JP2005086374A - Mobile station, communication control apparatus, and communication control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile communication system, a mobile station and a base station capable of appropriately selecting a cell to which a mobile station belongs even when cells having different environments are mixed.
A cellular base station and a hot spot base station transmit signals using a scrambling code corresponding to a cell type of a cell managed by the local base station. When the mobile station 300 receives a signal from the cellular base station 100 or the hot spot base station 200, the mobile station 300 identifies the scrambling code to be used for transmitting the signal, so that the mobile station 300 manages the cell managed by the transmission source base station. Detect cell type. Furthermore, the mobile station 300 preferentially selects the hot spot cell 250 managed by the hot spot base station 200 with a small propagation loss based on the detected cell type.
[Selection] Figure 1

Description

  The present invention relates to communication control in a mobile communication system having a mobile station and a plurality of base stations that can be communication partners of the mobile station.

  2. Description of the Related Art Recently, in order to improve the utilization efficiency of a frequency band for wireless communication, a mobile communication system represented by a wideband code division multiple access (W-CDMA) system constitutes a cellular mobile communication system. The same frequency band is used for each cell managed by each of the plurality of base stations. However, in the cellular mobile communication system using such a mobile communication system, since the same frequency band is used for a plurality of cells, the mobile station refers to the frequency band, so that Is difficult to identify. For this reason, in order to be able to identify the cell in which the mobile station is located, a different scrambling code is used for each cell in the downlink channel (downlink channel) from the base station to the mobile station. . By using a different scrambling code for each cell, there is also an effect of reducing the influence by randomizing interference from other cells in communication in a predetermined cell.

  In the cellular mobile communication system in which a different scrambling code is used for each cell as described above, the mobile station synchronizes with the optimum cell and performs the scrambling code used for that cell. Is identified. Such processing is called cell search. The mobile station selects the cell to which it belongs by this cell search.

  A conventional cellular mobile communication system generally has a cell configuration in which the transmission power of each base station is the same, and a number of cells are adjacent to each other around a predetermined cell. For this reason, the mobile station performs the cell search on the assumption that the cells managed by all the base stations are in the same environment (for example, the transmission power of the base stations managing the cells is the same). Specifically, the mobile station measures the reception power of the common pilot channel signal from each base station in the vicinity of the mobile station, and the cell managed by the base station that is the transmission source of the common pilot channel signal having the maximum reception power Is the optimal cell, is synchronized with that cell, and identifies the scrambling code used for that cell.

  On the other hand, in recent years, as represented by wireless LAN (Local Area Network) (for example, see Non-Patent Document 1), a closed space such as an office or a house, or a place where a large number of people such as an event venue or a station are concentrated The importance of mobile communication services in so-called hot spots is increasing. Against this background, cellular mobile communication systems typified by mobile phones not only have a wide continuous service area as in the past, but also a service area at a hot spot. It is expected that it will be necessary to provide services in line with In that case, a cell (cellular cell) in a conventional cellular mobile communication system and a cell (hot spot cell) covering a hot spot are mixed in the service area of the mobile communication system.

These cellular cells and hot spot cells have different environments. For example, a cellular cell has features such as a large coverage area of one cell, a large transmission power of a base station that manages the cell, a large number of adjacent cells that interfere with communication in the cell, and a high antenna height of the base station. . On the other hand, the hot spot cell has a feature such that the coverage area of one cell is narrow, the transmission power of the base station that manages the cell is small, there are few adjacent cells that interfere with communication in the cell, the antenna height of the base station is low Have
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  However, in a mobile communication system in which cellular cells and hot spot cells are mixed in the service area, the cell managed by the base station that is the transmission source of the common pilot channel signal having the maximum received power is the optimal cell for the mobile station. Is not limited.

