CN100459802C - A method and system for implementing cellular communication system handover - Google Patents

Abstract

The present invention relates to a method and system for realizing switching of a cellular communication system in the technical field of wireless communication. A moving speed estimation device is introduced to estimate the moving speed of a user and report it to RNC. The RNC sets switching parameters and adjusts switching according to the estimated moving speed. policy, sending a handover instruction to the user equipment. The invention effectively improves the fast reliability of the switching operation of the cellular communication system.

Description

A method and system for implementing cellular communication system handover

technical field

The invention relates to the technical field of wireless communication, in particular to a method and system for realizing switching of a cellular communication system.

Background technique

With its unique advantages of flexibility and convenience, mobile communication meets people's requirements for communication technology in modern society, and has become the fastest-growing communication method since the mid-1980s. However, users need to constantly switch between different cells, different frequencies, and different systems during the process of moving. The third-generation mobile communication systems all have a fully functional switching system.

Handover is one of the basic functions of cellular wireless communication systems, mainly including hard handover, soft handover and softer handover. When a hard handoff occurs, the mobile station first breaks the connection with the original radio network controller, and then gets in touch with the new radio network controller.

In order to improve the reliability of communication during handover, the concept of soft handover and softer handover has been introduced in the CDMA (Code Division Multiple Access) system. When soft handoff occurs, when the mobile station starts to contact a new radio network controller, it does not immediately interrupt the communication with the original radio network controller, but maintains the communication with multiple radio network controllers at the same time. Softer handover occurs between different sectors of the same radio network controller, which is a special case of soft handover.

Soft handoff plays the role of diversity of traffic channels at the junction of two radio network controller coverage areas, which can bring more stable voice quality, reduce call drops caused by handover, and ensure communication reliability. A typical soft switching system block diagram is shown in Fig. 1.

The existing system does not consider the handover speed requirements of UEs with different moving speeds during handover. According to different moving speeds, the handover strategy in RRM (Radio Resource Management) can be optimized to a certain extent. For example, for high-speed mobile users, try to reduce the switching delay to avoid disconnection and interruption caused by untimely switching; for low-speed users, you can measure for a longer period of time to make switching more reliable.

Now take the soft handover of WCDMA as an example to illustrate the existing handover technology.

A series of mechanisms are adopted in WCDMA soft handover to ensure the reliability of handover. When the difference in pilot strength is greater (smaller) than the handover threshold minus (plus) the hysteresis threshold and remains stable for a period of time (reporting time hysteresis), the handover process is controlled by the RNC (Radio Network Controller) . This process is described in detail below.

During the handover process, the UE measures the power of each cell by measuring the reference pilot of each cell, such as the size of PCPICH_Ec_Io in UMTS (Universal Mobile Telecommunications System), and compares the measured pilot value with the threshold value of handover To judge whether to report, the RNC decides whether to perform handover according to the measurement report of the UE and the soft handover decision criterion. Figure 2 is a typical soft handover algorithm flow of a WCDMA system, where the meanings of the parameters used are as follows:

AS_Th: threshold of soft handover;

AS_Th_Hyst: hysteresis threshold of soft handover;

AS_Rep_Hyst: replacement hysteresis threshold;

ΔT: reporting time;

AS_Max_Size: the maximum value of the activation set;

Best_Ss: the cell with the strongest pilot frequency measured in the active set;

Worst_Old_Ss: the cell with the weakest pilot measured in the active set;

Best_Cand_Set: detect the cell with the strongest pilot measured in the set;

Meas_Sign: Observation cell measurement and filtered pilot value.

The meanings of the soft handover events 1A, 1B, and 1C described in FIG. 2 are as follows:

1A: If during ΔT, Meas_Sign>=(Best_Ss-As_Th+As_Th_Hyst), and the active set is not full, add the observed cell to the active set of the UE;

1B: If the active set is full, and during ΔT, Best_Cand_Ss>=(Worst_Old_Ss+As_Rep_Hyst), replace the weakest cell in the active set of the UE with the strongest cell in the observed set;

1C: If during ΔT, Meas_Sign<=(Best_Ss-As_Th-As_Th_Hyst), delete the observed cell from the active set of the UE;

The above is the algorithm principle of handover. A typical handover includes the following process: measurement control->measurement report->handover judgment->handover execution->new measurement control. The specific steps are as follows:

1) The UE continuously monitors the pilot strength of the active set and the monitoring set on the carrier frequency (the active set and the monitoring set are notified to the UE by the RNC);

2) The UE compares the measurement result with the threshold value provided by the RNC, and if the criterion of the measurement report is met, the UE sends the measurement report to the RNC;

3) According to the UE's measurement report and the RNC's handover decision algorithm, the RNC sends the new active set list to the UE, ordering the UE to add, delete, and replace cells from the active set;

4) After receiving the handover instruction message, the UE adds the pilot into the effective pilot set and sends a handover completion message to start new measurement control.

