CN1464665A - Method for switching between different systems in CDMA communication system - Google Patents

Abstract

The present invention proposes a method for switching between systems in a CDMA communication system, wherein the method of controlling the compressed mode can greatly reduce the frequency of use of the compressed mode in the measurement of different systems, and reduce the impact of the compressed mode on system performance; During the measurement, the method of activating multiple compressed mode styles at the same time greatly reduces the use of transmission signaling and achieves the purpose of optimizing system performance. By adopting the CDMA mobile communication system of the present invention, multiple compressed mode configurations do not overlap when performing different system measurements, which can ensure the rationality and accuracy of compressed mode configuration, and avoid failure caused by overlapping compressed mode modes. The inter-system switching judgment algorithm proposed by the invention reduces the possibility of misjudgment and prevents ping-pong switching caused by signal fluctuations.

Description

The Method of Switching Between Different Systems in CDMA Communication System

Technical field

This patent relates to the inter-system handover of the communication system, in particular to the method of inter-system handover in the CDMA cellular mobile communication system, and the control and use method of the downlink compressed mode required for the inter-system handover.

Background technique

In a traditional time division multiple access (TDMA) mobile communication system, a mobile station generally occupies one time slot for every N time slots for communication, and is in an "idle" state in other time slots, so the mobile station can use these idle time slots to The target frequency is measured so that the mobile station reports the channel condition of the target frequency to the network. However, unlike the TDMA system, the Code Division Multiple Access (CDMA) cellular mobile communication system uses codewords to distinguish different users, and users can continuously receive signals of a certain frequency in time, and they do not have "idle time" like in TDMA. Time slots" to measure different frequencies. Therefore, for a mobile station with only one receiver, if the base station continuously sends signals on the downlink channel, the mobile station must continuously receive downlink signals, and cannot simultaneously measure signals of different frequencies. To realize the measurement of signals of different frequencies, the downlink compression mode must be used.

As shown in Figure 1, in the compressed mode, a period of transmission "gap" is formed in the wireless frame through techniques such as code puncturing. In this gap, the base station does not transmit any data to the mobile station, and the mobile station can use the radio frequency The receiver switches to the target frequency to be monitored and measures the target frequency. Figure 3 shows the parameters of the compressed pattern pattern (Pattern). It can be seen that the size and relative position of the transmission gap (gap) and the length of the pattern determine a compressed mode pattern.

If the compression mode is used frequently, it will definitely have a bad impact on the performance of the system:

1) Technologies such as code punching reduce the redundancy of data. According to information theory, in order to make up for this loss, the data after punching must be transmitted with power P/t (as shown in Figure 1, where P is uncompressed frame transmission power, t is the compression rate), the increase of the power will affect the performance of the system.

2) In the compression mode, it will cause the transmission power to jump, and the fluctuation caused will reduce the performance of the system.

3) The compressed mode is not only used for measuring the target frequency, but also for establishing synchronization between the mobile station and the target frequency. Therefore, the "gap" time in compressed mode will be longer.

In view of the adverse effects of the above points, in a CDMA system, it is very important to reduce the frequency of use of the compressed mode, thereby reducing the impact of the compressed mode on system performance.

In the CDMA system, it is often necessary to use the compressed mode for the inter-system handover of the mobile terminal. The inter-system handover refers to switching the mobile station in the call state from one system to another system, and trying to keep the communication of the mobile station uninterrupted. As mentioned in this patent, switch from the CDMA system to the GSM system. Before inter-system handover, the network will determine that the mobile terminal performs inter-system measurement to provide necessary information for inter-system handover. Since the frequency of the GSM system is different, it is necessary to start the compressed mode to measure the frequency signal of the adjacent GSM cell.

The normal process of GSM measurement is: first, the mobile station initiates the measurement of the broadcast channel RSSI (Received Signal Strength Indicator, Received Signal Strength Indicator) of the adjacent GSM cell; SB, Synchronization Burst), decode the base station identification code (BSIC, BaseStationIdentify Code) and GSM cell observation time difference information; after successfully obtaining the BSIC, the value of the BSIC must be continuously reconfirmed to prevent the BSIC from changing, and update the GSM cell observation time difference information . The above three processes are called GSMRSSI (Received Signal Strength Indicator) measurement, initial BSIC (Base Station Identify Code) confirmation measurement, and BSIC re-confirmation measurement. Each of the three measurements uses three different compressed mode styles. If compressed mode reconfiguration is performed repeatedly, the burden of transmission signaling and the complexity of control will be seriously increased, and the impact on system performance will be increased.

