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Efficient Coexistence Mechanisms for LTE and WiFi in Unlicensed Spectrum

Efficient Coexistence Mechanisms for LTE and WiFi in Unlicensed Spectrum

Date19th Oct 2020

Time09:00 AM

Venue google meet link:



The LTE networks are struggling to meet the ever increasing mobile data demand due to scarcity of the licensed spectrum. To overcome this situation, it is proposed to supplement the existing licensed spectrum with the freely available 5GHz unlicensed spectrum, where a fraction of the data demand is served in the unlicensed spectrum. In this context, two variants have been proposed namely LTE-U and LAA. However, the deployment of conventional LTE technology in the 5GHz band will greatly degrade the performance of other incumbent technologies such as WiFi due to stark differences in their channel access mechanisms. Therefore, LTE must employ a proper coexistence mechanism to coexist with WiFi harmoniously.

In this study, we propose a Q-learning based Dynamic Frame Selection (DFS) algorithm. DFS selects the best LTE-TDD frame configuration which ensures fair coexistence between LTE-U and WiFi. Furthermore, we propose the use of reduced power subframe to limit interference to the co-channel users and increase channel utilization. By extensive simulations, we show the effectiveness of our proposed DFS algorithm when compared to existing algorithms in the literature.

LAA uses Listen Before Talk (LBT) as its coexistence mechanism. Also, WiFi employs Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) as its coexistence mechanism, which works on energy detection in the carrier. Furthermore, multi-carrier aggregation is used by both LAA and WiFi to increase the capacity. We first propose an analytical model to measure the effects of different transmit power of LAA on the coexistence of LAA and WiFi in multi-carrier aggregation scenario. Our analytical model uses SINR based collision, which allows the possibility of concurrent transmissions which is not considered in other analytical models. Moreover, we propose a coexistence method named Carrier Aggregation with Transmit Power Control (CATPC) which dynamically adjusts the LAA transmit power. CATPC provides a better opportunity for WiFi devices, better channel utilization, and energy efficient transmission by LAA. Through extensive simulations, we demonstrate the effectiveness of CATPC when compared to other coexistence methods proposed in the literature.


Himanshu Kushwaha, CS17S010

Computer Science & Engineering