Showing papers on "Communications system published in 1997"

Applications of antenna arrays to mobile communications. I. Performance improvement, feasibility, and system considerations

Abstract: The demand for wireless mobile communications services is growing at an explosive rate, with the anticipation that communication to a mobile device anywhere on the globe at all times will be available in the near future. An array of antennas mounted on vehicles, ships, aircraft, satellites, and base stations is expected to play an important role in fulfilling the increased demand of channel requirement for these services, as well as for the realization of the dream that a portable communications device the size of a wristwatch be available at an affordable cost for such services. This paper is the first of a two-part study. It provides a comprehensive treatment, at a level appropriate to nonspecialists, of the use of an antenna array to enhance the efficiency of mobile communications systems. It presents an overview of mobile communications as well as details of how an array may be used in various mobile communications systems, including land-mobile, indoor-radio, and satellite-based systems. It discusses advantages of an array of antennas in a mobile communications system, highlights improvements that are possible by using multiple antennas compared to a single antenna in a system, and provides details on the feasibility of antenna arrays for mobile communications applications.

Rayleigh fading channels in mobile digital communication systems .I. Characterization

Abstract: When the mechanisms of fading channels were first modeled in the 1950s and 1960s, the ideas were primarily applied to over-the-horizon communications covering a wide range of frequency bands. The 3-30 MHz high-frequency (HF) band is used for ionospheric communications, and the 300 MHz-3 GHz ultra-high-frequency (UHF) and 3-30 GHz super-high-frequency (SHF) bands are used for tropospheric scatter. Although the fading effects in a mobile radio system are somewhat different than those in ionospheric and tropospheric channels, the early models are still quite useful to help characterize fading effects in mobile digital communication systems. This tutorial addresses Rayleigh fading primarily in the UHF band. That affects mobile systems such as cellular and personal communication systems (PCS). Part I of the tutorial itemizes the fundamental fading manifestations and types of degradation.

Computer conferencing system with real-time multipoint, multi-speed, multi-stream scalability

Abstract: An improved networked computer communications system handles arbitrary streams of data, and transports at varying speeds those streams where intermediate updates can be dropped if they are obsoleted by later arriving data updates, optimizing the utilization of network and node resources. Complex buffering by system server software allows distributed, parallel, or redundant processing, transmission, and storage for performance, reliability, and robustness. Various parameters of the system can be monitored, and the system can be reconfigured automatically based on the observations. Varied techniques reduce the perceived end-to-end latency and take advantage of software and hardware capabilities that assets connected to the system may possess. One conferencing system allows conference participants to share all or a portion of the display seen on their computer screens. The conferees may be at sites removed from each other, or may view a recorded presentation or archived conference at different times. Conference participants are either “presenters” who can modify the display or “attendees” who cannot modify the display. A pointer icon, which can be labeled to identify the conferee, is displayed on the shared image area. Each conferee can modify the position of his or her own pointer, even when not presenting, so that every participant can see what each conferee is pointing to, should a conferee choose to point to an element of the display. These and other features apply to other data streams shared in the conference or in meetings where there is no shared-image data stream.

Adaptive, performance-optimizing communication system for communicating with an implanted medical device

Abstract: An adaptive, performance-optimizing communication system for communicating with an implanted medical device in which signals are transmitted and received in accordance with predetermined, interrelated operational parameters, such as transmission rate, transmitter power, and the like. Various aspects of system performance, including bit error rate in received signals, the strength of received signals, the signal-to-noise ratio of received signals, the presence of local RF noise and non-telemetry related RF signals, and the like, are dynamically monitored by the communication system, to determine whether predetermined system performance goals are being met. If it is determined that one or more system performance goals are not being met, one or more operational parameters may be automatically adjusted so that desired performance can be achieved.

