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Repeater basics | Repeater types in WiFi, LTE, Satellite, Optical, Microwave

This page describes repeater basics and repeater types. It explains functions of WiFi repeater, Microwave repeater, Satellite repeater, LTE repeater and Optical repeater. It mentions difference between repeater and amplifier. It mentions advantages and disadvantages of repeater.

Introduction:
As we know there is a limit for any communication system to transmit the information. The coverage distance depends on modules used at the transmitter side viz. modulation scheme, amplifier, data format of the signal etc. In order to increase the communication distance of the system repeaters are used.

What is repeater?

• Repeater is a device which receives the signal and retransmits the signal after amplification. It may or may not does frequency conversion before retransmission depending upon applications of use.
• It usually consists of receiver, amplifier, frequency converter and transmitter.
• In some systems, repeater also does baud rate conversion before retransmission.
• Repeater is used for wired medium (e.g. telephone line repeater, fiber optical cable repeater etc.) as well as wireless medium (e.g. satellite repeater, microwave repeater, wifi repeater, LTE repeater etc.).

Repeater types | WiFi, Microwave, Satellite, LTE and Optical

Following are the two main repeater types based on data type it can handle.
Analog Repeater: It can amplify the analog signal in order to boost its amplitude. Usually trunking system employs FDM type of multiplexer which uses multiple analog signals in the form of current or voltage whose amplitude gets attenuated over transmission medium. The analog repeater is used here. It cosists of linear amplifier and filters.
Digital Repeater or Digipeater: It can amplify the digital signal to compensate for losses over medium. Digital signal can be in any binary formats such as NRZ, RZ etc. It is also known by name "Digipeater". This digipeater helps in pulse re-shaping, demodulation, decoding and re-synchronization at the receiver end.

Let us understand repeater types based on technologies it can serve viz. telephone line, fiber optic, microwave link, satellite link, wlan network, lte network and so on.

Microwave Repeater

Microwave Repeater

In microwave link, repeater is employed between transmitting station and receiving station. Depending upon distance between them, there may be one or multiple repeater stations in between. This type of repeaters use sensitive receivers, high power transmitters and high mounted antennas.

They are very effective to increase the communication range of microwave link. In microwave relay stations, one repeater pickes the signal at one frequency, amplifies it and retransmits it on another frequency to the next repeater in the chain. The next repeater does the same task. This way string of repeater stations relay signals to greater distances. The distance between two repeater stations is usually 20 to 60 miles. The antennas are mounted at very high altitudes. Refer Microwave Repeater >>.

Satellite Repeater

As we know communication satellites are located at about 36000 Km (i.e. 22369 miles) above the ground. Hence repeaters used in the satellite cover greater distances. Satellite repeater receives the uplink signal from the ground, amplifies it and does frequency conversion to appropriate downlink frequency before retransmission to the earth.

The receiver, amplifier and transmitter functionalities of the repeater is known as transponder in satellite domain. For C band satellite, it receives at 6GHz frequency and transmits at 4 GHz frequency using down conversion with suitable LO (Local Oscillator). Refer difference between Repeater vs Transponder >> for more information.

WiFi Repeater | WLAN Repeater

WiFi Repeater is based on IEEE 802.11 a/b/g/n standard. It extends the coverage range supported by a wifi router to larger region usually between two rooms. WiFI repeater operates either in 2.4 GHz or 5 GHz band as supported by WLAN standard. 2.4 GHz supports 14 frequency channels spaced at 5MHz apart.

Wifi router operating at 2.4 GHz receives signal at one channel frequency (say 2412 MHz) and transmits it on another channel frequency (say 2422 MHz) after necessary amplification as per designed specification.
Refer WiFi Repeater >> and difference between WiFi Booster vs WiFi Repeater >> for more information.

LTE Repeater

LTE Repeater

As shown in the figure, LTE repeater receives the signal from LTE eNB (e.g. base station) and re-transmits it after amplification towards UEs. As it amplifies noise along with the signal, SNR degrades. As a result, LTE relay is used which has FEC (Forward Error Correction) functionalities in addition to amplification. Hence SNR is maintained. Refer difference between LTE Repeater vs LTE Relay >>.

Optical Repeater

It is used in fiber optic communication system. It receives the optical signal in electric form. It performs reshaping and amplification operations before retransmission. Due to signal reconstruction before amplification, signal is less distorted. Refer difference between Optical Repeater Vs Optical Amplifier >>.

Difference between Repeater and Amplifier

Optical Repeater vs Optical Amplifier

Let us understand difference between repeater and amplifier.
Amplifier: It amplifies the input signal to boost its amplitude on the same frequency. It does not involve any frequency conversion.
Repeater: It amplifies the input signal as well as does frequency conversion before retransmission. This means repeater consists of amplifier and frequency converter.
➤Also refer difference between Transparent repeater vs Regenerative Repeater >> for more information.

Advantages of Repeater | Disadvantages of repeater

Following are the advantages of repeater.
➤It extends the distance typically covered by wired or wireless medium.
➤It does not affect the performance of the network by suitably performing its task on the signal.
➤Repeaters are available which can use different mediums for reception and transmission.
➤It does not increase or decrease the network traffic.

Following are the disadvantages of repeater.
➤It is not possible to connect different network architectures using repeater. For this router or gateway is needed.
➤The number of repeaters to be used are limited between two ends. More repeaters create noise on the wire which results into packet collisions or problems in the packet detection (at the receiver).
➤Repeaters do not perform segmentation of the network.
➤Repeaters do not perform filtering of the data.

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