Method and system for the OFDM multicarrier transmission of digital broadcasting signals

• US 6,522,700 B1
• Filed: 02/08/1999
• Issued: 02/18/2003
• Est. Priority Date: 03/14/1996
• Status: Expired due to Fees

• Current Assignee: Media Broadcast GBMH
• Original Assignee: Deutsche Telekom AG
• Inventors: Zimmermann, Gerd, Schulze, Henrik
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US09/142,807
• Time in Patent Office: 1,471 Days
• Field of Search: 375/260, 375/295, 375/308, 375/279-281, 455/59, 370/203-211, 381/3
• US Class Current: 375/295
• CPC Class Codes: H04H 20/47 specially adapted for stereophonic broadcast systems
• CPC Class Codes: H04H 20/72 of terrestrial networks
• CPC Class Codes: H04H 2201/20 digital audio broadcasting [DAB]
• CPC Class Codes: H04L 27/2602 Signal structure

Abstract

An improved DAB transmission system with which a higher net data rate can be achieved while maintaining the same system quality, or the same system quality can be achieved with a much lower signal-to-noise ratio on the receiver side at the same net data rate. A symbol mapper is connected directly downstream from a convolution encoder instead of to the block generator; as in the case of prior DAB systems. A multi-stage channel encoder, to which the data substreams of a source data stream are distributed, is used. The source data stream is processed on the complex symbol level and not on the bit level, as in the case of prior DAB systems.

Claims

1. A method for OFDM multicarrier transmission of digital broadcasting signals comprising:

generating at least one source data stream divided into a plurality of frames having a predetermined length;

splitting the at least one source data stream into N parallel data substreams;

encoding each of the N data substreams with a respective channel encoder having a predetermined code rate so as to form N encoded output sequences of M bits;

combining the encoded output sequences into N-tuples and mapping each N-tuple to a complex symbol of a 2^N-PSK symbol alphabet;

combining the complex symbols into blocks of a predefined size;

frequency-interleaving the complex symbols in each block to respective subcarriers; and

generating an analog OFDM signal from the complex symbols, frequency interleaved, in each block and broadcasting the OFDM signals to receiving equipment.

2. The method as recited in claim 1 wherein the digital broadcasting signals include digital added-value services.

3. The method as recited in claim 1 wherein the encoding step includes convolution-encoding.

4. The method as recited in claim 1 further comprising time-interleaving the complex signals resulting from the mapping step.

5. The method as recited in claim 1 further comprising setting N to a value greater than or equal to 3.

6. The method as recited in claim 1 wherein the frequency-interleaving step forms frequency-interleaved complex symbols, and further comprising performing a differential modulation on each of the respective different subcarriers on the frequency-interleaved complex symbols to form modulated complex symbols.

7. The method as recited in claim 6 further comprising performing an inverse discrete Fourier transform on the modulated complex symbols.

8. The method as recited in claim 1 wherein the at least one source data stream includes a plurality of source data streams, and further comprising time-division multiplexing, after the mapping step, the complex symbols originating from the plurality of source data streams.

9. A digital OFDM multicarrier transmission system comprising:

a transmitter including;

at least one set of at least N parallel-connected channel encoders having a predetermined code rate, each channel encoder for encoding one respective data substream of a set of at least one set of N parallel data substreams, each of the at least one set of N parallel data substreams generated by breaking down at least one source data stream divided into a plurality of frames having a predetermined length;

a symbol mapper connected to outputs of the channel encoders for mapping N-bit tuples to complex symbols of a 2^N-PSK symbol alphabet;

a block generator for combining a predetermined number of the complex symbols into a block;

a multicarrier modulator for modulating the complex symbols combined into the block;

a frequency interleaver connected between the block generator and the multicarrier modulator for frequency-interleaving the complex symbols, which are modulated, in each block; and

a device for generating analog OFDM signals from the complex symbols in each block and for broadcasting the analog OFDM signals.

10. A system as recited in claim 9 wherein the system transmits digital broadcasting signals including digital added-value services.