Network session management

Abstract: A communication system providing telephony communication across combined circuit switched and packet switched networks, such as a telephone network and the Internet, which are connectable to terminals, such as telephones and computers, for selective communication therebetween. The communication system includes an authorization and account control object in the packet switched network, multiple gateways between the circuit switched and packet switched networks providing controlled connectivity between those networks, and an information retrieval object in the packet switched network, wherein the authorization and account control object maintains a substantially real time record of user accounts and usage, and the information and retrieval object provides substantially real time retrieval of selected information from the authorization and account control object. The retrieval object provides on demand to terminals which provide authentication for access to an identified account information regarding that account. The information regarding the account is substantially real time information including information with respect to communications in progress, which are chargeable to the account which has been authenticated. The authorization and account control object is preferably a unitary logical object having distributed instances thereof handling multitudinous accounts of widely separated terminals. The retrieval object provides isolation of the authorization and account control object permitting simultaneous multitasking by the authorization and account control object and the retrieval object respectively.

Modular notebook and PDA computer systems for personal computing and wireless communications

Abstract: A small light weight modular microcomputer based computer and communications systems, designed for both portability and desktop uses. The systems make use of a relative large flat panel display device assembly (2), an expandable hinge device (10), battery power source (9), keyboard assembly (16), and wireless communications devices (32, 51). The systems are capable of bi-directional realtime communications of voice, audio, text, graphics and video data. Both wire-based or wireless communications methods and devices are implemented. Wireless communications devices may include one or more telephone-like handsets (14) and/or earset (34). The wireless communication devices may include one or more antennae (32). Systems can be configured in a portable arrangement similar to conventional notebook computers, but can be quickly and easily disassembled and re-assembled for office desktop uses. Systems may consist of a base computer unit (100) comprising wireless communication devices may act as a relay station relaying voice and other data between the handset or earset and external wide area communications networks. The system may be capable of performing, personal digital assistant (PDA), cellular telephone, conventional notebook computer, desktop computer functions.

Rayleigh Fading Channels in Mobile Digital Communication Systems Part II: Mitigation

Abstract: For pt. I see ibid., vol. 35, no. 7, p. 90, 1997. In Part I of this tutorial, the major elements that contribute to fading and their effects in a communication channel were characterized. In Part II, these phenomena are briefly summarized, and emphasis is then placed on methods to cope with these degradation effects. Two particular mitigation techniques are examined: the Viterbi equalizer implemented in the Global System for Mobile Communication (GSM), and the RAKE receiver used in CDMA systems built to meet Interim Standard 95 (IS-95).

Wireless machine monitoring and communication system

Abstract: A wireless machine monitoring and communication system includes one or more machine monitors (4a-m) which attach to one or more machines to sense a physical characteristic of the machine, such as vibration or temperature, and to produce wireless transmissions corresponding to the sensed characteristic. A command station (6) executes machine status polling in accordance with a time-division communication protocol and processes machine status data obtained during polling to determine the status of the machine. The machine monitor incorporates a wireless transmitter (430, 440) for transmitting at least status information, and the command station (6) incorporates a wireless receiver (618) for receiving monitor transmissions. To conserve power, the machine monitors (4a-m) are turned on only at preprogrammed times in accordance with the time-division communication protocol. Each machine monitor (4a-m) includes a receiver (430) and the command station (6) includes a transmitter (604) to enable the command station to send commands to each machine monitor. A microcomputer (418) in each monitor analyzes sensor data and a memory (422) stores the analyzed sensor data. Repeaters (8a-e) are employed as necessary to assist in propagating wireless transmissions throughout the system. A tachometer sensor (5a-c) is employed at each machine to provide monitors and sensors with information relating to machine speed. A computer network (10) is connected to the command station (6) for transferring data and for controlling the overall operation of the system.

Apparatus and method for recording, communicating and administering digital images

Abstract: A communication system includes at least one telephone unit, a transmission system for communicating from the telephone unit, and a server for receiving information via the transmission system. The telephone unit includes a digital image pick up by which images are recorded, transmitted to the server, and stored in the server depending upon classification information which characterizes the digital images and which is associated with the digital image data. The classification information is determined by an analysis unit in the server.

