JP2002124906A - CDMA wireless mobile device and cell search method thereof - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce current consumption of a CDMA wireless mobile device and improve standby time. SOLUTION: In a first stage, a CDMA wireless mobile device despreads a P-SCH signal using a PSC and detects slot timing (step S301). Subsequently, the process proceeds to the second stage, and the CP of the fifteen frame timing candidates is determined using the peripheral station scramble code.
The ICH is despread, and the frame timing is detected (step S303). The CDMA wireless mobile device of the present invention detects the frame timing by performing despreading with the peripheral station scrambling code broadcasted by the broadcast information at all frame timings based on the slot timing detected in the first stage. I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a W-CDMA radio mobile station and a cell search method thereof.
The present invention relates to a W-CDMA wireless mobile device and a cell search method for reducing standby current by reducing current consumption by reducing the number of times code despreading is performed.

[0002]

2. Description of the Related Art FIG. 1 is a flowchart showing a conventional cell search method in a CDMA radio mobile station. FIG. 2 is a diagram for explaining a detection process in a conventional cell search procedure. Hereinafter, FIGS. 1 and 2
, A conventional cell search will be described.

A cell search by a CDMA radio mobile station generally uses a search method divided into three stages. First, in the first stage, the CDMA wireless mobile device
The slot timing is detected using a P-SCH (Primary-Synchronization CHannel) signal. The P-SCH is located at the head of each slot, and its spreading code (Primary Synchronization Code; PSC) is common to all cells. Therefore, the CDMA wireless mobile device is
By inputting the received signal to the matched filter corresponding to the spread code, the slot timing is detected as shown in FIG. 2A (step S101).

Next, in the second stage, S-SCH (Second
ary-Synchronization CHannel) is used to detect the frame timing and the scramble code group. The S-SCH is arranged at the head of each slot, and the spreading codes are 64 different spreading codes (Secondary Synchronsatio) having a period of 15 slots (one frame).
n Code; SSC) sequence is used. Each of the 64 types of spreading code sequences is associated with a scrambling code group including eight scrambling codes, thereby facilitating detection of a scrambling code performed later.

[0005] For this reason, a CDMA wireless mobile device is
As shown in FIG. 2 (b), at all frame timings based on the slot timing detected at the first stage, despreading is performed on all of the spreading code (SSC) sequences to obtain a frame timing and a scrambling code group. Is detected (step S103).

[0006] In the third stage, a scrambling code is specified using a common pilot channel (CPICH) to which a different scrambling code is applied for each cell. Based on the frame timing detected in the second stage, the CDMA wireless mobile device performs despreading with all scramble codes belonging to the scramble code group detected in the second stage, as shown in FIG. 2C. Thus, a scramble code is detected (step S105).

Then, it is determined whether a timing or a code is detected in each operation (step S10).
7) If it is determined that the detection is successful, the BCCH (Broa) is used by using the scramble code detected in the third step.
dcast Control CHannel) signal is despread (step S109). If decoding of the BCCH information is successful, C
The wireless mobile device of the DMA system enters an area standby state. BCC
The H information includes a scrambling code of a peripheral station.
Hereinafter, this scramble code is referred to as “peripheral station scramble code”.

If it is determined in step S107 that the timing or code cannot be detected in each operation, the first operation is performed until the decoding of the BCCH information is successful.
The process from the stage is intermittently repeated. At this time, C
The DMA type wireless mobile device goes out of service.

[0009] Even in the standby mode, a three-stage cell search is performed periodically or as needed to perform synchronous control.

As described above, the conventional CDMA radio mobile station performs a considerable amount of code despreading during the three-stage cell search.

[0011]

However, when a large amount of code despreading is performed as described above, the current consumption during execution of the code despreading process is large.
There is a problem that the standby time of the wireless mobile device of the system becomes short.

Also, in the out-of-service standby state, it is necessary to intermittently perform code despreading in order to detect a communication carrier. If a CDMA radio mobile station is out of service for a long time, the standby time is reduced. There was a problem that it became shorter.

Further, in the conventional three-stage cell search method,
In order to improve the standby time during out-of-service standby, it is necessary to increase the execution interval of the cell search during out-of-service standby, that is, the execution cycle. Therefore, when the CDMA wireless mobile device moves from outside the service area to the service area, there is a problem in that the time required to recognize that the wireless mobile device exists in the service area increases.

