Apparatus and method for transmitting information and apparatus and method for receiving information

• US 6,314,289 B1
• Filed: 05/17/1999
• Issued: 11/06/2001
• Est. Priority Date: 12/03/1998
• Status: Expired due to Term

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Breiling, Marco, Stoessel, Jan, Gerhauser, Heinz, Eberlein, Ernst
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Tran, Congvan
• Application Number:
  US09/202,729
• Time in Patent Office: 904 Days
• Field of Search: 455/427, 455/3.02, 455/10, 455/12.1, 455/137, 714/701, 714/746, 714/764, 714/751, 714/752, 714/758, 714/767, 714/763, 714/786, 375/290, 375/264, 375/225, 375/250
• US Class Current: 455/427
• CPC Class Codes: H04B 7/0604 with predefined switching scheme
• CPC Class Codes: H04B 7/0671 using different delays between antennas
• CPC Class Codes: H04B 7/0894 using different delays between antennas
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/06 using space diversity

Abstract

An apparatus for transmitting information comprises a bitstream source for providing a bitstream representing the information, a redundancy adding encoder for generating an encoded bitstream, which is arranged to output, for a first number of input bits, a second number of output bits, the second number of output bits having at least twice as many output bits as the first number of input bits, wherein the second number of output bits includes two portions of output bits, each portion of output bits individually allowing the retrieval of information represented by the first number of input bits, and the first portion of output bits being coded based on the bitstream in a different way with respect to the second portion of output bits. The apparatus further comprises a partitioner for partitioning the second number of output bits into the two portions of output bits and a transmitter for transmitting the output bits of the first portion via a first channel and the output bits of the second portion via a second channel, the second channel being spatially different from the first channel. An inventive receiving apparatus combines the signals received via the first and second channels and uses both channel signals for channel decoding by removing redundancy. Thus, the transmitting receiving system is suitable for providing time and/or space diversity and, in the optimal case, provides a C/N value which is greater than 4.3 dB with respect to a two-channel system comprising a duplicator in the transmitter and a channel-controlled switch in the receiver.

Claims

1. An apparatus for transmitting information, comprising:

a bitstream source for providing a bitstream representing the information;

a redundancy adding encoder for generating an encoded bitstream based on the bitstream provided by the bitstream source wherein the encoder is arranged to output, for a first number of input bits, a second number of output bits, the second number of output bits having at least twice as many output bits as the first number of input bits, and wherein the second number of output bits includes two portions of output bits, each portion of output bits individually allowing the retrieval of information represented by the first number of input bits, and the first portion of output bits being coded based on the bitstream in a different way with respect to the second portion of output bits;

a partitioner for partitioning the second number of output bits into the two portions of output bits;

a transmitter for transmitting the output bits of the first portion via a first channel and the output bits of the second portion via a second channel, the second channel being spatially different from the first channel;

the transmitter being a single transmitter;

the first channel being defined by the single transmitter and a first position of a mobile receiver;

the second channel being defined by the single transmitter and a second position of the mobile receiver; and

the transmitter further includes delay means for delaying the second portion of output bits transmitted via the second channel such that time diversity is obtained.

2. An apparatus for transmitting information, comprising:

a bitstream source for providing a bitstream representing the information;

a redundancy adding encoder for generating an encoded bitstream based on the bitstream provided by the bitstream source wherein the encoder is arranged to output, for a first number of input bits, a second number of output bits, the second number of output bits having at least twice as many output bits as the first number of input bits, and wherein the second number of output bits includes two portions of output bits, each portion of output bits individually allowing the retrieval of information represented by the first number of input bits, and the first portion of output bits being coded based on the bitstream in a different way with respect to the second portion of output bits;

a partitioner for partitioning the second number of output bits into the two portions of output bits; and

means for transmitting the output bits of the first portion via a first channel and the output bits of the second portion via a second channel, the second channel being spatially different from the first channel;

the means for transmitting including a first transmitter and a second transmitter spaced apart from the first transmitter;

the first channel being defined by the first transmitter and the receiver; and

the second channel being defined by the second transmitter and the receiver such that space diversity is obtained.

3. The apparatus of claim 2, in which:

the first and second transmitters include two satellites in different orbital positions, such that the first channel is defined by an uplink connection from earth to the first satellite and a downlink connection from the first satellite to a receiver on earth, and such that the second channel is defined by a uplink connection from earth to the second satellite and a downlink connection from the second satellite to the receiver on earth.

4. The apparatus of claim 2, in which:

one transmitter includes a satellite; and

the other transmitter includes a terrestrial sender such that terrestrial diversity is obtained.

