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  Date:1st Jun 2012

Wireless connectivity in smart home tech: ZigBee vs Wi-Fi
By Surjit Lahiri VP, Mindteck (India)Ltd

Home automation technologies are seen as integral additions to the Smart grid. The ability to control lighting, appliances, HVAC as well as Smart Grid applications (load curtailment, demand response, real-time power usage and price reporting) will become vital as Smart Grid initiatives are rolled out. Over many years ZigBee , an IEEE based 802.15.4 low power wireless protocol has gained significant adoption footprint from networking wireless industrial sensors to networking smart home appliances and now smart grid devices. Wi-Fi on the other hand has deeply entrenched itself in almost every internet enabled household. The trend for smart home appliances is on an upswing with well known appliance manufacturers like LG, GE, Whirpool taking the leadership in this space. Here below ZigBee and Wi-Fi -the two most popular wireless protocols are compared listing their merits/demerits and their adoptability into smart home appliances

ZigBee Vs Wi-Fi:

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 members are hard at work on rolling out lower-power chipsets that could compete with ZigBee's advantages there in the future.

Market penetration: Most smart meters that are being deployed in North America have ZigBee radios to communicate with home energy devices. Wi-Fi's penetration has been limited to wireless thermostats and other devices - though the ubiquity of Wi-Fi in the home could push more energy-aware devices to support it.

Robustness: ZigBee device makers have overcome early problems with smart meter-home device connectivity by boosting power from 10 milliwatts to 100 milliwatts, the maximum allowed for the unlicensed 2.4GHz spectrum in which it operates. The latest iteration of Wi-Fi known as 802.11n is capable of streaming video and longer-range applications, and "it tends to win in a foot race" against ZigBee.

Interference: ZigBee has built-in frequency agility and inter-packet spacing to allow it to work amidst interference found in a typical home. It's also a mesh networking technology, which means that every in-home device can also help propagate the network around obstacles.

Interoperability and ubiquity: The first version of ZigBee's energy-specific technology, Smart Energy Profile(SEP) 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. 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.

Conclusion: If appliance manufacturers don't agree on a single standard, they won't build the radios into their appliances - which means that the promise of energy savings and peak demand reductions from smart appliances cannot be realized. For home appliances, the alternative to built-in radio communication is external communication modules - but that option is significantly more costly and far too complicated for consumers. Over 99% of US smart meters that include a HAN interface use ZigBee - with total installations nearing 10 million meters. Furthermore, utilities have committed to tens of millions more ZigBee-enabled meters.

So: If meters are to send price and control signals directly to smart appliances and smart thermostats, those devices must include ZigBee radios. Alternatively, the meter can communicate with a gateway that, in turn, communicates with smart devices.

Of course, neither ZigBee nor Wi-Fi camps claim that they've got the be-all and end-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.

About ZigBee
ZigBee is the set of specs built around the IEEE 802.15.4 wireless protocol. The standard itself is regulated by a group known as the ZigBee Alliance, with over 300 members worldwide. ZigBee is targeted at radio-frequency (RF) applications that require a low data rate, long battery life, and secure networking. Due to its low power output, ZigBee devices can sustain themselves on a small battery for many months, or even years, making them ideal for install-and-forget purposes used in wireless sensor networks needing low bandwidth data communications in domains like Smart energy, Healthcare, Building/Home Automation, Consumer Electronics etc. The technology defined by the ZigBee specification is intended to be simpler and less expensive than other WPANs, such as Bluetooth. ZigBee devices can work seamlessly with other networks such as Wi-Fi, Broadband Ethernet and GPRS via a low cost gateway. ZigBee Alliance is coming up with ZigBee IP standards for seamless device integration with IP based networks doing away with the need to have a gateway device -further reducing the system cost. In addition, ZigBee comes with template applications profiles for various domains such as Healthcare, Smart Energy, Home Automation, Lighting etc, which helps OEM ecosystems roll out specific domain compliant smart appliances easily and helps end customer with ease in setup and usage.

About Wi-Fi
Wi-Fi surely needs no introduction. "Wi-Fi" is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11 family of standards. Wi-Fi is used by over 700 million people. There are over four million hotspots (places with Wi-Fi Internet connectivity) around the world, and about 800 million new Wi-Fi devices are sold every year. The 802.11g standard for wireless networking supports a maximum bandwidth of 54 Megabits per second (Mbps) making it more suitable for data intense applications. Wi-Fi based smart home appliances are seeing a slower adoption particularly due to high silicon cost and lack of application profiles ecosystem. Semiconductor giants like Broadcom are pushing adoption of Wi-Fi into smart appliances via a new range of chips and software toolkits. Wi-Fi Alliance is jointly working with ZigBee alliance on development of Smart Energy Profile 2.0 for Wi-Fi chips to enable ease of adoption.

Author: Srinivasa Reddy N
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