---
# System prepended metadata

title: WG7
tags: [Spec]

---

# WG7
###### tags: `Spec`

# O-RAN.WG7.DSC.0-v02.00
## Deployment Scenarios and Base Station Classes

* Deploy Scenarios
```
eMBB
URLLC
```
* Base Station Architecture: Background
    * Split Architecture
    * Integrated architecture

## Split Architecture

![Split Architecture](https://i.imgur.com/Fli9kUj.png)
 
    * Note that the term optional is used to indicate there may be a deployment case where a switch or FHGW may not be needed 
    * O-CU shall be located at the data center and O-DU can be placed either at the data center or at the cell site
    
* following three criteria
```txt
* O-RAN WG4 (open fronthaul interface group) released interfaces
* O-RAN approved publicly (e.g., small cell forum or etc.) available external interfaces
* Fronthaul interfaces made available and published as part of an O-RAN approved WG7 reference design
```
* associated terminologies will be used throughout all WG7 specifications
    * O-DU~7-2~ &harr; FHGW~7-2→8~ &harr; O-RU~8~
* where the fronthaul gateway does not perform a protocol translation
    * O-DU~6~ &harr; FHGW~6~ &harr; O-RU~6~
    * O-DU~7-2~ &harr; FHGW~7-2~ &harr; O-RU~7-2~
    * O-DU~8~ &harr; FHGW~8~ &harr; O-RU~8~
(split finction is in wg4)
* split function
    * Split option 6 
        * All PHY functions will reside in O-RU~x~ while MAC functions will be performed in O-DU~x~. In other words, only un-coded user data is on FH. In this case the terminology O-DU~6~ and O-RU~6~ is used.
    * Split option 7-2
        *  the PHY is split into High and Low PHY functions where High PHY functions (coding, rate matching, scrambling, modulations and layer mapping) are performed in O-DU~x~ while O-RU~x~ performs the Low PHY functions (precoding, remapping, digital beamforming, IFFT and CP insertion). All I/Q samples are in frequency domain. In this case the terminology O-DU~7-2~ and O-RU~7-2` is used
    * split option 8
        * All PHY functions are performed in O-DUx. This means that O-RU~x~ function is limited to RF to baseband conversion and vice versa. The I/Q samples on FH interface are in time domain. In this case the terminology O-DU~8~ and O-RU8 is used.
        
![integrated Architecture](https://i.imgur.com/E5ThO28.png)

## Deployment Scenarios

### Indoor Picocell

![Indoor Picocell](https://i.imgur.com/7xW96pF.png)

### Outdoor Picocell

![Outdoor Picocell](https://i.imgur.com/AUXMuxp.png)

![Outdoor Picocell](https://i.imgur.com/OXT9FTZ.png)

### Outdoor Microcell

![](https://i.imgur.com/ieZrKIR.png)

![](https://i.imgur.com/0MAmhgL.png)

### Integrated access and backhaul (IAB)

![](https://i.imgur.com/NELlR3b.png)

![](https://i.imgur.com/ttrm5t2.png)

### Outdoor Macrocell

![](https://i.imgur.com/we0HoIL.png)

## Base Station Type Classification

![](https://i.imgur.com/Rh85KDD.png)

### Indoor
#### split function
![](https://i.imgur.com/SXfIIKg.png)
#### The integrated architecture
![](https://i.imgur.com/smq0XRd.png)

### Outdoor
#### Picocell
![](https://i.imgur.com/ahiWgOO.png)
#### Microcell
![](https://i.imgur.com/05cNaAZ.png)
![](https://i.imgur.com/mtueYBk.png)

### Integrated access and backhaul (IAB)
![](https://i.imgur.com/eBcF3gj.png)
#### Macrocell
![](https://i.imgur.com/LBO0D47.png)


### Key performance indicators
#### peak data rate
![](https://i.imgur.com/NrAP9nu.png)
#### Peak spectral efficiency
* Peak spectral efficiency (bps/Hz) = Peak data rate (bps)/ bandwidth (Hz).
![](https://i.imgur.com/ERLxv9r.png)
#### Bandwidth
![](https://i.imgur.com/jiDUFNg.png)
#### Control plane latency
![](https://i.imgur.com/rpzUGWO.png)
#### User plane latency
![](https://i.imgur.com/9ZIGfT8.png)
#### Mobility
![](https://i.imgur.com/zGUZq84.png)


