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(RSS) Electronic tether for Wireless Devices attached to POS

IP.com Disclosure Number: IPCOM000021169D
Original Publication Date: 2003-Dec-31
Included in the Prior Art Database: 2003-Dec-31
Document File: 1 page(s) / 42K

Publishing Venue

IBM

Abstract

Wireless computing devices are pervasive in many personal and business applications and include devices such as lap top computers, handheld Personal Digital Assistants (PDAs), cell phones, game controllers, bar code scanners, printers, etc. Various wireless communications channels include 802.11a,b,g and Bluetooth which are used to communicate data between the mobile device and a fixed base station. These wireless data channels may simplify usage of the mobile devices but pose a new problem of the device being lost or stolen. It is desireable for a means of physical security to detect when a wireless device has been moved beyond a predetermined boundry such as outside of a room or building.

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(RSS) Electronic tether for Wireless Devices attached to POS

Electronic tethers of various forms have been invented to sound an alarm when the wireless device wanders away from the base station. These usually require a dedicated communication link to sense proximity between devices and their base stations. Radio Frequency (RF) links are one method currently in practice. As the wireless device exceeds the range of the RF transmitter a visible message is displayed on the base station or an error signal is transmitted along the wireless data channel to the mobile device instructing that an audible alarm be sounded. This method requires a 2nd wireless channel dedicated to security. This increases power consumption and lowers battery life in portable devices, as well as increases product cost. A simpler method exists which uses the basic wireless data communication channel as the security means. This method relies on the fact that the wireless data channel itself is range limited. As the effective communication range is exceeded data throughput and data errors begin to increase. This reduces overall performance and can be an indicator to software control algorithm that the general proximity between the two exceeds a predetermined limit. An audible alarm or displayed message can then be used as a warning. There are several key concepts required for implementing this method. A software algorithm will monitor the data transmission error rate (retry rate or data throughput) of the wireless data channel. When the data channel is idle, a digital 'good link' data message of sufficient length is periodically transmitted so the algorithm will have traff...