KR100566249B1 - Fast cell searching apparatus and method in umts system - Google Patents

Abstract

end. The technical field to which the invention described in the claims belongs

High speed cell search apparatus and method for asynchronous code division multiple access communication system

I. The technical problem that the invention is trying to solve

The present invention provides an apparatus and method for acquiring a scramble code number at the same time of acquiring frame synchronization during cell search in an asynchronous code division multiple access communication system.

All. Summary of Solution of the Invention

A cell search apparatus of an asynchronous code division multiple access communication system transmits a second synchronous channel comprising a first section having second sync code information and a scramble code number information and having a second section continuous to the first section. And a terminal for acquiring the scramble code number at the same time as acquiring frame synchronization.

la. Important uses of the invention

Used for cell search in asynchronous systems.

Asynchronous code division multiple access, communication system

Description

FAST CELL SEARCHING APPARATUS AND METHOD IN UMTS SYSTEM}             

1 is a view showing a structure of a synchronization channel (SCH) according to the prior art.

2 is a diagram illustrating a synchronization channel structure according to the present invention;

3 illustrates a channel generator according to an embodiment of the present invention.

4 is a diagram illustrating a terminal structure for obtaining energy of a second section of a second synchronization channel according to an exemplary embodiment of the present invention.

5 is a diagram illustrating a cell search procedure of a terminal according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a detailed procedure of the scramble code number confirmation subroutine in FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an asynchronous code division multiple system (CDMA) communication system, and more particularly, to a fast cell searching apparatus and method.

As shown in FIG. 1, in the Universal Mobile Telecommunication System (UMTS) system, one frame is 10ms, and one frame includes 16 timeslots. The sync channel divides one time slot into 10 sections and outputs the first sync code Cp and the second sync code Cs for 256 chips in the first section of the slot, and outputs "0" in the remaining sections. Here, a channel for transmitting the first sync code in the first section of each slot is called a first sync channel, and a channel for transmitting the second sync code in the first section of each slot is called a second sync channel. The first synchronization code used as the first synchronization channel is a unique code Cp commonly used by all base stations, and the second synchronization channel represents 32 different group codes by combining 17 codes by 16. That is, each group has 16 scrambled codes (= long code).

In the UMTS system, a dedicated physical channel (DPCH) and a common control physical channel (CCPCH) are channels used physically and are commonly used by call channels for all subscribers or all subscribers. It is a channel. The channel is divided into channel division codes to be multiplied with each channel. The data multiplied by the channel division codes are added together and multiplied by the scramble code. The synchronous channel is added to the wireless unit.

In the UMTS system having the channel structure as described above, the mobile station acquires timeslot synchronization using the first synchronization channel during cell search. Frame synchronization is obtained using 32 group codes in the second synchronization channel, and 16 scramble codes belonging to the obtained group among 32 groups are correlated with the common control physical channel to obtain final cell synchronization. Here, the scramble code has 2 ¹⁸ cycles.

However, a problem of the cell search proposed by the ETSI W-CDMA UMTS RTT is that a long code, that is, a scramble code, cannot be found immediately during cell search. In order to find out the scramble code, the scramble code group information found in the cell search must be correlated with the scramble codes that may exist in the group to find out the scramble code currently used by the base station. In this case, if a large number of scramble codes exist in the scramble code group, there is a problem that it takes too much time to find the scramble code.

In other words, the mobile station synchronizes slots with the first synchronization channel, and it is assumed that synchronization occurs when the output value of the matching filter is the largest. The code C ₀ (= C _p ) used here is an unmodulated orthogonal gold code code of 256 chips. "0" in C ₀ means that the 8-bit register value in the orthogonal gold code is 0. All base stations use C ₀ as a synchronization code of the first synchronization channel. If slot synchronization is correct, the corresponding group code is found by synchronizing 10ms frame, and the long code to be finally obtained is found by correlating 16 long codes existing in the obtained group. The 32 group codes are made as shown in Table 1 below.

