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ORAN

Functional Split Option 7 & ORAN Alliance Specifie

In this option as shown in Fig below the lower physical layer functions and RF circuits are located in the DU(s). The upper protocol layers including the upper physical layer functions reside in the CU. There are multiple realizations of this option including asymmetrical implementation of the option in the downlink and uplink (e.g., option 7-1 in the uplink and option 7-2 in the downlink). A compression technique may be applied to reduce the required transport bandwidth between the CU and the DU.This option can to some extent relax the fronthaul throughput requirements and allows centralized scheduling and joint processing in both transmit and receive sides.Also this option will allow traffic aggregation from NR and LTE transmission points to be centralized and can facilitate the management of traffic load between NR and LTE transmission points.The following represent different forms where this option can be implemented:Option 7-1: In this variant, the fast Fourier transform (FFT), CP removal (OFDM processing), and possibly PRACH processing is implemented in the uplink and in the DUs, and the remaining physical layer functions reside in the CU. In the downlink, inverse FFT (IFFT) and CP insertion blocks (OFDM processing) reside in the DUs and the rest of physical layer functions will be performed in the CU. This variant would allow implementation of advanced receivers.Option 7-2: In this variant, FFT, CP removal, resource de-mapping, and possibly MIMO decoding functions are implemented in the DU in the uplink and the remaining physical layer functional processing are performed in the CU. In the downlink, IFFT, CP addition, resource mapping, and MIMO precoding functions are performed in the DU, and the rest of physical layer processing is performed in the CU. This variant also allows the use of advanced receivers for enhanced performance.Option 7-3: This downlink only option implements the channel encoder in the CU, and the rest of physical layer functions are performed in the DU(s). This option can reduce the fronthaul throughput requirements as the payloads consist of the encoded bits.Split Option 7-2x: It is a specification for functional splitting between ORAN DU (O-DU) & ORAN RU (O-RU) adopted by ORAN fronthaul specification.This split option has been introduced by ORAN Alliance to translate highly inefficient CPRI traffic to eCPRI using the low order physical layer 1 processing (Low PHY). In the DL, OFDM phase compensation iFFT, CP addition, and digital beamforming functions reside in the O-RU as well as precoding for Category B O-RUs. The rest of the PHY functions including resource element mapping, precoding, layer mapping, modulation, scrambling, rate matching and coding reside in the O-DU. Precoding must be in the O-DU for Category A O-RU support but this only applies if the number of precoder output spatial streams is 8 or less, otherwise precoding must be in the (Category B) O-RU.In the UL, OFDM phase compensation (for all channels except PRACH) , FFT, CP removal and digital beamforming functions reside in the O-RU. The rest of the PHY functions including resource element de-mapping, equalization, de-modulation, de-scrambling, rate de-matching and de-coding reside in the O-DU.In general, the required fronthaul bandwidth becomes smaller as more functions become entrusted to the O-RU for example compared to CPRI in which O-RU handles only the RF function section only, placing IFFT/FFT processing in O-RU can prevent an increase in the fronthaul required bandwidth caused by over sampling applied to OFDM signal in the time domain. Similarly placing DL precoding in the O-RU can prevent the increase in the required fronthaul bandwidth that occurs when number of MIMO spatial stream is greater than the number of MIMO layers.Next topic will be CPRI & ECPRI functionalities and advantages stay tuned..

Admin

August 08, 2021

20 Min Read

ORAN

Types Of Functional Splits In ORAN/5G NR

Types of Splits:We have three categories of splitsHigh Layer SplitsLow Layer SplitsDouble SplitsHigh Layer Split: It consist of split 2,3,4 & 5.The benefits of opting this functional splits are drastically reduced bandwidth, latency tolerant i.e for long distances.Low Layer Split: It consists of split 6,7 &8. The benefits of opting this functional split are cost effective RRH, Ideal for COMP. It has High Bandwidth requirements and very tight latency requirements.Double Split: Double splits are the splits in which two splits have been considered between RAN i.e CU,DU & RU. Practically we have two double a) Option 2 & 6 , b) option 2 & 7.2.Below figure represents the functional split:B-Haul: Back Haul,F-Haul :Front HaulChoosing a Functional Split:When considering the functional split defining a fronthaul interface there are two competing interests:a) There is a benefit in keeping an O-RU as simple as possible because size, weight, and power draw are primary deciding considerations and the more complex an O-RU, the larger, heavier and more power-hungry the O-RU tends to be.b) There is a benefit in having the interface at a higher level which tends to reduce the interface throughput relative to a lower-level interface – but the higher-level the interface, the more complex the O-RU tends to be.To resolve this, O-RAN has selected a single split point, known as “7-2x” but allows a variation, with the precoding function to be located either “above” the interface in the O-DU or “below” the interface in the O-RU.O-RUs within which the precoding is not done are called “Category A” O-RUs while O-RUs within which the precoding is done are called 27 “Category B” O-RUs.When O-RU Category A is supported by O-DU it is mandatory to support a total number of precoded streams of up to 8. Support for more than 8 precoded streams is optional.Stay tuned for more updates on Split option 7.2x which is an ORAN Split.

