JPWO2008004299A1 - Wireless communication system, base station apparatus, and mobile station apparatus - Google Patents

Abstract

Provided are a radio communication system, a mobile station apparatus, and a base station apparatus that realize high-speed mobile communication while improving frequency utilization efficiency. The wireless communication system includes a mobile station and a base station, and the mobile station and the base station communicate wirelessly using a plurality of communication channels and pilot channels corresponding to the communication channels. A mobile station comprising power control means for setting at least one of the plurality of communication channels as a priority channel and setting a transmission power of a pilot channel corresponding to the priority channel higher than a transmission power of a pilot channel corresponding to another communication channel; Comprises measurement means for measuring the reception level of the pilot channel transmitted from the base station, and determination means for determining at least one of the plurality of communication channels as an available communication channel according to the reception level.

Description

  The present invention relates to a radio communication system, a base station apparatus, and a mobile station apparatus that perform channel allocation control.

  In mobile communication systems, a third-generation mobile phone system using a CDMA (Code Division Multiple Access) system has been put into practical use. In recent years, a next-generation mobile communication system that enables higher-speed communication has been studied. (See Non-Patent Document 1 below). For this next-generation mobile communication system, application of an OFDM (Orthogonal Frequency Division Multiplexing) system is being considered in place of the CDMA system. The OFDM scheme is a scheme in which transmission data is divided into a plurality of pieces, the divided transmission data is mapped to a plurality of orthogonal carrier waves (subcarriers), and transmitted in parallel on the frequency axis.

  In such a mobile communication system using the OFDM scheme, it is necessary to assign different frequency bands to adjacent base stations. This is because if adjacent base stations perform radio communication using the same frequency band, interference will occur between them. However, in order to increase the frequency utilization efficiency, it is desirable that each base station can use the same frequency band as much as possible.

On the other hand, a method of making the frequency repetition distance variable according to the distance of the mobile station from the base station has been proposed (see Non-Patent Document 2 below). The frequency repetition distance is a distance (number of cells) required when considering an arrangement in which adjacent base stations do not use the same frequency band in each base station (cell). In this method, when the mobile station is far from the base station, the repeat distance is increased (for example, repeat distance 3) to prevent interference with an adjacent base station, and when the mobile station is close to the base station. For example, by reducing the repetition distance (for example, repetition distance 1, that is, all frequency channels can be used), the frequency utilization efficiency is improved.
Technical Specification Group Radio Access Network, "Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN) (Release 7)", 3rd Generation Partnership Project, 3GPP TR 25.913 V7.2.0, December 2005 Samsung, "Flexible Fractional Frequency Reuse Appro", 3rd Generation Partnership Project TSG-RAN WG1, R1-051341, 8.2, November 2005

  However, a specific method for applying the above-described method for changing the frequency repetition distance to a mobile communication system has not been proposed and is a problem.

  An object of the present invention is to provide a radio communication system, a mobile station apparatus, and a base station apparatus that realize high-speed mobile communication while improving frequency utilization efficiency.

  The present invention employs the following configuration in order to solve the above-described problems. That is, according to the present invention, a base station apparatus that wirelessly communicates with a mobile station using a plurality of communication channels and pilot channels corresponding to each communication channel uses at least one of the plurality of communication channels as a priority channel. Power control means is provided for setting the transmission power of the pilot channel corresponding to the priority channel higher than the transmission power of the pilot channel corresponding to the other communication channel.

  According to the present invention, a mobile station that receives a signal transmitted from a base station apparatus may or may not be able to receive all pilot signals depending on its location. The cases other than this include, for example, a case where only a pilot signal set with a high transmission power is received, and a case where another pilot signal having a low reception level is received together with the pilot signal.

  Accordingly, the mobile station can determine an available communication channel by detecting the pilot signal.

  That is, the present invention provides a measuring means for measuring a reception level of a pilot channel transmitted from a base station apparatus as described above, and at least one of the plurality of communication channels used by the base station apparatus according to the reception level. It is also related with a mobile station apparatus provided with the determination means which determines to the communication channel which can be used.

