Autonomous uplink intercell interference coordination in LTE systems with adaptively-tuned interference limits

The inter-cell interference (ICI) problem in OFDMA wireless systems is a major impediment to attain high rates particularly for cell-edge users in reuse-1 systems. Interference mitigation techniques combat ICI by using proper resource allocation. Centralized allocation is not practical, particularly in heterogeneous networks, as it requires intensive signaling about interference and channel state information that may not always be practically available. This paper presents a framework for autonomous uplink inter-cell interference coordination in OFDMA wireless systems based on imposing an interference limit for each resource block in each cell. This framework gives a suboptimal closed form autonomous power allocation that can be applied autonomously at each terminal. We also propose two semi-autonomous heuristic and optimal adaptive schemes that use the overload indicator signal in LTE to tune the interference limits in order to achieve fairness among cells by alleviating the interference seen by the overloaded cells. Simulations show that the new suboptimal scheme exhibits the same performance as our initial scheme in [1] which imposes an overall interference limit per cell. However, the two main advantages of the new framework are the ability of each terminal to calculate its power independently and that the adaptive interference limit schemes can be applied to adjust the level of interference seen by each cell. Simulations also show that the adaptive schemes achieve fairness among cells by increasing the rates of the overloaded cells at the expense of slightly reducing the rates of the lightly loaded cells.