A promising next generation wireless network model would combine the benefits of third generation cellular networks with those of Wireless Local Area networks. Integration of the wide geographical range of the former and the high data rates of the latter would provide hotspots with unprecedented capabilities that would revolutionize wireless communication. The achievement of these objectives crucially involves the development of integration architecture. Factors such as authentication, cost-performance benefit, security, accounting, handoff latency, mobility support, and billing mechanisms decide the integration point. In this article, we review two existing 3G-WLAN integration architectures: Tight and Loose Coupling. The study is performed via experimental simulation tests using OPNET in settings where the Universal Mobile Telecommunications Network (UMTS) network connects to a WLAN network at different integration points. These are the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support Node (GGSN). Simulations of the two integration schemes studied measure the parameters and the application delays that occur in cases of direct communication across the UMTS-WLAN networks without first accessing external data networks. The results obtained from this study are compared. The application types studied include FTP, HTTP and VOIP. The parameters measured include load, throughput and end-to-end packet delay. © Research India Publications.