5. The apparatus of claim 2, in which the transmitter further includes delay means for delaying the second portion of output bits transmitted via the second channel such that time diversity is obtained.

6. An apparatus for transmitting information, comprising:

a bitstream source for providing a bitstream representing the information;

a redundancy adding encoder for generating an encoded bitstream based on the bitstream provided by the bitstream source wherein the encoder is arranged to output, for a first number of input bits, a second number of output bits, the second number of output bits having at least twice as many output bits as the first number of input bits, and wherein the second number of output bits includes two portions of output bits, each portion of output bits individually allowing the retrieval of information represented by the first number of input bits, and the first portion of output bits being coded based on the bitstream in a different way with respect to the second portion of output bits, the redundancy adding encoder including a convolutional encoder for obtaining a code rate less than or equal to 0.5, wherein the code rate is the ratio of the first number of input bits to the second number of output bits, the convolutional encoder combining a current input bit to be encoded with at least one of a certain number of preceding input bits;

a partitioner for partitioning the second number of output bits into the two portions of output bits; and

a transmitter for transmitting the output bits of the first portion via a first channel and the output bits of the second portion via a second channel, the second channel being spatially different from the first channel.

7. The apparatus of claim 6, in which:

the certain number of preceding bits is 6; and

the convolutional encoder comprises three generator polynominals g₁, g₂ and g₃ having the following binary form;

g₁=1100111,

g₂=1011101, and

g₃=1110011.

8. The apparatus of claim 6 which further comprises a puncturing unit operative to discard at least one predetermined bit of the encoded bitstream such that the second number of output bits is an even number, wherein the first and second portions of output bits comprise the same number of output bits.

9. An apparatus for transmitting information, comprising:

a bitstream source for providing a bitstream representing the information;

a redundancy adding encoder for generating an encoded bitstream based on the bitstream provided by the bitstream source wherein the encoder is arranged to output, for a first number of input bits, a second number of output bits, the second number of output bits having at least twice as many output bits as the first number of input bits, and wherein the second number of output bits includes two portions of output bits, each portion of output bits individually allowing the retrieval of information represented by the first number of input bits, and the first portion of output bits being coded based on the bitstream in a different way with respect to the second portion of output bits;

a partitioner for partitioning the second number of output bits into the two portions of output bits; and

a transmitter for transmitting the output bits of the first portion via a first channel and the output bits of the second portion via a second channel, the second channel being spatially different from the first channel;

the redundancy adding encoder is operative to code the bitstream provided by the bitstream source in a bit-by-bit fashion;

the partitioner includes a parallel storage for storing a predetermined amount of output bits of the convolutional encoder;

a parallel-to-serial converter for producing a serial stream of the stored bits to be partitioned into the first and second portion of output bits is provided; and

a de-multiplexer for performing the partition of the serial stream of output bits into the first and second portions is provided.

10. An apparatus for receiving information, the information being represented by an encoded bitstream, the encoded bitstream being encoded such that its redundancy is at least doubled with respect to a bitstream from which the encoded bitstream is derived, and that, for a first number of bits of the bitstream, the encoded bitstream comprises a second number of bits, the second number of bits having at least twice as many bits as the first number, and wherein the second number of bits includes two portions of bits, each portion of bits individually allowing the retrieval of information represented by the first number of bits, and the first portion of the bits being encoded in a different way with respect to the second portion of bits, the apparatus comprising:

receiving means for receiving the first portion of bits via a first channel and the second portion of bits via a second channel, the first and the second channels being spatially different from each other;

a combiner for combining the first and the second portions the combiner including a depuncturing unit for performing a depuncturing operation on the first and second portions of bits to compensate for a puncturing operation performed in a transmitter; and

a decoder for decoding the coded bitstream by removing redundancy from the coded bitstream, the decoder using the first and second portions of bits combined by the combiner.

11. The apparatus of claim 10, in which the receiving means further includes delay means for delaying the portion of bits received via one channel to compensate for a delay imposed on the portion of bits received via the other channel.

12. The apparatus of claim 11, in which the combiner includes a multiplexer for multiplexing first and second portions into a form suitable for the decoder.

13. An apparatus for receiving information, the information being represented by an encoded bitstream, the encoded bitstream being encoded such that its redundancy is at least doubled with respect to a bitstream from which the encoded bitstream is derived, and that, for a first number of bits of the bitstream, the encoded bitstream comprises a second number of bits, the second number of bits having at least twice as many bits as the first number, and wherein the second number of bits includes two portions of bits, each portion of bits individually allowing the retrieval of information represented by the first number of bits, and the first portion of the bits being encoded in a different way with respect to the second portion of bits, the apparatus comprising:

receiving means for receiving the first portion of bits via a first channel and the second portion of bits via a second channel, the first and the second channels being spatially different from each other;

a combiner for combining the first and the second portions;

a decoder for decoding the coded bitstream by removing redundancy from the coded bitstream, the decoder using the first and second portions of bits combined by the combiner,

the decoder comprising a soft decision decoder processing probabilities in that a received bit represents a high or low state rather than an actual wave form characteristic of the received bitstream; and

depuncturing means for compensating for a puncturing operation in a transmitter is provided and attributes to a bit to be depunctured equal probabilites for the high and low states.

