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The use of a flexible transmit multiple-beam antenna (MBA) connected to a nonlinear satellite repeater is investigated as a means of adaptive resource allocation in a common-user communications network comprising different types and deployments of earth terminals. Such a general-purpose network is typically encountered in hybrid systems architectures supporting international command and control functions, e.g., in defense alliances or in maritime mobile services shared by several national administrations. A priori strategies for the adjustment of MBA gains and carrier powers are determined such that the performance of an FDMA or CDMA network is optimized (in terms of the chosen strategy), taking account of realistic uplink, repeater, and downlink noise contributions. Simple formulas are derived for evaluation and comparison of different repeater and antenna designs in the various possible operational scenarios; these formulas obviate the need for detailed a priori allocation of all link parameters in the assessment of network traffic capacity, fading margins, etc. Numerical studies of three hypothetical network scenarios are included to illustrate the increased significance of nonlinear effects (such as intermodulation noise) in any satellite system in which a flexible transmit MBA can enhance the performance. This emphasizes the need for careful planning and operational control of such flexible systems.