Study On Resource Allocation Scheme For LTE In Unlicensed Band

In order to meet the challenges of mobile data traffic surges and the shortage of spectrum resources in licensed spectrum, deployment of LTE system in unlicensed band (LAA/LTE-U) using carrier aggregation technology is attracting more and more attention. Currently, some wireless hotspots such as Wi-Fi have been deployed in unlicensed band. Traditional LTE system deployed in unlicensed band will cause interference to Wi-Fi system. In particular, unlicensed spectrum has the characteristics of open sharing. Wireless hotspots deployed in unlicensed band can free use the unlicensed spectrum. How to allocate resources fairly and improve resource utilization becomes an urgent problem to be solved.This paper proposes three resource allocation schemes for LTE system in unlicensed band. The first scheme is based on listen before talk (LBT)mechanism, including no LBT, FBE-LBT, LBE-LBT with fixed back off window size and LBT-LBT with variable back off window size. This scheme mainly solves the problem of interference between LTE and Wi-Fi and allocating time domain resource. The second scheme is based on SDN flexible network architecture. Spectrum resource allocation between two systems in unlicensed band is modeled into a repeated game model. In addition, decision tree theory is used to predict the network state information for system to make better decisions in the stage of repeated game. In order to encourage the coexistence system to share spectrum resources, an encouragement mechanism is proposed in repeated game. The third scheme dynamically adjusts downlink and uplink timeslots according to the traffic based on LBT mechanism. This scheme breaks the traditional fixed time slot setting in LTE system so that timeslot resource could be allocated more flexibly.The system level simulation platform of LTE system and Wi-Fi system in unlicensed band is developed. The above three resource schemes are evaluated on the simulation platform. Simulation results show that the first resource allocation scheme based on LBT mechanism makes LTE system occupy the public resource fairly and reasonably. At the same time, the scheme also makes LTE and Wi-Fi harmonious coexistence in unlicensed band. The dynamic downlink scheme of spectrum resource allocation improves the spectrum utilization efficiency and system performance. The third scheme realizes adaptive configuration of uplink and downlink subframes according to current network load, which improves the rationality of time domain resource allocation and the user experience.