Research On Resource Allocation In Licensed Assisted Access System

The recent explosive growth in mobile traffic and numbers of smart devices has led to increasing scarcity in network capacity to meet high data rate and low latency requirements from users. Extending cellular networks, such as the long term evolution (LTE), to unlicensed bands to obtain more spectrum becomes a hot research. Licensed assisted access(LAA) is an emerging system, which uses carrier aggregation (CA) to aggregate carriers in licensed and unlicensed bands, delivers critical information and guarantees quality of service (QoS) in the licensed band,and opportunistically boosts data rate in the unlicensed band. LAA can increase the capability of wireless networks, and improve reliability due to using LTE to access unlicensed bands. Hence, LAA systems have a great prospective.This work is supported by the transverse research project "Research on Broadband Mobile Communication System Network Architecture Evolution in the Future". It is very important to study how to allocate resource optimally in LAA systems, which can enhance system throughput and make full use of spectrum resource. There have many wireless networks, and they rely on contention-based access mechanisms to transmission in unlicensed bands. In order to coexist with other systems, listen before talk (LBT), discontinuous transmission on a carrier with limited maximum transmission duration functionalities are required for LAA systems. Therefore, not only the optimal subcarriers and power allocation in licensed bands but also the uncertain usage feature in unlicensed bands should be taken into account in research on resource allocation in LAA systems.In this thesis, the basic concepts and main challenges of LAA are introduced and the research present condition of resource allocation for LAA is summarized firstly. Then, resource allocation algorithms for LAA single-cell and multi-cell systems are proposed.A hidden node aware joint licensed and unlicensed resource allocation algorithm for LAA single-cell systems is proposed. An adaptive unlicensed band weight factor is introduced to reflect the impact of WiFi hidden nodes due to the LBT mechanism in unlicensed bands, and a resource allocation optimization problem is formulated to maximize the throughput of LAA with QoS guarantee, then an iteration-based solution is obtained by optimizing subcarriers and power allocation in the licensed band and fraction of time allocation in the unlicensed band with fixed power. Extensive simulation results are given to evaluate the performance and validate the effectiveness of the proposed algorithm.The basic application of LBT can preclude frequency reuse in LAA multi-cell systems. Considering a significant amount of spectrum resource can be used and carrier selection functionality is required to augment capacity in unlicensed bands, the model of carrier selection in unlicensed bands is established, and a Q-learning based resource allocation algorithm for LAA multi-cell systems is proposed. Simulation results are given to evaluate the performance and validate the effectiveness of the proposed algorithm.