KR20020012418A - Apparatus and method for measuring the power of cells in asynchronous mobile communication system - Google Patents

Abstract

PURPOSE: An apparatus and a method for measuring cell power for constructing an active set in asymmetric mobile communication system are provided to reduce time required for constructing the active set for a terminal and reduce power consumption. CONSTITUTION: Each base station reports information related to transmission time of frames repeated at predetermined periods to an RNC(Radio Network Controller)(S100). The RNC calculates frame transmission time difference between the base stations(S200). The RNC constructs an information table of frame transmission time difference between the base stations by using relative frame transmission time difference(S210). The RNC transmits information related to frame transmission time difference between the base stations to each base station(S220). Each base station transmits information to all terminals within own cell(S300).

Description

Apparatus and method for measuring cell power for active set configuration in asynchronous mobile communication system {APPARATUS AND METHOD FOR MEASURING THE POWER OF CELLS IN ASYNCHRONOUS MOBILE COMMUNICATION SYSTEM}

TECHNICAL FIELD The present invention relates to an asynchronous mobile communication system, and more particularly, to an apparatus and method for measuring power of neighboring cells to configure an active set for handover.

The mobile communication system of IMT (International Mobile Telecommunication) 2000 currently being standardized may be classified into a synchronous mobile communication system between base stations and an asynchronous mobile communication system between base stations. A synchronous mobile communication system is called a CDMA-2000 (Code Division Multiple Access 2000) system or an IS-2000 system. An asynchronous mobile communication system is called a wideband code division multiple access (W-CDMA) system or a universal mobile telecommunication system (UMTS).

FIG. 1 is a diagram illustrating a physical channel structure in an asynchronous mobile communication system between base stations. The physical channel structure enables cell searching.

Referring to FIG. 1, a physical channel includes a first common control physical channel (P-CCPCH), a first synchronization channel (P-SCH) and a second synchronization channel (S-SCH). Structured as Secondary Synchronization Channel). In a base station asynchronous mobile communication system, one frame is 10ms long and is composed of 16 time slots (Slot # 1 to Slot # 16) (Tframe = 16 * Tslot). In the first and second sync channels, the sync code c _p (c _s ^{i, k} ) is transmitted from the base station only for a time interval corresponding to 1/10 of the time slot length ^, and any information is transmitted for the remaining time intervals. It doesn't work.

2 illustrates a typical cell structure and arrangement of a mobile communication system.

In the inter-base station or inter-cell asynchronous mobile communication system as shown in FIG. 2, adjacent cells (base stations) such as cell 1, cell 2, ... cell 6 and cell 7 are identified by their own scrambling codes. This is possible. As such a scrambling code, a gold code for changing a code phase between cells may be used. The terminal is provided with information on what kind of cell code is used in an adjacent cell from a cell (base station) to which it belongs. However, it should be noted that, unlike the synchronous mobile communication system between base stations, in the asynchronous mobile communication system, although the code type of the adjacent cell is known, information on the start time of the code cannot be known.

Now, assuming that a terminal communicates with a base station of cell 1, the terminal is provided with information about cell codes used in base stations adjacent to cell 1 from its base station. The terminal searches for a cell code having a strong received signal strength among cell codes of adjacent cells from information provided from its base station. When the terminal transmits the information related to the searched code to its base station, the base station determines whether to include the corresponding neighbor cell in an active set for handover. As such, the terminal performs an operation as a searcher searching for an adjacent cell in order to find a cell code having a strong received signal strength.

The role of the explorer can be broadly divided into two. One is the initial synchronous acquisition process, and the other is the steady state operation. The initial synchronization acquisition process means that when the terminal is powered on, it finds a base station to which the terminal currently belongs so that it can receive a broadcasting message. Steady-state operation is further divided into two categories: first, multipath search to find a signal path that is more suitable for demodulation in a call state or idle state, and second, to continuously detect power levels of adjacent base stations. To manage adjacent base stations.

