The Comp System Uplink Detection Reference Signal Design

Coordinated multiple point (CoMP) transmission technology, through cooperation processing of multiple cells, can increase the throughput of cell-edge users, improve the edge coverage area, reduce the interference of cell-edge, and improve the spectrum efficiency. As a key technology of LTE-A, it is worthy of attention and further study. Sounding reference signal, as an important reference signal, is set to detect the channel quality. According to the detecded channel quality, eNodeB can carry out frequency domain scheduling and precoding. SRS feedback mechanism have been considered one of the feedback mechanisms in CoMP system. So, sounding reference signal is very important for the CoMP system. But the SRS structure in Rel-8 applies in CoMP system will lead to SRS transmission interference among users in different cells, and the performances aren't accepted. Therefore, the focus of this subject is to reducing SRS interference of CoMP system and improving the SRS multiplexing capacity.Through simulation and analysis, the results show that SRS serial's correlation coefficient of different groups is high. The SRS interference of different users may caused by different group SRS or different length or overlapping. According to the proposals which is put forward by some research institutes, summary several the enhanced SRS structure design, that is time division multiplexing(TDM), frequency division multiplexing (FDM), code division multiplexing (CDM) and the combination of them. The performance of the enhanced SRS structure are in line with each other, but the cost of CDM lower about 50% than TDM and FDM. Taking the SRS multiplexing capacity into account, the combination of FDM and CDM design is a better solution.As the transmit antennas of the uplink user and the number of active user enchance in Rel-10, the SRS multiplexing capacity is increased. In order to satisfy this requirement,two schemes are analyzed. One scheme is parameter configuration method. Through this method one can rapid find every SRS transmission sub-frame, and reduce the SRS interference by the TDM orthogonal structure. Another solution is to reduce the density of the SRS, thus, more SRS can transmission by frequency division multiplexing (FDM). At the same time, expanding the SRS cyclic shift, so that more SRS sequence can be used by code division multiplexing (CDM). The simulation and anlysis show that the second scheme save SRS overhead, so it is considered a better scheme. The simulation results show that the performances meets the requirements of CoMP system if the enhanced SRS applied in CoMP system, and the SRS interference is reduced effectively.