Methods and systems to mitigate inter-cell interference

• US 20090245197A1
• Filed: 08/23/2006
• Published: 10/01/2009
• Est. Priority Date: 08/23/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Boumendil, Sarah, Tong, Wen, Ma, Jianglei, Zhu, Peiying, Jia, Ming, Le Strat, Evelyne
• Granted Patent: US 9,258,102 B2
• Time in Patent Office: Days
• US Class Current: 370/330
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0032 Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0057 Physical resource allocation for CQI
• CPC Class Codes: H04L 5/0062 Avoidance of ingress interference, e.g. ham radio channels
• CPC Class Codes: H04L 5/0073 Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005
• CPC Class Codes: H04W 16/02 Resource partitioning among network components, e.g. reuse partitioning
• CPC Class Codes: H04W 16/12 Fixed resource partitioning

Abstract

The present invention provides methods and devices for mitigating inter-cell interference in communication environments having a plurality of cells. In some embodiments, a time-frequency transmission resource that includes multiple sub-carriers over multiple OFDM symbol intervals is partitioned into a first zone and a second zone. In the first zone, transmissions are transmitted on at least one frequency sub-band which is common to all of the plurality of cells. In the second zone, transmissions are transmitted on at least one frequency sub-band which is used by less than all of the plurality of cells, so as to mitigate inter-cell interference. In some embodiments, in the first zone transmissions are transmitted using a transmission power which is common to all of the plurality of cells and in the second zone transmissions are transmitted using a transmission power which is used by less than all of the plurality of cells so as to mitigate inter-cell interference.

Claims

1. A method for execution in an OFDM communications environment having a plurality of cells, comprising:

for a transmitter corresponding to a first cell;

partitioning a time-frequency transmission resource comprising a plurality of sub-carriers over a plurality of OFDM symbol intervals into a first zone and a second zone;

in the first zone, transmitting on at least one set of sub-carriers which is used by all of the plurality of cells;

in the second zone, transmitting on at least one set of sub-carriers which is used by less than all of the plurality of cells so as to mitigate inter-cell interference.

2. The method of claim 1, wherein when at least one other cell of the plurality of cells uses a same first and second zone partitioning of a respective time-frequency transmission resource, the method further comprises:

the at least one other cell, in the second zone, transmitting on at least one set of sub-carriers which is different than the set of sub-carriers used by the transmitter of the first cell.

3. The method of claim 1 wherein transmitting in the second zone on at least one set of sub-carriers further comprises:

transmitting on at least one set of sub-carriers which is different than sets of sub-carriers used by transmitters corresponding to respective cells adjacent to the first cell.

4. The method of claim 1, further comprising:

for a transmitter corresponding to a second cell;

partitioning an OFDM transmission resource into a first zone and a second zone in coordination with the partitioning of the time-frequency transmission resource of the first cell such that zone partitioning of the first and second cells is the same;

in the second zone, transmitting on at least one set of sub-carriers which is different than the at least one set of sub-carriers used by the transmitter of the first cell.

5. The method of claim 1, further comprising:

for a transmitter corresponding to a second cell;

partitioning an time-frequency transmission resource into a first zone and a second zone independently of the partitioning of the OFDM transmission resource of the first cell.

6. The method of claim 1 wherein partitioning the time-frequency transmission resource into a first zone and a second zone is based on time division multiplexing (TDM).

7. The method of claim 1 wherein partitioning the time-frequency transmission resource into a first zone and a second zone is based on frequency division multiplexing (FDM).

8. The method of claim 1 wherein partitioning the time-frequency transmission resource into a first zone and a second zone is based on combined TDM/FDM.

9. The method of claim 1 further comprising inserting control information in a control channel formed in at least one OFDM symbol in the time-frequency transmission resource.

10. The method of claim 1 further comprising inserting scattered pilot symbol information in the time-frequency transmission resource.

11. The method of claim 10 further comprises inserting the pilot symbol information of the transmitter of the first cell in the time-frequency transmission resource with a pattern that is the same as the other cells of the plurality of cells, but is shifted in time and/or frequency with respect to the other cells.

12. The method of claim 10 wherein inserting scattered pilot symbol information comprises inserting pilot symbols into the at least one time-frequency channel resource for transmission on N transmitting antenna where N>

=1, the method further comprising;

for each antenna partitioning N time-frequency channel resources to be simultaneously transmitted on N antennas into a set of corresponding first zones and a set of corresponding second zones, each set of corresponding first zones consisting of a first zone for each of the N time-frequency channel resources and each set of corresponding second zones consisting of a second zone for each of the N time-frequency channel resources, all the first and second zones in a given set of corresponding zones having a common size and location;

in the set of corresponding first zones, transmitting on the at least one set of sub-carriers which is used by all of the plurality of cells; and

in the set of corresponding second zones, transmitting on the at least one set of sub-carriers which is used by less than all of the plurality of cells to mitigate inter-cell interference between the at least two cells.