  For example, there is a base station that manages a hot spot cell in the vicinity of a mobile station (hereinafter referred to as “hot spot base station” as appropriate), and a base station that manages a cellular cell in a distance (hereinafter referred to as “cellular base station” as appropriate). Suppose that there is a In this case, since the transmission power of the hot spot base station is smaller than the transmission power of the cellular base station, in the mobile station, the reception power of the common pilot channel signal from the cellular base station is greater than the common pilot signal from the hot spot base station. It may be larger than the received power of the signal. As a result, the mobile station may select the cellular cell managed by the cellular base station as the optimum cell. However, since the hot spot base station is located closer to the mobile station than the cellular base station, the propagation loss in communication with the mobile station is small. Therefore, in practice, the hot spot cell managed by the hot spot base station is the optimum cell. That is, if the cell search method in the conventional cellular mobile communication system is applied to a mobile communication system in which cellular cells and hot spot cells are mixed as it is, the mobile station may not be able to select an optimal cell.

  The present invention solves the above-described problems, and provides a mobile communication system, a mobile station, and a base station that can appropriately select a cell to which a mobile station belongs even when cells having different environments are mixed. The task is to do.

  In order to solve the above-described problem, the present invention provides, as described in claim 1, environment detection means for detecting an environment of a cell managed by a base station, and the base station detected by the environment detection means. The mobile station comprises cell selection means for selecting a cell to which the own station belongs based on the environment of the cell to be managed.

  Further, according to a second aspect of the present invention, in the mobile station according to the first aspect, the environment detection unit includes a broadcast channel signal from the base station in a cell managed by the base station. When the environment is included, the environment of the cell managed by the base station is detected from the broadcast channel signal from the base station.

  Further, according to the present invention, as described in claim 3, in the mobile station according to claim 1, the environment detecting unit is configured to transmit a signal to a cell environment managed by the base station, and to transmit signals by the base station. When a scrambling code to be used is associated, when the base station receives a signal from the base station, the base station specifies a scrambling code to be used for transmission of the signal, whereby the base station Detect the environment of the cell managed by.

  Further, according to a fourth aspect of the present invention, in the mobile station according to the first aspect, the environment detection unit is configured to transmit the signal to the cell environment managed by the base station and the base station to transmit a signal. When the scrambling code to be used is associated, when the signal from the base station is received, the base station to be identified is detected by detecting the environment of the cell managed by the base station. Limit scrambling code candidates to be used for transmission.

  According to a fifth aspect of the present invention, in the mobile station according to the third or fourth aspect, the environment detecting unit includes a slot boundary detecting unit that detects a slot boundary of the received signal, and the received signal. Frame boundary detection means for detecting a frame boundary of the frame, scrambling code group detection means for detecting a scrambling code group, and an optimum scrambling code among the scrambling code groups detected by the scrambling code group detection means Scrambling code specifying means for specifying.

  Further, according to the present invention, as described in claim 6, in the mobile station according to any one of claims 1 to 5, the cell selection means includes a cell managed by a base station having a small propagation loss. Select preferentially as a cell to which it belongs.

  Further, according to the present invention, as described in claim 7, in the mobile station according to any one of claims 1 to 6, the cell selection unit is configured to transmit a signal from a plurality of signals transmitted from the base stations. When the cell managed by the base station that is the transmission source of the signal with the maximum received power at the station is a hot spot cell, the hot spot cell is selected as the cell to which the own station belongs.

  According to another aspect of the present invention, there is provided a communication control device comprising an environment notification means for notifying the cell environment managed by the base station into the cell.

  Further, according to a ninth aspect of the present invention, in the communication control device according to the eighth aspect, the environment notification means includes the environment of the cell managed by the base station in the broadcast channel signal. To the cell managed by the base station.

  The communication control device according to claim 8, wherein the environment notification unit includes: a cell environment managed by the base station; and a signal transmission by the base station. When a scrambling code used for the base station is associated, a signal is transmitted using a scrambling code corresponding to the cell environment managed by the base station.

  The present invention provides a communication control method in a mobile communication system comprising a communication control device, a mobile station, and a plurality of base stations that can be communication partners of the mobile station. The control device notifies the cell environment managed by the base station to the cell managed by the base station, and the mobile station detects the cell environment managed by the base station, and the environment detection means Based on the detected cell environment managed by the base station, the cell to which the mobile station belongs is selected.