Admin

August 08, 2021

20 Min Read

ORAN

Function Splits In ORAN/5G-NR:

Function Splits in ORAN/5G NR:Centralized baseband processing was introduced several years ago to ease installation of base stations in large buildings. Digital radio interfaces and remote radio heads (RRHs) both was enabled by it, which allowed the connection between RRHs and digital baseband units (BBUs) to be carried over fiber.The concept introduced to span larger areas involving many radio sites while still using a central BBU. With the increase in deployment fiber and availability of required fronthauls (FHs) became a major problem. In recent years, due to new 5G requirements, 3GPP and other standards bodies started different activities to address this issue.By distributing protocol stacks between different components (different splits between CU & DU ), solution providers focus on addressing the tight requirements for a near perfect fronthauls between RRHs and BBUs. This splitting is basically known as function split in 5G NR.Below figure represents functional split in 5G NR:Functional Splits:Option 1 (RRC/PCDP 1A-like split)Option 2 (PDCP/RLC Split 3C-like split)Option 3 (High RLC/Low RLC split, Intra RLC split)Option 4 (RLC-MAC split)Option 5 (Intra MAC split)Option 6 (MAC-PHY split)Option 7 (Intra PHY split)Option 8 (PHY-RF split)Option 1 (RRC/PDCP, 1A-like split):  RRC is in the central unit while PDCP, RLC, MAC, physical layer and RF are kept in the distributed unit. Thus the entire user plane is in the distributed unit.Option 2 (PDCP/RLC split): Option 2 may be a base for an X2-like design due to similarity on U-plane, but some functionality may be different e.g. C-plane since some new procedures may be needed. There are two possible variants available in this option.Option 2-1: Split U-plane only (3C like split): In this split option, RRC, PDCP are in the central unit. RLC, MAC, physical layer and RF are in the distributed unit.Option 2-2: In this split option, RRC, PDCP are in the central unit. RLC, MAC, physical layer and RF are in the distributed unit.  In addition, this option can be achieved by separating the RRC and PDCP for the CP stack and the PDCP for the UP stack into different central entities.Option 3 (High RLC/Low RLC Split): In this option, two approaches are taken based on Real time/Non-Real time functions split which are as follows:Option 3-1 Split based on ARQOption 3-2 Split based on TX RLC and RX RLCOption 3-1 Split based on ARQLow RLC may be composed of segmentation functions;High RLC may be composed of ARQ and other RLC functions;This option splits the RLC sublayer into High RLC and Low RLC sublayers such that for RLC Acknowledge Mode operation, all RLC functions may be performed at the High RLC sublayer residing in the central unit, while the segmentation may be performed at the Low RLC sublayer residing in the distributed unit. Option 3-2 Split based on TX RLC and RX RLCLow RLC may be composed of transmitting TM RLC entity, transmitting UM RLC entity, a transmitting side of AM and the routing function of a receiving side of AM, which are related to downlink transmission.High RLC may be composed of receiving TM RLC entity, receiving UM RLC entity and a receiving side of AM except for the routing function and reception of RLC status reports, which are related to uplink transmission.Option 4 (RLC-MAC split): In this split option, RRC, PDCP, and RLC are in the central unit. MAC, physical layer, and RF are in the distributed unit.Option 5 (Intra MAC split):Central Unit- Higher part of the MAC layer (High-MAC), RLC and PDCP.Distributed Unit – RF, physical layer and lower part of the MAC layer (Low-MAC).High-MAC sub layer : the centralized scheduling in the High-MAC sub layer will be in charge of the control of multiple Low-MAC sub layers. It takes high-level centralized scheduling decision. Low-MAC Sublayer the time-critical functions with stringent delay requirements (e.g. HARQ) or the functions where performance is proportional to latency (e.g. radio channel and signal measurements from PHY, random access control). It reduces the delay requirements on the fronthaul interface.Option 6 (MAC-PHY split): The MAC,RLC, PDCP & RRC are in the central unit (CU). PHY layer and RF are in the DU.Option 7 (Intra PHY split): We have 3 types of Sub splits in option 7 as given below:Option 7-1 UL: FFT, CP removal and possibly PRACH filtering functions reside in the DU, the rest of PHY functions reside in the CU.Option 7-1 DL : iFFT and CP addition functions reside in the DU, the rest of PHY functions reside in the CU.Option 7-2 UL: FFT, CP removal, resource de-mapping and possibly pre-filtering functions reside in the DU and rest of PHY functions reside in the CU.Option 7-2 DL:  iFFT, CP addition, resource mapping and precoding functions reside in the DU, the rest of PHY functions reside in the CU.Option 8 (PHY-RF split): This option allows to separate the RF and the PHY layer. Legacy C-RAN. Option 7.2 is called as ORAN split option. For more updates on types of splits and advantages stay tuned on ORAN page of site.

Admin

August 08, 2021

20 Min Read

ORAN

RU/DU/CU Architecture

Radio Unit Interface & Architecture :5G NR radio unit shall be connected to DU through fronthaul RAN low layer split. The DU shall be connected to the CU which connects to the 5G enabled EPC to work along with LTE eNB in Non StandAlone (NSA) mode. At a later time, when the 5G core is ready, the CU will connect to the 5G core as well to support StandAlone (SA) mode Option 2.For the local display Status Indicator LED in the radio unit, it shall have at least the following status indicators:• One for fronthaul transport interface (optical fiber or wireless) indicating on/off status• One for power supply to show on/off status• One for radio transmission link on/off statusFigure below shows RU Interface & Architecture RequirementsRadio Unit HardwareThe radio unit shall be designed in a modular format that each module is connected through a standard interface such as PCIe. The RU is composed of RF front end, digital front end, Ethernet fronthaul transport, synchronization and lower PHY layer baseband processing. The RU functional module diagram is shown in Figure belowThe lower PHY layer processing shall be done by using FPGAs or ASICs. It includes functions of FFT/iFFT, CP addition, PRACH and digital beamforming.The RF front end is composed of antenna element arrays, bandpass filters, power amplifiers, low noise amplifiers, digital analog converters, and analog digital converters.The digital front end consists of digital up converter, digital down converter, digital pre-distortion and crest factor reduction.Distributed Unit:The Distributed Unit (DU) connects to multiple radio units in the southbound interface, and to the Centralized Unit (CU) in the northbound interface. The DU has a centralized, virtualized baseband pool that performs the functions of high PHY layer, MAC and RLC, synchronization, OAM, Ethernet, as well as F1 interface function. The DU function module diagram is shown in Figure below:Distributed Unit Capacity and Software Support:The distributed unit is the baseband processing unit that handles high physical layer, MAC and RLC layer with network function virtualization. The operating system for DU shall support RHEL CentOS 7.x, Ubuntu 16.xx or later release versions. RAN performance KPIs shall be guaranteed under the virtualization implementation. Features such as DPDK, SRIOV are required to enhance the performance. Given the maturity and security, virtualization shall be implemented in VM. Implementation in container will be considered in the future when it becomes mature.Centralized UnitThe Centralized Unit (CU) shall perform the layer three functions such as the functions of RRC, PDCP, SDAP, X2-U, F1-U, NG-U, S1-U, X2AP (X2-C), F1AP (F1-C), NGAP (NG-C), S1AP (S1-C) and OAM . Figure below is the diagram that shows the functions that the CU will perform:NG-U/C interface is used to connect with the 5G core network while the S1-U/C interface is used to connect to the 5G enabled EPC. The simultaneous connection with both core networks is required in order to support different UE capabilities. The initial implementation with connecting to EPC only for NSA architecture is accepted.Ref: Control, User and Synchronization Plane Specifiction, ORAN-WG4.CUS.0-v02.00, Management Plane Specification, ORAN-WG4.MP.0-v02.00.00