The role of synchronization in digital communications using chaos. I . Fundamentals of digital communications

Abstract: In a digital communications system, data is transmitted from one location to another by mapping bit sequences to symbols, and symbols to sample functions of analog waveforms. The analog waveform passes through a bandlimited (possibly time-varying) analog channel, where the signal is distorted and noise is added. In a conventional system the analog sample functions sent through the channel are weighted sums of one or more sinusoids; in a chaotic communications system, the sample functions are segments of chaotic waveforms. At the receiver, the symbol may be recovered by means of coherent detection, where all possible sample functions are known, or by noncoherent detection, where one or more characteristics of the sample functions are estimated. In a coherent receiver, synchronization is the most commonly used technique for recovering the sample functions from the received waveform. These sample functions are then used as reference signals for a correlator. Synchronization-based receivers have advantages over noncoherent ones in terms of noise performance and bandwidth efficiency. These advantages are lost if synchronization cannot be maintained, for example, under poor propagation conditions. In these circumstances, communication without synchronization may be preferable. The main aim of this paper is to provide a unified approach for the analysis and comparison of conventional and chaotic communications systems. In Part I, the operation of sinusoidal communications techniques is surveyed in order to clarify the role of synchronization and to classify possible demodulation methods for chaotic communications.

Method and apparatus for integration of a wireless communication system with a cable t.v. system

Abstract: The present invention is a method and apparatus for integrating a personal communication system with a cable television plant. A set of radio antenna devices (RAD) (50A-50I) are connected to the cable plant (4). The RADs (50A-50I) provide frequency conversion and power control of signal received from the cable plant for wireless transmission to the remote units (24A-24C). The RADs (50A-50I) also provide power control and frequency conversion of wireless signals received from the remote units for transmission by the RADs (50A-50I) onto the cable plant (4). In addition to the functions of standard base stations and centralized controller, the CATV base station must also compensate for gain variations in the cable plant (4). The downstream power control is regulated by a RAD (50A-50I) reference signal which can be hidden within the CDMA signal for maximum efficiency.

System and method for equalizing the delay time for transmission paths in a distributed antenna network

Abstract: A communication system and method are provided for equalizing delay of transmission paths in a distributed antenna network. The distributed antenna network includes a plurality of remote antenna units, a central unit or a base station connected to the remote antenna units by transmission media, where each connection between the base station and one of the remote antenna units forms a separate transmission path having an associated delay time, a delay detector for determining the associated delay time of the separate transmission paths for each of the remote antenna units, and a delay compensator for adjusting the associated delay times in response to the delay detectors so that all of the associated delay times are substantially equalized. The system and method allow the delay parameters for the entire network to be set upon installation and then to be periodically updated without physical intervention by an operator. The detection and compensation allow for equalization of delay time differences that could not otherwise be compensated in the base stations of mobile stations of conventional systems and methods. Furthermore, the equalization synchronizes the bursts so that air frame timing between cells served by the remote antenna units is enhanced and the hand-off performance therebetween is improved.

Band-changing repeater with protocol or format conversion

Abstract: A repeater allows terminals of a first communications system, employing a first air protocol or radio interface, to communicate with terminals of a second communications system, employing a second air protocol or radio interface different from the first. Where the first and second air protocols differ only in operating frequency, but are otherwise compatible, the repeater may linearly translate signals from the first operating frequency to the second operating frequency, and vice versa, without demodulating and remodulating the signals. Where the air protocols differ in other ways, the repeater receives and demodulates signals from the first system, converts the signals to a common format, and remodulates and retransmits the signals according to the second air protocol (and vice versa), in the same frequency bands or in different frequency bands. The repeater translates control and signalling information transmitted in compliance with one air protocol to a format which complies with the other air protocol and has the same or equivalent effect. For each of the two communications system, the repeater emulates the functions of a terminal in that communications system, so that corresponding terminals in that system may communicate transparently with the repeater. The repeater provides a connection between the two emulated terminals, thereby allowing a terminal of the first system to use the repeater to communicate with an otherwise incompatible terminal of the second system.

