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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

by 05 8y ago

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).

mercer 8y ago
> 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?
- woah 8y ago
  There are many reasons. Miniaturized equipment, limited battery, nodes moving around randomly, etc
  - mercer 8y ago
    Can you point me (a complete layman in this area) in a particular direction to get a bit more of a solid understanding of this area? I wouldn't even really know what search terms to use...
- 05 8y ago
  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.
  - mercer 8y ago
    Thanks! aside from being informative, your comment gives me quite a number of specific terms to google :).

by 05 8y ago

mercer 8y ago

> 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?

woah 8y ago
There are many reasons. Miniaturized equipment, limited battery, nodes moving around randomly, etc
- mercer 8y ago
  Can you point me (a complete layman in this area) in a particular direction to get a bit more of a solid understanding of this area? I wouldn't even really know what search terms to use...
05 8y ago
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.
- mercer 8y ago
  Thanks! aside from being informative, your comment gives me quite a number of specific terms to google :).