Admin

August 08, 2021

20 Min Read

ORAN

High Level Architecture Of ORAN

As per WG1 ORAN alliance spec, figure shown below, the radio side includes Near-RT RIC, O-CU-CP, 17 O-CU-UP, O-DU, and O-RU functions. The E2 interface connects O-eNB to Near-RT RIC. O-eNB does support O-DU and O-RU functions with an Open Fronthaul interface between them.Figure: High Level Architecture ORANService Management and Orchestration (SMO): The SMO is a consolidation of a wide variety of management services and provides many network management like functionalities. In a Service Provider’s Network, the SMO may provide management services that go well beyond RAN management and can include things such as: Core Management, Transport Management, End to End Slice Management etc. The key capabilities of the SMO that provide RAN support in O-RAN are:• FCAPS (Fault, Configuration, Accounting, Performance, Security) interface to O-RAN Network Functions• Non-RT RIC for RAN optimization• O-Cloud Management, Orchestration and Workflow Management.The SMO performs these services through four key interfaces to the O-RAN Elements.• A1 Interface between the Non-RT RIC in the SMO and the Near-RT RIC for RAN Optimization• O1 Interface between the SMO and the O-RAN Network Functions for FCAPS support• Optionally, and only in the hybrid model, Open Fronthaul M-plane interface between SMO and O-RU for FCAPS support• O2 Interface between the SMO and the O-Cloud to provide platform resources and workload management.FCAPS: It is Fault, Configuration, Accounting, Performance, Security which includes following operations:“Start-up” installationSW managementConfiguration managementPerformance managementFault ManagementFile ManagementNon-RT RIC:Non-Real Time RAN Intelligent Controller (Non-RT RIC) is the functionality internal to the SMO in O-RAN architecture that provides the A1 interface to the Near-Real Time RIC.The primary goal of Non-RT RIC is to support intelligent RAN optimization by providing policy-based guidance, ML model management and enrichment information to the near-RT RIC function so that the RAN can optimize, e.g., RRM under certain conditions. It can also perform intelligent radio resource management function in non-real-time interval (i.e., greater than 1 second).Non-RT RIC can use data analytics and AI/ML training/inference to determine the RAN optimization actions for which it can leverage SMO services such as data collection and provisioning services of the O-RAN nodes.O-Cloud Management, Orchestration and Workflow Management :The SMO provides the capability of managing the O-Clouds as well as providing support for the orchestration of platform and application elements and workflow management. The SMO utilizes the O2 interface to the O-Cloud to provide these capabilities. The O2 interface supports the management of the cloud infrastructure and the use of the cloud resources allocated to the RAN. The example functionalities should be supported but are not limited to the following:•Discovery and administration of O-Cloud Resources• Scale-In, Scale-Out for O-Cloud• FCAPS (PM, CM, FM, Communication Surveillance) of O-Cloud• Software Management of Cloud Platform• Create, Delete Deployments and Associated Allocated O-Cloud Resources.Near-RT RIC:It is a logical function that enables near real-time control and optimization of E2 nodes functions and resources via fine grained data collection and actions over the E2 interface with control loops in the order of 10 ms-1s. The Near-RT RIC hosts one or more xApps that use E2 interface to collect near real-time information (e.g. on a UE basis or a Cell basis) and provide value added services. The Near-RT RIC control over the E2 nodes is steered via the policies and the enrichment data provided via A1 from the Non-RT RIC.O-CU-CP: The O-CU-CP terminates the NG-c, X2-c, Xn-c, F1-c and E1 interfaces as well as the RRC and PDCP (for SRB) protocols towards the UE.O-CU-UP: The O-CU-UP terminates the NG-u, X2-u, S1-u, Xn-u, F1-u and E1 interfaces as well as the PDCP and SDAP protocols towards the UE.O-eNB :O eNB is the eNB which is capable to work with ORAN architecture.The O-eNB terminates the S1, X2 and E2 interfaces as well as the RRC, PDCP, RLC, MAC and PHY layers of the LTE-Uu radio interface towards the UE in case O-eNB is an eNB.O-Cloud: O-Cloud is a cloud computing platform comprising a collection of physical infrastructure nodes that meet O-RAN requirements to host the relevant O-RAN functions (i.e., Near-RT RIC, O-CU-CP, O-CU-UP, and O-DU), the supporting software components (such as Operating System, Virtual Machine Monitor, Container Runtime, etc.) and the appropriate management and orchestration functionsInterfaces in O-RAN Architecture:A1 Interface: A1 interface is between Non-RT-RIC and the Near-RT RIC functions. A1 is the interface between the Non-RT RIC function in SMO and the Near-RT RIC function. A1 interface supports three types of services as given below:• Policy Management Service• Enrichment Information Service• ML Model Management Service.O1 Interface: The O1 interface is between O-RAN Managed Element and the management entity,for operation and  management, by which FCAPS management, PNF (Physical Network Function) software management, File management shall be achieved.O2: Interface between management entities and the O-Cloud for supporting O-RAN virtual network functions.