Dynamic device driver

Abstract: A data communication system for allowing communication between various devices and various operating systems across various types of networking systems. The data communication system includes a host computer system (10) with a display device (15) and a processor (17) for generating signals for the display device, at least one peripheral device (56), and a dynamic device driver (42) for allowing two-way communication between the peripheral device and the host computer system. The dynamic device driver includes an operating system specific portion (33), configured for the operating system of the host computer system, and an operating system independent device driver portion (34), configured for the peripheral device. The operating system includes a linking mechanism (19) for allowing two-way communication between the operating system specific portion and the operating system independent device driver portion, thus allowing two-way communication between the processor and the peripheral device.

A high data rate communications network employing an adaptive sectored antenna

Abstract: A high data rate communication system (12) that employs an adaptive sectored antenna (46) is disclosed. The high data rate communication system (12) includes an antenna subsystem (28) for receiving and transmitting data. The antenna subsystem (28) is adapted to be spatially steered. A radio frequency transceiver (32) that is coupled to the antenna subsystem (28) and that selectively generates a bit error rate (BER) signal (206) and a receive signal strength indication (RSSI) signal (210) based upon a received antenna training sequence is also provided. The system (12) also includes a beam steering state machine (200) that is coupled to the radio frequency transceiver (32) and that selectively generates a BER_PASS signal (207) and an RSSI_PASS signal (209) based upon whether the BER signal (206) is in a first logical relationship with a predetermined BER signal and the RSSI signal (210) is in a second logical relationship with a predetermined RSSI signal. An antenna controller (38) is coupled to the antenna subsystem (28) and the beam steering state machine (200) and selectively generates antenna control signals (220) to spatially steer the antenna subsystem (28) based upon the BER_PASS signal (207) and the RSSI_PASS signal (209).

Personal communication device voice mail notification apparatus and method

Abstract: A communication system (100) includes at least one mobile communication device having a message indicator device, and a voice mail messaging center (104). The voice mail messaging center includes a voice mailbox (112) associated with the at least one mobile communication device (118). The voice mail messaging center directs a call to the voice mailbox associated with the at least one mobile communication device for recording a message when the mobile communication device is unable to receive the call. The voice mail messaging center optimizes communication from the messaging center to the mobile communication device when a voice mail message is recorded and the voice mailbox previously contained no messages, a second message indicator when the voice mailbox is full, and a third message indicator when the voice mailbox becomes empty.

Power transmission system, IC card and information communication system using IC card

Abstract: The present invention comprises a power transmission system, an IC card, and an information communication system using an IC card. In the power transmission system, power is transmitted by radio from the power transmission device to the IC card. In the IC card, the transmitted induced power is converted into a DC voltage, the transmitted induced power or a voltage corresponding to the induced power is detected, and a desired DC voltage to be suppled to the internal circuit is obtained in controlling resistance the detected induced power or the voltage corresponding to the induced power.

Video composition and position system and media signal communication system

Abstract: A video signal compositing system uses advanced communication techniques to make compositing with virtual studio, blue screen, multi-color compositing, dynamic blue screen, add insertion, synthetic transfiguration, or panoramic displays more economical. A data communication system comprises a number of shared communications channels for transmitting data streams in a bi-directional manner. Multiple interface subsystems are coupled to the communications channels. The interface subsystems have a time slot controller that allocates time slots between the communication channels. A router is used in conjunction with the interface subsystems to define the time slots in which data on the shared communications channels are valid. Processing elements connected via the interface subsystem allow reconfiguration, via the shared communications channels, of processing operations performed. Shared communications channels solve problems in video timing and routing of video signals, including but limited to video compositing and spatial positioning. Multiple mask, dynamic tracking, 3-D depth imaging, image processing and stereoscopic imaging enhance image compositing on systems ranging from NTSC video, to HDTV, to panoramic display systems.

