In the race between ZigBee and Wi-Fi to network energy-smart homes, ZigBee has so far taken the lead. But that doesn’t mean Wi-Fi is giving up. The two camps have made much of their comparative advantages in the field, including differences in cost, power usage, reliability and relative technical maturity. At the same time, both are making their technologies interoperable, which indicates a good amount of cooperation amidst the competition.
So, where do the two technologies place in the race for the home energy management market? I’ve talked with both the ZigBee Alliance and Wi-Fi Alliance to lay out where they differ and where they work well together, as well as with the Electric Power Research Institute (EPRI) on its research into both. Here are some conclusions:
Market penetration. Most smart meters currently deployed in North America have ZigBee radios that communicate with home energy devices. Wi-Fi’s penetration has been limited to wireless thermostats and other devices (TVs, energy dashboards, etc.), though the ubiquity of Wi-Fi in the home could push more energy-aware devices. And while ZigBee may be inside lots of smart meters, few beyond pilot projects are actively connecting to home devices, which makes sense, given the infancy of the market.
Cost. ZigBee was built with low-power sensors and controls in mind, and has much lower processing, memory and power requirements than Wi-Fi as a result. The Wi-Fi Alliance counters that its members are hard at work on lower-power chipsets that could compete with ZigBee’s advantages there.
Reliability and robustness. Early tests of 10-milliwatts ZigBee radios in smart meters showed issues in maintaining reliable connections to in-home devices. Most have overcome this by boosting power to 100 milliwatts, the maximum allowed for the unlicensed 2.4GHz spectrum. But ZigBee will have to compete against other technologies, including the latest iteration of Wi-Fi, known as 802.11n. EPRI has tested the technology, which is capable of streaming video and longer-range applications, and “it tends to win in a foot race” against ZigBee, EPRI technical executive Craig Rodine told me.
Interference. Last year, EPRI did a test of ZigBee communications in a single-story ranch home in Pleasanton, Calif.; the network had trouble reaching certain areas. Higher-power Wi-Fi-enabled devices could avoid some of these problems. On the other hand, the ZigBee Alliance says its frequency agility and inter-packet spacing technologies allow ZigBee to work well amidst interference.
Wireless mesh vs. point-to-point. ZigBee is a wireless mesh technology, with each device serving as both receiver and sender of data. That helps solve some of the potential interference problems noted in EPRI’s study, with each ZigBee-enabled home energy hub, smart thermostat and other device meshing around trouble spots. Wi-Fi, on the other hand, is a point-to-point technology, although there is work underway on a mesh version of Wi-Fi.
Interoperability and ubiquity. The first version of ZigBee’s energy-specific technology, Smart Energy Profile 1.0, had some problems with ZigBee Alliance-certified devices failing to interoperate. The new Smart Energy Profile 2.0 is meant to solve that problem, and Rodine suggests that ZigBee’s work with the Wi-Fi Alliance — including the creation of an Internet protocol (IP) stack for SEP 2.0 — is part of that effort. After all, the Wi-Fi Alliance has one of the most trusted certification regimes in the world, with tens of thousands of certified devices that have proven interoperability.
Network self-diagnosis and “self-healing.” Utilities will want smart meter-connected home devices to report signal strength and effective packet transfer at varying intervals to make sure the network is working as advertised. Wi-Fi, with its long history of enterprise deployments, has plenty of this network management technology in place. But ZigBee’s mesh architecture provides similar self-diagnosis and self-healing capabilities.
A final note — neither ZigBee nor Wi-Fi backers claim that they’re the end-all, be-all technology for networking energy-smart homes. Combinations that use Wi-Fi as a backbone and ZigBee as a link to multiple end-points are likely to see greater adoption as both teams work to integrate their technologies.
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