Base Station

A base station is a public mobile communication base station, which is a form of radio station. It refers to a radio transceiver station that transmits information with mobile phone terminals through a mobile communication switching center in a certain radio coverage area. Its types can be divided into the following categories: Macro base stations, distributed base stations, SDR base stations, repeaters, etc.

Macro base station

Macro base stations refer to the wireless signal-transmitting base stations of communication operators. Macro base stations cover a long distance, generally 35 km. They are suitable for areas with scattered traffic in suburbs. They have omnidirectional coverage and high power. Micro base stations are mostly used in cities, covering distance is small, usually 1-2km, with directional coverage. Microbase stations are mostly used for blind coverage in urban hot spots. Generally, the transmit power is very small, and the coverage distance is 500m or less. The equipment power of macro base stations is generally 4-10W, which is converted into a wireless signal ratio of 36-40dBm. Adding the gain of 20dBi of the base station coverage antenna is 56-60dBm.

Distributed Base Station

Distributed base stations are a new generation of modern products used to complete network coverage. Its main feature is to separate the radio frequency processing unit from the traditional macro base station baseband processing unit and connect it through optical fiber. The core concept of the distributed base station structure is to separate the traditional macro base station baseband processing unit (BBU) and radio frequency processing unit (RRU). The two are connected via optical fiber. During network deployment, the baseband processing unit, core network, and wireless network control equipment are concentrated in the computer room and connected to the radio frequency remote unit deployed at the planned site through optical fiber to complete network coverage, thus reducing construction and maintenance costs and improving efficiency.

The distributed base station divides the traditional macro base station equipment into two functional modules according to functions. The baseband, main control, transmission, clock, and other functions of the base station are integrated into a module called the baseband unit BBU (Base Band Unit). The unit is small in size and the installation location is very flexible; the mid-range radio frequency such as a transceiver and power amplifier is integrated into another called remote radio frequency module, and the radio frequency unit RRU (Remote Radio Unit) is installed at the antenna end. The radio frequency unit and the baseband unit are connected through optical fibers to form a new distributed base station solution.

SDR Base Station

SDR (Software Definition Radio) is "software defined radio", which is a wireless broadcast communication technology, more precisely, it is a design method or design concept. Specifically, SDR refers to a wireless communication protocol based on software definition rather than dedicated hardware implementation. There are currently three mainstream SDR hardware platform structures: GPP-based SDR structure, Field Programmable Gate Array (FPGA)-based SDR (Non-GPP) structure, and GPP + FPGA/SDP-based hybrid SDR structure. The SDR structure based on GPP is as follows.

The SDR base station is a base station system designed and developed based on the SDR concept. Its biggest feature is that its radio frequency unit can be programmed and redefined, and can realize intelligent allocation of spectrum and support for multiple network modes, that is, it can be used on the same platform equipment. Technologies to implement different network models, as shown in the figure below, the GSM+LTE network is implemented on the same set of equipment.

RP repeater

RP repeater: The RP repeater is composed of components or modules such as antennas, RF duplexers, low-noise amplifiers, mixers, ESC attenuators, filters, power amplifiers, etc., including uplink and downlink amplification links.

The basic principle of its work is: to use the forward antenna (donor antenna) to receive the downlink signal of the base station into the repeater, amplify the useful signal through the low-noise amplifier, suppress the noise signal in the signal, and improve the signal-to-noise ratio (S/N). ); then it is down-converted to an intermediate frequency signal, filtered by a filter, amplified by the intermediate frequency, and then up-converted to radio frequency, amplified by a power amplifier, and transmitted to the mobile station by the backward antenna (retransmission antenna); at the same time, the backward antenna is used The uplink signal from the mobile station is received and processed by the uplink amplification link along the opposite path: that is, it passes through the low-noise amplifier, down-converter, filter, intermediate amplifier, up-converter, and power amplifier before being transmitted to the base station. This achieves two-way communication between the base station and the mobile station.

An RP repeater is a wireless signal relay product. The main indicators to measure the quality of a repeater include the degree of intelligence (such as remote monitoring, etc.), low IP3 (less than -36dBm without authorization), low noise factor (NF), overall machine reliability, good technical services, etc.

RP repeater is a device that connects network lines and is often used for bidirectional forwarding of physical signals between two network nodes.

Repeater

The repeater is the simplest network interconnection device. It mainly completes the functions of the physical layer. It is responsible for transmitting information bit by bit on the physical layer of two nodes and completing the signal copy, adjustment, and amplification functions to extend the length of the network.

Due to loss, the signal power transmitted on the line will gradually attenuate. When the attenuation reaches a certain level, it will cause signal distortion, thus leading to reception errors. Repeaters are designed to solve this problem. It completes the connection of physical lines, amplifies the attenuated signal, and keeps it the same as the original data.

Compared with base stations, it has the advantages of a simple structure, less investment, and convenient installation. It can be widely used in blind areas and weak areas that are difficult to cover, such as shopping malls, hotels, airports, docks, stations, stadiums, entertainment halls, subways, tunnels, etc. It can be used in various places such as highways and islands to improve communication quality and solve problems such as dropped calls.

The composition of mobile communication repeaters varies depending on the type.

(1) wireless repeater

The downlink signal is received from the base station and amplified to cover the direction of the user; the uplink signal is received from the user and sent to the base station after amplification. To limit the band, a band-pass filter is added.

(2) Frequency Selective Repeater

To select the frequency, the uplink and downlink frequencies are down-converted to the intermediate frequency. After the frequency selection and band-limiting process is performed, the up-link and downlink frequencies are restored by up-conversion.

(3) Optical fiber transmission repeater station

The received signal is converted into an optical signal through photoelectric conversion, and after transmission, the electrical signal is restored through electro-optical conversion and then sent out.

 (4) frequency shift transmission repeater

Upconvert the received frequency to microwave, then downconvert it to the originally received frequency after transmission, amplify it, and send it out.

 (5) Indoor repeater

The indoor repeater is a simple device, and its requirements are different from those of the outdoor repeater. The composition of mobile communication repeaters varies depending on the type.

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