John S. Baras


Congestion Management and Medium Access Control in Satellite Data Networks

Xiaoming Zhou

Doctoral Dissertation, Date: 2005, Advisor: John S. Baras

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Satellites are now being used to carry Internet traffic which brings new opportunities as well as new challenges to the satellite industry. Our goal in this dissertation is to design efficient and fair transport layer and medium access control layer protocols for satellite networks. Three problems have been addressed in this dissertation.

The first problem is to improve TCP performance over satellite networks and a protocol called receiver window backpressure protocol (RWBP) is proposed to be used inside the satellite networks. RWBP has newly designed congestion control, error control and buffer management schemes. And it requires less reverse channel bandwidth without sacrificing the forward channel throughput. RWBP can still maintain good performance even when there is high priority traffic such as streaming video, audio competing with the TCP traffic in the satellite networks.

The second problem is to investigate the transfer of short messages with delay constraints in the reverse channel. A multichannel random access protocol called FMCSA is proposed in this dissertation. FMCSA combines random access with packet level forward error correction (FEC) coding for new messages and scheduled retransmissions for partially received messages. Through analysis and simulations, we show that FMCSA can achieve higher throughput and lower delay than slotted Aloha.

In the third problem, we conduct a capacity and performance study for interactive data services in wireless access networks. We evaluate the performance of several MAC protocols such as slotted Aloha, static TDMA, Aloha/periodic stream and combined free demand assignment multiple access (CFDAMA) using realistic web traffic models. Based on the performance evaluation, we propose a new MAC protocol. Our new MAC protocol called CPFDAMA explores the correlation between forward channel data packets and reverse channel acknowledgement packets. CPFDAMA combined with RWBP in the transport layer outperforms the proposed protocols in term of both channel utilization and page response time.

On the whole, we address the Internet access in satellite networks from a system perspective. Our work can be used to improve the performance of current systems and it also can be used to design next generation satellite networks.

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