NTT Docomo has released a white paper with an initial vision of what 6G will entail. Since every mobile generation since 2G has increased speeds and lowered latency, while connection density grew dramatically between 4G and 5G, we might look first to those metrics for change.
Docomo suggests peak data rates of 100 Gbps, latency under one millisecond and device connection density of 10 million devices in each square kilometer would be design goals.
Along with continued progress on the coverage dimension, 6G standards might extend to space, sky and sea communications as well. Docomo also believes quality of service mechanisms exceeding “five nines” and device performance (no charging devices, cheaper devices) would be parts of the standard.
Looking at commercial, economic or social impact, since the 3G era we have tended to see a lag of execution compared to expectations. In other words, many proposed 3G use cases did not emerge until 4G. Some might say a few key 4G use cases will not flourish until 5G is well underway.
For that reason, we might also discover that many proposed 5G innovations will not actually become typical until the 6G era. Autonomous vehicles are likely to provide an example.
So Docomo focuses on 6G outcomes instead of network performance metrics. Docomo talks about “solving social problems” as much as “every place on the ground, sky, and sea” having communications capability. Likewise, 6G might be expected to support the cyber-physical dimensions of experience.
Also, 5G is the first mobile platform to include key support for machine-to-machine communication, instead of primarily focusing on ways to improve communication between humans. Docomo believes 6G will deepen that trend.
It is worth noting that the 5G spec for the air interface entails availability higher than the traditional telecom standard of “five nines” (availability of 99.999 percent). 5G networks are designed to run at “six nines.” So 6G might well run at up to “seven nines” (99.99999 percent availability).
The legacy telecom standard of five nines meant outages or service unavailability of 5.26 minutes a year. The 5G standard equates to less than 32 seconds of network unavailability each year. A seven nines standard means 3.16 seconds of unavailability each year.
Some might say 4G was the first of the digital era platforms to design in support for internet of things (machines and computers talking to machines and computers) instead of the more traditional human mobile phone user. That trend is likely to be extended in the 6G era, with more design support for applications and use cases, with artificial intelligence support being a key design goal as well.
In part, that shift to applications and use cases is more important as the wringing of traditional performance out of the network becomes less critical than new use cases taking advantage of performance boosts.
As it already is the case that almost no consumer users actually “need” gigabit speeds, much less speeds in the hundreds of megabits per second, so few human users or sensors will actually “need” the 6G levels of throughput and latency.
Architecturally, the evolution towards smaller cells will continue, in part to support millimeter wave frequencies, in part to assure better connectivity. Where traditional cell architectures have emphasized non-overlapping coverage, 6G networks might use orthogonally non-aligned cells (overlapping), deliberately overlapping to assure connectivity.
That almost certainly will require more development of low-cost beam forming and signal path control. Having cheap artificial intelligence is going to hope, one might suggest.
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