CN1564495A - Load balancing method in system of broad band CDMA - Google Patents

Abstract

The invention discloses a load balancing method in a wideband code division multiple access system, comprising the following steps: RNC obtains measurement values reflecting the load status of each cell from base stations of the same coverage and different frequency cells; After accessing the bearer setup message, compare the load of the current cell with the same coverage and different frequency cells, and select the target cell for the UE according to the set load balancing handover conditions; after the target cell accepts the action, send the radio bearer setup command to the UE , carrying the information and resource information of the target cell; after the UE completes the radio bearer establishment action, it returns a radio bearer establishment complete message in the target cell. The method of the present invention can well ensure that when the UE service is established in the WCDMA system, some UEs will be switched to receive services in the same coverage cell with a lower load earlier, so as to realize load balancing and system capacity maximization, and also facilitate subsequent UEs smooth access.

Description

A Load Balancing Method in Wideband Code Division Multiple Access System

technical field

The invention relates to a load balancing method in a Wideband Code Division Multiple Access (WCDMA for short) system, in particular to an inter-frequency load balancing method for cells with the same coverage and different frequencies.

Background technique

With the wide application and rapid development of mobile communication systems, many key technologies in the mobile system are becoming more and more perfect. While realizing the normal communication of users, it is also necessary to consider how to obtain the best performance so that both the system and user equipment can obtain the order. People are satisfied with the effect. From the perspective of the system, it is hoped to connect as many users as possible.

Compared with other systems (such as GSM system and CDMA system), the WCDMA system has many special features. Soft capacity and support for variable rate services are its major features. In the WCDMA system, the wireless environment in which the user equipment (User Equipment, hereinafter referred to as UE) is moving is constantly changing. When the UE is far away from the base station or the wireless environment deteriorates, if the original Rate transmission, in order to ensure its quality of service QoS (Quality of Service), under the action of closed-loop power control, the base station will inevitably send signals with higher power, and the capacity of the system will also change accordingly. If appropriate measures can be taken to enable the UE to receive services in a suitable cell, for the system, on the one hand, the system capacity can be fully utilized to ensure the smooth access of subsequent UEs, and on the other hand, relatively Good quality of service.

For an area that uses different frequency cells with the same coverage, the sum of the capacities of multiple cells with the same coverage and different carrier frequencies constitutes the total capacity that can be achieved in this area. How to balance the load between frequencies to achieve the maximum capacity in multi-carrier frequency areas is a topic worthy of study.

There is no specific implementation method for WCDMA system load balancing in the existing technical specifications. In the Chinese patent application with the patent application number 00127302.7, "a method for load balancing preprocessing in a mobile communication system" is disclosed. In the mobile communication system, the method modifies the system information by measuring the load conditions of adjacent cells Parameters, that is, parameters that control the user to select a cell, so as to guide the user to access in a cell with a relatively low load. However, the technical solution for load balancing in this patent application can only be used for the processing of same-frequency cells, and it is aimed at potential users who have not yet accessed the system. How to handle users who access the system.

Contents of the invention

The technical problem to be solved by the present invention is to provide a load balancing method in a broadband code division multiple access system, which can perform inter-frequency load balancing based on the loads of different-frequency cells with the same coverage when establishing services.

In order to solve the above technical problems, the invention provides a load balancing method in a wideband code division multiple access system, comprising the following steps:

(a) The radio network controller obtains the measurement value reflecting the load status of each cell from the base stations of the same coverage and different frequency cells;

(b) After the radio network controller receives the radio access bearer establishment message of the core network for the user equipment, it compares the loads of the current cell and its same-coverage and different-frequency cell, and combines the set load balancing handover conditions for the user equipment Select the target area;

(c) Perform an admission action in the target cell, and send a radio bearer establishment command to the user equipment after completion, carrying information about the target cell and resource allocation information;

(d) After the radio bearer establishment action on the user equipment side is completed, a radio bearer establishment complete message is returned in the target cell.

The above-mentioned method may have the following characteristics: said step (a) may further include the following steps:

The radio network controller sends a cell common measurement control command to the base stations of the same coverage and different frequency cells, including the set measurement amount and parameters related to the reporting method;

After receiving the public measurement control command, the base station performs measurement according to requirements, and reports the measurement result to the radio network controller when the reporting condition is met;

The radio network controller stores the measurement results reported by the base stations for use when needed.

The above method may have the following characteristics: the measured value is the total received broadband power, or the transmitted carrier power, or the received total broadband power and the transmitted carrier power.

The above method may have the following characteristics: the manner in which the base station reports the measurement value to the radio network controller is a periodic reporting manner or an event-triggered reporting manner.

