Method and device for diversity transmission/reception

• US 6,741,838 B2
• Filed: 12/15/2000
• Issued: 05/25/2004
• Est. Priority Date: 12/15/1999
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Tsujimoto, Ichiro
• Primary Examiner(s): Vuong, Quochien B.
• Application Number:
  US09/736,427
• Publication Number:
  US 20010004585A1
• Time in Patent Office: 1,257 Days
• Field of Search: 455/101, 455/102, 455/103, 455/118, 455/132, 455/133, 455/137, 455/277.1, 455/272, 455/273, 455/232.1, 455/234.1, 455/138, 375/299, 375/347
• US Class Current: 455/101
• CPC Class Codes: H04B 7/0613 using simultaneous transmission H04B7/0686 takes precedence
• CPC Class Codes: H04B 7/0865 Independent weighting, i.e. weights based on own antenna reception parameters

Abstract

A transmission side device combines two independent transmission signals (S1, S2) together to produce two combined signals, i.e., a sum signal (S1+S2) and a difference signal (S1−S2), and transmits the produced signals over two radio wave propagation paths, respectively. After the sum signal and the difference signal are received by the reception side device, the sum signal and the difference signal, as received, are subjected to an AGC control operation and a complex-level multiplication operation with a weighting coefficient based on correlation control, and then separated into two, restored, independent signals.

Claims

1. A diversity transmission/reception method, comprising the steps of:

receiving two transmission signals (S1 and S2) independent of each other;

combining the two transmission signals to produce two combined signals through addition and subtraction, respectively;

transmitting the combined signals over two propagation paths, respectively;

receiving the signals which have been transmitted over the two propagation paths, respectively; and

restoring the two transmission signals.

2. A diversity transmission/reception device, comprising:

a transmission side device for receiving two transmission signals independent of each other, combining the two transmission signals to produce two combined signals through addition and subtraction, respectively, and transmitting the combined signals over two propagation paths, respectively;

and a reception side device for receiving the signals which have passed through the two propagation paths, respectively, and extracting the two transmission signals by eliminating one of the transmission signals from one of the combined signals and by eliminating the other one of the transmission signals from the other one of the combined signals, respectively.

3. A diversity transmission/reception device according to claim 2, the transmission side device comprising:

modulation means for modulating the transmission signals using carrier waves of the same frequency so that one of the transmission signals has a phase which is shifted by π

/2 from that of the other one of the transmission signals;

means for adding the two modulated signals together;

means for transmitting the signal obtained through the addition as a first reception signal;

means for subtracting one of the two modulated signals from the other one of the two modulated signals; and

means for transmitting the signal obtained through the subtraction as a second reception signal, and the reception side device comprising;

first amplification means for amplifying the first reception signal;

second amplification means for amplifying the second reception signal;

first multiplication means for multiplying a given weighting coefficient to an output from the first amplification means;

second multiplication means for multiplying a given weighting coefficient to an output from the second amplification means;

means for adding together respective outputs from the first multiplication means and the second multiplication means;

means for subtracting the output from one of the first and second multiplication means from the output from the other one of the first and second multiplication means;

first correlation control means for performing a correlation operation between an output from the addition means and the output from the first amplification means so as to provide a weighting coefficient to the first multiplication means; and

second correlation control means for performing a correlation operation between an output from the subtraction means and the output from the second amplification means so as to provide a weighting coefficient to the second multiplication means.

4. A diversity transmission/reception device according to claim 2, the transmission side device comprising:

modulation means for modulating the transmission signals using carrier waves of the same frequency so that one of the transmission signals has a phase which is shifted by π

/2 from that of the other one of the transmission signals;

means for adding the two modulated signals together;

means for transmitting the signal obtained through the addition as a first reception signal;

means for subtracting one of the two modulated signals from the other one of the two modulated signals; and

means for transmitting the signal obtained through the subtraction as a second reception signal, and the reception side device comprising;

first amplification means for amplifying the first reception signal;

second amplification means for amplifying the second reception signal;

first multiplication means for multiplying a given weighting coefficient to an output from the first amplification means;

second multiplication means for multiplying a given weighting coefficient to an output from the second amplification means;

means for adding together respective outputs from the first multiplication means and the second multiplication means;

means for subtracting the output from one of the first and second multiplication means from the output from the other one of the first and second multiplication means;

first re-modulation means for re-modulating a demodulated signal obtained by demodulation of the first reception signal and inputting the re-modulated signal, instead of the output from the addition means, to the first correlation control means; and

second re-modulation means for re-modulating a demodulated signal obtained by demodulation of the second reception signal and inputting the re-modulated signal, instead of the output from the subtraction means, to the second correlation control means.

