CN100362903C

CN100362903C - A method of hard switch between heterogeneous systems for WCDMA system

Info

Publication number: CN100362903C
Application number: CNB2005100690629A
Authority: CN
Inventors: 张景宝; 郭华志
Original assignee: Beijing Northern Fiberhome Technologies Co Ltd
Current assignee: CICT Mobile Communication Technology Co Ltd
Priority date: 2005-05-11
Filing date: 2005-05-11
Publication date: 2008-01-16
Anticipated expiration: 2025-05-11
Also published as: CN1671243A

Abstract

The present invention relates to an alien system hard switch method for a wideband code division multiple access (WCDMA) system. The method is especially suitable for application in the primary stage of the establishment of third generation of a mobile communication system network; the method of the present invention can be used for well guaranteeing the effective realization of the alien system hard switch required by the WCDMA system, improve the signal quality of user communication in an optimal mode and reduce the transmitting power of UE and the interference to other cells. The method of the present invention also relates to the technological contents of the treatment of wireless network emergency situations, the scheduling among modules in the integral system and the planning layout of a 3G system network; the switch method of the present invention is also suitable for other code division multiple access systems.

Description

Inter-system hard switching method for wideband code division multiple access system

Technical Field

The invention relates to a method for inter-system hard handover of a Wideband Code Division Multiple Access (WCDMA) system, which is particularly suitable for the initial establishment application of a third generation mobile communication system network. The invention also relates to the technical contents of processing of wireless network emergency, scheduling among modules in the whole system and network planning layout of the 3G system, and the switching method of the invention is also suitable for other Code Division Multiple Access (CDMA) systems.

Background

The application of mobile communication systems is becoming more and more widespread, and many key technologies in the systems are becoming more and more sophisticated, but some problems still need to be solved, and cell switching is one of the main problems. In a cellular radio communication system, a radio communication coverage area is composed of a number of partly overlapping cells. When a mobile user moves in this area, it often happens that the mobile user in a connected state with a cell is handed over from one cell to another cell. In the first and second generation cellular mobile communication systems, for a frequency used by a given cell, other neighboring cells are no longer available, i.e., there is a spatial separation between cells using the same frequency, resulting in frequency reuse. Therefore, the handover of a mobile subscriber between cells is mainly performed on channels of different frequencies, and all old radio links of the mobile subscriber need to be released before a new radio link of the mobile subscriber is established.

Since the third generation (3G) WCDMA mobile communication system is in the initial stage of network establishment, its network coverage must be limited, and meanwhile, for smooth transition between the second generation (2G) mobile communication system service and the third generation (3G) mobile communication system service, the 3G WCDMA system must support the user terminal (UE) to switch between the 3G WCDMA system and the existing GSM/GPRS network, such as TDMA, of the 2G system. The WCDMA and GSM standards support inter-handover between WCDMA and GSM. When a UE served by a 3G system moves, due to changes in the surrounding environment or a rapid increase in the number of users in the current 3G system cell, the communication quality of the UE in the 3G system network deteriorates, and if the requirement of the UE on the communication quality cannot be met well only through soft handover in the 3G system, in an area covered by a 2G network, it is necessary to consider adopting inter-system hard handover between the 3G system and the 2G system to obtain better communication quality. Before implementing the hard handover, the quality of signals of different cells of the 2G network, which are measured and reported, needs to be comprehensively evaluated, and the UE is timely handed over to a system with better quality, that is, the inter-system hard handover is implemented. Since hard handover may result in a call drop, reducing the risk of call drop is an important consideration in implementing inter-system handover.

The WCDMA system of 3G has many special features compared with other 2G systems such as GSM system and CDMA system, and since the commercial development time of 3G in each country is relatively short, there is no inter-system hard handover method in the prior art that can reduce the risk of call drop, so it is necessary to provide an inter-system hard handover method that can effectively provide inter-system hard handover with the 2G system and reduce the risk of call drop at the initial stage of network establishment of the WCDMA system of 3G.

Disclosure of Invention

The invention aims to provide a method for hard handover of different systems in a wideband code division multiple access system, which is based on event trigger reporting. The technical principle adopted in the method of the present invention is explained below.

In the specification of 3gpp TS 25.331, two methods can be selected when a measurement report of a UE in a WCDMA system is specified to be reported to a Radio Network Controller (RNC): a periodic reporting mode and an event trigger reporting mode. The method is mainly provided by adopting an event triggering and reporting mode. In the method, events defined in a 3GPP TS 25.331 specification are fully utilized for selective and reasonable combined use, so that frequent unnecessary inter-system hard handover is avoided as much as possible, and UE acquires as much link support as possible in the inter-system hard handover, thereby reducing the risk of call drop.

