A centralized algorithm for dynamic TDD frame reconfigurations in synchronized HetNets

Traffic demands of mobile radio network have been tremendously increasing in the recent years due to the enormous success of smartphones and their continuous feature evolution requiring higher data rates. Heterogeneous networks (HetNets) consisting of low-power small cells underlying the existing macro cells represent the preferred solution to increase the capacity of cellular systems by means of spatial spectrum reuse. Static uplink/downlink time-division duplexing (TDD) configurations of existing networks cannot satisfy the varying traffic patterns of large number of small cells, which vary among cells and over time. In this paper we propose and evaluate a centralized algorithm for dynamic TDD frame configuration to which operates on a cluster-based cellular network, maximize the network throughput and preserving fairness. Our algorithm is characterized by only O(n log n) time complexity (with n cells in the network), which allows for instantaneous network-wise reconfigurations minimizing overhead. The algorithm is proven to be optimal and time efficient. Extensive simulation results using realistic application traffic have shown the superiority the proposed solution against static TDD configurations of LTE systems. Throughput improvements up to 43% as well as reductions in queued traffic at cells up to 52% are obtained using separate utility functions designed for throughput maximization and fairness respectively.