Standardization of Z-Wave

A standard can be defined generally as a construct that results from reasoned, collective choice and enables agreement on solution of recurrent problems. A standard can be viewed as striking a balance between the requirements of users, the technological possibilities and associated costs of producers, and constraints imposed by goverment for the benefit of society in general.

More functionally, an industry standard is a set of specifications to which all elements of products, processes, formats, or procedures under its jurisdiction must conform. The process of standarization is the pursuit of this conformity.

As a standard, it must have four basic functions: Quality/Reliability, Information standards, Compatibility/Interoperability, Variety Reduction. I am going to analyze Z-wave standard based on these four basic function.



Quality/Reliability
Standards are developed to specify acceptable product or service performance along one or more demensions such as functional levels, performance variation, service lifetime, efficiency, safety and environmental impact.

Many RF technologies communicate across the public bands. Consequently, the public band are crowed with interference, resulting in poor reliabilty for most RF technologies. Z-Wave minimizes these "noise and distortion" problems by using transmission mechanisms such as 2-way acknowledgement, condensed frame formats and random back-off algorithms, ensuring highly reliable communication between all the devices in the network



Information Standards
Standards help provide evaluated scientific and engineering information in the form of publications, electronic data bases, terminology, and test and measurement methods for describing quantifying, and evaluting product attributes.

All the information about Z-Wave technology is open to the users, including product information, publications, evaluation of Z-wave technolgy and so on. The related information could be found in the websites:
http://www.zen-sys.com
http://www.z-wavealliance.org
http://www.zwaveworld.com



Compatibility/Interoperability
Standards specify properties that a product must have in order to work with complementary products within a product or service system.

In Z-Wave, interoperability is guaranteed by use of the appropriate Device Class Specification and by the Z-Wave Certification Program. The Device Class Specification governs standardization on command and device level for all home control products. The work is carried out in the Z-Wave Alliance ensuring that all relevant market inputs from Z-Wave partners are injected into the Device Classes. The certification program ensures that all products, which carry the Z-Wave logo, have gone through the certification process.



Variety Reduction
Standards limit a product to a certain range or number of characteristics such as size or quality levels.

All the products carried Z-wave logo work in the same frequency bands and are applied in the mesh network. They have the same protocol stack and frame structure. Before puting in market, the products must go through the Z-Wave certification and the Device Class Specification to ensure the achievement of requirments and quality.



Z-Wave is not an open standard. The industry leading device specifications of Z-Wave will be made available royalty free based on a reasonable and non-discriminatory (RAND)-Z model. With RAND-Z Zynsys promises to license the technology at no charge. But the implementers still have to get the licenser's permission to implement. So while the licenser may not make money off the deal they can still stop any products they don't like or do more subtle things like drag out the licensing process. To accelerate the adoption of Z-Wave standard, Z-Alliance and its members strive to develop and open Z-Wave technology further. The figure following shows the standardization process of Z-Wave.




Figure from :http://www.z-wavealliance.org

Battles between the standards for wireless sensor network

Wireless Sensor Network (WSN) is one of the most popular applications in the area of wireless technology. However there is no uniform standard yet since it is an emerging application. Today, many research centres and organizations all over the world are working on the developement of this technology and differents standards have been introduced. They are ZigBee, Z-Wave, Bluetooth, Wibree, 6loWPAN and so on. Among those technical standards, ZigBee and Z-Wave are the maturest, competing to become a standard for WSN. I have already described Z-Wave standard in the previous articles. Next let's look at ZigBee technology and analyze theirs advantage and disadvantage.

ZigBee is a low-cost, low-power, wireless mesh networking standard, using low-power digital radios based on the IEEE 802.15.4 standard for wireless personal area networks (WPANs). ZigBee is defined by the ZigBee Alliance.

Both Zig Bee alliance and Z-Wave 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 is clearly targeted at home control applications. Those include not just traditional home control applications, such as lighting, HVAC, drapes, windows shades, garage doors and integration with alarm panels, but also entertainment control and digital home healthcare devices.

In contrast, ZigBee does not have a clear target market but instead broadly addresses practically all applications: toys, body network devices, PC peripherals, home control, large-scale building controls, industrial sensor networks, logistics, RFID and even homeland security and military-battlefield applications. The challenge for ZigBee is that those target segments have vastly differing requirements.

Mesh networking is a suitable vehicle to extend the reach of wireless communication to cover entire homes. But since both ZigBee and Z-Wave operate in license-exempt frequency bands, interference could destroy robustness and reliability.

For ZigBee, this risk is especially large, since the vast majority of IEEE802.15.4 solutions offered today use the 2.4-GHz band exclusively. Wireless LANs use the same band and typically operate at between 100 and 1,000 times the transmitter power. Further, more and more WLAN users operate directed antennas that are available in mass retail. With the use of WLANs for bandwidth-hungry applications (such as HDTV video) growing, and with 802.11n increasing WLAN use in consumer electronic applications, the risk for interference rises.

The leadership of the ZigBee Alliance publicly denies that a problem exists and points to the interference risk at 915 MHz, where hardly any high-volume data devices exist for home use. But simulations performed by the task group that developed IEEE 802.15.4-2006 clearly show that WLAN heavily interferes with ZigBee. Measurements by OEMs have confirmed these simulations. The ISA SP100 group, citing the interference problems, has rejected the idea of using 15.4 as defined and used in ZigBee today.

In fact, several OEMs have left ZigBee and joined Z-Wave. Large initiatives, including a $150 million project at Telepathx, have abandoned ZigBee after measuring interference, and the U.S. Army FCS Mobile Node Test at White Sands, N.M., reported harmful interference between WLAN and ZigBee.

In comparision with Z-Wave, ZigBee pays a higher price. The reason is not just for its "committee"-inflated complexity and proliferation of options, but also for the more-complex 15.4 DSSS/O-QPSK PHY and the very feature-rich MAC protocol layers. Its solutions are more than twice the size of the Z-Wave memory and chip. The level of complexity of Z-Wave is comparable to the lowest-cost two-way wireless solutions in the market. Further developments in semiconductor technology will not significantly alter that ratio. This gives Z-Wave a sustainable cost benefit over ZigBee and has contributed to the volume leadership Z-Wave enjoys in wireless home control.