The present invention has been made in order to solve such a problem. It is an object of the present invention to reduce the number of times code despreading is performed, thereby achieving a CDM.
It is an object of the present invention to provide a CDMA wireless mobile device and a cell search method for reducing the current consumption of the A wireless mobile device and improving the standby time.

[0015]

In order to achieve the above object, the present invention is directed to a CDMA radio mobile station, wherein a peripheral station scramble code included in a control channel is transmitted. A first storage unit for storing, and a detecting unit for despreading a common pilot signal using the peripheral station scrambling code stored in the first storage unit and detecting a frame timing; The code is broadcast by broadcast information transmitted from the wireless base station.

Therefore, the operation time of the CDMA wireless mobile device can be reduced, and as a result, the standby time can be improved.

According to a second aspect of the present invention, there is provided the CDMA wireless mobile device according to the first aspect, further comprising first storage means for storing the peripheral station scramble code, and the detection means comprising: It is characterized in that the peripheral station scramble code whose timing has already been measured is removed from the peripheral station scramble code stored in the first storage means and used.

Therefore, the cell search is performed by excluding the scrambling code of the sector where the wireless mobile station is located and the scrambling code of the sector for which the frame timing has already been detected from the neighboring scrambling codes, thereby performing despreading. Can be further reduced.

Further, the invention described in claim 3 is the first invention.
2. The wireless mobile device of the CDMA system according to claim 1, further comprising second storage means for storing the peripheral station scramble code broadcasted by the new broadcast information, wherein the detection means is stored in the first storage means. Using the newly given peripheral station scrambling code, which is detected by comparing the peripheral station scrambling code with the peripheral station scrambling code stored in the second storage means. Features.

Therefore, in the next cell search, by using the selected scramble code preferentially, it is possible to detect the destination sector in a short time even during high-speed movement. As a result, the cell search execution time can be reduced.

According to a fourth aspect of the present invention, in the CDMA wireless mobile device according to the first, second, or third aspect, the number of times that the detection means detects the frame timing continuously is measured. Measurement means
When the number of times exceeds a predetermined threshold value, the detecting means selects and uses a spreading code sequence for specifying a scrambling code group including a plurality of scrambling codes.

According to the present invention, when the radio mobile station moves from the outside of the service area to the service area, the conventional cell search is performed without using the peripheral station scramble code stored in the inside of the radio mobile station. This makes it possible to recognize that the mobile device exists within the service area.

[0023] The invention according to claim 5 is characterized in that CDMA
A first mobile step of storing a peripheral station scrambling code included in a control channel, and using the peripheral station scrambling code stored in the first storing step. A detection step of despreading a common pilot signal and detecting a frame timing is provided, and the peripheral station scramble code is broadcasted by broadcast information transmitted from a radio base station.

According to a sixth aspect of the present invention, in the cell search method for a CDMA wireless mobile device according to the fifth aspect, the detecting means includes the peripheral station scramble stored in the first storing step. The present invention is characterized in that the peripheral station scramble code whose timing has already been measured is removed from the code and used.

The invention described in claim 7 is the same as the invention described in claim 5.
3. The cell search method for a CDMA wireless mobile device according to claim 2, further comprising a second storage step of storing the peripheral station scramble code broadcasted by the new broadcast information, wherein the detection step comprises the first storage. Using the newly given peripheral station scrambling code, which is detected by comparing the peripheral station scrambling code stored in the step and the peripheral station scrambling code stored in the second storing step, with priority It is characterized by the following.

Further, the invention according to claim 8 is the cell search method for a CDMA radio mobile station according to claim 5, 6 or 7, wherein the number of times the detection step is continuously executed is measured. A measuring step, wherein the detecting step compares the number of times with a predetermined threshold value, and specifies a scramble code group including a plurality of scramble codes when the number of times exceeds the threshold value. And selecting and using a spreading code sequence to be used.

As described above, the present invention mainly has a function of executing a frame timing detection operation by using a peripheral station scrambling code broadcasted by broadcast information in a cell search operation of a CDMA wireless mobile device. Characteristic.

[0028]

Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, the present invention
It is assumed that the three-step flow shown in FIG. 1 is completed, and the peripheral station scramble code obtained from the BCCH information is stored in advance in a storage device of a CDMA wireless mobile device.

(First Embodiment) FIG. 3 is a flowchart showing a cell search procedure according to one embodiment of the present invention. FIG. 4 is a diagram for explaining a detection process in the cell search procedure of the present invention.

