EAC - Voluntary Voting System Guidelines

Name : | James Johnson
Organization : | N/A
Post Date : | 9/30/2005
Section Comments
Section : | 6.7
Page no. : |
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Comment : | How far can optical wireless devices transmit signals? Theoretically using optical, the transmission distance is limited only by the output power of the source and the sensitivity of the detector. With a suitably sensitive detector, optical radiations from planets orbiting stars in other solar systems have been detected. Therefore in theory a transceivers could be designed to operate at the proper power level and communicating with a high gain receiver could operate over any desired distance. Form a practical standpoint however, when using Devices conforming to Short-Range IrDA Data Physical Layer specifications standard [IrDA 1.0 and 1.1] distances are limited to 1.0 meter (~3.3 feet). At this distance devices provide near error free (1 error bit in 109 bits transmitted) communication at a data rate of 115.2 Kb/s or over 14,000; 8-bit characters per second plus overhead. Directional transmitters (IR LEDs) exist for transmitting at longer distances up to 30 or 40 ft. Using IrDA-Control-PHY devices can transmit at 75 Kbps up to 16ft. There are manufacturers that offer cradles for IrDA devices like PDAs that allow them to operate over extended distances. A transceiver manufactured by Optical Paths support distances of over 100 feet at data rates up to 115kbps. Later generation of their products will support distance of up to 500 feet using the IrDA v1.1 / Fast Infrared specification allowing transmissions at 4.Mb/s. Under the existing NIST/IEEE P1583 specifications a manufacturer could install a system capable of operating at these extended distances as no maximum distance or power setting is stated. [Statements submitted to NIST Technical Guidelines Development Committee]