General principles for the design of a multiple-access system for large numbers of terminals transmitting to a single hub station are discussed. The importance of understanding the nature of the traffic to be carried by the network is emphasized. After some discussion of multiple access options for steady traffic and for slowly varying traffic, the use of random-access protocols for rapidly varying traffic is explained. Two general random-access protocols have been used in a variety of data networks, ALOHA and CDMA. Although these two techniques have different origins and are generally thought of as separate, they are in fact but different ways of looking at the same basic signals. The author shows that the use of multiple spreading codes in a CDMA network is not necessary in order to achieve multiple access capability. A single code can greatly reduce the complexity of a CDMA system. He introduces a spread-spectrum version of an ALOHA channel (spread ALOHA) which is equivalent to a CDMA channel with a common spreading code for all users. The equivalence the author demonstrates opens the door to a variety of techniques commonly used in ALOHA channels which can significantly increase both the throughput and the efficiency of the spread-spectrum channel.>

The use of satellite channels for very small-aperture terminal (VSAT) data networks such as spread spectrum and ALOHA is reviewed. Certain basic aspects of the architecture of VSAT data networks are discussed. Although spread spectrum and ALOHA have different origins and are sometimes represented as competing technologies, they can in fact be characterized as different ways of viewing the same low-dimensional signals in a high-dimensional signal space. After a brief introduction to the architecture of VSAT networks, it is shown how a simple linear transformation of conventional ALOHA packets called spread ALOHA leads to signals identical in all respects to the most common form of spread-spectrum signals. Two practical consequences of this theoretical result are discussed. First, for the case of small earth stations it is not possible to find an Access technique with a higher throughput than spread ALOHA. Second, the use of different spreading sequences for different users in a packet network using spread spectrum is not necessary for user separation.>

Packet broadcasting is a form of data communications architecture which can combine the features of packet switching with those of broadcast channels for data communication networks. Much of the basic theory of packet broadcasting has been presented as a byproduct in a sequence of papers with a distinctly practical emphasis. In this paper we provide a unified presentation of packet broadcasting theory. In Section II we introduce the theory of packet broadcasting data networks. In Section III we provide some theoretical results dealing with the performance of a packet broadcasting network when the users of the network have a variety of data rates. In Section IV we deal with packet broadcasting networks distributed in space, and in Section V we derive some properties of power-limited packet broadcasting channels, showing that the throughput of such channels can approach that of equivalent point-to-point channels.