Improved SRS design and channel estimation for LTE-advanced uplink

In 3GPP long term evolution (LTE) specification for uplink, single antenna for transmission is adopted due to its simplicity. However, when it evolves to LTE-A, more transmit antennas are needed for higher spectrum efficiency, which means more reference signals. In the physical uplink share channel (PUSCH) of LTE-A, the estimated channel based on sounding reference signal (SRS) is used for precoder and modulation and coding scheme (MCS) selection. In this paper, an improved SRS design is proposed, which achieves minimum interference between different reference signals. More importantly, it is perfectly backwards compatible with the SRS in LTE uplink. In addition, we propose an improved SRS channel estimation for multiple transmit antennas. Simulation results show that the proposed SRS design leads to less channel estimation error, and the proposed SRS channel estimation can reach similar accuracy to exponential power delay profile (PDP) channel estimation, while with much lower complexity.