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The article addresses the end-to-end performance of TCP in a scenario where WCDMA is used as the access link. In particular, the performance gain that can be achieved by placing a TCP split connection proxy in the WCDMA core network is examined. It is well known that performance enhancing proxies are able to improve the performance of TCP over wireless links that suffer from impairments. However, while previous work on TCP proxies for wireless systems either focused on other wireless systems, like wireless LAN or satellites, or provided a more generic framework, we address in detail the characteristics of a WCDMA access scenario supported by a TCP proxy. The characteristics of WCDMA as perceived by TCP are discussed thoroughly. We argue that the motivation for introducing a proxy is only to overcome problems stemming from a large bandwidth delay product and not to assist local transport layer error recovery at the wireless link. Based on simulations that consider both link layer protocols and TCP, the end-to-end performance for file downloads is investigated. Simulation results show that a proxy can significantly improve performance in the case of high data rates like 384 kb/s. For lower data rates, like 64 and 128 kb/s, it is sufficient to use a well configured TCP implementation.