MIMO WIRELESS COMMUNICATION SYSTEM AND METHOD BY A PLURALITY OF BASE STATIONS AND MOBILE STATION

• US 20080192682A1
• Filed: 04/07/2008
• Published: 08/14/2008
• Est. Priority Date: 10/07/2005
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: YOSHIDA, Shousei, MATSUMOTO, Mariko
• Granted Patent: US 8,265,675 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data

Abstract

A MIMO wireless communication system capable of relaxing a reduction in a transmission rate on a cell end far from a base station and ensuring a high transmission rate for a mobile station, irrespectively of a distance from the base station is provided.

In a state 1 in which a mobile station 21 is away from a first base station 11, a distance between the first base station and the mobile station is short, a propagation line state is good, and high speed transmission is possible. Therefore, the mobile station checks a propagation line quality and instructs only the first base station to transmit data to the mobile station. When the mobile station moves to a state 2, a transmission line state between the mobile station and the first base station is worse but the mobile station is communicable with a second base station along with a reduction in a possible transmission data rate. Therefore, the mobile station issues a request to divide the data to the first base station and the second base station and to transmit the divided data to the mobile station, and holds MIMO communication with the two base stations. When the mobile station moves to a location in a state 3, the mobile station cannot communicate with the first base station, the propagation line state with respect to the second base station is good, and high speed transmission is possible. The base station requests only the second base station to transmit the data and communicates with the second base station.

Claims

1. A wireless communication system including a plurality of base stations and mobile stations, wherein

the plurality of base stations includes a unit distributing data to be communicated with a certain mobile station and transmitting different data to the certain mobile station by MIMO (Multi-Input Multi-Output), respectively in a state in which the certain mobile station simultaneously communicates with and connects to a plurality of base stations in a region in which a propagation line quality is bad, and

the mobile station includes a plurality of antennas;

and a unit receiving the data transmitted by the MIMO, by the MIMO.

2. The wireless communication system according to claim 1, comprising a control unit controlling the mobile station to hold a data communication only with a single base station out of the plurality of base stations if an expected transmission rate is obtained by a communication between the mobile station and the single base station, and switching a transmission or reception method to the MIMO transmission or reception method for distributing the data using a plurality of base stations if the expected transmission rate is not obtained.

3. The wireless communication system according to claim 1, comprising:

a mobile station including a transmission line quality estimating unit detecting a transmission line quality between each of the plurality of base stations and the mobile station, and a control unit exerting a control to transmit an inquiry about a communicable data rate to each of the base stations by notifying each of the base stations of the transmission line quality, to select a combination of base stations necessary to satisfy a data rate expected value using the communicable data rate received from each of the base stations, to notify the base stations of the selected combination, and to perform the MIMO transmission or reception with the base stations; and

a plurality of base stations each including a control unit that exerts a control to select a modulation method and the communicable data rate in response to the inquiry about the transmission line quality from the mobile station, to notify the mobile station of the modulation method and the communicable data rate, and to select and distribute data addressed to the mobile station according to an instruction from the mobile station.

4. The wireless communication system according to claim 1, comprising:

a mobile station including a transmission line quality estimating unit detecting a transmission line quality between each of the plurality of base stations and the mobile station, and a control unit exerting a control to select a combination of base stations to be communicated with the mobile station based on the transmission line quality, to notify each of the base stations of the selected combination, and to perform the MIMO transmission or reception with the base stations; and

a plurality of base stations each including a control unit that exerts a control to select and distribute data addressed to the mobile station according to an instruction from the mobile station.

5. The wireless communication system according to claim 1, comprising:

a mobile station including a transmission line quality estimating unit detecting a transmission line quality between each of the plurality of base stations and the mobile station, and a control unit exerting a control to notify each of the base stations of the transmission line quality, and to perform the MIMO transmission or reception with the plurality of base stations according to an instruction from each of the base stations; and

a base station including a control unit that exerts a control to select a modulation method and a communicable data rate in response to a notification of the transmission line quality from the mobile station, to communicate the communicable data rate among a plurality of base stations, to select a combination of base stations to be communicated with the mobile station so as to satisfy a data rate expected value for the mobile station using the communicable data rate, and to perform the MIMO transmission or reception with the mobile station.

