Method and apparatus for interference rejection

• US 6,526,271 B1
• Filed: 10/20/1999
• Issued: 02/25/2003
• Est. Priority Date: 02/27/1998
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Horikawa, Izumi, Iwaoka, Atsushi, Tatsumi, Akinori, Hiramatsu, Katsuhiko, Watanabe, Masatoshi, Uesugi, Mitsuru, Kato, Osamu, Miya, Kazuyuki
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): BEAMER, TEMICA M
• Application Number:
  US09/403,026
• Time in Patent Office: 1,224 Days
• Field of Search: 455/501, 455/67.1, 455/67.3, 455/67.6, 455/63, 455/115, 455/226.1, 455/226.2, 455/295, 455/296, 375/227, 375/228, 375/284, 375/285, 375/296, 375/346, 375/348, 370/286, 370/289, 370/317, 370/332, 370/333, 370/334
• US Class Current: 455/296
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 1/71072 Successive interference cancellation
• CPC Class Codes: H04W 52/08 Closed loop power control

Abstract

A small number of users who provide high interference in the other users, such as a user transmitting a high rate signal, are selected beforehand. First, a signal of the user is demodulated to generate a replica, and a difference between a received signal and the replica is calculated, thereby canceling the interference in signals of the other users, and further improving the system capacity.

Claims

1. A base station apparatus, comprising:

a receiver that receives a signal which includes signals transmitted from a plurality of mobile stations, said plurality of mobile stations being divided into at least a first mobile station that causes a relatively large amount of interference to other mobile stations and at least a second mobile station that causes relatively little interference to other mobile stations;

a mobile station identifier that identifies the first mobile station of said plurality of mobile stations as a specific mobile station;

a first demodulator that extracts a signal transmitted from the specific mobile station out of the signal received by said receiver and demodulates the extracted signal;

a generator that generates at least one replica from the demodulation result of said first demodulator;

an interference canceler that cancels interference, caused by the signal transmitted from the specific mobile station, from the received signal by using the received signal and the at least one replica; and

a second demodulator that extracts a signal transmitted from the second mobile station out of the received signal after interference cancellation and demodulates the extracted signal.

2. The base station apparatus according to claim 1, further comprising a reception estimator that estimates a reception quality of the signal transmitted from the specific mobile station, wherein said interference canceler performs the interference cancellation only in the case where reception quality of the signal transmitted from the specific mobile station is above a predetermined level.

3. The base station apparatus according to claim 1, further comprising a reception estimator that estimates a reception quality of the signal transmitted from the specific mobile station, wherein said interference canceler performs weighting corresponding to a level of the estimated reception quality, and performs interference cancellation.

4. The base station apparatus according to claim 1, further comprising:

a reception estimator that estimates a reception quality of the signal transmitted from the specific mobile station, and

an offset adder that adds an offset to a value of the reception quality that is estimated.

5. The base station apparatus according to claim 1, further comprising a timing offsetter that determines a difference between an operation timing of said first demodulator and an operation timing of said second demodulator.

6. The base station apparatus according to claim 1, wherein said mobile station identifier identifies a mobile station located a shorter distance from said base station apparatus than a predetermined distance, as the specific mobile station.

7. The base station apparatus according to claim 1, wherein said mobile station identifier identifies a mobile station with a higher transmission rate than a predetermined transmission rate, as the specified mobile station.

8. The base station apparatus according to claim 1, wherein said first demodulator comprises a matched filter.

9. The base station apparatus according to claim 1, further comprising a pilot symbol controller that controls transmission so as to increase a power of a pilot symbol of the first mobile station included in the received signal more than a power of a pilot symbol of the second mobile station.

10. The base station apparatus according to claim 1, further comprising a power adjuster that adjusts transmission power control information of the specific mobile station to control transmission.

11. The base station apparatus according to claim 1, further comprising:

an antenna with a radiation pattern, and

a radiation pattern controller that controls the radiation pattern of the antenna in accordance with the signal of the specific mobile station.

12. An interference cancellation method, comprising:

receiving a signal which includes signals transmitted from a plurality of mobile stations, said plurality of mobile stations divided into at least a first mobile station that causes a relatively large amount of interference to other mobile stations and at least a second mobile station that causes relatively little interference to other mobile stations;

setting the first mobile station of said plurality of mobile stations as a specific mobile station;

extracting a signal transmitted from specific mobile station out of the received signal and first demodulating the extracted signal;

generating at least one replica from the demodulation result of said first demodulation;

canceling interference, caused by the signal transmitted from the specific mobile station, from the received signal, by using the received signal and the replica; and

extracting a signal transmitted from the second mobile station out of the signal after the interference cancellation and second demodulating the extracted signal.

13. The interference cancellation method according to claim 12, wherein, canceling is performed only when reception quality of the signal transmitted from the specific mobile station is above a predetermined level.

14. The interference cancellation method according to claim 12, wherein, in canceling, weighting is performed corresponding to a level of the quality of the signal of the specific mobile station to execute the interference cancellation.

15. The interference cancellation method according to claim 12, further comprising offsetting time for determining a difference between an operation timing of said first demodulating and an operation timing of said second demodulating.

16. The interference cancellation method according to claim 12, further comprising controlling a pilot symbol that executes transmission control so as to increase a power of a pilot symbol of the first mobile station included in the received signal, more than a power of a pilot symbol of the second mobile station.

17. The interference cancellation method according to claim 12, further comprising adjusting transmission power control information on the specific mobile station to perform transmission control.

18. The interference cancellation method according to claim 12, further comprising controlling a radiation pattern of an antenna in accordance with the signal of the specific mobile station.