Showing papers on "Communications system published in 1983"

Digital and analog communication systems

Abstract: From the Publisher: Exceptionally up-to-date, this book provides a broad introduction to basic analog and digital principles and their application to the design and analysis of real- world communication systems. It provides readers with a working knowledge of how to use both classical mathematical and personal computer methods to analyze, design, and simulate modern communication systems. MATLAB is integrated throughout. Study-aid examples and homework problems are included, many of which require solution via a personal computer. MATLAB illustrative examples and plots are included. Balanced coverage of both analog and digital communication systems with an emphasis on the design of digital communication systems. Case studies of modern communication systems are provided. Over 500 problems provided. For electrical engineers.

Automatic-repeat-request error control schemes

Abstract: ERROR DETECTION incorporated with automatic-repeatrequest (ARQ) is widely used for error control in data communications systems. This method of error control is simple and provides high system reliability. If a properly chosen code is used for error detection, virtually error-free data transmission can be attained. This paper surveys various types of ARQ and hybrid ARQ schemes, and error detection using linear block codes.

Integrated interactive restaurant communication method for food and entertainment processing

Abstract: An interactive restaurant communication system (10) provides integrated food and entertainment processing which enables restaurant patrons to accomplish both food selection and select and receive entertainment on a common video monitor (56) at their table. The patrons can obtain menus for individual food selection on the video monitor (56) at their tables and individually enter their orders into a table station "intelligent" terminal (12, 14, 16, 18, 20) at their tables. In addition they can select from and interactively play a variety of remotely retrievable interactive entertainment activities using the video monitor (56) while waiting for the food to arrive, and if desired, where applicable, have the food and entertainment charges automatically added to a composite bill which may be printed at the table station terminal (12, 14, 16, 18, 20) or at a remote central location. The food and entertainment functions of the terminal (12, 14, 16, 18, 20) are down-line loaded from a central data base (22, 32) in response to terminal requests therefor.

Simultaneous transmission of two information signals within a band-limited communications channel

Abstract: A co-channel communications system is disclosed which permits a digital data signal to be simultaneously transmitted with a communications medium signal such as telephone voice or television video. The data signal or signals are converted into very low multifrequency signals consisting of fundamental frequencies and harmonics which span the communications bandwidth. Because a number of frequencies are used for each data signal, the signal level of the data signals can be greatly suppressed relative to the communications medium signal to a level such that there is no perceptible degradation of the telephone voice or television video. Synchronous detectors for each frequency transmitted, including harmonic frequencies, are utilized to recapture and regenerate the data signals transmitted.

Recorded program communication system.

Abstract: A two-way telephone network (16) between a subscription television broadcast location and a plurality of subscriber stations (12) having standard broadcast signal receivers provides dialed telephone links through which subscribers select recorded programs in a library at the broadcast location for reception on the standard signal receivers, the broadcast signals being transmitted along one-way signal paths (18) from the broadcast transmitter to the subscriber stations Signal processing at the broadcast location and special signal detection and traffic control at the subscriber stations prevents unauthorized reception

Method and apparatus for assigning duplex radio channels and scanning duplex radio channels assigned to mobile and portable radiotelephones in a cellular radiotelephone communications system

Abstract: A unique method and apparatus for efficiently assigning duplex radio channels and scanning duplex radio channels assigned to mobile and portable radiotelephones in a cellular communications system (Fig 1) Each cell (10, 20, 30) includes a base station radio (111, 121, 131) having a signalling channel and a plurality of voice channels, and a base site controller (112, 122, 132) adapted to utilize the methods embodying the present invention for controlling communications paths to mobile and portable radiotelephones The base station radios (Fig 2) include a signalling transceiver (250) operable on the signalling channel, a plurality of voice transceivers (220, 230) each operable on a voice channel, and a scanning receiver (240) for sampling the signal strength of active radiotelephones Transmitters of the signalling transceivers (250) and voice transceivers (220, 230) are combined (210) and coupled to an omnidirectional antenna (212); and the receivers of the signalling transceiver (250), voice transceivers (220, 230) and scanning receiver (240) are coupable to one or more of six sector antennas (214) In practicing the methods of the present invention, the microprocessor (358) controlled base site controller maintains high quality communications paths to mobile and portable radiotelephones by periodically monitoring their signal strength and when signal strength degradations are detected, either changing the base station sector antennas (214) coupled to voice transceivers (220, 230), increasing or decreasing radiotelephone power output, or handing radiotelephones off to another cell

