The Method of Point-to-point Wireless Bridge to Avoid Interference
Point-to-point wireless bridge is a wireless network bridge; wireless bridge point-to-point is one of the wireless transmission methods.
1. The principle of point-to-point wireless bridge
The access point still acts as a central controller for wireless stations in its BSS (Basic Service Set), but it only communicates with one other wireless bridge. Through the "Preferred BSS ID" setting, the MAC of the peer AP can identify the specified AP. Of course, the peer AP also needs to perform the same configuration to achieve point to point transmission. For example: same SSID, same channel, same application mode.
2. Introduction to Wireless Bridge
Wireless bridges are designed for point-to-point interconnection using wireless for long-distance data transmission.
To understand the wireless bridge from the function, 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. So it can be widely used in the interconnection between different buildings. At the same time, according to different protocols, wireless bridges can be divided into 802.11b or 802.11G in the 2.4GHz band and 802.11a wireless bridges in the 5.8GHz band. The wireless bridge has three working modes, point-to-point, point-to-multipoint, and relay connection. It is especially suitable for long-distance communication in cities. It has 2 access methods, IP interface access and IP+E1 dual interface access.
Under the condition of no tall obstacles (mountains or buildings), one-to-one speed networking and temporary networking for field operations. Its working distance depends on the environment and the antenna, and the point-to-point microwave interconnection is now 7km. A pair of 27dbi directional antennas can achieve 10km point-to-point microwave interconnection. The 12dbi directional antenna can realize point-to-point microwave interconnection of 2km; a pair of wireless bridges that only realize the function of the link layer are transparent bridges, and the 24dbi directional antenna with network layer functions such as routing can realize heterogeneous The devices connected to the network are called wireless routers, which can also be used as layer 3 bridges.
Wireless bridges are usually used outdoors and are mainly used to connect two networks. It is impossible to use only one wireless bridge, but more than two, while APs can be used alone. The wireless bridge has high power, long transmission distance (up to about 50km), strong anti-interference ability, etc. It does not have its own antenna, and is generally equipped with a parabolic antenna to achieve long-distance point-to-point connection.
Now there are 802.11n wireless bridges on the market, and the transmission rate can reach more than 300Mbps. However, due to various factors, the actual rate is far lower than the value advertised by the merchant. However, compared with the development of the 11g rate, it is believed that more new products will be derived with the emergence of new technologies. It has indeed improved a lot, which also makes it possible for us to require high bandwidth and high transmission rate. With the continuous development of technology, it is believed that more new products will be derived with the emergence of new technologies.
3. Introduction of point to point wireless bridge transmission mode
In the application of wireless bridge, there are the following modes: point-to-point transmission, point-to-multipoint transmission and relay transmission mode. Among them, point-to-point is the most intuitive and most commonly used transmission method.
In the point-to-point wireless bridge transmission mode, the wireless bridge can be used to connect two networks located at different locations, generally consisting of a pair of wireless bridge devices and a pair of antennas. The point-to-point wireless bridge-to-bridge should be set to the same channel, only need to change one channel, the other will automatically change to the corresponding channel. Between two points that are far apart, in order to achieve a better bridging effect, it is necessary to install a high-gain antenna before the transmitter and receiver of the wireless bridge.
The point-to-point wireless bridge transmission mode is mainly used in the point-to-point transmission mode of the wireless bridge, which is often used in engineering projects with a long transmission distance or a wide distribution of monitoring points.
4. The method of point to point wireless bridge to avoid interference
As the name suggests, a point to point wireless bridge is a bridging of wireless networks. It uses wireless transmission to build a bridge for communication between two or more networks. Point to point wireless bridges are divided into circuit-type bridges and data-type bridges in terms of communication mechanisms.
4.1 Interference from external buildings
When the wireless signal encounters the occlusion of the object during the transmission process, if the transmission distance of the signal is not far, the transmission direction will change to a certain extent by means of refraction under the occlusion environment, and the signal will be reflected and attenuated. . Although the signal can be received, the signal strength of the received signal is very weak, and the bandwidth will be greatly attenuated.
