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When deploying wireless monitoring and installing wireless bridges, point-to-multipoint transmission is often used. What should you pay attention to when using this method and how can you achieve good transmission results? Feng Runda Xiao Bian sums up the following points with everyone.
First, in which case will use point-to-multipoint transmission?
Point-to-multipoint refers to the situation where multiple transmitters correspond to one receiver. For wireless bridges, point-to-multipoint transmission is a slightly more complex method. Because the loss of signals during transmission is greater than point-to-point (one-to-one) transmission, this method is suitable for those monitoring points. More concentrated, larger number, and closer transmission distances.
Figure: Feng Runda Bridge point-to-multipoint transmission topology
If the transmission distance is long or the monitoring points are scattered, the point-to-point transmission mode is better. Because of the small loss in this method, it can ensure long-distance transmission of signals and data.
Second, the establishment of point-to-multipoint transmission should pay attention to what?
1, front camera
When the front-end camera is a network camera, point-to-multipoint transmission can be used. If it is an analog camera, it is only suitable for one-to-one transmission.
In addition, we must also consider the pixel problem of network cameras. The higher the pixel number of the camera is, the larger the code stream is. When multiple transmitters transmit the monitoring data of the camera to the receiver bridge, the data will be very large, the receiver bridge may not be able to bear, and it will result in packet loss, severe delay, etc. phenomenon. So that kind of ultra-high definition camera is definitely not suitable for use in point-to-point transmission.
2, bandwidth issues
When using point-to-multipoint transmission, the pressure at the receiving end is not large, so try to choose a bridge device with a large transmission rate. In other words, a wireless bridge with a large bandwidth is selected, and usually 5.8G devices are used. This not only ensures the smooth transmission of monitoring data, but also makes the monitoring screen smoother.
For the bandwidth problem, consider the pixels of the front-end camera, the required bandwidth, the transmission distance, etc. If the pixels are too high or the transmitted data is too large, high bandwidth will be required. When designing a point-to-multipoint transmission, it is necessary to integrate Taking into account the bandwidth, the number of receiving devices can be increased.
Figure: Fengrunda Partial Bridge Selection Reference
3, transmission distance
In order to ensure good transmission effect, and at the same time, it is beneficial to the angle setting of the transmitting end and the receiving end. Generally, the distance cannot be too far. It is better not to exceed 8 kilometers, and the best effect is within 3 to 5 kilometers. In short, the closer the distance, the better. However, if the transmission distance is less than 1000 meters, omnidirectional reception may be considered.
In addition, if the receiver and the transmitter must be far away from each other due to environmental restrictions, the transmission link must be guaranteed to be on the same line at a minimum. Otherwise, the transmission picture quality cannot be guaranteed.
4, the angle problem
Including two problems: between the transmitting end, between the transmitting end and the receiving end. Generally, the angle between the two transmitting ends should not be too large, preferably around 20°. The angle between the transmitting end and the receiving end can be 60°, 90°, 180°, etc. The specific choice of the angle needs to be determined according to the monitoring point and the distance. The monitoring point is more and the angle will be larger.
5, the proportion should not be too large
Although wireless bridges can perform one-to-many transmission, there are also degrees. At most, they do not exceed one pair of eight. Otherwise, the receiver will not be able to afford so much data, which will compromise the transmission effect. So it's best not to exceed 1:8, with 1:4 being the best.
Third, application examples
If there is a tower crane wireless monitoring project, wireless bridges are used to transmit 1 to 4, and 4 transmitters are respectively connected with 200 W cameras. The distance between each camera is between 200-300 meters, and A is the receiver. After the equipment is installed, it is found that the monitoring screen is stuck. What should I do about this situation?
Analysis and troubleshooting:
There are many reasons why the monitoring screen is stuck, such as insufficient negotiation speed (poor angle), large attachment interference, large code stream, and tower crane movement. 200W camera 4 distance 200-300 meters between, from the figure you can see, the angle is right, looks like no problem.
However, a closer look reveals that the four transmitters have 3 and 4 in the front and 1 and 2 in the back. There is only one receiver A, indicating that the receiver bridge must be aligned with 3 and 4, so there is no way to align it with 1 and 2, and the vertical angle is only 30 degrees. We know that the tower crane will move. When the distance between 1 and 2 is further away from 3 and 4, the signal received by the receiving end will become worse and worse, and the monitoring picture will naturally become stuck.
Solution: increase the receiver
1 and 2 use one receiving end to receive, 3 and 4 use the other receiving end to receive, and the receiving end is placed on the same side at different heights to avoid mutual interference between the bridges.
This article summarizes the considerations of wireless bridges in point-to-multipoint transmission from two aspects: theoretical knowledge and practical application. Fengrunda Wireless Bridge has no cumbersome configuration and is easy to use. It supports master-slave mode (one master or one slave or one master and multiple slaves). It is easy to expand and maintain.