Methods And Apparatus For Compensating For Propagation Delays In Coordinated Multi-Point Transmission

• US 20120275507A1
• Filed: 04/27/2011
• Published: 11/01/2012
• Est. Priority Date: 04/27/2011
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Renesas Mobile Corporation (Renesas Electronics Corporation)
• Inventors: Roman, Timo E., Koivisto, Tommi T., Enescu, Mihai, Schober, Karol
• Granted Patent: US 8,638,867 B2
• Time in Patent Office: Days
• US Class Current: 375/226
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• CPC Class Codes: H04B 7/0417 Feedback systems
• 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 7/0626 Channel coefficients, e.g. channel state information [CSI]

Abstract

Systems and techniques for communication using coordinated multi-point transmission. In one embodiment, an apparatus comprises at least one processor and a memory storing a set of computer instructions, configured. The processor is configured to cause the apparatus to determine a linear phase variation between at least first and second transmissions from first and second transmission points based at least in part on a propagation delay difference between the first and second transmissions, and transmit the phase variation information for at least the first and the second transmissions. An apparatus configured to operate as a transmission point in a network receives linear phase variation information indicating phase variation experienced by at least one user equipment resulting from a propagation delay difference between at least the apparatus and a second apparatus operating as a second transmission point and manages transmission so as to control phase variation resulting from the propagation delay difference.

Claims

1. An apparatus comprising:

a processing system comprising at least one processor and a memory storing a set of computer instructions, wherein the processing system is configured to;

cause the apparatus to compute a linear phase variation based at least in part on a propagation delay difference between at least a first radiofrequency transmission from at least a first transmission point and at least a second radiofrequency transmission from at least a second transmission point; and

transmit the phase variation information for at least the first and the second transmissions.

2. The apparatus of claim 1, wherein the processing system is configured to cause the apparatus to measure a propagation delay difference between the first and the second transmissions and compute the phase variation based on the measured propagation delay difference.

3. The apparatus of claim 1, wherein the processing system is configured to cause the apparatus to estimate the phase variation in the frequency domain.

4. The apparatus of claim 1, wherein the first and the second radiofrequency transmissions each comprise a plurality of sub-bands and wherein the processor causes the apparatus to compute a phase variation for each sub-band based at least in part on the propagation delay between the first and the second transmission with respect to each sub-band.

5. The apparatus of claim 1, wherein the first transmission point is a reference transmission point and wherein the apparatus receives radiofrequency transmissions from each of the second transmission points and a plurality of additional transmission points and computes phase variation information based at least in part on respective propagation delay differences between transmissions from the reference transmission point and each of the second and the additional transmission points.

6. The apparatus of claim 1, wherein the memory stores a codebook indexing each of a plurality of codes to a specific phase variation value and wherein transmission of the phase variation information comprises transmission of a code indexed to the phase variation value.

7. The apparatus of claim 6, wherein the codebook comprises codes based on a phase shift keying (PSK) complex alphabet.

8. The apparatus of claim 7, wherein the phase shift keying alphabet is selected based at least in part on a quantization error exhibited by a multi-transmission point feedback combiner of at least one of the transmission points.

9. The apparatus of claim 1, wherein the apparatus is a user equipment conducting communication using orthogonal frequency division multiplexing (OFDM) and wherein the apparatus is operative to receive OFDM transmissions from the transmission points.

10. The apparatus of claim 1, wherein the apparatus is configured to provide channel state information feedback in support of coordinated multi-point transmission from multiple transmission points.

11. A method comprising:

receiving at least a first radiofrequency transmission from a first transmission point and a second radiofrequency transmission from a second transmission point;

operating a processor to compute a linear phase variation based at least in part on propagation delay differences between transmissions from at least the first and the second transmission point; and

transmitting the phase variation information to at least one of the transmission points.

12. The method of claim 11, wherein the first and the second radiofrequency transmissions each comprise a plurality of sub-bands and wherein the phase variation is computed based at least in part on the propagation delay with respect to corresponding sub-bands of the first and second transmissions and wherein computing a phase variation comprises computing a phase variation for each sub-band.

13. The method of claim 11, wherein the first transmission point is a reference transmission point, wherein receiving at least first and second radiofrequency transmissions comprises receiving radiofrequency transmissions from each of the second transmission points and a plurality of additional transmission points, and wherein phase variation information is computed based at least in part on respective propagation delay differences between transmissions from the reference transmission point and each of the second and the additional transmission points.

14. The method of claim 11, further comprising storing a codebook indexing each of a plurality of codes to a specific phase variation value and wherein transmission of the phase variation information comprises transmission of a code indexed to the phase variation value.

15. The method of claim 14, wherein the codebook comprises codes based on a phase shift keying (PSK) complex alphabet.

16. The method of claim 11, wherein the radiofrequency transmissions are orthogonal frequency division multiplexing (OFDM) transmissions.

17. An apparatus comprising:

a processing system comprising at least one processor and a memory storing a set of computer instructions, wherein the processing system is configured to;

cause the apparatus to operate as a transmission point in a cellular communication network, the processor being configured to control communication by the apparatus so as to engage in coordinated multi-point transmission (CoMP) with at least one other transmission point for a user equipment operating in the network;

receive linear phase variation information indicating phase variation experienced by at least one user equipment resulting from a propagation delay difference between at least the apparatus and a second apparatus operating as a second transmission point; and

manage transmission to the user equipment so as to control phase variation resulting from the propagation delay difference.

18. The apparatus of claim 17, wherein engaging in coordinated multi-point transmission comprises engaging in joint processing transmission.

19. The apparatus of claim 17, wherein the memory stores a codebook indexing each of a plurality of codes to a specific phase variation value and wherein receiving the phase variation information comprises receiving a code indexed to the phase variation value.

20. The apparatus of claim 19, wherein the codebook comprises codes based on a phase shift keying complex alphabet.

21. The apparatus of claim 17, wherein managing transmission so as to control phase variation comprises performing M-PSK quantization, wherein M is an integer.

22. The apparatus of claim 21, wherein the value of M is selected based at least in part on a quantization error of a CoMP multi-cell feedback combiner operating in the network.

23. The apparatus of claim 17, wherein the apparatus is a transmission point conducting communication using orthogonal frequency division multiplexing (OFDM).