JP2006186519A - Cell search processing apparatus, mobile station with cell search processing apparatus mounted thereon, and cell search processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cell search processing apparatus, a mobile station with the cell search processing apparatus mounted thereon, and a cell search processing method capable of reducing the power consumption in the case of a selection composite state wherein data transmitted from a plurality of base stations are received, correctly received data of the base stations are selected, and the selected data are combined. <P>SOLUTION: The television receiver comprises: a CPICH level measurement section 203 for measuring channel quality such as reception electric field strength of synchronization wireless channels of the base stations or the like; a transmission timing storage section 205 for storing a data transmission timing of each base station; and a cell selection section 204, and selects a threshold value with respect to the channel quality used for selecting the base stations on the basis of a timing difference when the same data are transmitted so as to select the base stations of selection composite objects thereby reducing the number of received data of the stations and reducing the power consumption. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cell search processing apparatus and a cell search processing method mounted on a mobile station in a mobile communication system, and more particularly to a cell search processing apparatus and a cell search processing method suitable for use in CDMA communication or the like.

  In mobile communication systems such as mobile phone devices that are currently in widespread use, mobile stations that divide a wireless area into a plurality of wireless areas called “cells” and have moved into the cell by providing a base station for each cell By communicating with the mobile station, the mobile station is configured to communicate with the base station with the best channel quality. Each base station always transmits a signal of the synchronization radio channel of the mobile station with a fixed transmission power. The transmitted radio wave propagates through space while being attenuated, and the attenuation increases as the propagation distance increases. Therefore, when the mobile station receives this transmitted radio wave, the channel quality of the synchronization radio channel from the near base station is good, and the channel quality of the synchronization radio channel from the far base station is poor.

  The waiting mobile station measures and monitors the channel quality of the synchronization radio channel to find the optimal radio channel for the base station for communication, and then enters standby operation at the base station optimal for communication. This prepares for outgoing and incoming calls. Finding the synchronization radio channel and measuring the channel quality of the found synchronization radio channel is called “cell search”. As the mobile station moves, the status of the synchronization radio channel coming from each base station changes. Therefore, it is important for the mobile station to always perform this cell search, select an optimal base station for communication, and enter a standby operation at the optimal base station in order to maintain the call rate and the incoming rate.

  In addition, in order to improve reception performance, data carrying the same information is transmitted from a plurality of base stations, and the mobile station decodes the data independently for each base station, and correctly corrects the error from the base station. There is a case where selective synthesis is performed by selecting and combining data to obtain final decoded data. However, the transmission timing of the data carrying the same information from the plurality of base stations does not synchronize the transmission timing between the plurality of base stations.

  The conventional cell search processing device and cell search processing method measure the channel quality such as the received electric field strength of the synchronization radio channel of each base station, and select the base stations to be connected in order from the base station with the best channel quality. Yes. Then, path selection, despreading, rake combining, and error correction processing are performed for the selected base station. A similar method is also used for the cell search processing apparatus and the cell search processing method when selective combining is used for receiving specific data from a plurality of base stations.

  FIG. 14 shows an example of the relationship between the level of channel quality and time of synchronization radio channels from a plurality of conventional base stations. In FIG. 14, the horizontal axis indicates time and the vertical axis indicates the line quality level. The higher the line quality level, the better the line quality. Further, for each base station, A to E are attached for identification. The base station A, the base station B, and the base station D are marked with a circle to indicate that three stations are selected in order from a base station having a good channel quality, that is, a high channel quality level.

FIG. 14 shows a base station B, a base station D, a base station A, a base station E, and a base station C arranged in order from the base station with the highest channel quality level. Therefore, if three base stations are selected in the selection combining, the base station B, the base station D, and the base station A are selected in descending order of the line quality level. Here, it is assumed that the base station B has the highest channel quality level, and only the base station B can correctly perform error correction processing. The order of reception is the base station A, base station B, and base station D, performing the receiving operation in the order of the time axis from left to right. Although only the base station B can correctly perform error correction processing, that is, data can be correctly received, path selection, despreading, and error correction processing are performed for the base station A having low channel quality received at an early time. Therefore, the amount of processing for the base station A increases and the power consumption increases.
Japanese Patent Laying-Open No. 2001-78245 (page 9 in FIG. 7)

  In the conventional cell search processing apparatus and cell search processing method, when selective combining is used for receiving specific data from a plurality of base stations, a plurality of base stations are selected in order of good channel quality, that is, in the order of high channel quality level. Receive the same data. However, although the channel quality is selected in order from the highest level, all the receiving base stations have good channel quality to the extent that error correction processing can be performed correctly, that is, indicate that the channel quality is high. It is not a thing. It is assumed that a base station that transmits the same data and has the latest time among the plurality of base stations that receive it has the highest channel quality and can correctly perform error correction only with this base station. In this case, although a base station with a high channel quality level that can correctly perform error correction processing at a later time is transmitted, a path with a lower channel quality level that transmits the same data at an earlier time is transmitted. Since selection, despreading, and error correction processing are performed, there is a problem in that the amount of processing for a base station having a low channel quality level increases and power consumption increases.

  The present invention has been made to solve the conventional problem, and when performing selective synthesis, the base station is selected so that the received data of the base station received at an early time can be correctly subjected to error correction processing. Cell search processing apparatus and cell search processing apparatus capable of reducing power consumption by reducing the number of times the same data transmitted from the base station is received and reducing the number of base stations performing reception processing in the mobile station It is an object to provide a mobile station and a cell search processing method.

