Investigations into code division multiple access (CDMA) have shown that frequency hopping (FH) possesses many of the advantages claimed by direct sequence (DS) spread spectrum techniques. This paper investigates the theoretical and practical implementation issues associated with designing a FH modem. The criteria which are explored include areas which are specifically associated with the frequency hopping nature of the modem, such as the the hopping synthesizer, hop duration, and hop bin separation. Furthermore, consideration is made of the impact of frequency hopping on more general design issues, such as coding, modulation, and multiple access. Work at the Centre for Communications Research (CCR) in Bristol has been carried out to develop a practical implementation of a prototype frequency hopped modem. The paper includes the modem design, and preliminary performance in an additive white noise channel.
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