Receiver stomp-and-restart in a distributed MU-MIMO system using RSSI separation

• US 9,668,149 B1
• Filed: 05/25/2016
• Issued: 05/30/2017
• Est. Priority Date: 05/25/2016
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Stager, Paul J., Silverman, Matthew A., Hart, Brian D., Kloper, David
• Primary Examiner(s): Tran, Khai
• Application Number:
  US15/163,915
• Time in Patent Office: 370 Days
• Field of Search: 375347, 375349, 370221, 370328, 370334, 370350
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• 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 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0885 with combination
• CPC Class Codes: H04L 25/03 Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
• CPC Class Codes: H04L 43/16 Threshold monitoring
• CPC Class Codes: H04W 88/085 Access point devices with remote components

Abstract

A system and method are provided for performing stomp-and-restart techniques in distributed MU-MIMO system. A plurality of radio head devices are provided that are configured to be deployed separated from each other in a coverage region of interest of a wireless network. A central processor subsystem is provided that is in communication with the plurality of radio head devices. The central processor subsystem configured to perform several operations based on downconverted samples received from the plurality of radio head devices.

Claims

1. A system comprising:

a plurality of receiver devices configured to be deployed separated from each other in a coverage region of interest of a wireless network, each receiver device including a plurality of antennas and a downconverter associated with each antenna configured to downconvert received signals transmitted by two or more client devices, each downconverter configured to produce downconverted samples of the received signals at each of the plurality of antennas; and

a central processor subsystem in communication with the plurality receiver devices, the central processor subsystem configured to;

receive the downconverted samples from the plurality of receiver devices;

after start-of-packet detection of a first packet by one or more of the plurality of receiver devices based on the downconverted samples, group receiver devices into disjoint sets based on measurements related to signal strength or signal-to-interference ratio of the downconverted samples associated with the first packet;

decode the first packet using downconverted samples received by a first set of receiver devices;

determine that a stronger second packet is being received by a particular set of receiver devices while the first packet is being decoded when the stronger second packet is detected on any antenna of the particular set of receiver devices;

continue to decode the first packet using downconverted samples from the first set of receiver devices but without downconverted samples from the particular set of receiver devices associated with the stronger second packet; and

decode the second packet using downconverted samples from receiver devices in the particular set of receiver devices and using downconverted samples from any one or more additional antennas of a receiver device that detected the second packet.

2. The system of claim 1, wherein the central processor subsystem is configured to group the receiver devices such that each decoding set has a sufficient number of antennas to process a maximum number of expected spatial streams in a single packet unit transmitted by one or more of the client devices.

3. The system of claim 2, wherein the central processor subsystem is configured to, in grouping the receiver devices, order the receiver devices according to receive signal strength or signal-to-interference ratio of downconverted samples obtained from the respective receiver devices.

4. The system of claim 1, wherein the central processor subsystem is configured to determine that the stronger second packet is being received based on a receive restart indication sent by a receiver device in the particular set of receiver devices.

5. The system of claim 1, wherein one or more receiver devices that detect the second packet with a receive signal strength greater than a threshold are configured to send a receive abort/unlock condition notification to the central processor subsystem.

6. The system of claim 5, wherein the central processor subsystem is configured to decode the second packet using downconverted samples from the one or more receiver devices that sent the receive abort/unlock condition notification.

7. The system of claim 1, wherein the central processor subsystem is configured to null downconverted samples associated with the second packet when decoding the first packet.

8. The system of claim 1, wherein the central processor subsystem is configured to select downconverted samples for the one or more additional antennas based on receive signal strength or signal-to-interference ratio.

9. The system of claim 1, wherein the central processor subsystem is configured to null downconverted samples associated with the first packet when decoding the second packet.

10. The system of claim 1, wherein the receiver devices in the first set of receiver devices are configured to generate spatial nulling data associated with the first packet and to supply the spatial nulling data to the central processor subsystem for use in nulling the first packet when decoding the second packet.