The method of the invention uses two preconditions: firstly, a geographical cell where the UE is located has multi-system coverage, namely a 3G WCDMA system and a 2G GSM system are simultaneously arranged, otherwise, the UE cannot perform inter-system hard handover; secondly, an event trigger reporting mode is used in the measurement control command.

According to the specification of the 3gpp TS 25.331 specification, the following events in the specification are adopted for the method of the present invention:

(1) Event 3A: the estimated quality of the currently used UTRAN frequency is below a certain threshold and the estimated quality of the other systems is above a certain threshold;

(2) Event 3B: the estimated quality of the other systems is below a certain threshold;

(3) Event 3C: the estimated quality of other systems is above a certain threshold;

(4) Event 3D: in other systems the best cell change is made.

According to the technical specification, no matter which of the four events the UE measurement result belongs to, the UE reports the event to the RNC in the WCDMA system.

In applying the method of the present invention, the WCDMA system is in four states and performs state transitions between the four states while performing the various steps of the method of the present invention. The specific contents of the four states are as follows:

state a: the UE keeps measuring the downlink carrier frequency of each cell required by the soft handover in the WCDMA system, reports the estimated quality of the same-frequency measurement calculated according to the measurement result and reports the information of the measured cell in the WCDMA system; the estimated quality of the above-mentioned co-frequency measurements in a WCDMA system is calculated according to the following formula (1).

In the formula (1), Q _UTRAN An estimated quality representing the active set at the current UTRAN usage frequency;

M _UTRAN the estimated quality of the active set in other units of the current UTRAN usage frequency may be Ec/No or RSCP of the downlink;

M _i the measurement quality of cell i in the active set;

N _A the number of cells in the active set;

M _Best measurement results for the strongest cell in the active set;

w is the weight coefficient transmitted from RNC of WCDMA to UE;

the measured value is the signal-to-noise ratio (Ec/No), M, of the downlink carrier frequency _UTRAN 、M _i 、M _Best In decibels (dB);

the measured value is the received signal level (RSCP) of the downlink carrier frequency, M _UTRAN 、M _i 、M _Best In milliwatts (mW);

state b, called as inter-system measurement state, where the RNC sends an inter-system measurement command to the UE, and the UE measures signals of cells around the inter-system and reports the measurement result, usually measuring, for example, the taught signal strength indication (RSSI) of a carrier in the GSM system;

and c, state: the RNC stores the related information of the different system cells contained in the event reported by the UE and waits for the subsequent measurement result;

and a state d: and in the switching execution state, the RNC executes the inter-system hard switching to switch the UE from the 3G WCDMA system to the 2G system.

The invention relates to a different system hard switching method for WCDMA system, which comprises the following steps:

step 1, in a state a, if UE reports that the measured estimated quality of the intra-frequency measurement in the WCDMA system is lower than a certain predetermined threshold to RNC, initiating inter-system measurement, namely, a Radio Network Controller (RNC) of the WCDMA system sends an inter-system measurement command to the UE, and under the condition that the geographical area where the UE is located has inter-system coverage, for example, under the condition that 2G GSM system cell coverage exists, the UE is required to measure the inter-system, measure the estimated quality of the inter-system, report the measurement result to RNC, and switch from the state a to a state b;

step 2, in state b, when the RNC analyzes the different system measurement report, the quality of the same frequency signal reported by the UE is higher than a certain predetermined threshold, which indicates that the quality of the WCDMA system signal can meet the service requirement of the UE, and the state b enters state a;

step 3, in state b, UE carries out inter-system measurement, if RNC receives a 3C measurement report event reported by UE, RNC stores inter-system cell information contained in the report event, and enters state C from state b;

step 4, in the state c, the UE carries out inter-system measurement, if the RNC receives a 3D measurement report event reported by the UE, the best cell of the inter-system is updated, and the state c is kept;

step 5, in the state c, the UE carries out the measurement of the different systems, and if all the cells in the different systems reported to the RNC meet the event 3B, the state c enters the state B; if some cells in the different system reported to RNC meet the event 3B, deleting the cells and keeping in the state c;

step 6, in state c, when the RNC analyzes the different system measurement report, the quality of the same frequency signal reported by the UE is higher than a certain predetermined threshold, which indicates that the quality of the WCDMA system signal can meet the service requirement of the UE, and the state c enters state a;

and 7, if the cell quality meets the event 3A, selecting a corresponding cell from the cells, namely selecting the cell with the best measurement quality. And when the cell is selected, referring to the best cell stored in the step 4 as a selection basis, selecting the best cell to execute the inter-system hard handover, and entering a state d from a state c.

In the above method for inter-system hard handover, in step 1, in state a, the condition for initiating inter-system measurement further includes: cell congestion, or link quality degradation, or the user terminal moving to the cell border, or intra-system soft handover is not allowed.

The above-mentioned method for hard handover between different systems is characterized in that in step 3, handover can be performed only when the signal quality of the cell of different system meets a certain condition, so as to avoid the negative effect of unnecessary handover on the system itself.

