Study On Key Technology O Heterogeneous Networks In LTE-Advanced System

To realize high data transmission rate in cellular networks and further improve the spectral efficiency, heterogeneous network (HetNet) has been widely discussed in the 3GPP LTE-A recently. Among many candidate HetNet scenarios, Macro-Pico HetNet has drawn great attention to eliminate coverage holes in the macro-only system, mitigate the traffic loading of MeNB and improve system capacity in hot spots. Owing to a difference in the transmission power between the nodes in HetNet, the coverage of the picocells is much smaller than that of the macrocells. The overload of macrocells will be caused due to the unevenly distributed traffic load To solve this problem, it is necessary to adopt cell range expansion (CRE) method,which uses a bias threshold to make more users select low power cells as their serving cells.Carrier aggregation is a key technology in LTE-A, which can support wider transmission bandwidth by aggregating a plurality of component carriers to increase spectrum utility. In LTE-A system, component carrier (CC) is necessary. If all the UEs select high quality CCs, it will lead to the load imbalance which can not guarantee the maximum of system throughtout. In order to maximize the spectrum utility of system, HetNet tends to adopt the same frequency resource between the Macro and Pico. The UEs in the range expansion region which will suffer severe interference from macrocells are mainly cell edge users of macrocells. In this paper, an adaptive frequency resource allocation scheme and a CC Selection scheme based utility balance are proposed The contribution of this paper are as follows.According to the interference situation of every victim CRE UE, we decide the available PRB resource set of every MeNB. Since MUE experiences slight interference from pico, pico can use full frequency band The main motivation of the scheme is to mitigate the downlink interference and maximize the system throughput. The system-level simulation results show that comparing with the co-channel FA and OFA method,our proposed AFA scheme could reduce interference and achieve higher frequency utility.Then this paper introduce two kinds of existing CC selection methods which are the RSRP measurement based CC selection and load balance based CC selection. But these methods will cause load imbalance and may be performes not effective in achieving optimal system throughput. To solve the above problems, a utility balance based CC selection scheme is proposed The system-level simulation results show that comparing with the traditional scheme, the proposed scheme can achieve high system throughput gain under goo load balance.