Spread Spectrum
Spread spectrum technologies on satellite networks enable specific applications that are extremely important to both government and military organizations. The need for high-speed connectivity from a moving vehicle has increased, while the requirement for secure communications continues to be essential.
There are a number of considerations when designing a network for high-speed communication in a mobile environment. The size of the antenna, bandwidth and the amount of interference can all impact connectivity.
With few exceptions, a moving vehicle will require a small antenna. To accommodate market demand antenna manufactures have been working diligently on developing either stabilized parabolic antennas or phased array antennas with very, very small apertures and profiles. These remarkably small and agile antennas, while a triumph of technology, are still limited and provide a challenge for heightened connectivity.
In general, larger antennas produce tighter beams that can focus on the satellite more directly. Smaller antennas—like the ones mentioned above—spread radio frequency energy over a wide area. Smaller antennas also have low gain characteristics, requiring more power to ensure the receiving terminal hears the remote signal. These high rate signals often cause interference with adjacent satellites
Spread spectrum is a feature on the satellite router that diffuses powerful, high rate signals by “spreading out” the transmissions to minimize the interference to adjacent satellites, without limiting connectivity to the desired satellite. This feature eliminates virtually any adjacent satellite interference.
Building on this technology, iDirect has developed Direct Sequence Spread Spectrum over TDMA. In Direct Sequence Spread Spectrum, a pseudo noise code is injected into the data stream at a given “chip” rate. The resultant data stream is modulated at a lower spectral density. Using TDMA ensures only one remote in the network ever transmits at a time.
With only one remote transmitting at a time, the total spread factor for a given network can be much lower than CDMA based spread spectrum systems. This innovation enables military or government organizations to spread signals at a much lower rate than CDMA or CRMA solutions. It also provides more efficient use of ultra small antennas on aircraft, maritime and land-based vehicles.