Automatic meter reading data communication system

Abstract: An automatic meter reading data communication system having an integrated digital encoder and two-way wireless transceiver that is attachable to a wide variety of utility meters for meter data collection and information management. The integrated encoder and transceiver communicates commodity usage information over a two-way 900 MHz spread spectrum local area network (LAN) to a remotely located communication node. The communication node transmits this data to a utility service provider over a commercially available fixed wide area network (WAN). The utility service provider may also request data from the communication node over the same fixed wide area network.

Adaptive channel allocation method and apparatus for multi-slot, multi-carrier communication system

Abstract: A method and system of adaptive channel allocation in a multi-carrier, multi-slot system (220) is provided. In the method and system a subset of M channels is chosen from a larger set of N channels available for communications on a link (300, 330). As communications take place on the link (300, 330), signal quality (C/I) measurements on the channels of the subset of M channels and interference (I) measurements on the channels of the group of N channels are periodically performed. The C/I and I measurements are then used to reconfigure the subset of M channels to reduce co-channel interference on the link (300, 330).

Multi-rate wireless communications system

Abstract: A flexible multi-rate communications system (100) is disclosed. It supports a plurality of distributed user terminals (104-106) in full-duplex simultaneous communications with a central base station (102), where each user terminal is provided on demand with one of multiple bit rates at a negotiated quality of service (QOS). In one embodiment of this system (100), each user is assigned a variable bit rate, a variable processing gain, a variable transmit power, and a unique fixed rate spreading code. This results in a constant bandwidth signal received at a relative power level corresponding to the negotiated QOS. The above embodiment can be implemented in Frequency Division Duplexing and Time Division Duplexing configurations. This system (100) can be used in wireless local loop, mobile cellular, and wireless multimedia access systems.

Method and apparatus for performing mobile assisted hard handoff between communication systems

Abstract: A method and apparatus for performing inter-system hard handoff between communication systems (S1, S2) or inter-frequency hard handoff within a CDMA communication system is disclosed. The purpose of this invention is to reduce the probability of dropped calls during intersystem hard handoff. In the event that a hard handoff attempt is unsuccessful, the mobile station (18) will return to the original system (S1) with information which the communication system of the present invention uses to assist in the performance of future handoff attempts. Alternatively, with no handoff attempt made, the mobile station (18) monitors the destination system (S2), then returns to the original system (S1) with information used to assist in subsequent handoff attempts. The information returned from monitoring a CDMA system consists of results of a search for one or more pilots given at offsets in a specific list provided to the mobile station (18) by the base station (B1-B5) or a set of offsets based upon a predetermined search algorithm.

Galvanic transdermal conduction communication system and method

Abstract: A bi-directional galvanic conduction transdermal communication system is disclosed. The system includes an internal communication device implanted inside the body of a patient and an external communication device. The external communication device includes an external transmitter which transmits a carrier signal into the body of the patient during communication from the internal communication device to the external communication device. The carrier signal causes galvanic conduction to occur through the skin of the patient. The internal communication device includes an internal modulator that modulates the carrier signal with information stored in the internal communication device by selectively controlling the level of galvanic conduction that occurs through the skin of the patient. During external to internal communication, an external modulator modulates the carrier signal with information contained in the external communication device. Accordingly, the majority of the energy required for communication between the external and internal communication devices, regardless of the direction, is provided by the external communication device.

Communication system using geographic position data

Abstract: A wireless communication system employs directive antenna arrays and knowledge of position of users to form narrow antenna beams to and from desired users and away from undesired users to reduce co-channel interference. By reducing co-channel interference coming from different directions, spatial filtering with antenna arrays improves the call capacity of the system. A space division multiple access (SDMA) system allocates a narrow antenna beam pattern to each user in the system so that each user has its own communication channel free from co-channel interference. The position of the users is determined using geo-location techniques. Geo-location can be derived via triangulation between cellular base stations or via a global positioning system (GPS) receiver.

