JP5002322B2 - Base station apparatus and radio resource use method in mobile communication system - Google Patents

Description

  The present invention generally relates to the technical field of mobile communication, and more particularly to a base station apparatus and method in a mobile communication system.

  In this type of technology, research and development on next-generation mobile communication systems is proceeding at a rapid pace. For example, in order to realize a fixed and mobile convergence (FMC) service, research on ultra-small base stations is underway. Has been. In this communication system, various cells are allowed to coexist in the same region, and in addition to a macro cell, a pico cell, a femto cell, and the like may exist. Furthermore, a home base station (Home eNB) that allows only a specific user to access is also proposed. The micro base station is called “Home NB” in the third generation (3G) and “Home eNB” (hereinafter collectively referred to as “Home eNB”) in the super 3G (S3G). These are desired to be realized with a size, price, setting conditions, and operating conditions that can be installed at home. Home eNB is described in Non-Patent Document 1, for example.

In this way, there are various cells in the same area in the future, and there is a possibility that various services will be performed, and it is expected that appropriate communication will be performed in each cell. However, the required level of communication quality desired in each of these cells may not be the same. For example, when a pay-per-use cell and an inexpensive flat-rate cell coexist, it may be desirable that the former communication quality is superior. In addition, it may be desirable to maintain a high-quality communication with a tighter tolerance for delay in a cell in which more users (particularly, users performing real-time communication) are located. Alternatively, the quality of a cell that is processing more traffic may be improved. As described above, various requests for communication quality may occur depending on various cells and / or services, but it is difficult to appropriately respond to these requests using conventional technology.
3GPP TSG RAN # 35, RP070209, 6-9March 2007

  An object of the present invention is to give priority to communication in a specific cell in a mobile communication system over communication in another cell.

A base station apparatus according to an aspect of the present invention provides:
A base station apparatus in a mobile communication system,
Means for acquiring at least the priority value that takes a higher value as the number of users residing in the cell increases for the base station device and the adjacent base station device;
First interference power received when the base station apparatus uses the first radio resource, and second interference received when the base station apparatus uses the second radio resource of the adjacent base station apparatus When the power satisfies a predetermined magnitude relationship and the priority of the base station device is higher than the priority of the adjacent base station device, the base station device uses the second radio resource and A base station apparatus having means for notifying an adjacent base station apparatus to use the first radio resource to the adjacent base station apparatus and performing communication using the second radio resource .

  According to the present invention, communication in a specific cell in a mobile communication system can be prioritized over communication in another cell.

  The base station (eNB) by one form of this invention notifies the indicator which shows the priority of an own station to a periphery base station. The notification may be notified wirelessly as broadcast information (BCH), or may be transmitted through a network (for example, an X2 interface) between base stations. In the case of radio, the neighboring base station may directly receive the BCH, or may report to the base station after the mobile station receives it. The base station compares the priority of its own station with the priorities of neighboring base stations. Depending on the comparison result, the radio resources (used frequency, time slot, code, space, uplink interference amount, base station transmission power, etc.) used by the base station are changed. As an example, each frequency band is changed so that the frequency band of the base station is replaced with the frequency band of an adjacent base station. The priority is the radio resource usage status (frequency used, time, code, space, uplink interference amount, base station transmission power, etc.), communication type, base station type, accommodated traffic volume, total number of users in the serving cell, real-time communication The base station may determine autonomously according to the number of users and the ratio thereof.

  As a result, it is possible to reliably improve the communication quality of the base station having a high priority. In conventional base stations, it is difficult to perform such priority control. According to an aspect of the present invention, each base station can appropriately and appropriately set an appropriate radio resource according to the priority by communicating the priorities with each other. In other words, regarding this priority control, an instruction by an upper node such as a mobility management entity (MME: Mobility Management Entity) is not essential.

