usICIC A Proactive Small Cell Interference Mitigation Strategy for Improving Spectral Efficiency of LTE Networks in the Unlicensed Spectrum

The deployment of Long Term Evolution (LTE) in the unlicensed spectrum (LTE-U) [1] has been gaining significant industry momentum in recent months. It is also known as Licensed Assisted Access (LAA), which is an on-going R13 study item in the 3rd Generation Partnership Project (3GPP). The U.S. 5 GHz Unlicensed National Information Infrastructure (UNII) bands [2] that are currently under consideration for LTE deployment in the unlicensed spectrum contain only a limited number of 20 MHZ channels. Thus in a dense multi-operator deployment scenario, one or more LTE-U small cells have to co-exist and share the same 20 MHz unlicensed channel with each other and with the incumbent Wi-Fi. In this paper, we present the scenario and demonstrate in section III that in the absence of an explicit interference mitigation mechanism, there will be a significant degradation in the overall LTE-U system performance for LTE-U co-channel co-existence in countries that do not mandate Listen-Before-Talk (LBT) requirements. We then present the network layer (L3 and above) unlicensed spectrum Inter Cell Interference Coordination (usICIC) mechanism as a time-domain multiplexing technique for interference mitigation for the sharing of an unlicensed channel by multi-operator LTE-U small cells. Through extensive simulation results, we also demonstrate that our proposed usICIC mechanism will result in 40% or more improvement in overall LTE-U system performance