DISTRIBUTED ANTENNA SYSTEM, DISTRIBUTED ANTENNA SWITCHING METHOD, BASE STATION APPARATUS AND ANTENNA SWITCHING DEVICE

• US 20120134279A1
• Filed: 11/21/2011
• Published: 05/31/2012
• Est. Priority Date: 11/25/2010
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: TAMAKI, TSUYOSHI
• Granted Patent: US 8,630,268 B2
• Time in Patent Office: Days
• US Class Current: 370/248
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0691 using subgroups of transmit antennas

Abstract

In a distributed antenna system in which plural antennas are dispersed spatially, a base station apparatus 102 collects the terminal throughput of the uplink and downlink communication, the number of simultaneous communication terminals, and the information on a radio propagation channel from a distributed antenna to a terminal antenna, and estimates the throughput in each communication mode from the number of simultaneous communication terminals and the radio propagation channel information, selects a communication mode by comparing the estimated throughput with a request value, connects the distributed antenna and the base station apparatus 102 in an antenna connection pattern in the selected communication mode, and switches the communication mode between the base station device and the terminal to continue the communication, when the terminal throughput is below the request value, or above the request value plus a certain threshold value.

Claims

1. A distributed antenna system comprising a base station apparatus having a plurality of antenna ports, a terminal having a plurality of terminal antennas, a plurality of remote radio units dispersed spatially so as to accommodate one or more distributed antennas,

the distributed antenna system further comprising an antenna switch for switching the connection between the one or more distributed antennas and the plurality of antenna ports in the base station apparatus,

the base station apparatus:

for collecting terminal throughput for uplink and downlink communications, number of simultaneous communication terminals, and radio propagation channel information from the each distributed antenna to the each terminal antenna;

for selecting a group of a predetermined number of the distributed antennas in descending order of the received power of a pilot signal or a control signal from the terminal, as an antenna cluster, from among the plurality of distributed antennas, or holding a group of a predetermined number of the distributed antennas in descending order of the received power of the pilot signal, as antenna cluster information, by transmitting or receiving beforehand the pilot signal between the distributed antennas, and selecting the antenna cluster corresponding to the distributed antenna having the highest received power of the pilot signal or the control signal from the terminal, utilizing the antenna cluster information, or selecting the antenna cluster corresponding to the distributed antenna for use in the current communication mode; and

for communicating on one of a plurality of communication modes that are different in communication speed or throughput, the one of the plurality of communication modes being decided depending on whether only one terminal makes the communication or a plurality of terminals make the communication simultaneously at a certain time, and which one or more antennas of the selected antenna cluster and the selected terminal antennas are allocated to a transmitting/receiving antenna;

in which, for judging the switching of the communication mode,

by computing an estimated throughput in any other communication mode than a first communication mode in current communication, and selecting a second communication mode in which the estimated throughput satisfies a request value and the communication speed or throughput is higher than in the first communication mode, when the terminal throughput of uplink or downlink communication is below the request value or number of simultaneous connection terminals is above a preset threshold,

while on the other hand, by computing an estimated throughput in any other communication mode than the first communication mode in current communication, and selecting the second communication mode in which the estimated throughput satisfies the request value and the communication speed or throughput is lower than in the first communication mode, when the terminal throughput of uplink or downlink communication is above the request value plus a certain threshold value or the number of simultaneous connection terminals is below a preset threshold;

wherein,

in computing the estimated throughput, a setting is made in which one or more antennas from among the selected antenna cluster and terminal antennas are allocated to be a transmitting/receiving antenna, and the antenna ports of the base station apparatus corresponding to the set number of distributed antenna are allocated;

the base station apparatus creates an antenna connection pattern representing the correspondence between the predetermined number of distributed antenna and the plurality of antenna ports, in the selected second communication mode and the selected predetermined number of the distributed antenna, and notifies the antenna connection pattern to the antenna switch;

the antenna switch receives the antenna connection pattern from the base station apparatus; and

the antenna switch switches the correspondence between the predetermined number of distributed antenna and the plurality of antenna ports in accordance with the designated antenna connection pattern,

thereby switching the communication mode between the base station apparatus and the terminal to continue the communication.

