JP2013012874A - Communication system, communication method, base station, and mobile station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the throughput of a registered mobile station with a femto base station while at the same time to reduce interference with an unregistered mobile station.SOLUTION: In a communication system in which a mobile station not registered with a first base station communicates with a second base station, a mobile station provides a receiving unit for receiving a radio signal transmitted by the first base station and a radio signal transmitted by the second base station, and a transmitting unit for transmitting reception signal information related to the received radio signal, and the first base station provides a receiving unit for receiving the reception signal information transmitted by the mobile station, and a transmitting unit for intermittently transmitting a radio signal based on the reception signal information.

Description

  The present disclosure relates to a communication system, a communication method, a base station, and a mobile station.

  There are femto base stations to eliminate areas with poor radio wave conditions such as building gaps, indoors, underground malls, and high-rise areas. The femto base station is installed in a small office such as a home or SOHO (Small Office / Home Office), and covers a limited range with a radius of about several tens of meters. The femto base station is connected to a cellular phone core network via a fixed line connected to a fixed telephone in the home, that is, a general line such as a telephone line, an optical fiber, or a cable for CATV (Common Antenna TeleVision).

  As shown in FIG. 1, a cell (femto cell) formed by the above-described femto base station may overlap with a cell (macro cell) formed by a macro base station.

  This is because the femto base station is set not only in the dead zone outside the macro cell but also in the macro cell, thereby improving the communication environment such as a place where the radio wave condition in the macro cell is bad.

  In addition, while it is forced to reinforce facilities for increasing voice and data communication traffic, the introduction of femto base stations reduces costs compared to adding macro base stations, leading to the mobile phone's core network. Many mobile phone operators expect femto base stations to spread because the load can be reduced. Therefore, in order to spread the femto base stations, it is conceivable that the mobile phone operators provide femto base stations that can be easily purchased by individuals.

  For the femto base stations that can be purchased, it has been proposed to provide a user restriction for performing communication only with mobile stations registered by the purchased user.

  FIG. 2 is a schematic diagram showing a communication state between a femto base station and a mobile station with user restrictions.

  The femto base station 21 is a femto base station that can be purchased by an individual user. By registering 23 in the figure with the femto base station 21, the femto base station 21 permits communication with the registered mobile station 23. To do. That is, the femto base station 21 restricts the mobile stations that permit communication to only the mobile stations that are registered in the own station.

  Therefore, even if the unregistered mobile station 24 exists in the femtocell 22, the femto base station 21 and the unregistered mobile station 24 cannot communicate. For such an unregistered mobile station 24, the radio signal transmitted by the femto base station 21 may cause interference.

  FIG. 3 is a schematic diagram illustrating a problem of interference caused by a radio signal of the femto base station.

  In the figure, reference numeral 33 denotes an unregistered mobile station that is not registered in the femto base station 32 and is not allowed to communicate with the femto base station 32. In the figure, 34 is a registered mobile station of the femto base station 32, and communication with the femto base station 32 is permitted.

  At this time, since the unregistered mobile station 33 exists near the femto base station 32, the signal transmitted from the femto base station 32 to the registered mobile station 34 also interferes with the unregistered mobile station 33. There is a risk. In other words, even if the unregistered mobile station 33 exists in a place where the received power from the femto base station 32 is large, communication with the femto base station 32 is not permitted, so that the handover to the femto base station 32 cannot be performed. Communicate with the macro base station 31. Therefore, as the unregistered mobile station 33 approaches the femto base station 32 and the received power from the femto base station 32 increases, the signal from the femto base station 32 becomes an interference for the unregistered mobile station 33. .

  To solve the above problem, when the radio resource of the mobile station that receives the control channel from the macro base station detects high interference, the mobile station that detected the interference reduces the interference to the femto base station. There has been proposed a method in which a request to be transmitted is transmitted and the femto base station reduces transmission power (see, for example, Patent Document 1).

Special table 2011-514040

  However, when the above technique is applied, there is a possibility that the original service cannot be provided to the user who purchased the femto base station.

  For example, assume that a user purchases a femto base station to cover a dead zone. At this time, the unregistered mobile station detects interference from the femto base station, and notifies the femto base station of an interference reduction request, whereby the femto base station reduces the transmission power.

