WO2013190818A1

WO2013190818A1 - Network control method and apparatus, server and base station in mobile communication system

Info

Publication number: WO2013190818A1
Application number: PCT/JP2013/003765
Authority: WO
Inventors: 潤式田; 石井　直人; ブンサーンピタックダンロンキジャー
Original assignee: 日本電気株式会社
Priority date: 2012-06-20
Filing date: 2013-06-17
Publication date: 2013-12-27

Abstract

[Problem] To provide a network control method and apparatus, a server and a base station wherein the throughput of the whole system can be improved when a backhaul link is a bottleneck. [Solution] In a mobile communication system including a relay station (20), it is determined whether the communications of mobile terminals (30) connected to the relay station (20) are restricted by a backhaul link between a base station (10) and the relay station (20) or by a relay access link between the relay station (20) and the mobile terminals (30), and, if the communications are restricted by the backhaul link, a control is performed such that the connection destination of other mobile terminals (40) currently connected to the base station (10) is switched to the relay station.

Description

Network control method and apparatus, server and base station in mobile communication system

The present invention relates to a mobile communication system to which relay transmission is applied, and more particularly to a network control method and apparatus thereof, and a server and a base station having a network control function.

In 3GPP LTE (Long-Term Evolution) -Advanced, in order to improve the transmission data volume per unit time (hereinafter referred to as throughput) and expand the system coverage, a relay station ( Relay transmission is used for transmission via Relay Node). Adoption of relay transmission has an advantage that a transmission line is not required because the base station and the relay station are wireless lines, and the system can be constructed at low cost.

A relay station (hereinafter abbreviated as RN) used for relay transmission has the same cell identifier as a base station (Donor eNodeB, hereinafter abbreviated as DeNB) to which the RN belongs, or is different from DeNB. Depending on whether the cell identifier is When the RN has the same cell identifier as the DeNB, the mobile terminal (User （Equipment, hereinafter abbreviated as UE) recognizes the presence of the RN, and transmits the signal transmitted from the RN to the DeNB. It is considered. On the other hand, when the RN has a unique cell identifier, the RN forms an independent cell different from the DeNB, so that the RN is recognized as one of the base stations when viewed from the UE.

FIG. 1 shows an example of a mobile communication system that employs relay transmission using an RN having a unique cell identifier. As shown in FIG. 1, in a system in which DeNB1 forms a macro cell MCELL and RN2 forms a relay cell RCELL, the UE is connected to either the macro cell MCELL or the relay cell RCELL. Hereinafter, the UE connected to the macro cell MCELL is referred to as MUE, and the UE connected to the relay cell RCELL is referred to as RUE. In addition, between DeNB1 and RN2, between RN2 and RUE3, and between DeNB1 and MUE4 are respectively connected by the radio | wireless line, and DeNB1 and the core network 5 are connected by the wired line.

The connection between the UE and the cell is established by a procedure in which the UE selects a cell, makes a connection request to the selected cell, and the requested cell permits the connection. Cell selection is based on the received signal quality (RSRP (Reference Signal Received Power) or RSRQ (Reference Signal Received Quality)) measured using a cell-specific reference signal and system information (SIB: System Information Block). This is performed based on the notified offset value. By setting an offset value in the UE, it is possible to select a cell with a reception signal quality that is not the best as a connection destination, so that it is possible to optimize traffic load distribution between cells by the offset setting value. Such a cell selection method is disclosed in Non-Patent Document 1, and the parameters of system information (SIB) are described in Non-Patent Document 2 (Sec. 6.3.1, pp. 146-159). RSRP or RSRQ) is disclosed in Non-Patent Document 3, respectively. However, since changing the system information is accompanied by an increase in the processing amount of the UE, it is not desirable to change the setting value frequently.

Also, since the quality of the radio channel varies depending on the movement of the UE, the UE may need to switch the connected cell (handover). The cell to which the UE is connected determines which cell to handover based on the received signal quality (RSRP or RSRQ) of the own cell and neighboring cells reported from the UE and the offset value unique to each cell. .

