Method, apparatus, and system for mitigating pilot signal degradation by employing cell-specific pilot subcarrier and common pilot subcarrier techniques in a multi-carrier cellular network

• US 8,432,891 B2
• Filed: 08/17/2011
• Issued: 04/30/2013
• Est. Priority Date: 01/29/2004
• Status: Active Grant

• Current Assignee: Neo Wireless LLC (f/k/a CFIP NCF LLC) (FIG LLC (d/b/a Fortress Investment Group LLC))
• Original Assignee: Neocific Incorporated
• Inventors: Li, Xiaodong, Lo, Titus, Li, Kemin, Huang, Haiming
• Primary Examiner(s): Magloire, Vladimir
• Assistant Examiner(s): Sarwar, Babar
• Application Number:
  US13/212,116
• Publication Number:
  US 20110299474A1
• Time in Patent Office: 622 Days
• Field of Search: 370/350, 370/324, 370331-332, 370/319, 370/344, 370/329, 370/338, 370/328, 370/203, 370/280, 370/342, 370/335, 455 6711- 6713, 455/423, 455/503, 455/115.1, 455436-444, 455/502, 455/552.1, 455/562.1, 455/422.1, 455/434, 455/525
• US Class Current: 370/350
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04J 11/005 of intercell interference
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 25/03834 using pulse shaping
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/26134 Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain
• CPC Class Codes: H04L 27/2637 with direct modulation of individual subcarriers
• 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 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0016 Time-frequency-code
• CPC Class Codes: H04L 5/0028 Variable division signaling therefor H04L5/0092
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 16/02 Resource partitioning among network components, e.g. reuse partitioning
• CPC Class Codes: H04W 72/044 : based on the type of the allocated resource
• CPC Class Codes: H04W 72/0446 : Resources in time domain, e.g. slots or frames

Abstract

A multi-carrier cellular wireless network (400) employs base stations (404) that transmit two different groups of pilot subcarriers: (1) cell-specific pilot subcarriers, which are used by a receiver to extract information unique to each individual cell (402), and (2) common pilots subcarriers, which are designed to possess a set of characteristics common to all the base stations (404) of the system. The design criteria and transmission formats of the cell-specific and common pilot subcarriers are specified to enable a receiver to perform different system functions. The methods and processes can be extended to other systems, such as those with multiple antennas in an individual sector and those where some subcarriers bear common network/system information.

Claims

1. In a multi-cell, Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system comprising a plurality of mobile stations and base stations in a plurality of groups of cells, a base station in a cell within a group of cells having a transmitter that is synchronized in time and frequency with transmitters of other base stations in the group of cells and configured for transmitting different types of pilot subcarriers within a same frequency band that is divided into a plurality of subcarriers, the base station comprising:

a transmitter component that is configured to transmit cell-specific pilot subcarriers to enable reception of cell-specific data by mobile stations in the cell, wherein;

the cell-specific pilot subcarriers possess characteristics specific to the cell; and

at least some of the cell-specific pilot subcarriers are not aligned in frequency subcarrier index with cell-specific pilot subcarriers transmitted by another base station in the group of cells; and

a transmitter component that is configured to transmit common pilot subcarriers to enable reception of common data by mobile stations in the group of cells, wherein;

the common pilot subcarriers possess characteristics common to common pilot subcarriers transmitted by other base stations in the group of cells;

the common pilot subcarriers are aligned in frequency subcarrier index with common pilot subcarriers transmitted by other base stations in the group of cells; and

frequency-domain signal randomization is applied on the common pilot subcarriers, wherein the frequency-domain signal randomization on the common pilot subcarriers is selected to be the same within the group of cells and wherein the frequency-domain signal randomization on the common pilot subcarriers is selected to be different from frequency-domain signal randomization applied on common pilot subcarriers transmitted by base stations in a different group of cells in the system.

2. The base station of claim 1, wherein the cell-specific pilot subcarrier characteristics include phases and amplitudes of the cell-specific pilot subcarriers, and the common pilot subcarrier characteristics include phases and amplitudes of the common pilot subcarriers.

3. The base station of claim 1, further comprising a transmitter component that computes the cell-specific and common pilot subcarrier characteristics and inserts cell-specific and common pilot subcarriers in between data subcarriers contained in an electronic memory.

4. The base station of claim 1, further comprising a transmitter component configured to control independently a transmission power of the cell-specific pilot subcarriers and a transmission power of the common pilot subcarriers.

5. The base station of claim 4, wherein the transmission power of the cell-specific pilot subcarriers is higher than the transmission power of the common pilot subcarriers.

6. The base station of claim 4, wherein the transmission power of the cell-specific pilot subcarriers is lower than the transmission power of the common pilot subcarriers.

