“TCP PERFORMANCE ANALYSIS OVER UMTS-HSDPA SYSTEMS”

Abstract

This thesis is undertaken to analyze the performance of TCP over UMTS-HSDPA networks in broadband cellular mobile communication. First, The TCP modeling is done and the implications to implement TCP in wireless Networks are presented. Various solutions to implement TCP in wireless networks are presented. Then the architectural concepts regarding UMTS and HSDPA are presented. The simulation of UMTS-HSDPA systems is carried out with the help of EURANE extension to NS2 because NS2 itself cannot simulate HSDPA. The simulation of TCP performance over UMTS-HSDPA is performed with respect to the throughput, TCP variants, Buffering at nodes, and the scheduling at the Node B. After analyzing the trace files created after running the corresponding TCL scripts, the parameters are plotted with the help of MATLAB. The performance analysis is based upon those plots and some references whenever necessary.

TCP throughput in wired and wireless conditions is compared. Results show that the throughput decreases with increasing congestion rate but due to HARQ implemented in HSDPA, the decrease in throughput is not so drastic. The TCP throughput depends also on the type of solutions implemented in each TCP variant. Generally, more buffer in node B increases throughput but not always as increased buffering increases delay in retransmission. The delay in RR scheduler increases twice as the throughput increase. Max C/I the increase in delay is linear than throughput with increase of buffer size. FCDS scheduling, it is better for a moderately large buffer size.

The TCP throughput in UMTS-HSDPA can be increased with the use of hybrid schedulers, introducing proxy server, and using buffer adaptive buffer size as per application requirement. The use of MIMO OFDM technology can be used to increase the throughput as in HSDPA+.