Wide area coverage radio communication system and method

Abstract: A wide area coverage radio communication system of the type adapted to relay a message substantially simultaneously from a plurality of fixed location sites to a plurality of portable or mobile units includes a plurality of repeaters at each of the sites. Each of the repeaters is arranged to transmit and receive on a respective different frequency duplex pair or channel. Control means at one of the sites senses channel availability at all of the sites and causes one repeater at each of the sites to transmit the message on its respective different frequency. Access to the system by the portable units is provided on a trunked basis through the control means.

Array signal processing

Abstract: Array signal processing (ASP) represents a class of antenna system where the output from an array is subjected to various forms of signal processing (e.g. phase and amplitude control, time delay or frequency translation) in order to produce outputs which can simultaneously provide angular information relating to several different directions. A different aspect of ASP which has received considerable attention over the last few years is adaptive arrays and null steering antennas. Here, instead of defining a number of wanted directions for receiving signals we can specify some wanted and some unwanted directions; the latter may contain high-level interfering signals which must be minimised by means of directional nulls in the patterns. In some cases the directions of these nulls may be fixed or pre-programmed, but in many cases the antenna response must be adaptive. This means that the shape of the directional pattern is determined in response to the angular distribution of received signals in order to try to meet some desirable criterion. The simplest form of adaptive and null steering antenna is probably the sidelobe canceller. This can steer a single directional null within the sidelobe region of a normal directional pattern. Multiple null adaptive arrays in general define a 'wanted direction' and then introduce one or more feedback controls to minimise the signals from all other directions. Null steering systems have applications in radar, sonar and communication systems. In the latter case, there may be additional complications if it is not possible to specify the direction of the wanted signals.

Method and apparatus for dynamically selecting transmitters for communications between a primary station and remote stations of a data communications system

Abstract: A data communications system (Figure 1) that covers a geographic area divided into a plurality of non-overlapping zone (Figure 2) and includes a general communications controller (GCC, 104), a plurality of channel communications modules (CCM 106, 108, 110, 112) and associated transmitters (114, 120, 124) and receivers (116, 118, 122, 126, 128), and a plurality of portable radios (130, 132, 134). Message signals carrying alphanumeric information are communication between the GCC (104) and the portable radios (130, 132, 134) by way of a radio channel. Each CCM (106, 108, 110, 112) takes a signal strength measurement every time it receives a message signal from a portable radio (130, 132 or 134). The GCC (104) gathers the signal strength measurements from the CCM receivers (116, 118, 122, 126, 128) receiving the same message signal and computes an adjusted signal strength for each zone. The GCC (104) then selects the zone having the largest adjusted signal strength for determining the location of the portable radio (130, 132 or 134) that transmitted the message signal. Whenever the GCC (104) transmits a message signal to a portable radio, the CCM transmitter (114, 120, 124) is used that covers the zone having the largest adjusted signal strength for the last transmission from that portable radio (130, 132, 134). Since the GCC (104) can be simultaneously transmitting message signals to portable radios (130, 132, 134) in other zones using non-interfering CCM transmitters (114, 120, 124), information throughput is greatly enhanced.

Catv communication system

Abstract: A two way digital communication arrangement utilizes a CATV system to provide bidirectional data transport service between any two points within the CATV system. The headend receives an upstream message and selectively rebroadcasts such message on the downstream portion of the spectrum. System intelligence is thus distributed throughout the system as server and subscriber nodes can be located anywhere in the CATV network. In order to obtain access to the CATV communication resources, user equipment at each node must attach a frame verifier (FV) code to each respective message. The headend examines the FV and permits rebroadcast of messages only if the FV code indicates that the user is authorized.

