JP5111182B2 - Radio base station control apparatus and radio base station control method - Google Patents

Radio base station control apparatus and radio base station control method Download PDF

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JP5111182B2
JP5111182B2 JP2008072467A JP2008072467A JP5111182B2 JP 5111182 B2 JP5111182 B2 JP 5111182B2 JP 2008072467 A JP2008072467 A JP 2008072467A JP 2008072467 A JP2008072467 A JP 2008072467A JP 5111182 B2 JP5111182 B2 JP 5111182B2
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JP2009231983A (en
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武雄 大関
養幸 畑川
雅之 中野
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株式会社Kddi研究所
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  The present invention relates to a radio base station control apparatus and a radio base station control method in a radio communication system using a multiple input multiple output (MIMO) technique.

Conventionally, the MIMO technology is known as one of the technologies for improving the frequency utilization efficiency of a wireless communication system. FIG. 6 shows a basic conceptual diagram of a MIMO wireless communication system. In FIG. 6, a transmitting station wirelessly transmits different data signals from a plurality of transmitting antennas at the same frequency. The receiving station receives and restores the transmitted radio signal by a plurality of receiving antennas. At the time of restoration, if the channel matrix H is ideally known, the transmission signal can be separated by multiplying the reception signal by the inverse matrix of the channel matrix H. As shown in the example of FIG. When different data signals are transmitted from the transmission antennas, data communication can be performed at a maximum speed of four times. Thereby, the frequency utilization efficiency is improved. The conventional MIMO wireless communication system described in Patent Document 1 performs simultaneous communication by MIMO between a plurality of base stations and one wireless terminal.
JP 2007-134844 A

  However, in the conventional MIMO wireless communication system described in Patent Document 1 described above, when there is a difference in the reception power of the radio signal transmitted from each base station in the wireless terminal, the reception characteristics of the radio signal with the smaller reception power As a result, the assumed communication quality cannot be obtained. Another problem is how to provide communication quality in accordance with QoS (Quality of Service) required for wireless terminal communication.

  The present invention has been made in view of such circumstances, and its object is to perform simultaneous communication in the downlink direction (direction from the base station to the radio terminal) by MIMO between a plurality of base stations and one radio terminal. A wireless base that can appropriately apply MIMO according to the wireless reception environment in the wireless terminal and control the base station to provide communication quality according to the QoS required for communication of the wireless terminal A station controller and a radio base station control method are provided.

  In order to solve the above problems, a radio base station control apparatus according to the present invention is a radio base station control apparatus in a radio communication system that performs simultaneous downlink communication by MIMO between a plurality of base stations and one radio terminal. A base station MIMO cooperation controller that determines whether or not to perform MIMO simultaneous communication based on a wireless reception environment in the wireless terminal, and a requested QoS information holding unit that stores QoS information required for communication of the wireless terminal; A radio packet scheduler that performs transmission scheduling when transmitting a radio packet to the radio terminal for a plurality of base stations that are subjected to MIMO simultaneous communication when performing MIMO simultaneous communication, and the radio packet scheduler includes: Base station MIMO scheme and transmission schedule based on QoS required for wireless terminal communication And controlling.

  In the radio base station control apparatus according to the present invention, the radio packet scheduler includes estimated communication quality calculation means for calculating communication quality that can be realized with a radio terminal by the MIMO scheme of the base station, and the estimated communication It is characterized in that it is determined whether the quality satisfies the QoS required for communication of the wireless terminal.

  In the radio base station controller according to the present invention, the radio packet scheduler is based on a radio reception environment in a radio terminal, and a MIMO scheme emphasizing frequency efficiency and a communication quality emphasis as a combination of MIMO schemes of a plurality of base stations. A combination of MIMO schemes having the highest frequency efficiency is selected from among the MIMO schemes, and in the selected combination of MIMO schemes, a radio resource is set in advance from a base station / radio terminal pair having a lower estimated communication quality. It is characterized by making an assignment decision.

  In the radio base station control apparatus according to the present invention, the radio packet scheduler attempts to change the MIMO scheme of the base station when the amount of available radio resources or the requested QoS is not compatible.

  In the radio base station control apparatus according to the present invention, the radio packet scheduler changes the MIMO scheme from frequency efficiency emphasis to communication quality emphasis.

  In the radio base station control apparatus according to the present invention, the radio packet scheduler verifies whether radio resources can be secured by a new MIMO scheme for a packet to which radio resources have already been allocated.

  In the radio base station control apparatus according to the present invention, the radio reception environment is represented by SINR, CINR, received power, estimated throughput in a radio layer, or position of a radio terminal.

  In the radio base station control apparatus according to the present invention, the requested QoS level includes an IP packet delay time, jitter, an IP communication throughput to which the IP packet belongs, or a packet error rate.