The inter-system hard handover method is characterized in that in step 4, the measured inter-system cell information is stored and compared and sorted to obtain the cell with the best quality, so that a satisfactory inter-system cell is selected to perform inter-system hard handover processing during handover execution.

The inter-system hard handover method is characterized in that in step 5, the measured inter-system cell information is stored and compared to obtain a cell with poor quality, and the cell with poor quality is deleted when the quality is low to a certain degree, which is beneficial to avoiding the storage of too much unnecessary inter-system cell information in the memory.

The method for switching between different systems is characterized in that in the steps 2 and 6, the UE simultaneously reports the measurement reports of the same frequency, different frequency and different systems, so that the system can select the carrier frequency meeting the UE service requirement according to the signal current situation of the wireless network in time, and the mutual scheduling among the submodules of the switching overall module is also reflected.

The above-mentioned method for hard handover between different systems is characterized in that in step 7, only when the signal quality of the cell of different systems reaches a certain degree, that is, the handover requirement can be fully satisfied, and when there is enough capacity to carry the current service of the UE, the hard handover between different systems is executed, thereby ensuring the success rate of hard handover and avoiding frequent handover at the cell boundary.

In an emergency situation, for example, the quality of a 3G cell serving the UE is sharply reduced, a higher service request initiated by the UE suddenly occurs in the cell, so that the coverage of the cell is reduced, and the load is increased, which causes problems of signaling delay and call drop of other UEs, etc., an inter-system hard handover method in an emergency situation, that is, single event decision, may be adopted. Generally, the estimated quality of intra-frequency measurements in WCDMA systems is used as a decision condition for emergency situations. When the estimated quality of the co-frequency measurement of the WCDMA system is lower than a preset threshold, the conventional switching method is changed into a switching method of single event judgment.

The invention relates to a different system hard switching method for WCDMA system emergency, which comprises the following steps:

step 1, in a state a, an RNC sends a different system measurement command to UE, informs the UE in the command, does not make judgment of events 3B, 3C and 3D, requires the UE not to report the three events, reduces a trigger threshold of the event 3A, shortens trigger time of the 3A event, informs the UE of an adjustment result, and enters a state B from the state a;

step 3, as long as the measurement report has the different system information, the state b enters the state c, thus shortening the period of switching judgment and simultaneously reducing the difficulty of switching judgment;

step 4, in the state c, when the RNC analyzes the different system measurement report, the same frequency signal quality reported by the UE is higher than a certain predetermined threshold, which indicates that the signal quality of the WCDMA system can meet the service requirement of the UE, and the state c enters the state a;

and step 5, in the state c, as long as the RNC receives that the reporting event of the UE is the event 3A, directly selecting the cell with the best quality in the cells of the different systems according to the related information of the cells of the different systems contained in the reporting event to execute the hard handover of the different systems, and entering the state d from the state c.

The method for the inter-system hard handover in the emergency case of the invention omits the steps 4 and 5 in the conventional method, so that the inter-system handover can be rapidly and effectively carried out in the emergency case, and the UE can be ensured to obtain good quality service. The emergency inter-system hard handover method substantially solves the problem that the UE is located at the edge of the 3G cell and needs emergency handover, and has the characteristics of short judgment period, simple execution condition and the like.

The method for hard handover between different emergency systems is characterized in that in step 1, when an emergency occurs, the RNC defines an event reported by the UE and a decision threshold and trigger time of the event in a measurement control command sent to the UE, and this operation enables the UE to be handed over to a different system cell as soon as possible in the emergency.

The hard handover method for different emergency systems is characterized in that in steps 1 and 5, the RNC specifies that the UE only reports a 3A event in an emergency, specifies a trigger threshold and trigger time of the 3A event at the same time, and only applies the 3A event when the judgment is performed, so that the series of operations shorten the period of the handover judgment, and simultaneously reduce the difficulty of the handover judgment, so that the system can find different system cells more easily for handover processing.

The emergency inter-system hard handover method is characterized in that: whenever an emergency notification is received, an emergency handling mode is switched to, so as to ensure that the service connection is maintained as soon as possible in the emergency to avoid call drop.

In the method of the present invention, the measurement control command sent by the RNC to the UE in step 1 includes measurement of information quantities such as measurement quantity of inter-system cells at the UE end, cells to be measured, filter coefficients of the measurement, reporting periods, and CPICH information of cells with the same frequency, and the reporting mode of the measurement report of the UE is set to event reporting; the cell and adjacent cell information of the UE comprises a primary scrambling code of the cell, signal power of a primary common pilot channel, a transmission diversity identifier and the like.

