ABSTRAKSI: Universal Mobile Telecommunication System (UMTS) merupakan jaringan seluler generasi ke-3 yang memungkinkan akses Internet berkecepatan tinggi. UMTS mampu menyediakan kecepatan data yang maksimal dari 64kb/s hingga mencapai 2Mb/s pada tipe lingkungan yang berbeda. UMTS dirancang untuk mampu melayani akses internet seperti layanan Internet pada umumnya. Layanan data dalam UMTS menggunakan TCP sebagai protokol transportnya. Awalnya TCP didesain untuk media kabel, tetapi pada UMTS terdapat media udara yang bersifat tidak stabil dimana bit error rate TCP yang terjadi cukup tinggi.
Pada tugas akhir ini dilakukan penelitian dan pengujian performansi TCP pada empat karakteristik UMTS Dedicated Channel (DCH) berdasarkan variasi window size TCP yang digunakan yaitu 5,10,15,dan 20 berdasarkan parameter throughput ,end-to-end delay,dan packet loss. Karakteristik kanal DCH ditentukan oleh bit rate dan transmission time interval (TTI) yang digunakan.
Berdasarkan hasil penelitian diperoleh hasil nilai throughput akan meningkat sesuai peningkatan window size TCP dan downlink bit rate DCH, nilai end-to-end delay meningkat sesuai peningkatan window size TCP, nilai end-toend delay menurun sesuai dengan peningkatan downlink bit rate DCH, presentase packet loss meningkat sesuai dengan peningkatan window size TCP dan downlink bit rate DCH.Kata Kunci : Kata kunci : UMTS, TCP, DCH, window size, Internet.ABSTRACT: Universal Mobile Telecommunications System (UMTS) is a thirdgeneration cellular network that enables high-speed wireless Internet access. It can provide maximum data-rates ranging from 64kb/s to 2Mb/s in different environmental types. UMTS is designed to provide access to the existing Internet services as well as to UMTS specific services. It is widely known that TCP does not perform efficiently in wireless links where the bit error rate is high enough. This final project has as main target to evaluate the performance of TCP data transfer over the UMTS air interface, by means of a rather detailed simulation model.
We examine the performance of TCP over 4 characteristic UMTS Dedicated Channels (DCHs) with window size variation (5, 10, 15, and 20) . The characteristic of DCH depend on different bit rates and Transmission Time Intervals (TTIs).
From the experiment, the result is as the window size of TCP and downlink bit rate of the DCH increases, the throughput and the percentage of packet loss increase. It is obvious that as the downlink bit rate of the DCH increases, the end-to-end delay decrease and as the window size of TCP increases, the end-to-end delay increase.Keyword: Keywords: UMTS, TCP, DCH, window size, Internet.