Showing papers on "Communications system published in 1979"

Modeling and Performance Evaluation of Nonlinear Satellite Links-A Volterra Series Approach

Abstract: An analytical solution to the problem of modeling bandpass nonlinear channels and evaluating the performance of digital communication systems operating on them is presented. A method based on a Volterra series representation of the overall channel is first proposed, which allows one to extend to nonlinearities with memory the well-known concepts of complex envelope of bandpass signals and low-pass equivalent of bandpass linear systems. The general results previously mentioned are then applied to digital satellite communication systems operating over nonlinear channels. The effect of a nonlinear amplifier located in the satellite is considered, in combination with that of transmitting and receiving filters located in the Earth stations. In addition, both uplink and downlink noise are taken into account. Basic advantages of this approach are the generality it offers to the analysis and the fact that it allows accurate evaluation of the error probability in a short computer time.

Electronic audio communication system

Abstract: An advanced electronic telecommunication system is provided for the deposit, storage and delivery of audio messages. A Voice Message System (10) interconnects multiple private branch exchanges (12) of a subscriber with a central telephone office (22). Individual subscriber users may access the Voice Message System (10) through ON NET telephones (18) or OFF NET telephones (24). The Voice Message System (10) includes an administrative subsystem (60), call processor subsystem (62) and a data storage subsystem (64). The Voice Message System (10) enables the user to deposit a message in data storage subsystem (64) for automatic delivery to other addressees connected to the system. The Voice Message System (10) also enables a user to access the system to determine if any messages have been in the data storage subsystem (64) for him. Pre-recorded instructional messages are deposited in the data storage subsystem (64) for instructing a user on his progress in using the system. A Universal Control Board is a programmable electronic digital signal processing means for controlling certain functions of the administrative subsystem (60), call processor subsystem (62) and data storage subsystem (64).

Fiber optics communication system

Abstract: A fiber optics transceiver transmits and receives either synchronous or asynchronous data through a fiber optics data communication cable. The transceiver is connected to one end of the cable and communicates with an identical transceiver at the other end of the cable. The transceiver includes a transmitter for converting electrical digital data from a data source connected to the transmitter to optical flux for the cable. For asynchronous data, the flux comprises a train of positive-going pulses when the data is at a logical ONE, and a train of negaitve-going pulses when the data is at a logical ZERO. The train of pulses is interspaced at a fixed time interval and is restarted at each transition of the data between the logical ONE and logical ZERO state. For synchronous data, the flux comprises a train of positive-going pulses when the data is at a logical ONE, and a train of negative-going pulses when the data is at a logical ZERO. Each of the pulses in the train correspond to one transition of a clock waveform to which the data is synchronized. The transceiver also includes a receiver for converting optical flux from the cable to electrical digital data for data equipment connected to the receiver. For flux generated from asynchronous data, the receiver reconstructs the data. For flux generated from synchronous data, the receiver reconstructs both the data and the clock to which the data was synchronized. The transceiver also includes provisions for indicating the operationality of the data communications system formed by the two transceivers and the cable.

Digital bus communications system

Abstract: A time division multiple access communications system includes a plurality of terminals coupled to a common signal path, or bus. In one form of the invention, time slots are allocated on a relatively static basis to various requesting terminals to establish communication links over the bus. Control of bus access and communication link formation is distributed over the entire system, wherein at least one terminal having the slot allocation capability may address selected other terminals and allocate the capability among those other terminals. In a second form, subscriber terminals contend for access to the bus. In a third form, a dual mode communication system is provided incorporating both the allocation and contention modes of operation.

The Sydney coordinated adaptive traffic system

Abstract: The Department of Main Roads, New South Wales is currently installing a utc system of 1,000 sets of traffic signals in the Sydney metropolitan area of 1500 km2. The system comprises 11 regional minicomputers which are supervised by one centrally located minicomputer. All of the local controllers are microcomputers. The system architecture is one of distributed intelligence with a comprehensive and flexible communication system. An important feature is its integral cableless link mode of operation as a fall back option. The plans and schedules for this operation are stored in the microcomputers from the regional computer and the local clocks are regularly checked. The normal mode of coordination is the dynamic method first developed for the Sydney CBD system of 150 sets of signals. The method dynamically adjusts cycle, split and offsets in response to variations in traffic demand and capacity. Sufficient evidence exists to show that the method can produce significant improvements in delay reduction when compared to the optimised fixed time methods preferred by most other authorities. The system design incorporates facilities for centralised volume counting, control of reversible lanes and variable message signs (a).

