JP2012054736A - Mobile communication system and load distribution method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve average throughput in an overall mobile communication system by controlling automatic load distribution to base stations in the system, while the load condition of the overall system is taken into consideration.SOLUTION: The information of NE antenna to be controlled and the information of a coverage area change range when an antenna tilt angle is changed are provided in advance in an EMS. An NE acquires traffic information with a predetermined period, so as to transmit to the EMS and an NMS. Based on the traffic information, an NE having a heavy load and an NE adjacent thereto are selected. Based on the information of the coverage area change range and the traffic information, the change amount of the antenna tilt angle is calculated, and the load distribution is performed by controlling the tilt angle by the transmission of a tilt angle change command.

Description

  The present invention relates to a mobile communication technology, and more particularly to a load distribution technology in a mobile communication system.

  Mobile communication systems (1xEVDO, HSDPA, LTE, WiMAX, etc.) after the 3.5th generation specialize in data communication, and apply a high data rate encoding method to terminals with good reception quality. The throughput of the entire area (cell) covered by the base station has been successfully improved. However, since wireless terminals are mobile, the number of connections of each base station in a mobile communication system is not uniform. In many cases, users are biased within the sector. Thus, when the number of connections in a cell of a specific base station increases and the load on the cell (or sector) increases, the average value of the throughput of the entire cell (or sector) decreases. On the other hand, the cell (or sector) immediately adjacent to the cell (or sector) where the user is biased has a small number of connected calls, a small load, and a high average value of the throughput of the entire cell (or sector) in many cases. . In a mobile communication system, it is always required to cope with a case where the user is biased to a specific cell (or sector) and throughput is lowered.

As one of the correspondences, in Patent Document 1, in the base station configured by dividing the radio zone into a plurality of sectors, the value of the total downlink transmission power for each sector is equalized between the sectors. A technique for controlling the directivity of the variable directivity antenna in each sector is disclosed.
In Patent Document 2, the base station acquires a value indicating the load state of the own station and a value indicating the load state of another adjacent base station, and the value indicating the load state of the own station has a predetermined value. If exceeded, select another base station whose load status value is less than the predetermined value, and connect the selected other base station to the next wireless connection from a plurality of wireless communication terminals wirelessly connected to the local station The wireless communication terminal as a candidate is extracted, the extracted wireless communication terminal is notified that the wireless connection is to be released, and the wireless communication terminal wirelessly communicates with other selected base stations based on the notification. A technique for establishing a connection is disclosed.

JP 2004-297291 A JP 2008-2111645 A

The technique disclosed in Patent Document 1 is load distribution control in one base station, and the base station distributes the load of one sector where there is no base station to another sector. The technology described in Patent Document 2 selects another base station that can distribute the load when the base station has exceeded its predetermined load state, and further selects all the base stations connected to the base station. The wireless communication terminal is inquired of wireless connection destination candidates. The technique described in Patent Literature 2 needs to make an inquiry to a wireless communication terminal connected to the selection of a base station capable of load distribution or the own station after detecting that the own station is in a load state, It is difficult to perform real-time load balancing control in an environment where the load state changes from moment to moment. Furthermore, in the case of a system in which base stations of different vendors are mixed, load information may not be acquired from other adjacent base stations.
In addition, when selecting an adjacent base station with a small load state value as a load distribution destination and handing off a wireless communication terminal having that base station as the next wireless connection destination candidate, if there are many such terminals, There is also a possibility that the handoff will cause the neighboring base station to which the handoff is to be placed into a high load state. In addition, a situation may occur in which wireless communication terminals handoff one after another from another base station in a high load state. For this reason, a single base station does not perform load distribution control by looking only at its own surroundings, but by looking at the load state of the entire mobile communication system, load distribution control that improves the overall throughput of the mobile communication system The mechanism of was needed.

  The present invention has been made to solve the above-mentioned problems, and automatically performs load balancing control of base stations in the system while considering the load state of the entire mobile communication system. The purpose is to improve the throughput.

