Showing papers on "Wireless published in 1997"

Situation information system

Abstract: A wireless system for providing services and time-critical information about places and events to mobile computers and their users proximate to their current locations or potential destinations within enclosed areas, urban landscapes, and open areas, including travel distances and transit times, entertainment, merchants' messages, area attractions, communications, current locations of system users, and traffic congestion information and user-generated information from bar-coded objects and digital photographs of scenes and other materials. Included is a combination low-radiation dosage-reception handset for wireless communications which includes bar-code reader and digital camera peripheral devices for mobile computers, a bracket for interfacing a mobile computer with radio to external systems, and methods for improving the operations of computer reception, search, and display of such information for the edification, efficiency, and enjoyment of computer users.

Space-time processing for wireless communications

Abstract: This paper reviews space-time signal processing in mobile wireless communications. Space-time processing refers to the signal processing performed in the spatial and temporal domain on signals received at or transmitted from an antenna array, in order to improve performance of wireless networks. We focus on antenna arrays deployed at the base stations since such applications are of current practical interest.

A resource estimation and call admission algorithm for wireless multimedia networks using the shadow cluster concept

Abstract: The shadow cluster concept can be used to estimate future resource requirements and to perform call admission decisions in wireless networks. Shadow clusters can be used to decide if a new call can be admitted to a wireless network based on its quality-of-service (QoS) requirements and local traffic conditions. The shadow cluster concept can especially be useful in future wireless networks with microcellular architectures where service will be provided to users with diverse QoS requirements. The framework of a shadow cluster system is completely distributed, and can be viewed as a message system where mobile terminals inform the base stations in their neighborhood about their requirements, position, and movement parameters. With this information, base stations predict future demands, reserve resources accordingly, and admit only those mobile terminals which can be supported adequately. The shadow cluster concept involves some processing and communication overheads. These overheads have no effect on wireless resources, but only on the base stations and the underlying wireline network. It is shown how base stations determine the probabilities that a mobile terminal will be active in other cells at future times, define and maintain shadow clusters by using probabilistic information on the future position of their mobile terminals with active calls, and predict resource demands based on shadow cluster information. In addition, a call admission algorithm is introduced, which uses current traffic and bandwidth utilization conditions, as well as the amount of resources and maximum allowable "dropping probability" being requested. Performance results showing the advantages of the shadow cluster concept are also included.

Wireless telephony for collecting tolls, conducting financial transactions, and authorizing other activities

Abstract: The following procedures describe the use of cellular telephones and other analog or digital wireless communication devices to conduct transactions and activities. These procedures effectively allow such devices to function as an electronic wallet, a wireless PIN pad, and a contactless Smart Card.

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.

Airborne broadband communication network

Abstract: A deployed group of airborne vehicles (AV) provide relay communication service among mobile and airborne customers by using a directed phased array antenna (PAA). The PAAs provide broadband communication with mobile customers. Each AV has a wireless link to one or more neighboring AVs forming an airborne inter-networked mesh constellation for routing traffic between mobile customers. The AV constellation includes gateway members that maintain high capacity point-to-point satellite or terrestrial base station links for communication connectivity outside the aggregate coverage area of the AV constellation. A constellation is managed by an operations control center whose duties include positioning and scheduling replacement of the constellation AVs and routine network management functions, to implement the rapidly deployable, broadband, mobile, wireless communication network.

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.

Establishing wireless communications services via high-altitude aeronautical platforms: a concept whose time has come?

Abstract: The focus of this article is high altitude aeronautical platforms (HAAPs) such as airships, planes, helicopters, or some hybrid salutions which could operate at stratospheric altitudes for significant periods of time, be low-cost, and be capable of carrying sizable, multipurpose communications payloads. Of particular interest are ways to implement cellular/PCS or high-speed data networks in airborne platforms. From a communications perspective, HAAPs would have many advantages over both their terrestrial and satellite counterparts. If HAAPs prove to be reasonably stable, reliable, and not too costly, they will offer considerable opportunities for wireless services provision, and the introduction of innovative communications concepts such as cell scanning and stratospheric radio relays.

