ZigBee Protocol __ Wireless sensor network

ZigBee can be divided into three basic levels: Physical layer/Data link layer, ZigBee stack layer and application layer

The basic functions of each layer are as follows: (1) Physical layer/Data Link layer: Physical layer and data transmission media, responsible for the transformation of physical media and bits, and the transformation of data bits and upper-layer data frames. The data link layer is responsible for addressing functions, sending data to determine the destination address of the data sent, and the source address of the data when receiving the data. In addition, the physical Layer/Data link layer is also responsible for the assembly of packets or data frames and the resolution of the data frames received.

(2) ZigBee stack layer: ZigBee stack layer is composed of network layer and security platform, which provides the connection between application layer and IEEE802.15.4 physical layer/Data link layer, which is composed of several stack levels related to network topology, routing and security.

(3) Application layer: The application layer contains the applications running on the network node, giving the node its own function, the main function of the application layer is to convert the input into digital data, or convert the digital data into the output

Ii. The main features of the ZigBee protocol

The main features of the ZigBee protocol are as follows:

(1) Save electricity. ZigBee Network node Equipment has a short working period, low power to send and receive information, and the use of sleep mode, so its special energy-saving

(2) reliable. Because the collision avoidance mechanism is used, and the special time slot is reserved for the communication service needing fixed broadband, the competition and conflict are avoided when the data is sent, and the MAC layer adopts the fully validated data transmission mechanism, each sending packet must wait for the acknowledgement of the receiver, thus ensuring the reliability

(3) cheap. With the commercialization of products, ZigBee Communication module prices are expected to be reduced to 1.5~2.5 dollars

(4) Short delay. The ZigBee node sleeps and works only 15ms

(5) Large network capacity.

(6) Safety

Third, ZigBee network layer

1. Network layer function

The network layer provides an appropriate interface between the MAC layer and the application layer to perform addressing and routing functions by stimulating the action of the MAC layer, and its main tasks include:

① initiates a network and assigns network addresses

② add devices to the network or remove devices from the network

③ Route information to destination node

④ to encrypt the data that is sent

⑤ performs routing addressing and stores routing tables in a mesh network

2. Network Layer Service Specification

The network layer contains network layer data entities (Nlde) and Network layer management entities (Nlme).

1 Network Layer Data entity (Nlde)

Nlde will provide the following types of services:

① Common Network Layer Protocol Data Unit (NPDU): Nlde can be generated from the application support sub-tier PDU via an additional appropriate protocol header NPDU

② specific topological routes: Nlde can transmit NPDU to an appropriate device that enables the final transmission of the device, or through the next device of the final destination device

2 Network layer Management entity (NIME)

Nlme provides the following services:

① Breeding a new device

② set up a network

③ joins or leaves a network

④ Assignment Address

⑤ found near the table

⑥ Discovery Route

⑦ Receive control

3, Network layer data frame format

The network layer data frame format includes frame control field, destination address/source address, broadcast radius, broadcast serial number, frame load