MIMO wireless communication system and method by a plurality of base stations and mobile station

• US 8,265,675 B2
• Filed: 04/07/2008
• Issued: 09/11/2012
• Est. Priority Date: 10/07/2005
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Matsumoto, Mariko, Yoshida, Shousei
• Primary Examiner(s): NGUYEN, HAI V
• Application Number:
  US12/098,917
• Publication Number:
  US 20080192682A1
• Time in Patent Office: 1,618 Days
• Field of Search: 455/509
• US Class Current: 455/509
• 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 36/304 due to measured or perceived resources with higher communication quality

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, the mobile station 21 checks a propagation line quality and instructs only the first base station 11 to transmit data to the mobile station 21.

In a state 2, the mobile station 21 issues a request to divide the data to the first base station 11 and the second base station 12 and to transmit the divided data to the mobile station 21, and holds MIMO communication with the two base stations.

In a state 3, the mobile station 21 requests only the second base station 12 to transmit the data and communicates with the second base station 12.

Claims

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

the plurality of base stations include a unit distributing data addressed to a certain mobile station between two or more base stations selected from a group of base stations that can simultaneously communicate with the certain mobile station if a predetermined data rate cannot be obtained by data communication between the certain mobile station and a single base station, and simultaneously transmitting the distributed data from the respective base stations to the certain mobile station by a MIMO (Multi-Input Multi-Output) transmission method, the distributed data being different from the respective base stations;

the at least one mobile station includes a plurality of antennas and a unit receiving the data transmitted from the selected base stations by the MIMO transmission method, by a MIMO reception method using the plurality of antennas, and performs data communication only with a single base station by a non-MIMO transmission or reception method if the predetermined data rate can be obtained by the data communication between the certain mobile station and the single base station; and

the selection of base stations is carried out by;

measuring transmission line quality between the mobile station and each of peripheral base stations;

notifying the base stations of the measured transmission line quality;

receiving communicable data rates from the base stations;

rearranging the received data rates in a descending order;

if a maximum data rate among the received data rates is higher than a predetermined data rate, deciding to select the base station communicable at the maximum data rate;

if the maximum data rate is not higher, calculating the number k of base stations satisfying that a sum of data rates of top k base stations in descending order is higher than the predetermined data rate;

if the calculated number k exceeds a number N of MIMO antennas owned by the mobile station, deciding to select top N base stations; and

if the calculated number k does not exceed the number N, deciding to select top k base stations.

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 a predetermined data 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 predetermined data 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 predetermined data rate 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 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.

5. The wireless communication system according to claim 3,

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

6. 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.

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 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 predetermined data rate for the mobile station using the communicable data rate, and to perform the MIMO transmission or reception with the mobile station.

8. 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 predetermined data rate 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.

9. 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 predetermined data rate 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.

10. 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 predetermined data rate 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.

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

the base station includes a unit distributing data addressed to a certain mobile station between two or more sectors selected from a group of sectors that can simultaneously communicate with the certain mobile station if a predetermined data rate cannot be obtained by data communication between the certain mobile station and a single sector, and simultaneously transmitting the distributed data from the respective sectors to the certain mobile station by a MIMO transmission method, the distributed data being different from the respective sectors;

the at least one mobile station includes a plurality of antennas and a unit receiving the data transmitted from the selected sectors by the MIMO transmission method, by a MIMO reception method using the plurality of antennas, and performs data communication only with a single sector by a non-MIMO transmission or reception method if the predetermined data rate can be obtained by the data communication between the certain mobile station and the single sector; and

the selection of sectors is carried out by;

measuring transmission line quality between the mobile station and each of peripheral sectors;

notifying the base station of the measured transmission line quality;

receiving communicable data rates from the base station;

rearranging the received data rates in a descending order;

if a maximum data rate among the received data rates is higher than a predetermined data rate, deciding to select the sector communicable at the maximum data rate;

if the maximum data rate is not higher, calculating the number k of sectors satisfying that a sum of data rates of top k sectors in descending order is higher than the predetermined data rate;

if the calculated number k exceeds a number N of MIMO antennas owned by the mobile station, deciding to select top N sectors; and

if the calculated number k does not exceed the number N, deciding to select top k sectors.

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 a predetermined data 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 predetermined data 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 predetermined data ratefor 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 at least one mobile station, including steps of:

causing the plurality of base stations to distribute data addressed to a certain mobile station between two or more base stations selected so as to satisfy a predetermined data rate from a group of base stations that can simultaneously communicate with the certain mobile station if the predetermined data rate cannot be obtained by data communication between the certain mobile station and a single base station, and to simultaneously transmit the distributed data from the respective base stations to the certain mobile station by a MIMO transmission method, the distributed data being different from the respective base stations;

causing the at least one mobile station having a plurality of antennas to receive the data transmitted from the selected base stations by the MIMO transmission method, by a MIMO reception method using the plurality of antennas, and to perform data communication only with a single base station by a non-MIMO transmission or reception method if the predetermined data rate can be obtained by the data communication between the certain mobile station and the single base station; and

the selection of base stations is carried out by;

measuring transmission line quality between the mobile station and each of peripheral base stations;

notifying the base stations of the measured transmission line quality;

receiving communicable data rates from the base stations;

rearranging the received data rates in a descending order;

if a maximum data rate among the received data rates is higher than a predetermined data rate, deciding to select the base station communicable at the maximum data rate;

if the maximum data rate is not higher, calculating the number k of base stations satisfying that a sum of data rates of top k base stations in descending order is higher than the predetermined data rate;

if the calculated number k exceeds a number N of MIMO antennas owned by the mobile station, deciding to select top N base stations; and

if the calculated number k does not exceed the number N, deciding to select top k base stations.

