How low-band 5G will underpin always-on connections

When the fifth generation of mobile cellular connectivity was unveiled, there was breathless talk of its transformative effects.

The reality has been rather less impressive.

There are 4G networks capable of distributing data faster than 5G, while the latter’s rollout has been delayed by legal challenges, coronavirus and violent resistance from conspiracy theorists.

Today, there’s little benefit to having a 5G mobile data contract for your handset, and few consumers have bothered signing up to one.

In large measure, this is because we’re only currently using a sliver of the 5G network’s potential bandwidth.

At present, 5G data is exclusively distributed using frequencies between 3.4 and 3.6GHz – midway between the bandwidths harnessed by dual-band broadband routers.

However, this won’t remain the case forever. And the introduction of low-band 5G in particular will finally unleash this technology’s potential for always-on connectivity.

They go high, we go low-band

When digital data is broadcast through the air, it’s transmitted at a specific frequency which electronic devices can receive and interpret.

As frequencies increase, the distance data can reliably travel declines. However, the volume of data which can be distributed increases – as does the speed at which it’s carried.

The ultimate plan for 5G is to use high-frequency local transmitters to broadcast gigabit data speeds across the 24-39GHz wavebands, within a radius of around one square mile.

That will support the intensive activities promised at 5G’s launch, like latency-free gaming and 4K streaming through mobile devices.

However, we were also promised 5G would be universally available. No more climbing up children’s slides to get a signal, as The Thick of It unforgettably depicted.

This always-on connectivity will rely on low-band 5G, broadcast at around 700MHz. At this frequency, transfer speeds are relatively sluggish, but range is huge.

Analogue TV towers broadcasting on the 600MHz frequency covered hundreds of square miles, so a similarly-sized cellular mast transmitting at 700MHz should service a comparable catchment area.

And although connections would be slow compared to high-band coverage, T-Mobile has achieved 225Mbps over low-band 5G – still much faster than today’s typical 4G connections.

This guaranteed connectivity will be required if 5G is to achieve its full potential in areas like self-piloting vehicles, where momentary signal loss simply can’t be contemplated.

The slowest 5G connections should be comparable with today’s 4G, while the fastest will eclipse anything currently achievable – even across full fibre broadband services.

However, these two extremes will be supported by a mid-band 5G network, using the existing 3.4-3.6GHz frequencies as well as other unused data bands.

Ofcom’s long-delayed 700MHz frequency auctions will take place in March, allowing the UK’s big four mobile networks to finally begin broadcasting low-band signals.

After that, mid-band and high-band transmission will be prioritised, enabling consumers to finally experience 5G’s potential for the first time.