This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2008-209952, filed on Aug. 18, 2008, the entire contents of which are incorporated herein by reference.
The present invention relates to a data transmission control method and a base transceiver station.
In recent years, MIMO (Multiple Input Multiple Output) communication is adopted in the field of radio communication.
MIMO is a technology in which communication is performed by using a plurality of antennas each set up on a transmitting side and a receiving side, and is one of the important technologies supporting fourth-generation mobile communication.
MIMO is divided into a diversity transmission method by which the same data is transmitted from a plurality of antennas for the purpose of improving communication quality and a space division multiplexing method by which different data is transmitted from a plurality of antennas for the purpose of improving throughput. Moreover, each method is divided into an open loop method and a closed loop method.
In the open loop MIMO communication method by space division multiplexing, different data is transmitted from a plurality of antennas, regardless of feedback information.
In the closed loop MIMO communication method by space division multiplexing, receiving quality for combinations of antennas on the receiving side is measured and feedback of the combination among these combinations that provides optimal quality is given. The transmitting side uses the feedback information to decide the combination of antennas used for transmission.
A base transceiver station 1701 includes a radio equipment controller 1702, N modules #1 to #N of radio equipment 1703 connected thereto, and M antennas 1704 connected to each module of the radio equipment 1703.
In the radio equipment controller 1702, a line terminating unit 1706 terminates a network line to which upper-level equipment is connected and transmits/receives a communication signal to/from the upper-level equipment.
A baseband signal processing unit 1705 encodes and modulates a transmission signal transmitted from the line terminating unit 1706. The baseband signal processing unit 1705 sends out a baseband transmission signal obtained as a result to a digital interface 1713 constituted by optical fibers #1 to #N to which the modules #1 to #N of the radio equipment 1703 are connected via an interface unit 1707. The baseband signal processing unit 1705 also receives, via the interface unit 1707, a baseband transmission signal received from the modules #1 to #N of the radio equipment 1703 via the digital interface 1713 #1 to #N. The baseband signal processing unit 1705 decodes and demodulates a received signal and sends out a received signal obtained as a result to the line terminating unit 1706.
A call processing control unit 1709 controls signaling such as the start, update, and end of a call to a mobile station, such as a mobile phone, and, based on the signaling, instructs the baseband signal processing unit 1705 to start/end an operation or the like.
A maintenance monitoring unit 1708 monitors operating states of the baseband signal processing unit 1705 and the interface unit 1707. When a failure occurs, the maintenance monitoring unit 1708 notifies the upper-level equipment of failure information thereof via the line terminating unit 1706. The maintenance monitoring unit 1708 also notifies, via the line terminating unit 1706, the upper-level equipment of failure information from the modules #1 to #N of the radio equipment 1703 received via the interface unit 1707.
In the radio equipment 1703, an interface unit 1710 terminates a communication signal input/output via a digital interface 1713.
A transceiver amplifying unit 1711 amplifies a baseband transmission signal transmitted from the radio equipment controller 1702 via the digital interface 1713 and the interface unit 1710 in power and transmit the baseband transmission signal from the antennas 1704 #1 to #M. The transceiver amplifying unit 1711 also amplifies a received signal received by the antennas 1704 #1 to #M and sends the received signal to the radio equipment controller 1702 via the interface unit 1710 and the digital interface 1713.
A maintenance monitoring unit 1712 monitors states of the transceiver amplifying unit 1711 and the interface unit 1710. When a failure occurs, the maintenance monitoring unit 1712 notifies the radio equipment controller 1702 of failure information thereof from the interface unit 1710 via the digital interface 1713.
In the above configuration of the base transceiver station 1701, for example, an interface called CPRI (Common Public Radio Interface) is used as the digital interface 1713 #1 to #N connecting the modules #1 to #N of the radio equipment 1703 and the radio equipment controller 1702.
