RAN Slicing and QoS Management

RAN slicing creates independent virtualized sub-networks that convert user requirements to different QoS requirements on the network. User requirements are service requirements as specified in CFSSpecs.
These requirements cover scenarios for creating RAN subnet slices and modifying RAN subnet slices as required by created or modified services.

One of the service requirements for creating or modifying a RAN subnet-slice relates to Quality of Service (QoS). QoS Profile allows mapping of packets flowing from UE to Data Network using QoS flows and Data Radio Bearers (DRBs). In 5GNR QoS flows represent logical streams of data packets that have specific QoS requirements.
Rules in the UE and in the RAN map QoS Flows to DRBs. Setting up QoS Profiles and mapping rules is part of the design time activity for the slice.

The following diagrams illustrate a logical diagram of QoS in RAN.

In the figure, each cell is identified by the radio beam and frequency of a Remote Radio Head (RRH) sector.
The Tracking Area Code identifies each cell in a Tracking area
TAI = PLMN ID + TAC
PLMN-ID = MCC + MNC

Ultimately the RAN subnet slice would have its QoS Profile defined at design time via the NST and then mapped to QoS definitions in the CFSSpec. These definitions abstract a specific QoS Profile in the RFSSpec representing the Slice Profile.

QoS characteristics are considered representative of service usage as they are relevant to dynamic decisions made during operations of QoS flow, such as using the priority level as a tiebreaker when two flows compete for resources.
There are many scenarios for QoS events, as seen in the 5G QoS Identifier, 5QI Table available from 3GPP and ETSI.

QoS ER and logical relationships are shown below.

From the figure, each RAN slice is associated with a specific set of QoS parameters that define the desired quality of the slice and its performance characteristics, such as latency, throughput, packet loss, and reliability. These parameters represent the requirements of the applications or services the slice supports and comprise the QoS Profile.

In this example, the slice consumes resources that are primarily radio resources in terms of physical resource blocks in a radio beam that makes up the sector of a cell.

Multiple QoS flows can be mapped to the same QoS Profile.
However, each QoS flow is associated with a single QoS Profile represented by 5QI. The 5QI value defines a set of QoS parameters, such as priority and packet error rate, that can be applied to multiple QoS flows, each identified by its unique QoS Flow Identifier. At runtime, the QoS characteristics work with a priority level.

Multiple QoS flows can be associated with a single RAN slice, as long as the QoS flows have similar QoS requirements that can be met by the same RAN slice. For example, multiple QoS flows carrying video streaming traffic with similar QoS requirements may be associated with a single RAN slice designed to support high data rates and low latency.

If we assume RAN slicing is at the MAC layer (does Qos Scheduling), the Physical Radio Blocks (PRBs) on the radio beams from RRH are allocated to a slice, performed dynamically depending on users allocated to the slice and traffic conditions.

The QoS scheduler determines the appropriate allocation of resources for the RAN slice. The QoS scheduler also assigns Dedicated Radio Bearers (DRBs) to the slice. DRBs are logical connections between the user equipment (UE) and the core network, enabling the transfer of data and control information. Each DRB is associated with specific QoS parameters and represents a dedicated channel for the slice to communicate with the network.

By allocating DRBs based on the QoS requirements, the QoS scheduler enables the identification and creation of different slices within the RAN. Each slice can have its own allocated resource set, including DRBs, allowing for the isolation and customization of services based on the associated QoS parameters.

Mapping of QoS flows to be discussed in future.