KR20090032518A - Method and apparatus for load balancing during handover in wideband communication system - Google Patents

Abstract

A method and an apparatus for balancing a load during handover in a wideband communication system are provided to balancedly distribute wireless resources to multi users in the wideband communication system comprised of sub cells, thereby maximizing a wireless use ratio. When a handover request is received from a terminal, a load check target sub cell is selected(102). Load check is requested to the selected sub cell so that a device receives a report of a load state(104,106). A load state result is reported through a handover response message or a base station handover request message to the terminal(108).

Description

METHOD AND APPARATUS FOR LOAD BALANCING DURING HANDOVER IN WIDEBAND COMMUNICATION SYSTEM}

The present invention relates to load balancing in a communication system, and more particularly, to a method and apparatus for load balancing in handover in a broadband communication system.

In the conventional circuit switched based communication network such as Code Division Multiple Access (CDMA) or Global System for Mobile (GSM), since the required capacity and allocated radio resources are constant for each connection, Load Balancing is performed. You only need to check the number of subscribers and connections. In the following description, one connection is called a service flow (hereinafter referred to as "SF").

However, various traffic characteristics (e.g. real-time vs non-real-time, fixed bits) in 3rd generation and later wireless networks such as World Interoperability for Microwave Access (hereinafter referred to as "WiMAX") or 3rd Generation Partnership Project (3GPP) and / or 3GPP2. A single base station must simultaneously support multimedia applications with rate vs. variable bit rate, and advanced access technologies (AMC, HARQ, PF scheduling, and MIMO) are applied differently according to each traffic characteristics, so that the number of subscribers and the number of connections can be checked. It is difficult to do load balancing. Due to these various traffic characteristics, Call / Connection Admission Control (hereinafter referred to as "CAC") must also check the bandwidth requirements for each connection by traffic type, and the RF scheduler also requires processing time for each connection. There is a burden to schedule the differential.

In relation to load balancing, the current broadband wireless communication system standard (eg, IEEE 802.16) has the following problems.

First, in case of a handover, after moving to a target subcell and performing a ranging request (HO_RNG_REQ) for handover, if the corresponding FA (Frequency Assignment) load is large based on the number of calls (or the number of users), another FA in the target sector is TLV. The base station reports to the terminal through a ranging response (HO_RNG_RSP) message for handover. In this case, since the terminal operation is not clearly defined in a spec, the terminal may perform an initial network entry procedure using another available FA. Therefore, if the terminal performs an initial network entry procedure to another FA, the handover procedure may be as long as that.

Second, the UE can know which subcells exist around itself with reference to the BSID (Base Station ID) listed in the NBR-ADV (Neighbor Advertisement) message, and can be used when requesting a handover (MSHO-REQ). . However, the terminal cannot check the load state of each subcell by itself. Here, the subcells and the BSIDs have one-to-one matching. In addition, there is no way to directly inform the UE of the load status from the serving base station, and for BSIDs with a heavy load among BSIDs in which the UE reports a radio state (eg, CINR / RSSI) through the MSHO-REQ. By not performing a handover response (MSHO-RSP), it is possible to indirectly inform the load state. If there is no allowable BSID among the BSIDs requested by the UE, the remaining BSIDs in the NBR-ADV need to be rescanned. Usually, since the candidate BSIDs are 6 or more, the terminal scans only a part and loads the serving base station again. The procedure for querying the status can be repeated.

As described above, the present invention proposes a method and apparatus for maximizing wireless utilization by balancing radio resources to multiple users in a handover in a broadband wireless communication system including one or more subcells.

According to a first aspect of the present invention for achieving the above objects, in a broadband communication system, a method for operating a base station for load equalization during handover, wherein a load check target subcell (Sub-) is received when a handover request is received from a terminal. Selecting a cell, requesting a load check to the selected subcell, reporting a load status, and notifying the terminal of a result of the load status through a handover response message or a base station handover request message; Characterized in that it comprises a.

According to a second aspect of the present invention for achieving the above objects, in a broadband communication system, a method for operating a base station for load equalization during handover, wherein a load check target subcell (Sub-) is received when a handover request is received from a terminal. Cell), a process of performing a load check based on a load state periodically reported from the neighboring subcells after selecting the load check sub-cell, and a handover response message or a base station based on the load check result. And notifying the terminal through a handover request message.

According to a third aspect of the present invention for achieving the above objects, in a broadband operation system, a method for operating a terminal for load balancing in a handover, the load state of sub-cells through a handover response message or a base station handover request message And a step of receiving the notification and scanning the handover target BSIDs by determining the load state.

According to a fourth aspect of the present invention for achieving the above objects, a base station apparatus for load equalization during handover in a broadband communication system, when receiving a handover request from a terminal, a sub-cell to be checked for load A sub-cell selection unit for selecting a load), a load check requesting unit for requesting a load check of the selected sub-cells through a backhaul network, a load checking unit for reporting a load state of the requesting sub-cells through the backhaul network; And a load status notification unit for notifying the terminal of the load status result through a handover response message or a base station handover request message.