In general, factors affecting the handover process mainly include: UE measurement filtering time, handover threshold, hysteresis threshold, and reporting time lag.

It can be seen from the above handover process that in the prior art, the UE measures and filters the pilot strength of the observed cell during handover, and when the result meets the criteria of the measurement report, the UE sends the measurement report to the RNC for handover decision; when the UE's When the moving speed is high, the fixed handover mechanism, such as the fixed threshold hysteresis and reporting time hysteresis, cannot track the changes of the UE in time, and cannot switch in time, so handover drops and interruptions may occur.

Contents of the invention

In view of the problems existing in the above-mentioned prior art, the object of the present invention is to provide a method and system for realizing handover of a cellular communication system, using a moving speed estimating device to estimate the moving speed of a mobile user, and adjusting a handover strategy according to the estimated moving speed , realizing the fast and reliable switching process.

The purpose of the present invention is achieved through the following technical solutions:

A system for realizing handover of a cellular communication system, comprising a base station, a radio network controller RNC, user equipment, and a handover processing unit, wherein the handover processing unit is used to perform handover processing operations according to a handover instruction sent by the RNC, and further includes:

The mobile speed estimation device is used to estimate the mobile speed of the user and report it to the RNC. The RNC sets handover parameters according to the estimated mobile speed, adjusts the handover strategy, and sends a handover instruction to the user equipment; the handover parameters include any of the following or Any combination thereof: filtering time of pilot measurement results, switching threshold, threshold hysteresis, and reporting time hysteresis.

The device for estimating the moving speed is installed at the base station end or the user equipment end.

A method for implementing cellular communication system handover, comprising:

A. Estimate the user’s moving speed and send it to RNC;

B. The RNC sets handover parameters according to the estimated moving speed, and adjusts the handover strategy; the handover parameters include any one of the following or any combination thereof: filtering time of pilot frequency measurement results, handover threshold, threshold hysteresis, and reporting time hysteresis;

C. The RNC sends a handover instruction to the user equipment according to the determined handover strategy to perform a handover operation.

The estimation of the moving speed in the step A is completed by the base station or the user equipment.

Described step A comprises:

The base station or the user equipment transmits the moving speed estimation result to the RNC through an explicit or implicit method.

Described step A comprises:

Estimate the velocity of mobile users using level crossing ratio or Doppler spectrum.

Said step B further comprises:

Presetting no less than one category of moving speed, determining the category to which the estimated moving speed of the user belongs, setting switching parameters and adjusting a switching strategy according to the category of moving speed.

It can be seen from the above-mentioned technical solution provided by the present invention that the present invention estimates the speed of the mobile user by introducing a mobile speed estimation device, and the RNC adjusts the handover strategy according to the speed estimation result, effectively improving the fast and reliable handover operation of the cellular communication system sex.

Description of drawings

FIG. 1 is a schematic diagram of a switching system in the prior art;

FIG. 2 is a schematic diagram of a soft handover algorithm in the prior art;

Fig. 3 is a schematic diagram 1 of the switching system of the present invention;

Fig. 4 is a second schematic diagram of the switching system of the present invention;

Fig. 5 is the flow chart of method operation of the present invention;

Figure 6 is a schematic diagram of the level crossing rate;

FIG. 7 is a schematic diagram of the relationship between the Doppler spectrum and the moving speed.

Detailed ways

The core idea of the present invention is to provide a method and system for realizing switching of a cellular communication system, which uses a moving speed estimation device to estimate the moving speed of a mobile user, and adjusts a handover strategy according to the estimated moving speed, thereby realizing a fast and reliable handover process sex.

The present invention provides a system for realizing handover of a cellular communication system. The system includes a mobile speed estimation device, an RNC (radio network controller), a NB (base station), a UE (user equipment) and a handover processing unit; the mobile speed estimation device It is used to estimate the moving speed of the mobile user, which can be installed on the UE side, as shown in Figure 3, or on the UE side, as shown in Figure 4; the RNC is used to set the switching according to the moving speed of each user Threshold for handover control; the handover processing unit is used to perform handover processing operations according to the handover instruction sent by the RNC; the NB is used for exchanging handover requests and instructions between the UE and the RNC; the UE is used for each cell Measure and report pilot energy.

