Matched filter bank

A radio receiver comprising:

• a matched filter bank comprising a plurality of filter modules for generating correlation-strength data from a sampled radio signal, each filter module being configured to cross-correlate the sampled signal with data representing a respective filter sequence, wherein each filter sequence comprises a respective constant portion and a respective variable portion, the variable portion being positioned before the constant portion, wherein each constant portion is constant over time;
• a decision unit configured to use the correlation-strength data to generate a sequence of decoded symbols from the sampled signal, wherein the matched filter bank and/or decision unit are configured to determine the value of each symbol in the sequence in part based on the value of a respective earlier decoded symbol from the sequence of decoded symbols;
• and
• one or more feedback paths from an output of the decision unit for feeding the value of the respective earlier decoded symbol back to the matched filter bank;
• wherein each variable portion depends on one or more of the earlier decoded symbols received over said one or more feedback paths;
• wherein the radio receiver further implements at least one of the following:
• i) wherein the matched filter bank and/or decision unit are configured to determine the value of each symbol in the sequence of decoded symbols in part based on the values of a plurality of respective earlier decoded symbols from the sequence of decoded symbols;
• or
• ii) wherein the constant portions across all the filter sequences of the matched filter bank contain every integer value from zero to the number of filters in the matched filter bank minus one;
• or
• iii) wherein the variable portions in each filter sequence have a common length and, when determining the value of a symbol of the sequence of decoded symbols, are all equal to a same sequence of one or more earlier decoded symbols;
• or
• iv) wherein the radio receiver is configured to decode each symbol in the sequence of decoded symbols by applying the matched filter bank once, for each symbol, and identifying a best-matched filter, and by decoding the symbol as the value in the filter sequence of the best-matched filter at a position corresponding to the symbol;
• or
• v) wherein the radio receiver is configured to apply the matched filter bank to the sampled signal a plurality of times, with different respective time offsets, when decoding each symbol, and the radio receiver further comprises a hard symbol decision block configured to determine a symbol of the decoded sequence by receiving a best-matched filter for each of the plurality of time offsets and decoding the value of the symbol position in the decoded sequence by applying a decision process to a respective plurality of symbol values corresponding to the symbol position from across the plurality of best-matched filter.