Method and apparatus for interfacing stations in a multiloop communications system

Abstract: A multiloop communications system and a method of routing data between stations is disclosed. The communications system has a plurality of interconnected communications loops, each of the loops including a ring-connected set of nodes providing data flow unidirectionally from one node to the next, each of the nodes being capable of passing data through itself along its loop, extracting data from its loop or injecting data into its loop. A first subset of each loop's set of nodes are local nodes which interface a station to its respective loop. A second subset of each loop's set of nodes are gateway nodes which interface to a gateway node of another of the loops. Each of the stations has a logical address unique within the system and each of the nodes has a functional address unique within each node's respective loop. A first station transmits data to a second station via the first station's local node, the local node forming a packet including the functional address of a node providing a route to the second station and further including the logical address of the second station. If the path to the second station includes a transfer to another loop, the gateway node on the transmitting loop transfers the logical address of the second station to the gateway node of the receiving loop. The gateway node of the receiving loop forms a new packet of data utilizing the logical address of the second station and a table which specifies the functional address of the route to be taken to second station. The system and method additionally provides for alternate routing in the case when the most direct path between the transmitting and receiving stations is inoperative.

Multiple access digital communications system

Abstract: OF THE DISCLOSURE An unslotted radio frequency multiple access bus communications system employing a contention listen-while-talk (LWT) protocol. The system includes a plurality of remotely located terminals coupled to a communications bus. The bus includes a pair of oppositely directed, unidirectional signal paths which are connected at one end so that one path is an inbound path to that end and the second is an outbound path from that end. Each of the remote terminals includes a bus interface unit (BIU) coupled to both the inbound and outbound paths at the remote location. Each BIU is adapted to transmit and receive modulated carrier signals on the inbound and outbound paths, respectively. When a terminal wishes to send a message to another terminal, the terminal's BIU initially performs an rf carrier sensing operation to make an initial determination as to whether or not any other subscriber is transmitting on the inbound path. In the event no carrier is detected, the BIU confirms this determination by first beginning to transmit a message packet modulated on a carrier signal and addressed to the desired receiving terminal on the inbound path, and then monitoring the outbound path during a collision window. If the transmitted message is received intact by the transmitting terminal within this collision window, the transmitting terminal's BIU determines that no collision has taken place between its message and a message sent by another terminal or noise, and that the transmitting terminal has gained access to the bus Thereafter, the BIU may transmit any remaining portion of its message packet on the inbound path However, in the event a collision is detected, the transmitting terminal's BIU aborts its transmission and then backs off for a random time period before again attempting to gain access to the bus and transmit its message.

Communications system and network

Abstract: A communications system and network wherein communications links between subscribers are established by retrodirective oscillating loops between each subscriber and a node station. Provision is also made for establishment of retrodirective oscillating loops between nodes so that remotely located subscribers can communicate. Information is transmitted between subscribers by using a mixing process in the node whereby information transmitted from one subscriber to a node is transferred to a carrier signal transmitted between nodes or between a second node and another subscriber. A sampling technique is also described for use in the node which greatly minimizes the amount of apparatus required to implement the mixing process.

Distribution automation system

Abstract: A data communications system for conveying load control commands, power usage data, and other data on electric power lines. A remote module for reading the power usage meters and controlling loads is disposed at each power usage location. A group of remote modules convey their power usage data to an associated communications terminal to be accumulated, organized and stored. The group also receives load control commands from the communications terminal to cause them to initiate specific load control functions. There are a plurality of communications terminals disposed at various intervals along the primary distribution feeders. A central control unit collects the usage data from the remote modules, generates load control commands, and the like. Communications between the control unit and a destination communications terminal are relayed by the intermediate communications terminals. If an intermediate communications terminal should fail to relay communications properly, the central control unit and the other communications terminals isolate and by-pass the malfunctioning unit. If a communications terminal should fail to communicate properly with its associated group of remote modules, another communications terminal can be programmed to assume its function.

