01 What is the purpose of the IEEE802.15.4 agreement?
The IEEE802.15.4 standard aims to provide a wireless personal area network (WPANs) for data transmission over relatively short distances. Unlike wireless local area networks (WLANs), the connection achieved through WPANs only involves little or no infrastructure, so it has the characteristics of small size, energy saving and low cost, and is suitable for solutions for various devices.
02what are the characteristics of the IEEE802.15.4 protocol?
The rate of wireless data transmission includes 250kb/s, 100kb/s, 40kb/s, and 20kb/s
Support two network topologies, star and point-to-point
There are two address formats, 16-bit and 64-bit, of which the 64-bit address is the only extended address in the world.
Optional guaranteed time slot ((GTSs)
Carrier sense multiple access with collision avoidance (carrier sense multiple access with collision avoidance, CSMA-CA)
Support confirmation (ACK) mechanism to ensure transmission reliability
With low power consumption
With channel energy detection (ED)
With link quality indication (LQI)
Works on 16 channels in the 2.4G ISM band, 30 channels in the 915 band, and 3 channels in the 868 band
03what are the types of equipment?
In the IEEE802.15.4 network, according to the communication capabilities of the device, it can be divided into Full function Device (FFD) and Reduced Function Device (RFD).
FFD runs in the network in three roles: coordinator, (PAN) coordinator, and device.Communication is possible between FFD devices and between FFD devices and RFD devices. There is no direct communication between RFD devices. It can only communicate with FFD devices or forward data out through an FFD device.
RFD is suitable for very simple applications, such as optical switches or passive infrared sensors. They do not need to send large amounts of data and may only be associated with one FFD at a time, so RFD can be achieved with minimal resources and memory capacity.
04 Network topology
The IEEE 802.15.4 network includes two network topologies, star and peer-to-peer, as shown in the following figure：
●Full-featured device (full-featured device, FFD)
○Reduced Function Device (Reduced Function Device, RFD)
←→Communication process
In a star structure, all equipment communicates with the central equipment PAN network coordinator. In this kind of network, the network coordinator generally uses a continuous power system for power supply, while other equipment uses battery power.
Unlike star networks, peer-to-peer networks can communicate directly between any two devices as long as they are within the wireless radiation range of each other. In peer-to-peer networks, a network coordinator is also required to implement functions such as managing link state information and authenticating device identity.
05 Protocol architecture
Upper Layers (Upper Layer)
It consists of a network layer (providing network configuration, operation, and message routing) and an application layer (providing the expected functions of the device). The upper layer exceeds the scope defined by the 802.15.4 standard, such as ZigBee's network layer and application layer.
MAC (Media access control) layer
It is characterized by beacon management, channel access, GTS management, frame verification, frame confirmation, association and separation.In addition, the MAC layer provides hooks for implementing security mechanisms applicable to applications.
PHY (physical layer)
It is characterized by activated and turned off radio transceivers, channel energy detection (ED), link quality indication (LQI) for receiving data packets, channel selection, idle channel evaluation (CCA), and transmission and reception of data packets through physical media. Wireless frequency bands include 868-868.6 MHz (European 868 band), 902-928 MHz (North American 915 band), 2400-2483.5 MHz (global 2.4G ISM band).
Ebyte Electronic Technology Co., Ltd. specializes in the development and production of wireless data transmission modules with various functions in various frequency bands. The products have been widely used in various application scenarios such as the Internet of Things, consumer electronics, industrial control, medical, smart home, highway, etc. If you have any needs, please contact email:service-es-@cdebyte.com Or visit the website:https://www.es-ebyte.com/
No comments yet