WO2006017983A1

WO2006017983A1 - A method of load handover of mobile communication system

Info

Publication number: WO2006017983A1
Application number: PCT/CN2005/001271
Authority: WO
Inventors: Jiancheng Du
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2004-08-16
Filing date: 2005-08-16
Publication date: 2006-02-23
Also published as: WO2006017983A8; CN1738477A; CN100373986C

Abstract

The present invention discloses a method of load handover of mobile communication system which allows the handover can be carried out based on the existing network devices without modifying or adding interface when the handover is performed across the different BSCS. Based on the method, the BSC first transmits the load handover request to Mobile Switch Center (MSC); the said MSC selects the optimum target cell from the table of neighbour cell of source cell, and determines whether the target cell could support the new load, if yes, starts the load handover from the source cell to the optimum target cell, otherwise, rejects the said load handover request.

Description

Mobile communication system load switching method

The present invention relates to mobile communication technologies, and in particular, to a load switching method for a cross-base station controller in a mobile communication system.

Background technique

In WCDMA systems, handover technology is a key technology to support users' global roaming. It is an important function of WCDMA systems and is unique to cellular systems, directly affecting the performance of the entire system. As is known to those skilled in the art, the so-called handover is when a mobile station ("MS") calls a communication channel from one cell to another during a call. Switching operations occur frequently during MS communication. For example, when the quality of the call is degraded due to external interference, or because there are too many users in one cell and cannot guarantee the normal use of all users, the current communication service will be switched to the new channel and communication will continue. The communication link between the original base station and the MS will likely be replaced by the communication link between the new base station and the MS. There are several classification methods for switching types. According to the connection establishment and release between MS and network, it can be divided into: softer switching, soft switching and hard switching. According to the reason of switching, it can be basically divided into edge switching and load switching. Among them, the edge switching is that when the transmission quality is acceptable, if the MS is connected to another cell to the total level, or when the communication quality can be greatly improved, the serving cell of the MS can be changed. However, the edge switching may be inconsistent with the locally optimized transmission quality, and the edge switching cannot be performed when the transmission quality is not good. The load switching is the traffic switching when a cell is congested and the neighboring cell is idle. This network load-based handover can balance the traffic between cells and prevent cell overload, but must be handled carefully. Because it contradicts the edge switching criteria, because such switching will inevitably disturb the cell planning and increase the interference level in the surrounding area.

Both edge switching and load switching are initiated by the base station controller. The efficiency of handover is often closely related to the accuracy of the information of the handover target cell as known by the base station controller. Especially in the load switching process, the load switching situation is various. When load switching is required, the base station controller must fully understand the current load information of the target cell, no matter what the situation is. Here, there are two general considerations: If the target cell and the source cell are under the control of the same base station controller, and the base station controller is responsible for radio resource allocation, then it is naturally understood The load situation of each cell in the jurisdiction, that is, understanding both the target cell and the load information of the source cell, the load switching algorithm is very simple. However, if the target cell and the source cell are managed by different base station controllers, for example, in the case of cross-system load handover, the base station controller corresponding to the target cell and the source cell may be located in the same mobile switching center (Mobile Switching Center, called "MSC"). Or cross-MSC, in which case it is possible to switch from a WCDMA system to a Global System for Mobile Communication (GSM) system, or conversely, this cross-system load switching algorithm is very complex, resulting in this situation. The load switching under is inefficient.

In the prior art, in the face of handling load switching in a relatively complicated situation, as shown in FIG. 1, the wideband code division multiple access system 10 includes a user 103, which accesses the system through the base station 102, and the base station controller 101 is responsible for controlling the base station 102. And connected to the mobile switching center 100 through the Iu interface 104. In WCDMA, the base station controller may also be called a radio network controller (Radio Network Controller, called "RNC"), and the base station may also be called Node B (Node B).

Another system in Fig. 1 is a global mobile communication system 11, which includes a user 113, which is connected to the system via a base station 112, which is responsible for controlling the base station 112 and is connected to the mobile switching center 110 via the A interface 114.

It is assumed that the base station controller corresponding to the target cell and the source cell is located at two different MSCs, and is switched from the WCDMA system to the GSM system or vice versa. That is, the user 103 in the wideband code division multiple access system 10 needs to switch to the channel in the global mobile communication system 11, or the user 113 in the global mobile communication system 11 needs to switch to the channel in the wideband code division multiple access system 10, The base station controller needs to know the load information of the target cell by the following two methods:

The first way: the load information is directly transmitted between the base station controllers of the two systems by the newly added Iur-g interface 12 between the base station controller 101 and the base station controller 111; the respective base station controllers know the target The load information of the cell can make a decision on whether to perform load switching.

