Practical on-the-move satellite communications for present and future mobile warfighters

As the battlefield becomes increasingly non-contiguous, improved warfighter mobility becomes critical and timely information transfers more difficult. Communication, especially beyond line-of-sight (BLOS), stands out as the key component enabling seamless information transfer across the battlefields. The satellite transmission path remains stalwart in closing the BLOS communications gap but presents several practical problems during operations. The mobile satellite user requires an antenna that remains low profile during travel and yet provides solid communication link closure. An antenna meeting such physical demands tends to be smaller and less efficient than those normally associated with satellite communications' on-the-move (SATCOM OTM). Because of these limitations, the mobile SATCOM antenna finds its performance limited in terms of transmit and receive gain. This limited gain decreases the information transfer rate (or data date) and hence the amount of critical knowledge key to the battle. Such problems pose themselves as challenges to the modern communications engineer. This paper examines the practical satellite operation parameters under typical conditions. This includes systems such as DSCS and Intelsat as well as extensions to the wideband gapfiller satellite (WGS) and future generation MILSTAR systems (the transformational satellite (TSAT)). Results presented include cases using various satellite parameters such as transponder gain, ground user uplink power, satellite downlink power and ground user antenna aperture size. Several cases detail system performance illustrating where the signals progress from bandwidth-limited to power-limited operation as the antenna aperture approaches the limited size available for COTM. Additionally, novel modulation overlays such as the baseband injected pilot carrier (BIPC) on QPSK provide signal-to-noise improvements enabling the smaller antenna apertures to effectively establish SATCOM OTM links. Such improvements range up to 3 dB over conventional QPSK without the overlay and only increase the signal bandwidth by 5%. Overall, the paper presents several successful SATCOM OTM operational options under typical satellite conditions. These options open the door to establishing successful critical information transfer for the present and next generation mobile warfighter