Assume that when the open loop MIMO transmission method by space division multiplexing is adopted as the communication method between a base transceiver station and a mobile station, the interface unit 1710 or the transceiver amplifying unit 1711 of the radio equipment 1703 fails. In this communication method, a plurality of modules of the radio equipment 1703 transmit different data from a plurality of the antennas 1704 regardless of feedback information. Thus, data transmitted from the failed antenna 1704 may not be decoded in the mobile station such as a mobile phone and an error occurs, leading to abnormal communication.
Assume that when the closed loop MIMO transmission method by space division multiplexing is adopted as the communication method between a base transceiver station and a mobile station, the interface unit 1710 or the transceiver amplifying unit 1711 of the radio equipment 1703 fails. In this communication method, feedback information from the mobile station is used to decide the combination of the antennas 1704 used for transmission. Thus, the antenna 1704 related to a failed portion is considered to be removed as a choice, but if the feedback time is long, abnormal communication may be caused after all.
When user multiplexing by the OFDM (Orthogonal Frequency Division Multiplexing) method is used, frequency resources (shared channel) are used by time division and it may take some users several seconds for feedback. The feedback time may further be prolonged due to a determination time of feedback information in a mobile station or an error of feedback information by an up receiving environment.
A collection operation of failure information illustrated in
Thus, in the open loop MIMO transmission method by space division multiplexing, a failure of a data processing unit (such as a transceiver amplifying unit and interface unit) related to an antenna portion in radio equipment will lead to abnormal communication.
In the closed loop MIMO transmission method by space division multiplexing, when a data processing unit (such as a transceiver amplifying unit and interface unit) related to an antenna portion in radio equipment fails, communication will be restored by feedback information from a mobile station. However, abnormal communication continues before feedback is received.
According to an aspect of the invention, a data transmission control method in a radio communication system with a mobile station having a plurality of antennas and a base transceiver station having a plurality of antennas, the data transmission control method includes detecting a failure of radio equipment connected to each of the plurality of antennas of the base transceiver station or to each of specified groups of antennas to perform radio communication processing for a connected antenna, and outputting failure information corresponding to the detected failure. The data transmission control method includes determining a failed antenna based on the failure information, and exercising control so that generation processing of transmission code words corresponding to the failed antenna is not performed.
The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.
A first aspect shown below may be premised on a base transceiver station (101) that performs radio communication by the multiple input multiple output (MIMO) radio communication method using a plurality of antennas set up in a mobile station and a plurality of antennas (1704) set up in the local station.
Maintenance monitoring units (104, 106) detect a failure of a plurality of pieces of radio equipment (103) connected to each of the plurality of antennas set up in the local station or to each of specified groups of antennas to perform radio communication processing for a connected antenna and output failure information (201, 202, 601, and 602) corresponding to the detected failure.
A baseband signal processing unit (105) determines a failed antenna based on the failure information when a baseband signal is processed and exercises control so that generation processing of transmission code words corresponding to the failed antenna will not be performed.
A second aspect shown below may be premised on a base transceiver station (101) that performs radio communication by the multiple input multiple output (MIMO) radio communication method using a plurality of antennas set up in a mobile station and a plurality of antennas (1704) set up in the local station and includes a plurality of pieces of radio equipment (103) connected to each of the plurality of antennas set up in the local station or to each of specified groups of antennas to perform radio communication processing for a connected antenna and a radio equipment controller (102) connected to the plurality of pieces of radio equipment via individual digital interfaces (1713, CPRI) to perform baseband signal processing of a communication signal.
A first maintenance monitoring unit (106) in each piece of radio equipment detects a failure of the radio equipment thereof and outputs first failure information (201) corresponding to the detected failure to the digital interface to which the radio equipment is connected.
A second maintenance monitoring unit (104) in the radio equipment controller collects the first failure information of each piece of radio equipment from each digital interface and outputs second failure information (202) obtained by summarizing each piece of the first failure information.
A baseband signal processing unit (105) in the radio equipment controller determines a failed antenna based on the second failure information when a baseband signal is processed and exercises control so that generation processing of transmission code words corresponding to the failed antenna will not be performed.
