Method and system for interference reduction

• US 8,086,181 B2
• Filed: 12/07/2010
• Issued: 12/27/2011
• Est. Priority Date: 05/23/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Wee, Daniel, Li, Hang, Yang, Weidong, Xu, Guanghan
• Primary Examiner(s): Pan, Yuwen
• Assistant Examiner(s): Ayotunde, Ayodeji
• Application Number:
  US12/961,741
• Publication Number:
  US 20110076954A1
• Time in Patent Office: 385 Days
• Field of Search: None
• US Class Current: 455/63.1
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 11/005 of intercell interference
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 16/18 Network planning tools
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: H04W 88/12 Access point controller devices

Abstract

A method and system for interference reduction for telecommunication systems are disclosed. The system comprises a base station control device (BCD) for configuring one or more parameters for operating one or more base stations (BSs), a first BS covering a first cell having one or more mobile terminals therein, a second BS covering a second cell neighboring to the first cell and sharing a predetermined frequency band with the first cell, wherein one or more radio frames constructed for communications between the first BS and any mobile terminal of the first cell and one or more radio frames constructed for communications between the second BS and any mobile terminal of the second cell are distinguishable by defining different channel configuration sets having one or more operation parameters, wherein the parameters includes a training sequence, a spreading code, and a channel observation window position.

Claims

1. A method comprising:

at a base station, receiving uplink signals transmitted from at least one mobile terminal, the uplink signals being sent using a training sequence assigned to the at least one mobile terminal;

estimating a vector channel impulse response for the mobile terminal based on the training sequence contained in the uplink signals;

estimating a spatial signature based on the training sequence for the mobile terminal;

generating one or more uplink nulling weights for the mobile terminal using the estimated spatial signature and interference information representing interfering signals;

generating a scalar channel impulse response from the vector channel impulse response, wherein generating the scalar channel response comprises performing a nulling operation based on the vector channel impulse response with the uplink nulling weights to derive the scalar channel impulse response;

detecting one or more uplink symbols contained in uplink signals received from the mobile terminal using the scalar channel impulse response;

generating one or more downlink nulling weights from the uplink nulling weights;

beamforming downlink signals via a plurality of antennas of the base station to the mobile terminal using the downlink nulling weights;

computing an interference intensity after the nulling operation using the uplink nulling weights; and

determining whether to switch a carrier for the mobile terminal based on the interference intensity.

5. The method of claim 1, and further comprising generating the interference information from signals received by the base station during a channel observation window corresponding to a time frequency slot in which no signals are transmitting within a cell coverage area of the base station such that only interfering signals from adjacent cell coverage areas may occur.

6. The method of claim 1, wherein estimating the spatial signature further comprises computing the spatial signature based on the vector channel impulse response.

7. The method of claim 1, wherein estimating the spatial signature comprises computing the spatial signature using the training sequence sent in a probing channel by the mobile terminal to the base station.

17. The method of claim 1, and further comprising the mobile terminal sending the carrier switch request to the base station using an uplink control channel.

18. The method of claim 1, and further comprising the mobile terminal sending the carrier switch request using a probing channel.

2. A method comprising:

at a base station, receiving uplink signals transmitted from at least one mobile terminal, the uplink signals being sent using a training sequence assigned to the at least one mobile terminal;

estimating a vector channel impulse response for the mobile terminal based on the training sequence contained in the uplink signals;

estimating a spatial signature based on the training sequence for the mobile terminal;

generating one or more uplink nulling weights for the mobile terminal using the estimated spatial signature and interference information representing interfering signals;

generating a scalar channel impulse response from the vector channel impulse response, wherein generating the scalar channel response comprises performing a nulling operation based on the vector channel impulse response with the uplink nulling weights to derive the scalar channel impulse response;

detecting one or more uplink symbols contained in uplink signals received from the mobile terminal using the scalar channel impulse response;

generating one or more downlink nulling weights from the uplink nulling weights;

beamforming downlink signals via a plurality of antennas of the base station to the mobile terminal using the downlink nulling weights;

determining at the mobile terminal an interference intensity; and

determining whether to send a carrier switch request from the mobile terminal to the base station based on the interference intensity.

3. The method of claim 2, and further comprising the mobile terminal sending the carrier switch request to the base station using an uplink control channel.

4. The method of claim 2, and further comprising the mobile terminal sending the carrier switch request using a probing channel.

19. The method of claim 2, and further comprising generating the interference information from signals received by the base station during a channel observation window corresponding to a time frequency slot in which no signals are transmitting within a cell coverage area of the base station such that only interfering signals from adjacent cell coverage areas may occur.

20. The method of claim 2, wherein estimating the spatial signature further comprises computing the spatial signature based on the vector channel impulse response.

