System and method for multiple-input multiple-output (MIMO) radio communication

• US 20040023621A1
• Filed: 07/25/2003
• Published: 02/05/2004
• Est. Priority Date: 07/30/2002
• Status: Active Grant

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Inventors: Vaidyanathan, Chandra, Sugar, Gary L.
• Granted Patent: US 7,194,237 B2
• Time in Patent Office: Days
• US Class Current: 455/103
• CPC Class Codes: H04B 7/0434 using multiple eigenmodes
• CPC Class Codes: H04B 7/0465 taking power constraints at power amplifier or emission constraints, e.g. constant modulus, into account
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0697 using spatial multiplexing

Abstract

A system, method and device for MIMO radio communication of multiple signals between a first device having N plurality of antennas and a second device having M plurality of antennas. At the first device, a vector s representing L signals [s₁ . . . s_L] to be transmitted is processed with a transmit matrix A to maximize capacity of the channel between the first device and the second device subject to a power constraint that the power emitted by each of the N antennas is less than or equal to a maximum power. The power constraint for each antenna may be the same for all antennas or specific or different for each antenna. For example, the power constraint for each antenna may be equal to a total maximum power emitted by all of the N antennas combined divided by N. The transmit matrix A distributes the L signals [s₁ . . . s_L] among the N plurality of antennas for simultaneous transmission to the second device. At the second device, the signals received by the M plurality of antennas are processed with receive weights and the resulting signals are combined to recover the L signals.

Claims

1. A method for radio communication between a first device having N plurality of antennas and a second device having M plurality of antennas, comprising a step of processing a vector s representing L signals [s₁ . . . s_L] with a transmit matrix A that is computed to maximize capacity of the channel between the first device and the second device subject to a power constraint that the power emitted by each of the N plurality of antennas is less than or equal to a maximum power, whereby the transmit matrix A distributes the L signals [s₁ . . . s_L] among the N plurality of antennas for simultaneous transmission to the second device.

2. The method of claim 1, wherein the step of processing comprises processing the vector s with the transmit matrix A that is computed subject to the power constraint being different for one or more of the N plurality of antennas.

3. The method of claim 1, wherein the step of processing comprises processing the vector s with the transmit matrix A that is computed subject to the power constraint being the same for each of the N plurality of antennas.

4. The method of claim 3, wherein the step of processing comprises processing the vector s with the transmit matrix A that is computed subject to the power constraint for each of the N plurality of antennas being equal to a total maximum power emitted by all of the N plurality of antennas combined divided by N.

5. The method of claim 4, wherein the step of processing comprises multiplying the vector s with the transmit matrix A, where the transmit matrix A is equal to VD, where V is the eigenvector matrix for H^HH, H is the channel response from the first device to the second device, D=diag(d₁, . . . ,d_L) and |d_p|² is the power of the p^th one of the L signals.

6. The method of claim 5, wherein when N≦

M, the step of processing comprises multiplying the vector s with the transmit matrix A, where D=I·

sqrt(P_max/N), and I is the identity matrix, such that the power transmitted by each of the N plurality of antennas is the same and equal to P_max/N.

7. The method of claim 5, wherein when N<

M, the step of processing comprises multiplying the vector s with the transmit matrix A, where D=sqrt(d·

P_max/N_Tx)·

I, such that the power transmitted by antenna i for i=1 to N is (d·

P_max/N)·

(VV^H)_ii, and d_p=d for p=1 to L.

8. The method of claim 7, wherein the step of processing comprises multiplying the vector s with the transmit matrix A, where d=1/z and z=max{(VV^H)_ii}, such that the maximum power from any of the N plurality of antennas is P_max/N and the total power emitted from the N plurality of antennas combined is between P_max/M and P_max.

9. The method of claim 7, wherein the step of processing comprises multiplying the vector s with the transmit matrix A, where d=1, such that the power emitted by antenna i for i=1 to N is (P_max/N)·

(VV^H)_ii, and the total power emitted from the N plurality of antennas combined is P_max/M.

10. The method of claim 1, and further comprising the steps at the second device of receiving at the M plurality of antennas signals transmitted by the first device, and processing signals received at each of the plurality of M antennas with receive weights and combining the resulting signals to recover the L signals.

11. The method of claim 1, wherein each of the L signals is baseband modulated using a multi-carrier modulation process, and wherein the step of processing comprises multiplying the vector s with a transmit matrix A(k) at each of a plurality of sub-carriers k.