  For example, the determination unit determines a communication channel corresponding to a pilot channel having a reception level larger than a predetermined threshold among the reception levels measured by the measurement unit as an available communication channel.

  In addition, the mobile station apparatus according to the present invention may further include transmission means for generating channel information related to an available communication channel determined as described above and transmitting the channel information to the base station.

  Thereby, the base station apparatus according to the present invention uses a communication channel corresponding to channel information transmitted from the mobile station among the plurality of communication channels to transmit data addressed to the mobile station. It is sufficient to further include selection means for selecting as follows.

  With such a configuration, the base station apparatus according to the present invention can recognize communication channels that can be used by each mobile station based on channel information transmitted from each mobile station. For example, a communication channel in which channel information is not sent may be recognized as a channel that is not usable for the mobile station apparatus.

  Here, the above-described channel information may be, for example, information based on CQI (Channel Quality Indicator) information or other channel estimation values, or identification information for identifying an available communication channel. May be.

  As described above, according to the present invention, the mobile station apparatus can determine an appropriate available channel according to its location by measuring the reception level of the pilot channel. As a result, even if a plurality of identical communication channels are assigned to adjacent base station apparatuses, usable channels that do not cause interference are determined in the mobile station apparatus, so that high communication quality is maintained. High frequency utilization efficiency can be realized.

  Note that the present invention may relate to a mobile communication system having the above mobile station apparatus and base station apparatus. The present invention may be a method for causing a computer to realize any of the functions described above. Further, the present invention may be a program or a circuit for realizing any of the functions described above. Further, the present invention may be a program in which such a program is recorded on a computer-readable storage medium.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless communications system, mobile station apparatus, and base station apparatus which implement | achieve high-speed mobile communication, aiming at the improvement of frequency utilization efficiency can be provided.

FIG. 1 is a diagram showing a system configuration of a wireless communication system in the present embodiment. FIG. 2 is a block diagram showing an outline of a functional configuration of the base station apparatus. FIG. 3 is a diagram illustrating an example of a radio frame format of the OFDM signal. FIG. 4 is a diagram showing transmission power of pilot channels P1, P2, and P3 in the base station BS1. FIG. 5 is a diagram showing transmission power of pilot channels P1, P2 and P3 in the base station BS2. FIG. 6 is a diagram conceptually showing an example of the relationship between the pilot channel transmission power and the available channel of the mobile station in the wireless communication system of this embodiment. FIG. 7 is a block diagram showing an outline of a functional configuration of the communication terminal apparatus.

Explanation of symbols

MS1, MS2 Communication terminal equipment (mobile station)
BS1, BS2 Base station equipment (base station)
101, 201 Antenna 120 Transmitter 110 Receiver 111, 202 Receiver 113 Response information collection unit 121, 203 Transmitter 122 Pilot data generation unit 123 Broadcast information generation unit 127 Scheduler 129, 129-1, 129-2, ... 129-n Pilot data holding unit 124, 210 Control unit 125 Combining unit 205 Pilot determining unit 207 Response information generating unit 208 Data processing unit

  Hereinafter, a radio communication system according to an embodiment of the present invention will be described with reference to the drawings. The configuration of each of the following embodiments is an exemplification, and the present invention is not limited to the configuration of each of the following embodiments.

[Embodiment]
Hereinafter, the radio | wireless communications system in embodiment of this invention is demonstrated using FIG. FIG. 1 is a diagram showing a system configuration of a wireless communication system in the present embodiment. The radio communication system according to the present embodiment includes base station apparatuses BS1 and BS2 (hereinafter also simply referred to as base stations), and a mobile communication switching station apparatus (not shown) that performs exchange control of signals received at these base stations. Etc. The wireless communication system in the present embodiment provides a predetermined communication service to communication terminal apparatuses MS1 and MS2 (hereinafter also simply referred to as mobile stations) connected to the wireless communication system by performing wireless communication with base stations BS1 and BS2. I will provide a. Note that the base station apparatuses BS1 and BS2 are adjacent to each other.

