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17 May 2022

Samsung focuses on sub-THz spectrum, AI and duplexing in its 6G vision

Samsung has set out its own view of the roadmap to 6G in a white paper, ‘6G Spectrum: Expanding the Frontier’, calling for a huge expansion of millimeter wave spectrum availability to support the innovations that the industry can deliver.  


Last time Samsung offered significant details about its 6G R&D efforts and vision was in mid-2020, when it published its first white paper on the topic, though last fall it also made a pledge to invest $205bn over three years in chips for advanced technologies, including 6G. In 2020, Samsung was also focusing on high frequency spectrum, including the sub-Terahertz bands around 100 GHz. However, even two years ago, the discussion seemed bluesky and somewhat abstract, whereas in mid-2022, vendors and operators are well aware that it may be only six years until 6G standardization processes begin, and eight years before the first deployments.  


Of course, there is still significant dispute and uncertainty over what 6G will look like, especially whether it will be an enhancement of 5G or something new. From the commercial point of view, operators are insistent that they cannot support another complete change of architecture, and that they will need at least two decades to get the most out of their 5G investments, in terms of performance and ROI. 


But they made that argument at the start of 5G, and were defeated by an industry rush towards a new platform. The counter-argument to the ‘no more Gs’ view is that the user experiences required in the emerging world of metaverses and ubiquitous AI will not be adequately supported by current technologies. Brand new architectures and protocols will be essential.  


Not all the investment in developing these will come from the conventional telecoms industry. Hyperscalers are currently in the catseat for developing the conventions and frameworks that govern a cloud-based world, and they will be very influential in 6G, whatever that looks like – though potentially there will be additional hyperscalers, or other new power players, to join the mix. That would ease the burden on telcos and their supply chains, of supporting the whole financing of the 5G-Advanced and 6G era roll-outs, but it would also threaten to sideline them in the value chain. 


One thing that most players agree upon is that high frequency spectrum will be important to support the capacity and network/edge density that emerging, hyper-real digital worlds will require. Current spectrum allocations will run out swiftly once 6G use cases start to be developed, argues Samsung in its latest discussion of its own interpretation of the roadmap. Opening up sub-THz bands, which can go all the way up to 300 GHz, will be essential to enable terabit connections and support applications such as immersive extended reality (XR). 


“Exclusive use for mobile communications in the limited frequency resources is becoming more and more difficult. It leads us to examine sub-THz band to find a massive amount of greenfield contiguous spectrum,” Samsung said in the white paper released Sunday. It envisages the ‘midband’, which currently hovers around 2.5 GHz to 3.5 GHz for 5G, moving up as high as 24 GHz, claiming the 7 GHz to 24 GHz range can support “faster data speed and reasonable coverage”, although the sub-1 GHz band would remain essential for indoor penetration and ubiquitous coverage. 


But even 24 GHz will not support enough capacity for 6G purposes and, while the millimeter wave bands (in 5G, from 24 GHz to 92 GHz) will arguably be more important and monetizable in 6G, the upper boundary must be raised to 300 GHz for ultra-high capacity and ultra-low latency services. 

This is not a discussion for the distant future, argues the Korean vendor. Regulators and policy makers also need to start evaluating the options for opening up and allocating 6G spectrum as soon as possible, Samsung argues, because of the “fundamental and technical challenges” of deploying commercial wireless networks in these frequencies.  


There are other reasons, beyond Samsung’s, that mean 6G is no longer just a bluesky discussion or a piece of marketing nonsense.  


The semiconductor industry needs to start work on R&D to understand how very high frequencies can be supported in mainstream processes and affordable chips. This was a significant challenge to the use of mmWave spectrum for commercial wireless communications, even though the bands had long been used by the defence industry, until IBM and Toshiba scored a major breakthrough in 2007, implementing 60 GHz modems in CMOS, bringing the cost down to mass market levels. Similar work will be needed to make sub-THz commercially viable for modem and device makers. 


Also, there are decisions to be made about spectrum sharing or repurposing, since many  sub-THz are already in use for applications such as astronomy, space exploration and radio location service. More disputes between the telecoms and satellite/space industries may loom if the issues and solutions are not addressed at an early stage. 


The two specific sub-THz spectrum bands that Samsung has identified as being of particular interest are the W-band (92-114.25 GHz) and the D-band (130-174.8 GHz) – are heavily used by radio astronomy and space research, and the W-band currently includes some small segments where radio transmissions are banned entirely. 3GPP conducted a preliminary examination of the W-band in relation to 5G, and so some research is already underway, but Samsung points out that it would take many years to  

complete a spectrum plan that would support commercial services. 


The paper is not all about new spectrum for new use cases. It also discussed the potential to repurpose, eventually, all the currently allocated mobile bands for 6G in order to support new applications and experiences, but also evolutions of current ones, from a common network and platform.  


To add substance to its argument, Samsung details its own test of sub-THz spectrum to deliver 6Gbps data rates over 15 meters indoors, and 2.3Gbps over 120 meters outdoors.  


It also identifies a few candidate technologies that could help to achieve full 6G experiences, even if they are being initially developed for 5G. These include reconfigurable intelligent surface (RIS) panels, which support very flexible beamsteering to improve the range and penetration of high frequency signals.  


There is also a focus on emerging duplex methods such as cross-division duplex (XDD) and full duplex. The former could improve the propagation distance of TDD uplink signals by up to two times, “dramatically enhancing the coverage of the TDD system often used in high frequency bands”. 


Full duplex is a technology that has been developed in cable, 5G and WiFi networks to support simultaneous transmission and reception in the same frequency, doubling data rates because there is no need to divide by frequency or time. Samsung has trialled this technology in mmWave bands and it is also the focus of several start-ups such as Kumu. Samsung said it achieved a 1.9 times improvement in data rate in its test, with the base station and terminal placed 100 meters apart. 


Of course, AI will be an inherent part of 6G – not just a tool to enhance automation and analytics as it is in 5G, but present in every element and process of the 6G platform. Two examples given by Samsung are AI-based non-linearity compensation (AI-NC) and AI-based energy saving (AI-ES). The former could be used to improve signal coverage and quality – Samsung has run tests that achieved 1.9 times better coverage for high speed uplink data transmissions with 1.5 times better speed. 


AI-ES is another technology that is starting to be developed and deployed for 5G, but could have a far greater impact in 6G if the future networks are designed from scratch with AI concepts in mind. AI-ES adjusts parameters for switching power on or off, or up and down, at selected base stations, depending on traffic load, while keeping network QoS consistent for the users.  


Sunghyun Choi, head of the Advanced Communications Research Center at Samsung Research, commented that Samsung’s 6G vision is to bring “the next hyper-connected experience to every corner of life”.