FIG. 1 shows a mobile communication system according to an embodiment of the present invention. The mobile communication system 1000 is a system to which, for example, Long Term Evolution (LTE), Super 3G, Evolved UTRA and UTRAN may be applied. The mobile communication system 1000 includes a base station (eNB: eNode B) 200n (200 ₁ , 200 ₂ , 200 ₃ ,...; N is a positive integer) and a plurality of mobile stations 100 _n (100 ₁ ) communicating with the base station 200n. , 100 ₂ , 100 ₃ ,...; N is a positive integer). The base station 200n may be a base station that does not restrict users accessing in a macro cell, a pico cell, a femto cell, or the like, or may be a home base station (Home eNB) that can be accessed only by a specific user. Various cell configurations may be used. For example, a plurality of cells may coexist in the same area. Home base station in the region 50 ₂ of a certain macro cell in the illustrated example (Home eNB) 50 ₃ cells may be set. The base station 200n is connected to an upper station, for example, a mobility management device (MME / UPE) or an access gateway device (aGW) 300, and the MME / UPE 300 is connected to the core network 400. The mobile station 100n is connected to any cell and performs communication. The mobile station 100n is any communication terminal used by the user. The communication terminal used by the user is more generally a user equipment (UE: User Equipment), which may be a mobile terminal or a fixed terminal.

  FIG. 2 is a flowchart showing one of the operations performed in the base station 200n. This flow shows an operation example for updating the priority of a cell. `` Cell priority '' is a metric that indicates how high the quality of communication is required for the cell, and radio resources (( Used frequency, time slot, code, space, uplink interference amount, base station transmission power, etc.) are set.

  In step S1, a timer is started to measure a certain observation period T.

  In step S2, various quantities that affect the communication quality are observed. Specific examples of such amounts include the usage status of radio resources (frequency used, time slot, code, space, uplink interference amount, base station transmission power, etc.), traffic volume, total number of users in the serving cell, service type The number of users, their ratio, the degree of congestion, etc. may be included. Examples of the number of users for each service type include the number of users that require high QoS such as voice communication, the number of users that may have relatively low QoS such as data communication, and the like. These various quantities are observed and aggregated during the observation period T described above.

  In step S3, it is determined whether or not the observation period T has expired. If it has not expired, the process returns to step S2 to continue observation, and if it has expired, the flow proceeds to step S4.

  In step S4, the priority of the own station (base station) is updated based on the amount observed and aggregated in step S2 and the type of base station eNB, etc. (updating only changes from one value to another) It may also include maintaining the same value.)

  The priority may be derived from various viewpoints. For example, the base station type may be added to the priority. There are macro cell base stations (Macro eNB) that can be accessed by unspecified users, and home cell home base stations (Home eNB) that only specific users can access, and the macro cells are charged according to the amount of traffic. However, it is assumed that the home cell is an inexpensive flat-rate system. In this case, the priority of the macro cell may be set higher than the priority of the home cell. Alternatively, the home cell fee may be set higher than the macro cell, the home cell priority may be set higher than the macro cell priority, and high-quality communication may be performed in the home cell.

  From the viewpoint of improving communication quality for a larger number of users, the priority of cells having a large traffic capacity and the number of users may be set high, and the priority of cells having a small number of users may be set low.

  The service type or QoS may be added to the priority. For example, a higher priority may be set as the number of users performing communication (for example, voice communication, real-time data communication, etc.) in which delay is not allowed is greater. Alternatively, a low priority may be set if there are a large number of users performing communications that are relatively easy to allow delay (for example, non-real-time data communications).

  FIG. 3 shows a state in which priority elements are derived from the viewpoint of the base station type, the amount of accommodated traffic, the number of voice users, etc., and the priority of one cell is derived by summing those priority elements. In the illustrated example, for convenience of explanation, the priorities and priority elements for a plurality of cells are expressed in a table format, but the content of a specific cell corresponds to one row in the table. The content of the priority element and the method for deriving the priority shown in the drawing are merely examples, and various priorities may be defined. In any case, a priority is uniquely derived for the cell from one or more sets of various quantities observed and aggregated in step S2. Note that the priority may be referred to as a priority indicator (ePI: eNB Priority Indicator).

