--- /dev/null
+.. Copyright (c) 2019 Intel
+..
+.. Licensed under the Apache License, Version 2.0 (the "License");
+.. you may not use this file except in compliance with the License.
+.. You may obtain a copy of the License at
+..
+.. http://www.apache.org/licenses/LICENSE-2.0
+..
+.. Unless required by applicable law or agreed to in writing, software
+.. distributed under the License is distributed on an "AS IS" BASIS,
+.. WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+.. See the License for the specific language governing permissions and
+.. limitations under the License.
+
+.. |br| raw:: html
+
+ <br />
+
+Architecture Overview
+=====================
+
+.. contents::
+ :depth: 3
+ :local:
+
+This section provides an overview of the xRAN architecture.
+
+.. _introduction-1:
+
+Introduction
+------------
+
+The front haul interface, according to the ORAN Fronthaul specification,
+performs communication between O-RAN |br|
+Distributed Unit (O-DU) and O-RAN
+Radio Unit (O-RU) and consists of multiple HW and SW components.
+
+The logical representation of HW and SW components is shown in Figure 1.
+
+.. image:: images/Architecture-Block-Diagram.jpg
+ :width: 600
+ :alt: Figure 1. Architecture Block Diagram
+
+Figure 1. Architecture Block Diagram
+
+|br|
+|br|
+
+From the hardware perspective, two networking ports are used to
+communicate to the Front Haul and Back (Mid) Haul network as well as to
+receive PTP synchronization. The system timer is used to provide a
+“sense” of time to the gNB |br|
+application.
+
+From the software perspective, the following components are used:
+
+- Linux PTP provides synchronization of system timer to GPS time:
+
+- Ptp4l is used to synchronize oscillator on Network Interface
+ Controller (NIC) to PTP GM.
+
+- Phc2sys is used to synchronize system timer to oscillator on NIC.
+
+- DPDK to provide the interface to the Ethernet port.
+
+- xRAN library is built on top of DPDK to perform U-plane and C-plane
+ functionality according to the ORAN Fronthaul specification.
+
+- 5GNR reference PHY uses the xRAN library to access interface to O-RU.
+ The interface between the library and PHY is defined to communicate
+ TTI event, symbol time, C-plane information as well as IQ sample
+ data.
+
+- 5G NR PHY communicates with the L2 application using the set of
+ MAC/PHY APIs and the shared memory interface defined as WLS.
+
+- L2, in turn, can use Back (Mid) Haul networking port to connect to
+ the CU unit in the context of 3GPP specification.
+
+In this document, we focus on the details of the design and
+implementation of the xRAN library with respect to providing Front Haul
+functionality for both mmWave and Sub-6 scenarios
+
+The xRAN M-plane is not implemented and is outside of the scope of this
+description. Configuration files are used to |br|
+specify selected M-plane
+level parameters.
+
+ORAN FH Threads
+---------------
+
+ORAN FH Thread Performs:
+
+- Symbol base “time event” to the rest of the system based on System
+ Clock synchronized to GPS time via PTP
+
+- Baseline polling mode driver performing TX and RX of Ethernet packets
+
+- Most of the packet processing such as Transport header, Application
+ header, Data section header and interactions with the rest of the PHY
+ processing pipeline.
+
+- Polling of other call back function that was registered.
+
+ORAN FH thread created the independent of usage of xRAN as an interface
+to the Radio.
+
+Communication between L1 and xRAN layer is performed using a set of
+callback functions where L1 assigned callback and xRAN layer executes
+those functions at a particular event or time moment. Detailed
+information on callback function |br|
+options and setting as well as design,
+can be found in the sections below.
+
+Sample Application Thread Model
+-------------------------------
+
+Configuration of a sample application for both O-DU and O-RU follows the
+model of 5G NR l1app application in the |br|
+section of xRAN only. No BBU or
+FEC related threads are needed as minimal xRAN functionality is used
+only.
+
+.. image:: images/Sample-Application-Threads.jpg
+ :width: 600
+ :alt: Figure 3. Sample Application Threads
+
+Figure 3. Sample Application Threads
+
+|br|
+|br|
+
+In this scenario, the main thread is used only for initializing and
+closing the application. No execution happens on core 0 during run time.
+
+Functional Split
+----------------
+
+Figure 1 corresponds to the O-RU part of the xRAN split. Implementation
+of the RU side of the xRAN protocol is not |br|
+covered in this document.
+
+.. image:: images/eNB-gNB-Architecture-with-O-DU-and-RU.jpg
+ :width: 600
+ :alt: Figure 4. eNB/gNB Architecture with O-DU and RU
+
+Figure 4. eNB/gNB Architecture with O-DU and RU
+
+|br|
+|br|
+
+More than one RU can be supported with the same implementation of the
+xRAN library and depends on the configuration of gNB in general. In this
+document, we address details of implementation for single O-DU – O-RU
+connection.
+
+The ORAN Fronthaul specification provides two categories of the split of
+Layer 1 functionality between O-DU and O‑RU: Category A and Category B.