The second mode: the cell load information is transmitted to the MSC by the respective base station controller through the A interface or the Iu interface. That is, the base station controller 111 transmits the own cell load information to the mobile switching center 110 through the A interface 114, or the base station controller 101 transmits the own cell load information through the Iu interface 104 to the mobile switching center 100. Finally, the mobile switching center 110 and mobile switching The central office 100 exchanges the cell load information of each other through the corresponding network, and then sends the information to the base station controllers under their respective jurisdictions, and makes a decision on whether or not the load can be switched.

In the prior art solution, the collection, analysis, and processing of the target cell information for the load switching are all performed by the base station controller, so that for the load switching across the base station controller, different base station controllers need to be added. An additional Iur-g interface is used for communication. As the addition or modification of the interface causes changes in many network elements of the access network and the core network, the new interface is re-tested, which is costly and difficult to maintain.

Summary of the invention

In view of this, the main object of the present invention is to provide a mobile communication system load switching method, so that load switching across a base station controller does not require modification or addition of an interface, and is directly implemented on an existing network device.

To achieve the above object, the present invention provides a mobile communication system load switching method, including:

A. The base station controller sends a load switching request to the mobile switching center.

B. The mobile switching center selects an optimal target cell from a neighbor cell list of the source cell, and determines whether the best target cell can withstand a new load, and if yes, performs from the source cell to the best The load switching of the target cell, otherwise, the load switching request is rejected.

among them:

The mobile switching center obtains information about all cells in the neighbor cell list of the source cell, obtains the available resource probability according to the information, and selects the cell with the highest probability of available resources as the best target cell;

Whether or not the available resource probability of the best target cell exceeds a set threshold determines whether it can withstand a new load.

The neighboring cell table of the source cell and the available resources of all cells in the neighbor cell list of the source cell are pre-configured;

The method further includes:

The mobile switching center queries the neighboring cell list of the source cell according to the received load switching request, and if the random target cell is not included in the neighboring cell table of the source cell, the random port is randomly The target cell is in a neighbor table of the source cell. The method performs load switching from the source cell to the best target cell according to the following steps:

Transmitting, by the mobile switching center, a handover request to a base station controller of the best target cell; the mobile switching center transmitting a load handover command to the source cell base station controller, where the source cell base station controller sends a handover request to a user equipment Switch commands.

The information of the cell includes statistical information and configuration information.

The statistics information includes the number of location updates of the cell in the current time period, and the current number of calls of the cell in the current time period, where the configuration information includes the maximum number of calls of the cell in the busy time period, and the available resource probability and location The number of location updates is inversely proportional, and the available resource probability is proportional to the difference between the maximum number of calls minus the number of current calls.

The load switching method of the present invention is applicable to load switching between a wideband code division multiple access mobile communication system and a global mobile communication system.

By comparison, it can be found that the technical solution of the present invention is different from the prior art in that the target cell information processing, selection judgment and the like are directly performed by the MSC to complete the load switching; and the cell is obtained by learning the message from the base station controller on the MSC side. Information: The probability of the available resources of the cell is measured by information such as the current number of calls of the cell, the number of location updates, and the maximum number of calls, and the target cell for load handover is selected.

The difference in this technical solution brings about a more obvious beneficial effect, that is, since the load switching process is basically completed by the MSC, the communication across the base station controller is avoided, and the cost brought about by adding or modifying the interface is removed; The MSC side automatically acquires cell information for learning RNC messages, which greatly improves the efficiency of load switching, and reduces the load switching operation. The comprehensive statistical information and configuration information are used to more accurately measure the available resource probability of the cell, which is greatly improved. 'The reliability of load switching.

DRAWINGS

1 is a schematic diagram of cross-system load switching in the prior art;

2 is a flow chart of a common MSC load handover in accordance with one embodiment of the present invention.

detailed description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings. The invention directly adopts the MSC to collect, analyze and process the target cell information of the load switching, whereby the MSC completes the target cell load judgment, the target cell selection, and the load switching timing of the load handover, so that different base station controllers or different systems are used. The load switching can be done efficiently and independently of each base station controller. The target cell information in the MSC may be obtained through initial configuration, or may be learned by using a message of a radio network controller (Radio Network Control, called "RC"), thereby reducing the implementation complexity of the load switching. The RNC here may also be referred to as a base station controller. In addition, the MSC side calculates the available resource probability of the cell by using the configuration information such as the current number of times of the cell, the number of times of the location update, and the maximum number of calls, so as to determine whether the load switching of the cell is feasible and select the target cell for optimal load handover. , improve the reliability of load switching.

