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  • What Equipment Does The Communication Base Station Consist Of? What Is The Relationship Between Them?
    May 19, 2018

    The base station subsystem mainly includes two kinds of equipment: base station transceiver (BTS) and base station controller (BSC).

    Base station transceiver

    A tall antenna is often seen on the roof, which is part of the base station transceiver. A complete base station transceiver includes wireless transmitting / receiving equipment, antenna and special signal processing part of all wireless interfaces. The base station transceiver can be regarded as a wireless modem, which is responsible for receiving and sending mobile signals. In a certain area, in a certain area, a number of sub stations and transceiver stations form a honeycomb network. By controlling the transmission and reception of signals between the transceiver and the transceiver to achieve the transmission of mobile communication signals, the area within this range is the network coverage we often say. If there is no transceiver, it will not be possible to complete the transmission and reception of mobile phone signals. The area where the base station transceiver can not be covered is also the blind area of the mobile phone signal. Therefore, the range of transmitting and receiving signals of the base station directly relates to the quality of the network signal and whether the mobile phone can operate normally in this area.

    Under the control of the base station controller, the base station transceiver completes the control of the base station and the conversion between the wireless channel, and realizes the radio transmission between the mobile communication signal and the mobile platform through the air wireless transmission and the related control functions. The transceiver can decode and send each user's wireless signal.

    The antenna used in the base station is divided into the transmitting antenna and the receiving antenna, and there are omnidirectional and directional points. In general, there are three modes of configuration: full direction and full direction; the direction of direction and orientation. From the literal, we can understand the difference in each way, the full direction is mainly responsible for the full range of signal transmission; the receiving full direction is a receiving signal of the azimuth; the orientation means to send and receive only to a fixed angle. Generally, the base station with few channels, such as in the suburbs, often uses full direction and full direction, while the number of base stations with more channels use full direction and direction, and the establishment of base stations is more dense than in the suburbs.

    Since the signal is transmitted to the base station may be relatively weak, and there is a certain degree of signal interference, the preselected device is necessary.

    Modules are filtered and amplified for dual frequency conversion, amplification and frequency discrimination. The input high frequency signal is sent to the first frequency converter after amplification. The frequency of the first oscillating signal provided by the frequency converter is 766.9125-791.8875MHz, and the first intermediate frequency signal of 123.1MHz is produced after the down conversion. After the first intermediate frequency signal is amplified, filtered and mixed, a second intermediate frequency signal (21.3875MHz) is generated. After amplification and filtering, the first intermediate frequency signal is sent to the intermediate frequency integrated block. The audio output signal and the reception signal intensity indication signal (RSSI) produced by the intermediate frequency integrated block (including the second intermediate frequency signal amplifier, the limiter and the frequency discriminator) are sent to the audio / control board. In the audio signal control board, the odd number and the even number of signals are continuously compared by the diversity switch, and the stronger signals are selected and the audio signals are selected through the audio signal. The circuit is sent to the mobile control center.

    The working principle of the base station transmitter is that the carrier frequency signal provided by the frequency synthesizer and the modulated signal of the 766.9125-791.8875MHz and the 168.1MHz's modulated signal are filtered into the dual balanced frequency converter and the RF signal with a frequency of 935.0125-959.9875MHz is obtained. The RF signal is then filtered and amplified into the driving stage, and the driver is driven. The output power of the class is about 2.4W, and then added to the power amplifier module. The power control circuit adopts negative feedback technology to automatically adjust the output power of the front drive stage or the driving stage to maintain the output power of the driving stage on the rated value. That is, the received signal is stable and then sent out, which can effectively reduce or avoid the loss of the communication signal in the wireless transmission, and ensure the quality of the communication of the user. The function of the power amplifier module is to enlarge the signal to 10W, but it depends on the actual situation. If the radius of the signal is larger, the amplifier module of 25W or 40W can be used to enhance the transmission radius of the signal.

    Base station controller

    The base station controller includes wireless transceiver, antenna and related signal processing circuit. It is the control part of the base station subsystem. It mainly consists of four components: cell controller (CSC), voice channel controller (VCC), signaling channel controller (SCC) and multiplex terminal interface (EMPI) for expansion. A base station controller usually controls several base station transceivers, through the remote commands of the transceiver and mobile station, and the base station controller is responsible for all the management of the mobile communication interface, mainly the distribution, release and management of the wireless channel. When you use a mobile phone, it is responsible for opening a signal channel for you. When it ends, it closes the channel and leaves it to others. In addition, the handoff of mobile stations in the control area is also controlled. The controller is responsible for switching between the other base stations and maintaining a connection with the mobile switching center, if you use a mobile phone to send the signal to another base station.

    When the GSM system is over the area, the switching mode is used, that is, when the user reaches the cell boundary, the cell phone will cut off the original base station first and then establish contact with the base station of the new service area. When the new service area is busy, the call channel can not be provided, then the line phenomenon will occur. Therefore, users should avoid using the blind area at four corners to reduce the probability of dropped calls when using mobile phone calls.

    The core of the controller is switched network and public processor (CPR). The public processor controls and controls the internal modules of the controller, and is connected with the operation maintenance center (OMC) through the X.25 communication protocol. The switching network will complete the internal exchange of 64kbit/s data / voice traffic channels between interfaces and interfaces. The controller is connected to the mobile switching center through the interface device digital repeater (DTC), and is connected to the transceiver through the interface device terminal controller (TCU) to form a simple communication network.

    In the entire cellular mobile communication system, the base station subsystem is a bridge between mobile station and mobile center, and its status is extremely important. The number of base stations in the entire coverage area, the location of the base station in the cellular cell, the performance of the related components in the base station subsystem and other factors determine the communication quality of the whole cellular system. The selection and construction of base stations has become an important part of the modern mobile communication network.