Load Balancing for M2M Random Access in LTE HetNets

In heterogeneous LTE networks, an incoming user can either join the femto or the macro base station at the random access stage. We consider a system that has a single macro base station and a number of femtocells in its coverage area. We study the problem of optimally choosing either the femto or the macro station based on the knowledge of the traffic arrival rate and the number of backlogged users in both cells. In this paper, we derive the optimal static policy of choosing the base stations that minimizes the average access delay. We also develop various dynamic policies based on the information about the arrivals and backlogged users, and compare their performance against each other and with the optimal static policy. We observe that some of these dynamic policies give very good performance, which provides a lower bound of performance. In addition, a dynamic policy that utilizes only the backlog levels, although not always as good as the optimal static policy, is robust and still stable for a wide range of arrival rates.