Urban road lighting increasingly uses LED lighting technology instead of traditional lighting technology, the purpose is to reduce the consumption of electricity. Since LED uses a low-voltage DC power supply, it is convenient for additional detection and control circuits, which makes it easy for further energy-saving depletion of street light network. For the management and control of the street light network, it is possible to use electric carrier communication technology, and can also develop rapidly, so that short-range wireless communication technologies have exceeded power carrier communication technologies in terms of application cost, reliability and communication rate, etc. ZigBee short-range wireless communication technology. This paper proposes a solution that constructs a short-range wireless communication technology to build an LED street light wireless sensing network. You can switch, dimming, etc., or more lamps or multi-lamp or multi-lamp or all lights of the LED street light. , Current parameters and other detection, thereby achieving intelligent management of LED street network networks. As a wireless sensing network, its architecture should include four basic levels: physical layer and data link layers, network layers, and application layers. The LED street light wireless sensing network uses IEEE 802.15.4 standard as its physical layer and data link layer technology, the network layer is integrated with the application layer, using single-jump, double jump, and three relay communication modes as a network. The foundation of the agreement. This article focuses on the architecture of the LED wireless sensing network, which is based on the composition of the network topology and communication nodes, discusses the network layer protocol package format, routing working principle, and node communication design.
Network system
The network system of the wireless sensing network is the basis for the network layer to implement routing, including node composition and network topology.
Signature of the street light sensing network node
The street light network consists of a uniform septum, and each LED street light is a communication node of the network to build a wireless sensing network. Figure 1 shows the composition of the wireless sensing network LED street lamp node, in addition to the circuit of the illumination portion, the sample, the detection of the LED light emission brightness, and PWM control and other circuits of the LED light emission luminance are also attached. Each LED street lamp is both a sensor node and a network routing node; each node contains a microcontroller (MCU, such as CC2530), has a RF communication function, which can also receive signals can also receive signals; each node has 32bit (bit ) ID number. By adopting the IEEE 802.15.4 protocol standard in the physical layer and the MAC layer, all of these nodes are organically combined together with the protocol of the network layer, and all of these nodes constitute the LED street light wireless sensing network. Since some existing network layers and application layer protocols such as ZigBee, RF4CE, etc. is not very suitable for LED street light sensing network applications, so they need to redesign the network layer and application layer protocol.
Network topology
The distribution of LED lights, each LED lights network node configured as a wireless communication network, the topology shown in Figure 2, (A) is a signal point by point (single hop) relay transfer topology, (b) is a signal Partition (double hop) relay transmission topology diagram. To facilitate the design and discussion of the web application protocol, the following definition is made:
(1) All nodes can be divided into 2 categories, namely LED street light nodes (referred to as LED nodes, such as A1 A2 ... AN, B1 B2 ... BN) and street light controller nodes (referred to as control nodes, such as A, B);
(2) The distance between adjacent nodes is L, and the radius of wireless signal coverage of each node is greater than or equal to 2L;
(3) According to the relative position of the node, the node can be divided into a forward-driven node and a subsequent node, and the controller is nearing node, and is far from the controller is a subsequent node. For example, A1 is a A2 front drive node, and A3 is an A2 subsequent node; the sympathy B2 is a B4 front drive node, and B6 is a B4 subsequent node, and so on.
(4) Control between the control node and the LED node, the LED node can be communicated with each other as long as the wireless signal can be covered, and there is no need to set a base station or a special route coordination device.
(5) The 32bitid number of each node consists of two parts, which are network IDs and node addresses (numbers), all of which are 16bit. The network ID of all nodes of the same street light network is the same; from the control node, the node address is arranged in a large order.
Network protocol
The street light sensing network protocol includes the definition of the protocol package and the definition of the routing protocol, its design goal is simple, practical, and easy to implement.
Network protocol package format
The information package of street light sensing network protocols has three types, which are command packets, parameter packets, and response confirmation packages.
