The authors discuss many satellite communications systems and technology concepts that can be expected by the year 2000. Challenges and changes that are taking place in the commercial market place are discussed. Technology advances that promise to enable future communications satellites to capture their share of the future marketplace are discussed. Current, near-term, and far-term technologies are discussed.>

This paper describes an analog speech scrambler using the FFT technique (FFT scrambler). The FFT scrambler provides highly secured scrambled signal by permuting a large number of FFT coefficients. Important items to be considered in the designing of the FFT scrambler are discussed, such as FFT frame length, permutation of FFT coefficients, and frame synchronization, in addition to the configuration of the experimental FFT scrambler. Possible causes for the degradation of the descrambled signal, such as transmission channel group delay and intersymbol interference, are also discussed, together with experimental results.

The limitation in the effective use of the geostationary orbit is the intersatellite interference problem. A theoretical approach to realize an optimal usage of the orbit is provided in this paper, with particular attention to the constraints of service arcs, existence of spotbeam operating systems and different frequency plannings. The problem is formulated as a nonlinear programming problem and the sequential unconstrained minimization technique is applied to solve it numerically. Example computations are also given and various interference criteria are evaluated in terms of orbit utilization.