Mitigations in TCP Performance for Jitter and Loss in W-CDMA Networks

† DoCoMo Communication Laboratories, USA Inc. ‡ Department of Information and Computer, Keio University Summary We are facing two major cause of performance degradation in TCP traffic over wireless network such as W-CDMA that utilizing link ARQ mechanisms; jitter and loss in streams of segments. For mitigating the degradations, we explored and achieved as follows; 1) Leveraging the link layer optimizations techniques and established standardization, we evaluated the contribution of Eifel for WCDMA network against jitter. As a result, we can recommend the use of STO avoidance mechanism, such as Eifel. Eifel improved the throughput by around 25 kbps at BLER 10% sample, even with unoptimized link parameters. This result will have substantially impact for network operation because if we could assume the presence of STO avoidance mechanism, the network can be optimized more toward link efficiency on the trade-off curve. 2) We proposed an improvement for the Fast Timeout algorithm with loss retransmission mechanism for strengthen in loss recovery. Simulation results yield the following; a sender using the proposed algorithms holds one half of the previous cwnd value and so avoids unnecessary throughput degradation even if duplicate ACKs arrive following a timeout and the retransmitted segment is lost. The proposed algorithm overcomes Fast timeout at most around 33 kbps of improvement in throughput for single set of recovery in our simulation settings.