Toward Efficient and Fair Coexistence in Unlicensed Bands: A Unified Analytical Framework for Optimal Access Design

Description

The unlicensed spectrum has garnered huge attention since the Obama administration of the United States identified the unlicensed airwaves as a key economic driver in the White House’s 2014 Economic Report. The new unlicensed bands released in the past few years not only boost the capacity of WiFi networks, but also fuel new services for the Long-Term Evolution (LTE) cellular networks that traditionally operate at the licensed spectrum.Thanks to its free-to-use nature, the unlicensed spectrum has accommodated a large number of wireless communication systems, which may strongly interfere with each other if not properly designed. It has been widely reported that the performance of Wireless Personal Area Networks (WPAN) may significantly deteriorate due to the coexisting WiFi networks in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band. For another popularly used unlicensed band, the 5 GHz Unlicensed Natural Information Infrastructure (U-NII) band, serious performance degradation of WiFi networks was also observed when they coexist with the newly joined LTE networks. With the growing popularity of the Internet of Things, it can be expected that a common scenario in the coming decade would be a massive number of wireless devices transmitting over unlicensed bands using various standards. Ensuring their fair and efficient coexistence is thus becoming an increasingly pressing issue, which is especially critical in the uplink access as the deluge of access requests may easily paralyze the whole network and cause strong inter-network interference.To address this grave challenge, it is crucial to establish a unified analytical framework, within which different access mechanisms of coexisting networks in the unlicensed spectrum can all be analyzed and further optimized. Unfortunately, existing analytical models are usually customized for specific standards, and the differences in protocol details render it difficult to generalize the results from one to another. In this project, we will develop a unified theoretical framework for representative networks in the unlicensed ISM and U-NII bands to characterize and optimize the access performance in various coexistence scenarios. Our goal is three-fold: (1) We will establish a unified model that can capture the essence of various access schemes and incorporate the key features of coexistence. (2) We will characterize the effects of coexistence on the optimal access performance. (3) We will propose access strategies for achieving fair and efficient coexistence by characterizing the joint optimal tuning of access parameters of coexisting networks as well as developing distributed algorithms to implement the optimal tuning. Built upon the PI’s expertise and ongoing studies on coexistence of multi-standard WiFi networks, the proposed research will not only extend the fundamental theory of random access, but also contribute to the optimal access design of next-generation communication networks.