Telecommunications – Radiotelephone system – Special service
Reexamination Certificate
2000-01-19
2003-10-14
Vuong, Quochien (Department: 2685)
Telecommunications
Radiotelephone system
Special service
C455S517000, C370S908000
Reexamination Certificate
active
06633757
ABSTRACT:
TECHNICAL FIELD
The invention concerns wireless local area networks and the communication between the devices forming such a network. More specifically, the present invention relates to a communication scheme which allows a first device within the wireless local area network to determine whether some other device which provides a certain service is in adjacency of the first device, e.g. within the same room.
BACKGROUND OF THE INVENTION
Computer terminals and peripherals have become dramatically smaller and more portable. Personal computers and peripherals are small enough to sit on the desk at work. Smaller still are lap top computers and notebook computers. There are computer terminals which are small enough to be mounted in a vehicle such as a delivery truck. Still smaller are the hand held terminals typically used for their portability features where the user can carry the terminal in one hand and operate it with the other. A physical connection of the above devices by means of cables or fibers might have drawbacks, such as configuration constraints because of the limited length of the cable, limited number of ports on the computer thus limiting the number of peripherals that can be attached, cumbersome reconfiguration of hardwired devices, etc. Note that there are some peripheral interface systems where the limited number of ports on the computer does not really limit the number of peripherals. Universal Serial Bus (USB) and IEEE 1394 (Firewire) are examples of peripheral bus systems capable of supporting a large number of devices on a single port. Ethernet is an example of a communication system where the cable is used as a shared medium (other examples are token ring, FDDI (Fiber Distributed Data Interface), and DQDB (Distributed Queue Dual Bus)).
The smaller the devices get, the more important it becomes to replace wired-based physical connections by wireless ad-hoc connections (e.g. body networks, radio frequency connections, or infrared connections), since physically connecting the computer terminals, peripherals, and other devices by means of cables or fibers severely reduces the efficiency gained by making the units smaller. Ad-hoc connections are required where devices move around, enter an area and exit the area. The term ad-hoc refers to the need for frequent network reorganization.
Local area communication is rapidly evolving into what can be called personal local area networks, which are networks for communication between local peers or subsystems. These kind of networks will herein be referred to as local networks. Wireless communication is of particular importance in such local networks. There are different wireless communications approaches known that have been developed and designed with an eye on the communication between peers or subsystems of such local networks.
GTE Corporation has developed a short-range radio-frequency (RF) technique which is aimed at giving mobile devices such as cellular phones, pagers and handheld personal computers (PCs) a smart way to interact with one another. GTE's technique is tentatively named Body LAN (local area network). The original development of Body LAN was via a wired vest with which various devices were connected (hence the name Body LAN). This graduated to an RF connection a couple of years ago.
Xerox Corporation has developed a handheld computing device called PARC TAB. The PARC TAB is portable yet connected to the office workstation through base stations which have known locations. The PARC TAB base stations are placed around the building, and wired into a fixed wired network. The PARC TAB system uses a preset knowledge of the building layout and the identifiers of the various base stations to decide where a PARC TAB portable device is by the strongest base station signal. A PARC TAB portable device has a wireless interface to the base stations. The PARC TAB system assumes that the PARC TAB portable device is always connected to the network infrastructure. The location of each portable PARC TAB device is always known to the system software. The base stations establish regions and are connected to power supplies. PARC TAB communication systems have a star topology.
In an attempt to standardize data communication between disparate PC devices several companies, including Ericsson, IBM, Intel, Nokia, and Toshiba established a consortium to create a global standard for wireless RF-based connectivity between fixed, portable and mobile devices. There are many other adopter companies. The proposed standard comprises an architecture and protocol specifications ranging from the physical layer up to the application layer. The technology will for instance enable solutions to automatically synchronize application information kept in mobile devices with similar information kept in a fixed desktop computer when users enter their offices. Enabling seamless voice and data transmission via wireless, short-range radio, the Bluetooth technology will allow users to connect a wide range of devices easily and quickly, without the need for cables, expanding communications capabilities for mobile computers, mobile phones and other mobile devices. The Bluetooth operating environment is not yet fully defined, but there are expected to be similarities with the IrDA (Infrared Data Association) specification and the Advanced Infrared (AIr) specification. Other aspects that probably will find their way into Bluetooth might stem from the IEEE standard 802.11 and/or HIPERLAN, as promulgated by the European Telecommunications Standards Institute (ETSI).
Bluetooth radio technology provides a mechanism to form small private ad-hoc groupings of connected devices away from fixed network infrastructures. Bluetooth makes a distinction between a master unit—which is a device whose clock and hopping sequence are used to synchronize all other devices—and slave units in the same network segment. In other words, the Bluetooth approach is centralized. A query-based discovery scheme is used for finding Bluetooth devices with an unknown address. Queries are also centralized at a registry server. It is a drawback of such a centralized approach that there is a central point of failure. It is another disadvantage of such a system that more overhead is required than in a distributed scheme. The main problem of such a system is in locating a single registry server, and what to do if it disappears. If a random two devices encounter each other they must first recognize each other's presence, then decide which is the registry server, and then go about their business of communicating. It is this continual selection and re-selection of a leader that causes the increased overhead. The alternative is to expect users to carry one device that they always have with them, and make it always the leader.
This, however, is not always a practical option. Further details can be found in Haartsen, Allen, Inouye, Joeressen, and Naghshineh, “Bluetooth: Vision, Goals, and Architecture” in the Mobile Computing and Communications Review, Vol. 1, No. 2. Mobile Computing and Communications Review is a publication of the ACM SIGMOBILE.
HomeRF (based on Shared Wireless Access Protocol (SWAP)) is another example of an operating environment which can be used to connect devices. A HomeRF Working Group was formed to provide the foundation for a broad range of interoperable consumer devices by establishing an open industry specification for wireless digital communication between PCs and consumer electronic devices anywhere in and around the home. The working group, which includes the leading companies from the personal computer, consumer electronics, peripherals, communications, software, and semiconductor industries, is developing a specification for wireless communications in the home called the SWAP. The HomeRF SWAP system is designed to carry both voice and data traffic and to interoperate with the Public Switched Telephone Network (PSTN) and the Internet; it operates in the 2400 MHz band and uses a digital frequency hopping spread spectrum radio. The SWAP technology was derived fr
Hermann Reto
Husemann Dirk
Moser Michael
Nidd Michael
Schade Andreas
Herzberg Louis P.
International Business Machines Corp.
Law Office of Charles W. Peterson, Jr.
Vuong Quochien
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