  According to the present invention, the mobile station detects a cell environment managed by the base station, and selects a cell to which the mobile station belongs based on the detected cell environment. For this reason, even when cells having different environments coexist, the mobile station can appropriately select the cell to which the mobile station belongs in consideration of the environment.

  As described above, according to the present invention, it is possible to appropriately select a cell to which a mobile station belongs even when cells having different environments coexist.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration example of a mobile communication system according to an embodiment of the present invention. In the figure, the mobile communication system can provide both a cellular mobile communication service and a mobile communication service at a hot spot. This mobile communication system includes cellular base stations 100-1, 100-2, and 100-3 (hereinafter referred to as these base stations 100-1, 100-2, and 100-) as communication control apparatuses for providing cellular mobile communication services. 3 are collectively referred to as “cellular base station 100” as appropriate, and hot spot base stations 200-1, 200-2, 200-3, and 200− as communication control apparatuses for providing mobile communication services in the hot spot. 4 (hereinafter, these hot spot base stations 200-1, 200-2, 200-3 and 200-4 are appropriately referred to as “hot spot base station 200”) and a mobile station 300.

  Among these, the cellular base stations 100-1, 100-2, and 100-3 are cellular cells 150-1, 150-2, and 150-3 (hereinafter referred to as cellular cells 150-1, 150-2, and 150-3, respectively). (Referred to as “cellular cell 150” as appropriate). In the cellular mobile communication service, these cellular cells 150 constitute a wide and continuous service area. The hot spot base stations 200-1, 200-2, 200-3, and 200-4 are hot spot cells 250-1, 250-2, 250-3, and 250-4 (hereinafter, these hot spot cells 250). -1, 250-2, 250-3 and 250-4 are appropriately referred to as “hot spot cells 250”). In the hot spot mobile communication service, these hot spot cells 250 form scattered service areas.

  FIG. 2 is a diagram illustrating a configuration example of the cellular base station 100 and the hot spot base station 200. As shown in the figure, the cellular base station 100 and the hot spot base station 200 include an antenna 101, a transmission / reception unit 102, an environment notification unit 104, and a scrambling code table 106.

  The environment notification unit 104 includes a cell type as a cell environment managed by the own station in the broadcast channel signal, specifically, information indicating whether the cell managed by the own station is a cellular cell or a hot spot cell. The process including the output to the transmission / reception unit 102 is performed.

  Alternatively, the environment notification unit 104 performs a process of diffusing a transmission target signal with the scrambling code used at the time of transmission based on the scrambling code table 106 and outputting the signal to the transmission / reception unit 102.

  FIG. 3 is a diagram showing an example of the scrambling code table 106. The scrambling code table 106 shown in the figure shows N × M scrambling codes.

  These N × M scrambling codes are assigned to M scrambling code groups 1 to N in order to enable fast cell search. The scrambling codes 1 to (N−1) M assigned to the scrambling code groups 1 to N−1 are signals from the cellular base station 100 (for example, the cell managed by the cellular base station 100 is a cellular cell). This is information used when notifying the mobile station 300 of 150, and is used for transmission of 0) of the binary control information of 0 and 1. On the other hand, the scrambling codes (N−1) M + 1 to NM assigned to the scrambling code group N are signaled by the hot spot base station 200 (for example, the hot spot base station 200 has a cell managed by itself) This is information used when notifying the mobile station 300 that it is a spot cell 250, and is used for transmitting 1) of binary control information of 0 and 1.

  In the cellular mobile communication service, a wide and continuous service area is configured by the cellular cells 150 managed by each cellular base station 100, and therefore there are many other cellular cells 150 adjacent to one cellular cell 150. On the other hand, in the mobile communication service at a hot spot, since the hot spot cells 250 managed by each hot spot base station 200 constitute a scattered service area, other hot spot cells adjacent to one hot spot cell 250 are arranged. 250 is a small number. Also, different scrambling codes need to be associated between adjacent cells in order to avoid interference. Therefore, as shown in FIG. 3, the scrambling code used by the cellular base station 100 is set to be larger than the scrambling code used by the hot spot base station 200, so that the cellular base station It is possible to prevent the scrambling codes used by 100 from becoming insufficient or assigning more scrambling codes to the hot spot base station 200 than necessary.

