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6 things you should know about PoE for IP Camera system - by Unifore Security |
Since the rapid development of network video surveillance, technical barriers are getting higher and higher, manufacturers offer technical support is also becoming comprehensive and systematic. Tom is a sales representative in video surveillance industry for several years, everyday exchanges ideas with security integrators. In the exchange of technology, integrators and installers often feel confused on Power over Ethernet (PoE) problems, Tom feel the importance of PoE technology, herein, Tom invited a PoE expert to provide comprehensive information about PoE.

#1 What's Power over Ethernet (PoE)?

PoE stands for Power over Ethernet, it's a technology that transmits both data and power supply simultaneously to network devices (such as VoIP phones, Wireless AP, network camera etc) without changing existing Cat.5 cable network structure.  PoE allows you to supply power to a networking device using the same cable that transmits the data, which in turn, greatly reduce the cost of installation and maintenance.

A complete PoE system includes Power Sourcing Equipment (PSE) and Powered Device (PD) two parts.

Power Sourcing Equipment (PSE): The equipment supports PoE function such as PoE switch, PoE injector (midspan) etc.

Powered Device (PD): IP/network cameras in video surveillance system.


24CH PoE Switch
24CH PoE Switch

Note: Currently, PoE technology has two standards - IEEE802.3af and IEEE802.3at.

#2 Is PoE technology reliable?

On technical perspective, PoE technology has been developed for many years, now PoE technology is in mature stage. However, current video surveillance market faces cost pressure, the quality of selected PoE switch and Cat5 cable is too poor, or the project design is unreasonable, may result in the maintenance workload of PoE project is huge, so integrators hold the common view that PoE technology is not stable.

For network video surveillance projects, different from common network cabling, data transmission is huge, power consumption is high, additionally requires 24/7 days continuous working, choosing high quality PoE device and cable can ensure the reliability of system.

#3 What's the advantage of PoE?

1. Simple cabling, reduce installation cost

Centralized power supply, one network cable can transmit data and power supply, PoE enables network devices no longer require extra power supply, greatly reduce the installation cost and time.

2. Safe and convenient

Power Sourcing Equipment only provides power supply to PoE-enabled devices. For example, PoE switch only transmit power supply when it detects the connection of PoE-enabled devices. This can avoid the risk of leakage. Users can mix use existing non-PoE device and PoE-enabled devices, both of them can co-exist.

3. Convenient for maintenance

Similar to data transmission, PoE can be managed through Simple Network Management Protocol (SNMP). This function can offer shut down at night, remote reset etc functions.

Simple Network Management Protocol (SNMP) is a popular protocol for network management. It is used for collecting information from, and configuring, network devices, such as servers, printers, hubs, switches, and routers on an Internet Protocol (IP) network.

#4 Possible problems or disadvantages of PoE?

1. Power insufficient, powered device can't boot: 802.3af PoE standard maximum output power is below 15.4W, this is sufficient to provide power supply for most of IP cameras. However, this output power is not sufficient for high power consumption devices such as network PTZ camera.

2. Centralized risk: Generally, a PoE switch connects to multiple IP cameras, if PoE network switch encounters any problems, all IP cameras will stop working.

3. High equipment and maintenance cost: Compared to other power supplying methods, PoE technology increases maintenance workload, when considering security and stability, separate power supply is best.

#5 How to select PoE switch?

1. Power consumption of IP camera: PoE network switch adopts different standards, the output power is also different. For example, IEEE802.3af can support powered devices that don't exceed 15.4W. As cable transmission will consume power, IEEE802.3af can provide power supply to powered devices that don't exceed 12.95W. According to IEEE802.3at standard, IEEE802.3at PoE switch can work with powered devices that don't exceed 25W.

2. Max. support powered devices: PoE switch has an important parameter - total power. Under IEEE802.3af standard, If 24CH PoE switch's total power reaches 370W, then each ports can get sufficient power (370/15.4=24), but if based on IEE802.3at standard, each port supports 30W, the PoE switch only can provide power supply to 12 ports (370/30=12).


PoE IEEE 802.3af Technical Specification
PoE IEEE 802.3af Technical Specification

3. Required quantity of ports, whether having Optical Fiber port, or network management, bandwidth (10/100/1000M).

#6 What's the PoE transmission range? advice on selecting cable?

PoE transmission range is 100 meters, recommend to use Cat5 Ethernet cable.

You should be cautious when buying the Ethernet cable from China. PoE IEEE802.3af standard requires PSE output power is 15.4W, after 100 meters transmission, the PD can receive 12.95W power, according to 802.3af standard current value - 350ma to calculate, the resistance value of 100 meters Ethernet cable should be (15.4-12.95W)/350ma = 7 Ohm or (15.5-12.95)/350ma = 7.29 Ohm.

