Base stations include micro cells and macro cells. A base station (BS), a public mobile communication base station, is a form of radio station. It refers to a radio transceiver station that transmits information to mobile phone terminals through a mobile communication switching center in a limited radio coverage area. The base station is the basic unit that constitutes a cellular cell in mobile communication, and completes the communication and management functions between the mobile communication network and mobile communication users.
1 Glossary
Microcell is a technology developed on the basis of macrocell. Compared with the macro cell, its transmitting power is relatively small, generally around 2W; the coverage radius is about 100m to 1km; the base station antenna is placed in a relatively low place, such as under the roof, 5m to 10m above the ground, wireless beam refraction, The reflection and scattering are in buildings or inside buildings, and are limited to the inside of the street. Micro cells were originally used to increase wireless coverage and eliminate "blind spots" in macro cells. At the same time, because the micro cell base station with low transmit power allows a smaller frequency reuse distance, and the number of channels in each unit area is large, the business density has been greatly increased. It can be placed on the "hot spot" of the macro cell. Meet the requirements of both the quality and capacity of the small area.
In the initial stage of network construction of macro cellular mobile phones, the coverage radius of cellular cells is relatively large, generally about 1 to 2.5 kilometers, and some even reach more than 20 kilometers, so they are called "macro cell" cells.
A repeater (repeater) is a co-frequency amplification device, which refers to a radio transmission relay device that enhances the signal during wireless communication transmission. The basic function of a repeater is a radio frequency signal power booster. In the downlink, the repeater picks up the signal from the existing coverage area of ​​the donor antenna, and isolates the signal outside the band pass through a band-pass filter. The filtered signal is amplified by the power amplifier and transmitted to the waiting area again. Covered area. In the uplink path, the mobile phone signals of the mobile stations in the coverage area are processed by the uplink amplification link and transmitted to the corresponding base station in the same working manner, so as to achieve the signal transmission between the base station and the mobile phone.
Optical fiber connection is required between RRU (remote radio module) and BBU (baseband processing unit). The technical feature of RRU (Radio Remote Unit) is that the base station is divided into two parts: the near-end unit (Radio Server) and the remote unit (RRU). The two parts are connected by optical fiber, and the interface is based on open The CPRI or IR interface can be connected stably with equipment from mainstream manufacturers. BBU (Building Base bandUnite) indoor baseband processing unit
Macro cell
Microcell
Repeater
2 Features of micro cell, base station, macro cell, repeater and BBU+RRU
1) Macro base station, straight point, iron tower station, the bigger one, one station covers dozens of kilometers. The cost and construction period are greater.
2) Micro base stations, small base stations installed in buildings or dense areas, have small coverage and low user volume.
3) The repeater cannot be used alone. It amplifies the base station signal and transmits it to a place that the base station cannot cover.
4) BBU+RRU is a remote radio technology. The 3G network uses a large number of distributed base station architectures. The RRU (remote radio module) and the BBU (baseband processing unit) need to be connected by optical fiber. One BBU can support multiple RRUs.
5) Principle and difference: The base station has its own frequency point, frequency range, number of users, good network, easy to plan, and of course the cost is higher; the repeater borrows the resources of the base station, and its number of users is occupied The base station resources are cheap and easy to cover, but the network is not good and planning is difficult. If the signal leaks into the coverage area of ​​the base station, it will affect it.
3 Features and differences of micro cell, macro cell and repeater
1) Macro cells generally refer to cabinets, a cell configuration can reach 12 carriers, and the transmission power is also relatively large, such as 47db, suitable for wide coverage or normal coverage in urban or suburban areas, and a computer room needs to be established;
2) The size of a micro cell is like a water heater, generally only has 2 carrier configurations, of course, some can be cascaded to increase the configuration of several micro cells, but the power is small, generally 33db, suitable for urban replenishment points, indoor coverage, etc., it is not necessary The machine room can be done by hanging it in a weak current well;
3) As the construction of macro stations in urban areas tends to be saturated, and the development of deeper coverage places more and more demands on micro cells and repeaters;
Micro-cells will occupy a large market position in indoor coverage. At present, there are many and dense high-rise buildings in cities, and they are shielded. Outdoor signals cannot penetrate indoors well. It is necessary to increase coverage in buildings. Now indoor coverage is being built in various parts of the country. It's still relatively large.
