CN1599468A - Method and device for zone-cross switchover of mobile communication system - Google Patents

Abstract

The invention provides a method and device for handover of a mobile communication system. The method includes the steps of: receiving a user (UE) measurement report; checking the original cell and the target cell according to the measurement report; searching for a corresponding differentiated handover decision strategy; judging whether it is necessary according to the measurement report and the differentiated handover decision strategy Perform handover, if necessary, handover to the target cell; if no handover is required, do not perform handover. The device of the present invention includes: a receiving device; a storage device; an acquisition device; a judging device; Utilizing the present invention can solve the problem of switching off calls.

Description

Method and device for handover in mobile communication system

technical field

The present invention relates to a mobile communication system, in particular to a method and device for handover of the mobile communication system.

Background technique

In order to facilitate those of ordinary skill in the art to understand the present invention, the terms used in this description are listed as follows:

CDMA code division multiple access code division multiple access

CIO: Cell Individual Offset Cell Individual Offset

HCS: Hierarchical Cell Structure Hierarchical Cell Structure

NodeB: NodeB base station (there can be several cells under a base station)

RNC: Radio Network Controller Wireless Network Controller

UE: User Equipment Mobile Station (Mobile Phone, Drive Test Equipment)

WCDMA: Wideband Code Division Multiple Access Wideband Code Division Multiplexing

Primary cell: the cell where the UE currently resides and receives services

Target cell: the cell that triggers the measurement report, and this cell will be the target of the handover when the handover is decided

In the existing cellular mobile communication system, the coverage of a large geographic area is usually divided into several cells, and a low-power transmitter (base station) is used to cover each cell to establish communication with users. The coverage radius of the cell is small, but many A single cell can cover an entire large geographic area. At the same time, using the same frequency in different cells can greatly improve the utilization of spectrum resources; adding cells using different frequencies in areas with dense users can increase the system capacity in this area.

When a mobile station leaves a cell and enters another cell, the signal received by the mobile station from the original cell must become weaker and weaker, while the signal it receives from the cell entering the cell will become stronger and stronger. In order to maintain the communication quality of the mobile station, it is necessary to transfer the connection of the mobile station from the original base station to the newly entered base station with stronger signal. This is the concept of handover in the cellular mobile communication system.

Figure 1 shows a typical handover process. It should be known that this figure is only a schematic flow chart. The steps are summarized as follows: UE finds that the quality of the current cell is degraded during the moving process, and after the quality of the target cell improves to meet certain conditions, it informs the RNC through a measurement report (a kind of signaling), and establishes a wireless communication connection with the UE directly during this process The NodeB undertakes the transmission task and transfers the signaling to the RNC. The RNC judges whether handover is necessary according to the measurement report submitted by the UE. If there is no handover, it does not respond, and the UE sends the measurement report to the RNC again at an appropriate time (for example, the measurement report can be sent again after a period of time in the cycle report) Report; if the RNC judges that handover is required, it will notify NodeB and UE through a handover command, and the two will perform the actual handover task, and the UE will establish a wireless connection with the new cell and start enjoying communication services.

To sum up, the decision of the RNC on the handover is the key to decide when the UE performs the handover. If the judgment is early, the UE is too far away from the new cell, and the UE cannot obtain satisfactory service after handover, and the call may be dropped; if the judgment is late, the UE is already far away from the original cell, and also cannot obtain satisfactory service May drop calls.

To solve this problem, the industry currently focuses on optimizing step ① in the figure, that is, the UE judges when the quality of the target cell meets certain conditions. In the protocol, various events are defined for UE measurement, such as the quality of the target cell is higher than an absolute value, the difference between the quality of the target cell and the quality of the main cell is lower than a threshold, etc., and the filter coefficient, hysteresis, and delay are designed A series of parameters such as trigger time make the UE measurement mechanism more flexible, and intend to solve the problem of RNC's decision on handover from the timeliness of measurement report reporting.

Such a solution has certain limitations for special scenarios. Special consideration is required when the transmission channels of individual cells vary greatly or the characteristics of individual cells require the services of this cell to require special cell services.

