Remote Radio Head for CPRI and 4G, 5G & LTE Networks

A Remote Radio Head (RRH) is a remote radio transceiver that connects to a radio base station unit through an electrical or wireless interface. The RRH is termed “Remote” as it is usually installed on a mast-top, or tower-top location that is physically some distance away from the base station hardware which is often mounted in an indoor rack-mounted location.

In wireless technologies including GSM, CDMA, UMTS, and LTE, this radio equipment operates remotely from the BTS/NodeB/eNodeB, and is also called Remote Radio Head. RRHs are used to extend the coverage of these base stations, particularly in areas such as rural regions or tunnels. Typically, they connect to the BTS/NodeB/eNodeB using fibre optic cables and Common Public Radio Interface protocols.

What is a Remote Radio Head (RRH)?

Remote radio heads (RRHs) are critical components in modern distributed base stations, housing the RF circuitry, analogue-to-digital/ digital-to-analogue converters, and up/ down converters. They also have operation and management processing capabilities and a standardised optical interface for connection to the base station. Industry-standard interfaces such as CPRI and OBSAI ensure hardware interoperability and enable faster time-to-market for complete solutions, which will become increasingly true as LTE networks are deployed. RRHs simplify MIMO implementation, increase base station efficiency and enable easier physical location for gap coverage problems. RRHs use the latest RF technologies, such as GaN RF power devices and envelope tracking within the RRH RFPA.

Fibre to the Antenna (Fibre to the Antenna, FTTA)

Fourth-generation (4G) and beyond infrastructure deployments include the implementation of Fibre to the Antenna (FTTA) architecture. FTTA architecture has enabled lower power requirements, distributed antenna sites, and a reduced base station footprint than conventional tower sites. The use of FTTA will promote the separation of power and signal components from the base station and their relocation to the top of the tower mast in a Remote Radio Head (RRH).

Wireless to the Antenna (WTTA)

Using Wireless (Microwave, Millimeter Wave, Free Space Optics) links instead of fibre allows the Remote Radio Head (RRH) to be connected without need for fibre optics. By avoiding the needs for digging, trenches, leased circuits from telcos, dark fibre or way-leaves for disrupting busy city streets, 4G/ LTE networks can be realised very quickly with installation taking hours rather than days, weeks or months. WTTA is being pioneered by vendors such as Wireless Excellence with the CableFree MMW and FSO product lines.

RRH technology

The remote radio head (RRH) contains the base station’s RF circuitry plus analogue-to-digital or digital-to-analogue converters and up/ down converters.

It is sitting on top of cell tower that mainly performs following functions:

• Converting optical signals to electrical signals and vice versa using CPRI.
• In the transmitter section of the RRH, it converts digital signals to RF and amplifies that signal to the desired power level and Antenna connected to it, radiates the RF signal in air.
• In the Receiver section of RRH, it receives the desired band of signal from antenna and amplifies it.
• Converts RF signal back to digital signal in the receiver chain.

RRH has been made of RF transmitter chain and RF receiver chain which includes the ADC (Analogue to digital converter), DAC (Digital to analogue converter), Mixer, PA (Power amplifier), LNA (Low Noise Amplifier) etc. The Basic Block diagram of an RRH is shown below:

The RRH is connected to the Base band unit (BBU) via fibre optical cable which uses CPRI format signals. Optical cable is used because it has less loss and it is cheaper as compared to RF Coaxial cable, especially at the CPRI bit rates which can be 6Gbps up to 10Gbps or more. One base-band unit is connected to multiple RRHs depending upon the capability of base-band unit. The following example shows 3 RRHs connected to one baseband unit to provide 3 sectors of coverage:

For Further Information

Please Contact Us for more information on our exciting range of solutions using LTE technology.