5G with Dynamic Spectrum Sharing (DSS) is a game-changer
Wireless Service Providers can tap spectrum currently used for 4G to launch nationwide 5G coverage with a simple network software upgrade, and deploy a โ5G Readyโ network to operate on 4G today, with easy upgrade to 5G without disruption.
What is Dynamic Spectrum Sharing (DSS)?
Dynamic Spectrum Sharing (DSS) is emerging as a key part of mobile service providersโ 5G strategy. Using cellular base stations with DSS offers the lowest total cost of ownership (TCO) to launch 5G in bands currently used for 4G โ enabling nationwide 5G coverage in short time after launch. Dynamic Spectrum Sharing allows an existing LTE carrier to operate 5G New Radio (NR) and LTE simultaneously โ with a simple software upgrade. The solution is based on innovative intelligent scheduler algorithms that enable optimal performance as the mix of 4G and 5G devices in the network changes over time.
From the early stages of research into 5G NR, when developers began to map 5G transmissions to time-frequency resources, the developers created the possibility for holes in the 5G transmission grid which could be used for 4G LTE transmissions. This means that, by simultaneously sharing frequency bands which are already available today, service providers can fire up 5G on existing LTE bands without actually shutting off LTE. This means that, as well as having the option to roll out 5G on existing DSS-compatible 4G hardware, operators can keep the LTE network up and running while starting 5G. This can make it far easier for operators to transition to 5G in the coming years.
How does DSS work?
The 5G physical layer is designed to be so similar to 4G in 3GPP that DSS becomes feasible with the same subcarrier spacing and similar time domain structure. DSS is designed to be backwards compatible with all existing LTE devices. communication service providers (CSPs) therefore need to maintain LTE cell reference signal (CRS) transmission. 5G transmission is designed around LTE CRS in an approach called CRS rate matching.
DSS with 5G carrier aggregation (CA) releases the full potential of the technology, especially when combined with standalone (SA) architecture. CA provides the highest data rates while SA maximizes low-band coverage and access to 5G services. DSS will be supported by a growing number of 5G devices from 2020 onwards, with widespread support for devices with DSS, SA and CA available during the course of 2021. The
introduction of DSS capability therefore aligns with the growing availability of devices
One option is for DSS to use a single shared baseband card for 4G and for 5G, which obviously precludes a multi-vendor solution for 4G and 5G. The other option is to keep the existing 4G baseband and add a new 5G baseband. The scheduling between the two baseband functions is then based on a fast Xp interface between 4G and 5G. This interface is not open and works only for a single vendor, so CSPs must use the same vendor in 4G and 5G if they use DSS
Conclusions
DSS is a great solution for flexibly refarming spectrum to 5G. Operators can build a โ5G readyโ network today, operating in 4G, and switch over partially โ or fully โ to 5G at any later date, without losing back-compatibility for 4G device users
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