  In order to solve the conventional problems, the cell search processing apparatus of the present invention transmits channel quality measuring means for measuring channel quality of synchronization radio channels of a plurality of base stations and the same data from the plurality of base stations. Transmission timing storage means for storing the timing difference, and cell selection means for selecting a reception target base station by switching a threshold value for the reception quality of the synchronization radio channel according to the timing difference.

  In particular, the cell selection means of the present invention first selects the base station having the highest level of the channel quality of the measured synchronization radio channel. Second, the threshold for the channel quality level of the synchronization radio channel is set to be the highest channel quality for the base station that is slower in timing when the same data is transmitted than the base station with the highest selected channel quality. Set a value lower than the level. Third, in addition to the selected base station, the channel quality level of the next reception target base station to be selected is equal to or higher than the set threshold value, and the base station is selected in descending order from the threshold value. ing.

With this configuration, when the same data transmitted from multiple base stations is selectively combined, the same data is received at the earliest time because the level of the channel quality of the base station receiving the earliest time is the highest. The possibility that the data can be normally received by the data of the base station is increased. If the data can be normally received by the data of the base station received at the earliest time, it is not necessary to receive and select and combine the same data of the second and subsequent base stations. As a result, it is no longer necessary to receive the base station that is transmitted at the second and subsequent times, and the data that was successfully received at the base station that receives at the earliest time is received by the second and subsequent base stations. By not doing so, it is possible to reduce the number of base stations to receive or the number of data to be received, thereby reducing power consumption.

  In addition, the cell selection means of the present invention first selects a base station with the earliest timing at which the same data is transmitted among base stations having a channel quality level value of a synchronization radio channel equal to or higher than a predetermined threshold. select. Second, a threshold is set for the channel quality level of the synchronization radio channel used for selecting a plurality of other reception target base stations. In the case of a base station whose transmission timing is later than the base station selected in the first, the second threshold is set to a value lower than the predetermined threshold used in the first selection. Third, using the threshold value set in the second, a plurality of other reception target base stations are selected from the base station in the descending order of the margin from the threshold value when the channel quality level is equal to or higher than the set threshold value. have.

  With this configuration, when the same data transmitted from a plurality of base stations is selectively combined, there are few base stations with a high channel quality level among base stations whose transmission timing is later than the base station with the highest channel quality. On the other hand, when there are many base stations with high channel quality among the base stations with early transmission timing, the channel quality level is higher among the base stations with earlier transmission timing than the base station with the highest channel quality level. A reception target base station can be selected. By receiving a base station with a high line quality level at an early time, the possibility of normal reception at an early time increases. If the data can be normally received by the data of the base station received at an earlier time, it is not necessary to receive and select and combine the same data of the base station at a later time. As a result, it is not necessary to receive a base station that is transmitted at a later time, and data that can be normally received by a base station that receives at an earlier time is not received by the same data from the base station at a later time, Power consumption can be reduced by reducing the number of base stations to receive or the number of data to be received.

  The cell selection means of the present invention first selects a base station with the highest level of measured line quality. Second and third, a threshold is set for the channel quality level of the synchronization radio channel used to select other base stations to be received. As the threshold value to be set, different values are set for a base station whose base data is transmitted earlier and later than the base station selected first. Second, in the case of a base station that transmits the same data earlier than the first selected base station, the threshold is set to a value lower than the highest channel quality level of the first selected base station. To do. Third, in the case of a base station that transmits the same data later than the base station selected in the first, the threshold is set to be lower than the threshold set in the second. Fourth, a plurality of reception target base stations other than the base station selected first are base stations in the order of the line quality level that is greater than or equal to the threshold values set in the second and third and the margin from the threshold value is large. It has a configuration for selecting a station.

  With this configuration, when the same data transmitted from a plurality of base stations is selectively combined, a base station with a high channel quality level is selected among base stations whose transmission timing is later than a base station with the highest channel quality level. On the other hand, when there are many base stations with a high channel quality level among base stations with early transmission timing, the channel quality level is higher among the base stations with the earlier transmission timing than the base station with the highest channel quality level. A high reception target base station can be selected. By receiving a base station with a high line quality level at an early time, the possibility of normal reception at an early time increases. If the data can be normally received by the data of the base station received at the earlier time, it is not necessary to receive and select and combine the same data of the base station at the later time. As a result, it is not necessary to receive a base station that is transmitted at a later time, and the number of base stations to receive or the number of data to be received can be reduced to reduce power consumption.

In the cell selection means of the present invention, first, the base station having the highest measured line quality level is selected. Secondly, in the case of a base station whose transmission timing is later than that of the base station selected in the first, the threshold used for selecting a plurality of other reception target base stations is lower than the highest line quality level and the highest line. Set the value according to the quality level. The threshold is set to a high value when the highest line quality level is a high value, and to a low value when the highest line quality level is a low value. Each set value is determined in advance according to the highest line quality level. Third, a plurality of reception target base stations other than the base station selected first select a base station in order of a line quality level that is equal to or higher than a set threshold value and a margin from the threshold value is large. Have.

  With this configuration, when the same data transmitted from multiple base stations is selected and combined, if the highest line quality level is high enough to be normally received by one base station, it is selected first. It is highly possible that only the base station with the highest line quality level received at the earlier time can receive normally, and the base station with the lower line quality level that can be received normally at a later time is lower. There is no need to use it for selective synthesis. Therefore, by setting the threshold used for selecting other multiple reception target base stations to a high value, setting the required level of line quality high, and by tightening the selection criteria for the reception target base station Thus, it is possible to reduce the number of reception target base stations and reduce power consumption.

