Showing papers on "Telecommunications link published in 1978"

Advanced data link controller

Abstract: A bit-oriented data link controller provides the interface between a microcomputer or terminal and a data communications link. The data link controller is capable of accommodating the three most commonly available bit-oriented data link control protocols, namely Synchronous Data Link Control SDLC, High Level Data Link Control HDLC, and Advanced Data Communications Control Procedure ADCCP. The data link controller provides the data communications interface for both primary and secondary stations in stand-alone, polling, and loop configurations.

A Polarization Control System for Satellite Communications with Multiple Uplinks

Abstract: Orthogonal polarizations will be more and more widely used in satellite communications in the near future because of their efficiency in utilizing the spectrum, but the currently designed compensation control systems can compensate for signals coming from only one uplink station. This paper therefore discusses generally the control schemes feasible to solve the multiple Uplink problem, in which there are many stations transmitting uplink signals simultaneously. The general approach proposed is that for each uplink station two Compensators can be used to compensate for the uplink and, downlink separately. This will require the station to transmit its own pilot signals and receive them back from the satellite as the control reference. Two basic techniques can be used to realize this approach. The first, correlation technique, is based on the assumption that an obtainable correlation between uplink and downlink cross-polarizations exists, and tries to compensate for uplink and downlink separately using this correlation. The second, separate link technique, uses an additional pair of pilotsignals to obtain seiJarate control references and decouples the compensations of uplink and downlink. The discussions indicate that the separate downlink technique, whose design considerations and system performance are examined carefully is most attractive.

Communications: Spot beams promise satellite communication breakthrough: Focused antenna beams with frequencies accessed by time division can mean higher uplink power and more powerful communication service

Abstract: A technique has been found that uses TDMA to provide high antenna gain over a wide area of coverage. This scanning spot-beam antennas technique provides higher uplink power and more powerful communication service.

Packet switching in a processing satellite

Abstract: This brief note represents a simple but significant change in the thinking that is applied to satellite packet switching. It demonstrates that in a precessing satellite there is no fundamental limitation to the efficiency and throughput of packet switching systems. With a minimal impact on spacecraft weight and power, throughput is increased by providing more capacity on the uplink than on the downlink. Efficiency is increased because the power-intensive downlink is more fully utilized. A slotted ALOHA example is given to show how the performance can be made to go from that of conventional slotted ALOHA to that of a TDM system. Several possible variations and far-reaching implications are indicated.

Apparatus and method for controlling crosspolarization of signals in a frequency reuse system

Abstract: Apparatus and method for controlling the crosspolarization of signals in a satellite communications, frequency reuse system. Each earth station in the system includes one crosscoupling network that compensates for the crosspolarization of signals transmitted by such earth station uplink to the satellite due to the propagative medium around such earth station, and an adaptive feedback control system having another crosscoupling network that compensates for the crosspolarization of signals received from the other earth stations due to such propagative medium around such earth station.

Telecommunications Technology in the 1980s

Abstract: An overview of advances in telecommunications technology that can be anticipated in commercial systems during the 1980s.

Data communications networks

Abstract: This paper addresses the development of Canada's data communications networks in the context of the development of Canada's resources for all Canadians. Communications provide a means to conserve and/or make more effective use of other valuable Canadian resources. Also these networks are resources themselves. These aspects are discussed with particular reference to TCTS's most recent data network, Datapac, a commercial packet-switched network.

The communication system

Abstract: The paper discusses the salient features of system design considerations for both uplink and downlink, subsystem details and the in-orbit performance of the communication system forAryabhata.

Performances of regenerative and non-regenerative satellite repeaters with MPSK signalling

Abstract: Linear (translation), hard-limited, and demod/remod types of satellite repeaters are considered in this paper. Both uncoded and coded multiple phase shift keyed (MPSK) signals are assumed to be transmitted through these repeaters. Relative performances of these repeaters in the presence of uplink and downlink noises are then compared quantitatively. Probabilities of bit errors and the computational cutoff rates are computed for 2, 4, and 8 phases PSK signals, with uplink and downlink SNRs as parameters.