Browse Prior Art Database

Infrared Microbroadcasting Network for In-House Data Communication

IP.com Disclosure Number: IPCOM000048250D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 3 page(s) / 97K

Publishing Venue

IBM

Related People

Gfeller, F: AUTHOR

Abstract

This article describes a wireless microbroadcast network for in-house data communication, based on an infrared carrier, to interconnect clusters of terminal stations located within the same room or shop floor. The network allows flexible and easy to change interconnection of many terminals free from cable constraints.

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Infrared Microbroadcasting Network for In-House Data Communication

This article describes a wireless microbroadcast network for in-house data communication, based on an infrared carrier, to interconnect clusters of terminal stations located within the same room or shop floor. The network allows flexible and easy to change interconnection of many terminals free from cable constraints.

Fig. 1 is an overall view of the system. It comprises a controller connected to a host computer system and a plurality of transponders connected to the host by an electrical bus arrangement. Transponders are located at the ceiling. Many terminal stations are located on the floor. Data are transferred between controller and transponders as electrical signals, and between transponders and stations as infrared signals. Thus, the transponders include circuitry for converting signals from electrical to infrared form, and vice versa.

The transport system architecture for the network, shown in Fig. 2, is tailored to the specific properties of the infrared channel. It provides a down-link infrared channel operating at a carrier frequency of, e.g., 200 kHz, which is used in broadcast mode. The up-link infrared channel operates at, e.g., 400 kHz (twice the down-link frequency). Access to the up-link channel is controlled by the well-known Carrier Sense Multiple Access (CSMA) method with collision detection.

Each of the terminal stations A1...A7 is equipped with a network adapter and an infrared (IR) modem. Each transponder has an up-link section comprising an infrared (IR) receiver, a carrier tracking phase locked loop (PLL), a frequency divider, and a line driver, and a down link section comprising a line receiver, a low-pass (LP) filter and an infrared (IR) sender.

At the controller, one transponder port is provided for each transponder, and one host port for the host. Ports and controller are interconnected by a bus system comprising four buses: a transponder bus for data, a transponder select bus, a request transponder bus, and an enable transponder bus for request and control signals. Each port comprises a line receiver, a line driver, and two AND gates.

When a signal is received from a transponder, it is transferred as access request via the request transponder bus to the controller. The controller, via the transponder select bus, can grant access to the transponder bus for one transponder by enabling the respective AND gate. The controller can further selectively enable down-link transfer of data from the transponder bus to individual transponders by enabling respective AND gates via the enable transponder bus. The same mechanism is used for data transfer to and from the host.

The functions of each IR modem in a terminal station include transmission and reception using the frequency-shift keying (FSK) method, as well as carrier sensing and collision detection of collided data packets.

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Each packet entered at any modem is transmitted across t...