A method for quickly selecting a cell after radio link failure of a mobile terminal

Abstract

The application discloses a method for quickly selecting a cell after a radio link failure of a mobile terminal, and relates to the field of mobile communication.The method comprises the following steps: obtaining and maintaining effective neighbor cell information of a serving cell where the mobile terminal is located; when a radio link failure is found, a new round of measurement is started for the effective neighbor cell, and the latest measurement result is obtained; cells whose measurement results meet threshold conditions are screened out and sorted from high to low, and a suitable cell is found according to the sorting result; if a suitable cell is not found, all supported frequency bands are searched again until a suitable cell is found, and a neighbor cell relationship is saved.The application is suitable for cell selection after a radio link failure, and can improve the cell selection speed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mobile communication, and in particular to a method for quickly selecting a cell after a radio link failure of a mobile terminal. BACKGROUND

[0002] In a mobile communication system, radio link failure is a situation that terminals often encounter. Due to the mobility of terminals and the complexity of wireless signal transmission environment, a certain degree of radio link failure is unavoidable.

[0003] To cope with the impact of radio link failure, when a terminal finds a radio link failure, cell selection needs to be performed. However, due to the burstiness and irregularity of radio link failure, there are mainly two methods for cell selection after radio link failure in the prior art. One is to directly search all supported frequency bands one by one, and to try synchronization one by one until camping is completed. This method cannot achieve the purpose of quickly and accurately selecting a good cell. The other method is to perform neighbor cell measurement in a connected state and save neighbor cell information (previous neighbor cell information), and after a radio link failure, to directly select and synchronize a cell according to the neighbor cell information measured in the connected state. This method has two disadvantages. One is that it depends on the neighbor cell measurement result in the connected state. The other is that it does not consider the state of the previously measured cell at the current time. For the former, when neighbor cell measurement has not been started, the terminal will blindly synchronize. For the latter, it is easy to cause a situation where time is consumed but synchronization cannot be performed. For example, when a terminal suddenly enters a poor signal area (such as an elevator, a garage, a corner of a building, or the like), the terminal in the connected state may not have been configured with connected state neighbor cells or may not have started neighbor cell measurement due to a good signal of the previous serving cell. As a result, the terminal blindly synchronizes without accurate reference information for cell selection, which prolongs the cell selection time and reduces the user experience of the terminal. SUMMARY

[0004] The present application aims to provide a method for quickly selecting a cell after a radio link failure of a mobile terminal to improve the speed of selecting a new cell after a radio link connection failure of the mobile terminal.

[0005] The technical solution adopted by the present application is as follows.

[0006] A method for quickly selecting a cell after a radio link failure of a mobile terminal, which is executed by the mobile terminal and includes the following steps.

[0007] Acquire and maintain valid neighbor cell information of the serving cell where the mobile terminal is located;

[0008] When the wireless link connection fails, measurements are taken of each valid neighboring cell to obtain the measurement results.

[0009] Cells that meet the threshold conditions in the measurement results are selected, sorted, and synchronized in sequence according to the sorting order to find cells that can be used for camping.

[0010] If camping fails, the system will search for cells in all supported frequency bands again until a campable cell is found, and then save the neighbor relationships of that campable cell.

[0011] Preferably, the effective neighbor cell information only includes the list of neighbor cells obtained before the wireless link connection failed.

[0012] Preferably, the effective neighbor information includes neighbor information obtained by the mobile terminal in the idle state.

[0013] Preferably, the acquisition and maintenance of valid neighbor cell information of the serving cell where the mobile terminal is located includes:

[0014] Obtain neighbor cell information from the broadcast information of the serving cell, filter out blacklisted and prohibited cells, and update the filtered results to the valid neighbor cell information;

[0015] Obtain neighbor cell information for the measurement configuration in connected state, filter out blacklisted and prohibited cells, and update the filtered results to the valid neighbor cell information;

[0016] Retrieve the saved supplementary neighbor cell list. If neighbor cell information for the currently serving cell exists, update it to the valid neighbor cell information.

[0017] Preferably, when the wireless link connection fails, the measurement is performed on each valid neighboring cell to obtain the measurement results, including:

[0018] When the wireless link connection fails, measurements are taken of each valid neighboring cell, and the historical measurement results are updated with the latest measurement results.

[0019] Preferably, the process of sorting the cells that meet the threshold conditions from the screening results, synchronizing them sequentially according to the sorting order, and finding cells suitable for camping includes:

[0020] Based on the set threshold conditions, cells that meet the threshold conditions are selected from the measurement results;

[0021] The selected communities are sorted in descending order of measurement results;

[0022] Synchronize sequentially according to the sorting order, synchronizing to the first community that meets the residency conditions.

