JP2011142375A - Base station controller and radio resource allocation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the through-put of a user terminal positioned at a cell boundary, and also to suppress the deterioration of the total through-put of a cellular mobile communication system. <P>SOLUTION: A base station controller 10 includes: a radio resource allocation part for securing, in a base station 1 communicating with the user terminal 2, radio resources corresponding to single-site connection or multi-site connection being the communication method of the user terminal 2 which is determined by comparing frequency use efficiency, when the user terminal 2 performs the single-site connection, with frequency use efficiency when the user terminal 2 performs the multi-site connection; and a radio resource allocation frequency control part for making the increase/decrease, in radio resource allocation frequencies of the user terminal 2 performing the multi-site connection, opposite to the increase/decrease in the number of base stations 1 performing the multi-site connection with the user terminal 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a base station control device and a radio resource allocation method.

  In recent years, in the mobile phone service in Japan, the third generation called IMT-2000 (International Mobile Telecommunications 2000) represented by W-CDMA (Wideband Code Division Multiple Access) and CDMA2000 (Code Division Multiple Access 2000). Mobile communication systems are becoming popular. Further, as the IMT-2000 advanced system and the IMT-2000 next-generation system, a standard for a fourth generation mobile communication system called IMT-Advanced is being formulated.

  IMT-Advanced aims to achieve a transmission rate of 1 Gbps when moving at low speed and a transmission rate of 100 Mbps when moving at high speed. In order to realize such high-speed communication, it is necessary to use a communication method using a wide frequency band. As one of such communication methods, orthogonal frequency division multiple access (Orthogonal Frequency Division) Multiple Access (OFDMA) system is known. The OFDMA scheme is a scheme in which a wide frequency band is divided into orthogonal narrow bands called subcarriers, and information is transmitted on each subcarrier. According to this OFDMA method, frequency characteristics generated in a radio apparatus are corrected for each subcarrier, or frequency multiplex transmission and frequency division multiple access are adaptively performed with respect to time variations of frequency characteristics generated in a transmission path. Therefore, it is attracting attention as one of the leading transmission methods for realizing broadband communication.

  In addition, the multiple input multiple output (MIMO) technique using a plurality of antennas receives signals individually transmitted from a plurality of antennas on the transmission side by the plurality of antennas on the reception side, and receives the received signals. As a technique for improving frequency utilization efficiency by separating spatial signals from the signal.

  In the cellular mobile communication system, a plurality of base stations are arranged, and a continuous communication service area is constructed by the communication area (cell) of each base station. When applying a communication method using, a guideline for allocating the entire frequency band to each cell is conceivable due to the limitation of the usable frequency region. In this case, for a mobile station located in the vicinity of the base station, the desired signal from the communication base station can be received at a high level, and the radio signal from the adjacent base station is lowered due to distance attenuation. The user throughput can be expected to increase as an effect of broadband communication. However, for mobile stations located at cell boundaries, not only the level of the desired signal decreases due to distance attenuation, but also the radio signal of the adjacent base station becomes an interference signal at the same level as the communication signal, greatly degrading the communication quality. There is a problem that the effect of broadband communication cannot be obtained sufficiently. This problem becomes conspicuous especially in the downlink (line from the base station to the mobile station) because the transmission power of the base station is larger than that of the mobile station.

  For example, Patent Documents 1, 2, and 3 disclose countermeasures against the problem. In this conventional technology, a base station controller for controlling a plurality of base stations is provided, and the base station controller performs communication using a MIMO technology or the like in cooperation with a plurality of base stations to a mobile station at a cell boundary. Control multiple base stations.

  In the prior art described in Patent Document 4, each base station (own cell base station, other cell base station) performs control including a pilot channel including a pilot signal and at least control information necessary for communication with a mobile station. An OFDM signal in which a channel and a traffic channel including user data information are multiplexed is transmitted. The mobile station receives the desired signal from the own cell base station and the interference signal from the other cell base station, and based on the channel information acquired from the pilot signal and the received control information, a signal separation technique in MIMO (for example, A desired signal and an interference signal are detected using maximum likelihood estimation (Maximum Likelihood Detection (MLD) method, etc.), and an interference signal from another cell base station is removed to obtain a desired signal from the own cell base station.

  Non-Patent Document 1 proposes a base station cooperation technique using FFR (Fractional Frequency Reuse) technology. In the base station cooperation method described in Non-Patent Document 1, in addition to the subchannel group assigned to the outer cell in the conventional FFR, a new subchannel group for base station cooperation MIMO transmission is assigned, and base station cooperation communication is performed. The radio resources in the subchannel group allocated for the base station cooperative MIMO transmission are allocated to the user terminal that performs the above.

JP 2007-134844 A JP 2007-043332 A International Publication No. 2006/016485 Pamphlet JP 2009-100116 A

Ishii Hayato, Yoshimoto Akiyo, Hattori Takeshi, Ozeki Takeo, Suzuki Toshinori, “Examination of Communication Capacity of Multi-Base Station Cooperative MIMO Transmission System Using FFR”, IEICE Society Conference, B-5-48, p397, 2009 September

  When performing base station cooperative communication using the prior arts of Patent Documents 1, 2, and 3 described above, a state occurs in which one user terminal located at a certain cell boundary occupies radio resources of a plurality of base stations. . This relatively reduces the frequency of radio resource allocation to other user terminals that are located near the base station and should be able to obtain high throughput, thereby reducing the total throughput of the cellular mobile communication system. One factor. The prior arts of Patent Document 4 and Non-Patent Document 1 are techniques for improving user throughput at a cell boundary, but do not solve the problem of suppressing a decrease in total throughput of a cellular mobile communication system. .

