On 3/2/16 9:18 AM, Alberto di Bene wrote:
On 3/2/2016 4:30 PM, jimlux wrote:
New Horizon's telecom design is here:
http://www.boulder.swri.edu/~tcase/NH%20RF%20Telecom%20Sys%20ID1369%20FINAL_Deboy.pdf
...........................................
Jim, thanks.
Quite a lot of material to read... I am sure it will be useful for a
new ham-related program I am writing.
I have already implemented the old standard Voyager 1 and 2 k=7, r=1/2
Viterbi decoder, but am looking
around to find maybe something a bit better... certainly I won't
implement a k=1784 code... :-)
Turbo codes are nice because the rates are 1/3 or 1/6. The uncoded data
is every 3rd or 6th bit. So if you have good SNR, you don't need the
decoder to see the telemetry.
For what it's worth, Turbo codes are patented by France Telecom.
I think there are some decoder implementations for FPGA out there, but
probably not open source/free.
For new missions, LDPC is where it's at.
There are open source LDPC implementations for the various codes, both
in C and in VHDL/Verilog.
for the long block lengths, since LDPC is used in DVB-S2, there's a fair
amount of stuff around.
There's some very nice short length (few hundred bits, I think) LDPC
codes which were developed for uplink/command applications. Basically to
replace the existing BCH codes for uplink.
If you google "LDPC Andrews" you'll find most of it. Ken Andrews here
at JPL did most of the implementations of our LDPC encoders and decoders.
TNX
73 Alberto I2PHD
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