METHOD AND APPARATUS FOR SCHEDULING RESOURCES AND AVOIDING INTERFERENCE IN A MULTI-CELLULAR WIRELESS COMMUNICATION SYSTEM

• US 20100130223A1
• Filed: 12/20/2006
• Published: 05/27/2010
• Est. Priority Date: 08/15/2006
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Wan, Lei, Liao, Jingyi
• Granted Patent: US 8,385,939 B2
• Time in Patent Office: Days
• US Class Current: 455/453
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/0051 of dedicated pilots, i.e. pilots destined for a single user or terminal
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04L 5/0075 Allocation using proportional fairness
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal
• CPC Class Codes: H04W 72/541 using the level of interference

Abstract

Resources in a multi-cellular wireless communication system are scheduled. A beam pattern associated with at least one mobile terminal located within one of the cells is identified and assigned to a slot, providing at least one stream to said at least one mobile terminal. At least one other mobile terminal located within said cell having the same beam pattern associated therewith as that of said identified beam pattern to be served during said slot is scheduled. The assigned beam pattern in said cell is communicated to at least one interfering cell.

Claims

1. A method for scheduling resources in a multi-cellular wireless communication system, the method comprising the steps of:

identifying a beam pattern associated with at least one mobile terminal located within one of the cells;

assigning said identified beam pattern to a slot, said slot comprises a plurality of resource blocks, said identified beam pattern providing at least one stream to said at least one mobile terminal; and

scheduling at least one other mobile terminal located within said cell having the same beam pattern associated therewith as that of said identified beam pattern to be served during said slot for a resource block.

2. A method according to claim 1, wherein the method further comprises the step of:

communicating said assigned beam pattern in said cell to at least one interfering cell for avoiding interference between cells of a multi-cellular wireless communication system.

3. A method according to claim 2, wherein the step of communicating said assigned beam pattern comprises communicating said assigned beam pattern using different pilots in each beam.

4. A method according to claim 2, wherein the step of communicating said assigned beam pattern comprises communicating said assigned beam pattern by inter-cell communication.

5. A method according to any of the preceding claims, wherein the step of assigning said identified beam pattern for each slot comprises assigning said identified beam pattern according to a round robin mechanism for all the beams having at least one active mobile terminal to cover.

6. A method according to any of the preceding claims, wherein the step of assigning said identified beam pattern for each slot comprises assigning said identified beam pattern based on the traffic load of each beam, such that beams having a higher load are scheduled as a priority.

7. A method according to any of the preceding claims, wherein the method further comprises the steps of:

determining the optimal beam pattern sequences of all interfering cells for at least one subsequent slot, said determination being based on a pre-defined criteria; and

communicating the selected beam pattern for each slot based on said determined beam pattern sequences to at least one interfering cell.

8. A method according to claim 7, wherein the step of determining the optimal beam sequences for said at least one subsequent slot comprises determining the optimal beam pattern sequences based on the criteria of obtaining the maximum system throughput.

9. A method according to claim 7, wherein the step of determining the optimal beam pattern sequences for said at least one subsequent slot comprises determining the optimal beam pattern sequences based on the criteria of finding the beam pattern sequences with a minimum system inter-cell interference for each slot.

10. A method according to any of claims 7-9, wherein each cell decides its next best served beam patterns from the determined beam pattern sequences for the next slot or slots based on the pre-defined criteria.

11. A method according to any of claims 7-10, wherein the step of determining the optimal beam pattern sequences and the step of communicating the beam pattern sequences of the interfering cells comprises determining the optimal beam pattern sequences and communicating said beam pattern sequences in at least one central node and then transmitting or broadcasting from said central node to all interfered cells.

12. A method according to any of claims 7-10, wherein the step of determining the optimal beam pattern sequences and the step of communicating the beam pattern sequences of the interfering cells comprises determining the optimal beam pattern sequences and communicating said beam pattern sequences in one base station and then transmitting or broadcasting from said base station by direct inter-base station communication.

13. A method according to any of claims 7-12, wherein a hierarchical solution is used to find a suboptimal solution of cells'"'"' beam patterns, by letting some target cells use a pre-assigned beam pattern selection, such as round robin, for all beams which have active mobile terminals to cover, and let their neighbour interfering cells coordinate to select their optimal beam patterns that achieve a reduced localised inter-cell interference.

14. A method according to any of the preceding claims, wherein the method further comprises the step of:

appending a scheduling scheme such as Proportional Fair scheduling in both Time and Frequency domain (PFTF) to a mobile terminal for each specific slot.

