Hybrid time-spatial multiplexing for wireless broadcast messages through antenna radiation beam synthesis

• US 8,195,240 B2
• Filed: 04/15/2008
• Issued: 06/05/2012
• Est. Priority Date: 04/18/2007
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Jin, Hang, Grabner, John, Guo, Li, Liu, Qingwen
• Primary Examiner(s): Corsaro, Nick
• Assistant Examiner(s): Chambers, Tangela T.
• Application Number:
  US12/103,406
• Publication Number:
  US 20080261658A1
• Time in Patent Office: 1,512 Days
• Field of Search: 455/562.1, 455/561, 455/446, 370/336, 370/337, 370/345
• US Class Current: 455/562.1
• CPC Class Codes: H04W 16/28 using beam steering
• CPC Class Codes: H04W 48/12 using downlink control channel
• CPC Class Codes: H04W 72/51 based on terminal or device properties

Abstract

A hybrid time-spatial multiplexing technique is provided for beamforming broadcast messages to mobile stations that may be within a coverage region or cell of a base station. The coverage region is divided into a plurality of segments. The mobile stations are assigned to at least one of the segments based on their locations within the coverage region or other criteria. The base station computes beamforming antenna weights which are configured to produce a radiation beam pattern from a plurality of antennas of the base station to respective ones of each of the plurality of segments in the region. A broadcast message is transmitted to each segment of the region in a time-division multiplexed manner using the beamforming antenna weights associated with the radiation beam pattern for the corresponding segment.

Claims

1. A method comprising:

dividing a region in which a first communication device wirelessly communicates with one or more of a plurality of second communication devices into a plurality of segments;

assigning respective ones of the second communication devices to a group of the segments;

monitoring locations of the second communication devices and adjusting assignment of the second communication devices to the segments based on the monitoring;

generating beamforming antenna weights that are configured to produce a radiation beam pattern from a plurality of antennas of the first communication device to respective ones of each of the plurality of segments in the region; and

transmitting a broadcast message from the first communication device to each segment of the region in a time-division multiplexed manner using the beamforming antenna weights associated with the radiation beam pattern for the corresponding segment such that the broadcast message is not transmitted during the same time interval to segments of different regions that are immediately adjacent to each other, and if the segments of different regions share a common boundary, a size of the common boundary is smaller than that of a common boundary of a region without segmentation so as to reduce inter-region interference of broadcast messages.

2. The method of claim 1, wherein dividing comprises dividing the region into the plurality of segments such that none of the plurality of segments overlaps.

3. The method of claim 1, wherein dividing comprises dividing the region into the plurality of segments such that at least two of the segments at least partially overlap.

4. The method of claim 1, wherein assigning comprises assigning one or more second communication devices to more than one segment, and wherein for one or more second communication devices that are assigned to more than one segment, transmitting comprises transmitting the broadcast message to all segments to which the one or more communication devices are assigned using the corresponding beamforming antenna weights for those segments until the first communication device receives a message indicating that the one or more second communication devices has received the broadcast message.

5. The method of claim 1, wherein assigning is based on a location of a second communication device.

6. The method of claim 1, wherein assigning is based on a direction of arrival associated with signals received from a second communication device.

7. The method of claim 1, wherein assigning is based on a path loss between the first communication device and a second communication device.

8. The method of claim 1, wherein assigning is based on a round trip delay of signals between the first communication device and a second communication device.

9. The method of claim 1, wherein assigning is based on a spatial signature associated with a second communication device.

10. The method of claim 1, wherein assigning is based on a response to a broadcast message received by a second communication device when the broadcast message was transmitted by the first communication device to a segment in the region.

11. The method of claim 1, and further comprising transmitting a unicast message to particular second communication device assigned to a segment using beamforming antenna weights that are configured to form a beam intended for the particular second communication device during a time period in which a broadcast message is transmitted to the segment in which the particular second communication device is assigned.

12. The method of claim 1, wherein monitoring further comprises monitoring one or more of direction of arrival information, spatial signatures, distance to the first communication device, and round-trip delay of the second communication devices, and wherein adjusting assignment of the second communication devices to the segments is based on the monitoring.

13. A method comprising:

dividing a region in which a first communication device wirelessly communicates with one or more of a plurality of second communication devices into a plurality of segments;

assigning one or more second communication devices to at least one of the segments;

generating beamforming antenna weights that are configured to produce a radiation beam pattern from a plurality of antennas of the first communication device to respective ones of each of the plurality of segments in the region; and

transmitting a broadcast message from the first communication device to each segment of the region in a time-division multiplexed manner using the beamforming antenna weights associated with the radiation beam pattern for the corresponding segment wherein when the first communication device communicates with second communication devices in multiple regions that are adjacent to each other, said dividing and transmitting are performed such that a broadcast message is not transmitted during the same time interval to segments of different regions that are immediately adjacent to each other, and if the segments of different regions share a common boundary, a size of the common boundary is smaller than that of a common boundary of a region without segmentation so that inter-region interference of broadcasted messages is reduced.

