Wireless communication system, weight control apparatus, and weight vector generation method

• US 20020051430A1
• Filed: 10/31/2001
• Published: 05/02/2002
• Est. Priority Date: 10/31/2000
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Obayashi, Shuichi, Kasami, Hideo
• Granted Patent: US 7,042,860 B2
• Time in Patent Office: Days
• US Class Current: 370/319
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 16/28 using beam steering

Abstract

Signals received by a plurality of antenna elements are supplied to a beam forming circuit via a distributor. The beam forming circuit weights and combines the signals to output a reception signal corresponding to a beam having a predetermined directionality pattern. A weight used to control weighting and combining is set by a weight controller. Upon receiving a registration request from an unregistered terminal, the weight controller calculates a weight vector used to form a beam having null directionality toward that terminal, and maximum directionality toward the range of an area other than an area where the terminal is located of a plurality of areas obtained by dividing the area covered by the antenna elements in accordance with direction.

Claims

1. A wireless communication system which allows simultaneous communications with a plurality of terminals by space-division multiplex access, comprising:

a plurality of antenna elements that receive a signal transmitted from the terminals;

a plurality of beam forming units configured to output reception signals corresponding to beams having predetermined directionality patterns by weighting and combining reception signals received by said plurality of antenna elements; and

a controller configured to set weight vectors used to control weighting and combining in said plurality of beam forming units, wherein when said controller receives a registration request from an unregistered terminal, said controller calculates and stores at least one of said weight vectors used to form a beam having;

null directionality toward the unregistered terminal; and

maximum directionality toward a specific area other than an area where the unregistered terminal is located of areas obtained by dividing a cover area covered by the wireless communication system.

2. A system according to claim 1, wherein upon calculating the weight vector for the unregistered terminal, said controller calculates the weight vector in correspondence with each of cases in which areas separated not less than a predetermined angle from the area to which the terminal belongs are set as the specific area.

3. A system according to claim 1, wherein upon calculating the weight vector for the unregistered terminal, said controller calculates the weight vector used to form the beam having null directionality toward the terminal by making predetermined repetitive calculations on the basis of the reception signal from the terminal using a corresponding one of initial weight vectors which are prepared for the respective areas and are used to form beams having maximum directionality toward the areas as an initial value of the weight vector.

4. A system according to claim 3, wherein said controller stores terminal-area information indicating an area to which a registered terminal belongs and looks up the terminal-area information upon calculating the weight vector for the unregistered terminal, and if a registered terminal which belongs to the same area as the unregistered terminal is found, said controller calculates the weight vector for the unregistered terminal using the weight vector already calculated for the registered terminal as an initial value of the weight vector.

5. A system according to claim 1, wherein upon obtaining the area to which the terminal belongs, said controller compares reception states of signals from the terminal when initial weight vectors which are prepared in advance for the respective areas and are used to form beams having maximum directionality toward the areas are set in the beam forming unit, and determines an area to which maximum directionality of a beam formed by a weight vector in a best reception state of the signal from the terminal is pointed as the area to which the terminal belongs.

6. A system according to claim 5, wherein the best reception state is a reception state with maximum reception power or signal to noise power ratio.

7. A system according to claim 1, wherein when said controller simultaneously communicates by space-division multiplex access with a first terminal which is located within a first area of the areas obtained by dividing the cover area covered by the self system in accordance with direction, and a second terminal which is located within a second area different from the first area,

said controller controls, for the first terminal, the beam forming unit which is to be associated with the first terminal using a first weight vector used to form a beam having null directionality toward the second terminal and maximum directionality toward the first area to which the first terminal belongs, and

said controller controls, for the second terminal, the beam forming unit which is to be associated with the second terminal using a second weight vector used to form a beam having null directionality toward the first terminal and maximum directionality toward the second area to which the second terminal belongs.

8. A weight control apparatus for an adaptive array which comprises a plurality of beam forming units for outputting reception signals corresponding to beams having predetermined directionality patterns by weighting and combining reception signals received by a plurality of antenna elements, comprising:

a storage unit configured to store weight vectors which can be set in the beam forming units and are used to control weighting and combining;

a unit configured to select and set predetermined ones of the weight vectors stored in said storage unit in the plurality of beam forming units, respectively; and

a unit configured to calculate a weight vector used to form a beam having null directionality toward a terminal for which the weight vector is to be registered, and maximum directionality toward a specific area other than an area where that terminal is located of areas obtained by dividing a cover area covered by the antenna elements.

