When one thinks of wireless meshed networking for home control and automation, for many of us, the name Zigbee comes to mind, largely because of the effective marketing of the Zigbee Alliance. Though well known, Zigbee is not the only technology active in this space. Z-Wave is promoting strong and gaining ground. This column has addressed both technologies in the past, but it is time to take another look as remote monitoring and control applications heat up and the battle between Zigbee and Z-Wave continues.

To summarize, most Zigbee products operate in the 2.4 GHz unlicensed ISM band, though the technology works in the 900 MHz neighborhood as well. Zigbee is recognized as Freescale technology backed by the Zigbee Alliance. Physical layer (PHY) data rate is about 250 kbps, which is fine for control applications. Zigbee is aligned with the IEEE 802.15.4 standard.

Z-Wave products operate in the 900 MHz unlicensed ISM band operating with a 40 kbps PHY rate, again fine for control applications. Z-Wave technology is attributed to Zensys Corporation and is backed by the Z-Wave Alliance.

Both alliances include long lists of well-known corporations. Both technologies are battery-operated and, therefore, consume very little power. Each employs mesh networking, which enables daisy-chaining nodes throughout a premises and the utilization of multiple communications paths. Although the range of a node is a maximum of 30 meters, mesh networking makes the range essentially limitless in high-density applications where there are many nodes.

Z-Wave has grown strong with an expanding membership and a large buffet of interoperable products. Back in April, the Z-Wave Alliance announced that both Intel and Monster had joined the Alliance as principle members. Shortly thereafter, Intel Capital invested heavily in Zensys stating that Zensys and the Z-Wave Alliance have products out there, which are cost-effective and are interoperable. This is a strong endorsement for Z-Wave.

Z-Wave has a new confidence in the market success of its Alliance members. They believe they have achieved an overwhelming array of products and applications in the home market that Zigbee cannot overcome. Home market inertia seems to be in their favor.

What’s more, Z-wave emphasizes that Zigbee is plagued with 2.4 GHz interference issues that do not exist in the 900 MHz band. Most Zigbee products share a busy ISM band with Wi-Fi. Allegedly, the IEEE 802.15.4 task group performed tests last year that clearly show interference to Zigbee devices from Wi-Fi devices. Z-Wave claims that such interference issues do not exist in the 900 MHz region because there is no ubiquitous data communications technology at work there.

Furthermore, Z-Wave claims that the 900 MHz spectrum has better range and penetration capability than the higher-band devices. This can be a real advantage in the home environment where signals must penetrate walls and other obstacles.

With a membership now well over 160 and more than 170 products on the market, Zensys and the Z-Wave Alliance have strong momentum. On the other hand, the Zigbee Alliance says not so fast.

The Zigbee camp points out that Z-Wave is still proprietary with Zensys as the single chip source – implying that this is not an open standard that engenders multiple-chip sources. The Zigbee Alliance claims that its strength and success is based on the open-standard development work of the IEEE.

Countering this, Zensys has recently announced a licensing program for the Z-Wave technology, making it possible for other semiconductor manufacturers to produce Z-Wave-compatible ICs and solutions. The advantages of the open regulatory standard (IEEE 802.15.4) vs. the ‘proprietary’ Z-Wave standard are no longer clear. In addition, Z-Wave proponents point out that ‘committee-created’ technologies often become appended monsters that result in complex and costly implementations. Indeed, the Zigbee MAC and PHY layers have grown in complexity, leading to higher costs and power consumption.

Still, the Zigbee camp sees the growing complexity as feature enhancements that address wider market needs, particularly in the commercial arenas. On Oct. 2, the ZigBee Alliance announced it has approved comprehensive new features for the ZigBee specification giving more choices to manufacturers as they design ZigBee products. These new features significantly expand the capabilities of ZigBee, connecting dramatically different devices into a single, easy to install and use network.

According to the Zigbee Alliance, the ZigBee specification offers all the wide-ranging features released in 2006, and adds new features, giving manufacturers greater flexibility when designing innovative ZigBee products. An expanded set of features, known as ZigBee PRO, maximizes all the capabilities of ZigBee and facilitates ease-of-use and advanced support for larger networks.

Highlights of the expanded ZigBee PRO feature set include:

- Network scalability – Improved support for larger networks offering more management, flexibility.
performance choices
- Fragmentation – New ability to divide longer messages and enable interaction with other protocols and systems.
- Frequency agility – Networks dynamically change channels should interference occur.
- Automated device address management – Optimized for large networks with added network management and configuration tools.
- Group addressing – Offers additional traffic optimization needed for large networks.
- Wireless commissioning – Enhanced with secure wireless commissioning capabilities.
- Centralized data collection – Tuned specifically to optimize information flow in large networks.

Bob Heile, chairman of the ZigBee Alliance offers his perspective - “ZigBee now gives unparalleled choices for companies looking for the right low-power, low-cost wireless networking standard. These new features make ZigBee stronger and play a key role in expanding ZigBee’s value as a key part of innovative advanced metering infrastructure (AMI) programs for utility companies around the world. No other technology can wirelessly connect an exterior utility meter to an interior home automation network or building control networks as efficiently and effectively as ZigBee.”

With the addition of these new features to the ZigBee specification, the Alliance is shifting its attention to development efforts facilitating the deployment of the technology for energy management and efficiency, specifically in areas like public application profiles for advance metering infrastructure (AMI). Public application profiles enable end-to-end, multivendor interoperable solutions in markets such as AMI, home automation, commercial building automation and telecommunications.

The ZigBee Alliance has multimarket and global appeal along with steadily growing membership with more than 225 companies from 28 countries spanning six continents.

While the battle between the two camps continues, one can’t help but notice that these two competing mesh technologies are actually finding their own ground. This divergence is such that, as time passes, the two camps are competing less over the same turf. Z-Wave has found its place in the home with a respectable array of home appliance applications while Zigbee has gone more industrial and commercial with their new feature set and capabilities.

So who will win? That’s no longer the question. I believe both technologies will not only survive, but thrive in different markets. I am looking through the rhetoric to see a battle that has become fictitious. Two winners have already emerged – one at home and the other in the commercial environment.

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