When the method of the invention is applied, the method of the inter-system hard switching under the conventional condition is used as much as possible. Because the existing 2G network has reached complete coverage, when the 3G network is laid out in the initial construction stage, the edges of all cells of the 3G network are arranged in the coverage concentration area of the 2G network as much as possible, so that the inter-system hard handover can find the inter-system cell suitable for handover as soon as possible, and the decision time of the handover is shortened. In the existing 2G network, the overlapping coverage of cells and the irregularity of network deployment make our 3G network deployment unable to achieve ideal effects, inevitably, in the cell boundary region of the 3G network, it may also be the cell edge of the 2G network, so, it is necessary to uniformly configure various parameters required by the method for hard handover between different systems under conventional and emergency situations of this invention, and set corresponding triggering conditions, for example, using the quality of the carrier signal of the 3G system measured by the UE to be lower than a predetermined threshold as the triggering condition, and once the quality estimated by the same frequency signal is well lower than the set threshold, immediately start the emergency handover method. When setting parameters for the conventional switching method and the emergency switching method, a higher threshold value can be set for each event for the conventional switching method so as to ensure that a cell switched by the UE fully meets the service requirement of the UE; for the emergency switching method, a lower threshold value can be set for each event to ensure that the UE can be switched to other cells in time and quickly, so as to maintain the continuity of the UE service and avoid the occurrence of call drop as much as possible.

In the method of the invention, the number of the reported cells in each reporting event is more than or equal to 1. The value of W is between 0.3 and 0.8. The corresponding hysteresis value in each decision event is between 1.5dB and 3 dB.

In order to achieve the above-mentioned method of the present invention with good effect in implementation, the following steps should be taken in planning the layout of the WCDMA system: 1) Continuous coverage is guaranteed with existing 2G networks: counting the distribution of WCDMA users, providing continuous coverage in the area where the WCDMA users are rare by means of the existing 2G network, and providing key coverage in the hot spot area; 2) Ensuring the success rate of the hard handover of the different systems: in order to avoid a call drop phenomenon caused by handover failure, it is necessary to avoid the overlapping of handover areas between systems as much as possible in the aspect of planning and layout, that is, the handover area of the WCDMA is set in the important coverage area of the 2G network as much as possible, so as to ensure that when the UE of the WCDMA system performs inter-system hard handover, the cell of the 2G network can have sufficient resource reservation for the service of the UE in the WCDMA system.

The method of the invention has reasonable logic and high efficiency, can well ensure the effective realization of the different system hard switching required by the WCDMA system, improves the signal quality of user communication in an optimal mode, reduces the transmitting power of UE and the interference to other cells. The method of the invention can reduce the probability of the call drop phenomenon from two aspects. In the first aspect, frequent switching can be avoided by reasonable parameter setting and comprehensive processing of common-frequency measurement in the WCDMA system. Since each inter-system hard handover involves the risk of a dropped call, the dropped call phenomenon can be reduced by reducing the number of times of handover occurs. The method of the invention is divided into a conventional method and an emergency method, and sets the condition for entering the emergency, thereby not only ensuring that the UE is switched to the different system cell as soon as possible in the emergency, but also preventing the possibility of increasing call drop caused by the UE being in a situation of frequent switching, and greatly influencing the service quality. In fact, in the inter-system measurement state b and the inter-system hard handover decision state c, if the estimated quality of the intra-frequency measurement reported by the UE has improved, it is not necessary to perform the inter-system hard handover operation at the risk of call drop, and therefore, the conventional method and the emergency method of the present invention both include the step of returning to the state a from the state b or the state c. In the emergency different-system hard switching method, because the event needing to be judged is simple and is matched with a 2G system during 3G network distribution, the UE can be ensured to be switched to a satisfactory different-system cell in a hard mode in time, and the quality of service to the UE is not influenced when the quality of the cell currently served by the system is reduced rapidly.

Drawings

Fig. 1 is a diagram illustrating states and steps of an inter-system hard-cut method based on event-triggered reporting according to the present invention;

fig. 2 is a diagram illustrating states and steps of a method for inter-system hard decision in emergency based on event triggered reporting according to the present invention;

FIG. 3 is a schematic diagram of a cell structure of a 3G WCDMA system collocated with a 2G GSM system;

fig. 4 is a schematic diagram showing the basic technical principle of the handover decision method in the method of the present invention;

fig. 5 shows an embodiment of inter-system hardware based on event triggered reporting using the method of the present invention.

Detailed Description

The method makes full use of the measurement result reported by UE event trigger in the WCDMA system, and comprehensively evaluates the signal quality of each inter-system cell monitored by the UE and the signal quality of the current cell of the system in the RNC, thereby determining whether inter-system hard handover is necessary.

The following describes the embodiments in further detail with reference to the accompanying drawings.

The various states and method steps of the inter-system hard handoff method for an emergency in a wcdma system under conventional conditions using the present invention are shown in fig. 1.