In the first stage, as shown in FIG. 4A, the CDMA radio mobile station uses the PSC to perform P-S
The CH signal is despread, and the slot timing is detected (step S301). The P-SCH is arranged at the head of each slot, and its spreading code is common to all cells. Therefore, the CDMA wireless mobile device of the present invention
The slot timing is detected by inputting the received signal to a matched filter corresponding to the spreading code.

Subsequently, the process proceeds to the second stage. As shown in FIG. 4 (b), the CPICH is despread with respect to the 15 frame timing candidates using the peripheral station scramble code to detect the frame timing. Perform (Step S30)
3). The CDMA wireless mobile device of the present invention uses a peripheral station scramble code broadcasted by broadcast information on a broadcast channel transmitted from a base station at all frame timings based on the slot timing detected in the first step. The common pilot channel (CPIC)
The frame timing is detected by performing the despreading of H).

The processing in the first and second stages is repeated until the detection of the slot timing and the frame timing is successful (step S305).

FIG. 5 is a diagram for specifically explaining the present embodiment. As shown in FIG.
The CDMA radio mobile station that is stationary in the cell is the CPCIH transmitted from the base station in the cell where the radio mobile station is located.
Level, that is, the own station level is below the threshold,
A cell search is performed to detect a transition from sector to sector, that is, a transition destination in zone transition.

FIG. 6 is a flowchart showing a cell search procedure according to this embodiment. The own station level is compared with the threshold value (step S601). If the own station level is equal to or less than the threshold value, the cell search according to the present embodiment is performed (step S603). Then, it is determined whether or not the zone transition criterion is satisfied (step S605). If the peripheral station level satisfies a predetermined zone transition criterion,
The base station decodes the BCCH of the detected carrier and refers to the broadcast information (step S607). If the peripheral station level does not satisfy the predetermined zone shift criterion, the zone shift destination cannot be detected. In this case, the cell search is intermittently repeated.

In such a state, by reducing the number of scramble codes for despreading, the operation time of the CDMA wireless mobile device can be reduced, and the standby time can be improved.

(Second Embodiment) FIG. 7 is a view for specifically explaining another embodiment of the present invention. For example, B
The total number of peripheral station scramble codes broadcast by the CCH and the number of own station scramble codes are 6 in total.
The scramble code of the peripheral station and the scramble code of the local station provided to the CDMA wireless mobile device 709 whose serving sector is the sector # 0 in the cell of the wireless base station 701 are sector # 0, sector # 1, It is assumed that the scramble code is for sector # 5, sector # 9, sector # 16, and sector # 19. Also, sector # 1 and sector # 5
Assume that the frame timing has already been detected, the sectors for which the frame timing should be detected by the cell search are sector # 9, sector # 16, and sector # 19.
It is.

When performing a cell search in such a state, the CDMA radio mobile station performs a cell search only on a sector whose frame timing is unknown and performs a synchronization process.

FIG. 8 is a flowchart showing a cell search procedure according to this embodiment. First, the CDMA wireless mobile device uses the PSC to despread the P-SCH signal and detects slot timing (step S8).
01). Next, a peripheral station scramble code whose frame timing is not known is selected from the scramble codes stored in the mobile device based on the broadcast information (step S803). More specifically, the selection process removes, from the peripheral station scramble code, the scramble code of the cell in which the CDMA wireless mobile device is located and the peripheral station scramble code for which the measurement has been completed and the frame timing has been detected. It is performed by At all frame timings based on the detected slot timing, the selected peripheral station scrambling code is
The PICH is despread (step S805).

Then, it is determined whether or not the carrier has been detected successfully (step S807). If the carrier has been detected, the frame timing and the peripheral station scramble code from which the frame timing has been detected can be determined (step S809). ).

As described above, by performing the cell search while excluding the serving sector and the sector for which the frame timing has already been detected, the number of scramble codes for performing despreading can be further reduced. As a result, the operation time of the CDMA wireless mobile device can be reduced, and the standby time can be improved.

(Third Embodiment) FIG. 9 is a view for explaining another embodiment of the present invention. For example, assuming that the number of peripheral station scramble codes broadcasted by the BCCH and the number of scramble codes of the own station are 6, the serving sector is a sector # in the cell of the radio base station 901.
It is assumed that the peripheral station scrambling code given to the CDMA wireless mobile device which is 0 is a scrambling code of sector # 0, sector # 1, sector # 5, sector # 9, sector # 16, and sector # 19. Also, sector # 9
The scrambling code of the peripheral station and the scrambling code of the local station stored in the CDMA wireless mobile device that has moved to the above are sector # 0, sector # 8, sector # 9, and sector #
It is assumed that the scramble code is 10, sector # 16, and sector # 19.

