KR20080026248A - Method and apparatus for cell searching of cell reselection in portable communication system - Google Patents

Abstract

A cell searching method and apparatus for re-selecting a cell of a mobile terminal are provided to search every cell for cell re-selection although the cell searching method does not meet the condition of cell re-selection conditions, if cell re-selection is failed by a certain number of times. A communicating unit(210) receives information of a corresponding hierarchical cell. A count management unit(202) initializes the failed number of cell re-selections or increases the failed number of cell re-selection according to an instruction of a controller(200). The controller(200) processes to search a neighbor cell available for cell re-selection and perform cell re-selection, and if the cell re-selection is failed, the controller(200) controls the count management unit(202) to instruct increasing of the failed number of the cell re-selection. If the failed number of cell re-selections is greater than or the same as a maximum threshold value, the controller(200) instructs to search cells of every adjacent layer.

Description

TECHNICAL AND APPARATUS FOR CELL SEARCHING OF CELL RESELECTION IN PORTABLE COMMUNICATION SYSTEM}

1 illustrates a mobile communication system having a general hierarchical cell structure according to the present invention;

2 is a block diagram showing the configuration of an apparatus for improving a cell reselection process in a portable terminal according to an embodiment of the present invention;

3 is a flowchart illustrating a cell reselection process in the same mobile communication system according to another embodiment of the present invention;

4 is a flowchart illustrating a cell reselection process between different adjacent mobile communication systems (InterRAT) according to another preferred embodiment of the present invention.

The present invention relates to cell reselection of a portable terminal, and more particularly, to a method and apparatus for increasing cell reselection probability of a portable terminal using a network having a hierarchical cell structure.

With the development of communication technology, it is possible to efficiently provide multimedia services to users by constructing mobile communication system composed of single layer structure with hierarchical cell structure composed of cells with various characteristics in one region.

 In other words, it is possible to provide high quality service anytime, anywhere, without restriction of time and place by configuring multi-layered cells with different radius of cells with different characteristics such as pico cell, micro cell, macro cell and mega cell. It is possible.

1 is a diagram illustrating a mobile communication system having a general hierarchical cell structure.

Referring to FIG. 1, the hierarchical cell structure (HCS) represents a hierarchical cell environment in which cells providing different types of transmission rates overlap.

The HCS may design a plurality of micro cells 120 in a region of one macro cell 110, and design a plurality of pico cells 130 in the micro cell 120. In addition, data rates may be differently classified according to distances from the base station 100.

That is, it has a different data rate from a near place to a far place with respect to the base station 100 of the macro cell 110. For example, in the center of the base station 100, it is possible to service at a transmission rate of 384 Kbps, the farther away from the center, the lower the Ec / Ior, the lower the transmission rate in the order of 114Kbps, 64Kbps and 12.2Kbps.

In general, in the HCS system, the macro cell 110 provides a service for a fast mobile user and a low speed data transmission service, and the micro cell 120 provides a service for a low speed mobile user and a high speed data transmission service. . In addition, the pico cell 130 may more stably provide a service of an image and a video that are difficult to support in the micro cell 120 and the macro cell 100.

This is because the macro cell 110 has a large cell radius but difficult data transmission at high speed, and the micro cell 120 has a small cell radius while high cell data enables high speed data transmission.

In addition, the method of providing a service according to the load of the cell to the macro cell 110 or the microphone 120 may be different. That is, when the load of a particular micro cell 120 is very large, a method of providing a service to a fast mobile user in the macro cell 110 may be considered.

In the above HCS, in order to provide a better service to a user, a cell reselection is performed to move to a cell that satisfies a condition for providing a better service.

That is, when it is determined that the received electric field strength of the serving cell is smaller than the cell reselection threshold received from the network, cell reselection is performed to move to a cell having a good reception intensity.

However. Although the service field cannot be maintained due to a small reception field strength of the serving cell, when the cell reselection threshold of a small intensity is received according to an incorrect network design of the operator, the portable terminal has a high priority in order to perform cell reselection. The problem is that the cell reselection success rate is lowered by trying to search only neighboring cells.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for improving a cell reselection success rate in a hierarchical cell structure.

Another object of the present invention is to provide a method and apparatus for searching for neighbor cells by checking the number of cell reselection failures.

