Showing papers on "Communications system published in 1989"

Code division multiple-access techniques in optical fiber networks. II. Systems performance analysis

Abstract: For pt.I see ibid., vol.37, no.8, p.824-33 (1989). In Part I a technique based on optical orthogonal codes was presented to establish a fiber-optic code-division multiple-access (FO-CDMA) communications system. The results are used to derive the bit error rate of the proposed FO-CDMA system as a function of data rate, code length, code weight, number of users, and receiver threshold. The performance characteristics for a variety of system parameters are discussed. A means of reducing the effective multiple-access interference signal by placing an optical hard-limiter at the front end of the desired optical correlator is presented. Performance calculations are shown for the FO-CDMA with an ideal optical hard-limiter, and it is shown that using an optical hard-limiter would, in general, improve system performance. >

Portable hybrid communication system and methods

Abstract: A laptop device includes a personal computer, a cellular transceiver, a speakerphone, and a hybrid communications control unit. The device has connectors for attaching a headset, cellular control unit, land telephone line, and additional speakers and microphones. The micro-processor-controlled hybrid communications control unit includes a modem, a data access arrangement, and a tone generator as well as digital, analog, and power switches. The hybrid communications control unit switches the communications components and provides, under program control, the proper protocols, level, and impedance matching to connect the modem, speakerphone, headset, speaker/microphone, or cellular control unit to the landline or to the cellular network via the transceiver. Matching and switching operations are automatic and transparent to the user. The unit can also connect two of the terminal devices or connect the cellular and landlines for call relaying. The device is capable of connecting plural calls at the same time. The hybrid communications control unit may be controlled by its internal firmware, by toggle switches, or by commands issued from the personal computer.

Mobile radio data communication system and method

Abstract: In an exemplary embodiment, a test signal is sent by a base station at a suitable point in a communi­ications protocol. According to the evaluation of the test signal transmission, a relatively high data rate or a lower more conservative data rate is selected by a mobile unit for the transmission of a relatively lengthy data message. The test signal can be associated with a query from a mobile unit having a message to send, or with a contention polling message from the base. Such test signal can be transmitted at the lower data rate where its transmission characteristics (e.g. signal strength, jitter or quality of transmission of known information) can be used to predict probable feasibility of transmission at the higher data rate, but most preferably the test signal is part of a high data rate contention poll which may alternate with a low data rate contention poll.

Wireless Optical Communication Systems

Abstract: Wireless Optical Communication Systems addresses the problem of designing efficient signaling and provides a link between the areas of communication theory and modem design for amplitude constrained linear optical intensity channel. Topics include historical perspective, channel impairments, amplitude constraints and the characteristics of popular optoelectronic components. A variety of wireless optical channel topologies are presented along with a survey and analysis of present day signalling techniques employed for these channels. The author provides a unifying framework for signalling design which allows the channel constraints to be represented geometrically and permits the use of modem design principles from electrical channels. Modulation schemes are designed using the formalism of lattice codes and a design process for signalling sets is specified. The use of multiple-input/multiple-output (MIMO) wireless optical channels to improve the spectral efficiency of links is explored. The basic spatio-temporal modem design problem is specified and a spatial multiplexing gain is quantified. New spatial discrete multitone modulation is proposed and the unique features are discussed. Based on measurements on an experimental prototype, a channel model is formulated and a realizable spatio-temporal coding scheme is simulated to quantify performance gains. This volume is organized for professional and academic readers engaged in modem design for wireless optical intensity channels. Significant background material is presented on both the properties as well as on fundamental communications principles. Wireless Optical Communication Systems can be used by physicists and experimentalists as an introduction to signalling design as well as communication systems designers.

Spread spectrum communications system for networks

Abstract: Spread spectrum chirps (i.e., wideband frequency packets) are propagated on a local area network in a hostile communications environment, such as a powerline or a crowded radio frequency band. chirps are self-synchronizing, data bit (or subdata bit) in length and detectable by all network nodes, to allow the contention resolution and collision detection needed to support carrier-sense based network protocols. A matched filter of the same time length and encoding sequence as the transmitted chirp provides the self-synchronized chirp reception at each receiver.

Satellite cellular telephone and data communication system

Abstract: A system for facilitating global cellular/trunked mobile communication is disclosed. This system permits communication with hand held and mobile mounted cellular telephones. The system permits two-way communications anywhere on or above the earth up to a particular height above the earth of several hundred nautical miles. The system employs a number of low-earth orbiting satellites moving about the earth in orbit. Links are provided from the satellites directly to the users and via the public switched telephone network to other users. The satellites are interconnected via links in a ring structure surrounding the earth. Switching is performed by each of the satellites. In addition, each of the satellites hands off a call as it moves out of the range of a particular user.

