Interference Coordination Of Reference Signals For IMT-Advanced Systems

Orthogonal Frequency Division Multiple Access (OFDMA) is introduced into IMT-Advanced Systems, which can realize the orthogonality of the intra-cell UEs. However, the interferences between the inter-cell UEs still exist. Therefore, it is a must to do some extra designs to avoid the inter-cell interferences. Reference signals are utilized for the channel estimation and data demodulation, which need better interference coordination than data. The interference coordination for reference signals in IMT-Advanced system is always in a high light of the international studies.First of all, the design for uplink reference signals in Rel-8 system is studied and researched in this work. The interference between Sounding Reference Signals (SRS) is analyzed as well as that between Short-RACH (S-RACH). According to the standards, an interference coordination scheme is proposed.Moreover, link-level simulation which is relevant to the study is introduced in the paper as well. Firstly, two simulation platforms are illustrated, one is the no-HARQ platform with separate MCS, the other is close-looped HARQ platform. Secondly, three channel estimation algorithms, which are LS, LMMSE and 2D-viena filter respectively, are introduced.Based on the design of downlink RS, Channel State Information RS is also studied. Some link-level simulation is done to compare the throughputs of different reference signal patterns. Results show that the performances of the three kinds of patterns are almost the same in scenarios with a velocity of 3km/h and 30km/h. Moreover, the impact of introducing CSI-RS muting scheme on Rel-8 UEs and the gain of the muting scheme for IMT-Advanced systems are simulated as well. Results show that CSI-RS muting has little impact on Rel-8 UEs and brings some benefits to CSI-RS inter-cell measurement.