Interference suppression in wireless backhaul network using collaborative weight update scheme

• US 8,630,267 B1
• Filed: 11/24/2009
• Issued: 01/14/2014
• Est. Priority Date: 11/24/2009
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Jin, Hang
• Primary Examiner(s): MATTIS, JASON E
• Application Number:
  US12/624,501
• Time in Patent Office: 1,512 Days
• Field of Search: 370/252, 370/329, 370/332
• US Class Current: 370/332
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04L 25/03955 in combination with downlink estimations, e.g. downlink path losses
• CPC Class Codes: H04W 16/28 using beam steering

Abstract

Coordinated transmission of sounding messages between base stations and feeder stations in a wireless backhaul network is provided to facilitate accurate observations by each base station of signals from its serving feeder station and from other feeder stations in order to generate interference nulling beamforming weights for transmission to and/or reception from its serving feeder station. Likewise, these techniques facilitate accurate observations by each feeder station of signals from the base station(s) it serves and from other base stations in order to generate interfering nulling beamforming weights for transmission to and/or reception from the base station(s) it serves.

Claims

1. A method comprising:

at a base station operating in a wireless network configured to serve wireless client devices, receiving at a plurality of antennas of the base station downlink sounding messages in corresponding downlink sounding frames, wherein each downlink sounding frame is appended to a separate downlink network traffic subframe that is transmitted by respective ones of a plurality of feeder stations operating in a wireless backhaul network, and wherein the downlink sounding frames are each allocated to a single feeder station in accordance with a time division scheme in which no two feeder stations transmit a downlink sounding message in the same downlink sounding frame;

transmitting from the base station uplink sounding messages in a particular one of a plurality of uplink sounding frames, wherein each uplink sounding frame is appended to a separate uplink network traffic subframe, and wherein the uplink sounding frames are each allocated to a single base station in accordance with the time division scheme for uplink sounding to feeder stations;

generating spatial signature information with respect to a serving feeder station for the base station based on downlink sounding messages received from the serving feeder station in downlink sounding frames designated for the serving feeder station;

generating interference spatial signature information based on signals received during downlink sounding frames other than the downlink sounding frames designated for the serving feeder station; and

based on the spatial signature information for the serving feeder station and the interference spatial signature information, generating interference nulling beamforming weights for use by the base station when transmitting uplink backhaul traffic signals to the serving feeder station and/or for use when receiving downlink backhaul traffic signals from the serving feeder station.

2. The method of claim 1, and further comprising selecting one of the plurality of feeder stations to be the serving feeder station for service in the wireless backhaul network by evaluating downlink sounding messages received for two or more of the plurality of feeder stations.

3. The method of claim 2, and further comprising obtaining from received downlink sounding messages a feeder station identifier that identifies the feeder station that transmitted the downlink sounding message, a frame index that identifies an index for the downlink sounding frame in which the downlink sounding message is transmitted, a frame index divisor that represents a total number of frames to be transmitted in a cycle comprised of a plurality of downlink sounding frames and a plurality of uplink sounding frames, and a starting frame index indicating a starting frame index for uplink sounding frames to be used for sending uplink sounding messages for initial uplink sounding to the feeder station identified by the feeder station identifier.

4. The method of claim 3, wherein upon selecting one of the plurality of feeder stations to be the serving feeder station, further comprising transmitting an uplink sounding message during an uplink sounding frame derived from the starting frame index for uplink sounding frames to be used for initial uplink sounding to the serving feeder station, wherein the uplink sounding message contains a base station identifier for the base station and the feeder station identifier for the feeder station that is selected to be the serving feeder station.

5. The method of claim 4, and further comprising determining whether any of the downlink sounding messages received from the feeder station that is selected to be the serving feeder station contains a base station identifier that matches the base station identifier for the base station which indicates acceptance of the selected feeder station as the serving feeder station, and if so, obtaining an uplink sounding frame assignment contained in the downlink sounding message that also contains the base station identifier for the base station.

6. The method of claim 5, and further comprising transmitting uplink sounding messages at an uplink sounding frame in each cycle according to the uplink sounding frame assignment and based on the frame index divisor.