In step 1 shown in fig. 1, the rnc sends a measurement command of the different systems to the UE, specifies the physical quantity to be measured, the reported physical quantity, the measured filtering coefficient (used for filtering the measured value in the UE), and the measured cell information, sets the measurement reporting mode as an event-triggered reporting mode, and specifies parameters related to handover, such as the number of reported measurement reports, the reporting interval, and the like, for the UE. The purpose is to make the UE measure according to the specific requirements given by the RNC, wherein the provision of some information can facilitate the UE to report the measurement results required by the algorithm judgment, which is beneficial to quickly making the judgment results to carry out the inter-system switching.

In step 2 shown in fig. 1, the UE keeps the same frequency measurement of the current WCDMA system while performing the inter-system measurement according to the inter-system measurement command of the RNC, and once a cell in the current WCDMA system meets the current service requirement of the UE, the RNC immediately notifies the UE to terminate the inter-system measurement, i.e., returns to the same frequency measurement state. If future WCDMA systems are developed to apply multi-layer cell coverage and thus introduce multiple carrier frequencies, inter-frequency measurements need to be made. At this time, if the pilot frequency measurement in the WCDMA system finds that the pilot frequency cell meets the service requirement of the UE, the RNC will also terminate the inter-system measurement immediately, avoiding the inter-system handover.

In step 3 shown in fig. 1, after receiving the measurement control information, the ue starts inter-system measurement according to the specific requirements in the command, filters the measurement result by using the filter coefficient given in the measurement control command, and uploads the event 3C to the RNC by using the measurement report message when the measurement result meets the condition of reporting the event 3C. All the measurement results reported by the UE enable the RNC to have sufficient reference basis when carrying out switching judgment. When UE reports 3C event, it switches into different system hard switching judgment state, at this time, RNC stores the different system cell information contained in the reported event, and waits for the later measurement result to make judgment.

In step 4 shown in fig. 1, the ue reports a measurement event 3D, and updates the best cell of the different system, because there is more than one cell reported in the event 3C before, and the events are reported continuously, the stored cells may be sorted according to quality, only if the estimated quality of a certain cell in the different system is higher than a predetermined threshold T3D, the cell may be queued as a best cell candidate, only the cell with the highest estimated quality may be queued at the first place during queuing, and when an event 3D is reported, the first cell may be queued as the best cell for handover. The purpose of event 3D introduction is mainly to make reference for determining the cell for performing the inter-system hard handover at the time of subsequent decision.

In step 5 shown in fig. 1, the ue reports a measurement event 3B, and if all the cells of the different systems stored in the RNC satisfy the event 3B in the hard handover decision state c of the different systems, returns to the measurement state B of the different systems, and waits for reporting new information of the cells of the different systems; if only a part of the cells in the heterogeneous system meet the event 3B, the part of the cells are deleted. Since there is more than one cell reported in the event 3C before, and the events are reported continuously, the stored cells can be sorted according to quality, and when the stored cell quality cannot meet the handover requirement, the cells are deleted. The purpose of introducing the 3B event is mainly to reduce unnecessary cells in subsequent decisions, and when the signal quality of the cells of the different systems cannot meet the current service requirement of the UE, it is not necessary to make corresponding handover decisions for these cells, and deleting these cells with poor quality can reduce the burden of the system on the hard handover decisions of the different systems.

In step 6 shown in fig. 1, according to the measurement command indication of the RNC, the UE keeps measuring the current system while performing inter-system measurement, and once the current WCDMA system has a cell that meets the current service requirement of the UE, the RNC immediately notifies the UE to terminate the inter-system measurement, and returns to the intra-frequency measurement state a at c. If the WCDMA system is developed in the future to introduce multiple frequencies using multi-layer cell coverage, the inter-frequency measurements are also performed simultaneously. If the pilot frequency measurement finds that the pilot frequency cell of the WCDMA system can meet the service requirement of the UE, the RNC can also terminate the inter-system measurement and the inter-system hard handover judgment immediately so as to avoid unnecessary operation of the system.

In step 7 shown in fig. 1, the ue reports the measurement event 3A, and in state c, if the cell quality satisfies the event 3A, there may be more than one cell, and a corresponding selection needs to be made among these cells, and obviously, the cell with the best quality should be selected. When selecting the cell, it can be seen that the necessity of the operations in steps 4 and 5 is needed, we can refer to the best cell stored by the RNC in step 4 to make the inter-system handover cell, execute the inter-system hard handover, and the RNC sends a handover command to the UE to enter the state d. Meanwhile, unnecessary decision selection process is avoided by the operation of step 5.

Fig. 2 is a schematic diagram illustrating states and steps of a hard handover control method for reporting a different system as an event trigger for solving an emergency situation, which is to ensure that a UE can be handed over to a different system cell as soon as possible in the emergency situation.

