Product category:
Wireless process sensors
News Release from: Moore Industries International | Subject: WLM
Edited by the Processingtalk Editorial
Team on 12 July 2007
Increased security on WLM Wireless Link
Module
The WLM employs Spread Spectrum Frequency Hopping technology and robust error detection and correction for increased wireless security
The WLM Wireless Link Module from Moore Industries provides accurate, reliable and secure wireless connectivity between remote field sites WLM, a bi-directional, wireless module, employs frequency hopping spread spectrum technology and 32-bit CRC error correction for secure, robust communications
This article was originally published on Processingtalk on 25 Aug 2008 at 8.00am (UK)
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The WLM supports either Ethernet or serial (RS-485) communications at speeds up to 188 kbps and ranges up to 25 miles, and operates at FCC license-free frequency ranges of 902-928MHz or 2.4-2.483GHz.
Many users are concerned that wireless communications can be "hacked" into by intruders.
For increased security, the WLM employs frequency hopping spread spectrum (FHSS) technology, where the transmitter changes the frequency at which it is broadcasting in a random pattern.
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Only a receiver programmed with the exact same algorithm is able to listen to and follow the message.
Of all the wireless technologies on the market, FHSS is the most secure.
For an intruder to successfully tune into a WLM system, he needs to know the frequencies used, the hopping sequence, the dwell time, and any included encryption.
Given that for the 2.4 GHz band the maximum dwell time is 400msec over 75 channels, it is almost impossible to detect and follow a FHSS signal if the receiver is not configured properly.
In addition, the WLM has high security features such as dynamic key encryption and 32 bit CRC error correction for secure, robust communications.
For increased security, the WLM is user-configurable via a PC-based HyperTerminal interface.
It is also available pre-configured from the factory.
The Crowded Spectrum.
In many plants that are converting to wireless, interference problems may arise because of crowded radio spectrums.
The WLM allows multiple networks to use the same band (called "co-location") because of different spread spectrum hopping patterns.
The WLM uses orthogonal hopping routines, which allow multiple radio networks to be in the same vicinity without causing interference with each other.
This is needed when designing large networks.
Lab studies show that up to 15 FHSS WLM networks may be co-located; in some wireless technologies, only three networks may be co-located.
Designed for use in field environments, the WLM operates in temperatures from -40 to 167F (-40 to 75C) and humidity of 0-95%RH.
It mounts on a DIN rail, supports Ethernet and RS-485 serial communications (including Modbus), and can be configured for a Master-Slave network, where one Master WLM can communicate with an unlimited number of "slave" WLMs.
A WLM network can be used with remote data acquisition equipment, PCs, PLCs, RTUs and any process control devices equipped with a serial (RS-485), Ethernet or Modbus port.
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