the biggest feature of trunking communication is that PTT(Push To Talk) is adopted for voice communication, which is connected in a push-to-talk way, the called party can answer without going off-hook, and the connection speed is fast, and it can support group calling and other functions. Its operation mode is mainly simplex and half-duplex, and it mainly adopts dynamic channel allocation, and users have different priority levels and special functions, so they can respond to all calls when communicating.
back to its emergence, the concept of cluster really comes from the concept of "relay" in wired telephone communication. In 198, the concept grade of "trunk" curve published by E．C．Mo1ina proved that the probability of several trunk lines of a group of users can greatly improve the utilization rate of trunk lines. The concept of "trunking" is applied to radio communication system, and the channel is regarded as a relay. The concept of "trunking" can also be understood from another angle, that is, compared with electromechanical (vertical and horizontal) switches, the wired relay is regarded as a wireless channel, the switch marker is regarded as the controller of the trunking system, and when the relay is fully utilized, it can be considered as a trunking channel. The cluster system controller can dynamically and automatically optimally allocate the limited channels to all users of the system, which is actually the channel full utilization or the term "channel utilization" that we often use.
development history
cluster
cluster
China began to introduce the simulated cluster system in 1989 and put it into use in 199. With the development of digital communication technology, trunking communication system has also begun to develop to the second generation of digital technology. The most important feature is that TDMA (Time Division Multiple Access) and CDMA (Code Division Multiple Access) communication modes are adopted. However, the application of trunking communication in China mainly stays at the level of analog technology, and the application of digital trunking is less. At the same time, in order to meet their different use requirements, cluster users have adopted the scheme of building cluster communication networks independently, so there are many problems in the interconnection between networks, the use of frequency resources and the overall construction of cluster networks of many enterprises. In addition, by controlling the core technology and setting up intellectual property protection barriers such as patents, foreign communication giants make the internal interfaces basically closed, the technology openness is poor, and the market price of systems and terminal equipment remains high, which also restricts the industrialization process and scale application of digital trunking in China. In view of the "embarrassing" situation of digital trunking industry development in China, the Ministry of Information Industry took the lead in formulating the development plan of China trunking technology, and included digital trunking in the basic telecommunications business category for the first time in the new Regulations on Telecommunications Management, and organized six major domestic telecom operators to carry out 8-megabit digital trunking commercial experiments in China. According to the operators' experiments, China Satcom has carried out commercial experiments of ZTE's GoTa * * network based on CDMA technology in Jinan, Nanjing and Tianjin, and China Tietong has carried out commercial experiments of ZTE's GOTA based on CDMA technology and Huawei's GT8 based on GSM technology in Shenyang, Changchun and Chongqing. Judging from the commercial experiments in recent years, it is not ideal, in terms of operating costs, market demand, operating mode and the success of relevant standards