Optimization of GSM/UMTS Inter-System Handover times provided by Connectivity Maps

Cellular networks are particularly suitable for the provision of vehicular online services due to their high coverage rates. In addition to LTE, the most widely used networks for mobile data services are GSM (2G) and UMTS (3G) with several enhancements. In the vicinity of UMTS cell boundaries it comes to Inter-System Handovers (ISHO) to switch over to a GSM network, which usually covers large areas. The ISHO can result in unfavorable situations such as significant delays and long communication disruptions. In the opposite direction the handover is often performed late, so that networks with higher capacities and lower latencies remain unutilized. In this paper ISHO times are optimized by the use of context data from a Connectivity Map. Vehicles which go around can be exploited to collect data on the current network properties. Afterward they are transferred to a central server where predictions of the future connectivity can be estimated. The newly gained knowledge can be made available to the vehicles for optimizing the handover times. With a novel developed trigger, the cellular device is actively influenced to initiate the handover. Thus, the negative effects are significantly reduced. Based on an evaluation scenario, the differences between common network-dependent and the Connectivity Map supported handovers are investigated.