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.

Low-profile enhanced-bandwidth PIFA antennas for wireless communications packaging

Abstract: The development of small integrated antennas plays a significant role in the progress of the rapidly expanding military and commercial communications applications. The recent advances in RF and microwave high-density circuit packaging technologies in multifunction wireless communications systems have called for the parallel development of compact and efficient antennas that can be used over a wide frequency range. This paper addresses the development and characterization of several low-profile and integrated antennas with enhanced bandwidth for wireless communications systems. The new radiators are developed by adding parasitic elements or tuning devices to a familiar integrated antenna-the planar inverted F antenna (PIFA). Simulations based upon the finite-difference time-domain (FDTD) method and method of moments (MoM) are used to model the performance of the antennas. Comparisons with measured results on fabricated antenna structures are provided for simulations validation.

CDMA mobile station wireless transmission power management with adaptive scheduling priorities based on battery power level

Abstract: A method adapts scheduling priorities in a CDMA wireless communications system to conserve battery power in mobile terminals operating within the system. A base station, within the system, receives battery power level information and other setup information from mobile terminals operating within the service area of the base station during call setup procedures. Based on the battery power level information and other setup information, the base station adapts scheduling priorities for the mobile terminals to expedite wireless transmissions from those mobile terminals reporting low battery power levels. The base station schedules the transmissions from low battery power mobile stations to be clustered together in a low-power time slot which is separate in time from the scheduled transmissions from high battery power mobile stations. The base station transmits a power control message to the low battery power mobile stations, to reduce the transmission power required for those mobile stations during the low-power time slot.

ARQ error control for fading mobile radio channels

Abstract: In this paper, we study the correlation properties of the fading mobile radio channel Based on these studies, we model the channel as a one-step Markov process whose transition probabilities are a function of the channel characteristics Then we present the throughput performance of the Go-Back-N and selective-repeat automatic repeat request (ARQ) protocols with timer control, using the Markov model for both forward and feedback channels This approximation is found to be very good, as confirmed by simulation results

Vibration monitor and transmission system

Abstract: An apparatus is disclosed consisting of one or more machine monitors which attach to one or more machines to sense a physical characteristic of the machine, such as vibration or temperature, and produce wireless transmissions corresponding to the sensed characteristic, and a command station which receives the transmissions from the machine monitors and processes the information to give an indication of the condition of the machine. The machine monitor incorporates a wireless transmitter to transmit the sensor data, and the command station incorporates a wireless receiver to receive the sensor data. In the preferred embodiment of the invention, the machine monitors are not continuously on, but turn on only at preprogrammed times according to turn-on commands generated by a timer circuit within each machine monitor. In another preferred embodiment, each machine monitor includes a receiver and the command station includes a transmitter to enable the command station to send commands to each machine monitor. Each machine monitor includes a microcomputer to analyze the sensor data and a memory to store the analyzed sensor data prior to transmission to the command station. A repeater receives the sensor data transmissions from the machine monitors and retransmits the data to the command station when, due to site conditions, the machine monitors are beyond the receiving range of, or out of the line of sight to the command station.

Orthogonal frequency division multiplexing system with dynamically scalable operating parameters and method thereof

Abstract: The scaleable OFDM system according to the principles of the present invention provides increased flexibility and adaptability by providing scaling of the operating parameters and/or characteristics for the OFDM system. For example, control circuitry can scale the bit rate by scaling of the OFDM symbol duration, the number of carriers and/or the number of bits per symbol per carrier. Scaleability permits the scaleable OFDM system to operate in various communications environments requiring various operating parameters and/or characteristics. By scaling the operating parameters and/or characteristics of the OFDM system when control circuitry determines that different operating parameters and/or characteristics are necessary or advantageous, the control circuitry can dynamically change the operating parameters and/or characteristics, thereby providing compatibility or the desired performance. For example, by dynamically scaling the bit rate, widely varying signal bandwidths, delay spread tolerances and signal-to-noise ratio (SNR) requirements can be achieved. As such, a scaleable OFDM system is particularly suitable for application in mobile, wireless communication devices, which support a variety of services, in a variety of environments, indoor as well as outdoor and in radio channels with differing bandwidths.

