Showing papers on "Communications system published in 1995"

Introduction to Spread Spectrum Communications

Abstract: From the Publisher: Besides the traditional military application areas, there is a growing and intense interest in spread spectrum communications systems for evolving civil applications, e.g., cellular-mobile communications, personal communications, and satellite-mobile communications. Ideal for those who need to get up to speed or current quickly in this area, this self-contained exploration of spread spectrum system analysis and applications provides a solid theoretical background along with an abundance of examples of specific analysis/design situations, and exposes readers to the most recent research and developments in the field. Covers basic digital communication and spread spectrum concepts, and features exceptionally complete treatments of important hot topics such as spectrum spreading sequences; the code acquisition and tracking process; the effects of jamming on spread spectrum communications and the use of coding/interleaving to combat the detrimental effects of jamming; designing spread spectrum systems for low probability of the intercept; and the design of code division multiple access systems, wit h examples. Contains a complete set of technical appendices. For electrical engineers and others with a background in linear systems and probability/random processes who want a cutting-edge overview of the principles, research, and developments of spread spectrum systems.

Patient care and communication system

Abstract: The present invention relates to a patient care and communication system which utilizes a central processing system and a plurality of remote stations electrically connected to the central processing system to facilitate visual and data communications. Each remote station includes telephone circuitry which is connected to a private branch exchange for telephone communications between stations. In addition, the private branch exchange is connected to a telephone exchange and a plurality of telephones for facilitating telephone communication therebetween. The central processing system facilitates the visual and data communications between the plurality of remote stations, and includes a system for determining which of the plurality of remote stations are transmitting the visual and data communications and which of the plurality of remote stations are to receive the visual and data communications. The central processing system also includes a system which establishes a communication link between the transmitting stations and the receiving stations. The remote stations include a processing system which also facilitates the visual, data and telephone communications and a display for displaying the visual communications. The present invention also includes a staff and/or patient locator system, in which each remote station includes an infrared receiver that receives infrared transmissions from a portable transmitter worn by a staff member or patient. The infrared transmissions include identity information associated with the person wearing the transmitter. The identity information is then transferred to the central processing system which determines the identity and location of each person wearing a portable transmitter.

Network-based multimedia communications and directory system and method of operation

Abstract: A communications system (10) is provided which comprises a plurality of network hubs (12, 14 and 16). Network hubs (12, 14 and 16) are interconnected through a communications network (18). The system (10) interconnects messaging systems (24, 26, 28, 30, 32, 34, 36, 40, 42 and 44) having disparate capabilities and using disparate communications protocols. The network hubs use numbers of connection processors (52 and 54) to interact with the messaging systems. A hub database (68) and message store (58) are used to store control information and messaging information within the network hubs. A network processor (60) is used to interact with other hubs within the communications system (10). A message router (72), connection manager (74), data replicator (76), and an administrative event manager (78) are used to control the operations of the hub in processing a message.

Digital Speech: Coding for Low Bit Rate Communication Systems

Abstract: From the Publisher: A detailed account of the most recently developed digital speech coders designed specifically for use in the evolving communications systems. Discusses the variety of speech coders utilized with such new systems as MBE IMMARSAT-M. Includes an in-depth examination of the important topic of code excited linear prediction (CELP).

Hierarchical communication system providing intelligent data, program and processing migration

Abstract: A hierarchical communication system, arranged in a spanning tree configuration, is described in which wired and wireless communication networks exhibiting substantially different characteristics are employed in an overall scheme to link portable or mobile computing devices. Copies of data, program code and processing resources are migrated from their source toward requesting destinations based on request frequency, communication link costs and available local storage and/or processing resources. Each appropriately configured network device acts as an active participant in network migration. In addition, portable two-dimensional (2-D) code reading terminals are configured to wirelessly communicate compressed 2-D images toward stationary access servers that identify the code image through decoding and through comparison with a database of images that have previously been decoded and stored.

Method and system for channel allocation using power control and mobile-assisted handover measurements

Abstract: A method and system for the adaptive allocation of channels within a radio communication system, specifically a cellular network, is presented. The allocation method takes advantage of measurements made by the mobile radiotelephone and allocates channels based on the carrier to interference ratio. Using adaptive power control, consideration is given to maintaining an acceptable carrier to interference ratio while at the same time minimizing transmit power. Exemplary embodiments consider independent allocation of the uplink and downlink as well as independent determination of the uplink and downlink power levels. Other exemplary embodiments also give consideration to an efficient method for slot allocation in a TDMA communication system.