The offset value used in the handover process is a parameter different from the setting in the system information (SIB) used at the time of cell selection described above, and handover failure or frequent occurrence can be achieved by setting each UE individually. Optimized to avoid. The setting of the offset value is described in Non-Patent Document 2 (Sec. 6.3.5, pp. 213-214). Note that the handover execution condition based on the received signal quality (RSRP or RSRQ) and the offset value is determined by the operating policy of the communication carrier.

The offset value used at the time of cell selection or handover described above has been set based on the radio wave environment and traffic load analysis results from a driving test or the like. The introduction of self-organizing network (SON: “Self-Organizing” Network) technology, which is autonomously performed by the network, is being promoted. SON optimizes base station configuration parameters by collecting and analyzing information about network quality measured by terminals and base stations. Note that collection / analysis of measurement information and parameter optimization may be performed in a distributed manner by each base station, or may be performed in a centralized manner by a network management apparatus that can communicate with a plurality of base stations.

However, the throughput of the UE 3 connected to the relay cell RCELL in the relay transmission as shown in FIG. 1 is the theoretical value of the throughput of the line between DeNB and RN (hereinafter referred to as the backhaul link) and the line between the RN and UE ( Hereinafter, it is influenced by the relationship with the theoretical value of the throughput of the relay access link. Here, the theoretical value of the throughput is a value determined by the channel quality of the line and the amount of available resources, and corresponds to a throughput value that can be realized when a sufficient amount of transmission data exists on the transmission side. When the theoretical value of the throughput of the backhaul link is larger than the theoretical value of the throughput of the relay access link, the relay access link becomes a bottleneck, and conversely, the theoretical value of the throughput of the backhaul link is larger than the theoretical value of the throughput of the relay access link. Is smaller, the backhaul link becomes a bottleneck. When the backhaul link is a bottleneck, even if relay transmission is introduced, the capacity of the relay access link is not fully utilized, and thus the system throughput cannot be sufficiently improved.

The received signal quality offset value used at the time of cell selection or handover described above is set for the purpose of traffic load distribution, handover control, etc., and does not consider the bottleneck of the line. Therefore, since the offset value is set without considering the bottleneck of the line, there is a possibility that the throughput cannot be sufficiently improved when the backhaul is in a bottleneck state.

Therefore, an object of the present invention is to provide a network control method and apparatus, a server, and a base station that can improve the throughput of the entire system when a backhaul link is a bottleneck.

The network control method according to the present invention is a network control method in a mobile communication system including a relay station, in which communication of a mobile terminal connected to the relay station is performed between the first communication link between the base station and the relay station and the relay Determining which of the second communication links between the station and the mobile terminal is restricted, and when restricted by the first communication link, connection of another mobile terminal connected to the base station Control is performed to switch the destination from the base station to the relay station.
A network control apparatus according to the present invention is a network control apparatus in a mobile communication system including a relay station, and a mobile terminal connected to the relay station communicates with a first communication link between the base station and the relay station and the relay. A determination means for determining which of the second communication links between the mobile station and the mobile terminal is restricted, and another mobile connected to the base station when restricted by the first communication link Control means for controlling to switch the connection destination of the terminal from the base station to the relay station.
The base station according to the present invention is a base station in a mobile communication system including a relay station, and communication of a mobile terminal connected to the base station is performed between the first communication link and the relay between the base station and the relay station. A determination means for determining which of the second communication links between the mobile station and the mobile terminal is restricted, and another mobile connected to the base station when restricted by the first communication link Control means for controlling to switch the connection destination of the terminal from the base station to the relay station.
The server according to the present invention is a server in a mobile communication system including a base station and a relay station, and communication of a mobile terminal connected to the base station is performed between the first communication link between the base station and the relay station, and the relay station. A determination unit for determining which of the second communication links between the relay station and the mobile terminal is restricted; and when restricted by the first communication link, another unit connected to the base station Control means for controlling to switch the connection destination of the mobile terminal from the base station to the relay station.
A mobile communication system according to the present invention is a mobile communication system including a macro cell formed by a base station and a relay cell formed by a relay station connected to the base station, wherein the base station connects to the relay cell. Determining means for determining which of the first communication link between the base station and the relay station and the second communication link between the relay station and the mobile terminal is restricted by Control means for controlling to switch a connection destination of another mobile terminal connected to the macro cell from the base station to the relay station when restricted by the first communication link.
A mobile communication system according to the present invention is a mobile communication system including a macro cell formed by a base station and a relay cell formed by a relay station connected to the base station, wherein a server connected to the base station includes the relay cell Determines whether communication of a mobile terminal connected to the mobile station is restricted by a first communication link between the base station and the relay station or a second communication link between the relay station and the mobile terminal And a control means for controlling to switch the connection destination of another mobile terminal connected to the macro cell from the base station to the relay station when restricted by the first communication link. It is characterized by.

