News Researchers demo ultra-low-power Passive Wi-Fi

I never considered WiFi to be very power hungry but having thought about it i guess it must be seeing as (i think) they're mini radio transmitters and how big some commercial transmitters were.

 

There's no such thing as a free lunch in physics.

Less power used means less power transmitted, which consequently translates into worse SNR (assuming one can establish a bidirectional connection in the first place ...).

Plus there's the bit about "passive WiFi" re-modulating and re-radiating received signals, which does nothing for power savings at the remote end (so only one end of a connection can employ this "passive WiFi").

Interesting achievement from technical point of view though although I don't see it ever making a significant impact (I'm not into "smart" houses due to security concerns and this is pretty much useless for any other use).

 

Powering cat cams for longer would be a boon for all them YouTube videos, how can that not be considered a significant impact.

 

Alecto - have a read about M2M and IoT. It's MASSIVE

 

Perhaps if they develop some custom bulletproof protocol that gives 100% priority to reliability - but to me, reliability and low power consumption do not often go hand in hand. Not in industrial areas. Pretty much every single sensor/actuator/etc is connected by wire and higher level control systems do not really like missing or erratic signals.

Also in industry where you have motors, big inverters, long power cables carrying massive currents and generally a lot of EM noise, low power wireless might not be the best solution.

Personally I would expect this in IoT, which has been picking up speed nicely in last few months.

 

Ah, did not know that, seems I spend too much time with my type of machines and it starts to show
Thanks for the heads up!

 

Surely anything utilising the wifi would be powered anyway?

 

Wifi is incredibly power hungry - many people aren't aware, because they never turn it off. For my phone, my battery might last 3 days with wifi on. With it off, it lasts a full week. My laptop might last 3 hours with wifi, and around 4 or 5 hours with wifi off.

I would like to clarify that it doesn't matter if I'm actively using the internet connection. If I do, the lifespan shrinks even more.


As for practicality, I definitely see a lot of great purposes for this (particularly in robotics) but generally speaking, passive wifi doesn't have much leverage in such purposes:
* If you need the bandwidth, 802.11b speeds might not be good enough. Other forms of wifi will outperform it; maybe even non-passive b will outperform, since it's a more "solid" connection.
* If you need good range at low energy consumption, there are plenty of low-power radios that have ranges of hundreds of meters. Slow data rate (usually 9600bps or less) though.
* Depending on the version of Bluetooth you're looking at, you can effectively get the same speed, range, reliability, and security with BT. BT is usually a much cheaper technology, but, I'm not sure if it's more power efficient than passive wifi.


I'm not trashing this feature though. There are definitely uses for passive wifi, but it's definitely a niche.

 

I understand that, and I did read that part. But under what conditions? Even when bluetooth has an established connection, it uses almost no energy at all if there is no data being transmitted. Wifi, however, will use more energy than Bluetooth even if there isn't an established connection (in my experience, anyway).

So, it's not that I don't think passive wifi can't use 1000x less energy, but it could be at the cost of reliability, speed, and/or security (in comparison to bluetooth).