  The present invention has been made in view of such circumstances, and its purpose is to improve the throughput of user terminals located at cell boundaries and to suppress a decrease in the total throughput of the cellular mobile communication system. It is an object of the present invention to provide a base station control apparatus and a radio resource allocation method capable of performing the above.

  In order to solve the above-described problems, a base station control apparatus according to the present invention includes a plurality of base stations, and a plurality of base stations are configured in a cellular mobile communication system in which a continuous communication service area is constructed by a communication area of each base station. A base station control apparatus for controlling a base station of the mobile station, wherein the mobile station communication method is determined by comparing the frequency use efficiency when the mobile station is connected to a single site and the frequency use efficiency when the mobile station is connected to a multisite. A radio resource allocation unit that secures radio resources according to a single site connection or multi-site connection at a base station that communicates with the mobile station, and an increase or decrease in radio resource allocation frequency of a mobile station that performs multi-site connection, And a radio resource allocation frequency control unit that reverses the increase / decrease in the number of base stations that perform multi-site connection with a mobile station.

  In the base station control apparatus according to the present invention, the radio resource allocation frequency control unit is configured to set a radio resource allocation frequency of a mobile station performing multi-site connection to a radio resource allocation frequency of a mobile station performing single site connection. It is limited to a fraction of the number of base stations that perform multi-site connection with mobile stations.

  In the base station control apparatus according to the present invention, the radio resource allocation frequency control unit includes a counter unit that counts, for each mobile station, the number of times a mobile station that performs multi-site connection is selected as a radio resource allocation candidate. Based on the value of the counter, it is characterized in determining whether or not to allocate radio resources to a mobile station that performs multi-site connection that is a radio resource allocation candidate.

  In the base station control apparatus according to the present invention, the radio resource allocation frequency control unit includes a residue calculation unit that performs a residue calculation on the value of the counter by the number of base stations that perform multi-site connection with the mobile station. And

  In the base station control apparatus according to the present invention, the radio resource allocation frequency control unit evaluates a mobile station that performs multi-site connection with respect to an evaluation value of each mobile station used when selecting a radio resource allocation candidate mobile station. The value is set to be a fraction of the base station that performs multi-site connection with the mobile station.

  In the base station control apparatus according to the present invention, the frequency utilization efficiency when a mobile station makes a multi-site connection is higher than the frequency utilization efficiency when the mobile station makes a single-site connection. ) × (number of base stations performing multisite connection with the mobile station) ”times or more, and a communication method selection unit that selects multisite connection as a communication method of the mobile station is provided. To do.

  A radio resource allocation method according to the present invention is a radio resource allocation method in a cellular mobile communication system in which a plurality of base stations are arranged and a continuous communication service area is constructed by the communication area of each base station. A single-site connection, which is a communication method of the mobile station, determined by comparing the frequency utilization efficiency when the mobile station makes a single-site connection with the frequency utilization efficiency when the mobile station makes a multi-site connection. Alternatively, a step of securing radio resources according to multi-site connection in a base station that communicates with the mobile station, and the base station controller increases or decreases radio resource allocation frequency of a mobile station that performs multi-site connection. And a step of performing control so as to be opposite to increase / decrease in the number of base stations that perform multi-site connection with a mobile station.

  In the radio resource allocating method according to the present invention, the base station control device sets a radio resource allocation frequency of a mobile station performing multi-site connection to a radio resource allocation frequency of a mobile station performing single site connection. The number of base stations that perform multi-site connection is limited to one-fifth.

  In the radio resource allocation method according to the present invention, the communication method selection unit of the base station controller or the mobile station has a frequency use efficiency when the mobile station is connected to a multisite, and the mobile station is connected to a single site. As a communication method of the mobile station, only when “(predetermined frequency utilization efficiency improvement rate) × (number of base stations performing multi-site connection with the mobile station)” times or more than the frequency utilization efficiency of The method further includes selecting a site connection.

  According to the present invention, it is possible to improve the throughput of a user terminal located at a cell boundary and suppress a decrease in the total throughput of the cellular mobile communication system.

It is a schematic block diagram of the cellular mobile communication system which concerns on one Embodiment of this invention. It is a conceptual diagram which shows the logic structure of an OFDM radio | wireless resource. It is an example of the radio | wireless resource allocation method which concerns on this invention. It is another example of the radio | wireless resource allocation method which concerns on this invention. It is another example of the radio | wireless resource allocation method which concerns on this invention. It is another example of the radio | wireless resource allocation method which concerns on this invention. It is Example 1 of the base station controller 10 which concerns on this invention. It is a flowchart which shows the procedure of the radio | wireless resource allocation method which concerns on the base station controller 10 shown in FIG. It is Example 2 of the base station controller 10 which concerns on this invention. 10 is a flowchart showing a procedure of a radio resource allocation method according to the base station controller 10 shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a cellular mobile communication system according to an embodiment of the present invention. In FIG. 1, a cellular mobile communication system includes a plurality of base stations 1 each providing a cell, a mobile station (user terminal) 2 that communicates by wireless connection to the base station 1, and a base that controls the plurality of base stations 1. It has a station controller 10. In FIG. 1, two base stations 1 (the base station identifier is A and B), a cell 3A provided by the base station 1 (A), and a cell provided by the base station 1 (B) 3B is illustrated.

