Energy efficient IP reachability for push service in NATted LTE systems

As smartphones have become increasingly pervasive, large amount of mobile data traffic has started to overwhelm the networks. Surprisingly, according to [1], the main cause of network congestion in cellular networks today is not only the data traffic generated by smartphones, but also the underlying signaling from the smartphone applications such as push email, instant messaging, and social network services. Such signaling is inevitable as the service providers need to provide always connected service to users. Among multiple signaling burdens, we consider “keepalive” message that is widely used to make a persistent IP connection for most push services in order to keep Network Address Translation (NAT) tables refreshed. Keepalive messages not only overburden the cellular network due to accompanied signaling traffics, but also significantly reduce the battery life of smartphones. In this paper, we propose a method that makes the push service possible without a keepalive mechanism for NATted network system. When the application servers have data to send to some UE given that the UE´s information such as IP address and port number is not available in the servers, they first request this information from the network instead of maintaining a persistent IP connection. Our proposal helps increasing the battery life of the smartphone and relieving the overhead of the network. Simulation results show that the proposed scheme can reduce both battery power consumption and signaling traffic of UE by more than about 30% and 20%, respectively, compared to the keepalive-based legacy mechanism.