  It is assumed that channels CH1, CH2, and CH3 are assigned to the base station apparatuses BS1 and BS2 for communication, respectively. Further, one of the communication channels is assigned as a priority channel so that the base station apparatuses BS1 and BS2 are different from each other. In this embodiment, it is assumed that channel CH1 is assigned as a priority channel to base station BS1, and channel CH2 is assigned as a priority channel to base station BS2. The priority channel is a communication channel that can be preferentially used in the base station. Note that the present invention does not limit the number of priority channels. For example, the priority channels of the base station BS2 may be channels CH2 and CH3.

  Reference numerals 1 and 2 shown in FIG. 1 indicate communication areas (cells) of the base stations BS1 and BS2, respectively. In the following description, as shown in FIG. 1, the case where the mobile station MS1 is located far from the base station and the mobile station MS2 is located near the base station will be described as an example. The base stations BS1 and BS2 have functional units related to the present invention described below, and the same applies to the mobile stations MS1 and MS2. Hereinafter, the base station devices (BS1 and BS2) and the communication terminal devices (MS1 and MS2) will be described.

[Base station equipment]
First, an outline of a functional configuration of the base station apparatuses (BS1 and BS2) will be described with reference to FIG. FIG. 2 is a block diagram illustrating an outline of a functional configuration of the base station apparatus. As shown in FIG. 2, the base station apparatus generally includes an antenna 101, a transmission unit 120, and a reception unit 110.

  The transmission unit 120 receives data to be transmitted (transmission data) and control information from other functional units (not shown), and receives these data from the antenna 101 as radio signals using communication channels assigned to each base station. Send it out. The receiving unit 110 receives signals received by the antenna 101, demodulates and decodes control information and received data from these signals, and sends the obtained data to another functional unit (not shown).

  Each of these functional units may be realized by a hardware circuit, or may be realized by loading a control program stored in a memory into a CPU (Central Processing Unit) and executing it. Good. FIG. 2 shows only functional units related to the present invention.

<Receiver>
The reception unit 110 includes a receiver 111, a response information collection unit 113, and the like. The receiver 111 performs processing such as analog / digital conversion, demodulation, and decoding on the radio signal received by the antenna 101 to obtain control information and received data (user data). The receiving unit 110 passes the obtained control information to the response information collecting unit 113.

  This control information includes downlink channel information (direction from the base station to the mobile station) generated by the mobile station. In this embodiment, CQI (Channel Quality Indicator) information is used as the channel information. Note that this embodiment does not limit the type of channel information. The CQI information is generated for each communication channel of the received signal in the mobile station, and is sent to the base station as information corresponding to each communication channel. A method for generating the CQI information will be described later.

  The response information collection unit 113 acquires CQI information from the control information passed from the receiver 111. The response information collection unit 113 passes the CQI information associated with each communication channel to the scheduler 127 of the transmission unit 120.

<Transmitter>
The transmission unit 120 includes a transmitter 121, a pilot data generation unit 122, a broadcast information generation unit 123, a scheduler 127, and the like.

  The transmitter 121 includes a serial / parallel converter, a modulator, an inverse Fourier transform (IDFT (Inverse Discrete Fourier Transform) or IFFT (Inverse Fast Fourier Transform)), a parallel / serial converter, a guard interval insertion unit, a digital / analog It has a conversion part, a frequency conversion part, etc. That is, the transmitter 121 uses these functional units to control information passed from other functional units (not shown), transmission data sent from the scheduler 127 (user data), pilot data sent from the pilot data generating unit 122 Generates a multiplexed OFDM signal. The generated OFDM signal is finally subjected to high frequency conversion and transmitted from the antenna 101.