According to a fifth aspect of the present invention for achieving the above objects, in a base station apparatus for load equalization during handover in a broadband communication system, when receiving a handover request from a terminal, a load check target subcell (Sub-Cell) ), A subcell selecting unit for selecting the subcell, a load checking unit performing a load check based on a load state periodically reported from the neighboring subcells after selecting the subcell to be loaded, and a handover result of the load checking result. And a load status notification unit for notifying the terminal through a response message or a base station handover request message.

 In a broadband wireless communication system consisting of one or more subcells, there is an advantage of maximizing wireless utilization by balancing radio resources among multiple users.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of related well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, a method and apparatus for load balancing during handover in a broadband communication system will be described.

1 to 4, a base station is divided into several sectors and one or several FAs are assigned. In addition, one sector is divided into several sub-cells. Accordingly, a BSID (Base Station ID) is allocated to each subcell so that the subcell and the BSID are matched one-to-one. However, since one FA can be allocated to several sectors, the FA and BSID do not match one-to-one.

1 is a flowchart illustrating an operation of a base station for performing load balancing in a broadband wireless communication system according to a first embodiment of the present invention. 1 illustrates a case in which a requirement of a corresponding UE is transmitted to a target subcell and a load check subject is a target subcell.

Referring to FIG. 1, when the base station receives a handover request (MSHO-REQ) from the terminal in step 100, the base station selects a load check target subcell in step 102. In this case, the handover request message includes BSIDs for one or more neighboring subcells obtained by scanning by the UE.

For example, as a method of selecting the load check target subcell, a method of selecting BSIDs designated by the terminal through a handover request message, and the same BSIDs in addition to the BSIDs designated by the terminal through a handover request message. There is a method of selecting all other BSIDs allocated to a sector (when several BSIDs are assigned to one sector), a method of selecting all BSIDs listed in a NBR-ADV (Neighbor Advertisement) message, and the like.

Thereafter, the base station requests a load check from the target subcell through the backhaul network in step 104.

Thereafter, the base station receives a load status report from the target subcell through the backhaul network in step 106. At this time, for example, the load check method in the target subcell, for example, the first, the number of subscribers and the method of checking the CPU load (subscriber rating information can be added when considering the user QoS), the second, downlink, uplink of the corresponding terminal, respectively In this case, the total bandwidth required for the network is calculated for each of the Minimum Reserved Rate and the Maximum Sustained Rate, so the total number of bandwidths is four (DL minimum reserved rate). , UL minimum reserved rate, DL maximum sustained rate, UL maximum sustained rate. Depending on the implementation, the number of QoS flows may also be reported. Third, the method of performing CAC based on QoS type (UGS, ertPS, rtPS, nrtP), minimum guaranteed data rate, and maximum sustained data rate for each QoS flow of the corresponding UE (CAC accept threshold is different for each QoS type). to be. Here, CID (Connection ID) and radio resource reservation may or may not be made in advance.

In step 106, the base station notifies the terminal of the load check result through a handover response message or a base station handover request message. Here, the load check selection target has three examples in step 102, the load check range is one of the methods mentioned in step 104, so a total of nine combinations can be considered, and each combination is notified whether or not to allow can do.

If there is an acceptable BSID among the BSIDs requested by the UE, the UE may list all allowable BSIDs or list the allowable BSIDs according to the load and transmit the list to the UE. If the BSID requested by the UE is full of loads, the BSID requested by the UE is full of loads, and another BSID that is allowable in the same sector may be additionally transmitted.

If there is no BSID among the BSIDs requested by the UE, the BSID does not transmit the BSID while transmitting the BSHO-RSP and informs the UE of allowable subcells not attempted by the UE through BSHO-REQ in consideration of the load. Scan the appropriate subcells to help handover or inform the list of NBR-ADVs that the UE has not attempted through SCN-RSP, start scanning, and if the UE performs SCN-REP, the wireless situation is a ping-pong phenomenon. Considering the load, the subcells are checked and the allowable subcells are informed through BSHO-REQ (the effect of reducing the BSID to be searched by the UE among the BSIDs in the NBR-ADV. None). If there are several allowable FAs, the UE may request scanning for FAs that have the same radio frequency reported by the UE in the same sector as the best BSID or have the same frequency band.

Thereafter, the base station terminates the load balancing procedure.

2 is a flowchart illustrating an operation of a base station for performing load balancing in a broadband wireless communication system according to a second embodiment of the present invention. 2 illustrates a case in which BSIDs included in a NBR-ADV (Neighbor Advertisement) message periodically report a load status to a serving subcell, and the serving subcell becomes a load check subject.