  A radio base station control method according to the present invention is a radio base station control method in a radio communication system that performs simultaneous downlink communication by MIMO between a plurality of base stations and one radio terminal, wherein radio reception at the radio terminal A first step for determining whether or not to perform MIMO simultaneous communication based on the environment, and when performing MIMO simultaneous communication, transmit a wireless packet to the wireless terminal for a plurality of base stations subject to simultaneous MIMO communication A second step of performing transmission scheduling at the time, wherein in the second step, the MIMO scheme and transmission schedule of the base station are controlled based on QoS required for communication of the wireless terminal .

  According to the present invention, when performing simultaneous downlink communication between a plurality of base stations and one wireless terminal by MIMO, MIMO is appropriately applied according to the wireless reception environment in the wireless terminal, and the wireless terminal There is an effect that the base station can be controlled to provide communication quality according to QoS required for communication.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing a configuration of a MIMO wireless communication system according to an embodiment of the present invention. In FIG. 1, a radio base station controller 1 is connected to a backbone network (Internet protocol (IP) network). The plurality of base stations 2 are connected to the radio base station control device 1 by communication lines. The wireless terminal 3 performs wireless communication with the base station 2.

  In the following description, a configuration related to wireless communication in the downlink direction (direction from the base station 2 to the wireless terminal 3) according to the present invention will be described.

  The wireless terminal 3 performs downlink wireless communication with one or a plurality of base stations 2. Between the plurality of base stations 2 and one wireless terminal 3, simultaneous downlink communication (hereinafter referred to as “MIMO simultaneous communication”) is performed by MIMO in which the plurality of base stations 2 cooperate. The radio base station control device 1 applies the MIMO simultaneous communication appropriately according to the radio reception environment in the radio terminal 3 and also provides each base station to provide the communication quality according to the QoS required for the radio terminal 3 communication. 2 is controlled.

  FIG. 2 is a block diagram showing a configuration of the radio base station control device 1 according to the present embodiment. In FIG. 2, the radio base station controller 1 includes an inter-base station MIMO cooperation controller 11, a radio packet scheduler 12, a request QoS information holding unit 13, an IP packet queue information holding unit 14, an IP packet queue 15, and a radio packet building unit 16. Have The radio packet construction unit 16 is provided corresponding to each of the base stations 2.

  The inter-base station MIMO cooperation controller 11 controls the simultaneous MIMO communication. The wireless packet scheduler 12 performs transmission scheduling when the base station 2 transmits a wireless packet to the wireless terminal 3. In transmission scheduling, radio resources are allocated to IP packets in a radio transmission cycle. Examples of radio resources include time resources and frequency resources.

  The requested QoS information holding unit 13 stores the QoS information requested by the IP communication performed by the wireless terminal 3. Examples of the requested QoS level include IP packet delay time, jitter, IP communication throughput to which the IP packet belongs, packet error rate, and the like.

  The IP packet queue information holding unit 14 stores IP packet information (packet address information (destination address, source address), packet size, total number of packets, etc.) stored in the IP packet queue 15. The IP packet queue 15 stores IP packets transmitted to the wireless terminal 3. The wireless packet construction unit 16 converts the IP packet addressed to the wireless terminal 3 into a wireless packet. The radio packet is sent to the corresponding base station 2.

  Next, the operation of the inter-base station MIMO cooperation controller 11 will be described.

  The inter-base station MIMO cooperation controller 11 controls the simultaneous MIMO communication based on the reception environment information indicating the wireless reception environment in the wireless terminal 3. The reception environment information includes information for each base station 2. The wireless terminal 3 sends reception environment information indicating its own wireless reception environment for each base station 2 to the base station 2 (base station # 1 in the example of FIG. 2). The base station 2 sends the reception environment information received from the wireless terminal 3 to the wireless base station control device 1. Examples of the reception environment information include information such as SINR (Signal to Interference and Noise Power Ratio), CINR (Carrier to Interference and Noise Power Ratio), reception power, estimated throughput in the radio layer, and position of the radio terminal 3. .

  The inter-base station MIMO cooperation controller 11 determines whether or not to perform MIMO simultaneous communication based on the reception environment information. At that time, determination conditions for determining whether or not to perform MIMO simultaneous communication based on the reception environment information are determined in advance. The criterion for setting the determination condition is that communication quality can be improved by performing MIMO simultaneous communication. Therefore, when the reception environment information satisfies the determination condition, it is determined that communication quality can be improved by performing simultaneous MIMO communication. Hereinafter, a method for determining whether or not to perform MIMO simultaneous communication based on reception environment information will be described with reference to some embodiments.

  In the first embodiment, SINR, CINR, or estimated throughput information in the radio layer is used as reception environment information. As the determination condition, a limit value that can be expected to improve communication quality by performing MIMO simultaneous communication is used. For example, when SINR information is used as reception environment information, a limit value of SINR that can be expected to improve communication quality by performing MIMO simultaneous communication is determined, and the limit value is set as a threshold value for determination. In this case, when the SINR represented by the reception environment information is equal to or greater than the threshold, it is determined that communication quality can be improved by performing MIMO simultaneous communication.