FIG. 2 is a schematic diagram of a handover of at least a particular cell (such as a tunnel) among multiple adjacent cells. When the UE is located in the main cell-X cell, there are four adjacent cells A, B, C, and D. Among them, A cell is a tunnel cell with a section of railway inside, so it can be judged that if the UE moves from the main cell to A cell If it is, then it must be in the train, and the speed will not be lower than 60 kilometers per hour. In this case, if the same measurement reporting mechanism and RNC decision algorithm as those of other cells are still used, it is bound to be too late to perform handover, resulting in call drop. Pay attention to the particularity of the tunnel scenario. Once the user moves into the tunnel without switching to a new cell, the signal from the original cell will not be received immediately, resulting in call drop.

Special scenarios like this cannot be solved by common solutions, because UE cannot know its moving direction, nor does it know the particularity of the scene it is in. It can only measure according to the parameters configured by the network, and the parameters of network configuration At most, it can only be configured according to the cell, that is, as long as the UE is located in the primary cell, it will use the parameters configured by the primary cell, and the same measurement reporting mechanism will be adopted no matter whether it moves to A, B or other cells.

In order to overcome these shortcomings, a CIO (CellIndividual Offset, cell independent offset) solution is provided in the communication protocol, and different CIO offsets can be set for different cells, so that when the UE is measuring, it An offset can be added to the measured quality of the target cell to determine whether the condition is satisfied and whether a measurement report needs to be sent. Through such a method, the UE can report the measurement report in advance when the target cell is still relatively poor, thereby triggering the handover in advance.

However, the CIO is only valid until the UE sends a measurement report. If the RNC is set to switch only after receiving 3 measurement reports and the quality of the target cell continues to increase, assuming that the UE sends a measurement report every 500 milliseconds, then from the time when the UE starts sending the first measurement report to when the RNC officially decides to switch The delay must be at least 1 second. During this time, the 120km/h express train has traveled 33m. Such a long distance is located at the edge of the cell, and the range of its signal change may have exceeded the amount of advance that the CIO can bring.

An implementation scheme of HCS (Hierarchical Cell Structure, hierarchical cell structure) is also provided in the existing communication protocol. This scheme divides cells into different levels, and defines different levels of priority for each level. In UE's idle mode, cell selection and reselection and in connection mode handover, the appropriate target can be selected according to different levels of priority. district.

However, the HCS hierarchical structure is effective for the entire network, and it is impossible to define several levels only for a special scenario. In a WCDMA network, the HCS level is related to the coverage of the cell and is divided into a macro cell layer and a micro cell layer. Cells at different levels can cover the same area. Due to the inherent co-channel interference effect in the WCDMA network, cells of different levels must use different frequency points, so the priority cannot be distinguished in the cells of the same level.

Therefore, it is desirable to treat different cell handovers differently, especially different cells at the same level.

Contents of the invention

The purpose of the present invention is to provide a more flexible and effective handover decision algorithm for the above-mentioned shortcomings of the prior art.

The present invention provides a method for handover of a mobile communication system, comprising the steps of:

receiving user (UE) measurement reports;

Viewing the original cell and the target cell according to the measurement report;

Searching for a corresponding differentiated handover decision strategy according to the original cell and the target cell;

According to the measurement report and the differentiated handover decision strategy, it is judged whether handover is required, and if necessary, handover is performed to the target cell; if handover is not required, no handover is performed.

Optionally, the differentiated handover decision strategy is determined according to properties of the original cell and the target cell.

Preferably, the step of determining the properties of the original cell and the target cell includes predetermined values according to the properties of the original cell and the target cell, and/or a predetermined function related to at least one measurement report and the properties of the cell.

Optionally, the differentiated handover decision strategy predetermined according to the properties of the original cell and the target cell includes:

When there is a target cell, handover is performed once a measurement report is received, and/or

When the target cell is greater than a predetermined threshold, handover is performed once a measurement report is received, and/or

When there is a target cell, handover is performed upon receipt of a secondary measurement report, and/or

Two measurement reports are received consecutively and the quality of the target cell in the second measurement report is not lower than that of the first measurement report, and the handover is decided, and/or

decision to switch upon receipt of three consecutive measurement reports, and/or

After receiving three consecutive measurement reports and the quality of the target cell in each measurement report is not lower than the previous measurement report, it is decided to perform handover.

Preferably, the differentiated handover decision strategy is predetermined according to the properties of the original cell and the target cell, including:

When there is a target cell, a measurement report is received, and at least the previous measurement report of the measurement report meets a predetermined condition before switching, and/or

When the target cell is larger than the predetermined threshold, a measurement report is received, and at least the previous measurement report of the measurement report meets a predetermined condition, and then handover is performed.

