What is the minimum bandwidth ?
if I wanted to establish voice and SMS only communication service what would be the best spectrum of radio band and minimum bandwidth requirements
- amania_rLv 71 month agoFavorite Answer
SMS has no minimum bandwidth requirement although traditionally it was carried over a 64Kbps SS7 signalling channel.
Traditional voice (1G and 2G networks) is carried over a 64Kbps channel but these days with 3G/4G it's all just data and isn't channelized.
But you can't just use radio spectrum - it's highly regulated as it is shared by everything from aircraft, maritime, military, emergency services etc and it's very easy to interfere with other bands.
- ?Lv 71 month ago
Voice can be compressed to very low data rates (<10Kbps) by using lossy algorithms. Cell phones have used some very aggressive compression methods but the resulting quality was poor. Today modulation technology has provided better RF efficiency allowing for better audio quality. Data can also be compressed but requires loss-less methods.
- derframLv 71 month ago
A simple AM signal will have a bandwidth of 2x the maximum modulating frequency. A single sideband (SSB) signal will require half of that and improve the efficiency of the transmitter.
SMS is a defined protocol. If you simply want to send digital data and are not concerned about how fast you send it, you can reduce the required bandwidth to near zero.
- Markus ImhofLv 71 month ago
Too many variables - there is no single "best" and "minimum" requirements based on those few constraints you gave.
Range, number of subscribers, do you want a cell based setup, do you want/need baseless operation, coexistence with other services, legal regulations, etc. pp. ad. inf.
Short google... this cisco paper https://www.cisco.com/c/en/us/support/docs/voice/v... for example quotes numbers below 10 kbps for a voice connection. How much radio bandwidth you'll need for that data rate will then depend on the SNR you can reliably achieve - a 1024 QAM would just need to transmit 10 symbols/s for these 10 kbps (ok, make it 20 symbols/s if you want to include a reasonable protocol overhead) - but would in reality only work within a couple of dozen (unobstructed) meters around the counterpart.
On the other hand, you could set up a pseudo-randomized spread spectrum system that would require an enormous bandwidth, but only a very low power per bandwidth, efffectively flying under the radar of all other users of this frequency and/or enabling thousands of users to communicate simultaneously.
On the third hand, if you want to use existing hardware (always the cheapest option, especially considering that, in practice, that hardware has to be ok'ed by umpteen certification bodies in each country you would want to use it), you'll have to go with what this hardware offers (and what the certifcation/frequency authorities in the respective countries you want to operate in will permit/offer you as spectrum).
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- billrussell42Lv 71 month ago
depends on distance and power. And what FCC license you have, assuming this is in the US.