+
+.. image:: images/Functional-Split.jpg
+ :width: 600
+ :alt: Figure 5. Functional Split
+
+Figure 5. Functional Split
+
+|br|
+
+Data Flow
+---------
+
+|br|
+
+Table 3 lists the data flows supported for a single RU with a single
+Component Carrier.
+
+|br|
+|br|
+
+Table 3. Supported Data Flow
+
++---------+----+-----------------+-----------------+----------------+
+| Plane | ID | Name | Contents | Periodicity |
++---------+----+-----------------+-----------------+----------------+
+| U-Plane | 1a | DL Frequency | DL user data | symbol |
+| | | Domain IQ Data | (PDSCH), | |
+| | | | control channel | |
+| | | | data (PDCCH, | |
+| | | | etc.) | |
++---------+----+-----------------+-----------------+----------------+
+| | 1b | UL Frequency | UL user data | symbol |
+| | | Domain IQ Data | (PUSCH), | |
+| | | | control channel | |
+| | | | data (PUCCH, | |
+| | | | etc.) | |
++---------+----+-----------------+-----------------+----------------+
+| | 1c | PRACH Frequency | UL PRACH data | slot or symbol |
+| | | Domain IQ Data | | |
++---------+----+-----------------+-----------------+----------------+
+| C-Plane | 2a | Scheduling | Scheduling | ~ slot |
+| | | Commands | information, | |
+| | | | FFT size, CP | |
+| | | (Beamforming is | length, | |
+| | | not supported) | Subcarrier | |
+| | | | spacing, UL | |
+| | | | PRACH | |
+| | | | scheduling | |
++---------+----+-----------------+-----------------+----------------+
+| S-Plane | S | Timing and | IEEE 1588 PTP | |
+| | | Synchronization | packets | |
++---------+----+-----------------+-----------------+----------------+
+
+|br|
+|br|
+
+.. image:: images/Data-Flows.jpg
+ :width: 600
+ :alt: Figure 6. Data Flows
+
+Figure 6. Data Flows
+
+|br|
+|br|
+
+Information on specific features of C-Plane and U-plane provided in
+Section 6.0. Configuration of S-plane used on test |br|
+setup for simulation
+is provided in Appendix Appendix 2.
+
+Data flow separation is based on VLAN (applicable when layer 2 or layer
+3 is used for the C/U-plane transport.)
+
+#. The mechanism for assigning VLAN ID to U-Plane and C-Plane is assumed
+to be via the M-Plane.
+
+VLAN Tag is configurable via the standard Linux IP tool (refer to
+Appendix Appendix 1).
+
+No Quality of Service (QoS) is supported.
+
+|br|
+|br|
+
+.. image:: images/C-plane-and-U-plane-Packet-Exchange.jpg
+ :width: 600
+ :alt: Figure 7. C-plane and U-plane Packet Exchange
+
+Figure 7. C-plane and U-plane Packet Exchange
+
+|br|
+|br|
+
+Timing, Latency, and Synchronization to GPS
+-------------------------------------------
+
+The ORAN Fronthaul specification defines the latency model of the front
+haul interface and interaction between O-DU and 0-RU. This
+implementation of the xRAN library supports only the category with fixed
+timing advance and Defined Transport method. It determines O-DU transmit
+and receive windows based on pre-defined transport network |br|
+characteristics, and the delay characteristics of the RUs within the
+timing domain.
+
+Table 4 below provides default values used for the implementation of
+O-DU – O-RU simulation with mmWave scenario. Table 5 and Table 6 below
+provide default values used for the implementation of O-DU – O-RU
+simulation with |br|
+numerology 0 and numerology 1 for Sub6 scenarios.
+Configuration can be adjusted via configuration files for sample |br|
+application and reference PHY. However, simulation of the different
+range of the settings was not performed, and |bR|
+additional implementation changes might be required as well as testing with actual O-RU. |br|
+The
+parameters for the front haul network are out of scope as a direct
+connection between O-DU and 0-RU is used for simulation.