If a metal object is encountered during the propagation, it will also increase the attenuation of the signal. If there is occlusion transmission in the case of transmitting video signals, then the signal stability must be difficult to guarantee. The transmission of network signals does not require much bandwidth, so the transmission of network signals in a sheltered environment can basically meet the requirements.
Therefore, when choosing the installation location of the wireless monitoring equipment, try to make the middle unobstructed as much as possible, and the middle from the transmitting end to the receiving end is visible, so as to avoid the attenuation of the microwave signal, and the monitoring center can receive high-strength wireless signals, thereby improving the Monitor the effect. If there is an obstruction between the transmitting end and the receiving end, we can avoid the intermediate obstruction by relaying.
4.2 Interference from similar equipment
In the wireless monitoring system, the analog wireless monitoring system is a fool. We can only check the interference source slowly, while the digital wireless monitoring equipment belongs to the intelligent wireless monitoring system. We only need to scan it through the software. The same frequency nearby, so you can avoid this frequency when setting.
At present, wireless monitoring equipment can be seen everywhere, such as mobile, Unicom signal towers, walkie-talkies, wireless, etc. These are all transmitted by wireless signals, which will definitely interfere with wireless monitoring equipment. For digital wireless monitoring equipment, avoid the signal interference of surrounding similar equipment or equipment with the same function. The signal source of this interference signal may be the normal signal source in our system, and the receiving end may not receive the signal or receive the same signal due to the same frequency or proximity, making it difficult for the receiving terminal to identify.
In this case, we can adjust the frequency of the wireless device, choose a clean channel, or change the position of the transmitter or receiver of the wireless device to increase the distance between the devices.
4.3 How to judge whether the bridge is interfered
It can be judged by monitoring the screen. If there are packet loss, screen instability, clutter, black stripes, ripples, etc., if there is a device that is disturbed, you need to find the cause one by one.
Not all equipment interferes with wireless, such as mobile, Unicom signal towers, walkie-talkies, wireless phones, etc., have no effect on wireless microwave equipment. When there is an interference source, you can adjust the frequency of the equipment, or choose a location far away from the interference source to install, thus greatly reducing the interference to wireless microwave equipment.
4.4 In addition to interference, point to point wireless bridges have six common failures:
4.4.1 Unable to transmit or receive signals: Start with simple problems first, check the network cable first, then replace the crystal head, and finally check whether the network port of the device is damaged.
4.4.2 The monitor display is blurry and intermittent, and the signal strength of the point to point wireless bridge is very low: if this happens, first check whether the distance between the point to point wireless bridges is within the applicable distance; secondly, check whether the antenna angle is correct, or Try a higher gain antenna.
4.4.3 If there is only one P/S light on the point to point wireless bridge, but it cannot be pinged: first, restore the wireless bridge to factory settings, and then reconfigure it; then replace the PoE power module to see if it can be used normally, if not , just use the network cable to directly connect the point to point wireless bridge to the computer to see if it can be connected; if it cannot be connected, it means that the wireless bridge is broken.
4.4.4 Communication is interrupted after thunderstorm: First, check whether the PoE power supply is burned out, then check whether the network port is normal, and finally check whether the main board of the device is burned out due to lightning strikes. Under normal circumstances, it is recommended to take lightning protection measures before installing a point to point wireless bridge in a thunderstorm area.
4.4.5 After the connection to the point to point wireless bridge is normal, the PoE indicator turns off, and turns on immediately after disconnecting the link: first, check whether the wireless bridge is short-circuited. If it is short-circuited, the wireless bridge needs to be replaced.
4.4.6 Discontinuous transmission signal: First, we need to check whether the channels at both ends of the point to point wireless bridge are consistent, then check whether the country code is different, and finally check whether the version of the wireless bridge is the same (this is sorted according to the frequency of problems). , the further back, the less likely it is.