When they aren't transmitting, nodes go into a sleep mode and draw only a few microamps of power. They can wake up in about 15 ms. Sensor nodes can be interrogated periodically, or they can wake up on their own as programmed. With its attributes of low power and many years of battery life, ZigBee fits applications other wireless technologies simply can't handle.
And if you're looking to take advantage of the benefits of mesh wireless, ZigBee is a great choice. It substantially minimizes the required amount of mesh design and software development.
ZigBee Applications
Let's put it this way. ZigBee addresses most of the applications that Bluetooth, Wi-Fi, Ultra-Wideband (UWB), cell phones, and other wireless technologies don't cover.
ZigBee's low cost, low power, small size, and ensured interoperability-will lure engineers who want to make some part of their product wireless. And with a fully defined standard as well as available hardware and software, adding ZigBee wireless will be relatively easy. Get ready for the "peel and stick" phase of wireless.
It's essential for the the industry to first address the most interesting and potentially voluminous applications. Once volume is established (as was the case with Bluetooth in cell phones), a ZigBee module that costs less than $5 will become reality. As a result, ZigBee will hop into many other low-volume applications.
The sector with the greatest potential is home automation. The industry has identified over 200 possible home wireless applications, creating the volume needed to make ZigBee the wireless king. But because consumers demand the cheapest and easiest-to-use products, companies are proceeding with caution.
So far, the industrial sector heads the list for ZigBee adoption, with products for building monitoring and control and AMR. Testing, validating, and improving industrial/commercial ZigBee will lead to better home products. As they say, applications are limitless (see "Top 12 ZigBee Apps,").
Designing With ZigBee
Assuming you have a wireless application, your first task is to decide which technology to use. Cost, availability, speed, range, and power consumption apply. But don't forget to factor in time-tomarket and the engineering talent at your disposal, mainly wireless expertise and software-development capabilities. There are six technology options:
- Infrared (IR): It's the cheapest of all, but it offers the shortest range and operates via line-of-sight only. Data rates reach 16 Mbits/s.
- ISM wireless: These inexpensive chips operate in the 315-, 433-, and 902-to 928-MHz range. There are lots of inexpensive modules too, but no standard protocol. It's best for really simple applications.
- Bluetooth: This fast (to 3 Mbits/s), low-cost technology features a range of typically 10 to 100 m. It's highly developed, with many profiles. It also offers PAN ad-hoc (non-mesh) networking capability.
- Wi-Fi: Also known as 802.11a/b/g, it's widely available. Though more expensive, Wi-Fi offers very high data rates to 54 Mbits/s and the longest range (100 m). Wi-Fi transceivers consume more power and are more difficult to integrate into a mesh network.
- ZigBee: It's the newest technology. It trades off a low data rate (up to 250 kbits/s) for very low power consumption and an inherent mesh capability. Few formal profiles are available now, but more are on the way. Prices will drop as volume builds. It has the greatest potential among the wireless options.
- UWB: Ultra-Wideband is now available in chip and module form. Its very high speed (100 to 480 Mbits/s) and short range (less than 10 m) tend to typecast it as a video and high-speed data (USB) solution in consumer products. No mesh capability exists at this time.
Mesh networking extends your wireless possibilities by offering longer range at lower cost via radio relay. Mesh also adds a major benefit—reliability. It solves many problems associated with wireless adoption. Oh, by the way, it just so happens that ZigBee offers mesh.
If you select ZigBee, your next choice is the frequency band. In Europe, there's only one choice—868 MHz. In the U.S. and the rest of the world, the 2.4-GHz band is the most useful, and that's where most chips and modules operate.
Only a few 915-MHz modules are available, but their advantage is longer range (up to 1000 m outside) and greater penetration of walls and other obstacles. ZigBee's 2.4-GHz maximum range is 400 m outside and about 30 m inside. It can penetrate one concrete wall, but not two.
If you feel secure in your wireless design abilities and programming acumen, you can buy your own chips and dig right in. Don't forget the need for a good antenna. Reference designs can really help here too. The ZigBee Alliance has "blessed" six ZigBee-compliant development platforms, and more are on the way.
Because chip design is tied so closely to the IEEE 802.15.4 and ZigBee Alliance standards, the features and specs are very similar. How do you distinguish one from another? Besides a good reference design and development platform, look for specs like high receiver sensitivity (for longer range and greater reliability) and sleep current drain (for longer battery life).
If you want to avoid the whole wireless part of the design, go for a complete module. A wide variety of companies makes complete packaged modules on pc boards or in a housing or dongle, including antenna. To use such a module, all you have to do is connect a battery and your sensor for monitoring applications or a battery and your actuator in a control application.
At this point, your design involves the writing or the code for your unique application. Keep in mind that most chip and module vendors have software development platforms. Also, third-party software is becoming more common for popular applications, especially sensor nets and mesh.
ZigBee Down the Line
Like most wireless technologies, there's a roadmap. While most of us aren't part of the inside group planning the future, we can guess what's on the roadmap based on tradition, innuendo, and common sense.
First, you can expect more profiles from the Alliance. You'll also see more products, mainly software, to speed your development. Hardware-wise, we might expect a higher-speed version some time in the distant future. Right now, though, speed isn't a major issue for most applications. But by adjusting the modulation, designers should be able to double today's 250-kbit/s speeds.
Finally, changes to the radio to permit mobile applications are in the works. ZigBee, as is, probably can handle modest speeds on moving nodes from 10 to 15 mph. But higher-speed handling needs a change in technology if speeds to 100 mph are desired, such as in RFID or other mobile applications.
