Probability of Coexistence of LTE-LAA and WLAN Systems Based on Delay Constraints

Abstract

To support efficient spectrum sharing and related standardization efforts in unlicensed spectrum, it is important to develop analytical tools to accurately quantify coexistence performance between long-term evolution license assisted access (LTE-LAA) and incumbent systems, such as wireless local area network (WLAN). Though joint throughput of spectrum sharing LTE-LAA and WLAN systems has been extensively studied, there lacks a systematic study on a high level metric - the probability of coexistence (PoC), which indicates whether coexistence is successful or not probabilistically. Another problem is that the majority of available results either ignored delay constraints, or studied only the mean (or variance) of delay, but have not considered the delay distribution and its impact on throughput. To address these problems, we define and analyze the original PoC metrics between LTE-LAA and WLAN systems based on two practical delay constraints. The first PoC is derived from the joint distribution probability of delays for successful transmissions; and the second PoC is defined upon the joint probability of delay-constrained throughput (DCT) of LAA and WLAN systems. To address the technical difficulties involved, we design a novel analytical framework to evaluate the moment generating function and cumulative distribution function (CDF) of the delay, and a new method to evaluate the DCT and its CDF. Consequently, the PoCs can be evaluated accurately with low complexity. The analytical results are verified by our Monte Carlo simulations, which demonstrate impacts of delay and throughput requirements on the PoCs, and illustrate design tradeoffs and insightful findings. These results provide theoretical and practical value for designing improved LTE-LAA and WLAN systems, and may be extended to other emerging spectrum sharing communication systems.