A third aspect shown below may be premised on a base transceiver station (101) that performs radio communication by the multiple input multiple output (MIMO) radio communication method using a plurality of antennas set up in a mobile station and a plurality of antennas (1704) set up in the local station while controlling a combination of antennas based on feedback information from the mobile station.
Maintenance monitoring units (104, 106) detect a failure of a plurality of pieces of radio equipment connected to each of the plurality of antennas set up in the local station or to each of specified groups of antennas to perform radio communication processing for a connected antenna and output failure information corresponding to the detected failure.
A baseband signal processing unit (105) determines a failed antenna based on the failure information when a baseband signal is processed and, if the failed antenna is contained in antennas specified by the feedback information, exercises control so that generation processing of transmission code words is performed in a combination of antennas that does not contain the failed antenna.
A fourth aspect shown below may be premised on a base transceiver station (101) that performs radio communication by the multiple input multiple output (MIMO) radio communication method using a plurality of antennas set up in a mobile station and a plurality of antennas (1704) set up in the local station while controlling a combination of antennas based on feedback information from the mobile station and includes a plurality of pieces of radio equipment (103) connected to each of the plurality of antennas set up in the local station or to each of specified groups of antennas to perform radio communication processing for a connected antenna and a radio equipment controller (102) connected to the plurality of pieces of radio equipment via individual digital interfaces (1713, CPRI) to perform baseband signal processing of a communication signal.
A first maintenance monitoring unit (106) in each piece of radio equipment detects a failure of the radio equipment thereof and outputs first failure information corresponding to the detected failure to the digital interface to which the radio equipment is connected.
A second maintenance monitoring unit (104) in the radio equipment controller collects the first failure information of each piece of radio equipment from each digital interface and outputs second failure information obtained by summarizing each piece of the first failure information.
A baseband signal processing unit (105) in the radio equipment controller determines a failed antenna based on the second failure information when a baseband signal is processed and, if the failed antenna is contained in antennas specified by the feedback information, exercises control so that generation processing of transmission code words is performed in a combination of antennas that does not contain the failed antenna.
In the above third and fourth aspects, if the number of streams that can be transmitted deceases due to a combination of antennas, the baseband signal processing unit may be configured to adjust the amount of data in generation processing of transmission code words.
The above second and fourth aspects may be configured to further include an interface failure detection unit (1707) that detects a failure of each digital interface and outputs third failure information (601) corresponding thereto in the radio equipment controller so that the second maintenance monitoring unit outputs the second failure information (202, 602) obtained by summarizing each piece of the first failure information (201) and the third failure information.
In the above first to fourth aspects, the baseband signal processing unit may be configured to set the data size of transmission code word of antennas for which no transmission code word is generated to zero (S904 and S1304).
An embodiment will be described below in detail with reference to drawings.
In the configuration of the base transceiver station illustrated in
Differences between the configuration in
The maintenance monitoring unit 104 collects not only failure information of the radio equipment 1031# to #N, but also failure conditions of the radio equipment controller 102 itself.
In
After starting fault monitoring (S201), the maintenance monitoring unit 106 in the radio equipment 103 detects that the transceiver amplifying unit 1711 has failed (S202). In this case, the maintenance monitoring unit 106 determines for which antenna of the antennas 1711 #1 to #M the failed transceiver amplifying unit 1711 is intended (S203). The maintenance monitoring unit 106 sends out antenna failure information 201 based on a determination result thereof.
The antenna failure information 201 is received by the maintenance monitoring unit 104 in the radio equipment controller 102 via the interface unit 1710 in the radio equipment 103, the digital interfaces 1713, and the interface unit 1707 in the radio equipment controller 102.
After receiving the antenna failure information 201 from the radio equipment 103, the maintenance monitoring unit 104 in the radio equipment controller 102 creates equipment failure information 202 (
In
If the base transceiver station 101 and the upper-level equipment are connected by an IP network, a notification to the upper-level equipment can be made, for example, by using SNMP (Simple Network Management Protocol).