The above method may have the following characteristics: in the step (b), the process of the radio network controller selecting the target cell according to the load of the cell further includes the following steps:

(b1) The radio network controller inquires about the load situation of each same-coverage and different-frequency cell, and judges whether there is a same-coverage and different-frequency cell whose load is lower than that of the current cell. If it exists, perform the next step, otherwise, perform step (b3) ;

(b2) taking the same-coverage inter-frequency cell with lower load as the target cell for establishing the service, and performing step (c);

(b3) Take the current cell as the target cell for establishing the service, and execute step (c).

In order to avoid frequent equalization processing that may occur and effectively reduce the possibility of call drop due to inter-frequency hard handover, in the process of selecting the target cell according to the load of the cell, the above-mentioned radio network controller may further include before the step (b1) Step: judging whether the current cell load is lower than a preset threshold value, if yes, execute step (b3), otherwise execute step (b1).

In order to avoid frequent equalization processing that may occur, and maintain the service quality of the currently accessed user equipment to the greatest extent, in the above method, after the step (b1), it may further include the step of: judging that the current cell load exceeds its same coverage and different frequency cell Whether the load difference reaches the preset hysteresis threshold, if yes, execute step (b2), otherwise execute step (b3).

The above method may have the following characteristics: when comparing the loads between cells, only the total received broadband power or the transmitted carrier power is compared, or the total received wideband power and the transmitted carrier power are compared comprehensively.

The above method may have the following characteristics: in the step (c), the radio network controller includes the following actions when the target cell accepts: allocate resources to the user equipment, and complete the establishment or re-establishment of the radio link with the base station The configuration preparation is to determine the time point for establishment or reconfiguration; the information of the target cell includes frequency information and scrambling code information of the target cell.

The above method may have the following characteristics: after the step (d), it also includes a step: after the radio network controller receives the radio bearer establishment completion message, it feeds back a radio access bearer establishment response message to the core network, and then enters the normal communication process.

It can be seen from the above that the method of the present invention is simple, logical and efficient, and can well ensure that when the UE service is established in the WCDMA system, some UEs will be switched to receive services in the same coverage cell with a lower load earlier, so that multiple The load of the same-coverage and different-frequency cells can better achieve load balance, so as to maximize the capacity of the entire system and facilitate the smooth access of subsequent UEs.

In addition, the method of the present invention can also avoid possible frequent equalization processing from two aspects. On the one hand, when the current cell load is lower than a set threshold, regardless of the load status of the same-coverage and different-frequency cells, there is no need to perform equalization processing. It is believed that the current cell at this time still has a better ability to accept new users; On the other hand, when comparing the loads of the two cells, by setting a hysteresis threshold, only when the load difference between the current cell and the same-coverage inter-frequency cell exceeds the hysteresis threshold, the load balancing process is performed, thereby maximizing Maintain the service quality of the currently connected UE in a timely manner.

Description of drawings

Fig. 1 is the main flowchart of the load balancing control method of the embodiment of the present invention;

Fig. 2 is the flowchart of common measurement between RNC and Node B of the embodiment of the present invention;

Fig. 3 is a message flow diagram during public measurement according to an embodiment of the present invention;

Fig. 4 is the flow chart of the RNC selection target cell process of the embodiment of the present invention;

Fig. 5 is a flow chart of messages when a service is established according to an embodiment of the present invention.

Detailed ways

Embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The present invention is applied to a WCDMA system composed of a core network (CN), a terrestrial radio access network (UTRAN) and a user equipment (UE). The UTRAN includes many radio network subsystem sets (RNS) connected to the CN through the Iu interface. A RNS includes a radio network controller (RNC) and one or more base stations (Node B). Node B includes one or more cells, connected to RNC through Iub interface. RNCs in each RNS can also exchange information through the Iur interface.

The main flow of the load balancing control method in this embodiment is shown in Figure 1, including the following steps:

Step 100, RNC regularly obtains receiving total wideband power (RTWP) and transmitting carrier power (TCP) value reflecting the cell load situation from the Node Bs of each same coverage inter-frequency cell;

Step 110, after the RNC receives the radio access bearer setup message for a single UE from the core network (CN), it compares the loads of the current cell and its same-coverage, different-frequency cell, and selects a UE for the UE in combination with preset load balancing handover conditions. target area;

Step 120, perform actions such as acceptance in the target cell, and then send a radio bearer establishment command to the UE, and carry information related to the target cell and resource information in the command message;

Step 130, after the UE completes the radio bearer establishment action, it returns a radio bearer establishment complete message in the target cell.

In step 100, RTWP is a quantity that directly reflects the uplink interference of the cell, and TCP is a quantity that directly reflects the downlink transmission power of the cell. Under the conditions determined by the cell plan, the two measurement quantities can respectively represent the uplink and downlink transmission power of a cell. Downstream load conditions. In the 3GPP TS 25.331 specification, the reporting of the public measurement report of the Node B in the WCDMA system can choose periodic reporting or event-triggered reporting, and this embodiment adopts the periodic reporting method.

