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22 November 2022

MediaTek releases 5G chipset but WiFi 7 capability steals the show

Taiwan’s fabless semiconductor firm MediaTek has claimed to be first to market with a WiFi 7-ready smartphone platform based on a chipset that primarily targets 5G.

The new chipset, called Dimensity 9200, also highlights the rising importance of support for immersive gaming and high-resolution image capture at the chip level to harness the increased capabilities of either 5G or WiFi 7. Increased energy efficiency is also critical, both for sustaining battery life and avoiding overheating under assault from more computationally intensive applications, as JC Hsu, general manager of MediaTek’s wireless communications business, was keen to underline.

“MediaTek’s Dimensity 9200 combines ultimate performance with significant power savings, extending battery life and keeping smartphones cool,” said Hsu.

The firm indicated that new technologies on the chip saved power consumption by up to 30% compared to its previous 5G versions. Power management is enhanced by a dual-antenna system allowing intelligent switching rapidly between high performance and ultra-low power according to varying user needs.

The firm also noted 6.5Gbps headline data rates and incorporation of machine learning algorithms on the chip to improve connectivity performance by, for example, accelerating network search and recovery out of dead zones.

MediaTek further claimed that Dimensity 9200 is the first smartphone chip to integrate an ARM Cortex X3 processor core with operating speeds over 3 GHz, as well as the first to feature the ARM Immortalis-G715 graphics processing unit (GPU), with a hardware-based ray-tracing engine. Hardware for ray-tracing has become standard on commercial graphics cards since 2018, allowing simulation of various optical effects such as shadows, reflections, motion blur and field depth, but it is relatively new to standard system-on-chip (SoC) designs.

It is a recursive process that begins by tracing paths pixel-by-pixel onto the projected image, and then taking account of lighting effects from neighboring areas as a result of refraction, reflection, or other methods, using basic principles of 3D geometry.

The WiFi 7 support in the SoC comes before formal standardization next year but can still be taken as market-ready because all the fundamental specifications have been settled. These include the operating spectrum and Multi-Link Operation (MLO) –  three-link operation in this case, across the long-established 2.4 GHz and 5 GHz WiFi bands, as well as the 6 GHz band introduced with WiFi 6E and currently being rolled out.

Combined with access to additional spectrum higher in the 6 GHz spectrum, including the upper bands above 6.5 GHz, MLO will achieve similar benefits for WiFi as its counterpart, carrier aggregation, does for cellular. It allows multiple frequency blocks to be assigned to the same user or device. The key step here is that under WiFi 7, the access point (AP) is in control of channel selection rather than the client, so that end devices can be switched transparently between them without disassociation in the process imposing latency. In this way WiFi 7 will achieve more deterministic latency with less variation over a session, as well as the greater capacity enabled by wider channels.

The focus, then, is on a combination of higher throughput and lower latency as required for demanding use cases in both the consumer and enterprise spheres, such as cloud gaming, extended reality (XR) and industrial edge compute. On the capacity front the key step is supporting 320 MHz-wide channels, which although theoretically achievable in any band, is in practice only possible in the 6 GHz band because that is where the spectrum is available. The objective is to reach speeds of 30Gbps at least for sustainable bursts by combining those 320 GHz channels in the 6 GHz arena with the lower 2.4 GHz and 5 GHz bands, which can then also be used for lower priority best effort processes.

The one trickier aspect concerns not the frequency bands themselves but the maximum power output allowed for WiFi 7 indoors and outdoors. This issue surfaced first in the USA, where regulator FCC had to reconcile the requirements of new unlicensed users with legacy licensed users such as operators of fixed satellite services (FSS).

At first this looked like hobbling WiFi in this band, but then the FCC came up with its two-tier Automated Frequency Coordination (AFC) system, to shield incumbent licensed users while allowing WiFi devices to operate at higher output to ensure adequate range. One category was defined for low-power APs for indoor WiFi-only use, and others for standard-power APs for indoor and outdoor use.

Early this year, the FCC conditionally approved AFC schemes from a number of vendors, including Broadcom, Google, Nokia, Federated Wireless and Qualcomm, as well as the WiFi Alliance. This involved testing followed by a probation period during which any member of the public could conduct tests.

AFC appears to fix the power output problem, but that only applies in the USA, and MediaTek suggests that means that users in other countries may not get the full benefit of WiFi 7’s increased capacity. That seems curious since the power output restrictions AFC addresses were themselves imposed only in the USA. The implication is that similar restrictions apply in other jurisdictions, a point that MediaTek was unable to comment on.

It is clear that there is still debate and uncertainty over the allocation of spectrum across the upper part of the 6 GHz band, which is needed to achieve the full promise of WiFi 7, both at country and global level. The USA took a lead here by considering the whole 5.925-7.125 GHz band in its considerations almost from the outset, followed by some other quite early movers, such as South Korea, Brazi, and Saudi Arabia, but Europe lagged behind by focusing only on the lower half of the band. This was not of much consequence for WiFi 6/6E but would be, if still unresolved for WiFi 7, because it might preclude use of those larger 32 MHz channels.

Europe seems to have been waiting for the World Radio Conference 2023 conference, scheduled for September and October next year, to resolve the issue at a global level, but meanwhile the industry is already moving towards early WiFi 7 deployments around that time. The key step will be enabling use of this band for higher-power outdoor use, with the first move being low-power indoor use, as with the FCC AFC schemes.

Some countries, such as the UK, have embarked on the first step, with regulator Ofcom starting a consultation to add the 6425-7070 MHz band to its Shared Access licensing framework for low-power, indoor use, in February 2022. But Ofcom cited lack of demand in that upper 6 GHz band and so decided not to proceed with proposals to add that to the shared framework.

Ofcom then began to focus more on assessing whether high-power licence exemption could be a suitable use of the band, promising to feed that into preparations for WRC-23.

The global picture for WiFi 7 spectrum will not then be clear until after WRC-23 in almost a year’s time. But platforms such as MediaTek’s could presumably be adjusted in software for different deployment situations providing they support the underlying MLO.