5. The distributed antenna system according to claim 1, wherein the result of capacity computation based on radio channel information between the antenna of the remote radio unit and the antenna of the terminal is made the estimated throughput.

6. The distributed antenna system according to claim 1, wherein the communication mode switching processing part stores an actual result of throughput in the communication mode selected in the past communication, the past actual result value of throughput being made the estimated throughput in switching the communication modes.

7. The distributed antenna system according to claim 1, wherein the antenna connection pattern capable of connecting a send signal of one antenna port in the base station apparatus to all the antennas for transmission over a wide area, and receiving the signal from all the antennas is set in the antenna switch

to switch the antenna connection pattern, by measuring the received power of a signal transmitted by the terminal, in which the antenna having the highest received power is made the transmitting antenna of the base station apparatus, and a predetermined number of antennas in descending order of the received power are made the receiving antennas of the base station apparatus.

8. The distributed antenna system according to claim 1, wherein an antenna cluster including a predetermined number of antennas for the antenna having the highest received power of the pilot signal or the control signal is selected from among the plurality of antennas, or an antenna cluster including a predetermined number of antennas in descending order of the received power is selected.

9. The distributed antenna system according to claim 1, wherein the antenna connection pattern for connecting the antenna of the remote radio unit and the antenna port of the base station apparatus is set in the antenna switch so as to receive the pilot signal or the control signal transmitted from one antenna of any one remote radio unit at any other antenna than the transmitting antenna, and

the base station apparatus obtains the received power by making the channel estimation of the pilot signal or the control signal, and forms the antenna cluster in descending order of the received power from among the antennas to which the pilot signal or the control signal is transmitted.

10. The distributed antenna system according to claim 1, wherein, when the base station apparatus and the terminal switch from the communication with one transmitting antenna of any one remote radio unit to the Multiple Input Multiple Output (MIMO) communication using a plurality of transmitting/receiving antennas, the antenna cluster corresponding to one transmitting antenna of any one remote radio unit is selected as the antenna candidates for use in the MIMO communication to make the MIMO communication.

11. The distributed antenna system according to claim 1, wherein the communication modes include two or more of SU-SISO/MU-SISO/SU-SIMO/MU-SIMO/SU-MIMO/MU-MIMO that are combinations of any one of the Single User Single Input Single Output (SISO) communication, Single Input Multiple Output (SIMO) communication, and Multiple Input Multiple Output (MIMO) communication, and a single user mode (Single User) in which only one terminal makes the communication at a certain time or a multi-user mode (Multi-User) in which a plurality of terminals make the simultaneous communication at a certain time.

12. The distributed antenna system according to claim 1, wherein the maximum ratio combine of any number of antenna signals equal to or less than the number of antennas dealt with by the antenna switch device is made for connection to the antenna port of the base station apparatus.

13. The distributed antenna system according to claim 1, further comprising an output limiting functional part for measuring the received power for each antenna and not outputting the received power near the noise level.

2. Abase station apparatus in a distributed antenna system comprising the base station apparatus having a plurality of antenna ports, a terminal having a plurality of terminal antennas, a plurality of remote radio units dispersed spatially so as to accommodate one or more distributed antennas, and an antenna switch for switching the connection between the one or more distributed antennas and the plurality of antenna ports in the base station apparatus,

the base station apparatus comprising:

a signal processing part for collecting terminal throughput for uplink and downlink communications, number of simultaneous communication terminals, and radio propagation channel information from the each distributed antenna to the each terminal antenna;