According to the present invention, the total throughput of the entire system can be improved.

FIG. 1 is a configuration diagram showing an example of a mobile communication system employing relay transmission. FIG. 2 is a schematic diagram of a mobile communication system for explaining the basic operation of network control according to the present invention. FIG. 3 is a sequence diagram showing a network control operation in the mobile communication system according to the first embodiment of the present invention. FIG. 4 is a block diagram illustrating a configuration example of the base station (DeNB). FIG. 5 is a block diagram illustrating a configuration example of the relay station (RN). FIG. 6 is a block diagram illustrating a configuration example of a mobile terminal (UE). FIG. 7 is a flowchart showing a network control method according to the first embodiment of the present invention. FIG. 8 is a flowchart showing a network control method according to the second embodiment of the present invention. FIG. 9 is a network configuration diagram showing a schematic configuration of a mobile communication system according to the second embodiment of the present invention.

According to the embodiment of the present invention, when the backhaul link becomes a bottleneck, the connection destination of the mobile terminal connected to the macro cell is switched from the macro cell to the relay cell. Thereby, the channel quality of the macro access link can be improved and the throughput of the entire system can be increased. The basic operation of network control according to the present invention will be described below with reference to FIG.

1. Basic Operation First, as shown in FIG. 2, the theoretical value of the throughput of a radio channel (hereinafter referred to as a macro access link) between the DeNB (base station) 10 and the MUE (mobile terminal) 40 connected to the macro cell is expressed as follows. The theoretical value of the throughput of the backhaul link between the TP _MA , the DeNB 10 and the RN (relay node) 20 is the theoretical value of the throughput of the relay access link between the TP _BH , the RN 20 and the RUE (mobile terminal) 30 connected to the relay cell. It is assumed that the value is TP _RA and the backhaul link is a bottleneck, that is, TP _BH <TP _RA . As an example, the theoretical value of the throughput of each link is defined as follows.

Theoretical value of throughput of each link = (Average frequency utilization efficiency of each link) x (Available frequency bandwidth of each link)
Here, the frequency utilization efficiency is a throughput per unit frequency (bit / s / Hz), and its magnitude depends on the channel quality.

It is expressed.

When the backhaul link is a bottleneck (TP _BH <TP _RA ), as described above, the throughput of the RUE is limited by the backhaul link, and the capacity of the relay access link is not fully utilized. In the network control according to the present invention, the capacity of the relay access link can be effectively used by handing over a MUE having a relatively deteriorated channel quality among the MUEs connected to the macro cell to the relay cell.

More specifically, as shown in FIG. 2, when UEx having poor channel quality connected to the macro cell is handed over to the relay cell, the average frequency utilization efficiency of the macro access link is improved, and the theoretical value of the throughput of the macro access link ( MUE total throughput) increases from TP _MA to TP ' _MA . By handing over UEx to the relay cell, the average frequency utilization efficiency of the relay access link is deteriorated, and the theoretical value of the throughput is expected to deteriorate from TP _RA to TP ′ _RA . However, if there is no change in the state where the backhaul link is a bottleneck (TP _BH <TP ' _RA ), the total RUE throughput (TP' _RUE × N ' _RUE ) is TP _BH , and the UEx before handover control Does not fluctuate. Therefore, the network control according to the present invention can increase the total throughput of the MUE without changing the total throughput of the RUE, and can improve the total throughput of the entire system.

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the drawings. Although the present invention does not limit the subject of network control, as will be described below, in the first embodiment of the present invention, the DeNB is used, and in the second embodiment, a server other than the base station is used as the subject of network control. As an example.