Admin

August 08, 2021

20 Min Read

ORAN

O-RAN:Challenges In ORAN & Function Migration Of 4

Challenges in ORAN/ORAN Deployment.With the move towards Open RANs, operators and integrators need to test that all the Technology works together before it goes into the live network. Best scenario of this challenge concerns the wide range of components being used by different vendors. How do you deliver the best possible service when optimising the configuration of the control plane? Secondly Operators also need to see how this technology interacts with legacy 4G equipment in the network, and how it responds to different UE environments.Another major challenge is, once the technology has been deployed, when a problem arises who solves it and how do you do this? With an Open RAN network, when a problem arises, you must work with multiple vendors to resolve the issue. Who takes the responsibility to resolve the issue when there are multiple vendors involved?Performance perspective ORAN Challenges:Below are the points to focus whenever an operator is adopting ORAN deployment to overcome the challenges:Meeting the Key performance Indicator in a multi-vendor environment.E2E network performance.Keeping an eye on performance when large number of UE’s connected to network with different scenarios.Synchronization of fronthaul (O DU to O RU connection). Here Synchronization plane plays an important role.PHY & MAC coordination: As we are now aware that O-RU contains some functionalities of PHY layer which we call it as Low Phy. So PHY-MAC coordination plays an important role to maintain the performance of ORAN.To overcome the performance related challenges there are lots of use cases an operator can execute and follow, below are some of them:Multi-Vendor Interoperability Test for:ResilienceRobustnessReliabilityFunctionalityPerformanceSystem level Testprotocol compliance tests for open interfaces and protocolsStability TestingStress TestingHigher availability Testing.4G RAN Architecture Versus 5G RAN architecture: Block DiagramAs shown in Figure above, some user plane functions in the 4G LTE core have been moved to the CU and DU, layer 2 (L2) non-real-time and layer 3 (L3) functions have been moved from the BBU to the CU, L2 real-time functions to the DU and layer 1 (L1) functions split between the DU and RU. The mapping of functions to devices results in different “split options” with regard to which layers of the protocol stack are mapped to which device. While the split between CU and DU is now formally defined by 3GPP, there are a number of split options still to be considered for the DU/RU interface.

Admin

August 08, 2021

20 Min Read

ORAN

ORAN -Why,What,When?

Now question here comes in mind Why, What , When ORAN.Why ORAN:Most of the CAPEX required to build a wireless network is related to the RAN segment, reaching as high as 80% of the total network cost. Any reduction in the RAN equipment cost will significantly help the bottom line of wireless operators as they struggle to cope with the challenges of ever increasing mobile traffic and flat revenues. So the deployment cost could drop if if an open architecture is used. Operators are also realizing that opening up the RAN for only 5G will not reduce the overall network cost. The operators believe that modernizing their legacy networks, in addition to deploying 5G, will reduce their overall network OPEX as they will have one unified network to run and will be able to make time and cost-saving remote upgrades to the overall site.What is different types of RAN ?C RAN- It is a deployment model where a BBU that was doing digital processing could be located in a data centre and not on the site itself – under the radio or RRH (remote radio head unit) where the radio processing was happening – and was instead connected to the baseband unit via a dedicated high-bandwidth connection. The C-RAN required a new fronthaul interface, and various industry standards such as the Common Public Radio Interface (CPRI) and the Next Generation Fronthaul Interface (NGFI) evolved to enable these new interfaces between the radios and baseband.V RAN- With vRAN, the proprietary hardware remains as it is, but the BBU gets replaced by a COTS server rather than proprietary hardware. The software that runs on the BBU is virtualized to run on any COTS server. The proprietary interfaces remain as they are.So its very important to understand that VRAN is not necessarily ORAN. VRAN still contains proprietary interfaces and purpose-built hardware.Whereas Open RAN is a movement to define and build 2G, 3G, 4G and 5G RAN solutions based on a general-purpose, vendor-neutral hardware and software-defined technology. Open RAN Is the disaggregation of hardware and software: the RRU / RRH hardware becomes a COTS hardware that can be purchased from any OEM or RAN hardware vendor. The BBU is the same as in the case of vRAN: COTS server + vendor’s proprietary software with virtualized functions.The Open RAN vision is that the RAN is open within all aspects, with the interfaces and operating software separating the RAN control plane from the user plane, building a modular base station software stack that operates on commercial-off-the-shelf (COTS) hardware The software enabled Open RAN network architecture enables a “white box” RAN hardware – meaning that baseband units, radio units and remote radio heads can be assembled from any vendor and managed by Open RAN software to form a truly interoperable and open network.Figure below represents the working of ORAN Deployment Model.When ORAN?The Open RAN TIP group in 2016 has brought together operators, traditional equipment vendors and startups that are using open source technologies and open approaches to get the solution for high costs in the telecom equipment required during deployment.As part of the Telecom Infra Project (TIP), Facebook is working with telecom service providers and operators to accelerate innovation, new technology, to help the industry build the networks of the future. Through this program, Facebook is working with operators in areas that have not been covered with any kind of communication services in various geographies throughout the globe. The cost attractions of Open RAN enabled by interoperability could prove important in such diversified markets from high-income to low-income markets.The O-RAN Alliance was formed after the merger of the C-RAN alliance and XRAN. The O-RAN Alliance publishes new RAN specifications, releases open software for the RAN, and supports its members in integration and testing of their implementations.

