Radio communication apparatus employing a rake receiver

• US 6,408,039 B1
• Filed: 03/10/1999
• Issued: 06/18/2002
• Est. Priority Date: 03/11/1998
• Status: Expired due to Term

• Current Assignee: Inphi Corporation
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Ito, Katsutoshi
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Bayard, Emmanuel
• Application Number:
  US09/265,800
• Time in Patent Office: 1,196 Days
• Field of Search: 375/130, 375/136, 375/347, 375/349, 370/335, 370/342, 370/441, 370/479, 455/134, 455/132, 455/135, 455/137, 455/146, 455/272, 455/273, 455/500, 455/149, 342/444, 342/463, 342/465
• US Class Current: 375/347
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers

Abstract

A radio communication apparatus having a rake receiver for searching and combining reception paths. The apparatus includes at least one combination searcher/finger unit which performs a searcher operation for detecting signals on the reception paths and estimates the signal strength of each of the signals. The searcher/finger unit also performs a finger operation which outputs a demodulated symbol in response to a command signal generated by an assignment unit. The assignment unit assigns either a searcher operation or a finger operation to the searcher/finger unit in accordance with the number of reception paths transmitting a signal suitable for demodulation.

Claims

1. A radio communication apparatus including a rake receiver for searching and combining reception paths comprising:

at least one combination searcher/finger unit, said at least one combination searcher/finger unit performing

a searcher operation for detecting signals on the reception paths and estimating the signal strength of each of said signals; and

a finger operation for outputting a demodulated symbol in response to a command signal; and

an assignment unit for generating said command signal, said assignment unit assigning either said searcher operation or said finger operation in accordance with the number of reception paths transmitting a signal suitable for demodulation.

2. A radio communication apparatus according to claim 1 wherein a plurality of said combination searcher/finger units are provided and wherein said assignment unit comprises:

a multipath detector, said multipath detector detecting a first reception path having the strongest signal strength and a second reception path having a signal strength which is a predetermined amount less than said strongest signal strength; and

a finger assignment unit coupled to said multipath detector, said finger assignment unit assigning a first set of said plurality of combination searcher/finger units to provide finger operation for said reception paths up to the number of reception paths detected by said multipath detector, and for assigning a second set of said plurality of combination searcher/finger units to provide searcher operation.

3. A radio communication apparatus according to claim 2 wherein the difference between the signal strengths of said first and second reception paths is 3 dB.

4. A radio communication apparatus including a rake receiver for searching and combining reception paths from a plurality of neighboring base stations comprising:

at least one combination searcher/finger unit, said at least one combination searcher/finger unit performing

a searcher operation for detecting signals on the reception paths from the plurality of neighboring base stations and estimating the signal strength of each of said signals; and

a finger operation for outputting a demodulated symbol in response to a command signal; and

an assignment unit for generating said command signal, said assignment unit assigning either said searcher operation or said finger operation in accordance with the number of neighboring base stations.

5. A radio communication apparatus according to claim 4 wherein said assignment unit comprising;

a multipath detector for detecting a reception path having a signal thereon of sufficient strength for demodulation thereof; and

a finger assignment unit for assigning one of said combination searcher/finger unit to function as a searcher if the number of neighboring base stations is below a first threshold value, for assigning two of said combination searcher/finger unit to function as a searcher if the number of said neighboring base stations is between the first threshold value and a second threshold value, and for assigning three of said combination searcher/finger unit to function as a searcher if the number of neighboring base stations is above the second threshold value, where said first threshold value is less than said second threshold value.

6. A radio communication apparatus according to claim 5, wherein said first threshold value is 7 and said second threshold value is 14.

7. A radio communication apparatus according to claim 5 wherein the number of neighboring base stations is set forth in a list transmitted from base station.

8. A radio communication apparatus including a rake receiver for searching and combining a plurality of useful reception paths comprising:

at least one combination searcher/finger unit, said at least one combination searcher/finger unit performing

a searcher operation for detecting signals on the reception paths and estimating the signal strength of each of said signals; and

a finger operation for outputting a demodulated symbol in response to a command signal; and

an assignment unit for generating said command signal, said assignment unit assigning either said searcher operation or said finger operation in accordance with the total signal strength of the useful reception paths, said useful reception paths being paths transmitting signals suitable for demodulation.