The present invention attempts to solve the load switching between the base station controllers by using a single cartridge technology, thereby avoiding major upgrade changes to the existing network. Typically applicable to, but not limited to, load switching from a WCDMA system to a GSM system.

It can be known from the principle of the invention that the primary problem to be solved by the present invention is to use some means to let the MSC know the target cell information of the target for load switching. Those skilled in the art will appreciate that the location update process is a basic function of mobility management, which is defined by the Home Location Register (HLR), MSC/Visitor Location Register (Visitor Location Register). The logical cooperation between entities such as "VLR" is completed. The HLR records the current location information of the mobile terminal and all user data; the VLR records relevant user data roaming to the mobile terminal controlled by the VLR; the MSC processes the location registration process of the mobile terminal, talks with the mobile terminal, and interacts with the HLR and the VLR. . Location updates include location registration, periodic location registration, user data deletion, and more. It can be seen that there are generally cell-based statistics about location updates in the MSC. Moreover, the mobile terminal performs periodic location update, and records the number of location updates LocUpNum in a period of time T in the MSC, which basically reflects the number of potential users in the cell; and also records the busy period T of each cell. The maximum number of calls within CallNumbusyH, this value can represent the maximum amount of resources available to the cell. In particular, this value is a statistical value, which is very useful in network network planning, because network resources are configured according to this value; The current call count CallNumCurrent of the current cell recorded in the MSC can also be utilized, and the value is defined as a period of time before the current time. The number of calls within T. After having the above three values, you can define the resource probability AresPro, which is defined as follows:

AResPro = ( CallNumbusyH - CallNumCurrent ) /LocUpNum Its meaning is to describe the possibility that a cell will accept a resource request in the current state without causing a cell overload. For example, when CallNumCurrent is large (of course, it is impossible to be greater than CallNumbusyH), it indicates that the cell is very busy within a period of time before the current time, causing AresPro to be small. If the load is switched at this time, it will occupy a relatively tight wireless channel. Resources may cause overload of the community. On the other hand, when CallNumCurrent is small, it indicates that the cell is idle in a period of time before the current time. The result of AresPro calculation is very large. At this time, the cell can take out the idle wireless channel and other resources to accept the load switching request. MSC owns AresPro, which is equivalent to understanding the information in the cell under its jurisdiction. For load switching, it is equivalent to having source cell information. In this case, you can define a degree. If AresPro exceeds this degree, you can accept load switching. If you do not, you cannot switch the load.

The load switching also needs to know the target cell information, and there are two methods for obtaining the target cell information. The first method is that the number of resources per cell is directly configured to the MSC or the neighbor relation table of the cell is directly configured to the MSC, but the method is It is necessary to make a large number of data configuration groups on the MSC side. The work is cumbersome and error-prone, and if the resources on the access network side change, it should be noted that these changes occur if a certain carrier board fails or a base station loses power. Or the dynamic channel of the traffic channel (Traffic Channel) and the Stand-alone Dedicated Control Channel (SDCCH) are generated in a certain cell of GSM, and the related protocol interfaces need to be modified to support The access network resource information is dynamically reported to the MSC, which is too expensive as described in the disadvantages of the prior art. Therefore, the present invention does not use this method to obtain target cell information.

The second method is adopted by the present invention, that is, the MSC can learn the neighbor information of the cell through learning. This is because although the cell neighboring information is not configured on the MSC side of the general source cell, the MSC has a learning function, that is, the access network initiates the handover every time. The source cell and the target cell information in the request command are extracted and recorded. After a period of learning, the MSC can obtain enough neighbor information, including the frequency of the neighboring cell, the scrambling code, and whether there is a transmit diversity. Wait.

The load switching is ultimately determined and initiated by the source base station controller. The following process is described in Figure 2. Next, for the description of the cylinderization, !_ is set to the common MSC case, and the situation across the MSC is similar:

This process generally consists of two major parts.

The first part is that the source base station controller sends a load switching request to the MSC directly connected thereto, and specifically includes two sub-steps of step 2000 and step 2100.

First, in step 2000, when the source base station controller decides to initiate a load handover, although the load condition of the target cell is not known, the blind handover may be performed, that is, only one of the neighboring cell tables is selected as the target cell. . The base station controller sends a load switching request to the MSC;

Next, in step 2100, the MSC queries the neighbor cell list of the source cell according to the received load handover request. If the random target cell is not included in the neighbor cell list of the source cell, the random target cell is added to the neighbor cell list of the source cell. . This is actually the learning process of MSC.