(1) Command package
Figure 3 (a) shows the command package format issued to the LED street node for the controller node. There are three types of commands: a broadcast command for all LED nodes throughout the network, a group command for a partial LED node, and a single point command for a single LED node.
Command packets are defined as follows:
Package type: is 1;
Destination Address: To specify the address of the LED node;
Package number: to the package number to the specified node;
Relay Mode: is 1, represents a single hop mode; is 2, represents a chain double-hop mode coupling; is 3, represents a double-hop mode odd chain;
The definition method of the command field is shown in Table 1, Table 1 lists only partial commands, and the command can be added as needed;
Table 1 Command Pack Command Field Definition
Command parameter field: used to indicate the brightness of the dimming, the lower the value, the lower the LED luminous brightness, the less power consumption, the value is 0, indicating the shutter;
The number of hops: command to the number of nodes required for the destination address, the value of all LED nodes of the street light network. When the command package is transferred, the number of hops is reduced every forward. When the hop value is 0, the command package is no longer forwarded.
(2) Parameter package
Figure 3 (b) shows the parameter package format uploaded for the LED street light network node. Polling timing of the control node can be acquired or instant query each LED within the network node state parameters, such as current value, the light emission and the luminance value of each parameter is sent only the LED junction to the control node after receiving the read command parameters Package. The parameter package is defined as follows:
Package type: 2;
Source address: The address of the upload parameter LED node;
Package number: Parameter package number issued for the upload parameter LED node;
Relash mode: Since the parameter package is only sent after the node receives the read status parameter command, the relay mode of the parameter packet is determined by the command package;
Status flag: 0 indicates that the corresponding LED node failures; 1, indicates that the corresponding node has a fault; 2, indicates that the corresponding node and the successor node has a fault;
Status parameters 1-3: For the relevant parameters of the LED node, such as current values, voltage values, and LED luminance values.
(3) Answering confirmation package
As shown in Figure 3 (c), the package format is confirmed. In order to achieve reliable transmission, each node needs to send a response confirmation packet after receiving the command package or parameter package. If the send (forwarding) party of the packet does not receive a response confirmation package within the set time, the re-send of the packet is initiated. Answer confirmation package Value of each field is as follows:
Packet Type: 3;
Node Address: Issue the address of the confirmation package node.
Confirmation Type: Receive a package type of the packet;
Confirmation number: The package serial number of the packet is received for the node;
Network routing protocol
The street light sensing network routing protocol is the forwarding mechanism for each node to the packet. Since the signal coverage of each node is limited, the information can only be sent to the neighboring node, and can only rely on multiple forwarding of the intermediate node to the distant node. According to the conditions defined above 1.2, the node forwarding packet can be divided into three modes, namely single-hopping mode, dual hopping mode, and variable hopping mode, each LED node will select according to the definition of the Power Power Pattern field.
Single hopping power mode
Figure 2 (a) shows the topology diagram of a single-stripping power mode. It is a relatively simple forwarding mode, requiring the radius range of each node wireless signal overlay to the node spacing L, and the packet only needs to forward the adjacent predecessor node or subsequent node forwarding. In this mode, the node processing is as follows:
① The node receives a command packet (FIG. 3 (a)), the precursor to the sending node receives the acknowledgment response packet; the number of hops is decremented command packet; Comparative own node address (NA) and the size of the command packet destination address , Equal, execute the command in the package and do not need to forward command packets, forward the packet to the subsequent node; if it is the broadcast command (the target address value is 0xfff), the command is transmitted while performing this command while being forwarded to the subsequent node Command package. The route address of forwarding is: Na + 1. When the command package is sent to an LED node in the network, the number of hops will be 1 after 1 will be 0, and the package will no longer be forwarded.
2 The node receives the parameter package (as shown in Figure 3 (b)), simply sending a reception confirmation package and forwarding node forwarding to the subsequent node, the routing address of the forwarding parameter packet is: NA-1.
3 When the node receives the command package or parameter package, the received confirmation package must be sent (as shown in Figure 3 (c)), when receiving the command package, confirm the type value
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