Explainer: What is 5G network slicing and why telcos oppose Trai's proposal

5G slicing rules have exposed a split over how network congestion should be measured, with Trai pushing safeguards and operators warning that its 80 per cent PRB threshold could constrain networks

The Telecom Regulatory Authority of India (Trai) released draft amendments in August to bring 5G network slicing under its quality-of-service (QoS) framework. The proposals include advance disclosures before launching a new slice, separate QoS requirements for different slices, and a requirement to keep Physical Resource Block (PRB) utilisation below 80 per cent in areas where slicing is deployed.

 

It is the PRB rules that the Reliance Jio, Bharti Airtel and Vodafone Idea (Vi) have now pushed back against. They argue that PRB utilisation is an internal network parameter and does not directly tell the regulator whether customers are actually receiving poor service.

 

 

That disagreement gets to the heart of the 5G slicing debate: how do you allow operators to give a network different characteristics for different users or services without allowing those specialised services to hurt everyone else?

What is 5G network slicing?

A mobile network normally has to serve very different kinds of traffic using the same underlying infrastructure. A person watching a video, an industrial robot that needs very low latency and a security camera sending a constant stream of data may have very different connectivity requirements.

Network slicing allows an operator to create multiple virtual networks on top of the same physical network. Each slice can be configured for a particular requirement, such as higher reliability, lower latency or more consistent throughput.

 

Think of the physical network as a shared road. Instead of sending every vehicle through exactly the same traffic system, the operator can create virtual lanes with different rules and performance characteristics. The underlying towers, spectrum and other infrastructure are still shared, but network resources can be allocated differently.

 

Network slicing is primarily associated with 5G, particularly 5G Standalone (SA). The 5G SA architecture has a dedicated 5G core and was designed with network slicing as a built-in capability. 5G Non-Standalone networks, which use a 4G core, do not offer the same end-to-end slicing capabilities.

 

That does not mean 4G cannot prioritise traffic or allocate resources differently. Long-Term Evolution (LTE) has its own mechanisms for managing radio resources and quality of service. In fact, PRB itself is a basic unit used by both 4G LTE and 5G radio networks. But the virtual, end-to-end network slicing being discussed in India's current regulatory debate is a 5G capability.

How 5G slicing reached India's consumers

For much of India's 5G rollout, the focus was on getting faster mobile broadband to as many people as possible. Network slicing introduced a different possibility: using the same 5G infrastructure to provide differentiated connectivity.

 

Bharti Airtel brought that debate into the consumer market in May 2026 when it launched Priority Postpaid, India's first commercial consumer offering based on 5G network slicing. The service was designed to provide postpaid users with a more consistent network experience, particularly when traffic demand was high.

 

Airtel later renamed the service Fast Lane while retaining the underlying 5G slicing technology.

 

This was significant because network slicing had generally been discussed in the context of enterprise applications. A factory could, for example, require a low-latency slice for industrial equipment, while another customer could use the same network for ordinary broadband traffic.

Airtel extended the concept to ordinary consumers by putting postpaid subscribers on a dedicated slice. That immediately raised a question around India's net neutrality framework: if two subscribers are accessing the same internet services, can one receive a better network experience simply because they are on a different plan?

 

Trai initially indicated that Airtel's service did not appear to violate existing net neutrality rules, while continuing to examine whether it could affect the experience of other 5G users.

 

Jio and Vi took different positions during that debate. Jio argued that network slicing is a legitimate 5G capability while seeking safeguards around how differentiated services are implemented. Vi raised concerns about preferential treatment based on the type of subscriber.

 

The scale of India's 5G market makes the issue more relevant.

 

According to the June 2026 edition of the Ericsson Mobility Report, India had 430 million 5G subscriptions at the end of 2025, accounting for 35 per cent of total mobile subscriptions. While 4G remains the dominant technology with a 46 per cent share, the report forecasts its subscriber base to decline sharply from around 570 million in 2025 to nearly 160 million by 2031 as users migrate to 5G networks.

Why did Trai propose new rules?

Airtel's launch gave Trai a practical example of something that had previously been largely a technology discussion.

 

The regulator's concern is that if an operator reserves or dynamically allocates network capacity to a specialised slice, there needs to be some way of ensuring that ordinary users do not end up with worse service because of it.

 

Trai's August consultation paper therefore proposed amendments to its 2024 QoS regulations. Under the draft, operators planning to introduce a new 5G network slice would have to provide details of the proposed and existing slices at least 21 days before launch. Each Enhanced Mobile Broadband (eMBB) slice would also be treated as a separate tariff offering with its own QoS requirements.

 

The most important proposal concerns network capacity.

 

Trai wants operators to monitor PRB utilisation in cells where slicing is deployed. Less than 1 per cent of tested 5G cells should have daily PRB utilisation above 80 per cent. If utilisation stays above 80 per cent for five days in a month, the operator would have to augment capacity. If congestion continues, the affected cells could eventually have to be removed from network slicing.

 

The logic is that a slice should not consume so much of a cell's available radio capacity that the remaining users are left with insufficient headroom.

 

This is where the telecom operators have drawn the line.

Why are operators pushing back?

Airtel, Jio and Vi agree that customer QoS needs to be protected. Their disagreement is over how Trai proposes to measure that risk.

 

In its comments to Trai, Airtel argued that PRB utilisation is an internal radio-resource indicator rather than a customer-facing QoS metric. According to the company's submission, higher PRB utilisation does not automatically mean customers are experiencing poor service.

 

Airtel also argued that an arbitrary 80 per cent ceiling could force operators to add capacity to cells that are already delivering satisfactory throughput. That could result in what the company described as artificial network constraints and inefficient allocation of capital.

 

Jio made a similar argument. In its submission, Jio said making 80 per cent utilisation a mandatory trigger to suspend slicing would be operationally unfeasible because modern 5G networks are designed to use spectrum efficiently even at high utilisation levels. Jio also argued that tying slicing to utilisation could effectively restrict how operators use their auctioned spectrum.

 

Vi has also opposed a cell-level utilisation threshold. The operator argued that slicing is specifically intended to be useful when network resources are constrained, and that if spare capacity is available, users can already access the highest possible throughput.

The debate is not as clear-cut

There is some support for the operators' technical argument outside the telecom companies.

 

The GSMA, the global telecom industry association, said PRB utilisation is a useful internal planning indicator but should not be used on its own as a regulatory measure of congestion or QoS. High utilisation during a cell's busiest period does not necessarily prove that users are receiving poor service or that a particular slice caused the load, the GSMA said in its submission.

 

But there is also a case for having a capacity safeguard.

 

In its submission to Trai, The Dialogue, a public policy think tank, supported the idea of using capacity utilisation as a safeguard against slices degrading the wider network, although it argued that Trai should use other measures alongside it.

 

The Digital Communications India Forum (DCIF) also supports the basic idea of a safeguard. In its submission to Trai, it said network slicing should not adversely affect ordinary subscribers and that PRB utilisation could be used as an early-warning and capacity-planning indicator. But it also argued that PRB should be correlated with actual consumer outcomes such as throughput, latency and availability, rather than being treated as the sole measure of congestion.

 

That is ultimately the problem Trai is trying to solve. A network can show high internal resource utilisation while still delivering good service to customers. At the same time, a slice that receives preferential treatment during congestion could potentially affect users outside that slice.

 

The regulator therefore has to decide whether PRB utilisation should be a hard regulatory threshold, one of several indicators, or replaced by metrics that directly measure what customers experience.