Dynamic Spectrum Sharing (DSS) – Making 5G Real in 2020

Early adoption/success of 5G hinges on a number of parameters. In the context of US market, an oft-cited parameter is broad availability of mid-band spectrum (e.g. CBRS 3.5GHz and C-Band). But, on the ground today, another parameter is quietly making 5G a “Reality”, even before the arrival of mid-band spectrum. That secret parameter is Dynamic Spectrum Sharing (DSS).

So, What’s Dynamic Spectrum Sharing?

As defined here, Dynamic Spectrum Sharing (DSS) is a technology that allows the deployment of both 4G LTE and 5G New Radio (NR) in the same frequency band and dynamically allocates spectrum resources between the two technologies based on dynamic user demand. For example, let’s consider an operator with 20MHz of spectrum. If they want to offer 5G service, they also need to maintain backward compatibility to their existing 4G LTE service. In the absence of DSS, let’s say, the operator allocates 10MHz of spectrum to 4G LTE and cram all their LTE users into that 10MHz of spectrum. The remaining 10MHz of spectrum is used for 5G, even if there are not a lot of 5G users initially. DSS solves this rigid allocation problem. With DSS, the operator doesn’t have to split the spectrum to have dedicated resources for their 4G LTE or 5G service. Instead, the entire spectrum can be dynamically shared between the two technologies as needed.

Figure-1: 5G NR and LTE TDD DSS Verification by China Mobile and Huawei [Mobile World Live]

DSS enables the allocation of spectrum instantaneously, giving the best possible performance for a mix of 4G and 5G devices on the available capacity.

Why is DSS So Important?

5G new radio (NR) can be deployed in both mm-wave and sub-6GHz spectrums. One of my earlier blog posts shows the 2 frequency ranges (FR) that a 5G NR can adopt-

·        Frequency Range 1 (FR1): 450MHz – 7.125GHz

·        Frequency Range 2 (FR2): 24.25GHz – 52.6GHz

DSS, as part of 3GPP Release 15, allows operators to dynamically allocate some of their existing 4G LTE spectrum to 5G and use existing radio equipment (assuming they are 5G NR-capable) to deliver 5G services by deploying a software upgrade. While FR2 frequencies provide hotspot like capacity boost, FR1 frequencies are considered “inevitable” for any meaningful 5G launch. This need for 5G coverage is magnified in the US market where all 3 initial 5G related spectrum auctions have focused on millimeter-wave (auction 101 for 28GHz, auction 102 for 24GHz, and auction 103 for upper 37GHz, 39GHz, and 47GHz). Sub-6GHz mid-band focused auctions (auction 105 for CBRS 3.5GHz or auction 107 for C-Band 3.7-3.98GHz) are in the horizon, but yet to take place.

That’s where DSS comes to the rescue. In his blog post, Olivier Blanchard @ Futurum has argued that DSS, as 5G’s secret accelerator, starts changing the game in 2020. 

Figure-2: Same cell tower and spectrum dynamically switching between 4G and 5G through DSS [everything RF]

As Olivier narrated, DSS allows a cell tower to segregate slivers of spectrum already being used by 4G users in a specific location; and let a 5G phone user access 5G using that band. In the farming analogy that he used in the blog, DSS allows to plant peppers (5G service) in the gaps between turnips (4G service), and thus maximize every inch of the field. For mobile operators, mobile users, and mobile chipmakers, this is a game-changer as it removes a hurdle that had, for the last two decades considerably slowed down the pace of adoption during transitions between 2G to 3G, then 3G to 4G. DSS will allow 5G phones to operate in multi-mode (all incarnations and subcategories of 4G and 5G like 4G, 4G+, 5G e, 5G, and at some point 5G+) without having to wait for a critical mass of mobile users to upgrade their phones to 5G.

While there are several moving pieces in the DSS ecosystem, top stakeholders such as chipmaker Qualcomm and network infrastructure vendor Ericsson, expect the spectrum maximizing technology to be implemented for commercial use sometime this year. That’s extra ordinary compared to the “re-farming” process (typically taking up to a decade), whereby bands had to be completely cleared of users, of say 4G, before that band could be used to support 5G users.