  Each base station 1 is connected to the core network 5 via the backbone network 4. The backbone network 4 and the core network 5 each have a router 6. The base station controller 10 is provided in the backbone network 4 and is connected to each base station 1 by wire.

  In the cellular mobile communication system according to the present embodiment, the base station 1 and the user terminal 2 include a plurality of antennas, and even when the base station 1 and the user terminal 2 communicate on a one-to-one basis, the plurality of base stations 1 cooperate with each other. Even when communicating with one user terminal 2, transmission using MIMO technology (MIMO transmission) can be performed. Types of MIMO transmission (MIMO mode) include transmission diversity such as maximum ratio combining transmission diversity, space-time coding such as space-time coding, eigenbeam space multiplexing, and combinations thereof.

  In the cellular mobile communication system according to the present embodiment, the OFDMA method is used as the multiple access method between the base station 1 and the user terminal 2. In the present embodiment, it is assumed that the correspondence relationship (mapping method) between logical radio resources and physical radio resources is common to all base stations. When using OFDMA and MIMO transmission, a radio resource includes a time domain, a frequency domain, and a spatial domain. When performing MIMO transmission in which a plurality of base stations 1 cooperate with one user terminal 2, it is necessary to allocate the same radio resource to the plurality of base stations in cooperation.

  The base station controller 10 acquires information on the base station 1 to be controlled and information on the user terminal 2 connected to the base station 1 from each base station 1. The base station controller 10 assigns the radio resources of all the base stations 1 to be controlled at once. The base station controller 10 transmits the radio resource allocation result to each base station 1.

  In the following description, “single site connection” means that one user terminal 2 and one base station 1 perform one-to-one communication, and “multisite connection” means one user terminal 2 and a plurality of base stations 1. Indicates one-to-many communication.

  The base station controller 10 controls a plurality of base stations 1, and a plurality of base stations cooperate with each other to perform multi-site connection using MIMO transmission or the like to the user terminals 2 on the cell boundaries. It is possible to improve the throughput of the user terminal 2 in the network.

  Next, the concept of the radio resource allocation method according to the present embodiment will be described with reference to FIGS. Hereinafter, the base station 1 whose base station identifier is A is referred to as base station A, and the base station 1 whose base station identifier is B is referred to as base station B. Here, the multi-site connection is assumed to be two-base station cooperation in which two base stations A and B cooperate.

  FIG. 2 is a conceptual diagram showing a logical configuration of each OFDM radio resource of base station A and base station B. In FIG. 2, the horizontal axis represents time (in time slot units), and the vertical axis represents frequency (in subcarrier units). FIG. 2 shows a logical configuration, and the frequency on the vertical axis does not correspond to the physical subcarrier frequency. For this reason, the logical radio resource allocation result is further mapped to physical radio resources. A resource block (RB), which is a radio resource allocation unit, includes a plurality of subcarriers and OFDM symbols. For example, in LTE (Long Term Evolution), one RB is composed of 12 subcarriers and 7 OFDM symbols.

  Here, for convenience of explanation, as shown in FIG. 2, it is assumed that base station A and base station B each have six RBs for one radio resource allocation scheduling (hereinafter simply referred to as scheduling). . Further, it is assumed that one RB is assigned to one user terminal 2. Further, it is assumed that each base station A, B allocates 8 RBs to any user terminal 2 per scheduling.

  FIG. 3 is an example of a radio resource allocation method. In the example of FIG. 3, there are six user terminals 2-1 to 6 (hereinafter referred to as UE (User Equipment) 1 to 6). Among UE1-6, UE1 and UE3 perform multi-site connection. In the radio resource allocation method of FIG. 3, in order to maintain fairness among users, the number of RBs allocated to one user terminal 2 is the same. For user terminals 2 (UE1, UE3) performing multi-site connection, in one radio resource allocation, both RBs of base station A and base station B (consisting of the same subchannel and the same time slot) RB) must be allocated. Therefore, a total of two RBs, one RB of base station A and one RB of base station B, are allocated to UE1 and UE3, respectively, by one radio resource allocation. On the other hand, for each user terminal 2 (UE2, UE4, UE5, UE6) that performs single site connection, radio resource allocation for allocating one RB is performed twice, and a total of two RBs are allocated. Accordingly, the user terminal 2 that performs multi-site connection in cooperation with two base stations has a radio resource allocation frequency of “1 / (number of cooperation) = 1/2” compared to the user terminal 2 that performs single-site connection. Thereby, two RBs are allocated to each of the UEs 1 to 6.

  In addition, when performing 3 base station cooperation in which 3 base stations 1 cooperate, 3 base stations 1 allocate a common RB to a user terminal 2 performing multi-site connection in one radio resource allocation. Therefore, a total of 3 RBs are allocated by each base station 1 allocating one RB. Therefore, in order to maintain fairness with the user terminal 2 that performs single-site connection, the user terminal 2 that performs multi-site connection in cooperation with the three base stations allocates radio resources to the user terminal 2 that performs single-site connection. The frequency is “1 / (number of linkages) = 1/3”.