  The environment notification unit 104 in the cellular base station 100 uses the scrambling codes 1 to (N−1) M assigned to the scrambling code groups 1 to N−1. Specifically, the environment notification unit 104 in the cellular base station 100 uses any one of the scrambling codes 1 to (N-1) M assigned to the scrambling code groups 1 to N-1. Spread the signal to be transmitted.

  On the other hand, the environment notification unit 104 in the hot spot base station 200 uses the scrambling codes (N−1) M + 1 to NM assigned to the scrambling code group N. Specifically, the environment notification unit 104 in the hot spot base station 200 uses one of the scrambling codes (N−1) M + 1 to NM assigned to the scrambling code group N to transmit Spread the signal.

  The transmission / reception unit 102 transmits the signal from the environment notification unit 104 to the cellular cell 150 or the hot spot cell 250 managed by the own station via the antenna 101. Further, the transmission / reception unit 102 receives a signal from the mobile station 300 in the cellular cell 150 or the hot spot cell 250 managed by the own station via the antenna 101.

  FIG. 4 is a diagram illustrating a configuration example of the mobile station 300. As shown in the figure, the mobile station 300 includes an antenna 301, a transmission / reception unit 302, a received power measurement unit 304, an environment detection unit 306, a scrambling code table 308, and a cell selection unit 310.

  The transmission / reception unit 302 outputs the signal to the environment detection unit 306 each time it receives a signal from the cellular base station 100 or the hot spot base station 200 via the antenna 301. In addition, the transmission / reception unit 302 transmits a transmission target signal via the antenna 301. The reception power measurement unit 304 measures the reception power of the signal received by the transmission / reception unit 302 and notifies the environment detection unit 306 every time the cell search operation is activated when the mobile station 300 is turned on or in standby. .

  Based on the received power notified from the received power measuring unit 304, the environment detecting unit 306 identifies a signal having the maximum received power among the signals received by the transmitting / receiving unit 302.

  Furthermore, the environment detection unit 306 detects the cell type of the cell managed by the base station that has transmitted the signal based on the identified signal having the maximum received power.

  Specifically, when the signal from the base station is a broadcast channel signal, and the broadcast channel signal includes the cell type of the cell managed by the transmission source base station, the following processing is performed. . That is, the environment detection unit 306 extracts the cell type included in the broadcast channel signal with the maximum received power identified, and based on the extracted cell type, the cell type of the cell managed by the transmission source base station is a cellular cell. Or a hot spot cell.

  When the signal from the base station is spread by the scrambling code used by the base station, the environment detection unit 306 detects the slot boundary detection function 321, the frame boundary detection function 322, and the scrambling code group detection. The function 323 and the scrambling code specifying function 324 perform the following processing. The signal from the base station includes two synchronization channels called PSCH (Primary Synchronization Channel) and SSCH (Secondary Synchronization Channel) for each slot. The PSCH uses a scrambling code PSC (Primary Synchronization Code) common to all slots in all cells, and is transmitted by the base station in a slot cycle. On the other hand, the SSCH uses a different scrambling code SSC (Secondary Synchronization Code) for each slot, and an SSC sequence is formed by one frame and is repeatedly transmitted by the base station at a frame period. This SSC sequence is different for each cell and is associated with a scrambling code group to which a scrambling code used by the base station belongs.

  First, the slot boundary detection function 321 of the environment detection unit 306 inputs a signal having the maximum received power to a matched filter corresponding to PSC, and averages it over a plurality of slots in order to reduce the influence of noise and interference. I do. Further, the slot boundary detection function 321 detects the slot boundary by selecting the timing with the largest average correlation value. Here, in a mobile communication system employing an Orthogonal Frequency and Code Division Multiplexing (OFCDM) scheme, the slot boundary is the OFCDM symbol timing.

