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IP Core Products > Codecs > Reed-Solomon |
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Reed-Solomon decoder,
Reed-Solomon errors
only |
| Product codes: CMS0013,
CMS0007 |
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A Reed-Solomon Codec core for use in many wireless applications including
802.16 and DVB-T/DVB-C/DVB-S.
The Reed-Solomon code has message length K and
codeword length N. The symbols for the code are integers between 0 and 2M-1,
which represent elements of the finite field GF(2M). The difference N - K must
be an even integer. An (N, K) Reed-Solomon code can correct up to T=(N-K)/2 byte
(symbol) errors in each codeword.
Commsonic offers two RS Codec products - a
full-featured Errors and Erasures Codec(CMS0013) and an Errors-Only
Codec(CMS0007).
The Errors and Erasures Codec is intended for applications
such as IEEE802.16 that require code puncturing (dynamic control over the number
of parity symbols that are used by the code) or with systems such as DVB-MPE
that use erased symbols (symbols where the decode confidence is low).
The
Errors-Only Codec does not support code puncturing or erased symbols and is
optimized to provide a compact design for application that require a fixed
number of parity symbols such as MPEG/DVB-T/DVB-S/DVB-C.
A typical
application of this core would be for the 802.16 wireless MAN standard where the
options would be set as follows:
N=255, K=239, T=8, GF(256) i.e.
M=8.
G(x)=(x-α0)(x-α1) … (x-α2T-1).
α=2, J0=0.
P(x) = x8 + x4 + x3 + x2
+ 1.
A RS encoder is also available. |
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Block diagram
Click on image for further information
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Downloads
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Standards compliance
Symbol Size (M): Usually 8-bit.
Maximum number of correctable errors per packet: Tmax.
Field Generator or Primitive Polynomial: P(x).
RS Code generator polynomial: G(x)=(x-αJ0+0)(x-αJ0+1) … (x-αJ0+2T-1).
Value of primitive root: α.
Value of integer J0.
Erasure Enable - synthesizes the logic required to decode erased symbols. †
Variable T - synthesizes the logic required for codes shortened by
puncturing check symbols. † |
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Register settings
N (up to 2M-1 bits per symbol).
T (up to Tmax). † |
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Dynamic packet size handling
A valuable feature in 802.16 and other applications is the ability to manage
new N and T settings for each packet that arrives. The N and T parameters are
loaded at the start of packet and can be changed immediately afterwards if the
following packet requires a new configuration. † denotes Errors and Erasures
codec only (CMS0013).
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