Soft handoff in OFDMA system

• US 8,537,782 B2
• Filed: 08/29/2012
• Issued: 09/17/2013
• Est. Priority Date: 06/22/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Ma, Jianglei, Tong, Wen, Jia, Ming, Zhu, Peiying, Fong, Mo-Han, Zhang, Hang
• Primary Examiner(s): DOAN, PHUOC HUU
• Application Number:
  US13/597,921
• Publication Number:
  US 20120327905A1
• Time in Patent Office: 384 Days
• Field of Search: 370/331, 370/480, 370/320, 370/210, 455/442, 375/267
• US Class Current: 370/331
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04B 7/0691 using subgroups of transmit antennas
• CPC Class Codes: H04W 36/00692 using simultaneous multiple data streams, e.g. cooperative multipoint [CoMP], carrier aggregation [CA] or multiple input multiple output [MIMO] allocation of physical resources in CoMP or in CA H04L5/0035
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection

Abstract

Soft handoff in an OFDMA system is disclosed. If the pilot signal strength for a base station exceeds the defined threshold, the base station is added to an active set list. Subcarriers in a plurality of orthogonal frequency division multiplexing (OFDM) symbols are divided and allocated into subchannels. The OFDM symbols are divided and multiplexed. A soft handoff zone with a first dimension of the subchannels and a second dimension of the divided and multiplexed OFDM symbols is defined. The soft handoff zone has subcarriers with a subchannel definition, for example, an identical permutation.

Claims

1. A method for receiving data in an orthogonal frequency division multiplexing access (OFDMA) system comprising:

a device receiving a plurality of orthogonal frequency division multiplexing (OFDM) symbols representing data from a transmitting device, said plurality of OFDM symbols comprising a first plurality of subcarriers, said first plurality of subcarriers being defined in a soft handoff zone and said first plurality of subcarriers in said soft handoff zone having a subchannel definition, wherein the soft handoff zone comprises;

a first dimension of subchannels, said first dimension of subchannels comprising said first plurality of subcarriers; and

a second dimension of divided and multiplexed OFDM symbols; and

the device processing the received symbols to recover the data from the transmitting device.

2. The method of claim 1, wherein the device comprises a mobile station.

3. The method of claim 1, wherein said first plurality of subcarriers is divided in a frequency domain.

4. The method of claim 1, wherein said subchannel definition is identical for each of said first plurality of subcarriers.

5. The method of claim 1, wherein said subchannel definition is a subcarrier permutation.

6. The method of claim 1, wherein said first plurality of subcarriers is divided and multiplexed using time division multiplexing.

7. The method of claim 1, wherein receiving the plurality of OFDM symbols further comprises receiving the plurality of OFDM symbols via a plurality of antennas, said plurality of antennas receiving the first plurality of subcarriers from a first base station and a second plurality of subcarriers from at least one second base station, wherein said first plurality of subcarriers and said second plurality of subcarriers are in said soft handoff zone and form a macro-diversity transmission.

8. The method of claim 7, wherein said macro-diversity transmission is a multi-input multi-output (MIMO) transmission, and said first base station and said one or more than one second base stations provide a plurality of antennas to form an antenna pool.

9. The method of claim 7, wherein said received first plurality of subcarriers is different from said received second plurality of subcarriers.

10. The method of claim 7, wherein said received first plurality of subcarriers is identical to said received second plurality of subcarriers, and all or some antennas in said antenna pool transmit said subcarriers in a same data region, achieving a combination of radio frequency (RF) signals from said first base station and said one or more than one second base stations.

11. The method of claim 7, wherein said received first plurality of subcarriers is in a first data region, and wherein said received second plurality of subcarriers is transmitted through a second set of antennas in a second data region of a same size, wherein the first plurality of subcarriers and the second plurality of subcarriers are soft-combined to achieve diversity combining and soft combining gain.

12. The method of claim 1, wherein said received first plurality of subcarriers is transmitted through a first set of antennas in a first data region, and said received second plurality of subcarriers is transmitted through a second set of antennas in a second data region, wherein said first plurality of subcarriers and said second plurality of subcarriers are separately decoded to achieve data rate increase.

13. A non-transitory, computer accessible memory medium storing program instructions for receiving data in an orthogonal frequency division multiplexing access (OFDMA) system, wherein the program instructions are executable to:

receive a plurality of orthogonal frequency division multiplexing (OFDM) symbols representing data from a transmitting device, said plurality of OFDM symbols comprising a first plurality of subcarriers, said first plurality of subcarriers being defined in a soft handoff zone and said first plurality of subcarriers in said soft handoff zone having a subchannel definition, wherein the soft handoff zone comprises;

a first dimension of subchannels, said first dimension of subchannels comprising said first plurality of subcarriers; and

a second dimension of divided and multiplexed OFDM symbols; and

process the received symbols to recover the data from the transmitting device.

14. The non-transitory, computer accessible memory medium of claim 13, wherein the program instructions are executable by a mobile station.

