Method And Apparatus For Error Detection In A Communication System
A method processes a data packet in a first sequence of disjoint original segments of the same length. The method includes modifying a first of the original segments of the first sequence by modifying one or more symbols therein. A start of the data packet is located in the first of the original segments and is positioned after a first digital data symbol therein. The method also includes modifying a last of the original segments of the first sequence by modifying one or more digital data symbols therein. An end of the data packet is located in the last of the original segments and is located before the last digital data symbol therein. The method also includes determining a remainder sequence by effectively performing a polynomial division on a second sequence of disjoint segments that are derived from the first sequence. Each segment of the second sequence corresponds to and is derived from one of the original segments of the first sequence. The segments of the second sequence have the length of the original segments of the first sequence. A first of the derived segments of the second sequence is the modified first of the original segments. A last of the derived segments of the second sequence is derived from the modified last of the original segments.
1 . A method of processing a data packet located in a first sequence of disjoint original segments, each original segment of the first sequence having the same length, comprising:
modifying a first of the original segments of the first sequence by modifying one or more symbols therein, a start of a data packet being located in the first of the original segments and being after a first symbol therein;
modifying a last of the original segments of the first sequence by modifying one or more symbols therein, an end of the data packet being located in the last of the original segments and being before the last symbol therein; and
determining a remainder by performing a polynomial division on a second sequence of disjoint derived segments, each segment of the second sequence corresponding to and being derived from one of the original segments, the segments of the second sequence having the length of the original segments, a first of the derived segments of the second sequence being the modified first of the original segments, a last of the derived segments of the second sequence being the modified last of the original segments.
2 . The method of claim 1 , wherein each derived segment that does not include the start or end of the data packet is equal to the corresponding one of the original segments.
3 . The method of claim 1 , wherein the modifying steps include masking portions of the original segments outside of the data packet such that said portions will contribute in a predetermined amount to the remainder determined by the polynomial division.
4 . The method of claim 1 , wherein the modifying a first of the original segments modifies symbols at the start of the data packet.
5 . The method of claim 4 , wherein the modifying steps include masking portions of the original segments outside of the data packet such that said masked portions will contribute in a predetermined amount to the remainder determined by the polynomial division.
6 . The method of claim 1 , wherein the modifying of a last of the original segments modifies symbols at the end of the data packet.
7 . The method of claim 6 , wherein the modifying steps include masking portions of the original segments outside of the data packet such that said masked portions will not contribute to the remainder determined by the polynomial division when a cyclic redundancy check of the data packet vanishes.
8 . The method of claim 1 , further comprising:
producing a third sequence by performing a symbol-by-symbol subtraction of a sequence of symbols from the first sequence such that a data packet located in the third sequence becomes a valid codeword of an error control code that is based on a polynomial division.
9 . The method of claim 8 , wherein the sequence of symbols is found from the remainder determined be the performing a polynomial division on a second sequence.
10 . The method of claim 1 , further comprising:
writing an evaluated value of a cyclic redundancy check for the data packet into a specific one of the segments of the first sequence in response to the end of the data packet being in the specific one of the segments of the first sequence.
11 . The method of claim 10 ,
wherein the modifying further includes receiving a number indicative of the location of the end of the packet in the specific one of the segments of the first sequence; and
wherein the writing includes determining a location to write the evaluated value based on the received number.
12 - 20 . (canceled)