CN1571292A - A method for controlling inter-frequency load balancing in WCDMA system - Google Patents

Abstract

The invention discloses an inter-frequency load balancing control method in a wideband code division multiple access system, comprising the following processing steps: RNC obtains information reflecting cell load status from Node B at regular intervals; The actual measured load and the load of the different-frequency cell with the same coverage determine whether it is necessary to perform an equalization action; if it is decided to perform an equalization action to an inter-frequency cell, select some UEs in the cell and send an inter-frequency hard handover to these UEs command; the UE performing the handover returns a complete message in the inter-frequency cell. By adopting the method of the present invention, it can be well ensured that the WCDMA system selects part of UEs to switch to the same-coverage and different-frequency cells with lower load to receive services as soon as possible during the system operation, so that the load of multiple same-coverage and different-carrier-frequency cells is relatively low. The load balance is well realized, so as to maximize the capacity of the entire system, and also facilitate the smooth access of subsequent UEs.

Description

A method for inter-frequency load balancing control in wideband code division multiple access system

technical field

The present invention relates to a load balancing method in a Wideband Code Division Multiple Access (WCDMA) system (hereinafter referred to as WCDMA), especially according to the load measurement value of a cell and its same coverage cell, that is, using the received total broadband power (Received Total Wide Band Power) (hereinafter referred to as RTWP) and/or Transmitted Carrier Power (hereinafter referred to as TCP) to determine the specific method of inter-frequency load balancing control of the system during operation.

Background technique

With the wide application and rapid development of mobile communication systems, many key technologies in mobile systems are becoming more and more perfect. While realizing normal communication of users, it is also necessary to consider how to obtain the best performance, and obtain the best performance for both the system and user equipment. Better satisfactory results, from the perspective of the system, it is hoped to access as many users as possible.

In the WCDMA system, when the user equipment (User Equipment,) (hereinafter referred to as UE) is moving, the wireless environment is changing all the time. When the UE is far away from the base station or the wireless environment deteriorates, if the UE remains For the original rate transmission, in order to ensure its QoS (Quality of Service), under the effect 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.

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. If appropriate measures can be taken, the UE can receive Service, for the system, can better guarantee the access of subsequent UEs in the cell with higher load; for the user, it can get relatively better service quality. For the area where the same coverage and different frequency cells are used, the sum of the capacities of multiple same coverage and different carrier frequency cells constitutes the total capacity that can be achieved in this area. How to maximize the capacity of multi-carrier frequency areas is a topic worth studying. .

The Chinese patent application with the patent application number 00127302.7 "A method for load balancing preprocessing in a mobile communication system" explains that in a mobile communication system, by measuring the load conditions of adjacent cells and modifying system information parameters, that is, controlling user Select the parameters of the cell, so as to guide the user to access in the cell with relatively low load. The idea described 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. However, the patent application does not give an explanation on how to deal with the situation of inter-frequency cells. There is no corresponding processing method in this patent application as to how to deal with users who have already accessed the system.

Contents of the invention

The purpose of the present invention is to solve the problem that there is no specific implementation method for load balancing of WCDMA systems in the existing technical specifications, especially for cells with the same coverage and different frequencies, and proposes an inter-frequency load balancing based on load measurement during system operation method.

In the 3GPP TS 25.33l specification, it is stipulated that in the WCDMA system, the public measurement report of the Node B can be reported in two ways: periodic reporting and event-triggered reporting. This method is mainly described for the periodic reporting method, but it is also applicable in the event-triggered reporting method.

The load balancing control method of the present invention comprises the following steps:

(1) The radio network controller RNC (Radio Network Controller) regularly obtains information reflecting the load status of the cell from the Node B;

(2) The radio network controller RNC determines whether it is necessary to perform a balancing action according to the preset load threshold parameters, the actual load measured by the cell, and the load of the same coverage and different frequency cells;

(3) If it is decided to perform an equalization action to an inter-frequency cell, select some user equipment UEs in the cell, and send an inter-frequency hard handover command to these UEs;

(4) The user equipment UE performing the handover returns a complete message in the inter-frequency cell.