25. A method according to any of the preceding claims, whereby the assignment of one beam pattern for each slot is carried out as a round robin beam selection for all the beams which have active users to cover.

26. A method according to any of the preceding claims, whereby the assignment of one beam pattern for each slot is based on the traffic load carried by each beam, such that the beams that have higher load to carry are more likely to be scheduled.

27. A method according to any of the preceding claims, whereby optimal beam sequences of all interfering cells for one or several following slots are calculated and the selected beam pattern for each slot based on said calculated beam sequences are then communicated to each cell, said selection is based on a pre-defined criteria.

28. A method according to claim 27, whereby the beam selection for one or several following slots is based on the criteria of obtaining maximum system throughput.

29. A method according to claim 27, whereby the beam selection for one or several following slots is based on the criteria of finding the cells beam sequences with a minimum of system inter-cell interference for each slot.

30. A method according to any of claims 27-29 whereby each cell decides its next best served beams from the calculated beam sequences for the next slot or slots based on the pre-defined criteria.

31. A method according to any of claims 27-30, whereby the calculation of the optimal beam sequences and the communication of the interfering cells beam sequences is carried out in one or more central node such as an RNC/aGW or some specific base stations and are then transmitted or broadcast from said central node to all interfered cells.

32. A method according to any of claims 27-30, whereby the communication of the interfering cells beam sequences is carried out by direct inter-base station communication.

33. A method according to any of claims 27-32, whereby a hierarchical solution is used to find a suboptimal solution of cells'"'"' beam patterns, by letting some target cells use a pre-assigned beam selection, such as round robin, for all the beams which have active users to cover, and let their neighbor interfering cells coordinate to reduce the localized inter-cell interference.

34. A method according to any of the preceding claims, whereby a scheduling scheme such as Proportional fair scheduling in both time and frequency domain (PFTF) is appended to the selected user for each specific slot.

15. Apparatus for scheduling resources in a multi-cellular wireless communication system, the apparatus comprising:

an identifier for identifying a beam pattern associated with at least one mobile terminal located within one of the cells;

means for assigning said identified beam pattern to a slot, said slot comprises a plurality of resource blocks, said identified beam pattern providing at least one stream to said at least one mobile terminal; and

a scheduler for scheduling at least one other mobile terminal located within said cell having the same beam pattern associated therewith as that of said identified beam pattern to be served during said slot for a resource block.

16. Apparatus according to claim 15, wherein the apparatus further comprises:

a communication means for communicating said assigned beam pattern in said cell to at least one interfering cell for avoiding interference between cells of a multi-cellular wireless communication system.

17. A wireless communication system comprising a plurality of cells, each cell comprising:

at least one mobile terminal located within one of said plurality of cells; and

a base station, said base station comprising;

an antenna array for transmitting at least one beam pattern;

a beam forming means for forming said at least one beam pattern;

an identifier for identifying a beam pattern transmitted by the antenna array associated with at least one mobile terminal located within one of the cells;

means for assigning said identified beam pattern to a slot, said slot comprises a plurality of resource blocks, said identified beam pattern providing at least one stream to said at least one mobile terminal; and

a scheduler for scheduling at least one other mobile terminal located within said cell having the same beam pattern associated therewith as that of said identified beam pattern to be served during said slot for a resource block.

18. A wireless communication system according to claim 17 comprising a plurality of cells, wherein said base station of each cell further comprises:

a communication means for communicating said assigned beam pattern in said cell to at least one interfering cell.

19. A system according to claim 17 or 18, wherein said beam forming means forms beams using fixed beam forming.

20. A system according to claim 17 or 18, wherein said beam forming means forms beams using adaptive beam forming.

21. A system according to claims 17-20, wherein wireless communication is Orthogonal Frequency Division Multiple Access.

22. A method for scheduling resources in a multi-carrier cellular radio system with a multi-user smart antenna system characterized by the steps of

assigning one beam pattern for each slot of a sub-carrier, said beam pattern allows bearing of one or several streams to one or several users;

selecting users with the same beam orientation as candidates to be served during each slot;

communicating the assigned beam pattern or beam orientation in a specific cell to interfering cells such that inter-cell interference can be avoided.

23. A method according to claim 22 whereby the beam pattern or beam orientation in a specific cell is communicated to interfering cells by using different dedicated pilots in each beam.

24. A method according to claim 22 whereby the beam pattern or beam orientation in a specific cell is communicated to interfering cells by inter-cell communication.

35. A scheduler for scheduling of radio resources in a cellular radio system, characterized by means for carrying out the method according to any of claims 22-34.