# Daily Report day 6
::: success
27/07/2021
:::

## 1. Aspects : Functional Split and Open Fronthaul Interface (OFI)

:::info
### A. 5G

#### 5G New Radio (NR)
- Scalable numerologies for
- Low Latency and Ultra Reliability
- Beamforming
- New channel coding
- LDPC for data channel
- Polar coding for control channel
- flexible and modular RAN architecture:
- split front haul, split control- and user-plane (CUPS)
- Native end-to-end support for Networking Slicing

#### 5G NR Radio Frame

#### 5G Network Architecture

#### 5G System Architecture

:::

:::info
### B. Functional Split
A functional split determines the amount of functions left locally at the antenna site, and the amount of functions centralized at a high processing powered datacenter. A number of different functional splits are currently being investigated to be used for NR. In NR the radio processing-- and baseband-- functions from the 3rd Generation Partnership Project (3GPP) protocol stack are split up into a Distributed Unit (DU) and a Centralized Unit (CU).
The functional split determines how many Base Station (BS) functions to leave locally, close to the user, with the benefit of relaxing fronthaul network bitrate and delay requirements, and how many functions to centralize with the possibility of achieving greater processing benefits.

#### Control/User Plane Separation (CUPS)

CUPS (Vertical Split)
- First step to introduce SDN to the RAN
- Separate CP and UP
- Consistent Cp in multi-vendor networks
- More challenges for lower layer splits

Central Unit/Distributed Unit split (Horizontal split)
- Centralization gain in terms of performance and scale
- Shift functionalities to different locations
- reduce the cost of RAN

#### RAN Functional Split

#### Hierarchical RRM
Central RRM located at CU coordinate the lower layer functions accross multiple DUs. The general functionalities of central RRM are:
- radio resource allocation
- Call admission
- Call selection
- Load balancing
- Lobility
- Multi-connectivity
MAC dynamic scheduler is the most important part of RRM
- needs context information to fulfill the user's QoS
- variable TTI size scheduling
- Punctured/preempitive scheduling
:::

:::info
### C. O-RAN Fronthaul Interface
Fronthaul interface -is a protocol connecting the baseband unit (BBU) and Remote radio head (RRH). Carriersignal along the basestation and antenna using fiber Ethernet.
#### Important functions for Fronthaul
Transporting data between DU and RU. Splits functionality between O-RU and O-DU. Enables multivendor RU and DU interoperability. Increases transmission bandwidth through split option 7-2x. Downlink and Uplink bits processing.

#### Common Public Radio Interface (CPRI)
Exiting CPRI specifications implemented on C-RAN in vender-specific, which is difficult for the interoperability of DU and RU. The fronthaul interface for O-RAN aims to support the need for wider frequency bandwidth in FHI and achieve multi-vendor RAN in the 5G era.

#### Fronthaul Topology

#### Protocol Stack
In the C/U-Plane, The O-RAN fronthaul specifications support a protocol stack that transmits signals used by eCPRI or Radio over Ethernet (RoE) directly over Ethernet and an optional protocol stack that transmits the signals over User Datagram Protocol (UDP)/IP.
In the S-Plane, meanwhile, the O-RAN fronthaul specifications support a protocol stack that transmits signals used in Precision Time Protocol (PTP) and SyncE over Ethernet.
In the M-Plane, the O-RAN fronthaul specifications support a protocol stack that transmits signals used in NETwork CONFiguration protocol (NETCONF) over Ethernet/IP/Transmission Control Protocol (TCP)/Secure SHell (SSH).
:::

## 2. Summary
:::info
A functional split determines the amount of functions left locally at the antenna site, and the amount of functions centralized at a high processing powered datacenter. A number of different functional splits are currently being investigated to be used for NR. In NR the radio processing-- and baseband-- functions from the 3rd Generation Partnership Project (3GPP) protocol stack are split up into a Distributed Unit (DU) and a Centralized Unit (CU).
Fronthaul interface -is a protocol connecting the baseband unit (BBU) and Remote radio head (RRH). Carriersignal along the basestation and antenna using fiber Ethernet.
:::

## 3. Comment
Functional split and fronthaul interface are interrelated. The fronthaul interface is also used in functional split applications.

---
# <center>Discussion with Team</center>
--