A novel measurement of error vector magnitude for TD-LTE termination

With the appearance of Time Division-Long Term Evolution (TD-LTE) standard in succession, investigation and measurement of TD-LTE termination performance has been a distinctive bottleneck in the process of its development. So it is a great practical significance to research of TD-LTE termination testing instrument with integrated testing function of RF, physical layer, protocol stack. As an important testing indicator of TD-LTE termination RF conformance, error vector magnitude (EVM) is used to measure modulated signal quality efficiently and integrally, witch is relative offset between symbol before demodulation and ideal symbol at receiver. So far, EVM measurement algorithm in TD-LTE system has not been reasonably considered, especially there is a lack of accurate and clipping measurement. To solve the problem, from the theory of EVM calculation, based on physical uplink share channel, an effective EVM measurement of frequency offset compensation has been proposed. In the proposed algorithm, the reference symbol has been directly frequency offset compensated after hard decision in the demodulation forward module to avoid the influence of frequency error. Simulation and experiment results show that the complexity and resource is enormously reduced, and the measured EVM is precise in the proposed algorithm.