[0023] Preferably, the measurement result is the signal quality.

[0024] Preferably, the step of re-searching for cells in all supported frequency bands until a cell suitable for camping is found, and saving the neighbor cell relationships of the suitable cell, includes:

[0025] Among all cells in the supported frequency bands, exclude all cells, blacklisted cells, and prohibited cells from the valid neighbor cell information;

[0026] Search within the excluded neighborhoods until a neighborhood that meets the residency criteria is found;

[0027] Save the neighbor relationships between the hostable cell and the serving cell to a supplementary neighbor list.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] This invention acquires and maintains valid neighbor cell information of the serving cell when the mobile terminal is idle, and also supplements it with a supplementary neighbor cell list, rather than acquiring neighbor cell information only in the connected state. Therefore, in the event of a wireless link connection failure without obtaining new connected state neighbor cell information and neighbor cell measurement results, a suitable cell can be searched for for connection from the valid neighbor cell information, instead of blindly matching unknown cells one by one. Compared to the current method of trying one cell after another in all frequency bands, it can access a new cell faster. Compared to the current method of directly synchronizing with cells selected from the neighbor cell information measured in the connected state, this invention re-performs cell measurement, which greatly improves the synchronization success rate and thus improves the efficiency of reconnection. For end users, this can improve the user experience. Attached Figure Description

[0030] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0031] Figure 1 This is a schematic diagram illustrating the steps of a method for quickly selecting a cell after a mobile terminal's wireless link fails, provided by the present invention.

[0032] Figure 2 This is a flowchart illustrating an LTE single-mode terminal as an example provided by the present invention. Detailed Implementation

[0033] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0034] Any feature disclosed in this specification (including any appended claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0035] The overall idea of ​​this invention is that the mobile terminal saves and updates the effective neighbor cell information of its serving cell in idle, connected, and other states for future use. When the mobile terminal suddenly changes from connected state to a wireless link connection failure state (i.e., dropped connection, no signal), without obtaining the neighbor cell information from the connected state or enabling neighbor cell measurement in the connected state, it first attempts to access a new cell from the effective neighbor cell information. Only if no suitable cell is found within the cell corresponding to the effective neighbor cell information does it then perform a signal search. In this way, it can access a suitable cell even without obtaining the neighbor cell information from the connected state, and the selection of a new suitable cell is faster.

[0036] This invention uses an LTE single-mode terminal as an example to illustrate a method for a mobile terminal to select a cell after a wireless link connection failure.

[0037] Example 1

[0038] After synchronizing with the LTE network, the terminal parses a partial list of available neighbor cells from the relevant messages of the current cell, and then retrieves the neighbor cell information of the current serving cell from previously stored data to form another partial list of available neighbor cells. Both together constitute the valid neighbor cell information of the current serving cell. The valid neighbor cell information obtained from different accessed cells is different, therefore it needs frequent maintenance and updates. The main purpose of the maintained valid neighbor cell information (i.e., the valid neighbor cell list) is to respond to situations where the mobile terminal suddenly experiences a radio link connection failure, enabling it to quickly measure and connect to available cells. Therefore, it only contains the neighbor cell list obtained before the radio link connection failure.

[0039] The aforementioned valid neighbor cell information includes neighbor cell information broadcast by the current serving cell, neighbor cell information configured in connected state, and excludes cells that cannot be accessed—such as blacklisted and prohibited cells—as well as the neighbor cell information portion of the currently serving cell from the previously saved supplementary neighbor cell list (if any). Thus, the acquisition and maintenance of valid neighbor cell information for the currently serving cell includes:

[0040] 1) Obtain neighbor cell information from the broadcast information of the currently serving cell, filter out blacklisted and prohibited cells, and update the filtered results into the valid neighbor cell information;

[0041] 2) Obtain neighbor cell information configured in connected state, filter out blacklisted and prohibited cells, and update the effective neighbor cell information with the filtered results; and

[0042] 3) Retrieve the saved supplementary neighbor cell list. If neighbor cell information for the currently serving cell exists, update it to the valid neighbor cell information.

[0043] Since the effective neighbor cell information is measured when the invalid link connection fails, the new connected state neighbor cell information has not yet been obtained. Therefore, the neighbor cell information configured in the connected state in 2) above was obtained in the connected state before the wireless link failure.

[0044] When the wireless link connection fails, each effective neighbor cell in the effective neighbor cell information is measured to obtain the corresponding measurement results. For example, the signal quality of each cell is measured. The signal quality evaluation indicators are common knowledge in the field, such as SINR (signal-to-interference-plus-noise ratio), RSRP (reference signal received power), RSSI (carrier received signal strength), or RSRQ (reference signal received quality).