14. The apparatus of claim 13 in which the decoder includes a Viterbi decoder performing maximum likelihood decoding using the state information of the first and second channels.

15. The apparatus of claim 14 in which the decoder further comprises a Reed-Solomon decoder fed by the Viterbi decoder for undoing a Reed-Solomon encoding performed in the transmitter.

16. The apparatus of claim 13 in which:

the decoder comprises a signal to noise ratio evaluating means for determining a channel having a low signal to noise ratio; and

a bit replacing means for replacing the bits of a portion of bits received via a channel having a low signal to noise ratio by values equivalent to a lower reliability for the high and low states.

17. The apparatus of claim 13 in which the receiving means comprises, for each channel, a QPSK demodulator for providing the first and the second portions of bits.

18. A method of transmitting information, comprising the following steps:

providing a bitstream representing the information;

generating a redundancy added encoded bitstream based on the bitstream provided in the step of providing, wherein for a first number of input bits, a second number of output bits is generated, the second number of output bits having at least twice as many output bits as the first number of input bits, and wherein the second number of output bits includes two portions of output bits, each portion of output bits individually allowing the retrieval of information represented by the first number of input bits, and the first portion of output bits being coded based on the bitstream in a different way with respect to the second portion of output bits;

partitioning the second number of output bits into the two portions of output bits; and

transmitting by use of a single transmitter the output bits of the first portion via a first channel and the output bits of the second portion via a second channel, the second channel being spatially different from the first channel;

the first channel being defined by the single transmitter and a first position of a mobile receiver;

the second channel being defined by the single transmitter and a second position of the mobile receiver; and

the step of transmitting comprising the following substeps;

transmitting the first portion of output bits; and

delaying the second portion of output bits before transmitting via the second channel such that time diversity is obtained.

19. A method of transmitting information, comprising the following steps:

providing a bitstream representing the information;

generating a redundancy added encoded bitstream based on the bitstream provided in the step of providing, wherein for a first number of input bits, a second number of output bits is generated, the second number of output bits having at least twice as many output bits as the first number of input bits, and wherein the second number of output bits includes two portions of output bits, each portion of output bits individually allowing the retrieval of information represented by the first number of input bits, and the first portion of output bits being coded based on the bitstream in a different way with respect to the second portion of output bits;

partitioning the second number of output bits into the two portions of output bits; and

transmitting the output bits of the first portion via a first channel and the output bits of the second portion via a second channel, the second channel being spatially different from the first channel

the step of transmitting being carried out by a first transmitter and a second transmitter spaced apart from the first transmitter;

the first channel being defined by the first transmitter and the receiver; and

the second channel being defined by the second transmitter and the receiver such that space diversity is obtained.

20. The method of claim 19, in which:

the first and second transmitters include two satellites in different orbital positions, such that the first channel is defined by an uplink connection from earth to the first satellite and a downlink connection from the first satellite to a receiver on earth, and such that the second channel is defined by a uplink connection from earth to the second satellite and a downlink connection from the second satellite to the receiver on earth.

21. The method of claim 19, in which:

one transmitter includes a satellite; and

the other transmitter includes a terrestrial sender such that terrestrial diversity is obtained.

22. The method of claim 19, in which the step of transmitting further includes the following substeps:

delaying the second portion of output bits transmitted via the second channel such that time diversity is obtained.

23. A method of transmitting information, comprising the following steps:

providing a bitstream representing the information;

generating a redundancy added encoded bitstream based on the bitstream provided in the step of providing, wherein for a first number of input bits, a second number of output bits is generated, the second number of output bits having at least twice as many output bits as the first number of input bits, and wherein the second number of output bits includes two portions of output bits, each portion of output bits individually allowing the retrieval of information represented by the first number of input bits, and the first portion of output bits being coded based on the bitstream in a different way with respect to the second portion of output bits;

the generating step being carried out by means of a convolutional encoder for obtaining a code rate less than or equal to 0.5, wherein the code rate is the ratio of the first number of input bits to the second number of output bits, the convolutional encoder combining a current input bit to be encoded with at least one of a certain number of preceding input bits;

partitioning the second number of output bits into the two portions of output bits; and

transmitting the output bits of the first portion via a first channel and the output bits of the second portion via a second channel, the second channel being spatially different from the first channel.

