Abstract
Previous \TCP\ performance investigations for wireless systems focus on \TCP\ throughput degradation due to packet loss on the error-prone wireless link. Since cellular mobile networks like \GPRS\ and \UMTS\ include a strong link layer error protection, using adaptive Forward Error Correction and Automatic Repeat Request schemes, a bad quality of the wireless link does not mainly result in \IP\ packet loss but rather in an additional packet delay. Furthermore \TCP\ congestion control has to deal with hand-offs and temporary link layer disconnections in cellular mobile networks leading to a significant packet delay variation and packet disordering. This paper analyzes the performance of \TCP\ in cellular mobile networks, focusing on the packet delay and disordering problem. We find spurious retransmissions and \TCP\ timeouts being a dominant cause for throughput degradation. Finally we propose an algorithm to filter spurious \TCP\ retransmissions at the Base Station to increase \TCP\ performance and increase overall wireless link capacity.
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