As early as the 1930s, electrical communication technology began to be applied, and it has been used to meet the internal communications and command and dispatch requirements of government departments, industrial and mining enterprises, energy, public security and other organizations. With the continuous expansion of the scope of application, in order to meet the demand for more personalized and differentiated professional users, radio communication technology has gone through several development processes and expanded more technical means and service types. From the perspective of business requirements, from the development of basic voice intercom communication to voice intercom plus data communication, and then extended to provide multimedia business mode of voice intercom + data communication + video communication; from a technical perspective, from the simulation Talking about the development of digital intercom, in recent years, with the continuous development of LTE and public network technologies, the application of multimedia intercom communication can be realized through LTE private network or 3G/4G public network. In the following, we will conduct a comparative analysis of analog intercom, digital intercom, LTE private network intercom, and public network intercom from business and technical perspectives.

Several kinds of conventional building intercom technology comparison

Analog Intercom System

Analogue intercom system refers to the use of analog modulation technology for walkie-talkie-to-speaker communication systems. It mainly adopts amplitude modulation/frequency modulation to directly transmit analog speech (due to the advantages of transmission performance, the systems still in use are mostly frequency modulation methods. In addition, it is also possible to use DTMF to transmit a very small amount of low-speed data information.

At present, the professional intercom area is still based on analog intercom. However, the analog intercom system has the problems of low frequency resource utilization, poor confidentiality of calls, single service types and other issues that can no longer meet the communication needs of industry customers. Since analog walkie-talkie technology is backward and wastes precious radio frequency resources, it is from a technical perspective. , industry demand, and national policy and other aspects, analog walkie-talkie was eliminated by the digital walkie-talkie is only a matter of time.

In terms of national policy, on December 12, 2009, the Ministry of Industry and Information Technology formally released “No. 666 Document” for digital walkie-talkies, which expressly stipulates the timetable for the transition of digital walkie-talkie manufacturers from analog technology systems to digital technology systems: from 2011 1 The month begins with "analog to digital". After the five-year transition period, the digital walkie-talkie will completely replace the analog walkie-talkie. The Notice on Strengthening the Management of Radio Transmitting Equipment in the 450-470MHz Frequency Band issued by the Ministry of Industry and Information Technology promoted the introduction of unified standards. The "modulus number" is imperative.

Digital Intercom System

Compared with analog intercom systems, digital intercom systems bring many revolutionary changes to professional mobile communications. First, digital technology can make more efficient use of radio spectrum resources. Digital communication systems can carry multiple traffic channels on one channel to accommodate more users. Second, provide integrated voice and data services. Users can get more and more accurate information to provide work efficiency. Compared with analog communication technology, digital communication systems have stronger data processing capabilities, allowing more data to be integrated into a wireless communication device, making the user's application solution more complete. Third, digital communication technology can improve voice quality in a wider range and improve communication quality. Because digital communication technology has an in-system error correction function, it can transmit accurate voice and data over a wider range, reducing speech distortion and Data error rate. The digital system has an excellent ability to suppress environmental noise and can listen to clear speech in a very noisy environment. Fourth, the digital intercom system has features such as high spectral efficiency, clear speech, long battery life, strong communication confidentiality, strong anti-interference ability, and long communication distance. It also has single call, group call, full call, and emergency call. Distant/resurrection and other functions, while the system also supports SMS, GPS and other data transmission value-added features.

LTE private network intercom system

LTE is the next-generation evolution technology of 3G. It is called 3.9G and has 100Mb/s data download capability. It is considered as the mainstream technology that evolves from 3G to 4G. The main performance objectives of the 3GPP-initiated LTE project include: providing a downlink 100Mb/s and uplink 50Mb/s peak rate in a 20MHz spectrum bandwidth; improving the performance of cell-edge users; increasing cell capacity; reducing system delays; The transmission delay is less than 5ms. The migration time of the control plane from the sleep state to the active state is less than 50ms. The migration time from the camping state to the active state is less than 100ms. It supports a 100km radius cell coverage and can provide 350km/h high-speed mobile users. , 100kb / s access services; support for paired or unpaired spectrum, and flexible configuration 1.25MHz to 20MHz bandwidth.

LTE's own technology has the following advantages: First, the spectrum efficiency is relatively high, and currently can reach 5-10bps/Hz; Second, the flexible scheduling capabilities of uplink and downlink can also carry diversified high-bandwidth services to meet the transmission of multimedia services such as video Demand; Third, LTE is an all-IP architecture, it is easy to deploy applications, add new features, low network construction costs, can meet a variety of industry users for wireless communications network Jian Jian network, wide coverage, easy maintenance, high resistance Destruction demand; Fourth, TD-LTE as the international mainstream technology, the future technology evolution is very clear, special network system can evolve with the development of technology; Fifth, the short delay of the call, to meet the professional intercom performance requirements; Is to provide rich multimedia services, in addition to realize the cluster intercom service, but also to achieve video, data, business software features.

3G/4G public network intercom system

The public network intercom service is based on the cluster service platform of 3G/4G mobile public network and uses Push to Talk (PTT) technology to provide customers with mobile communication network coverage through a professional mobile terminal with public network intercom function. Half-duplex cluster communication service within.

The public network intercom has the following advantages: First, the distance is not limited, the mobile phone signal coverage area, free intercom calls; Second, digital signals, sound quality is clear, loud voice; Third, the confidentiality of calls is strong, will not generate frequency The same leads to leakage; Fourth, rich multimedia communication capabilities, can achieve voice, video, data services; Fifth, the construction cost is low, relying on public mobile networks, without the need to deploy base stations; Sixth, can extend the powerful multimedia scheduling capabilities.