  Reducing the transmission power by the femto base station is equivalent to reducing the cell range and covering the area. Therefore, if the femto base station reduces the cell range, the dead zone covered by the femto base station will partly revive, and the registered mobile stations present in the restored dead zone area Communication will be cut off suddenly. Even if a user of a registered mobile station purchases a femto base station personally and installs it at home, there is a risk that an area incapable of communication will occur at home due to an instruction from a third party. This can be an impediment to purchasing will by femto base stations.

  However, since the number of femto base stations is expected to increase in the future, the influence of interference caused by the femto base stations is increased by increasing the number of femto base stations considering only registered mobile stations. In other words, the increased interference may cause the communication status of unregistered mobile stations to deteriorate even in public places.

  One of the objects of the disclosed communication system, communication method, base station, and mobile station has been devised in view of the above-described problems, and improves the throughput of the registered mobile station of the femto base station and at the same time moves out of registration. To reduce the interference on the station.

  In addition, the present invention is not limited to the above-mentioned object, and is an effect derived from each configuration shown in the embodiment for carrying out the invention to be described later. I can do it.

  In order to solve the above-mentioned problem, the invention disclosed herein is a communication system in which a mobile station that is not registered in a first base station communicates with a second base station. The mobile station transmits a radio signal transmitted by the first base station. And a reception unit that receives a radio signal transmitted by the second base station, and a transmission unit that transmits reception signal information related to the received radio signal. The first base station receives reception signal information transmitted by the mobile station. And a transmitter that intermittently transmits a radio signal based on the received signal information.

  According to the present disclosure, the femto base station performs intermittent transmission based on information received from an unregistered mobile station, so that the femto base station performs interference reduction without reducing the cell range. . Therefore, the invention of the present disclosure can maintain communication with a registered mobile station while reducing interference given to an unregistered mobile station.

Schematic diagram showing the relationship between femtocells and macrocells Overview diagram showing communication status between femto base station and mobile station Schematic diagram showing the femto base station interference problem 1 is a schematic diagram of a communication system according to a first embodiment. Functional block diagram of unregistered mobile station according to the first embodiment Hardware configuration diagram of unregistered mobile station according to the first embodiment Functional block diagram of a femto base station according to the first embodiment Hardware configuration diagram of femto base station according to the first embodiment The figure which shows an example of the channel for interference reduction request | requirement which concerns on 1st Embodiment. The flowchart which shows the process and operation | movement when the registration mobile station which concerns on 1st Embodiment determines an interference level. The flowchart which shows the process and operation | movement of the random access function part of the femto base station which concerns on 1st Embodiment. The flowchart which shows the process and operation | movement of the timing determination part of the femto base station which concerns on 1st Embodiment. Schematic diagram of a communication system according to the second embodiment Functional block diagram of a femto base station according to the second embodiment The flowchart which shows the process and operation | movement of the random access function part of the femto base station which concerns on 2nd Embodiment. The flowchart which shows a process and operation | movement about the process and operation | movement of the frequency determination part of the femto base station which concerns on 2nd Embodiment. Schematic diagram of a communication system according to the third embodiment Functional block diagram of unregistered mobile station according to the third embodiment Functional block diagram of a femto base station according to the third embodiment The figure which shows an example of the channel determined by the stop request | requirement frequency determination part of the unregistered mobile station which concerns on 3rd Embodiment. The figure which shows an example of matching with the channel for interference reduction request | requirement which the channel determination part of the femto base station which concerns on 3rd Embodiment determines, and a frequency band The flowchart which shows the process and operation | movement of the random access function part of the femto base station which concerns on 3rd Embodiment. The flowchart which shows the process and operation | movement of the frequency detection part of the femto base station which concerns on 3rd Embodiment. Overview diagram of communication system according to fourth embodiment Functional block diagram of unregistered mobile station according to the fourth embodiment Functional block diagram of a femto base station according to the fourth embodiment Functional block diagram of a macro base station according to the fourth embodiment Overview diagram of communication system according to fifth embodiment The figure which shows an example of the radio signal which performs the transmission stop of the femto base station which concerns on 5th Embodiment

<First Embodiment>
In the first embodiment, in a communication system in which an unregistered mobile station of a femto base station communicates with a macro base station, the unregistered mobile station transmits a radio signal transmitted by the femto base station and a radio signal transmitted by the macro base station. The femto base station intermittently transmits the radio signal based on the information related to the radio signal transmitted by the mobile station.

