The Institute of Electrical and Electronics Engineers (IEEE) in a 2003 survey of current commercial and military M2M sensor user requirements highlighted several factors affecting wireless M2M sensor networks. In order of importance, these factors are: data reliability; battery life; cost; transmission range; data rate; data latency; physical size; and data security.
As indicated however, the application will drive use, design and cost characteristics. For example, one user set from the IEEE survey had the following requirements among these selected parameters:
• Transmission distance: M2M sensor to node: 32% less than 10 meters, 41% from 10 to 100 meters, 27% over 1000 meters
• Minimum M2M sensors per node: 20% at 5 or less, 15% at more than 50
• Battery life: 30% at 1 month or less, 10% at greater than 24 months
• Latency: 10% at less than 10 milliseconds, 45% at 10 to 250 ms, 30% greater than 2000 ms
• Data rate: 18% at 100 or more messages per second, 23% at 10 to 100 per second, 34% at 1 to 10 per second, 16% at 100 seconds or greater per message
As these data illustrate, applications have vastly different needs. New technologies will enable yet an even greater array of applications and with those applications will come design and cost trade-offs. A 2002 study by the U.S. Department of Energy (DoE) highlighted several reasons forwireless networking of M2M sensors in industrial applications:
• Wireless is now cheaper to install, as wiring costs range from $100 to more than $1,000 per foot to install in harsh environments
• Wires crack or fail, adding to maintenance costs that wireless avoids
• Connectors are the single biggest failure point in wired networks
• Wireless provides flexibility in placement that wired M2M sensors cannot
• Wireless enables rapid deployment
At volumes, MEMS and other semiconductor approaches allow integration of multiple functions and lower-cost packaging into a more reliable package than a wired M2M sensor. The DoE has forecast that, by 2010, the cost of wireless M2M sensor systems could be one-tenth the cost of current wired systems.
Applications, including many for M2M sensors, require non-traditional antennas in order to achieve higher gain, allowing reduction in transmitter battery power and better reception in “dead spots”. They allow w multiple frequency operation within a single antenna permitting integration of multiple applications or realtime frequency tuning and provide wider channel bandwidth for large data rate requirements.
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