Method and apparatus for enabling soft handoff in an OFDMA-based communication system

• US 8,565,773 B2
• Filed: 03/12/2007
• Issued: 10/22/2013
• Est. Priority Date: 03/17/2006
• Status: Active Grant

• Current Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Soong, Anthony C. K., Yang, Yunsong, Lu, Jianmin, Lee, Jung Woon
• Primary Examiner(s): Kim, Wesley
• Assistant Examiner(s): NGUYEN, DINH
• Application Number:
  US11/685,037
• Publication Number:
  US 20070224989A1
• Time in Patent Office: 2,416 Days
• Field of Search: 370/203, 370/206, 370/208, 370/310, 370/311, 370/318, 370/328, 370/331, 370/335, 370/338, 370/342, 455/423, 455/436, 455/438, 455/439, 455/442, 455/443, 455/447, 455/450, 455/452.2, 455/458, 455/553.1, 455/562.1, 455/574
• US Class Current: 455/442
• 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 36/185 using make before break

Abstract

A method of enabling a soft handoff in a communication system, wherein the communication system includes a plurality of sectors and each of the plurality of sectors includes at least one base station is disclosed. The method includes: providing at least one mobile station; setting identical resources for serving the mobile station from each of the plurality of base stations in each sector; designating at least a plurality of base stations in at least one sector to participate a soft handoff; and performing a soft handoff.

Claims

1. A method of managing data transmission during a soft handoff in a communication system, the method comprising the steps of:

generating, from a mobile station, a pilot signal strength report for each sector of a base station in communication with the mobile station, wherein the communication system is an orthogonal frequency division multiplexing (OFDM)-based system;

receiving, at the mobile station, a plurality of soft handoff groups from the base station in accordance with the pilot signal strength report generated by the mobile station, wherein at least one of the soft handoff groups contains more than one sector;

measuring, by the mobile station, a combined pilot signal strength of each combined pilot signal;

selecting, by the mobile station, a desired soft handoff group in accordance with the measured combined pilot signal strengths;

updating member sectors in the mobile station'"'"'s current soft handoff group responsive to the desired soft handoff group;

wherein the mobile station communicates the desired soft handoff group to the base station using a reverse channel quality indicator (CQI) channel;

assigning a covering sequence for the reverse CQI channel for each soft handoff group that the base station forms for the mobile station;

communicating to the mobile station the covering sequence for each soft handoff group;

covering the reverse CQI channel by the mobile station with the covering sequence associated with the desired soft handoff group; and

transmitting the reverse CQI channel by the mobile station setting a transmit power for the desired soft handoff group.

2. The method of claim 1, wherein each soft handoff group contains at least one sector.

3. The method of claim 1 wherein the base station determines grouping of sectors from a list of potential soft handoff sectors in accordance with a physical location of each sector.

4. The method of claim 1 wherein the base station determines grouping of sectors from a list of potential soft handoff sectors in accordance with a capability of fast backhaul communications between the sectors.

5. The method of claim 1 wherein the base station determines grouping of sectors from a list of potential soft handoff sectors in accordance with a traffic load condition of each sector.

6. The method of claim 1 wherein the covering sequence is a Walsh code.

7. The method of claim 1 wherein the base station updates member sectors in the current soft handoff group in accordance with the desired soft handoff group indicated, and its capability to support such a group.

8. The method of claim 7 wherein the base station accepts the desired soft handoff group as a current serving soft handoff group if the base station can support it, and denies it and continues to use an existing current serving soft handoff group as the current soft handoff group if the base station cannot support the desired soft handoff group.

9. The method of claim 8 further including communicating the acceptance of the desired soft handoff group to the mobile station by the base station.

10. The method of claim 1 further including using a same hopping pattern by each member sector of a given one of the soft handoff groups that the base station forms.

11. A base station for transmitting data to a mobile station in soft handoff, the base station comprising:

a scheduler adapted to receive from a particular mobile station a desired soft handoff group request in accordance with a combined pilot signal strength comparison of potential soft handoff groups measured by the mobile station, wherein at least one of the soft handoff groups contains more than one sector, the scheduler adapted to assign, in accordance with the desired handoff group request, resources of a plurality of sectors that participate in soft handoff for transmission of particular data to the particular mobile station;

a plurality of remote modules, each containing a radio frequency processing unit for at least one sector of the base station, wherein the base station is in an orthogonal frequency division multiplexing (OFDM)-based system;

a main module that comprises base band processing units for the plurality of remote modules of at least one cell;

a communicative connection between the plurality of remote modules and the main module;

reporting a combined channel quality indicator (CQI) with the combined pilot strength from member sectors of the desired soft handoff group to the base station by the mobile station; and

selecting a modulation and coding scheme (MCS) by the base station for the data transmission to the mobile station in accordance with the combined CQI report from the mobile station.

12. The base station of claim 11, further comprising a backplane that connects one main module with at least another main module.

13. The base station of claim 11, further comprising a fast inter-base station connection that connects one main module at a first base station with another main module at a second base station.

14. The base station of claim 11, further comprising a singular hopping pattern for sectors in the desired soft handoff group for the mobile station.

15. The base station of claim 11, wherein the scheduler is adapted to assign resources of the plurality of sectors from a list of potential soft handoff sectors in accordance with a physical location of each sector.

16. The base station of claim 11, wherein the scheduler is adapted to assign the plurality of sectors from a list of potential soft handoff sectors in accordance with a capability of fast backhaul communications between the sectors.

17. The base station of claim 11, wherein the scheduler is adapted to assign the plurality of sectors from a list of potential soft handoff sectors in accordance with a traffic load condition of each sector.