  In order to solve the above problems, the present invention provides a network element (hereinafter referred to as NE) to which a plurality of wireless terminals are connected, a plurality of element managers (hereinafter referred to as EMS) to which a plurality of NEs are connected, In a mobile communication system having a network manager (hereinafter referred to as NMS) to which the EMS is connected, the coverage area is changed when the current antenna tilt information and tilt angle are changed for each EMS controlled by the EMS. Keep range information. The NE acquires traffic information for storing messages transmitted from the wireless terminal at a predetermined cycle, and transmits the traffic information to a plurality of connected EMSs. Multiple EMSs transmit the traffic information received from the NE to the NMS at a predetermined period, and select the NE with a high load and the NE adjacent to the NE based on the traffic information, and the antenna tilt angle. The amount of change is calculated. Further, a tilt angle change instruction including the calculated tilt angle change amount is transmitted to each NE, and the NE changes the tilt angle of the antenna based on the tilt angle change instruction.

  According to the present invention, while considering the load state of the entire mobile communication system, the base station in the system is automatically controlled to perform load distribution control, thereby improving the average throughput of the entire mobile communication system. it can.

It is a figure explaining the structure of the mobile communication system in one Embodiment of this invention. It is a figure explaining the structure of the network element in one Embodiment of this invention. It is a figure explaining the structure of the element manager in one Embodiment of this invention. It is a flowchart explaining the processing content of the element manager in one Embodiment of this invention. It is a flowchart explaining the processing content of the network element in one Embodiment of this invention. It is a figure which shows the structural example of the table which a network element and an element manager have. It is a figure explaining the change of the antenna tilt angle and the change of the sector cover range. It is a figure explaining the change of the antenna tilt angle and the change of the sector cover range. It is a figure explaining the change of the antenna tilt angle and the change of the sector cover range. It is a figure explaining the change of the antenna tilt angle and the change of the sector cover range.

Embodiments of the present invention will be described below with reference to the drawings.
In this embodiment, paying attention to SON (Self Organizing Network) introduced as one specification of LTE, load distribution control based on the configuration of a centralized management type SON will be described.

FIG. 1 is a diagram for explaining the configuration of a mobile communication system in an embodiment of the present invention.
FIG. 1 shows an example of the configuration of a mobile communication system that realizes a centralized management type SON. SON is a technology that optimizes the network autonomously, and collects and analyzes SON information such as radio signal reception quality and data throughput from operating base stations and wireless terminals as appropriate, and the entire network is optimized. So that the base station settings are autonomously changed. A SON configured to centrally manage and analyze SON information transmitted from a base station in a network is called a centralized SON.

  In FIG. 1, base stations (hereinafter NE: network element) 301 to NE 303 are vendor 1 NEs and have vendor 1 interfaces. NE304 to NE306 are vendor 2 NEs and have vendor 2 interfaces. The example of FIG. 1 shows a configuration in which the NE of vendor 1 and the NE of vendor 2 are connected to element managers (hereinafter referred to as EMS) 201 and EMS 202 for each vendor. The EMS 201 and EMS 202 are further connected to a network manager (hereinafter referred to as NMS) 101.

  Here, whether the NE has a single sector configuration or a multi-sector configuration, the process and configuration described below are the same in terms of content, only depending on whether it is a cell unit or a sector unit. It is. Therefore, in the following embodiments, a case of a multi-sector configuration will be described. If a sector is read as a cell, the case of a single sector configuration can be explained in the same manner.

  In the present embodiment, the NE 301 to NE 306 transmit SON information to both the EMSs 201 and 202 at a predetermined interval (for example, at an interval of 5 minutes). In this embodiment, the SON information is called traffic information. The traffic information of the present embodiment includes the location information of the wireless terminal connected to the NE, the number of NE sector connections, and the sector average throughput of the NE. The NE includes a call detail information log (CDL: Call Detail Log) that temporarily stores a message sent from the wireless terminal, and the position information of the wireless terminal is acquired from the CDL. The number of NE sector connections and the sector average throughput of NE are obtained as statistical data by calculating a numerical value per unit time based on CDL information.