5. A diversity transmission/reception device according to claim 2, the transmission side device comprising:

modulation means for modulating the transmission signals using carrier waves of the same frequency so that one of the transmission signals has a phase which is shifted by π

/2 from that of the other one of the transmission signals;

means for adding the two modulated signals together;

means for transmitting the signal obtained through the addition as a first reception signal;

means for subtracting one of the two modulated signals from the other one of the two modulated signals; and

means for transmitting the signal obtained through the subtraction as a second reception signal, and the reception side device comprising;

first amplification means for amplifying the first reception signal;

second amplification means for amplifying the second reception signal;

first multiplication means for multiplying a given weighting coefficient to an output from the first amplification means;

second multiplication means for multiplying a given weighting coefficient to an output from the second amplification means;

means for adding together respective outputs from the first multiplication means and the second multiplication means;

means for subtracting the output from one of the first and second multiplication means from the output from the other one of the first and second multiplication means;

first preamble generation means for generating a first preamble signal and inputting the first preamble signal, instead of the output from the addition means, to the first correlation control means;

second preamble generation means for generating a second preamble signal and inputting the second preamble signal, instead of the output from the subtraction means, to the second correlation control means;

first gate means for allowing the output from the first amplification means to be input to the first correlation means at a timing at which the first preamble signal appears to the first reception signal; and

second gate means for allowing the output from the second amplification means to be input to the second correlation means at a timing at which the second preamble signal appears to the second reception signal.

6. A diversity transmission/reception device according to claim 2, comprising:

means for monitoring characteristics of the propagation paths; and

means for, when a quality of at least one of the propagation paths degrades, stopping the signal combining operation on the transmission side.

7. A diversity transmission/reception device according to claim 6, wherein the monitoring means is means which detects a decrease in a reception signal level to or below a predetermined value based on at least one of the outputs from a first and second correlation control means.

8. A diversity transmission/reception device, comprising a transmission side device and a reception side device, the transmission side device comprising:

addition means for receiving two transmission signals (S1 and S2) independent of each other to produce an output signal (S1+S2);

subtraction means for receiving the two transmission signals (S1 and S2) independent of each other to produce an output signal (S1−

S2);

first transmission means for diversity-transmitting the output signal (S1+S2) from the addition means to a first propagation path as a first reception signal; and

second transmission means for diversity-transmitting the output signal (S1−

S2) from the subtraction means to a second propagation path as a second reception signal, and the reception side device comprising;

first and second reception means for receiving the first and second reception signals which have passed through the first and second propagation paths, respectively;

first and second automatic gain controlling means for receiving, as their inputs, the outputs from the first and second reception means, respectively;

first and second multiplication means for subjecting the output signals from the first and second automatic gain controlling means to complex multiplication with weighting coefficients (W1 and W2) so as to produce output signals (x1 and x2), respectively;

addition means and subtraction means receiving, as their inputs, the output signals (x1 and x2) from the first and second multiplication means so as to produce outputs (y1=x1+x2) and (y2=x1−

x2), respectively;

first correlation control means for performing a correlation operation between a first input and a second input, the first input being the output (y1=x1+x2) from the addition means and the second input being the output from the first automatic gain controlling means, so as to provide the weighting coefficient (W1) to the first multiplication means; and

second correlation control means for performing a correlation operation between a first input and a second input, the first input being the output (y2=x1−

x2) from the subtraction means and the second input being the output from the second automatic gain controlling means, so as to provide the weighting coefficient (W2) to the second multiplication means.

9. A diversity transmission/reception device according to claim 8, wherein the two transmission signals (S1 and S2) independent of each other are signals which are obtained by modulating carrier waves of the same frequency whose phases are shifted from each other by about π

/2.

