From Scroll to Stream: How 5G Instantly Adjusts Your Data Path

Adarsh Saini
Jul 25
5 min read

Dynamic Bearer Allocation in 5G: What Happens When QoS Changes?

Imagine you're browsing social media on your smartphone, a task that doesn’t require significant network resources. Suddenly, you receive a high-definition video call. Instantly, the service requirements change :- low latency, high reliability, and sufficient bandwidth become critical. The network must respond in real time, reallocating resources to meet the updated Quality of Service (QoS) requirements. This transition is enabled through dynamic bearer allocation in 5G.

But what exactly are Data Radio Bearers (DRBs)? DRBs are logical channels that transport user data between the device (UE) and the network, each configured with specific QoS parameters such as latency, reliability, and throughput. These parameters enable the network to differentiate between traffic types and allocate resources accordingly. By adjusting DRBs in response to application demands, the network maintains the required service quality across various use cases.

4G also supports the dynamic allocation of Data Radio Bearers (DRBs), but the key difference in 5G lies in its on-the-fly, flow-based QoS management. This enables the network to respond more accurately and efficiently to varying user and application demands, supporting a broader range of services with more stringent performance requirements.

The diagram illustrates the distinction between bandwidth usage with and without QoS enforcement.

How 5G Detects and Responds to QoS Changes (Backed by 3GPP)

In 5G, each type of service runs through a bearer, a virtual connection associated with one or more QoS flows. These flows are governed by parameters such as latency, reliability, and throughput, ensuring consistent performance depending on the service type (e.g., voice call vs. video streaming). These concepts are defined in the 3GPP specifications, particularly in TS 23.501 (System Architecture) and TS 23.502 (Procedures).

When a user's service type changes, such as moving from web browsing to a video call, the network must adapt the bearer setup accordingly. This change is detected by the Policy Control Function (PCF) or Application Function (AF), which notifies the Session Management Function (SMF). As specified in 3GPP TS 23.502, the SMF evaluates whether the current QoS flow can meet the new service requirements or if a new one must be established.

Component	Function
UE (User Equipment)	Sends and receives user traffic; initiates QoS requests.
gNB	Allocates DRBs; maps QoS flows to RLC and PDCP layers.
UPF (User Plane Function)	Routes data packets; applies QoS policies and traffic steering.
SMF (Session Management Function)	Manages session context and bearer setup/modification.
PCF (Policy Control Function)	Provides QoS and policy rules to SMF.

Network Functions Behind Bearer Reallocation

Once the need for change is confirmed, the SMF collaborates with the Access and Mobility Management Function (AMF) and the gNB (Next Generation Node B) to modify or reassign the Data Radio Bearers (DRBs). The gNB, as defined in 3GPP TS 38.300, is responsible for configuring these DRBs to reflect the updated QoS profile. This may involve reusing an existing DRB, mapping multiple QoS flows to a single bearer, or establishing a new one.

These updates are transmitted to the User Equipment (UE) using RRC signaling protocols, specifically described in TS 38.331, ensuring the ongoing session is not disrupted.

Real-Time, Intelligent Decision-Making

Bearer decisions are influenced by key parameters defined in TS 23.501, including:

· 5QI (5G QoS Identifier): 5QI is a scalar value that maps to a predefined set of QoS characteristics such as priority level, packet delay budget, and packet error rate. It standardizes QoS treatment across the network for different types of traffic (e.g., voice, video, or web).

· ARP (Allocation and Retention Priority): ARP defines the priority of a QoS flow during resource contention, determining whether a bearer can be established or retained under limited network capacity. It is critical for congestion management and admission control.

· GBR/Non-GBR Status (Guaranteed Bit Rate): GBR bearers ensure a minimum guaranteed data rate for latency-sensitive services like voice or video calls. Non-GBR bearers provide best-effort delivery, suitable for less sensitive applications such as web browsing or file transfers.

For example, a Zoom meeting may require a low-latency bearer with 5QI = 2, while YouTube video streaming may use a bearer with 5QI = 8, prioritizing throughput over latency.

If the network encounters congestion or the user moves between cells, the SMF can dynamically re-evaluate the setup to maintain QoS and optimize resource use.

This diagram shows how different types of data from your smartphone (such as video calls or streaming) are handled in a 5G network. Each data flow is matched with a specific path based on its quality requirements, then routed through the network to the appropriate service, such as WhatsApp, Netflix, or voice calls, as referenced from: https://www.techplayon.com/5g-quality-of-service/

Companies Actively Using or Contributing to 5G QoS Technologies

Leading telecom and technology companies, such as Qualcomm, Ericsson, and Huawei, are at the forefront of advancing dynamic QoS management and bearer reallocation in 5G. These firms are driving innovation through patented technologies and practical network deployments.

Case Study: Vodafone and Ericsson – AI-Driven QoS in Spain

Vodafone and Ericsson worked together on a real-world 5G trial in Spain to test how artificial intelligence (AI) can help improve network performance. In this trial, AI was used to monitor how users were using the network, including streaming videos, making calls, or playing games, and then predict what kind of service they would need next.

Based on these predictions, the system automatically adjusted network settings such as how quickly data needed to be delivered (delay budget) and how important that data was (priority). This helped keep the user experience smooth, especially when users were moving between areas (like during handovers) or when the network was busy. The trial showed that AI can play a big role in making 5G networks smarter and more responsive in real-time situations.

Conclusion: Flexibility and Performance, Defined by 3GPP

The 3GPP-defined architecture and procedures empower 5G networks to dynamically reallocate bearers in real time, responding to evolving Quality of Service (QoS) demands. Key control plane functions, including the Policy Control Function (PCF), Session Management Function (SMF), Access and Mobility Management Function (AMF), and the gNB, collaborate to orchestrate on-the-fly adjustments of Data Radio Bearers (DRBs) based on service type, user behavior, and network conditions. This fine-grained, flow-based QoS management marks a significant evolution from previous generations, enabling application-aware resource allocation for services ranging from ultra-low-latency gaming to high-throughput video streaming.

However, these advancements are not without challenges. Real-time bearer reallocation requires ultra-low signaling latency, efficient coordination across control plane entities, and intelligent traffic classification, all of which place significant demands on processing power and system design. To overcome these constraints, ongoing research is focused on AI-driven QoS prediction, edge-based traffic optimization, and autonomous network slicing. These innovations aim to further enhance network responsiveness, reduce signaling overhead, and pave the way for next-generation services such as tactile internet, immersive AR/VR, and mission-critical IoT.

3GPP References