This paper presents a simple phasor model for analyzing coherent direct-sequence, pseudonoise (PN), spread-spectrum carriers accessing limiting repeaters in the presence of strong interference. Limiting repeaters are found in several applications, one being satellite relays. The model used provides a rigorous upper bound on system bit error rate depending only on an equivalentEb/N0. Presented for the first time is an application of the model to RF limiters having an AM-to-PM conversion effect. For quadriphase PN, receiverEb/N0is given by the heuristic approach of replacing the limiter with an average power-limited linear device plus an additional lossLdue to limiting. As long as there is no AM-to-PM conversion in the limiter,Lis the same as that obtained by passing multitone CW plus noise through the limiter. For quadriphase PN carriers passing through a limiter with AM-to-PM conversion,Lcan depend on the type of coherent phase tracker used.Eb/N0for biphase PN, in contrast to quadriphase PN, need not have the usual heuristic form given by quadriphase PN.

A problem in the use of satellite Demand-Assigned Multiple Access (DAMA) results from spectrum limitations at each ground terminal due to avoiding frequency interference to nearby terrestrial microwave radio relay. Frequency Division Multiple Access (FDMA/DAMA) can operate with a terminal-by-terminal assignment of frequency channels out of the total band available to the satellite. Time Division Multiple Access (TDMA) requires the use of the full band at all the terminals. The effect on satellite bandwidth utilization must be evaluated to determine the advantage, if any, of FDMA channel-by-channel assignment. A linearized traffic model is presented for making such an analysis. The FDMA/DAMA traffic load allowed by spectrum constraints falls off as a function of the manner in which frequency channels and traffic are distributed over the terminals. Additionally, a somewhat more complex geometric model is proposed.

Constraints on capacity allocation are investigated for circuit-switched demand access to a common transmission resource by user communities with differing traffic intensity and capacity requirements. A simple birth-death steady-state traffic model is used together with a geometrical representation of any given set of constraints placed upon user access. State probabilities have a simple product form which holds for a wide class of constraint sets. Performance characteristics are intrinsic to the upper surface of the constraint set.

This paper investigates the problem of estimating the effects of interference to a coherent phase-shift-keyed (CPSK) digital carrier. Paralleling Saltzberg [1], the principal tool utilized is the CramérChernoff bounding technique. The interference effects can be characterized by equating the larger interferers to an equivalent coherent canceling sine wave and the remaining interferers to an equivalent incoherent source of thermal noise. Subject to an envelope constraint, any allocation of the interferers between a canceling sine wave and thermal noise is allowed. Conditions are developed for the case: 1) when all the interference should be allocated to thermal noise; and 2) when as much as possible of the interference should be allocated to a canceling sine wave. This provides insight into the formal procedure of equating interference as additional thermal noise.

This paper considers the problem of intersymbol interference in a binary communication system and the optimization of a class of linear receivers to minimize the effects of this interference. The class of correlation receivers is chosen for investigation, and maximizing the probability of correct reception is used as the performance criterion. The optimum decision level as well as optimum impulse response is determined for receivers with and without memory where a priori knowledge of the channel characteristics are available. The performances of these receivers are evaluated and compared with nonoptimum linear receivers.