2. First Embodiment 2.1) System Operation As shown in FIG. 3, each of RN 20, RUE 30 and MUE 40 measures channel quality (operations S101 to S103), and RN 20 and MUE 40 directly transmit the measured channel quality to DeNB1. Then, the RUE 30 transmits to the RN 20 (operation S104). The DeNB 10 calculates the frequency use efficiency of the macro access link and the backhaul link based on the channel quality received from the MUE 40 or the RN 20 (Operation S105). The frequency utilization efficiency can also be derived from the received signal quality (RSRP or RSRQ). Further, the DeNB 10 calculates the amount of resources allocated to each RN using the scheduling information (Operation S106). The RN 20 calculates the frequency use efficiency of the relay access link using the channel quality received from the RUE 30 (Operation S107), and transmits information on the calculated frequency use efficiency to the DeNB 10 (Operation S108).

When receiving information on the frequency usage efficiency of the relay access link from the RN 20, the DeNB 10 uses the information on the frequency usage efficiency, the calculated frequency usage efficiency, and the amount of resources allocated to each RN, and the backhaul link and the relay. The theoretical value of the throughput of the access link is calculated (operation S109), and the offset value of the received signal quality for each RN of each MUE is determined using the calculated frequency utilization efficiency of each link (operation S110). As described above, by setting an offset value, handover from a macro cell to a relay cell can be promoted for a MUE (particularly a UE having a deteriorated reception quality). Hereinafter, configurations and functions of the DeNB 10, the RN 20, and the UE for performing such a system operation will be described.

2.2) Base station DeNB
As illustrated in FIG. 4, the DeNB 10 includes a transmission path interface unit 11, a baseband signal processing unit 12, and a radio frequency signal processing unit 13. The baseband signal processing unit 12 includes an upper layer processing unit 121, a MAC (Medium Access Control) layer processing unit 122, a physical layer processing unit 123, a channel quality calculation unit 124, and an offset value determination unit 125. The function of each processing unit will be described by taking as an example the case of a downlink that sends data from the DeNB 10 to the UE.

The transmission path interface unit 11 receives user data from the core network 5 and transfers the received data to the upper layer processing unit 121. The upper layer processing unit 121 performs PDCP (Packet Data Convergence Protocol) layer processing such as encryption on the received data, and RLC (Radio Link Control) layer processing such as division / combination of user data, and MAC layer processing unit 122. The upper layer processing unit 121 also performs RRCRR (Radio Resource Control) layer processing for handling control messages. The MAC layer processing unit 122 performs multiplexing, retransmission processing (hybrid ARQ), and scheduling processing of data transferred from the higher layer processing unit 121. The data multiplexing method and the retransmission processing control method are determined by the scheduling process. Further, the modulation method and coding rate in the physical layer processing unit 123 are also determined by the scheduling process. The physical layer processing unit 123 performs encoding, modulation, and the like on the data transmitted from the MAC layer processing unit 122 to generate a baseband signal, and transfers the baseband signal to the radio frequency signal processing unit 13.

The radio frequency signal processing unit 13 performs conversion processing, band limitation processing, and amplification processing of the baseband signal transferred from the physical layer processing unit 123 of the baseband signal processing unit 12 into a carrier frequency band signal, and finally from the antenna. Send.

In the case of an uplink, the processing route reverses that of the downlink described above. That is, the radio frequency signal processing unit 13 converts the radio frequency signal received from the MUE or RN into a baseband signal, and the baseband signal processing unit 12 performs physical layer processing, MAC layer processing, and higher layer processing on the baseband signal. Finally, the transmission path interface unit 11 transfers the data to the core network 5.

The channel quality calculation unit 124 of the baseband signal processing unit 12 acquires the CQI (Channel Quality Indicator) reported from each MUE or RN and the scheduling information of the DeNB from the MAC layer processing unit 122, and the macro access link and back Calculate the frequency utilization efficiency of the hall link and the amount of resources allocated to each RN. Further, the channel quality calculation unit 124 uses the calculated frequency utilization efficiency, the amount of resources allocated to each RN, and the information on the frequency utilization efficiency of the relay access link reported from the RN, and the backhaul link and the relay access link. And calculates the calculated theoretical value of the throughput and the frequency utilization efficiency to the offset value determination unit 125.

