Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
2000-01-19
2003-03-11
Gravini, Stephen (Department: 3622)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S522000
Reexamination Certificate
active
06532368
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns wireless local area networks and the communications between the devices forming such a network. More specifically, the present invention relates to a communication scheme which allows devices within the wireless local area network to announce their service and/or discover services provided by other devices.
2. Description of the Related Art
Computer terminal 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 may have drawbacks, such as configuration constraints which limit the number of peripherals that can be attached or cumbersome reconfiguration of hardware devices. Note that there are some cable or fiber-based communication systems where the limited number of ports on the computer may not limit the number of peripherals. Ethernet is one example of a communications system where the cable is used as a shared medium (other examples are token ring, FDDI (Fiber Distribution Data Interface), and DQDB (Distributed Queue Dual Bus)).
The smaller the devices get, the more important it becomes to replace fixed physical connections with 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 are moved within an area, enter an area, or exit an 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 networks will herein be referred to as local networks. Wireless communication is of particular importance in such local networks. There are wireless communication approaches that have been developed and designed with an eye on the communication between peers or subsystems of such local networks.
A typical example of a local network is the personal area network (PAN) which grew out of work between two research groups at the Massachusetts Institute of Technology's (MIT) Media Laboratory. The PAN technology uses a tiny electrical current to transmit a user's identification and other information from one person to another, or even to a variety of everyday objects such as cars, public telephones, and automated teller machines (ATMs). Information is transferred via microprocessors that are placed in PAN transmitters and receivers the size of a thick credit card. The digital data is then sent or received via a tiny external electric field. The small signal is conducted by the body's natural salinity and carries the information, unnoticed, through the body. The natural salinity of the human body makes a person an excellent conductor of electrical current. The PAN technology takes advantage of this conductivity. The low frequency and power of the signal ensures that the information, which is coded to the individual, does not travel beyond the body and can only be received by something, or someone, in contact with the body. The speed at which the information is currently transmitted is equivalent to a 2400-baud modem. Theoretically, 400,000 bits per second could be communications using this method. The PAN is a typical example of an ad-hoc body network which does not require any fixed cabling or the like.
The PAN technology has potential applications in business, medical, retail, and even in personal arenas. Business associates could, for example, exchange electronic business cards with a handshake, corporate security devices could automatically log users on and off computer systems, and subway commuters could pay for a ride by walking through a turnstile. PAN technology could also enable people to carry digital versions of their medical records for instant access by emergency medical technicians; calling card numbers could automatically be sent from a wallet to a payphone; and ATMs and automobiles would be able to immediately distinguish their owners as they approach. Another application lies with securities traders, needing the ability to quickly and reliably log on and off while on the trading floor, for entering purchases and sales. Even household devices, such as CD players, televisions and toasters, could identify and adapt to individual preferences and tastes using PAN technology. The PAN networks are usually point to point where the human body serves as a broadcast communications medium.
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 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.
Xerox Corporation has developed a handheld computing device called PARC TAB. The PARC TAB is portable yet connected to the user's office workstation through base stations which have known locations. The PARC TAB base stations are placed around a building, and wired into a fixed wired network. The PARC TAB system uses a preset building layout and identifiers of the various base stations to determine its location based on the strongest base station signal. A PARC TAB portable device has a wireless interface to the base stations. The PAC 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 single synchronization protocol (code-named Bluetooth) to address problems arising from the proliferation of various mobile devices. There are many other adaptor companies. The proposed solutions would automatically synchronize mobile devices when end-users enter their offices. Enabling seamless voice and data transmissions via wireless, short-ranged ratio, the Bluetooth technology will allow users to connect to 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 (ALr) specification. Further developments in Bluetooth may 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. A dra
Hild Stefan G.
Husemann Dirk
Nidd Michael
F. Chau & Associates LLP
Gravini Stephen
Percello Louis J.
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