1. What is wireless network

Wireless network, as the name implies, is a way to build a network without relying on a network cable. It is mainly realized by using wireless communication technology. There are mainly two ways of implementing wireless networks (such as 4G, 3G or GPRS) through mobile communication networks and wireless local area networks (WiFi).

  1. What is wireless bridge

The wireless network bridge, as its name implies, is the bridging of wireless networks. It uses wireless transmission to build a communication bridge between two or more networks. In addition to the basic characteristics of wired network bridges, wireless network bridges work in 2.4G or 5.8G frequency bands that do not require a wireless license, so they are more convenient to deploy than other wired network equipment.

 

To understand the role of a wireless network bridge, it can be used to connect two or more independent network segments. These independent network segments are usually located in different buildings, hundreds of meters to tens of kilometers apart, and can be widely used in different buildings. The interconnection between things.

 

At the same time, according to different protocols, wireless bridges can be divided into 2.4GHz bands 802.11b, 802.11g and 802.11n, and 5.8GHz bands 802.11a and 802.11n wireless bridges.

 

  1. The meaning of wireless bridge 2.4G and 5.8G

2.4G bridge:

The advantages are low frequency, large wavelength and strong diffraction ability. Simply put, the transmission performance is good, and the transmission path is slightly blocked and it is not a big problem. Then there is the relatively low cost.

 

The disadvantage is that there are many devices that use the 2.4G frequency band, and the electromagnetic wave signals emitted by the bridge are easily interfered by signals emitted by other devices, resulting in a decrease in transmission quality. Then it is limited by the transmission bandwidth of the 2.4GHz frequency band itself, which generally does not exceed 300Mbps

 

5.8G bridge:

The advantages are high frequency, relatively pure channel, and large transmission bandwidth. The transmission bandwidth starts at 433Mbps and can easily reach more than 1Gbps. It is suitable for scenarios with high data transmission requirements.

 

The disadvantage is that the frequency is high, the signal wavelength is short, the penetration is poor, and there can be no obstruction during the propagation. The cost of 5.8G equipment is higher than that of 2.4G, and it is still in the popularization stage.

 

The wireless bridge transmission system usually consists of two or more wireless devices. Due to the two-way transmission of data, each device needs to have the ability to send and receive wireless signals.

 

  1. The working principle of wireless bridge

The working principle of a wireless network bridge is that the network bridge uses air as a medium to transmit signals. Simply put, one end of the network bridge converts the signal in the network cable into a wireless electromagnetic wave signal and directionally transmits it into the air. The role of the bridge at the other end is just the opposite. It receives wireless electromagnetic wave signals in the air and converts them into wired signals.

 

Wireless electromagnetic wave signals can be transmitted using air as the transmission medium, which can solve many difficult problems in wired deployment and construction: such as highways, rivers, mountain streams, or road hardening, wired deployment and construction difficulties.

 

Wireless bridge networking has obvious advantages. It can realize point-to-point or point-to-multipoint network connection over a distance of up to 50 kilometers, and the data transmission speed is up to 108Mbps. Effectively solve the problem of network connectivity in the interval. As long as the wireless signal coverage area, the client can easily access the network, converge the system, without any wiring, and the wireless terminal can achieve zero-configuration access, so it is very easy to maintain and expand the network .

 

Network bridges are generally used in the following scenarios: wireless data collection, monitoring data transmission (outdoor and elevator), outdoor wireless coverage, outdoor long-distance wireless bridging, private ISP wireless broadband, unmanned monitoring station data return, etc.

 

  1. How to choose the right bridge

Wireless network bridge is a kind of wireless monitoring transmission equipment commonly used in the field of wireless monitoring. Although it is also a wireless device like wireless AP and wireless router, it is not used to build wifi coverage, but to wirelessly transmit video data. Like the switch in wired monitoring, wireless bridge is an important transmission device in wireless monitoring, and it is widely used in the two major fields of outdoor monitoring video transmission and elevator monitoring video transmission.

 

There are many types of wireless bridges on the market. How to choose a bridge that suits your needs? We will answer you from the following aspects.

 

① Transmission distance

The transmission distances required for wireless monitoring projects are not the same. There are also many transmission distances of wireless bridges. Some transmit 1 to 3 kilometers, some transmit 3 to 5 kilometers, some transmit 5 to 10 kilometers, and some transmit 20. More than kilometers, it must be determined according to the monitored transmission distance. As far as possible, the maximum transmission distance of the bridge is greater than the monitoring transmission distance. Because the rain, fog, snow and other weather in the actual application environment will cause the transmission performance of the bridge to decrease, the engineering construction should be predicted. Leave sufficient performance margin.

