Distributed offloading strategy with interference avoidance for heterogeneous cellular networks

To make full utilize the limited resources in heterogeneous cellular networks (HCNs), a proper offloading scheme is widely advocated. However, such scheme often lead to a bad result that the offloaded users achieves lower signal-to-interference-plus-noise-ratios (SINRs) than these users in macro-cells. To partially alleviate the SINR degradation, we consider an interference avoidance technique, i.e., a resource (frequency) partitioning strategy that turns off some fraction of such resource in a macrocell and saves it for low-power base stations (BSs). Naturally, an optimal offloading scheme should be closely coupled with the resource partitioning, and in turn an optimal partition decides the offloading performance. In this paper, we maximize a sum-utility with joint offloading and interference avoidance for HCNs. Considering that the formulated problem is in a nonlinear mixed-integer form and difficult to tackle, we introduce a dual decomposition method to develop an effective distributed algorithm. We reveal that load balancing, by itself, is insufficient, and additional interference avoidance is required for improving the system performance. Meanwhile, we show that the proposed scheme can provide a load balancing gain and an interference avoidance gain.