The method adopted in the existing related technology is that the mobile station will use compressed mode to carry out GSM measurement before switching from the CDMA system to the GSM system, and the three processes of GSM measurement use three different compressed mode styles respectively, without adopting control and A way to reduce the frequency with which compressed mode is used. This patent proposes a method for controlling the compression mode and reducing the frequency of use of the compression mode during inter-system switching, and on this basis, an inter-system switching algorithm is proposed.

Contents of Invention

In order to reduce the frequency of use of the compressed mode in different system measurements in the CDMA communication system when switching between different systems, and to reduce the impact of the compressed mode on system performance during the switching of different systems in the CDMA communication system, the present invention proposes a CDMA communication system that implements the system Among them, the method of controlling the compression mode can greatly reduce the frequency of use of the compression mode in the measurement of different systems, and reduce the impact of the compression mode on the system performance; and the inter-system switching judgment algorithm is to reduce the possibility of misjudgment , to prevent ping-pong switching caused by signal fluctuations.

Method of the present invention comprises the steps:

Step a, the system performs algorithm initialization, including compression mode initialization and inter-system switching decision algorithm initialization;

Step b, the network detects that the quality of the active set of the mobile station is degraded, and then enters the control compression mode to start the algorithm;

Step c, if the starting condition of the compressed mode is satisfied, that is, the quality of the active set of the mobile station is lower than a threshold value, and the quality of the active set of the mobile station is still lower than the threshold value after a period of time delay, then start the compressed mode and enter Step d, if not satisfied, go to step i;

Step d, the mobile station performs different system measurement;

Step e. During the inter-system measurement, when the quality of the active set of the mobile station becomes better and is higher than a threshold value, and after a period of delay, the quality of the active set of the mobile station is still higher than the threshold value, then Close the compression mode, enter the control compression mode to close the algorithm, and enter step f; otherwise enter step g;

Step f, if the closed condition of the compressed mode is satisfied, the network closes the compressed mode, stops the measurement of the cell of the different system by the mobile station, and then enters step i; step d;

Step g, the network receives the different-system measurement result reported by the mobile station, and makes a decision according to the inter-system handover decision algorithm. If the judgment result is to perform inter-system handover, go to step h, otherwise the mobile station continues to perform different-system measurement, that is, go to step d ;

Step h, executing the handover process between systems, and switching the mobile station to a different system;

Step i, end.

The initialization described in step a includes: compressed mode initialization, including setting the mobile station active set quality threshold value and delay time for controlling the compression mode start, and setting the mobile station active set quality threshold value for controlling the compression mode closing and delay time, to set the compressed mode pattern sequence during inter-system measurement; inter-system handover decision algorithm initialization, including setting the mobile station active set quality threshold value, different system quality threshold value and delay time in the inter-system handover decision algorithm.

The inter-system handover decision algorithm described in step g is that when the following three conditions are met, the network makes an inter-system handover decision and decides to handover the mobile station to a different system. Condition 1: The quality of the active set of the mobile station is very poor, lower than a certain threshold; Condition 2: The signal quality of the different system is better, higher than a certain threshold; Condition 3: After a period of delay, still Condition 1 and Condition 2 are met;

In the condition one of step c, step e and step g system switching algorithm, if the active set uses the signal chip power CPICH Ec/No(The ratio of transmit energy per chip of Common PilotChannel to the Common PilotChannel to the received noise) as the quality measurement quantity, then the threshold value range of the active set quality is -24dB to 0dB; if the active set is based on the ratio of the chip energy on the common pilot channel to the noise power spectral density Channel) as the quality measurement quantity, then the threshold value range of the active set quality is -115dBm to 0dBm.

The range of the threshold value of the signal quality of the different system in the second condition of the system handover algorithm in step g is -115dBm to 0dBm.