10. A diversity transmission/reception device according to claim 8, wherein:

the first and second correlation control means comprise means for calculating the weighting coefficients (W1 and W2), respectively, so that each of the output (y1) from the addition means and the output (y2) from the subtraction means of the reception side device has an amplitude that is in proportion to the square of a respective one of the first and second reception signals and is in phase with the respective one of the first and second reception signals.

11. A diversity transmission/reception device according to claim 10, wherein:

gains of the first and second automatic gain controlling means are in proportion to 1/|ρ

1| and 1/|ρ

2|, respectively (where ρ

1 and ρ

2, each being a complex number, denote transmission coefficients of the first and second propagation paths, respectively); and

the weighting coefficients (W1 and W2) are W1=k1ρ

1*/|ρ

1| and W2=k2ρ

2*/|ρ

2|, respectively (where k1 and k2 denote proportional constants, and ρ

1* and ρ

2* denote complex conjugates of ρ

1 and ρ

2, respectively).

12. A diversity transmission/reception device according to claim 8, comprising means for monitoring a signal level of each of the first and second reception signals and for, when the signal level of at least one of the first and second reception signals decreases to or below a predetermined value, stopping the signal combining operation on the transmission side.

13. A diversity transmission/reception device comprising a transmission side device and a reception side device, the transmission side device comprising:

addition means for receiving two transmission signals (S1 and S2) independent of each other to produce an output signal (S1+S2);

subtraction means for receiving the two transmission signals (S1 and S2) independent of each other to produce an output signal (S1−

S2);

first transmission means for diversity-transmitting the output signal (S1+S2) from the addition means to a first propagation path as a first reception signal; and

second transmission means for diversity-transmitting the output signal (S1−

S2) from the subtraction means to a second propagation path as a second reception signal, and the reception side device comprising;

first and second reception means for receiving the first and second reception signals which have passed through the first and second propagation paths, respectively;

first and second automatic gain controlling means for receiving, as their inputs, the outputs from the first and second reception means, respectively;

first and second multiplication means for subjecting the output signals from the first and second automatic gain controlling means to complex multiplication with weighting coefficients (W1 and W2) so as to produce output signals (x1 and x2), respectively;

addition means and subtraction means receiving, as their inputs, the output signals (x1 and x2) from the first and second multiplication means so as to produce outputs (y1=x1+x2) and (y2=x1−

x2), respectively;

a first modulator for re-modulating the first reception signal which has been demodulated and providing the re-modulated signal, instead of the output from the addition means, to the first correlation control means; and

a second modulator for re-modulating the second reception signal which has been demodulated and providing the re-modulated signal, instead of the output from the subtraction means, to the second correlation control means.

14. A diversity transmission/reception device comprising a transmission side device and a reception side device, the transmission side device comprising:

addition means for receiving two transmission signals (S1 and S2) independent of each other to produce an output signal (S1+S2);

subtraction means for receiving the two transmission signals (S1 and S2) independent of each other to produce an output signal (S1−

S2);

first transmission means for diversity-transmitting the output signal (S1+S2) from the addition means to a first propagation path as a first reception signal; and

second transmission means for diversity-transmitting the output signal (S1−

S2) from the subtraction means to a second propagation path as a second reception signal, and the reception side device comprising;

first and second reception means for receiving the first and second reception signals which have passed through the first and second propagation paths, respectively;

first and second automatic gain controlling means for receiving, as their inputs, the outputs from the first and second reception means, respectively;

first and second multiplication means for subjecting the output signals from the first and second automatic gain controlling means to complex multiplication with weighting coefficients (W1 and W2) so as to produce output signals (x1 and x2), respectively;

addition means and subtraction means receiving, as their inputs, the output signals (x1 and x2) from the first and second multiplication means so as to produce outputs (y1=x1+x2) and (y2=x1−

x2), respectively;

first preamble generation means for generating a first preamble signal and inputting the first preamble signal, instead of the output from the addition means, to the first correlation control means as a reference signal;

second preamble generation means for generating a second preamble signal and inputting the second preamble signal, instead of the output from the subtraction means, to the second correlation control means as a reference signal;

first gate means for allowing the output from the first automatic gain controlling means to pass therethrough so as to be input to the first correlation means at a timing at which the first preamble signal appears to the first reception signal; and

second gate means for allowing the output from the second automatic gain controlling means to pass therethrough so as to be input to the second correlation means at a timing at which the second preamble signal appears to the second reception signal.