15. The non-transitory, computer accessible memory medium of claim 13, wherein said first plurality of subcarriers is divided in a frequency domain.

16. The non-transitory, computer accessible memory medium of claim 13, wherein said subchannel definition is identical for each of said first plurality of subcarriers.

17. The non-transitory, computer accessible memory medium of claim 13, wherein said subchannel definition is a subcarrier permutation.

18. The non-transitory, computer accessible memory medium of claim 13, wherein said first plurality of subcarriers is divided and multiplexed using time division multiplexing.

19. The non-transitory, computer accessible memory medium of claim 13, wherein receiving the plurality of OFDM symbols further comprises receiving the plurality of OFDM symbols via a plurality of antennas, said plurality of antennas receiving the first plurality of subcarriers from a first base station and a second plurality of subcarriers from at least one second base station, wherein said first plurality of subcarriers and said second plurality of subcarriers are in said soft handoff zone and form a macro-diversity transmission.

20. The non-transitory, computer accessible memory medium of claim 19, wherein said macro-diversity transmission is a multi-input multi-output (MIMO) transmission, and said first base station and said one or more than one second base stations provide a plurality of antennas to form an antenna pool.

21. The non-transitory, computer accessible memory medium of claim 19, wherein said received first plurality of subcarriers is different from said received second plurality of subcarriers.

22. The non-transitory, computer accessible memory medium of claim 19, wherein said received first plurality of subcarriers is identical to said received second plurality of subcarriers, and all or some antennas in said antenna pool transmit said subcarriers in a same data region, achieving a combination of radio frequency (RF) signals from said first base station and said one or more than one second base stations.

23. The non-transitory, computer accessible memory medium of claim 19, wherein said received first plurality of subcarriers is in a first data region, and wherein said received second plurality of subcarriers is transmitted through a second set of antennas in a second data region of a same size, wherein the first plurality of subcarriers and the second plurality of subcarriers are soft-combined to achieve diversity combining and soft combining gain.

24. The non-transitory, computer accessible memory medium of claim 13, wherein said received first plurality of subcarriers is transmitted through a first set of antennas in a first data region, and said received second plurality of subcarriers is transmitted through a second set of antennas in a second data region, wherein said first plurality of subcarriers and said second plurality of subcarriers are separately decoded to achieve data rate increase.

25. A mobile station, configured to perform orthogonal frequency division multiplexing access (OFDMA) communication, comprising:

one or more antennas configured to receive a plurality of orthogonal frequency division multiplexing (OFDM) symbols representing data from a transmitting device, said plurality of OFDM symbols comprising a first plurality of subcarriers, said first plurality of subcarriers being defined in a soft handoff zone and said first plurality of subcarriers in said soft handoff zone having a subchannel definition, wherein the soft handoff zone comprises;

a first dimension of subchannels, said first dimension of subchannels comprising said first plurality of subcarriers; and

a second dimension of divided and multiplexed OFDM symbols; and

processing hardware coupled to the one or more antennas, wherein the processing hardware is configured to processing the received symbols to recover the data from the transmitting device.

26. The mobile station according to claim 25, wherein said first plurality of subcarriers are divided in frequency domain.

27. The mobile station according to claim 25, wherein said subchannel definition is identical for each of said first plurality of subcarriers.

28. The mobile station according to claim 25, wherein said subchannel definition is subcarrier permutation.

29. The mobile station according to claim 25, wherein said first plurality of subcarriers is divided and multiplexed using time division multiplexing.

30. The mobile station according to claim 25, wherein the one or more antennas comprise a plurality of antennas, said plurality of antennas receiving a first plurality of subcarriers from a first base station and a second plurality of subcarriers from one or more than one second base stations, said first plurality of subcarriers and said second plurality of subcarriers are in said soft handoff zone forming a macro-diversity transmission.

31. The mobile station according to claim 30, wherein said macro-diversity transmission is a multi-input multi-output (MIMO) transmission, said first base station and said one or more than one second base stations provide a plurality of antennas to form an antenna pool.

32. The mobile station according to claim 30, wherein said received first plurality of subcarriers is different from said received second plurality of subcarriers, thus achieving higher throughput.

33. The mobile station according to claim 32, wherein said received first plurality of subcarriers is identical to said received second plurality of subcarriers, and all or some antennas in said antenna pool transmit said subcarriers in same data region, achieving a combination of RF signals from said first base station and said one or more than one second base stations.

34. The mobile station according to claim 32, wherein said received first plurality of subcarriers is in a first data region, and wherein said received second plurality of subcarriers is transmitted through a second set of antennas in a second data region of same size, wherein the first plurality of subcarriers and the second plurality of subcarriers are soft-combined to achieve diversity combining and soft combining gain.

35. The mobile station according to claim 25, wherein said received first plurality of subcarriers is transmitted through a first set of antennas in a first data region, and said received second plurality of subcarriers is transmitted through a second set of antennas in a second data region, wherein said first plurality of subcarriers and said second plurality of subcarriers are separately decoded to achieve data rate increase.