6. The wireless communication system according to claim 1, comprising:

a base station including a transmission line quality estimating unit detecting a transmission line quality between the base station and the mobile station, and a control unit exerting a control to select a modulation method and a communicable data rate in response to the transmission line quality detected by each of the base stations, to communicate the communicable data rate among a plurality of base stations, to select a combination of base stations for satisfying a data rate expected value for the mobile station using the communicable data rate with respect to the same mobile station, and to perform the MIMO transmission or reception with the mobile station; and

a mobile station including a control unit that exerts a control to perform the MIMO transmission or reception according to an instruction from the base station.

7. The wireless communication system according to claim 1, comprising:

a mobile station including a transmission line quality estimating unit detecting a transmission line quality between each of the plurality of base stations and the mobile station, and a control unit exerting a control to notify a radio network controller connected to the plurality of base stations of the transmission line quality, and to perform the MIMO transmission or reception with the base stations according to an instruction from the radio network controller;

a radio network controller including a control unit exerting a control to select a modulation method and a communicable data rate to each of the base stations in response to the transmission line quality transmitted via the base station from the mobile station, to select a combination of base stations necessary to satisfy a data rate expected value for the mobile station, to notify each of the base stations and the mobile station of the selected combination, and to perform the MIMO transmission or reception with the base stations of the selected combination; and

a plurality of base stations controlled by the radio network controller.

8. The wireless communication system according to claim 1, comprising:

a plurality of base stations each including a transmission line quality estimating unit detecting a transmission line quality between each of the plurality of base stations and the mobile station;

a radio network controller including a control unit exerting a control to select a modulation method and a communicable data rate available to each of the base stations in response to the transmission line quality, to select a combination of base stations so that a sum of the communicable data rates with respect to the same mobile station satisfies a data rate expected value for the mobile station, and to perform MIMO transmission or reception among the base stations of the selected combination and the mobile station; and

a mobile station performing the MIMO transmission or reception according to an instruction from the radio network controller via the base stations.

9. The wireless communication system according to claim 3,

wherein the plurality of base stations are connected to one another by a network, and comprise a selecting unit causing the respective base stations to independently select packets addressed to the single mobile station and received from the network.

10. The wireless communication system according to claim 3,

wherein each of the plurality of base stations exerts a retransmission control.

11. A wireless communication system including a base station constituting a plurality of sectors and a mobile station, wherein

the base station includes a unit distributing data to be communicated with a certain mobile station and simultaneously transmitting different data to the certain mobile station by MIMO in a state in which the certain mobile station simultaneously communicates with and connects to antennas for a plurality of sectors in a region in which a propagation line quality is bad, and

the mobile station includes a plurality of antennas and a unit receiving the data transmitted by the MIMO, by the MIMO.

12. The wireless communication system according to claim 11, comprising a control unit controlling the mobile station to hold a data communication only with an antenna or antennas of a single sector out of the antennas of the plurality of sectors if an expected transmission rate is obtained by a communication between the mobile station and the antennas of the single sector, and switching a transmission or reception method to the MIMO transmission or reception method for distributing the data using the antennas of the plurality of sectors if the expected transmission rate is not obtained.

13. The wireless communication system according to claim 11, comprising:

a mobile station including a transmission line quality estimating unit detecting a transmission line quality between each of the antennas of the plurality of sectors and the mobile station, and a control unit exerting a control to notify the base station of the transmission line quality, and to perform the MIMO transmission or reception according to an instruction from the base station; and

a base station including a control unit exerting a control to select a modulation method and a communicable data rate for the antennas of the plurality of sectors in response to a notification of the transmission line quality from the mobile station, to select a combination of sectors necessary to satisfy a data rate expected value for the mobile station, to notify the mobile station of the selected combination, and to perform the MIMO transmission or reception.

14. The wireless communication system according to claim 11, including a plurality of base stations constituting a plurality of sectors and a mobile station, comprising:

a base station distributing and transmitting data addressed to the single mobile station by the MIMO using the antennas of the plurality of sectors of each of the base stations; and

a mobile station receiving signals from the antennas of the plurality of sectors of each of the plurality of base stations by the MIMO.

15. A wireless communication method by a plurality of base stations and a mobile station, including steps of:

causing the plurality of base stations to distribute data to be communicated with a certain mobile station and to transmit different data to the certain mobile station by MIMO, respectively in a state in which the certain mobile station simultaneously communicates with and connects to a plurality of base stations in a region in which a propagation line quality is bad, and

causing the mobile station to receive the data transmitted by the MIMO, by the MIMO.

