Out-of-sequence packet arrivals due to layer 2 ARQ and its impact on TCP performance in W-CDMA networks

Data transmission over wireless networks has attracted more attention with the growth of the Internet and wireless networks. However, TCP is tuned to perform well in wired networks where the error rates are very low and packet losses occur mostly because of congestion. Therefore, the performance of TCP can be severely affected by high bit error rate characterizing wireless links. We clarify the performance of TCP over wireless links of IMT-2000 in which selective-repeat ARQ is performed for recovering lost PDUs of Layer 2 on the links. ARQ can cause out-of-order delivery of SDUs, which will result in TCP performance degradation. In particular we examine the impact of the timeout timer employed to maintain sequence integrity.