In step 1 shown in fig. 2, in state a, the UE always maintains the same-frequency measurement state of soft handover in the WCDMA system, and once it is determined that the estimated quality of the same-frequency measurement is significantly reduced, that is, it is determined that an emergency occurs, the RNC sends an inter-system measurement command to the UE, and notifies the UE in the command that events 3B, 3C, and 3D are no longer determined, and requires the UE to no longer report the three events, and at the same time, reduces the trigger threshold T3Aother of event 3A, shortens the trigger time of event 3A, and notifies the UE of the adjustment result.

In step 2 shown in fig. 2, in state b, the UE constantly keeps measuring the co-frequency signals, and once the estimated quality of the co-frequency signals measured by the UE is higher than a certain threshold, the WCDMA system meets the service requirement of the UE, and the co-frequency signals meet the soft handover condition in the WCDMA system, and returns to state a from state b. It should be noted that the measurement in this case is performed simultaneously with the measurement of the inter-frequency system, and in the future, the WCDMA system is developed to apply the multi-layer cell coverage to introduce multiple frequencies, and the measurement of the inter-frequency in the WCDMA system is also performed simultaneously.

In step 3 shown in fig. 2, as long as the inter-system hard information report indicates the presence of an inter-system, the state b directly enters the state c.

In step 4 shown in fig. 2, in state c, once the UE finds that the intra-frequency cell signal is above a certain threshold, it returns to state a from state c. It should be stated that, at this time, the UE is still required to perform measurement, the measurement is performed simultaneously by using the same frequency measurement and the inter-system measurement, and in the future, WCDMA is developed to apply multi-layer cell coverage to introduce multiple frequencies, and the inter-frequency measurement in the WCDMA system is also performed simultaneously.

In step 5 shown in fig. 2, the ue reports the measurement event 3A, and directly selects the best cell to perform inter-system hard handover.

Fig. 3 is a schematic diagram of a cell structure of a 3G WCDMA system collocated with a 2G, e.g., GSM, system. As shown in fig. 3, in the initial stage of 3G networking, continuous coverage of the mobile communication network needs to be achieved through the 2G network, and in this case, hard handover of a different system is inevitably introduced. Although the cell edge of the 3G network should be located in the important coverage area of the 2G network as much as possible at the beginning of the 3G network layout, the overlapping of the handover areas between the 3G system and the 2G system cannot be completely avoided due to the limitation of the geographical environment and the influence caused by the wireless environment. As shown in fig. 3, in the area where the user a is located, there is coverage of a base station (Node B) of a WCDMA system, and there is coverage of a Base Station (BS) of a GSM system of a different system. If user a continues to move away from the NodeB at this point, soft handover in the WCDMA system is not possible, and inter-system hard handover will be the only option. At this time, the measurement of the user a will have a plurality of measurement reporting events at the same time. Accordingly, in the event of reporting the inter-system measurement, since the user a is located in the overlapping coverage area of the edge of the 2G system cell, the reported inter-system measurement report is likely to include information of a plurality of 2G cells. If the same frequency measurement result does not meet the emergency condition, the RNC selects a best different system cell for the final switching execution and executes different system hard switching processing by adopting the conventional different system hard switching method of the invention. In the case of user B shown in fig. 3, the mobile speed is very fast and the direction of movement is away from Node B, which will soon leave the coverage of Node B. At this time, the result of the same-frequency measurement shows that the signal quality of the WCDMA system is rapidly reduced, and the emergency condition is met. In this case, the emergency switching method of the present invention is adopted to ensure that the UE is rapidly switched to the cell of the different system, and to ensure the continuity of the service. In the user C shown in fig. 3, the user initiates a data service occupying a large amount of radio resources, which has a certain impact on the current cell in the WCDMA system, and if the impact on the service quality of other users in the cell is large, the RNC decides to switch the user C out of the WCDMA system. If the RNC judges that the influence degree of the user C on the service quality of the whole cell is large, an emergency switching method is adopted to quickly switch the user C to a 2G system; otherwise, if the influence of the user C on the WCDMA system cell is small, the RNC decides to adopt a conventional handover method.

Fig. 4 is a schematic diagram showing the basic technical principle of the handover decision method in the method of the present invention, which has been embodied in the conventional case inter-system hard handover and emergency case inter-system hard handover methods of the present invention.

Fig. 5 is an embodiment of an event triggered reporting inter-system hard handover decision. In fig. 5 there are the combined estimated qualities of the two system cell carrier frequencies, the solid line 1 represents the estimated quality of the co-channel measurement in the WCDMA system, and the dashed lines 2 and 2' the estimated qualities of the two 2G cells around the ue. The estimated quality T3B and T3C of the system in fig. 5 are respectively the predetermined threshold values of the event 3B and the event 3C, the estimated quality T3A for own system is the predetermined threshold value of the estimated quality of the co-channel measurement of the current WCDMA system in the event 3A, and the estimated quality T3A for other system is the predetermined threshold value of the estimated quality of the different system in the event 3A.