FIG. 3 is a diagram specifically illustrating a search operation, particularly an initial acquisition process, in an asynchronous W-CDMA mobile communication system.

Referring to FIG. 3, the initial synchronization acquisition process 100 is divided into a first step 110, a second step 130, and a third step 150. The first step 110 is to find slot sync using the P-SCH. The second step 130 is to find a group of code and frame sync using S-SCH. A third step 150 is to find a scrambling code using P-CCPCH. Components for performing each step of operation are shown in FIGS. 4 to 6, respectively.

4 illustrates a hardware configuration for performing the operation of the first step shown in FIG.

Referring to FIG. 4, the matched filter 111 searches for various hypotheses for the P-SCH code, which is an input signal. Adder 112 and sample buffer 113 perform asynchronous accumulation for each hypothesis. The maximum selector 114 determines the maximum of the asynchronous cumulative result values as the slot timing of the current base station. The maximum selector 114 outputs a slot timing sync index of the current base station.

FIG. 5 illustrates a hardware configuration for performing the operation of the second step shown in FIG.

Referring to FIG. 5, in a second step, a fast Hadamard transform (FHT) is performed on a code of an S-SCH using a slot timing sync index obtained in the first step. From the result with the largest value, frame sync and group identification are performed. The operation of the fast Hadamard transform includes S-SCH correlators 131 and 132, a 17 x 16 correlation result array 133, a recalculation block 134 and a 32 x 16 detection array. 135), and frame synchronization and group identification are performed by selection maxima 136. In this case, the S-SCH correlators 131 and 132 use an S-SCH code as an input signal and input a slot timing index.

FIG. 6 illustrates a hardware configuration for performing the operation of the third step shown in FIG.

Referring to FIG. 6, in the third step, a correlation value is calculated using P-CCPCH for 16 scrambling codes belonging to the group obtained in the second step in accordance with the frame synchronization obtained in the second step. The scrambling code having the maximum value is determined as the scrambling code of the base station to which it belongs. In the operation of obtaining a correlation value using the P-CCPCH for the 16 scrambling codes, the sixteen correlators 151 and 152 use the P-CCPCH as an input signal, and also the slot timing synchronization index obtained in the first step and the second step. The correlation is obtained by inputting the obtained frame synchronization and base station group number, and the post detector accumulators 153 and 154 are connected to the rear ends of the correlators 151 and 152, respectively. The maximum selector 155 determines the scrambling code having the largest correlation value among the correlation values obtained for the 16 scrambling codes as the scrambling code of the base station to which it belongs.

Under the configuration as shown in FIG. 4 to FIG. 6, the terminals perform a search operation as shown in FIG. 3. Looking at the neighbor cell search process performed in the terminal to configure the active set for the handover of the terminal once again as follows.

Now, when the terminal cell is referred to as the first active cell, a first step (time slot synchronization) is performed in another time interval in the time slot with the first active cell in one time slot period as shown in FIG. 1. In this step, when a time interval in which a correlation value of a received signal has a peak value is detected in a time interval different from the first active cell, the time interval is assumed to be a time slot synchronization of an adjacent cell.

Next, by performing step 2 with reference to the time slot synchronization of the neighboring cell obtained in step 1, the frame synchronization of the neighboring cell and the group code to which the cell belongs are searched and identified. After the second step is completed, the terminal performs a third step of verifying whether the group code found in the second step is correctly found in the code list of the adjacent cell provided from the base station.