  FIG. 3 shows an example of a radio frame format of the OFDM signal generated by the transmitter 121. It is assumed that the transmitter 121 in this embodiment generates an OFDM signal having such a radio frame format. According to the example shown in FIG. 3, the communication channels assigned to the own base station are channels CH1, CH2, and CH3. Also, pilot channels P1, P2, and P3 corresponding to each communication channel are respectively arranged.

  Further, the transmitter 121 sends a notification signal based on the notification information transmitted from the notification information generation unit 123 to the antenna 101 as needed. Thereby, this notification signal is transmitted from the antenna 101. The broadcast information generation unit 123 generates broadcast information including identification information for identifying the own base station, communication resource information, and the like, and passes this broadcast information to the transmitter 121.

  The pilot data generation unit 122 includes a pilot data holding unit 129 (129-1, 129-2, ..., 129-n), a control unit 124, a synthesis unit 125, and the like. The pilot data generation unit 122 generates pilot data (pilot signal) subjected to transmission power control by the control unit 124 and sends the pilot data to the transmitter 121.

  The pilot data holding unit 129 holds pilot data corresponding to the communication channels CH1, CH2, and CH3 (pilot data holding units 129-1, 129-2, and 129-3). The pilot data corresponding to each channel is given predetermined transmission power based on an instruction from the control unit 124, and each pilot data is arranged by the combining unit 125 and sent to the transmitter 121.

  As shown in FIG. 4 or 5, the control unit 124 holds information regarding transmission power of each pilot channel corresponding to each communication channel allocated to the own base station, and each pilot is based on this information. Determine the transmission power to be given to the channel. FIG. 4 shows the transmission power of pilot channels P1, P2 and P3 in the base station BS1, and FIG. 5 shows the transmission power of pilot channels P1, P2 and P3 in the base station BS2.

  Since channel CH1 is assigned to base station BS1 as a priority channel, the transmission power of pilot channel P1 corresponding to channel CH1 is higher than pilot channels P2 and P3 corresponding to other channels CH2 and CH3. Is set. Similarly, since the channel CH2 is assigned as the priority channel to the base station BS2, the transmission power of the pilot channel P2 corresponding to the channel CH2 is higher than the pilot channels P1 and P3 corresponding to the other channels CH1 and CH3. It is set to be.

  As a result, the mobile station that has received the pilot channel can determine which channel should be used for transmission. FIG. 6 is a diagram conceptually illustrating an example of a relationship between pilot channel transmission power and an available channel of a mobile station in the wireless communication system of the present embodiment. In FIG. 6, as described above, in the base station BS1, the transmission power of the pilot channel P1 corresponding to the priority channel CH1 is set to be higher than the others, and the base station BS2 It is shown that the transmission power of pilot channel P2 corresponding to CH2 is set to be higher than the others.

  In such a case, the mobile station existing in the vicinity area (reference numeral 11) of the base station BS1 can receive all the pilot channels, but the movement existing in the area away from the base station BS1 (reference numeral 1). The station receives only the pilot channel P1 or the pilot channels P2 and P3 having a low reception level. Thereby, mobile station MS1 shown in FIG. 6 can determine that it should transmit using channel CH1 corresponding to pilot channel P1.

  Similarly, a mobile station that exists in the vicinity area (reference numeral 21) of the base station BS2 can receive all pilot channels, but a mobile station that exists in an area away from the base station BS2 (reference numeral 2) Only the pilot channel P2 or the pilot channels P1 and P3 having a low reception level are received. Thereby, the mobile station MS2 shown in FIG. 6 can determine that it can transmit using all the channels CH1, CH2 and CH3.

  The scheduler 127 arranges transmission data (user data) sent from other functional units (not shown) in which symbol of any of the communication channels CH1, CH2 and CH3 allocated to the own base station, etc. To decide. At this time, scheduler 127 determines the arrangement of transmission data to each mobile station based on the CQI information of each mobile station passed from response information collection section 113. Since the CQI information is transmitted in association with each channel from each mobile station, the scheduler 127 selects a channel to which transmission data to each mobile station is to be allocated based on the CQI information.