Admin

August 08, 2021

20 Min Read

ORAN

ORAN Introduction

IntroductionBefore understanding the architecture of ORAN, First we need to understand the LTE architecture which consist of EPC,eNB and the RF Antenna Unit.The functions in LTE RAN are split so that the Baseband Unit (BBU) and the Remote Radio Head (RRH) can be separated physically. This allows the RRH to be located closer to the antenna, while the BBU can be located in center shown in fig.1afig.1aNow Coming to 5G RAN Architecture as show in fig 1b5G Architecture consist of :a) 5G COREb) 5G RAN divided in to two parts – BBU and RU.c) RF antenna UnitFig 1bBBU is split into CU and DU. Now the question comes What is CU and DU?CU: CU is the centralized unit that runs the RRC,SDAP and PDCP layers.CU further divided into CU CP & CU UP CU-CP: Central Unit – Control Plane: a logical node hosting the RRC and the control plane part of the PDCP protocol CU-UP: Central Unit – User Plane: a logical node hosting the user plane part of the PDCP protocol and the SDAP protocolDU: Distributed Unit: a logical node hosting RLC/MAC/High-PHY layers based on a lower layer functional split.RU: Radio Unit: a logical node hosting Low-PHY layer and RF processing based on a lower layer functional split. More specific in including the Low-PHY layer (FFT/iFFT, PRACH extraction).Now Question comes in mind what is ORAN? What is the need of ORAN?The objective of the O-RAN Alliance is to clearly define requirements for an open, virtualized and interoperable RAN. It has defined two core principles to guide this mission, namely openness and intelligence.In the case of intelligence, the O-RAN architecture has introduced a new type of Software Defined Network (SDN) controller called the RAN Intelligent Controller (RIC), which is responsible for automating the deployment of RAN functions in response to service needs. This includes a near real-time (near-RT) RIC and a non-near-real-time (non-RT) RIC. Both RICs make decisions based on analysis of data collected in the network using deep learning and artificial intelligence.In the case of openness, the O-RAN architecture is based on well defined, open interfaces to enable interoperability between implementations from multiple vendors. This includes the fronthaul interface between the O-DU and O-RU based on split option 7.2x.Near-RT RIC: O-RAN near-real-time RAN Intelligent Controller: a logical function that enables near-real-time control and optimization of RAN elements and resources via fine-grained data collection and actions over E2 interface. It may include AI/ML workflow including model training, inference and updates.Non-RT RIC: O-RAN non-real-time RAN Intelligent Controller: a logical function within SMO that enables non-real time control and optimization of RAN elements and resources, AI/ML workflow including model training, inference and updates, and policy-based guidance of applications/features in Near-RT RIC.Overall Architecture of O-RANFigure below provides a high-level view of the O-RAN architecture. It shows that the four key interfaces – namely, A1, O1, Open Fronthaul M-plane and O2 – connect SMO (Service Management and Orchestration) framework to O RAN network functions and O-Cloud. Figure below also illustrates that the O-RAN network functions can be VNFs (Virtualized Network Function), i.e., VMs or Containers, sitting above the O-Cloud and/or PNFs (Physical Network Function) utilizing customized hardware. All O-RAN network functions are expected to support the O1 interface when interfacing the SMO framework.The Open Fronthaul M-plane interface, between SMO and O-RU, is to support the O-RU management in hybrid model.It is an optional interface to the SMO that is included for backward compatibility purposes.It is intended for management of the O-RU in hybrid mode only.O1: Interface between management entity and O-RAN managed elements.SMO a Service Management and Orchestration system.A1-Interface between Non RT RIC & Near RT RIC.O2- Interface between SMO & O cloud.

Admin

August 08, 2021

20 Min Read

ORAN

Functional Split Option 7 & ORAN Alliance Specifie

In this option as shown in Fig below the lower physical layer functions and RF circuits are located in the DU(s). The upper protocol layers including the upper physical layer functions reside in the CU. There are multiple realizations of this option including asymmetrical implementation of the option in the downlink and uplink (e.g., option 7-1 in the uplink and option 7-2 in the downlink). A compression technique may be applied to reduce the required transport bandwidth between the CU and the DU.This option can to some extent relax the fronthaul throughput requirements and allows centralized scheduling and joint processing in both transmit and receive sides.Also this option will allow traffic aggregation from NR and LTE transmission points to be centralized and can facilitate the management of traffic load between NR and LTE transmission points.The following represent different forms where this option can be implemented:Option 7-1: In this variant, the fast Fourier transform (FFT), CP removal (OFDM processing), and possibly PRACH processing is implemented in the uplink and in the DUs, and the remaining physical layer functions reside in the CU. In the downlink, inverse FFT (IFFT) and CP insertion blocks (OFDM processing) reside in the DUs and the rest of physical layer functions will be performed in the CU. This variant would allow implementation of advanced receivers.Option 7-2: In this variant, FFT, CP removal, resource de-mapping, and possibly MIMO decoding functions are implemented in the DU in the uplink and the remaining physical layer functional processing are performed in the CU. In the downlink, IFFT, CP addition, resource mapping, and MIMO precoding functions are performed in the DU, and the rest of physical layer processing is performed in the CU. This variant also allows the use of advanced receivers for enhanced performance.Option 7-3: This downlink only option implements the channel encoder in the CU, and the rest of physical layer functions are performed in the DU(s). This option can reduce the fronthaul throughput requirements as the payloads consist of the encoded bits.Split Option 7-2x: It is a specification for functional splitting between ORAN DU (O-DU) & ORAN RU (O-RU) adopted by ORAN fronthaul specification.This split option has been introduced by ORAN Alliance to translate highly inefficient CPRI traffic to eCPRI using the low order physical layer 1 processing (Low PHY). In the DL, OFDM phase compensation iFFT, CP addition, and digital beamforming functions reside in the O-RU as well as precoding for Category B O-RUs. The rest of the PHY functions including resource element mapping, precoding, layer mapping, modulation, scrambling, rate matching and coding reside in the O-DU. Precoding must be in the O-DU for Category A O-RU support but this only applies if the number of precoder output spatial streams is 8 or less, otherwise precoding must be in the (Category B) O-RU.In the UL, OFDM phase compensation (for all channels except PRACH) , FFT, CP removal and digital beamforming functions reside in the O-RU. The rest of the PHY functions including resource element de-mapping, equalization, de-modulation, de-scrambling, rate de-matching and de-coding reside in the O-DU.In general, the required fronthaul bandwidth becomes smaller as more functions become entrusted to the O-RU for example compared to CPRI in which O-RU handles only the RF function section only, placing IFFT/FFT processing in O-RU can prevent an increase in the fronthaul required bandwidth caused by over sampling applied to OFDM signal in the time domain. Similarly placing DL precoding in the O-RU can prevent the increase in the required fronthaul bandwidth that occurs when number of MIMO spatial stream is greater than the number of MIMO layers.Next topic will be CPRI & ECPRI functionalities and advantages stay tuned..

