Orthogonal frequency division multiplexing symbol diversity combiner for burst interference mitigation
View Patent ↗The invention disclosed in this application describes a diversity combiner that operates as a maximal ratio combiner (MRC) when no interference is detected and as a selection combiner when Orthogonal Frequency Division Multiplexing symbol errors are detected with high probability by using a symbol error detection method based on computing a symbol by symbol path error metric.
1. A method of receiving and decoding a redundant orthogonal frequency division multiplexing (OFDM) transmission having packet A containing OFDM symbols and repeat packet B containing OFDM symbols where both whole packet A and whole packet B have failed decoding by using an interference mitigation selection combiner method wherein for each OFDM symbol the bits produced from the OFDM symbols are identified and combined according to the following method comprising:
first identifying packet A's individual OFDM symbols as packet A n 's OFDM symbols and packet B's individual OFDM symbols as packet B n 's OFDM symbols with n indicating a symbol number from n=0 to n=N and where N=total number of OFDM symbols −1;
then computing a cumulative packet A OFDM symbol path metric from error correction code for each OFDM symbol that produces a bit in whole packet A and a cumulative packet B OFDM symbol path metric from error correction code for each OFDM symbol that produces a bit in whole packet B;
then computing a cumulative whole packet A path metric from error correction code for all OFDM symbols that produce a bit in whole packet A and a cumulative whole packet B path metric from error correction code for all OFDM symbols that produce a bit in whole packet B;
then computing a packet A threshold by adding said cumulative whole packet A path metric's mean to a predetermined constant times the standard deviation of said cumulative whole packet A path metric and computing a packet B threshold by adding said cumulative whole packet B path metric's mean to a predetermined constant times the standard deviation of said cumulative whole packet B path metric;
then if packet A n 's OFDM symbols have a cumulative packet A OFDM symbol path metric exceeding said packet A threshold and packet B n 's OFDM symbols have cumulative packet B OFDM symbol path metric exceeding said packet B threshold the bits produced from said packet A n 's OFDM symbols weighted by said cumulative packet A OFDM symbol path metric and added to bits produced by said packet B n 's OFDM symbols weighted by said cumulative packet B OFDM symbol path metric and selected to be decoded;
then if packet A n 's OFDM symbol has a cumulative packet A OFDM symbol path metric exceeding said packet A threshold but packet B n 's OFDM symbol has a cumulative packet B OFDM symbol path metric that does not exceed said packet B threshold bits from packet B n 's OFDM symbol are selected to be decoded;
then if packet B n 's OFDM symbol has a cumulative packet B OFDM symbol path metric exceeding a said packet B threshold but packet A n 's OFCM symbol has a cumulative packet A OFDM symbol path metric that does not exceed said packet A threshold bits from packet A n 's OFDM symbol are selected to be decoded;
then if packet A n 's cumulative packet A OFDM symbol path metric is below said packet B threshold and packet B n 's cumulative packet B OFDM symbol path metric is below said packet B threshold bits produced from both packet A n 's OFDM symbol and packet B n 's OFDM symbol are added as a function of the probability produced by the an OFDM symbol estimation method and processed using a maximal ratio combiner and then selected to be decoded; and
then final error decoding said selected bits.
2. The method of claim 1 wherein if said final error decoding fails then said threshold level is increased in predetermined increments and repeating said increasing until a predetermined maximum threshold level is met or the decoding is successful.