# O-RAN.WG7.FHGW-HRD.0-v01.00
### O-RAN White Box Hardware Working Group Hardware Reference Design Specification for Fronthaul Gateway
* split architecture 
![](https://i.imgur.com/sRVlVNi.png)
* FHGW (Fronthaul Gateway) may be placed with the following O-RAN specified interfaces
    * The interface between O-DU and FHGW is Open Fronthaul (Option 7-2x).
    * The interface between FHGW and RU is an LLS option specified by O-RAN. 
    * The interface between FHGW and RU may not support Open Fronthaul (Option 7-2x).

![](https://i.imgur.com/AioxEYB.png)

* Low PHY function in the fronthaul gateway converts the CPRI/low level split interface between the RU and Open Fronthaul (Option 7-2x).
    * using a packet-based network
### 
![](https://i.imgur.com/LC3LVhF.png)
```txt
    * point-to-point
        direct connect
    * mesh
        connect through other network element
```

![](https://i.imgur.com/58lcZaX.png)
* need two interfaces for connectivity towards the O-DUs

### low PHY function
1) FFT/IFFT (Lower-PHY DL/UL)
2) PRACH detection (Lower-PHY UL)
3) Handling of C-Plane/M-plane messages
4) Timing and synchronization of RU
5) eCPRI framing/de-framing and switching
6) CPRI framing/de-framing and switching
7) CPRI to eCPRI conversion
8) I/Q compression on eCPRI and CPRI links

### Timing
* WG4 CUS specification 
* uses SyncE and PTP to provide frequency, phase and Time-of Day to necessary endpoints.

![](https://i.imgur.com/SetJcAx.png)

## Hardware Architecture and Requirements
* In case of a FHGW, the combination of RU and FHGW acts as an O-RU


![](https://i.imgur.com/qNXhM8q.png)

* Network Processing Unit
    * provides the packet transport functions of the FHGW. 
* Radio Signal Processor/Accelerator
    * from the low-level split-8 to O-RAN fronthaul interface (Split 7-2)
    * implements the Low PHY capabilities mentioned in section
    * can be implemented using a FPGA, DSP engine or ASICs
* CPU
    * controls the transport capabilities and the Radio software which controls the radio signal processor
* Memory
    * used to store the runtime data and software for the NOS and Radio software
* Storage
    * store operating system, application software, firmware, operational status of Fronthaul Gateway
* Timing Components
    * used to implement IEEE 1588 PTP and Synchronous Ethernet functionalities.
    * key components
        * GNSS
        * OCXO
        * DPLL
        * Servo
* GNSS
    * Global Navigation Satellite System provides Time of the Day and Synchronization pulse (PPS) to the timing module to recover the clock and phase
* OCXO(Oven controlled crystal oscillator)
    * provides the stable reference clock to the timing module with reference to which the PTP clock is generated
    * used to validate the other recovered clocks are within the required PPM offset or not
* DPLL(Digital Phase lock loop)
    * generate the PTP clock steered by the servo algorithm
    * ensures that the generated clock meets the required specifications in terms of Jitter
* Servo
    * analyses the timestamps from the ethernet packets, performs appropriate filtering and steers the DPLL to generate the PTP clock and Phase alignment of the clock to the primary clock source.
* Ethernet PHY 
    * physical level ethernet connectivity

### FHGW~7-2→8~

![](https://i.imgur.com/ZOIVgCR.png)

![](https://i.imgur.com/P5fRZ49.png)

ORAN traffic = [12 (AxCs) x 14 (symbols) x 1200 (REs) x 32 (bisIQ) ] / 1 ms + C/S/M-plane + Pkt_headeroverhead ~ 6.5 Gbps

![](https://i.imgur.com/SeL9q5b.png)

![](https://i.imgur.com/u89mb4N.png)

* A reference clock signal to the NPU and FPGA at predetermined frequency from PTP domain
* A One-Pulse per Second (PPS) reference signal where the transition from low to high as sampled by the clock 
* A lower speed bus carrying the seconds value of Time of Day. The 48 bits of seconds value is provided serially on this signal. 


![](https://i.imgur.com/PPA0rbo.png)
* Scalability and flexibility
    * red line is Scalability and flexibility