Optionally, the predetermined condition determines that the user enters the target cell in a specific manner, and the at least previous measurement report and the measurement report meet the predetermined condition corresponding to the specific manner.

Preferably, the predetermined condition includes that the user enters the target cell with a specific route and/or the user enters the target cell with a speed greater than a predetermined speed.

Optionally, the specific route is a vector.

Preferably, the step of switching if not required further includes: discarding the report; and/or

Set the state according to the differentiated handover decision strategy, and wait for the next measurement report.

The present invention also provides a device for handover of a mobile communication system, including:

a receiving device, configured to receive a UE measurement report;

The storage device stores the characteristics of each cell and the differentiated handover decision strategy for mutual handover determined according to the characteristics;

An obtaining device, configured to obtain the original cell and the target cell according to the measurement report, and search for a corresponding differentiated handover decision strategy in the storage device according to the original cell and the target cell;

judging means, judging whether handover is required according to the measurement report and the differentiated handover decision strategy,

switching means, switching to the target cell according to the result of the judging means; or not switching;

Wherein, the differentiated handover decision strategy is determined according to properties of the original cell and the target cell.

With the present invention, when the RNC makes a handover decision, different decision strategies can be adopted according to the situation of the cell where the UE currently resides and the information of the reported target cell. In this way, the function of early or delayed handover can be completed, and it can play a more powerful and flexible role in various special scene applications in actual network planning, thereby solving the problem of handover call drop.

Description of drawings

Figure 1 shows a typical handover process;

Fig. 2 shows a handover schematic diagram of at least a special cell (such as a tunnel) among a plurality of adjacent cells;

Fig. 3 is the principle flow chart of realizing the differentiated judgment method of the present invention;

Fig. 4 is a flow chart of an embodiment of implementing the method in Fig. 3 in a specific multi-changing environment cell.

Detailed ways

The present invention provides methods and apparatus for solving handovers with particular neighbor cells. In order to make it easier for those skilled in the art to understand and realize the present invention, the embodiments of the present invention are described in conjunction with the accompanying drawings.

Fig. 3 is a flow chart of the principle of implementing the differentiated judgment method of the present invention. FIG. 4 is a flowchart of an embodiment of implementing the method of FIG. 3 in the cell of FIG. 2 . First, after receiving the measurement report, the RNC checks the original cell and the target cell. Search for differentiated handover decision strategies. If the target cell is a common cell, handover is performed according to the usual rules. If the target cell is a special cell, handover is performed according to predetermined rules. This is the handover condition of the differentiated handover decision strategy in the figure. If the switching condition is satisfied, the decision is made to switch, otherwise, the report is discarded.

Usually, in this technical field, a unified decision algorithm is used for all cells, that is, no matter what the original cell is or what the target cell is, as long as the measurement report is reported, the same decision strategy is adopted, and most of the optimization is concentrated on the UE On the measurement report algorithm on the side, such as setting filter coefficients, hysteresis, and delayed trigger time, etc., the introduction of CIO is also optimized on the UE side. During UE measurement, an offset value can be added to the measurement results of a certain cell before event judgment. See if the measurement report is submitted. However, note that the measurement parameters of the UE are configured by the RNC, and the RNC can obtain much more cell neighbor relations and geographic location information than the UE, so setting differentiated handover decision strategies for different cells in the RNC is more than optimal The measurement report parameters on the UE side should be more flexible and effective.

However, HCS manages cells based on a layered structure. The protocol was first proposed for UE to obtain more information during cell selection, and this information can also be used in RNC to make differentiated handover decisions. However, due to the wide definition of the hierarchy, it is not only effective for a single cell, so it still cannot solve the handover problem in special scenarios.

The differentiated handover decision strategy of the present invention is realized by the RNC according to the difference of the cells, and adopts different strategies for different cells. If the RNC needs to make a handover decision based on the reported measurement report, it can flexibly control the number of times the measurement report to start the handover is reported according to the difference between the original cell and the target cell, so as to achieve differentiated decision.

Referring to Figure 2 again, according to the basic working process of mobile communication, the RNC at the convergence layer has more network planning information than the UE, and it can completely know that cell B is a tunnel scenario cell through configuration. Therefore, in the situation in Figure 2 In , although the UE still reports the measurement report according to the original rules, the RNC can treat it differently when making a decision. For example, when the quality of cell B, C, or D is reported in the measurement report reported by the UE, the RNC must wait until the UE reports three consecutive reports and the quality value continues to increase before deciding to perform handover. However, once the measurement report reported by the UE is found Report A in the middle, if the quality of the cell is better, only one report is needed, and the RNC can decide to perform handover, so as to ensure that the handover can be performed earlier and faster when the UE moves to the A cell to avoid call drop. Through such a differentiated decision algorithm, the RNC can more flexibly control the handover of the UE in various scenarios, thereby ensuring high enough user satisfaction all the time.