13. The method of claim 1, wherein in the first zone, transmitting on at least one set of sub-carriers comprises transmitting with a frequency re-use-1 scheme.

14. The method of claim 1, wherein in the second zone, transmitting on at least one set of sub-carriers comprises transmitting with a fractional frequency re-use scheme.

15. The method of claim 14 wherein transmitting with a fractional frequency re-use scheme for the transmitter comprises transmitting at least one of channel control information, data, and pilot symbol information in M locations of an OFDM symbol and nulls in N locations of the OFDM symbol, in which the OFDM symbol has M+N locations, where the nulls are used for at least one of channel control information, data, and pilot symbol information in other cells of the plurality of cells.

16. The method of claim 14 wherein transmitting with a fractional frequency re-use scheme further comprises transmitting pilot symbol information having a pattern in the time-frequency transmission resource of the transmitter of the first cell that is the same as the other cells, but is shifted in time and/or frequency with respect to the other cells.

17. The method of claim 14 wherein a sub-channel definition using the fractional frequency re-use scheme is defined as L sub-carrier pairs with a given separation across J consecutive OFDM symbols when the transmission resource has K sub-bands, each of the K sub-bands consisting of L consecutive sub-carriers.

18. The method of claim 1, wherein the at least one set of sub-carriers in the second zone comprises a plurality of contiguous sub-carriers.

19. The method of claim 1, wherein the at least one set of sub-carriers in the second zone comprises a plurality of contiguous sub-carriers.

20. The method of claim 1, wherein the plurality of OFDM symbols comprises an odd number of OFDM symbols.

21. The method of claim 1, wherein the partitioning of the at least one time-frequency transmission resource into the first zone and the second zone is dynamically configurable.

22. The method of claim 1, wherein the time-frequency transmission resource is one of an OFDM transmission resource and a transformed OFDM transmission resource.

33. An OFDM transmitter adapted to perform the method of claim 1.

35. The OFDM transmitter of claim 33, wherein the time-frequency transmission resource is one of an OFDM transmission resource and a transformed OFDM transmission resource.

23. A method for execution in an OFDM communications environment having a plurality of cells, comprising:

for a transmitter corresponding to a first cell;

partitioning an time-frequency transmission resource comprising a plurality of sub-carriers over a plurality of OFDM symbol intervals into a first zone and a second zone;

transmitting in the first zone using a transmission power which is used by all of the plurality of cells;

transmitting in the second zone using a transmission power which is used by less than all of the plurality of cells so as to mitigate inter-cell interference.

24. The method of claim 23 wherein transmitting in the second zone using a transmission power which is used by less than all of the plurality of cells further comprises:

transmitting using a transmission power which is larger than a transmission power used by transmitters corresponding to respective cells adjacent to the first cell.

25. The method of claim 23, further comprising:

for a transmitter corresponding to a second cell;

partitioning an time-frequency transmission resource into a first zone and a second zone in coordination with the partitioning of the OFDM transmission resource of the first cell such that zone partitioning of the first and second cells is the same;

transmitting in the second zone using a transmission power which is less than a transmission power used in the first zone which is used by all of the plurality of cells.

26. The method of claim 23, further comprising:

for a transmitter corresponding to a second cell;

partitioning an time-frequency transmission resource into a first zone and a second zone independently of the partitioning of the OFDM transmission resource of the first cell.

27. The method of claim 23 wherein partitioning the time-frequency transmission resource into a first zone and a second zone is based on any one of a group consisting of time division multiplexing (TDM), frequency division multiplexing (FDM), and combined TDM/FDM.

28. The method of claim 23 further comprising inserting control information in a control channel formed in at least one OFDM symbol in the time-frequency transmission resource.

29. The method of claim 23 further comprising inserting scattered pilot symbol information in the time-frequency transmission resource.

30. The method of claim 23 wherein the plurality of OFDM symbols comprises an odd number of OFDM symbols.

31. The method of claim 23 wherein the partitioning of the at least one time-frequency transmission resource into the first zone and the second zone is dynamically configurable.

32. The method of claim 23, wherein the time-frequency transmission resource is one of an OFDM transmission resource and a transformed OFDM transmission resource.

34. An OFDM transmitter adapted to perform the method of claim 23

36. A communication network comprising:

a plurality of telecommunication cells, each cell comprising an OFDM transmitter, the OFDM transmitter in each respective cell adapted to;

partition an time-frequency transmission resource comprising a plurality of sub-carriers over a plurality of OFDM symbol intervals into a first zone and a second zone;

in the first zone, transmit on at least one set of sub-carriers which is used by all of the plurality of cells;

in the second zone, transmit on at least one set of sub-carriers which is used by less than all of the plurality of cells so as to mitigate inter-cell interference.

37. The communication network of claim 36 wherein at least two OFDM transmitters coordinate the partition of the time-frequency transmission resource used by each respective OFDM transmitter and selection of the set of sub-carriers used to transmit in the second zone by each respective OFDM transmitter.