POE is the abbreviation of Power over Ethernet, referring to the fact that without any change in the existing Ethernet Cat.5 wiring infrastructure, it can also provide direct current technology for a number of IP based terminals (such as IP phones, wireless LAN access point AP, network cameras, etc.). It is a switch that supports Ethernet power supply, that is, Ethernet power supply. In many cases, because of the inconvenient deployment of power supply or the high cost of deploying power and improving the safety of electricity, it will consider the way of PoE to supply power to the related equipment through the network line. At most times, the devices that can be powered by POE have IP monitoring cameras, wireless AP and IP phones, and the power of the devices is different and may also require the support of different standard PoE devices. The most commonly used PoE standards are IEEE802.3af (15.4W) and IEEE802.3at (25.5W).
Shenzhen Huambo Chi electric (WBLINK) provides a variety of models, different bandwidth (100 megabytes, Gigabit), different ports (optoelectronic mixing), and different power supply PoE switches. It includes 4/8/16/24/48 ports (including a variety of upper interface combinations), and a variety of POE switches that support 15.4W, 30W, 60W, and 90W for user selection.
As we all know, the Ethernet standard stipulates that the transmission distance is the farthest distance of 100 meters, and the data delay and packet loss may occur over 100 meters, because the signal is interfered with each other when the signal is transmitted in the twisted pair line and is disturbed by the external electromagnetic wave, at the same time, the cause of the parasitic capacitance and the parasitic inductance between the wires is caused by the wires. Signal attenuation and distortion will result in signal attenuation after long distance.
But not all network lines are limited within 100 meters, in actual operation, the network can also be more than 100 meters of effective transmission, good quality can reach about 120 meters, that is, oxygen free copper Cat.5 network lines, or 6 types of network lines. This line can effectively reduce the interference of itself, and also avoid the interference from the series and the outside world, so the transmission is far away. In fact, it is true that the distance between the power supply and transmission depends on the quality of the network line. The power signal transmission can be more than one hundred meters, or even up to 200 meters.
The 5 line is the most common kind of wire on the market now, but the quality is quite different. In order to reduce costs, many manufacturers replace copper wires with copper, copper clad iron and copper clad steel. If you want to maximize the effectiveness of PoE, you must use good quality cable.
Now many PoE manufacturers have launched 150 meters, long distance 250 meters power supply, and even 500 meters transmission distance POE switch. Do not say that the standard POE switch transmission distance is 100 meters, and the actual use of the best distance within 80 meters is best, this is what is going on, the following small editor to answer for you to parse.
As mentioned above, the distance of the PoE power supply is determined by the transmission distance of the data signal. The simple power can be transmitted far, but the transmission distance of the data signal is determined by the network line, and the transmission distance of the ordinary 5 class line data signals is about 100 meters. To ensure the quality of construction, 80-90 meters are generally taken. Note that the transmission distance here refers to the maximum rate, for example, 100M.
Many manufacturers note that the transmission distance of POE switches can reach 150 meters, but in practical applications, ordinary POE switches want to reach the 150 meter transmission distance and have strict requirements on the quality of the network lines. It is necessary to use more than 6 lines and increase the cost of use. Even so, if the internal circuit of the POE switch is very common, it is very common. The network switching chip and the POE power supply management chip are not possible to achieve the network 100M and 150 meters transmission distance, even with high quality network lines. Even if they are reluctant to use, the power consumption will be increased, the power consumption exceeds the PoE power supply, and it is very unstable, the packet width and the signal are seriously attenuated, resulting in the instability of the signal. Fixed, PoE switch equipment aging, late maintenance is difficult.
Huambo Zhi Dian standard series POE switch can transmit 150 meters easily and steadily on the basis of Cat.5 and quality assurance above medium.
The reason is that the Huambo Chi electric POE switch uses high quality import chip, optimizes the circuit anti-interference design, and uses high performance 52V power supply, and can guarantee the stable and reliable transmission of 150 meters through the function integration of the switching chip. In the POE switch IEEE802.3af/at standard, the equipment allows the supply of 44V-57V DC voltage. The Huambo Chi electric POE switch uses a standard of 52V power, which can reduce the loss of the line and provide more power for the electrical equipment. The line loss of 48V's normal supply voltage is about 4W, while the normal line loss of 52V's power supply voltage is 3W.
Some low quality and cheap POE switches use extremely common chips and even used devices, which can only be equipped with standard 48V power supply, because their inferior devices can't adapt well to the wide DC voltage range of 44V-57V. If 52V or more voltage is used, the stability will be reduced and overload.