Distributed architecture for a wireless data communications system

Abstract: A data communications system characterized by the combination of a base station connected to a plurality of repeaters for communicating with remote terminals in response to outgoing data from a host computer and for communicating with the host computer in response to incoming data from the remote terminals Each repeater is assigned a coverage area with in a predetermined communications area to support data communications with the remote terminals located within its coverage area In response to incoming data, a repeater conducts a signal amplification operation and outputs amplified incoming data to the base station via a first communications link The base station processes the amplified incoming data and, in turn, generates processed incoming data for distribution to the host computer via a second communications link The base station also processes the outgoing data from the host computer to generate processed outgoing data, and sends transmitted outgoing data to each repeater via the first communications link Each repeater connected to the base station can amplify the transmitted outgoing data, and outputs amplified outgoing data to the remote terminals within its coverage area

Navigation information system

Abstract: A navigation information system comprises a communications system having a fixed part (11 to 20) and at least one mobile part (1 to 10), the fixed part including a data storage and processing means (15) for identifying the location of a mobile unit, generating guidance information appropriate to that location and transmitting it to the mobile unit. By locating most of the complexity with the service provider, in particular the navigation computer (15) and geographical database (17), the system can be readily updated and the capital cost of the in-vehicle system, which in its simplest form may be a standard cellular telephone (1), can be minimised. The user makes a request for guidance information, and the system, having determined the user's present location, then transmits instructions to the user. The user's present location can be determined by means such as a Satellite Positioning System (7).

Communication network having a plurality of bridging nodes which transmit a beacon to terminal nodes in power saving state that it has messages awaiting delivery

Abstract: An apparatus and a method for routing data in a radio data communication system having one or more host computers, one or more intermediate base stations, and one or more RF terminals organizes the intermediate base stations into an optimal spanning-tree network to control the routing of data to and from the RF terminals and the host computer efficiently and dynamically. Communication between the host computer and the RF terminals is achieved by using the network of intermediate base stations to transmit the data.

Implementing the Viterbi algorithm

Abstract: The Viterbi algorithm, an application of dynamic programming, is widely used for estimation and detection problems in digital communications and signal processing. It is used to detect signals in communication channels with memory, and to decode sequential error-control codes that are used to enhance the performance of digital communication systems. The Viterbi algorithm is also used in speech and character recognition tasks where the speech signals or characters are modeled by hidden Markov models. The article explains the basics of the Viterbi algorithm as applied to systems in digital communication systems, and speech and character recognition. It also focuses on the operations and the practical memory requirements to implement the Viterbi algorithm in real-time. >

System and method for mobile communications in coexistence with established communications systems

Abstract: A mobile communications system (10) provides communications with mobile users (22) in the interference zones (32) of communications services having priority of use of the frequency band in which the mobile user operates. The frequency band has been previously allocated for use by other services, such as fixed microwave service (FMS) (26); however, by means of the invention, the mobile user is able to conduct communications on a subband or subbands in that frequency band. A position locating system (12) determines the position of the mobile user, and if the user (22) is within an interference zone (30), the mobile user is assigned subbands for operation in the previously allocated frequency band that is outside the subbands of the FMS (26). The system may have surface and/or satellite nodes and a network controller that monitors the mobile user's position and controls the nodes and user to subbands. Mobile users are isolated from the FMS sites either by continuous management of their frequency assignments, by calculations and commands sent from the network controller to the mobile user or by computations of the mobile user's unit.

Multitone spread spectrum multiple access communications system in a multipath Rician fading channel

Abstract: The paper proposes a new multiple access communications system based on the combination of multitone transmission and direct sequence spectrum spreading (DS/SS). Multitone transmission is proposed because the associated larger symbol duration is favorable to combat the effects of multipath propagation. The multiple access capability of the system is achieved by means of DS/SS which also helps to combat the presence of several paths. On the other hand, DS/SS is also attractive to decrease the multiple access interference. The performance of this system is investigated for a multipath, slowly Rician fading and frequency selective channel, and a suboptimal receiver based on matched filters. The multiple access interference is also taken into account, A model for the computation of the bit error probability is derived for QPSK modulation of the orthogonal tones by the spread symbols. The system performance is investigated for selection diversity and maximal ratio combining (RAKE reception). Then the influence of the number of tones is investigated for given bandwidth, bit rate and transmission power. The positive effect of a multitone spread spectrum transmission is demonstrated. >

Secure authorization and control method and apparatus for a game delivery service

Abstract: A communications system for the delivery of digital data programs to a remote location includes a transmitter for transmitting a signal having the digital data programs and a communications terminal (177) located at the remote location. The communications terminal (177) includes a control circuit (200) including authorizing circuitry responsive to authorization data for authorizing the communications terminal to access authorized ones of the digital data programs in one of a first and second authorization mode. For example, automatic authorization modes for game play may comprise an arcade mode and a rental mode, simulating manual access methods i.e. paying for play at a video arcade or for rental of games from a video game store. Moreover, new games may be accessed without charge by the game player if authorized according to a free service authorization map.

