DECT NR+: A technical dive into non-cellular 5G

[throw0101b]

From a few days ago, "What is DECT-2020 New Radio (NR), and how big a deal is it?":

* https://news.ycombinator.com/item?id=39849335

[martinky24]

Same OP, same linked domain. Interesting. This blog post is significantly more thorough than the last one they posted.

[londons_explore]

Smart move calling what is effectively an entirely new standard "DECT" to get free use of DECT's old frequency bands that are barely used by their original use for cordless phones anymore...

[_trampeltier]

DECT is still used a lot in factorys even today. It's way faster to type a short number, usually between 100 .. 999. The often used contacts you know anyway and you don't have to search in contacts. If the phone drops, nobody does care. DECT phones on work are great.

Ask HN: Why no mobile phone can also be used as a DECT phone? https://news.ycombinator.com/item?id=20909535

[gruez]

The bands themselves are unlicensed; anyone can use them. You don't have to be specifically called "DECT" to use them.

[jschveibinz]

This can be a game-changer for certain low bandwidth unlicensed applications where the ongoing cost of cellular or satellite service makes the application economically infeasible. I could envision a whole layer of startup opportunities based on this technology from commercial applications like pets, construction, fleet management, security, and agriculture to a gazillion defense and intel applications. If I were younger, I would definitely dig into this further and compare it to LoRA and other existing radio technologies. Cheers!

[thijson]

This seems to be an order of magnitude better than LoRa (https://lora-alliance.org/ not https://arxiv.org/abs/2106.09685). LoRa doesn't have all the features this one does like OFDM, TDM, FDM, and HARQ. I didn't know there's spectrum dedicated for DECT use.

[londons_explore]

Why limit mesh topologies to cluster-trees? There are plenty of more efficient ways to route data...

I'd design it having message flooding for peer discovery (no hop limit, but a bandwidth limit - never use more than 0.1% of the total throughput for flooded messages).

Then, once connections are established, pick a few best routes, and send some proportion of data down each. Weight the paths via a cost function that takes into account load of each node, power use/availability of each node, impact of each flow on other flows (prefer getting nodes to transmit who cause least interference to other flows), etc.

Over time, adjust proportions of data down different routes to minimize the cost function.

[5ADBEEF]

This is what Wirepas is doing with their mesh network. They have a DECT version coming soon

[londons_explore]

Is this an unauthenticated mesh? Ie. might my neighbours device be forwarding data for my device and vice versa?

[londons_explore]

I want to see more unauthenticated mesh protocols.

By allowing 'unauthenticated' meshing, the total radio throughput in a typical urban environment is dramatically increased. By 2x or more often. Typical packets will take more hops at much reduced transmit powers each time.

The main reason not to do so is "what if my neighbour has crappy devices and black holes all my packets".

But your neighbour can already jam the whole spectrum and block all your packets. We design devices to meet specifications for a reason - and if the spec says "you must forward all packets according to this spec", and you mod your device to blackhole your neighbours packets, then the FCC will consider that jamming and treat it the same.

[5ADBEEF]

Not an unauthenticated mesh. This will be up user implementation iirc

[Animats]

Who administers the network? How is it monitored? This has the complexity of a small cellular network.

[sargun]

Does there exist DECT NR+ equipment yet? I imagine you can use the same RANs for this as "5G", but those are ridiculously expensive. What about mobile devices?

[aidenn0]

TFA mentions this[1], but it's not IoT cheap.

1: https://www.mouser.com/ProductDetail/Nordic-Semiconductor/NR...

[solarkraft]

Great! Another thing that can be bashed into the term "5G" for marketing unrelated technologies.