In the process of starting the compressed mode in step c, multiple compressed mode pattern sequences are configured at the same time, and the transmission gaps of the configured multiple compressed mode patterns within one pattern length do not overlap.

When GSM measurement is performed, the three compressed mode patterns of RSSI measurement, initial BSIC confirmation measurement and BSIC reconfirmation measurement are simultaneously activated. At the same time, the multiple compressed mode pattern sequences follow the order of RSSI measurement, initial BSIC confirmation measurement, and BSIC reconfirmation measurement, and their transmission gaps are successively distributed in the compressed mode pattern length TGPL frame.

The beneficial effects of the present invention are:

(1) Adopting the CDMA mobile communication system of the present invention, by controlling the use of the downlink compressed mode, its usage frequency can be greatly reduced, and the impact of the compressed mode on system performance can be reduced.

(2) Adopting the CDMA mobile communication system of the present invention, adopting the method for simultaneously activating multiple compressed mode styles when performing different system measurements, greatly reducing the use of transmission signaling, and achieving the purpose of optimizing system performance.

(3) Adopting the CDMA mobile communication system of the present invention, multiple compressed mode styles are configured without overlapping when performing different system measurements, which can ensure the rationality and accuracy of compressed mode configuration, and avoid failures caused by overlapping compressed mode styles.

(4) By adopting the handover judgment algorithm in the present invention, the probability of successful handover between systems can be improved, and the probability of ping-pong handover can be reduced.

Description of drawings

FIG. 1 is a schematic diagram of a compressed mode frame structure and transmission power.

Fig. 2 is a schematic diagram of the positions of the mobile terminal and the base station during the implementation of the present invention.

FIG. 3 is a schematic diagram of a compressed mode style parameter structure.

Fig. 4 is a flow chart of a handover method between different systems using the method of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 2 is the schematic diagram of the position of mobile terminal and base station in the implementation process of the present invention

Now the present invention is described in conjunction with FIG. 2 , assuming that cell 1 is a CDMA cell with a frequency of f1, and cell 2 is a GSM cell with a frequency of f2. The mobile station is initially located in cell 1. When the mobile station moves to cell 2, the strength of the pilot signal received from cell 1 begins to weaken, and as the mobile station continues to move to cell 2, the strength of the pilot signal received from cell 1 drops to a certain threshold value and After a period of time delay and still below this threshold, the network decides to start the compressed mode to allow the mobile station to measure the GSM cell. During the startup process of compressed mode, three compressed mode styles are activated at the same time for GSM RSSI measurement, initial BSIC confirmation measurement and BSIC reconfirmation measurement, and the network has been configured that these three compressed mode styles do not overlap. During the measurement, if the mobile station receives the signal of cell 1 and its pilot strength is higher than a certain threshold value and is still higher than this threshold value after a period of time delay, the measurement result will be Report to the network, the network decides to close the compression mode, and the mobile station stops measuring the GSM cell. After the GSM measurement is completed, the mobile station reports the measurement results to the network, and the network makes a judgment. If the strength of the pilot signal received from cell 1 is very weak and falls below a certain threshold, the signal strength of cell 2 is measured. Better, if a certain threshold value is exceeded, the signal strength of cell 1 is still lower than a certain threshold value and the signal strength of cell 2 is still higher than a certain threshold value after a period of time delay, then the network decides to carry out inter-system Handover, handover the mobile station to the GSM cell.

If the quality of the mobile station's active set becomes better after the compressed mode is started for a period of time, and the quality of the active set is higher than a certain threshold and is still higher than the threshold after a period of time delay, then the compressed mode is controlled to stop. Similarly, the purpose of passing a period of time delay here is to observe whether the signal quality is stable or whether it shows an upward trend. As shown in Figure 2, when the mobile station moves to point B, the control compression mode starts, and then point B moves to point C for a certain distance. The handover condition is met, and then the mobile station returns to point B and continues to move to point A and the center of the cell. The signal quality received by the mobile station from cell 1 is getting better and better, and the signal quality from cell 2 is getting worse and worse. There is no need to prepare the mobile station to switch to the cell 2, so the compressed mode can be controlled to be turned off, and the measurement of the GSM cell 2 can be stopped. Obviously, this method of controlling the start and stop of the compressed mode can greatly reduce the use time of the compressed mode.

