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| Effect of the Asymmetry between Downlink and Uplink on TDD-MIMO Systems |
| Dai Kang①; Song Rong-fang①②③ |
| ①College of Communication & Information Engineering, Nanjing University of Posts & Telecommunications, Nanjing 210003, China; ②National Mobile Communications Research Laboratory, Southeast University, Nanjing 210096, China; ③ZTE Corporation, Nanjing 210012, China |
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Abstract Time-Division Duplex (TDD) and Multiple-Input Multiple-Output (MIMO) are the key techniques in the beyond third generation (B3G) mobile communication systems. In the conventional literatures on TDD, the channel state information at transmitter is obtained by assuming the reciprocity between uplink and downlink. However, affected by the unbalance of the Radio-Frequency (RF) circuitries in practice, the reciprocity between uplink and downlink can not be maintained, which will cause a decrease of the performance. In this paper, the asymmetry effect is analyzed in detail and the RF feedback strategy is proposed to eliminate it. Simulation results show that the RF feedback strategy performs much better than the conventional uplink reuse and the capacity of the MIMO systems is greatly improved.
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Received: 06 April 2006
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2007, Vol. 29 