Referring to FIG. 2, when the base station receives a handover request (MSHO-REQ) from the terminal in step 200, the base station proceeds to step 202 and selects a load check target subcell. In this case, the handover request message includes BSIDs for one or more neighboring subcells obtained by scanning by the UE. The method for selecting a load check target subcell may use the method described above with reference to FIG. 1.

Thereafter, the base station periodically receives a load status from neighboring subcells in step 204 and performs a load check based on the load status reported in step 206. In the load checking scheme, the number of subscribers described above and the CPU load (the number of allowable subscribers per subscriber class may be considered in consideration of user QoS), available bandwidth for uplink and downlink for each subcell, and CAC acceptance threshold for each QoS type, etc. The load check may be performed considering at least one.

In step 208, the base station notifies the terminal of the load check result through a handover response message (BSHO-RSP) or a base station handover request message (BSHO-REQ).

Thereafter, the base station terminates the load balancing procedure.

3 is a flowchart illustrating an operation of a terminal for performing load balancing in a broadband wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the terminal receives a handover message in step 300 and receives a load status notification.

Thereafter, the terminal determines the load state in step 302 to perform the handover target BSIDs through a predetermined procedure.

Thereafter, the terminal terminates the load balancing procedure.

4 is a diagram illustrating a base station apparatus for performing load balancing in a broadband wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the base station 400 includes a handover control unit 402, a subcell selecting unit 404, a load checking unit 406, a load check requesting unit 408, a load state notification unit 410, The load balancing control unit 412 is configured.

The handover control unit 402 processes a handover request message from the terminal or transmits a handover request message to the terminal when necessary. The handover request message includes base station IDs (BSIDs) for one or more neighboring subcells. Here, the subcell and the BSID are matched one-to-one.

The subcell selecting unit 404 receives the BSID from the handover control unit 402 and selects sub-cells to be loaded, and then the load checking unit 406 or the load checking requesting unit 408. To pass). For example, when the load check subject is the target base station, the subcell selecting unit 404 delivers the selected BSIDs to the load check request unit 408, and when the load check subject is the serving base station, the load check. The BSIDs selected by the unit 406 are delivered.

The sub-cell selecting unit 404 assigns the BSIDs designated by the terminal through a handover request message to the same sector as the designated BSIDs in addition to the BSIDs designated by the terminal through a handover request message. The sub-cells are selected using one of "method of selecting all other BSIDs" and "method of selecting all BSIDs listed in a NBR-ADV (Neighbor Advertisement) message".

The load check request unit 408 requests a load check to the selected sub-cell BSID through a backhaul network when the load check subject is a target base station, and the load check unit 406 requests through the backhaul network. The load status for the subcell is reported. When the load checking subject is the serving base station, the load checking unit 406 performs the load checking in consideration of the selected BSID received from the subcell selecting unit 404 and the load status of the neighboring subcell periodically reported. .

In other words, when the load check subject is the target base station, the serving base station delivers the requirements of the terminal to the target base station, and is informed of the load check result from the target base station. On the other hand, when the load check subject is the serving base station, the serving base station performs the load check by using the load state of the neighboring subcell periodically reported. At this time, considering the number of subscribers, CPU load, and user QoS, consider the number of allowable subscribers by subscriber class, or consider the total bandwidth required for each of downlink and uplink of the corresponding UE, or call / access for each QoS type. The load check is performed considering the Call / Connection Admission Control (CAC) threshold.

The load status notification unit 410 is provided from the load check unit 406 and notifies the terminal of the load status result through a handover response message or a base station handover request message. For example, if there is an acceptable BSID among the BSIDs requested by the terminal, the load status notification unit 410 may list “all acceptable BSIDs”, “list of allowable BSIDs sorted according to load”, “allowed”. Among the BSIDs that are possible and not under heavy load, the UE selects one of only the BSIDs having the best radio status reported by the terminal (RSSI or CINR) ". When the BSID requested by the terminal is full of load, another BSID that is allowable in the same sector may be additionally listed and notified.

The load balancing control unit 412 controls the handover control unit 402 and the load state notification unit 410 to perform an overall load balancing procedure.

For example, the load balancing control unit 412 periodically receives a load status report from the neighboring subcells, or when there is no allowable BSID among the BSIDs requested by the terminal, an acceptable subcell or FA not attempted by the terminal. To request scanning or to use the terminal for handover.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is a flowchart illustrating an operation of a base station for performing load balancing in a broadband wireless communication system according to a first embodiment of the present invention;

2 is a flowchart illustrating an operation of a base station for performing load balancing in a broadband wireless communication system according to a second embodiment of the present invention;

3 is a flowchart illustrating a terminal operation for performing load balancing in a broadband wireless communication system according to an embodiment of the present invention;

4 is a diagram of a base station apparatus for performing load balancing in a broadband wireless communication system according to an exemplary embodiment of the present invention.