In the CDMA system of the prior art, when the mobile station is in cell 1, it is likely that when the received signal strength of cell 1 is relatively good, the compressed mode is started to measure the GSM cell, which obviously prolongs the use time of the compressed mode. Or the mobile station moves to the edge of the cell and then returns to the center of the cell, and the signal quality is very good, so using the compressed mode all the time will inevitably cause waste of resources and cause unnecessary interference to system performance. By adopting the method of the invention, the startup and shutdown of the compression mode can be controlled, the use time of the compression mode can be reduced, and the impact of the compression mode on system performance can be reduced.

The method of the present invention activates three compressed mode pattern sequences at the same time, which may cause the overlapping of multiple transmission slots in the same frame. The 3GPP protocol requires that when multiple compressed mode style sequences are activated at the same time, the following conditions must be met:

(1) It is guaranteed that at least one of the three consecutive frames is not compressed.

(2) Ensure that the end time of the first transmission gap (gap) in two consecutive compressed frames differs by at least 8 time slots from the start time of the second gap.

Referring to FIG. 3 , from the GSM measurement compressed mode style recommended in the 3GPP protocol, there are three options for the length (TGPL) of the compressed mode style: 8 frames, 12 frames, or 24 frames. When the TGPL is equal to 8 frames, there is a high possibility that the sequence of the three compression modes overlaps, so the TGPL is selected as 12 or 24 frames.

In a pattern-length TGPL frame, configure GSM to measure three transmission gaps of the compressed mode pattern according to the above requirements, which can ensure that the transmission gaps of the three compressed mode patterns do not overlap in the same frame.

The three compressed mode patterns are distributed in the pattern length TGPL frame according to the order of RSSI measurement, initial BSIC confirmation measurement, and BSIC reconfirmation measurement, so that the GSM cell after RSSI measurement can quickly enter BSIC confirmation measurement and BSIC reconfirmation measurement.

Concrete flow process of the present invention is as shown in Figure 4:

Step a, perform algorithm initialization, including compression mode initialization and inter-system handover decision algorithm initialization; said initialization includes: compression mode initialization, including setting the mobile station active set quality threshold value and delay time for controlling the compression mode startup, Set the mobile station active set quality threshold and delay time that control the compression mode to be closed, and set the compressed mode pattern sequence during inter-system measurement; initialize the inter-system handover decision algorithm, including setting the mobile station active set in the inter-system handover decision algorithm Quality threshold, different system quality threshold and delay time;

Step b, the network detects that the quality of the active set of the mobile station is deteriorating, and enters the control compression mode to start the algorithm;

Step c, if the starting condition of the compressed mode is satisfied, that is, the quality of the active set of the mobile station becomes worse and is lower than a certain threshold value, and the quality of the active set of the mobile station is still lower than this threshold value after a period of time delay, then Start the compressed mode; during the process of starting the compressed mode, configure multiple compressed mode pattern sequences at the same time, and the transmission gaps of multiple compressed mode patterns configured within one pattern length do not overlap.

Step d, the mobile station performs different system measurement;

Step e, in the process of measuring different systems, if the network detects that the quality of the active set of the mobile station becomes better, then enter the closed algorithm of the control compressed mode, and enter step f; otherwise enter step g; the closed algorithm of the controlled compressed mode is, when The quality of the active set of the mobile station becomes better and is higher than a certain threshold value, and after a period of delay, the quality of the active set of the mobile station is still higher than this threshold value, then close the compressed mode;

Step f, if the closed condition of the compressed mode is satisfied, the network closes the compressed mode, stops the measurement of the cell of the different system by the mobile station, and then enters step i; step d;

Step g, the network receives the measurement results of different systems reported by the mobile station, and according to the inter-system handover judgment algorithm, if the judgment result is inter-system handover, proceed to step h, otherwise the network continues to wait for the mobile station to report the measurement results, that is, enter step d; The inter-system handover decision algorithm is as follows: when the following three conditions are met, the network makes an inter-system handover decision and decides to handover the mobile station to a different system. Condition 1: The quality of the active set of the mobile station is very poor, lower than a certain threshold; Condition 2: The signal quality of the different system is better, higher than a certain threshold; Condition 3: After a period of delay, still Condition 1 and Condition 2 are met;

Step h, executing the handover process between systems, and switching the mobile station to a different system;

Step i, end.