In step (1), the radio network controller (RNC) obtains the received broadband power RTWP and the transmitted carrier power TCP value of the load condition of the cell, including the following steps;

(1.1) The RNC sends a public measurement control command for the cell to the Node B, requiring the measurement of the received broadband power RTWP and/or the transmitted carrier power TCP value, and setting the reporting conditions. For the periodic reporting method, the reporting period needs to be set etc. For event reporting, it is necessary to set the reporting threshold, trigger time, etc.;

(1.2) The Node B reports to the RNC the uplink receiving broadband power RTWP and/or transmitting carrier power TCP value of the corresponding cell when the reporting condition in the measurement control command sent by the RNC is met;

(1.3) RNC stores the results reported by Node B for use when needed.

In the above step (2), the radio network controller RNC inquires and compares the load status of multiple cells currently covered with the same coverage, and decides whether it is necessary to perform a balancing action in combination with the preset threshold parameters. The judgment of the load status can have The following methods:

(2.1) In a system mainly limited in the uplink direction, only the received wideband power RTWP received in the uplink direction can be selected as a reference for load comparison among cells.

(2.2) In a system mainly limited in the downlink direction, only the TCP value of the transmit carrier power in the downlink direction can be selected as a reference for load comparison among cells.

(2.3) In systems where the uplink and downlink directions need to be considered comprehensively, the received broadband power RTWP received in the uplink direction and the transmit carrier power TCP value in the downlink direction can be used simultaneously as a reference for load comparison between cells.

According to the set processing method, when the load of a cell is higher than a set threshold value of the cell with the same coverage and different frequency, it is decided to perform a balancing action.

In addition, it may also be considered that when the load of the cell is below a certain threshold, no balancing action is performed regardless of the load status of the different-frequency cells with the same coverage.

In the above step (3), the RNC selects the appropriate UE according to the decision made in the step (2), and sends a reconfiguration message to it to perform inter-frequency hard handover. The message may include the following content: A. Cell frequency information; B. scrambling code information of the cell; C. allocated resource information. There are but not limited to the following methods for selecting UE:

(3.1) Select UEs that are not in soft handover state.

(3.2) Selecting UEs with lower service quality (QoS) requirements, considering priority, delay requirements, etc.

(3.3) Select a UE with a lower service rate.

The method described in the present invention is simple, logical, and high in efficiency, and can well ensure that a part of UEs in the WCDMA system are selected to switch to receive services in same-coverage and different-frequency cells with lower loads as soon as possible during system operation, so that multiple simultaneous The load of cells covering different carrier frequencies can be well balanced, 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, by setting a threshold, under this threshold, regardless of the load status of the same-coverage and different-frequency cells, there is no need to perform equalization processing. new users; on the other hand, when comparing the loads of the two cells, a hysteresis threshold can be set, and only when the loads of the two cells exceed the hysteresis threshold can the real load balancing process be performed, thereby maximizing the maintenance of the currently connected users. QoS of the incoming UE.

Description of drawings

Fig. 1 is the overall flowchart of load balancing between frequency when the system is running in Embodiment 1 of the present invention;

Fig. 2 is the message flowchart of RNC and Node B when load balancing between frequencies during system operation of the present invention;

Fig. 3 is the message flow diagram between RNC and UE when the system of the present invention is running and load balancing between frequencies;

FIG. 4 is a general flowchart of load balancing between frequencies during system operation in Embodiment 2 of the present invention.

Detailed ways

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 reported current cell load and the load of the same-coverage and different-frequency cells, it is comprehensively determined whether it is necessary for the UE in service communication to be balanced to other cells. Different carriers and frequencies cover the same cell.

