A Research On Inter-Cell Interference Coordination In Lte System

In response to the trend of mobile, broadband and IP technology of global wireless communications, and compete with emerging technologies, such as WiMAX and Wi-Fi,3GPP proposed the long-term 3G evolution (3G LTE) at the end of 2004. The aim of LTE is to achieve higher data rates, lower latency, improved system capacity and coverage, as well as lower costs. And the orthogonal frequency division multiple access (OFDMA) approach is adopted in the downlink of LTE, which can provide orthogonal subcarriers and ensure orthogonality between symbols. Thus it can effectively avoid inter-symbol interference (ISI) and greatly enhance the ability to resist frequency selective fading. Because of the constraints of spectrum resource, however, inter-cell interference (ICI) will seriously affect the data rate at the cell edge. Therefore, effective measures must be taken to mitigate inter-cell interference, so as to achieve the requirements of LTE——higher peak rate and larger throughput of the users at the edge. In this thesis, the inter-cell interference coordination (ICIC) techniques are simulated and analyzed, and the major work is reflected in the following three parts.In the first part, part frequency reuse (PFR) scheme and soft frequency reuse (SFR) of ICIC are analyzed based on the 19 cells cellular system. During the simulation, the changes in SINR distribution, cell throughput and coverage are studied by changing some major parameters which can influence the system performance. It is shown that the system performance is greatly improved by using interference coordination technology; In the real system different traffic needs should be taken into account to allocate the bandwidth and power, so that the system performance can get maximal improved.In the second part, an adaptive SFR scheme is analyzed in the urban macro-cell (UMa) simulation environment of LTE. The four models given by adaptive SFR are simulated respectively to observe SINR distribution, sector throughput and coverage. It is shown that if the best coverage is needed, the mode 4 should be selected; if a larger throughput is needed, the mode 3 should be chosen when the center traffic is large, while the mode 2 should be chosen when the edge traffic is large. Then, with the example of SINR distribution as switching criteria, the switching between four modes is carried out to support that appropriate mode should be selected according to the real-time system needs.Two simulation environment of LTE are established separately in the third part, i.e. urban macro-cell and rural macro-cell (RMa), and joint application of macro diversity and interference coordination that uses soft frequency reuse are studied based on the previous work. Depending on the statistic information of sector position, which causes the most serious interference to the users in target sector, two different cooperative sets and macro diversity schemes are presented. These schemes are simulated in combination with soft frequency reuse model. Simulation results show that compared with the RMa, the system performance is worse in UMa environment; with the combination of SFR and macro diversity, system performance can be improved, and appropriate macro diversity schemes and cooperative sets can achieve greater enhancement.