Claims (9)

1. A method for switching between different systems in a CDMA communication system, characterized in that the method comprises the steps: a. The system performs algorithm initialization, including compression mode initialization and inter-system switching decision algorithm initialization; b. The network detects that the quality of the active set of the mobile station is deteriorating, and then enters the control compression mode to start the algorithm; c. If the starting condition of the compressed mode is satisfied, that is, it is lower than a threshold value, and the quality of the active set of the mobile station is still lower than the threshold value after a period of time delay, start the compressed mode and enter step d, if not satisfied , enter step i; d. The mobile station performs different system measurements; e. In the process of inter-system measurement, when the quality of the active set of the mobile station becomes better and is higher than a threshold value, and after a period of delay, the quality of the active set of the mobile station is still higher than the threshold value, then close Compression mode, enter the control compression mode to close the algorithm, and enter step f; otherwise enter step g; f. If the closed condition of the compressed mode is satisfied, the network closes the compressed mode, stops the mobile station from measuring the cell of the different system, and then enters step i; if the closed condition of the compressed mode is not met, the mobile station continues to perform the measurement of the different system, that is, enters the step d; g. The network receives the different-system measurement result reported by the mobile station, and makes a judgment according to the inter-system handover judgment algorithm. If the judgment result is to perform inter-system handover, enter step h, otherwise the mobile station continues to perform different-system measurement, that is, enter step d; h. Execute the handover process between systems, and handover the mobile station to a different system; i. End. 2. The method for switching between different systems in a CDMA communication system as claimed in claim 1, wherein the compressed mode initialization described in step a includes setting the active set quality of the mobile station that controls the compressed mode startup Threshold value and delay time, set the mobile station active set quality threshold value and delay time that control the compressed mode to close, set the compressed mode style sequence when different systems are measured; switch between the systems described in step a Judgment algorithm Initialization includes setting the mobile station active set quality threshold value, different system quality threshold value and delay time in the inter-system handover decision algorithm. 3. The method for switching between different systems in a CDMA communication system as claimed in claim 1, wherein, in said step c and step e, if the active set uses CPICH Ec/No as the quality measure, then The range of the threshold value is -24dB to 0dB; if the active set uses CPICH RSCP as the quality measurement quantity, the range of the threshold value is -115dBm to 0dBm. 4. The method for switching between different systems in a CDMA communication system according to claim 1, wherein the decision algorithm for switching between systems described in step g is that when the following three conditions are met simultaneously, Condition 1: The active set quality of the mobile station is lower than a predetermined threshold; Condition 2: The signal quality of the different system is higher than a predetermined threshold; Condition 3: After a period of delay, conditions 1 and 2 are still met; The network makes an inter-system handover decision and decides to handover the mobile station to a different system. 5. The method for switching between different systems in a CDMA communication system according to claim 4, wherein the threshold value in said condition one is, if the active set uses CPICH Ec/No as the quality measure, Then the range of the threshold value is -24dB to 0dB, if the active set uses CPICH RSCP as the quality measurement quantity, then the range of the threshold value is -115dBm to 0dBm. 6. A method for switching between different systems in a CDMA communication system according to claim 4, characterized in that the threshold value range of signal quality of different systems in the second condition is -115dBm to 0dBm. 7. The method for switching between different systems in a CDMA communication system as claimed in claim 1, characterized in that, during step c starting the compressed mode process, multiple compressed mode pattern sequences are configured simultaneously, and within one pattern length Configure the transmission slots of multiple compressed mode styles not to overlap. 8. The method for switching between different systems in a CDMA communication system as claimed in claim 7, wherein when performing GSM measurement, the three items of RSSI measurement, initial BSIC confirmation measurement, and BSIC re-confirmation measurement are simultaneously activated. Compressed mode style. 9. The method for switching between different systems in a CDMA communication system according to claim 8, wherein when performing GSM measurement, the plurality of compressed mode pattern sequences follow RSSI measurement, initial BSIC confirmation measurement, BSIC Re-confirm the measurement sequence, and its transmission gaps are successively distributed in the compressed mode pattern length TGPL frame.

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