Uplink Signal Bandwidth Characterization from Channel State Information

• US 20130286863A1
• Filed: 04/30/2012
• Published: 10/31/2013
• Est. Priority Date: 04/30/2012
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Silverman, Matthew A., Stager, Paul J., Hart, Brian D., Janani, Mohammad, Hedayat, Ahmadreza
• Granted Patent: US 9,066,244 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04B 7/0404 the mobile station comprising multiple antennas, e.g. to provide uplink diversity
• CPC Class Codes: H04L 5/001 the frequencies being arranged in component carriers
• CPC Class Codes: H04L 5/0039 Frequency-contiguous, i.e. with no allocation of frequencies for one user or terminal between the frequencies allocated to another
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 72/046 the resource being in the space domain, e.g. beams
• CPC Class Codes: H04W 72/542 using measured or perceived quality

Abstract

Techniques are provided to determine whether or not incident power at a wireless communication device in at least two frequency channels is from the same device. Incident power in frequency channels allocated to a basic service set in a wireless network is received at a plurality of antennas of the wireless communication device. Channel state information is computed for at least two frequency channels allocated to the basic service set. One or more metrics are generated based on the channel state information in the two frequency channels. The one or more metrics are evaluated to characterize an uplink signal bandwidth associated with the two channels to determine whether or not the incident power in the two channels is from the same device.

Claims

1. A method comprising:

at a wireless communication device having a plurality of antennas, receiving incident power in frequency channels allocated to a basic service set in a wireless network;

computing channel state information for at least two frequency channels allocated to the basic service set;

generating one or more metrics based on the channel state information in the two frequency channels; and

evaluating the one or more metrics to characterize an uplink signal bandwidth associated with the two channels to determine whether or not the incident power in the two channels is from the same device.

2. The method of claim 1, wherein when evaluating determines that the incident power in the two channels is from the same device, further comprising computing downlink beamforming weights based on the channel state information for the two channels to use for downlink transmissions to the device.

3. The method of claim 1, wherein when evaluating determines that the incident power in the two channels is not from the same device, further comprising discarding the channel state information for one of the two channels.

4. The method of claim 1, wherein generating comprises generating a plurality of metrics, and wherein evaluating comprises performing logical and/or arithmetic combining of two or more of the plurality of metrics to determine whether or not incident power in the two channels is from the same device.

5. The method of claim 4, wherein generating comprises generating a channel state information subcarrier correlation metric between corresponding positive and negative subcarriers at a boundary of the two channels;

time-based correlation metrics for channel state information in the two channels, respectively;

power correlation metrics for the two channels, respectively; and

a coherence bandwidth for the two channels, respectively.

6. The method of claim 5, wherein generating the channel state information subcarrier correlation metric comprises computing a correlation between the channel state information at one or more positive subcarriers in the uplink signal bandwidth with channel state information at corresponding one or more negative subcarriers.

7. The method of claim 5, wherein generating the time-based correlation metrics comprises generating a correlation between channel state information for time separated uplink packets in one channel and a correlation between channel state information for time separated uplink packets in the other channel.

8. The method of claim 5, wherein generating the power correlation metrics for the two channels comprises generating an average power of the channel state information at corresponding one or more pairs of subcarriers for each of the two channels.

9. The method of claim 5, wherein generating the average coherence bandwidth for the two channels comprises generating an average coherence bandwidth for each of the two channels based on a span of subcarriers that are highly correlated in the respective channels.

10. The method of claim 1, wherein generating the one or more metrics comprises generating for a first channel a first quantity equal to sum(CSI(i)*conj(CSI(i+1))) and for a second channel that is adjacent to the first channel a second quantity equal to sum(CSI(i)*conj(CSI(i+1))), where CSI(i) is the channel state information of subcarrier i, CSI(i) is a vector, conj( ) is a conjugate operation, and sum( ) is a summation over the same subsets of subcarriers in the first and second channels, and wherein evaluating comprises computing a difference between a real portion of the first quantity and a real portion of the second quantity, and comparing the difference with a threshold such that when the difference is less than the threshold, it is determined that the incident power in the first and second channels is from the same device.