The difference between macro cell and micro cell lies in the level of wireless resource (carrier frequency) configuration, the former is greater than the latter.
The base station is a macro cell, and the repeater is used in enterprises, buildings, and shopping malls to receive the wireless signal of the macro cell—amplify—and then cover the building. The micro cell is also used in buildings and shopping malls.
The difference between a repeater and a micro cell is that the signal source of the former is in a remote base station, which is responsible for receiving and amplifying, and it does not increase capacity. The latter is a signal source itself, increasing capacity.
4 Capacity and coverage of micro cell, macro cell and repeater
The propagation loss of 1800 is 6DB more than that of 900 in free space, and the diffraction ability is poor, but the difference between the building penetration loss is not big, and 1800 is slightly better. Therefore, for the macro station, the dual-frequency network is usually 900 to ensure coverage, and 1800 to absorb traffic.
The traditional cellular network is composed of macrocells, and the coverage radius of each cell is mostly 1km to 25km, and the base station antenna is made as high as possible. In the actual macrocell, there are usually two special tiny areas. The first is "blind spots", which are shadowed areas caused by obstacles during the propagation of radio waves, and the communication quality in this area is severely inferior; the second is "hot spots", busy areas formed by the uneven distribution of space business loads. It supports most of the services in macrocell. The solution to the above two "points" problems often relies on methods such as setting up repeaters and splitting communities. In addition to economic reasons, in principle, these two methods cannot be used indefinitely, because the expansion of the system coverage will reduce the communication quality; to improve the communication quality, the capacity is often sacrificed. In recent years, with the sharp increase in business requirements, these methods have become more prestigious, and this has led to micro-cellular technology.
——The coverage radius of the microcell is 30m～300m, the base station antenna is lower than the roof height, and the propagation is mainly along the line of sight of the street, and the signal leakage on the roof is small. Therefore, microcell was initially used to increase radio coverage and eliminate "blind spots" in macrocell. Since the microcell base station with low transmit power allows a small frequency reuse distance, and the number of channels in each unit area is large, the service density has been greatly increased, and the RF interference is very low, so it is placed in the "hot spot" of the macrocell. It can meet the requirements of both quality and capacity of this small area.
——In fact, microcells are mainly placed in "hot spots" within macrocells. Cells of different sizes overlap, and base stations with different transmission powers are in close proximity and exist simultaneously, which makes the entire communication network present a multi-layered structure. The switching of adjacent microcells all return to the macrocell where they are located. The wide-area high-power coverage of the macrocell can be regarded as the upper layer network of the macrocell and serves as a "safety net" for mobile users when moving between the two microcells. A large number of microcells It constitutes a micro-cellular lower-layer network. With the further growth of capacity requirements, operators can install the third or fourth microcell layer according to the same rule. A multi-layered network is often a multi-element cellular system composed of an upper-layer macrocellular network and several lower-layer microcellular networks.
——Intelligent cell refers to the cell where the base station adopts an adaptive antenna system with high resolution array signal processing capability, intelligently monitors the location of the mobile station, and transmits the determined signal power to the mobile station in a certain way. For the uplink, the adaptive antenna array receiving technology can greatly reduce multiple access interference and increase the system capacity; for the downlink, the effective area of ​​the signal can be controlled within a radius of 100～100 near the mobile station. Within the range of 200 wavelengths, the co-channel interference is reduced. The intelligent cell can be either a macrocell or a microcell. Using the concept of smart cells for network design can significantly increase system capacity and improve system performance.
Indoor distribution: It is a distributed system covering indoors, which should include signal sources and antenna feed systems; signal sources include macro stations, microcellular repeaters, etc.
Macro cell: Macro station, which is generally referred to as a base station, has the largest capacity
Micro cell: Compared with macro cell, the capacity and coverage are smaller
Repeater: It is essentially an amplifier and does not have the function of a base station. It only amplifies the signal of the base station cell, which is an extension of the base station signal. The capacity depends on the donor cell.
Micro cell cannot be expanded (2 carrier frequency), macro cell can be expanded as needed
The signal source of the indoor distribution system has the following access methods:
(1) The macro cell is used as the source to access the signal distribution system;
(2) Microcell is used as a source to access the signal distribution system;
(3) The repeater is used as a signal source to connect to the signal distribution system.