Below in conjunction with accompanying drawing, the implementation of technical scheme is described in further detail:

When the method of the present invention is applied in the WCDMA system, in the measurement control command, the periodic reporting scheme is adopted for public measurement, and it also has important reference significance for the event-triggered reporting method.

The flow process of method core idea of the present invention is as shown in Figure 1, as can be seen from Figure 1:

Step 101, the RNC sends a common measurement control command (Common Measurement InitiationRequest) to the Node B, requiring the Node B to periodically measure and report the measured value of RTWP and/or TCP; in sending the measurement control command, the gap (Report Periodicity InitiationRequest) of periodic reporting is also included. ), filter coefficient (Measurement Filter Coefficient), etc.;

Step 102, the Node B receives the public measurement control command sent by the RNC, and performs measurement according to the requirements, and reports the measurement results when the reporting conditions are met;

Step 103, after the RNC receives the reported result, store the RTWP and/or TCP value related to each cell reported by the Node B; RTWP is a quantity that directly reflects the uplink interference of the cell, and TCP directly reflects the downlink transmit power of the cell A quantity of , under the conditions determined by the cell planning, the two measurement quantities can respectively represent the uplink and downlink load conditions of a cell;

Step 104, after receiving the measurement information (RTWP and/or TCP) of the cell load, the RNC compares the load situation between different frequency cells with the same coverage, and if the load between the different frequency cells with the same coverage is relatively close, the inter-frequency load is not triggered Balance action, see step 108, otherwise, select appropriate UE in the cell with higher load, and prepare for inter-frequency hard handover, that is, step 105, that is, allocate appropriate resources to these UEs in the target cell with lower load, and The base station establishes a wireless link, etc.;

Step 106, after completing all preparations on the RAN (Radio Access Network) side, the RNC sends an inter-frequency hard handover (reconfiguration) message to the UE, and the inter-frequency hard handover message is one of the following three types: a physical channel reconfiguration message , transmission channel reconfiguration message, radio bearer reconfiguration message;

In step 109, the UE returns an inter-frequency hard handover (reconfiguration) complete message, which corresponds to the inter-frequency hard handover in step 106, and is one of the following three types: physical channel reconfiguration complete message, transport channel reconfiguration complete message, radio bearer reconfiguration complete message.

Figure 2 is the message flow between RNC and Node B during the processing. Corresponding to step 101 and step 102 in Figure 1:

RNC sends a common measurement order (Common Measurement Initiation Request) to each Node B, step 201, the command contains some important information such as measurement amount, reporting method, filter coefficient, etc.; Return public measurement initial response (Common MeasurementInitiation Response) to RNC, step 202, and start to measure, when measuring while Node B finds and reaches reporting condition, Node B sends common measurement report (Common MeasurementReport) to RNC when reaching reporting condition ), step 203, for the periodic report mode, just report the measurement result once to RNC at regular intervals, step 204.

Fig. 3 is a flow of dedicated messages related to UE during processing. Corresponding to steps 105, 106, 107 in Figure 1:

After the RNC finds that the load of the same-coverage and different-frequency cell reaches a predetermined gap, it selects a suitable UE in the cell with a higher load, and prepares corresponding resources in the target cell (that is, the same-coverage and different-frequency cell with a lower load), and sends it to the target cell. The Node B corresponding to the target cell sends a radio link reconfiguration prepare message (Radio Link Reconfiguration Prepare), see step 301, after the Node B receives this message, the Node B will also reserve resources for the corresponding UE and return to the radio link Reconfiguration ready message (Radio Link Reconfiguration Ready), see step 302, RNC, after receiving this message, determines the point in time when handover will be performed, and sends radio link reconfiguration submission (RadioLink Reconfiguration Commit) to Node B, see Step 303, then send an inter-frequency hard handover (reconfiguration) command to the UE, see step 304, the command may be a physical channel reconfiguration or transport channel reconfiguration or radio bearer reconfiguration message, after the UE completes the air synchronization, send RNC returns inter-frequency hard handover (reconfiguration) completion message, see step 305, this message is corresponding to inter-frequency hard handover command, may be that physical channel reconfiguration completes or transport channel reconfiguration completes or radio bearer reconfiguration completes message, then Enter the normal communication process.