As shown in fig. 5, in the initial stage before t1, the UE operates on the WCDMA system carrier frequency, and the RNC initiates the inter-system measurement at this time. As shown in fig. 5, the estimated quality curve 1 of the WCDMA system shows a decreasing trend of the estimated quality as a whole, while the carrier frequency signal quality curves 2 and 2' of the two cells of the 2G system have an increasing trend. At this time, the signal quality of the WCDMA system can also meet the service requirement of the UE, and can also be used continuously.

As shown in fig. 5, at time T1, the carrier frequency signal quality curve 2 of one cell of the 2G system reaches a predetermined threshold T3C and is maintained for time T. At this time, the UE reports a 3C event, the RNC analyzes the event, and stores the cell 2 reported in the event 3C as a basis for a later decision.

As shown in fig. 5, at time t2, the carrier frequency signal quality curves 2 and 2' of the two cells of the 2G system vary in intensity and last for time t. At this time, the UE reports a 3D event, the RNC analyzes the event 3D, queues and compares the estimated quality curves 2 and 2' of the two cells, and stores the different system cell with the highest estimated quality as the best cell in the RNC for reference in the subsequent judgment execution.

As shown in fig. 5, at time T3, the estimated quality of carrier frequency 2' of one cell of the 2G system reaches below a predetermined threshold T3B and lasts for time T. At this time, the UE reports a 3B event, the RNC analyzes the event 3B, deletes the stored inter-system cell 2', and does not make a decision on the 2G cell carrier frequency 2' in the subsequent decision.

As shown in fig. 5, at time T4, the estimated quality curve 1 of WCDMA co-frequency measurement of 3G system is below a certain threshold T3A for own system, while the cell carrier frequency 2 of 2G system is above a certain threshold T3A for other system and lasts for time T. At this time, UE reports 3A event, RNC analyzes the event 3A, selects 2G system cell carrier frequency 2 to execute different system hard switching.

Although the present invention has been described above by way of examples, these specific examples are not intended to limit the scope of the present invention. The scope of the present invention should not be limited to these specific examples, but may cover various modifications based on the above-described embodiments and equivalents thereof.

Claims

1. A method for hard switching between different systems in WCDMA system includes following steps:

step 1, in a state a, if UE reports that the measured estimated quality of the intra-frequency measurement in the WCDMA system is lower than a certain preset threshold to RNC, initiating inter-system measurement, namely, a radio network controller RNC of the WCDMA system sends an inter-system measurement command to the UE, and under the condition that the geographical area of the UE is covered by the inter-system, the UE is required to measure the inter-system, measure the estimated quality of the inter-system, report the measurement result to the RNC, and switch from the state a to a state b;

step 2, in state b, when the RNC analyzes the different system measurement report, the same frequency signal quality reported by the UE is higher than a certain predetermined threshold, which indicates that the signal quality of the WCDMA system can meet the service requirement of the UE, and the state b enters into state a;

step 3, in the state b, the UE carries out inter-system measurement, if the RNC receives a measurement report event 3C reported by the UE, the RNC stores inter-system cell information contained in the report event, and the RNC enters the state c from the state b;

step 4, in the state c, the UE carries out inter-system measurement, if the RNC receives a measurement report event 3D reported by the UE, the best cell of the inter-system is updated, and the state c is kept;

step 6, in the state c, when the RNC analyzes the different system measurement report, the same frequency signal quality reported by the UE is higher than a certain predetermined threshold, which indicates that the signal quality of the WCDMA system can meet the service requirement of the UE, and the state c enters the state a;

step 7, if there are a plurality of cells whose cell quality satisfies the event 3A, selecting the corresponding cell from the cells, that is, selecting the cell with the best measurement quality; when selecting the cell, referring to the best cell stored in the step 4 as the selection basis, selecting the best cell to execute the inter-system hard handover, and entering a state d from a state c;

wherein, the event 3A indicates that the estimated quality of the currently used UTRAN frequency is lower than a certain threshold and the estimated quality of other systems is higher than a certain threshold, the event 3B indicates that the estimated quality of other systems is lower than a certain threshold, the event 3C indicates that the estimated quality of other systems is higher than a certain threshold, and the event 3D indicates the best cell change in other systems.