  The inter-base station MIMO cooperation controller 11 compares the determination conditions with the information of each base station 2 included in the reception environment information, and performs simultaneous MIMO communication when the information of the plurality of base stations 2 satisfies the determination conditions. decide. Then, two or more predetermined number of base stations 2 are selected as the base station that performs MIMO simultaneous communication with the wireless terminal 3 from the one that best satisfies the determination condition.

  On the other hand, when the number of base stations 2 satisfying the determination condition is 1 or less, the inter-base station MIMO cooperation controller 11 determines that simultaneous MIMO communication with the wireless terminal 3 is not possible.

  In the second embodiment, reception power information is used as reception environment information. As a determination condition, a difference in received power from each base station 2 is used. As a determination condition, a limit value of a received power difference that can be expected to improve communication quality by performing MIMO simultaneous communication is determined, and the limit value is set as a determination threshold value.

  The inter-base station MIMO cooperation controller 11 calculates a difference between the received powers from the received power information of each base station 2 included in the received environment information, and compares the received power difference of the calculation result with a threshold value. The inter-base station MIMO cooperation controller 11 determines to perform the simultaneous MIMO communication when there is a received power difference equal to or less than the threshold. Then, among the groups of base stations 2 corresponding to the received power difference that satisfies the threshold condition, two or more base stations 2 having the smallest received power difference are simultaneously communicated with the wireless terminal 3 by MIMO. Select to base station.

  On the other hand, the inter-base station MIMO cooperation controller 11 determines that MIMO simultaneous communication with the wireless terminal 3 cannot be performed when there is no difference in received power equal to or less than the threshold.

  In the third embodiment, information on the position of the wireless terminal 3 is used as reception environment information. As the determination condition, a difference in distance between the wireless terminal 3 and each base station 2 (distance between terminal base stations) is used. As a determination condition, a limit value of a distance difference between terminal base stations that can be expected to improve communication quality by performing MIMO simultaneous communication is determined, and the limit value is set as a determination threshold value.

  The inter-base station MIMO cooperation controller 11 calculates the distance between the terminal base stations for the wireless terminal 3 and each base station 2 from the position information of the wireless terminal 3 included in the reception environment information. The position information of the base station 2 is set in advance. The inter-base station MIMO cooperation controller 11 calculates the difference between the distances between the terminal base stations, and compares the calculated distance difference between the terminal base stations with a threshold value. The inter-base station MIMO cooperation controller 11 determines to perform MIMO simultaneous communication when there is a distance difference between terminal base stations equal to or less than the threshold. Then, in the group of base stations 2 corresponding to the distance difference between the terminal base stations that satisfies the threshold condition, two or more predetermined numbers of base stations 2 from the one with the smallest distance difference between the terminal base stations are assigned to the wireless terminal 3 is selected as a base station that performs MIMO simultaneous communication.

  On the other hand, the inter-base station MIMO cooperation controller 11 determines that MIMO simultaneous communication with the wireless terminal 3 is not possible when there is no distance difference between the terminal base stations equal to or less than the threshold.

  As a modification of the third embodiment, a terminal base station distance difference corresponding to a position where the wireless terminal 3 can exist is calculated in advance, and a base station selection database is created based on the calculation result. Also good. The base station selection database stores information of two or more predetermined numbers of base stations 2 capable of performing MIMO simultaneous communication with the wireless terminal 3 in association with the position information of the wireless terminal 3. In this case, the inter-base station MIMO cooperation controller 11 searches the base station selection database based on the position information of the wireless terminal 3 included in the reception environment information, and performs two or more simultaneous MIMO communications with the wireless terminal 3 as a search result. Information on a predetermined number of base stations 2 is acquired. If there is no search result of the base station selection database, it is determined that MIMO simultaneous communication with the wireless terminal 3 cannot be performed.

  The above is the embodiment of the method for determining whether or not to perform the MIMO simultaneous communication based on the reception environment information.

  The inter-base station MIMO cooperation controller 11 instructs the radio packet scheduler 12 on two or more predetermined numbers of base stations 2 that perform MIMO simultaneous communication with the radio terminal 3.

  On the other hand, if the inter-base station MIMO cooperation controller 11 determines that the MIMO simultaneous communication with the radio terminal 3 cannot be performed, the base station 2 that performs radio communication with the radio terminal 3 on a one-to-one basis is instructed to the radio packet scheduler 12. To do. Based on the reception environment information, the inter-base station MIMO cooperation controller 11 selects the base station 2 with the best wireless reception environment in the wireless terminal 3 as the base station 2 that performs wireless communication with the wireless terminal 3 on a one-to-one basis. For example, the base station 2 that is the best wireless reception environment in the wireless terminal 3 is determined based on one or more information of SINR, CINR, received power, estimated throughput in the wireless layer, and position of the wireless terminal 3.

