Communication system for broadcasting to mobile users

• US 6,304,609 B1
• Filed: 03/31/1999
• Issued: 10/16/2001
• Est. Priority Date: 05/29/1997
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Smigla, Terrence R., Martin, Donald R., Stephens, Scott A.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Ha, Dac V.
• Application Number:
  US09/282,362
• Time in Patent Office: 930 Days
• Field of Search: 375/224, 375/225, 375/227, 375/267, 375/259, 375/285, 375/295, 375/296
• US Class Current: 375/259
• CPC Class Codes: H03M 13/2742 Irregular interleaver wherein the permutation pattern is not obtained by a computation rule, e.g. interleaver based on random generators
• CPC Class Codes: H03M 13/2757 Interleaver with an interleaving rule not provided for in the subgroups H03M13/2703 - H03M13/2753
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0019 in which mode-switching is based on a statistical approach
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/02 by diversity reception

Abstract

A communication system (10) implemented to be specifically matched to the time and spatially dependent statistics of a transmission channel (36). The communication system (10) is used for broadcasting over the channel (36) to users in a coverage region (18). The communication system (10) includes a transmitter (12) having an error correction encoder (30) and a weighted interleaver (32). The error correction encoder (30) includes a first input to receive data bits and a first output. The error correction encoder (30) expands each data bit received at said input by an encoder rate. The weighted interleaver (32) includes a second input to receive the expanded data bits and a second output. The weighted interleaver (32) has a non-uniform delay distribution between a minimum delay and a maximum delay to interleave the expanded data bits by the non-uniform delay distribution. The communication system (10) also employs a weighted link margin matched to the time and spatially dependent statistics of the transmission channel.

Claims

1. A method for broadcasting over a channel to users in a coverage region, said method comprising the steps of:

selecting a communication system architecture;

defining a performance metric based upon the communication system architecture selected;

determining communication system performance requirements based upon the defined performance metric;

mapping the performance metric as a function of position in the coverage region to determine required weighted link margins across the coverage region;

selecting antenna gain patterns of a transmit and a receive antenna to generate the required link margins; and

transmitting a signal from the transmit antenna to the receive antenna in the coverage region based upon the required link margins.

2. The method as defined in claim 1 further comprising expanding data bits from a signal in an error correction encoder and interleaving said expanded data bits by a delay distribution non-uniform in probability between a minimum delay and a maximum delay in a weighted interleaver.

3. A method for broadcasting over a channel to users in a coverage region, said method comprising the steps of

receiving data bits at a first input of an error correction encoder;

expanding each data bit received at the first input by an encoder rate;

receiving the expanded data bits at the second input to a weighted interleaver;

interleaving the expanded data bits by a non-uniform delay distribution between a minimum delay and a maximum delay; and

transmitting the expanded and interleaved data bits over the channel.

4. The method as defined in claim 3 further comprising the step of deinterleaving and decoding tee expanded and interleaved data bits in a receiver having a complimentary weighted de-interleaver and decoder.

5. The method as defined in claim 4 further comprising the steps of:

transmitting signals in the coverage region to a receive antenna in the receiver; and

weighting link margins across the coverage region to counteract regional variations in the propagation environment in the coverage region.

6. The method as defined in claim 4 further comprising the step of detecting channel fade conditions in a demodulator in the receiver and nulling a received signal if a channel fade condition is detected.

7. The method as defined in claim 6 further comprising the step of flagging a received signal if a channel fade condition is detected.

8. The method as defined in claim 3 further comprising the step of applying the data bits received by the error correction encoder to a compression algorithm prior to being received by the error correction encoder.

9. A method for broadcasting over a channel to users in a coverage region, said method comprising the steps of:

providing a transmitter having a first signal path operable to route first data bits and a second signal path operable to mute second data bits;

expanding each first data bit by a first encoder rate;

expanding each second data bit by a second encoder rate;

interleaving the expanded first data bits by a delay distribution between a first minimum delay and a first maximum delay;

interleaving the expanded second data bits by a delay distribution between a second minimum delay and a second maximum delay; and

transmitting the expand and intereaved first and second data bits over the channel.

10. The method as defined in claim 9 further comprising the steps of:

compressing the first data bits by a first compression algorithm; and

compressing the second data bits by a second compression algorithm.

11. The method as defined in claim 10 further comprising detecting channel fade conditions in a demodulator in the receiver and nulling a received signal if a channel fade condition is detected.

12. The method as defined in claim 9 further comprising the steps of:

transmitting communication signals in the coverage region to a receive antenna in a receiver; and

weighting link margins across the coverage region to counteract regional variations in the propagation environment in the coverage region.

13. The method as defined in claim 12 further comprising the steps of:

flagging a received signal if a channel fade condition is detected.