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The fundamental objectives which guide the design of a packet multiple-access technique for satellite networks with large numbers of earth stations are explained. Among these objectives are low peak power in the transmitters, low average power from the satellite transponder, high channel capacity, and low complexity of the multiple-access receiver. The author reviews the fundamentals of satellite packet multiple access and relates these fundamentals to the objectives listed. Code division multiple-access (CDMA) and ALOHA multiple access are described in terms of these fundamentals. A simple linear transformation of conventional ALOHA access, called spread ALOHA, is described. For the case of a low signal-to-noise ratio in the receiver and a low duty cycle of individual and identical transmitters, it is not possible to find a multiple-access method at the same average power and are the same bandwidth which is more efficient than spread ALOHA.>

The development of the ALOHA system packet broadcasting network at the University of Hawaii illustrates a number of general principles about the relationship between information theory and the design of real information systems. An anecdotal account is given of the development of the ALOHA system, emphasizing the interaction of the theory and the design of the experimental network. In addition, some preliminary results are described on the comparison of ALOHA channels and spread spectrum channels when used for packet communications.

This paper provides a general method of calculating the mean-square bandwidth (and other spectral moments) of an arbitrary zero-memory nonlinear transformation of a stationary random process. The method is valid when the original process is an arbitrary combination of other random processes. It can be used to determine the mean-square bandwidth (or the spectral moments) of the transformed process either before or after that process is passed through a bandpass filter. Five examples of the application of this method are provided simplifying and generalizing known results, as well as providing new results.

This paper deals with the optimal use of a sequence of prior observations in order to recognize patterns. The class of pattern recognition problems which we treat is completely general in that the results may be applied to patterns of a visual, aural or electromagnetic origin. We show that the use of prior observations for pattern recognition may be described as a process of learning the statistical characteristics of the patterns involved. The mathematical description of the learning process is analyzed in order to obtain optimal (i.e., minimum probability of error) solutions to various types of pattern recognition problems. These solutions to the mathematical problem are then interpreted in terms of the systems implementation they imply. The optimum systems are shown to consist of banks of generalized correlators. Under assumption of independent measurements, the optimum systems reduce to a class of systems which function by reinforcing desired responses.

The properties of iterated binary channels are investigated. An ordering (defined by the symbol\supset) of communication channels with two possible inputs and any number of possible outputs is defined. For any two such channelsC_1andC_2, this ordering has the property that ifC_1 \supset C_2, the minimum average loss when usingC_1will be less than the minimum average loss usingC_2, independent of the losses assigned to the various errors, and independent of the statistics of the source. This ordering is applied to 1) the general binary channel, 2) the iterated binary symmetric channel, and 3) the unreliable binary symmetric channel when used with many iterations. Curves allowing one to use the ordering are given, and an example using these curves is worked out.

A class of systematic codes has been obtained which will correct all single errors and all double errors which occur in adjacent digits. These codes use significantly fewer checking digits than codes which correct all double errors. In addition, because of inherent regularities in their structure, these codes may be instrumented in a strikingly simple fashion.