[0045] As mentioned earlier, valid neighbor cell information includes neighbor cell information configured in connected state as well as other neighbor cell information, meaning that all or part of these cells already have measurement results. However, it is obvious that when the radio link connection fails, these cells may also become inaccessible. Therefore, the original measurement results should not be used directly as the basis for synchronization feasibility (i.e., the existing technology). It is necessary to re-measure and update (replace) the historical measurement results with the new measurement results as the basis for synchronization.

[0046] Cells meeting the threshold conditions are selected from the measurement results and ranked. Clearly, the threshold conditions are pre-set. The selected cells are ranked according to a specific indicator. The threshold condition is a fundamental condition; cells not meeting this condition do not need to be considered for connection. For cells meeting the threshold conditions, they are synchronized sequentially according to the ranking order to find a cell suitable for camping. Usually, the cell synchronized first is most likely to meet the camping conditions, thus allowing the fastest access to a new cell. Therefore, the selected cells are ranked from highest to lowest measurement result. The mobile terminal synchronizes sequentially, synchronizing (accessing) to the first cell that meets the camping conditions. Camping conditions are common knowledge in the field and are explained in relevant wireless mobile communication protocols (e.g., TS25.304), and are not the focus of this invention; therefore, they will not be described in detail here.

[0047] Valid neighbor cell information does not guarantee the presence of cells that meet the mobile terminal's threshold or camping conditions; that is, it does not guarantee that the mobile terminal will be able to access a cell listed in the valid neighbor cell information. Therefore, when the mobile terminal fails to camp in a valid neighbor cell, it re-searches for cells across all supported frequency bands until a campable cell is found. This process is similar to existing methods for responding to wireless link connection failures. Furthermore, this invention also stores the neighbor cell relationships of campable cells as a backup, for example, as supplementary neighbor cell information to be used as valid neighbor cell information in case of subsequent connection failures in the same location.

[0048] It should be noted that since the effective neighbor cell information has already been traversed before performing a full frequency band scan, it is unnecessary to retry cells from the effective neighbor cell information in this process, thus improving search efficiency. Specifically, when searching for cells, all cells in the effective neighbor cell information, as well as blacklisted and prohibited cells, are excluded from the cells in all supported frequency bands. The search continues within this excluded range until a cell meeting the camping criteria is found. The neighbor cell relationship between the found campable cell and the previously served cell is then saved to a supplementary neighbor cell list for later use.

[0049] As can be seen from the implementation scheme described above, when a wireless link failure is detected, the effective neighboring cells can be remeasured immediately to obtain the latest neighboring cell measurement results, and the signal can be quickly and accurately synchronized to the cell with good signal, reducing invalid synchronization and improving the cell dwell speed.

[0050] Example 2

[0051] like Figure 1 , Figure 2 As shown, the method for quickly selecting a cell after a mobile terminal's radio link fails includes the following steps:

[0052] S101. Obtain and maintain valid neighbor cell information of the serving cell where the mobile terminal is located.

[0053] Specifically, after the terminal synchronizes with the LTE network, it decodes the cellAccessRelatedInfo information in the SystemInformationBlockType1 message of the current cell. If the PLMN (Public Land Mobile Network) or TAI (TA Identifier) ​​is blocked, or the cellBarred indicator is "barred", the current cell is added to the blocked cell list. When the terminal successfully camps on the LTE cell, it parses the SystemInformationBlockType4 and SystemInformationBlockType5 messages of the current cell, saves the cell information in the IntraFreqNeighCellList to the co-frequency neighbor cell list, saves the information in the interFreqCarrierFreqList to the adjacent frequency list, and saves the cells in the interFreqNeighCellList and interFreqBlackCellList to the inter-frequency neighbor cell list and the blacklist cell list, respectively. It integrates the information from each list and extracts the available neighbor cells to the effective neighbor cell list (i.e., effective neighbor cell information). It retrieves the previously saved supplementary neighbor cell list; if neighbor cell information for the currently serving cell exists, it updates the effective neighbor cell list.

[0054] S102. When a wireless link connection failure is detected, a new round of measurement is initiated for the effective neighboring cells to obtain the latest measurement results.

[0055] Specifically, when the terminal enters the connected state but has not yet received the RRCConnectionReconfiguration message, the underlying layer triggers "out-of-sync" indications more than or equal to N310 times, and eventually T310 times out, causing link failure and initiating the cell selection process. At this point, since the RRCConnectionReconfiguration message has not yet been received, neighbor cell information for the connected state is not available, and neighbor cell measurements for the connected state have not been initiated. Therefore, the information in the effective neighbor cell list is the result of updates made by the terminal in idle and connected states before the radio link failure. A new round of cell signal measurements is then initiated based on the current effective neighbor cell list.