24. The method of claim 23, in which:

the certain number of preceding bits is 6; and

the convolutional encoder comprises three generator polynominals g₁, g₂ and g₃ having the following binary form;

g₁=1100111,

g₂=1011101, and

g₃=1110011.

25. The method of claim 23 which further comprises the step of puncturing to discard at least one predetermined bit of the encoded bitstream such that the second number of output bits is an even number, wherein the first and second portions of output bits comprise the same number of output bits.

26. A method of transmitting information, comprising the following steps:

providing a bitstream representing the information;

generating a redundancy added encoded bitstream based on the bitstream provided in the step of providing, by coding the bitstream provided by the bitstream source in a bit-by-bit fashion, wherein for a first number of input bits, a second number of output bits is generated, the second number of output bits having at least twice as many output bits as the first number of input bits, and wherein the second number of output bits includes two portions of output bits, each portion of output bits individually allowing the retrieval of information represented by the first number of input bits, and the first portion of output bits being coded based on the bitstream in a different way with respect to the second portion of output bits;

producing a serial stream of the stored bits to be partitioned into the first and second portion of output bits by the step of parallel-to-serial converting;

partitioning the second number of output bits into the two portions of output bits by de-multiplexing; and

transmitting the output bits of the first portion via a first channel and the output bits of the second portion via a second channel, the second channel being spatially different from the first channel.

27. A method of receiving information, the information being represented by an encoded bitstream, the encoded bitstream being encoded such that its redundancy is at least doubled with respect to a bitstream from which the encoded bitstream is derived, and that, for a first number of bits of the bitstream, the encoded bitstream comprises a second number of bits, the second number of bits having at least twice as many bits as the first number, and wherein the second number of bits includes two portions of bits, each portion of bits individually allowing the retrieval of information represented by the first number of bits, and the first portion of the bits being encoded in a different way with respect to the second portion of bits, the method comprising the following steps:

receiving the first portion of bits via a first channel and the second portion of bits via a second channel, the first and the second channels being spatially different from each other;

combining the first and the second portions;

performing a depuncturing operation on the first and second portions of bits to compensate for a puncturing operation performed in a transmitter; and

decoding the coded bitstream by removing redundancy from the coded bitstream, wherein the first and second portions of bits combined in the step of combining are used in the step of decoding.

28. The method of claim 27, in which the step of receiving further includes the step of delaying the portion of bits received via one channel to compensate for a delay imposed on the portion of bits received via the other channel.

29. The method of claim 27, in which the step of combining includes the step of multiplexing the first and second portions into a form suitable for the step of decoding.

30. The method of claim 27, in which the step of receiving comprises, for each channel, the step of QPSK demodulating for providing the first and the second portions of bits.

31. A method of receiving information, the information being represented by an encoded bitstream, the encoded bitstream being encoded such that its redundancy is at least doubled with respect to a bitstream from which the encoded bitstream is derived, and that, for a first number of bits of the bitstream, the encoded bitstream comprises a second number of bits, the second number of bits having at least twice as many bits as the first number, and wherein the second number of bits includes two portions of bits, each portion of bits individually allowing the retrieval of information represented by the first number of bits, and the first portion of the bits being encoded in a different way with respect to the second portion of bits, the method comprising the following steps:

receiving the first portion of bits via a first channel and the second portion of bits via a second channel, the first and the second channels being spatially different from each other;

combining the first and the second portions; and

decoding the coded bitstream by removing redundancy from the coded bitstream by soft decision decoding to process probabilities such that a received bit represents a high or low state rather than an actual wave form characteristic of the received bitstream, wherein the first and second portions of bits combined in the step of combining are used in the step of decoding; and

a step of depuncturing for compensating for a puncturing operation in a transmitter is carried out and attributes to a bit to be depunctured equal probabilites for the high and low states.

32. The method of claim 31 in which the step of decoding includes a Viterbi decoder performing maximum likelihood decoding using the state information of the first and second channels.

33. The method of claim 32 in which the step of decoding further comprises a Reed-Solomon decoder fed by the Viterbi decoder for undoing a Reed-Solomon encoding performed in the transmitter.

34. The method of claim 31, in which:

the step of decoding includes the step of signal to noise ratio evaluating for determining a channel having a low signal to noise ratio; and

the step of bit replacing for replacing the bits of a portion of bits received via a channel having a low signal to noise ratio by equal probabilities for the high and low states is carried out.

35. The method of claim 31, in which the step of receiving comprises, for each channel, the step of QPSK demodulating for providing the first and second portions of bits.