Coexistence Of LTE-U And Wi-Fi Systems With LBT And ABS Method

With the fast increasing of wireless devices in numbers,data demand of users grow explosively.To solve this problem,increasing the licensed spectrum for cellular network is an effective method.Licensed spectrum is limited,but there is a large amount of unlicensed spectrum,so it ' s reasonable to consider that we can make the LTE system run on the unlicensed spectrum.And the coexistence of LTE-U and Wi-Fi system remains the biggest technical challenge.So this paper investigates the coexistence of LTE-U and Wi-Fi and makes some improvements.The contribution of this paper can be summarized as follows. 1) A system-level simulation is designed,which not only considers the performance difference of different algorithms under different scenarios,but also can compare the algorithms under different parameter settings.Using this method,we can more objectively compare the performance of different algorithms under the same standard.2) A LBT-based coexistence mechanism is proposed,which can dynamically change the CCA threshold based on the specific environment and data transmission demand of the eNB.With this method,we can achieve a better balance between spectrum reuse and interference coordination,which will eventually increase the total throughput of the whole system.3) A ABS-based coexistence mechanism is proposed,which can dynamically change the number of blank sub-frames of the LTE system based on the data transmission demand of the Wi-Fi system. With this method,we not only maintain the high spectrum reuse of the LTE system,but also provide sufficient coexistence space for the Wi-Fi system.On the basis of the researches in this paper,to achieve the peaceful coexistence of LTE-U and Wi-Fi system,there are still a lot of other problems for further study, one is the traffic offloading between licensed and unlicensed spectrum,the other is the sharing scheme of the same unlicensed spectrum between different operator.