Research On Interference Coordination Based On Abs Configuration And Carrier Aggregation In Heterogeneous Networks For LTE-A

In recent years, with the popularity of mobile intelligent terminal and the wide application of various kinds of real-time multimedia services, traffic in broadband wireless network is growing at an exponential rate. Consequently it is the growth of demand for higher quality of cover and higher data rate services. With respect to the fast-growing of users’demand, the most serious problem is the scarcity of spectrum resources. In order to improve the spectrum efficiency, LTE-Advanced (LTE-A) further reduces the cell size compared to LTE, but because of the terrain, building layout, and other conditions, the cell size cann’t be reduced unlimited. Especially for indoor, hot spots, coverage holes and other special scenes, simply reducing cell size cann’t effectively solve the problem. Thus3GPP proposed heterogeneous networks technique to solve the problem in the LTE-A standard-setting process, so as to enhance the overall system performance.Heterogeneous network is a new network model, which is composed of macro base station and low-power nodes such as pico base station, femto base station and relay within its coverage area. Deployment of heterogeneous networks may reduce the distance between the user and the base station nodes, effectively improve the spectrum efficiency in unit area and the communication quality in hot spots, blinding spots and the cell edge. As an excellent way to enhance system performance, heterogeneous networks face a lot of technical challenges, among which the inter-cell interference problem due to the change of network topology and the deployment in same frequency of heterogeneous networks is particularly the most important.In macro-picocell scenes, due to the difference of macrocell and picocell’s transmission power, using the traditional cell access criterion will limite the number of users served by picos, thereby the system performance gain of deploying picos cann’t be achieved. Therefore the cell range extension was introduced to balance the load between macrocell and picocell in heterogeneous networks. However, using the CRE technology will cause strong downlink interference to users located at the edge of the picocell, especially the users in the extended area of picocell from the macrocell. Therefore, this thesis proposes an enhanced cell interference coordination scheme jointly optimizing the CRE bias and the ABS ratio. The scheme can adjust the CRE bias according to the load condition between macrocells and picocells, and adjust the ABS according to the stabilized bias, then find the ABS ratio to maximize the system thoughput. Carrier aggregation is a new technology proposed in LTE-A, which can extend system bandwidth by aggregating a plurality of component carriers. LTE-A system supports cross-carrier scheduling after using CA technology, which can improve the flexibility of scheduling and can be used to solve the inter-cell interference problem in heterogeneous networks. This thesis presents an interference coordination scheme based on cross-carrier scheduling, which allows macrocell to be silent on the Control Channel (CCH) of part of the carriers, and reduces its transmit power on the Data Channel (DCH) of these carriers unless the overall system performance is not damaged, so as to reduce its interference to users on the edge of picocell within its coverage.