In FIG. 1, SON information (traffic information) sent from NE301 to NE303 and NE304 to NE306 is stored in tables of EMS201 and EMS202, respectively. The EMS 201 and EMS 202 further transmit SON information (traffic information) sent from the NE to the NMS 101. EMS 201 and EMS 202 also transmit and receive SON information (traffic information) between EMSs when a line is installed between EMSs.
In the configuration of the mobile communication system realizing the centralized management type SON of the present embodiment, the SON information (traffic information) is also transmitted from the NE to the NMS 101 via the EMS 201 and EMS 202. Since the SON information (traffic information) is transmitted at intervals of 5 minutes, the SON information (traffic information) held by the EMS 201, EMS 202, and NMS 101 is updated every 5 minutes. The EMS 201, EMS 202, or NMS 101 controls the NE based on the SON information (traffic information). As shown in FIG. 1, when one NE is connected to a plurality of EMSs, the NMS 101 may determine which EMS controls the NEs or may determine in advance. In this way, the mobile communication system of this embodiment includes NEs from different vendors because EMS and NMS share SON information (traffic information) updated in real time (for example, every 5 minutes). By controlling the NE of the entire mobile communication system, the throughput of the entire network is increased.

Next, the configuration of the NE will be described.
FIG. 2 is a diagram illustrating the configuration of the NE according to the embodiment of the present invention.

  As shown in FIG. 2, the NE 301 includes an antenna 311 and a tilt angle changing device 312. The radio base station control device 313 of the NE 301 acquires the location information of the radio terminal from the CDL information stored in the table 314, for example, every 5 minutes, and the sector connection held as statistical data in the table 314 as described above. Get the number, sector average throughput. Then, the traffic information transmitting device 315 transmits the position information, the number of sector connections, and the sector average throughput of those wireless terminals as traffic information to an EMS that is a node above the NE and manages a plurality of NEs. The traffic information tilt angle change instruction acquisition unit 316 receives the tilt angle change instruction sent from the EMS, and stores information such as the tilt angle included in the tilt angle change instruction in the table 314. The radio base station control device 313 converts the tilt angle information stored in the table 314 into a tilt angle control signal, and outputs the tilt angle control signal to the tilt angle change device 312 to tilt the antenna 311. Adjust the angle to control the area covered by radio waves emitted from the antenna.

Next, the configuration of the EMS will be described.
FIG. 3 is a diagram illustrating the configuration of the EMS in the embodiment of the present invention.
The traffic information acquisition unit 211 of the EMS 201 receives traffic information from the NE every five minutes, for example. The traffic information acquisition unit 211 passes the received information to the traffic information time table 212 and stores it. The information processing device 213 reads from the traffic information time table 212, for example, every 5 minutes. The information processing device 213 first compares the read traffic information with the traffic information comparison device 214, and then determines the sector that needs to change the tilt angle with the tilt change target sector selection device 215. Further, based on the acquired traffic information, the tilt angle change angle calculation device 216 calculates the tilt angle change angle, and stores the tilt angle change angle in the tilt change table 217 together with information on the sector that needs to be changed. Then, a tilt angle change instruction is transmitted from the tilt angle change instruction transmitting device 218 to the NE that manages the sector every 5 minutes. Further, the tilt change target sector selection device selects the adjacent sector of the sector that transmitted the tilt angle change instruction from the neighbor list, and selects the adjacent sector that requires the tilt angle change from the traffic information of the adjacent sector. The tilt angle change angle calculating device calculates the change angle of the tilt angle of the selected adjacent sector. Then, the information is stored in the tilt angle change table, and the tilt angle change instruction is transmitted from the tilt angle change instruction transmission device of the target sector to the NE that manages the target adjacent sector. The selection of the adjacent sector and the calculation of the tilt angle change angle of the adjacent sector may be performed together with the selection of the first sector and the calculation of the change angle of the tilt angle. You may go after it is over.

  If the EMS that manages the adjacent sector whose tilt angle is to be changed is another EMS, the information on the tilt angle change angle is also transmitted to the EMS and also to the NMS of the upper node. The EMS 201 collects the traffic information of the sector under the management from the adjacent EMS (EMS that manages the neighboring sector existing in the neighbor list of the sector to be managed) and the upper node NMS, and registers it in the traffic information time table 212. Keep it.

