Mohammad R. Khawer

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) has been gaining significant industry momentum in recent months. The US 5-GHz Unlicensed National Information Infrastructure (UNII) bands 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 coexist 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 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 cochannel coexistence in countries that do not mandate listen-before-talk (LBT) requirements. We then present the unlicensed spectrum intercell interference co-ordination (usICIC) mechanism as a time-domain multiplexing technique for interference mitigation for the sharing of an unlicensed channel by multioperator 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.

Practical LTE and WiFi Coexistence Techniques Beyond LBT

Coexistence with WiFi is the key issue for unlicensed band LTE. The main coexistence mechanism is listen-before-talk, whereby radio frequency energy is sensed over a short period and compared to a threshold. Given the default energy thresholds, the energy sensing range is much less than the cell range. Either technology can experience a collision due to transmissions being below energy detection threshold. Currently, WiFi is agnostic to unlicensed band LTE. To improve coexistence, a relay-based communications channel is proposed whereby LTE announces its presence. Legacy WiFi APs may be programmed to interpret and respond by firmware upgrade . Higher performance for both networks is demonstrated via more effective radio frequency channel selection and adaptive energy detection thresholding.

Design strategies for the application server architecture/configuration (and its functions) in next-generation communication systems

The market trend for next-generation communication systems has been toward miniaturization to meet the stunning ever increasing demand for wireless mobile data, leading to the need for distributed and parallel processing system configurations that are 10 times or more cost effective, flexible, high capacity, energy efficient, and scalable. Reducing cost and size while increasing capacity and scalability requires several design paradigm shifts. This article presents design strategies to meet these goals.