A New Multiple Access Technique For Use With Satellite Networks

The Multiple Access Discrete Address System described is particularly applicable to future digital modulation systems. A high degree of efficiency is achieved using methods which provide the advantages of time division without the critical dependence on precise timing characteristic of more conventional techniques. A performance comparison with current fm/fdm is provided. In communicating through a satellite repeater, a modulation technique must be selected to serve two separate functions. The first is the address function which must permit the receiver to separate the desired signal from other transmis-- sions simultaneously using a given repeater. The second function is to transfer a message between two users. This presentation relates to the first function and describes a Multiple Access Discrete Address System that has unique features, particularly applicable to future digital communications networks . In a sense, a satellite communications link is nothing more than a microwave circuit with an unattended repeater. One of the prime differences, however, is that due to the high cost of the satellite a number of circuits must use the same repeating amplifier. It is also a characteristic that the satellite is severely power limited. This power limitation at the present time is not a technological limit, but results from the sharing of frequency band with ground-based systems and international agreements covering satellite radiated power. The multiple users combined with the power limit places constraints on the system and is the fundamental reason for the presence of a multiple access problem. It may also be observed that in any communications network it is necessary for the receiver to be able to select a particular transmission of interest from the multiple signals that it has access to; hence, the requirement for discrete addressing