A structured overview of digital communications--A tutorial review--Part II

Abstract: I N THE first part of this two-part paper, a structure and hierarchy were developed for tracing the key signal processing steps of a typical digital communications system. With the structure as a guide, formatting, source coding, and modulation transformations were examined. Also treated were potential trade-offs for power-limited and bandwidth-limited systems. In Part II, the signal processing overview continues with channel coding, multiplexing and multiple access, frequency spreading, encryption, and synchronization. To complete the overview, fundamental link analysis relationships are reviewed in the context of a satellite repeater channel.

The Use of Computer-Monitored Data in Information Science and Communication Research.

Abstract: As computer-based information retrieval and communication systems become more commonplace, researchers have a greater opportunity to evaluate the uses and impacts of new communication technologies The systems and the kinds of data now available are discussed along with advantages and disadvantages of using computer-monitored data

Electronic audio communication system with user controlled message address

Abstract: An advanced electronic telecommunications system is provided for the deposit, storage and delivery of audio messages to both user and non-users with limited access provided to the non-user under the control of the user. A Voice Message System (10) interconnects multiple private 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). Selected non-users may be allowed access through the OFF NET telephones (24), the scope of the access of the selected non-users being determined by a subscriber user. 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 addresses connected to the system. The user is also able to deposit a message in a receive-only portion of the data subsystem (60) for access by a selected non-user. The Voice Message System (10) also enables a user to access the system to determine if any messages have been in data storage subsystem (64) for him. Prerecorded instructional messages are deposited in the data storage subsystem (64) for instructing a user or a selected non-user on their progress in using the system.

Fundamental issues of multiple accessing

Abstract: : Fundamental issues of multiple accessing are identified. These issues include transmitter asynchronism, variability of the set of active users, feedback, and degree of codebook knowledge among the users. Various multiple access schemes are examined under these issues. These issues are subsequently modeled and analysed using an information theoretic framework. We discover that the capacity region of the asynchronous multiple access channel is different from that of the synchronous channel. For communication systems with users having random message generation time, we demonstrate that its channel capacity resembles that of an asynchronous channel even though the users are synchronous, if decoding delay is constrained to be much smaller than the message inter- arrival time. We investigate communication with restricted decoder structure. New information theoretic quantities that incorporate the decoding metric used are discovered and examined. Using these quantities, we provide a rigorous and novel treatment for the theory of jamming. These mathematical techniques provide insight for achieving reliable communication in a multiple access environment where each user may not know the codebook of the other users and a jammer may be present. We then apply the general theory developed to three specific asynchronous channel without feedback, namely the OR channel, the spread spectrum channel and the collision channel. Practical and novel coding schemes are suggested. Maximum throughput, error rate and decoding complexity are analysed.

Technique for dynamic scheduling of integrated circuit- and packet-switching in a multi-beam SS/TDMA system

Abstract: The present invention relates to a technique for dynamic scheduling of integrated circuit- and packet-switching in accordance with rapidly changing demand in a multibeam satellite switched, time division multiple accessed (SS/TDMA) environment. It is equally applicable to terrestrial communication systems, or more broadly to any type of centralized scheduling system involving arbitration of contention for resources among a plurality of users or equipments. All of the scheduling is performed onboard the satellite by a scheduler (6, 8) under the direction of a controller (4). The controller contains all the information related to both circuit requests ([cij ]) and packet requests ([pij ]) in matrix form, where it constructs these matrices from requests for service from each zone to each zone on a frame-by-frame or possibly less frequent basis, which it receives from the ground via an order-wire facility. The scheduler performs, for each of the slots of a frame, a least-choice assignment of the circuit requests contained in the controller. The scheduler then applies the same least-choice procedure to assign packets to switch positions not already assigned to the circuit traffic. The least-choice assignment yields efficient bandwidth and transponder utilization. Provision is also made for prioritizing or preempting both the circuit and packet traffic employing a movable-boundary or other protocols. At the completion of both the circuit and packet assignments for a particular slot, the controller broadcasts the slot schedule to the earth stations.

Data signalling system.

