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Fiber-To-The-Antenna (FTTA)

(San Francisco, California, U.S.A. - Jeffrey M. Wang)


Fiber-to-the-Antenna (FTTA) is a broadband network architecture in which optical fiber is used to connect the remote radio head (RRH) to the base station in new antennas, or retrofitted in existing ones, to replace all or part of the coax local loop. One advantage of fiber-optic cable is that it is easier to install because it is lighter than coax cable. 

Signal integrity and increased energy efficiency are also driving FTTA deployment. Coaxial cables add noise and degrade signal quality, thus requiring tower amplifiers. By placing the RRH at the top of the antenna and generating signals from there, short coaxial jumpers can be used, thus eliminating tower amplifiers. As for power consumption, unlike traditional base stations where power amplifiers must be cooled using air conditioning, RRHs located at the top of a tower can simply take advantage of ambient cooling. 

Another advantage of optical fiber is that baseband units (BBU) no longer have to be stuck to the RRH. The BBUs can be moved to wherever it is most convenient. 

Most importantly, FTTA is required to support low-latency, high-speed backhaul and increase traffic bandwidth.


- Remote Radio Head

A Remote Radio Head (RRH) or Remote radio unit (RRU) is the RF circuitry of a base station enclosed in a small outdoor module. The RRH performs all RF functionality like transmit and receive functions, filtering, and amplification. It also contains analog-to-digital or digital-to-analog converters and up/down converters. An RRH can also provide advanced monitoring and control features that allow operators to optimize performance from a remote, centralized location. 

The RRH is usually mounted near the antenna to reduce transmission line losses and is connected to the main, digital portion of the base station (BBU) with an optical fiber.


[Wireless Fronthaul - The Fiber Optic Association (FOA)]

- Cell Site

A cell site, cell tower, or cellular base station is a cellular-enabled mobile device site where antennas and electronic communications equipment are placed—typically on a radio mast, tower, or other raised structure—to create a cell (or adjacent cells) in a cellular network. The raised structure typically supports antenna and one or more sets of transmitter/receivers transceivers, digital signal processors, control electronics, a GPS receiver for timing (for CDMA2000/IS-95 or GSM systems), primary and backup electrical power sources, and sheltering.


- Distributed Antenna Systems

An outdoor distributed antenna system (DAS) is a network of spatially separated antenna nodes connected to a central office via a transport medium that provides wireless service within a geographic area. By splitting the transmitted power among several antennas, the coverage remains the same, but it requires less power and is more reliable. Essentially, penetration and shadowing losses can be overcome with less power, and a line-of-sight channel is present more frequently, thus reducing fade depths and delay spread. 

An indoor DAS requires a cellular signal source that is connected to either a base station or a bidirectional amplifier (a.k.a. a repeater). In the case of a repeater, a donor antenna is required to pull the signal from the nearest macrocell site. When the RF signal is sent to the headend equipment or DAS interface, it is converted to light. Fiber-optic cables distribute the signal to remote units on each floor of the building that then convert it back to an RF signal, amplify it and distribute it to indoor antennas (directional or omnidirectional) via coaxial cables.




[More to come ...]


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