  For example, when the CQI information related to the mobile station MS1 is only for the channel CH1, the scheduler 127 arranges transmission data for the mobile station MS1 in a predetermined symbol in the channel CH1. Further, when the CQI information related to the mobile station MS2 includes all of the channels CH1, CH2, and CH3, the scheduler 127 arranges transmission data to the mobile station MS2 in any of the channels CH1, CH2, and CH3. Note that the present invention does not limit a specific arrangement determining method by the scheduler 127, such as whether the transmission data is arranged in any of a plurality of channels or in which symbol in the channel.

[Communication terminal device]
Next, an outline of a functional configuration of the communication terminal device (mobile station) (MS1 and MS2) will be described with reference to FIG. FIG. 7 is a block diagram illustrating an outline of a functional configuration of the communication terminal device. As shown in FIG. 7, the mobile station includes an antenna 201, a receiver 202, a transmitter 203, a pilot determination unit 205, a response information generation unit 207, a data processing unit 208, a control unit 210, and the like. Each of these functional units may be realized by a hardware circuit, or may be realized by loading a control program stored in a memory into a CPU (Central Processing Unit) and executing it. Good. In FIG. 7, only functional units related to the present invention are shown.

<Receiver>
The receiver 202 includes a frequency conversion unit, an analog / digital conversion unit, a guard interval removal unit, a serial / parallel conversion unit, a Fourier transform (DFT (Discrete Fourier Transform) or FFT (Fast Fourier Transform)) unit, and a parallel / serial conversion unit. A demodulator, a decoder and the like. The receiver 202 demodulates and decodes the OFDM signal received by the antenna 201 using these functional units, and sends the obtained user data, control data, and the like to the data processing unit 208.

  In addition, the receiver 202 sends a pilot signal out of signals obtained as a result of frequency conversion, digital conversion, and Fourier transform of the received OFDM signal to the pilot determination unit 205. In the example of the radio frame format shown in FIG. 3, pilot signals P 1, P 2 and P 3 are passed to pilot determination section 205.

<Data processing section>
The data processing unit 208 processes user data sent from the receiver 202. In addition, the data processing unit 208 sends user data to be transmitted, control information, and the like to the transmitter 203.

<Transmitter>
The transmitter 203 includes a serial / parallel converter, a modulator, an inverse Fourier transform (IDFT or IFFT) unit, a parallel / serial converter, a guard interval insertion unit, a digital / analog converter, a frequency converter, and the like. The transmitter 203 uses these functional units to generate an OFDM signal in which user data and control information transmitted from the data processing unit 208 are multiplexed. The generated OFDM signal is finally subjected to high frequency conversion and transmitted from the antenna 201.

<Pilot judgment unit>
Pilot determining section 205 receives the pilot signal passed from receiver 202 and measures the reception level of each pilot signal. The pilot signal is arranged so as to correspond to the communication channel assigned to each base station as described above. Therefore, pilot determination section 205 measures the reception level of the pilot signal corresponding to each channel transmitted from the base station. The pilot determination unit 205 sends the measured pilot signal reception level indicated by the control unit 210 to the response information generation unit 207 in a form associated with the communication channel corresponding to the pilot signal.

<Response information generator>
Response information generation section 207 generates CQI information for each channel based on the reception level passed from pilot determination section 205. For example, the response information generation unit 207 may store a CQI information table in which a reception level and CQI information are associated with each other, and generate the CQI information by referring to the CQI information table. The generated CQI information is sent to the transmitter 203.

<Control unit 210>
Control section 210 selects a pilot signal reception level measured by pilot determination section 205 that should generate CQI information. Control unit 210 instructs pilot determination unit 205 of the selection result. For example, the control unit 210 holds a predetermined threshold in advance, and instructs the pilot determination unit 205 to send the reception level of the pilot signal having a reception level larger than the predetermined threshold to the response information generation unit 207.