  Next, the frame boundary detection function 322 and the scrambling code group detection function 323 of the environment detection unit 306 detect a frame boundary (frame timing) and a scrambling code group. Specifically, the frame boundary detection function 322 and the scrambling code group detection function 323 calculate SSCH transmission timing based on the detected slot boundary. Further, the frame boundary detection function 322 and the scrambling code group detection function 323 despread the received signal by SSC at the transmission timing. Then, the frame boundary detection function 322 and the scrambling code group detection function 323 average the correlation values according to all possible frame timings and SSC sequences, and detect the frame timings and SSC sequences with the maximum average correlation values. .

  Further, the scrambling code specifying function 324 of the environment detection unit 306 specifies the scrambling code. Specifically, the scrambling code specifying function 324 receives a common pilot channel spread by a different scrambling code for each cell, and, based on the scrambling code table 308, detects a scrambling code group. Which scrambling code is used is detected. The scrambling code table 308 is the same as the scrambling code table 106 in the base station, and is shown in FIG. 3, for example.

  Next, the environment detection unit 306 refers to the scrambling code table 308 and uses the specified scrambling code by the cellular base station 100 or the hot spot base station 200. Determine if there is. For example, when the specified scrambling code is assigned to any of the scrambling code groups 1 to N-1 in FIG. 3, the environment detection unit 306 determines that the specified scrambling code is a cellular base station. If it is determined to be used by the station 100 and is assigned to the scrambling code group N in FIG. 3, the specified scrambling code is used by the hot spot base station 200. Judge that there is.

  Furthermore, when the specified scrambling code is used by the cellular base station 100, the environment detection unit 306 is the cellular base station 100, and the base station that is the transmission source of the signal with the maximum received power is the cellular base station 100. It detects that the cell type of the cell managed by the cellular base station 100 is a cellular cell. On the other hand, when the specified scrambling code is used by the hot spot base station 200, the environment detection unit 306 indicates that the base station that is the transmission source of the signal with the maximum received power is the hot spot base station 200. Then, it is detected that the cell type of the cell managed by the hot spot base station 200 is a hot spot cell.

  When the cell type of the cell managed by the base station of the signal having the maximum received power is a hot spot cell, the cell selection unit 310 manages the base station of the signal source having the maximum received power. The hot spot cell 250 to be selected is selected as the cell to which the own station belongs.

  On the other hand, if the cell type of the cell managed by the base station of the signal having the maximum received power is not a hot spot cell, in other words, if it is a cellular cell, the environment detection unit 306 selects the cellular cell 150. Exclude from candidates. Furthermore, the environment detection unit 306 identifies a signal having the maximum received power among signals from other base stations other than the cellular base station 100 that manages the cellular cell 150 excluded from the selection candidates. When the received power is less than the predetermined value, the cell selection unit 310 manages the cellular base station 100 that transmits a signal having the maximum received power among the cellular cells 150 excluded by the environment detection unit 306. The cellular cell 150 is selected as the cell to which the local station belongs. On the other hand, when the received power is greater than or equal to the predetermined value, the environment detection unit 306 manages the cell managed by the base station that is the transmission source of the signal based on the identified signal with the largest received power, as in the above-described process. Detect cell type. Furthermore, when the detected cell type is a hot spot cell, cell selection section 310 selects hot spot cell 250 managed by the base station that is the source of the signal as the cell to which the own station belongs.

  In such processing, when the hotspot base station 200 is included in a transmission source base station of a signal whose received power at the mobile station 300 is equal to or greater than a predetermined value, the mobile station 300 is more likely to receive a signal from the cellular base station 100. Even when the received power is larger than the signal from the hot spot base station 200, the hot spot cell 250 managed by the hot spot base station 200 is preferentially selected.

  The reason why the mobile station 300 performs such cell selection will be described below. In general, the transmission power of hot spot base station 200 is smaller than the transmission power of cellular base station 100. Further, as shown in FIG. 5, when the distance between the mobile station 300 and the hot spot base station 200 is shorter than the distance between the mobile station 300 and the cellular base station 100, the mobile station The station 300 preferably selects a hot spot cell 250 managed by the hot spot base station 200 that is present near the station 300. Therefore, as described above, the mobile station 300 is managed by the hot spot base station 200 even when the signal from the cellular base station 100 has a higher reception power than the signal from the hot spot base station 200. The hot spot cell 250 to be selected is preferentially selected.