  In the radio resource allocation method of FIG. 3 described above, the radio resource allocation frequency of the user terminal 2 that performs multi-site connection is set to “1 / (number of cooperation)” of the radio resource allocation frequency of the user terminal 2 that performs single-site connection. . Thereby, it can adjust so that the number of RB allocated to one user terminal 2 may become the same number, and can maintain the fairness between users.

  4 and 5 are other examples of the radio resource allocation method. In FIG. 4, among six UEs 1 to 6, UE 1, UE 2, and UE 5 belong to the base station A, and UE 3, UE 4, and UE 6 belong to the base station B. UE1 and UE3 are capable of multi-site connection, and the other user terminals 2 (UE2, UE4, UE5, UE6) perform single-site connection. Further, for convenience of explanation, it is assumed that all user terminals 2 can transmit the data amount “1” per RB when the single site connection is performed. In addition, when UE1 performs multisite connection and UE3 performs multisite connection, the degree of improvement in the amount of data transmission with respect to single site connection is the same.

  FIG. 4 shows an example of radio resource allocation when the base station A and the base station B perform single site connection to all user terminals 2. <1> in FIG. 4 indicates a data amount “1” that can be transmitted by the RB to which each user terminal 2 is assigned. In FIG. 4, the total transmission data amount of the cellular mobile communication system (base station A and base station B) is 12.

  FIG. 5 shows an example of radio resource allocation when UE1 and UE3 perform multi-site connection. In the example of FIG. 5, it is assumed that UE1 and UE3 can transmit a data amount “2” that is twice that of single-site connection by performing multi-site connection. Here, the above-described radio resource allocation method of FIG. 3 is used. As a result, UE1 and UE3 that perform multi-site connection in cooperation with two base stations have a radio resource allocation frequency of “1 / (number of linkages) to user terminal 2 (UE2, UE4, UE5, UE6) that performs single-site connection. ) = 1/2 ". Therefore, as shown in FIG. 5, UE1 and UE3 that perform multi-site connection in cooperation with two base stations are each assigned two RBs by one radio resource assignment, and transmission data is transmitted by the two RBs. The quantity “2” is obtained. On the other hand, each of the user terminals 2 (UE2, UE4, UE5, UE6) performing single site connection is assigned two RBs by two radio resource assignments, and the transmission data amount is “2”.

  In the examples of FIGS. 4 and 5 described above, the total transmission data amount of the cellular mobile communication system (base station A and base station B) is 12, and the radio resource allocation of the user terminal 2 performing multi-site connection is shown. By setting the frequency to “1 / (number of linkages)”, it is possible to prevent a decrease in total throughput of the cellular mobile communication system due to multi-site connection. However, both the user terminal 2 that performs multi-site connection and the user terminal 2 that performs single-site connection have a data transmission amount of 2, and there is no throughput improvement effect by performing multi-site connection.

  Here, in order to obtain a user throughput improvement effect of n times by performing multisite connection, throughput of “n × 2 = n × (number of cooperation)” times that of single site connection is achieved by performing multisite connection. There is a need to improve. FIG. 6 is an example of a radio resource allocation method for improving the throughput of the user terminal 2 that performs multi-site connection as compared to the example of FIG. In the example of FIG. 6, UE1 and UE3 that perform multi-site connection each realize a data transmission amount “4” using two RBs. In order to obtain a double user throughput improvement effect by performing multi-site connection, it is necessary to obtain a throughput improvement of “2 × 2 = 4” times by single-site connection by performing multi-site connection. It shows that there is.

  Therefore, in order to maintain the total throughput of the cellular mobile communication system, the frequency utilization efficiency in the case of multi-site connection is “(predetermined frequency utilization efficiency) relative to the frequency utilization efficiency in the case of single-site connection. The multi-site connection is made to the user terminal 2 only when the improvement rate is n) × (number of cooperation) ”times or more.

  Next, an example of the base station controller 10 according to the present embodiment will be described.

  In the following embodiment, distributed data mapping is used as a mapping method from a logical RB table to a physical RB table. In the distributed data mapping, when allocating physical radio resources, it is mapped and transmitted to subcarriers distributed evenly over the entire frequency band of the cellular mobile communication system. With the distributed data mapping, the effect of averaging the drop in the received signal level due to fading can be obtained. Moreover, the effect of averaging the difference in the received signal level between the cooperative base stations can be expected. Therefore, in this embodiment, scheduling in the frequency direction is not performed. Also, the mapping from the logical RB to the physical radio resource is performed after the logical RB allocation processing in a certain time slot. Here, logical RB allocation performed for one mapping to physical radio resources is referred to as scheduling timing. Therefore, the scheduling timing is a time slot unit.

  Further, in the embodiment described below, it is assumed that double-throughput can be obtained by performing multi-site connection (a predetermined frequency utilization efficiency improvement rate is 2) compared to single-site connection.

  In the following description, the user terminal 2 that performs multi-site connection is referred to as a multi-site connection terminal, and the user terminal 2 that performs single-site connection is referred to as a single site connection terminal.