[Operation example]
Next, an operation example of the wireless communication system in the present embodiment will be described with reference to FIG. In the example of FIG. 6, as described above, the base station BS1 transmits a signal set such that the transmission power of the pilot channel P1 corresponding to the priority channel CH1 is higher than the others, and the base station BS2 Is transmitting a signal set such that the transmission power of pilot channel P2 corresponding to priority channel CH2 is higher than the others. The mobile station MS1 is located near the cell edge in the communicable area 1 of the base station BS1, and the mobile station MS2 is located near the base station in the communicable area 2 of the base station BS2.

  When receiving the signal transmitted from the base station BS1, the mobile station MS1 extracts a pilot signal from the signal (receiver 202). The mobile station MS1 measures the reception level of pilot signals arranged in each channel (pilot determination unit 205). At this time, the reception level of pilot channel P1 is high, and the reception levels of other pilot channels P2 and P3 are low.

  The mobile station MS1 determines that a channel in which a pilot signal having a reception level higher than a predetermined threshold is arranged is an available channel (control unit 210). In this case, the mobile station MS1 determines that the communication channel CH1 corresponding to the pilot channel P1 is an available channel.

  The mobile station MS1 generates CQI information related to the available channel CH1 (response information generation unit 207). The mobile station MS1 transmits this CQI information to the base station BS1 together with information indicating that the CQI information is that of the channel CH1.

  Receiving this CQI information, the base station BS1 determines that transmission data to the mobile station MS1 should be transmitted through the channel CH1 because this CQI information is transmitted only for the channel CH1 (scheduler 127). .

  On the other hand, when receiving a signal transmitted from the base station BS2, the mobile station MS2 extracts a pilot signal from the signal (receiver 202). Mobile station MS2 measures the reception level of pilot signals arranged in each channel (pilot determination unit 205). At this time, since the mobile station MS2 is located in the vicinity of the base station BS2, the reception levels of the pilot channels P1, P2, and P3 are increased.

  The mobile station MS2 determines that a channel in which a pilot signal having a reception level higher than a predetermined threshold is arranged as an available channel (control unit 210). In this case, the mobile station MS2 determines that the channels CH1, CH2, and CH3 in which the pilot channels P1, P2, and P3 are arranged are usable channels.

  The mobile station MS2 generates CQI information related to the available channels CH1, CH2, and CH3, respectively (response information generation unit 207). The mobile station MS2 transmits each CQI information to the base station BS2 together with information indicating that each CQI information belongs to each channel CH1, CH2, and CH3.

  The base station BS2 that has received the CQI information has been sent about the channels CH1, CH2, and CH3, so that the transmission data to the mobile station MS2 should be transmitted through the channels CH1, CH2, and CH3. Is determined (scheduler 127).

<Operation and effect in this embodiment>
Hereinafter, the operation and effect of the wireless communication system in the above-described embodiment will be described. In the wireless communication system according to the present embodiment, the same plurality of communication channels are assigned to each adjacent base station apparatus, and at least one of the channels is assigned as a priority channel so that the adjacent base station apparatuses do not overlap each other. It is done.

  Each base station apparatus sets the transmission power of the pilot channel corresponding to the priority channel assigned to itself to be higher than the transmission power of the pilot channel corresponding to the other communication channels.

  As a result, the mobile station apparatus that has received the pilot signal transmitted from the base station apparatus can receive all the pilot signals according to the position when the mobile station apparatus is in a position close to the base station apparatus. However, when it exists in a position far from the base station apparatus, only the pilot signal corresponding to the priority channel or other pilot signals are received in a state where the reception level is low at the same time.

  That is, in the mobile station apparatus, a pilot signal is extracted from the received signal, the reception level of each extracted pilot signal is measured, and a pilot having a reception level higher than a predetermined threshold among the measured reception levels A communication channel corresponding to the signal is determined as an available channel. The mobile station apparatus generates CQI information for each communication channel determined as an available channel, and transmits the CQI information to the base station apparatus.