  On the other hand, if the highest channel quality level is not high enough to be normally received by one base station, it is normally received only by the base station with the highest channel quality level received at the earlier selected time. It is unlikely to be possible. Therefore, it is possible to increase the number of base stations to be received at a later time, increase the number of selective combination candidates, and perform selective combination using data with the highest possible line quality from among them. It is necessary to improve the rate. Therefore, the threshold used for selecting other plurality of reception target base stations is set to a value lower than the value used when the channel quality is high enough to allow normal reception by only one base station. In other words, by setting the required line quality level low, without increasing the criteria for selecting the target base station, the number of target base stations that are candidates for selective combining to be received at a later time is increased and the error rate is improved. Can be achieved.

  According to the present invention, when selecting a base station to be received at the time of selective combining, a threshold for channel quality used when selecting a base station is determined based on a timing difference at which the same data is transmitted. By switching to a base station with a slow transmission timing based on the base station with the highest base station, it is possible to receive a base station with a high channel quality at an early time, thereby reducing the number of base stations to be received, Power consumption can be reduced.

  Hereinafter, a cell search processing device, a mobile station equipped with the cell search processing device, and a cell search processing method according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a system diagram for explaining the operation of the cell search processing apparatus and the cell search processing method according to Embodiment 1 of the present invention. In FIG. 1, when selective combining is used for receiving specific data from a plurality of base stations, Data # 0, which is the same data transmitted from the base station A101 and the base station B102, is transmitted with a data timing difference. ing. The mobile station 100 independently decodes data for each base station, and selects data from the base station that has been correctly error-corrected as final decoded data.

FIG. 2 shows a block diagram of mobile station 100 equipped with the cell search processing apparatus according to the first embodiment of the present invention. In FIG. 1, a mobile station 100 includes an antenna 201 that receives radio waves, a high-frequency reception processing unit 202 that performs high-frequency processing, a cell search processing device 200 that selects a reception target base station, and a path that selects a path with large received power. A search processing unit 206; a despreading processing unit 207 that performs despreading on the assigned path; a rake combining processing unit 208 that performs rake combining of data in the despreading processing unit 207; and an error correction process that performs error correction. Unit 209, CRC determination processing unit 210 for performing CRC determination processing by adding a bit for cyclic redundancy check (hereinafter abbreviated as CRC) for error detection of decoded data, and a CRC determination result This is a configuration having a selective synthesis processing unit 211 that performs selective synthesis. FIG. 2 shows the main part of the present invention in the configuration of the mobile station, and, for example, means relating to transmission are omitted.

  Here, the cell search processing device 200 includes a CPICH (Common Pilot Channel) level measuring unit 203 that measures channel quality such as received field strength of the synchronization radio channel of each base station, and the channel of the synchronization radio channel according to the timing difference. A cell selection unit 204 that selects a reception target base station by switching a threshold value for quality, and a transmission timing storage unit 205 that stores a timing difference at which the same data of each base station is transmitted. The transmission timing information of each base station is transmitted from the base station to the mobile station in advance, and is received and demodulated by the mobile station and stored in the transmission timing storage unit 205.

  FIG. 3 shows a flowchart for explaining the operation of the cell search processing apparatus and the cell search processing method according to Embodiment 1 of the present invention. The operation of selecting a reception target base station in FIG. 3 will be described. First, the CPICH level measurement unit 203 of the cell search processing device 200 performs CPICH level measurement, which is a synchronization radio channel, for each base station that may be a reception target (S301). Next, the transmission timing of each base station stored in the transmission timing storage unit 205 is referred to (S302). Based on the CPICH level and transmission timing of each measured base station, a cell to be selected and combined is selected (S303). In the cell selection in step 303, data from a plurality of base stations are required to perform selective combining. Therefore, if there are a plurality of reception target base stations, a plurality of base stations are selected. For a plurality of selected base stations, a determination is made as to whether the data is unacquired data or reception target data that cannot be normally received by another base station (S304). In the case of data to be received, path search is performed (S305), and despreading is performed on the allocated path (S306). Thereafter, rake combining of data (S307), error correction (S308) is performed, and CRC determination is performed (S309). If the CRC determination result is OK (S310), the data is transferred to the upper layer (S311). In the selective combining, as described with reference to FIG. 1, the same data transmitted with a data timing difference is received from different base stations, and the data that has been successfully received is selected. When receiving the same data already received from the base station that is transmitting the same data at a later time (S312), if the CRC determination result is OK in step 310 and the data can be acquired normally, Since it is not necessary to perform reception again, it is excluded from the reception selection target base stations (S313). If there is data to be received next (S314), processing of the next data is started (S315). Since the received data of the base station excluded from the reception target base station is not the reception target data, it is determined in step 304, and processing such as path search, despreading, rake combining, and error correction is not performed. In this way, the processing amount is reduced. When the CRC determination result is NG (S310), if there is a base station that transmits the same data as the data for which the CRC determination result is NG in step 310 at a later time (S316), the data is the reception target. (S317). The CRC determination result is NG, and it is necessary to continue reception for data acquisition, so that it is determined as reception reception target data in step 304 via steps 314 and 315 (S304), path search, despreading, Continue processing such as rake synthesis and error correction.

  Note that the path search in step 305 need not be performed for each data as long as the subsequent processing is performed at the same path timing. Further, in step 304, the data to be received is determined, and if it is not the data to be received, all the processes after the path search are not performed. However, some of the path search, despreading, rake synthesis, error correction, etc. It is also possible not to perform only the process.