  FIG. 7 is Example 1 of the base station controller 10 according to the present embodiment. 7, the base station controller 10 includes a control unit 11, a core NW side input / output interface 12, a scheduling unit 13, a connected base station information acquisition / holding unit 14, a connected terminal information acquisition / holding unit 15, and a BS side input / output interface. 16 and an MS connection allocation counter 17.

  The control unit 11 controls each unit in the base station controller 10. The core NW side input / output interface 12 is connected to the core network 5 to transmit and receive data. The scheduling unit 13 has a function of allocating radio resources, a function of controlling radio resource allocation frequency, and a function of selecting a communication method. The connected base station information acquisition / holding unit 14 acquires and holds information on the base station 1 to be controlled. The connection terminal information acquisition / holding unit 15 acquires information about the user terminal 2 connected to the base station 1 to be controlled from each base station 1 and holds it. The BS-side input / output interface 16 is connected to the base station 1 to be controlled and transmits / receives data.

  The MS connection allocation counter 17 is provided for each user terminal 2. The MS connection allocation counter 17 is used to set the radio resource allocation frequency of the multi-site connection terminal to “1 / (number of cooperation)”. In the first embodiment, when the scheduling unit 13 selects a certain user terminal 2, the number of times of RB allocation is set with respect to the number of selections of the user terminal 2 only when the user terminal 2 is a multi-site connection terminal. Limit to “1 / (number of linkages)”. For this purpose, the MS connection allocation counter 17 counts the number of times the multi-site connection terminal is selected.

  FIG. 8 is Example 1 of the radio resource allocation method according to the present embodiment. FIG. 8 shows a processing procedure for logical radio resource allocation at one scheduling timing. The process in FIG. 8 is executed at each scheduling timing.

  In FIG. 8, steps S <b> 1 to S <b> 5 are performed for all user terminals 2. In step S1, the scheduling unit 13 calculates frequency use efficiency in each MIMO mode. Specifically, based on the radio quality information transmitted from the user terminal 2 to the base station controller 10 via the connected base station 1, the MCS that is the maximum transmission capacity for all MIMO modes, depending on whether or not there is a multi-site connection. Select (Modulation and Coding Scheme) to calculate the frequency utilization efficiency.

At this time, the expected value of the number of bits that can be transmitted (expected value of throughput) can be used as the frequency utilization efficiency. The expected value of throughput can be calculated by the following equation (1).
(Number of bits that can be transmitted with the selected cooperation pattern and the radio resource allocated by MCS once) × (1-PER) (1)
However, the PER is obtained from the carrier pattern and the noise power ratio (CINR) of the user terminal 2 when the cooperation pattern selected for the user terminal 2 and the MCS is used. Indicates the packet error rate.

  The radio quality information is, for example, CINR, received signal strength, received power difference from each neighboring base station, and the like. In the calculation of CINR, since the signal from the cooperative base station should be a carrier component, the CINR is calculated for each combination of the cooperative base stations. In this embodiment, since distributed data mapping is used, an average value of all subcarriers within one scheduling timing (for example, one time slot) is used for the radio quality information.

  Next, in step S2, the scheduling unit 13 uses the frequency utilization efficiency calculated in step S1, the maximum value of frequency utilization efficiency when performing multisite connection, the MIMO mode and MCS information at that time, and the single site. The maximum value of the frequency utilization efficiency when the connection is made, the MIMO mode and MCS information at that time are held.

Next, in step S3, the scheduling unit 13 determines the following expression (2) using the maximum value of the frequency use efficiency held in step S2.
(Maximum frequency use efficiency of multi-site connection) ≧ (predetermined frequency use efficiency improvement rate) × (number of linkages) × (maximum value of frequency use efficiency of single site connection) (2)
Here, in the present embodiment, it is assumed that double throughput can be obtained by performing multi-site connection compared to single-site connection. Therefore, since the predetermined frequency utilization efficiency improvement rate is 2, the above equation (2) becomes the following equation (3).
(Maximum frequency use efficiency of multi-site connection) ≧ 2 × (Number of linkages) × (Maximum frequency use efficiency of single-site connection) (3)

  When the above equation (3) is established (step S3, YES), multi-site connection is selected for the user terminal 2 in step S4. If the above equation (3) is not satisfied (step S3, NO), single site connection is selected for the user terminal 2 in step S5.

  Through the above steps S1 to S5, either multi-site connection or single-site connection is selected for all user terminals 2.

  Next, in step S <b> 6, the scheduling unit 13 calculates each metric value for all user terminals 2. For the calculation of the metric value, an evaluation formula such as Proportional Fairness (PF) or round robin is used. In this embodiment, the metric value of the user terminal 2 is calculated by the following equation (4) using PF.

However, M _(i) (t) is a metric value at time t of the user terminal 2 whose terminal identifier is i. R _{ave (i)} (t) is the average throughput up to time t of the user terminal 2 whose terminal identifier is i. R _{inst (i)} (t) is the cooperation pattern (multi-site connection or single-site connection) at time t of the user terminal 2 whose terminal identifier is i and the instantaneous throughput that can be transmitted by MCS. γ is a fairness factor, and the default value is 1.

