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I. Introduction:
The Internet of Things equips sensors to various real objects such as power grids, railways, bridges, tunnels, highways, buildings, water supply systems, dams, oil and gas pipelines, and household appliances, and is connected through the Internet to run specific programs to achieve remote control. Or achieve direct communication between objects and things. Through the Internet of Things, central computers can be used to centrally manage and control machines, equipment, and personnel. Remote control can also be performed on home devices and automobiles, as well as locating and preventing items from being stolen. In many of these applications, there is no single power supply technology, and PoE (Power Over Ethernet) is a technology that can transmit power and data over Ethernet to twisted-pair devices. Through this technology, including Internet telephony, wireless base stations, network cameras, hubs, smart terminals, modern intelligent office equipment, computers, etc., devices can all use PoE technology to provide power to complete the operation of various devices. The electronic devices that are powered by the network can be used without an additional power outlet, so at the same time, the time and money for configuring the power line can be saved, resulting in a relatively low cost of the entire device system.
With the wide application of Ethernet, RJ-45 network sockets are commonly used in the world. Therefore, various PoE devices are compatible. PoE does not need to change the cable structure of the Ethernet circuit to operate. Therefore, the PoE system not only saves costs, but is easy to install and also has the ability to remotely power on and power off, and the “Intellig†intelligent power supply can solve the problem. The power supply challenges required by networked terminals will play a very important role in the future development of the Internet of Things.
Second, the main application of PoE in the Internet of Things
With the development of technology and applications, the connotation of the Internet of Things continues to expand and new understandings have emerged. The Internet of Things (IoT) is an extension of applications and networks of communication networks and the Internet. It uses sensing technology and intelligent devices to perceive and identify the physical world. Network transmission interconnection, calculation, processing, and knowledge mining to achieve human and object, object and object information interaction and seamless connection, to achieve real-time control of the physical world, precise management and scientific decision-making purposes. Therefore, the network will no longer be passively satisfying the needs of users, but will actively perceive changes in user scenarios and conduct information exchanges to provide personalized services for users. Here are the main application scenarios of current "PoE" technology in the Internet of Things.
1. The application of PoE wireless AP in the Internet of Things The impact of wireless network technology on people is indisputable. The application scope of wireless LAN is more and more widely used in large offices, smart warehouses, university campuses, shopping malls, and airports. , conference and exhibition centers, hotels, airports, hospitals, bars, coffee shops, etc. to achieve the need for people to access the Internet anytime, anywhere. In the process of deploying a wireless network, the most important task is the reasonable and effective installation of a wireless AP (Access Point). The TG cloud platform can give a reasonable and effective set of management. In the larger wireless network coverage projects, the number of wireless APs is distributed in various parts of the building. APs generally need network cables to connect switches, and they must be connected externally. DC power supply. Resolving power and management on the spot will greatly increase the cost of construction and maintenance. The "Powerup" power supply switch solves the centralized power supply problem of the wireless AP through the Power over Ethernet (PoE), which can greatly solve the problem of local power acquisition and later AP management encountered during project construction. To avoid partial power outages, individual APs cannot function properly. In this solution, it is necessary to use an AP device with a device that supports the 802.3af/802.3af protocol to achieve network cable power supply. If the AP does not support the 802.3af/802.3af protocol function, you can directly add data to the PoE synthesizer to complete this power supply function. As shown in Figure 1: 
2. Application of PoE remote monitoring in the Internet of Things In recent years, due to the rapid development of social economy and information technology, various industries in the country have generated unprecedented demand for video surveillance. The application field is getting wider and wider. In addition to special industries such as finance, government, and transportation, digital monitoring has been applied or is being implemented in communities, hotel public places, factories, and shopping malls. The scale and radiation area are getting bigger and bigger. A typical example is the "Peace China" project. The scope of the project involves the entire city, with tens of thousands of cameras. The video surveillance products also develop from the local DVR mode to the IP Camera network.
However, the installation of network video surveillance equipment is restricted by the environment, which seriously affects the development of network video surveillance. In addition to the need for network cameras to transmit video signals over network cables, network cameras used in network video surveillance must provide sufficient power for them throughout the day. In the implementation process, it often happens that because of the inability to provide a stable power supply, the installation location of the camera has to be redesigned, and the redesign of the installation site may result in a monitoring blind spot, rendering the security monitoring meaningless.
Normally, a properly working network camera needs to connect two wires, a network cable, and a wire. The following conditions can cause the network monitoring lens to fail to install:
1, the camera installation position without power.
2. The camera is installed with a power source, but it is a lighting power source and cannot provide all-weather power supply.