an antenna selection part for selecting a group of a predetermined number of the distributed antennas in descending order of the received power of a pilot signal or a control signal from the terminal, as an antenna cluster, from among the plurality of distributed antennas, or holding a group of a predetermined number of the distributed antennas in descending order of the received power of the pilot signal, as antenna cluster information, by transmitting or receiving beforehand the pilot signal between the distributed antennas, and selecting the antenna cluster corresponding to the distributed antenna having the highest received power of the pilot signal or the control signal from the terminal, utilizing the antenna cluster information, or selecting the antenna cluster corresponding to the distributed antenna for use in the current communication mode; and

a communication mode switching processing part for communicating on one of a plurality of communication modes that are different in communication speed or throughput, the one of the plurality of communication modes being decided depending on whether only one terminal makes the communication or a plurality of terminals make the communication simultaneously at a certain time, and which one or more antennas of the antenna cluster and the terminal antennas selected by the antenna selection part are allocated to a transmitting/receiving antenna;

in which the communication mode switching processing part judges the switching of the communication mode,

by computing an estimated throughput in any other communication mode than a first communication mode in current communication, and selecting a second communication mode in which the estimated throughput satisfies a request value and the communication speed or throughput is higher than in the first communication mode, when the terminal throughput of uplink or downlink communication is below the request value or number of simultaneous connection terminals is above a preset threshold,

while on the other hand, by computing an estimated throughput in any other communication mode than the first communication mode in current communication, and selecting the second communication mode in which the estimated throughput satisfies the request value and the communication speed or throughput is lower than in the first communication mode, when the terminal throughput of uplink or downlink communication is above the request value plus a certain threshold value or the number of simultaneous connection terminals is below a preset threshold;

wherein,

in computing the estimated throughput, a setting is made in which one or more antennas from among the selected antenna cluster and terminal antennas are allocated to be a transmitting/receiving antenna, and the antenna ports of the base station apparatus corresponding to the set number of distributed antenna are allocated;

the signal processing part creates an antenna connection pattern representing the correspondence between the predetermined number of distributed antenna and the plurality of antenna ports, in the second communication mode and the predetermined number of the distributed antenna that are selected by the communication mode switching processing part and the antenna selection part, and notifies the antenna connection pattern to the antenna switch; and

the antenna switch switches the correspondence between the predetermined number of distributed antenna and the plurality of antenna ports in accordance with the designated antenna connection pattern,

thereby switching the communication mode between the base station apparatus and the terminal to continue the communication.

14. The base station apparatus according to claim 2, wherein the result of capacity computation based on radio channel information between the antenna of the remote radio unit and the antenna of the terminal is made the estimated throughput.

15. The base station apparatus according to claim 2, wherein the communication mode switching processing part stores an actual result of throughput in the communication mode selected in the past communication, the past actual result value of throughput being made the estimated throughput in switching the communication modes.

16. The base station apparatus according to claim 2, wherein the antenna connection pattern capable of connecting a send signal of one antenna port in the base station apparatus to all the antennas for transmission over a wide area, and receiving the signal from all the antennas is set in the antenna switch

to switch the antenna connection pattern, by measuring the received power of a signal transmitted by the terminal, in which the antenna having the highest received power is made the transmitting antenna of the base station apparatus, and a predetermined number of antennas in descending order of the received power are made the receiving antennas of the base station apparatus.

17. The base station apparatus according to claim 2, wherein an antenna cluster including a predetermined number of antennas for the antenna having the highest received power of the pilot signal or the control signal is selected from among the plurality of antennas, or an antenna cluster including a predetermined number of antennas in descending order of the received power is selected.

18. The base station apparatus according to claim 2, wherein the antenna connection pattern for connecting the antenna of the remote radio unit and the antenna port of the base station apparatus is set in the antenna switch so as to receive the pilot signal or the control signal transmitted from one antenna of any one remote radio unit at any other antenna than the transmitting antenna, and

the base station apparatus obtains the received power by making the channel estimation of the pilot signal or the control signal, and forms the antenna cluster in descending order of the received power from among the antennas to which the pilot signal or the control signal is transmitted.