Next, the processing flow of EMS and NE will be described.
FIG. 4A is a flowchart for explaining the processing contents of the EMS in the embodiment of the present invention.
The EMS collects sector traffic information from the traffic information table, for example, every 5 minutes (S401), and compares the number of connections in each sector with a predetermined threshold (S402). If there is a sector in which the connection number of the sector exceeds the predetermined connection number threshold, the number of connections is further checked for other sectors, and the sector having the maximum connection number is selected (S403). If the number of connections is less than or equal to the threshold value in all sectors in S402, the process returns to step S401 for reading traffic information.
The EMS targets the sector selected in S403 to be changed in the direction of decreasing the tilt angle, and subsequently selects adjacent sectors to be changed in the direction of increasing the tilt angle from the position information of the wireless terminal and the neighbor list.
Next, a tilt angle change angle is calculated for a sector to be changed in a direction to decrease the tilt angle and a sector to be changed to a direction in which the tilt angle is increased in an adjacent sector of the sector (S405). Then, a tilt angle change instruction to be transmitted to each sector and the tilt angle change angle are stored in a table, and a tilt angle change instruction is transmitted to all sectors whose tilt angle is to be changed (S406).
When such a series of operations ends, the process returns to S401 for collecting traffic information again.

FIG. 4B is a flowchart for explaining processing contents of the NE in the embodiment of the present invention.
For example, the NE reads the traffic information and the tilt angle change instruction from a table storing the traffic information of the sector managed by the NE and the tilt angle change instruction transmitted from the EMS every 5 minutes, for example. The NE sends the traffic information of the read sector to the EMS (S412), and checks whether the tilt angle change instruction has been issued from the EMS, and if so, the tilt angle control signal based on the tilt angle change angle. Is transmitted to the tilt angle changing device, the tilt angle of the antenna is changed as instructed, and the process returns to S414 and S411. If there is no tilt angle change instruction, the process returns to S411 in the instruction waiting state.

Next, the configuration of the table that NE and EMS have will be described.
FIG. 5A is a diagram illustrating a configuration example of an EMS traffic information time table.
FIG. 5B is a diagram illustrating a configuration example of an EMS tilt angle change table.
FIG. 5C is a diagram showing a configuration example of the NE traffic information / tilt angle change time table.
FIG. 5D is a diagram illustrating a configuration example of the NE traffic information / tilt angle change time table.

  The traffic information time table of the EMS shown in FIG. 5A includes a cell number, a sector number when the NE has a multi-sector configuration, the number of connections in the cell (the sector in the case of a sector configuration), and the cell (sector It has location information of each wireless terminal connected to that sector in the case of a configuration, and information on average throughput of a cell (in the case of a sector configuration, that sector). The traffic information time table is updated every 5 minutes, for example, and the latest data is stored.

  The description so far has been based on the configuration of a single sector. However, in the description using FIG. 5, as an example, six NEs NE1 to NE6 are connected to the EMS, and each of the six NEs is a cell. 1 to 6 are formed, and these cells are described as having a three-sector structure. Further, it is assumed that sector 1 of cell 1, sector 3 of cell 2, sector 2 of cell 5 and sector 1 of cell 6 are adjacent to each other and are in the neighbor's neighbor list (can be handed off). . The threshold value of the number of connections per sector for determining whether or not load distribution is necessary is 5000.

  In FIG. 5A, the sector 1 of the cell 1 and the sector 3 of the cell 2 have exceeded the threshold number of connections, and the number of connections is large in the tilt angle change target sector selection device in the EMS information processing device. Sector 1 of cell 1 is selected as a sector whose tilt angle is to be lowered. In addition, the tilt angle changing target sector selecting device selects the sector 3 of the adjacent cell 2 as a sector for increasing the tilt angle. Next, the tilt angle change angle is calculated by the tilt angle change angle calculation device of the information processing apparatus. The tilt angle change angle calculation device has a built-in simulator for calculating the radio wave quality of the area accompanying the change of the tilt angle. This simulator has in advance the transmission power and antenna height of each sector managed by the EMS, the current tilt angle data, and the like. For each sector managed by the EMS, data is also stored in advance for the range that can be covered when the tilt angle of the antenna is changed. Based on the wireless terminal position information (traffic map) and the sector average throughput, the simulator determines to which wireless terminal the sector should be covered in order to distribute the load. It is calculated how many times the tilt angle should be changed for the sector to cover. For example, the tilt angle of cell 1 sector 1 is decreased by 2 degrees, and the tilt angle of sector 3 of cell 2 is increased by 3 degrees.

