Abstract

With the development of the high speed and heavy-haul transportation in railway, real-time and multimedia communication becomes more and more important. Wireless broadband technology is required to support the railway services. In order to plan and enhance the efficiency of the wireless bandwidth utilization, it is crucial to understand the traffic features and service requirements of different railway services consuming network resources. In this paper, we focus on the traffic measurement for the train dispatching telephone system (TDTS), which is one of the important railway services. Based on WiMAX, we implemented VoIP-based TDTS, that is, iTDTS in our previous work. In this paper, we propose an approach to measure the voice traffic of iTDTS using the method of port monitor and protocol analysis. In iTDTS system, we adopt G.729 speech codec standard as the voice compression and decompression standard. Based on G.729, we make the theoretical analysis about the voice traffic of iTDTS in WiMAX networks. Besides, we also do the experiments according to the four kinds of calls in iTDTS. Our efforts show that the experimental results well match with the theoretical results except for some redundant packets. During the four kinds of call in TDTS, the voice traffics are stable, well supported by WiMAX networks and satisfy with the railway service requirement.

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