9. A radio communication apparatus according to claim 8 which includes a plurality of combination searcher/finger units and wherein said assignment unit comprises;

a multipath detector for detecting reception paths among said plurality of reception paths having a signal thereon of sufficient strength for demodulation thereof;

a searcher calculator for calculating a total reception signal strength by adding the signal strengths of all of said plurality of reception paths; and

a finger assignment unit for assigning three of said combination searcher/finger units to function as a searcher if said total reception signal strength is below a first threshold value, for assigning two of said combination searcher/finger units to function as searchers if the total reception signal strength is between said first threshold value and a second threshold value, and for assigning one of said combination searcher/finger units to function as a searcher if said total reception signal strength is above said second threshold value, said first threshold value being smaller than said second threshold value.

10. A radio communication apparatus according to claim 9 wherein said first threshold value is −

14 dB and second threshold value is −

10 dB.

11. A radio communication apparatus including a rake receiver for searching and combining reception paths comprising:

at least one combination searcher/finger unit, said at least one combination searcher/finger unit performing

a searcher operation for detecting signals on the reception paths and estimating the signal strength of each of said signals; and

a finger operation for outputting a demodulated combined signal in response to a command signal;

a signal processor for calculating a reception frame error rate of said combined signal; and

an assignment unit assigning either said searcher operation or said finger operation in accordance with said reception frame error rate.

12. A radio communication apparatus according to claim 11 which includes a plurality of combination searcher/finger units and wherein said assignment unit comprises:

a multipath detector for detecting reception paths among said plurality of reception paths having a signal thereon of sufficient strength for demodulation thereof; and

a finger assignment unit for assigning three of said combination searcher/finger units to function as searchers if the reception frame error rate is below a first threshold value, for assigning two of said combination searcher/finger units to function as searchers if the reception frame error rate is between the first threshold value and a second threshold value, and for assigning one of said combination searcher/finger units to function as a searcher if the reception frame error rate is above the second threshold value, where said first threshold value is smaller than said second threshold value.

13. A radio communication apparatus according to claim 12, wherein, the first threshold value is 1% and the second threshold value is 3%.

14. A radio communication apparatus including a plurality of base stations and a rake receiver for searching and combining reception paths comprising:

at least one combination searcher/finger unit, said at least one combination searcher/finger unit performing

a searcher operation for detecting signals on the reception paths and estimating the signal strength of each of said signals; and

a finger operation for outputting a demodulated symbol in response to a command signal; and

an assignment unit for generating said command signal, said assignment unit assigning either said searcher operation or said finger operation in accordance with a reception modes having an initial synchronizing mode for synchronizing with one of the base stations, a call waiting-mode for waiting for a call from the synchronized base station and a communication mode for communicating to the synchronized base station.

15. A radio communication apparatus according to claim 14 which includes a plurality of combination searcher/finger units and wherein said assignment unit further comprises:

a multipath detector for detecting a reception path having a sufficient signal strength for demodulation;

a finger assignment unit for assigning all of said combination searcher/finger units to function as a searcher if the reception mode is an initial synchronizing mode, for assigning a larger number of said combination searcher/finger units that function as a searcher than said combination searcher/finger units that function as a finger if the reception mode is a call waiting mode and for assigning a smaller number of said combination searcher/finger units that function as a searcher than said combination searcher/finger units that function as a finger operation if the reception mode is a communication mode.

16. A method of assigning a searcher operation or a finger operation for a plurality of combination searcher/finger units, which comprising the steps of;

detecting signals on reception paths between a base station and a mobile station;

estimating the signal strength of each of said signals; and

assigning either said searcher operation or said finger operation in accordance with the number of reception paths transmitting a signal suitable for demodulation.

17. The method of claim 16, wherein the number of said reception paths suitable for demodulation is the sum of the reception path having the strongest signal strength and the other reception paths having a signal strength which is a predetermined amount less that said strongest signal strength.