Multi-hop packet radio networks

Abstract: An adaptative communication system utilizes opportunistic peak-mode transmissions to transmit data between originating and destination stations, via one or more intermediate stations. Each station monitors the activity of other stations in the network, storing connectivity information for use in subsequent transmissions. Each station also sends out probe signals from time to time, to establish which other stations are in range. Messages are then sent across the network from station to station, with confirmation data being transmitted back to the originating station, until the destination station is reached. Old messages, which would otherwise clog the network, are timed out and deleted. A communication network and transceiver apparatus for use in the network are also disclosed.

Real-time multi-user game communication system using existing cable television infrastructure

Abstract: A complete multi-user game playing environment is described which provides game playing services to cable television subscribers over existing cable networks. A game player located at the end of a cable network connection has a computer or other game playing device attached to the cable network through a front end adapter card. A game playing server is located at the cable headend and is equipped with back end communications cards for full duplex communications over the cable network with a plurality of game players. A plurality of uplink frequencies are used by the servers to communicate with the game players and a pluralities of downlink frequencies are used to communicate from the game players to the server. The communications are controlled by the server to prevent communication collision on the cable network over the same frequencies by having the server control a dynamically-changing time and frequency division multiple access protocol. The multi-user game playing server includes hardware and software where the game server includes a multi-threaded operating system which controls user access to a plurality of concurrently-operating games. The operating system allows users to join, play, change and quit any number of a plurality of provided games. Each of the plurality of concurrently operating games is a separate process in a multitasking environment while each of the operating threads are event-driven context-switched threads to control user access and communications over the cable network. The game playing information and game access information is traded between the server and the plurality of the game players using a predefined packet protocol which is very tolerant of lost packet data. The user's game equipment attached to the cable network includes devices such as personal computers, special set-top game controllers or existing video game playing equipment.

Cell site demodulation architecture for a spread spectrum multiple access communication systems

Abstract: An integrated demodulation processor used in a modem for a spread spectrum communications system despreads multipath receive signals then uses a time sliced transform processor to process the multiple signals in to a single series of soft decision results. The demodulation processor uses a single transform engine which operates on a time slice basis. The output of the processor engine cascade through a pipeline processor which, on a time slice basis, operates on signals corresponding to each multipath receive signal. The processed results are dual maxima decoded to provide soft decision data.

Communication system with handset for distributed processing

Abstract: A communication system, comprising at least one mobile handheld telephone handset adapted to communicate with a telephone network handling system. The handset comprises means to produce first signals dependent thereupon, means to produce a voice transmission signal and means to transmit the voice transmission signal. The handset also comprises first processing means to carry out a speech recognition process to produce initial feature analysis parameter coefficients data dependent thereupon. The first processing step preserves predetermined information. The handset further comprises means to produce a data transmission. The telephone network handling system comprises means to receive the voice signal, means to forward the voice signal, and means to receive and process the data transmission signal. The telephone handling system also comprises means to carry out the remote second processing step in a speech recognition process on the regenerated data.

Low power, short range point-to-multipoint communications system

Abstract: A point-to-multipoint or two-way communications system is provided by a nodal transmitter located in a node with a plurality of nodal antennas radiating different polarization signals about the node. The system includes subscriber stations with directional antennas adapted to receive signals radiated from the nodal transmitter. The system may additionally include capability for transmitting and radiating subscriber signals to the nodal transmitter location for two-way communications.

Method and apparatus for conveying a communication signal between a communication unit and a base site

Abstract: A communication system (100) employs a method (600) and apparatus (101) for conveying a communication signal between a communication unit (105) and a base site (101) that services a sectorized coverage area (103). The communication unit (105) transmits an uplink communication signal (113) to the base site (101). The base site (101) receives (603) the uplink communication signal (113) and determines (605) an approximate location of the communication unit (101) within a first portion (111) of a sector (108) of the sectorized coverage area (103). A downlink communication signal is then transmitted (609, 613) to the communication unit (105) based on the approximate location of the communication unit (105) using an antenna structure that produces a beamwidth (117) narrower than an angular width of the sector (108).

System having virtual session manager used sessionless-oriented protocol to communicate with user device via wireless channel and session-oriented protocol to communicate with host server

Abstract: A communication system includes a virtual session manager (225) for establishing and maintaining a sessionless communication path with a user device (201) on the one hand and a session-oriented communication path with a host system (231). The session-oriented connection with the host system permits normal access to, e.g., LAN-based applications, while the virtual session between the virtual session manager and user permits this access to be carried out remotely without the expense of a dedicated/circuit-switched or other session-oriented connection.

Multilevel data communication system including local and host systems

Abstract: A computerized system for managing freight or the like which is picked up at various points and delivered to other various destinations, and more particularly to such a system which utilizes hand-held terminals, scanners and printers which are linked together by a micro link radio to each other and by a wide area network radio link to a main area station which can receive and transmit information to a plurality of sets of terminals, printers and the like for managing an overall freight system.

