Fronthaul, Midhaul and Backhaul are used to connect RU, DU and CU and the core network together.
They tells us about the transport network architecture.
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What is Fronthaul ?
It is the link between RRU and BBU. or RRU and DU.
It has a latency requirement for 100 to 250 µs one way.
They are implemented by vendor and the interfaces are proprietary.
What is Midhaul ?
It is the link between DU and CU.
They are connected through F1 interface.
What is Backhaul ?
It is the link between CU and Core Network.
They are connected through NG interface.
What is DU ?
DU stands for Distributed Unit.
It handles RLC, MAC and parts of PHY layer. It is placed close to RRU.
What is CU ?
CU stands for Centralized Unit.
It handles RRC and PDCP layers.
One CU is connected to multiple DU.
Relation between RRU DU CU:
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What is AAU ?
AAU stands for Active Antenna Unit.
It is nothing but the antenna.
What is BBU ?
BBU stands for Base Band Unit.
It is used to manage the whole base station that include operating. maintenance and signalling processing.
Provides the interface to RRU.
What is RRU ?
RRU stands for Remote Radio Unit.
It sits in between antenna in one end and BBU on the other.
It is connected to BBU through CPRI and converts RF signal into data signal and vice versa.
It performs preprocessing, amplification, filtering, carrier generation.
What is an Antennas ?
There are 2 types of Antennas. one for Outdoor Coverage and another for Indoor coverage.
Outdoor Coverage:
Here the shape of the antenna decides signal coverage.
Indoor Coverage:
Ceiling omnidirectional antenna
Ceiling Directional antenna