A dedicated mobile communication system with no base station using frequency hopping spread spectrum multiple access

The realization of an FH-SSMA (frequency-hopping spread-spectrum multiple-access) communication system useful for 16 mobile subscribers within an area of 5 miles diameter is considered. The subscriber´s information is digitized with the help of a CVSD (continuously variable slope detector) codec at the rate of 16 kb/s which is sent through a 4/16 orthogonal encoder giving coded data of rate 64 kb/s. The subscriber´s address is chosen by a 4-bit binary code which in turn selects the address signal to be generated. The data are BFSK (binary frequency-shift keying)-modulated in such a way that the data bit and the 4-bit address will together select the frequency of the synthesizer giving out the frequency-coded address signal with modulation. Using noncoherent FH-BFSK techniques at the receiver, FH code acquisition and tracking are obtained. The entire system for 16 mobile subscribers occupies 2.4 MHz bandwidth for two-way communication. The receiver performance is represented by a P_e (probability of error) of 10^-3