11. The system of claim 10, wherein the spatial nulling data is for use in nulling the first packet in a frequency domain, or for nulling the first packet in a time domain.

12. The system of claim 10, wherein the central processor subsystem is configured to further process the spatial nulling data to compensate for carrier frequency offset of the first packet with respect to the second packet using carrier frequency offset correction, a Fast Fourier Transform, or a general Digital Fourier Transform, estimation of spatial nulling per subband comprised of one or more subcarriers, and a filter bank using coefficients based on Digital Fourier Transform coefficients, wherein the filter bank splits a frequency channel into constituent subbands that are individually nulled.

13. A method comprising:

receiving transmitted signals from two or more client devices at a plurality of receiver devices separated from each other in a coverage region of interest of a wireless network, each receiver device including a plurality of antennas;

producing downconverted samples of received signals at each of the plurality of antennas of each receiver device;

performing start-of-packet detection of a first packet by one or more of the plurality of receiver devices based on the downconverted samples;

after start-of-packet detection of the first packet, grouping receiver devices into disjoint sets based on measurements related to signal strength or signal-to-interference ratio of the downconverted samples associated with the first packet;

decoding the first packet using downconverted samples received by a first set of receiver devices;

determining that a stronger second packet is being received by a particular set of receiver devices while the first packet is being decoded when the stronger second packet is detected on any antenna of the particular set of receiver devices;

continuing to decode the first packet using downconverted samples from the first set of receiver devices but without downconverted samples from the particular set of receiver devices associated with the stronger second packet; and

decoding the second packet using downconverted samples from receiver devices in the particular set of receiver devices and using downconverted samples from any one or more additional antennas of a receiver device that detected the second packet.

14. The method of claim 13, wherein determining that the stronger second packet is being received is based on a receive restart indication sent by a receiver device in the particular set of receiver devices.

15. The method of claim 14, further comprising the one or more receiver devices that detect the second packet with a receive signal strength greater than a threshold are configured to generate a receive abort/unlock condition notification.

16. The method of claim 15, wherein decoding the second packet comprises decoding the second packet using downconverted samples from the one or more receiver devices that generated the receive abort/unlock condition notification.

17. The method of claim 13, further comprising nulling downconverted samples associated with the second packet when decoding the first packet, and nulling downconverted samples associated with the first packet when decoding the second packet.

18. One or more non-transitory computer readable storage media encoded with instructions that, when executed by a processor, cause the processor to perform operations comprising:

performing start-of-packet detection of a first packet received by one or more of a plurality of receiver devices based on downconverted samples generated by one or more of the plurality of receiver devices from transmit signals received from two or more client devices in a wireless network, the plurality of receiver devices being separated from each other in a coverage region of interest of the wireless network, each receiver device including a plurality of antennas;

after start-of-packet detection of the first packet, grouping receiver devices into disjoint sets based on measurements related to signal strength or signal-to-interference ratio of the downconverted samples associated with the first packet;

decoding the first packet using downconverted samples received by a first set of receiver devices;

determining that a stronger second packet is being received by a particular set of receiver devices while the first packet is being decoded when the stronger second packet is detected on any antenna of the particular set of receiver devices;

continuing to decode the first packet using downconverted samples from the first set of receiver devices but without downconverted samples from the particular set of receiver devices associated with the stronger second packet; and

decoding the second packet using downconverted samples from receiver devices in the particular set of receiver devices and using downconverted samples from any one or more additional antennas of a receiver device that detected the second packet.

19. The non-transitory computer readable storage media of claim 18, wherein the instructions for determining that the stronger second packet is being received is based on a receive restart indication sent by a receiver device in the particular set of receiver devices.

20. The non-transitory computer readable storage media of claim 18, wherein the instructions for decoding the second packet comprise instructions for decoding the second packet using downconverted samples from the one or more receiver devices that sent a receive abort/unlock condition notification indicating that the one or more receiver devices detected the second packet with a receive signal strength greater than a threshold.