Abstract
As the railroad industry in North America pursues the further expansion of their wireless communications capabilities in support of many different railroad applications, such as Positive Train Control and wireless wayside monitoring, it faces a critical challenge due to the rapidly worsening congestion and over-utilization of RF spectrum resources. Thus, the rail industry is exploring the use of underutilized non-traditional RF bands. One such example is the 160 MHz RF band. In this paper we present initial results from our comprehensive evaluation and RF solutions design effort for the 160 MHz band, with the aim of maximizing communications throughput while complying with current regulatory requirements such as channelization and emission mask regulations. Accomplishing this investigation involves capturing and evaluating all parameters impacting the signal and its spectral characteristics, such as sampling rate and the root-raised-cosine filter parameters (roll-off, filter span, etc.), in order to adhere to channel width mandates and avoid adjacent channel interference. Our results assist with formulating bit rate and symbol rate selections to maximize performance within FCC-mandated spectral mask requirements for this RF band. For our comprehensive investigation we evaluated signals modulated using QAM, Mil188QAM, APSK, DVB-S2/S2X/SH-APSK, PSK and PAM, with different modulation orders ranging from 2 to 256. We then further expanded our work by considering Orthogonal Frequency Division Multiplexing (OFDM) and its corresponding parameters, e.g., FFT size, cyclic prefix, guard bands and more. This research is designed to pave the way to enable vital rail applications for non-traditional RF bands, or expand critical applications such as Positive Train Control into bands such as 160 MHz.