  Next, the operation of the wireless packet scheduler 12 will be described.

  When receiving an instruction to perform MIMO simultaneous communication with the wireless terminal 3 from the inter-base station MIMO cooperation controller 11, the wireless packet scheduler 12 applies the MIMO scheme to two or more predetermined numbers of base stations 2 to be subjected to simultaneous MIMO communication. And transmission scheduling for transmitting a wireless packet to the wireless terminal 3 are performed. Details of this operation will be described later.

  On the other hand, when the wireless packet scheduler 12 receives an instruction to perform one-to-one wireless communication with the wireless terminal 3 from the inter-base station MIMO cooperation controller 11, the wireless packet scheduler 12 Transmission scheduling is performed when a wireless packet is transmitted to the wireless terminal 3. In this transmission scheduling, it is preferable to consider the QoS required in the IP communication related to the wireless terminal 3.

  The radio packet scheduler 12 causes the IP packet queue 15 to output an IP packet to the radio packet construction unit 16 corresponding to the transmission base station 2 according to the transmission scheduling result. Further, in the case of simultaneous MIMO communication, the base station 2 is instructed about the MIMO scheme.

  The wireless packet construction unit 16 receives the IP packet output from the IP packet queue 15, converts the IP packet into a wireless packet, and transmits the wireless packet to the base station 2.

  Next, the operation of the radio packet scheduler 12 when performing MIMO simultaneous communication will be described in detail with reference to FIG. 3, FIG. 4 and FIG. 3, 4, and 5 are flowcharts showing a flow of control processing performed by the wireless packet scheduler 12.

  The wireless packet scheduler 12 performs control processing for each IP packet in the IP packet queue 15. At that time, the wireless packet scheduler 12 acquires the address information of the IP packet from the IP packet queue information holding unit 14, and holds the QoS information requested by the IP communication specified by the acquired address information. Obtained from the unit 13. The wireless packet scheduler 12 recognizes the request QoS related to the IP packet based on the acquired request QoS information.

  In the following description, for convenience of explanation, two base stations 2 that perform MIMO simultaneous communication (hereinafter referred to as base stations # 1 and # 2) are assumed, and the base stations # 1 and # 2 are configured as one wireless terminal 3 (hereinafter referred to as “base station # 1”). It is assumed that MIMO simultaneous communication is performed with a wireless terminal. Note that the same can be applied to the case where three or more base stations 2 perform MIMO simultaneous communication.

  First, in FIG. 3, in step S1, an initial value “0” is set to a variable i representing a packet number. The packet number is uniquely assigned to each IP packet in the IP packet queue 15. Therefore, the packet number is from “0” to “total number of packets in the IP packet queue 15 −1”.

  Next, in step S2, the MIMO schemes of the base stations # 1 and # 2 are determined based on the radio reception environment from the base station # 1 and the radio reception environment from the base station # 2 in the radio terminal. At this time, the combination of the MIMO scheme of the base station # 1 and the MIMO scheme of the base station # 2 is selected so as to have the highest frequency efficiency.

  Examples of the MIMO scheme include a spatial multiplexing (SM) scheme and a space time coding (STC) scheme. The SM scheme improves transmission speed by transmitting different data from a plurality of transmission antennas, and is a MIMO scheme with an emphasis on frequency efficiency. The STC scheme reduces the required signal-to-noise power ratio (SNR) by performing coding in the time direction and the spatial direction, and is a MIMO scheme emphasizing communication quality.

  As a combination of the MIMO scheme, the combination of the SM scheme and the SM scheme has the highest frequency efficiency, the combination of the SM scheme and the STC scheme has the next highest frequency efficiency, and the combination of the STC scheme and the STC scheme has the lowest frequency efficiency. Information on combinations of MIMO schemes corresponding to the respective ranks of frequency efficiency is set in advance. Furthermore, information on the MIMO scheme (SM scheme or STC scheme, or both SM scheme and STC scheme) that can be used depending on the wireless reception environment is set in advance. Based on these pieces of information, the MIMO scheme that can be used in the radio reception environment from the base station # 1 in the radio terminal and the MIMO scheme that can be used in the radio reception environment from the base station # 2 in the radio terminal are grasped, and the base station # The combination of the MIMO schemes with the highest frequency efficiency is selected from the available MIMO schemes 1 and # 2. Information on the selection results (the MIMO scheme of base station # 1 and the MIMO scheme of base station # 2) is recorded.

  Next, in step S3, the communication quality (for example, SNR) that can be realized by the MIMO scheme of the base station # 1 and the MIMO scheme of the base station # 2 selected in step S2 is determined between the base station # 1 and the wireless terminal, and the base station # 1. And between wireless terminals. Hereinafter, this calculated value is referred to as “estimated communication quality”. Information on the estimated communication quality of the base station # 1 and information on the estimated communication quality of the base station # 2 are recorded.

