On Selecting a Frequency Band for Mobile WiMAX in Railroad Networks

Abstract:

The North American freight railroad industry continues to strive for improving the safety and security of their operations. This requires a cost-effective and reliable communication network between the dispatch and control centers, the trains and operators, and wayside devices. However, a suitable high-performance network technology to provide coverage for the last segment – between this network infrastructure and the wayside devices and trains – is yet to be determined. One candidate technology for it, Mobile WiMAX, has been shown to provide very favorable performance for railroad applications.
The Federal Communications Commission (FCC) issues licenses for Mobile WiMAX in several spectrums, among which 2.5 GHz and 3.65 GHz are the most popular. The 2.5 GHz band achieves a significantly higher communication range due to its higher allowed maximum transmit signal power, and lower signal strength loss while it traverses over the air. Consequently, fewer base stations are required to provide the same coverage area. However, licensing operations in 3.65 GHz is significantly less costly and time consuming, making it an attractive choice for network deployments. A detailed study of both bands is required to establish whether the lower performance of 3.65 GHz can be compensated by the financial benefits of using it. In this paper, we provide performance analysis and quantitative comparison of the propagation characteristics of the two bands by testing commercial-off-the-shelf (COTS) equipment in both laboratory and field environments. The results enable interested parties to select a frequency band that addresses the requirements of their specific applications and constraints.