FIG. 10 is a diagram for explaining selection of a scramble code performed in the cell search according to the present embodiment. Among the peripheral station scramble codes updated after the movement of the CDMA wireless mobile station, the newly added peripheral station scramble codes are the scramble codes of the sectors # 8 and # 10.

FIG. 11 is a flowchart showing a cell search procedure according to this embodiment. Due to the lowering of the own station level, the cell search is activated (step S1101), and the zone is shifted to a sector satisfying the shift criterion (step S110).
1103). Next, the notification information of the zone transfer destination is detected and stored in the storage device (step S1105). And
The peripheral station scramble code before the zone shift stored in the storage device is compared with the peripheral station scramble code after the zone shift (step S1107), and the peripheral station scramble code added after the zone shift is selected. The priority of use of the selected peripheral station scramble code is increased so that the peripheral station scramble code is preferentially used at the time of starting the next cell search (step S110).
9).

By performing such processing, by using these scramble codes with priority in the next cell search, it becomes possible to detect the destination sector in a short time when moving at high speed. Since the cell search execution time can be reduced, the standby time can be improved.

(Fourth Embodiment) FIG. 12 is a view for specifically explaining another embodiment of the present invention. Power ON
When the user moves in the non-service area while maintaining the state and returns to the service area again, the service area of the return destination is not limited to the area of the peripheral station stored inside the CDMA wireless mobile device. For example, when shopping in an underground mall or the like, the wireless base station 1
CD located in sector #a of the cell in which 201 exists
In order to return to the sector #a or a sector adjacent to the sector #a, the MA mobile station 1205 executes a cell search using the peripheral station scramble code stored inside the CDMA wireless mobile station 1205. By doing so, the serving sector can be detected.

Next, for example, C in the sector #a
It is assumed that the wireless mobile device 1207 of the DMA system travels a long distance in a place outside the metropolitan area and goes to the ground in the sector #b in the cell where the wireless base station 1203 exists.
When the sector #b is a sector that is not included in the peripheral station information received when the sector #a is located, the cell search is performed using the peripheral station scramble code stored inside the CDMA wireless mobile device. The sector #b cannot be detected.

In this case, the CDMA wireless mobile device 1207 existing outside the service area is replaced by the conventional cell search, that is, the CDMA wireless mobile device 1207 when returning to the service area.
By performing a cell search that does not use the peripheral station scrambling code stored inside the mobile station, it is possible to recognize that a CDMA wireless mobile device is present in the service area when moving from outside the service area to the service area.

FIG. 13 is a flowchart showing a cell search procedure according to this embodiment. The number of continuous repetitions of CPICH despreading is set to 1, and 1 is initialized (step S1).
301). Next, the CDMA wireless mobile device uses the PS
The slot timing is detected using the CH signal (step S1303). Subsequently, the slot timing detection is confirmed (step S1305). If the slot timing cannot be detected, the slot timing detection operation is repeated using the P-SCH signal.

On the other hand, if the slot timing can be detected, the CPICH is despread using the peripheral station scrambling code at all frame timings based on the detected slot timing (step S1).
307). Next, the detection of the carrier is confirmed (step S1305), and if the carrier is detected, the process ends with reference to the broadcast information (step S1311).

If no carrier is detected, the CPI
One is added to the number 1 of continuous repetitions of CH despreading (step S1313). The CPICH despreading continuous repetition number l is compared with a threshold value (step S1315). If l exceeds a predetermined number, the process proceeds to the conventional cell search,
A frame code is detected by selecting and using a spread code sequence for specifying a scramble code group composed of a plurality of scramble codes (step S13).
17). If the number of continuous repetitions of CPICH despreading does not exceed the predetermined number, the process returns to step S1307, and the operation of detecting the frame timing using the CPICH is repeated until the number of continuous repetitions of CPICH despreading exceeds the predetermined number.

[0051]

As described above, according to the present invention,
Despreading a common pilot signal using a peripheral station scrambling code, comprising detecting means for detecting frame timing, wherein the peripheral station scrambling code is broadcast by broadcast information transmitted from a radio base station. Therefore, the radio mobile station of the CDMA system has an effect of reducing the frequency of performing code despreading by using a spreading code sequence used at the time of frame timing detection as a neighboring station scrambling code broadcasted by BCCH information. . Specifically, in the conventional three-stage cell search, the number of times of performing the code despreading is 64 × 15 + 8 = 968 (times) at the maximum. On the other hand, the number of times of performing the code despreading in the present invention is at most 32 × 15 = 480 (times).