  Next, in step S4, it is determined whether the variable i is equal to or greater than the total number of packets in the IP packet queue 15. When the variable i is equal to or greater than the total number of packets in the IP packet queue 15, the processing is completed because all IP packets in the IP packet queue 15 have been processed. On the other hand, if the variable i is less than the total number of packets in the IP packet queue 15, the process proceeds to step S5.

  In step S5, it is determined whether or not the amount of available radio resources is insufficient for the size of the IP packet (i-th packet) to be processed for the pair of base station and radio terminal having a lower estimated communication quality. The free radio resource amount is the amount of radio resources that remain unallocated among radio resources that can be allocated to radio terminals. If the result of step S5 is that the amount of available radio resources is insufficient for the size of the i-th packet, the process proceeds to step S9 in FIG. On the other hand, if the free radio resource amount is sufficient for the size of the i-th packet, the process proceeds to step S6.

  In step S6, it is determined whether the worse estimated communication quality satisfies the requested QoS of the i-th packet. As a result, if the estimated communication quality of the worse one satisfies the request QoS of the i-th packet, the process proceeds to step S7. On the other hand, if the estimated communication quality of the worse one does not satisfy the requested QoS of the i-th packet, the process proceeds to step S16 in FIG.

  In step S7, the base station / wireless terminal pair with the lower estimated communication quality matches the i-th packet for both the free radio resource amount and the requested QoS, and therefore the base with the lower estimated communication quality for the i-th packet. Allocate radio resources for a set of stations and radio terminals. Thereafter, the process proceeds to step S8, where 1 is added to the variable i, and the next IP packet is set as a processing target.

  As a result of step S5, if the amount of free wireless resources is insufficient for the size of the i-th packet, the amount of free wireless resources is i for the pair of base station and wireless terminal having the better estimated communication quality in step S9 of FIG. Judge whether the packet number is insufficient. As a result, when the amount of free radio resources is insufficient for the size of the i-th packet, radio resources cannot be allocated to the i-th packet in the current transmission scheduling, so the i-th packet is carried over to the next transmission scheduling. Thereafter, the process proceeds to step S8 in FIG. 3, and 1 is added to the variable i to set the next IP packet as a processing target. On the other hand, when the free radio resource amount is sufficient for the size of the i-th packet, the process proceeds to step S10.

  In step S10, it is determined whether the better estimated communication quality satisfies the requested QoS of the i-th packet. As a result, if the better estimated communication quality satisfies the requested QoS of the i-th packet, the process proceeds to step S11. In step S11, since the set of the base station and the wireless terminal having the better estimated communication quality matches the i-th packet in both the free radio resource amount and the requested QoS, the base having the better estimated communication quality with respect to the i-th packet. Allocate radio resources for a set of stations and radio terminals. Thereafter, the process proceeds to step S8 in FIG. 3, and 1 is added to the variable i to set the next IP packet as a processing target.

  On the other hand, if the estimated communication quality of the better one does not satisfy the requested QoS of the i-th packet as a result of step S10, the free radio resource amount of the base station and wireless terminal having the better estimated communication quality is the size of the i-th packet. Therefore, an attempt is made to satisfy the requested QoS of the i-th packet by changing the MIMO method. First, in step S12, it is determined whether it is possible to change the MIMO scheme of the base station / wireless terminal set with the better estimated communication quality. At this time, it is determined whether or not it is possible to change to a MIMO system having a frequency efficiency lower than that of the current MIMO system. That is, the communication efficiency is improved by reducing the frequency efficiency. When a MIMO scheme having a frequency efficiency lower than that of the current MIMO scheme can be selected, the radio resource allocation is reviewed by the MIMO scheme having a lower frequency efficiency. As a result, it is verified whether radio resources can be secured in the MIMO scheme with low frequency efficiency for the IP packets to which the radio resources of the combination of the base station and the radio terminal having the better estimated communication quality have already been allocated. If this verification is successful (radio resources can be secured in the MIMO scheme with low frequency efficiency for the radio resource assigned IP packet), it is determined that the MIMO scheme with low frequency efficiency can be changed. On the other hand, if the verification is unsuccessful (the radio resource cannot be secured with the MIMO scheme with low frequency efficiency for the radio resource assigned IP packet), it is determined that the MIMO scheme with low frequency efficiency cannot be changed.

  As a result of step S12, if the MIMO scheme of the base station and wireless terminal group with the better estimated communication quality can be changed, the process proceeds to step S13. On the other hand, if it is impossible to change the MIMO scheme of the base station / wireless terminal set with the better estimated communication quality, the request QoS of the i-th packet cannot be satisfied with the current transmission scheduling. Carry over to the next transmission scheduling. Thereafter, the process proceeds to step S8 in FIG. 3, and 1 is added to the variable i to set the next IP packet as a processing target.