It is mentioned above, even if the high performance POE switch 100M can only reach 150 meters, and the transmission distance is about 250 meters. In fact, there are some ways. If the rate is reduced to 10M, that is, the transmission bandwidth is 10M, the transmission distance can be extended to 250 meters (the quality of the network line), and this technology can not be used. Providing high bandwidth and bandwidth compression from 100M to 10M, it is not easy to monitor high-definition smooth transmission of images. While many manufacturers are promoting their products to support the transmission of 250 meters, they have not mentioned a single drop to 10M bandwidth, and they have the suspicion of deliberately concealing the customers. POE switches usually transfer 250 meters to design a transfer switch for users to choose whether to use or not.
Not all POE switches can easily transmit 250 meters as long as they are reduced to 10M bandwidth, which depends on the quality of the switch. If the switch internal switch chip is too poor in self-adaptive ability and the power chip management ability is not strong, even if the 10M transmission is forced, it can not guarantee a stable transmission of 250 meters or even 150 meters. . I buy a POE switch on the Internet, which is called 250 meters transmission, using super five kinds of strict network lines, more than 130 meters, even the network signal is not, talk about nothing 250 meters.
Huambo Chi electric WB-P0401-E, WB-P0802-EX and other standard series of POE switches, in the network Cat.5 and quality assurance in the middle and so on, can easily and steadily transmit 250 meters (10M bandwidth transmission).
Huambo Zhi Dian supports the 250 meter standard POE switch with optimized design, mainly in 2 aspects:
Due to the requirement of transmission distance 250, POE adopts high power design, POE power chip adopts imported high quality industrial grade chip. The power management module can intelligently recognize IEEE802.3af/at standard, automatic power regulation, and use 8 core intelligent power supply technology. In order to realize this function, the power supply is built with built-in power and built-in power. The advantage is that it can optimize the specific design, automatically measure the power demand of the receiving end and the cable transmission impedance and so on. It is analyzed and calculated by the intelligent power management module. The instruction to the internal power supply circuit adjusts the linear voltage input to match the automatic power output of the terminal receiving device. Because of the extension of the cable distance, the probability of the cable being destroyed is increased, and the over current / overvoltage protection circuit is designed. At the same time, the POE standard design ensures that the non POE equipment only passes the data, does not supply power, is stable and reliable, and eliminates the burning machine.
As mentioned above, it is very difficult for ordinary switches to reach 250 m transmission, and there must be strict requirements for the network cable. If the quality of the cable is slightly worse, the transmission distance will be greatly reduced. How does the POE switch of Huambo Zhi electric power guarantee the transmission of 250 meters? In the same way, data exchange chips still use industrial grade import chips, compliance with IEEE 802.3, IEEE802.3u, 802.3x standards, 10M/100M self-adaptive ability, and comprehensive use of Hyper-Trans technology, the transmission distance can be easily reached 250 meters.
High definition video surveillance brings more clear and realistic visual effects, and its massive video data also poses a greater challenge to the network transmission environment. Some customers and switch manufacturers believe that POE transmission from 100M to 10M bandwidth 250 meters transmission, not easy to monitor high definition transmission of image, easy to cause delay, also can not guarantee the monitoring of high definition, real-time, fluency requirements, and claimed that 10M can transmit the maximum of 2 720P high definition signal, 1080P signal 1 roads can not be transmitted. Lose.
At present, H.264 video compression standard is still the mainstream of the monitoring market, many manufacturers (including mainstream manufacturers) 720P network camera factory is the default bit stream is 4~6 megabyte, 1080P factory is the default stream is 6~10, frame rate 25FPS, 10M transmission bandwidth in the actual operation should be considered according to 6 ~7M to calculate, according to this calculation, 1080P perturbation Even 1 cameras can't be accessed. Is this really the case?
In fact, the above statement is very one-sided or even wrong. The following will be parsed for you:
From the video camera stream, for example, the 720P network camera factory is the default code flow is 6M, the 1080P factory is the default bit stream is 8M, this is a very conservative setting when the factory, the user in the actual use, the specific analysis, we know, each camera installation location is different, the monitoring site is different, lenses are different, lens The camera has a different view, the camera has a fixed focus, a rotating ball machine, so we should do some optimization of the factory stream, many small and medium-sized customers even part of the integrator, because of the lack of professional knowledge, the default rate of the camera, the frame rate never made changes will be directly used, thus resulting in access to the belt There is no need to increase the width of the bandwidth, the bandwidth resources of the original very abundant resources, resulting in a large waste of resources, artificial bandwidth resource constraints, so it is no wonder that the 10M bandwidth connected to the 1 1080P HD cameras are difficult.
