5 ms·
This won't replace HAM radio in a disaster scenario. This might provide a long-distance digital comms capability post-disaster. Even then, LoRa throughput is so
by missosoup 7y ago
This won't replace HAM radio in a disaster scenario. This might provide a long-distance digital comms capability post-disaster. Even then, LoRa throughput is so low that I don't see how it would be useful unless an entire region goes full zombie apocalypse and this network replaces... I don't know, messenger pigeons?
In a long range configuration, LoRa has a theoretical max throughput of about 140bps (bits) and that's assuming only one device is transmitting and no packet loss.
LoRa is built for low power, long range, low throughput sensor networks. It's not really suitable for a chatty mesh network. To get an idea of the intended use for it, take a look at LoRaWAN limits:
* An average of 30 seconds uplink time on air, per day, per device.
* At most 10 downlink messages per day, including the ACKs for confirmed uplinks.
* A good goal is to keep the application payload under 12 bytes, and the interval between messages at least several minutes.
- sitkack 7y agoA messenger pigeon could at least cary 1TB of micro sd card data. LoRa is like less than the symbol rate of honey bees.
- TimTheTinker 7y ago“Never underestimate the bandwidth of a station wagon full of tapes going down the highway.” -Andrew Tanenbaum ... or a carrier pidgeon with an SD card, it would seem :-)
- eeZah7Ux 7y agoSD cards are tiny. Probably 20 or 30TB.
- blotter_paper 7y agoThis seems to check out. Given 1TB micro SD cards, a card weight of 2.55 grams each, a carrier pigeon being able to hold 75 grams, and the unrealistic but good enough assumption of no further weight being carried (e.g. tape or something else to keep everything from falling off the pigeon), we get 75 / 2.55 = 29.4117647059 (or 29 even taking the floor, since it doesn't make much sense for a pigeon to carry a partial card). All these numbers are from google summaries, without further source checking.
- Matumio 7y agoYeah but during zombie apocalypse you don't know what else that pigeon might be carrying.
- AstralStorm 7y agoAlso your TB sized packet might get lost, or eaten. Couriers are more reliable, though still not perfect.
- dmos62 7y agoBut if you lose that carrier pigeon to zombie crows, you lose the SD cards. No factory to make new ones. The risk/reward ratio would be intolerable.
- noonespecial 7y agoWhat is the symbol rate of an sd laden carrier pigeon? African or European?
- deleted 7y ago[deleted]
- missosoup 7y agoWell, you have to know these things when you're a king, you know.
- Johnny555 7y agoIn a long range configuration, LoRa has a theoretical max throughput of about 140bps (bits) and that's assuming only one device is transmitting and no packet loss. Human speech has an average rate of 39bps.
- vvanders 7y agoYou might want to let Motorola know since DMR needs needs multiple orders of magnitude(2-4 kbps) for their voice codec.
- Johnny555 7y agoThat's the bitrate of a codec to transmit speech that humans can hear and understand... but the actual rate of data communicated by speech is about 39 bps -- and that's pretty universal, regardless of language: https://www.sciencemag.org/news/2019/09/human-speech-may-have-universal-transmission-rate-39-bits-second https://www.sciencemag.org/news/2019/09/human-speech-may-hav...
- missosoup 7y agohow is this number useful or comparable to digital codecs that are being discussed here? It's an interesting piece of research sure, but I don't see the relevance
- Johnny555 7y agoBecause voice comms are typically used by hams in disaster response -- you pointed out that LoRa tops out at 140 bits, so I responded that that's still 3X faster than voice.
- missosoup 7y agoAs explained above, the most efficient voice codecs still need orders of magnitude more than that. This magical 39 bit codec doesn't exist and probably won't ever exist. Even if it did exist, it loses information like timing, identity of the speaker (how they sound), and their tone. By the time you encode all of that, you'll be right back around the range of dmr. And if you're willing to discard all that, then just use digital text in the first place.
- madengr 7y agoThe SX1276 will do 9380 bps at its lowest sensitivity, so it could be boosted, depending on range. FSK mode will go much faster. I wonder if these disaster radios will auto negotiate rates.
- namibj 7y agoI would probably prefer a DSSS with a DSSS-compatible CSPRNG similar to AES/CFB. Does anyone know such a cryptographic system?