Admin

August 07, 2021

20 Min Read

ORAN

Types Of Functional Splits In ORAN/5G NR

Types of Splits:We have three categories of splitsHigh Layer SplitsLow Layer SplitsDouble SplitsHigh Layer Split: It consist of split 2,3,4 & 5.The benefits of opting this functional splits are drastically reduced bandwidth, latency tolerant i.e for long distances.Low Layer Split: It consists of split 6,7 &8. The benefits of opting this functional split are cost effective RRH, Ideal for COMP. It has High Bandwidth requirements and very tight latency requirements.Double Split: Double splits are the splits in which two splits have been considered between RAN i.e CU,DU & RU. Practically we have two double a) Option 2 & 6 , b) option 2 & 7.2.Below figure represents the functional split:B-Haul: Back Haul,F-Haul :Front HaulChoosing a Functional Split:When considering the functional split defining a fronthaul interface there are two competing interests:a) There is a benefit in keeping an O-RU as simple as possible because size, weight, and power draw are primary deciding considerations and the more complex an O-RU, the larger, heavier and more power-hungry the O-RU tends to be.b) There is a benefit in having the interface at a higher level which tends to reduce the interface throughput relative to a lower-level interface – but the higher-level the interface, the more complex the O-RU tends to be.To resolve this, O-RAN has selected a single split point, known as “7-2x” but allows a variation, with the precoding function to be located either “above” the interface in the O-DU or “below” the interface in the O-RU.O-RUs within which the precoding is not done are called “Category A” O-RUs while O-RUs within which the precoding is done are called 27 “Category B” O-RUs.When O-RU Category A is supported by O-DU it is mandatory to support a total number of precoded streams of up to 8. Support for more than 8 precoded streams is optional.Stay tuned for more updates on Split option 7.2x which is an ORAN Split.

