Study Of Enhanced Inter-cell Interference Coordination For LTE-A Heterogeneous Network

LTE, as the 3G long term evolution technology,has a higher spectrum efficiency and wider system bandwidth,thanks to its flat network architecture and the use of OFDM and MIMO.But the current technology is approaching the theoretical capacity of single link, sothe 3GPP introduces heterogeneous network in LTE-Advanced to provide better network coverage and higer rate.The home e Node B, namely He NB or Femto, has become an important node in LTE-A heterogeneous network. It can provide flexible network coverage for family, enterprise and public hot spot, with low cost, low power, self-installation and self-configuration. But when the Femtos are deployed in the same frequency with the Macro e Node B and run in the close subscriber group(CSG) mode, they may lead to severe downlink interference to the macro UE(MUE) which is not allowed to access to them. The 3GPP proposes enhanced inter-cell interference coordination(e ICIC) in release 10 to handle this problem.The e ICIC consists of time domain technique, frequency domain technique and power control. This paper mainly focus on the almost-blank subframe(ABS) in time domain technique, and the power control schemes. In the almost-blank subframes, Femto stops all the transmition except the common reference signal(CRS), in order to eliminate the interference to MUE in the downlink control channel and data channel. This paper introduces and discusses an ABS offset based algorithm, which can protect the performance of the Macro UE as well as saving the performance of Femto UE(FUE) from dropping to much. As far as the power control scheme is concerned, the 3GPP proposes four baseline power control algorithms, and this paper makes some improvement by enabling them to ajust the power according to the change of the Femto network, as well as concludesan scheme that can be implemented.Making use of an LTE system level simulation platform, this paper setups an e ICIC simulation system with the scenarios and parameters that 3GPP recommends, and evaluates the performance of the time domain ABS algorithm and power control schemes, to prove them effective and advanced. At last, this paper concludes some shortcomings in the research and expects some improvement in the future.