Cyclic trellis-coded modulation

• US 6,578,173 B2
• Filed: 01/04/2002
• Issued: 06/10/2003
• Est. Priority Date: 11/23/1994
• Status: Expired due to Fees

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: AT&T Wireless Services Incorporated (AT&T, Inc.)
• Inventors: Alamouti, Siavash M.
• Primary Examiner(s): MOISE, EMMANUEL LIONEL
• Application Number:
  US10/039,038
• Publication Number:
  US 20020059551A1
• Time in Patent Office: 522 Days
• Field of Search: 714/792, 714/752, 714/755, 714/756, 714/786, 714/787, 714/788, 714/795, 714/796, 714/800, 375/242, 375/244, 375/261, 375/262, 375/263, 375/264, 375/265, 375/286, 375/341
• US Class Current: 714/792
• CPC Class Codes: H03M 13/235 Encoding of convolutional codes, e.g. methods or arrangements for parallel or block-wise encoding
• CPC Class Codes: H03M 13/25 Error detection or forward error correction by signal space coding, i.e. adding redundancy in the signal constellation, e.g. Trellis Coded Modulation [TCM] modulation codes H03M13/31
• CPC Class Codes: H03M 13/256 with trellis coding, e.g. with convolutional codes and TCM
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 27/3427 in which the constellation is the n - fold Cartesian product of a single underlying two-dimensional constellation

Abstract

A universal method of trellis encoding signals mapped according to any signal constellation format involves constructing an encoder output table and a state transition table. The encoder output table defines the output symbol of an encoder given the input symbol and the present state of the encoder, while the state transition table defines the next state of the encoder given the present state of the encoder and the input applied to the encoder. The output table and the next state table are constructed with the objective of providing maximal distances between the branches of the trellis diagram without any regards for the shift register implementation of the code. Cyclic trellis-coded modulation is an example of such codes without feed-forward or feed-back shift register implementations, and with equal or better performance than “optimal” shift register trellis codes with 16 states or less. The cyclic trellis codes for both AWGN and Rayleigh fading applications can be constructed for any signal constellation without resorting to exhaustive searches.

Claims

1. A method of encoding signals mapped according to any signal constellation format comprising:

dividing the signal constellation points into two symmetrical sets of symbol points; and

be

cyclic trellis encoding data to be mapped according to said signal constellation.

2. A data encoder comprising:

a cyclic trellis encoder; and

a transmitter coupled to said cyclic trellis encoder.

3. A data encoder for use in data communication application, wherein a plurality of input data values are trellis encoded to form output data, said data encoder comprising:

an input;

an encoder circuit coupled to said input said encoder circuit having a plurality of present states, and responsive to said plurality of input data values on said input to transition to a next state, the next states corresponding to each input being cyclically shifted for different ones of said present states; and

an output coupled to said encoder circuit, said output responsive to said encoder circuit to generate output data.

4. A digital data encoder, comprising:

a trellis encoder, the trellis encoder adapted to trellis encode data to be mapped for signal constellations which can be set partitioned such that each level of set partitioning results in substantially increased minimum Euclidean distance between points of said signal constellation, and the trellis encoder adapted to trellis encode data to be mapped for signal constellations which cannot be set partitioned such that each level of set partitioning results in substantially increased minimum Euclidean distance between points of said signal constellation.

5. A method of trellis encoding which is applicable to all signal constellations having an even number of constellation points, comprising:

defining all the paths merging out of a state and into the same state; and

providing substantially near maximal spacing between outputs on said state transition paths for signal constellations selected from the group consisting of 8 PSK, 16 Star QAM, 16 QAM and 16 PSK.

6. A trellis encoder, comprising:

a state machine encoder with limited state transition paths wherein said state transition paths are defined to provide the minimum number of two branch state transition paths out of all possible state transition paths between the same state.

7. A trellis encoder, comprising:

a state machine encoder with limited state transition paths, said paths defined by a next state table having a series of rows and columns, the contents of said rows and columns formed by a sequence of consecutive integers, said table including two rows wherein each row contains the identical integers, said table including two rows wherein each row contains the identical integers and wherein the last integer in one of said rows is the first integer in the other row, while the sequence of integers in each of said rows is otherwise maintained.

8. A trellis encoder, comprising:

a state machine which trellis encodes input data signals, wherein said input data signals are mapped according to a modulation scheme such that a signal constellation defined by said modulation scheme cannot be set partitioned such tat each level of set partitioning results in a substantially increased minimum Euclidean distance between points of said signal constellation.