09-05-2012, 10:33 AM
Bluetooth, ZigBee, and Wibree: A Comparison of WPAN Technologies
[attachment=21621]
Introduction and Background
Wireless Personal Area Network (WPAN) designs have been flourishing in recent years. The
pervasive success of Bluetooth has been a boon to all devices in the IEEE 802.15 working
group. As competing and complementary standards are formed within this working group, a
successful embedded system designer must understand the differences between the
technology standards. It is the goal of this paper to examine three: Bluetooth, ZigBee, and
Wibree.
First, a short history: Wibree is a technology that has been under development by Nokia since
2001 [13]. It was originally adapted from the Bluetooth specification, and in 2006, the Bluetooth
Special Interest Group (SIG) announced it would be adopting Wibree into the Bluetooth
specification [12]. Integrated Bluetooth/Wibree devices are not yet shipping, though Nordic
Semiconductor has published a preliminary product specification [14]. While the Wibree and
Bluetooth specs are being integrated, the new name of the Wibree technology has changed
several times. In this paper, I will continue to use the Wibree name.
While Wibree has been under development, the competing IEEE 802.15.4 technology of
ZigBee has been available to the public for several years. ZigBee was designed as a lowpower,
low-cost, low-speed solution [1], and has many benefits over Bluetooth, though fewer
benefits over Wibree.
Detailed Technology Comparison
Below I will analyze a limited set of characteristics for the three technologies.
Frequency Band
All three technologies operate in the unlicensed 2.4 GHz spectrum, while ZigBee can also
operate at reduced speeds at 915MHz and 868 MHz [7].
Antenna and Hardware
Wibreeʼs adoption into the Bluetooth spec was directly related to the fact that it can coexist on
BT hardware. Devices that wish to take advantage of both Bluetooth and Wibree will not need
to add extra hardware; one antenna will do for both. ZigBee support, however, requires its own
hardware and antenna. [11]
Power and Battery Life
ZigBee, designed to be a low-power alternative to Bluetooth, offers 30mW performance
compared to Bluetoothʼs 100mW [10]. However, Dr. Bob Iannucci, Senior Vice President and
Technology Advisor at Nokia, claims that Wibree is “up to 10 times more energy efficient than
Bluetooth” [5], putting Wibree around 10mW.
ZigBee is designed to “run for six months to two years on just two AA batteries” [2]. This results
from its ability to lock into a transmission time slot and sleep in between. Bluetooth, however,
must stay awake for the convenience of quick response time, which results in battery life on
the order of days. This led to Wibreeʼs design goal of 1-2 years on a single battery. [12]
Range
Both Bluetooth and Wibree are designed to operate within a 10m range, though Bluetooth 2.1
now states a maximum range of 30m [10]. ZigBee, being designed to enable “home and
industry automation” [4], allows a maximum range of 75m.
Data Rate
Wibree has caught up to Bluetoothʼs original data rate at 1Mbps [13], while Bluetooth has
proceeded to reach maximum rates of 3Mbps. ZigBee intentionally lags far behind these
numbers, sacrificing data rates for power savings, and so transmits only 20-250Kbps. [6]
Component Cost
In 2003, when ZigBee was targeting a $2 component cost, Bluetooth support cost $5 per
device [2]. Now Bluetooth pricing has fallen to $3, while ZigBee costs $2 [10]. More
importantly, integrating Wibree into an existing Bluetooth implementation adds around 20¢,
making Wibree a much more attractive addition to Bluetooth-enabled devices than ZigBee.
Network Topologies
Bluetooth and Wibree operate primarily in ad hoc piconets, where a master device controls
multiple slaves. These piconets are limited to 8 devices. ZigBee has far greater flexibility in this
arena, supporting mesh and star configurations [3]. Mesh networks offer resilience against
severed connections, as Coordinator devices can reroute traffic as needed. Star configurations
at the ends of the mesh allow clusters of ZigBee devices to interact with the outside world,
while the mesh devices focus on data transmission.
Security
All three technologies support state-of-the-art 128-bit encryption, and all three continue to be
scrutinized for key distribution vulnerabilities and the like.
Time to Wake and Transmit
One of ZigBeeʼs greatest strengths over Bluetooth has been its freedom to sleep often. This
comes from its quick wake-from-sleep design. A ZigBee device “can wake up and get a packet
across a network connection in around 15 milliseconds,” while a Bluetooth device would take 3
seconds. [2] A Wibree device would presumably behave more like the ZigBee device, but this
remains to be seen.