Communications, information, maintenance diagnostic and training system

Abstract: A data and communication system including a hand-held unit (17) and an infrared communication satellite (10) is used to provide for the interchange of data between a host computer (13), individual personal computers (15), the hand-held computing unit (17) and factory machinery, including process controllers.

Guaranteed reliable broadcast network

Abstract: This system guarantees reliable data transmission for one-to-one, one-to-many and/or many-to-many communications among data processing stations over a communications network. A general solution is presented, and a new concept (the arbitrator node) is discussed in detail. Special logical nodes and a new communications protocol are used so that a message is guaranteed to be received if a receiver(s) wants to receive the message even though a receiver(s) may be busy, slow or temporarily powered off. An optional management station controls orderly start and stop of group communications or conferences, and may also handle secure, confidential communications. This guaranteed, reliable, one-to-one, one-to-many or many-to-many system can be applied to overcome previously unsolved problems.

Propagation effects handbook for satellite systems design. A summary of propagation impairments on 10 to 100 GHz satellite links with techniques for system design

Abstract: The NASA Propagation Effects Handbook for Satellite Systems Design provides a systematic compilation of the major propagation effects experienced on space-Earth paths in the 10 to 100 GHz frequency band region It provides both a detailed description of the propagation phenomenon and a summary of the impact of the effect on the communications system design and performance Chapter 2 through 5 describe the propagation effects, prediction models, and available experimental data bases In Chapter 6, design techniques and prediction methods available for evaluating propagation effects on space-Earth communication systems are presented Chapter 7 addresses the system design process and how the effects of propagation on system design and performance should be considered and how that can be mitigated Examples of operational and planned Ku, Ka, and EHF satellite communications systems are given

Modulation and demodulation system employing AM-PSK and FSK for communication system using digital signals

Abstract: A communication network having a first broadband communications channel or transmitting bus and a second broadband communications channel or receiving bus, wherein the first broadband communications channel is for passing information upstream to a head end and the second broadband communications channel is for passing information downstream from the head end to remote nodes. All nodes of the system are coupled to both the first communications channel and the second communications channel. According to the invention, modulation of signals applied to the first communication channel is optimized for burst communication from a plurality of sources to central control at the head end, and modulation applied to the second communications channel is optimized for continuous communication from the central source to a target node.

Frequency division multiplex guardband communication system for sending information over the guardbands

Abstract: A frequency division multiplex guardband communication system is provided which increases the communication capability of conventional FDM systems with negligible effect on overall system performance. The additional capacity is achieved through the use of guardbands which lie between the information bands of the FDM. To avoid interfering with recovery of the FDM information, the amount of new signal energy added to the individual guardbands is well below the guardband noise level.

Channel selection in a multi-frequency radio data communication system

Abstract: A method and apparatus are disclosed for improved channel selection in a multi-frequency radio data communications system whereby a minimum level of signal/service quality may be maintained at all times without unduly impacting channel loading considerations. Specialized idle messages are utilized in the outbound channel of the radio system which are required in any event but include added information for the monitoring remote terminals to determine channel quality and take appropriate action by selecting a new channel to operate on if channel quality falls below a preset threshold level.

On-site communication system with rf shielding having pager identification capability

Abstract: An on-site communication system includes a system for identifying communication receivers including acknowledge back capability and operating within the on-site communication system, and for controlling the delivery of messages to the communication receivers. The identification system operates on the same frequency as the on-site communication system, and includes an RF shielded enclosure for momentarily shielding the communication receivers from messsages transmitted on the on-site communication system. The RF shielded enclosure provides interference free identification of the communication receivers as the communication receivers pass through the enclosure, and enables the determination of those communication receivers which are operating within the coverage area of the on-site communication system, and those communication receivers which have left the coverage area of the on-site communication system.

Mobile communication systems

Abstract: From the Publisher: Presents the fundamental aspects of mobile communications systems. Covers the radio communications channel, its wide-band and narrow-band characterization, and its utilization in mobile and cellular communications systems. Both analogue and digital systems are considered, with emphasis on the latter. Discusses the propagation of signals (including propagation in urban areas), the interference created by the terrain, digital techniques associated with two-way, speech-based communication systems, the TACS cellular system, and digital techniques for high capacity cellular systems. Illustrated.

Method and apparatus for controlling transmission of voice and data signals

Abstract: The present invention provides a control circuit for controlling the path of voice and data signals in a communication system which comprises at least a speaker phone (28), a cellular transmit/receive unit (TRU) (16), a cellular (CU) handset (20) and a computer (12) having at least a communications software program (68), a keyboard (64) and an I/O port (30) for communications. The control circuit receives voice and data signals from a plurality of different input sources and routes or switches the received voice and data signals to different selectable destinations. The control circuit comprises analog switching circuitry (54), a CPU (32), a modem (56), landline interface circuitry (38), TRU interface circuitry (40) and cellular handset interface circuitry (42) which are operatively connected together.