The offset value determination unit 125 determines the received signal quality offset value for each relay cell of the MUE, using the theoretical throughput value and the frequency utilization efficiency input from the channel quality calculation unit 124, as will be described later.

2.3) Relay node RN
As shown in FIG. 5, the RN 20 includes a baseband signal processing unit 22 and a radio frequency signal processing unit 23. The baseband signal processing unit 22 includes an upper layer processing unit 221, a MAC layer processing unit 222, a physical layer processing unit 223, and an access link quality calculation unit 224. Unlike the DeNB 10, the transmission path interface unit connected to the core network 5 is not provided. The functions of each processing unit of the RN 20 are basically the same as those of the DeNB 10 described above, but the upper layer processing unit 221 divides and multiplexes the data addressed to the RUE, and the physical layer processing unit 223 receives the received signal. It differs from DeNB10 in that quality is measured.

Downlink data transmitted from the DeNB 10 to the RUE via the RN is transmitted as data addressed to the RN obtained by multiplexing the data of a plurality of RUEs connected to the same relay cell. The multiplex processing of the data addressed to the RN is executed by the core network 5 and the division processing of the multiplexed data is executed by the upper layer processing unit 221 of the RN 20. The data of each divided RUE is subjected to higher layer processing (PDCP layer processing, RLC layer processing), MAC layer processing, physical layer processing, and radio frequency signal processing, and then transmitted to each RUE. On the other hand, in the case of an uplink, data received from a plurality of RUEs are multiplexed in the upper layer processing unit 221 of the RN 20 and transmitted to the DeNB 10 as data having a transmission source of RN.

The physical layer processing unit 223 measures the received signal quality (RSRP or RSRQ) using the cell-specific reference signal, and outputs the measured received signal quality to the upper layer processing unit 221. The upper layer processing unit 221 reports the received signal quality to the DeNB 10 as an RRC message.

The access link quality calculation unit 224 obtains the CQI reported from each RUE connected to the cell formed by the RN from the MAC layer processing unit 222, and calculates the average frequency use efficiency of the relay access link using the CQI. To do. The calculated frequency utilization efficiency is sent to the DeNB 10 by an RRC message as an example. Note that the information to be transmitted may be, for example, throughput instead of frequency utilization efficiency.

2.4) Configuration of the mobile terminal UE As shown in FIG. 6, the UE (RUE 30, MUE 40) includes an application layer processing unit 31, a baseband signal processing unit 32, and a radio frequency signal processing unit 33, and the baseband The signal processing unit 32 includes an upper layer processing unit 321, a MAC layer processing unit 322, and a physical layer processing unit 323.

The application layer processing unit 31 exchanges data with the upper layer processing unit 321. Similar to the physical layer processing unit 223 of the RN 20, the physical layer processing unit 323 measures the received signal quality (RSRP or RSRQ) and sends the measurement value to the higher layer processing unit 321. Note that the MAC layer processing unit 322 does not perform scheduling processing. Since information such as the modulation method and coding rate is sent from the connected DeNB 10 or RN 20, the UE may perform each process according to the information. The functions of the other processing units are basically the same as those of the DeNB 10 described above.

3. First embodiment (network control)
3.1) Offset value determination operation The processing of the offset value determination unit 125 of the DeNB 10 may be periodic or aperiodic, but in any case, the processing starts after the channel quality calculation unit 124 ends.

In FIG. 7, the offset value determination unit 125 first sets the index i of the RN connected to the DeNB 10 to an initial value (i = 1) (operation S201). Subsequently, data communication to the UE connected to the i-th RN (hereinafter referred to as RNi) is restricted by the backhaul link or the relay access link (that is, which line is the bottleneck) It is determined (operation S202).