Fig. 4 is a flow chart of an embodiment of implementing the method in Fig. 3 in a specific multi-changing environment cell. After the RNC receives the measurement report, it reads from the measurement report that the current primary cell is A and the target cell is B; query the data database in the table on the right as shown in the figure, and know that A is a common type and B is a tunnel type; query reservation Or a differentiated handover policy library that is adaptive to predetermined rules; according to the current measurement report, determine whether the handover judgment condition is met? If it is satisfied: judge to perform handover; otherwise, do not perform handover, set the state according to the differentiated handover decision strategy, and wait for the next measurement report. Although the invention is described through this embodiment, it should be known that the specific content of the differentiated handover policy library may be different according to different handover decision implementations.

Usually, before or during the actual network operation, network planners set different handover priority relationships for different adjacent cells according to the actual network layout. In the operating space shown in FIG. 2 , the handover priority of primary cell X to cell A is 2, and the priority of handover to cells B, C, and D is 6. Usually, this priority relationship is unidirectional. Assuming that the current primary cell is cell X, if the priority of handover from cell X to cell A is 2, the priority of handover from cell A to cell X is not necessarily 2. Can also be equipped with 6 levels.

For different handover priorities, configure differentiated handover decision algorithms. The configuration of this part can be open for network planners to define, or it can be pre-configured inside the RNC, or it can be adaptively configured according to the formula, and it is generally not allowed to modify after configuration. The following table is an example of a differentiated handover decision algorithm: switch priority Differentiated Handover Decision Algorithm Level 1 As long as the RNC receives a measurement report from the UE, it will decide to perform handover level 2 As long as the RNC receives a measurement report from the UE and the quality of the corresponding target cell exceeds an absolute threshold, it will decide to perform handover Level 3 RNC receives two consecutive measurement reports and decides to switch level 4 The RNC receives two consecutive measurement reports and the quality of the target cell in the second measurement report is not lower than the first measurement report, then decides to switch Level 5 RNC receives three consecutive measurement reports and decides to switch Level 6 The RNC receives three consecutive measurement reports and the quality of the target cell in each measurement report is not lower than the previous measurement report, then decides to switch

Then, the parameters of the handover measurement are set for the cell. Various handover measurement events are stipulated in the protocol, such as 1A events, and such events are reported when the difference between the quality of the target cell and the quality of the primary cell is lower than a threshold. For each handover measurement event, each cell can be set differently. For example, the threshold of the 1A event in the current primary cell is 5dB, and the threshold of the 1A event in the adjacent A cell can be set to 3dB. In this way, when the UE camps on the current primary cell A threshold parameter of 5dB is used for the cell. After moving to cell A and handover occurs, cell A will become the new primary cell. At this time, the UE starts to use the threshold parameter of 3dB. Through such cell-oriented parameter setting, the UE can be extremely flexibly controlled to perform measurement and report a measurement report. If the network planner does not set these parameters for the cell, the cell can also use default parameters configured for the RNC. This step of optimization is mainly aimed at before the UE reports the measurement report.

After the RNC receives the UE's measurement report, it can select a differentiated handover decision algorithm according to the information in the measurement report. The measurement report of the UE includes the information of the cell where the UE is currently camped on (primary cell, ie, cell X) and the target cell (eg, cell A) that triggers the event report. The RNC can search the handover priority set in step 1 according to these information, for example, the handover priority from cell X to cell A is 2.

The RNC queries the table defined by the differentiated handover decision algorithm according to the handover priority, and makes a handover decision accordingly.

In the embodiment, each cell is given a predetermined value for switching to another cell. In fact, due to the specific environment in the cell, it is necessary to determine whether to enter the tunnel on a train or a car according to several consecutive reports. Knowing the direction of the train or motorway, these can be judged by a predetermined function determined according to the specific terrain, such as when entering a report from an ordinary cell into a tunnel cell, it can be judged whether a special handover strategy is required according to at least one previous report.

Those skilled in the art should also know that the present invention can be used simultaneously with existing technologies such as CIO and HCS.

