Mobile WiFi-calling feature and algorithms

The increasing demand in mobile broadband services urged communication system operators to take advantage of small cells and the frequency reuse factor of one in 4G LTE. However, a key problem is the weak coverage of cellular networks within indoor places. On the other hand, wireless local area networks (WLAN), which have become increasingly popular over recent years, cover most of the interior areas in residential and commercial areas, as well as shopping malls. However, the problem of performance degradation when transitioning between open areas where cellular networks have coverage and indoor places where WiFi access points (AP) provide better connectivity, is of paramount importance to be tackled. The technology which allows seamless transition between WLAN and cellular networks is referred to as vertical hando. Vertical handover is the automatic fall-over (or switch) between two technologies aiming to maintain communication. However, the hando requires a certain amount of time to be implemented, which might result in temporary disconnection of the communication link, which results in call dropping. One way to alleviate the issue is to add a hand-o trigger node (HTN) which helps the mobile station to initiate vertical hando prior to reaching the WLAN coverage border. This way, the mobile station will have ample time to accomplish vertical hando before WiFi coverage is lost. This report outlines the background concept of vertical handover and presents the HTN methodology as a practical solution for seamless transition between WLAN and cellular networks. MATLAB simulations are presented to validate the efficacy of the proposed method.