 

②Transmission bandwidth

There are many transmission rates of wireless bridges, such as 150Mbps, 3000Mbps, 450Mbps, 600Mbps, 900Mbps, etc. Which rate to choose can be determined according to wireless monitoring requirements. What users actually need to consider is the transmission performance of the bridge at a specific distance, not the theoretical bandwidth data. For example, the theoretical transmission bandwidth of the IP-COM AP625 bridge is 433Mbps. At a distance of 2 kilometers, the measured point-to-point transmission bandwidth can reach 200Mbps, and it can load 25 200W cameras without pressure.

 

③Working frequency

There are two mainstream working frequencies of wireless bridges, 2.4G and 5.8G, and the characteristics of the two bridges are different. Generally speaking, 2.4G wireless bridge is the current mainstream frequency band, with good compatibility and good diffraction ability, but its anti-interference ability is relatively poor, especially when used in urban areas, it is susceptible to wireless signal interference from other WiFi devices. The 5.8G channel is relatively pure, has better anti-interference ability, long transmission distance, but poor diffraction ability.

 

In urban areas, downtowns, long-distance transmission, large camera stream, 2.4G interference is more, choose a 5.8G wireless bridge. Others, such as short transmission distance, relatively remote, less co-frequency interference, etc., use 2.4G wireless bridge

 

④Antenna

The antenna is an important accessory of the wireless network bridge, which is used to transmit and receive wireless signals. Without the antenna, the wireless network bridge cannot realize communication. There are many types of antennas, including omnidirectional antennas and directional antennas. The omnidirectional antenna is used for short-distance coverage and transmission. For long-distance bridging, a directional antenna should be selected. The larger the antenna gain, the better the performance of the wireless network bridge.

 

⑤Power supply mode

The working environment of wireless bridges usually involves some complex outdoor environments, such as forests, ports, tunnels, reservoirs, etc., so power supply is a more troublesome issue. Choosing a wireless bridge that supports POE network cable power supply can solve this problem well. All IP-COM bridges support PoE injector power supply, and the power supply distance can reach 60 meters.

 

⑥Protection level

Wireless network bridges mostly work outdoors, and the environment is changeable, such as rain, rain, snow, high temperature, etc. The first requirements are waterproof, dustproof, heat-resistant, and anti-condensation. For a qualified wireless bridge, these “quality” are necessary.

 

⑦ Pairing method

There are currently three mainstream pairing methods for bridges: key pair pairing, dial code pairing, and automatic pairing. In terms of the simplicity of engineering applications, especially for projects where dozens or hundreds of bridges are installed at once, automatic matching is undoubtedly the best choice. The IP-COM bridge supports automatic pairing when the two bridges are powered on under the factory state, which greatly reduces the workload.

 

  1. Wireless network bridge installation requirements

Wireless network bridge is an important transmission equipment in wireless surveillance, and it is widely used in two major fields, outdoor surveillance video transmission and elevator surveillance video transmission. In addition to selecting a suitable wireless bridge, we also need bridge equipment that can give full play to its performance advantages after installation to assist users in the project. Therefore, we must pay more attention to some installation requirements and precautions of the wireless bridge to avoid various problems later.

 

①Installation height

During the wireless transmission of the wireless bridge, obstacles such as trees, buildings, and large steel structures will weaken and block wireless signals. In order to improve the wireless transmission performance and prevent the signal from being damaged and the signal is weak, users should try their best to ensure that there are no obstacles in the transmission route of the wireless bridge during installation to meet the mutually visible transmission conditions at both ends.

Visibility at both ends cannot be simply understood as point-to-point visibility, which means that there must be no obstacles or potential obstacles in the Fresnel zone (radio wave term) propagated by the antenna. The main radio frequency energy between the antennas is transmitted in this area, so the transmitting antenna must be high enough above the obstacle to maintain a line of sight path between it and the receiving antenna to ensure the normal operation of the communication link.

