Bandwidth, Range, and Power Requirements
There are three key factors to consider when evaluating wireless technologies: bandwidth, range, and power requirements. When you compare wireless protocols based on IEEE 802.11 and IEEE 802.15.4, Wi-Fi has the advantage in bandwidth with a maximum bit rate of 54 Mbit/s, while 802.15.4 has the advantage in distance and power requirements. This is a typical trade-off made in wireless protocols. Wi-Fi offers significantly higher data rates, which require additional encoding; extra data requires additional radio traffic resulting in increased power consumption by the radio. This bandwidth and power trade-off is obvious in systems such as laptops or smart phones with integrated Wi-Fi that typically operate for a matter of days between recharging and provide high-speed data transfer, compared to a wireless sensor network based on IEEE 802.15.4 technology that might operate for years on standard AA batteries and transfer reduced data between sleep states.
For technologies based on IEEE 802.15.4, this trade-off in bandwidth also results in up to a 10X improvement in distance. At a maximum distance of 300 m and a bandwidth trade-off from 54 Mbit/s to 250 kbit/s, protocols based on IEEE 802.15.4 are ideal for low-speed, long-distance remote monitoring applications, while Wi-Fi is ideal for shorter-distance, higher-power, and higher-bandwidth applications.
Network Topology
In addition to total distance, protocols based on IEEE 802.15.4 offer a couple of options for network topologies. A Wi-Fi system is typically configured in a star topology with a center access point and clients up to 30 m from the access point. While standard Wi-Fi installations support repeaters or routers to extend distance and can be configured in a cluster or tree, they do not support meshing, which is the ability for a node or device to route packets back to the gateway. Many 802.15.4-based wireless sensor networks (WSNs) support star, cluster tree, and mesh networking topologies
2. What are the distances from my measurements to my data center or enterprise connection?
3. Which network topology do I need?
4. What is the system power source?
Figure . A Star, cluster tree, and mesh networking topologies.
Top Four Questions to Ask When Selecting a Wireless Technology
1. Which measurements do I need to address my application?2. What are the distances from my measurements to my data center or enterprise connection?
3. Which network topology do I need?
4. What is the system power source?
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