TABLE 1

Group 1: c1, c2, c3, c11, c6, c3, c15, c7, c8, c8, c7, c15, c3, c6, c11, c2

Group 2: c1, c2, c9, c3, c10, c11, c13, c13, c11, c10, c3, c9, c2, c1, c16, c16

Group 3: c1, c3, c16, c12, c14, c2, c11, c2, c7, c12, c16, c3, c1, c13, c4, c13

Group 4: c1, c4, c5, c4, c1, c10, c9, c8, c17, c14, c12, c14, c17, c8, c9, c10

Group 5: c1, c5, c13, c13, c5, c1, c7, c14, c3, c16, c8, c8, c16, c3, c14, c7

Group 6: c1, c6, c3, c5, c9, c9, c8, c3, c6, c1, c4, c2, c15, c15, c2, c4

Group 7: c1, c7, c10, c14, c13, c17, c3, c9, c9, c3, c17, c13, c14, c10, c7, c1

Group 8: c1, c8, c17, c6, c17, c8, c1, c15, c12, c5, c13, c7, c13, c5, c12, c15

Group 9: c1, c9, c7, c15, c4, c16, c16, c4, c15, c7, c9, c1, c12, c17, c17, c12

Group 10: c1, c10, c14, c7, c8, c7, c14, c10, c1, c9, c5, c12, c11, c12, c5, c9

Group 11: c1, c11, c4, c16, c12, c15, c12, c16, c4, c11, c1, c6, c10, c7, c10, c6

Group 12: c1, c12, c11, c8, c16, c6, c10, c5, c7, c13, c14, c17, c9, c2, c15, c3

Group 13: c1, c13, c1, c17, c3, c14, c8, c11.c10, c15, c10, c11, c8, c14, c3, c17

Group 14: c1, c14, c8, c9, c7, c5, c6, c17, c13, c17, c6, c5, c7, c9, c8, c14

Group 15: c1, c15, c15, c1, c11, c13, c4, c6, c16, c2, c2, c16, c6, c4, c13, c11

Group16: c1, c16, c5, c10, c15, c4, c2, c12, c2, c4, c15, c10, c5, c16, c1, c8

Group 17: c1, c17, c12, c2, c2, c12, c17, c1, c5, c6, c11, c4, c4, c11, c6, c5

Group 18: c2, c8, c11, c15, c14, c1, c4, c10, c10, c4, c1, c14, c15, c11, c8, c2

Group 19: c2, c9, c1, c7, c1, c9, c2,16, c13, c6, c14, c8, c14, c6, c13, c16

Group 20: c2, c10, c8, c16, c5, c17, c17, c5, c16, c8, c10, c2, c13, c1, c1, c13

Group 21: c2, c11, c15, c8, c9, c8, c15, c11, c2, c10, c6, c13, c12, c13, c6, c10

Group 22: c2, c12, c5, c17, c13, c16, c13, c17, c5, c12, c2, c7, c11, c8, c11, c7

Group 23: c2, c13, c12, c9,17, c7, c11, c6, c8, c14, c15, c1, c10, c3, c16, c4

Group 24: c2, c14, c2, c1, c4, c15, c9, c12, c11, c16, c11, c12, c9, c15, c4, c1

Group 25: c2, c15, c9, c10, c8, c6, c7, c1, c14, c1, c7, c6, c8, c10, c9, c15

Group 26: c2, c16, c16, c2, c12, c14, c5, c7, c17, c3, c3, c17, c7, c5, c14, c12

Group 27: c2, c17, c6, c11, c16, c5, c3, c13, c3, c5, c16, c11, c6.c17, c2, c9

Group 28: c2, c1, c13, c3, c3, c13, c1, c2, c6, c7, c12, c5, c5, c12, c7, c6

Group 29: c2, c2, c3, c12, c7, c4, c16, c8, c9, c9, c8, c16, c4, c7, c12, c13

Group 30: c2, c3, c10, c4, c11, c12, c14, c14, c12, c11, c4, c10, c3, c2, c17, c17

Group 31: c2, c4, c17, c13, c15, c3, c12, c3, c15, c13, c7, c4, c2, c14, c5, c14

Group 32: c2, c5, c7, c5, c2, c11, c10, c9, c1, c15, c13, c15, c1, c9, c10, c11

In Table 1, ci (2 <= i <= 17) represents an 8-bit register value of an orthogonal gold code having a length of 256. In addition, the characteristic of the group code is that even if one group code is cycle shifted 16 times or less, the same code as the other group code never appears. In other words, a group code is unique. You can use this uniqueness to know the beginning of a frame. Then, the scramble code used in the base station is obtained by correlating the 16 scramble codes in the acquired group code with the common control physical channel. At this time, the configuration of the 16 scramble codes in each group are values determined in advance between the base station and the mobile station. That is, as described above, when the scramble code is found by correlating all of the scramble codes of the corresponding group with the common control physical channel, there is a problem in that the cell search takes a long time.