Space diversity system in TDMA communication system

Abstract: A space diversity system in a TDMA communication system employing a communication satellite, in which in order to equalize the path lengths of respective sending paths at the start of communication, a pre-burst is sent out to one of the paths making up the diversity system in a time slot of one frame assigned to an instant station. A sub-burst is sent out to the other of the paths in the assigned time slot. A relative time difference between the pre-burst and the sub-burst is detected from signals sent back to the instant station from the communication satellite or signals received by a distant terrestral station via the communication satellite. On the basis of the result of a comparison operation of relative time difference between the pre-burst and the sub-burst at the time of their sending-out from the instant station with a relative time difference between the pre-burst and the sub-burst received via the communication satellite, variable delay means inserted in one of the paths is controlled so that the two relative time differences become equal to each other.

System for the quantitative measurement of impairments in the communication channel of a quadrature amplitude modulation data communication system

Abstract: A system is provided for measuring communication channel impairments in a data transmitting system which employs quadrature amplitude modulation. The system rotates each point of sampled eye diagram information by a phase angle determined by the ideal value of the received point information so that the rotated point has its nominally maximum component on the real axis.

Programmable master controller communicating with plural controllers

Abstract: A data communications system having a programmable master controller including memory means and command byte generating means and a plurality of additional controllers providing input data bytes to the master controller and having means for receiving command bytes from the master controller. The additional controllers are each connected to the master controller such that corresponding data bits are ORed together and means are provided for the simultaneous transmission of data bytes from the additional controllers to the master controller such that corresponding bits of the simultaneously transmitted bytes have mutually exclusive data therein.

An office communications system

Abstract: In developing a prototype of an ofice communications system, an office study was first done to specify requirements for the prototype. The study focused on the productivity of three groups of employees: principals, clerical personnel, and secretaries. With requirements set by the management of the ofice used as a framework, application requirements for end users of an ofice communications system were established. From a subset of these requirements the prototype was developed. The prototype system was designed as an experimental learning system to provide managers and professionals with an easy, fast, and direct method for handling their business communications. The prototype was set up on IBM premises for testing and evaluation. Results of this operation are included in the discussion.

Communication system and method having wide dynamic range digital gain control

Abstract: An automatic gain control system and method, utilizing a digital logic attenuator and control in a communication receiver, operates linearly over a wide dynamic range in the amplitude of input signals applied to the receiver to eliminate distortion and frequency intermodulation products inherent in single channel and multi-channel frequency multiplex communication systems.

Serial line communication system

Abstract: A serial line communication system is provided whereby a plurality of remote units are tied to a central site through a serial communication line. Each remote unit is provided with an automatic bit rate detection means. Messages returning from the remotes are checked at the central site for errors. If errors occur, the central site automatically retries to achieve error-free communication. If necessary to achieve error-free communication, the central site is provided with means for automatically shifting to a lower secondary bit rate to achieve communications with a particular remote. The central site then shifts back to the higher primary bit rate for communication with the next remote.

Electrical communications system

Abstract: Disclosed is a system for communicating electrical signals, digital and/or analog, from one location to another first over an RF communications link and then secondly over an optical communications link. A first digital memory is included on the transmitter side of the RF communications link so that a plurality of fixed or portable signal sources can feed data thereto in a desired sequence for subsequent transmission upon demand first to at least one second or interim digital memory at the end of the RF communications link and then to at least one third digital memory at the end of the optical communications link. The third memory is located in a terminal unit, fixed or portable, which is adapted to feed the data transmitted thereto to one or more utilization devices.

Bi-orthogonal PCM communications system employing multiplexed noise codes

Abstract: A bi-orthogonal PCM communications system employing multiplexed noise codeso provide enhanced protection against interference. Two system approaches are described--a first of which employs active, matched filter detection, whereas a second of which employs passive matched filter detection. The noise codes employed are of a type termed code mates having correlation functions which, upon detection, provide an impulse autocorrelation function. The described arrangements afford a transmission efficiency which extends towards Shannon's theorectical limit.

