CLEH — Cross layer enhanced handover for IMS sessions

Voice over WiFi (VoWiFi) is a complementary technology to Voice over Long Term Evolution (VoLTE) which utilizes IP Multimedia Subsystem (IMS) to provide a packet-switched voice service over WiFi network. VoWiFi extends the benefit of VoLTE sans cellular coverage. In the existing VoWiFi architecture, IMS sessions can be seamlessly handed over from LTE to WiFi (L2W) and vice versa (W2L). A major limitation of this approach is that direct handover from one VoWiFi AP (Access Point) to another VoWiFi AP (W2W) is not feasible. This results in disruption of IMS services such as call drop at each AP transition in areas with limited or no cellular coverage. Through our current work, we address this issue by devising a novel IMS session handover for W2W scenarios based on cross-layer parameter learning. We have utilized Real Simultaneous Dual Band (RSDB) feature available with Broadcom chip-set BCM4359 to realize our idea. The solution is verified with results obtained from live air experiments performed on Samsung Note5 running on Android M. We are able to achieve an average improvement of 67% in terms of call drops and 54% in terms of mute observed during IMS call as compared to legacy solutions.