Performance Optimization of VoIP Calls over Wireless Links Using

Abstract—Intelligent mobile terminals (or users) of next generation wireless networks are expected to initiate voice over IP (VoIP) calls using session set-up protocols like H.323 or SIP (session initiation protocol). To guarantee the service quality of such applications, the call set-up protocol should be robust against network impairments. In this paper, we analyze the performance of the H.323 call set-up procedure over wireless links using a simple call model under two modes of operations, namely, Regular and Fast Connect. The proposed model assumes the presence of a radio link protocol (RLP) and recommends that the VoIP packets be transferred without any RLP retransmissions, while H.323 control packets be transferred with RLP retransmissions. Our analytical models and detailed experiments show that the VoIP call set-up performance can undergo significant degradation if RLP is not used at all, even for moderately high frame error rates (FERs) in wireless links. On the other hand, a robust radio link layer, such as RLP, can improve the call-set-up delay performance as compared to the existing wireless voice call-set-up delay. Index Terms—Wireless network, H.323 protocol, link-level QoS, radio link protocol (RLP), performance study. æ