Shown in Fig. 2 is the specific flow of public measurement between RNC and Node B, comprising the following steps:

In step 200, the RNC sends a cell public measurement control command to the Node B, requiring the Node B to periodically measure and report the measured values of RTWP and TCP. In addition to the measured value, the transmitted measurement control command also includes the periodic reporting gap, filter coefficient, etc. information;

Step 210, the Node B receives the public measurement control command sent by the RNC, performs measurement according to the requirements, and regularly reports the measurement results to the RNC, that is, the RTWP and TCP measurement values of the same coverage of different frequency cells;

Step 220, the RNC stores the measurement results reported by the Node B for use when needed.

Fig. 3 shows the message flow corresponding to the above-mentioned public measurement flow between RNC and Node B:

Step 300, RNC sends a common measurement initiation request (Common MeasurementInitiation Request) to Node B;

Step 310, Node B returns a Common Measurement Initiation Response (Common Measurement Initiation Response) to the RNC when the Node B checks that it is capable of performing the measurement, and starts to measure;

Step 320, Node B sends a public measurement report (Common Measurement Report) to RNC when reaching the reporting condition;

Step 330, for the periodic reporting mode, the Node B reports the measurement results to the RNC at intervals.

The public measurement report of Node B can also adopt the event-triggered reporting method. For event reporting, in addition to the measurement quantity, the public measurement command sent by RNC to each Node B also needs to set the reporting threshold, trigger time and other parameters. Node When the set event is met, B reports the measurement result to the RNC.

When there is UE access, the specific process of service establishment is shown in Figure 4, including the following steps:

Step 400, when the RNC receives a radio access bearer establishment message (RAB AssignmentRequest) from the CN, it triggers a judgment action for inter-frequency equalization;

Step 410, the RNC compares the load situation of the different frequency cells with the same coverage, and judges whether the current cell load is lower than the preset threshold value, if yes, execute step 440, otherwise execute the next step;

Step 420, judging whether there is a same-coverage and different-frequency cell with a load lower than the current cell, if yes, perform the next step, otherwise, perform step 440;

Step 430, taking the same-coverage and different-frequency cell with a lower load as the target cell for establishing the service, and performing step 450;

Step 440, taking the current cell as the target cell for establishing the service;

Step 450, the RNC performs actions such as acceptance in the target cell, and sends a radio bearer establishment command to the UE after completion;

Step 460, after the UE completes the radio bearer establishment action, it returns a radio bearer establishment complete message in the target cell.

Above-mentioned process first judges whether the load of current sub-district is lower than a preset threshold value in step 410, if yes, then consider that the load of this sub-district is at a lower level, directly use current sub-district as the target sub-district of service establishment, need not The determination of inter-frequency load balancing is performed. This can effectively reduce the possibility of call drop caused by inter-frequency hard handover.

In the above step 420, when judging the load status, this embodiment comprehensively considers the uplink and downlink directions, and simultaneously uses the RTWP value in the uplink direction and the TCP value in the downlink direction as a reference for load comparison among cells. There may be multiple judgment rules for the load size. A simple example is that the load of the cell is considered to be large when the two measured values are large, and the load of the cell is considered to be small when the two measured values are small.

In a system where the uplink direction or the downlink direction is limited, only the RTWP value in the uplink direction or the TCP value in the downlink direction may be selected as a reference for load comparison among cells. Correspondingly, in these two cases, the measurement quantity in the public measurement control command sent by the RNC to the Node B may only include RTWP or TCP.

Further, when comparing the loads of the two cells, a hysteresis threshold can also be set, and when the difference between the load of the current cell exceeds the load of the inter-frequency cell with the same coverage and reaches the hysteresis threshold, the handover process in step 430 is executed; otherwise Step 440 is still performed, so as to maintain the service quality of the currently accessed UE to the greatest extent.

In step 450, when the RNC performs actions such as admission in the target cell, it needs to allocate appropriate resources to the corresponding UE, complete the establishment or reconfiguration preparation of the radio link with the base station, and determine the time point for establishment or reconfiguration, etc.; After completing all preparations on the radio access network (RAN) side, the RNC sends a radio bearer establishment message to the UE, and the command message carries the relevant information of the target cell (frequency information, scrambling code information) and the assigned For resource information, if the target cell is a same-coverage and different-frequency cell, the radio bearer setup message is essentially an inter-frequency hard handover command message.

In step 460, the RNC receives the radio bearer establishment complete message returned by the UE from the target cell, indicating that the radio bearer establishment action on the UE side has been successfully completed. The RNC can also feed back a response message of establishing a radio access bearer to the CN, and then enter into a normal communication process.