  Note that when the mobile station 300 is located as shown in FIG. 5, the environment detection unit 306 is a hot cell because the cell type of the cell managed by the base station that is the transmission source of the signal with the maximum received power is a cellular cell. In order to select the spot cell 250, the cell search is continuously repeated. At this time, the scrambling code corresponding to the base station that manages the selection candidate cell is used as the hot spot base station 200 that manages the hot spot cell. Can be limited to scrambling codes corresponding to. Thereby, when the environment detection unit 306 specifies the scrambling code based on the scrambling code table 308, the search target in the scrambling code table 308 is changed to the scrambling code used by the hot spot base station 200. The amount of processing and the processing time can be reduced, and the detection probability of the scrambling code can be improved.

  Next, the operation of the mobile station 300 will be described with reference to a flowchart.

  FIG. 6 is a first flowchart showing the cell selection operation of the mobile station 300. The figure shows the cell selection operation of the mobile station 300 when the cellular base station 100 or the hot spot base station 200 transmits a broadcast channel signal including the cell type of the cell managed by the own station.

  The mobile station 300 measures the reception power of the broadcast channel signal from the cellular base station 100 and the hot spot base station 200 every time the cell search operation is started when the power is turned on or during standby. Furthermore, the mobile station 300 identifies the broadcast channel signal having the maximum received power among the received broadcast channel signals (step 101).

  Next, the mobile station 300 extracts the cell type included in the broadcast channel signal with the maximum received power identified, and detects the cell type of the cell managed by the transmission source base station based on the extracted cell type (Step 102). Further, the mobile station 300 determines whether or not the detected cell type is a hot spot cell (step 103).

  When the cell type is a hot spot cell, the mobile station 300 determines that the cell corresponding to the cell type, in other words, the hot spot base station 200 that is the base station that is the transmission source of the broadcast channel signal including the cell type, The hot spot cell 250 to be managed is selected as a cell to which the own station belongs (step 104).

  On the other hand, when it is determined in step 103 that the cell type is not a hot spot cell, that is, when it is determined that the cell type is a cellular cell, the mobile station 300 excludes the cellular cell 150 from the selection candidates (step 105). ). Furthermore, the mobile station 300 identifies a broadcast channel signal having the maximum received power among broadcast channel signals from other cellular base stations 100 and hot spot base stations 200 other than the cellular base station 100 that manages the excluded cellular cell 150. (Step 106).

  Next, the mobile station 300 determines whether or not the received power of the broadcast channel signal with the maximum received power identified in step 106 is less than a predetermined value (step 107). When the received power is greater than or equal to a predetermined value, the mobile station 300 determines the cell type of the cell managed by the transmission source base station based on the cell type included in the broadcast channel signal with the identified received power being the maximum. The operation after the detection (step 102) is repeated.

  On the other hand, when the received power is less than the predetermined value, the mobile station 300 manages the cellular cell managed by the cellular base station 100 that is the transmission source of the broadcast channel signal with the largest received power, from among the cellular cells 150 excluded in step 105. 150 is selected as a cell to which the own station belongs (step 108).

  FIG. 7 is a second flowchart showing the cell selection operation of mobile station 300. The figure shows the cell selection operation of the mobile station 300 when the cellular base station 100 or the hot spot base station 200 transmits a signal using a scrambling code corresponding to the cell type of the cell managed by the local station. Show.

  The mobile station 300 measures the received power of signals from the cellular base station 100 and the hot spot base station 200 every time the cell search operation is activated when the mobile station 300 is turned on or in standby. Furthermore, the mobile station 300 identifies the signal having the maximum received power among the received signals (step 201).

  Next, the mobile station 300 detects the cell type of the cell managed by the base station that is the transmission source of the signal with the largest received power (step 202). Next, the mobile station 300 determines whether or not the detected cell type is a hot spot cell (step 203).

  When the cell type is a hot spot cell, the mobile station 300 manages the cell corresponding to the cell type, in other words, the hot spot base station 200 that is a base station that is a transmission source of a signal including the cell type. The hot spot cell 250 is selected as a cell to which the own station belongs (step 204).