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 a predetermined data rate is obtained by a communication between the certain 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 predetermined data rate is not obtained.

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

causing the plurality of base stations to distribute data addressed to a certain mobile station between two or more sectors selected from a group of sectors that can simultaneously communicate with the certain mobile station if a predetermined data rate cannot be obtained by data communication between the certain mobile station and a single sector, and simultaneously transmit the distributed data from the respective sectors to the certain mobile station by a MIMO transmission method, the distributed data being different from the respective sectors;

causing the at least one mobile station having a plurality of antennas to receive the data transmitted from the selected sectors by the MIMO transmission method, by a MIMO reception method using the plurality of antennas, and to perform data communication only with a single sector by a non-MIMO transmission or reception method if the predetermined data rate can be obtained by the communication between the certain mobile station and the single sector; and

the selection of sectors is carried out by;

measuring transmission line quality between the mobile station and each of peripheral sectors;

notifying the base station of the measured transmission line quality;

receiving communicable data rates from the base station;

rearranging the received data rates in a descending order;

if a maximum data rate among the received data rates is higher than a predetermined data rate, deciding to select the sector communicable at the maximum data rate;

if the maximum data rate is not higher, calculating the number k of sectors satisfying that a sum of data rates of top k sectors in descending order is higher than the predetermined data rate;

if the calculated number k exceeds a number N of MIMO antennas owned by the mobile station, deciding to select top N sectors; and

if the calculated number k does not exceed the number N, deciding to select top k sectors.

18. A wireless mobile station device comprising:

a plurality of antennas of MIMO reception for receiving signals from two or more base stations selected from a group of base stations that can simultaneously communicate with the wireless mobile station device if a predetermined data rate cannot be obtained by data communication between the wireless mobile station device and a single base station;

a MIMO separating unit separating the signals transmitted from the selected 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 selected base stations by a MIMO transmission or reception method, and to receive a signal from a single base station by a non-MIMO transmission or reception method if the predetermined data rate can be obtained by data communication between the wireless mobile station device and the single base station,

wherein the selection of base stations is carried out by;

measuring transmission line quality between the mobile station and each of peripheral base stations;

notifying the base stations of the measured transmission line quality;

receiving communicable data rates from the base stations;

rearranging the received data rates in a descending order;

if a maximum data rate among the received data rates is higher than a predetermined data rate, deciding to select the base station communicable at the maximum data rate;

if the maximum data rate is not higher, calculating the number k of base stations satisfying that a sum of data rates of top k base stations in descending order is higher than the predetermined data rate;

if the calculated number k exceeds a number N of MIMO antennas owned by the mobile station, deciding to select top N base stations; and

if the calculated number k does not exceed the number N, deciding to select top k 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 base stations and the wireless mobile station device,

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 predetermined data rate 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 wireless mobile station device 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 addressed to a certain mobile station between two or more base stations selected from a group of base stations that can simultaneously communicate with the certain mobile station if a predetermined data rate cannot be obtained by data communication between the certain mobile station and a single base station, and causing the two or more base stations to simultaneously transmit the distributed data from the respective base stations to the certain mobile station by a MIMO transmission method, the distributed data being different from the respective base stations, and to transmit the data addressed to the mobile station to a single base station by a non-MIMO transmission method if the predetermined data rate can be obtained by data communication between the certain mobile station and the single base station,

wherein the selection of base stations is carried out by;

measuring transmission line quality between the mobile station and each of peripheral base stations;

notifying the base stations of the measured transmission line quality;

receiving communicable data rates from the base stations;

rearranging the received data rates in a descending order;

if a maximum data rate among the received data rates is higher than a predetermined data rate, deciding to select the base station communicable at the maximum data rate;

if the maximum data rate is not higher, calculating the number k of base stations satisfying that a sum of data rates of top k base stations in descending order is higher than the predetermined data rate;

if the calculated number k exceeds a number N of MIMO antennas owned by the mobile station, deciding to select top N base stations; and

if the calculated number k does not exceed the number N, deciding to select top k 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 certain mobile station and a combination of data rates for satisfying a predetermined data rate for the single base station based on a transmission line quality between each of the base stations and the certain mobile station transmitted from each of the base stations or from the certain 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, from among data addressed to a single mobile station, signals allocated to the wireless base station device in the case of MIMO transmission or reception with two or more base stations selected from a group of base stations that can simultaneously communicate with the single mobile station if a predetermined data rate cannot be obtained by data communication between the single mobile station and a single base station; and

a control unit exerting a control to transmit the selected signals from the wireless base station device to the single mobile station in the case of MIMO transmission or reception with the selected base stations, 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 the base station if the predetermined data rate can be obtained by data communication between the single mobile station and the single base station,

wherein the selection of base stations is carried out by;

measuring transmission line quality between the mobile station and each of peripheral base stations;

notifying the base stations of the measured transmission line quality;

receiving communicable data rates from the base stations;

rearranging the received data rates in a descending order;

if a maximum data rate among the received data rates is higher than a predetermined data rate, deciding to select the base station communicable at the maximum data rate;

if the maximum data rate is not higher, calculating the number k of base stations satisfying that a sum of data rates of top k base stations in descending order is higher than the predetermined data rate;

if the calculated number k exceeds a number N of MIMO antennas owned by the mobile station, deciding to select top N base stations; and

if the calculated number k does not exceed the number N, deciding to select top k 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 each of the base stations and the single 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 predetermined data rate for the single 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.