  In step S13, the estimated communication quality between the base station with the better estimated communication quality and the wireless terminal is recalculated by the MIMO method determined to be changeable in step S12. In step S14, it is determined whether the estimated communication quality of the recalculation result satisfies the requested QoS of the i-th packet. As a result, when the estimated communication quality of the recalculation result satisfies the request QoS of the i-th packet, the process proceeds to step S15. On the other hand, if the requested QoS of the i-th packet is not satisfied even with the estimated communication quality of the recalculation result, the requested QoS of the i-th packet cannot be satisfied with the current transmission scheduling, so the i-th packet is used for the next transmission scheduling. carry forward. Thereafter, the process proceeds to step S8 in FIG. 3, and 1 is added to the variable i to set the next IP packet as a processing target.

  In step S15, the record is rewritten so that the MIMO scheme of the base station / wireless terminal set with the better estimated communication quality is changed to the MIMO scheme determined to be changeable in step S12. Further, the record is rewritten so that the estimated communication quality of the set of the base station and the wireless terminal having the better estimated communication quality is changed to the recalculation result in step S13. Further, since the set of the base station and the wireless terminal in which the MIMO scheme is changed is compatible with the i-th packet for both the free radio resource amount and the requested QoS, the base station and the wireless terminal having the MIMO scheme changed for the i-th packet. Allocate a set of radio resources. Thereafter, the process proceeds to step S8 in FIG. 3, and 1 is added to the variable i to set the next IP packet as a processing target.

  As a result of step S6 in FIG. 3, when the estimated communication quality of the worse one does not satisfy the required QoS of the i-th packet, in step S16 of FIG. It is determined whether the amount of available radio resources is insufficient for the size of the i-th packet. As a result, if the amount of free radio resources is insufficient for the size of the i-th packet, the process proceeds to step S18.

  On the other hand, if the result of step S16 is that the free radio resource amount is sufficient for the size of the i-th packet, the process proceeds to step S19, and it is determined whether the better estimated communication quality satisfies the requested QoS of the i-th packet. As a result, if the better estimated communication quality satisfies the requested QoS of the i-th packet, the process proceeds to step S20, and the radio resource of the set of the base station and radio terminal having the better estimated communication quality for the i-th packet Assign. Thereafter, the process proceeds to step S8 in FIG. 3, and 1 is added to the variable i to set the next IP packet as a processing target. As a result of step S19, if the better estimated communication quality does not satisfy the requested QoS of the i-th packet, the process proceeds to step S18.

  As a result of steps S16 and S19, if the set of the base station and the radio terminal with the better estimated communication quality does not match the i-th packet, the free radio resource amount of the set of the base station and the radio terminal with the lower estimated communication quality is Since the size of the i-th packet is sufficient, an attempt is made to satisfy the requested QoS of the i-th packet by changing the MIMO scheme. First, in step S18, it is determined whether it is possible to change the MIMO scheme of the base station / wireless terminal set having a lower estimated communication quality. At this time, it is determined whether or not it is possible to change to a MIMO system having a lower frequency efficiency than the current MIMO system so as to improve the communication quality by lowering the frequency efficiency. When a MIMO scheme having a frequency efficiency lower than that of the current MIMO scheme can be selected, the radio resource allocation is reviewed by the MIMO scheme having a lower frequency efficiency. As a result, it is verified whether or not radio resources can be secured by the MIMO scheme with low frequency efficiency for the IP packets to which the radio resources of the base station and radio terminal having the lower estimated communication quality have already been allocated. If this verification is successful (radio resources can be secured in the MIMO scheme with low frequency efficiency for the radio resource assigned IP packet), it is determined that the MIMO scheme with low frequency efficiency can be changed. On the other hand, if the verification is unsuccessful (the radio resource cannot be secured with the MIMO scheme with low frequency efficiency for the radio resource assigned IP packet), it is determined that the MIMO scheme with low frequency efficiency cannot be changed.

  As a result of step S18, if the MIMO scheme of the base station / wireless terminal set with the lower estimated communication quality can be changed, the process proceeds to step S21. On the other hand, if it is impossible to change the MIMO scheme of the base station / wireless terminal pair with the lower estimated communication quality, the requested QoS of the i-th packet cannot be satisfied with the current transmission scheduling. Carry over to the next transmission scheduling. Thereafter, the process proceeds to step S8 in FIG. 3, and 1 is added to the variable i to set the next IP packet as a processing target.

  In step S21, the estimated communication quality between the base station having a lower estimated communication quality and the wireless terminal is recalculated by the MIMO method determined to be changeable in step S18. In step S22, it is determined whether the estimated communication quality of the recalculation result satisfies the requested QoS of the i-th packet. As a result, when the estimated communication quality of the recalculation result satisfies the request QoS of the i-th packet, the process proceeds to step S23. On the other hand, if the requested QoS of the i-th packet is not satisfied even with the estimated communication quality of the recalculation result, the requested QoS of the i-th packet cannot be satisfied with the current transmission scheduling, so the i-th packet is used for the next transmission scheduling. carry forward. Thereafter, the process proceeds to step S8 in FIG. 3, and 1 is added to the variable i to set the next IP packet as a processing target.

