Abstract: The possibility of overload (saturation-lockup) condition of an ALPC satellite communication network is avoided by a scheme that grants network entry (allocates TWT power) to each link one at a time. As each link is granted entry into the network, the corresponding TWT probability density function is computed and then integrated to obtain a TWT cumulative distribution function. The required rain margin M.sub.r for a specified availability is determined from the cumulative margin. The computed margin M.sub.r is set equal to the initial satellite TWT operating point change (multiplicative factor) MR.sub.1 due to rain fade, MF.sub.1 =M.sub.r to ensure that network stability considerations and rain fades equally constrain network performance. This result is then used to compute the value of the corresponding multiplicative factor MF.sub.2.

Abstract: To measure the figure of merit (G/T) and beam radial pointing error of a satellite earth station multiple Y-factor measurement are taken using a "drift cut" procedure and then these measurements are processed using a maximum likelihood estimate (MLE) algorithm. For carrying out the "drift cut" measurement process, the earth terminal's antenna is positioned such that the antenna beam intersects the path of the apparent star motion with a predetermined declination offset and ahead of the current star position. As the star position approaches the stationary antenna beam position, power measurements uniformly spaced in time are recorded. These power measurement "samples" are then divided by the "cold sky" power measurement to obtain corresponding Y-factor measurements. To eliminate the problem of antenna pointing error and star ephemeris error, multiple drift cuts are carried out, each offset in declination by a different amount from the estimate star declination, to produce a matrix of Y-factor values.

Abstract: A repeatered, multichannel fiber optic communication network includes a plurality of full duplex fiber optic channels and one or more auxiliary channels. In order to supervise and control the operation of the network, for both data transmission and fault/maintenance actions, each terminal station contains a processor-based subsystem capable of network monitoring, first level maintenance action, fault isolation, and remote network control and status reporting. This processor-based subsystem interfaces with each fiber optic channel, with an orderwire communication link, and with external input/output devices and surveillance equipment. Three substantially autonomous processor-based sections which are dedicated to performing specific functions within the overall network operation are employed for carrying out these separate interfacing tasks.

Abstract: In a communication system containing a scheme for externally synchronizing and scrambling digital data signals, serial digital data signals to be transmitted are subdivided into prescribed numbers or sets between which additional or overhead bits are inserted, the resulting sequence being summed in a modulo-two adder with a multi-bit maximal length PN sequence, so that one of the overhead bits is one of the bits of the maximal length scrambling sequence.A multiplexing operation yields a higher data rate sequence which is then modulo-two added with the output of a scrambler and transmitted.At the receiver station, the incoming scrambled sequence is applied to timing recovery circuitry including a local framing sequence generator. The framing sequence is located and the stages of a separate shift register, which forms part of a descrambler PN sequence generator, are forced to a state which is coincident with the frame marker.

Abstract: A television communication system distributes plural VSB digitally encoded TV channels via an optical transmission link to one or more distribution terminals. At the headend the frequency band of each of the VSB signals is shifted down to baseband and transmitted in digital format. At each station along the network, the digitized baseband VSB television signal is converted into analog format and then reshifted through an up-converter to its original IF band so as to be compatible with the television receiver circuitry of the subscribers served by the distribution station. Advantageously, the present invention may employ optical communication techniques for coupling the digitally encoded frequency-shifted VSB television signals between stations. To maintain signal strength and quality, repeater units may be located in the optical communication link.