7. The method of claim 5, wherein upon failing to receive a downlink sounding message containing a base station identifier for the base station that indicates acceptance of the selected feeder station, selecting comprises selecting an other of the plurality of feeder stations to be the serving feeder station and repeating the obtaining, transmitting of an uplink sounding message to the other of the plurality of feeder stations, and receiving of downlink sounding messages from the other of the plurality of feeder stations to determine whether the other of the plurality of feeder stations has indicated acceptance of its selection to be the serving feeder station.

8. The method of claim 5, and further comprising including uplink sounding message type information in uplink sounding messages to be transmitted, wherein the uplink message type information indicates whether the uplink sounding message is for initial uplink sounding or is for ongoing uplink sounding based on the uplink sounding frame assignment.

9. The method of claim 1, wherein receiving downlink sounding messages comprises receiving downlink sounding messages during a time interval prior to a time interval during which downlink backhaul network traffic is transmitted in the backhaul network, and transmitting comprises transmitting uplink sounding messages during a time interval prior to a time interval during which uplink backhaul network traffic is transmitted in the backhaul network.

10. A method comprising:

at a feeder station that is part of a wireless backhaul network comprising a plurality of feeder stations each configured to communicate backhaul traffic to and from one or more base stations that serve wireless client devices in a wireless network, transmitting downlink sounding messages in designated downlink sounding frames among a plurality of downlink sounding frames, wherein each downlink sounding frame is appended to a separate downlink network traffic subframe is allocated to a single feeder station in accordance with a time division scheme in which no two feeder stations transmit a downlink sounding message in the same downlink sounding frame;

receiving uplink sounding messages in corresponding uplink sounding frames allocated for base stations to transmit uplink sounding messages, wherein each uplink sounding frame is appended to a separate uplink network traffic subframe, and wherein the uplink sounding frames are each allocated to a single base station in accordance with the time division scheme such that no two base stations transmit an uplink sounding message in the same uplink sounding frame;

generating spatial signature information with respect to a selecting base station that has selected the feeder station for service in the backhaul network based on uplink sounding messages received from the selecting base station in assigned uplink sounding frames;

generating interference spatial signature information based on signals received during uplink sounding frames other than the assigned uplink sounding frames for the selecting base station; and

based on the spatial signature information for the selecting base station and the interference spatial signature information, generating interference nulling beamforming weights for use by the feeder station when transmitting downlink backhaul traffic signals to the selecting base station and/or receiving signals from uplink backhaul traffic signals from the selecting base station.

11. The method of claim 10, wherein transmitting downlink sounding messages comprises transmitting information comprising a feeder station identifier that identifies the feeder station that transmits the downlink sounding message, a frame index that identifies an index for the downlink sounding frame in which the downlink sounding message is transmitted, a frame index divisor that represents a total number of frames to be transmitted in a cycle comprised of a plurality of downlink sounding frames and a plurality of uplink sounding frames, and a starting frame index indicating a starting frame index for uplink sounding frames to be used for sending uplink sounding messages for initial uplink sounding to the feeder station identified by the feeder station identifier.

12. The method of claim 11, and further comprising determining whether a received uplink sounding message contains a feeder station identifier for the feeder station indicating that the selecting base station has selected the feeder station for service in the backhaul network, which the uplink sounding message comprising a base station identifier that identifies the base station that has transmitted the uplink sounding message, and when the feeder station accepts its selection by the selecting base station, generating an uplink sounding frame assignment to the selecting base station such that the assigned uplink sounding frames for the selecting base station are not used by other base stations, and in downlink sounding messages that are transmitted by the feeder station during the designated downlink sounding frames, including an acceptance indication to the selecting base station that the feeder station accepts that it has been selected by the selecting base station and including in transmitted downlink sounding messages information indicating the uplink sounding frame assignment for the selecting base station to use when transmitting uplink sounding messages to the feeder station.

13. The method of claim 12, and further comprising sending a message to other feeder stations to advise them of the uplink sounding frame assignment made to the selecting base station so that other feeder stations do not make the same uplink sounding frame assignment to another base station.

14. The method of claim 11, and further comprising including in downlink sounding messages a feeder identifier for the feeder station, a base station identifier that corresponds to the base station identifier of the selecting base station and which presence of the base station identifier serves as the acceptance indication to the selecting base station.