After performing the above steps 1 to 3 as described above, when the code slot synchronization and the frame synchronization for the neighbor cell are obtained, the neighbor cell whose power level of the received signal is determined to be included in the active set is searched. The adjacent cells are called active second cells and included in the active set. If a cell having another timeslot synchronization is found at a time different from the slot synchronization of the cell in the active set, the same procedure as for searching for the active second cell is performed to find the active third cell, and the terminal repeats this process. Configure active sets for handover

As such, for the neighbor cell management, which is one of steady state operations, the searcher measures the power level of the neighbor cell and configures an active set according to the measurement result. In order to measure the power level of a cell, after obtaining a scrambling code and a frame sync, the correlation value in the pilot symbol interval of the P-CCPCH is obtained. You must get it. In this case, the frame transmission time between the base stations is irregular in the asynchronous mobile communication system, so it is not known at which timing the adjacent cells transmit the frame from the viewpoint of which cell. Therefore, in order to measure the power level of the neighbor cell, the code (scrambling code) and frame timing of the neighbor cell can be obtained only through three steps such as the initial synchronization acquisition process described above, and thus the power level for the neighbor cell. Can be measured. In this way, there is a disadvantage in that it takes a lot of time to measure the power level of the adjacent cells, and also requires a lot of power consumption of the terminal. That is, the terminal measures the power of the neighbor cell in order to configure an activity set for handover. In this case, the terminal knows the type of the neighbor cell code, but does not know the time information for each code. Therefore, the terminal must perform the operation of step 3 as shown as step 100 in FIG. However, it takes a lot of time to perform the operation of these three steps, resulting in a lot of power consumption.

Accordingly, an object of the present invention is to provide an apparatus and method for configuring an active set for handover of a terminal in an asynchronous mobile communication system.

Another object of the present invention is to provide an apparatus and method for reducing a time for determining a power level of a cell in order to configure an active set for handover of a terminal in an asynchronous mobile communication system.

Another object of the present invention is to provide an apparatus and method for reducing power consumed when determining a power level of a cell in order to configure an active set for handover of a terminal in an asynchronous mobile communication system.

According to the present invention for achieving these objects, an apparatus for measuring the power level of neighboring cells to configure an active set for handover of a terminal in a mobile communication system includes a radio network controller, a base station and a terminal. The radio network controller calculates a frame transmission time difference between base stations corresponding to adjacent cells, each of which uses a unique code. The base station receives information on the frame transmission time difference between the base stations from the radio network controller, and transmits the difference information and the base station-specific code information to all terminals in its cell. The terminal receives the difference information and the code information specific to the base station, and takes a correlation between the code information specific to the base station and the first common control channel (P-CCPCH) signal for each cell based on the difference information. The result value is determined as the power level of the corresponding cell.

1 illustrates a physical channel structure of an asynchronous mobile communication system.

2 illustrates an exemplary cell structure and layout of an asynchronous mobile communication system.

3 shows a schematic processing flow of a typical cell search operation.

4 is a diagram illustrating a configuration of a processing apparatus for a slot synchronization acquisition operation of the initial acquisition process illustrated in FIG. 3.

FIG. 5 is a diagram illustrating a configuration of a processing apparatus for group confirmation and frame synchronization acquisition operation of the initial acquisition process shown in FIG. 3. FIG.

FIG. 6 is a diagram illustrating a configuration of a processing device for a scrambling code check operation of the initial acquisition process illustrated in FIG. 3.

7 shows a process flow of a cell power measurement operation in accordance with the present invention.

8 and 9 show examples of frame transmission time differences between base stations calculated according to the present invention.

10 is a diagram illustrating a configuration of a terminal for measuring power of an adjacent cell according to the present invention.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Terms to be described later are defined in consideration of functions in the present invention, which may vary according to the intention or custom of the user or chip designer, and the definitions should be made based on the contents throughout the present specification.

In the following, the present invention will be described by taking an example of configuring an active set for handover in a state in which a terminal is located in cell 1 under a cell structure as shown in FIG. 2. It should be noted that the present invention is described by taking an example in which one base station is installed corresponding to each cell.

7 is a diagram illustrating a processing flow of measuring power levels of neighboring cells (base stations) in order to configure an active set for handover of a terminal according to the present invention.

