As the worldwide market of cellular phone increases, many subscribers have come to rely on cellular phone services. In catastrophes or mass call in situations, the load can be greater than what the cellular network can support, and the entire network may become completely non-functional. This raises serious concerns on the survivability of wireless cellular networks in order to provide necessary services such as 911 calls in those circumstances. In high load cases, overload control must be deployed to reserve network resource for emergency traffic and maintenance services. Over the past several years, many catastrophes have revealed the deficiencies of the existing overload control mechanisms in cellular networks. Improvement to the existing overload controls are needed in order to cope with unexpected situations. A key to the survivability of wireless cellular networks lies in the signaling services from database servers that support a call connection throughout its duration (e.g., for monitoring users' locations and supplying authentication codes for secure communications), this dissertation focuses on the overload control at the database servers.
As loss of different signaling services impacts a user's perception differently, the overload control
is proposed to provide differentiation and guaranteed classes of signaling services. Specifically, multi-class token rate controls are proposed due to theirs flexibility in various network configurations and advantages over other controls such as, percentage blocking and call gapping. The concept of adaptive control decision is used so that the proposed controls react quickly to changes in the load. A simulation based performance evaluation of the proposed control is conducted and compared with existing controls. It is shown that the proposed controls outperform the existing multi-class token based controls due to various reasons. First, the proposed controls use adaptive resource
sharing that guarantees a lower bound, where the percentage of resource sharing among classes
is adaptively set. The existing token rate controls either distribute resource among classes using
static ratios or completely share resources among classes. Although using static ratios guarantees the quality of service within each class, it lowers the total utilization of the server. Whereas,
allowing a complete resource sharing among classes may cause large load fluctuations in each class. Second, the proposed controls use the novel concept of integrating information on the availability of the radio resources into the control decision, allowing servers to save theirs resources from serving signaling that later on might be dropped due to unavailable radio resources.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-12282008-062231 |
| Date | 16 January 2009 |
| Creators | Sasanus, Saowaphak |
| Contributors | Dr. Prashant Krishnamurthy, Dr. Richard Thompson, Dr. David Tipper, Dr. Maria Kihl, Dr. James B. D. Joshi |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-12282008-062231/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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