Accordingly, an object of the present invention is to provide an apparatus and method for reducing cell search time in an asynchronous code division multiple access communication system.

Another object of the present invention is to provide an apparatus and method for simultaneously acquiring a scramble code at the time of acquiring frame synchronization during cell search in an asynchronous code division multiple access communication system.

A cell search apparatus of an asynchronous code division multiple access communication system for achieving the above objects comprises: a first section having second synchronous code information and a second section continuous with the scramble code number information; And a base station for transmitting the second synchronous channel and a terminal for acquiring the scramble code number at the same time as acquiring the frame synchronization.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, in adding the reference numerals to the components of each drawing, the same components have the same reference numerals as much as possible even if displayed on different drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In general, a mobile station searches for cells around it upon power-on. At this time, the mobile station synchronizes the cell with the largest energy in the slot using the primary synchronization channel in FIG. 2. After the slot synchronization is completed, the code group of the scramble code is found using the second synchronization channel, and thus frame synchronization is adjusted. At this time, the scramble code number Lb is obtained using 16 code sequences in the code group obtained in the frame synchronization. Here, the scramble code number Lb has a 16-bit value, and each scramble code has 18 bits.

There are 512 scramble codes between the base station and the mobile station. Each scramble code has a 10 msec period and is shifted by 80 chips at the frame boundary. Therefore, 512 scramble codes can be displayed by the scramble code number Lb. That is, if the scramble code number Lb is 17, the scramble code is a code that the code generator shows after 17 * 80 chips after the initial state.

3 illustrates a base station channel generator for a fast cell tamper according to the present invention.

Referring to FIG. 3, the first switch 311 is switched where the input is "1" during the first 256 chip cycles in the slot, and is switched where the input is "0" during the next (2560-256) chips. The multiplier 312 multiplies the data transmitted from the first switch 111 by the first synchronization code Cp and outputs the multiplier. The second switch 314 is switched where the input is "1" for the first 256 chip cycles in the slot, the input is switched to "bi" for the next 256 chip cycles, and the input for the next (2560-2 * 256) chip cycles. Is switched to "0". Here, "bi" is the i-th bit value when the scramble code number is represented by 16-bit binary number. The multiplier 315 multiplies the data transmitted from the second switch 314 by the second synchronous code Cs and outputs the multiplier. The adder 313 adds and outputs the output signal of the multiplier 312 and the output signal of the multiplier 31. If it is assumed that the scramble code number is 17, and it is expressed as 16 bits, it is (0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1) ₂ . Therefore, "0" data is transmitted in the second section of the first slot to the eleventh slot and the thirteenth slot to the fifteenth slot of the second sync channel, and the second sync in the second section of the twelfth and sixteenth slots. The code is transmitted The adder 316 adds all the channel signals multiplied by the channel classification code, and outputs the multiplier 317 by multiplying the output signal of the adder 316 by the scramble code C _scramb . The adder 318 adds the output signal of the adder 313 and the output signal of the multiplier 317 and transfers the output signal to the wireless unit.

The synchronization channel structure transmitted through the channel transmitter of FIG. 3 is shown in FIG.

Referring to FIG. 2, first, a first sync code Cp is transmitted every first 256 chip cycles in a slot. The mobile station synchronizes with the corresponding base station by acquiring the first synchronization code carried in the first synchronization channel, and synchronizes the frame synchronization using the second synchronization channel. In this process, the mobile station finds out the scramble code group and the scramble code number. The second synchronization channel transmits the second synchronization code Cs every first 256 chip cycles in the slot, as in the prior art. Here, according to the present invention, when the second synchronous code and the scramble code number are represented in binary for the 256-chip period subsequent to the first 256-chip cycle, the data multiplied by the corresponding bits (hereinafter referred to as the corresponding bits of the scramble code number) Cs ^{i, j} * bi). The terminal acquires scrambled group information through the second synchronous code Cs transmitted during the first 256 chip cycles, and transmits the information (Cs ^{i, j} * bi) transmitted during subsequent 256 chip cycles during the first 256 chip cycles. Correlate with synchronous code to obtain the corresponding bit of scramble group number. For example, as a result of correlating the second intervals in the slot, if the peak value appears in the 11th and 16th slots, it can be seen that the base station that is synchronized is using the scramble code number 17.

4 shows a structure of a mobile station for obtaining a scramble code number as described above.