According to a first aspect of the present invention for achieving the above objects, the cell retrieval method for cell reselection and the number of cell reselection failure times when the condition to search for cells of all adjacent layers in the standby state is not satisfied; Comparing the maximum threshold value, checking the existence of a cell providing a better service than a serving cell when the number of cell reselection failures is smaller than the maximum threshold value, and as a result of the checking, If it is determined that there is no cell providing good service, the method includes searching for a cell of a layer having a higher priority than that of the serving cell, performing cell reselection, and then returning to the standby state. .

According to a second aspect of the present invention for achieving the above objects, the cell search apparatus for cell reselection includes a communication unit for receiving information of a corresponding layer cell and the number of cell reselection failure times instructed by the controller; A count management unit for increasing the number of cell reselection failures, and performing a search and cell reselection of a neighboring cell capable of cell reselection, and causing the count manager to fail cell reselection if the cell reselection fails. And the control unit instructing to increase the number of times.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

In the following description, in order to increase the success rate of cell reselection in the hierarchical cell structure, it is determined that the cell is not a condition of cell reselection. If the cell reselection is failed for a predetermined number of times by searching for neighbor cells of a high priority or the same layer, the cell reselection is performed. An apparatus and a method for searching for cells of all layers will be described.

2 is a block diagram illustrating a configuration of an apparatus for improving a cell reselection process in a portable terminal according to an embodiment of the present invention.

Referring to FIG. 2, the portable terminal includes a control unit 200, a count management unit 202, a memory unit 204, an input unit 206, a display unit 208, and a communication unit 210. The role of the management unit 202 may be performed by the control unit 200, but in the present invention, the configuration is illustrated separately to describe each function. Therefore, when the product is actually implemented, all of them may be configured to be processed by the controller 200.

The control unit (MPU: Micro-Processer Unit) 200 controls the overall operation for the cell reselection process of the portable terminal. For example, when the portable terminal determines that the service can be maintained in the current cell despite the decrease in the strength of the received electric field of the cell in which the portable terminal exists, the mobile terminal has priority over the cell of the layer in which the portable terminal exists. If the cell reselection fails after the cell search according to the present invention, the count management unit 202 sets the number of cell reselection failures by one. When the cell reselection is successful or the search of all cells is completed, the count manager 202 is instructed to initialize the number of cell reselection failures.

In addition, when the number of cell reselection failures is greater than or equal to the maximum threshold value, the controller 200 searches for cells of all layers to determine whether the cell reselection is possible.

The count manager 202 increases the number of cell reselection failures by 1 when the cell reselection fails under the instruction of the controller 200. In addition, the count manager 202 initializes the accumulated count of cell reselection failures under the instruction of the controller 200.

The memory unit 204 includes a read only memory (ROM), a random access memory (RAM), and a flash ROM. The ROM stores microcode and various reference data of a program for processing and controlling the control unit 200 and the count management unit 202.

The RAM is a working memory of the controller 200, and stores temporary data generated while executing various programs. In addition, the flash ROM stores various updatable storage data such as a phone book, an outgoing message, and an incoming message.

The input unit 206 is a numeric key buttons of 0-9, menu button (menu), cancel button (clear), confirmation button, call button (TALK), end button (END), Internet access button, navigation key ( Or a plurality of function keys such as arrow keys) buttons and character input keys, and provides key input data corresponding to a key pressed by the user to the controller 200.

The display unit 208 displays status information generated during the operation of the communication terminal, a limited number of characters, a large amount of moving images and still images, and the like. The display unit 208 may use a color liquid crystal display (LCD).

The communication unit 210 performs a function of transmitting and receiving a radio signal of data input and output through an antenna. For example, in the case of transmission, after performing channel coding and spreading on the data to be transmitted, RF processing is performed to transmit the data. In the case of reception, the received RF signal is converted into a baseband signal. Information for restoring data by despreading and channel decoding the baseband signal, and determining the cell reselection condition according to the control unit 200 according to the present invention. Receive

In the following description, a method for resolving standby power consumption problems and improving a cell reselection success probability when receiving incorrect information due to an incorrect network design of the operator when cell reselection of the mobile terminal located in a hierarchical cell structure will be described in detail. will be.

3 is a flowchart illustrating a cell reselection process in the same mobile communication system according to an embodiment of the present invention.

Referring to FIG. 3, the control unit 200 first instructs the count management unit 202 to set the cell reselection failure count C to 0 in step 301, and proceeds to step 303 to camp on a service normally. )do. In operation 305, the controller 200 determines the state of the serving cell by measuring the received electric field strength Srxlev _{s of} the serving cell. In other words, the controller 200 compares the received electric field strength of the serving cell with the electric field strength of the neighboring cell and checks whether the cell reselection condition is satisfied.

