Spectrum efficient digital communications for 220-222 MHz narrowband land mobile channels

United Parcel Service (UPS) has developed 220-222 MHz land mobile radios and system technology to give its vehicle fleet high performance digital communications, with connections to local area and nationwide computer networks. Microprocessor-controlled modulation enables power-efficient nonlinear radios to deliver data rates of one bit per second per Hz, or higher, within a 4 kHz authorized bandwidth. Precise spectrum control allows full use of adjacent channels, with 5 kHz spacing between channel centers. Within each channel, signaling methods allow thousands of message transfers per hour. As demonstrated in field and bench tests, the system can serve both urban and rural areas, while sharing the RF band with technically and operationally diverse spectrum neighbors.