9. A weight vector generation method of generating a weight vector used to control weighting and combining upon obtaining reception signals corresponding to beams having predetermined directionality patterns by weighting and combining reception signals received by a plurality of antenna elements, the method comprising:

obtaining an area in which a terminal for which the weight vector is to be generated is located of a plurality of areas obtained by dividing a cover area covered by the plurality of antennas in accordance with direction; and

calculating the weight vector used to form a beam having;

null directionality toward the terminal; and

maximum directionality toward a specific area other than the area where that terminal is located of the plurality of divided areas.

10. A wireless communication system for making packet transmission control based on carrier sense, comprising:

a plurality of cells each of which includes

a plurality of wireless base stations which use radio channels that do not interfere with each other, and

at least one wireless terminal for communicating with the wireless base station,

each wireless base station includes;

a transmission adaptive array for making transmission beam control; and

a reception adaptive array for making reception beam control,

said reception adaptive array reducing an interference wave from the wireless base station in a neighboring cell that uses a radio channel which becomes an interference source to not more than a carrier sense level, and

an arbitrary location in the cell being covered by a transmission beam formed by said transmission adaptive array and a reception beam formed by said reception adaptive array of at least one wireless base station.

11. A system according to claim 10, wherein the neighboring cells use different radio channels.

12. A system according to claim 10, wherein an arbitrary location in the cell is covered by transmission beams formed by the transmission adaptive arrays and reception beams formed by the reception adaptive arrays of at least two wireless base stations.

14. A method according to claim 13, wherein suspension of packet transmission by the wireless base station for a predetermined period of time makes the radio terminal, which communicates with the wireless base station, roam to another wireless base station.

16. A method according to claim 15, wherein the wireless base station in the neighboring cell that uses the radio channel which becomes the interference source sends the multi-cast packet while setting the reception adaptive array not to receive any packet.

18. An adaptive array according to claim 17, wherein said interference generation unit comprises:

a reception disconnector configured to control said reception level suppression unit to suppress the output level of said reception beam forming circuit to not more than the predetermined value; and

a multi-cast packet transmission controller configured to issue a command to the wireless base station to send a multi-cast packet.

20. An adaptive array according to claim 19, wherein said interference suppression unit comprises:

a transmission disconnector configured to control said transmission level suppression unit to suppress the output level from the wireless base station to not more than the predetermined value; and

a weight controller configured to calculate and set the weight to be set in said reception beam forming circuit on the basis of the output form said reception beam forming circuit.

13. A method of controlling an adaptive array for a wireless base station,

wherein after a wireless terminal which communicates with the wireless base station roams to another wireless base station, and the wireless terminal which communicates with a wireless base station in a neighboring cell that uses a radio channel which becomes an interference source roams to another wireless base station,

a reception adaptive array of the wireless base station makes beam control to suppress reception power after combining of the reception adaptive array to less than a carrier sense level while the wireless base station in the neighboring cell that uses the radio channel which becomes the interference source sends a packet.

15. A method of controlling an adaptive array for a wireless base station,

wherein a reception adaptive array of a wireless base station makes beam control to suppress reception power after combining of the reception adaptive array to not more than a carrier sense level while a wireless base station in a neighboring cell that uses a radio channel which becomes an interference source sends a multi-cast packet.

17. An adaptive array connected to a wireless base station for making packet transmission control based on carrier sense, comprising:

a plurality of antenna elements that receive signals;

a reception beam forming circuit to form a beam by weighting reception signals received by said plurality of antennas;

a reception level suppression unit configured to suppress an output level of said reception beam forming circuit to not more than a predetermined value, and to provide the output thereof to the wireless base station;

a transmission level suppression unit configured to suppress an output level from the wireless base station to not more than a predetermined value;

a transmission beam forming circuit to form a beam by weighting the output from said transmission level suppression unit; and

an interference generation unit configured to generate an interference for sending a packet irrespective of the reception signals received by said plurality of antenna elements.

19. An adaptive array connected to a wireless base station for making packet transmission control based on carrier sense, comprising:

a plurality of antenna elements that receive signals;

a reception beam forming circuit to form a beam by weighting reception signals received by said plurality of antennas;

a reception level suppression unit configured to suppress an output level of said reception beam forming circuit to not more than a predetermined value, and to provide the output thereof to the wireless base station;

a transmission level suppression unit configured to suppress an output level from the wireless base station to not more than a predetermined value;

a transmission beam forming circuit to form a beam by weighting the output from said transmission level suppression unit; and

an interference suppression unit configured to calculate and set a weight to be set in said reception beam forming circuit on the basis of the output from said reception beam forming circuit while no packet is sent from said plurality of antenna elements.