Method and system for diversity using orthogonal frequency/division multiplexing

• US 20080159419A1
• Filed: 12/27/2006
• Published: 07/03/2008
• Est. Priority Date: 12/27/2006
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Novak, Robert, Earnshaw, Mark, Steer, David, Li, Xiao-Dong, Au, Kelvin Kar-Kin, Smith, Adrian
• Granted Patent: US 7,742,738 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity
• CPC Class Codes: H04L 27/2646 using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04W 56/0045 compensating for timing error by altering transmission time

Abstract

A method and system for achieving a link budget improvement in a diverse OFDM radio system by addressing the timing misalignment issue that can occur due to the differences in propagation time in signals between mobile stations and Radio Access Nodes. Timing misalignment is shared or split between the primary path to a primary Radio Access Node and a diverse path to a diverse Radio Access Node. The relative timing offsets between mobile stations are adjusted, the mobile stations are grouped into zones using a variety of different grouping techniques, and the transmission for each mobile station is scheduled, using one or more of a variety of scheduling techniques.

Claims

1. A method for improving overall link budget in a diverse communication system, the communication system including a plurality of terrestrial mobile stations in communication with one or more receiving stations, the method comprising:

determining relative timing differential values between the plurality of mobile stations when the mobile stations transmit to the one or more receiving stations via one or more diverse paths wherein the relative timing differential values result in a timing misalignment; and

resolving the timing misalignment by allocating the relative timing differential values among the one or more diverse paths.

2. The method of claim 1, wherein at least one of the one or more receiving stations is a satellite.

3. The method of claim 1, wherein allocating the relative timing differential values comprises performing ranging through each of the diverse paths and adjusting transmission timing to equalize the timing misalignment among the diverse paths.

4. The method of claim 3, further comprising grouping the mobile stations into zones based on their relative timing differential values such that the maximum timing differential value within a zone is less than or equal to a limit.

5. The method of claim 4, wherein the limit is based on a length of a cyclic prefix.

6. The method of claim 4, further comprising inserting guard carriers between mobile station transmissions for each zone.

7. The method of claim 4, further comprising scheduling the transmission of uplink signals for the mobile stations, wherein the uplink transmission for mobile stations within the same zone may be scheduled together.

8. The method of claim 3, further comprising grouping the mobile stations into geographic zones, wherein mobile stations within each geographic zone satisfy the timing requirements.

9. The method of claim 8, wherein mobile stations within each geographic zone schedule their uplink transmissions together.

10. The method of claim 4, further comprising sizing each said zone into one or more subchannel blocks, wherein mobile stations within each said subchannel block are scheduled to transmit uplink signals together.

11. The method of claim 4, further comprising sizing each said zone into a time division block, wherein mobile stations within each said time division block are scheduled to transmit uplink signals together.

12. The method of claim 4, further comprising sizing each said zone into one or more subchannel blocks and one or more time division blocks, wherein mobile stations within a common subchannel block and a common time division block are scheduled to transmit uplink signals together.

13. The method of claim 5, further comprising increasing the length of the cyclic prefix to decrease the likelihood of timing misalignment.

14. A base transceiver system for improving overall link budget in a diverse communication network, comprising:

a timing differential module, the timing differential module for determining relative timing differential values between mobile stations when the mobile stations transmit via diverse paths; and

a transmission module for distributing the relative timing differential values among the diverse paths.

15. The base transceiver system of claim 14, wherein the communication network includes one or more satellites.

16. The base transceiver system of claim 14, wherein the base transceiver system instructs the mobile stations to transmit ranging signals through the diverse paths and adjusts transmission timing to equalize timing error among the diverse paths.

17. The base transceiver system of claim 16, wherein the base transceiver system groups the mobile stations into zones based on their relative timing differential values such that the maximum timing differential value within a zone is less than or equal to a timing limit.

18. The base transceiver system of claim 17 wherein the timing limit is based on a length of a cyclic prefix.

19. The base transceiver system of claim 17, wherein the base transceiver system inserts guard carriers between mobile station transmissions for each zone.

20. The base transceiver system of claim 17, wherein the base transceiver system schedules the transmission of signals for the mobile stations, wherein the transmission of signals for the mobile stations within the same zone may be scheduled together.

21. The base transceiver system of claim 17, wherein the base transceiver system groups the mobile stations into geographic zones, wherein mobile stations within each geographic zone satisfy the timing requirements.

22. The base transceiver system of claim 21, wherein the base transceiver system schedules the transmission for mobile stations within each geographic zone together.

23. The base transceiver system of claim 17, wherein the base transceiver system apportions at least one of said zones into one or more subchannel blocks, wherein stations within each said subchannel block are scheduled to transmit signals together.

24. The base transceiver system of claim 17, wherein the base transceiver system apportions at least one of said zones into a time division block, wherein stations within each said time division block are scheduled to transmit signals together.

25. The base transceiver system of claim 17, wherein the base transceiver system, apportions at least one of said zones into one or more subchannel blocks and one or more time division blocks, wherein stations within a common subchannel block and a common time division block are scheduled to transmit signals together.

26. The base transceiver system of claim 18, wherein the base transceiver system increases the length of the cyclic prefix to decrease the likelihood of timing misalignment.

27. A method for improving overall link budget in a diverse communication system, the communication system including a plurality of terrestrial mobile stations in communication with one or more transmitting stations, the method comprising:

determining the relative timing differential values between the plurality of mobile stations when the mobile stations receive signals via diverse paths wherein the relative timing differential values result in a timing misalignment; and

resolving the timing misalignment by allocating the relative timing differential values among the diverse paths.

28. The method of claim 27, wherein at least one of the one or more transmitting stations is a satellite.

29. The method of claim 27, wherein allocating the relative timing differential comprises performing ranging through each of the diverse paths and adjusting transmission timing to equalize the timing misalignment among the diverse paths.

30. The method of claim 29, further comprising grouping the mobile stations into zones based on their relative timing differential values such that the maximum timing differential value within a zone is less than or equal to a limit.

31. The method of claim 30, wherein the limit is based on a length of a cyclic prefix.

32. The method of claim 30, further comprising scheduling the transmission of signals for the mobile stations, wherein the downlink transmission for mobile stations within the same zone may be scheduled together.

33. The method of claim 29, further comprising grouping the mobile stations into geographic zones, wherein mobile stations within each geographic zone satisfy the timing requirements.

34. The method of claim 33, wherein mobile stations within each geographic zone schedule their uplink transmissions together.

35. The method of claim 29, further comprising sizing each said zone into one or more sub-channel blocks, wherein mobile stations within each said sub-channel block are scheduled to receive downlink signals together.

36. The method of claim 29, further comprising sizing each said zone into a time division block, wherein mobile stations within each said time division block are scheduled to receive downlink signals together.

37. The method of claim 29, further comprising sizing each said zone into one or more subchannel blocks and one or more time division blocks, wherein mobile stations within a common subchannel block and a common time division block are scheduled to transmit uplink signals together.

38. The method of claim 31, further comprising increasing the length of the cyclic prefix to decrease the likelihood of timing misalignment.