# 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


* 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

* 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~ ↔ FHGW~7-2→8~ ↔ O-RU~8~
* where the fronthaul gateway does not perform a protocol translation
* O-DU~6~ ↔ FHGW~6~ ↔ O-RU~6~
* O-DU~7-2~ ↔ FHGW~7-2~ ↔ O-RU~7-2~
* O-DU~8~ ↔ FHGW~8~ ↔ 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.


## Deployment Scenarios

### Indoor Picocell


### Outdoor Picocell



### Outdoor Microcell



### Integrated access and backhaul (IAB)



### Outdoor Macrocell


## Base Station Type Classification


### Indoor
#### split function
#### The integrated architecture

### Outdoor
#### Picocell
#### Microcell

### Integrated access and backhaul (IAB)
#### Macrocell

### Key performance indicators
#### peak data rate
#### Peak spectral efficiency
* Peak spectral efficiency (bps/Hz) = Peak data rate (bps)/ bandwidth (Hz).
#### Bandwidth
#### Control plane latency
#### User plane latency
#### Mobility

# O-RAN.WG7.FHGW-HRD.0-v01.00
### O-RAN White Box Hardware Working Group Hardware Reference Design Specification for Fronthaul Gateway
* split architecture
* 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).


* 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
###

    * point-to-point
        direct connect
    * mesh
        connect through other network element

* 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.


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


* 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~



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



* 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.

* Scalability and flexibility
* red line is Scalability and flexibility