[0056] S103. Select and sort the cells whose measurement results meet the threshold conditions, and synchronize them sequentially according to the sorting results to find the appropriate cells.

[0057] Specifically, after the measurement is completed, weak coverage cells are filtered out according to the set weak coverage threshold conditions. The filtered cells are then sorted from high to low according to the measurement results. Cells are synchronized according to the sorting order. If the cell meets the camping conditions, the cell is camped.

[0058] S104. If no suitable cell is found, search all supported frequency bands again until a suitable cell is found, and save the neighbor cell relationship of the found cell.

[0059] Specifically, if no non-weak coverage cell is found, or if all found non-weak coverage cells fail to establish a connection, a re-search process is initiated. This re-search process excludes all measured cells from the candidate list, including both weak and non-weak coverage cells, as well as prohibited and blacklisted cells. When a suitable cell is found, the neighbor relationships between that cell and the serving cell are saved to a supplementary neighbor list for later use.

[0060] This embodiment describes the state of an LTE single-mode terminal when it enters the connected state and has not received the RRCConnectionReconfiguration message. If the RRCConnectionReconfiguration message has been received, it is necessary to extract the neighbor cell list and blacklist from the measConfig information, integrate the information from each list, and extract the available neighbor cells into the effective neighbor cell list. When the radio link fails, measurement, filtering of weak coverage cells, sorting, synchronization, etc. are started for the latest available neighbor cell list. Of course, these processes can be applied to other mobile communication systems.

[0061] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A method for fast cell selection after radio link failure of a mobile terminal, the method being performed by the mobile terminal, characterized in that, The application relates to a method for searching a cell to be camped on by a mobile terminal in a wireless communication system. In idle state and connected state, effective neighbor cell information of a service cell where the mobile terminal is located is acquired and maintained, including: acquiring neighbor cell information in broadcast information of the service cell, filtering out blacklisted cells and forbidden cells, and updating the filtered result to the effective neighbor cell information; In connected state, neighbor cell information of measurement configuration is acquired, blacklisted cells and forbidden cells are filtered out, and the filtered result is updated to the effective neighbor cell information; A saved supplementary neighbor cell list is searched, and if neighbor cell information of the current service cell exists, the neighbor cell information is updated to the effective neighbor cell information; When wireless link connection fails and no new connected state neighbor cell information and neighbor cell measurement result is obtained, each effective neighbor cell is measured to obtain a measurement result; Cells in the measurement result meeting threshold conditions are screened out and sorted, and the cells are synchronously searched according to the sorting order to find a cell to be camped on; If the cell to be camped on cannot be found, all cells in all supported frequency bands are searched until the cell to be camped on is found, and neighbor cell relation of the cell to be camped on is saved.

2. The method for quick cell selection after mobile terminal radio link failure according to claim 1, characterized in that, The effective neighbor cell information only contains neighbor cell lists acquired before wireless link connection fails.

3. The method for quick cell selection after mobile terminal radio link failure according to claim 1, characterized in that, When wireless link connection fails and no new connected state neighbor cell information and neighbor cell measurement result is obtained, each effective neighbor cell is measured to obtain a measurement result, including: When wireless link connection fails and no new connected state neighbor cell information and neighbor cell measurement result is obtained, each effective neighbor cell is measured to update a history measurement result with a latest measurement result.

4. The method for quick cell selection after mobile terminal radio link failure according to claim 1, characterized in that, The cells meeting threshold conditions in the measurement result are screened out and sorted, and the cells are synchronously searched according to the sorting order to find a cell to be camped on, including: The cells meeting threshold conditions in the measurement result are screened out according to set threshold conditions; The screened cells are sorted in descending order of measurement results; The cells are synchronously searched according to the sorting order, and the first cell meeting the camped-on condition is synchronized to.

5. The method for fast cell selection after radio link failure of a mobile terminal according to claim 1 or 4, characterized by, The measurement result is signal quality.

6. The method for quick cell selection after radio link failure of a mobile terminal according to claim 1, wherein, The cells in all supported frequency bands are searched until the cell to be camped on is found, and neighbor cell relation of the cell to be camped on is saved, including: All cells in the effective neighbor cell information, blacklisted cells and forbidden cells are excluded from all cells in all supported frequency bands; The cells after the exclusion are searched until the cell meeting the camped-on condition is found; Neighbor cell relation between the cell to be camped on and the service cell is saved to a supplementary neighbor cell list.

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