The introduction of IP protocols into wireless communication networks has long been considered unrealistic (not entirely impossible). So far, wireless networks only use proprietary protocols. Because IP protocols have high memory and bandwidth requirements, it is difficult to reduce the operating environment requirements to accommodate microcontrollers and low-power wireless connections.
The release of the draft IETF 6LoWPAN standard based on IEEE 802.15.4 for IPv6 communication is expected to change this situation. The low power operation potential of 6LoWPAN makes it ideal for applications ranging from handsets to instruments, and its built-in support for AES-128 encryption lays the foundation for robust authentication and security.
The IEEE 802.15.4 standard is designed to develop compact low-power, inexpensive embedded devices (such as sensors) that can run on batteries for one to five years. The standard uses a radio transceiver operating in the 2.4 GHz band to transmit information using the same frequency band as Wi-Fi, but its RF transmit power is only about 1% of Wi-Fi. This limits the transmission distance of IEEE 802.15.4 devices, so multiple devices must work together to transfer information and bypass obstacles on a longer distance.
The task of the IETF 6LoWPAN Working Group is to define how to use the IEEE 802.15.4 link to support IP-based communications while adhering to open standards and ensuring interoperability with other IP devices.
In recent years, low-rate wireless personal area network (LR-WPAN) technology integrating network technology, embedded technology and sensor technology has become a research hotspot. LR-WPAN is a network designed for short-range, low-rate, low-power wireless communication, and can be widely used in smart home appliances and industrial control.
The IETF organization formally established the IPv6 overLR-WPAN (6LowPan) working group in November 2004, and set out to develop an IPv6-based low-speed wireless personal area network standard, namely IPv6over IEEE 802.15.4, which aims to introduce IPv6 into IEEE 802.15.4. The underlying standard wireless personal area network. Its emergence has driven the development of short-range, low-rate, low-power wireless personal area networks. IEEE 802.15.4 is a typical representative of LR-WPAN, and its application prospects are very broad. The research based on it is in the ascendant.
However, IEEE802 15.4 only specifies the physical layer (PHY) and media access control (MAC) layer standards, and does not cover the above network layer specifications, and the IEEE 802 15.4 device density is very large, and it is urgent to implement networking. At the same time, in order to meet the interconnection and interoperability between devices of different equipment manufacturers, it is necessary to establish a unified network layer standard. With its unprecedented address space and openness, IPv6 has a great appeal to LR-WPAN.
IEEE 882.15.4 Technical Overview
IEEE 802.15.4 defines the PHY and MAC layers.
The main features of the IEEE802.15.4 standard: 1 low rate, for the 2.4GHz, 828MHz, 915MHz three frequency bands corresponding to 250Kb / s, 20Kb / s and 40Kb / s three rates; 2 low power consumption, can be used in standby mode 2 Section 5 dry battery drive for more than 6 months; 3 low cost, generally using bottom-end embedded devices with very limited hardware resources or smaller special equipment; 4 short distance, node signal coverage is limited, generally 10-100m; Low complexity, lower than the existing standard; 6 short frame length, maximum frame length is 127 bytes; 7 multi-topology, rich network topology, support two basic topologies and hybrid networking of star topology and point-to-point topology .
Application of 6LowPan in smart home wireless network system
With the rapid development of LR-WPAN and the increasing popularity of next-generation Internet technologies, 6LowPan technology will be widely used in many fields such as smart home and environmental monitoring. It is possible to enable people to control and apply large-scale sensor networks through the Internet. For example, in a smart home, 6LowPan nodes can be embedded in furniture and appliances. Realize the management of the smart home environment by interconnecting with the Internet via a wireless network.
Introduce the design and installation of this system on a family basis. Each home installs a home gateway and several wireless communication 6LowPan sub-node modules. A wireless network transceiver module (a product conforming to the 6LowPan technical standard) is connected to the home gateway and each child node, and data is transmitted between the gateway and the child nodes through the wireless network transceiver module. The structure and function of each part are as follows:
(1) Structure and function of the home gateway: 32-bit embedded RISC processor and uClinux operating system based on ARM architecture; automatic arming/defense prevention through door lock; in case of robbery or disease, press emergency button to automatically report to the management center Each household has its own webpage, which displays the cell notification, the working status and data of each part of the system through the webpage: the data of water, electricity and gas are sent to the property management center; the communication with the community management center via Ethernet; through the gateway The wireless 6LowPan (IEEE802.15.4) module communicates with each child node in the network.
(2) 6LowPan wireless communication sub-node function: 2-channel pulse quantity data acquisition, can collect water, electricity and gas 3 table data; 2-way security sensor switch quantity data acquisition, can carry out fortification/disarming alarm, security alarm (infrared curtain , door magnetism, window magnetism, glass breakage, etc.; 1 channel analog data acquisition; 1 channel analog data output; 1 relay contact output; wireless communication IEEE802.15.4 protocol and home gateway communication.
As an emerging technology in the field of short-range, low-rate, low-power wireless personal area networks. 6LowPan shows people a broad market prospect because of its low cost, convenience and practicality. Any application that requires low cost, small size, power saving, and dense distribution characteristics without requiring a device with a high transmission rate can be implemented using 6LowPan technology. For example: building condition monitoring, space exploration and so on. Therefore, the popularity of 6LowPan technology will definitely bring great convenience to people's work and life.
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