Abstract
We study the anti-interference performance of the 802.11 system when it works as Data Communication System (DCS) in Communication Based Train Control (CBTC). We first conduct extensive experiments on a 802.11b network to assess the ability on a lab test bed, then the outdoor experiments are also conducted. In the presence of jammer, we find that in each case of interference model, there exists a C/I threshold which determine the DCS-Access Point (DCS-AP) and DCS-Station Adapter (DCS-STA) communication performance. In the outdoor environment, different interference sources are adopted to investigate the data throughput value and other parameters of the DCS system under the critical state.
Highlights
Nowadays, most of the Communication Based Train Control (CBTC) systems in China use WLAN technology as its Data Communication System which setting wireless link between train and railway side [1,2]
The results shows according to the Data Communication System (DCS) requirements, the below two rows are satisfied, while the top four rows are failure
When DCS two carriers both under the AWGN interference,and carrier to Interference ratio (C/I)≤4.64dB, the throughout loss is higher than 10% and carrier is considered as failure
Summary
Most of the CBTC systems in China use WLAN technology as its Data Communication System which setting wireless link between train and railway side [1,2]. When DCS and interference source are using the same spreading method at the same band, for example both systems are WiFi, the DCS performance is dramatically degraded. In this case carrier to Interference ratio (C/I) will be critical. The DCS carrier central frequency is 2458MHz. When AWGN power is -40dBm, the spectrum analyzer indicates -65dBm/10MHz or -75dBm/1MHz for interference. The central frequencies are 2408MHz and 2458MHz. The interference source WiFi-AP is switched on and the transmitting frequency is 2412MHz which interferes with the carrier 1. The spectrum analyzer shows that I1 is -29.7dBm/22MHz or -43.1dBm/1MHz. The DCS power for C1 and C2 is -72.3dBm/1MHz. C1/I1=(-72.3)-(-43.1)=-29.2dB. The test data read from DEMO software and that from spectrum analyzer is very close and the difference is less than 1dB
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