The above causes the network camera to be unable to install, all in the power supply problem of the network camera. In order to properly install the network camera at the intended location, it is necessary to solve the power supply problem of the network camera. Since power cannot be supplied normally, you should consider using a network cable to power the camera. After all, deploying a network cable is much easier than deploying a strong cable. If you use a cable to power the network camera, the network camera can work as long as the data on the data exchange side is not interrupted. . The use of network cables to power the network cameras can be summarized as follows:
1. The network camera supports the 802.3af/802.3af protocol. You can use the PoE power supply device to power the network camera through the network cable.
2. The network camera does not support the 802.3af/802.3af protocol and cannot directly use the PoE device for power supply. Then need to use another auxiliary equipment - separator. The role of the splitter is to separate the power-integrated network cable into pure data network cables and power cables. In this way, the separation of data and power can be completed, and a single network cable can transmit data and provide power.
as shown in picture 2: 
In 2003 and 2009, the IEEE approved the 802.3af and 802.3at standards, respectively. It clearly specifies the power detection and control aspects of remote systems, as well as routers, switches, and hubs via IP cables to IP phones, security systems, and wireless. The method of supplying power to devices such as LAN access points is regulated. The release of IEEE802.3af and IEEE802.3at greatly promoted the development and application of PoE technology. Currently, "Unique" has launched industrial Ethernet products based on PoE technology to provide reliable and stable power supply for various network terminals in industrial control of the Internet of Things, such as temperature detection terminals, humidity detection terminals, and signal control terminals.
As shown in Figure 3: 
Third, the development trend of PoE in the Internet of Things 1. IEEE802.3af standard is currently the main application The standard provides that power can be supplied to the powered device through the RJ45 interface up to 13W, 48V power, which allows the device to use and transmit data consistent The cable provides or absorbs power. The standard specifies the functional and electrical characteristics of two optional power entities: a Power Device (or PD) and a Power Sourcing Equipment (or PSE). The standard is backward compatible. Earlier PoE devices will not conflict with the 802.3af standard and the effective power level will also be promising for future applications.
The IEEE802.3afPoE standard allows designers to provide up to 12.95W of power for a powered device (PD) over an Ethernet cable while meeting safety extra-low voltage (SELV) requirements. According to the IEEE 802.3af standard, PDs can be divided into four different levels according to the required power. Class 1 devices require 0.44 to 3.84W of operating power, Class 2 devices require 3.85W and 6.49W of power, and Class 3 devices have power ratings ranging from 6.5 to 12.95W. Designers can designate their devices to specific levels based on power requirements. The low-cost solution can use the general default level specification (Class0) to indicate that the required working power of the PD is between 0.44 and 12.95 W of operating power.
As an IEEE industry standard for the transmission of power over Ethernet cables, the development of Power over Ethernet (PoE) technology is very robust. This emerging technology powers CAT-5 cables that transport Ethernet data, simplifying the installation and deployment of powered devices (PDs). These devices include wireless access points, surveillance cameras, smart terminals, smart sensors, and VoIP phones.
Because the 802.3af standard power is below 13W, but the actual application process requires the use of more power terminals, such as cameras with full TG cloud platform, zoom lens, high-power high-speed dome camera, office automation equipment, such as The power of printers, fax machines, network intelligent terminals, small computers, and notebooks is mostly over 30W, so to further increase the power supply capacity of the channels, the power will be increased from the current 12.95W to more than 30W, which will also expand the PoE in security. The scope of applications in areas such as the field, office automation, and intelligent terminals and industrialized intelligent monitoring has expanded even further.
2. The IEEE 802.3at standard becomes the future trend Currently, the standard adopted by the PoE industry is IEEE 802.3af, which can only supply power to power-receiving equipment whose power is below 13W. Although it can meet the needs of traditional IP phones and webcams, it has high power, such as wireless LAN dual-band access, video telephony, PTZ video surveillance system (zoom with PTZ camera), smart terminals, and remote office equipment. The emergence of the application, the original 802.3af standard 13W power supply apparently can not meet the demand for this, the IEEE began in 2005 to develop a new PoE standard 02.3at (PoEPlus) to improve the PoE can transmit power.
The new standard was formally announced in 2009 as Power-over-Ethernet Plus (Po EP) IEEE802.3at, which defines a device with a power requirement higher than 12.95W as Class4 (this level is described in IEEE802.3af but remains For future use, the power level can be extended to 25W or higher. Currently, the highest PoE power supply equipment on the market is "U-UP" PoE power supply equipment, which can reach about 300W. Due to its ability to support higher power levels, this new standard will easily extend PoE applications to new areas. Examples are WLAN (wireless LAN), point-of-sale terminal equipment, switches, and tilt/zoom/cloud surveillance cameras.