  FIG. 4 explains in detail the cell selection in step 303 of FIG. After measuring the level of the CPICH that is the synchronization radio channel for each target base station (S301), the transmission timing of each base station stored in the transmission timing storage unit 205 is referred to (S302). . In step 303, the following three steps are performed to select a cell. First, a base station having the highest CPICH level among the measurements in step 301 is selected as a reception target base station (S41). Second, based on the transmission timing of each base station stored in the transmission timing storage unit 205, the CPICH used for selecting a base station other than the base station selected in step 41 from among a plurality of base stations that perform reception Set the threshold for comparing levels. That is, the threshold used for the base station that transmits the same data later than the base station selected in step 41 is set to a value lower than the CPICH level of the base station selected in step 41 (S42). Third, among the base stations having the CPICH level equal to or higher than the threshold, the reception target base stations are selected in order from the base station having the largest margin from the threshold (S43).

  FIG. 5 illustrates the threshold setting and cell selection described in FIG. FIG. 5 shows the relationship between the time at which the same data is transmitted from a plurality of base stations and the CPICH level. The time axis is taken from left to right, and the vertical axis shows the CPICH level. In FIG. 5, when the CPICH levels are arranged in descending order, the base station B, base station D, base station A, base station E, and base station C are obtained. Further, in the description with reference to FIG. 5, it is assumed that the number of base stations to be selected is three. First, the base station selected first in step 41 is the base station B with the highest CPICH level. Second, the threshold value 51 indicated by the dotted line set in step 42 is a threshold value used for the base stations C to E slower than the base station B selected in step 41, and the CPICH of the base station selected in step 41 The value is lower than the level. Third, in step 43, among the base stations D and E, which are base stations having a CPICH level equal to or higher than the threshold 51, the base station D and the base station E are set as reception target base stations in descending order of the margin from the threshold. select.

  FIG. 6 shows a timing diagram for explaining operations of the cell search processing apparatus and the cell search processing method according to Embodiment 1 of the present invention. FIG. 6 shows data contents transmitted from the base station B and the base station D with the timing difference from the left to the right, with the same data being provided with a timing difference. In FIG. 6, the data transmitted from the base station D is transmitted with the same data as the base station B with a timing difference 61, and the mobile station decodes the data independently for each base station and correctly corrects the error. Data from the corrected base station is selected as final decoded data. Here, for the data # 0 data of the base station B received by the mobile station at time T, the CRC determination result is OK. Therefore, at time T + 2 when the same data is transmitted from the base station D, the mobile station does not need to receive the data of the base station D, and thus power consumption can be reduced by not performing the reception process.

  Conversely, the case where the power consumption cannot be reduced will be described below. This is an operation when the CRC judgment result of the data received by the base station B is NG. The data of the data # 2 of the base station B received by the mobile station at the time T + 2 has a CRC determination result of NG. Therefore, at the time T + 4 when the same data is transmitted from the base station D, the mobile station receives the data of the base station D. Need to receive. Therefore, the reception process is also performed for the base station D. In this case, power consumption cannot be reduced.

  According to the cell search processing apparatus and the cell search processing method of Embodiment 1 of the present invention, when performing selective combining, the CPICH level of the base station that receives the same data at the earliest time becomes the highest. That is, the reliability of the data of the base station received earliest is the highest. Therefore, it is possible to reduce the necessity of receiving the base station whose reception time is the second and subsequent times, reduce the number of base stations or the number of data to be received, and reduce power consumption.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the cell search processing apparatus and cell search processing method according to the second embodiment of the present invention, first, a base station having the earliest transmission timing is selected from among base stations having a CPICH level equal to or higher than a predetermined threshold, The threshold value of the base station whose transmission timing is later than the base station selected in the first is set to a predetermined value lower than the threshold value used in the first, and third, the threshold value determined in the second or higher The base station is selected from the top in descending order of the margin from the threshold. The difference between the second embodiment and the first embodiment resides in that the base station with the earliest transmission timing is selected from among the base stations that are equal to or higher than a predetermined threshold for selecting the first base station. A block diagram of mobile station 100 incorporating the cell search processing apparatus according to the second embodiment of the present invention is the same as that in FIG. 2 according to the first embodiment, and the description thereof is omitted in the second embodiment. Further, the flowchart of the cell search processing apparatus and the cell search processing method of the second embodiment of the present invention is the same as that of FIG. 3 of the first embodiment, and the description of the same is omitted in the second embodiment.

  FIG. 7 shows the cell selection operation of the cell search processing apparatus and cell search processing method according to the second embodiment of the present invention. FIG. 7 explains the cell selection in step 303 of FIG. That is, the CPICH level that is the synchronization radio channel is measured for each target base station (S301). Next, the transmission timing of each base station stored in the transmission timing storage unit 205 is referred to (S302). Then, the cell selection step 303 is performed. First, a base station whose CPICH level is equal to or higher than a predetermined threshold measured in step 301 and has the earliest transmission timing is selected as a reception target base station (S71). . Here, the threshold used for the first base station selection is a value that can be normally received by selective combining if the CPICH level is equal to or higher than this threshold, but the setting can be changed. Second, based on the transmission timing of each base station stored in the transmission timing storage unit 205, a threshold value used for selecting a base station other than the one selected in step 71 from the plurality of base stations that perform reception is set. Set. That is, the threshold used for the base station that transmits the same data later than the base station selected in step 71 is set to a predetermined value lower than the threshold used in step 71 (S72). Third, among the base stations whose CPICH level is equal to or higher than the threshold set in step 72, base stations having a large margin from the threshold are selected as the reception target base stations in order from the top (S73).

