Trellis coding method and arrangement for fractional bit rates
AssigneeAT&T Bell Laboratories
InventorLee-Fang Wei
Life of this patent
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Abstract
A signal coding technique for use with fractional bit rates is disclosed which, for a given dimensionality, allows the use of smaller constellations, and thus provides greater robustness in the presence of various impairments, than would otherwise be the case yet entails essentially no decoding delay penalty. In this technique, one or more of the input bits are trellis encoded and the trellis-encoded bits identify one of a predetermined plurality of subsets of the signal constellation and the particular symbols selected for transmission from two or more identified subsets are chosen by the non-trellis-encoded bits interdependently.
Claims36
A method for encoding a stream of data bits to identify, from a predetermined 2N-dimensional constellation of symbols, N being a predetermined integer, a plurality of successive ones of the symbols that are to be transmitted over a communication channel at a predetermined symbol rate, the symbols of the constellation being divided into a predetermined plurality of 2N-dimensional subsets and the data bits occuring at a fractional bit rate relative to the symbol rate, the method comprising the steps of
- aggregating the bits occurring over a predetermined number of the symbol intervals, the predetermined number of intervals being such that an integral number of bits is aggregated,
- trellis encoding ones of the aggregated bits to identify, for each of the plurality of symbols, a respective subset from which that symbol is to be chosen, and
- choosing each of the plurality of symbols from their respective subsets jointly as a function of at least a particular group of the others of the aggregated bits.
A method for encoding, into 2N-dimensional symbols, N being an integer, a stream of input bits occurring at a fractional bit rate of r bits per 2N-dimensional symbol relative to a predetermined symbol rate, said 2N-dimensional symbols being selected from a 2N-dimensional constellation comprised of a concatenation of N/M 2M-dimensional constellations each of which is partitioned into a plurality of 2M-dimensional subsets of signal points, the method comprising the steps of
- encoding first ones of the input bits to identify a sequence of 2M-dimensional subsets, and
- identifying signal points from successive ones of the identified 2M-dimensional subsets jointly in response to at least a particular group of the others of the input bits, said particular bit group being associated with at least L 2N-dimensional symbol intervals, L being an integer greater than unity.
Apparatus for encoding a stream of data bits to identify, from a predetermined 2N-dimensional constellation of symbols, N being a predetermined integer, a plurality of successive ones of the symbols that are to be transmitted over a communication channel at a predetermined symbol rate, the symbols of the constellation being divided into a predetermined plurality of 2N-dimensional subsets and the data bits occurring at a fractional bit rate relative to the symbol rate, said apparatus comprising
- means for aggregating the bits occurring over a predetermined number of the symbol intervals, the predetermined number of intervals being such that an integral number of bits is aggregated,
- means for trellis encoding ones of the aggregated bits to identify, for each of the plurality of symbols, a respective subset from which that symbol is to be chosen, and
- means for choosing each of the plurality of symbols from their respective subsets jointly as a function of at least a particular group of the others of the aggregated bits.
Apparatus method for encoding, into 2N-dimensional symbols, N being an integer, a stream of input bits occurring at a fractional bit rate of r bits per 2N-dimensional symbol relative to a predetermined symbol rate, said 2N-dimensional symbols being selected from a 2N-dimensional constellation comprised of a concatenation of N/M 2M-dimensional constellations each of which is partitioned into a plurality of 2M-dimensional subsets of signal points, said apparatus comprising
- means for encoding first ones of the input bits to identify a sequence of 2M-dimensional subsets, and
- means for identifying signal points from successive ones of the identified 2M-dimensional subsets jointly in response to at least a particular group of the others of the input bits, said particular bit group being associated with at least L 2N-dimensional symbol intervals, L being an integer greater than unity.
Dependencies are inferred from the claim text.