Apparatus and method for downlink scheduling in a SDMA-enabled OFDMA wireless network

• US 8,098,632 B2
• Filed: 11/04/2005
• Issued: 01/17/2012
• Est. Priority Date: 01/21/2005
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: van Rensburg, Cornelius, Tsai, Jiann-An
• Primary Examiner(s): TRAN, PHUC H
• Application Number:
  US11/267,738
• Publication Number:
  US 20060164972A1
• Time in Patent Office: 2,265 Days
• Field of Search: 370/208, 370/334, 370/339, 455/552.1, 455/562.1
• US Class Current: 370/334
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04L 5/1469 using time-sharing
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 72/1273 of downlink data flows

Abstract

A scheduler for scheduling downlink transmissions of orthogonal frequency division multiple access (OFDMA) signals using spatially directed beams to a plurality of subscriber stations in a wireless network. The scheduler schedules the downlink transmissions as a function of frequency, time, and space. The scheduler further schedules downlink transmissions to a first subscriber station based on a first null space associated with at least one subscriber station previously scheduled to receive.

Claims

1. A base station capable of communicating with a plurality of subscriber stations in a wireless network, the base station comprising:

a transceiver capable of transmitting downlink orthogonal frequency division multiple access (OFDMA) signals to the plurality of subscriber stations;

an antenna array capable of transmitting the downlink OFDMA signals to the plurality of subscriber stations using spatially directed beams; and

a scheduling controller capable of scheduling downlink transmissions to the plurality of subscriber stations using spatially directed transmit beams, wherein the scheduling controller schedules a first one of the plurality of subscriber stations to receive in a first time-frequency slot based on a first null space of a matrix associated with at least one subscriber station previously scheduled to receive in the first time-frequency slot.

2. The base station as set forth in claim 1, wherein the scheduling controller is capable of determining a second one of the plurality of subscriber stations having a highest priority.

3. The base station as set forth in claim 2, wherein the scheduling controller determines the priority of the second subscriber station using a proportional fair sharing algorithm.

4. The base station as set forth in claim 2, wherein the second subscriber station is one of the at least one subscriber station previously scheduled to receive in the first time-frequency slot.

5. The base station as set forth in claim 2, wherein the scheduling controller is further capable of scheduling a third one of the plurality of subscriber stations to receive in the first time-frequency slot based on a second null space associated with the first subscriber station and the at least one subscriber station previously scheduled to receive in the first time-frequency slot.

6. The base station as set forth in claim 5, wherein the scheduling controller is further capable of comparing a received power associated with the third subscriber station to a minimum power threshold and wherein the scheduling controller, in response to a determination that the received power does not exceed the minimum power threshold, does not schedule the third subscriber station to receive in the first time-frequency slot.

7. The base station as set forth in claim 1, wherein the scheduling controller is further capable of scheduling a second one of the plurality of subscriber stations to receive in the first time-frequency slot based on a second null space associated with the first subscriber station and the at least one subscriber station previously scheduled to receive in the first time-frequency slot.

8. The base station as set forth in claim 7, wherein the scheduling controller is further capable of comparing a received power associated with the second subscriber station to a minimum power threshold and wherein the scheduling controller, in response to a determination that the received power does not exceed the minimum power threshold, does not schedule the second subscriber station to receive in the first time-frequency slot.

9. A wireless network comprising a plurality of base stations capable of communicating with subscriber stations, each one of the plurality of base stations comprising:

a transceiver capable of transmitting downlink orthogonal frequency division multiple access (OFDMA) signals to a plurality of the subscriber stations;

an antenna array capable of transmitting the downlink OFDMA signals to the plurality of subscriber stations using spatially directed beams; and

a scheduling controller capable of scheduling downlink transmissions to the plurality of subscriber stations using spatially directed transmit beams, wherein the scheduling controller schedules a first one of the plurality of subscriber stations to receive in a first time-frequency slot based on a first null space of a matrix associated with at least one subscriber station previously scheduled to receive in the first time-frequency slot.

10. The wireless network as set forth in claim 9, wherein the scheduling controller is capable of determining a second one of the plurality of subscriber stations having a highest priority.

11. The wireless network as set forth in claim 10, wherein the scheduling controller determines the priority of the second subscriber station using a proportional fair sharing algorithm.

12. The wireless network as set forth in claim 10, wherein the second subscriber station is one of the at least one subscriber station previously scheduled to receive in the first time-frequency slot.

13. The wireless network as set forth in claim 10, wherein the scheduling controller is further capable of scheduling a third one of the plurality of subscriber stations to receive in the first time-frequency slot based on a second null space associated with the first subscriber station and the at least one subscriber station previously scheduled to receive in the first time-frequency slot.

14. The wireless network as set forth in claim 13, wherein the scheduling controller is further capable of comparing a received power associated with the third subscriber station to a minimum power threshold and wherein the scheduling controller, in response to a determination that the received power does not exceed the minimum power threshold, does not schedule the third subscriber station to receive in the first time-frequency slot.

15. A method of communicating with a plurality of subscriber stations in a wireless network, the method comprising:

transmitting downlink orthogonal frequency division multiple access (OFDMA) signals to at least one subscriber station in a first time-frequency slot using spatially directed beams;

determining a first null space of a matrix associated with the at least one subscriber station; and

scheduling a first subscriber station to receive in the first time-frequency slot based on the first null space.

16. The method as set forth in claim 15, further comprising determining a second one of the plurality of subscriber stations having a highest priority.

17. The method as set forth in claim 16, wherein determining the priority of the second subscriber station comprises using a proportional fair sharing algorithm.

18. The method as set forth in claim 16, wherein the second subscriber station is one of the at least one subscriber station previously scheduled to receive in the first time-frequency slot.

19. The method as set forth in claim 16, further comprising:

determining a second null space associated with the first subscriber station and the at least one subscriber station; and

scheduling a third one of the plurality of subscriber stations to receive in the first time-frequency slot based on the second null space.

20. The method as set forth in claim 19, further comprising:

comparing a received power associated with the third subscriber station to a minimum power threshold;

in response to a determination that the received power does not exceed the minimum power threshold, refraining from scheduling the third subscriber station to receive in the first time-frequency slot.