15. The method of claim 14, wherein transmitting downlink sounding messages comprises transmitting information in each downlink sounding message indicating whether or not the feeder station has captured an uplink spatial signature for the selecting base station so as to inform the selecting base station whether to start sending uplink backhaul network traffic.

16. The method of claim 14, and further comprising terminating service to a base station that the feeder station had been serving when the feeder station fails to receive uplink sounding messages from the base station a predetermined number of consecutive instances of its assigned uplink sounding frame or in response to receiving from the base station an uplink sounding message containing information indicating the base station requests to terminate backhaul network service with the feeder station.

17. The method of claim 10, wherein transmitting downlink sounding messages comprises receiving downlink sounding messages during a time interval prior to a time interval during which downlink backhaul network traffic is transmitted in the backhaul network, and wherein receiving uplink sounding messages comprises receiving uplink sounding messages during a time interval prior to a time interval during which uplink backhaul network traffic is transmitted in the backhaul network.

18. A system comprising:

a plurality of base stations configured to operate in a wireless network and to serve wireless client devices in the wireless network;

a plurality of feeder stations configured to operate in a wireless backhaul network and to serve base stations in the wireless backhaul network;

wherein each base station is configured to transmit uplink sounding messages in a particular one of a plurality of uplink sounding frames, wherein each uplink sounding frame is appended to a separate uplink network traffic subframe, and wherein the uplink sounding frames are each allocated to a single base station for uplink sounding to feeder stations in accordance with a time division scheme such that no two base stations transmit an uplink sounding message in the same uplink sounding frame;

wherein each feeder station is configured to transmit downlink sounding messages in designated downlink sounding frames among a plurality of downlink sounding frames, wherein each downlink sounding frame is appended to a separate downlink network traffic subframe, and wherein each downlink sounding frame is allocated to a single feeder station in accordance with the time division scheme such that no two feeder stations transmit a downlink sounding message in the same downlink sounding frame;

wherein each base station is configured to receive downlink sounding messages in corresponding downlink sounding frames transmitted by respective ones of a plurality of feeder stations, generate spatial signature information for a serving feeder station for the base station based on downlink sounding messages received from the serving feeder station in downlink sounding frames designated for the serving feeder station, generate interference spatial signature information based on signals received during downlink sounding frames other than the downlink sounding frames designated for the serving feeder station, and based on the spatial signature information for the serving feeder station and the interference spatial signature information, generate interference nulling beamforming weights for use by the base station when transmitting uplink backhaul traffic signals to the serving feeder station and/or for use when receiving downlink backhaul traffic signals from the serving feeder station;

wherein each feeder station is configured to receive uplink sounding messages in corresponding uplink sounding frames, to generate spatial signature information for a selecting base station that has selected the feeder station for service in the backhaul network based on uplink sounding messages received from the selecting base station in assigned uplink sounding frames, generate interference spatial signature information based on signals received during uplink sounding frames other than the assigned uplink sounding frames for the selecting base station, and based on the spatial signature information for the selecting base station and the interference spatial signature information, generate interference nulling beamforming weights for use by the feeder station when transmitting downlink backhaul traffic signals to the selecting base station and/or receiving signals from uplink backhaul traffic signals from the selecting base station.

19. A base station apparatus comprising:

a plurality of antennas;

a receiver configured to generate a plurality of receive signals based on reception at respective ones of the plurality of antenna of downlink sounding messages in corresponding downlink sounding frames transmitted by respective ones of a plurality of feeder stations operating in a wireless backhaul network, wherein each downlink sounding frame is appended to a separate downlink network traffic subframe, and wherein the downlink sounding frames are each allocated to a single feeder station in accordance with a time division scheme in which no two feeder stations transmit a downlink sounding message in the same downlink sounding frame;

a transmitter configured to generate transmit signals to be transmitted by respective ones of the plurality of antennas; and

a controller configured to connect to the transmitter and the receiver, wherein the controller is configured to;

generate uplink sounding messages for transmission by the transmitter in a particular one of a plurality of uplink sounding frames allocated for uplink sounding;

generate spatial signature information with respect to a serving feeder station based on downlink sounding messages received from the serving feeder station in downlink sounding frames designated for the serving feeder station;

generate interference spatial signature information based on signals received during downlink sounding frames other than the downlink sounding frames designated for the serving feeder station; and

based on the spatial signature information for the serving feeder station and the interference spatial signature information, generate interference nulling beamforming weights for use when transmitting uplink backhaul traffic signals to the serving feeder station and/or for use when receiving downlink backhaul traffic signals from the serving feeder station.

