Views: 40 Author: Site Editor Publish Time: 2020-07-01 Origin: Site
Conventional co-channel simulcast system is to set up multiple relay stations in a region, so that each relay station forms a link interconnection and keeps working at the same frequency, thereby achieving effective coverage of wireless signals in a region and ensuring that the radio terminal is in the network can communicate smoothly anywhere. At present, the development of co-channel simulcast technology can solve the problem of communication blind spots and dead spots caused by co-channel interference in wireless communication, and further achieve seamless coverage of signals and expansion of communication range.
The principle of co-channel simulcast is to deploy multiple co-channel repeaters in the same area, thereby increasing the coverage of the wireless communication network and improving the reliability and security of intra-network communication. However, in practical applications, there are strict technical requirements for establishing a co-channel simulcast system. The traditional method is to use multiple ordinary relay stations to establish a communication network. Because of the lack of simulcast technology, the cross-coverage area of the two differential machines has serious co-frequency interference, which greatly affects the co-frequency difference of the private network and communication quality.
In developed countries, the links of the same-frequency simulcast system are mostly wired or multi-frequency wireless. Among them, the system control equipment and simulcast repeater equipment are expensive, and it is difficult to achieve large-scale promotion around the world.
The existing co-channel simulcast system starts from the root cause of co-frequency interference and uses the existing analog channel as a link, thereby saving the cost of the system and making it possible to promote and use the simulcast system. In addition, the system introduces satellite control technology, absolute time technology and voice delay synchronization technology, and establishes a unique signaling control system, which can judge the signals from different simulcast base stations, completely eliminating the root cause Co-channel interference, and realize the intelligent monitoring of the system, fully meet the requirements of simulcast technology from the performance.
1. Introduce satellite control technology and absolute time technology, use GPS clock signal to accurately lock the carrier frequency, and the frequency difference of the transmitted carrier of each simulcast station is less than 10Hz, which fully meets the simulcast technical requirements.
2. The channel machines used have undergone rigorous screening and precise debugging to ensure good consistency of the audio frequency-frequency characteristics, and the audio signal amplitude characteristics added to the modulation end of the transmitter are within 1dB.
3. Introduce voice delay technology to ensure that the control system has enough time to judge each call.
4. The unique signaling control system can select, control and manage multiple simulcast base stations.
5. The system structure is simple, the network is flexible and convenient, and the reliability is high. It can form a large-area co-frequency coverage network with less occupied frequency, low cost, and higher cost performance.
The selection of the base station of the same frequency simulcast system should be based on meeting the basic communication needs of the interphone. Regardless of which networking method is used, the selection of base stations should follow the basic requirements of reasonable layout and mature base station installation conditions to meet the daily management and maintenance of staff.
The biggest advantage of the conventional co-channel simulcast network for wireless links is that the choice of base station is not restricted by the condition of setting up restricted links and has higher flexibility. However, it should be noted that a reliable communication connection must be established between each simulcast base station and the central link relay, and the link frequency must not be interfered.
In the application process, when the wireless link method is adopted, a dedicated link radio station is required. The start-up time of the dedicated link radio station is short, which can be controlled within 10ms, thereby making the system delay shorter, reducing the inconvenience caused by the long delay during use, and ensuring the stability and reliability of the system link.
When using a wireless link co-frequency simulcast system, you need to ensure that the link frequency is not disturbed. Once the link frequency is interfered, it will cause the entire system's call to be seriously affected, or even paralyzed. In order to solve the interference problem, we provide two link methods for your reference:
The first is to add digital signaling to the link signal. If there is no established digital signaling in the link signal received by the simulcast controller, it is regarded as an interference signal in the link and the system will not forward it.
The second is to automatically change the link frequency. When the system detects that the link of a certain simulcast base station is interfered, it will issue an instruction to change the link frequency of all simulcast base stations in the system to the alternate link frequency at the same time until the link no longer has interference.