Claims (21)

A method of operating a base station for load balancing in handover in a broadband communication system, When receiving a handover request from the terminal, selecting a sub-cell to be loaded; Requesting a load check from the selected subcell and reporting a load state; And notifying the terminal of the load status result through a handover response message or a base station handover request message. The method of claim 1, The base station ID (BSID) for one or more neighboring subcells is included in the handover request message. The method of claim 3, wherein The subcell and the BSID are matched one-to-one. The method of claim 1, The sub-cell to be selected for the load check is "method of selecting BSIDs designated by the terminal through a handover request message" and "assigned to the same sector as the designated BSIDs in addition to the BSIDs designated by the terminal through a handover request message. Select all other BSIDs "," method of selecting all BSIDs listed in the NBR-ADV (Neighbor Advertisement) message ". The method of claim 1, When checking the load, considering the number of subscribers, CPU load, and user QoS, the number of allowable subscribers by subscriber class is considered, or the total bandwidth required for each of downlink and uplink of the corresponding UE is considered, or each QoS type is called. A method characterized by considering a Call / Connection Admission Control (CAC) threshold. The method of claim 1, The step of notifying the terminal of the load status result through a handover response message or a base station handover request message, If there is an acceptable BSID among the BSIDs requested by the terminal, the list of all allowable BSIDs, the list of acceptable BSIDs sorted according to the load, and the radio reported by the terminal among the allowable and unloaded BSIDs. Characterized in that the state (RSSI or CINR) is delivered by selecting one of the "best BSID list". The method of claim 6, If the BSID requested by the terminal is full of load, another BSID is additionally listed in the same sector. The method of claim 1, If there is no allowable BSID among the BSIDs requested by the UE, a request is made for scanning of allowable subcells or FAs not attempted by the UE or a list included in the NBR-ADV not attempted by the UE through a scanning response. The method further comprises the step of notifying the scanning request. A method of operating a base station for load balancing in handover in a broadband communication system, When receiving a handover request from the terminal, selecting a sub-cell to be loaded; Performing a load check based on a load state periodically reported from the neighboring subcells after selecting the load check target subcell; And notifying the terminal of the load check result through a handover response message or a base station handover request message. The method of claim 9, And receiving a load report periodically from the neighboring subcells. A method of operating a terminal for load balancing in a handover in a broadband communication system, Receiving a load status notification of sub-cells through a handover response message or a base station handover request message; And determining the load state to perform scanning on the handover target BSIDs. A base station apparatus for load equalization during handover in a broadband communication system, A subcell selecting unit which selects a load check target subcell when receiving a handover request from a terminal; A load check request unit requesting a load check to the selected subcell through a backhaul network; A load checker configured to report a load state of a requesting subcell through the backhaul network; And a load state notification unit for notifying the terminal of the load state result through a handover response message or a base station handover request message. The method of claim 12, And a base station ID (BSID) for at least one neighboring subcell in the handover request message. The method of claim 13, And the subcell and the BSID match one-to-one. The method of claim 12, The subcell selecting unit selects BSIDs designated by the terminal through a handover request message, and other BSIDs allocated to the same sector as the designated BSIDs in addition to the BSIDs designated by the terminal through a handover request message. And selecting a subcell using one of "selecting all" and "selecting all BSIDs listed in a NBR-ADV (Neighbor Advertisement) message". The method of claim 12, The load check unit When considering the number of subscribers, CPU load, and user QoS, consider the number of allowable subscribers by subscriber class, or consider the total bandwidth required for each downlink and uplink of the corresponding UE, or control call / access admission for each QoS type. A base station apparatus characterized by considering a (Call / Connection Admission Control: CAC) threshold. The method of claim 12, The load state notification unit If there is an acceptable BSID among the BSIDs requested by the terminal, the list of all allowable BSIDs, the list of acceptable BSIDs sorted according to the load, and the radio reported by the terminal among the allowable and unloaded BSIDs. And notifying one of BSIDs having the best status (RSSI or CINR) ". The method of claim 17, The load state notification unit If the BSID requested by the terminal is full of load, the base station apparatus, characterized in that additional list of allowable BSID in the same sector. The method of claim 12, And a load balancing controller requesting scanning for allowable FAs that the terminal has not attempted when there is no allowable BSID among the BSIDs requested by the terminal. A base station apparatus for load equalization during handover in a broadband communication system, A subcell selecting unit which selects a load check target subcell when receiving a handover request from a terminal; A load checker configured to perform a load check based on a load state periodically reported by the neighboring subcells after selecting the load check target subcell; And a load status notification unit for notifying the terminal of the load check result through a handover response message or a base station handover request message. The method of claim 20, The base station apparatus further comprises a load balancing control unit that receives the load status periodically from the neighboring subcells.

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