  On the other hand, when it is determined in step 203 that the cell type is not a hot spot cell, that is, when it is determined that the cell type is a cellular cell, the mobile station 300 excludes the cellular cell 150 from the selection candidates (step 205). ). Furthermore, the mobile station 300 identifies a signal having the maximum received power among signals from the cellular base stations 100 and hot spot base stations 200 other than the cellular base station 100 that manages the excluded cellular cell 150 (step 206). ).

  Next, the mobile station 300 determines whether or not the received power of the signal having the maximum received power identified in step 206 is less than a predetermined value (step 207). When the received power is greater than or equal to a predetermined value, the mobile station 300 determines the cell type of the cell managed by the transmission source base station based on the scrambling code used for the signal having the identified received power. The operation after the detection (step 202) is repeated.

  On the other hand, when the received power is less than the predetermined value, the mobile station 300 selects the cellular cell 150 managed by the cellular base station 100 that is the transmission source of the signal having the maximum received power from the cellular cells 150 excluded in step 205. The cell to which the own station belongs is selected (step 208).

  FIG. 8 is a third flowchart showing the cell selection operation of mobile station 300. In the figure, in a mobile communication system employing the OFCDM system, the cellular base station 100 or the hot spot base station 200 transmits a signal using a scrambling code corresponding to the cell type of the cell managed by the local station. The cell selection operation of the mobile station 300 in the case of performing is shown.

  The mobile station 300 detects the OFCDM symbol timing (step 301). Next, the mobile station 300 detects a frame timing and a scrambling code group based on the detected OFCDM symbol timing (step 302). Next, the mobile station 300 selects a scrambling code based on the detected frame timing and scrambling code group (step 303). Further, the mobile station 300 detects a cell type corresponding to the selected scrambling code (step 304). Specifically, the mobile station 300 refers to the scrambling code table, and whether the selected scrambling code is used by the cellular base station 100 or the hot spot base station 200. If the cell type is one used by the cellular base station 100, the cell type is detected as a cellular cell. If the cell type is one used by the hot spot base station 200, the cell type is a hot spot. Detect as a cell. Next, the mobile station 300 determines whether or not the detected cell type is a hot spot cell (step 305).

  When the cell type is a hot spot cell, the mobile station 300 manages the cell corresponding to the cell type, in other words, the hot spot base station 200 that is a base station that is a transmission source of a signal including the cell type. The hot spot cell 250 is selected as a cell to which the own station belongs (step 306).

  On the other hand, if it is determined in step 305 that the cell type is not a hot spot cell, that is, if it is determined that the cell type is a cellular cell, the mobile station 300 detects the next OFCDM symbol timing (step 307). . Furthermore, the mobile station 300 excludes scrambling codes (for example, scrambling codes 1 to (N−1) M in the scrambling code table of FIG. 3) corresponding to the cell type of the cellular cell from detection targets (step 308). . Thereafter, the mobile station 300 repeats the operation after the detection of the frame timing and the scrambling code group (step 302).

  As described above, in the mobile communication system according to the present embodiment, when the broadcast channel signal from the base station includes a cell environment managed by the base station, the mobile station 300 uses the broadcast channel signal. The cell type of the cell managed by the base station is detected. Alternatively, when the cell type of the cell managed by the base station and the scrambling code used by the base station for signal transmission are associated with each other, the mobile station 300 transmits a signal from the base station. By identifying the scrambling code to be used, the cell type of the cell managed by the base station is detected. Then, the mobile station 300 preferentially selects the hot spot cell 250 managed by the hot spot base station 200 with a small propagation loss based on the detected cell type. For this reason, even when the cellular cell 150 and the hot spot cell 250 coexist, the mobile station 300 can appropriately select a cell to which the mobile station 300 belongs in consideration of the cell type.

  In particular, when the cell type of the cell managed by the base station is associated with the scrambling code used by the base station for signal transmission, the mobile station 300 detects the cell type in the physical layer. The cell type can be quickly identified.

