Mechanism for Group Polling Without Precise Timing

• US 20140301374A1
• Filed: 04/05/2013
• Published: 10/09/2014
• Est. Priority Date: 04/05/2013
• Status: Active Grant

• Current Assignee: Cambium Networks Limited (Cambium Networks Corporation)
• Original Assignee: Cambium Networks Limited (Cambium Networks Corporation)
• Inventors: Malkawi, Mohammad Isam, Nusairat, Ashraf, Dahleh, Basman
• Granted Patent: US 9,131,509 B2
• Time in Patent Office: Days
• US Class Current: 370/336
• CPC Class Codes: H04L 12/189 in combination with wireless systems selective distribution or broadcast in wireless communication networks H04W4/06
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04L 12/56 Packet switching systems
• 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 74/06 using polling

Abstract

In a wireless communication network, to reduce the polling overhead it is proposed to poll several stations using the same polling frame. In order to be able to poll more than one station in the same frame, an access point can make use of the locations of stations relative to the access point. The location of each station relative to the access point will cause a different propagation delay for radio communications between the station and the access point. Based on the propagation delays, two or more stations may be grouped together for subsequent transmissions to the access point.

Claims

1. A method comprising:

at an access point in wireless data communication with two or more stations,

transmitting a single polling frame to a plurality of stations; and

receiving respective data transmissions from respective stations of the plurality of stations at respective times.

2. The method of claim 1 further comprising:

grouping the two or more stations according to propagation delay of radio transmissions from each respective station to the access point; and

transmitting the single polling frame to grouped stations.

3. The method of claim 2 further comprising:

grouping the two or more stations into two or more groups such that a difference in respective propagation delays between two or more respective stations is large enough so that a respective data transmission from one respective station will be completely received at the access point before beginning of receipt of a respective data transmission from another respective station.

4. The method of claim 3 further comprising:

receiving from the respective stations information about the respective propagation delays for each of the respective stations.

5. The method of claim 1 wherein transmitting a single polling frame comprises:

transmitting, in the single polling frame, a respective assigned duration field and a respective address field for each station of the plurality of stations.

6. The method of claim 5 further comprising:

determining propagation delays for transmissions from respective stations of the plurality of stations;

selecting a first station and a second station such that a difference in respective propagation delays between the first station and the second station is large enough so that a data transmission from the first station will be completely received at the access point before beginning of receipt of a data transmission from the second station;

based on the respective propagation delays, assigning transmission duration values for the first station;

formatting a polling frame including a first duration field populated with a first transmission duration value for the first station, a first address field populated with the medium access control (MAC) address of the first station, a second duration field populated with a second transmission duration value for the second station and a second address field populated with the MAC address of the second station; and

transmitting the polling frame for reception by both the first station and the second station.

8. The method of claim 1 further comprising:

receiving from the respective stations of the two or more stations information about the respective propagation delays of radio transmissions from each of the respective stations;

grouping the two or more stations into two or more groups using the respective propagation delays; and

transmitting a respective single polling frame to stations of each respective group of the two or more groups.

9. The method of claim 8 further comprising:

at the access point, receiving a timing request message transmitted by a station;

determining a request message receipt time for the reception of the timing request message at the access point;

extracting request message transmission time data from the timing request message transmitted by the station;

formatting a response message with the request message transmission time data, request message receipt time data corresponding to the determined request message receipt time and response message transmission time data corresponding to a transmission time for the response message; and

transmitting the response message for reception by the station; and

subsequently, receiving from the station information about the propagation delay of radio transmissions from the station determined using the information formatted in the response message.

10. The method of claim 8 further comprising:

receiving from one or more stations information about a changed propagation delay for the one or more stations;

using the information about the changed propagation delay, regrouping the two or more stations into new groups; and

transmitting subsequent polling frames to stations of respective new groups.

7. The method of claim 7 wherein receiving respective data transmissions from respective stations comprises:

receiving a MAC protocol data unit (MPDU) transmission from the first station in accordance with the first transmission duration value; and

receiving a MPDU transmission from the second station in accordance with the second transmission duration value.

11. An access point comprising:

a network interface operative for radio communication with a plurality of stations in a service area;

a scheduler operative to control radio communication of the network interface, the scheduler operative to;

determine information defining respective propagation delays for each respective station of the plurality of stations;

using the respective propagation delays, group the respective stations into two or more groups of stations such that a single polling frame can be sent to all stations of a respective group of stations to cause the respective stations of the respective group to respond to the single polling frame by transmitting respective transmissions so that the respective transmissions are received at the network interface at independent times; and

cause the network interface to transmit the single polling frame for each respective group of stations.

12. The access point of claim 11 further comprising:

a memory in data communication with the scheduler to store data defining the respective propagation delays for each respective station of the plurality of stations.

13. The access point of claim 12 wherein the network interface is operative to receive transmissions from the respective stations reporting respective propagation delays and to store the data defining the respective propagation delays in the memory.

14. The access point of claim 13 wherein the network interface is operative to communicate message timing information with a station to enable the station to determine the respective propagation delay for the station.

15. The access point of claim 14 wherein the network interface is operative to:

receive a timing request message transmitted by the station;

determine a request message receipt time for the reception of the timing request message at the access point;

extract request message transmission time data from the timing request message transmitted by the station;

format a response message with the request message transmission time data, request message receipt time data corresponding to the determined request message receipt time and response message transmission time data corresponding to a transmission time for the response message; and

transmit the response message for reception by the station and subsequent calculation of the respective propagation delay for the station.

16. An access point comprising:

a network interface operative for radio communication with a plurality of stations in a service area;

a media access control layer operative to format a group polling frame for transmission to two or more selected stations of the plurality of stations;

a scheduler operative to control radio communication of the network interface, the scheduler operative to;

receive information defining propagation delays for radio communication between the access point and respective stations,

select the two or more stations for receipt of the group polling frame, and

initiate transmission of the group polling frame by the network interface.

17. The access point of claim 16 wherein the network interface is operative to receive from the respective stations radio transmissions including data defining respective propagation delays for the respective stations.

18. The access point of claim 17 wherein the scheduler is responsive to the information defining propagation delays to assign the respective stations to two or more groups such that a difference in respective propagation delays between two or more respective stations is large enough so that a respective data transmission from one respective station will be completely received at the access point before beginning of receipt of a respective data transmission from another respective station.

19. The access point of claim 18 wherein the network interface is operative to receive from the respective stations radio transmissions including data defining updated respective propagation delays for one or more respective stations, and wherein the scheduler is responsive to the updated respective propagation delays to reassign the respective stations to two or more updated groups to reflect changes in the service area.