Secure optical-fiber communication system

Abstract: A data signal and a reference signal are multiplexed into a fiber optic communications link for transmission from a first secure location to a seond location. A replica of the reference signal is transmitted from the first location to the second location over a separate communication channel. At the second location, the angular phase difference between the reference signal and the replica thereof is continuously monitored. If the angular phase difference departs significantly from a specified value, an alarm is set as a warning that the fiber optic communications link has been compromised.

Multiple access communication system

Abstract: The multiple access communication system according to the invention comprises at least one primary station (2) and a plurality of secondary stations (32, 34, 36). The primary station (2) and the secondary stations (32, 34, 36) are interconnected via a network, e.g. a coaxial cable network or a hybrid fiber/coax network. The secondary stations (32, 34, 36) can transmit return signals in a return signal frequency band to the primary station (2). However, the secondary stations (32, 34, 36) are arranged for transmitting the return signals in only a part of the return signal frequency band containing relatively little noise, e.g. the upper part of the return signal frequency band. The network comprises means (40) for mapping the return signals of the secondary stations (32, 34, 36) onto the full return signal frequency band, e.g. by means of a frequency converter (48, 50). In this way, the communication system is much less sensitive to noise, while still the same number of secondary stations (32, 34, 36) can be handled by the communication system.

Multilayer perceptron structures applied to adaptive equalisers for data communications

Abstract: The authors demonstrate the application of multilayer perceptrons to the problem of equalization in digital communications systems. Following a brief description of the architecture of the multilayer perceptron, the authors investigate its capabilities as a channel equalizer and show that they are superior to those of the linear equalizer. The comparison is effected by simple examples that show graphically why the nonlinear architecture provides better results, and also by an investigation of bit-error rates in a higher dimensional situation. It is concluded that the multilayer perceptron offers advantages over the linear transversal equalizer in a number of areas. Its ability to form decision regions with nonlinear boundaries enables it to equalize both minimum-phase and non-minimum-phase channels without the introduction of any timing delay, a capability that may be of value in nonstationary environments. >

Method and means of operating a power line carrier communication system

Abstract: A power line carrier (PLC) communication system operating on a conventional three wire (Hot (H), Neutral (N) and Ground (G) wires) power line uses more than one of the several RF transmission lines that are defined by the three wire power line to improve communication between units of the PLC system. According to a first embodiment a PLC system transmitter sends out of phase RF signals across the H and G wires and across the N and G power wires to the PLC system receiver, which receives and combines both of the out of phase transmissions, and so even if one of these paths is severely attenuated, the other path can deliver a sufficiently strong RF signal to the receiver for effective communications. According to another embodiment three different pairs of the H, N and G wires of the power line are selected in sequence for transmission of the PLC system RF and the pair that results in the best communication between a system transmitter and receiver is used for continuing communication. Also included is a PLC telephone extension system for which there is full duplex communication between each of the extension telephones of the system at different locations in the premises and the premises telephone line.

Bus interconnection structure with redundancy linking plurality of groups of processors, with servers for each group mounted on chassis

Abstract: An interactive system for the transmission of media presentations has an interchassis communications system capable of quickly transmitting large amounts of data between its components. High efficiency of transmission is achieved by providing an industry standard interface for various types of chassis and processors forming the system. The processors and their interfaces used to transmit data within the system are interconnected so as to allow completion of the transmission of data between any two points within the system by no more than three hops between chassis.

Central postage data communication network

Abstract: A communication system for processing information for distribution, including: a central data station, a plurality of user stations, each of the user stations including a plurality of components forming a secure path for the proper distribution of the information, a communication link interconnecting the user stations with the central data stations, the central data station including means for periodically interrogating a user station for determining the operational status of each of the components, means located within the central data station for indicating an error condition in any one of the components, and means at the central data station for transmitting a condition signal from the central data station to the user station for indicating the error condition.