In-building modulated backscatter system

Abstract: In accordance with the present invention, a radio communications system is disclosed that can operate in one of several Modes which integrate in-building security, location determination, messaging, and data communications capabilities. The radio communication system includes at least one Interrogator for generating and transmitting a radio signal. One or more Tags of the system receive the radio signal. A Backscatter Modulator modulates the reflection of the radio signal using a subcarrier signal, thereby forming a reflected modulated signal. The Interrogator receives and demodulates the reflected modulated signal. The Interrogator can also transmit a first information signal to one or more tags, specifying which tags should respond using the Backscatter Modulator. In the Interrogation Mode, the Interrogator can determine the identity of the Tags in the reading field, and can exchange data with those Tags that have been identified. In the Location Mode, the radio communications system can instruct some or all Interrogators to determine the location of a Tag or Tags within the building, regardless of whether the Tag or Tags are in radio range of the Interrogation Mode. In the Messaging, or low speed data communications Mode, the radio communications system can instruct some or all Interrogators to transmit a command addressed to a particular Tag or Tags, regardless of whether the Tag or Tags are in the reading field of the Interrogation Mode, questing that Tag or Tags perform some action. Other embodiments of the Messaging Mode allow the Interrogator to transmit data in addition to a command to the Tag or Tags, and also for the Tag or Tags to transmit a signal back to the Interrogator. This radio communications system can be interconnected with other communications capabilities such as electronic mail, voice mail, location, inventory management, and other systems.

Method for transmitting data using a digital control channel of a wireless network

Abstract: An apparatus and method for transmitting data to and from a data collection device using the short message service functionality of the control channel of a personal communications system transmission protocol is disclosed. The method includes first transmitting a request for data from a remote device to the data collection device using the short message service portion of the digital personal communications system control channel transmission protocol. The requests are received a the data collection device and interpreted. According to the interpretation, the data collection device compiles the data that was requested by the remote device. The compiled data is transmitted to the remote device using the short message service portion of the digital personal communications system control channel transmission protocol.

Advanced call waiting and messaging system

Abstract: A communications system is designed to allow a call waiting subscriber who is already busy on a first call to receive information associated with a message being recorded by a second caller attempting to reach the subscriber. According to one aspect of the principles disclosed herein, a one-way conference call is established between the second caller and the subscriber as the message is being recorded to allow the subscriber to eavesdrop on the message. According to another aspect of the principles disclosed herein, an Automatic Speech Recognition system may transcribe the message being recorded into ASCII coded data that is delivered to the called party. The received message allows the subscriber to effectively assess whether the first call in progress should be interrupted to answer the second call in waiting.

Self-cancelling full-duplex RF communication system

Abstract: A method is presented herein whereby both transceivers of a full-duplex RF communications system can use the same spectrum at the same time. Self-interference is cancelled using a combination of antenna placement, analog RF suppression, and digital adaptive filtering. The details of this self-cancelling technique are presented.

High bandwidth delivery and internet access for airborne passengers

Abstract: A method and a communications system in which a request for data transmitted by an airborne transmitter over a low-bandwidth air-to-ground communication system uplink and received by a ground-based receiver. The requested data is then transmitted over a high-bandwidth communication system downlink, such as a DBS satellite system downlink, preferably using an MPEG-2 compression technique, and received by an airborne receiver located on the same aircraft as the airborne transmitter. The received request for data is transmitted to a data network that contains the requested data, such as the Internet or a private data network, using circuit-switched techniques. According to the invention, the requested data includes one of video information, audio information and textual information.

Multiple access communications system and method using code and time division

Abstract: A multiple access communications system and method using Code Division Multiple Access (CDMA) and Time Division Multiple Access (TDMA) comprises coding information signals with CDMA codewords to be transmitted over a common frequency spectrum, time compressing the CDMA codewords for transmission only during allocated timeslots, activating a receiver only during the allocated timeslots to receive and decompress the time compressed CDMA codewords, and decoding the decompressed CDMA codewords to recover the information signals.