Utilizing the system of the present invention, the present invention also provides a method for realizing switching of a cellular communication system. The operation flow of the method is shown in FIG. 5 . Referring to FIG. 5 , the method includes the following steps:

Step 10: the mobile speed estimation device estimates the mobile speed and sends it to the wireless network controller;

The estimation of the moving speed by the moving speed estimating device can be realized by the following two methods:

1) Judgment based on the level crossing rate: the moving speed determines the speed of the signal envelope change, that is, the number of times the envelope level passes a certain value within a certain period of time. Figure 6 shows a fragment of two user signal envelope curves in time, where there is one intersection point between the solid line and the reference level, and six intersection points between the dotted line and the reference level, so the change speed of the dotted line is fast, which means high speed of movement;

2) Judgment based on the Doppler spectrum: by estimating the Doppler spectrum, an estimated value of the moving speed can also be obtained. In the Doppler spectrum of two users as shown in Figure 7, the maximum frequency deviation of the Doppler spectrum represented by the dotted line is larger than the maximum frequency deviation of the Doppler spectrum represented by the solid line, so the doppler spectrum represented by the dotted line The user's mobile speed is high;

The estimation of the moving speed can be completed by either NB or UE. This embodiment takes the installation of the moving speed estimation device on the UE side as an example for illustration. If the moving speed is estimated by the UE, then the estimated result needs to be explicitly or implicitly Notify the RNC in the same way, first send it to the NB, and then send it to the RNC by the NB;

The explicit refers to setting special speed measurement indication signaling;

The implicit means that the speed information is implied through other information. For example, there are several pilot patterns with different time densities, which correspond to different moving speeds. When indicating the pilot pattern, the moving speed is also indicated at the same time. ;

Step 11: RNC sets the handover parameters and adjusts the handover strategy according to the above moving speed estimation result;

After receiving the moving speed estimation result of the moving speed estimation device, the RNC sets handover parameters according to the moving speed estimation result, including setting: filtering time of pilot frequency measurement results, handover threshold, threshold hysteresis, reporting time hysteresis, etc.;

For high-speed mobile users, the threshold hysteresis and reporting time hysteresis need to be adjusted smaller. For example, the switching threshold hysteresis of medium and low speeds is set to 3dB; while it can be reduced to 2dB for high-speed mobile users; the reporting time hysteresis is reduced from 100 milliseconds to 80 milliseconds, so that It can make the reporting criteria of high-speed sports users be met as soon as possible, and speed up the switching speed; for low-speed sports users, the opposite is true, so as to achieve as reliable switching as possible and avoid back-and-forth fluctuations during switching. By reducing the switching threshold and the filtering time of the pilot measurement results, it can also speed up the switching speed to a certain extent;

Since the adjustment of the switching strategy does not require an accurate speed estimate, in order to simplify the processing complexity, the speed estimate can be set to three ranges: high speed, medium speed, and low speed. For example, we can set different speeds according to the parameters in the table below scope:

Speed value km/hour speed category ＜30 low speed 30～120 medium speed ＞120 high speed

Each of the above values can be adjusted according to the specific situation;

Step 12: The RNC sends a handover instruction to the UE to perform a handover operation;

After the RNC sets the handover parameters, it carries the determined handover parameters in the handover instruction and transmits them to the UE for handover operation.

In summary, the present invention estimates the speed of the mobile user by introducing a mobile speed estimation device, and the RNC adjusts the handover strategy according to the speed estimation result, effectively improving the fast reliability of the handover operation of the cellular communication system.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (7)

1, a kind of system that realizes that cellular communication system switches, comprise base station, radio network controller (RNC), subscriber equipment and switching treatmenting unit, the hand-off process operation is carried out in the switching indication that described switching treatmenting unit is used for sending according to RNC, it is characterized in that, also comprises:

The moving speed estimation device is used for the estimating user translational speed, reports RNC, and RNC is provided with handoff parameter according to the translational speed of described estimation, adjusts switchover policy, sends to switch indication to subscriber equipment; Described handoff parameter comprises following each or its combination in any: pilot measurement result's filtering time, handoff threshold, thresholding sluggishness, report time lag.

2, a kind of system that realizes that cellular communication system switches as claimed in claim 1 is characterized in that described moving speed estimation device is installed on base station end or subscriber equipment end.

3, a kind of method that realizes that cellular communication system switches is characterized in that, comprising:

A, estimating user translational speed send RNC to;

B, RNC are provided with handoff parameter according to the translational speed of described estimation, adjust switchover policy; Described handoff parameter comprises following each or its combination in any: pilot measurement result's filtering time, handoff threshold, thresholding sluggishness, report time lag;

C, RNC send according to the switchover policy of determining and switch indication to subscriber equipment, carry out handover operation.

4, a kind of method that realizes that cellular communication system switches as claimed in claim 3 is characterized in that the estimation of translational speed is finished by base station end or subscriber equipment end in the described steps A.

5, as claim 3 or 4 described a kind of methods that realize that cellular communication system switches, it is characterized in that described steps A comprises:

Base station or subscriber equipment send the moving speed estimation result to RNC by the method for explicit or implicit expression.

6, a kind of method that realizes that cellular communication system switches as claimed in claim 3 is characterized in that described steps A comprises:

Utilize level crossing rate or Doppler frequency spectrum to estimate mobile subscriber's speed.

7, a kind of method that realizes that cellular communication system switches as claimed in claim 3 is characterized in that described step B further comprises:

Preestablish the translational speed classification that is no less than, the classification under the user moving speed of determining to estimate according to described translational speed classification, is provided with handoff parameter, adjusts switchover policy.

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