June 12 2020

Dynamic Spectrum Sharing, a Key Technology That Supports 5G in The Limited Spectrum

One of the key issues for the evolution of telecommunications networks is an optimal management of radio spectrum. Currently, to be able to deploy 5G capabilities it is necessary to make more licenced spectrum available for mobile service providers.

National and governmental agencies should play a key role in releasing this spectrum to service providers. In addition, given that certain parts of the radio frequency spectrums are already heavily congested, technological innovation also plays a significant role in proposing alternatives where government agencies cannot reach.

The National 5G Plan (Spanish 5G Plan, editor’s note) for 2018-2020 defines a series of actions related to the planning and management of radio spectrum aimed at ensuring the availability, in appropriate timeframes, of the different frequency bands necessary for the provision of communications services over 5G networks. To be able to offer a wide coverage, 5G services require a spectrum in the low spectrum ranges (below 1 GHz), medium spectrum (1 GHz-7 GHz) and high spectrum (+24 GHz). Actually, for 5G we are speaking about the following frequency ranges: FR1 (410 MHz-7.2 GHz) and FR2 (24.25 GHz-52.6 GHz), although the latest ITU-World Radio Conference-2019 has identified a new radio spectrum from 66 GHz to 71 GHz that will require a modification of the 3GPP’s specifications for FR2.

This National 5G Plan also establishes the process for the release of the second digital dividend, by which the 700 MHz band of the radio spectrum used so far by the Terrestrial Digital Television (Televisión Digital Terrestre, TDT) to enable that 5G telecommunications networks are deployed. The 700 MHz band auction was scheduled for the first half of 2020, but due to the Covid-19 crisis spectrum auctioning had to be delayed until early 2021. For the telecoms sector it is very important that this tender suffers as little delays as possible, since the low bands are key to the development of 5G technology. This is because it allows for widespread coverage in urban, suburban, and rural areas, and also contributes to the advancement of IoT services. 

Given the current situation, it is desirable to keep 5G spectrum prices moderate, as high prices could limit network investments and increase the cost of services. By the way, this is, among other, one of the recommendations that the GSMA gives in its 5G Spectrum GSMA Public Policy Position.

The Dynamic Spectrum Sharing Alternative

In order to help Communication Service Providers (CSPs) in evolving their networks to support 5G, versus finite spectrum resources, telecommunication equipment manufacturers together with the 3GPP have been developing new functionalities that allow the simultaneous sharing of radio spectrum between various generations of technologies (4G and 5G). This makes costly refarming unnecessary. Dynamic Spectrum Sharing (DSS) enables the coexistence of LTE (4G) and NR (5G) at the same carrier frequencies, and therefore on the same base station hardware. Through intelligent programming algorithms (scheduling), DSS allows sharing the same spectrum and adjusting the amount of spectrum available for each technology based on the needs of the users, which are measured in real time and therefore can change quickly.

One of the main advantages of using DSS is that it does not require new nodes to be introduced into the network; RAN product software already installed can be updated to include such functionality. From the point of view of 4G mobile devices, the combination of LTE and NR is transparent to them, so they will work without any modifications. While spectrum sharing has been focused on 4G and 5G, manufacturers are already working on new features such as the ability to simultaneously share traffic from three radio access technologies (3G, 4G, and 5G). It will also be interesting to employ higher bandwidth bands for 5G in DSS than for 4G (e.g. 20 MHz LTE and 50 MHz NR, instead of 20 MHz each).

DSS technology is of particular importance to operators who are deploying 5G in the existing low or medium band spectrum in order to achieve broad coverage with 5G services while making a more efficient use of spectrum assets.

While it is true that DSS presents some other challenges that needs to be overcome, such as the overhead added to traffic due to the increase of 4G and 5G control channels that are mandatory for network coordination and control purposes, it is also a fact that a significant number of operators around the world, such as Swisscom, Play, Telstra, Ooredoo, VodafoneZiggo, Telia, AT&T or Verizon, have seen the added value of DSS and have already started to deploy this technology on their networks. Many of these deployments use the ESS (Ericsson Spectrum Sharing) solution, which is one of the most effective solutions in dynamic spectrum allocation currently available. While there will still be operators who prefer to dedicate separate frequency bands to 4G and 5G respectively, there is no doubt that DSS will be key to speeding up the deployment of 5G and implementing new value-adding use cases regardless of the development of spectrum award processes and thus avoiding the deployment of expensive new radio infrastructures.


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