IEEE 802.15.4 Technology & Standard
- overview, or tutorial about the basics of the IEEE 802.15.4 standard and its associated technology and operation - includes IEEE 802.15.4a, 4c, 4d, 4g, 4f.
The IEEE 802.15.4 standard was developed to provide a framework and the lower levels for low cost, low power networks. It only provides the MAC and PHY layers, leaving the upper layers to be developed according to the market needs.
Accordingly the IEEE 802.15.4 standard may not be as widely known as some of the higher layer standards such as Zigbee which have been widely publicised. Nevertheless, the IEEE 802.15.4 technology and standard forms the basis, underpinning their operation and providing a reliable platform for their operation.
Now with technologies such as Zigbee being used in a large way, the use of IEEE 802.15.4 technology is corresponding increasing, and it is becoming an important standard. However with widespread marketing for Zigbee and other standards, IEEE 802.15.4 is less well known.
IEEE 802.15.4 basics
The IEEE 802.15.4 standard is aimed at providing the essential lower network layers for a wireless personal area network (WPAN). The chief requirements are low-cost, low-speed ubiquitous communication between devices. It does not aim to compete with the more commonly used end user-oriented systems such as IEEE 802.11 where costs are not as critical and higher speeds are demanded. Instead, IEEE 802..15.4 provides for very low cost communication of nearby devices with little to no underlying infrastructure.
The concept of IEEE 802.15.4 is to provide communications over distances up to about 10 metres and with maximum transfer data rates of 250 kbps. Anticipating that cost reduction will require highly embedded device solutions, the overall concept of IEEE 802.15.4 has been devised to accommodate this.
IEEE 802.15.4 standard
The IEEE 802.15.4 standard has undergone a number of releases. In addition to this there are a number of variants of the IEEE 802.15.4 standard to cater for different forms of physical layer, etc. These are summarised below in the table.
|IEEE 802.15.4 Version||Details and comments|
|IEEE 802.15.4 - 2003||This was the initial release of the IEEE 802.15.4 standard. It provided for two different PHYs - one for the lower frequency bands of 868 and 915 MHz, and the other for 2.4 GHz.|
|IEEE 802.15.4 - 2006||This 2006 release of the IEEE 802.15.4 standard provided for an increase in the data rate achievable on the lower frequency bands. This release of the standard updated the PHY for 868 and 915 MHz. It also defined four new modulation schemes that could be used - three for the lower frequency bands, and one for 2.4 GHz.|
|IEEE 802.15.4a||This version of the IEEE 802.15.4 standard defined two new PHYs. One used UWB technology and the other provided for using chirp spread spectrum at 2.4 GHz.|
|IEEE 802.15.4c||Updates for 2.4 GHz, 868 MHz and 915 MHz, UWB and the China 779-787 MHz band.|
|IEEE 802.15.4d||2.4 GHz, 868 MHz, 915 MHz and Japanese 950 - 956 MHz band.|
|IEEE 802.15.4e||This release defines MAC enhancements to IEEE 802.15.4 in support of the ISA SP100.11a application.|
|IEEE 802.15.4f||This will define new PHYs for UWB, 2.4 GHz band and also 433 MHz|
|IEEE 802.15.4g||This will define new PHYs for smart neighbourhood networks. These may include applications such as smart grid applications for the energy industry. It may include the 902 - 928 MHz band.|
Although new versions of the standard are available for use by any of the higher layer standards, Zigbee still uses the initial 2003 release of the IEEE 802.15.4 standard.
IEEE 802.15.4 applications
The IEEE 802.15.4 technology is used for a variety of different higher layer standards. In this way the basic physical and MAC layers are already defined, allowing the higher layers to be provided by individual system in use.
|Application or system||Description of the IEEE 802.15.4 application or system|
|Zigbee||Zigbee is supported by the Zigbee Alliance and provides the higher levels required for low powered radio system for control applications including lighting, heating and many other applications.|
|Wireless HART||WirelessHART is an open-standard wireless networking technology that has been developed by HART Communication Foundation for use in the 2.4 GHz ISM band. The system uses IEEE802.15.4 for the lower layers and provides a time synchronized, self-organizing, and self-healing mesh architecture.|
|RF4CE||RF4CE, Radio Frequency for Consumer Electronics has amalgamated with the Zigbee alliance and aims to provide low power radio controls for audio visual applications, mainly for domestic applications such as set to boxes, televisions and the like. It promises enhanced communication and facilities when compared to existing controls.|
|MiWi||MiWi and the accompanying MiWi P2P systems are designed by Microchip Technology. They are designed for low data transmission rates and short distance, low cost networks and they are aimed at applications including industrial monitoring and control, home and building automation, remote control and automated meter reading.|
|ISA100.11a||This standard has been developed by ISA as an open-standard wireless networking technology and is it described as a wireless system for industrial automation including process control and other related applications.|
|6LoWPAN||This rather unusual name is an acronym for "IPv6 over Low power Wireless Personal Area Networks" It is a system that uses the basic IEEE 802.15.4, but using packet data in the form of Ipv6.|
While the IEEE 802.15.4 standard may not be as well known as some of the higher level standards and systems such as Zigbee that use IEEE 802.15.4 technology as the underpinning lower levels system, it is nevertheless very important. It spans a variety of different systems, and as such provides a new approach - providing only the lower layers, and allowing other systems to provide the higher layers which are tailored for the relevant application.
By Ian Poole
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