Ericsson – Leading the Pack

Ericsson claims that it made the first ever 5G data call using DSS. The call was made in August, 2019 at Ericsson’s lab in Ottawa, Canada using an Ericsson macro radio that supported both 4G and 5G. A 5G mobile test device powered by the Qualcomm Snapdragon X55 5G Modem-RF System and a commercial LTE smartphone were used for the test. Last month (February, 2020), Ericsson announced that its DSS technology is in General Availability (GA) phase. Ericsson mentioned that 4 operators are already using its DSS: Swisscom, Telstra, Ooredoo (Qatar) and Play (Poland). Ericsson’s head of high-band and active antenna systems, Sibel Tombaz, even said that the company has 30 engagements with operators that are trialing and launching its DSS.

Ericsson has been testing its DSS with Qualcomm, using mobile devices powered by Qualcomm Snapdragon 865 and 765 Mobile Platforms with Snapdragon 5G Modem-RF Systems. It’s also been working with MediaTek and key device makers including Oppo, Sony, Xiaomi, LG, vivo and Wistron NeWeb Corp (WNC).

Huawei – Tracking Closely but Shut out from the US

Huawei released its Hybrid DSS (HDSS) at Huawei Products & Solutions launch in London on February, 2020. Huawei claims that its HDSS applies to the following 3 scenarios:

1.      5G large-bandwidth scenarios: Where 5G uses continuous large-bandwidth spectrum greater than 20MHz and 4G uses 20MHz

2.      Flexible bandwidth scenarios: Non-standard bandwidths of existing FDD spectrums such as 19.8MHz

3.      Triple-mode scenarios: Three network modes such as 2G/4G/5G, 3G/4G/5G, or NB/4G/5G can dynamically be shared

But, Huawei’s problem in terms of mass world-wide adoption, lies elsewhere. Its essentially prohibited from the North American market, thus making it out of consideration by some large-scale early adopters (e.g. Verizon, AT&T) of DSS.  

Nokia – Playing a Catchup Game?

Nokia is undeniably behind in the development of DSS but it’s making strides to catch up with its competitors. Nokia went on record just before end of 2019 that it would come out with software to support DSS in 2020. Hari Holma, a fellow of Nokia Bell Labs wrote in a blog post - “Nokia will introduce DSS as a software upgrade in line with commercial 5G FDD mass market device availability in 2020.” He continued that DSS would generate real performance gains with 5G standalone networks which are expected from 2021, delivering latency benefits in dense urban environments.

SdxCentral reported that Nokia will have to conduct more tests/trials and earn business with willing network operators before making their DSS product generally available. Nokia claims to be powering the first 5G FDD network in the Unites States (most likely of T-Mobile USA’s 600MHz deployment). This partially explains whey T-Mobile USA is not as aggressive as Verizon to deploy DSS, since their key supplier is not fully ready yet to implement the feature.

Samsung – Targeting 2nd Half of 2020?

FierceWireless reports that Samsung may have a commercial DSS product ready in the latter half of 2020. Samsung maintains that a DSS product is still in testing and development stages and doesn’t provide a firm commercial timeline yet.

However, on the device side, Samsung is making strides. Last month, in partnership with Keysight, Samsung reported that they are collaborating to validate DSS technology in Samsung’s new 5G modem. Immediately after that, Samsung also announced that it’s Galaxy S20, S20+, and S20 Ultra – all 3 new 5G smartphones will support DSS. The S20 Ultra and S20+ device variants support 5G at both sub-6GHz and millimeter-wave frequencies, while the S20 only supports sub-6GHz frequency.

