If a proposal to transmit 4800 bps as "data only" is in the works, then I strongly urge that some FEC be added utilizing both convolution and interleaving. 3600 bps on DV now has coding gain in AMBE and only has to recover 20 ms of voice frame. If the BER/CWER is >2% there's still some voice recovery to the ear, but fast fades are going to create significant burst errors unless interleaving is applied to a 4800 bps data only channel.
4800 bps with 2/3 convolutional coding and interleaving will result in a usable 3200 bps. Better yet an adaptive channel even better with GMSK. FEC shopuld also be done at the "controller before retransmission. If you get a noisy channel, ARQ will help but the throughput goes way down unless you have the air interface more robust. Craig KV5E --- In [email protected], "Steve Bosshard (NU5D)" <bossh...@...> wrote: > > How do you propose to pump a 9.6kb/s data stream through a 12.5 khz (in > reality) repeater or repeater receiver ? 4.8 - yes - 9.6 no. At least not > without changing the IF filters in the receiver and using twice the occupied > bandwidth. > > On Sun, Jun 27, 2010 at 3:58 PM, john_ke5c <k...@...> wrote: > > > > PA3YBR has already run DD over the 4800 signal on D-STAR. > > > > -- > NU5D - Nickel Under Five Dollars >
