Principle and application scheme of digital multi-point distribution system

Digital Multipoint Distribution System

　　1. Introduction to Digital Multipoint Distribution System

　　The digital multi-point distribution system combines the technical characteristics of 2G, 3G and WLAN networks to maximize the access of multiple network systems. At the same time, it uses optical fiber or Category 5 cables as the channel transmission medium for wireless signal distribution transmission. The entire system is implemented by a multi-mode source access unit (MSA), an extension unit (EU) and a remote unit (RU). The digital multi-point distribution system can effectively solve the problems of signal interference and large transmission loss, support the needs of mobile communication networks with multi-standard and multi-service access, and reduce the cost and complexity of the system, facilitating subsequent system maintenance.

　　EU is optional in the digital multi-point distribution system. When there is no EU, MSA can be directly connected to RU. Its operating principle is: in the downlink signal link, MSA is the access unit, which mainly processes the RF signal from the base station digitally, converts it into an optical signal, and then transmits it to EU and then to RU through optical cable/category 5 line. The RU unit restores the signal to RF signal, amplifies it, and outputs it to the coverage area; in the uplink signal link, RU digitally processes the RF signal from the user in the coverage area, converts it into an optical signal, and then transmits it to EU and then to MSA through category 5 line/optical cable. The MSA unit restores the signal to RF signal, amplifies it, and then sends it back to the base station. Its operating principle is shown in the figure below:

　　Working principle diagram of digital multi-point distribution system

　　The digital multi-point distribution system can not only provide transmission and coverage services for mobile communication networks such as 2G and 3G, but also realize the transmission and coverage of WLAN, meeting the operators' high-speed wireless data transmission needs.

　　2. Application scenarios and solutions of digital multi-point distribution system

　　Compared with the traditional coaxial cable indoor distribution coverage system, the digital multi-point distribution system has incomparable advantages. Its application scenarios include residential areas, office buildings, urban villages, hospitals, airports, stations, schools, stadiums and other areas.

　　(1) Cell coverage solution

　　Demand characteristics: The buildings in the community are relatively scattered, the network coverage environment is complex, the signal amplitude fluctuates greatly, and the owners have high requirements for the aesthetics of the environment.

　　The solution of using digital multi-point distribution system: select the central building of the community, and centrally set up the signal source base station and access unit in the central building, which can avoid the construction of multiple machine rooms and waste of construction investment. Place the remote units in different buildings and connect them to the access units using optical fiber or Category 5 cables. Optical fiber can avoid mutual interference with other signals. The remote units use CATV thin coaxial cables to connect the antennas nearby. The access units can be dynamically adjusted, the signal strength of the community antennas can be easily adjusted, the network management monitoring capabilities are accurate, and network resources can be used flexibly and effectively. The digital multi-point distribution system has compact equipment, thin and soft cables, and is easy to lay, which is easy to beautify the environment and meet the requirements of the owners.

　　(2) Elevator coverage solution

　　Demand characteristics: The signal changes as the elevator moves up and down, and the signal strength requirement is high.

　　Solution of digital multi-point distribution system: The equipment of digital multi-point distribution system is relatively small. The remote unit is placed on the top of the elevator car to ensure uniform signal coverage in the car and does not change with the movement of the elevator up and down. It is connected to the access unit with a relatively soft cable. The cable is bundled with the elevator cable and can move at the same time as the car.

　　(3) Venue coverage solution

　　Demand characteristics: The signal coverage area of ​​general venues is large, the capacity requirements during busy and off-peak hours vary greatly, the peak capacity requirements are large, different standard signals are required to be covered together, and the subsequent maintenance is relatively strict.

　　Solution of using digital multi-point distribution system: According to the needs and characteristics of the venue, choose a machine room to centrally place the signal source base station and access unit, which can save the number of machine rooms and reduce investment. Use optical fiber to connect the relay unit and the remote unit placed in each coverage area. Optical fiber transmission can avoid mutual interference of signal transmission. Through the regulation of the access unit in the machine room, the capacity adjustment within the coverage area can be achieved. The digital multi-point distribution system has a simple system design, convenient installation, perfect network management and monitoring system, and has little impact on the aesthetics of the environment.

　　(4) Hospital coverage solution

　　Demand characteristics: Hospital buildings are scattered, and because the hospital's operating rooms, electronic medical equipment, etc. have high requirements for electromagnetic radiation interference, special consideration needs to be given to solving the problem of electromagnetic radiation interference.

　　The solution of the digital multi-point distribution system is: select a relatively central building in the hospital, centrally set up the signal source base station and access unit in the building, set up a low-power signal source, use optical fiber transmission to connect the remote units placed in other buildings, and use CATV thin coaxial cables to connect the remote units to the distribution coverage antennas nearby. The antennas are arranged according to the principle of multiple antennas and low power, so that the user end can reduce the transmission power and electromagnetic radiation. For areas such as operating rooms that have strict requirements on the electromagnetic environment, remote units are set up independently. In special circumstances such as during surgery, the monitoring system of the digital multi-point distribution system is used to adjust the signal strength or turn off the signal coverage. The digital multi-point distribution system is easy to install, easy to set up, easy to wire, and has little interference with the hospital's electromagnetic environment.

　　(5) Network upgrade and transformation solutions

　　Demand characteristics: Since 3G signals operate at a higher frequency band, the upgrade from 2G to 3G systems requires minimal impact on the original network, and the problem of differences in transmission loss of different network signal distribution coverage and power matching of the outputs of different network signal source base stations must be solved.

　　Solution idea of ​​using digital multi-point distribution system: Using digital multi-point distribution system only builds a new source transmission trunk route, which has low requirements for the source (power source input) and is easy to achieve power matching of the source; digital multi-point distribution system has parallel multi-channel low-power output, and it is also very easy to find the power matching point with the original network distribution coverage system at different floors. At this power matching point, simply using the combination can realize the network transformation. The digital multi-point distribution system is simple in design, fast and convenient to install, easy and beautiful in wiring; the system is easy to open and debug.