Soft handoff in OFDMA system

• US 8,023,466 B2
• Filed: 06/22/2005
• Issued: 09/20/2011
• Est. Priority Date: 06/22/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Rockstar Bidco LP (Rockstar Consortium Inc.)
• Inventors: Ma, Jianglei, Tong, Wen, Jia, Ming, Zhu, Peiying, Fong, Mo-Han, Zhang, Hang
• Primary Examiner(s): DOAN, PHUOC HUU
• Application Number:
  US11/630,473
• Publication Number:
  US 20090129334A1
• Time in Patent Office: 2,281 Days
• Field of Search: None
• 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

The soft handoff in an OFDMA system. 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 have subcarriers with a subchannel definition, for example, an identical permutation.

Claims

1. A subscriber station in an orthogonal frequency division multiplexing access (OFDMA) system comprising:

a) receive circuitry adapted to receive and downconvert a plurality of OFDM signals, said plurality of OFDM symbols comprising a first plurality of subcarriers, said plurality of subcarriers being defined in a soft handoff zone comprising a first dimension of subchannels, said subchannels comprising said first plurality of subcarriers; and

a second dimension of divided and multiplexed OFDM symbols;

said first plurality of subcarriers in said soft handoff zone having a subchannel definition;

b) Fourier Transform (FT) logic adapted to provide an FT on each of said first plurality of subcarriers to generate a plurality of division-multiplexing coded signals; and

c) decoder logic adapted to provide division-multiplexing decoding on the plurality of divided-multiplexed coded signals to recover data from a base station.

2. The subscriber station according to claim 1, wherein said first plurality of subcarriers are divided in frequency domain.

3. The subscriber station according to claim 1, wherein said subchannel definition is identical for each of said first plurality of subcarriers.

4. The subscriber station according to claim 1, wherein said subchannel definition is subcarrier permutation.

5. The subscriber station according to claim 1, wherein said first plurality of subcarriers is divided and multiplexed using time division multiplexing.

6. The subscriber station according to claim 1, further comprising 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.

7. The subscriber station according to claim 6, 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.

8. The subscriber station according to 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 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.

9. The subscriber station according to claim 7, 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.

10. The subscriber station according to claim 6, wherein said received first plurality of subcarriers is different from said received second plurality of subcarriers, thus achieving higher throughput.

11. The subscriber station according to claim 6, 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.