Dear all what are the advantage or disadvantage when we prepend or append the Reed Solomon (RS) parity ? notation: systematic RScodec (n,k,t) n is code length k is message length t is correcting ability m = message m(0)...m(k-1) p = parity p(0)...p(2t-1) where 0 is MSB append style [m(0) ...m(k-1) p(0)..p(2t-1)] prepend style [p(0)..p(2t-1) m(0) ...m(k-1) ] case study: WiMax 802.16d (32,24,4)GF256 the code is shorten and puncture the spec is using prepend style [p(0)...p(7) m(0) ...m(23) ] [p(0)...p(7) 0*8 0*215 m(0)...m(23)] however if is append [m(0)...m(23) p(0) ...p(7) ] [0*215 m(0)...m(23) p(0) ...p(7) 0*8] from equation point of view as long as both encoder and decoder know where the position of parity there will be no problem to decode because Reed Solomon codec is linear and cyclic from implementation point of view in hardware, i prefer append style append encoder: i can output data and parity in order decoder: i can put receive data to syndrome calculator where everything is in order prepend encoder: need to put data in somewhere after I output parity byte after all message are encoded decoder: need to reorder before I put receive to syndrome calculator more waiting comparing to append style anyone has idea on why WiMax 802.16d using prepend style ?? am i missing something ? thank you
question on WiMax 802.16 ReedSolomon parity position
Started by ●August 24, 2007
Reply by ●October 24, 20072007-10-24
Hi, The better way to do RS decoder is to append the parity bytes after msg bytes,and the reason for that is same what u explained.. Jitu.>Dear all > >what are the advantage or disadvantage when we prepend or append theReed>Solomon (RS) parity ? > >notation: >systematic RScodec (n,k,t) >n is code length >k is message length >t is correcting ability >m = message m(0)...m(k-1) >p = parity p(0)...p(2t-1) >where 0 is MSB > >append style >[m(0) ...m(k-1) p(0)..p(2t-1)] > >prepend style >[p(0)..p(2t-1) m(0) ...m(k-1) ] > >case study: WiMax 802.16d (32,24,4)GF256 >the code is shorten and puncture > >the spec is using prepend style >[p(0)...p(7) m(0) ...m(23) ] >[p(0)...p(7) 0*8 0*215 m(0)...m(23)] > >however if is append >[m(0)...m(23) p(0) ...p(7) ] >[0*215 m(0)...m(23) p(0) ...p(7) 0*8] > >from equation point of view >as long as both encoder and decoder know where the position of parity >there will be no problem to decode >because Reed Solomon codec is linear and cyclic > >from implementation point of view >in hardware, i prefer append style >append >encoder: i can output data and parity in order >decoder: i can put receive data to syndrome calculator >where everything is in order > >prepend >encoder: need to put data in somewhere after I output parity byte after >all message are encoded >decoder: need to reorder before I put receive to syndrome calculator >more waiting comparing to append style > >anyone has idea on why WiMax 802.16d using prepend style ?? >am i missing something ? >thank you > > > > > > >