  In step S4 of FIG. 2, one priority is derived from a predetermined group of priority elements in each cell, and the priority of the cell is updated (the update includes both change and maintenance).

  In step S5, the updated priority is notified to the neighboring cells. The priority may be notified directly to the neighboring base station as broadcast information (BCH), or the mobile station may receive the BCH and report it to the neighboring base station. Moreover, you may notify via some network between base stations. From the viewpoint of simplified and prompt notification, it is desirable to notify the priority with broadcast information (BCH). Thereafter, the flow returns to step S1, and the described procedure is repeated. The priority may be updated periodically, irregularly, or updated when some event occurs. Some events include changes in radio resource usage such as the amount of uplink interference and tightness of base station transmission power, and the establishment and removal of base stations.

FIG. 4 shows how the radio resources of a cell are determined using priority. For convenience of explanation, a certain frequency band (carrier #X) is used in the first cell 50 ₁ (eNB1) in FIG. 1, and another frequency band (carrier #Y) is used in the adjacent second cell 50 ₂ (eNB2). Suppose that it was used. Among the steps shown in FIG. 4, the shaded blocks are related to the processing at the first base station (eNB1), and the unshaded blocks are related to the processing at the second base station (eNB2). .

  In step S1, the first and second base stations (eNB1, eNB2) operate on carriers #X and #Y, respectively.

  In step S2, the first base station eNB1 measures the interference power for each of several carrier candidates. In this embodiment, there are only two carrier candidates, carriers #X and #Y, but more candidates may be prepared. What is a carrier candidate may be determined in advance in advance, or may be notified from a higher-order node or another cell as necessary. The first base station eNB1 receives interference power (interference power 1) received from another cell when carrier #X is used, and interference power (interference power 2) received from another cell when carrier #Y is used. ).

  In step S3, the magnitude relation of the interference power measured for each carrier candidate is compared. In step S3, the comparison is performed in consideration of a certain offset “a”, not the magnitude comparison of the interference power itself. The offset is set so that the interference for a carrier candidate that is not currently used is larger than the actual interference power. Thus, the carrier can be prevented from being changed as much as possible, and the system can be stabilized. As a result of the size comparison, if the interference of the currently used carrier #X is considerably large, the flow proceeds to step S4. If not, the flow returns to step S2 to measure other cell interference power.

  In step S4, the priorities of the cells are compared. As described in step S5 of FIG. 2, the priority is updated in each base station, and the updated priority is notified to neighboring base stations by a broadcast signal (BCH) or the like. Therefore, the first base station eNB1 has already received the priority of the neighboring cell in addition to updating the priority of the own station. When the flow reaches step S4, the interference power 2 is considerably lower than the interference power 1. Therefore, if the first base station eNB1 uses the carrier #Y, the interference from other cells is considerably lower than that at the present time, and the quality of communication can be improved. Since the carrier #Y is currently used by the second base station eNB2, the first base station eNB1 is not allowed to change the carrier from #X to #Y without permission, but the first base station eNB1 From the viewpoint of interference suppression, the second base station eNB2 may use #Y for the carrier #X. However, if such a carrier change is made between the first and second base stations, the quality improvement for the cell of the first base station eNB1 is guaranteed, but the communication quality for the cell of the second base station eNB2 is Not guaranteed. This may be acceptable if the first base station has been set to a higher priority than the second base station, but should not be allowed otherwise. From this point of view, the priority of each base station is compared in step S4. If the priority of the first base station eNB1 is higher, the flow proceeds to step S5, otherwise the flow returns to step S2 or S3. .

  In step S5, exchange request signals for carriers #X and #Y are transmitted from the first base station eNB1 to the second base station eNB2.

  In step S6, such an exchange request signal is received by the second base station eNB2.

  In step S7, the priority is compared in the second base station eNB2 as well as in the first base station eNB1. This is because the priority may change over time. If the priority of the first base station eNB1 is higher, the flow proceeds to step S10, otherwise the flow proceeds to step S8.

