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[1] standard based on IEEE 802.15.4 for IPv6 communication is expected to change this situation. The low power 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 promoted the development of short-distance, 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 network layer and above 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 .
TO-220 Transistor Outline Package is a type of in-line package often used in high-power transistors and small and medium-sized integrated circuits.
It not only plays the role of mounting, fixing, sealing, protecting the chip and enhancing the electrothermal performance, but also connects to the pins of the package shell with wires through the contacts on the chip, and these pins pass through the wires on the printed circuit board. Connect with other devices to realize the connection between the internal chip and the external circuit.Because the chip must be isolated from the outside world to prevent impurities in the air from corroding the chip circuit and causing electrical performance degradation. On the other hand, the packaged chip is also easier to install and transport.
TO-220 package is a kind of in-line package that is often used for fast recovery diodes. TO-220AC represents a single tube with only two pins and only one chip inside.
The diodes are packaged in TO-220AC and can be used in switch mode power supplies (SMPS), power factor correction (PFC), engine drives, photovoltaic inverters, uninterruptible power supplies, wind engines, train traction systems, electric vehicles and other fields.
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