14. An apparatus comprising:

a plurality of antennas;

a transmitter coupled to the plurality of antennas, wherein the transmitter is configured to apply beamforming weights to a transmit signal to generate corresponding ones of a plurality of weighted signals that are supplied to respective ones of the plurality of antennas;

a controller coupled to the transmitter configured to;

store data representing division of a region into a plurality of segments in which one or more mobile stations may be located;

assign mobile stations to a group of the segments;

monitor locations of the mobile stations and adjust assignment of the mobile stations to the segments;

generate a plurality of beamforming weights for each segment that are supplied to the transmitter and are computed so as to produce a radiation beam pattern from the plurality of antennas to each of the plurality of segments in the region; and

supply a broadcast message to the transmitter for beamforming transmission to each of the segments in a time-division multiplexed manner using the beamforming weights for each segment such that the broadcast message is not transmitted during the same time interval to segments of different regions that are immediately adjacent to each other, and if the segments of different regions share a common boundary, a size of the common boundary is smaller than that of a common boundary of a region without segmentation so as to reduce inter-region interference of broadcast messages.

15. The apparatus of claim 14, wherein the controller is configured to, for one or more mobile stations that are assigned to more than one segment, supply the broadcast message to the transmitter for transmission to all segments to which the one or more mobile stations are assigned using the corresponding beamforming weights for those segments until a message is received indicating that the one or more mobile stations has received the broadcast message.

16. The apparatus of claim 14, wherein the controller is further configured to supply a unicast message to the transmitter for transmission to a particular mobile station assigned to a segment using beamforming weights that form a beam intended for the particular mobile station during a time period in which a broadcast message is transmitted to the segment in which the particular mobile station is assigned.

17. The apparatus of claim 14, wherein the control is configured to monitor one or more of direction of arrival information, spatial signatures, distance to the first communication device, and round-trip delay of the mobile stations, and to adjust assignment of the mobile stations to the segments is based on one or more of direction of arrival information, spatial signatures, distance to the first communication device, and round-trip delay.

18. Logic encoded in one or more tangible media for execution and when executed operable to:

store in a base station data representing division of a region into a plurality of segments in which one or more mobile stations may be located;

assign mobile stations to a group of the segments;

monitor locations of the mobile stations and adjust assignment of the mobile stations to the segments;

generate a plurality of beamforming weights for each segment that produce a radiation beam pattern when applied to a signal that is transmitted from a plurality of antennas of the base station to each of the plurality of segments in the region; and

apply the beamforming weights for each segment to a broadcast message for beamforming transmission of the broadcast message from the base station to each of the segments in a time-division multiplexed manner such that the broadcast message is not transmitted during the same time interval to segments of different regions that are immediately adjacent to each other, and if the segments of different regions share a common boundary, a size of the common boundary is smaller than that of a common boundary of a region without segmentation so as to reduce inter-region interference of broadcast messages.

19. The logic of claim 18, and further comprising logic that is configured to, for one or more mobile stations that are assigned to more than one segment, apply the broadcast message for transmission in the time-division multiplexed manner to all segments to which the one or more mobile stations are assigned using the corresponding beamforming weights until a message is received by the base station indicating that the one or more mobile stations has received the broadcast message.

20. The logic of claim 18, and further comprising logic that is configured to supply a unicast message for transmission to a particular mobile station assigned to a segment, and logic that is configured to apply beamforming weights that form a beam intended for the particular mobile station during a time period in which a broadcast message is transmitted to the segment in which the particular mobile station is assigned.

21. The logic of claim 18, wherein the logic that assigns comprises logic that assigns mobile stations to segments based on locations of the mobile stations within the region.

22. The logic of claim 18, wherein the logic that assigns comprises logic that assigns mobile stations to segments based on direction of arrival associated with signals received from mobile stations.

23. The logic of claim 18, wherein the logic that assigns comprises logic that assigns a mobile station based on a response received by the mobile station when the broadcast message was transmitted by the base station to a segment in the region.

24. The logic of claim 18, wherein the logic operable to monitor comprises logic operable to monitor one or more of direction of arrival information, spatial signatures, distance to the first communication device, and round-trip delay of the mobile stations, and the logic operable to adjust assignment of the second communication devices to the segments is based on one or more of direction of arrival information, spatial signatures, distance to the first communication device, and round-trip delay.

25. Logic encoded in one or more tangible media for execution and when executed operable to:

store in a base station data representing division of a region into a plurality of segments in which one or more mobile stations may be located;

assign mobile stations to at least one of the segments;

generate a plurality of beamforming weights for each segment that produce a radiation beam pattern when applied to a signal that is transmitted from a plurality of antennas of the base station to each of the plurality of segments in the region; and

apply the beamforming weights for each segment to a broadcast message for beamforming transmission of the broadcast message from the base station to each of the segments in a time-division multiplexed manner

wherein the logic that stores data comprises logic that stores data for segments in each of a plurality of regions some of which are adjacent to each other, and wherein the logic for applying comprises logic for applying beamforming weights to a broadcast message for transmission from the base station such that the broadcast message is not transmitted during the same time interval to segments of different regions that are immediately adjacent to each other, and if the segments of different regions share a common boundary, a size of the common boundary is smaller than that of a common boundary of a region without segmentation so that inter-region interference of broadcasted messages is reduced.