11. A system as recited in claim 9 further comprising a time interleaver connected downstream from the symbol mapper for time-interleaving the complex symbols.

12. A system as recited in claim 9 wherein each of the complex symbols in each block is assigned to a respective different subcarrier, the multicarrier modulator performing a differential modulation on each subcarrier, and wherein each channel encoder is a convolution encoder.

13. A system as recited in claim 9 wherein the at least one source data stream includes a plurality of source data streams, and further comprising a frame multiplexer for multiplexing the complex symbols originating from the plurality of different source data streams.

14. A system as recited in claim 9 further comprising a block interleaver connected downstream from each channel encoder.

15. A system as recited in claim 9 further comprising:

a block multiplexer; and

a transmitting part connected in parallel with the transmitter, the transmitter part for supplying a blocked 4-PSK symbol stream of the kind produced by a symbol mapper of a known DAB transmitter, the transmitting part being connected to the frequency interleaver via the block multiplexer;

the block generator being attached to the block multiplexer.

16. A system as recited in claim 9 wherein N is greater than or equal to 3.

17. A system as recited in claim 9 wherein the at least one source data stream includes a plurality of source data streams, and further comprising:

a receiver including;

an OFDM demodulator;

a differential demodulator;

a frequency deinterleaver;

a device for de-combining the predetermined number of the complex symbols from the block;

a demultiplexer for time-division demultiplexing the complex symbols originating from the plurality of different source data streams;

a time deinterleaver;

N parallel-connected metric calculators; and

a respective convolution decoder connected downstream from each of the metric calculators, an output of each convolution decoder being fed back to the respective metric calculator via an assigned complementary convolution encoder according to a selected symbol mapping rule.

18. A system as recited in claim 17 further comprising a block deinterleaver connected between each metric calculator and each convolution decoder, and a block interleaver connected between each convolution encoder and the respective metric calculator, each convolution encoder being capable of re-encoding a data bit stream detected.

19. A digital OFDM multicarrier transmitter for use in a digital OFDM multicarrier transmission system, the transmitter comprising:

at least one set of at least N parallel-connected channel encoders having a predetermined code rate, each channel encoder for encoding one respective data substream of a set of at least one set of N parallel data substreams, each of the at least one set of N parallel data substreams generated by breaking down a respective at least one source data stream divided into a plurality of frames having a predetermined length;

a symbol mapper connected to outputs of the channel encoders for mapping N-bit tuples to complex symbols of a 2^N-PSK symbol alphabet;

a block generator for combining a predetermined number of the complex symbols into a block;

a multicarrier modulator for modulating the complex symbols combined into the block;

a frequency interleaver connected between the block generator and the multicarrier modulator for frequency-interleaving the complex symbols, which are modulated, in each block; and

a device for generating analog OFDM signals from the complex symbols in each block and for broadcasting the analog OFDM signals.

20. A transmitter as recited in claim 19 wherein the transmission system transmits digital broadcasting signals including digital added-value services.

21. A transmitter as recited in claim 19 further comprising a time interleaver connected downstream from the symbol mapper for time-interleaving the complex symbols.

22. A transmitter as recited in claim 19 wherein each of the complex symbols in each block is assigned to a respective different subcarrier, the multicarrier modulator performing a differential modulation on each subcarrier, and wherein each channel encoder is a convolution encoder.

23. A transmitter as recited in claim 19 wherein the at least one source data stream includes a plurality of source data streams, and further comprising:

a receiver including;

an OFDM demodulator;

a differential demodulator;

a frequency deinterleaver;

a device for removing the predetermined number of the complex symbols from the block;

a demultiplexer for time-division demultiplexing the complex symbols from the plurality of source data streams;

a time deinterleaver;

N parallel-connected metric calculators; and

a respective convolution decoder connected downstream from each of the metric calculators, an output of each convolution decoder being fed back to the respective metric calculator via an assigned complementary convolution encoder according to a select symbol mapping rule.