As the bottleneck determination method, for example, the following two methods can be adopted. As a first example, a method of comparing the ratio of the theoretical values of the throughput of the backhaul link and the relay access link with a threshold value can be considered. As the theoretical value of the throughput, a value calculated by the channel quality calculation unit 124 is used, and an appropriate value may be set as the threshold value so that it is possible to determine which line is the bottleneck. As a second example, a method using the resource usage rate in RNi can be considered. In this case as well, as in the first example, the determination may be made by comparing with a threshold value. Note that the resource usage measurement processing and the exchange processing between adjacent base stations of the measured resource usage are supported by standard specifications.

If it is determined that the backhaul link is a bottleneck (“backhaul link” in operation 202), a UE that satisfies the following two conditions is searched when the connection destination is switched to a cell formed by RNi (operation S203). .
Condition 1: Improve communication quality (throughput as an example) of a cell connected before switching.
Condition 2: Data communication to UEs connected to RNi is restricted by the backhaul link (the backhaul link is a bottleneck).

Regarding Condition 1, the frequency utilization efficiency of each UE sent from the channel quality calculation unit 124 can be used. Regarding condition 2, the frequency utilization efficiency when the target UE connects to RNi is required, but it can be derived from the received signal quality (RSRP or RSRQ) reported from the UE.

If a control target UE that satisfies both of the

above conditions

1 and 2 is found (operation S204; YES), the received signal quality offset value Δ for the cell formed by RNi of the control target UE is determined (operation S205). The offset value Δ is set so that the UE to be controlled is handed over to RNi. That is, the offset value Δ is set to an appropriate value by considering the RSRP difference between the cell formed by RNi and the cell before switching and the handover control method.

When the offset value Δ is determined, when the relay access link is determined to be a bottleneck (“relay access link” in operation S202), or when a UE that satisfies both the

above conditions

1 and 2 is not found (operation S204; NO), it is determined whether or not the index i is a predetermined maximum value (max value) (operation S206). If the index i is the maximum value (operation S206; YES), the processing related to the determination of the offset value is terminated. If the index i is not the maximum value (operation S206; NO), the value of i is incremented by 1 (operation S207). Return to operation S202. Thus, the above-described processing S202 to S206 is repeated until the value of i reaches the maximum value.

3.2) Effect As described above, according to the first embodiment of the present invention, the received signal quality offset value of the UE for each relay cell in consideration of fluctuations in the communication quality of the bottleneck line and the connected cell. Is determined. For example, if the backhaul link is a bottleneck in the relay cell to be controlled, when the UE connection destination is switched to the relay cell to be controlled, the bottleneck state of the backhaul link is maintained, and the cell communication before connection switching If there is a UE that improves the quality, an offset value of the received signal quality is set for the UE to be handed over to the relay cell to be controlled. When the UE is handed over, the backhaul link is a bottleneck, so the total data amount transmitted to the UE connected to the relay cell to be controlled does not change and the communication quality of the handover source cell is improved. . Therefore, as a result, the total throughput of the entire system can be improved.

4). Second embodiment (network control)
4.1) Offset value determination operation The configurations of the DeNB 10, the RN 20, and the UE are as shown in FIGS. However, the processing method of the offset value determination unit 125 is different from that of the first embodiment. Hereinafter, a second embodiment of the present invention will be described with reference to a flowchart shown in FIG. The processing of the offset value determination unit 125 of the DeNB 10 may be periodic or aperiodic, but in any case, it starts after the processing of the channel quality calculation unit 124 ends.

8, the offset value determination unit 125 first sets the index i of the RN connected to the DeNB 10 to an initial value (i = 1) (operation S301). Subsequently, it is determined whether the data communication to the UE connected to RNi is restricted by the backhaul link or the relay access link (that is, which line is the bottleneck) (operation S302). The bottleneck determination method is as described above.

If the backhaul link is determined to be a bottleneck (“backhaul link” in operation 302), the UE improves the communication quality of the cell connected before switching when the connection destination is switched to the cell formed by RNi. Are listed (operation S303). In addition, in order to limit the number of UEs that can be entered in the list, for example, a condition such as “the RSRP difference between the connected cell and the cell formed by RNi is below the threshold” is added. Or setting the maximum number of UEs in the list is also conceivable.

