Optimized Strategy Of Interferences Coordination In Lte-advanced Heterogeneous Network

Currently, both of the data rate and the type of traffic, supported by the new band-brodening mobile communication system, are continuously raising and expanding, respectively. In the case of a surge in the volume of traffic, the distribution of it within a cell will be more uneven. In some areas where users are concentrated, there will be some data service hotspots. The traditional network topology may lead to the serious declined receiving SINR and QoS of users in some hot spots which are located in the cell edge, and it is also difficult to enhance the spectral efficiency of the system. To solve this problem,3GPP introduces a concept of heterogeneous network in LTE-A standard. In LTE-A heterogeneous network, those hot spots will be co-frequency covered by some small-scale low-power nodes (LPN), such as Pico and Femto cells, to enhance the user’s QoS. However, significant inter-cell interferences will be also introduced since the co-frequency networking between the macro and LPN cells. Complex heterogeneous network topologies and interference scenarios make traditional ICIC techniques difficult to apply. Therefore, the enhanced ICIC (eICIC) technologies are absolutely necessary.At present the major eICIC technologies include:cell range expansion, time domain eICIC as well as some new-technology-assisted eICIC. The cell range expansion refers to allowing more users to access to Pico cells to achieve load balance between macro cell and Pico cells whitin it, through setting certain bias value when processing cell selection; time domain eICIC means setting some almost blank subframes (ABS) in macro cell downlink physical layer channels to provide more time domain scheduling resources for some Pico cell users that suffer serious downlink interference from macro cell; other eICIC techniques are mainly based on power control or carrier aggregation.In this thesis, a time domain eICIC optimized scheme in LTE-A heterogeneous network is proposed. This scheme, based on LTE network architecture, effectively solves the problem of downlink inter-cell interference between macro and Picos, without affecting the original scheme of the network resource allocation. Cell range expansion and time-domain eICIC are used in this scheme, which, by combining the two technologies, establishe a reasonable mathematical model for solving the optimal cell range expansion bias value and macro cell ABS allocation ratio. Compared with the static eICIC algrithm, the proposed scheme can largely enhance the receiving SINR of interference victim users and increase the throughput of Pico cells.Additionally, for Femto cells, they only provide services for users within a closed subscriber group (CSG). Thus, the non-CSG users accessed in macro cell will be suffering serious downlink interference when they are very close to the Femto cells. In order to solve the inter-cell interference problem in macro, Pico and Femto cells coexistence scenarios, we analyze the prime issues when time-domain eICIC used in a scene which includes Femto cells. After that, a further optimized scheme is proposed, which, on the basis of the previous proposed eICIC scheme, is to address those issues. The system simulation results proved that the optimized scheme can largely increase the throughput of Macro and Pico cells and ensure the fairness among users belonging to different cells.