11. The method of claim 1, wherein generating the one or more metrics comprises generating for a first channel a first quantity equal to sum(CSI(i)+CSI(i+2))*conj(CSI(i+1))/((|CSI(i)|+|CSI(i+2)|)*|CSI(i+1)I) and for a second channel that is adjacent to the first channel a second quantity equal to sum(CSI(i)+CSI(i+2))*conj(CSI(i+1))/((|CSI(i)|+|CSI(i+2)|)*|CSI(i+1)|), where CSI(i) is the channel state information of subcarrier i, CSI(i) is a vector, conj( ) is a conjugate operation, and sum( ) is a summation over the same subsets of subcarriers in the first and second channels, wherein evaluating comprises computing a difference between a real portion of the first quantity and a real portion of the second quantity, and comparing the difference with a threshold such that when the difference is less than the threshold, it is determined that the incident power in the first and second channels is from the same device.

12. The method of claim 1, wherein generating the one or more metrics comprises computing a quantity equal to sum(RX1(i)*conj(RX1(i+1))*conj(RX2(i)*conj(RX2(i+1)))), where RX1(i) is the received signal at subcarrier i of a first channel and RX2(i) is the received signal at subcarrier i of a secondary channel that is adjacent to the first channel, and sum( ) is a summation over a subset of subcarriers in the first and second channels, computing an absolute value of the quantity, and wherein evaluating comprises comparing the absolute value of the quantity with a threshold such that when the absolute value of the quantity exceeds the threshold it is determined that the incident power in the first and second channels is from the same device.

13. The method of claim 1, wherein generating the one or more metrics comprises computing a first channel state information vector for a positive subcarrier (CSI₁) and a second channel state information vector for a corresponding negative subcarrier (CSI₂), and computing a quantity equal to abs(sum(CSI₁(i)*conj(CSI₂(i))/(|CSI₁(i)*CSI₂(i)|))), and where sum( ) is a summation over a subset of subcarriers in the first and second channels, comparing the quantity with a threshold such that when the absolute value of the quantity exceeds the threshold it is determined that the incident power in the first and second channels is from the same device.

14. An apparatus comprising:

a plurality of antennas;

a receiver coupled to the plurality of antennas and configured to produce antenna-specific receive signals;

a controller coupled to the receiver and configured to;

compute channel state information for at least two frequency channels allocated to a basic service set based on received incident power at the plurality of antennas in the two frequency channels;

generate one or more metrics based on the channel state information for the two frequency channels; and

evaluate the one or more metrics to characterize an uplink signal bandwidth associated with the two channels to determine whether or not the incident power in the two channels is from the same device.

15. The apparatus of claim 14, wherein when the controller determines that incident power in the two channels is from the same device, the controller is configured to compute downlink beamforming weights based on channel state information for the two channels to use for downlink transmissions to the device, and when the controller determines that the incident power in the two channels is not from the same device, the controller is configured to discard the channel state information for one of the two channels.

16. The apparatus of claim 14, wherein the controller is configured to generate a plurality of metrics, and to evaluate the plurality of metrics by performing logical and/or arithmetic combining of two or more of the plurality of metrics to determine whether or not incident power in the two channels is from the same device.

17. The apparatus of claim 16, wherein the controller is configured to generate a channel state information subcarrier correlation metric between corresponding positive and negative subcarriers at a boundary of the two channels;

time-based correlation metrics for channel state information in the two channels, respectively;

power correlation metrics for the two channels, respectively; and

a coherence bandwidth for the two channels, respectively.

18. One or more computer readable storage media encoded with software comprising computer executable instructions and when the software is executed by a processor operable to:

compute channel state information for at least two frequency channels allocated to a basic service set based on received incident power at a plurality of antennas of a wireless communication device in the two frequency channels;

generate one or more metrics based on the channel state information for the two frequency channels; and

evaluate the one or more metrics to characterize an uplink signal bandwidth associated with the two channels to determine whether or not the incident power in the two channels is from the same device.

19. The computer readable storage media of claim 18, further comprising instructions operable to compute downlink beamforming weights based on channel state information for the two channels to use for downlink transmissions to the device when it is determined that incident power in the two channels is from the same device, and to discard the channel state information for one of the two channels when it is determined that the incident power in the two channels is not from the same device.

20. The computer readable storage media of claim 18, wherein the instructions operable to generate one or more metrics comprise instructions operable to generate a plurality of metrics, and the instructions operable to evaluate comprise instructions operable to evaluate the plurality of metrics by performing logical and/or arithmetic combining of two or more of the plurality of metrics to determine whether or not incident power in the two channels is from the same device.

21. The computer readable storage media of claim 18, wherein the instructions operable to generate the plurality of metrics comprise instructions operable to generate a channel state information subcarrier correlation metric between corresponding positive and negative subcarriers at a boundary of the two channels;

time-based correlation metrics for channel state information in the two channels, respectively;

power correlation metrics for the two channels, respectively; and

a coherence bandwidth for the two channels, respectively.