How to solve these problems in the end? First from the 720P camera coding rate, the 720P effective pixel is 1280x720, according to the H.264 video compression standard, the normal condition is set to 2M, the frame rate 25FPS can meet the requirements, unless the monitored picture continues to be in large area of intense movement (such as the train runs fast in front of the train), in this extreme motion picture to ensure that the image is clear. The smooth transmission, it is necessary to set up more than 4M (factory settings are often considered according to this extreme case), other general conditions do not need to set such a high, in fact, the monitoring system is not much changed in a lot of site pictures, such as some rooms, even in the long time, no one in and out, the picture is basically immovable, Even if someone moves in and out, the movement of a person can't be very fast, even if the movement is fast, but the proportion of the motion picture to the monitor screen is not very large (that is, the ratio of the picture), so it is impossible for the extreme action picture to appear. According to the H.264 compression algorithm, the compression rate is very high, among which there are interframe and intra frame prediction (Estimation ) code, as long as there is no large change in the picture, the actual number of coded data is not very large. Under the same image quality, the code stream is set to 2-3M, so it is OK, so it is absolutely unnecessary to set the 6M bit rate, even according to the 6M set, there is no difference in the picture, and the bandwidth of the 4M is wasted. In addition, the camera can also be set into a variable bit stream to further save bandwidth. Most cameras also support double bit stream, the main stream and the sub bit stream, the main stream is generally video and HD, the sub bit stream is generally standard D1 or CIF standard, the sub stream is a general network transmission or the Internet transmission, so it is also possible. Further reducing the bitstream bit rate, such as 320K, further reduces bandwidth. Therefore, for 720P cameras, generally set to 1 to 3M code (including ball machine), can meet the requirements. Based on the same analysis, 1080P camera stream set to 2M-5M, can meet the requirements, the specific situation can be confirmed according to the installation site, do not do any modification according to the factory default settings, otherwise, 10M bandwidth will be considered to cause a surge, as two people carry a stretcher across the door and go into the door, but not to go, and not smooth. It's just like entering the door. Therefore, it is a sensible choice to reduce the default set rate or frame rate of the factory. There is another great benefit to reduce the bit stream setting, which is greatly reducing the space of the video hard disk.
The video frame rate (Frame rate) refers to the frame number of a picture that is refreshed per second. In fact, the video we see is played by frame by frame, and the frame is the basic unit of the video. The video file itself is made up of a lot of continuous pictures. It is simply understood that the frame rate is the number of pictures recorded in one second. Due to the special physiological structure of the human eye, if the frame rate of the picture is higher than 16, it will be considered coherent, which is called visual retention.
In general, the camera factory is set at the frame rate for a full frame rate (such as 25 frames). The higher the frame rate is, the higher the transmission bandwidth is. For the video surveillance system, it is acceptable to reduce the frame rate properly for some pictures. In fact, the human eye can not see any obvious differences between the 25 and 20 frames, and the 25FPS Falling to 20fps can reduce the bandwidth by 20%, so some less important sites can set the frame rate of the main stream lower (for example, 16~25fps), and the frame rate of the code stream is set to (5-20fps) so that bandwidth resources can be saved effectively.
With the progress of technology, H.265 is a new video coding standard developed by ITU-T VCEG after H.264. For high efficiency video coding (High Efficiency Video Coding), high compression ratio, accurate and stable control of bit stream, high definition and low bandwidth can be achieved. H.265 can realize the transmission rate of 1~2Mbps transmission 720P (resolution 1). 280*720) ordinary high definition audio and video transmission. It can achieve 1080P@30fps's mainstream HD video transmission efficiency on 2M-4M bandwidth.
From the above analysis, it can be concluded that the 250 meter 10M transmission of POE switches is of great use value.
Access to 720P, 1080P high-definition camera is completely without the problem, and will not appear the so-called video picture card, delay phenomenon, 250 meters transmission distance, expand the scope of the equipment, can partially replace the fiber and extender, reduce the cost of engineering. As long as it is not a super HD camera, it is still the most appropriate choice.
At present, Huambo electric power POE switch supporting 250 m transmission has been successfully applied in many monitoring projects.