  The case of reaching step S8 is a case where the priority of the second base station eNB2 is higher than that of the first base station eNB1 requesting the carrier exchange, and the carrier exchange is no longer desirable. Accordingly, the second base station eNB2 returns a signal indicating that the exchange is rejected to the first base station eNB1.

  In step S9, when there are other exchange base stations for carriers #X and Y, an exchange request signal is transmitted to the other base stations.

  In step S10, an exchange response signal indicating that the second base station eNB2 responds to the exchange request for the carriers #X and #Y is transmitted to the first base station eNB1.

  In step S11, the first base station eNB1 receives the exchange response signal.

  In step S12, the first base station eNB1 transmits a reception confirmation response to the second base station eNB2, and the second base station eNB2 receives it in step S13.

  In step S15, the first base station NB1 changes the carrier from #X to #Y.

  In step S16, the second base station NB2 changes the carrier from #Y to #X.

  When the carrier is changed in steps S15 and S16, if a mobile station exists in the cell, notification indicating that the carrier is changed and a necessary process are performed for each mobile station.

  The above procedure is performed in the first and second cell base stations (eNB1, eNB2), but may be performed between the second and third cell base stations. In order to simplify the explanation, there are only two carrier candidates, but three or more carrier candidates may be compared and examined. Priorities are compared in steps S4 and S7, but if priority update frequency is relatively low or if communication between base stations is performed at high speed, step S4 is integrated into step S7. Also good. However, from the viewpoint of reducing the exchange of exchange request signals between base stations, it is desirable that both steps S4 and S7 are performed as shown in FIG. Communication between base stations that may be performed in steps S5, S6, S8-S14, etc. may be performed by wire or may be performed by radio. When performed wirelessly, it may be via a mobile station.

  In the above description, the radio resource is a certain frequency band (carrier), but may be a time slot, a frequency block (resource block), transmission power, a code (code), or some combination thereof.

When the radio resource is a time slot, for example, whether or not the first base station changes the time slot from #X _T to #Y _T and the second base station changes the time slot from #Y _T to #X _T depends on the interference power. It may be determined from the viewpoints of the size and the priority level.

  If the radio resource is a frequency block (resource block), for example, it is possible to improve the quality of communication using the specific resource block by preventing the low priority base station from using the specific resource block as much as possible. Good.

  When the radio resource is the transmission power of the base station, for example, it is conceivable that the high priority base station transmits with strong power and the low priority base station transmits with low power.

  FIG. 5 shows a block diagram of a base station according to an embodiment of the present invention. FIG. 5 shows a base station 200n and one peripheral base station 200m. For simplicity, only one neighboring base station is depicted, but in practice there may be more than one neighboring base station. The base station 200n includes a signal reception unit 502, an accommodated traffic amount calculation unit 504, an ePI calculation unit 506, a broadcast signal generation unit 507, an ePI table storage unit 508, an ePI comparison unit 510, an interference power measurement unit 512, and an interference power comparison unit 514. , A radio resource control unit 516, an exchange request signal generation unit 520, an exchange response signal generation unit 522, a reception confirmation response signal generation unit 524, and a signal transmission unit 530.

  The signal reception unit 502 and the signal transmission unit 530 receive a signal from the neighboring base station 200m or the connected mobile station and transmit the signal thereto. The communication partner of the base station 200n is a user apparatus, an upper node (MME / UPE), etc., but in the example shown in the figure, attention is paid to communication with other base stations.

  The accommodated traffic amount calculation unit 504 measures the number of users performing wireless communication with the base station 200n. If necessary, the amount of data being communicated may be measured. For the sake of simplification, only the traffic amount calculation unit is illustrated, but as described in step S2 of FIG. 2, various amounts such as radio resource usage that affects communication quality are observed. Good (such amount is a priority factor).

  The ePI calculation unit 506 derives a priority or priority indicator (ePI) from priority elements such as traffic volume.

