Qixing Wang

Antenna Gain Mismatch Calibration for Cooperative Base Stations

In real environments, channel reciprocity cannot be directly exploited between uplink and downlink in time-division duplex (TDD) due to antenna gain mismatch. Previous work about antenna calibration mainly focused on single cell. This work proposes an adaptive scheme for antenna calibration between two cooperative BSs. The proposed scheme aims at achieving an equal ratio between antenna transmitter and receiver analog gains among cooperative BSs in flat fading channels. The essential idea is to relay calibration parameter through a calibration path. This procedure can be controlled by a certain BS dubbed primary BS. Evaluation of the proposed scheme is carried out by computer simulation.

A novel limited feedback mechanism based on mixed reciprocity and codebook in large scale 3D-MIMO systems

3D-MIMO, using two dimensional antenna array at base station, demonstrates promising throughput gain over conventional antenna system during recent academic and industry studies. To realize the performance gain, accurate channel state information (CSI) feedback is one essential aspect. However, traditional feedback method, either codebook based or reciprocity based, suffers from overhead and partial reciprocity issues, respectively. In this paper, a novel mixed feedback mechanism is proposed, in which reciprocity based feedback is complemented with minimal codebook based feedback, to enable full rank MIMO transmission but with minimal reference signal and CSI reporting overhead. The mechanism is optimized for the case with cross-polarized antenna at base station and two receive/one transmit antenna at UE, which is the most practical LTE cellular system configuration. Numerical evaluations verify that the mixed feedback mechanism can realize 3D-MIMO performance with minimal reference signal overhead, CSI reporting overhead and UE complexity.