One of the most striking changes in the 802.3at (PoEP) standard will be that it can control power distribution in more detail than existing standards. After the 802.3af-compliant PSE identifies the PD's level, it only needs to provide the maximum power allowed by the level definition. After the 802.3at system is powered up, a compliant PSE will be able to communicate with each PD using Level-2 software to determine peak and average power requirements. This new feature will allow designers to design PoE-compliant systems based on power budgets and bring the system's total power capability closer to system load requirements. Communication can also be established between peak load power and high current duration (eg, camera push-pull motors have higher short-term current requirements). However, the new standard has not yet fully defined this Level-2 communication.
Since the new standard is backwards compatible with the 802.3af standard, one of the major issues faced is how the PSE determines whether it is connected to an 802.3af-compliant PD or a new 802.3at-compatible PD (and how the PD makes a similar judgment to the PSE. ). To address this issue, the 802.3at standard will use the same features as in 802.3af to indicate a PoE-compliant PD, but this will add a second voltage pulse during the grading phase to indicate the 802.3at-compatible status of the PSE. The 802.3at-compliant PD will detect the second voltage pulse and determine that they are connected to the 802.3at-compatible PSE. Since the duration of the classification period meets the 802.3af time limit, PDs that are compatible with the current 802.3af standard will treat the second pulse only as part of the initial query and response.
3. Comparison between 802.3af and 802.3at:
Compared with 802.3af, 802.3at can output 2 times more power, and the output power of each port can be more than 30W, so it can greatly expand the application of PoE. Table 1 compares 802.3af with 802.3at. 
4. Opportunities and Challenges of PoE Technology:
PoE currently faces some challenges. For example, PoE technology allows powered devices to obtain more than 30W from each port, but not every powered device on a port requires 30W of power. Therefore, how to accurately sense each The need for electrical equipment is a very important issue, otherwise it may cause damage to the powered equipment or cause unsafe factors to the network infrastructure. In addition, since the cables are usually bundled and placed in the wiring closet, the problem of heat dissipation from the cable bundles needs to be considered. The cost issue is another challenge that PoE faces. Especially for PD manufacturers, adding PoE to a product means increasing costs.
In addition, there are four pairs of twisted pairs for the standard Category 5 cable, but only two of them are used in l0MBASE-T and 100MBASE-T. IEEE802.3af allows two uses. When the idle pin power is applied, pins 4 and 5 are positive, and pins 7 and 8 are negative. When the data pin is used for power supply, the DC power supply is added to the midpoint of the transmission transformer and does not affect the data transmission. In this way the pairs 1, 2 and the pairs 3, 6 can have any polarity. Current standards do not allow the simultaneous application of the above two conditions. The power supply device PSE can only provide one usage, and the power application device PD must be able to adapt to multiple situations at the same time. With the trend of the development of the IoT equipment to high-power power supply, all four pairs of twisted pair cables are required to be powered in the near future, and the power supply power is increased by increasing the power-carrying capacity to solve the demand for high-power power supplies.
In general, although PoE applications have resistance, the opportunities are greater than the challenges. The technology is increasingly perfected and deepened, and the scope of application is becoming wider and wider. Every change in technology will bring tremendous changes to the industry, and change will mean business opportunities. Although it faces many challenges, due to the huge market potential, various problems are constantly being improved by manufacturers. The "Unipu" intelligent power supply switch leads the industry revolution. It is believed that with the advent of the Internet of Things era, PoE technology will develop to support more powerful devices.
Fourth, the conclusion
The Internet of Things is an all-encompassing integrated network. Ethernet is a very important transmission method in the Internet of Things, and "U-UP" Power over Ethernet (PoE) is a revolutionary technology that passes the same five lines that currently carry Ethernet data. Category / Super Category 5 twisted-pair cables provide reliable DC power, extending the already very powerful capabilities of Ethernet. PoE will change the way that network devices supply power. Network administrators can make full use of existing network facilities and deploy new series of applications.
The emergence of PoE technology allows network designers to easily overcome the limitations of the original, with power semiconductor manufacturers to provide more kinds of switches and devices, coupled with new industry standards will support the use of higher power levels, this emerging technology It is bound to promote the emergence of a new generation of Internet of Things applications.
With the advent of the Internet of Things, various applications of the Internet of Things are constantly increasing and improving, and the demand for basic power supplies is more urgent. This article mainly discusses the application scenarios and development trends of PoE technology in the Internet of Things. Figure 2 PoE Internet of things, remote monitoring applications 3, PoE intelligent terminal applications in the Internet of Things When you call at home, if you suddenly lose power, the call will not be interrupted, this is because the telephone terminal power supply is a telephone company (exchange) switch Directly supplied through the telephone line. Imagine that if the sensors, controllers and intelligent terminal actuators of the Internet of Things in the Internet of Things can also be directly powered by Ethernet, then the costs of the entire wiring, power supply, labor, etc., may drop a lot, and can Extending surveillance to many remote applications, PoE technology is a vision of the IoT industry control industry.
Figure 1 PoE IoT wireless AP application
Figure 3 PoE Internet of Things Smart Terminal Application