General Packet Radio Service (GPRS) is an upgrade development of GSM and an indispensable component of 3G that provides both circuit and packet switched data communication ubiquitously. Wireless LAN (WLAN) is a network technology that lacks the flexible mobility management nevertheless is relatively cheap and gives much higher bandwidth than 3G. Combining these two techniques allows users to get a large coverage area with 3G and relatively high-speed data flow in WLAN spots. The essence is to identify and validate different solutions for interworking. These solutions will differ in the level of integration. A typical solution of tight integration is to physically connect the WLAN segment with the 3G networks, by making a new node that behaves either like a SGSN or a BSC in 3G systems. Another more loose solution is based on the usage of the mobile IP as a bridging technology. It is the recommended solution for it requires less of an effort to implement. This paper investigates those different solutions and proposal a new approach to improve the performance of the interworking.