  In the above-described embodiment, the case where information indicating whether the cell managed by the base station is a cellular cell or a hot spot cell is used as the cell type has been described. However, the transmission power of the base station and the base station manage the cell type. The present invention can also be applied to the case where information indicating the cell environment managed by the base station, such as the cell size (cell radius), is used as the cell type.

It is a figure which shows the structural example of a mobile communication system. It is a figure which shows the structural example of a base station. It is a figure which shows an example of a scrambling code table. It is a figure which shows the structural example of a mobile station. It is a figure which shows the received power in a mobile station. It is a 1st flowchart which shows the cell selection operation | movement of a mobile station. It is a 2nd flowchart which shows the cell selection operation | movement of a mobile station. It is a 3rd flowchart which shows the cell selection operation | movement of a mobile station.

Explanation of symbols

100-1, 100-2, 100-3 Cellular base station 101, 301 Antenna 102, 302 Transceiver 104 Environment notification unit 106, 308 Scrambling code table 150-1, 150-2, 150-3 Cellular cell 200-1, 200-2, 200-3, 200-4 Hot spot base station 250-1, 250-2, 250-3, 250-4 Hot spot cell 300 Mobile station 304 Received power measurement unit 306 Environment detection unit 310 Cell selection unit

Claims (11)

An environment detecting means for detecting an environment of a cell managed by the base station;
Cell selection means for selecting a cell to which the own station belongs based on the environment of the cell managed by the base station detected by the environment detection means;
A mobile station comprising: The mobile station according to claim 1, wherein
When the broadcast channel signal from the base station includes a cell environment managed by the base station, the environment detection means manages the broadcast channel signal from the base station based on the broadcast channel signal. A mobile station that detects the environment of a cell to be operated. The mobile station according to claim 1, wherein
The environment detection means receives a signal from the base station when the cell environment managed by the base station is associated with a scrambling code used by the base station for signal transmission. In addition, a mobile station that detects the environment of a cell managed by the base station by specifying a scrambling code used by the base station to transmit the signal. The mobile station according to claim 1, wherein
The environment detection means receives a signal from the base station when the cell environment managed by the base station is associated with a scrambling code used by the base station for signal transmission. In addition, a mobile station that limits the scrambling code candidates that the specified base station uses to transmit the signal by detecting the environment of a cell managed by the base station. In the mobile station according to claim 3 or 4,
The environment detection means includes
Slot boundary detecting means for detecting a slot boundary of the received signal;
Frame boundary detection means for detecting a frame boundary of the received signal;
Scrambling code group detection means for detecting a scrambling code group;
A scrambling code specifying means for specifying an optimal scrambling code from the scrambling code group detected by the scrambling code group detecting means;
A mobile station comprising: In the mobile station in any one of Claims 1 thru | or 5,
The cell selection means is a mobile station that preferentially selects a cell managed by a base station having a small propagation loss as a cell to which the own station belongs. In the mobile station in any one of Claims 1 thru | or 6,
The cell selection means is a hot spot cell when a cell managed by a base station that is a transmission source of a signal having the maximum received power among the signals transmitted from the plurality of base stations is a hot spot cell. A mobile station that selects a spot cell as a cell to which it belongs.   A communication control apparatus comprising environment notification means for notifying a cell environment managed by a base station into the cell. The communication control device according to claim 8, wherein
The environment notification unit includes a broadcast channel signal including a cell environment managed by the base station and transmits the signal to a cell managed by the base station. The communication control device according to claim 8, wherein
The environment notification means is configured to change the cell environment managed by the base station when the cell environment managed by the base station is associated with the scrambling code used by the base station for signal transmission. A communication control device that transmits a signal using a corresponding scrambling code. In a communication control method in a mobile communication system having a communication control device, a mobile station, and a plurality of base stations that can be communication partners of the mobile station,
The communication control device includes:
Notifying the cell environment managed by the base station into the cell managed by the base station;
The mobile station
Detect the environment of the cell managed by the base station,
A communication control method for selecting a cell to which the mobile station belongs based on an environment of a cell managed by the base station detected by the environment detection means.

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