The second most part of the process, the MSC selects the best target cell from the neighbor cell list of the source cell, and determines whether the best target cell can withstand the new load, and if so, proceeds from the source cell to the best target cell. The load is switched, otherwise, the load switch request is rejected. Each step after step 2200 belongs to this section.

In step 2200, the MSC of the target cell calculates the AresPro of the current cell, and the MSC obtains the available resource probability of the information of all the cells in the neighbor cell of the source cell, and selects the cell with the highest probability of available resources in the neighbor cell of the source cell. The best target cell; there are two options to achieve the above effects:

In the first scheme, the MSC directly configures the neighbor cell list of the source cell; or directly configures the available resource probability of all cells in the neighbor cell list of the source cell in the MSC; and selects the cell with the highest resource probability in the neighbor cell list of the source cell. For the best target area. The basis of this scheme is the first method of obtaining the target cell information as described above.

In the second scheme, the neighboring cell list of the source cell is dynamically established in the MSC. The MSC dynamically establishes the neighbor cell list of the source cell by learning the message of the base station controller. Then, the MSC calculates the available resource probability according to the statistical information and configuration information of all the cells in the neighbor cell list of the source cell. The statistics information includes the number of location updates of the cell in the current time period, the current number of calls of the cell in the current time period, and the configuration information includes the maximum number of calls of the cell in the busy time period, and the available resource probability is inversely proportional to the number of location updates. , available resource probability and maximum number of calls The difference between the number of current calls minus the number of calls is proportional. That is, the information of all cells in the neighbor list is analyzed according to the calculation formula of AresPro described above. Finally, the cell with the highest probability of available resources in the neighbor cell list of the source cell is selected as the best target cell.

In the following step 2300, it is determined whether the value of the cell resource probability in the neighboring cell table is greater than a certain threshold Thresthold, that is, whether the probability of the available resource of the best target cell exceeds a set threshold, and if yes, then Go to step 2400, otherwise go to step 2310.

In step 2310, since it is determined in step 2300 that the value of the cell resource probability in the neighbor list is the largest than the Threshold, it is not necessary to forward the request to the access network under the target cell MSC. A reject load switching request is sent to the source cell base station controller. The process ends.

Then, in step 2400, since it is determined in step 2300 that the value of the cell resource probability in the neighbor cell list is greater than the Threshold, the load switching from the source cell to the best target cell is performed; the specific two sub-stages are initially The base station controller of the best target cell sends a handover request; and then sends a load handover command to the source cell base station controller.

Finally, in step 2500, the source cell base station controller issues a handover command to the user equipment. The process ends.

Although the present invention has been illustrated and described with reference to the preferred embodiments of the present invention, those skilled in the art The spirit and scope of the invention is defined by the appended claims.

Claims

Rights request

A mobile communication system load switching method, comprising:

B. The mobile switching center selects an optimal target cell from a neighbor cell list of the source cell, and determines whether the best target cell can withstand a new load, and if so, performs from the source cell to the best The load switching of the target cell, otherwise, the load switching request is rejected.

The mobile communication system load switching method according to claim 1, wherein the mobile switching center obtains information of all cells in a neighbor cell list of the source cell, and obtains available resource probability according to the information. The cell with the highest probability of selecting the available resources is the best target cell. '

3. The mobile communication system load switching method according to claim 1, wherein whether the available resource probability of the best target cell exceeds a set threshold determines whether it can withstand a new load.

The mobile communication system load switching method according to claim 3, wherein the neighboring cell list of the source cell and the available resource probability of all cells in the neighbor cell list of the source cell are pre-configured.

The mobile communication system load switching method according to claim 4, further comprising: the mobile switching center querying the neighbor cell list of the source cell according to the received load switching request, if The random target cell is not included in the neighbor cell list of the source cell, and the random target cell is added to the neighbor cell list of the source cell.

6. The mobile communication system load switching method according to claim 5, wherein the load switching from the source cell to the optimal target cell is performed according to the following steps:

The mobile communication system load switching method according to claim 2, wherein the information of the cell includes statistical information and configuration information.

The mobile communication system load switching method according to claim 7, wherein the statistical information includes a number of location update times of the cell in the current time period, and the current time of the cell The current number of calls in the segment, the configuration information includes the maximum number of calls of the cell in the busy period, the available resource probability is inversely proportional to the number of location updates, and the available resource probability is subtracted from the maximum number of calls The difference in the number of current calls is proportional.

The mobile communication system load switching method according to any one of claims 1 to 8, wherein the load switching method is applicable to a wideband code division multiple access mobile communication system and a global mobile communication system. Load switching.