The device for handover of the present invention includes: a receiving device for receiving UE measurement reports; usually, it is located in NODE B of the WCDMA system; a storage device located in the RNC stores the characteristics of each cell and the characteristics determined according to the characteristics A differentiated handover decision strategy for mutual handover; obtaining means for obtaining the original cell and the target cell according to the measurement report, and according to the original cell and the target cell, determine the characteristics of the cell and search for the corresponding difference in the storage means Judgment strategy for handover; judging means, according to the measurement report and the differentiated handover decision strategy, judge whether handover is needed; switching means, according to the result of the judging means, switch to the target cell; or not switch ; Wherein, the differentiated handover decision strategy is determined according to the properties of the original cell and the target cell.

With the present invention, when the RNC makes a handover decision, different decision strategies can be adopted according to the situation of the cell where the UE currently resides and the information of the reported target cell. In this way, the function of early or delayed handover can be completed, and it can play a more powerful and flexible role in various special scene applications in actual network planning, thereby solving the problem of handover call drop.

Although the present invention has been described through the embodiments, those skilled in the art know that the present invention has many variations and changes without departing from the spirit of the present invention. For example, although in the description, the present invention is mainly described with the CDMA system, those skilled in the art Knowing that the present invention is applicable to TDMA systems including GSM systems and PCS systems and even FDMA systems, it is therefore intended that the appended claims cover such modifications and changes without departing from the spirit of the invention.

Claims (10)

1. A method for handover of a mobile communication system, characterized in that it comprises steps: receiving user (UE) measurement reports; Viewing the original cell and the target cell according to the measurement report; Searching for a corresponding differentiated handover decision strategy according to the original cell and the target cell; According to the measurement report and the differentiated handover decision strategy, it is judged whether handover is required, and if necessary, handover is performed to the target cell; if handover is not required, no handover is performed. 2. The method according to claim 1, wherein the differentiated handover decision strategy is determined according to properties of the original cell and the target cell. 3. The method according to claim 2, wherein the step of determining the properties of the original cell and the target cell includes predetermined values according to the properties of the original cell and the target cell, and/or with at least one measurement report and cell The nature of the predetermined function. 4. The method according to claim 3, wherein the differentiated handover decision strategy is a predetermined strategy according to the properties of the original cell and the target cell comprising: When there is a target cell, handover is performed once a measurement report is received, and/or When the target cell is greater than the predetermined threshold, handover is performed once a measurement report is received, and/or When there is a target cell, handover is performed upon receipt of a secondary measurement report, and/or Two measurement reports are received consecutively and the quality of the target cell in the second measurement report is not lower than that of the first measurement report, and the handover is decided, and/or decision to switch upon receipt of three consecutive measurement reports, and/or After receiving three consecutive measurement reports and the quality of the target cell in each measurement report is not lower than the previous measurement report, it is decided to perform handover. 5. The method according to claim 3, wherein the differentiated handover decision strategy is a strategy predetermined according to the properties of the original cell and the target cell comprising: When there is a target cell, a measurement report is received, and at least the previous measurement report of the measurement report meets a predetermined condition before switching, and/or When the target cell is larger than the predetermined threshold, a measurement report is received, and at least the previous measurement report of the measurement report meets a predetermined condition, and then handover is performed. 6. The method according to claim 5, wherein the predetermined condition determines that the user enters the target cell in a specific manner, and the at least previous measurement report and the measurement report meet the predetermined condition corresponding to the specific manner. 7. The method according to claim 6, wherein the predetermined condition includes that the user enters the target cell with a specific route and/or the user enters the target cell with a speed greater than a predetermined speed. 8. The method of claim 7, wherein the specific route is a vector. 9. The method according to any one of the preceding claims, wherein the step of switching if not required further comprises: discarding the report; and/or Set the state according to the differentiated handover decision strategy, and wait for the next measurement report. 10. A device for handover of a mobile communication system, characterized in that it comprises: a receiving device, configured to receive a UE measurement report; The storage device stores the characteristics of each cell and the differentiated handover decision strategy for mutual handover determined according to the characteristics; An obtaining device, configured to obtain the original cell and the target cell according to the measurement report, and search for a corresponding differentiated handover decision strategy in the storage device according to the original cell and the target cell; judging means, judging whether handover is required according to the measurement report and the differentiated handover decision strategy; switching means, switching to the target cell according to the result of the judging means; or not switching; Wherein, the differentiated handover decision strategy is determined according to properties of the original cell and the target cell.

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