  FIG. 8 illustrates threshold setting and cell selection described in FIG. FIG. 8 shows the relationship between the time at which the same data is transmitted from a plurality of base stations and the CPICH level. The time axis is taken from left to right, and the vertical axis indicates the CPICH level. In FIG. 8, when the CPICH levels are arranged in descending order, the base station C, base station B, base station E, base station A, and base station D are obtained. In the description with reference to FIG. 8, the number of base stations to be selected is assumed to be three. First, the base station selected first in step 71 is the base station A having the earliest transmission timing when the CPICH level is equal to or higher than the threshold value 81 indicated by a predetermined dotted line. Second, the threshold value 82 indicated by a dotted line set in step 72 is a threshold value used for base stations B to E whose transmission timing is later than that of the base station A selected in step 71, and in step 71, the base station is selected. It is a predetermined value lower than the threshold value 81 used in the above. Third, in step 73, among base stations B to E, which are base stations having a CPICH level equal to or higher than the threshold value 82, base station C and base station B are set as reception target base stations in descending order of the margin from the threshold value. select. The base station E is not selected because the number of base stations to be selected is three, but can be selected by increasing the number of base stations to be selected. In FIG. 8, the base stations selected by the base station A, base station B, and base station C are circled.

Here, the advantage of the cell selection method of the second embodiment will be described in the case where the CPICH level situation of a plurality of base stations measured by the mobile station is as shown in FIG. Assuming that the transmission timing of the base station C having the highest CPICH level selected first in the first embodiment is used as the time reference, there are many base stations whose CPICH level is equal to or higher than the threshold 81 at the earlier transmission timing. Station A and base station B exist. At the time when the transmission timing is late, there are few base stations whose CPICH level is the threshold value 81 or more, and only the base station E. At this time, the cell selection method of the second embodiment is advantageous for selecting a base station having a CPICH level at a time earlier in transmission timing than a certain threshold value as compared with the case of the first embodiment. That is, if the cell selection method of the first embodiment is used in the state of FIG. 8, first, the base station C having the highest CPICH level is selected, and secondly, the base station C selected first is selected. Also, a threshold 82 used for a base station with a later transmission timing is set, and third, a base station D and a base station E with a transmission timing later than the base station C and with a threshold 82 or higher are selected. That is, the cell selection method of Embodiment 1 is a method of selecting base station D and base station E, which are base stations at a transmission timing later than that of base station C having the highest CPICH level. And base station B cannot be selected. However, Embodiment 2 is a method of positively selecting a base station with an earlier transmission timing among base stations having a predetermined threshold value or more. In the case of FIG. 8, the transmission time is earlier and Base station A and base station B having a high CPICH level can be selected. In the above description, the threshold value is set as the threshold value 82 as an explanation when the method of the first embodiment is applied, but the threshold value 51 of the first embodiment used in FIG. 5 and the implementation used in FIG. It does not indicate that the threshold value 82 of form 2 is the same.

  According to the cell search processing apparatus and cell search processing method of Embodiment 2 of the present invention, when performing selective combining, the CPICH level is among the base stations whose transmission timing is later than the base station with the highest CPICH level. Even when there are few base stations that are high, that is, capable of normal reception by selective combining, a base station with a high CPICH level can be selected as a reception target base station among base stations with early transmission timing. The number of stations or the number of data can be reduced to reduce power consumption.

  Note that the predetermined threshold used in the first selection and the predetermined threshold lower than the threshold used in the first base station selection set in the second have some patterns instead of fixed values, The value can also be changed depending on the reception state of the mobile station.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. In the cell search processing apparatus and cell search processing method according to the third embodiment of the present invention, first, the base station having the highest CPICH level is selected, and secondly, the transmission timing is earlier than the base station selected in the first. The threshold of the base station is set lower than the value of the highest CPICH level of the base station selected in the first, and third, the threshold of the base station whose transmission timing is later than the base station selected in the first is set to the second The fourth threshold value is set to be lower than the threshold value used in (4), and fourthly, the base stations are selected from the top in descending order of the margin from the threshold value among the base stations equal to or higher than the threshold values set in the second and third. The difference between the third embodiment and the first embodiment is that the second threshold value is also set for a base station whose transmission timing is earlier than the base station selected in the first. The block diagram of mobile station 100 incorporating the cell search processing apparatus according to the third embodiment of the present invention is the same as that in FIG. 2 according to the first embodiment, and the description thereof is omitted in the third embodiment. Further, the flowchart of the cell search processing apparatus and the cell search processing method of the third embodiment of the present invention is the same as that of FIG. 3 of the first embodiment, and the description of the third embodiment is omitted.

FIG. 9 shows a cell selection operation of the cell search processing apparatus and cell search processing method according to the third embodiment of the present invention. FIG. 9 explains the cell selection in step 303 of FIG. The level measurement of CPICH that is a synchronization radio channel is performed for each target base station (S301). Next, the transmission timing of each base station stored in the transmission timing storage unit 205 is referred to (S302). Then, the cell selection step 303 is performed. First, the base station having the highest CPICH level measured in step 301 is selected as a reception target base station (S91). Secondly, referring to the transmission timing of each base station stored in the transmission timing storage unit 205, the same data is obtained from the base station having the highest CPICH level selected in step 91 among the plurality of base stations performing reception. The threshold used for the base station with the earlier transmission timing is set lower than the highest CPICH level (S92).
. Third, the threshold used for the base station that transmits the same data later than the base station with the highest CPICH level selected in step 91 is set to be lower than the threshold set in step 92 (S93). Fourthly, among the base stations whose CPICH level is equal to or higher than the threshold set in step 92 and step 93, base stations having a large margin from the threshold are selected in order from the top (S94).

