and N individual PIP constraints on each PU receiver. With quantized channel (from the SU-TX to each PU-RX) knowledge, three different quantized power allocation schemes are proposed corresponding to three distinct forms of CSI obtained regarding the channel from SU-TX to SU-RX link at SU-TX : full CSI, noisy estimated CSI and quantized CSI. Finally, we consider the joint optimization of the quantization regions and the transmission power codebook such that the outage probability of the SU is minimized while an ATP constraint at the SU and an AIP constraint on the PU are met. Explicit expressions for asymptotic behavior of the SU outage probability at high rate quantization are also developed.