Performance study of TCP/RLP/MAC in next generation CDMA systems

Improving TCP performance over wireless is very important for 3G and 4G networks. In this paper, we investigate the performance of local retransmissions in CDMA systems, which is used to improve the TCP performance over wireless links. In particular, link layer retransmissions (e.g. radio link protocol or RLP in IS9S and IS2000) and media access control in MAC layer retransmissions are studied in detail. Although there has been recent works in the performance modeling of RLP and MAC layer retransmissions [H. Lin et al., 2002], the wireless link errors are assumed to be independent and identically distributed. It is believed that a correlated fading channel model is a better approximation of the real world wireless channels. In this paper, we study the performance of a wireless data network based on the enhanced cdma2000 system (1XTREME). where link layer and MAC layer retransmissions are used. In particular, the performance is studied assuming the wireless channel to be correlated fading, where errors of consecutive frames are correlated. We introduce an analytical metric called RLP retransmission efficiency to evaluate the performance of different RLP scheme in terms of supporting TCP connections. With both analytical and simulation results, we show that: (i) highly correlated channels degrade the system more severely than low correlated channels: (ii) RLP retransmission scheme (1,1,1,1,1,1) performs better in highly correlated channels, while scheme (1,2,3) performs better in low correlated channels.