Abstract: A data signalling system for transmitting signals between at least one primary station and a plurality of secondary stations. The system is well adapted for use in multiple unit radio communications systems capable of noise and data communications. A register model is utilized which permits a highly flexible signalling system compatable with a wide range of communications networks. Data transfer is accomplished using fixed length data packets which are error correction encoded and transmitted utilizing PSK modulation.

D-Net, A New Scheme for High Data Rate Optical Local Area Networks

Abstract: The development of optical fiber point-to-point communications systems has generated substantial interest in the application of optical fiber to local area networks. The feasibility of using guided wave optical technology for local area networks is explored. Various network schemes, including Fibernet, Express-Net, and C-Net, are examined. A new scheme, D-Net, is disclosed which has the advantages of high efficiency, low bounded delay, simple protocol, and implementation flexibility.

Multipoint data communication system with collision detection

Abstract: An improved multipoint access data communication system with collision detection provides a duplicative communication medium, network interface units adapted for connection to transceivers on both media, transceivers adapted for connection to a plurality of network interface units, and a local collision detection circuit associated with each transceiver for detecting collisions between transmissions simultaneously attempted by two or more network interface units connected to the transceiver.

Simulation of Computer Communication Systems

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Digital voice storage system

Abstract: A digital voice storage system adapted for use in a multiple unit land mobile radio communications system. The system utilizes a PSK signalling system with fixed length data packets to control a system capable of multiple message storage of speech at mobile stations. Up to eight 64K dynamic RAMS are used in conjunction with a microprocessor to store up to 42 seconds of speech comprising up to eight separate messages. In addition, the system permits base interrogation of mobiles to determine if a message has been stored for review by the base operator and to determine the remaining recording capacity and total recording capacity of the mobile.

Method and apparatus for coding messages communicated between a primary station and remote stations of a data communications system

Abstract: A data communications system is described in which variable length messages are communicated between a general communications controller (GCC) and a plurality of portable and mobile radios. The variable length messages include a bit synchronization field, a message synchronization field and a plurality of channel data blocks for efficiently and reliably handling long strings of data or text. Each channel data block includes an information field, a parity field for error-connecting the information field and a channel state field indicating whether or not the radio channel is busy or free. The GCC is coupled to a cellular arrangement of channel communications modules (CCM's), which each include a radio transmitter and/or radio receiver. The mobile and portable radios communicate with the GCC by way of the CCM's.

Audiographics communication system

Abstract: An interactive graphics and audio communications system is disclosed The system enables users to communicate audibly and graphically over a single telephone connection

Communications system enabling radio link access for non-trunked radio units to a multifrequency trunked two-way communications systems

Abstract: An improved multifrequency trunked, two-way communications system is provided in which a plurality of conventional single channel radio units are provided access. The system includes a predetermined number of information channels that are shared by a plurality of trunked stations. A trunked controller assigns one of the information channels to a requesting trunked mobile unit. The requesting trunked mobile unit is enabled to operate on the assigned channel in response thereto. The improved communications system includes a radio access link which enables the single channel radio units to operate on an assigned information channel in the same manner as the trunked remote stations. The radio access link provides the plurality of conventional remote stations automatic access to the trunked system without requiring any modification of the conventional remote stations, and likewise without modification of the trunked remote stations and trunked controller.

System identification in communications system

Abstract: In communications systems, such as cordless telephone systems, in which synchronizing signals are transmitted at predetermined intervals on a signalling channel by base stations to say portable, battery-powered receivers, the need to send separate station identification signals is avoided by the synchronizing signals being transmitted from a base station in accordance with a predetermined signalling sequence, for example a pseudo-random sequence, and the receivers using the sequence as a base station identification signal.

Communications system having an addressable receiver

Abstract: A communications system having programmable, addressable receivers that receive, store, process and send digital and conventional video, audio and control signals for use in, among other things, a cable video network. Receivers in this system may receive conventional audio and composite video and digital data signals from sources such as a satellite transponder and video and audio from local sources. The digital data may be processed into textual video data by character generation techniques, as may be other digital dtat received from a local keyboard, local weather sensors or other digital data communications interfaces. The receivers may be addressed in units or groups for purposes of receiving individually, locally or regionally tailored text information and are typically controlled simultaneously from one control source. The system of the preferred embodiment is particularly well adapted for a weather cable network, since it fulfills the needs of data consumers throughout a large geographic area to have continual, current local and national weather information.