  The threshold value setting and cell selection described in FIG. 9 will be described with reference to FIG. FIG. 10 shows the relationship between the time when the same data is transmitted from a plurality of base stations and the CPICH level. The time axis is taken from left to right, and the vertical axis shows the CPICH level. In FIG. 10, when the CPICH levels are arranged in order from the base station, the base station C, the base station B, the base station E, the base station A, and the base station D are obtained. Further, FIG. 10 will be described assuming that the number of base stations to be selected is three. First, the base station selected first in step 91 is the base station C with the highest CPICH level. Second, the threshold value 101 indicated by the dotted line set in step 92 is a threshold value used for the base station A and base station B that are earlier than the base station C selected in step 91, and for the base station selected in step 91. The value is lower than the level of CPICH. Third, the threshold value 102 indicated by the dotted line set in step 92 is a threshold value used for the base station D and base station E that are slower than the base station C selected in step 91, and from the threshold value 101 set in step 92. It is a low value. Fourth, in step 94, the base station A and base station B whose CPICH level is equal to or higher than the threshold value 101, and the base station D and base station E whose threshold value is equal to or higher than 102, in order of increasing margin from the threshold value. E, base station B is selected as a reception target base station. In FIG. 10, the base stations selected by the base station B, the base station C, and the base station E are circled.

  Here, with respect to the advantages of the cell selection method according to the third embodiment, the situation of the CPICH level of a plurality of base stations measured by the mobile station will be described with reference to FIG. With the transmission timing of the base station C having the highest CPICH level as a time reference, there are a base station A and a base station B whose CPICH level is equal to or greater than the threshold 101 at a time when the transmission timing is early. It is the base station D and the base station E that have a CPICH level equal to or higher than the threshold 102 at a time when the transmission timing is late. The threshold 101 is higher than the threshold 102, and the base station selected using the threshold 101 has a higher CPICH level than the base station selected using the threshold 102. At this time, the cell selection method of the third embodiment is advantageous for selecting a base station having a high CPICH level at a time when the transmission timing is earlier than in the case of the first embodiment. That is, if the cell selection method of the first embodiment is used in the state of FIG. 10, first, the base station C having the highest CPICH level is selected, and secondly, the base station C selected first. Also, a threshold value 102 used for a base station having a later transmission timing is set, and thirdly, a base station D and a base station E having a transmission timing later than the base station C and a threshold value 102 or higher are selected. That is, the cell selection method of Embodiment 1 is a method of selecting base station D and base station E, which are base stations at a transmission timing later than that of base station C having the highest CPICH level. And base station B cannot be selected. Embodiment 3 is a method of positively selecting a base station whose transmission timing is earlier than that of the base station with the highest CPICH level and whose CPICH level is high. In the case of FIG. 10, it is possible to select the base station B whose transmission time is early and whose CPICH level is high. By selecting a base station that has an earlier transmission time and a higher CPICH level based on the base station having the highest CPICH, normal reception can be performed at an earlier time, and the number of base stations or received data that are received is reduced. be able to. In the above description, the threshold value is set as the threshold value 102 as an explanation when the method of the first embodiment is applied. However, the threshold value 51 of the first embodiment used in FIG. 5 and the implementation used in FIG. It does not indicate that the threshold value 102 of the form 3 is the same.

According to the cell search processing apparatus and the cell search processing method of Embodiment 3 of the present invention, when performing selective combining, the CPICH with the earliest transmission timing based on the transmission timing of the base station with the highest CPICH level Even if there are many base stations whose level is equal to or higher than the threshold and there are few base stations whose CPICH level is higher than the threshold when the transmission timing is late, the base station having a high CPICH level among the base stations whose transmission timing is early Can be selected as a reception target base station, the number of reception target base stations or the number of data can be reduced, and power consumption can be reduced.

  Note that the threshold value set in the second and the threshold value set in the third are not fixed values, but are values that can be set and changed depending on the CPICH level of the mobile station.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. In the cell search processing apparatus and cell search processing method according to the fourth embodiment of the present invention, first, the base station having the highest CPICH level is selected, and secondly, the transmission timing is later than the base station selected in the first. The threshold of the base station is set according to the highest CPICH level, and thirdly, the base station is selected in order from the top among the base stations that are equal to or higher than the threshold defined in the second. The difference between the fourth embodiment and the first embodiment is that the second threshold is set to a high value when it is high enough to allow normal reception by one base station according to the CPICH level of the base station selected in the first. If it is low enough to prevent normal reception by one base station, it is set to a low value. The block diagram of mobile station 100 incorporating the cell search processing apparatus according to the fourth embodiment of the present invention is the same as that in FIG. 2 according to the first embodiment, and the description thereof is omitted in the fourth embodiment. Further, the flowchart of the cell search processing apparatus and the cell search processing method of the fourth embodiment of the present invention is the same as that of FIG. 3 of the first embodiment, and the description of the same is omitted in the fourth embodiment.

