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REED-SOLOMON for 802.16

Started by pafnutius September 13, 2007
Hi,
I don't understand the specification 802.16, concerning FEC/Reed-Solomon.
May be someone can guide me to an answer?
I developped RS coder, decoder(255,239,8). It works fine. I have the same
results with the specification example. "The first test vector refers to
full
bandwidth (16 subchannels) using QPSK and overall coding rate 3/4. The RS
code you use is (40,36,2). According to the test vectors, if the input to
the RS coder is "D4 BA A1 12 F2 74 96 30 27 D4 88 9C 96 E3 A9 52 B3 15 AB
FD 92 53 07 32 C0 62 48 F0 19 22 E0 91 62 1A C1 00" (where the last 00 is
added manually as specified), the spec says the first 4 bytes of the
parity should "49 31 40 BF"  ". I have the same bytes. 
The problem occurs when I use shortened and punctured code. I can't
understand how can I decode: 0..202 = 0; 203..239 = D4 BA A1 12 F2 74 96
30 27 D4 88 9C 96 E3 A9 52 B3 15 AB FD 92 53 07 32 C0 62 48 F0 19 22 E0 91
62 1A C1 00; 240..244 = 49 31 40 BF; 244..254 =0
I mean how can I find the errors, if the parity bytes are shortened? I'm
stuck....
How do I need this shortening to be done correctly?
please.. just a brief answer...


>Hi, >I don't understand the specification 802.16, concerning
FEC/Reed-Solomon.
>May be someone can guide me to an answer? >I developped RS coder, decoder(255,239,8). It works fine. I have the
same
>results with the specification example. "The first test vector refers to >full >bandwidth (16 subchannels) using QPSK and overall coding rate 3/4. The
RS
>code you use is (40,36,2). According to the test vectors, if the input
to
>the RS coder is "D4 BA A1 12 F2 74 96 30 27 D4 88 9C 96 E3 A9 52 B3 15
AB
>FD 92 53 07 32 C0 62 48 F0 19 22 E0 91 62 1A C1 00" (where the last 00
is
>added manually as specified), the spec says the first 4 bytes of the >parity should "49 31 40 BF" ". I have the same bytes. >The problem occurs when I use shortened and punctured code. I can't >understand how can I decode: 0..202 = 0; 203..239 = D4 BA A1 12 F2 74 96 >30 27 D4 88 9C 96 E3 A9 52 B3 15 AB FD 92 53 07 32 C0 62 48 F0 19 22 E0
91
>62 1A C1 00; 240..244 = 49 31 40 BF; 244..254 =0 >I mean how can I find the errors, if the parity bytes are shortened? I'm >stuck.... >How do I need this shortening to be done correctly? >please.. just a brief answer... >
Yep, everyting is fine. Just erasures correction was't implemented ;)