Intercell Interference Coordination for Control Channels in LTE and LTE-A: An Optimization Scheme Based on Evolutionary Algorithms

Intercell Interference Coordination (ICIC) encompasses techniques aiming at reducing the intercell interference at cell edges, an issue affecting not only data but also control channels in Long Term Evolution (LTE) and LTE-Advanced (LTE-A). This paper presents several ICIC-based optimization schemes to improve the performance of the control channels: the Physical Downlink Control Channel (PDCCH) in LTE and the enhanced PDCCH (ePDCCH) in LTE-A. The study is focused on realistic deployments, where the amount of intercell interference received at different cells varies considerably, making very difficult the task of homogenizing the performance of the ePDCCH in the coverage area. The PDCCH is time-multiplexed, and hence, traditional ICIC schemes such as Soft Frequency Reuse cannot be applied. As an answer to this, LTE-A introduces the ePDCCH. This new structure increases the signaling capacity and allows frequency domain ICIC. However, the optimization of the ePDCCH poses a new problem. The resources devoted to the ePDCCH need to be borrowed from the data channels. In order to address these problems, several multiobjective optimization schemes based on evolutionary algorithms are proposed to adjusts the configuration of the control channels, and consequently, to reduce the consumption of control resources. The results show that significant capacity gains, up to 30 %, are obtained in severely interfered cells with notorious savings in terms of transmitted power.