  FIG. 11 shows the cell selection operation of the cell search processing apparatus and cell search processing method according to the fourth embodiment of the present invention. FIG. 11 explains the cell selection in step 303 of FIG. That is, the CPICH level that is the synchronization radio channel is measured for each target base station (S301). Next, the transmission timing of each base station stored in the transmission timing storage unit 205 is referred to (S302). Then, the cell selection step 303 is performed. First, the base station having the highest CPICH level measured in step 301 is selected as a reception target base station (S111). Second, referring to the transmission timing of each base station and the highest CPICH level stored in the transmission timing storage unit 205, a base station other than the one selected in step 111 is selected from the plurality of base stations performing reception. The threshold value used for this is set. The threshold is a value used for a base station whose timing of transmitting the same data is slower than that of the first selected base station. First, it is a value that is lower than the highest CPICH level of the selected base station and corresponds to the highest CPICH level. If the highest CPICH level is higher, the threshold is higher, and if the highest CPICH level is lower, The threshold value is set low (S112). Third, among base stations having a CPICH level equal to or higher than the threshold value determined in the second step, base stations having a large margin from the threshold value are sequentially selected as reception target base stations (S113).

FIG. 12 illustrates threshold setting and cell selection described in FIG. FIG. 12 shows the relationship between the time at which the same data is transmitted from a plurality of base stations and the CPICH level. The time axis is taken from left to right, and the vertical axis shows the CPICH level. FIG. 12 is a diagram in a case where the highest CPICH level is set high enough to allow normal reception by one base station and the threshold value is also set to a high value. When the CPICH levels are arranged in descending order, the base station B, the base station D, the base station A, the base station E, and the base station C are obtained. Also, a description will be given assuming that the maximum number of base stations to be selected is three stations. First, the base station selected first in step 111 is the base station B with the highest CPICH level. Second, the threshold value 121 indicated by the dotted line set in step 112 is a threshold value used for the base stations C to E that are slower than the base station B selected in step 111, and the base station B selected in step 111. The value is lower than the CPICH level. Here, the threshold value 121 is set to a high value because the CPICH level of the base station B is high enough to be normally received. Third, at step 113, the CPICH level is the threshold value 121.
The base station D as described above is selected. If there are a plurality of base stations having a threshold value of 121 or more, as in the first to third embodiments, the base stations are selected as the reception target base stations in descending order of the margin from the threshold value. In FIG. 12, the base stations selected by the base station B and the base station D are circled.

  FIG. 13 illustrates the threshold setting and cell selection described in FIG. FIG. 13 is the same diagram as FIG. 12, and a brief description is omitted because it overlaps with FIG. 12. FIG. 13 is a diagram in a case where the highest CPICH level is set to a value that is so low that a single base station cannot receive normally and the threshold value is also low. When the CPICH levels are arranged in descending order, the base station B, the base station D, the base station A, the base station E, and the base station C are obtained. Moreover, in FIG. 13, the number of base stations to be selected is described as three stations. First, the base station selected first in step 111 is the base station B with the highest CPICH level. Second, a threshold 131 indicated by a dotted line set in step 112 is a threshold used for base station C to base station E that is slower than base station B selected in step 111, and for the base station selected in step 111. The value is lower than the level of CPICH. Here, the threshold 131 is set to a low value because the CPICH level of the base station B is not high enough to be normally received. Thirdly, in step 113, the base station D and the base station E are selected as the reception target base stations in the descending order of the margin from the threshold among the base stations C to E having the CPICH level equal to or higher than the threshold 131. In FIG. 13, the base stations selected by the base station B, base station D, and base station E are circled.

  The threshold 131 is a value determined in advance according to the highest CPICH level, is not a fixed value, has several patterns, and is a value whose setting can be changed depending on the reception state of the mobile station.

  According to the cell search processing apparatus and the cell search processing method of Embodiment 4 of the present invention, the base station to be selected first selects the base station having the highest CPICH level and selects other base stations. The threshold is set according to the highest CPICH level. When the highest CPICH level is high, the reliability of the received data is high, so the probability that one base station can normally receive data increases. Therefore, it is not necessary to receive a base station having a low CPICH level, and the number of reception target base stations may be reduced. In other words, when the highest CPICH level is high, the threshold used to select a base station other than the base station with the highest CPICH level is set high to reduce the number of reception target base stations and reduce power consumption. Can do.

  On the other hand, when the highest CPICH level is low, the reliability of the received data is low, and thus the probability that one base station can normally receive data is low. Therefore, the threshold used for selecting a base station other than the base station with the highest CPICH level can be set low, the number of reception target base stations can be increased, and the error rate can be improved.

  In the above description, the transmission timing information has been transmitted from the base station in advance, and the mobile station has received and explained the example of performing data demodulation, but the transmission data from each base station is received by the mobile station, The method for calculating the transmission timing information from the received data can be similarly implemented.

  The cell search processing device, the mobile station equipped with the cell search processing device, and the cell search processing method of the present invention have a timing difference at which the same data is transmitted when selecting a cell to be received when performing selective combining. Based on this, the threshold for the channel quality is switched so that a base station with a high channel quality level can be received at an early time, the probability of reducing the number of base stations to be received is increased, and power consumption can be reduced. It is useful as a mobile station in a mobile communication system, particularly in CDMA communication.

System diagram for explaining the operation of the cell search processing apparatus and the cell search processing method according to Embodiment 1 of the present invention. Block diagram of a mobile station equipped with the cell search processing apparatus in Embodiment 1 of the present invention Flow chart for explaining the operation of the cell search processing apparatus and the cell search processing method in Embodiment 1 of the present invention Flow chart for explaining cell selection operation of cell search processing apparatus and cell search processing method in Embodiment 1 of the present invention The figure which shows line quality and time distribution for demonstrating the cell selection of the cell search processing apparatus and cell search processing method in Embodiment 1 of this invention, and the setting of a threshold value Timing diagram for explaining operation of cell search processing apparatus and cell search processing method in Embodiment 1 of the present invention Flow chart for explaining cell selection operation of cell search processing apparatus and cell search processing method in Embodiment 2 of the present invention The figure which shows line quality and time distribution for demonstrating the cell selection of the cell search processing apparatus and cell search processing method in Embodiment 2 of this invention, and the setting of a threshold value Flow chart for explaining cell selection operation of cell search processing apparatus and cell search processing method in Embodiment 3 of the present invention The figure which shows line quality and time distribution for demonstrating the cell selection of the cell search processing apparatus and cell search processing method in Embodiment 3 of this invention, and the setting of a threshold value Flow chart for explaining cell selection operation of cell search processing apparatus and cell search processing method in Embodiment 4 of the present invention The figure which shows the channel quality and time distribution for demonstrating the cell selection and the setting of a threshold value when the level of the highest CPICH of the cell search processing apparatus and cell search processing method in Embodiment 4 of this invention is high. The figure which shows the channel quality and time distribution for demonstrating the cell selection and threshold setting when the highest CPICH level of the cell search processing apparatus and the cell search processing method in Embodiment 4 of this invention is low The figure which shows line quality and time distribution for demonstrating the cell selection of the conventional cell search processing apparatus and the cell search processing method, and the setting of a threshold value

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Mobile station 101,102 Base station 200 Cell search processing device 203 CPICH level measurement part 204 Cell selection part 205 Transmission timing memory | storage part 210 CRC judgment processing part 211 Selection combining process part

Claims (11)

Channel quality measuring means for measuring the channel quality of the synchronization radio channels of a plurality of base stations, and transmission timing storage means for storing a timing difference at which the same data of the plurality of base stations is transmitted, A cell search processing device comprising cell selection means for selecting a reception target base station by switching a threshold for reception quality of a synchronization radio channel. The cell selection means selects the base station with the highest measured channel quality, and sets the threshold for the channel quality of the synchronization radio channel to the base station whose timing is the same as that of the selected base station that transmits the same data. In this case, the base station is set to a value lower than the channel quality, and the base station other than the base station having the highest selected channel quality selects a base station whose channel quality is equal to or higher than the threshold set in the above and has a large margin from the threshold. The cell search processing device according to claim 1, wherein the selection is performed. The cell selection means selects a base station having the highest channel quality among base stations having a channel quality equal to or higher than a predetermined threshold, and sets a threshold for the channel quality of the synchronization radio channel to be lower than the predetermined threshold. 2. The cell search process according to claim 1, wherein the base station other than the base station previously selected selects a base station having a larger margin from the threshold among the base stations having a channel quality equal to or higher than the set threshold. apparatus. In the case where the cell selection means selects a base station having the highest measured channel quality, and a base station whose timing for transmitting the same data as the threshold for the channel quality of the synchronization radio channel is earlier than the selected base station Is set to a value lower than the channel quality, and in the case of a base station where the same data is transmitted later than the selected base station, it is set lower than in the case of an early base station, and the previously selected base station 2. The cell search processing apparatus according to claim 1, wherein the base stations other than the base stations sequentially select base stations having a large margin from both threshold values among the base stations having the channel quality equal to or higher than both threshold values. . 5. The cell search processing device according to claim 2, wherein the set threshold value is set according to a selected level of the highest channel quality. A mobile station equipped with the cell search processing device according to any one of claims 1 to 5. A channel quality measuring step for measuring the channel quality of the synchronization radio channels of a plurality of base stations, and a transmission timing storing step for storing a timing difference at which the same data of the plurality of base stations is transmitted. Has a cell selection step of selecting a reception target base station by referring to the transmission timing difference stored in the transmission timing storage step, switching a threshold for the channel quality of the synchronization radio channel according to the timing difference. A cell search processing method characterized by the above. The cell selection step selects a base station having the highest measured channel quality at the time of cell selection, and transmits the same data as the threshold for the channel quality of the synchronization radio channel than the selected base station. In the case of a base station whose timing is late, the value is set to a value lower than the channel quality, and the base station other than the previously selected base station has a margin from the threshold value among base stations whose channel quality is equal to or higher than the set threshold value. The cell search processing method according to claim 7, wherein a large base station is selected in order. The cell selection step selects a base station having the highest channel quality among the base stations having a channel quality equal to or higher than a predetermined threshold when selecting a cell, and sets the threshold for the channel quality of the synchronization radio channel. The base station other than the previously selected base station selects a base station having a larger margin from the threshold among the base stations whose channel quality is equal to or higher than the set threshold. Item 8. The cell search processing method according to Item 7. In the cell selection step, when selecting a cell, the base station having the highest measured channel quality is selected, and the threshold value for the channel quality of the synchronization radio channel is transmitted from the selected base station. If the base station has an earlier timing, set it to a value lower than the channel quality. If the base station sends the same data later than the selected base station, set it lower than the earlier base station. The base station to be received other than the previously selected base station sequentially selects the base stations having a large margin from both thresholds among the base stations having the channel quality equal to or higher than both thresholds. The cell search processing method according to claim 7. The cell search processing method according to any one of claims 7 to 10, wherein the set threshold value is set according to a selected level of the highest channel quality.

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