2. A method for hard switching between different systems in emergency of WCDMA system includes following steps:

step 1, in a state a, an RNC sends an inter-system measurement command to UE, informs the UE in the command, does not make judgment on events 3B, 3C and 3D any more, requires the UE not to report the three events, reduces the trigger threshold of the event 3A, shortens the trigger time of the event 3A, informs the UE of an adjustment result, and enters a state B from the state a;

step 4, in state c, when the RNC analyzes the different system measurement report, the quality of the same frequency signal reported by the UE is higher than a certain predetermined threshold, which indicates that the quality of the WCDMA system signal can meet the service requirement of the UE, and the state c enters state a;

step 5, as long as the reporting event of the UE received by the RNC is an event 3A, directly selecting the cell with the best quality in the inter-system cells according to the inter-system cell related information contained in the reporting event to execute the inter-system hard handover, entering a state d from a state c;

wherein, event 3A indicates that the estimated quality of currently used UTRAN frequency is below a certain threshold and the estimated quality of other systems is above a certain threshold, event 3B indicates that the estimated quality of other systems is below a certain threshold, event 3C indicates that the estimated quality of other systems is above a certain threshold, and event 3D indicates the best cell change in other systems.

3. The inter-system hard handover method according to claim 1 or 2, wherein the specific execution steps in each state are as follows:

state a: the method comprises the following steps that a same-frequency measurement state is called, UE (user equipment) in the state keeps measuring downlink carrier frequencies of all cells required by soft handover in a WCDMA (wideband code division multiple access) system, the estimated quality of the same-frequency measurement calculated according to a measurement result is reported, and meanwhile, the information of the measured cells in the WCDMA system is reported;

and a state b: the method comprises the following steps that a different system measurement state is called, the RNC sends a different system measurement command to the UE in the state, the UE measures signals of cells around the different system, and a measurement result is reported;

and c, state c: the RNC stores the related information of the different system cells contained in the event reported by the UE and waits for the subsequent measurement result;

and a state d: called a handover execution state, the RNC executes an inter-system hard handover to hand over the UE from the WCDMA system to the inter-system.

4. The inter-system hard handover method according to claim 1, wherein in step 1, in state a, the condition for initiating inter-system measurement further comprises: cell congestion, or reduced link quality, or the user terminal moving to a cell border, or intra-system soft handover is not allowed.

5. The inter-system hard handover method according to claim 1, wherein in step 3, the handover can be performed only when the signal quality of the inter-system cell meets a certain condition, so as to avoid negative effects on the system itself caused by unnecessary handover.

6. The inter-system hard handover method according to claim 1, wherein in step 4, the measured inter-system cell information is stored and compared and sorted to obtain the best quality cell, so as to select a satisfactory inter-system cell for inter-system hard handover processing during handover execution.

7. The inter-system hard handover method according to claim 1, wherein in step 5, the measured inter-system cell information is stored and compared to obtain a cell with poor quality, and when the quality is low to a certain degree, the cell is deleted, which is beneficial to avoid storing too much unnecessary inter-system cell information in the memory.

8. The inter-system hard handover method according to claim 1, wherein in steps 2 and 6, the UE reports the measurement reports of the same frequency, different frequency and inter-system simultaneously, so that the system can select the carrier frequency meeting the UE service requirement in time according to the current signal status of the wireless network, and also embodies the mutual scheduling among the sub-modules of the handover total module.

9. The inter-system hard handover method according to claim 1, wherein in step 7, the inter-system hard handover is performed only when the signal quality of the inter-system cell reaches a certain degree, that is, when the handover requirement can be fully satisfied and there is sufficient capability to carry the current service of the UE, so that the success rate of the hard handover is ensured and frequent handover at the cell boundary is avoided.

10. An emergency inter-system hard handover method according to claim 2, wherein in step 1, when an emergency occurs, the RNC defines an event reported by the UE and a decision threshold and a trigger time of the event in an inter-system measurement command sent to the UE, which enables the UE to handover to the inter-system cell as soon as possible in the emergency.

11. The method of hard handover between different emergency systems according to claim 2, wherein in steps 1 and 5, the RNC specifies that the UE only reports the event 3A in an emergency, and specifies the trigger threshold and the trigger time of the event 3A at the same time, and only applies the event 3A when the decision is performed, which shortens the handover decision period and reduces the difficulty of the handover decision, so that the system can find different system cells more easily for handover processing.

12. The inter-system hard handover method according to claim 1 or 2, wherein: in the step 1, the inter-system measurement command sent by the RNC to the UE includes measurement quantity measured for the inter-system cell at the UE end, a cell to be measured, a measured filter coefficient, a reporting period, and measurement of CPICH information of a cell with the same frequency, and a reporting mode of a measurement report of the UE is set to event reporting.

13. The inter-system hard handover method according to claim 1 or 2, wherein the following steps are taken for the applied WCDMA system: firstly, counting the distribution of WCDMA users, providing continuous coverage in an area with few WCDMA users by means of the existing 2G network, and intensively covering a hotspot area; secondly, the overlapping of the switching areas among the systems is avoided on the cell of the WCDMA system, namely the switching area of the WCDMA is arranged in the key coverage area of the 2G network, so that the cell of the 2G network can have enough resource reservation for the service of the UE in the WCDMA system when the UE of the WCDMA system performs inter-system hard switching.