16. The wireless communication method according to claim 15, comprising steps of

holding a data communication only with a single base station out of the plurality of base stations if an expected transmission rate is obtained by a communication between the mobile station and the single base station, and switching to a MIMO transmission or reception method for distributing the data using a plurality of base stations if the expected transmission rate is not obtained.

17. A wireless communication method by a plurality of base stations constituting a plurality of sectors and a mobile station, including steps of:

causing the plurality of base stations to distribute data to be communicated with a certain mobile station and simultaneously transmit different data to the certain mobile station by MIMO, respectively in a state in which the certain mobile station simultaneously communicates with and connects to antennas of a plurality of sectors in a region in which a propagation line quality is bad, and

causing the mobile station to receive the data transmitted by the MIMO, by the MIMO.

18. A wireless mobile station device comprising:

a plurality of antennas of MIMO reception;

a MIMO separating unit separating signals transmitted from a plurality of base stations according to transmission line characteristics of the respective base stations;

a demodulating unit demodulating the separated signals from the respective base stations;

a decoding and MIMO data combining unit decoding the demodulated signals and for combining the signals from the respective base stations; and

a control unit exerting a control to receive the signals from the base stations by MIMO in a state of a MIMO transmission or reception with the plurality of the base stations, and to receive a signal from a single base station out of the plurality of base stations in a state of a non-MIMO transmission or reception with the plurality of the base stations.

19. The wireless mobile station device according to claim 18, further comprising a transmission line quality estimating unit detecting a transmission line quality between each of the plurality of base stations and the mobile station,

wherein the control unit exerts a control to transmit an inquiry about a communicable data rate to each of the base stations by notifying each of the base stations of the transmission line quality, to select a combination of base stations communicating so as to satisfy a data rate expected value using the communicable data rate received from each of the base stations, to notify the base stations of the selected combination, and to perform the MIMO transmission or reception.

20. The wireless mobile station device according to claim 18, further comprising a transmission line quality estimating unit detecting a transmission line quality between each of the plurality of base stations and the mobile station,

wherein the control unit exerts a control to select a combination of base stations to be communicated with the mobile station based on the transmission line quality, to notify each of the base stations of the selected combination, and to perform the MIMO transmission or reception.

21. A radio network controller comprising:

a network communication unit being connected to a network and holding a communication;

a distributing unit distributing data to be communicated with a certain mobile station between each of a plurality of base stations and the mobile station, and transmitting the distributed data to the plurality of base stations when the mobile station is in a state of a MIMO transmission or reception with the plurality of the base stations, and transmitting the data to be communicated with the mobile station to a single base station out of the plurality of base stations when the mobile station is in a state of a non-MIMO transmission or reception with the plurality of the base stations.

22. The radio network controller according to claim 21, further comprising a control unit transmitting an instruction to select a combination of base stations to be communicated with the mobile station and a combination of data rates for satisfying a data rate expected value for the single base station based on a transmission line quality between each of the base stations and the mobile station transmitted from each of the base stations or from the mobile station via the base stations, to cause the distributing unit to distribute data based on the combination of the base stations and the combination of the data rates, and to use the distributed data for the MIMO transmission or reception.

23. A wireless base station device comprising:

a plurality of antennas for MIMO transmission;

a transmission data selecting unit partially selecting signals allocated to a plurality of base stations, respectively by MIMO transmission or reception from among data for a single mobile station; and

a control unit exerting a control to transmit the signals from the plurality of base stations by MIMO using these allocated signals in a state of a MIMO transmission or reception, and to cause the selecting unit either to select all the data for the single mobile station or not to select any of the data for the single mobile station in a state of a non-MIMO transmission or reception with the plurality of the base stations.

24. The wireless base station device according to claim 23, further comprising a transmission line quality estimating unit detecting a transmission line quality between the base station and the mobile station.

25. The wireless base station device according to claim 23,

wherein the control unit exerts the control to select a modulation method and a communicable data rate available to each of the base stations in response to the transmission line quality, to select a combination of base stations so that a sum of the communicable data rates with respect to the same mobile station satisfies a data rate expected value for the mobile station, and to perform the MIMO transmission or reception.

26. The wireless base station device according to claim 23, further comprising a coding unit coding signals transmitted from a network and notified to the mobile station, wherein the coding unit is provided in front of the data selecting unit.

27. The wireless base station device according to claim 23,

wherein the plurality of base stations is connected to one another by a network, and packets addressed to the single mobile station received from the network are allocated to the respective base stations independently.

28. The wireless base station device according to claim 23, wherein the control unit exerts a retransmission control.