Multi-Radio Spectrum Sharing (MRSS) and/or Dual-Stack for Initial 6G Rollouts

Having presented the 6G spectrum approaches a few times, one of the discussion topics that always comes up is spectrum sharing in 6G. One of the key challenges in previous generational transitions has been how to efficiently reuse spectrum without degrading performance. I have blogged about the 5G Dynamic Spectrum Sharing (DSS) approach before. While DSS was introduced to allow 4G and 5G to share the same spectrum, its practical deployment was hindered by legacy overheads and the limitations of older equipment. Nokia has documented these issues and lessons learned from DSS in their whitepaper 'Simplifying Spectrum Migration from 5G to 6G'.

5G’s design, however, is far better suited to coexist with future 6G networks, making Multi-Radio Spectrum Sharing (MRSS) a promising tool for spectrum migration.

As we look towards the rollout of 6G in the 2030 timeframe, the telecom industry is focusing not only on new technologies but also on how to smoothly evolve from existing 5G deployments. Two critical enablers of this transition are MRRS and Dual-Stack approaches. These aim to maximise the value of existing investments while paving the way for new capabilities.

MRSS enables the simultaneous use of the same frequency band by both 5G and 6G. Unlike DSS, which was constrained by LTE reference signals and legacy device limitations, MRSS can leverage the flexible and forward-compatible 5G physical layer. This enables more efficient sharing without the interference challenges seen in earlier solutions. MRSS is expected to play a key role in the early phases of 6G deployment, especially in sub-7 GHz and low-band frequencies where broad coverage is essential. By deploying MMRSS in these bands, operators can deliver wide-area 6G coverage while continuing to serve 5G users.

However, not all areas will support MRSS immediately or across all bands. In such scenarios, a Dual-Stack strategy can complement MRSS. This involves devices with independent transceivers for 5G and 6G, allowing simultaneous and separate connections to both networks. By handling the complexity of interworking within the device, Dual-Stack simplifies network integration and enhances the user experience. This enables better throughput, greater reliability and more adaptable service delivery based on application needs or operator policies.

Dual-Stack also supports spectrum aggregation across different bands without impacting legacy services, while allowing continued use of existing 4G and 5G infrastructure, including voice and other operator capabilities. Since it separates the 5G and 6G radio access networks, there is no need for tight coupling between the two, giving operators more flexibility in how and where 6G is introduced.

As many operators are likely to have a mix of standalone (SA) and non-standalone (NSA) 5G deployments when 6G begins to roll out, both MRSS and Dual-Stack offer a practical and cost-effective path forward. The focus is not on forcing a hardware refresh, but on reusing as much existing infrastructure as possible, extending the return on current investments.

The next phase of 3GPP work, including Release 20, will study MRSS and 5G-6G mobility in greater detail. This will help standardise these mechanisms and provide guidance for global adoption.

With spectrum decisions expected at the World Radiocommunication Conference in 2027 (WRC-27), and new 6G bands likely to become available in the early 2030s, the industry is preparing for a smooth and evolutionary path to 6G. MRSS and Dual-Stack will be central to this transition, enabling continuity, efficiency and readiness for what lies ahead.

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