Research And Implementation On Radio Link Monitoring Algorithm In Lte-a System

The subject of this paper is research and implementation of radio link monitoring algorithm in LTE-A system. According to3GPP TS36.213, radio link monitoring is defined as RRC_CONNECTED user equipment monitoring the downlink quality of serving cell based on downlink cell-specific reference signal. Radio link monitoring is based on evaluation period. One evaluation period commonly includes several detection subframes. The adjacent detection subframes can be continuous or discontinuous in time. User equipment is required to filter detection results of all the detection subframes in one evaluation period and gets the value which can indicate the downlink quality in one evaluation period. Then user equipment should send out-of-sync or in-sync state to its upper layer. Layer1filtering is aimed at eliminating the influence of wireless fading channel. Radio link monitoring is an important aspect of radio resource management. It can influence mobile communication system performance and user experience. Therefore, it is necessary to study the algorithm related to radio link monitoring.This paper mainly includes two research points. The first point is research on influence of different bandwidth wiener filtering channel estimation on radio link monitoring performance in non-DRX reception mode. The second point is layer1filtering algorithm and evaluation period setting.In this paper, a link level radio link monitoring simulation platform is built using MATLAB simulation software. The platform includes transmission module, channel module, reception module, downlink quality assessment module. The platform strictly accord with3GPP technical specifications and can provide reliable simulation data for the research. Research results are based on analysis of the simulation data, as follows:1. This paper conducts quantitative analysis of different bandwidth wiener filtering channel estimation in non-DRX reception mode and gives BLER curves of3RB bandwidth,9RB bandwidth and whole bandwidth wiener filtering channel estimation in AWGN and ETU70channel environments;2. This paper uses normalized variance to research on layer1filtering algorithm of out-of-sync and in-sync detection in non-DRX reception mode. The layer1filtering algorithm in this paper includes two types. In the first type, filtered value is got by averaging all the MMI values of detected subframes in one evaluation period. In the second type, filtered value is got by alpha filtering algorithm. The paper analyzes the performance of the two filtering algorithms by using normalized variance in the case of discontinuous detection subframes and continuous detection subframes. Finally, alpha filtering parameters of out-of-sync and in-sync detection are given when the gap of adjacent detection subframes is10ms (one radio frame);3. This paper analyzes evaluation period setting in DRX reception mode. The DRX cycle is set as64ms and16ms. Moreover, this paper assumes that only one subframe is detected in one DRX cycle. Results in this paper verify the provision of evaluation period setting in DRX reception mode in3GPP TS36.133.