Harris Corporation

Charles R Patisaul

William C Adams, Jr

Peter H Halpern

James W Toy

Paul W Casper

Norman C Seiler

George A Waschka, Jr

Fred J Orlando

J Richard Jones

Willie T Burton, Jr

Thomas J Nixon

Ronald R Giri

Gerald S Duggan

Harold Iley

W B Ashley

Fred R McDevitt

Edwin R Tarmain

Donald G Monteith

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. These two factors, when expressed in decibels, may be added to the nominal (no rain) TWT operating point (also expressed in decibel notation) to predict the maximum TWT operating point value in response to rain stress at the specified system availability. This predicted maximum TWT operating point is then compared to the analytically determined value of the TWT stability point. If the TWT stability point is not exceeded for the current number of links then an additional link may be added, otherwise, the last link requesting entry into the network is denied access. After the maximum permissible number of terminals has been accommodated, the final actual values of TWT stability point, stability margin, and link availability are computed and the allocation process is terminated.

Optimal satellite TWT power allocation process for achieving requested

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. This matrix of drift cut Y-factors is then processed using a maximum likelihood estimate algorithm, to provide MLE measures of that earth terminal's figure of merit and beam radial pointing error.

Maximum likelihood estimation of G/T of satellite earth terminals using

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. Each section of the processor-based subsystem in a terminal station contains its own CPU and associated memory and is programmed to carry out specific functions identified with that section. Each section is interconnected with the other two so that, internally, the subsystem is fully integrated.

Repeatered, multi-channel fiber optic communication network having fault

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. This shift register is clocked at the incoming data rate by the recovered clock from a timing recovery circuitry and its output is modulo-two added with the incoming digital data stream, thereby recovering the original multiplexed data. In order to recover the original data, the descrambled sequence is applied to a demultiplexer which effectively deletes every overhead bit and outputs the original data at the original data rate.

Combined use of PN sequence for data scrambling and frame

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. Each repeater converts an incoming optical signal to an electrical signal for amplification and then reconverts the improved electrical signal back into optical form for further transmission along the link.

Digital, frequency-translated, plural-channel, vestigial sideband

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Melbourne, FL, United States of America

Charles R Patisaul