SAP: seamless authentication protocol for vertical handoff in heterogeneous wireless networks

802.11 standards support high data rates for a low price and thus provides an economical way for WLANs. On the other hand, 3G standards offer a much wider area of coverage that enables ubiquitous connectivity. The integration of them takes advantages from both sides and offers the possibility of achieving anywhere, anytime cost-efficient Internet access. To facilitate such integration, seamless vertical handoff is one of the major challenges because it needs to make physical movement transparent to mobile users and preserves application-level connectivity. Previous works did not consider the impact of authentication mechanisms on the performance of vertical handoff, especially on its delay. In a 3G-WLAN integration environment, since 3G and WLAN may use different authentication servers, when a mobile terminal hands over across them, certain authentication procedure needs to be performed. According to the literature, such authentication delay may be as high as hundreds of milliseconds, which is intolerable for delay-sensitive applications. We present seamless authentication protocols (SAPs) for vertical handoff in wireless heterogeneous networks, to reduce this delay. Simulation results show that SAP significantly reduces the delay caused by authentication procedures in vertical handoff.