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On Markov modeling of random access in communication systems

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dc.contributor.author Abdel-Hamid, Yousry Salaheldin
dc.date.accessioned 2012-05-10T22:57:26Z
dc.date.available 2012-05-10T22:57:26Z
dc.date.copyright 2012 en_US
dc.date.issued 2012-05-10
dc.identifier.uri http://hdl.handle.net/1828/3988
dc.description.abstract This dissertation considers the random access process in the Medium Access Control (MAC) of communications system. New MAC models are developed to improve the performance of random access based systems. The first contribution is the introduction of a general multichannel random access model with a variable radix. This model is general and can be applied to many existing MAC protocols that utilize random access. It is shown that using the standard Binary Exponential Backoff (BEB) to resolve collisions is not always the best choice. By adjusting the radix, contention efficiency can be improved significantly. The analytical results obtained are confirmed by simulation. The second contribution is the investigation of the variable radix backoff strategy with the contention-based bandwidth request (BW-REQ) mechanism in IEEE 802.16 systems. An analytical model of the BW-REQ procedure is presented which includes a variable radix in the backoff process. Analytical results are presented which show that the variable radix can easily be adjusted to the number of users and the available resources to enhance the efficiency of the Random Access Channel in the uplink subframe. Simulations results are presented to confirm the theory. The third contribution is the development of a reliable Quality of Service (QoS) mechanism for random access systems. The available resources are quantitatively categorized to provide differential services to two classes of users. The model is extended to employ a variable radix strategy. Results show that this strategy can be used in combination with differential services to provide an efficient QoS technique for random access. The fourth contribution is an optimized packet-based finite state Markov chain (FSMC) model for the physical channel. This model employs an equal average fade range duration (AFRD) strategy to partition the signal-to-noise ratio (SNR). The Nakagami-m fading channel model is used as it can span a wide range of fading conditions. The accuracy of the analytical results is confirmed by simulation. A cross-layer Markov model encompassing the FSMC model and a general multichannel random access model is introduced. Finally, a simulation toolbox using object oriented programming is presented. It was used to accurately simulate the models developed in this dissertation. This toolbox is general and can be used for a wide range of MAC models. en_US
dc.language English eng
dc.language.iso en en_US
dc.subject Markov chains en_US
dc.subject random access en_US
dc.subject WiMAX en_US
dc.title On Markov modeling of random access in communication systems en_US
dc.type Thesis en_US
dc.contributor.supervisor Gebali, Fayez
dc.contributor.supervisor Gulliver, T. Aaron
dc.degree.department Dept. of Electrical and Computer Engineering en_US
dc.degree.level Doctor of Philosophy Ph.D. en_US
dc.rights.temp Available to the World Wide Web en_US
dc.description.scholarlevel Graduate en_US


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