Obviously, standard Cat5 cable can meet this requirement. but there are many non-standard Ethernet network cables selling in the market, they are produced not strictly in accordance with the requirements of the standard network cable. Non-standard network cable utilizes other materials such as copper clad steel, copper clad aluminum, copper coated iron, etc. The resistance of these cables is big, not suitable for POE power supply. POE power supply must use oxygen-free copper material, namely, the standard network cable.

IP camera or network camera is a new product which combined with analog and network video streaming technologies, in addition to its image capturing functions like the conventional analog camera, IP camera has built-in video compression processor with web sever function, to compress raw video footage, then broadcast over Internet. The authorized users can access the data from anywhere with internet connection. With the birth of digital video compression H.264 standard, image quality of network transmission has a significant improvement. What's the common problem of IP camera?

#1. Can't find IP camera when you use search software

Foremost, rechecking whether power supply and Ethernet cables are connected correctly. If the problem still exists, checking the network setting for IP camera and your computer. Go to network connection, configure IP address to same IP segments, Subnet mask and default gateway must be same for both IP camera and computer. Ensuring IP camera and computer are in the same router

#2. Can't visit IP camera from Internet (WAN)

For this problem, there are two possible factors. Firstly, there is no port mapping for IP camera. As we know, IP camera requires port mapping for remotely access from Internet (WAN). Without port mapping, IP camera is only accessible from local network (e.g 192.168.1.20). To solve this problem, you just need to log in your local router, and enable port mapping for IP camera in virtual server menu. Secondly, if you use domain or DDNS service, making sure the domain point to correct IP address with correct port number.

#3. Connect 4 IP cameras, but only one IP camera displays images

This problem occurs when you didn't change the default IP address of IP cameras. After you bought the IP cameras, all of them were configured with a same IP address. With reason of IP conflict, when several IP cameras connect to router, one camera can work, but the rest of cameras can't connect to network. To solve this problem, you need to set an unique IP address for each of cameras.

How to change IP address for the Hisilicon IP Camera?

Accessing the camera with default IP address (e.g 192.168.1.20), then login with default account information. Go to "Device Config", then choose "Network", you can change the IP address for the camera.

Device Config - Hisilicon IP Camera

Network - IP Address Config

#4. PoE IP camera can't see at night (dark images)

Insufficient power supply, which caused the PoE IP camera can't turn on Infrared illuminators, thus images are black at night. PoE (Power over Ethernet) is useful technology which greatly reduced the cost on IP camera installation. But it also has drawbacks, the voltage will drop when PoE IP camera connects to a PoE Switch or NVR. Typically, IEEE802.3af standard PoE only can transmit 20-30 meters. To solve this, user should use high quality Ethernet cable, or shortening the connection distance.

#5. Video delay (video latency) when watch live video

Since network camera need to compress the video, before broadcast over Internet, every IP cameras encounter video latency, which is a common problem in IP video surveillance system. To minimize the video latency time, you can increase the bandwidth through upgrading your network infrastructure, also you can lower the bit-rate of streaming. Lowering the image resolution also helps to reduce the video delay time. Increasing the fps can allow IP camera output smooth video.

Do you experience any of these problems? Please make comments if these information is useful to you. If you experienced other problems which are related to IP camera, please write it down in below comment section.

#6. IP camera can't display images

If your IP camera can't display images, also you are not be able to access the IP camera, likely the IP camera doesn't boot correctly. Almost IP cameras work with DC12V power supply, power requirements are different. You can estimate the power requirements on the basis of IR range.
o IR, or IR range within 20 meters: Required Power Supply DC12V 1A
R range is within 20-30 meters: Required Power supply DC12V 1A
R range is within 30-50 meters: Required Power Supply DC12V 1.5A

Please note: A regular PoE switch, supports IEEE802.3af, this standard only provides maximum 15.4W power, which means the provided current is 1.25 ampere. In conclusion, the regular PoE switch only can work with IP cameras which require no more than 15.4W power.

#7. How to upgrade NVR firmware

If your IP camera connects to NVR, not all problems are caused by IP camera. Sometimes, the problem was caused by NVR. You may solve the problem through upgrading or updating NVR's firmware.

To update the firmware, you need to get the firmware file in a USB stick, which then has to connect USB port of NVR for upgrading.

Step 1. Go to "System Setting", choose "System" > "Upgrade"

Step 2. Select the firmware file, then click "Upgrade".

Step 3. When upgrading succeed, the NVR will reboot.

NVR can find IP camera but can't display image

If IP camera can be found through automatically search on NVR, this means the IP camera works properly, NVR detected and received correct video streaming parameters from IP camera. If your NVR shows video abnormal, you need to check the video resolution setting for both IP camera and NVR. The video resolution should be same as the NVR's recording resolution. If you use our IP camera and NVR, you need to choose the system's recording resolution as in below picture: