JP2002320272A - Searching method and communication terminal employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a searching method and a communication terminal capable of reducing time and power consumption spent for cell searching. SOLUTION: When a transmitted signal of a receiving frequency channel set in a control section 7 is received by a radio section 2, the level strength of the transmitted signal is measured in a signal strength measuring section 8, and is compared with a preset value in a signal strength comparing section 9. In response to the compared result in the section 9, a control section 7 decides the received frequency channel to be selected in the section 2, and controls a cell searching operation in a searcher section 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CDMA (Code D)
The present invention relates to a search method in a mobile communication system of an ivision multiple access (Ivision Multiple Access) system and a communication terminal apparatus using the search method. In particular, the present invention relates to WCDMA (Wideband Code).
Next-generation CDM such as e Division Multiple Access
The present invention relates to a search method used in a mobile communication system based on the A method and a communication terminal device using the search method.

[0002]

2. Description of the Related Art Spread-spectrum communication and a CDMA system using the spread-spectrum communication technology have features such as resistance to multipath fading, speeding up of data, good communication quality, and high frequency use efficiency. I have. Therefore, the spread spectrum communication and the CDMA system are receiving attention as promising communication systems for next-generation mobile communication and multimedia mobile communication. A transmission signal used in the spread spectrum communication and the CDMA system is spread by using a spread code, so that a bandwidth of a signal to be transmitted is spread to a much larger bandwidth than an original bandwidth. Sent. When such a transmission signal is received, the original bandwidth is restored by performing despreading.

In a next-generation mobile communication system using a CDMA system that handles transmission signals using such spread spectrum, a next-generation CDMA system such as the WCDMA system is being used. In a mobile communication system using this next-generation CDMA system (hereinafter referred to as “next-generation CDMA mobile communication system”), 5M
A system having a frequency bandwidth of about Hz is being put to practical use.

[0004] This next-generation CDMA mobile communication system includes:
Almost common frequency bands are allocated in the world so that global roaming can be performed by a communication terminal device common throughout the world. The communication system is also 3GPP (3rd Ge
neration Partnership Project). In this standard, 299 frequency channels are set in a 60 MHz frequency band, and a specific frequency channel is assigned to each country or each business operator. The communication terminal apparatus performs a cell search for a transmission signal from the base station for each of the 299 frequency channels, and recognizes a communicable base station, thereby enabling global roaming.

FIG. 7 is a block diagram showing an internal configuration of a receiving section of a conventional communication terminal apparatus. In the communication terminal device having the configuration shown in FIG. 7, the signal received by the antenna 1 is converted into an intermediate frequency signal by adjusting the gain in the radio unit 2, and is converted into a digital signal by the A / D converter 3. After this digital signal is subjected to despreading using a PN spreading code in a despreading synchronizing section 4, the signal component is synthesized in an information demodulating section 5 which performs a rake synthesizing function for synthesizing a signal component due to a multipath phenomenon. At the same time, synchronous detection is performed and demodulation is performed.

[0006] The digital signal is also supplied to a searcher unit 6, which outputs, for example, “3GPP specification TS25.214”.
The algorithm described in “v3.4.0 Annex C” is executed, a cell search is performed, and a cell for setting a receiving base station and a path for rake combining a received signal are set. When the set cell and path are provided to the control unit 7, the control unit 7 controls the wireless unit 2. Then, the radio unit 2 receives a transmission signal from the base station according to the set cell channel. Further, the information demodulation unit 5 rake-combines the transmission signals from the base station of the same cell, which are received by the radio unit 2 with a time delay according to the path timing set similarly.

Further, when the information demodulation unit 5 demodulates the digital signal from the despreading synchronization unit 4 as described above, first, the information demodulation unit 5 transmits a common pilot to which a symbol of a known code is transmitted. By performing arithmetic processing on the symbols of the channel, a channel estimation value for correcting errors in the reception frequency and the like is obtained. Then, using the complex conjugate according to the estimated channel value, the digital signal from the despread synchronizing unit 4 can be subjected to complex multiplication to demodulate.

In this communication terminal device, the searcher unit 6
Then, the first to third stages (for details of the first to third stages,

In the following three steps, the reception timing (path) of the reception signal and the PN spreading code of the cell are specified. Also, a two-stage cell search in which the second stage is omitted may be performed.

[0009]

However, in the above-mentioned communication terminal apparatus, since a cell search is performed for each channel, for example, when a cell search is performed in the entire 60 MHz band, all the 299 channels are required. Cell search must be performed. Therefore, particularly when the three-stage cell search is performed, the search time from when the base station is searched until the transmission signal is received becomes long, and when the power is turned on or the like, the communication becomes actually impossible. It takes a long time. In addition, there is also a problem that a large amount of power is consumed in the cell search operation due to such a long-time cell search.

[0010] In view of such a problem, an object of the present invention is to provide a search method and a communication terminal device capable of reducing time and power consumption for a cell search operation.

[0011]

To achieve the above object, a search method according to the present invention comprises the steps of specifying a timing of a transmission signal from a base station using a first spreading code common to all base stations. Identifying a second spreading code unique to each base station for despreading the transmission signal using a plurality of second spreading codes including a second spreading code unique to each base station. A search method for searching for a base station by switching a frequency channel to be received, wherein the signal strength of a received transmission signal from the base station is measured, and the measured signal strength is compared with a predetermined threshold value Determining the frequency channel to be received next, based on the comparison result between the signal strength and the predetermined threshold, after specifying the second spreading code specific to the base station;
It is characterized by having.

In such a search method, the signal strength of the transmission signal in the entire frequency band of each of the set frequency channels is measured, and the signal strength is compared with a predetermined first threshold value. The frequency channel to be used may be determined.

At this time, when the signal strength becomes lower than the first threshold value, it is determined that a base station using a channel near this frequency channel is not searched, and the timing and the second spreading code are specified. Instead, a frequency channel separated by a plurality of channels is set as a frequency channel to be switched next. When the signal strength is equal to or more than the first threshold, the timing and the second spreading code are specified, and an adjacent frequency channel is set as a frequency channel to be switched next.

Further, the signal strength of the transmission signal synchronized with the first spread code is measured, and the signal strength is determined by a predetermined second signal.
The frequency channel to be received next may be determined by comparing with a threshold value.

At this time, when the signal strength is equal to or more than the second threshold value, it is determined that there is a base station using this frequency channel, and that a base station using a channel near this frequency channel is not searched for. The separated frequency channel is set as the next frequency channel to be switched. Further, the signal strength is equal to the second signal strength.
When lower than the threshold, the adjacent frequency channel is
Next, it is set as the frequency channel to be switched.

Further, the signal strength of the transmission signal synchronized with the second spreading code is measured, and the signal strength is determined by a predetermined third signal.
The frequency channel to be received next may be determined by comparing with a threshold value.

At this time, when the signal strength is equal to or more than the third threshold value, it is determined that there is a base station that uses this frequency channel and that a base station that uses a channel near this frequency channel is not searched. The separated frequency channel is set as the next frequency channel to be switched. Further, the signal strength is equal to the third signal strength.
When lower than the threshold, the adjacent frequency channel is
Next, it is set as the frequency channel to be switched.

[0018] The signal strength of the transmission signal synchronized with the first spreading code is measured, and the signal strength is compared with a predetermined fourth threshold value, and the signal strength is synchronized with the first spreading code. According to the comparison result between the signal strength of the transmission signal and the fourth threshold, the frequency channel to be received next after specifying the timing of the transmission signal from the base station is determined, or the base station-specific first After specifying the second spreading code, it may be determined whether to determine the next frequency channel to be received.

The search method according to the present invention further comprises the steps of specifying a timing of a transmission signal from a base station using a first spread signal common to all base stations, and a second spreading code unique to each base station. Specifying a second spreading code unique to each base station for despreading the transmission signal using a plurality of second spreading codes, including: Measuring the signal strength of the received transmission signal from the base station; comparing the measured signal strength with a predetermined threshold; and determining the frequency channel to be received. And, having, by the comparison result of the signal strength and the predetermined threshold, determine the frequency channel to be received next after specifying the timing of the transmission signal from the base station, It is to determine to determine the frequency channel to be received next after identifying the base-station-specific second spreading code, and determining.

In such a search method, the first
The signal strength of the transmission signal synchronized with the spread code may be measured, and the signal strength may be compared with the predetermined threshold.

At this time, when the signal strength is equal to or greater than the predetermined threshold, it is determined that there is a base station using this frequency channel, and a second spreading code unique to the base station is specified. When the signal strength is lower than the predetermined threshold, it is determined that there is no base station that uses this frequency channel, and the operation of specifying the second spreading code unique to the base station is not performed.

In each of the above-described search methods, the cell search may be a two-stage cell search, and the step of specifying the second spreading code may be performed by using a third spreading code. Determining the group to which the second spreading code belongs, and identifying the base station-specific second spreading code from the plurality of second spreading codes in the group. It may be a staged cell search.

A communication terminal device according to the present invention comprises: a radio unit for receiving a transmission signal from a base station by switching a frequency channel; a searcher unit for searching for the base station from the transmission signal received by the radio unit; A control unit for controlling the radio unit and the searcher unit, switching the frequency channel to be received, and using a first spreading code common to all base stations for each of the switched frequency channels. After identifying the timing of the transmission signal from the base station, the base station-specific second spreading code for despreading the transmission signal using a plurality of second spreading codes including the base station-specific second spreading code is used. And a signal strength measuring unit for measuring a signal strength of the transmission signal, the signal strength measuring unit having a predetermined threshold value, and the signal strength measuring unit. A signal strength comparison unit that compares the measured signal strength of the transmission signal with the predetermined threshold value and sends a comparison result to the control unit, wherein the control unit receives the signal strength from the signal strength comparison unit. A frequency channel to be received next is determined from the comparison result to control the radio unit.

In such a communication terminal device, the signal strength measuring unit may measure the signal strength of the transmission signal in the entire frequency band of the frequency channel received by the radio unit. Absent. At this time, the control unit controls the AGC (Au) so that the signal level of the transmission signal output from the wireless unit is constant.
to Gain Control) control, the AGC amplifier gain value is given to the signal strength measurement unit, and the signal strength is measured.

In the signal strength measuring section, the searcher section may measure the signal strength of the transmission signal synchronized with the first spreading code. At this time, a correlation output value and an AGC amplifier gain value obtained by despreading with the first spreading code in the searcher unit are given to the signal strength measuring unit, and the signal strength is measured.

[0026] In the signal strength measuring section, the searcher section may measure the signal strength of the transmission signal synchronized with the second spreading code. At this time, a correlation output value and an AGC amplifier gain value obtained by despreading with the second spreading code in the searcher unit are given to the signal strength measuring unit, and the signal strength is measured.

Further, in the signal strength measuring section, the searcher section measures the signal strength of the transmission signal synchronized with the first spreading code, and the control section controls the signal strength in the signal strength comparing section. And determining whether to specify a second spreading code specific to each base station based on a comparison result between the signal strength of the transmission signal synchronized with the spreading code of 1 and the predetermined threshold value. The unit may be controlled.

Further, the communication terminal apparatus of the present invention comprises a radio section for switching a frequency channel to receive a transmission signal from a base station, and a searcher section for searching for the base station from the transmission signal received by the radio section. And a control unit that controls the radio unit and the searcher unit, and switches the frequency channel to be received, for each of the switched frequency channels, using a first spreading code common to all base stations. After identifying the timing of the transmission signal from the base station, each base station specific for despreading the transmission signal using a plurality of second spreading codes including a second spreading code unique to each base station. In a communication terminal device for specifying a second spreading code and searching for a base station, the communication terminal device has a signal strength measuring unit for measuring the signal strength of the transmission signal, a predetermined threshold value, and the signal strength measuring unit. A signal strength comparison unit that compares the signal strength of the transmission signal measured by the unit with the predetermined threshold, and sends a comparison result to the control unit, wherein the control unit includes the signal strength comparison unit. The searcher unit is controlled by determining whether or not to specify the second spreading code unique to each base station from the comparison result given by the base station.

In such a communication terminal apparatus, the signal strength measuring section may measure the signal strength of the transmission signal synchronized with the first spreading code in the searcher section.

In the above-mentioned communication terminal device, the cell search performed by the communication terminal device may be a two-stage cell search. When specifying the second spreading code, a third spreading code is used. Then, after determining the group to which the base station-specific second spreading code belongs, a three-step process of identifying the base station-specific second spreading code from a plurality of second spreading codes in the group is performed. Cell search may be used.

[0031]

Embodiments of the present invention will be described below.

<Configuration of Communication Terminal> First, the following first
A configuration of a communication terminal device common to the fifth to fifth embodiments will be described with reference to the drawings. FIG. 1 is a block diagram showing the internal configuration of the communication terminal device of the present invention.
Note that, in the communication terminal device of FIG. 1, portions used for the same purpose as the communication terminal device of FIG. 7 are denoted by the same reference numerals.

The communication terminal apparatus shown in FIG. 1 includes an antenna 1 for receiving a transmission signal from a base station, a radio section 2 for selecting a transmission signal of a reception frequency set by a control section 7, and a radio section 2 for selecting a transmission signal. An A / D converter 3 for converting a localized transmission signal into a digital signal; a despread synchronizing unit 4 for despreading the digital signal from the A / D converter 3 based on a PN spreading code; And an information demodulation unit 5 that performs rake synthesis on the digital signal despread by the despreading synchronization unit 4 and then performs synchronous detection and demodulation.

Thus, the transmission signal from the base station received by the antenna 1 is tuned by the radio unit 2 at the reception frequency of the set cell at each timing corresponding to the set path. The timing and the reception frequency are set by the control unit 7. Also, the radio unit 2
An auto gain controller (C) amplifier is provided, and the gain of the transmission signal from the base station is set to be constant.
The C amplifier gain value is controlled by the control unit 7.

When the transmission signal selected by the radio unit 2 is converted into a digital signal by the A / D converter 3, first, the PN spreading set by the searcher unit 6 is performed by the despreading synchronization unit 4. After the code is despread, the information demodulation unit 5 performs rake synthesis on the despread digital signal obtained for each path and then performs synchronous detection to demodulate the demodulated data. can get. As described above, the operation from reception of the transmission signal from the base station to demodulation into demodulated data is a common operation in each of the first to fifth embodiments.

The communication terminal device shown in FIG. 1 includes a searcher unit 6 for performing a cell search and setting a cell and a path, and a radio unit 2
And a control unit 7 for controlling the searcher unit 6, a signal strength measurement unit 8 for measuring the level strength of the received transmission signal from the base station, and a set value for the level strength measured by the signal strength measurement unit 8. And a signal strength comparing unit 9 for sending a comparison result to the control unit 7 in comparison with the above.

When configured as described above, the searcher unit 6
Is supplied with a digital signal from the A / D converter 3,
The cell and the path are set by performing a cell search based on the digital signal. The control unit 7 controls the cell search operation of the searcher unit 6 and performs A / D
The AGC amplifier gain of the radio unit 2 is controlled based on the level of the digital signal from the converter 3. The control unit 7 also controls the operation of the signal strength measurement unit 8.

The cell search operation of each of the searcher unit 6, the control unit 7, the signal strength measuring unit 8, and the signal strength comparing unit 9 will be described in the following first to fifth embodiments. Also, in the first to fifth embodiments, 60 MHz
It is assumed that 299 frequency channels are set in the frequency band of, and a next-generation CDMA mobile communication system standardized by 3GPP is used. The frequency channel numbers are defined as 0 to 298 for convenience. For simplicity, a channel determined for each reception frequency is referred to as a “reception frequency channel”, and a channel determined by a spread code in a transmission signal of the same frequency is referred to as a “code channel”.

<First Embodiment> A first embodiment of a communication terminal device configured as shown in FIG. 1 will be described with reference to the drawings. FIG. 2 is a flowchart illustrating a cell search operation of the communication terminal device of the present embodiment.

When the power of the communication terminal device is turned on or when the communication terminal device which has been out of the communicable area moves into the communicable area, the control unit 7 starts the cell search. The searcher unit 6 is controlled. First, the receiving frequency channel fid is set to No. 0 (ST
EP1). Accordingly, the radio unit 2 selects a channel at the reception frequency of the reception frequency channel 0. At this time, the signal selected by the radio unit 2 on the reception frequency channel 0 is A / A
The signal is converted into a digital signal by the D converter 3 and transmitted to the despreading synchronization section 4, searcher section 6, and control section 7, respectively.

Then, the control unit 7 requests the searcher unit 6 to execute the first stage of the three-stage cell search (STEP 2). The first stage is a stage in which the timing of a transmission signal from a base station is specified using a first spreading code common to all base stations. That is, in the searcher unit 6, in order to extract the first spreading code component from the digital signal from the A / D converter 3, despreading is performed using the first spreading code, and the peak timing of the correlation output is determined. The output value is detected.

While the operations in STEP 1 and STEP 2 are being performed, the control section 7 measures the level of the digital signal from the A / D converter 3 so that the level of the digital signal is always constant. AGC control of the radio unit 2 is performed.
That is, the control unit 7 controls the AGC amplifier gain value in the wireless unit 2 according to the level of the digital signal from the A / D converter 3. Then, A set by the wireless unit 2
The GC amplifier gain value is sent to the signal strength measuring unit 8,
The level strength RSSI of the transmission signal received by the radio unit 2 is calculated (STEP 3).

The level strength RS calculated by the signal strength measuring section 8 in the transmission signal of the set reception frequency channel
When the SI is transmitted to the signal strength comparing section 9, it is compared with a preset level strength set value rssi (STEP 4).
At this time, if the level strength RSSI is equal to or more than the set value rssi (Yes), it is determined that there is a transmission signal from the base station using the reception frequency channel set by the control unit 7. Then, the correlation output value when despreading by the first spreading code in the searcher unit 6 and the AGC amplifier gain value set in the control unit 7 are sent to the signal strength measuring unit 8 and are transmitted to the code channel. The level strength SCH of the digital signal is calculated (STEP 5).

When the signal level strength SCH of the signal in the code channel calculated by the signal strength measuring section 8 is transmitted to the signal strength comparing section 9, a preset value of the level strength is set.
This is compared with sch1 (STEP 6). At this time, if the level strength SCH is equal to or greater than the set value sch1 (Yes), it is determined that there is a possibility that there is a transmission signal from the base station using the currently searched reception frequency channel. Then, the control unit 7 requests the searcher unit 6 to execute the second stage of the three-stage cell search (STEP 7).

The second stage is a stage in which a group to which the second spreading code unique to each base station belongs is specified by using 16 types of third spreading codes common to all base stations. That is, in the searcher unit 6, in order to extract the third spreading code component from the digital signal from the A / D converter 3, the despreading is performed using the third spreading code at the timing detected in the first stage. Done. Then, the group to which the second spreading code unique to the base station belongs and its timing are detected from the correlation output value.

Thereafter, the control unit 7 requests the searcher unit 6 to execute the third stage of the three-stage cell search (STEP 8). The third stage is a stage of specifying one second spreading code from the plurality of second spreading codes using a plurality of second spreading codes belonging to the group detected in the second stage. . That is, in the searcher unit 6, in order to extract the second spreading code component unique to the base station from the digital signal from the A / D converter 3, the second spreading code component is detected in the second stage at the timing detected in the first stage. Despreading is performed by the plurality of second spreading codes. Then, a second spreading code unique to the base station is detected from the correlation output value.

When the operations of STEP 7 and STEP 8 are performed, the correlation output value obtained when the searcher unit 6 despreads by the second spreading code obtained in the second stage, and the AGC set by the control unit 7 The amplifier gain value is sent to the signal strength measuring unit 8, and the level strength CPICH of the digital signal in the code channel is calculated (STEP).
9).

When the signal level intensity CPICH in the code channel calculated by the signal intensity measuring unit 8 is sent to the signal intensity comparing unit 9, it is compared with a preset level intensity set value cpich (STEP 10). At this time, when the level intensity CPICH is lower than the set value cpich (No),
It is determined that there is a suspicion that there is no transmission signal from the base station using the set code channel.

Then, the signal strength comparing section 9 determines in STEP 5
Then, the level strength SCH of the signal in the code channel calculated by the signal strength measuring unit 8 is compared with a set value sch2 of a level strength preset to a level higher than the set value sch1 (STEP 11). At this time, the level intensity SCH
Is lower than the set value sch2 (No), it is determined that there is no transmission signal from the base station using the set code channel. Then, the control unit 18 adds 1 to the reception frequency channel fid, and sets an adjacent reception frequency channel as a next reception frequency channel to be checked (STEP 12).

In step 6, the level intensity SCH is set to the set value s.
Similarly, when it is lower than ch1 (No), it is also determined that there is no transmission signal from the base station using the currently searched reception frequency channel. Then, the control unit 18 adds 1 to the reception frequency channel fid, and sets an adjacent reception frequency channel as a next reception frequency channel to be checked (STEP 12).

Further, when the level intensity RSSI is lower than the set value rssi in STEP 4 (No), or in STEP 10
When the level intensity CPICH is equal to or greater than the set value cpich (Ye
s) Also, in step 11, the level intensity SCH is set to the set value sch2.
When this is the case (Yes), the control unit 18 sets a reception frequency channel obtained by adding fdelta to the reception frequency channel fid as a reception frequency channel to be examined next (STEP 13). Fdelta is desirably about 20 to 25.

That is, when the level strength RSSI is lower than the set value rssi, it is determined that there is no base station using a channel near the frequency channel under investigation.
Also, when the level intensity CPICH is equal to or more than the set value cpich,
When the level strength SCH is equal to or more than the set value sch2, it is determined that there is a transmission signal from the base station using the code channel at this time. Then, the reception frequency channel used by a base station other than the base station using the currently searched reception frequency channel around the communication terminal device is
It is determined that the frequency is not near the reception frequency channel currently being searched.

In STEP 12 or STEP 13, the reception frequency channel fid is set by the control unit 7, and
When the radio unit 2 is controlled, the control unit 7 determines whether the set reception frequency channel fid is smaller than 299 (STEP 14). At this time, the reception frequency channel
If fid is smaller than 299 (Yes), STEP again
The second and subsequent operations are performed, and a cell search operation is performed in the set reception frequency channel. When the reception frequency channel fid becomes 299 (No), the cell search operation is terminated.

As described above, when the cell search operation is performed, the code channel obtained when the level intensity CPICH becomes equal to or more than the set value cpich in STEP 10 or the STE
At P11, an optimal channel is selected from code channels obtained when the level intensity SCH is equal to or more than the set value sch2. Then, a transmission signal from a base station using the code channel is received, and finally, a cell and a path are set. When the cell and the path are set in this way, the transmission signal from the base station is received as described above.

<Second Embodiment> A second embodiment of the communication terminal device configured as shown in FIG. 1 will be described with reference to the drawings. FIG. 3 is a flowchart illustrating a cell search operation of the communication terminal device of the present embodiment. FIG.
, Steps having the same purpose as in FIG. 2 are denoted by the same reference numerals.

In the cell search operation of the communication terminal apparatus according to the present embodiment, as shown in the flowchart of FIG. 3, STEP5, STEP6, STE in the flowchart of FIG.
The operations of P9 to STEP11 are omitted. That is, S
In TEP4, the signal strength comparing section 9 compares the level strength RSSI of the transmission signal of the set frequency channel calculated by the signal strength measuring section 8 with the set value rssi, and uses the set frequency channel for the base station. Perform a station search.

When it is determined that a base station using the set frequency channel is nearby (Ye
s), after executing the second and third stages of the three-stage cell search operation in STEP7 and STEP8,
In TEP12, an adjacent reception frequency channel is set as a next reception frequency channel to be examined. If it is determined that there is no base station using the set frequency channel in the vicinity (No), the reception frequency channel obtained by adding fdelta to the reception frequency channel fid in STEP 13 is set as the next reception frequency channel to be checked. .

As described above, when the cell search operation is performed, the optimum channel is selected from the code channels obtained when the level strength RSSI is equal to or more than the set value rssi in STEP4. Then, a transmission signal from a base station using the code channel is received, and finally, a cell and a path are set. When the cell and the path are set in this way, the transmission signal from the base station is received as described above.

<Third Embodiment> A third embodiment of the communication terminal device configured as shown in FIG. 1 will be described with reference to the drawings. FIG. 4 is a flowchart illustrating a cell search operation of the communication terminal device of the present embodiment. FIG.
, Steps having the same purpose as in FIG. 2 are denoted by the same reference numerals.

In the cell search operation of the communication terminal apparatus of the present embodiment, as shown in the flowchart of FIG. 4, STEP3, STEP4, STE in the flowchart of FIG.
The operations of P9 to STEP11 and STEP13 are omitted. That is, in STEP 6, the signal strength comparing section 9 calculates the level strength SCH calculated by the signal strength measuring section 8 for the transmission signal of the set code channel by the set value s.
Compared with ch1, a search is made for a base station that uses the set code channel.

When it is determined that a base station using the set reception frequency channel is nearby (Y
es) After executing the second and third stages of the three-stage cell search operation in STEP7 and STEP8,
In STEP 12, an adjacent reception frequency channel is set as a next reception frequency channel to be examined. If it is determined that there is no base station using the set frequency channel (No), the process directly proceeds to STEP 12 and sets an adjacent reception frequency channel as a next reception frequency channel to be checked.

As described above, when the cell search operation is performed, the optimum channel is selected from the code channels obtained when the level strength SCH becomes equal to or more than the set value sch1 in STEP6. Then, a transmission signal from a base station using the code channel is received, and finally, a cell and a path are set. When the cell and the path are set in this way, the transmission signal from the base station is received as described above.

<Fourth Embodiment> A fourth embodiment of the communication terminal device configured as shown in FIG. 1 will be described with reference to the drawings. FIG. 5 is a flowchart illustrating a cell search operation of the communication terminal device of the present embodiment. FIG.
, Steps having the same purpose as in FIG. 2 are denoted by the same reference numerals.

In the cell search operation of the communication terminal apparatus of the present embodiment, as shown in the flowchart of FIG. 5, STEP3 to STEP6, STE in the flowchart of FIG.
The operation of P11 is omitted. That is, STEP10
Then, in the signal strength comparing section 9, the level strength CPICH of the transmission signal of the set code channel calculated by the signal strength measuring section 8 is compared with the set value cpich, and the base station using the set code channel is used. Search.

When it is determined that there is no base station using the set frequency channel in the vicinity (N
o) In STEP 12, an adjacent reception frequency channel is set as a next reception frequency channel to be examined. or,
If it is determined that a base station using the set code channel is nearby (Yes), the reception frequency channel obtained by adding fdelta to the reception frequency channel fid in STEP 13 is set as the next reception frequency channel to be checked.

As described above, when the cell search operation is performed, the optimum channel is selected from the code channels obtained when the level strength CPICH becomes equal to or more than the set value cpich in STEP10. Then, a transmission signal from a base station using the code channel is received, and finally, a cell and a path are set. When the cell and the path are set in this way, the transmission signal from the base station is received as described above.

<Fifth Embodiment> A fifth embodiment of the communication terminal device configured as shown in FIG. 1 will be described with reference to the drawings. FIG. 6 is a flowchart illustrating a cell search operation of the communication terminal device of the present embodiment. FIG.
, Steps having the same purpose as in FIG. 2 are denoted by the same reference numerals.

In the cell search operation of the communication terminal apparatus according to the present embodiment, as shown in the flowchart of FIG. 6, STEP3, STEP4, STE in the flowchart of FIG.
The operations of P6, STEP9, and STEP10 are omitted. That is, in STEP 11, the signal strength comparing section 9 calculates the level strength SCH calculated by the signal strength measuring section 8 for the transmission signal of the set code channel by the set value s.
Compared with ch2, a search for a base station using the set code channel is performed.

When it is determined that there is no base station using the set frequency channel in the vicinity (N
o) In STEP 12, an adjacent reception frequency channel is set as a next reception frequency channel to be examined. or,
If it is determined that a base station using the set code channel is nearby (Yes), the reception frequency channel obtained by adding fdelta to the reception frequency channel fid in STEP 13 is set as the next reception frequency channel to be checked.

As described above, when the cell search operation is performed, the optimal channel is selected from the code channels obtained when the level intensity SCH becomes equal to or more than the set value sch2 in STEP11. Then, a transmission signal from a base station using the code channel is received, and finally, a cell and a path are set. When the cell and the path are set in this way, the transmission signal from the base station is received as described above.

As described above, the first, second, fourth, and fifth
In the embodiment, the reception frequency channel to be searched can be skipped for every plural channels in STEP13. In the first and third embodiments, it is possible to set whether or not to perform the operations of the second stage and the third stage in the reception frequency channel to be searched. Therefore, as before,
In each of the reception frequency channels, it is not necessary to perform all the operations of the first to third stages, so that it is possible to reduce the time and power consumption required for cell search.

In the first to fifth embodiments, the case where a three-stage cell search is performed has been described.
The operation of the stage may be omitted. Also, the level strength SCH and level strength CPI of the transmission signal in the code channel
For CH, Ec / Io indicating the ratio of the reception level of the code channel to the reception level of the entire reception frequency channel including the code channel, RSCP indicating the reception level of the code channel, or the reception level of the code channel. Any of SIRs representing the ratio to noise may be used.

[0073]

According to the present invention, the signal strength is measured, and the frequency channel for searching the next base station can be determined based on the result of comparison with the set value. Therefore, since it is not necessary to search for a base station for all frequency channels for each channel, the number of frequency channels for searching for a base station can be limited. Further, it is possible to control whether or not to execute each step of the cell search. Therefore, it is not necessary to perform all steps of cell search in all frequency channels. As described above, the time required for cell search for searching for a base station for receiving a transmission signal can be reduced, and the power consumption for cell search can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an internal configuration of a main part of a communication terminal device of the present invention.

FIG. 2 is a flowchart showing a cell search operation of the communication terminal device according to the first embodiment.

FIG. 3 is a flowchart illustrating a cell search operation of the communication terminal device according to the second embodiment.

FIG. 4 is a flowchart illustrating a cell search operation of the communication terminal device according to the third embodiment.

FIG. 5 is a flowchart illustrating a cell search operation of the communication terminal device according to the fourth embodiment.

FIG. 6 is a flowchart showing a cell search operation of the communication terminal device according to the fifth embodiment.

FIG. 7 is a block diagram showing an internal configuration of a main part of a conventional communication terminal device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Radio part 3 A / D converter 4 Despread synchronization part 5 Information demodulation part 6 Searcher part 7 Control part 8 Signal strength measurement part 9 Signal strength comparison part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K022 EE02 EE36 5K067 AA21 AA43 BB04 CC10 CC24 EE02 FF16 HH22 JJ11 JJ37 JJ52 JJ54 JJ71

Claims (16)

[Claims] A step of identifying a timing of a transmission signal from a base station using a first spreading code common to all base stations;
Identifying a second spreading code unique to each base station for despreading the transmission signal using a plurality of second spreading codes including a second spreading code unique to each base station. A search method for searching for a base station by switching a frequency channel to be received, wherein a step of measuring a signal strength of a received transmission signal from the base station, and a step of comparing the measured signal strength with a predetermined threshold value And after determining the second spreading code specific to the base station, determining a frequency channel to be received next according to a result of comparison between the signal strength and the predetermined threshold value. Search method. 2. The signal strength of the transmission signal in the entire frequency band of each of the set frequency channels is measured, and the signal strength is compared with a predetermined first threshold to determine a next frequency channel to be received. 2. The search method according to claim 1, wherein the search is performed. 3. A method for determining a frequency channel to be received next by measuring a signal strength of the transmission signal synchronized with the first spreading code and comparing the signal strength with a predetermined second threshold value. The search method according to claim 1 or 2, wherein 4. A method for determining a frequency channel to be received next by measuring a signal strength of the transmission signal synchronized with the second spreading code and comparing the signal strength with a predetermined third threshold value. The search method according to any one of claims 1 to 3, wherein 5. A method for measuring a signal strength of the transmission signal synchronized with the first spreading code and comparing the signal strength with a predetermined fourth threshold value, wherein the signal strength is synchronized with the first spreading code. According to the comparison result between the signal strength of the transmission signal and the fourth threshold, the frequency channel to be received next after specifying the timing of the transmission signal from the base station is determined, or the base station-specific first 5. The search method according to claim 1, wherein after determining the second spreading code, it is determined whether to determine a frequency channel to be received next. 6. 6. Identifying the timing of a transmission signal from a base station using a first spread signal common to all base stations;
Identifying a second spreading code unique to each base station for despreading the transmission signal using a plurality of second spreading codes including a second spreading code unique to each base station. A search method for searching for a base station by switching a frequency channel to be received, wherein a step of measuring a signal strength of a received transmission signal from the base station, and a step of comparing the measured signal strength with a predetermined threshold value And determining the frequency channel to be received, comprising: comparing the signal strength with the predetermined threshold;
Whether to determine the frequency channel to be received next after specifying the timing of the transmission signal from the base station, or to determine the frequency channel to be received next after specifying the second spreading code unique to the base station Is determined. 7. The search method according to claim 6, wherein the signal strength of the transmission signal synchronized with the first spreading code is measured, and the signal strength is compared with the predetermined threshold. 8. The step of identifying the second spreading code includes the step of: using a third spreading code to determine a group to which the second spreading code unique to the base station belongs; A step of specifying a second spreading code specific to each base station from a second spreading code of (i). Method. 9. A radio unit for switching a frequency channel to receive a transmission signal from a base station, a searcher unit for searching for the base station from a transmission signal received by the radio unit, the radio unit and the searcher And a control unit for controlling the unit, and switching the frequency channels to be received, and for each of the switched frequency channels, the timing of the transmission signal from the base station using the first spreading code common to all base stations. After identifying the second spread code, the second spread code unique to each base station for despreading the transmission signal using a plurality of second spread codes including the second spread code unique to each base station is specified. And a communication terminal device for searching for a base station, comprising: a signal strength measurement unit for measuring a signal strength of the transmission signal; and a transmission signal having a predetermined threshold value and measured by the signal strength measurement unit. Comparing the signal strength of the signal with the predetermined threshold value, and a signal strength comparison unit that sends a comparison result to the control unit, the control unit, from the comparison result given from the signal strength comparison unit, A communication terminal device that determines a frequency channel to be received next and controls the radio unit. 10. The signal strength measurement unit according to claim 9, wherein the signal strength of the transmission signal in the entire frequency band of the frequency channel received by the radio unit is measured. Communication terminal device. 11. The signal strength measuring unit according to claim 9, wherein the searcher unit measures the signal strength of the transmission signal synchronized with the first spreading code. The communication terminal device according to claim 1. 12. The signal strength measuring section according to claim 9, wherein said searcher section measures said signal strength of said transmission signal synchronized with said second spreading code. The communication terminal device according to any one of the above. 13. The signal strength measuring unit measures the signal strength of the transmission signal synchronized with the first spreading code in the searcher unit, and the control unit controls the signal strength in the signal strength comparing unit. Based on the comparison result between the signal strength of the transmission signal synchronized with the spread code of 1 and the predetermined threshold value, determine whether to specify the second spread code unique to each base station,
The method according to claim 9, wherein the searcher unit is controlled.
The communication terminal device according to claim 12. 14. A radio unit for receiving a transmission signal from a base station by switching a frequency channel, a searcher unit for searching for the base station from a transmission signal received by the radio unit, the radio unit, and the searcher And a control unit for controlling the unit, and switches the frequency channel to be received, and for each of the switched frequency channels, the timing of the transmission signal from the base station using the first spreading code common to all base stations. After identifying the second spread code, the second spread code unique to each base station for despreading the transmission signal using a plurality of second spread codes including the second spread code unique to each base station is specified. And a communication terminal device for searching for a base station, comprising: a signal strength measuring unit for measuring the signal strength of the transmission signal; and A signal strength comparison unit that compares the signal strength of the signal with the predetermined threshold value and sends a comparison result to the control unit. A communication terminal apparatus that determines whether or not to specify a second spreading code specific to each base station, and controls the searcher unit. 15. The communication terminal according to claim 14, wherein the signal strength measuring unit measures the signal strength of the transmission signal synchronized with the first spreading code in the searcher unit. apparatus. 16. When specifying the second spreading code, after determining a group to which the second spreading code unique to the base station belongs by using a third spreading code, The communication terminal device according to any one of claims 9 to 15, wherein a second spreading code unique to each base station is specified from two spreading codes.