Digital demodulator and method of operation
AssigneeNEC Corporation
InventorShigeru Ono
Life of this patent
Estimating the term…
Abstract
A demodulator performs both synchronization and decoding concurrently by decoding a received preambleless signal according to Viterbi-decoding scheme and determining a time alignment function n(t) which indicates where the decoded sequence is located in a time period of the received signal. After converting the received preambleless signal to a received sequence in a sampling rate which is at least the predetermined symbol rate, a Viterbi decoder is synchronized with the received sequence while determining the time alignment function n(t) so that the Viterbi-decoded sequence is closest to the received sequence.
Claims15
A method for generating an output sequence from a received preambleless signal which does not include a signal for synchronization but includes a signal encoded by a convolutional code, the method comprising the steps of:
- a) converting the received preambleless signal to a received sequence at a sampling rate which is at least a predetermined symbol rate;
- and
- b) synchronizing a Viterbi decoder with the received sequence and decoding the received preambleless signal after bandpass filtering and an analog to digital conversion with the decoder synchronized by the received sequence to produce a Viterbi-decoded sequence as the output sequence while determining a time mapping so that the Viterbi-decoded sequence is closest to the received sequence, said step of synchronizing comprising:
- generating the output sequence w and the time mapping n(t) so as to minimize a cumulative distance D(w) represented by the following equation (1):
- ##EQU6## where t is a sampling index of the received sequence, T is the number of sampling points during the time period of the received signal, x.sub.t is the received sequence, f(w,n(t)) is an encoded signal generated from the output sequence w.
A demodulator for demodulating a received preambleless signal which does not include a signal for synchronization but is encoded by a convolutional code to produce an output sequence, the demodulator comprising:
- a Viterbi decoder decoding the received preambleless signal after bandpass filtering and analog to digital conversion to produce a Viterbi-decoded sequence;
- converter converting the received preambleless signal to a received sequence at a sampling rate which is at least a predetermined symbol rate;
- and
- a sync controller synchronizing the Viterbi decoder with the received sequence to produce the output sequence while determining a time mapping so that the Viterbi-decoded sequence is closest to the received sequence, said sync controller generating the output sequence w and the time mapping n(t) so as to minimize a cumulative distance D(w) represented by the following equation (1):
- ##EQU9## where t is a sampling index of the received sequence, T is the number of sampling points during a time period of the received signal, x.sub.t is the received sequence, f(w, n(t)) is an encoded signal generated from the output sequence w.
A method for demodulating a received preambleless signal which does not include a signal for synchronization but comprises a signal encoded by a convolutional code to produce an output sequence, the method comprising the steps of:
- a) converting the received preambleless signal to a received sequence at a sampling rate which is at least a predetermined symbol rate;
- b) decoding the received preambleless signal, after bandpass filtering and analog to digital conversion, into a Viterbi-decoded sequence at the predetermined symbol rate;
- and
- c) synchronizing the Viterbi-decoded sequence with the received sequence to produce the output sequence while determining a time mapping so that the Viterbi-decoded sequence is closest to the received sequence, said step of synchronizing comprising generating the output sequence w and the time mapping n(t) so as to minimize a cumulative distance D(w) represented by the following equation (1):
- ##EQU12## where t is a sampling index of the received sequence, T is the number of sampling points during a time period of the received signal, x.sub.t is the received sequence, f(w, n(t)) is an encoded signal generated from the output sequence w.
Dependencies are inferred from the claim text.