In operation 307, the controller 200 checks whether the mobile terminal can maintain a service in a cell in which the portable terminal currently exists. In step 307, the process of checking whether the service can be maintained is confirmed by comparing the received electric field strength Srxlev _s of the serving cell with the cell reselection threshold size S _seachHCS transmitted from the cell of the hierarchical cell structure. When the received electric field strength Srxlev _s of the serving cell is larger than the threshold S _seachHCS , it may be determined that the service cannot be maintained.

If it is determined in step 307 that the service is not maintained in the cell in which the portable terminal exists, the control unit 200 proceeds to step 319 in which cells of the same frequency and different frequencies of all adjacent layers are moved. After all cells have been searched to see if there is a cell capable of cell reselection, the controller 200 proceeds to step 321 to instruct the count manager 202 to initialize the cell reselection failure count C.

If it is determined in step 307 that the service can be maintained in the current cell in which the portable terminal is present, the controller 200 proceeds to step 309 and compares the cell reselection failure number C with the maximum threshold number N. do.

If, as a result of the comparison in step 309, the maximum threshold number of failures N is greater than or equal to C, the controller 200 performs the process of step 319.

On the other hand, when the comparison result of step 309, if the C is less than the N, the control unit 200 proceeds to step 311 to search for the cell of the layer having a higher priority than the layer cell in which the portable terminal exists, In step 313, a neighboring cell having the highest priority (a cell having a good cell reselection condition) is selected among the searched cells.

Here, in step 311, the method of searching for the neighboring cell is different according to the cell reselection threshold between the same frequencies that the portable terminal receives.

That is, when the strength (Sx) of the received electric field of the serving cell is smaller than the cell reselection threshold value (S _intrasearch ) between the same frequencies transmitted by the layer cell, the layer cell of the same or higher priority than the serving layer cell Search for neighbor cells. On the contrary, when the strength (Sx) of the received electric field of the serving cell is greater than the cell reselection threshold value (S _intrasearch ) between the same frequencies transmitted by the layer cell, it is better than the cell in which the portable terminal exists in the serving layer cell. It is determined that there is no cell providing the service, and the neighbor cell of the layer cell having a higher priority than the serving layer cell is searched.

In step 315, the controller 200 determines whether cell reselection to the cell neighbor cell is successful. That is, the check of the successful cell reselection is a process of confirming whether the cell is selected for cell reselection in step 313.

If the cell reselection succeeds, the controller 200 proceeds to step 317 and instructs the count manager 202 to initialize the number of cell reselection failures.

On the other hand, if the cell reselection fails, the controller 200 proceeds to step 323 and instructs the count manager 202 to increase the number of cell reselection failures by one, and then from step 303. Rerun

4 is a flowchart illustrating a cell reselection process between other adjacent mobile communication systems InterRAT according to another embodiment of the present invention.

Referring to FIG. 4, the control unit 200 first instructs the count management unit 202 to set the cell reselection failure count C to 0 in step 401, and then camps on the service normally in step 403. )do. In step 405, the controller 200 determines the state of the serving cell by measuring the received electric field strength Srxlev _{s of} the serving cell. In other words, the controller 200 checks whether less than a received signal strength (Srxlev _s) is a cell selection threshold (S _{HCS. RATm)} sent from the other mobile communication system of the hierarchical cell structure of the serving cell.

If the cell selection threshold S _HCS.RATm transmitted by another communication system of the hierarchical cell structure is greater than or equal to the received electric field strength Srxlev _s of the serving cell, the controller 200 proceeds to step 419. In order to perform a cell reselection process to a cell supporting another adjacent communication system, all neighboring neighbor cells are searched to determine whether a cell capable of cell reselection exists.

After checking whether there is a cell capable of cell reselection, the controller 200 proceeds to step 421 and instructs the count manager 202 to initialize the cell reselection failure count C.

On the other hand, if the cell selection threshold (S _{HCS . RATm} ) transmitted from another mobile communication system of the hierarchical cell structure is smaller than the received field strength (Srxlev _s ) of the serving cell, the controller 200 In step 409, the cell reselection failure number C and the maximum threshold number N are compared.

If, as a result of the comparison of step 409, the maximum threshold number of failures N is greater than or equal to C, the controller 200 performs the process of step 419 again.