 

② Angle and signal debugging

Since the quality of the wireless bridge signal is directly related to the bandwidth and stability of the link, the wireless bridge signal must be further debugged after the installation is completed (you can adjust the signal strength by adjusting the direction of the antenna on both sides, the elevation angle, etc.) ). You can check the signal strength according to the signal status indicator of the bridge device (three lights, three signals are the best, two are normal, and one is poor) or software. Detailed installation steps of outdoor wireless AP

 

③Lightning rod requirements

When wireless network bridges are installed in the field, if there are no tall buildings or lightning rod protection nearby, lightning protection measures need to be considered. Usually, lightning rods are used. Generally, when installing in urban areas or surrounding lightning rod protection, separate lightning rods are not required.

From the characteristics of the lightning rod, it can be seen that the lightning rod is lightning-inducing, and the lightning rod will discharge in the grounding path when it is struck by lightning. Therefore, the lightning rod and the protected equipment need to be insulated and isolated, otherwise the lightning rod will have a lightning strike effect on other equipment when it is discharged. Because lightning rods are more likely to cause lightning discharge than ordinary equipment due to their tip discharge characteristics, if the lightning rod cannot be insulated from the protected equipment, it will increase the probability of lightning strikes for other equipment. Therefore, the grounding of the lightning rod needs to be separated from the grounding of the equipment and cannot share the same ground.

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④Power requirements

The normal power supply input voltage of the PoE power supply module of the bridge is 100V~240V and the output voltage is 24V-48V. Any voltage lower or higher than this will affect the normal operation of the device or cause abnormal damage to the PoE power supply module. In view of the unstable and high voltage supply in the field, it is necessary to design a set of PoE power supply solutions (such as stabilized power supply, UPS power supply) that adapt to the working voltage.

Since the network bridge is a precision electronic device, it has high requirements for power supply and is susceptible to the impact and influence of other power supply equipment, so the power supply of the network bridge should be separated from other high-power equipment such as pumping units and oil pumps. When taking power at the same location, UPS, stabilized power supply or isolation transformer should be installed to filter out the influence and interference of high-power motors on the power supply during operation.

When using a PoE module to power the bridge through a network cable, it is recommended that the distance does not exceed 60 meters. Beyond this distance, it is recommended to move the transmission line near the bridge to meet the recommended power supply distance requirements.

 

⑤ Equipment grounding requirements

The wireless network bridge should be grounded. If the device is not grounded, it will cause problems such as abnormal operation and damage of the device. The grounding resistance of the device should be less than 4 ohms, and it should not share the grounding with lightning rods and strong current lines. If a PoE power supply ground wire is used, grounding is also required. Users can use the super Category 5 (or above) shielded network cable with ground wire and PoE adapter for grounding, which can conveniently and effectively prevent static electricity and lightning damage. The grounding wire and the grounding point should be made of waterproof tape and water-proof cement according to the waterproof requirements to prevent the grounding point of the grounding wire from being oxidized and rusted due to long-term exposure to the air.

 

  1. How to set up wireless network bridge

There are 4 common wireless bridge transmission modes, the distribution is point-to-point, point-to-multipoint, relay, and reflection. Here, the first monitoring combined with the picture will briefly introduce the characteristics of these 4 wireless transmission modes.

 

①Point-to-point transmission

The point-to-point transmission mode is the simplest transmission mode, which is what we often call PTP. It is transmitted by a single device, and then received by a single device. One-to-one transmission and reception are simple and direct. The point-to-point transmission mode of the wireless bridge is often used in situations where the transmission distance is long, or the monitoring points are widely distributed, and point-to-multipoint transmission cannot be achieved.

 

②Point-to-multipoint transmission

The point-to-multipoint transmission mode is developed based on the point-to-point transmission mode. It is often expressed as one receiving end to multiple transmitting ends. It is often used in situations where the transmission distance is relatively short, there are many monitoring points, and the distribution is dense.

 

③Relay transmission

The relay transmission mode is because the transmitting end and the receiving end have unavoidable obstructions that block the microwave signal, so a relay device is added in the middle, so that the microwave signal can be smoothly transmitted to the receiving end through the relay device. This mode needs to increase Transfer equipment increases equipment cost input, so it is generally not used when it is not necessary.

 

④Reflection transmission

Reflective transmission is the use of objects other than the transmission equipment for microwave transmission and transmission. For example, the transmitting end and the receiving end cannot be visible, but there is a large building or a mountain with a smooth rock wall in the middle. By adjusting the angle of the device, wireless communication is carried out by reflecting microwave signals from buildings or mountain peaks.

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