7. The base station of claim 1, wherein signals on the common pilot subcarriers transmitted by the base station add together with signals on common pilot subcarriers transmitted by other base stations in the group of cells at a mobile station within the group of cells.

8. The base station of claim 7, wherein a signal on an i^th common pilot subcarrier received by the mobile station at a time t_k from M cells in the group of cells is

9. The base station of claim 1, wherein signals on common pilot subcarriers transmitted by base stations in different groups of cells in the system become randomized interference at a mobile station within the group of cells.

10. The base station of claim 1, wherein the cell-specific pilot subcarriers enable a mobile station in the cell to determine cell-specific channel coefficients for a cell-specific channel, the cell-specific channel corresponding to a channel from the base station to the mobile station.

11. The base station of claim 1, wherein the cell-specific pilot subcarriers enable a mobile station in the cell to perform frame synchronization, frequency offset estimation, or timing estimation.

12. The base station of claim 1, wherein the common pilot subcarriers enable a mobile station in the cell to determine composite channel coefficients for a composite channel, the composite channel corresponding to an aggregate of different channels from base stations in the group of cells to the mobile station.

13. The base station of claim 1, wherein the common pilot subcarriers enable a mobile station in the group of cells to perform frame synchronization, frequency offset estimation, or timing estimation.

14. In a multi-cell, Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system comprising a plurality of mobile stations and base stations in a plurality of groups of cells, a mobile station being associated with a serving base station in a serving cell within a group of cells in the system and having a receiver configured to receive different types of pilot subcarriers within a same frequency band that is divided into a plurality of subcarriers, the mobile station comprising:

a receiver component configured to receive cell-specific pilot subcarriers from the serving base station in the serving cell, wherein;

the cell-specific pilot subcarriers possess characteristics specific to the serving cell; and

at least some of the cell-specific pilot subcarriers are not aligned in frequency subcarrier index with cell-specific pilot subcarriers transmitted by another base station in the group of cells; and

a receiver component configured to receive common pilot subcarriers from the serving base station and other base stations within the group of cells, wherein;

common pilot subcarriers transmitted by the serving base station and the other base stations possess characteristics common to the group of cells;

common pilot subcarriers transmitted by the serving base station are aligned in frequency subcarrier index with common pilot subcarriers transmitted by the other base stations in the group of cells; and

frequency-domain signal randomization applied on the common pilot subcarriers transmitted by the serving base station is selected to be the same within the group of cells and is selected to be different from frequency-domain signal randomization applied on common pilot subcarriers transmitted by base stations in a different group of cells in the system.

15. The mobile station of claim 14, wherein the cell-specific pilot subcarrier characteristics include phases and amplitudes of the cell-specific pilot subcarriers, and the common pilot subcarrier characteristics include phases and amplitudes of the common pilot subcarriers.

16. The mobile station of claim 14, wherein a signal on an i^th common pilot subcarrier received by the mobile station at a time t_k from M cells in the group of cells is

17. The mobile station of claim 14, wherein signals on common pilot subcarriers received by the mobile station from base stations in different groups of cells in the system become randomized interference.

18. The mobile station of claim 14, further comprising a receiver component configured to utilize the characteristics of the cell-specific pilot subcarriers to differentiate the cell-specific pilot subcarriers from cell-specific pilot subcarriers transmitted by another base station in another cell.

19. The mobile station of claim 14, further comprising a receiver component configured to determine cell-specific channel coefficients for a cell-specific channel based on the received cell-specific pilot subcarriers, the cell-specific channel corresponding to a channel from the base station to the mobile station.

20. The mobile station of claim 19, further comprising a receiver component configured to apply the cell-specific channel coefficients to signals on cell-specific data subcarriers received by the mobile station to compensate for cell-specific channel effects and recover cell-specific data carried by the cell-specific data subcarriers.

21. The mobile station of claim 14, further comprising a receiver component configured to utilize the received cell-specific pilot subcarriers for frame synchronization, frequency offset estimation, or timing estimation.

22. The mobile station of claim 14, further comprising a receiver component configured to determine composite channel coefficients for a composite channel based on the received common pilot subcarriers, the composite channel corresponding to an aggregate of different channels from base stations in the group of cells to the mobile station.

23. The mobile station of claim 22, further comprising a receiver component configured to apply the composite channel coefficients to signals on common data subcarriers received by the mobile station to compensate for composite channel effects and to recover common data carried by the common data subcarriers.

24. The mobile station of claim 14, further comprising a receiver component configured to utilize the received common pilot subcarriers for frame synchronization, frequency offset estimation, or timing estimation.