Subsequently, the index j for the list is set to an initial value j = 1 (operation S304). Whether the backhaul becomes a bottleneck when switching the jth UE (UEj) of the list to the cell formed by RNi, as in the case before data switching to the UE connected to RNi Is determined (operation S305). When it is determined that the backhaul is not a bottleneck (operation S305; NO), it is determined whether the value of j is a predetermined maximum value (operation S306). If the value of j is not the maximum value (operation S306; NO), the value of j is incremented by 1 (operation S307), and the processing returns to operation S305.

When it is determined that the backhaul link becomes a bottleneck (operation S305; YES), the received signal quality offset value Δ for the cell formed by RNi of the j-th UEj in the list is determined (operation S308). As in the first embodiment, the offset value Δ is set such that the control target UEj is handed over to RNi. That is, the offset value Δ is set to an appropriate value by considering the RSRP difference between the cell formed by RNi and the cell before switching and the handover control method.

When the offset value Δ is determined, the relay access link is determined to be a bottleneck (“relay access link” in operation S302), or the value of j is the maximum value (operation S306; YES), the index i Is a predetermined maximum value (max 値 value) or not (operation S309). If the index i is the maximum value (operation S309; YES), the processing related to the determination of the offset value is terminated. If the index i is not the maximum value (operation S309; NO), the value of i is incremented by 1 (operation S310). Return to operation S302. In this way, the above-described processes S302 to S310 are repeated until the value of i reaches the maximum value.

As described above, since the process of operation S305 is executed according to the order of the list, it is necessary to devise the order of UEs arranged in the list in order to shorten the UE search time. For example, there can be considered a method in which the improvement in communication quality due to switching of the connection destination is expected to be large, or the RSRP difference between the connected cell and the cell formed by RNi is small.

4.2) Effect In the second embodiment of the present invention, as in the first embodiment, data communication to the UE connected to the relay cell is limited (bottleneck) and the communication quality of the connected cell is reduced. Since the received signal quality offset value for each relay cell of the UE is determined by taking the fluctuations into account, the total throughput of the entire system can be improved. According to the second embodiment, after creating a list of UEs that improve the communication quality of the cell connected before switching by switching the connection destination, a line that becomes a bottleneck of the relay cell from the list Searching for a UE that does not change Therefore, UE can be searched more efficiently than the first embodiment. When creating a list, you can search more efficiently by devising the order.

5. 2nd Embodiment In 1st Embodiment mentioned above, although the determination process of offset value was performed in DeNB10, this invention is not limited to this embodiment, The network of the core network 5 and a mobile communication system is managed. When a server is used, the server can be provided with an offset value determination function.

9, the DeNB 10a has a configuration obtained by removing the functions of the channel quality calculation unit 124 and the offset value determination unit 125 from the configuration of the DeNB 10 illustrated in FIG. 4, and the server 6 includes the channel quality calculation unit 124 and the offset value determination unit. It has 125 functions. Since the basic operation according to the present embodiment is the same as that described in the first embodiment, a description thereof will be omitted.

The present invention can be applied to a mobile communication system employing relay transmission.

1, 10 DeNB
2, 20 RN
3, 30 RUE
4, 40 MUE
5 Core network
6 servers
MCELL macrocell
RCELL relay cell
11 Transmission path interface
12 Baseband signal processor
13 Radio frequency signal processor
121 Upper layer processing section
122 MAC layer processor
123 Physical layer processor
124 Channel quality calculator
125 Offset value determination unit
22 Baseband signal processor
23 Radio frequency signal processor
221 Upper layer processing section
222 MAC layer processor
223 Physical layer processor
224 Access link quality calculator
31 Application layer processing section
32 Baseband signal processor
33 Radio frequency signal processor
321 Upper layer processing section
322 MAC layer processor
323 Physical layer processor