In addition, in order to avoid too many frequent balancing actions, step 109 is added to the second embodiment shown in FIG. 4 on the basis of the first embodiment shown in FIG. If the set threshold value is yes, it is considered that the load of different frequency cells with the same coverage is at a low level. At this time, inter-frequency load balancing is not considered, and it will not have a great impact on the system. You can not perform balancing Action, which can more effectively reduce the possibility of call drop caused by inter-frequency hard handover.

Claims (6)

1, load balance control method between the frequency in a kind of broadband CDMA system is characterized in that, said method comprising the steps of:

(1) radio network controller regularly obtains reflection cell load condition information from Node B;

(2) radio network controller is according to the load of predefined load threshold parameter, sub-district actual measurement and with the load that covers alien-frequency district, and whether decision is necessary to carry out balanced action;

(3) if the equilibrium action to alien-frequency district is carried out in decision, then in this sub-district, select the part subscriber equipment, and send the order of direct-cut operation between frequency to these subscriber equipmenies;

(4) subscriber equipment of execution switching returns in alien-frequency district and finishes message.

2, load balance control method between the frequency in the broadband CDMA system according to claim 1 is characterized in that, described step (1) specifically may further comprise the steps:

(1.1) radio network controller sends at sub-district public-measurement control command to Node B, requires to measure to receive broadband power and/or emission carrier power value, and sets the condition that reports, and for the periodic report mode, needs to set the cycle that reports; For reporting events, need to set thresholding, the triggered time that reports;

(1.2) Node B is to the up reception broadband power of respective cell and/or emission carrier power value, during report condition in reaching the measurement control order that radio network controller sends, reports to radio network controller;

(1.3) radio network controller stores the result that Node B reports, and uses during for needs.

3, load balance control method between the frequency in the broadband CDMA system according to claim 1 and 2 is characterized in that, in the described step (2) decision whether be necessary to carry out balanced action one of can be in the following ways:

(2.1) be limited as in the main system at up direction, can only select the reception broadband power that adopts up direction to receive, as duty ratio reference between each sub-district, the reception broadband power that receives when the cell uplink direction is higher than it when covering respective doors limit value that alien-frequency district sets, and balanced action is carried out in decision;

(2.2) be limited as in the main system at down direction, can only select to adopt down direction emission carrier power value, as duty ratio reference between each sub-district, when cell downlink direction emission carrier power value was higher than its respective doors limit value that covers the alien-frequency district setting together, the equilibrium action was carried out in decision;

(2.3) in the system that the uplink and downlink direction need be taken all factors into consideration, the reception broadband power and the down direction emission carrier power value that can adopt up direction to receive simultaneously, as duty ratio reference between each sub-district, reception broadband power that receives when the cell uplink direction and down direction emission carrier power value are higher than it respectively when covering respective doors limit value that alien-frequency district sets, and balanced action is carried out in decision;

4, load balance control method between the frequency in the broadband CDMA system according to claim 3, it is characterized in that, can also set an Xiamen limit value, when the load of sub-district actual measurement during less than this Xiamen limit value, system does not carry out the equilibrium action, to avoid too much frequent balanced action.

5, load balance control method between the frequency in the broadband CDMA system according to claim 1, it is characterized in that the command messages of the direct-cut operation in the described step (3) comprises: the scrambling code information of cell frequency information, sub-district and the resource information of being distributed.

6, load balance control method between the frequency in the broadband CDMA system according to claim 1 or 5 is characterized in that, selects the subscriber equipment of direct-cut operation one of can be in the following ways or combination in the described step (3):

(3.1) selection is not in the subscriber equipment of soft changing state;

(3.2) select QoS to require lower subscriber equipment;

(3.3) select the lower subscriber equipment of service rate.

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