Showing papers on "Wi-Fi array published in 1993"

Development of WaveLAN®, an ISM band wireless LAN

Abstract: Wireless voice communications has seen a great many changes in the last few years, including the evolution of cordless telephones, cellular systems, and the development of standards for personal communications services (PCS). Recently, high-speed wireless local area networks (WLANs) have been getting more attention, both in marketing and research. This paper discusses the design philosophy in the development of NCR's WaveLAN®, and the technical tradeoffs.

Wireless local area network system

Abstract: A local area network system includes a wired backbone LAN (12) and at least one wireless LAN (14) cooperating with the backbone LAN (12) via an access point (22), which has a bridging function. When a source station (30) in the wireless LAN (14) transmits a packet to another station in the wireless LAN (14), the destination station should respond with an ACK signal. If no ACK signal is received by the source station, the packet is retransmitted. The access point (22) also receives the transmitted packet and if the access point (22) does not detect an ACK signal on the wireless channel', the access point (22) itself generates an ACK signal and retransmits the packet on the wireless LAN (14) or forwards the packet to the wired LAN (12) according to the packet destination address.

Tracking mobile users in wireless communications networks

Abstract: Tracking strategies for mobile wireless networks are studied, assuming a cellular architecture where base stations interconnected by a wired network communicate with mobile units via wireless links The cost of utilizing the wireless links for the actual tracking of mobile users is investigated A tracking strategy in which a subset of all base stations is selected and designated as reporting centers is proposed Mobile users transmit update messages only upon entering cells of reporting centers, while every search for a mobile user is restricted to the vicinity of the reporting center to which the user last reported It is shown that for an arbitrary topology of the cellular network (represented by the interference graph), finding an optimal set of reporting centers is an NP-complete problem Optimal and near-optimal solutions for important special cases of the interference graph are given >

Telephone call transfer between a wireless and wired telephone

Abstract: A wireless network controller supports telephone call between a wireless telephone and a wired telephone. First and second wired communication channels are connected to a telecommunication switch and the wired telephone, respectively. A third wired communication channel is coupled to a radio frequency base station that supports a plurality of concurrent wireless communication channels to wireless telephones. An interface circuit coupled to the first, second, and third channels switches the connection of the first channel associated with the telecommunication switch between the second and third channels, and hence between the wired and wireless telephones. Simultaneous connection to both the wireless and wired telephones is also supported. A conventional line terminating impedance is always presented to the switch regardless of whether one or both of the wireless and wired telephones are off-hook.

Mobile Wireless Computing: Solutions and Challenges in Data Management

Abstract: Mobile computing is a new emerging computing paradigm posing many challenging data management problems. We identify these new challenges and investigate their technical signi cance. New research problems include management of location dependent data, frequent disconnections, structuring distributed algorithms for mobile hosts, wireless data broadcasting, and energy e cient data access.

Method and apparatus for performing a hand-off in a wireless communication system

Abstract: An apparatus for performing a hand-off in a wireless communication system (100) comprises a plurality of fixed communication units (102) and a controller (104) coupled to the plurality of fixed communication units (102), and further comprises a portable communication unit (120). The fixed communication units receive (504) a common master synchronization signal from the controller, and receive (524) from the controller a request to monitor receivable transmissions from the portable communication unit (120) on the original channel. The fixed communication units perform (526) synchronous monitoring of the receivable transmissions from the portable communication unit (120) on the original channel, frame synchronization being established by the common master synchronization signal and maintained by maintaining bita synchronization while transmitting user data.

Methods for polling mobile users in a multiple cell wireless network

Abstract: A method for communicating information bidirectionally between a wired network (1) and a wireless network. The wireless network is of the type that includes header stations (12) each having a communication cell (2) associated therewith and one or more mobile communication units (10) disposed within the communication cell. The method includes a first step of, during a first portion of a wireless communication cycle, transmitting information over an uplink wireless communication channel from one or more of the mobile communication units to the header station. A second step of the method, accomplished during a second portion of the wireless communication cycle, transmits information over a downlink wireless communication channel from the header station to one or more of the mobile communication units. The information transmitted downlink includes frames of data received by the header station from the wired network. The first portion may be accomplished in part or in total by a CSMA protocol where the mobile units contend for access to the uplink communication channel. In one embodiment the header station initiates the first portion by transmitting to the header stations information for scheduling the sequence of the uplink transmissions.

Wireless local area network system with mobile station handover

Abstract: A local area network system (10) includes a wired backbone LAN (12) having a plurality of LAN segments (14, 16, 18) interconnected by transparent bridges (26, 44). A plurality of base stations (22, 52) are capable, of communicating with a mobile wireless station (30). In response to a decision at the mobile wireless station (30) to switch communication from a first base station (22) to a second base station (52) a handover request message (172) is transmitted from the mobile wireless station (30) via the backbone LAN (12) to the first base station (22) thereby updating dynamic filtering databases contained in the base stations (22, 52) and transparent bridges (26, 44) through which the handover request message (172) passes as to the new communication location of the mobile wireless station (30).

