Wireless Service Providers can tap spectrum currently used for 4G to launch nationwide 5G coverage with a simple network software upgrade, and deploy a “5G Ready” network to operate on 4G today, with easy upgrade to 5G without disruption. Dynamic spectrum sharing is widely viewed as a key short-term enabler of scaling out 5G networks quickly. Rather than the slow, expensive process of re-farming spectrum from one generation connectivity technology to the next, DSS lets operators operate LTE and 5G NR in the same band at the same time.
What is Dynamic Spectrum Sharing (DSS) ?
Dynamic Spectrum Sharing (DSS) is emerging as a key part of mobile service providers’ 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 – 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 – 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.
Dynamic spectrum sharing vs. static spectrum sharing
Static spectrum sharing or "spectrum re-farming" was a great transition from 2G and 3G to 4G. It's a very tiresome procedure with several constraints and huge preparation. Static spectrum sharing force mobile service providers to divise the spectrum betweend two rats with the same way all over the network and there is a high probability to impact network performances, otherwise it will create interference between RATs. Dynamic Spectrum Sharing will allow “soft” re-farming to NR with minimal impact to LTE performance.
Dynamic spectrum sharing advantages
Besides 5G NSA sites Wireless Service Providers can extend 5G coverage by activating DSS on 4G side network. DSS rollout benefits:
- Resuse existing 4G spectrum
- Resuse existing antenna
- Reuse existing RF
- Ressources shared dynamically between 4G and 5G
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.
Dynamic spectrum sharing scenarios
Wireless Service Providers can 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. Or deploy DSS with shared baseband card for 4G and for 5G, which obviously precludes a multi-vendor solution for 4G and 5G. The second solution it's the optimum scenario if the existing hardware supporting DSS Feature.
Frequency bands proposed for DSS between 4G and 5G
Deploying 5G in low spectrum bands enhances network coverage. In general, low spectrum bands deliver wider coverage than high spectrum bands. As a result, mobile network operators need to secure additional low-band NR bands or deploy coverage densification solutions.
By deploying 5G in low spectrum bands, coverage can be expanded at a faster rate. In addition, when 5G carrier aggregation (CA) is used to aggregate the low- and mid-bands, the control and signaling message can be transferred to the low frequency band, while the data rate can be boosted with extended coverage in mid-band. This has a direct improvement on the overall cell performance. As a result, mobile network operators can provide faster cell throughput and extended coverage.
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Carrier aggregation between TDD bands and FDD Mid bands
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