Patent RU-2163054-C2 (RU)
Title: Method and device for joint demodulation and decoding of continuous-phase binary modulation signals in convolutional-coding systems using character interleaving-deinterleaving system for multibeam radio channels
Inventor: ALYSHEV JU V
IPC: H04L27/22
Filed: 1998-06-16
Granted: 2001-02-10
Abstract: FIELD: electrical communications; digital message transmission over communication channels involving signal energy dissipation in time and frequency. SUBSTANCE: demodulating and decoding method involves splitting of signal received into two quadrature components used in computing quadrature pulse response of communication channel, transformation of computed quadrature response including parity of next code character number, shaping of predistortion quadrature signal, computing of quadrature signal difference by subtracting quadrature predistortion signal from signal received, shaping of two groups of reference signals corresponding to unmasked code sequence; differential quadrature signal is compared when analyzing channel response to signal item corresponding to character being demodulated with two groups of reference signals corresponding to two different hypotheses related to sign of character being demodulated at all possible unmasked sequences of accompanying code characters; value of primary metric being, essentially, minimal square of Euclidean distance between differential and reference signal is recorded for each of hypotheses; primary metrics are compared, and tentative decision is taken concerning sign of signal being demodulated which is then used for shaping quadrature predistortion signal; sequences of primary metrics are deinterleaved for each of hypotheses and then metrics of all possible edges are computed and stored using deinterleaved sequences of primary metrics considering number of binary characters; mentioned edges are used to compute metrics of all possible unmasked code sequences corresponding to all possible code-array paths; metrics of all possible sequences corresponding to code- array paths through each of its nodes are compared, lowest ones are chosen, corresponding code sequences are recorded, all chosen metrics are compared, lowest one is chosen, and first character corresponding to decoded sequence is recorded. Demodulating and decoding device implementing proposed method has quadrature splitter, storage device, communication-channel quadrature pulse response computing unit, inverter, parity switching unit, quadrature predistortion signal shaper, quadrature predistortion signal subtraction unit, first reference-signal shaping unit, first metric computing unit, comparison and selection unit, second reference-signal shaping unit, second metric computing unit, first deinterleaving unit, second deinterleaving unit, edge metric computing unit, path metric computing and minimal path metric comparison, selection, and storage unit, and decoded-character recording unit. Quadrature splitter outputs are connected to inputs of storage device whose outputs are connected to inputs of communication-channel quadrature pulse response computing unit and to first inputs of quadrature predistortion signal subtraction unit; first and second outputs of communication-channel quadrature pulse response computing unit are connected to first and second inputs of parity switching unit; in addition, first output of communication- channel quadrature pulse response computing unit is connected to input of inverter whose output is connected to third input of parity switching unit whose outputs are connected to inputs of first reference-signal shaping unit, to first inputs of quadrature predistortion signal shaper, and to inputs of second reference-signal shaping unit; outputs of quadrature predistortion signal shaper are connected to second inputs of quadrature predistortion signal subtraction unit whose outputs are connected to first inputs of first and second metric computing units; outputs of first reference-signal shaping unit are connected to second inputs of first metric subtraction unit; outputs of second reference-signal shaping unit are connected to second inputs of second metric computing unit; output of first metric computing unit is connected to input of first deinterleaving unit and to first input of comparison and selection unit; output of second metric computing unit is connected to input of second deinterleaving unit and to second input of comparison and selection unit whose output is connected to second input of quadrature predistortion signal shaper; outputs of first and second deinterleaving units are connected to inputs of edge metric computing unit whose output is connected to input of path metric computing and minimal path metric comparison, selection, and storage unit; output of the latter is connected to input of decoded character recording unit. EFFECT: enlarged functional capabilities. 2 cl, 1 dwg