Qualcomm – Enabling the Device Side of the Equation

As reported here, mobile platform leader Qualcomm is propelling the effort forward with crucial products. The DSS implementation timing is contingent on the availability of special chipsets that are required in mobile devices. On the modem front, Qualcomm has already delivered the Snapdragon X55, which supports DSS, and will be available in devices in 2020.  Snapdragon X55 5G modem can be paired with 5G mmWave antenna modules, RF transceivers for 5G sub-6 GHz and LTE, and sub-6 GHz RF front-end modules, to access all major spectrum bands. Here goes Qualcomm’s official announcement on this – “Snapdragon X55 is a 7-nanometer single-chip integrated 5G to 2G multimode modem that supports 5G NR mm-Wave and sub-6 GHz spectrum bands with up to 7 gigabits per second (Gbps) download speeds and 3 Gbps upload speeds over 5G, and Category 22 LTE with up to 2.5 Gbps LTE download speeds. The Snapdragon X55 5G modem is designed for global 5G rollouts with support for all major frequency bands, whether mm-Wave or sub-6 GHz, supports TDD and FDD modes of operations and is capable of both Standalone (SA) and non-standalone (NSA) network deployments – providing flexibility and enabling virtually all deployment types globally. In addition to deployments in greenfield frequency bands allocated for 5G, the Snapdragon X55 modem is engineered to support dynamic spectrum sharing between 4G and 5G, enabling operators to accelerate 5G deployments by using their existing 4G spectrum holdings to deliver both 4G & 5G services dynamically.”

So, Which Carriers are the Early Adopters?

The operator which has been the biggest advocate of DSS of late is Verizon Wireless. At Mobile World Congress Los Angeles 2019, Verizon announced their plan to introduce DSS into its network within 2020 from all 3 major infrastructure vendor partners – Ericsson, Nokia, and Samsung. Stadiums and entertainment arenas were mentioned as their initial DSS deployment targets. “[DSS] will be very important where we have large capacity needs, which would be venues, so while dynamic spectrum sharing will help improve all of our network it will be particularly important in places where you have lots and lots of people that are gathering” quoted Heidi Hemmer, Verizon’s VP of technology. Following the MWC LA announcement, Verizon went ahead with DSS trials at an Ericsson lab in Richardson, Texas. With partners Ericsson and Qualcomm, Verizon successfully tested DSS in over-the-air data call. Among major US operators, DSS capability is arguably most needed for spectrum-constrained Verizon. Verizon’s current 5G offer, based on millimeter-wave spectrum, is concentrated in urban pockets i.e. “hot spots”. DSS will enable it to offer nationwide 5G to counter T-Mobile’s claim of nation-wide 5G coverage using their 600MHz 5G NR deployment. Without DSS, Verizon will find it challenging to cover half of the US population with 5G by the end of 2020. Recently, FierceWireless reported that Verizon’s 2020 DSS rollout plan got a little bit ambiguous, but still it is sticking with it in the face of unrelenting competition vs. the likes of T-Mobile. Verizon owns spectrum in band 2 in the 1900 MHz range, band 4 in the 2100 MHz range, band 5 in the 850 MHz range, and band 13 in the 700 MHz range. FierceWireless has quoted Ookla analyst Milan Milanovic saying, “My assumption would be that they [Verizon] will use band 2, which is deployed everywhere and the AWS band 4. This is a good strategy to compete on 5G coverage.”    

Meanwhile, earlier this year, Vodafone announced that it has conducted the first test of 5G DSS, based on a combination of two low spectrum bands in its Dusseldorf lab. 800MHz and 700MHz were simultaneously used on a 5G non-standalone device, where 800MHz was used as the “anchor band” and 700MHz was used as the “shared band” between 4G and 5G. Vodafone highlighted the significance of low-band DSS in the context of deeper in-building coverage. In a blog post, Vodafone acknowledged its partners – equipment from Ericsson and Huawei, alongside Qualcomm’s X55 mobile test platform.

Among others, European operator Swisscom said about a year ago that it would use DSS from Ericsson as part of its 5G deployment. At that point, thanks to DSS, they expected to have 90% of its population covered with 5G by end of 2019.

In Closing

The Futurum blog nicely captures the value proposition of DSS in the context of 5G’s differentiation with earlier generations of mobile technologies. Essentially, this is another way through which 5G proves to be a radical departure from 4G. It highlights the degree to which the discussions we have about 5G need to start moving beyond gigabits per second speed tests. It’s not only about download speeds anymore. The focus here is on network intelligence. DSS is not made available only by squeezing the network itself. Rather, it came from the silicon side, and was fine-tuned by participants across the ecosystem, chief among them Qualcomm and Ericsson. Global 5G deployments began in 2019, but thanks to Dynamic Spectrum Sharing and solutions like the snapdragon X55 finding their way into 5G phones in 2020, transitioning from 4G to 5G will occur much faster and more smoothly than the transition from 3G to 4G.