25. In a multi-cell, Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system comprising a plurality of mobile stations and base stations in a plurality of groups of cells, a signal transmission method for a base station in a cell within a group of cells in the system, the base station having a transmitter that is synchronized in time and frequency with transmitters of other base stations in the group of cells and configured for transmitting different types of pilot subcarriers within a same frequency band that is divided into a plurality of subcarriers, the method comprising:

transmitting cell-specific pilot subcarriers to enable reception of cell-specific data by mobile stations in the cell, wherein;

the cell-specific pilot subcarriers possess characteristics specific to the cell; and

at least some of the cell-specific pilot subcarriers are not aligned in frequency subcarrier index with cell-specific pilot subcarriers transmitted by another base station in the group of cells; and

transmitting common pilot subcarriers to enable reception of common data by mobile stations in the group of cells, wherein;

the common pilot subcarriers possess characteristics common to common pilot subcarriers transmitted by other base stations in the cells within the group;

the common pilot subcarriers are aligned in frequency subcarrier index with common pilot subcarriers transmitted by other base stations in the group of cells; and

frequency-domain signal randomization is applied on the common pilot subcarriers, wherein the frequency-domain signal randomization on the common pilot subcarriers is selected to be the same within the group of cells and wherein the frequency-domain signal randomization on the common pilot subcarriers is selected to be different from frequency-domain signal randomization applied on common pilot subcarriers transmitted by base stations in a different group of cells in the system.

26. The method of claim 25, wherein the cell-specific pilot subcarrier characteristics include phases and amplitudes of the cell-specific pilot subcarriers and the common pilot subcarrier characteristics include phases and amplitudes of the common pilot subcarriers.

27. The method of claim 25, further comprising controlling a transmission power of the cell-specific pilot subcarriers and controlling a transmission power of the common pilot subcarriers, the transmission power of the cell-specific pilot subcarriers being controlled differently than the transmission power of the common pilot subcarriers.

28. The method of claim 25, wherein the transmission power of the cell-specific pilot subcarriers is higher than the transmission power of the common pilot subcarriers.

29. The method of claim 25, wherein the transmission power of the cell-specific pilot subcarriers is lower than the transmission power of the common pilot subcarriers.

30. In a multi-cell, Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system comprising a plurality of mobile stations and base stations in a plurality of groups of cells, a signal reception method for a mobile station associated with a serving base station in a serving cell within a group of cells in the wireless communication system, the mobile station including a receiver configured to receive different types of pilot subcarriers within a same frequency band that is divided into a plurality of subcarriers, the method comprising:

receiving cell-specific pilot subcarriers from the serving base station in the serving cell, wherein;

the cell-specific pilot subcarriers possess characteristics specific to the serving cell; and

at least some of the cell-specific pilot subcarriers are not aligned in frequency subcarrier index with cell-specific pilot subcarriers transmitted by another base station in the group of cells; and

receiving common pilot subcarriers from the serving base station and other base stations in the group of cells, wherein;

the common pilot subcarriers possess characteristics common to common pilot subcarriers transmitted by other base stations in the cells within the group;

common pilot subcarriers transmitted by the serving base station are aligned in frequency subcarrier index with common pilot subcarriers transmitted by the other base stations in the group of cells; and

frequency-domain signal randomization applied on the common pilot subcarriers transmitted by the serving base station is selected to be the same within the group of cells and is selected to be different from frequency-domain signal randomization applied on common pilot subcarriers transmitted by base stations in a different group of cells in the system.

31. The method of claim 30, wherein the cell-specific pilot subcarrier characteristics include phases and amplitudes of the cell-specific pilot subcarriers and the common pilot subcarrier characteristics include phases and amplitudes of the common pilot subcarriers.

32. The method of claim 30, further comprising utilizing the characteristics of the cell-specific pilot subcarriers to differentiate the cell-specific pilot subcarriers from cell-specific pilot subcarriers transmitted by another base station in another cell.

33. The method of claim 30, further comprising determining cell-specific channel coefficients based on the received cell-specific pilot subcarriers, the cell-specific channel coefficients characterizing a channel from the base station to the mobile station.

34. The method of claim 33, further comprising applying the cell-specific channel coefficients to signals on cell-specific data subcarriers received by the mobile station to compensate for cell-specific channel effects and recover cell-specific data carried by the cell-specific data subcarriers.

35. The method of claim 30, further comprising utilizing the received cell-specific pilot subcarriers for frame synchronization, frequency offset estimation, or timing estimation.

36. The method of claim 30, further comprising determining composite channel coefficients based on the received common pilot subcarriers, the composite channel coefficients characterizing an aggregate of different channels from base stations in the group of cells to the mobile station.

37. The method of claim 36, further comprising applying the composite channel coefficients to signals on common data subcarriers received by the mobile station to compensate for composite channel effects and to recover common data carried by the common data subcarriers.

38. The method of claim 30, further comprising utilizing the received common pilot subcarriers for frame synchronization, frequency offset estimation, or timing estimation.