  In the base station apparatus, communication channels that can be used by each mobile station apparatus are recognized based on the CQI information transmitted from each mobile station apparatus. For example, a communication channel in which CQI information is not transmitted is recognized as not an available channel for the mobile station device.

  Thus, according to the radio communication system in the present embodiment, the mobile station apparatus can determine an appropriate available channel according to the location by measuring the reception level of the pilot channel. As a result, even if a plurality of identical communication channels are assigned to adjacent base station apparatuses, usable channels that do not cause interference are determined in the mobile station apparatus, so that high communication quality is maintained. High frequency utilization efficiency can be realized.

[Modification]
In the wireless communication system in the above-described embodiment, OFDM is used as a wireless communication method between the base station and the mobile station. However, a TDMA (Time Division Multiple Access) method, a CDMA method, a W-CDMA method, and the like are used. You may make it utilize. In this case, the mobile stations MS1 and MS2 may be configured to correspond to the receiver 202 and the transmitter 203, and the base stations BS1 and BS2 may be configured to correspond to the communication method of the transmitter 121 and the receiver 111.

Claims (11)

In a base station apparatus that wirelessly communicates with a mobile station using a plurality of communication channels and pilot channels corresponding to each communication channel,
Power control means for setting at least one of the plurality of communication channels as a priority channel and setting transmission power of a pilot channel corresponding to the priority channel higher than transmission power of pilot channels corresponding to other communication channels;
A base station apparatus comprising: Selecting means for selecting a communication channel corresponding to channel information transmitted from the mobile station as a communication channel to be used for transmitting data addressed to the mobile station from the plurality of communication channels;
The base station apparatus according to claim 1.   The base station apparatus according to claim 1, wherein the power control unit determines the priority channel so as not to overlap between adjacent base station apparatuses. A plurality of communication channels and a pilot channel corresponding to each of the communication channels are allocated, and transmission power of a pilot channel corresponding to at least one of the plurality of communication channels is transmitted to a pilot channel corresponding to another communication channel. In a mobile station device that performs radio communication with a base station that is set higher than power,
Measuring means for measuring a reception level of a pilot channel transmitted from the base station;
Determining means for determining at least one of the plurality of communication channels as an available communication channel according to the reception level;
A mobile station apparatus comprising: The determining means determines a communication channel corresponding to a pilot channel having a reception level larger than a predetermined threshold among the reception levels measured by the measurement means as an available communication channel.
The mobile station apparatus according to claim 4.   The mobile station apparatus according to claim 4, further comprising transmission means for generating channel information related to the available communication channel and transmitting the channel information to the base station. In a mobile communication system having a mobile station and a base station, wherein the mobile station and the base station communicate wirelessly using a plurality of communication channels and pilot channels corresponding to the communication channels,
The base station
Power control means for setting at least one of the plurality of communication channels as a priority channel and setting transmission power of a pilot channel corresponding to the priority channel higher than transmission power of pilot channels corresponding to other communication channels;
The mobile station
Measuring means for measuring a reception level of a pilot channel transmitted from the base station;
Determining means for determining at least one of the plurality of communication channels as an available communication channel according to the reception level;
A mobile communication system comprising: The mobile station determination means determines a communication channel corresponding to a pilot channel having a reception level larger than a predetermined threshold among the reception levels measured by the measurement means as an available communication channel.
The mobile communication system according to claim 7.   The mobile communication system according to claim 7, wherein the power control means of the base station determines the priority channel so as not to overlap between adjacent base stations. The mobile station
Further comprising transmission means for generating channel information relating to the available communication channel and transmitting it to the base station;
The base station
Further comprising selection means for selecting at least one communication channel to be used for transmitting data addressed to the mobile station from the plurality of communication channels based on channel information transmitted from the mobile station.
The mobile communication system according to claim 7.   The mobile communication system according to claim 10, wherein the selection unit of the base station selects a communication channel corresponding to channel information transmitted from the mobile station as a communication channel used for transmitting data addressed to the mobile station. .

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