Referring to FIG. 7, in step S100, each base station reports information on a transmission time of a frame repeated in a preset period (for example, 10 ms period) to a radio network controller (RNC) which is a higher layer. . In the asynchronous mobile communication system, each cell uses a scrambling code that is distinguished from an adjacent cell, and it is well known that there is no regularity of frame transmission time between adjacent cells.

When the information on the frame transmission time is reported from the base stations managed by the radio network controller, the wireless network controller calculates a difference in the frame transmission time between the base stations in step S200. At this time, the wireless network controller calculates the difference in the frame transmission time between base stations in terms of the number of chips. The operation of converting the difference in the frame transmission time between the base stations into the number of chips is according to Equations 1 to 3 below. Assume that time t _i is the time when the base station of cell i transmits the frame, and time t _j is the time when the base station of cell j transmits the frame. The base station of each cell continuously transmits frames from t _i and t _j at a time corresponding to an integer multiple of 10 ms, which is a frame length. Therefore, assuming that the terminal assumes a reference cell as i, assuming that the terminal communicates with the base station of cell i, the relative time of cell j viewed from cell i becomes as shown in Equation 1 below.

In Equation 1, M _{i, j} is a result of performing a 10 ms modulo operation on a transmission time difference between frames transmitted from two cells. The M _{i, j} value is greater than 0 and has a value within the range of less than 10 ms.

Next, the wireless network controller multiplies the M _{i, j} value by a chip rate Rc to obtain the difference Di, j of the relative frame transmission time between cells. The difference D _{i, j} of the relative frame transmission time between cells may be obtained as in Equation 2 or Equation 3 below.

When the value of M _{i, j} is within 5 ms _, the difference D _{i, j} of the relative frame transmission time between cells is obtained using Equation 2 above. When the value of M _{i, j} is greater than 5 ms, the difference D _{i, j} of the relative frame transmission time between cells is calculated using Equation (3). That is, when the value of M _{i, j} exceeds 5 ms, the absolute value of the time calculated using the minus sign (-) is not exceeded 5 ms, and then the resultant value is multiplied by the chip rate Rc. At this time, since Rc is the chip rate used in the system, the unit of _{Di, j} is the number of chips.

8 and 9 are diagrams showing examples of difference values of relative frame transmission times between cells calculated by the radio network controller shown in FIG. 7.

FIG. 8 illustrates a case _where the value of D _{i, j,} which is a measure of how much phase the cell code of cell j has with respect to the cell code of cell _i, is negative. That is, the cell code phase of cell j is relatively advanced compared to the cell code of cell i.

For example, assuming chip rate Rc = 4.096 Mcps and t _j -t _i = -3 ms, the relative frame transmission time difference value M _{i, j} between cells becomes 7 ms according to Equation 1 above. Since this value exceeds 5 ms, when the above Equation 3 is applied, the relative transmission time difference D _{i, j} is-(10-7) ms x 4.096 Mcps = -12288 chip value. That is, the cell code of cell j is 12288 chips ahead of the cell code of cell i.

9 illustrates a case in which a value of D _{i, j,} which is a measure of how much phase the cell code of cell j has with respect to the cell code of cell _i, is positive. That is, the cell code phase of cell j is relatively behind the cell code of cell i.

For example, assuming that the chip rate Rc = 4.096 Mcps and t _j -t _i = 3ms, the relative frame transmission time difference value M _{i, j} between cells becomes 3ms according to Equation (1). Since this value is smaller than 5ms, when Equation 2 is applied, the relative transmission time difference D _{i, j} is 3ms × 4.096Mcps = 12288 chips. In other words, the cell code of the cell j represents 12288 chips behind the cell code of the cell i.

