Abstract
An adaptive control scheme of digital loop filter for automatic frequency control (AFC) is proposed to improve LTE downlink throughput in high-speed train (HST) channel. A mobile device in HST channel suffers from performance degradation due to the abrupt change in Doppler shift. In this case, a higher loop gain is desirable to quickly track the Doppler shift. However, in general, there is a fundamental trade-off between locking time and phase jitter performance in AFC. Therefore, it is crucial to identify the channel condition for adjusting AFC loop gain. In this paper, a wireless channel classification problem is formulated and the optimal classifier is derived by using support vector machine (SVM) algorithm. In particular, HST and non-HST channel environments are classified by exploiting the statistical distribution of the phase estimates. Experimental results show that the SVM-based adaptive loop gain control improves the throughput in HST channel.
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