RAP-a novel medium access control protocol for wireless data networks

Abstract: A novel medium access control scheme, randomly addressed polling (RAP), is proposed and studied. RAP used in wireless networks allows that the base stations poll successfully only knowing the active mobile nodes via decentralized control without knowing the exact mobile nodes under coverage. Therefore, RAP can provide seemingless services for wireless (data) networks with good utilization of channel(s), transparent to multiple physical transmission, power efficiency for mobile nodes, and no handoff for data services (soft handoff for time-bounded services). In addition, the RAP protocol in infrastructured wireless (data) network architectures can be practically implemented with simple hardware and thus well suited for the medium access control protocol for wireless LANs and other personal communication systems,. >

Infrastructure equipment in a wireless communication system serves different service providers

Abstract: Independent groups of wireless telephone subscribers (tenants) are supported by common infrastructure communication equipment including network controller (WNC) and a database that stores group membership A plurality of radio frequency base stations are disposed to provide wireless communications channels for the wireless telephones. A switched telecommunication office supports conventional wired communication channels. The WNC supports a plurality of base stations and can couple a wireless and wired communication channel together to provide a voice channel for a wireless telephone subscriber. The WNC only provides a voice channel to a requesting wireless telephone subscriber if the base station carrying the request has been assigned to handle the group that includes the the requesting subscriber as determined by the database.

Diversity and automatic link transfer for a TDMA wireless access link

Abstract: The paper describes diversity and automatic link transfer techniques which have been proposed for low-power digital wireless access to telephone networks using a TDMA architecture. Experimental results which quantify and demonstrate the performance of those techniques are presented. An experimental prototype radio link consistent with Bellcore's Technical and Framework advisories on wireless access was used to obtain the performance results. The present work is targeted towards understanding the implications to local exchange networks of wireless technology alternatives that could provide access to those networks. >

Wireless LAN Systems

Abstract: From the Publisher: This guide to wireless LAN systems describes the current technologies, spells out the pros and cons of each, and offers implementation insights that can save your company valuable installation time, money, and effort. It provides in-depth analyses of all aspects of indoor LAN wireless transmission techniques via RF and infrared waves.

Apparatus and methods for wireless communications

Abstract: The present invention discloses a wireless LAN, a peer-to-peer wireless LAN, a wireless transceiver and a method of transmitting data, all of which are capable of operating at frequencies in excess of 10GHz and in multipath transmission environments. This is achieved by a combination of techniques which enable adequate performance in the presence of multipath transmission paths where the reciprocal of the information bit rate of the transmission is short relative to the time delay differences between significant ones of the multipath transmission paths. In the LANs the mobile transceivers are each connected to, and powered by, a corresponding portable electronic device with computational ability.

Autonomous time synchronization among radio ports in wireless personal communications

Abstract: The implications for local exchange networks of wireless technology alternatives that could provide access to those networks are discussed. A practical "over-the-air" algorithm which is autonomously performed by individual ports and hierarchically controlled by the ports having the most reliable timing is described. This process involves only small overhead for demodulating special timing bits transmitted by other ports and adjusting timing accordingly. Computer simulations based on a TDMA (time division multiple access) system with port spacing of 2000-3000 ft and 500-kb/s transmission rate are used as an example to evaluate possible impacts on wireless access.

Optical wireless local area networks: enabling technologies : Advances in optical technology

Abstract: The new generation of laptop and pen computers will require wireless connectivity to fully exploit the potential of personal mobile computing. They are also likely to require broadband telecommunications services for video transmission and access to multimedia databases. The use of the optical spectrum for wireless communications avoids radio frequency planning constraints, and can provide almost infinite bandwidth for these future applications. This paper describes enabling technologies that enhance the range, speed and practicality of optical wireless

Use of two-way wireless messaging for personal telephone management

Abstract: This paper explores the intersection of two-way wireless data messaging and telephony, enabling nomadic end users to screen, select, and receive calls and exchange messages with callers independent of location. This is accomplished by combining features of the public local exchange telephone network, a Bellcore experimental software prototype application, a wireless data network, and a palm-top computer equipped with a wireless modem. The paper describes a demonstration which illustrates how an end user, through use of a palm-top personal computer equipped with wireless communication capability, can be alerted to incoming telephone calls and selectively route the calls to his or her current location and return messages to the caller. The demonstration identifies the value of providing seamless interconnectivity between wireline and wireless networks to meet the emerging communications needs of people on the move.

Optical wireless LANs: applications and systems

Abstract: The author discusses optical wireless LAN, discussing the advantages of optical rather than radio links; system issues such as propagation; system topologies and protocols; available commercial systems; and research into optical wireless LAN which has been carried out at BTL.

