Method and apparatus for turbo decoding of trellis coded modulated signal transmissions

DETAILED DESCRIPTION Briefly, the present invention implements an iterative decoding system within a Trellis Coded Modulation communications environment.
The improved Trellis-coded modulation transmitter and receiver system provides an improved telecommunications system capable of effectively carrying narrowband services while providing the flexibility to carry higher bandwidth services over the narrowband channel.
The present invention recognizes that the system architecture on the transmitter side of Trellis Coded Modulation communications systems can be likened to those of Serially Concatenated Convolutional Coding (SCCC) systems.
Following that recognition, the present invention applies interative Turbo decoding to Trellis Coded Modulation signals.
The present invention uses an interative process to accelerate signal decoding and increase receiver performance in a Trellis Coded Modulation environment.
In the present invention, the resulting coding gain is substantially greater and the decoding performance is substantially improved with a decrease in BER as compared with a conventional non-iterative approach.
Performance similar to SCC Turbo codes is expected.
In a disclosed embodiment of the present invention, the transmitter uses a channel encoder (consisting of either a convolutional encoder or a block encoder) as the outer encoder.
The signal to be transmitted is first input into the outer encoder.
The channel encoded signal is then passed through an interleaver and fed into a Trellis Coded Modulation encoder which acts as the inner encoder.
The encoded signal may then be transmitted over the channel.
On the decoding side, the disclosed embodiment of the present invention advantageously applies iterative decoding to decode the received Trellis Coded Modulated signals.
The iterative decoder that is used within the receiver may be similar to the decoder that is applied to Serially Concatenated Coding systems.
The system of the present invention is particularly applicable to data communications applications