A novel Frequency Selective sounding scheme for TDD LTE-advanced systems

In this paper we propose a novel Frequency Selective SRS (FS-SRS) scheme to improve the quality of CSI. According to the CQIs (channel quality indications), which are periodically reported by each user, and the bandwidth requirement of each user, BSs dynamically schedule each user to send SRSs only on the requisite bandwidth with best CQIs instead of on full bandwidth or on specified sub-bandwidth as in the current LTE TDD systems. Simulation results show that the proposed FS-SRS scheme outperforms the current schemes in estimation accuracy for various frequency-selective and/or time-selective fading channels. In addition, the proposed FS-SRS scheme offers unique advantages over the current schemes. Firstly, it is robust to frequency selective channels. Secondly, it is hardly impacted by timing offset. Thirdly, it is adaptive to the change of the underlying scheduler. Fourthly, it can increase SRS capacity. Finally, it can be extended to multi-user MIMO (multiple-input multiple-output) systems, called extended FS-SRS scheme. Moreover, the proposed schemes are applicable to the uplink SRS design in LTE-Advanced systems.