Referring to FIG. 4, the matched filter 411 correlates and outputs a second sync code of a first section acquired to a second section signal of a second sync channel. The accumulator 412 accumulates and outputs the output of the matched filter 411 in slot units. The selector 413 determines the output value of the accumulator 412 and outputs "1" when it is larger than the reference energy e_th, and outputs "0" when it is smaller. The output values are used to find out the scramble code number. As described above, if the mobile station acquires the scramble code group and thus frame synchronization, the mobile station can determine the scramble code number. As shown in FIG. 4, the matching filter 411 examines the result of correlating the orthogonal gold code for the first 256 chips to the signal received for 256 chips after 256 chips in each slot. In this case, the output energy is set to 2nd_e, and the 2nd_e is determined as "1" when it is larger than the reference energy by comparing the reference energy value e_thrkh that distinguishes the digital logic "1" and "0". If it is small, it is determined as "0" to obtain a final scramble code number.

Hereinafter, a cell search procedure of a mobile station according to the present invention will be described in detail with reference to FIGS. 5 and 6.

5 shows an overall cell search process, and FIG. 6 shows a detailed process of a subroutine for identifying a scramble code number during the cell search procedure.

First, referring to FIG. 5, in step 511, the mobile station searches for the attention cell to obtain a first synchronization channel received with the greatest energy, and synchronizes the first synchronization channel with the first synchronization channel. Thereafter, the mobile station acquires a second synchronization channel in step 513 based on the initial synchronization to synchronize frame synchronization. In operation 515, the scramble group number is obtained through the second synchronization codes transmitted through the second synchronization channel, and in operation 517, the scramble code number is obtained.

Referring to FIG. 6, the scramble code number acquisition process is performed. First, in step 611, the energy of the first section of the second synchronization channel is obtained, and the obtained result is stored in step 613. That is, the second synchronization code of the second synchronization channel is obtained through steps 611 and 613. In operation 615, the second interval of the second synchronization channel is correlated with the obtained second synchronization code to obtain energy of the second interval, and the calculated result is stored in operation 617. In operation 619, it is checked whether the group code is detected. In this case, when it is determined that the group code is not detected, the process proceeds to step 625, the next slot is designated, and the process returns to step 611 to perform the following steps. On the other hand, when it is determined in step 619 that the group cog is detected, the process proceeds to step 621 to find a frame boundary in a register that stores the results of the first section and the second section, and based on the frame boundary in step 623. Acquire a scramble code number.

After the above process is completed, the bit (b15, b14, b13, b12, b11, b10, b9, b8, b7, b6, b5, b4, b3, b2, b1, b0) for the scramble code number is completed. The terminal immediately demodulates a broadcasting channel (BCH) by using a code corresponding to the scramble code number.

As described above, in the asynchronous code division multiple access communication system, the scramble code of the base station can be obtained at the same time as the frame synchronization is acquired during the cell search, so that no separate processing is required to find the scramble code. That is, there is an advantage that the cell search time can be shortened. In addition, the mobile station can directly enter a broadcasting channel (BCH) demodulation with the obtained scramble code, thereby reducing the data demodulation time.

Claims (6)

A cell searching apparatus for an asynchronous code division multiple access communication system, A base station having a first section having second sync code information and scramble code number information and transmitting a second sync channel comprising a second section continuous to the first section; A fast cell search apparatus for an asynchronous code division multiple access communication system, characterized in that it comprises a terminal for acquiring frame synchronous and acquiring the scramble code number. The method of claim 1, The base station retransmits the second synchronous code transmitted in the first section with respect to " 1 " of the bit string representing the scramble code number in the second consecutive section. Cell Search Device. The method of claim 1, wherein the terminal, A correlator for correlating a signal received in the second section with the obtained second synchronization code; And a determiner for determining the scramble code number according to a correlation result of the correlator. A cell searching method of an asynchronous code division multiple access communication system, Transmitting, by the base station, a second synchronization channel comprising a first section having second sync code information and a second section having scramble code number information and continuing in the first section; And a terminal for acquiring the scramble code number simultaneously with acquiring frame synchronization. The method of claim 4, wherein The base station retransmits the second synchronous code transmitted in the first section with respect to " 1 " of the bit string representing the scramble code number in the second consecutive section. Cell search method. The method of claim 4, wherein The terminal, correlating a signal received in the second section with an acquired second synchronization code; And a method for determining the scramble code number according to the correlation result.

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