Figure 5 shows the message flow between UE, RNC and CN when the service is established in this embodiment:

Step 500, the RNC receives a radio access bearer establishment request message (RABAssignment Request) from the core network;

Step 510, according to the load information of the cells with the same coverage and different frequencies reported by the Node B, perform a balanced decision on whether to perform inter-frequency handover, determine the target cell, and complete admission and other actions;

Step 520, sending a radio bearer setup message (Radio Bearer Setup) to the UE;

Step 530, after the radio bearer setup action on the UE side is completed, return a radio bearer setup complete message (Radio Bearer Setup Complete) to the RNC;

In step 540, the RNC immediately feeds back a radio access bearer establishment response message (RABAssignment Response) to the CN, and then enters into a normal communication process.

In addition, if the current cell cannot be admitted due to reasons such as code resources, it can also try to be admitted in its same-coverage inter-frequency cell, and use the cell that can be admitted as the target cell.

In summary, the present invention makes full use of the measurement results reported by the Node B in the WCDMA system. In the RNC, according to the load measurement values of the current cell and its same coverage and different frequency cells, that is, each cell receives the total broadband power and/or transmits the carrier In the case of power, it is determined whether the UE that is establishing a service needs to be balanced to other same-coverage and different-frequency cells. The method of the present invention is simple, logical and high in efficiency, and can well ensure that when the UE service is established in the WCDMA system, some UEs will be switched to receive services in the same-coverage cells with lower loads earlier, so that multiple same-coverage and different-frequency The load of the cell can better achieve load balancing, so as to maximize the capacity of the entire system, and also facilitate the smooth access of subsequent UEs.

Claims (10)

1, the load equalization method in a kind of broadband CDMA system may further comprise the steps:

(a) radio network controller obtains the measured value of each cell load situation of reflection from each with the base station that covers alien-frequency district;

(b) radio network controller receives after core net sets up message to the RAB of subscriber equipment, and relatively current area and its are with the load that covers alien-frequency district, and the load balancing switching condition in conjunction with setting is described subscriber equipment selected target sub-district;

(c) admit action at described Target cell, send radio bearer to described subscriber equipment after finishing and set up order, carry the information of Target cell and the information of Resources allocation;

(d) after the radio bearer of described user equipment side foundation action is finished, in Target cell, return radio bearer foundation and finish message.

2, the method for claim 1 is characterized in that, described step (a) further may further comprise the steps:

Described radio network controller sends sub-district public-measurement control command with the base station that covers alien-frequency district to each, comprises the measuring amount of setting and the parameter relevant with reporting mode;

Described base station is measured after receiving described public-measurement control command as requested, when satisfying report condition, to described radio network controller reporting measurement result;

The measurement result that described radio network controller storage base station reports, supply and demand will the time use.

3, method as claimed in claim 2 is characterized in that, described measured value perhaps is the emission carrier power for receiving total wideband power, perhaps for receiving total wideband power and emission carrier power.

4, method as claimed in claim 2 is characterized in that, described base station is that periodic report mode or Event triggered report mode to the mode of radio network controller reporting measurement value.

5, the method for claim 1 is characterized in that, in the described step (b), radio network controller further may further comprise the steps according to the process of cell load select target sub-district:

(b1) described each load condition with the covering alien-frequency district of radio network controller inquiry judges whether to exist load to be lower than the same covering alien-frequency district of current area load, if exist, carries out next step, otherwise, execution in step (b3);

(b2) will load lower same covering alien-frequency district as setting up professional Target cell, execution in step (c);

(b3) with the Target cell of current area as the foundation business, execution in step (c).

6, method as claimed in claim 5, it is characterized in that, in the process of described radio network controller according to cell load select target sub-district, also comprise step before in described step (b1): judge whether the current area load is lower than default threshold value, if, execution in step (b3), otherwise execution in step (b1).

7, as claim 5 or 6 described methods, it is characterized in that, also comprise step after the described step (b1): judge that the current area load exceeds it and whether reaches default sluggish thresholding with the difference that covers the alien-frequency district load, if, execution in step (b2), otherwise execution in step (b3).

8, method as claimed in claim 5 is characterized in that, when carrying out the comparison of minizone load, only receives the comparison of total wideband power or emission carrier power, perhaps to receiving total wideband power and launching carrier power and comprehensively compare.

9, the method for claim 1, it is characterized in that, in the described step (c), radio network controller comprises following action when Target cell is admitted: give described user equipment allocation resource, finish and described base station between Radio Link foundation or reshuffle preparation, determine the time point that will set up or reshuffle; The information of described Target cell comprises the frequency information and the scrambling code information of Target cell.

10, the method for claim 1, it is characterized in that, described step (d) also comprises step afterwards: radio network controller is set up response message to RAB of core net feedback after receiving that message is finished in described radio bearer foundation, enters normal communication process then.

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