Emerging optical code-division multiple access communication systems

Abstract: All-optical systems, which perform signal processing functions optically so that the signal conversion from optical to electrical is done only when desired, are considered. Three such schemes are discussed, namely, fiber-optic code-division multiple-access (CDMA) systems, neuromorphic CDMA systems, and ultrashort-light-pulse CDMA systems. Fiber-optic CDMA systems in which incoherent optical signal processing techniques are used to establish optical CDMA systems are first examined. In particular, a novel class of sequences for incoherent fiber-optic CDMA systems, called optical orthogonal codes, are discussed. The codes are then applied to neuromorphic optical systems, and various applications of the networks are examined. Recent experiments that demonstrate the ability to encode and decode extremely fast, femtosecond optical pulses and that suggest the possibility of ultrahigh-speed CDMA systems based on ultrashort light pulses are described. >

Wireless indoor data communication system

Abstract: Described is an intraoffice communication system as the final communication link of a broadband, baseband, or fiber optic LAN. Each user or workstation is a node on the network and can transmit at high data rates with bit error rates of ≦10-9 in packets through the LAN. Message relaying transponders are placed on the ceiling and walls communicating by electromagnetic waves to individual workstations by broadcast. A novel multipath rejection scheme is combining transponder placements with pseudonoise coding for robust and secure data transmission. For the present state of the art if infrared is used, we estimate a minimum light collecting aperture (receive antenna) of 1 cm2 for transmission rates of 30 to 100 Mb/s.

Implementing OSI systems

Abstract: The correct and efficient implementation of complete open systems interconnection systems comprising the specified multiple layers of complex protocols is discussed. Also examined are the specification, design, and implementation issues and approaches at two levels: the realization of the individual protocols; and the construction of complete multilayer communication systems. The design of a multilayer communication subsystem which can run on the same processor as the applications or be confined to a front-end processor is discussed. >

Technique for improving the operation of decision feedback equalizers in communications systems utilizing error correction

Abstract: The combined benefits of decision feedback equalization and error correction coding are realized in a communications system by the use of a plurality of coders and decoders respectively disposed in the transmitter and receiver. The plurality of encoders and decoders is used to interleave the data symbols so that each coder and decoder is operative upon every Mth symbol, where M is the number of coders or decoders. By a judicious choice of M, both the probability of noise impairing the recovery of successive symbols and the error propagation effects inherent in decision feedback equalizers are reduced.

Optimum rate Reed-Solomon codes for frequency-hopped spread-spectrum multiple-access communication systems

Abstract: The authors consider a multiple-access frequency-hopped spread-spectrum communication system with Reed-Solomon codes. The performance measures of interest are an achievable region and the channel throughput. The achievable rate region is the set of all pairs of code rate and number of users for which communication is possible with error probability below a fixed value. The throughput measures the expected number of successful codeword transmissions per unit bandwidth. Two models of interference are considered. For these two models, the authors determine the optimal number of users for a given bandwidth and the optimal rate Reed-Solomon code that maximize the throughput. They also determine the achievable region for these models. >

Two-way radio communications system having selectable operating modes

Abstract: A radio communication system includes a base station (107, 109, 104, 105) and a plurality of remote units (202, 203, 210, 204) that can be operated in one of several modes. In the Message Storage mode, a caller is given the option to store a voice or numeric message for later transmission to the called remote unit. If caller enters an Override code, however, the system attempts to establish voice communication between the caller and the called remote unit. In the Call Screening mode, the caller's message is stored in the base station and, simultaneously, forwarded to the called remote unit. During reception of the message, the called remote unit can ''pickup'' the call and begin normal voice communications with the caller.

Distributed switching architecture for communication module redundancy

Abstract: Partner modules are assigned to a plurality of primary modules in a communications system, each partner module being adapted to route signals from the primary module to which it is assigned to a spare module in case the primary module fails. The partner modules preferrably also serve as primary modules for receiving signals from their associated communication lines. As a result, redundancy for a failed primary module is provided by a signal routing architecture that is distributed throughout the communications system.

Integrated communications system

Abstract: Information pathways for communications among personnel, among computers, and between personnel and computers, in a local communication system, including remote communications via leased lines or the public network is described. To a public central office, the present invention appears as a private branch exchange (PBX), served by many trunks, WATS, and "Foreign Exchange" lines, and providing all the standard PBX services; to the remote leased facility, it appears as a standard tie line terminator or, if the remote is another ICS, as a logical tie line terminator for which several logical tie lines are combined into each leased T1 line; to the in-house computer, it provides switched connection to other computers or to terminals at up to 19,200 Baud modulated data, at 32K-Baud for native (internal system) data (including 2K-Baud of forward error correction), or up to several gigabits direct binary transmission (such as the transmission scheme used with NDS and ANR displays, etc.); to the in-house human user, it appears as a unique electronic telephone which offers many special services to facilitate his communications with other people and with computers. Advanced features such as optional hands-off voice on/off hook control, personal identification by voice print and remote chart presentation are provided.

System for and method of assigning frequencies in a communications system with no central control of frequency allocation

Abstract: A system for and method of assigning frequencies in a mobile telephone communication system wherein there is no central control of frequency channel allocations and wherein such assignment is made by real time signal comparisons without reference to geographical patterns.