20. The base station of claim 19, where from a received downlink sounding message, the controller is configured to determine a feeder station identifier that identifies a feeder station that transmitted the downlink sounding message, a frame index that identifies an index for the downlink sounding frame in which the downlink sounding message is transmitted, a frame index divisor that represents a total number of frames to be transmitted in a cycle comprised of a plurality of downlink sounding frames and a plurality of uplink sounding frames, and a starting frame index indicating a starting frame index for uplink sounding frames to be used for sending uplink sounding messages for initial uplink sounding to the feeder station identified by the feeder station identifier.

21. The base station of claim 20, wherein upon selecting one of a plurality of feeder stations to be a serving feeder station, the controller is configured to cause the transmitter to transmit an uplink sounding message during an uplink sounding frame derived from the starting frame index for uplink sounding frames to be used for initial uplink sounding to the serving feeder station, wherein the uplink sounding message contains a base station identifier for the base station and the feeder station identifier for the feeder station that is selected to be the serving feeder station.

22. A feeder station apparatus comprising:

a plurality of antennas;

a receiver configured to generate a plurality of receive signals based on reception at respective ones of the plurality of antennas of uplink sounding messages in corresponding uplink sounding frames allocated for base stations to transmit uplink sounding messages, wherein each uplink sounding frame is appended to a separate uplink network traffic subframe, and wherein the uplink sounding frames are each allocated to a single base station in accordance with a time division scheme in which no two base stations transmit an uplink sounding message in the same uplink sounding frame;

a transmitter configured to generate transmit signals to be transmitted by respective ones of the plurality of antennas, including downlink sounding messages;

a controller configured to connect to the receiver and the transmitter, wherein the controller is configured to;

generate downlink sounding messages for transmission by the transmitter in designated downlink sounding frames among a plurality of downlink sounding frames allocated for feeder stations operating in a wireless backhaul network

generate spatial signature information for a selecting base station that has selected the feeder station for service in the backhaul network based on uplink sounding messages received from the selecting base station in assigned uplink sounding frames;

generate interference spatial signature information based on signals received during uplink sounding frames other than the assigned uplink sounding frames for the selecting base station; and

based on the spatial signature information for the selecting base station and the interference spatial signature information, generate interference nulling beamforming weights for use by the feeder station when transmitting downlink backhaul traffic signals to the selecting base station and/or receiving signals from uplink backhaul traffic signals from the selecting base station.

23. The feeder station of claim 22, wherein the controller is configured to generate downlink sounding messages that comprise a feeder station identifier that identifies the feeder station that transmits the downlink sounding message, a frame index that identifies an index for the downlink sounding frame in which the downlink sounding message is transmitted, a frame index divisor that represents a total number of frames to be transmitted in a cycle comprised of a plurality of downlink sounding frames and a plurality of uplink sounding frames, and a starting frame index indicating a starting frame index for uplink sounding frames to be used for sending uplink sounding messages for initial uplink sounding to the feeder station identified by the feeder station identifier.

24. The feeder station of claim 23, wherein the controller is configured to determine whether a received uplink sounding message contains a feeder station identifier for the feeder station indicating that the selecting base station has selected the feeder station for service in the backhaul network, which the uplink sounding message comprising a base station identifier that identifies the base station that has transmitted the uplink sounding message, and when the feeder station accepts its selection by the selecting base station, generating an uplink sounding frame assignment to the selecting base station such that the assigned uplink sounding frames for the selecting base station are not used by other base stations, and in downlink sounding messages that are transmitted by the feeder station during the designated downlink sounding frames, including an acceptance indication to the selecting base station that the feeder station accepts that it has been selected by the selecting base station and including in transmitted downlink sounding messages information indicating the uplink sounding frame assignment for the selecting base station to use when transmitting uplink sounding messages to the feeder station.