Admin

August 07, 2021

20 Min Read

ORAN

High Level Architecture Of ORAN

As per WG1 ORAN alliance spec, figure shown below, the radio side includes Near-RT RIC, O-CU-CP, 17 O-CU-UP, O-DU, and O-RU functions. The E2 interface connects O-eNB to Near-RT RIC. O-eNB does support O-DU and O-RU functions with an Open Fronthaul interface between them.Figure: High Level Architecture ORANService Management and Orchestration (SMO): The SMO is a consolidation of a wide variety of management services and provides many network management like functionalities. In a Service Provider’s Network, the SMO may provide management services that go well beyond RAN management and can include things such as: Core Management, Transport Management, End to End Slice Management etc. The key capabilities of the SMO that provide RAN support in O-RAN are:• FCAPS (Fault, Configuration, Accounting, Performance, Security) interface to O-RAN Network Functions• Non-RT RIC for RAN optimization• O-Cloud Management, Orchestration and Workflow Management.The SMO performs these services through four key interfaces to the O-RAN Elements.• A1 Interface between the Non-RT RIC in the SMO and the Near-RT RIC for RAN Optimization• O1 Interface between the SMO and the O-RAN Network Functions for FCAPS support• Optionally, and only in the hybrid model, Open Fronthaul M-plane interface between SMO and O-RU for FCAPS support• O2 Interface between the SMO and the O-Cloud to provide platform resources and workload management.FCAPS: It is Fault, Configuration, Accounting, Performance, Security which includes following operations:“Start-up” installationSW managementConfiguration managementPerformance managementFault ManagementFile ManagementNon-RT RIC:Non-Real Time RAN Intelligent Controller (Non-RT RIC) is the functionality internal to the SMO in O-RAN architecture that provides the A1 interface to the Near-Real Time RIC.The primary goal of Non-RT RIC is to support intelligent RAN optimization by providing policy-based guidance, ML model management and enrichment information to the near-RT RIC function so that the RAN can optimize, e.g., RRM under certain conditions. It can also perform intelligent radio resource management function in non-real-time interval (i.e., greater than 1 second).Non-RT RIC can use data analytics and AI/ML training/inference to determine the RAN optimization actions for which it can leverage SMO services such as data collection and provisioning services of the O-RAN nodes.O-Cloud Management, Orchestration and Workflow Management :The SMO provides the capability of managing the O-Clouds as well as providing support for the orchestration of platform and application elements and workflow management. The SMO utilizes the O2 interface to the O-Cloud to provide these capabilities. The O2 interface supports the management of the cloud infrastructure and the use of the cloud resources allocated to the RAN. The example functionalities should be supported but are not limited to the following:•Discovery and administration of O-Cloud Resources• Scale-In, Scale-Out for O-Cloud• FCAPS (PM, CM, FM, Communication Surveillance) of O-Cloud• Software Management of Cloud Platform• Create, Delete Deployments and Associated Allocated O-Cloud Resources.Near-RT RIC:It is a logical function that enables near real-time control and optimization of E2 nodes functions and resources via fine grained data collection and actions over the E2 interface with control loops in the order of 10 ms-1s. The Near-RT RIC hosts one or more xApps that use E2 interface to collect near real-time information (e.g. on a UE basis or a Cell basis) and provide value added services. The Near-RT RIC control over the E2 nodes is steered via the policies and the enrichment data provided via A1 from the Non-RT RIC.O-CU-CP: The O-CU-CP terminates the NG-c, X2-c, Xn-c, F1-c and E1 interfaces as well as the RRC and PDCP (for SRB) protocols towards the UE.O-CU-UP: The O-CU-UP terminates the NG-u, X2-u, S1-u, Xn-u, F1-u and E1 interfaces as well as the PDCP and SDAP protocols towards the UE.O-eNB :O eNB is the eNB which is capable to work with ORAN architecture.The O-eNB terminates the S1, X2 and E2 interfaces as well as the RRC, PDCP, RLC, MAC and PHY layers of the LTE-Uu radio interface towards the UE in case O-eNB is an eNB.O-Cloud: O-Cloud is a cloud computing platform comprising a collection of physical infrastructure nodes that meet O-RAN requirements to host the relevant O-RAN functions (i.e., Near-RT RIC, O-CU-CP, O-CU-UP, and O-DU), the supporting software components (such as Operating System, Virtual Machine Monitor, Container Runtime, etc.) and the appropriate management and orchestration functionsInterfaces in O-RAN Architecture:A1 Interface: A1 interface is between Non-RT-RIC and the Near-RT RIC functions. A1 is the interface between the Non-RT RIC function in SMO and the Near-RT RIC function. A1 interface supports three types of services as given below:• Policy Management Service• Enrichment Information Service• ML Model Management Service.O1 Interface: The O1 interface is between O-RAN Managed Element and the management entity,for operation and  management, by which FCAPS management, PNF (Physical Network Function) software management, File management shall be achieved.O2: Interface between management entities and the O-Cloud for supporting O-RAN virtual network functions.

Admin

August 07, 2021

20 Min Read

ORAN

O-RAN:Challenges In ORAN & Function Migration Of 4

Challenges in ORAN/ORAN Deployment.With the move towards Open RANs, operators and integrators need to test that all the Technology works together before it goes into the live network. Best scenario of this challenge concerns the wide range of components being used by different vendors. How do you deliver the best possible service when optimising the configuration of the control plane? Secondly Operators also need to see how this technology interacts with legacy 4G equipment in the network, and how it responds to different UE environments.Another major challenge is, once the technology has been deployed, when a problem arises who solves it and how do you do this? With an Open RAN network, when a problem arises, you must work with multiple vendors to resolve the issue. Who takes the responsibility to resolve the issue when there are multiple vendors involved?Performance perspective ORAN Challenges:Below are the points to focus whenever an operator is adopting ORAN deployment to overcome the challenges:Meeting the Key performance Indicator in a multi-vendor environment.E2E network performance.Keeping an eye on performance when large number of UE’s connected to network with different scenarios.Synchronization of fronthaul (O DU to O RU connection). Here Synchronization plane plays an important role.PHY & MAC coordination: As we are now aware that O-RU contains some functionalities of PHY layer which we call it as Low Phy. So PHY-MAC coordination plays an important role to maintain the performance of ORAN.To overcome the performance related challenges there are lots of use cases an operator can execute and follow, below are some of them:Multi-Vendor Interoperability Test for:ResilienceRobustnessReliabilityFunctionalityPerformanceSystem level Testprotocol compliance tests for open interfaces and protocolsStability TestingStress TestingHigher availability Testing.4G RAN Architecture Versus 5G RAN architecture: Block DiagramAs shown in Figure above, some user plane functions in the 4G LTE core have been moved to the CU and DU, layer 2 (L2) non-real-time and layer 3 (L3) functions have been moved from the BBU to the CU, L2 real-time functions to the DU and layer 1 (L1) functions split between the DU and RU. The mapping of functions to devices results in different “split options” with regard to which layers of the protocol stack are mapped to which device. While the split between CU and DU is now formally defined by 3GPP, there are a number of split options still to be considered for the DU/RU interface.