Referring back to FIG. 7, in step S210, the wireless network controller uses the relative frame transmission time difference value D _{i, j} value between cells obtained using Equations 1 to 3 below. As shown in Table 1, an information table of frame transmission time differences between base stations (cells) is configured.

division Cell 1 Cell 2 Cell 3 Cell 4 Cell 5 Cell 6 Cell 7 Cell 1 - D _2,1 D _3,1 D _4,1 D _5,1 D _6,1 D _7,1 Cell 2 D _1,2 - D _3,2 D _4,2 D _5,2 D _6,2 D _7,2 Cell 3 D _1,3 D _2,3 - D _4,3 D _5,3 D _6,3 D _7,3 Cell 4 D _1,4 D _2,4 D _3,4 - D _5,4 D _6,4 D _7,4 Cell 5 D _1,5 D _2,5 D _3,5 D _4,5 - D _6,5 D _7,5 Cell 6 D _1,6 D _2,6 D _3,6 D _4,6 D _5,6 - D _7,6 Cell 7 D _1,7 D _2,7 D _3,7 D _4,7 D _5,7 D _6,7 -

In Table 1, the horizontal row D _{j, i} represents the difference in the frame transmission time of the cell j with respect to the cell i in terms of the number of chips. When the wireless network controller creates a table as shown in Table 1, it is not necessary to calculate a space corresponding to an empty part of the table since all have a value of '0', and only the upper right or lower left of the diagonal line. Calculation, and the rest of the table can be more easily configured by using the relationship of D _{i, j} =-D _{j, i} .

The wireless network controller receives frame transmission time information from base stations managed by the wireless network controller and calculates relative frame transmission time difference information D _{j, i} values between base stations (cells) through Equations 1 to 3. After calculating and completing the table as shown in Table 1, the wireless network controller transmits the difference information of the frame transmission time between the base stations to each base station in step S220 of FIG. At this time _, the information of D _{i, j} is transmitted to the cell i. That is, the wireless network controller transmits all the values of the row in which the number of the cell is written in the <Table 1> to the specific cell.

In step S300, the base station receives information on the relative difference in frame transmission time between adjacent base stations from the radio network controller, and then transmits the information as shown in Table 2 below to all terminals in its cell. send. That is, the base station receives the information on the frame transmission time difference between the base stations from the radio network controller, and transmits the base station-specific code information with the difference information to all terminals in its cell. In this case, the base station transmits the difference information and the base station-specific code information to all terminals in its cell in the form of broadcasting through SCCPCH.

Cell ID Code ID Group ID Difference information of frame transmission time 2 C2 G2 D1,2 3 C3 G3 D1,3 4 C4 G4 D1,4 5 C5 G5 D1,5 6 C6 G6 D1,6 7 C7 G7 D1,7

Referring to Table 2, base station-specific code information includes a cell identifier (Cell ID) indicating a corresponding cell, a code identifier (Code ID) indicating a base station-specific code, and a group indicating a group to which the base station belongs. It consists of an identifier (Group ID). Gold code may be used as the cell identifier, and the group identifier indicates a group to which the gold code belongs. Information D _{i, j} on the difference in frame transmission time between the base stations indicates how much phase the cell code of cell j has based on cell i. D _{i, j} may have a positive value or a negative value, and the unit at this time may be represented by a chip unit as described above, or may also be represented by a sample unit. If D _{i, j} has a positive value, the code phase of cell i is earlier than the code phase of cell j as shown in FIG. 9. In contrast, the case where D _{i, j} has a negative value is a case where the code phase of cell i lags behind the code phase of cell j as shown in FIG. 8.

In step S400, the terminal receives the transmission time difference information between the base stations provided from the base station and the base station-specific code information, and uses the received information to configure the power level of the adjacent base station (cell) to configure an active set for handover. Perform an operation to measure. As mentioned above, the searcher of the terminal needs to periodically measure the power level of the neighboring base station to manage the neighboring base stations.

FIG. 10 is a diagram illustrating an operation of step S400 of FIG. 7, that is, a configuration of a terminal for periodically measuring a power level of an adjacent base station (cell). Although only an example of determining a power level of one cell is shown here, it should be noted that the present invention may determine the power level of all adjacent cells.