  Next, in step S7, the scheduling unit 13 compares the metric values of all the user terminals 2 calculated in step S6, and determines the user terminal 2 having the largest metric value as the user terminal 2 (hereinafter referred to as radio resource allocation candidate). Select as user terminal 2). As a result, if the selected user terminal 2 can be selected (step S8, YES), the process proceeds to step S9. If the selected user terminal 2 cannot be selected (step S8, NO), the process proceeds to step S18. Here, the case where the selected user terminal 2 cannot be selected is a case where the set of user terminals 2 from which the selected user terminal 2 is selected is empty.

  In step S <b> 9, the scheduling unit 13 confirms the cooperation pattern of the selected user terminal 2. As a result, if the cooperation pattern of the selected user terminal 2 is multi-site connection, the process proceeds to step S10, and if it is single-site connection, the process proceeds to step S14.

In step S10, the scheduling unit 13 increments the MS connection allocation counter 17 of the selected user terminal 2 by one. Next, in step S11, the scheduling unit 13 uses the counter value of the MS connection allocation counter 17 of the selected user terminal 2 after the count-up and the number of base station cooperation in the multi-site connection of the selected user terminal 2 to Equation (5) is calculated. The scheduling unit 13 determines the radio resource allocation frequency of the selected user terminal 2 that performs multi-site connection using the calculation result of Expression (5).
(MS connection allocation counter value of selected user terminal 2) mod (number of linkages) (5)
However, mod represents a remainder operation, and “X mod Y” is a remainder obtained by dividing X by Y.

  When the calculation result of Expression (5) is 1, the determination result of the radio resource allocation frequency is acceptable (step S11, OK), and the process proceeds to step S12. When the calculation result of Expression (5) is other than 1, the determination result of the radio resource allocation frequency is rejected (step S11, NG), the radio resource is not allocated to the selected user terminal 2, and the process goes to step S16. move on.

  In step S12, the scheduling unit 13 determines whether or not radio resources can be allocated to the selected user terminal 2 based on the number of cooperation of base station cooperation in the multi-site connection of the selected user terminal 2 and the MIMO mode. To do. For example, in the case of two base station cooperation (the number of cooperation is 2), it is essential that the two base stations 1 communicating with the selected user terminal 2 through the base station cooperation are not assigned the same radio resource area. .

  If it is determined in step S12 that radio resources can be allocated to the selected user terminal 2, the process proceeds to step S13. If the result of step S12 is that radio resources cannot be allocated to the selected user terminal 2, the radio terminal is not allocated to the selected user terminal 2, and the selected user terminal 2 is the user terminal from which the selected user terminal 2 is selected. Delete from the set of 2 and return to step S7.

  In step S <b> 13, the scheduling unit 13 allocates a common unallocated radio resource of the plurality of base stations 1 that communicates with the selected user terminal 2 through base station cooperation to the selected user terminal 2. Thereafter, the process proceeds to step S16.

  In step S14, the scheduling unit 13 determines whether the base station 1 to which the selected user terminal 2 performing single site connection has an assignable radio resource (radio resource assignment is possible) or not (radio resource assignment is not possible). To do. If it is determined in step S14 that radio resource allocation is possible, the process proceeds to step S15. If it is determined in step S14 that radio resource allocation is not possible, radio resources are not allocated to the selected user terminal 2, and the selected user terminal 2 is deleted from the set of user terminals 2 from which the selected user terminal 2 is selected. Return to step S7.

  In step S15, the scheduling unit 13 holds information on the selected user terminal 2 that performs single site connection. This retained information includes the terminal identifier of the selected user terminal 2 and the number of required RBs. Here, radio resources are not yet allocated to the selected user terminal 2 performing single site connection, but the radio resource amount (number of unallocated RBs in the logical resource table) required by the selected user terminal 2 is stored as allocated. .

In step S <b> 16, the scheduling unit 13 updates the average throughput R _{ave (i)} (t) for all user terminals 2. The average throughput R _{ave (i)} (t) is updated by the calculation result of the following equation (6) or (7). Equation (6) is used for the user terminal 2 to which the radio resource is allocated at time t. Equation (7) is used for the user terminal 2 to which radio resources are not allocated at time t. However, Expression (6) is used for the selected user terminal 2 in which the determination result of the radio resource allocation frequency has failed in Step S11.

  Where β is a time constant.

  Next, in step S17, the scheduling unit 13 confirms whether there is a radio resource (unallocated RB) that can be allocated to the base station 1 to be controlled. As a result, when there is a radio resource that can be allocated, the process returns to step S6, and when there is no radio resource that can be allocated, the process proceeds to step S18.

  In step S18, the scheduling unit 13 allocates radio resources to the single site connection terminal determined to allocate radio resources based on the single site connection terminal information held in step S15.

  The base station controller 10 transmits the radio resource allocation result to each base station 1 to be controlled. The radio resource allocation result is information indicating which radio resource (RB) is allocated to which user terminal 2 for each base station 1.

  The processes in steps S15 and S18 for the single site connection terminal described above are processes for efficiently allocating radio resources in distributed data mapping. In multi-site connection, it is necessary to allocate radio resources common to a plurality of base stations in consideration of the combination of cooperative base stations. On the other hand, in the single site connection, only the radio resource of one base station that accommodates the single site connection terminal may be allocated. For this reason, from the viewpoint of the efficiency of radio resource allocation, radio resources are allocated to the multi-site connection terminal at the beginning with a high degree of freedom in radio resource allocation. Then, since it is expected that unassigned radio resources remain in each base station in a distributed manner, in order to utilize this remaining radio resource for a single site connection terminal, only a required radio resource amount is secured in step S15. In step S18, actual radio resource allocation is performed.

