NeTS: Small: Collaborative Research: Can LTE & WiFi Live Happily Ever After?

University Of Chicago, Chicago IL

Investigators

Abstract

There is a pressing need for more efficient use of existing spectrum to sustain the explosive growth in wireless data. The two most common and widely used broadband wireless access networks are cellular and Wi-Fi which traditionally have operated in very different spectrum regulatory domains: cellular over licensed spectrum allowing exclusive use whereas Wi-Fi has been designed for the unlicensed bands where there is no interference protection by rule. This difference has led to fundamentally different system architectures: cellular systems are centrally controlled where users are allocated resources in frequency and/or time in a way so as to minimize intra-cell and inter-cell interference. Wi-Fi on the other hand, has been designed to operate in an environment where interference between like and unlike systems must be tolerated. Of late, there has been increasing interest in deploying systems originally intended for licensed, cellular bands in the unlicensed bands that are currently primarily used by Wi-Fi, with minimal changes. This creates a new and largely under-explored heterogeneous interference scenario: a scheduled system (cellular) coexisting with a collision avoidance protocol (Wi-Fi). Currently, multiple coexistence solutions have been proposed by industry players, often reflecting existing vested interests and selective use-cases and test scenarios that promote one side or the other. An unbiased study of these various solutions is necessary to settle the ongoing debate on this issue, and can have vital impact on the usage of a large swath of spectrum under consideration. In this project, this fundamental coexistence problem between dissimilar systems will be studied in an unbiased manner, using analysis, simulation and experiments. The research will have three main thrusts and a parallel experimental plan that focuses on system level simulation complemented by a hardware test-bed. Prior to developing schemes for fair sharing, the very concept of fairness needs to be defined suitably. This will be the focus of the first thrust where air-time, throughput and access are the fairness metrics that will be evaluated. The second and third thrusts will propose, analyze, simulate and test coexistence schemes that cellular systems can deploy to ensure fair sharing with Wi-Fi, and that Wi-Fi can deploy to ensure fair sharing with cellular. The latter research area is necessary since in the unlicensed spectrum Wi-Fi does not have any priority over other systems as long as both obey the the Federal Communications Commission rules. The experimental software and hardware platforms will be used to test the coexistence schemes developed in the project. The results of the project, including software code and data sets, will be made public on an ongoing basis and also be used to influence standardization and regulations governing coexistence in the unlicensed bands.