Data detector for a data communication system

Abstract: A data communication system for use in the control and monitoring of mobile stations, for example, in a bus monitoring system, from a central station over a communication channel carrying both data and voice information. Information is encoded into digital messages having a start code followed by one or more data blocks. The start code identifies the beginning of the data block that follows and enables synchronization of clock circuitry to the received data frequency. The data blocks have N digital words with M binary bits where one word is a parity word and N-1 words are data words. Each of the data words has a data portion and parity portion coded for correction of at least one error. Reliability is enhanced by a data detector which discriminates between data and noise or voice to provide an indication of the presence of data. In transmitting the digital messages, the bits of the N words in each data block are interleaved to provide protection against error bursts.

Distributed function communication system for remote devices

Abstract: To effect an accurate transmission of data between processing equipment and a plurality of peripheral devices, first and second interfaces are employed for reconstructing and transmitting the data over a communications link such as a conductor pair. The first interface termed a master terminal which is coupled to a common control module by way of a common control bus, receives instruction, address, and data information from the processor, and transmits a serial data code containing all this information to a plurality of second interfaces, termed slave terminals. Each slave terminal is coupled to a set of peripheral devices by a common bus and when a peripheral device recognizes its address being present in the code received from the master terminal, the slave terminal responds to complete the transaction with the master terminal and the addressed peripheral device.

Fiber-optical data-communication system using carriers of different wavelengths

Abstract: A plurality of data-transmitting stations communicate with respective data-receiving stations via channels using optical carriers of different wavelengths, the several channels sharing a common light guide between an optical multiplexer at an outgoing terminal and an optical demultiplexer at an incoming terminal. To minimize cross-talk between channels, the data streams modulating their carriers are so synchronized that the signal peaks appearing beyond the demultiplexer on any pair of spectrally adjacent channels are relatively offset by half a signal period of their data streams or of the faster one of these two data streams. The synchronization can be carried out through electronic control of the channel modulators at the transmitting stations or with the aid of optical delay lines inserted in every other channel upstream of the multiplexer. A similar phase relationship is maintained between incoming and outgoing data streams at a subscriber station having a transmitter and a receiver communicating via an optical duplexer with a single light guide.

Mobile telephone channel exchange system

Abstract: A mobile telephone communication system is provided with a plurality of mobile units having a transmitter-receiver capable of being tuned to a plurality of radio channels. A plurality of base stations are provided with receivers capable of detecting carrier level drop-off and a control station is operable to command the given base station to transmit an instruction to the mobile unit commanding it to transmit its signal over a channel which is common to all of the base stations. The control station is then operable to detect an increased carrier level in a zone corresponding to a second base station, and to instruct each of the base stations to transmit a signal over the common channel commanding the mobile unit to switch channels to an idle channel corresponding to a second base station.

Multi-direction time division multiplex communication system

Abstract: The inventive system includes a central station and a plurality of satellite stations which communicate on a time division multiplex basis. The central station generates frame synchronizing and clock signals, along with digital communication signals, which are suitably modulated into channel time slots. During its individually assigned channel time slot, each satellite station extracts the frame and clock signals and demodulates the communication signals which were directed to it. The extracted frame and clock signals are used in the satellite station to retime the communication signals which are sent in bursts of modulated carrier waves from the satellite stations to the central station. The central station demodulates the bursts of carrier waves to transmit the intelligence therein to its destination. The advantage is that many stations can share the same frequency and thereby make more efficient use of the transmission capacity.

Modeling communications protocols by automata

Abstract: Using a pair of finite-state automata to model the transmitter-receiver protocol in a data communications system, we derive lower bounds on the size of automata needed to achieve reliable communication across an error-phone channel. We also show that, at the cost of increasing the size of the automata, a transmission rate close to the theoretical maximum can be achieved.

System for in-service quantitative performance analysis of data communications system

Abstract: A data communication system is provided comprising, at a plurality of locations, data terminal equipment. Communication equipment adapted to transmit and/or receive data from location to location is provided at each location connected to the terminal equipment and interconnected between locations through a suitable communications channel or media. An auxiliary signal processor is provided at each location interfaced with the communications equipment and deriving from the communications equipment on a noninterfering basis, information relating to the status of the channel, communications equipment, and data terminal equipment. A central controller is provided at a central location and auxiliary communication equipment is provided at each location interconnected with the central controller and with the auxiliary signal processor.