On the other hand, when the comparison result of step 409, if C is less than the N, the control unit 200 proceeds to step 411 to check whether there is a cell that provides a better service than the cell of the layer where the portable terminal exists. . That is, the process of step 411 is S _limit received from the network _{. SearchRAT} comparing _.M the reception electric field intensity (Sx) of the current serving cell and determines whether the service state than the serving cell layer good cell is present.

If, test results, the cell current is present the service state better than the serving cell in step 411 when layer (Sx> S _{limit. SearchRAT .M),} the control unit 200 to perform cell reselection to a different mobile communication system, In order to search for cells of a layer having a higher priority or the same as that of the serving layer cell.

On the other hand, if, in step 411 check result, if the current serving cell layer than the service status is a good cell is not present (Sx <S _{limit. SearchRAT .M),} the control section 200 adjacent the other neighbors of the mobile communication system Maintain services in the current cell without performing a cell search.

In operation 415, the controller 200 determines whether cell reselection to the neighboring cell is successful. If the cell reselection succeeds, the control unit 200 proceeds to step 417 to instruct the count manager 202 to initialize the number of cell reselection failures.

On the other hand, if the cell reselection fails, the controller 200 proceeds to step 425 and instructs the count manager 202 to increase the number of cell reselection failures by one, and then from step 403. Rerun

Standby power consumption caused by searching for high priority cells without performing a full cell search to perform cell reselection due to a poor network design of the operator when the receiving field strength of the serving cell is sufficiently weakened according to the above method. The efficiency of cell reselection can be reduced.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, when the reception field strength of the serving cell does not satisfy the cell reselection condition in the conventional cell reselection process, a cell reselection success probability generated by searching only cells having a high priority or the same as the present invention is described. If the cell reselection fails for a predetermined number of times, even if the cell reselection condition is not satisfied, all cells for cell reselection may be searched.

Claims (11)

In the cell search method for cell reselection, Comparing the number of cell reselection failure times with the maximum threshold value if the condition for searching for cells in all adjacent layers is not satisfied in the standby state; Determining whether a cell providing a better service than a serving cell exists when the number of cell reselection failures is smaller than the maximum threshold value; As a result of the check, when it is determined that there is no cell providing a better service than the serving cell, after searching for a cell of a layer having a higher priority than that of the serving cell, cell reselection is performed, and the process returns to the standby state. Process comprising a process. The method of claim 1, If it is determined that there exists a cell that provides a better service than the serving cell, the method may further include searching for a cell of a layer having the same or higher priority as that of the serving cell and performing cell reselection. Characterized in that the method. The method of claim 2, And when the cell reselection is performed, initializing the number of cell reselection failures. The method of claim 2, And increasing the number of cell reselection failures when the cell reselection fails. The method of claim 1, Performing cell reselection by searching for cells of all adjacent layers when the cell reselection failure count is greater than or equal to the maximum threshold value; And after retrieving the cells of all adjacent layers, initializing the number of cell reselection failures. The method of claim 1, The cell reselection process, Information of the corresponding layer cell for intra frequency measurement received from the network, information of the corresponding layer cell for inter frequency measurement, Inter Radio Access Technologies (RAT) measurement Performing at least one of information of a corresponding layer cell. In the cell search apparatus for cell reselection, A communication unit for receiving information of the corresponding layer cell; A count management unit for initializing the number of cell reselection failures or increasing the number of cell reselection failures by an instruction of a control unit; And a control unit for processing the cell reselection and the cell reselection to perform the cell reselection, and instructing the count manager to increase the number of cell reselection failures when the cell reselection fails. Device. The method of claim 7, wherein The control unit, And if the number of cell reselection failures is greater than or equal to a maximum threshold value, instructing to search for cells of all adjacent layers. The method of claim 8, The control unit, And if the number of cell reselection failures is smaller than the maximum threshold value, instructing to search for a layer cell having the same or higher priority than the serving layer cell. The method of claim 9, The control unit, And if the cell reselection succeeds or retrieves all neighbor cells for the cell reselection, instructing the count manager to initialize the number of cell reselection failures. The method of claim 10, The control unit, Information of the corresponding layer cell for intra frequency measurement received from the network, information of the corresponding layer cell for inter frequency measurement, Inter Radio Access Technologies (RAT) measurement And performing a cell reselection process using at least one piece of information of a corresponding layer cell.

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