A Comparison Study of Modulation Techniques of Data Communication for HST in CBTC Systems

This paper presents a comparison study of modulation techniques of data communication in Communication-Based Train Control (CBTC) Systems applied to HST for Jakarta-Bandung. The signalling system is the most crucial part of HST as the center of operation control. CBTC systems are the next generation of signalling technology that adopts the integration of equipment on trains and land base by using wireless communication to collect position information and control signals from trains. The systems can reduce wayside equipment significantly and facilitate other advantages such as high traffic densities and the adoption of single-driver or unmanned trains. The general-purpose 2.4 GHz band usage, which is appropriate for many different regions. The CBTC system has also been made robust enough to prevent signal interferences from other wireless users and reliable for any mission-critical situations. However, LTE-R wireless communication supports more advanced broadband applications to help public safety and railway organizations compared to GSM-R. The ability of Long Term Evolution (LTE) wireless communications has been undoubtedly chosen by the leading professional mobile radio communication which faster supports mission-critical voice and broadband services in the future. GMSK modulation (Gaussian Minimum Shift Keying) is proven as an effective form of modulation for GSM-R. Signal transmission phases in the GMSK scheme are continuous and being smoothed by a Gaussian filter. Meanwhile, QPSK (Quadrature Phase Shift Keying) is a suitable modulation scheme for LTE-R. In QPSK, dual information bits are combined into a symbol which is immediately modulated by nominating one within the four possible carrier phase shift states without using another carrier frequency. In the implementation, the selection of the modulation techniques is based on the required specifications and affordability of the infrastructures.