  In the first embodiment, the user terminal 2 transmits wireless information to the base station controller 10 via the base station 1, and the base station controller 10 determines the cooperation pattern of the user terminal 2. The user terminal 2 may execute the above-described steps S1 to S5 to determine a cooperation pattern and transmit the result to the base station controller 10.

  FIG. 9 is Example 2 of the base station controller 10 according to the present embodiment. In FIG. 9, the same reference numerals are given to the portions corresponding to the respective portions in FIG. The base station controller 10 of the second embodiment shown in FIG. 9 has the same configuration as that of FIG. 7, but does not include the MS connection allocation counter 17. Hereinafter, differences from the first embodiment will be mainly described.

  FIG. 10 is Example 2 of the radio resource allocation method according to this embodiment. FIG. 10 shows a processing procedure for logical radio resource allocation at one scheduling timing. The process in FIG. 10 is executed at each scheduling timing. In FIG. 10, steps S31 to S33 are the same as steps S1 to S3 in FIG.

  As a result of step S33, when the above equation (3) is established (step S33, YES), the scheduling unit 13 selects multi-site connection for the user terminal 2 in step S34. Next, in step S35, the scheduling unit 13 calculates the metric value of the multi-site connected user terminal 2 by the following equation (8). Formula (8) is a calculation formula using PF.

However, M _(i) (t) is a metric value at time t of the user terminal 2 whose terminal identifier is i. The number of cooperation is the number of cooperation of base station cooperation in the multi-site connection of the user terminal 2 whose terminal identifier is i. R _{ave (i)} (t) is the average throughput up to time t of the user terminal 2 whose terminal identifier is i. R _{inst (i)} (t) is the instantaneous throughput that can be transmitted by multi-site connection and MCS of the user terminal 2 whose terminal identifier is i at time t. γ is a fairness factor, and the default value is 1. The calculation formula used for updating the average throughput R _{ave (i)} (t) is the same as that for PF.

  In the first embodiment, the MS connection allocation counter 17 is provided in order to limit the radio resource allocation frequency of the multi-site connection terminal to “1 / (number of cooperation)”. On the other hand, in the second embodiment, in order to limit the radio resource allocation frequency of the multisite connection terminal to “1 / (number of cooperation)”, the metric value of the multisite connection terminal is expressed as shown in Expression (8). “1 / (Number of linkages)”.

  As a result of step S33, when the above equation (3) is not satisfied (step S33, NO), the scheduling unit 13 selects single site connection for the user terminal 2 in step S36. Next, in step S37, the scheduling unit 13 calculates the metric value of the user terminal 2 connected to the single site by the following equation (9). Formula (9) is a calculation formula using PF.

However, M _(i) (t) is a metric value at time t of the user terminal 2 whose terminal identifier is i. R _{ave (i)} (t) is the average throughput up to time t of the user terminal 2 whose terminal identifier is i. R _{inst (i)} (t) is an instantaneous throughput that can be transmitted by single-site connection and MCS of the user terminal 2 whose terminal identifier is i at time t. γ is a fairness factor, and the default value is 1.

  Next, in step S38, the scheduling unit 13 compares the metric values of all user terminals 2 calculated in steps S35 and S37, and determines the user terminal 2 having the largest metric value as the user terminal 2 ( Select as selected user terminal 2). As a result, if the selected user terminal 2 can be selected (step S39, YES), the process proceeds to step S40. If the selected user terminal 2 cannot be selected (step S39, NO), the process proceeds to step S45. Here, the case where the selected user terminal 2 cannot be selected is a case where the set of user terminals 2 from which the selected user terminal 2 is selected is empty.

  In step S <b> 40, the scheduling unit 13 determines whether radio resources can be allocated to the selected user terminal 2. This determination is the same as step S12 in FIG. 8 for multi-site connection terminals, and the same as step S14 in FIG. 8 for single-site connection terminals. If it is determined in step S40 that radio resources can be allocated to the selected user terminal 2, the process proceeds to step S41. If it is determined in step S40 that radio resources cannot be allocated to the selected user terminal 2, the radio terminal is not allocated to the selected user terminal 2, and the selected user terminal 2 is selected as the user terminal from which the selected user terminal 2 is selected. Delete from the set of 2 and return to step S38.

  In step S41, the scheduling unit 13 confirms the cooperation pattern of the selected user terminal 2. If the connection is single site connection, the process proceeds to step S43. If the connection is multisite connection, the process proceeds to step S42.

  In step S <b> 42, the scheduling unit 13 allocates to the selected user terminal 2 unallocated radio resources common to the plurality of base stations 1 that communicate with the selected user terminal 2 through base station cooperation. Thereafter, the process proceeds to step S44.

  In step S43, the scheduling unit 13 holds information of the selected user terminal 2 that performs single site connection. This retained information includes the terminal identifier of the selected user terminal 2 and the number of required RBs. Here, radio resources are not yet allocated to the selected user terminal 2 performing single site connection, but the radio resource amount (number of unallocated RBs in the logical resource table) required by the selected user terminal 2 is stored as allocated. .