FIG. 5B shows a configuration example of a tilt angle change table provided in the EMS.
The tilt angle change table is made up of cell number, sector number and tilt angle change angle information to be changed. Information is passed from the information processing apparatus of the EMS and stored in the tilt angle change table. In the example of FIG. 5B, since sector 1 of cell 1 and sector 3 of cell 2 are sectors of the tilt angle change target cell, values are entered in the columns of the tilt angle change angle, respectively. Since sector 2 of cell 5 and sector 1 of cell 6 are not subject to tilt angle change, the tilt angle change angle column is “0”.

FIGS. 5C and 5D show a configuration example of the traffic information / tilt angle change time table provided in the NE of cell 1 and the NE of cell 2 that are tilt angle change targets.
The traffic information / tilt angle change time table in FIGS. 5C and 5D includes the sector number of the tilt angle change target sector, the number of connections of the sector, the position information of the wireless terminals connected to the sector, and the sector average. It has information on the throughput and the tilt angle change angle of the sector. In the traffic information / tilt change time table, sector traffic information (number of connections, wireless terminal position information, sector average throughput) is accumulated, and tilt angle change angle data is received from the EMS and stored. FIGS. 5C and 5D show only information for one sector, but in reality, information for three sectors is stored and is always updated to the latest data. Sent to EMS every 5 minutes.

FIG. 6 is a diagram for explaining how the sector coverage is changed by changing the antenna tilt angle.
The sector area is reduced by lowering the antenna tilt angle. Conversely, when the antenna tilt angle is increased, the sector area expands.

The manner in which the sector coverage is changed by changing the tilt angle of the antenna, the deviation in the number of connections is corrected, and the load is distributed will be described with reference to FIGS.
First, FIG. 7 shows an example in which a sector of NE1 with a large number of users and a sector of NE2 with a small number of users exist at a certain time. There are variations in load between adjacent sectors.
FIG. 8 is a conceptual diagram showing a target area for solving the variation in load between the sector of NE1 and the sector of NE2.
The sector of NE2 is a sector in the list (neighbor list) of wireless cells that are candidates for handoff reported from the sector of NE1. The neighbor list is updated when an NE is added or deleted, and the updated neighbor list information is also transmitted to the EMS / NMS. If there is a bias in the number of connected users between sectors, the tilt of the sector antenna with a large load is adjusted downward according to the flow described above, and an adjacent sector with a small load adjacent to the sector is selected, and the tilt angle of the sector is selected. Adjust so that is raised.
FIG. 9 shows the cover range after changing the tilt angle. In accordance with the flow of this embodiment, the tilt angle of the NE1 sector and the NE2 sector is controlled so as to change the cover range to the target position based on the position information of the wireless terminal, thereby connecting to a sector with a high load. Wireless terminals can be handed off to adjacent sectors, and the sector load can be distributed.

  In the present embodiment described above, the NE has a traffic information / tilt change information time table, and traffic information (wireless terminal location information, number of sector connections, sector average throughput) based on CDL information updated in real time. ) Is acquired and created, and stored in the traffic information / tilt change information time table. The information is then passed to the EMS and the NMS that is above it. The EMS / NMS has a traffic information time table and a tilt change information table, compares the traffic information collected from each subordinate cell, decides the sector for tilt change, calculates the tilt angle change angle, To pass. The NE whose tilt is to be changed changes the tilt angle based on the information.