Admin

August 07, 2021

20 Min Read

ORAN

ORAN Introduction

IntroductionBefore understanding the architecture of ORAN, First we need to understand the LTE architecture which consist of EPC,eNB and the RF Antenna Unit.The functions in LTE RAN are split so that the Baseband Unit (BBU) and the Remote Radio Head (RRH) can be separated physically. This allows the RRH to be located closer to the antenna, while the BBU can be located in center shown in fig.1afig.1aNow Coming to 5G RAN Architecture as show in fig 1b5G Architecture consist of :a) 5G COREb) 5G RAN divided in to two parts – BBU and RU.c) RF antenna UnitFig 1bBBU is split into CU and DU. Now the question comes What is CU and DU?CU: CU is the centralized unit that runs the RRC,SDAP and PDCP layers.CU further divided into CU CP & CU UPCU-CP: Central Unit – Control Plane: a logical node hosting the RRC and the control plane part of the PDCP protocolCU-UP: Central Unit – User Plane: a logical node hosting the user plane part of the PDCP protocol and the SDAP protocolDU: Distributed Unit: a logical node hosting RLC/MAC/High-PHY layers based on a lower layer functional split.RU: Radio Unit: a logical node hosting Low-PHY layer and RF processing based on a lower layer functional split. More specific in including the Low-PHY layer (FFT/iFFT, PRACH extraction).Now Question comes in mind what is ORAN? What is the need of ORAN?The objective of the O-RAN Alliance is to clearly define requirements for an open, virtualized and interoperable RAN. It has defined two core principles to guide this mission, namely openness and intelligence.In the case of intelligence, the O-RAN architecture has introduced a new type of Software Defined Network (SDN) controller called the RAN Intelligent Controller (RIC), which is responsible for automating the deployment of RAN functions in response to service needs. This includes a near real-time (near-RT) RIC and a non-near-real-time (non-RT) RIC. Both RICs make decisions based on analysis of data collected in the network using deep learning and artificial intelligence.In the case of openness, the O-RAN architecture is based on well defined, open interfaces to enable interoperability between implementations from multiple vendors. This includes the fronthaul interface between the O-DU and O-RU based on split option 7.2x.Near-RT RIC: O-RAN near-real-time RAN Intelligent Controller: a logical function that enables near-real-time control and optimization of RAN elements and resources via fine-grained data collection and actions over E2 interface. It may include AI/ML workflow including model training, inference and updates.Non-RT RIC: O-RAN non-real-time RAN Intelligent Controller: a logical function within SMO that enables non-real time control and optimization of RAN elements and resources, AI/ML workflow including model training, inference and updates, and policy-based guidance of applications/features in Near-RT RIC.Overall Architecture of O-RANFigure below provides a high-level view of the O-RAN architecture. It shows that the four key interfaces – namely, A1, O1, Open Fronthaul M-plane and O2 – connect SMO (Service Management and Orchestration) framework to O RAN network functions and O-Cloud. Figure below also illustrates that the O-RAN network functions can be VNFs (Virtualized Network Function), i.e., VMs or Containers, sitting above the O-Cloud and/or PNFs (Physical Network Function) utilizing customized hardware. All O-RAN network functions are expected to support the O1 interface when interfacing the SMO framework.The Open Fronthaul M-plane interface, between SMO and O-RU, is to support the O-RU management in hybrid model.It is an optional interface to the SMO that is included for backward compatibility purposes.It is intended for management of the O-RU in hybrid mode only.O1: Interface between management entity and O-RAN managed elements.SMO a Service Management and Orchestration system.A1-Interface between Non RT RIC & Near RT RIC.O2- Interface between SMO & O cloud.

Admin

August 07, 2021

20 Min Read

ORAN

ORAN -Why,What,When?

Now question here comes in mind Why,What , When ORAN.Why ORAN:Most of the CAPEX required to build a wireless network is related to the RAN segment, reaching as high as 80% of the total network cost. Any reduction in the RAN equipment cost will significantly help the bottom line of wireless operators as they struggle to cope with the challenges of ever increasing mobile traffic and flat revenues. So the deployment cost could drop if if an open architecture is used. Operators are also realizing that opening up the RAN for only 5G will not reduce the overall network cost. The operators believe that modernizing their legacy networks, in addition to deploying 5G, will reduce their overall network OPEX as they will have one unified network to run and will be able to make time and cost-saving remote upgrades to the overall site.What is different types of RAN ?C RAN- It is a deployment model where a BBU that was doing digital processing could be located in a data centre and not on the site itself – under the radio or RRH (remote radio head unit) where the radio processing was happening – and was instead connected to the baseband unit via a dedicated high-bandwidth connection. The C-RAN required a new fronthaul interface, and various industry standards such as the Common Public Radio Interface (CPRI) and the Next Generation Fronthaul Interface (NGFI) evolved to enable these new interfaces between the radios and baseband.V RAN- With vRAN, the proprietary hardware remains as it is, but the BBU gets replaced by a COTS server rather than proprietary hardware. The software that runs on the BBU is virtualized to run on any COTS server. The proprietary interfaces remain as they are.So its very important to understand that VRAN is not necessarily ORAN. VRAN still contains proprietary interfaces and purpose-built hardware.Whereas Open RAN is a movement to define and build 2G, 3G, 4G and 5G RAN solutions based on a general-purpose, vendor-neutral hardware and software-defined technology. Open RAN Is the disaggregation of hardware and software: the RRU / RRH hardware becomes a COTS hardware that can be purchased from any OEM or RAN hardware vendor. The BBU is the same as in the case of vRAN: COTS server + vendor’s proprietary software with virtualized functions.The Open RAN vision is that the RAN is open within all aspects, with the interfaces and operating software separating the RAN control plane from the user plane, building a modular base station software stack that operates on commercial-off-the-shelf (COTS) hardware The software enabled Open RAN network architecture enables a “white box” RAN hardware – meaning that baseband units, radio units and remote radio heads can be assembled from any vendor and managed by Open RAN software to form a truly interoperable and open network.Figure below represents the working of ORAN Deployment Model.When ORAN?The Open RAN TIP group in 2016 has brought together operators, traditional equipment vendors and startups that are using open source technologies and open approaches to get the solution for high costs in the telecom equipment required during deployment.As part of the Telecom Infra Project (TIP), Facebook is working with telecom service providers and operators to accelerate innovation, new technology, to help the industry build the networks of the future. Through this program, Facebook is working with operators in areas that have not been covered with any kind of communication services in various geographies throughout the globe. The cost attractions of Open RAN enabled by interoperability could prove important in such diversified markets from high-income to low-income markets.The O-RAN Alliance was formed after the merger of the C-RAN alliance and XRAN. The O-RAN Alliance publishes new RAN specifications, releases open software for the RAN, and supports its members in integration and testing of their implementations.

Admin

August 07, 2021

20 Min Read