Finally, customized TD-LTE waveforms were created via Signal Studio software from Agilent Technologies. To characterize the performance of the subsystem for LTE applications, these waveforms were compliant with 3GPP LTE TDD specifications. The transmission bandwidth was set to 20 MHz, with data channel modulation types of QPSK, 16QAM, and 64QAM. Similar to the approach used in the first test case, waveforms were downloaded to the FPGA for continuous play.
Figure 9 shows the measurement results with the VSA for a TD-LTE signal with 64QAM modulation. Table 2 shows the measured EVM performance levels for the other two modulation types, with 3GPP specified as a comparison.9 The maximum EVM of three modulation types was only 2.8% RMS, far exceeding the 3GPP requirements. Figure 10 shows a TD-LTE trial network using the MIMO subsystem and a BSC platform designed by Alcatel-Lucent Shanghai Bell, with the two subsystems communications by means of LAN cable; the left-hand corner of Fig. 10 shows a trial network communicating through optical fiber.
In short, the subsystem is suitable for TD-LTE base stations, making effective use of flexible and compact MIMO transceivers. As the measurement results show, it provides performance levels that more than meet the needs of modern TD-LTE systems.
This work was supported in part by the National Natural Science Foundation of China under Grant No. 60702163, and in part by the National Science and Technology Major Project of China under Grant 2010ZX03007-002-01, and 2011ZX03004-003. The authors would also like to acknowledge the assistance and support of Alcatel-Lucent Shanghai Bell Co. Ltd.
Lianqing Ji, Ph.D. Candidate
Jianyi Zhou, Professor
Ke Zhou, Ph.D. Candidate
Jianfeng Zhai, Vice-Professor
State Key Laboratory of Millimeter Waves, School of Information Science and Engineering, Southeast University, Nanjing, Jiangsu, 211111, People's Republic of China.
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