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公开(公告)号：DE68915758D1
公开(公告)日：1994-07-07
申请号：DE68915758
申请日：1989-07-07
Applicant: IBM
Abstract: In a trellis-coded modulation (TCM) transmission system, data bits are grouped into bit blocks (13), and each such bit block is encoded to select a fixed number w of symbols from a given symbol set (14). The symbols are subdivided into subsets, and each subset includes a few outer symbols and a greater number of inner symbols. Each symbol represents one particular transmission signal value. A first portion (17) of each bit block is separated into w bit subgroups, each of which is separately expanded by a convolutional encoder (20) to obtain a bit combination (19, 15) for specifying one of the symbol subsets. The remaining portion (21) of each bit block is expanded by a block coder (22) to obtain w bit subgroups (23), each being a bit combination (25, 16) for selecting one particular symbol out of a specified subset; outer symbols are selected less frequently than inner symbols (e.g. one outer symbol per bit block). The arrangement allows to transmit a non-integer number of data bits per symbol, and further allows to operate with single-symbol TCM, i.e. transmitting and decoding each symbol separately.
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公开(公告)号：DE68915758T2
公开(公告)日：1994-12-08
申请号：DE68915758
申请日：1989-07-07
Applicant: IBM
Abstract: In a trellis-coded modulation (TCM) transmission system, data bits are grouped into bit blocks (13), and each such bit block is encoded to select a fixed number w of symbols from a given symbol set (14). The symbols are subdivided into subsets, and each subset includes a few outer symbols and a greater number of inner symbols. Each symbol represents one particular transmission signal value. A first portion (17) of each bit block is separated into w bit subgroups, each of which is separately expanded by a convolutional encoder (20) to obtain a bit combination (19, 15) for specifying one of the symbol subsets. The remaining portion (21) of each bit block is expanded by a block coder (22) to obtain w bit subgroups (23), each being a bit combination (25, 16) for selecting one particular symbol out of a specified subset; outer symbols are selected less frequently than inner symbols (e.g. one outer symbol per bit block). The arrangement allows to transmit a non-integer number of data bits per symbol, and further allows to operate with single-symbol TCM, i.e. transmitting and decoding each symbol separately.
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公开(公告)号：DE3577167D1
公开(公告)日：1990-05-17
申请号：DE3577167
申请日：1985-08-28
Applicant: IBM
Abstract: For adaptively adjusting the gain in a modem receiver comprising two amplifiers (15, 19), the following steps are performed: for a buffer (21), a Hilbert filter (23), and an equalizer (27), a respective energy indicator (p 2 max , u 2 avg , x 2 avg ) is generated from the signal samples in the respective delay line. Each energy indicator is compared to an associated upper target level (4L u , 3Lp, 1.19 L x ), and for the equalizer also to an associated lower target level - (0.84 L x ). If necessary, a gain correction factor (S) initially set to 1.0 is modified to obtain an overall gain that keeps delay line energies within desired targets. Target comparisons are made so that excess energy in the buffer or Hilbert filter result in a rapid gain reduction whereas average equalizer energy is used for slow adaptations.After a gain change, all acquired samples in the delay lines are also multiplied by the correction factor (S) so that none is lost during gain acquisition. Gain is distributed between the two amplifiers in a swapping operation without modifying the adjusted overall gain.
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4.发明专利
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