19. The base station apparatus according to claim 2, wherein, when the base station apparatus and the terminal switch from the communication with one transmitting antenna of any one remote radio unit to the Multiple Input Multiple Output (MIMO) communication using a plurality of transmitting/receiving antennas, the antenna cluster corresponding to one transmitting antenna of any one remote radio unit is selected as the antenna candidates for use in the MIMO communication to make the MIMO communication.

20. The base station apparatus according to claim 2, wherein the communication modes include two or more of SU-SISO/MU-SISO/SU-SIMO/MU-SIMO/SU-MIMO/MU-MIMO that are combinations of any one of the Single User Single Input Single Output (SISO) communication, Single Input Multiple Output (SIMO) communication, and Multiple Input Multiple Output (MIMO) communication, and a single user mode (Single User) in which only one terminal makes the communication at a certain time or a multi-user mode (Multi-User) in which a plurality of terminals make the simultaneous communication at a certain time.

21. The base station apparatus according to claim 2, wherein the maximum ratio combine of any number of antenna signals equal to or less than the number of antennas dealt with by the antenna switch device is made for connection to the antenna port of the base station apparatus.

22. The base station apparatus according to claim 2, further comprising an output limiting functional part for measuring the received power for each antenna and not outputing the received power near the noise level.

3. An antenna switch device in a distributed antenna system comprising a base station apparatus having a plurality of antenna ports, a terminal having a plurality of terminal antennas, and a plurality of remote radio units dispersed spatially so as to accommodate one or more distributed antennas, the antenna switch device switching the connection between the plurality of remote radio units and the base station apparatus,

the antenna switch device comprising:

a control part for receiving an antenna connection pattern from the base station apparatus, the antenna connection pattern representing the correspondence between a predetermined number of distributed antennas and the plurality of antenna ports in a second communication mode and the predetermined number of distributed antennas that are selected in order to switch a first communication mode to the second communication mode, during communication on one of the plurality of communication modes that are different in communication speed or throughput, the communication mode being decided depending on whether only one terminal makes the communication or a plurality of terminals make the communication simultaneously at a certain time, and which one or more antennas from among the selected antenna cluster and terminal antennas are allocated to be a transmitting/receiving antenna; and

a reception switch combine processing part and a send switch part for making switching of the correspondence between the predetermined number of distributed antennas and the plurality of antenna ports for an uplink and a downlink communication under the control of the control part in accordance with the designated antenna connection pattern;

wherein,

the communication mode is switched between the base station apparatus and the terminal by switching the connection between the one or more distributed antennas and the plurality of antenna ports of the base station apparatus to continue the communication.

23. The antenna switch device according to claim 3, wherein the antenna connection pattern capable of connecting a send signal of one antenna port in the base station apparatus to all the antennas for transmission over a wide area, and receiving the signal from all the antennas is set in the antenna switch

to switch the antenna connection pattern, by measuring the received power of a signal transmitted by the terminal, in which the antenna having the highest received power is made the transmitting antenna of the base station apparatus, and a predetermined number of antennas in descending order of the received power are made the receiving antennas of the base station apparatus.

24. The antenna switch device according to claim 3, wherein an antenna cluster including a predetermined number of antennas for the antenna having the highest received power of the pilot signal or the control signal is selected from among the plurality of antennas, or an antenna cluster including a predetermined number of antennas in descending order of the received power is selected.

25. The antenna switch device according to claim 3, wherein the antenna connection pattern for connecting the antenna of the remote radio unit and the antenna port of the base station apparatus is set in the antenna switch so as to receive the pilot signal or the control signal transmitted from one antenna of any one remote radio unit at any other antenna than the transmitting antenna, and

the base station apparatus obtains the received power by making the channel estimation of the pilot signal or the control signal, and forms the antenna cluster in descending order of the received power from among the antennas to which the pilot signal or the control signal is transmitted.

26. The antenna switch device according to claim 3, wherein, when the base station apparatus and the terminal switch from the communication with one transmitting antenna of any one remote radio unit to the Multiple Input Multiple Output (MIMO) communication using a plurality of transmitting/receiving antennas, the antenna cluster corresponding to one transmitting antenna of any one remote radio unit is selected as the antenna candidates for use in the MIMO communication to make the MIMO communication.

