ZigBee network infrastructure
Original link: https://blog.csdn.net/chinsanyl/article/details/104857952
table of Contents
1 Introduction
ZigBee is a technology used in short-range wireless communications technology and at a low rate, ZigBee past also known as "HomeRF Lite" and "FireFly" technology, unified technology called ZigBee. Mainly for short-range, low-power and high transmission rate is not a variety of electronic devices for data transfer between applications and typically have periodic data, intermittent data and low-latency data transmission. More features and network architecture, ZigBee networks are widely used in home automation, home security, industrial control, environmental control, medical care and transportation.
2. Network architecture
Full ZigBee protocol stack from top to bottom by the application layer, the application convergence layer, network layer, data link layer and physical layer. The following layers to act in a ZigBee structure:
Physical Layer: ZigBee protocol structure as the lowest, provides the most basic services, a layer provides services for the MAC layer, such as the interface data and the like. Also played a role in interactions with real (physical) world;
The MAC layer: responsible for establishing a wireless data link between the different devices, maintenance, end, confirm the data transmission and reception;
Network / security layer: to ensure integrity of the data transmission and, at the same time to encrypt data;
Application / supporting layer: a plurality of devices according to the design requirements for communication between the object and;
Which, ZigBee protocol architecture is the most characteristic two: power and ad hoc networks.
3. Advantages
ZigBee is a wireless connection, you can work at 2.4GHz (worldwide epidemic), 868MHz (popular in Europe) and 915 MHz ( USA popular on) three bands, each having up to 250kbit / s, transmission 20kbit / s and 40kbit / s of rate, its transmission distance is in the range of 10-75m, but may continue to increase. As a wireless communication technology, ZigBee has the following characteristics:
(1) Low power: Due to the low transmission rate of ZigBee, only 1mW transmit power, and the use of a sleep mode, low power consumption, very low power ZigBee devices. It is estimated that, ZigBee devices relying on two AA batteries can last up to six months to use a period of about 2 years, which is unmatched by other wireless devices.
Low (2) Cost: ZigBee module initial cost of around $ 600, it is estimated will soon be down to $ 1.5-2.5, and ZigBee protocol is royalty-free. For low-cost ZigBee is a critical factor.
(3) Short Delay: delay and communications from hibernation activation delay is very short, a typical search apparatus 30ms latency, sleep activation delay is 15ms, active device channel access delay is 15ms. Thus ZigBee technology suitable for demanding wireless control delay (e.g., industrial control applications, etc.) applications.
(4) capacity network: a star structure ZigBee network can accommodate up to 254 up to 100 may be present at the same time from the ZigBee network device and a master device, a region, and the network of flexible.
(5) reliability: collision avoidance strategy adopted, while the dedicated time slot is reserved for a fixed bandwidth communication services need to avoid competition and collision of transmission data. The MAC layer uses a completely acknowledged data transfer mode, each packet transmission must wait for confirmation recipient. If a problem occurs during transmission can be retransmitted.
(6) Safety: ZigBee offers based cyclic redundancy check packet integrity check (CRC) to support authentication and certification, using the AES-128 encryption algorithm , each application flexibility to determine its security attributes.
4. Network Topology
4.1. Network role
1) Coordinator (English name: ZigBee Coordinate, often abbreviated as: ZC). Coordinator in a ZigBee network, there is one and only one coordinator, it began building the network and network maintenance functions in the network. It is the central hub for the entire network. Is the highest level of the parent node.
2) Routers (English name: ZigBee Router, often abbreviated as: ZR), the router in a ZigBee network can either act as a parent, can also act as a child node, forwarding information and assistance coordinator maintenance functions of the network.
3) a terminal (English name: ZigBee End-Device, often abbreviated as: ZED), a terminal in a ZigBee network, which most simple function, can join the network, for the child node endmost device. It can only communicate with its parent node, the communication between the two terminals if necessary, must be single-hop communication or multi-hop through the parent node. ZigBee network is permissible maximum number of nodes present, only low power to allow a network device.
4.2. Network architecture
1) star network: ZigBee network belongs to one of the simplest star network topology in a ZigBee network. Comprising a coordinator (central node), and a plurality of routers and terminals (subsidiary nodes). The configuration as shown in FIG. The structure of the network, each node can only node affiliated with the communication center, if necessary communication between the subsidiary nodes, data must be forwarded via the central node.
2) a tree network: ZigBee coordinator contains a tree network, composed of a plurality of terminals and routers. Its network topology is as shown in FIG. ZigBee tree network can be seen as a plurality of star network, each branch of the branches (the node with the router) can be seen as "central node" consisting star network, each word can only communicate with its parent node device, most senior parent is the coordinator.
In a tree network, the coordinator will build up the entire network, as the router receiving point, outward diffusion of the network in a tree. Formed between the node and the node "multi-hop communication" by the intermediate routers. Compared with the star network, tree network on capacity and robustness has been greatly improved.
2) a mesh network: ZigBee mesh network is based on a ZigBee network tree structure topology is shown below. ZigBee mesh networks, in addition to all the functions satisfy the ZigBee network tree, the communication relationship between a neighboring routers exist, that the dynamic distribution network more flexible routing capability is more stable and reliable. Can give full play to the advantages of ZigBee self-organizing network.