  In step S23, the record is rewritten so that the MIMO scheme of the base station / wireless terminal pair with the lower estimated communication quality is changed to the MIMO scheme determined to be changeable in step S18. Furthermore, the record is rewritten so that the estimated communication quality of the pair of the base station and the wireless terminal with the worse estimated communication quality is changed to the recalculation result in step S21. Further, since the set of the base station and the wireless terminal in which the MIMO scheme is changed is compatible with the i-th packet for both the free radio resource amount and the requested QoS, the base station and the wireless terminal having the MIMO scheme changed for the i-th packet. Allocate a set of radio resources. Thereafter, the process proceeds to step S8 in FIG. 3, and 1 is added to the variable i to set the next IP packet as a processing target.

  According to the control processing of the radio packet scheduler 12 in the case of the MIMO simultaneous communication described above, the free radio resource amount and the requested QoS for the i-th packet are preceded by the combination of the base station and the radio terminal having the lower estimated communication quality. The wireless resource is allocated by determining whether or not it is compatible. The reason for this is that if the estimated QoS is poor and the requested QoS can be provided, the estimated communication quality is expected to be excessive, and therefore the i-th packet is estimated from the poor estimated communication quality. This is to avoid the use of the radio resource with the better estimated communication quality unnecessarily by trying to meet the requirements, and to effectively use the radio resource.

  In the embodiment described above, it may be configured to control from which transmitting antenna of which base station the i-th packet is transmitted. In this case, the estimated communication quality is calculated for each transmission antenna. Then, in order from the transmission antenna with the lower estimated communication quality, an attempt is made to match the i-th packet.

Next, some examples of changing the MIMO scheme are given.
(1) When there are two transmission antennas per base station, an example of changing the MIMO scheme is shown in equation (1). In the equation (1), the SM system is changed to the STC system for the two systems of transmission symbol data S 1 and S 2 .

(2) When there are four transmission antennas per base station, an example of changing the MIMO scheme is shown in equation (2). In equation (2), the four transmission symbol data S 1 , S 2 , S 3 , S 4 are changed from the SM method alone to the combined use of the SM method and the STC method, and further changed to the STC method alone. Yes.

  As described above, according to the present embodiment, it is determined whether or not to perform MIMO simultaneous communication based on the wireless reception environment in the wireless terminal. Thereby, it is possible to appropriately apply MIMO according to the radio reception environment in the radio terminal, and it is possible to effectively utilize MIMO in terms of communication quality. Furthermore, the MIMO scheme and transmission schedule of the base station are controlled based on the QoS required for communication of the wireless terminal. As a result, the base station can be controlled to provide communication quality corresponding to the QoS required for communication of the wireless terminal.

Further, according to the present embodiment, the following effects can be obtained.
When the requested QoS level is different among a plurality of communication connections addressed to a wireless terminal, the base station is configured so that each packet is MIMO-transmitted by an appropriate MIMO scheme from the transmission antenna of the base station that meets the requested QoS. Can be controlled. For example, when MIMO simultaneous communication is performed between a plurality of base stations for a certain wireless terminal, a best effort data packet with a low required QoS level is transmitted from a transmission antenna with a high communication quality by the SM method. While increasing the frequency efficiency, it is possible to perform control such that communication reliability is improved by transmitting a control packet having a high delay request level from a transmission antenna having a certain level of communication quality by the STC method. This contributes to efficient allocation of radio resources and improvement of feasibility of QoS guarantee.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

It is a conceptual diagram which shows the structure of the MIMO radio | wireless communications system which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the radio base station control apparatus 1 which concerns on the same embodiment. It is a flowchart which shows the flow of the control processing which the radio | wireless packet scheduler 12 shown in FIG. 2 performs. It is a flowchart which shows the flow of the control processing which the radio | wireless packet scheduler 12 shown in FIG. 2 performs. It is a flowchart which shows the flow of the control processing which the radio | wireless packet scheduler 12 shown in FIG. 2 performs. 1 is a basic conceptual diagram of a MIMO wireless communication system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wireless base station control apparatus, 2 ... Base station, 3 ... Wireless terminal, 11 ... Inter-base station MIMO cooperation controller, 12 ... Wireless packet scheduler, 13 ... Request QoS information holding part, 14 ... IP packet queue information holding part, 15 ... IP packet queue, 16 ... wireless packet building unit

Claims (8)