27. The antenna switch device according to claim 3, wherein the communication modes include two or more of SU-SISO/MU-SISO/SU-SIMO/MU-SIMO/SU-MIMO/MU-MIMO that are combinations of any one of the Single User Single Input Single Output (SISO) communication, Single Input Multiple Output (SIMO) communication, and Multiple Input Multiple Output (MIMO) communication, and a single user mode (Single User) in which only one terminal makes the communication at a certain time or a multi-user mode (Multi-User) in which a plurality of terminals make the simultaneous communication at a certain time.

28. The antenna switch device according to claim 3, wherein the maximum ratio combine of any number of antenna signals equal to or less than the number of antennas dealt with by the antenna switch device is made for connection to the antenna port of the base station apparatus.

29. The antenna switch device according to claim 3, further comprising an output limiting functional part for measuring the received power for each antenna and not outputting the received power near the noise level.

4. A distributed antenna switching method in a distributed antenna system comprising a base station apparatus having a plurality of antenna ports, a terminal having a plurality of terminal antennas, a plurality of remote radio units dispersed spatially so as to accommodate one or more distributed antennas, and an antenna switch for switching the connection between the one or more distributed antennas and the plurality of antenna ports in the base station apparatus,

the base station apparatus:

for collecting terminal throughput for uplink and downlink communications, number of simultaneous communication terminals, and radio propagation channel information from the each distributed antenna to the each terminal antenna;

for selecting a group of a predetermined number of the distributed antennas in descending order of the received power of a pilot signal or a control signal from the terminal, as an antenna cluster, from among the plurality of distributed antennas, or holding a group of a predetermined number of the distributed antennas in descending order of the received power of the pilot signal, as antenna cluster information, by transmitting or receiving beforehand the pilot signal between the distributed antennas, and selecting the antenna cluster corresponding to the distributed antenna having the highest received power of the pilot signal or the control signal from the terminal, utilizing the antenna cluster information, or selecting the antenna cluster corresponding to the distributed antenna for use in the current communication mode; and

for communicating on one of a plurality of communication modes that are different in communication speed or throughput, the one of the plurality of communication modes being decided depending on whether only one terminal makes the communication or a plurality of terminals make the communication simultaneously at a certain time, and which one or more antennas of the selected antenna cluster and the selected terminal antennas are allocated to a transmitting/receiving antenna;

in which, for judging the switching of the communication mode,

by computing an estimated throughput in any other communication mode than a first communication mode in current communication, and selecting a second communication mode in which the estimated throughput satisfies a request value and the communication speed or throughput is higher than in the first communication mode, when the terminal throughput of uplink or downlink communication is below the request value or number of simultaneous connection terminals is above a preset threshold,

while on the other hand, by computing an estimated throughput in any other communication mode than the first communication mode in current communication, and selecting the second communication mode in which the estimated throughput satisfies the request value and the communication speed or throughput is lower than in the first communication mode, when the terminal throughput of uplink or downlink communication is above the request value plus a certain threshold value or the number of simultaneous connection terminals is below a preset threshold;

wherein,

in computing the estimated throughput, a setting is made in which one or more antennas from among the selected antenna cluster and terminal antennas are allocated to be a transmitting/receiving antenna, and the antenna ports of the base station apparatus corresponding to the set number of distributed antenna are allocated;

the base station apparatus creates an antenna connection pattern representing the correspondence between the predetermined number of distributed antenna and the plurality of antenna ports, in the selected second communication mode and the selected predetermined number of the distributed antenna, and notifies the antenna connection pattern to the antenna switch;

the antenna switch receives the antenna connection pattern from the base station apparatus; and

the antenna switch switches the correspondence between the predetermined number of distributed antenna and the plurality of antenna ports in accordance with the designated antenna connection pattern,

thereby switching the communication mode between the base station apparatus and the terminal to continue the communication.