8. A method comprising:

at a base station, receiving uplink signals transmitted from at least one mobile terminal, the uplink signals being sent using a training sequence assigned to the at least one mobile terminal;

estimating a vector channel impulse response for the mobile terminal based on the training sequence contained in the uplink signals;

estimating a spatial signature based on the training sequence for the mobile terminal, wherein estimating the spatial signature comprises computing the spatial signature using the training sequence sent in a probing channel by the mobile terminal to the base station;

generating one or more uplink nulling weights for the mobile terminal using the estimated spatial signature and interference information representing interfering signals;

generating a scalar channel impulse response from the vector channel impulse response;

detecting one or more uplink symbols contained in uplink signals received from the mobile terminal using the scalar channel impulse response;

generating one or more downlink nulling weights from the uplink nulling weights;

beamforming downlink signals via a plurality of antennas of the base station to the mobile terminal using the downlink nulling weights; and

scheduling transmissions at the mobile terminal in the probing channel using predetermined hash operations based on at least one broadcasted frame number and at least one mobile terminal specific equipment identification number.

9. The method of claim 8, wherein scheduling comprises adding random delays to transmission timings in the probing channel to reduce intra-cell interference.

10. A method comprising:

at a base station, receiving uplink signals transmitted from at least one mobile terminal, the uplink signals being sent using a training sequence assigned to the at least one mobile terminal;

estimating a vector channel impulse response for the mobile terminal based on the training sequence contained in the uplink signals;

estimating a spatial signature based on the training sequence for the mobile terminal;

generating one or more uplink nulling weights for the mobile terminal using the estimated spatial signature and interference information representing interfering signals;

generating a scalar channel impulse response from the vector channel impulse response;

detecting one or more uplink symbols contained in uplink signals received from the mobile terminal using the scalar channel impulse response, wherein the detected symbols are symbols either in a traffic or control portion of a frame, or in an information portion of a probing channel;

generating one or more downlink nulling weights from the uplink nulling weights; and

beamforming downlink signals via a plurality of antennas of the base station to the mobile terminal using the downlink nulling weights.

11. A system comprising:

a base station configured to wirelessly communicate with one or more mobile terminals in a coverage area;

at least one mobile terminal configured to send uplink signals to the base station and to receive downlink signals transmitted by the base station;

wherein the base station is configured to;

estimate a vector channel impulse response for the mobile terminal based on the training sequence contained in uplink signals transmitted by the mobile terminal;

estimate a spatial signature based on the training sequence for the mobile terminal;

generate one or more uplink nulling weights for the mobile terminal using the estimated spatial signature and interference information representing interfering signals;

generate the scalar channel response by performing a nulling operation based on the vector channel impulse response with the uplink nulling weights to derive the scalar channel impulse response;

detect one or more uplink symbols contained in uplink signals received from the mobile terminal using the scalar channel impulse response;

generate one or more downlink nulling weights from the uplink nulling weights;

beamform downlink signals via a plurality of antennas of the base station to the mobile terminal using the downlink nulling weights;

compute an interference intensity after the nulling operation using the uplink nulling weights; and

determine whether to switch a carrier for the mobile terminal based on the interference intensity.

13. The system of claim 11, wherein the base station is configured to generate the interference information from signals received by the base station during a channel observation window corresponding to a time frequency slot in which no signals are transmitting within a cell coverage area of the base station and thus only interfering signals from adjacent cell coverage areas may occur.

14. The system of claim 11, wherein the base station is configured to estimate the spatial signature by computing the spatial signature based on the vector channel impulse response.

15. The system of claim 11, wherein the base station is configured to estimate the spatial signature using the training sequence sent in a probing channel sent by the mobile terminal to the base station.

12. A system comprising:

a base station configured to wirelessly communicate with one or more mobile terminals in a coverage area;

at least one mobile terminal configured to send uplink signals to the base station and to receive downlink signals transmitted by the base station;

wherein the base station is configured to;

estimate a vector channel impulse response for the mobile terminal based on the training sequence contained in uplink signals transmitted by the mobile terminal;

estimate a spatial signature based on the training sequence for the mobile terminal;

generate one or more uplink nulling weights for the mobile terminal using the estimated spatial signature and interference information representing interfering signals;

generate a scalar channel impulse response from the vector channel impulse response;

detect one or more uplink symbols contained in uplink signals received from the mobile terminal using the scalar channel impulse response;

generate one or more downlink nulling weights from the uplink nulling weights; and

beamform downlink signals via a plurality of antennas of the base station to the mobile terminal using the downlink nulling weights;

wherein the mobile terminal is configured to determine an interference intensity and to determine whether to send a carrier switch request to the base station based on the interference intensity.

16. A system comprising:

a base station configured to wirelessly communicate with one or more mobile terminals in a coverage area;

at least one mobile terminal configured to send uplink signals to the base station and to receive downlink signals transmitted by the base station;

wherein the base station is configured to;

estimate a vector channel impulse response for the mobile terminal based on a training sequence contained in uplink signals transmitted by the mobile terminal;

estimate the spatial signature using the training sequence sent in a probing channel by the mobile terminal to the base station;

generate one or more uplink nulling weights for the mobile terminal using the estimated spatial signature and interference information representing interfering signals;

generate a scalar channel impulse response from the vector channel impulse response;

detect one or more uplink symbols contained in uplink signals received from the mobile terminal using the scalar channel impulse response;

generate one or more downlink nulling weights from the uplink nulling weights; and

beamform downlink signals via a plurality of antennas of the base station to the mobile terminal using the downlink nulling weights;

wherein the mobile terminal is configured to schedule transmissions in the probing channel using predetermined hash operations based on at least one broadcasted frame number and at least one mobile terminal specific equipment identification number.