Modeling and performance analysis of Wi-Fi networks coexisting with LTE-U

Abstract

In order to cope with the exponential growth of mobile traffic, mobile operators need to access more spectrum resources. LTE in unlicensed spectrum (LTE-U) has been proposed to extend the usual operation of LTE in licensed spectrum to cover also unlicensed spectrum. However, this extension poses significant challenges especially regarding the coexistence between LTE-U and legacy systems like Wi-Fi. In case of LTE-U adopts Time-Division Multiplexing (TDM) schemes to share the spectrum with Wi-Fi, we expect performance degradations of Wi-Fi networks. In this paper, we quantify the impact of TDM schemes on Wi-Fi performance in a coexistence scenario. We provide detailed analytical models using two different random walk approaches to compute the probability of collision faced by Wi-Fi stations and their throughput performance. Besides, we derive the performance results using an exponential approximation which shows its insufficiency to capture the exact behavior. We implement the coexistence in the NS3 simulator and we show that the models estimate accurately the collision probability and the throughput experienced by Wi-Fi. The models are then used to study and compare different coexistence schemes showing for instance that the Wi-Fi frame size has a non-negligible impact on the performance of Wi-Fi users.

Survey of Spectrum Sharing for Inter-Technology Coexistence

“…b) Fixed duty cycle with different transmission patterns: The authors in [121], [124], [132], [133], [164] further considered different transmission patterns for LTE with fixed duty cycle, in order to either study the coexistence performance of fixed duty cycling itself, or as a baseline for other coexistence mechanisms. In general it was reported that, regardless of the transmission pattern, a fixed duty cycle for LTE could affect the Wi-Fi performance significantly.…”

“…In general it was reported that, regardless of the transmission pattern, a fixed duty cycle for LTE could affect the Wi-Fi performance significantly. For instance, the authors in [164] estimated the probability of collision and throughput for Wi-Fi via analytical models and ns-3 simulations, for LTE with a fixed duty cycle of 50% and different sub-frame transmission patterns. It was found that the Wi-Fi performance strongly depended on the packet size.…”

“…−vs. standalone [121], [122], [124], [127], [139], [145], [156], [157], [164], [168]; −vs. channel selection [133], [155]- [157], [166]; −vs.…”

“…channel selection [133], [155]- [157], [166]; −vs. other duty cycle variants [121], [124], [127], [132], [133], [155], [163], [164], [168]; −vs. LBT variants [124], [132], [133], [143], [145], [153], [155]- [157]; −vs.…”

“…−vs. power control [130], [139] Other −fairness (implicitly) for Wi-Fi vs. coexistence with itself [153], [155]- [157], [164] −fair coexistence for Wi-Fi as half the throughput of standalone Wi-Fi [164]; −max. network utility with fairness for Wi-Fi as airtime vs. coexistence with itself [166]; −proportional fair rate allocation for Wi-Fi and LTE [143], [167]; −maximize overall throughput with fairness as same airtime for LTE & Wi-Fi [134]; −maximize capacity and minimize Tx power [168] −simulations [124], [127], [132]- [134], [139], [143], [145], [153], [155]- [157], [163]- [165], [168]; −analytical [130], [132], [153], [164], [166]- [168] −measurements [121], [122], [130], [165] −throughput [121], [122], [124], [127], [130], [133], [134], [139], [143],…”