Method and apparatus for performing search acquisition in a CDMA communications system

Abstract: A novel an improved method of acquisition in a spread spectrum communication system is presented. In the present invention, a large window of PN chip offset hypotheses are searched and if an energy signal is found that might indicate the presence of the pilot signal having one of the chip offsets of the large search window, then a search of a subset of offset hypotheses, or small window, is searched.

Method for providing service and rate negotiation in a mobile communication system

Abstract: A method and apparatus for negotiating service configuration in a digital communication system is disclosed. In an exemplary embodiment the service negotiation system is implemented in a wireless spread spectrum communication system. The service configuration comprises data rates, frame formats and types of services. Types of service may include speech encoding, facsimile or digital data services. Further described herein is a digital transmitter and receiver using the service negotiation system to provide service configuration mutually acceptable at both ends of a communication link.

Wireless diffuse infrared lan system

Abstract: A wireless diffuse infrared local area network communication system (10) is provided for enclosed areas. The communication system includes a controller (12) and a substantially omnidirectional infrared transceiver (16a) disposed on an inside wall of the enclosed area (11) operatively interconnected with the controller. The system further includes a remote station (14) and means, operatively connected to the remote station, for transceiving a communicated signal with the substantially omnidirectional infrared transceiver.

Laser Communications in Space

Abstract: Past, present, and future architecture and applications system design methodology optical design the communication receiver the acquisition receiver the tracking receiver key technologies configuring the system trading RF and laser communications for your system size, weight, and power trends in laser crosslinks laser communications applications.

System and method for a communication system

Abstract: A method and a structure for providing electronic mail, facsimile transmission and file transfer maintain a data base in which the communication parameters of a local computer are maintained separately from the communication parameters of a remote computer which communicates the local computer. The data base includes an electronic address book in which a method and a structure are provided for specifying person, group, computer, calling card and service data. The person type data includes specification of a preference for data, or facsimile transmission. Service information are efficiently added because of modularly designed application programming interface. A method and a structure are also provided to allow synchronization between files residing on different computers.

Personal communication systems using multiple hierarchical cellular overlays

Abstract: A personal communication system with multiple hierarchical cellular overlays is considered. The system can include a terrestrial segment and a space segment. The terrestrial trail segment, consisting of microcells and macrocells, provides high channel capacity by covering service areas with microcells. Overlaying macrocells cover spots that are difficult in radio propagation for microcells and provide overflow groups of channels for clusters of microcells. At the highest hierarchical level, communications satellites comprise a space segment. The satellite beams overlay clusters of terrestrial macrocells and provide primary access for satellite-only subscribers. Call attempts from cellular/satellite dual subscribers are first directed to the terrestrial cellular network, with satellites providing necessary overlay. At each level of the hierarchy, hand-off calls are given priority access to the channels. The mathematical structure is that of a multilayer hierarchical overflow system. An analytical model for teletraffic performance (including hand-off) is developed. Theoretical performance measures are calculated for users having different mobility characteristics. These show the carried traffic, traffic distribution, blocking, and forced termination probabilities. >

Personal communication system and method of use

Abstract: A personal communication system for communication with another entity uses global positioning system receiver, phone book storage, and audio input as alternative forms of generating position data. A transmitter communicates a service request and the position data to the other entity, which in turn, relays the request to the appropriate party. Alternatively, the personal communicator may directly contact the desired individual. The personal communicator also includes a plurality of command buttons to control operation and a display to provide the user with instructions and data. The personal communicator also includes a sound generator to generate a loud sound upon manual command by the user or by remote command from the other entity. The transmitter can be an analog data link or part of any packet data radio communication link.

Airborne radiotelephone communications system

Abstract: The airborne radio communications system of the present invention enables an airborne radio to communicate with the ground based cellular radiotelephone system. The present invention also enables the ground based system to keep track of the location of the airborne radiotelephone and page it when a call from the ground based telephone system is received. The ground base station is connected to upward radiating antennas that form airborne cells. As the aircraft with the radio flies through the airborne cells, the airborne relay receives the signals from the base station and relays them to the radio. If the radio is transmitting signals, the relay transmits those signals, through the airborne cells, to the base station. As the aircraft moves from cell to cell, the radio is handed off to the next cell to maintain communications with the ground.

Radiowave Propagation and Antennas for Personal Communications

Abstract: Introduction. Fixed-Site Antennas. The Radio Communication Channel. The Radio Frequency Spectrum. Communications Using Earth-Orbiting Satellites. Radiowave Propagation - Radio Test Sites. Radiowave Propagation - The Urban and Suburban Paths. Waves in Multipath Propagation. Receiver Sensitivity and Transmitted Fields. Simulated Human Body Devices. Loop, Dipole and Patch Antennas. A Radio Communication System. Appendices.