IEEE
www.ieee802.org/15
ZigBee Alliance
www.zigbee.org
When they aren't transmitting, nodes go into a sleep mode and draw only a few microamps of power. They can wake up in about 15 ms. Sensor nodes can be interrogated periodically, or they can wake up on their own as programmed. With its attributes of low power and many years of battery life, ZigBee fits applications other wireless technologies simply can't handle.
And if you're looking to take advantage of the benefits of mesh wireless, ZigBee is a great choice. It substantially minimizes the required amount of mesh design and software development.
ZigBee Applications
Let's put it this way. ZigBee addresses most of the applications that Bluetooth, Wi-Fi, Ultra-Wideband (UWB), cell phones, and other wireless technologies don't cover.
ZigBee's low cost, low power, small size, and ensured interoperability-will lure engineers who want to make some part of their product wireless. And with a fully defined standard as well as available hardware and software, adding ZigBee wireless will be relatively easy. Get ready for the "peel and stick" phase of wireless.
It's essential for the the industry to first address the most interesting and potentially voluminous applications. Once volume is established (as was the case with Bluetooth in cell phones), a ZigBee module that costs less than $5 will become reality. As a result, ZigBee will hop into many other low-volume applications.
The sector with the greatest potential is home automation. The industry has identified over 200 possible home wireless applications, creating the volume needed to make ZigBee the wireless king. But because consumers demand the cheapest and easiest-to-use products, companies are proceeding with caution.
So far, the industrial sector heads the list for ZigBee adoption, with products for building monitoring and control and AMR. Testing, validating, and improving industrial/commercial ZigBee will lead to better home products. As they say, applications are limitless (see "Top 12 ZigBee Apps,").
Designing With ZigBee
Assuming you have a wireless application, your first task is to decide which technology to use. Cost, availability, speed, range, and power consumption apply. But don't forget to factor in time-tomarket and the engineering talent at your disposal, mainly wireless expertise and software-development capabilities. There are six technology options:
- Infrared (IR): It's the cheapest of all, but it offers the shortest range and operates via line-of-sight only. Data rates reach 16 Mbits/s.
- ISM wireless: These inexpensive chips operate in the 315-, 433-, and 902-to 928-MHz range. There are lots of inexpensive modules too, but no standard protocol. It's best for really simple applications.
- Bluetooth: This fast (to 3 Mbits/s), low-cost technology features a range of typically 10 to 100 m. It's highly developed, with many profiles. It also offers PAN ad-hoc (non-mesh) networking capability.
- Wi-Fi: Also known as 802.11a/b/g, it's widely available. Though more expensive, Wi-Fi offers very high data rates to 54 Mbits/s and the longest range (100 m). Wi-Fi transceivers consume more power and are more difficult to integrate into a mesh network.
- ZigBee: It's the newest technology. It trades off a low data rate (up to 250 kbits/s) for very low power consumption and an inherent mesh capability. Few formal profiles are available now, but more are on the way. Prices will drop as volume builds. It has the greatest potential among the wireless options.
- UWB: Ultra-Wideband is now available in chip and module form. Its very high speed (100 to 480 Mbits/s) and short range (less than 10 m) tend to typecast it as a video and high-speed data (USB) solution in consumer products. No mesh capability exists at this time.
Mesh networking extends your wireless possibilities by offering longer range at lower cost via radio relay. Mesh also adds a major benefit—reliability. It solves many problems associated with wireless adoption. Oh, by the way, it just so happens that ZigBee offers mesh.
If you select ZigBee, your next choice is the frequency band. In Europe, there's only one choice—868 MHz. In the U.S. and the rest of the world, the 2.4-GHz band is the most useful, and that's where most chips and modules operate.
Only a few 915-MHz modules are available, but their advantage is longer range (up to 1000 m outside) and greater penetration of walls and other obstacles. ZigBee's 2.4-GHz maximum range is 400 m outside and about 30 m inside. It can penetrate one concrete wall, but not two.
If you feel secure in your wireless design abilities and programming acumen, you can buy your own chips and dig right in. Don't forget the need for a good antenna. Reference designs can really help here too. The ZigBee Alliance has "blessed" six ZigBee-compliant development platforms, and more are on the way.
Because chip design is tied so closely to the IEEE 802.15.4 and ZigBee Alliance standards, the features and specs are very similar. How do you distinguish one from another? Besides a good reference design and development platform, look for specs like high receiver sensitivity (for longer range and greater reliability) and sleep current drain (for longer battery life).
If you want to avoid the whole wireless part of the design, go for a complete module. A wide variety of companies makes complete packaged modules on pc boards or in a housing or dongle, including antenna. To use such a module, all you have to do is connect a battery and your sensor for monitoring applications or a battery and your actuator in a control application.
At this point, your design involves the writing or the code for your unique application. Keep in mind that most chip and module vendors have software development platforms. Also, third-party software is becoming more common for popular applications, especially sensor nets and mesh.
ZigBee Down the Line
Like most wireless technologies, there's a roadmap. While most of us aren't part of the inside group planning the future, we can guess what's on the roadmap based on tradition, innuendo, and common sense.
First, you can expect more profiles from the Alliance. You'll also see more products, mainly software, to speed your development. Hardware-wise, we might expect a higher-speed version some time in the distant future. Right now, though, speed isn't a major issue for most applications. But by adjusting the modulation, designers should be able to double today's 250-kbit/s speeds.
Finally, changes to the radio to permit mobile applications are in the works. ZigBee, as is, probably can handle modest speeds on moving nodes from 10 to 15 mph. But higher-speed handling needs a change in technology if speeds to 100 mph are desired, such as in RFID or other mobile applications.
IEEE
www.ieee802.org/15
ZigBee Alliance
www.zigbee.org