RRU-Remote Radio Unit: Function,Concept,Details

In this post, we will explain the concept, function and details of RRU- Remote Radio Unit which is used in telecom and telecommunication field.

Topics Covering:

  1. RRU Definition and Overview
  2. Radio remote Unit Functions
  3. RRU Hardware Description & many more

1.RRU: Definition and Overview:

Radio Remote Unit(RRU) is the distributed and integrated frequency unit that connects to an operators network with the User Equipment’s (UE’s) like Cell Phone and mobile devices.

rru radio remote unit mounting in tower
Fig: RRU mounting in Tower

The logical term “distributed and integrated” is because traditionally the radio architecture for cellular system is based on a single-standalone system (Base Stations) usually installed indoor but now, the cellular architecture is divided.

So now the BTS (Base Transceiver Station) is the integration of various radio unit like BBU and RRU. Despite installing only in indoor, radio units are now install in the tower below the Antenna.

The RRU is connected to the base station via the fiber optic link which is bi-directional link. The optical interface link is also known as CPRI (Common Public Radio Interface). CPRI is a interface protocol developed by combination of major telecom equipment’s manufacturing company like Nokia, Alcatel, Cisco and many more.

The RRU helps to reduce the coaxial feed line losses, increase system efficiency and provide high level of flexibility in cellular site construction. Undoubtedly, this helps in upgrading to new equipment’s and devices more easily.

Note: Till now you have completed RRU basic overview. Now you will read RRU concept, function and details in more depth.

2. RRU Functions: 

1) Acts as a Transceiver: transmit and receive the user signals to the base station and vice-versa.

2) Provides back to back support and connectivity between user equipment’s like power, delay,etc.

3) Control and process the EM signals received from the Antenna via Jumper(Hollow Guide).

4) Provide interface between two physical  link: Optical and EM (Electromagnetics).

5) Provide Controlling support of the Auxiliary equipment’s like  RCU (Remote Control Unit) for electrical tilt adjustment generally known as RET(Remote Electrical Tilt).

6) Generate and sends the different signals like   VSWR, RET, ACT,etc. 

3. RRU Hardware Description:

remote radio unit hardware description
Fig: RRU Port

RRU consist of different ports for different purposes. So, I have summarize the ports that are common among various companies like Huawei, ZTE, Ericsson, Alcatel-Lucent, Orange,etc.

1) CPRI Port:  There is 2 port generally name as CPRI0 and CPRI1. However there may be 1’s in some model. The name at suffix may vary. Its function is to connect to BBU.

2) RF Port: We say it as a Jumper port. Generally, the number of jumper port may vary with model and company’s architecture. At least there is 2 jumper port, one of which is for Tx(Transmission) and another for Tx/Rx(Transmission/Receiver also known as Transceiver). The RF port is conneted to the Antenna via Jumper Cable. 

3) RET Port: There is at least one RET port for connection to RCU. Mostly, the connector is DB9 in Huawei but may vary with other company’s. RCU is connected to the Antenna. RET cable connects the RCU and RRU.

4) Power Supply Port: There is one port for powering the RRU. Mostly blue and black. Blue is for negative (-) and black is for zero(0). Generally all RRU operates in -48V.

5) Ground Port: There is two OT port for the grounding. The ground cable: mostly copper wire, one end is connected to RRU and another end into Bus Bar nearby RRU. Thus it provides the surge and high voltage protection of RRU and thus keeping safe from natural weather and climates. 

Thus, from above topic, you came to know more details, concept and functions of rru in telecommunication field.

If you find this post useful, please share or if something is missing or if you want more concept, ideas and details of other telecom equipment’s please leave comment in the comment section below. So, I will try to include those topics in my coming post.

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