Spread spectrum CDMA systems for wireless communications

Abstract: From the Publisher: Spread spectrum CDMA systems are becoming widely accepted and promise to play a key role in the future of wireless communications. This comprehensive new book explains the main issues of spread spectrum CDMA and makes its practical applications available to network engineers and managers. Packed with nearly 1,000 equations, it also provides the mathematical tools necessary to apply the technology to your own wireless system. In clearly written presentations, Spread Spectrum CDMA Systems for Wireless Communications outlines the main advantages of the spread spectrum technique, describes its key elements, and also... ? Presents important code acquisition strategies for direct sequence (DS) and frequency hopping (FH) systems — and the mathematics used for their analysis ? Compares various code tracking loop systems, such as Delay Lock Loop (DLL) and Tau Dither Loop (TDL) ? Details receiver configurations based on CCD, SAW, and DSP matched filters ? Examines system capacity issues related to the CDMA cellular network ? Explains the CDMA overlay, packetized transmission in CDMA networks, and the problems of multiuser detection You also strengthen your understanding of important topics such as automatic threshold detection, sequential and in lock/out of lock detectors, and discrete tracking loops for slow frequency hopping (SFH). Chapter-end appendices provide insight into the newest CDMA standards, including the IS-95 standard. The practical design guidelines presented throughout the book make it a valuable reference tool for network designers, while updates on various performance aspects help mobilecommunications managers make better, more informed choices for their own systems. The book also serves as an excellent primer for post-graduate students in communications.

Method of using fingerprints to authenticate wireless communications

Abstract: Disclosed are a system and a method employing a user's fingerprint to authenticate a wireless communication. The user's personal fingerprint is employed as the secret key in the context of a modified 'challenge-response' scenario. The system includes a fingerprint capture module on a mobile personal wireless communication device (e.g., a wireless telephone) and a central authentication system coupled to a conventional mobile switching center. The central authentication system contains information that associates each mobile identification number ('MIN') with a particular user's fingerprint. When a wireless communication is to be initiated, the central authentication system engages in a challenge-response authentication with the mobile switching station or the wireless phone using the stored fingerprint associated with the MIN through the common air interface. The correct response from the mobile station will only be generated when the user's fingerprint entered through the fingerprint capture module attached to the mobile station matches the information sent from the central authentication system, and only calls placed from authorized users are connected.

Method and apparatus for addressing a wireless communication station with a dynamically-assigned address

Abstract: A method, and associated apparatus, for providing a wireless communication station (52) with a dynamically-assigned address which provides a temporary address to route data to the wireless communications station (52). A temporary address is assigned to the wireless communication station (52) to permit data, such as packet data, to be communicated between the wireless communication station (52) and a correspondent host (54). Once communication with the wireless communication station (52) is terminated, the temporary address can be reassigned and reused pursuant to subsequent communications with another wireless communication station.

Modular/printed circuit card for wireless telecommunications

Abstract: A modular telecommunications system configured for wireless telecommunication in accordance with a pre-selected standard. Modular units are adapted to be secured within other items of electronic equipment for establishing a telecommunications link with a wireless network. The modular telecommunications unit comprises a housing for mounting a radio transceiver therein. The housing includes a plurality of contacts arranged along a first end, the contacts being adapted for engagement with contacts in the electronic equipment, and at least one radio connector disposed along the second, opposite end of the housing and connected to the radio transceiver within the housing whereby the radio transceiver can be coupled to an antenna to enable communication therefrom.