The 5ESS® wireless mobile switching center

Abstract: The growing market for wireless telecommunications services is resulting in a strong movement toward digitizing these services. Currently, three digital wireless standards are specified. Each includes a mobile switching center (MSC) as the centralized network switching and call control entity. The MSC must be adaptable to a variety of network and service environments, and must support a broad range of sophisticated end-user services. AT&T's 5ESS® Switch supports the MSC function for two of the three digital wireless standards, and is an integral component of the AT&T MSC product for the third standard. Reuse of the existing hardware platform, designing wireless functionality as incremental extensions of the existing software architecture, and support of intelligent network (IN) capabilities on the 5ESS MSC, results in a uniquely matched solution for providing wireless services in a wide variety of network environments and applications.

Wireless LAN technologies and applications

Abstract: Wireless local area networks (LANs) and personal communications services (PCS) represent the growth sectors of the communications network technology of the 1990s. While PCS will support primarily voice communications, wireless LANs will typically support data communications. The authors discuss wireless LAN technologies, including infrared and RF transmission. The potential use of wireless LAN technologies for multimedia communications (voice, data, and imagery) are presented. The research activities in this growing technology area are also described. >

CASSIOPEE: A hybrid wireless LAN consisting of an infrared cellular network and a token bus backbone LAN

Abstract: The work presented concerns the study and the implementation of an in-house wireless local area network which allows fixed standard devices (Wired End System) and mobile devices (Moving End System) to interconnect. The topology presented consists of an industrial token bus backbone LAN and infrared wireless star subnets. The different access points are distributed around a "U" model. Details are given about a specific addressing method of the moving stations. The access method to the infrared medium, the tracking of the moving stations and the routing handling are partially distributed; a Hybrid Network Controller provides the complementary undistributed resources.

A 2.45 GHz wireless IC card system for automatic gates

Abstract: A 2.45-GHz wireless IC card system has been developed for a noncontact-type train station automatic gate system. This system consists of compact transmitter-receiver equipment and noncontact wireless IC cards. The newly developed technology used in this system comprises a small dual-port slot antenna for the card, a modulation-demodulation scheme for stable data transmission, and a cochannel carrier allocation system for operation with multiple gates. Operation of this wireless card system has been successfully demonstrated. >

A self-organizing wireless LAN system

Abstract: A self-organizing method of a decentralized LAN is proposed, its characteristics are evaluated by computer simulation based on a simple network model. It is found that this decentralized network self-organizing method can be adopted to established wireless LAN systems by adding a few functions. This method is extremely simple and the functions which each station must have are very few.

C-MCMA: a new multiple access protocol for centralized wireless local networks

Abstract: The development of wireless local area networks depends, to a large extent, on the availability of flexible and efficient multiple access techniques that cope with the constraints imposed by the wireless propagation environment. In this paper we consider centralized network topologies, with a base station exchanging data packets with a set of portable terminals. We propose a new multiple access protocol whereby the portable terminals compete for the uplink access to the channel with minipackets in response to controlling commands, issued by the base station. Accordingly, the protocol is called centralized minipacket competition multiple access (C-MCMA). In order to judge on the efficiency of C-MCMA its performance is compared with that of the busy channel multiple access protocol with collision detection (BCMA/CD), taking into account receiver capture effects and downlink traffic. It is concluded that for a wide range of values for the parameters of the models considered C-MCMA outperforms BCMA/CD. >

Apparatus and method for servicing wireless subscribers in a wireline environment

Abstract: A wireless interface block (115) allows wireless service to a plurality of wireless subscribers in a public branch exchange (PBX) wireline environment. Wireless interface block (115) provides the necessary signalling information to base-stations (120-122) in the wireless system via a time slot interchange (218), a processor (206), and a signalling interface (200). By implementing wireless interface block (115) between a PBX (103) and the wireless system, wireless telephone is provided to the wireless system in the PBX wireline environment while all the features and functions of PBX (103) are maintained.

Circuit based data transport for a wireless access communications system

Abstract: The interest in wireless data communications has been increasing, in part due to new wireless communications services and the availability of the portable data terminals such as notebook computers. This paper describes a Go-Back-N automatic repeat request (ARQ) radio link protocol for data transport over a TDMA/TDM Wireless Access Communications System (WACS). The paper investigates the throughput performance as a function of message length, signal-to-noise ratio and fading rate. Results show that 88% efficiency is achieved for signal-to-noise ratio exceeding 18 dB. This work is targeted towards understanding the implications to local exchange networks of wireless technology alternatives that could provide access to those networks.

Design considerations for a broadband indoor wireless system

Abstract: The growth of wireless personal communications systems (PCS) in the coming decade is expected to be dramatic, with some projected forecasts for the U.S. market alone of the order of $3 billion by 1997. At the same time, the full-scale development of high-speed ATM-switched networks and the evolution towards 'third generation' portables will make the integration of wireless and optical systems not only desirable but necessary. This study considers a future indoor wireless network operating in the MM-wavelength spectrum and capable of supporting broadband services like video teleconferencing and transmission of high resolution images on top of the traditional ones that include cordless telephony and paging. A point of view and a general framework for the interface of this system to a public switched ATM network are suggested here.