12. A radio communication device, comprising:

a. N plurality of antennas;

b. N plurality of radio transmitters each coupled to a corresponding one of the plurality of antennas;

c. a baseband signal processor coupled to the N plurality of radio transmitters to process a vector s representing L signals [s₁ . . . s_L] with a transmit matrix A that is computed to maximize capacity of the channel between the first device and the second device subject to a power constraint that the power emitted by each of the N plurality of antennas is less than or equal to a maximum power, whereby the transmit matrix A distributes the L signals [s₁ . . . s_L] for simultaneous transmission to the second device by the N plurality of antennas.

13. The device of claim 12, wherein the baseband signal processor processes the vector s with a transmit matrix A that is computed subject to the power constraint being different for one or more of the N plurality of antennas.

14. The device of claim 12, wherein the baseband signal processor processes the vector s with a transmit matrix A that is computed subject to the power constraint being the same for each of the N plurality of antennas.

15. The device of claim 14, wherein the baseband signal processor processes the vector s with a transmit matrix A that is computed subject to the power constraint for each of the N plurality of antennas being equal to a total maximum power emitted by all of the N plurality of antennas combined divided by N.

16. The device of claim 15, wherein the baseband signal processor multiplies the vector s with the transmit matrix A, where the transmit matrix A is equal to VD, where V is the eigenvector matrix for H^HH, H is the channel response from the device to another device having M plurality of antennas, D=diag(d₁, . . . ,d_L) and |d_p|² is the power of the p^th one of the L signals.

17. The device of claim 16, wherein when N≦

M, the baseband signal processor multiplies the vector s with the transmit matrix A that is computed where D=I·

sqrt(P_max/N), and I is the identity matrix, such that the power transmitted by each of the N plurality of antennas is the same and equal to P_max/N.

18. The device of claim 16, wherein when N<

M, the baseband signal processor multiplies the vector s with the transmit matrix A that is computed where D=sqrt(d·

P_max/N_Tx)·

I such that the power emitted by antenna i for i=1 to N is (d·

P_max/N)·

(VV^H)_ii, and d_p=d for p=1 to L.

19. The device of claim 18, wherein the baseband signal processor multiplies the vector s with the transmit matrix A that is computed where d=1/z and z=max{(VV^H)_ii56 such that the maximum power from any antenna of the N plurality of antennas is P_max/N and the total power emitted from the N plurality of antennas combined is between P_max/M and P_max.

20. The device of claim 18, wherein the baseband signal processor multiplies the vector s with the transmit matrix A that is computed where d=1, such that the power emitted by antenna i for i=1 to N is (P_max/N)·

(VV^H)_ii, and the total power emitted from the N plurality of antennas combined is P_max/M.

21. The device of claim 12, wherein each of the L signals is baseband modulated using a multi-carrier modulation process, and the baseband signal processor multiplies the vector s with a transmit matrix A(k) at each of a plurality of sub-carriers k.

22. A radio communication system comprising:

a. a first device comprising;

i. N plurality of antennas;

ii. N plurality of radio transmitters each coupled to a corresponding one of the plurality of antennas; and

iii. a baseband signal processor coupled to the N plurality of radio transmitters to process a vector s representing L signals [s₁ . . . s_L] with a transmit matrix A that is computed to maximize capacity of the channel between the first device and the second device subject to a power constraint that the power emitted by each of the N plurality of antennas is less than or equal to a maximum power, whereby the transmit matrix A distributes the L signals [s₁ . . . s_L] for simultaneous transmission to the second device by the N plurality of antennas;

b. a second device comprising;

i. M plurality of antennas;

ii. M plurality of radio receivers each coupled to a corresponding one of the plurality of antennas; and

iii. a baseband signal processor coupled to the N plurality of radio receivers to process signals output by the plurality of radio receivers with receive weights and combining the resulting signals to recover the L signals [s₁ . . . s_L].

23. The system of claim 22, wherein the baseband signal processor of the first device processes the vector s with the transmit matrix A that is computed subject to the power constraint being different for one or more of the N antennas.

24. The system of claim 23, wherein the baseband signal processor of the first device processes the vector s with the transmit matrix A that is computed subject to the power constraint being the same for each of the N plurality of antennas.

25. The system of claim 24, wherein the baseband signal processor of the first device processes the vector s with the transmit matrix A that is computed subject to the power constraint for each of the N antennas being equal to a total maximum power emitted by all of the N antennas combined divided by N.

26. The system of claim 25, wherein the baseband signal processor of the first device multiplies the vector s with the transmit matrix A, wherein the transmit matrix A is equal to VD, where V is the eigenvector matrix for H^HH, H is the channel response from the device to another device having M plurality of antennas, D=diag(d₁, . . . ,d_L) and |d_p|² is the power of the p^th one of the L signals.