After receiving the CPRI link failure information 601 from the radio equipment 103, the maintenance monitoring unit 104 in the radio equipment controller 102 creates equipment failure information 602 (
In
A scheduler 801 checks the amount of data stored in a data buffer 802 and notifies an encoding/modulation unit 803 of the data size in accordance with the amount of accumulated data.
The encoding/modulation unit 803 draws up data from the data buffer 802 in accordance with the notified data size to perform encoding and modulation processing by space division. As a result, baseband transmission signals 805 divided into four spaces #1 to #4 are output from the encoding/modulation unit 803.
Each of these baseband transmission signals 805 #1 to #4 is amplified in power by each transmission unit 103 #1 to #4 corresponding to the radio equipment 103 in
At this point, the scheduler 801 analyzes the equipment failure information 202 (
When the equipment failure information 602 (
The data size notified from the scheduler 801 is stored in a storage area for each antenna i of a data size storage memory 804 in the encoding/modulation unit 803. The encoding/modulation unit 803 determines the data size of code word from the antenna number i=0 (step S1001) to i=the number of antennas (step S1005) sequentially (step S1006) according to the operation flow chart illustrated in
In the example in
Thus, if radio equipment fails in an open loop MIMO transmission system by the space division multiplexing method, wasteful transmission of valid data can be avoided. If a notification of the equipment failure information 202 or 602 is received from the maintenance monitoring unit 104, the baseband signal processing unit 105 can immediately avoid transmission of valid data toward the antenna 1704 belonging to the radio equipment 103 (
A scheduler 1101 determines the size of data that can be transmitted based on feedback information from a mobile station. The scheduler 1101 checks the amount of data stored in a data buffer 1102 and calculates the size of data to be transmitted based on the number of code words and data size obtained from the feedback information and the amount of data accumulated in the data buffer 1102. The scheduler 1101 notifies an encoding/modulation unit 1103 of the calculated data size.
The encoding/modulation unit 1103 draws up data from the data buffer 1102 in accordance with the notified data size to perform encoding and modulation processing by space division. As a result, baseband transmission signals 1105 divided into four spaces #1 to #4 are output from the encoding/modulation unit 1103.
The scheduler 1101 also decides the combination for each of the antennas 1704 for pre-coding processing based on feedback information and notifies a pre-coding unit 1106 of the combination. The pre-coding unit 1106 uses the received combination information to perform pre-coding processing on the baseband transmission signals 1105. The pre-coding unit 1106 outputs each transmission output signal obtained as a result of performing pre-coding processing to each of the antennas 1704 via each of the transmission units 103 (the radio equipment in
At this point, the scheduler 1101 analyzes the equipment failure information 202 (
When the equipment failure information 602 (
At this point, the scheduler 1101 determines whether code words can be transmitted to the i-th antenna 1704 from the antenna number i=0 (step S1301) to i=the number of antennas (step S1305) sequentially (step S1306) according to the operation flow chart illustrated in
The data size notified from the scheduler 1101 is stored in a storage area for each antenna i of a data size storage memory 1104 in the encoding/modulation unit 1103. The encoding/modulation unit 1103 determines the data size of code word from the antenna number i=0 (step S1401) to i=the number of antennas (step S1405) sequentially (step S1406) according to the operation flow chart illustrated in
In the example in
Thus, if radio equipment fails in a closed loop MIMO transmission system by the space division multiplexing method, wasteful transmission of valid data can also be avoided. If a notification of the equipment failure information 202 or 602 is received from the maintenance monitoring unit 104, the baseband signal processing unit 105 can immediately avoid transmission of valid data toward the antenna 1704 belonging to the radio equipment 103 (
In open loop MIMO communication by the space division multiplexing method, as described above, abnormal communication due to an antenna failure can be prevented without waiting for instructions from the upper-level equipment.
In closed loop MIMO communication by the space division multiplexing method, call continuation can be ensured by minimizing a period of communication stop due to an antenna failure without waiting for instructions from the upper-level equipment.
All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
Number | Date | Country | Kind |
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2008-209952 | Aug 2008 | JP | national |