5 Micro base stations, micro cells, and fiber optic repeaters in indoor distribution, what are the similarities and differences, what do they mean~!
The so-called micro base station should refer to the indoor station. Some indoor base stations directly couple signals from the macro station, while others directly add the base station in the computer room for indoor distribution. The micro cell can be compared with the macro cell. The function is similar to that of a macro station, except that its power is small, and the coverage range is small. The coverage distance is between 100m-1Km. It can increase the system capacity. Generally, it is used in conjunction with a macro base station and installed in a place with dense traffic to increase the system. Capacity and quality are targeted at user density. For example, Beiguo Mall and Beiguo Xiantianxia, ​​because of the large number of users, the traffic intensive is the problem of installing micro-cells to solve the problem, while for repeaters, it can be understood as signal Repeater, the first thing that needs to be explained is that the repeater can pull the signal of the macro or micro cell to the weak coverage area, increasing the utilization rate of the base station signal, but it cannot increase the system capacity, so the repeater cannot be used in places with dense traffic. There are many repeaters, such as co-frequency repeaters and frequency shift repeaters, and optical fiber repeaters are produced with the maturity of optical fiber technology! The optical fiber repeater is composed of a near end and a far end. The near end is generally installed in the computer room, while the remote end is installed in the area that needs to be covered according to the design needs. The advantages of using an optical fiber repeater are that the transmission distance is large but the loss is small. The loss is much smaller than using the same frequency repeater and feeder! Moreover, the optical fiber repeater can adopt a one-to-many method, and the installation is flexible, and other active components are not allowed, so the interference to the system is much smaller. But it works well.
There are many types of indoor distribution systems:
1) Direct coverage of micro cells
2) Micro cell + dry release coverage method
3) Micro cell + fiber optic repeater coverage method
4) Direct coverage of macro base station
5) Macro base station + dry amplifier direct coverage
6) Macro base station + fiber optic repeater coverage method
The function of the coupler and the combiner is exactly the opposite. The coupler is used at the receiving end, and the combiner is used at the transmitting end. The coupler divides the received wireless signal into several channels to different receivers, and the combiner combines several channels of radio frequency signals from different transmitters into one channel and sends them to the antenna for transmission.
The coupler and the base station combiner are different. The coupler requires unequal distribution of the input signal, and the output end includes a coupling end and a through end. There is only one input terminal and two output terminals.
The base station combiner combines the two input signals of the base station into one, or mixes the two signals and outputs two channels. What is needed is high power and low insertion loss. There are two input ports, and there can be one or two output ports.
The bridge is a same-frequency combining device, and the realization principle of the coupler is also different.
The difference between power splitter and combiner:
(1) The difference between power splitter and combiner
1. The power divider is a device that realizes signal distribution.
2. The combiner combines signals of the same frequency band and different frequency bands.
3. There is no problem in using the combiner as a power splitter
4. When using the power splitter as a combiner, please note that the input signal requirements are equal amplitude.
5. But pay attention to the power capacity and frequency range when using both.
(2) The difference between the principle of power splitter and combiner
In my opinion, duplexers and combiners are different. Duplexers are generally used at the output and input of equipment to isolate signals of different frequency bands. For example: the uplink and downlink signals of mobile communications. Combiners are generally used in power synthesis in hardware circuits. For example: To get a 40dbm signal, you can combine two power amplifiers with an output power of 20dbm. Their internal structural principles should also be different. The inside of the duplexer should be a filter cavity (large duplexer), and the inside of the combiner should be a coupling circuit.
(3) The difference between power divider and combiner
The term "combiner" has been used in two places. It is necessary to distinguish one from being an inter-frequency combiner, also called an antenna duplexer. In simple terms, several filters share one port to save the number of antennas. On another occasion, it is also called a combiner. I would like to call it a power combiner. Turning the power divider upside down is a power combiner, right?
Euroblock, short for "European-style terminal block"; is a combination of a low-voltage disconnect (or pluggable) connector and terminal block commonly used for microphones and line-level audio signals , and for control signals such as RS-232 or RS-485. It is also known as the Phoenix connector and comes from a German Phoenix Electric Company, which was established in 1981 in Harrisburg, Pennsylvania, USA. Also known as "Plug-in Terminal Blocks" or "Two-Piece Terminal Blocks".
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