Trellis coding technique to improve adjacent channel interference protection ratio in land mobile radio systems

A method of configuring a communication system, said system including a transmitter having an encoder with a memory length L and capable of being in a plurality of encoder states coupled to a mapper for mapping the encoder states to a phase angle signal, a pair of parallel branches coupled to an output of the mapper, each branch having a transmit filter coupled to the mapper for filtering the phase angle signal with a transfer function Q(f), a digital-to-analog (D/A) converter coupled to the transmit filter for sampling the filtered signal, a low pass filter and a modulator coupled in series with the D/A converter, a summer coupled to the modulator of each branch, and a transmit antenna coupled to the summer, said system further including a receiver comprising a circuit including a receive antenna, a first down converter, a receive filter having a power spectrum H.sub.r (f), a second down converter, an analog-to-digital converter and a decoder all serially coupled;

• said method comprising the steps of:
• a) choosing a desired minimum acceptable Euclidean distance (DMED) between a set of symbol points;
• b) choosing a symbol period, T.sub.s ;
• c) choosing a number of input bits to be shifted into the encoder at each said symbol period thereby determining an encoder alphabet having M entries;
• d) choosing a number of bits to be output by the encoder during each said symbol period to determine a length of an encoder output code and a number of constellation points;
• e) setting a probability associated with each said encoder alphabet entry uniformly to a single predetermined value thereby fixing a probability matrix X.sub.v ;
• f) setting a probability associated with each encoder output code uniformly to a single predetermined value thereby fixing a probability matrix Y.sub.v ;
• g) permutating all possible encoder states with all said encoder alphabet entries to result in a plurality of encoder sets U;
• h) choosing an encoder set as a present encoder set;
• i) adapting the encoder to provide a plurality of encoder output codes u from the present encoder set U according to the encoder's present state and a presently received encoder alphabet entry;
• j) determining a minimum Euclidean distance, d.sup.2.sub.min, associated with the present encoder set U;
• k) comparing d.sup.2.sub.min calculated from step "j" with DMED, if d.sup.2.sub.min does not exceed DMED, the present encoder set U is discarded;
• l) repeating steps "h"-"k" for all encoder sets U;
• m) empirically determining the peak to average power ratio of the encoder for each encoder set U that have not been discarded;
• n) choosing an encoder set from the encoder sets that have not been discarded having the greatest peak to average power ratio as the optimum coding set;
• o) adapting the transmitter to transmit the optimum coding set for all future transmissions;
• p) adapting the decoder to decode signals it receives according to the optimum coding set.

A method of configuring a communication system, said system including a transmitter having an encoder with a memory length L and capable of being in a plurality of encoder states coupled to a mapper for mapping the encoder states to a phase angle signal, a pair of parallel branches coupled to an output of the mapper, each branch having a transmit filter coupled to the mapper for filtering the phase angle signal with a transfer function Q(f), a digital-to-analog (D/A) converter coupled to the transmit filter for sampling the filtered signal, a low pass filter and a modulator coupled in series with the D/A converter, a summer coupled to the modulator of each branch, and a transmit antenna coupled to the summer, said system further including a receiver comprising a circuit including a receive antenna, a first down converter, a receive filter having a power spectrum H.sub.r (f), a second down converter, an analog-to-digital converter and a decoder all serially coupled;

• said method comprising the steps of:
• a) choosing a desired minimum acceptable value, (MPR), of power ratio P.sub.ib /P.sub.ab ;
• b) choosing a symbol period, T.sub.s ;
• c) choosing a number of input bits to be shifted into the encoder at each said symbol period thereby determining an encoder alphabet having M entries;
• d) choosing a number of bits to be output by the encoder during each symbol period to determine a length of an encoder output code and a number of constellation points;
• e) setting a probability associated with each said encoder alphabet entry uniformly to a single predetermined value thereby fixing a probability matrix X.sub.v ;
• f) setting a probability associated with each said encoder output code uniformly to a single predetermined value thereby fixing a probability matrix Y.sub.v ;
• g) permutating all possible encoder states with all encoder alphabet entries to result in a plurality of encoder sets U;
• h) choosing an encoder set as a present encoder set;
• i) determining a P.sub.ib /P.sub.ab ratio for the present encoder set U according to the following equation:
• ##EQU15## where and the superscript H indicates Hermitian or conjugate transpose operator, M=number of input alphabet entries, N=number of encoder states, L=memory length of the shift register encoder, and T.sub.s is the symbol duration;
• j) adapting the encoder to provide a plurality of encoder output codes u from the present encoder set U according to the encoder's present state and a presently received encoder alphabet entry;
• k) comparing MPR with P.sub.ib /P.sub.ab calculated from step "i", if P.sub.ib /P.sub.ab does not exceed MPR, the present encoder set U is discarded,
• l) repeating steps "h"-"k" for all encoder sets U;
• m) determining minimum Euclidean distance between coded sequences, d.sup.2.sub.min for each encoder set U that have not been discarded;
• n) choosing from the encoder sets that have not been discarded an encoder set having the greatest d.sup.2.sub.min as the optimum coding set;
• o) adapting the transmitter to transmit the optimum coding set for all future transmissions;
• p) adapting the decoder to decode signals it receives according to the optimum coding set.