Research Of The Transmission Performance On WLAN Integrated With 3G

Nowadays, the 3rd Generation Mobile Communication System (3G) is developing fast. At the same time, WLAN(Wireless Local Area Network)is poised to become an important application.3G can provide wide-covered services but it has a low datarate. WLAN has a high datarate, but it covers a small area. Therefore, High-speed and low-price wireless data services can be provided by seamless link between 3G and WLAN. WLAN is promising to be integrated with 3G.How to integrated WLAN with 3G and how to transmit voice and video over WLAN integrated with 3G will be problems that need to be solved quickly.Six schemes for integrating 3G with WLAN has been discussed, which are from simple link to seamless operation between the two systems.According to the extend of depending on each other, there are two modes of integrating WLAN and 3G: the loose coupling mode and the tight coupling mode.In the tight coupling mode, WLAN acts as a Radio Access Network, which is connected with 3G and shares the common resources. In the loose coupling mode, WLAN only shares AAA (Authentication,Authorization and Accounting)server and is not connected with 3G.After the integration, VoWLAN(Voice over Wireless Local Area Network)will be an import application supporting seamless voice services. Its performance are mainly voice QoS (Quality of Service)and voice capacity. As to the capacity problem, the proposed Multiplex-Multicast scheme can improve the capacity by close to 100% without changing the standard 802.11 protocol, which can be deployed over the loose coupling mode above. In the scheme, packets from several VoIP(Voice over Internet Protocol)streams has been multiplexed into one multicast packet for transmission over the WLAN.Compared to the voice transmission over WLAN, high-quality video transmission is more difficult to be achieved. Wireless video coding and WLAN video transmission has become the focuses. Among the Wireless video codings, FGS(Fine granularity scalability) is a fire-new scalable video coding method. Several cross-layer techniques has been studied, in which the transmission mechanism over application layer and link layer are both considered .