+
+|br|
+|br|
+
+Table 4. Front Haul Interface Latency (numerology 3 - mmWave)
+
++------+------------+-------------------+-------------------+----------------+------------+
+| | Model | C-Plane | U-Plane | | |
+| | Parameters | | | | |
++------+------------+-------------------+-------------------+----------------+------------+
+| | | DL | UL | DL | UL |
++------+------------+-------------------+-------------------+----------------+------------+
+| O-RU | T2amin | T2a_min_cp_dl=50 | T2a_min_cp_ul=50 | T2a_min_up=25 | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | T2amax | T2a_max_cp_dl=140 | T2a_max_cp_ul=140 | T2a_max_up=140 | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | | Tadv_cp_dl | NA | NA | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | Ta3min | NA | NA | NA | Ta3_min=20 |
++------+------------+-------------------+-------------------+----------------+------------+
+| | Ta3max | NA | NA | NA | Ta3_max=32 |
++------+------------+-------------------+-------------------+----------------+------------+
+| O-DU | T1amin | T1a_min_cp_dl=70 | T1a_min_cp_ul=60 | T1a_min_up=35 | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | T1amax | T1a_max_cp_dl=100 | T1a_max_cp_ul=70 | T1a_max_up=50 | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | Ta4min | NA | NA | NA | Ta4_min=0 |
++------+------------+-------------------+-------------------+----------------+------------+
+| | Ta4max | NA | NA | NA | Ta4_max=45 |
++------+------------+-------------------+-------------------+----------------+------------+
+
+|br|
+|br|
+|br|
+
+Table 5. Front Haul Interface Latency (numerology 0 - Sub6)
+
++------+----------+----------+----------+----------+----------+
+| | Model | C-Plane | U-Plane | | |
+| | Pa | | | | |
+| | rameters | | | | |
++------+----------+----------+----------+----------+----------+
+| | | DL | UL | DL | UL |
++------+----------+----------+----------+----------+----------+
+| O-RU | T2amin | T | T | T2a_mi | NA |
+| | | 2a_min_c | 2a_min_c | n_up=200 | |
+| | | p_dl=400 | p_ul=400 | | |
++------+----------+----------+----------+----------+----------+
+| | T2amax | T2 | T2 | T2a_max | NA |
+| | | a_max_cp | a_max_cp | _up=1120 | |
+| | | _dl=1120 | _ul=1120 | | |
++------+----------+----------+----------+----------+----------+
+| | | Ta | NA | NA | NA |
+| | | dv_cp_dl | | | |
++------+----------+----------+----------+----------+----------+
+| | Ta3min | NA | NA | NA | Ta3 |
+| | | | | | _min=160 |
++------+----------+----------+----------+----------+----------+
+| | Ta3max | NA | NA | NA | Ta3 |
+| | | | | | _max=256 |
++------+----------+----------+----------+----------+----------+
+| O-DU | T1amin | T | T | T1a_mi | NA |
+| | | 1a_min_c | 1a_min_c | n_up=280 | |
+| | | p_dl=560 | p_ul=480 | | |
++------+----------+----------+----------+----------+----------+
+| | T1amax | T | T | T1a_ma | NA |
+| | | 1a_max_c | 1a_max_c | x_up=400 | |
+| | | p_dl=800 | p_ul=560 | | |
++------+----------+----------+----------+----------+----------+
+| | Ta4min | NA | NA | NA | T |
+| | | | | | a4_min=0 |
++------+----------+----------+----------+----------+----------+
+| | Ta4max | NA | NA | NA | Ta4 |
+| | | | | | _max=360 |
++------+----------+----------+----------+----------+----------+
+
+|br|
+|br|
+|br|
+
+Table 6. Front Haul Interface Latency (numerology 1 - Sub6)
+
++------+------------+-------------------+-------------------+----------------+------------+
+| | Model | C-Plane | U-Plane | | |
+| | Parameters | | | | |
++------+------------+-------------------+-------------------+----------------+------------+
+| | | DL | UL | DL | UL |
++------+------------+-------------------+-------------------+----------------+------------+
+| O-RU | T2amin | T2a_min_cp_dl=285 | T2a_min_cp_ul=285 | T2a_min_up=71 | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | T2amax | T2a_max_cp_dl=429 | T2a_max_cp_ul=429 | T2a_max_up=428 | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | | Tadv_cp_dl | NA | NA | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | Ta3min | NA | NA | NA | Ta3_min=20 |
++------+------------+-------------------+-------------------+----------------+------------+
+| | Ta3max | NA | NA | NA | Ta3_max=32 |
++------+------------+-------------------+-------------------+----------------+------------+
+| O-DU | T1amin | T1a_min_cp_dl=285 | T1a_min_cp_ul=285 | T1a_min_up=96 | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | T1amax | T1a_max_cp_dl=429 | T1a_max_cp_ul=300 | T1a_max_up=196 | NA |
++------+------------+-------------------+-------------------+----------------+------------+
+| | Ta4min | NA | NA | NA | Ta4_min=0 |
++------+------------+-------------------+-------------------+----------------+------------+
+| | Ta4max | NA | NA | NA | Ta4_max=75 |
++------+------------+-------------------+-------------------+----------------+------------+
+
+|br|
+|br|
+|br|
+
+IEEE 1588 protocol and PTP for Linux\* implementations are used to
+synchronize local time to GPS time. Details of the configuration used
+are provided in Appendix Appendix 2. Local time is used to get Top of
+the Second (ToS) as a 1pps event for SW implementation. Timing event is
+obtained by performing polling of local time using |br|
+clock_gettime(CLOCK_REALTIME,..)
+
+All-time intervals are specified with respect to GPS time which
+corresponds to OTA time.
+
+|br|
+|br|
+|br|
+
+Virtualization and Container-Based Usage
+----------------------------------------
+
+xRAN implementation is deployment agnostic and does not require special
+changes to be used in virtualized or |br|
+container-based deployment options.
+The only requirement is to provide one SRIOV base virtual port for
+C-plane and one port for U-plane traffic per O-DU instance. This can be
+achieved with the default Virtual Infrastructure Manager (VIM) as well
+as using standard container networking.
+
+
+
Code Review / o-du / phy.git / blobdiff