Therefore, the standby current consumption is reduced, and the CD
It is possible to improve the standby time of the MA-type wireless mobile device.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a conventional cell search method in a CDMA wireless mobile device.

FIG. 2 is a diagram for explaining a detection process in a conventional cell search procedure, where (a) is a first stage of a cell search,
(B) is a figure for demonstrating a 2nd stage, (c) is a figure for demonstrating a 3rd stage.

FIG. 3 is a flowchart illustrating a cell search procedure according to an embodiment of the present invention.

4A and 4B are diagrams for explaining a detection process in a cell search procedure according to the present invention, wherein FIG.
(B) is a figure for demonstrating a 2nd stage.

FIG. 5 is a diagram for specifically explaining an embodiment of the present invention.

FIG. 6 is a flowchart illustrating a cell search procedure according to an embodiment of the present invention.

FIG. 7 is a diagram for specifically explaining an embodiment of the present invention.

FIG. 8 is a flowchart showing a cell search procedure according to an embodiment of the present invention.

FIG. 9 is a diagram for specifically explaining an embodiment of the present invention.

FIG. 10 is a diagram illustrating selection of a scramble code performed in a cell search according to an embodiment of the present invention.

FIG. 11 is a flowchart illustrating a cell search procedure according to an embodiment of the present invention.

FIG. 12 is a diagram for specifically explaining an embodiment of the present invention.

FIG. 13 is a flowchart illustrating a cell search procedure according to an embodiment of the present invention.

[Explanation of symbols]

501, 709, 909, 1205, 1207 Wireless mobile device 502, 701, 703, 705, 707, 901, 9
03,905,907,1201,1203 Wireless base station 503 Weak electric field area 505 Out of service area

Claims (8)

[Claims] 1. A first storage means for storing a peripheral station scrambling code included in a control channel, and despreading a common pilot signal using the peripheral station scrambling code stored in the first storage means. And a detecting means for detecting a frame timing, wherein the peripheral station scramble code is broadcast by broadcast information transmitted from a wireless base station. 2. The method according to claim 1, wherein the detecting means uses the peripheral station scramble code stored in the first storage means excluding the peripheral station scramble code for which the frame timing has already been detected. Item 1
The wireless mobile device according to the above CDMA system. 3. The peripheral station scrambling code stored in the first storage unit, wherein the second storage unit stores the peripheral station scramble code notified by the new broadcast information. 2. A newly assigned peripheral station scrambling code, which is detected by comparing the peripheral station scrambling code stored in the second storage means with the peripheral station scrambling code, is used with priority. 5. The wireless mobile device of the CDMA system according to 1. 4. A measuring device for measuring the number of times the detection of the frame timing is continuously performed by the detecting device, wherein the detecting device, when the number of times exceeds a predetermined threshold value, 4. The CDMA radio mobile station according to claim 1, wherein a spreading code sequence for specifying a scrambling code group including a plurality of scrambling codes is selected and used. 5. A first storing step of storing a peripheral station scrambling code included in a control channel, and despreading a common pilot signal using the peripheral station scrambling code stored in the first storing step, A detecting step of detecting a frame timing, wherein the peripheral station scrambling code is broadcast by broadcast information transmitted from a radio base station.
Cell search method of a wireless mobile device of the system. 6. The detecting step uses the peripheral station scrambling code stored in the first storing step, excluding the peripheral station scrambling code for which the frame timing has already been measured. Item 6. A cell search method for a CDMA wireless mobile device according to Item 5. 7. A second storage step for storing the peripheral station scramble code broadcasted by the new broadcast information, wherein the detecting step comprises: storing the peripheral station scramble code stored in the first storage step; 6. The method according to claim 5, wherein the newly assigned peripheral station scramble code detected by comparing with the peripheral station scramble code stored in the second storage step is used with priority. Cell search method for a CDMA wireless mobile device. 8. A measuring step for measuring the number of times the detecting step is continuously executed, wherein the detecting step compares the number of times with a predetermined threshold value, and the number of times is equal to the threshold value. 8. The mobile communication system according to claim 5, wherein a spreading code sequence for specifying a scrambling code group including a plurality of scrambling codes is selected and used when the number exceeds a predetermined value. Machine cell search method.