Referring to FIG. 10, the terminal transmits the information as shown in Table 2, that is, information (D _{i, j} ) of the frame transmission time difference between the base stations to which the base station belongs and base station specific code information. Receives (Cell ID, Code ID, Group ID), and determines the power level of the adjacent cell. The terminal includes a correlator 210 for this operation. The correlator 210 performs correlation between base station-specific code information (Code ID, Group ID) and input signal for each cell based on the information (D _{i, j} ) of the frame transmission time difference between the base stations received from the base station. Take The input signal is a first common control channel (P-CCPCH) signal. More specifically, the correlator 210 determines the transmission time of the corresponding cell for determining the cell power level based on the frame transmission time difference information (D _{i, j} ) between the base stations _, and determines the P-CCPCH signal. A correlation between code information (Code ID, Group ID) unique to the base station is taken. In this case, the base station-specific code information received from the base station includes a cell identifier (Cell ID), a code identifier (Code ID) and a group identifier (Group ID). However, as described above, FIG. 10 is limited to an operation of determining a power level for one cell. Here, the base station-specific code information includes only a code identifier (Code ID) and a group identifier (Group ID). It is shown. The correlation result by the correlator 210 is output after being post-detected and accumulated by the post detector & accumulator 220.

In one embodiment, the correlator 210 is therefore provided with three of the cell 1 and the frame transmission time difference information between cells D _1,2 2:00 to perform the operation of determining the power level for the cell 2 from the base station, the current serving cell, the base station 1 The time shifted by D ₁ , ₂ from the frame transfer time may be assumed to be the cell 2 transmission time. That is, the correlator 210 performs correlation between base station-specific code information (Code ID C2, Group ID G2) and P-CCPCH signal for cell 2 based on the transmission time of cell 2. In this case, the correlation result value by the correlator 210 is output after being post-detected and accumulated by the post-detector & accumulator 220, and this output value is a determination value of the power level for the second cell.

In the above example, only the operation of determining the power level of the second cell among the plurality of adjacent cells has been described. However, the operation of determining the power level of the desired cell among the plurality of adjacent cells may also be performed. For example, when determining the power level for cell 3, the terminal determines the frame transmission time of cell ₃ from the difference information D _1,3 of the frame transmission time for cell 3, and determines the transmission time. As a reference, the correlator 210 takes a correlation between the code identifier C3 and the group identifier G3 and the P-CCPCH signal for the cell 3 and outputs the correlation result as a determination value of the power level of the cell 3.

Meanwhile, in the present invention, a plurality of window processes are performed on a determination value of a power level for a predetermined cell output from the post-detector & accumulator 220 in consideration of a transmission delay from a base station to a terminal. The largest value among the values is output as a judgment of the power level. The terminal includes a switching unit 230, a plurality of (w) buffers 241 to 244, and a maximum value selector 250 for processing considering the transmission delay. Each of the plurality of buffers 241 to 244 stores a window corresponding to each of the w hypotheses, and then processes the output values from the detector & accumulator 220 using the corresponding window. The switching unit 230 is connected between the post detector & accumulator 220 and the respective buffers 241 to 244 for processing w windows for output values from the post detector & accumulator 220, and the post detector & accumulator. Output values from 220 are sequentially provided to the respective buffers 241 to 244. The maximum selector 250 outputs the largest output value among the w output values from the buffers 241 to 244 as a power level determination value of the corresponding cell.

When the power level determination values of all neighbor cells are determined, the controller (not shown) sets an adjacent cell having the largest value among the determined determination values, that is, a cell having the largest power intensity to the active set for handover of the terminal. Consists of.

Using the above scheme, the terminal does not need to go through steps 1 and 2 as in the initial synchronization acquisition process, and also in step 3, only one single correlator is used in the initial synchronization acquisition process. You only need to use the correlator. As we test the hypotheses of w hypotheses, all we need is a buffer to store the results as many hypotheses.