Implementation and performance evaluation of Indirect TCP

Abstract: With the advent of small portable computers and the technological advances in wireless communications, mobile wireless computing is likely to become very popular in the near future. Wireless links are slower and less reliable compared to wired links and are prone to loss of signal due to noise and fading. Furthermore, host mobility can give rise to periods of disconnection from the fixed network. The use of existing network protocols, which were developed mainly for the high bandwidth and faster wired links, with mobile computers thus gives rise to unique performance problems arising from host mobility and due to the characteristics of wireless medium. Indirect protocols can isolate mobility and wireless related problems using mobility support routers (MSRs) as intermediaries, which also provide backward compatibility with fixed network protocols. We present the implementation and performance evaluation of I-TCP, which is an indirect transport layer protocol for mobile wireless environments. Throughput comparison with regular (BSD) TCP shows that I-TCP performs significantly better in a wide range of conditions related to wireless losses and host mobility. We also describe the implementation and performance of I-TCP handoffs.

Ultra-wide bandwidth signal propagation for indoor wireless communications

Abstract: An ultra-wide bandwidth (UWB) signal propagation experiment is performed in a typical modern office building in order to characterize the UWB signal propagation channel. The bandwidth of the signal used in this experiment is in excess of one GHz. The robustness of the WVB signal to fades is quantified through histogram and cumulative distribution of the received energy in various locations of the building. The results show that UWB signal does not suffer fades.

Capability addressable network and method therefor

Abstract: A wireless, peer-to-peer, capability addressable network (22) is disclosed. The network (22) accommodates any number of peers (20). Network connections are formed based upon proximity between peers (20) and upon a needs and capabilities evaluation (82). Networks (22) support three classifications of service capabilities: service requesting, service providing, and service relaying. Wireless communications occur at a sufficiently low power to form a detection zone (28) of less than five meters for many peers (20).

Cellular communication system with dedicated repeater channels

Abstract: A cellular communication system in which dedicated repeater controller transceivers are included in base stations and wireless base stations. The repeater controller transceivers are configured to operate on a different channel as compared to communications received by or transmitted directly from mobile terminals. By utilizing a dedicated channel for communications between the base stations and wireless base stations, the contention areas formed by overlapping cell areas is effectively eliminated. The different channels may be based on differences in parameters using infrared communication techniques.

Improving performance of TCP over wireless networks

Abstract: Transmission Control Protocol (TCP) assumes a relatively reliable underlying network where most packet losses are due to congestion. In a wireless network, however, packet losses will occur more often due to unreliable wireless links than due to congestion. When using TCP over wireless links, each packet loss on the wireless link results in congestion control measures being invoked at the source. This causes severe performance degradation. In this paper, we study the effect of: burst errors on wireless links; packet size variation on the wired network; local error recovery by the base station; and explicit feedback by the base station, on the performance of TCP over wireless networks. It is shown that the performance of TCP is sensitive to the packet size, and that significant performance improvements are obtained if a good packet size is used. While local recovery by the base station using link-level retransmissions is found to improve performance, timeouts can still occur at the source, causing redundant packet retransmissions. We propose an explicit feedback mechanism, to prevent these timeouts during local recovery. Results indicate significant performance improvements when explicit feedback from the base station is used. A major advantage of our approaches over existing proposals is that no state maintenance is required at any intermediate host. Experiments are performed using the Network Simulator (NS) from Lawrence Berkeley Labs. The simulator has been extended to incorporate wireless link characteristics.

Network protocol method, access point device and peripheral devices for providing for an efficient centrally coordinated peer-to-peer wireless communications network

Abstract: A network protocol method (300), access point device (600) and peripheral devices (700, 800) provide an efficient centrally coordinated peer-to-peer wireless communications network wherein the access point device: (1) broadcasts a block assignment that specifies a wireless source peripheral device and a wireless destination peripheral device; (2) receives, from the wireless destination peripheral device, sequence information; (3) determines whether the sequence information represents one of: a negative acknowledgment and a positive acknowledgment with a sequence number; (4) forwards an acknowledgment to the wireless source peripheral based on the sequence information, and repeats steps (1)-(4) until N blocks of data, N a predetermined integer, have been transferred from the wireless source peripheral to the wireless destination peripheral.