Railroad air brake system

Abstract: A radio communication control system for a lead unit and a plurality of remote units is disclosed. The system has a protocol for establishing a communication link between the lead unit and the one or more remote units in the system which prevents any of the units in that system from processing messages or commands from other units in other train systems or processing messages or commands originating from units within a train system which are addressed to other units within the system. The communication system also includes a communications channel contention system for minimizing the probability of multiple units transmitting on the common communication channel at the same time and for insuring that the highest priority communications in each train are transmitted first in time measured from the end of the latest transmission on the radio communications channel. The invention also includes apparatus for verifying the establishment of the communications link by signaling through the mechanical coupling in the train and monitoring the radio response. The invention further includes an improved flow rate sensor for use in a remote unit for determining when significant air flows occur into the brake pipe of the remote unit. The invention further includes an air pressure regulation system which prevents the fluctuation of the air pressure in the equalizing reservoir of the lead and remote units consequent from either leakage or change in the ambient temperature.

Portable radio for a zoned data communications system communicating message signals between portable radios and a host computer

Abstract: A data communications system is described that covers a geographic area divided into a plurality of non-overlapping zones and includes a general communications controller (GCC), a plurality of channel communications modules (CCM) and associated transmitters and receivers, and a plurality of portable radios. Message signals carrying alphanumeric information are communicated between the GCC and the portable radios by way of a radio channel. Each CCM takes a signal strength measurement every time it receives a message signal from a portable radio. The GCC gathers the signal strength measurements from the CCM receivers receiving the same message signal and computes an adjusted signal strength for each zone. The GCC then selects the zone having the largest adjusted signal strength for determining the location of the portable radio that transmitted the message signal. Whenever the GCC transmits a message signal to a portable radio, the CCM transmitter is used that covers the zone having the largest adjusted signal strength for the last transmission for that portable radio. Since the GCC can be simulataneously transmitting message signals to portable radios in other zones using non- interfering CCM transmitters, information throughput is greatly enhanced.

Passive transmission of data over cable TV systems

Abstract: A communications system which enables enhanced services to be provided over cable TV systems. The design of the system is such that amplification is not required. Therefore, two-way transmission is possible on the low band of "two-way capable" cable systems and intermediate power failures do not affect transmission. Transmission of data takes place in the low band frequency range of five to thirty megahertz. The system design is such that it can withstand over a hundred dB loss between the remote terminal and the head-end. Carrier frequencies, when received, are interleaved for purposes of decoding and microprocessor based controls are used for automatic gain control and error correction. In a preferred embodiment of the invention, two thousand five hundred carriers, each transmitting eight digital data channels of information can be simultaneously transmitted from remote terminals without any effect whatsoever on the TV signals being transmitted at the high band frequencies. The resulting system is a very economical and dependable method to achieve passive transmission of data over cable TV systems.

A Distributed Experimental Communications System

Abstract: The packet experimental communications system (packet XCS) is a new experimental voice and data switch. It uses a local-area network (LAN) for digital voice transmission, with local intelligence for switching. The packet XCS also has highly distributed control. The individual sites cooperate to provide user services as well as internal data management. We have learned that several local networks, including CSMA/CD networks, can be made to work well for voice transmission and that highly distributed control is practical in such a system. A system has been constructed which is used as a testbed for distributed voice and data communications experiments. This system is purely for experimentation and does not indicate a direction for future Bell System product offerings.

Arq equipped data communication system

Abstract: A data communication system having an automatic request for repetition ("ARQ") function shifts down its MODEM rate to a slower value when the number of trials of retransmission has reached a predetermined value. In the present system, the predetermined value is supplied from the receiver to the transmitter prior to transmission operation of data from the transmitter to the receiver, thereby allowing to maintain a high use rate of the transmission line without significantly decreasing the overall data transmission speed.