  The notification signal generation unit 507 creates a notification signal. The broadcast signal may include various pieces of information unique to the cell, but it should be noted that priority may be included in the present embodiment. The priority may be notified to neighboring base stations by a signal other than the broadcast signal.

  The ePI table storage unit 508 stores the priority updated by the ePI calculation unit 506. In addition to priority, priority elements may be stored as needed.

  The ePI comparison unit 510 compares the priorities of the respective base stations as in step S4 of FIG. 4, and radio resources (frequency used, time slot, code, space, uplink interference amount, base station transmission power, etc.) It is determined whether or not a change is required. The determination result is notified to the radio resource control unit 516.

  The interference power measurement unit 512 determines, for each candidate, how much interference is received when the candidates are used for various radio resource candidates, as performed in step S2 of FIG. taking measurement.

  The interference power comparison unit 514 examines the magnitude relationship of interference expected in each radio resource candidate. The radio resource control unit 516 is notified of the magnitude relationship.

  The radio resource control unit 516 manages radio resources allocated to each mobile station.

  The exchange request signal generation unit 520 determines whether or not the radio resource should be changed based on at least one of priority level and interference power level. If it is to be changed, an exchange request signal is created and transmitted as done in step S5 of FIG.

  The exchange response signal generation unit 522 creates an exchange response signal as performed in step S10 of FIG. 4 when changing the radio resource according to the exchange request signal received from another cell.

  If the radio resource can be changed as desired, the reception confirmation response signal generation unit 524 creates a reception confirmation response signal as performed in step S12.

It is a figure which shows a mobile communication system. It is a flowchart for updating the priority of a cell. It is a figure which shows the example of a table which shows a priority and a priority element for every cell. 6 shows a flowchart for determining radio resources of a cell using priority. 1 shows a block diagram of a base station according to one embodiment of the present invention.

Explanation of symbols

1000 Mobile communication system
50 _n cells
100 _n mobile station
200 _n base station
300 MME / UPE
400 core network
502 Signal receiver
504 Traffic volume calculation section
506 ePI calculator
507 Notification signal generator
508 ePI table storage
510 ePI comparator
512 Interference power measurement unit
514 Interference power comparator
516 Radio resource control unit
520 Exchange request signal generator
522 Exchange response signal generator
524 Reception confirmation response signal generator
530 signal transmitter

Claims (6)

A base station apparatus in a mobile communication system,
Means for acquiring at least the priority value that takes a higher value as the number of users residing in the cell increases for the base station device and the adjacent base station device;
First interference power received when the base station apparatus uses the first radio resource, and second interference received when the base station apparatus uses the second radio resource of the adjacent base station apparatus When the power satisfies a predetermined magnitude relationship and the priority of the base station device is higher than the priority of the adjacent base station device, the base station device uses the second radio resource and A base station apparatus comprising: means for notifying the adjacent base station apparatus that the adjacent base station apparatus should use the first radio resource, and performing communication using the second radio resource .   The base station apparatus according to claim 1, wherein the priority is updated regularly or irregularly. It said first and second radio resource, the base station apparatus according to claim 1 or 2 using the frequency, specified by the transmission time slot or the base station power. A method for using radio resources in a mobile communication system , comprising:
The first base station apparatus obtains a priority value that takes a higher value as the number of users residing in the cell increases at least for the first base station apparatus and the adjacent second base station apparatus,
The first interference power received when the first base station apparatus uses the first radio resource, and the first base station apparatus uses the second radio resource of the second base station apparatus And the second interference power received in the case satisfies a predetermined magnitude relationship, and the first base station device has a higher priority than the second base station device, the first A radio resource use method comprising: a base station device using the second radio resource, and the second base station device communicating using the first radio resource .   The radio resource usage method according to claim 4, wherein the priority is updated regularly or irregularly.   The radio resource usage method according to claim 4 or 5, wherein the first and second radio resources are designated by a use frequency, a time slot, or base station transmission power.

Images