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Performance evaluations of wireless Internet access using the Wireless Applications Protocol

University of British Columbia

The popular Internet protocol stack, TCP/IP, is not suitable for low bandwidth, high latency wireless channels. Problems associated with TCP's throughput in wireless conditions has necessitated the development of alternative protocols that can provide efficient means of transmitting Internet content over a wireless network. Wireless Applications Protocol (WAP) is one such alternative to using TCP/IP for accessing Internet services over wireless channels. In this thesis, the performance of two different WAP network configurations, one being more secure than the other is evaluated and compared under varying Internet and wireless conditions. Effect of asymmetric conditions is also studied. Possibility of providing WAP services over wireless bearers with no error recovery Link Layer is also evaluated experimentally. Simulations indicate that the secure configuration, termed as the alternate configuration (AC), has a better performance than non-secure standard configuration (SC) for good (1% FER) and average (6% FER) wireless conditions. SC has better performance on bad wireless conditions (44% FER, <1000 bps throughput). Performance of AC is affected primarily by wireless conditions whereas performance of SC is affected primarily by Internet conditions. Primary factor that degrades AC's performance is flooding of the wireless channel by redundant reply packets from the server end causing long waiting times on the wireless channel queues. Additionally, under bad wireless conditions, if there is asymmetry present on the channel, AC is unusable. SC's performance degrades under degraded (congested) Internet conditions because TCP's employs congestion avoidance mechanisms and reduces its throughput on detecting congestion on the Internet. Another result of consequence is that under good and average wireless and Internet conditions, presence of the error recovery Link Layer has minimal effect on performance of AC and SC. Some solutions to cushion effect of bad wireless conditions on AC's performance are proposed and tested. The solutions proposed are the use of duplicate packet filtering at link layer level and use of larger reply timers and gradually increasing timers at the WAP gateway. First solution is not employable if data decryption is used. The other two gateway end solutions improve AC's performance under bad wireless conditions but decrease its performance under good and average wireless conditions. This leads to the conclusion that better flow control mechanisms are needed in WTP such that the traffic generation (of retransmissions) at the server is sensitive to conditions on the wireless channel.

Thesis/Dissertation

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2009-09-30

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http://hdl.handle.net/2429/13432

Electrical and Computer Engineering

University of British Columbia

UBCV

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