Re: [Freetel-codec2] Codec2 repeater

Oops, I obviously meant multi-user multi-carrier, aka on demand carrier allocation. Was tired last night. Here is my motivation: in our country we have a national analog network based on svxlink, and when a user transmits he is heard across the country on a single audio channel, but this means

Re: [Freetel-codec2] Codec2 repeater

Hi Gullik, Using Carson's rule, minimum orthogonal shift 4-FSK looks like it occupies slightly less bandwidth than minimum orthogonal shift 2-FSK (but slightly less != half the bandwidth). The minimum frequency shift between adjacent FSK tones for them to be orthogonal is half of the symbol

Re: [Freetel-codec2] Codec2 repeater

indeed commercial 4FSK implementations are more about bandwidth than sensitivity. Frequency spacing between to tones is bandwidth optimizated not system sensitivity optimized. if we consider each of the 4 tones of 4FSK  being received by a separate receiver (easier to conceptualize) , each

Re: [Freetel-codec2] Codec2 repeater

Hmm, if we think of a modulation index around 1, Carsons rule says Bt = 2*(deltaF + fm ). If it is the modulation index that governs SNR in the recovered baseband, the same index will occur at 1/2 deltaF if we reduce fm by 2, i.e. symbol rate. Thus 4FSK would require half the swing ( for

Re: [Freetel-codec2] Codec2 repeater

Hi Glen, I think David might have been referring to the OFDM mode used by FreeDV, ie single user multicarrier. I was talking about multi-user single carrier. Cheers, Adrian On 12/4/17, glen english wrote: > Hi Adrian > > Please describe the differences asyou understand

Re: [Freetel-codec2] Codec2 repeater

Hi Adrian Please describe the differences asyou understand them between OFDMA and OFDM Are you sure ... ? Glen :-) On 5/12/2017 7:36 AM, Adrian Musceac wrote: OFDMA (not OFDM) -- Check out the vibrant

Re: [Freetel-codec2] Codec2 repeater

> > + OFDM isn't needed unless your bandwidth is significantly wider, as its > a flat fading channel. Single carrier PSK/QAM is fine and has a better > PAPR. M-QAM only needed if you want wideband data, not needed for voice > as we have good compression. > > + Can't seen any good reason for FDMA,

Re: [Freetel-codec2] Codec2 repeater

Hi Adrian, Fine business on your experiments. My thoughts: + I like 4FSK as it's constant amplitude, simplifying the PA and rx (limiting amps can be used at IF), and the modems are easy to get working at ideal performance. It's reasonably bandwidth and power efficient, especially as we

[Freetel-codec2] Codec2 repeater

Hello, Yesterday I commited support for same-mode Codec2 repeater (digital to digital). Apart from voice frames, now station identifiers and text messages also get digipeated. For now the Codec2 audio gets decoded if forwarded over the VoIP connection and re-encoded at the other end for RF