As described above, the present invention measures the power of the corresponding cell by using the cell code of the neighboring cell provided from the base station and the relative frame transmission time difference information between the cells, without having to go through a three-step cell search process. It is possible to shorten the time required to configure an active set for the purpose and to reduce the power consumption.

Claims (13)

An apparatus for measuring a power level of adjacent cells to configure an active set for handover of a terminal in a mobile communication system, A wireless network controller for calculating a frame transmission time difference between base stations corresponding to adjacent cells, each of which uses a different unique code; A base station receiving information on a frame transmission time difference between base stations from the radio network controller, and transmitting the difference information and code information specific to the base station to all terminals in its cell; Receiving the difference information and the code information specific to the base station, taking a correlation between the code information specific to the base station and the first common control channel (P-CCPCH) signal for each cell based on the difference information, and the correlation result value The device comprising a terminal for determining the power level of the corresponding cell. The method of claim 1, wherein the base station-specific code information includes a cell identifier (ID) indicating a corresponding cell, a code identifier (ID) indicating a base station-specific code, and a group identifier (ID) indicating a group to which the base station belongs. Apparatus comprising a. The terminal of claim 1, wherein the terminal determines a transmission time of a corresponding cell for determining a cell power level based on the difference information, and the first common control channel (P-CCPCH) signal and code information specific to the base station. And a correlator to take the correlation between. The terminal of claim 3, wherein the terminal comprises: A plurality of buffers each of which stores a window, and takes a correlation value using a corresponding window for an output value from the correlator in consideration of a transmission delay; And a maximum value selector for outputting a maximum value of the output values of the buffers as the correlation result value. 5. The apparatus of claim 4, wherein the terminal further comprises a switching unit connected between the correlator and the buffers and sequentially providing output values from the correlator to the buffers. The apparatus of claim 1, wherein the wireless network controller calculates a frame transmission time difference between base stations corresponding to adjacent cells, converts the calculation result into a number of chips, and transmits the difference information to the base station as the difference information. . The apparatus of claim 1, wherein the base station transmits the difference information and code information specific to the base station to all terminals belonging to the base station in the form of broadcasting. What is claimed is: 1. A method of measuring power levels of adjacent cells to configure an active set for handover in a mobile communication system, (A) transmitting, by the base stations corresponding to adjacent cells using different unique codes, the frame transmission time information to the radio network controller; (B) the radio network controller receiving frame transmission time information from the base stations and calculating a frame transmission time difference between the base stations; (C) a base station receiving information on a frame transmission time difference between base stations from the radio network controller, and transmitting the difference information and code information specific to the base station to all terminals in the cell; The terminal receives the difference information and the base station-specific code information, and takes into account the correlation between the base station-specific code information for each cell and the first common control channel (P-CCPCH) signal based on the difference information. And (d) determining the result value as the power level of the corresponding cell. The method of claim 8, wherein the base station-specific code information includes a cell identifier (ID) indicating a corresponding cell, a code identifier (ID) indicating a base station-specific code, and a group identifier (ID) indicating a group to which the base station belongs. Method comprising a. The method of claim 8, wherein in step (d), the transmission time of the corresponding cell for determining the cell power level is determined based on the difference information, and the first common control channel (P-CCPCH) is determined by one correlator. ) Taking a correlation between a signal and the base station specific code information. The method of claim 10, Processing a correlation value using a plurality of windows for a correlation result value by the correlator in consideration of a transmission delay; And selecting a maximum value among the correlation values processed by the plurality of windows and outputting the maximum value as a power level value of a corresponding cell. The method of claim 8, wherein the wireless network controller calculates a frame transmission time difference between base stations corresponding to adjacent cells, converts the calculation result into a number of chips, and transmits the difference information to the base station as the difference information. . The method of claim 8, wherein the base station transmits the difference information and the code information specific to the base station to all terminals belonging to the base station in the form of broadcasting.