Claims

A network control method in a mobile communication system including a relay station,
Whether the communication of the mobile terminal connected to the relay station is restricted by the first communication link between the base station and the relay station or the second communication link between the relay station and the mobile terminal Judgment,
When restricted by the first communication link, control to switch the connection destination of another mobile terminal connected to the base station from the base station to the relay station,
A network control method.
The network according to claim 1, wherein the other mobile terminal is a mobile terminal whose communication quality is improved when the connection destination is switched from the base station to the relay station. Control method.
3. The network control method according to claim 2, wherein the other mobile terminal is a mobile terminal in which the restriction of the communication by the first communication link is further maintained.
When the connection destination of the other mobile terminal is switched from the base station to the relay station, the mobile terminal whose communication quality of the base station is improved is listed,
When the connection destination of the listed mobile terminal is switched from the base station to the relay station, the mobile terminal that maintains the communication restriction by the first communication link is selected as the other mobile terminal.
The network control method according to claim 3.
5. The network control method according to claim 1, wherein the other mobile terminal is selected from a plurality of mobile terminals connected to the base station based on received signal quality. 6. .
6. The network control according to claim 5, wherein the other mobile terminal is preferentially selected from mobile terminals having a small difference between the received signal quality for the base station and the received signal quality for the relay station. Method.
A network control device in a mobile communication system including a relay station,
Whether the communication of the mobile terminal connected to the relay station is restricted by the first communication link between the base station and the relay station or the second communication link between the relay station and the mobile terminal Determination means for determining;
Control means for controlling to switch the connection destination of another mobile terminal connected to the base station from the base station to the relay station when restricted by the first communication link;
A network control apparatus comprising:
The control means selects, as the other mobile terminal, a mobile terminal whose communication quality of the base station is improved when the connection destination of the other mobile terminal is switched from the base station to the relay station. The network control device according to claim 7, characterized in that:
The network control device according to claim 8, wherein the control means further selects a mobile terminal that maintains the communication restriction by the first communication link as the other mobile terminal.
The control means lists mobile terminals whose communication quality of the base station improves when the connection destination of the other mobile terminal is switched from the base station to the relay station. 10. The mobile terminal that maintains the communication restriction by the first communication link when the connection destination is switched from the base station to the relay station is selected as the other mobile terminal. The network control device described.
11. The control unit according to claim 7, wherein the control unit selects the other mobile terminal from a plurality of mobile terminals connected to the base station based on received signal quality. Network controller.
The said control means selects the said other mobile terminal preferentially from the mobile terminal with a small difference of the received signal quality with respect to the said base station, and the received signal quality with respect to the said relay station. The network control device described.
The network control device according to any one of claims 7 to 12, wherein the network control device is installed in the base station.
13. The network control device according to claim 7, wherein the network control device is installed in a network management device that manages the mobile communication system.
A base station in a mobile communication system including a relay station,
Communication of a mobile terminal connected to the base station is restricted by any one of a first communication link between the base station and the relay station and a second communication link between the relay station and the mobile terminal. Determination means for determining whether or not
Control means for controlling to switch the connection destination of another mobile terminal connected to the base station from the base station to the relay station when restricted by the first communication link;
A base station characterized by comprising:
A server in a mobile communication system including a base station and a relay station,
Communication of a mobile terminal connected to the base station is restricted by any one of a first communication link between the base station and the relay station and a second communication link between the relay station and the mobile terminal. Determination means for determining whether or not
Control means for controlling to switch the connection destination of another mobile terminal connected to the base station from the base station to the relay station when restricted by the first communication link;
The server characterized by having.
A mobile communication system including a macro cell formed by a base station and a relay cell formed by a relay station connected to the base station,
The base station is
Whether the communication of the mobile terminal connected to the relay cell is restricted by the first communication link between the base station and the relay station or the second communication link between the relay station and the mobile terminal Determining means for determining
Control means for controlling to switch the connection destination of another mobile terminal connected to the macro cell from the base station to the relay station when restricted by the first communication link;
A mobile communication system comprising:
A mobile communication system including a macro cell formed by a base station and a relay cell formed by a relay station connected to the base station,
A server connected to the base station
Whether the communication of the mobile terminal connected to the relay cell is restricted by the first communication link between the base station and the relay station or the second communication link between the relay station and the mobile terminal Determining means for determining
Control means for controlling to switch the connection destination of another mobile terminal connected to the macro cell from the base station to the relay station when restricted by the first communication link;
A mobile communication system comprising:
19. The relay station in the mobile communication system according to claim 17 or 18, further comprising link quality calculation means for calculating information on channel quality of the second communication link and reporting the information to the base station. .