  With this configuration, this embodiment enables the EMS / NMS to control the load of each sector of the NE in the entire system based on the sector traffic information updated in real time. It is possible to perform load distribution control corresponding to load conditions that change every moment. Moreover, even when the vendors are different and the interfaces are different, by adopting such a configuration, traffic information including the sectors of NEs of different vendors can be collected and load distribution can be controlled. In the system of the present embodiment, since the EMS / NMS always performs load sharing control between sectors based on traffic information, it is considered that the handoff destination neighboring cell does not fall into a high load state.

101 Network Manager 201, 202 Element Manager 211 Traffic Information Acquisition Unit 212 Traffic Information Time Table 213 Information Processing Device 214 Traffic Information Comparison Device 215 Tilt Angle Change Target Sector Selection Device 216 Tilt Angle Change Angle Calculation Device (Built-in Simulator)
217 Tilt angle change table 218 Tilt angle change instruction transmission device 219 Neighbor list 301 to 306 Network element 311 Antenna 312 Tilt angle change device 313 Radio base station control device 314 Table 315 Traffic information transmission device 316 Traffic information tilt angle change instruction acquisition unit

Claims (8)

A mobile communication system having a network element connected to a plurality of wireless terminals, a plurality of element managers each connected to a plurality of network elements, and a network manager to which the plurality of element managers are connected. And
When the element manager changes the current antenna information and the information on the change range of the cover area and the antenna tilt angle when the antenna tilt angle is changed for each network element controlled by the element manager Has a simulator that simulates the change range of
The network element acquires traffic information of the network element at a predetermined cycle based on information transmitted from the wireless terminal, and transmits the traffic information to the connected element managers. The plurality of element managers transmit the traffic information received from the network element to the network manager at the predetermined period, and based on the traffic information, select the network element having a high load and Select a network element adjacent to the network element, and change the load range using the simulator based on the current antenna information and the change information of the coverage area when the antenna tilt angle is changed and the traffic information. The change amount of the tilt angle of the antenna for load distribution is calculated for each network element and the adjacent network element, and the tilt angle change instruction including the calculated change amount of the tilt angle is calculated for each network element. The mobile communication system, wherein the network element changes the tilt angle of the antenna based on the tilt angle change instruction.   2. The mobile communication system according to claim 1, wherein the traffic information includes the number of connections of network elements, location information of connected wireless terminals, and average throughput of network elements.   The mobile communication system according to claim 1, wherein the network element includes a plurality of sectors, and the tilt angle of the antenna is controlled in units of sectors.   The network element includes a plurality of types of network elements having different interfaces between the network element and the element manager, and the network manager performs control between the element managers to thereby control the plurality of different types of network elements. 2. The mobile communication system according to claim 1, wherein tilt angle change control of the entire mobile communication system including elements is performed. Load distribution method in mobile communication system having network element connected to a plurality of wireless terminals, a plurality of element managers connected to a plurality of network elements, and a network manager connected to the plurality of element managers Because
Each of the element managers has current antenna information and information on the change range of the cover area when the antenna tilt angle is changed for each network element controlled by the element manager,
The network element acquires traffic information of the network element at a predetermined cycle based on information transmitted from the wireless terminal, and transmits the traffic information to the connected element managers. The plurality of element managers transmit the traffic information received from the network element to the network manager at the predetermined period, and based on the traffic information, select the network element having a high load and When the network element adjacent to the network element is selected and the current antenna information and the tilt angle of the antenna are changed, the high-load network For placement and adjacent network element, calculating a change amount of the tilt angle of the antenna, for each network element, and transmits the tilt angle change instruction including the amount of change in the tilt angle the calculated,
The load distribution method in a mobile communication system, wherein the network element changes the tilt angle of an antenna based on the tilt angle change instruction.   6. The load distribution method according to claim 5, wherein the traffic information includes the number of connections of network elements, location information of connected wireless terminals, and average throughput of network elements.   6. The load distribution method according to claim 5, wherein the network element includes a plurality of sectors, and the tilt angle of the antenna is controlled in units of sectors.   The network element includes a plurality of types of network elements having different interfaces between the network element and the element manager, and the network manager performs control between the element managers to thereby control the plurality of different types of network elements. 6. The load distribution method according to claim 5, wherein tilt angle change control of the entire mobile communication system including elements is performed.

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