[attachment=21621]
Introduction and Background
Wireless Personal Area Network (WPAN) designs have been flourishing in recent years. The
pervasive success of Bluetooth has been a boon to all devices in the IEEE 802.15 working
group. As competing and complementary standards are formed within this working group, a
successful embedded system designer must understand the differences between the
technology standards. It is the goal of this paper to examine three: Bluetooth, ZigBee, and
Wibree.
First, a short history: Wibree is a technology that has been under development by Nokia since
2001 [13]. It was originally adapted from the Bluetooth specification, and in 2006, the Bluetooth
Special Interest Group (SIG) announced it would be adopting Wibree into the Bluetooth
specification [12]. Integrated Bluetooth/Wibree devices are not yet shipping, though Nordic
Semiconductor has published a preliminary product specification [14]. While the Wibree and
Bluetooth specs are being integrated, the new name of the Wibree technology has changed
several times. In this paper, I will continue to use the Wibree name.
While Wibree has been under development, the competing IEEE 802.15.4 technology of
ZigBee has been available to the public for several years. ZigBee was designed as a lowpower,
low-cost, low-speed solution [1], and has many benefits over Bluetooth, though fewer
benefits over Wibree.
Detailed Technology Comparison
Below I will analyze a limited set of characteristics for the three technologies.
Frequency Band
All three technologies operate in the unlicensed 2.4 GHz spectrum, while ZigBee can also
operate at reduced speeds at 915MHz and 868 MHz [7].
Antenna and Hardware
Wibreeʼs adoption into the Bluetooth spec was directly related to the fact that it can coexist on
BT hardware. Devices that wish to take advantage of both Bluetooth and Wibree will not need
to add extra hardware; one antenna will do for both. ZigBee support, however, requires its own
hardware and antenna. [11]
Power and Battery Life
ZigBee, designed to be a low-power alternative to Bluetooth, offers 30mW performance
compared to Bluetoothʼs 100mW [10]. However, Dr. Bob Iannucci, Senior Vice President and
Technology Advisor at Nokia, claims that Wibree is “up to 10 times more energy efficient than
Bluetooth” [5], putting Wibree around 10mW.
ZigBee is designed to “run for six months to two years on just two AA batteries” [2]. This results
from its ability to lock into a transmission time slot and sleep in between. Bluetooth, however,
must stay awake for the convenience of quick response time, which results in battery life on
the order of days. This led to Wibreeʼs design goal of 1-2 years on a single battery. [12]
Range
Both Bluetooth and Wibree are designed to operate within a 10m range, though Bluetooth 2.1
now states a maximum range of 30m [10]. ZigBee, being designed to enable “home and
industry automation” [4], allows a maximum range of 75m.
Data Rate
Wibree has caught up to Bluetoothʼs original data rate at 1Mbps [13], while Bluetooth has
proceeded to reach maximum rates of 3Mbps. ZigBee intentionally lags far behind these
numbers, sacrificing data rates for power savings, and so transmits only 20-250Kbps. [6]
Component Cost
In 2003, when ZigBee was targeting a $2 component cost, Bluetooth support cost $5 per
device [2]. Now Bluetooth pricing has fallen to $3, while ZigBee costs $2 [10]. More
importantly, integrating Wibree into an existing Bluetooth implementation adds around 20¢,
making Wibree a much more attractive addition to Bluetooth-enabled devices than ZigBee.
Network Topologies
Bluetooth and Wibree operate primarily in ad hoc piconets, where a master device controls
multiple slaves. These piconets are limited to 8 devices. ZigBee has far greater flexibility in this
arena, supporting mesh and star configurations [3]. Mesh networks offer resilience against
severed connections, as Coordinator devices can reroute traffic as needed. Star configurations
at the ends of the mesh allow clusters of ZigBee devices to interact with the outside world,
while the mesh devices focus on data transmission.
Security
All three technologies support state-of-the-art 128-bit encryption, and all three continue to be
scrutinized for key distribution vulnerabilities and the like.
Time to Wake and Transmit
One of ZigBeeʼs greatest strengths over Bluetooth has been its freedom to sleep often. This
comes from its quick wake-from-sleep design. A ZigBee device “can wake up and get a packet
across a network connection in around 15 milliseconds,” while a Bluetooth device would take 3
seconds. [2] A Wibree device would presumably behave more like the ZigBee device, but this
remains to be seen.