  1. In a radio base station controller in a radio communication system that performs simultaneous downlink communication by MIMO between a plurality of base stations and one radio terminal,
    An inter-base station MIMO cooperation controller that determines whether to perform MIMO simultaneous communication based on a radio reception environment in a radio terminal;
    A request QoS information holding unit for storing QoS information required for communication of a wireless terminal;
    A wireless packet scheduler that performs transmission scheduling when transmitting wireless packets to the wireless terminal for a plurality of base stations targeted for simultaneous MIMO communication when performing MIMO simultaneous communication;
    The wireless packet scheduler controls the MIMO scheme and transmission schedule of the base station based on QoS required for communication of the wireless terminal ,
    The wireless packet scheduler includes estimated communication quality calculating means for calculating communication quality that can be realized with a wireless terminal by the MIMO scheme of the base station, and the estimated communication quality is determined by the QoS required for communication of the wireless terminal. Determine if you are satisfied,
    A radio base station control device.
  2. In a radio base station controller in a radio communication system that performs simultaneous downlink communication by MIMO between a plurality of base stations and one radio terminal,
    An inter-base station MIMO cooperation controller that determines whether to perform MIMO simultaneous communication based on a radio reception environment in a radio terminal;
    A request QoS information holding unit for storing QoS information required for communication of a wireless terminal;
    A wireless packet scheduler that performs transmission scheduling when transmitting wireless packets to the wireless terminal for a plurality of base stations targeted for simultaneous MIMO communication when performing MIMO simultaneous communication;
    The wireless packet scheduler controls the MIMO scheme and transmission schedule of the base station based on QoS required for communication of the wireless terminal ,
    The wireless packet scheduler
    Based on the radio reception environment in the radio terminal, as a combination of MIMO schemes of a plurality of base stations, select the combination of the MIMO scheme with the highest frequency efficiency from the MIMO scheme emphasizing frequency efficiency and the MIMO scheme emphasizing communication quality,
    In the combination of the selected MIMO schemes, the radio resource allocation determination is performed first from the base station / radio terminal pair having a lower estimated communication quality,
    A radio base station control device.
  3. The radio base station controller according to claim 1 or 2 , wherein the radio packet scheduler attempts to change the MIMO scheme of the base station when the free radio resource amount or the requested QoS is incompatible.
  4. The radio base station controller according to claim 3 , wherein the radio packet scheduler changes the MIMO scheme from frequency efficiency to communication quality.
  5. The radio base station control apparatus according to claim 3 or 4 , wherein the radio packet scheduler verifies whether radio resources can be secured by a new MIMO scheme for a packet to which radio resources have already been allocated.
  6. The radio base station according to any one of claims 1 to 5 , wherein the radio reception environment is represented by SINR, CINR, reception power, estimated throughput in a radio layer, or a position of a radio terminal. Control device.
  7. A radio base station control method in a radio communication system that performs simultaneous downlink communication by MIMO between a plurality of base stations and one radio terminal,
    A first step of determining whether to perform MIMO simultaneous communication based on a wireless reception environment in a wireless terminal;
    A second step of performing transmission scheduling when transmitting wireless packets to the wireless terminal for a plurality of base stations targeted for simultaneous MIMO communication when performing MIMO simultaneous communication; and
    In the second step, the MIMO scheme and transmission schedule of the base station are controlled based on QoS required for communication of the wireless terminal ,
    In the second step, communication quality achievable with the wireless terminal is calculated by the MIMO scheme of the base station, and it is determined whether the estimated communication quality satisfies QoS required for communication of the wireless terminal,
    And a radio base station control method.
  8. A radio base station control method in a radio communication system that performs simultaneous downlink communication by MIMO between a plurality of base stations and one radio terminal,
    A first step of determining whether to perform MIMO simultaneous communication based on a wireless reception environment in a wireless terminal;
    A second step of performing transmission scheduling when transmitting wireless packets to the wireless terminal for a plurality of base stations targeted for simultaneous MIMO communication when performing MIMO simultaneous communication; and
    In the second step, the MIMO scheme and transmission schedule of the base station are controlled based on QoS required for communication of the wireless terminal ,
    In the second step,
    Based on the radio reception environment in the radio terminal, as a combination of MIMO schemes of a plurality of base stations, select the combination of the MIMO scheme with the highest frequency efficiency from the MIMO scheme emphasizing frequency efficiency and the MIMO scheme emphasizing communication quality,
    In the combination of the selected MIMO schemes, the radio resource allocation determination is performed first from the base station / radio terminal pair having a lower estimated communication quality,
    And a radio base station control method.
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EP2317805B1 (en) * 2009-10-29 2014-04-23 Mitsubishi Electric R&D Centre Europe B.V. Method and system for selecting at least one wireless telecommunication device for a coordination session
EP2515451B1 (en) * 2010-01-27 2017-08-02 ZTE Corporation Data transmission method and system for cooperative multiple input multiple output beam-forming
JP5425687B2 (en) * 2010-03-30 2014-02-26 株式会社Kddi研究所 MIMO control device
US9320042B2 (en) 2010-04-09 2016-04-19 Hitachi, Ltd. Wireless communication system with multiple base stations cooperating to transmit data
JP5443293B2 (en) * 2010-07-28 2014-03-19 京セラ株式会社 Base station, communication system, and handover destination determination method
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