
How real simultaneous dual band Wi-Fi enables next-gen in-vehicle connectivity - rbanffy
https://www.embedded.com/electronics-blogs/say-what-/4460853/How-real-simultaneous-dual-band-Wi-Fi-enables-next-generation-in-vehicle-connectivity
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wallflower
I've heard that we will not be able to have autonomous cars until 5G is
everywhere. 4G is simply not fast enough to support any near real-time car to
car communication.

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Gys
'If intelligent traffic management becomes a reality in future cities, more
and more self-driving cars will appear on the road. To guarantee traffic
safety, when a control command, braking for example, is sent to a car, the car
must receive the command within 1 ms.

The latency of a 4G network cannot meet this requirement. With the latency of
4G network, a car driving at 100 km/h still moves 1.4 m from the time it finds
a obstacle to the time when the braking command is executed.

Under the same condition, with the latency on a 5G network, the car will move
just 2.8 cm, and this performance is comparable with the standard of an anti-
lock braking system (ABS).'

From:
[https://www.huawei.com/minisite/5g/en/defining-5g.html](https://www.huawei.com/minisite/5g/en/defining-5g.html)

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crooked-v
> To guarantee traffic safety, when a control command, braking for example, is
> sent to a car, the car must receive the command within 1 ms.

> With the latency of 4G network, a car driving at 100 km/h still moves 1.4 m
> from the time it finds a obstacle to the time when the braking command is
> executed.

I'm a fan of self-driving cars, but I would never buy one that depends on an
external network to know when to brake.

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patagonia
So car-to-car communication is likely to be supported by industry before
mobile-to-mobile communication is widespread. Based on cars requiring real-
time, local data. Sad.

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05
The only mobile to mobile communications that make sense _are_ widespread -
WiFi direct and Bluetooth; both AirDrop and Airplay utilize WiFi direct. Peer
to peer protocols on mobile is a great way to achieve horrible bandwidth, even
worse latency and excellent battery drain. There are no benefits vs just using
direct connections over ipv6 (where available). If you need local real-time
data on a smartphone, just use a BLE beacon for low bandwidth or WiFi
multicast for high.

Also V2V is vaporware that isn’t actually needed for safe self-driving cars,
because the cars have to safely interact with human-driven vehicles (the
majority of cars on the road for the next 10 years).

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mercer
> Peer to peer protocols on mobile is a great way to achieve horrible
> bandwidth, even worse latency and excellent battery drain.

Is there some purely technical reason why this is the case, or is it mostly
that nobody has bothered to make this efficient/fast?

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05
Modern radios’ high power efficiencies are achieved through multiple means;
adaptive signal strength and low duty cycles are some of those. Both antennas
being small and low on the ground means much lower RSSI, which causes higher
adaptive transmission power and higher duty cycle due to lower SnR meaning
lower bandwidth and increased retransmissions. Normally, device negitiates a
paging interval at which it gets new data notifications from the base station.
With multiple devices, you have to wake up N times as often because each of
your N peers has a different paging time, and you’d have to also wake up even
more for new peer discovery. Average one-way latency can’t be lower than half
the length of your paging period when your receiver is off times the number of
hops to the target.

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mercer
Thanks! aside from being informative, your comment gives me quite a number of
specific terms to google :).

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Endy
I'm just waiting for the massive deadly accidents to happen when some teenager
hacks the system and decides to have "fun".