Automatic gain control circuit in multi-direction time division multiplex communication system

Abstract: The invention is primarily--although not exclusively--directed to an earth-to-satellite communication system using time division multiplex over a common frequency. An automatic gain control circuit in a receiver unit of the ground or central station receives burst signals transmitted in time slots individually assigned to a plurality of satellite stations. The satellite stations are dispersed in multiple directions, which means that the burst signals which they transmit are not received by the central station with the same amplitude. The inventive automatic gain control circuit causes all of the burst signals to achieve a uniform amplitude within the central station. First, the receiver separates and feeds back the various burst signals into a plurality of individually associated branches. Equipment in the separate branches amplifies the individual feedback signals, using low band-pass amplifiers, and then compounds them into a single gain control signal. These control signals adjust the gains of the individual burst signals. The advantage is that the gain may stabilize on individual time slot pulses without a destabilizing effect from grossly different amplitudes of pulses received during intermediate time slots.

The simulcasting technique: An approach to total-area radio coverage

Abstract: The simulcasting technique described provides total-area radio coverage on an automatic basis where the use of multiple transmitter and receiver sites is required to achieve acceptable communications coverage over rugged terrain or wide areas. In this technique the same audio information is simultaneously broadcast over several transmitters operating on a single nominal-carrier frequency. Special attention must be given to transmitter-frequency stability and audio envelope characteristics. A master tone-distribution system is essential when incorporating a continuous tone-controlled squelch system (CTCSS). Use of the simulcasting technique reduces effects of fading in a mobile environment through transmitter space diversity. An application of the simulcasting technique to a coordinated FM-UHF law-enforcement communications system in Orange County, CA, is described.

Communication method and system

Abstract: This communication system reduces required data transmission channel capacity by encoding source words into encoded words with usually less binary bits for transmission. Features of the invention include a hashing algorithm which transforms the source words into psuedorandom code words used for both transmission and addresses in a vocabulary memory. Before transmission each source word and its hash code is checked against a pre-recorded vocabulary memory to decide which should be transmitted.

Facsimile communication system

Abstract: PURPOSE:To report securely a communication message to a facsimile terminal even in case that the facsimile terminal is engaged, by using a selective calling receiver such as a pocketable bell using radio waves as a reporting method of extracting and reporting a communication message to a facsimile terminal in a facsimile communication system that offers the storage service of a mail box, etc CONSTITUTION:When communicating message addressed to terminal 11 are stored in memory 14, storage converter 13 sends callig signal 24 for calling corresponding facsimile terminal 11 to radio unit 16 via signal line 15 Unit 16 converts this signal 24 into radio calling signal matched with radio transmission line 17 and signal 25 is sent to pocketable bell 18 Receiving calling signal 25, pocketable bell 18 sends terminal control signal 26 to terminal 11 To extract a communication message addressed to itself, facsimile terminal 11 transmits communication-message extraction request signal 27 including a predetermined key number from automatic transmitter 20 to converter 13 through circuit 12 Converter 13 makes sure of the coincidence of the key number of decoding the request signal and then sends communication message 23 is memory 14 to terminal 11

Efficient Packet Satellite Communications

Abstract: This paper gives an extensive analysis of a Packet satellite (PACSAT) communications system that uses a digital processing satellite in a packet data network. It is shown that multiple uplinks coupled with on-board switching and storage can provide significant gains in throughput, efficiency, and margin against instability. Design tradeoffs are presented and the theoretical results are verified by extensive computer simulations.

Digital communication system fault isolation circuit

Abstract: There is disclosed, for use in a digital communication system, a fault detector circuit operable for removing faulty stations from the system. The disclosed circuit uses a distributed bypass isolation technique and may be used with individual stations or with groups of stations. A multi-bit delay register is connected across each station or station group and the output of the delay register is compared with the output of the parallel stations. When differences in the compared bits are detected the parallel stations are immediately isolated from the system and the bits from the delay register are placed in the system to preserve synchronism. This arrangement has the advantage of allowing immediate corrective action to occur to protect the sanity of the system. In situations where the system is divided into a voice digital bus and a data digital bus different error techniques may be employed for each bus.