Emergency locator device transmitting location data by wireless telephone communications

Abstract: A portable emergency locator device includes a global positioning system (GAS) receiver generating location data and a wireless telephone transceiver for transmitting the location data as digital data to a called station during a two-way voice conversation via a wireless telephone network (cellular, PCS, or satellite). The emergency locator device can be implemented as a conventional wireless telephone having interfaces for receiving the location data from an external GAS receiver and vehicle status data from external vehicle control systems. The data received from the interfaces is stored in an internal memory for transmission to the called station in response to an emergency event trigger.

Asynchronous multimedia multihop wireless networks

Abstract: Personal communications and mobile computing will require a wireless network infrastructure which is fast deployable, possibly multihop, and capable of multimedia service support. The first infracture of this type was the packet radio network (PRNET), developed in the 70's to address the battlefield and disaster recovery communication requirements. PRNET was totally asynchronous and was based on a completely distributed architecture. It handled datagram traffic reasonably well, but did not offer efficient multimedia support. Recently, under the WAMIS and Glomo ARPA programs several mobile, multimedia, multihop (M/sup 3/) wireless network architectures have been developed, which assume some form of synchronous, time division infrastructure. The synchronous time frame leads to efficient multimedia support implementations. However, it introduces more complexity and is less robust in the face of mobility and channel fading. In this paper; we examine the impact of synchronization on wireless M/sup 3/ network performance. First, we introduce MACA/PR, an asynchronous network based on the collision avoidance MAC scheme employed in the IEEE 802.11 standard. There, we evaluate and compare several wireless packet networks ranging from the total asynchronous PRNET to the synchronized cluster TDMA network. We examine the tradeoffs between time synchronization and performance in various traffic and mobility environments.

High data rate CDMA wireless communication system

Abstract: A novel and improved method and apparatus for high rate CDMA wireless communication is described. A set of individually gain adjusted subscriber channels are formed via the use of a set of orthogonal subchannel codes. The set of sub-channel codes are comprised of four Walsh codes. The pilot data and control data are combined onto one channel. The remaining two transmit channels are used for transmitting non-specified digital data including user data or signaling data, or both.

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.

Fair scheduling in wireless packet networks

Abstract: Fair scheduling of delay and rate-sensitive packet flows over a wireless channel is not addressed effectively by most contemporary wireline fair scheduling algorithms because of two unique characteristics of wireless media: (a) bursty channel errors, and (b) location-dependent channel capacity and errors. Besides, in packet cellular networks, the base station typically performs the task of packet scheduling for both downlink and uplink flows in a cell; however a base station has only a limited knowledge of the arrival processes of uplink flows.In this paper, we propose a new model for wireless fair scheduling based on an adaptation of fluid fair queueing to handle location-dependent error bursts. We describe an ideal wireless fair scheduling algorithm which provides a packetized implementation of the fluid model while assuming full knowledge of the current channel conditions. For this algorithm, we derive the worst-case throughput and delay bounds. Finally, we describe a practical wireless scheduling algorithm which approximates the ideal algorithm. Through simulations, we show that the algorithm achieves the desirable properties identified in the wireless fluid fair queueing model.

Multimedia call signalling system and method

Abstract: A system and method for performing call signalling for multimedia call setups. A user equipped with calling terminals of various types may initiate a call from any of these terminals, and the call is intercepted and handled by the system. A calling agent looks up an E-mail address for the called party, and sends a setup request E-mail to a called agent associated with the called party. The called agent determines the current terminal that the callee is using, and together with the calling agent a call medium and other parameters are established. Then a connection is made between a calling terminal and the current terminal. This provides a generic signalling system for a callee using a wireline terminal, wireless terminal, or H.323 terminal to be connected to a called terminal also being any one of these or other types.