  In step S44, the scheduling unit 13 confirms whether there is a radio resource (unallocated RB) that can be allocated to the base station 1 to be controlled. As a result, when there is a radio resource that can be allocated, the process returns to step S31, and when there is no radio resource that can be allocated, the process proceeds to step S45.

  In step S45, the scheduling unit 13 allocates radio resources to the single site connection terminals determined to allocate radio resources based on the information on the single site connection terminals held in step S43.

  The base station controller 10 transmits the radio resource allocation result to each base station 1 to be controlled. The radio resource allocation result is information indicating which radio resource (RB) is allocated to which user terminal 2 for each base station 1.

  In the second embodiment, the user terminal 2 transmits wireless information to the base station controller 10 via the base station 1, and the base station controller 10 determines the cooperation pattern of the user terminal 2. The user terminal 2 may execute the above-described steps S31 to S37 to determine the cooperation pattern and the metric value, and transmit the result to the base station controller 10.

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.
For example, in the above-described embodiment, the base station controller 10 is provided in the backbone network 4, but this is not a limitation, and the base station controller 10 is provided in a distributed manner in each base station 1. You may comprise so that 10 may cooperate with the base station controller 10 of the base station 1 which adjoins.

DESCRIPTION OF SYMBOLS 1 ... Base station, 2 ... Mobile station (user terminal), 10 ... Base station controller (base station control apparatus), 11 ... Control part, 12 ... Core NW side input / output interface, 13 ... Scheduling part (radio resource allocation part, Radio resource allocation frequency control unit, communication method selection unit), 14 ... connection base station information acquisition / holding unit, 15 ... connection terminal information acquisition / holding unit, 16 ... BS side input / output interface, 17 ... MS connection allocation counter

Claims (9)

In a cellular mobile communication system in which a plurality of base stations are arranged and a continuous communication service area is constructed by the communication area of each base station, a base station control device that controls a plurality of base stations,
A radio resource corresponding to a single-site connection or multi-site connection, which is a communication method of the mobile station, determined by comparing the frequency use efficiency when the mobile station makes a single-site connection and the frequency use efficiency when making a multi-site connection A radio resource allocating unit secured in a base station that communicates with the mobile station;
A radio resource allocation frequency control unit that reverses increase / decrease in radio resource allocation frequency of a mobile station performing multi-site connection with increase / decrease in the number of base stations performing multi-site connection with the mobile station;
A base station control device comprising: The radio resource allocation frequency control unit is configured to set a radio resource allocation frequency of a mobile station performing multi-site connection to a radio station allocation frequency of a mobile station performing single-site connection, and a base station performing multi-site connection with the mobile station. Limit to a fraction of
The base station control device according to claim 1. The radio resource allocation frequency control unit
A counter unit that counts the number of times a mobile station that performs multi-site connection is selected as a radio resource allocation candidate for each mobile station, and performs multi-site connection that is a radio resource allocation candidate based on the value of the counter Determine whether to allocate radio resources to the mobile station;
The base station control device according to claim 2.   The base station according to claim 3, wherein the radio resource allocation frequency control unit includes a residue calculation unit that performs a residue calculation on the value of the counter by the number of base stations that perform multi-site connection with the mobile station. Control device. The radio resource allocation frequency control unit
With respect to the evaluation value of each mobile station used when selecting a radio resource allocation candidate mobile station, the evaluation value of the mobile station that performs multi-site connection is reduced to a fraction of the number of base stations that perform multi-site connection with the mobile station. To
The base station control device according to claim 2. The frequency utilization efficiency when a mobile station is connected to a multi-site is higher than the frequency utilization efficiency when the mobile station is connected to a single site by “(predetermined frequency utilization efficiency improvement rate) × (multi-site connection with the mobile station. The number of base stations to perform)) only when it is more than double, a communication method selection unit that selects multi-site connection as the communication method of the mobile station
The base station control apparatus according to claim 1, further comprising: A radio resource allocation method in a cellular mobile communication system in which a plurality of base stations are arranged and a continuous communication service area is constructed by a communication area of each base station,
The base station controller that controls a plurality of base stations is a communication method of the mobile station determined by comparing the frequency use efficiency when the mobile station makes a single site connection and the frequency use efficiency when a mobile station makes a multisite connection Securing radio resources according to single-site connection or multi-site connection at a base station that communicates with the mobile station;
The base station controller controls the increase / decrease in the radio resource allocation frequency of the mobile station performing multi-site connection to be opposite to the increase / decrease in the number of base stations performing multi-site connection with the mobile station;
A radio resource allocating method comprising: The base station controller determines the radio resource allocation frequency of a mobile station performing multi-site connection with respect to the radio resource allocation frequency of a mobile station performing single-site connection, and the number of base stations performing multi-site connection with the mobile station. Limit to one part,
The radio resource allocation method according to claim 7.   The communication method selection unit included in the base station controller or the mobile station has a frequency usage efficiency when the mobile station is connected to the multi-site more than the frequency usage efficiency when the mobile station is connected to the single site. (Frequency utilization efficiency improvement rate) × (number of base stations that perform multi-site connection with the mobile station) ”only when it is greater than or equal to a multiple, the method further includes the step of selecting multi-site connection as the communication method of the mobile station The radio resource allocation method according to claim 7 or 8, wherein

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