Adaptive quality of service management in wireless /mobile networks.
Item
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Title
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Adaptive quality of service management in wireless /mobile networks.
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Identifier
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AAI9969732
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identifier
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9969732
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Creator
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Sherif, Mahmoud R.
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Contributor
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Adviser: Ibrahim Habib
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Date
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2000
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Electronics and Electrical | Computer Science
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Abstract
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In wireless ATM based networks, admission control is required to reserve resources in advance for calls requiring guaranteed services. In the case of a multimedia call, each of its substreams (i.e. video, audio and data) has its own distinct quality of service (QoS) requirements (e.g. cell loss rate, delay, jitter, etc.). The network attempts to deliver the required QoS by allocating an appropriate amount of resources (e.g., bandwidth, buffers). The negotiated QoS requirements constitute a certain QoS level that remains fixed during the call (static allocation approach). Accordingly, the corresponding allocated resources also remain unchanged. In this thesis, an adaptive allocation of resources algorithm based on genetic algorithms is proposed and analyzed. In contrast to the static approach, each substream declares a preset range of acceptable QoS levels (e.g., high, medium, low) instead of just a single one. As the availability of resources in the wireless network varies, the algorithm selects the best possible QoS level that each substream can obtain. In case of congestion, the algorithm attempts to free up some resources by degrading the QoS levels of the existing calls to lesser ones. This is done, however, under the constraint of achieving maximum utilization of the resources while, simultaneously, distributing them fairly among the calls. The degradation is limited to a minimum value predefined in a user defined profile (UDP). Genetic algorithms have been used to solve the optimization problem. From the user perspective, the perception of the QoS degradation is very graceful and happens only during over-load periods. The network services, on the other hand, are greatly enhanced due to the fact that the call blocking probability is significantly decreased. Simulation results, for a cellular-based wireless network, demonstrate that the proposed algorithm performs well in terms of increasing the number of admitted calls while utilizing the available bandwidth fairly and effectively. The thesis also proposes a QoS based channel borrowing algorithm (QCBA) that allows a cell (in a cellular system) to borrow some free channels from any neighboring cell to accommodate new calls. The criteria for choosing the free channel include not only the number of free channels but also the QoS levels in the donor cell. The criteria is also extended to include the effect of channel locking on the number of free channels and the QoS levels on the locked cells. Simulation results shows that the QCBA decreases the call blocking rate while increasing the average QoS level.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