  That is, in the first embodiment, the femto base station recognizes that there is an unregistered mobile station that is receiving interference by notifying the femto base station of information related to the radio signal received by the unregistered mobile station. .

  Then, when there is an unregistered mobile station receiving interference, the femto base station performs intermittent transmission, thereby reducing interference with the unregistered mobile station.

  In addition, as a technique for reducing interference caused by the femto base station, the femto base station intermittently stops transmitting radio signals.

  In the first embodiment, the interference reduction request is an example of information related to the radio signal, but the information related to the radio signal is not limited to the interference reduction request, for example, information indicating the reception power of the macro base station and the presence / absence of interference. Etc.

  The communication system according to the first embodiment will be described with reference to FIGS.

  FIG. 4 is a schematic diagram of the communication system according to the first embodiment.

  As shown in FIG. 4, the communication system according to the first embodiment realizes interference reduction in the communication system in which the unregistered mobile station 43 of the femto base station 42 communicates with the macro base station 41.

  The macro base station 41 is a public base station, and one base station can radiate radio waves in the range of several kilometers to several tens of kilometers. This range is called a cell. The macro base station 41 is installed on the rooftops of buildings or condominiums, utility poles, telephone boxes, and the like, and in some suburbs and mountains, it is installed using steel towers.

  As described above, the femto base station 42 is a base station for eliminating areas with poor radio wave conditions such as building gaps, indoors, underground malls, and high-rise areas. The femto base station 41 is installed in a small office such as a home or SOHO, and covers a range (femtocell) having a radius of about several tens of meters. The femto base station is connected to the core network via a fixed line connected to a fixed telephone in the home, that is, a telephone line, an optical fiber, a cable for CATV, and the like.

  Further, the femto base station 42 can be purchased by an individual user or the like, and communicates with the mobile station 44 by registering the mobile station 44 in the femto base station 42. For example, it becomes possible to register by recording the ID of the mobile station owned by the purchased user in the femto base station.

  The mobile station 43 communicates with the macro base station 41 and is a non-registered mobile station for the femto base station 42, and the femto base station 42 does not communicate with the mobile station 43. The mobile station 44 is a registered mobile station for the femto base station 42 and communicates with the femto base station 42 when it belongs to the cell range of the femto base station 42.

  Hereinafter, the operation of the communication system in the first embodiment will be described.

  When the mobile station 43 determines that the radio signal transmitted by the femto base station 42 causes interference, the mobile station 43 transmits an interference reduction request to the femto base station 42. At this time, the mobile station 43 transmits an interference reduction request to the femto base station 42 using the random access channel.

  When the femto base station 42 receives the interference reduction request from the mobile station 43, the femto base station 42 determines the timing for stopping the transmission of the radio signal, and implements intermittent transmission by periodically stopping the transmission of the radio signal at the determined timing. .

  It is one of the features of the present invention to use a random access channel when notifying an interference reduction request.

  In the prior art, an interference reduction request is transmitted to the femto base station by a unicast message or the like, but this cannot guarantee whether a femto base station having a user restriction can be recognized.

  This is because when the femto base station provides a user restriction that allows communication only to mobile stations that have already been registered in the femto base station, the femto base station rejects access from unregistered mobile stations. Configuration is taken. Therefore, even if an unregistered mobile station transmits a unicast message to the femto base station, the femto base station does not accept the message before confirming the content. That is, when the femto base station recognizes that the message is transmitted from an unregistered mobile station, the femto base station is likely to discard the message.

  Therefore, in the prior art, unless the interference reduction request is recognized by the femto base station, the femto base station does not reduce the transmission power and the interference with the unregistered mobile station is not mitigated. Using a message is only a wasteful power consumption for an unregistered mobile station.

  Here, the present invention proposes a method for solving this problem by using a random access channel.

  Moreover, even if it is permitted to receive a unicast message, the unregistered mobile station uses radio resources that should be exclusively occupied only by the registered mobile station at the femto base station. It is not preferable.

  The present invention proposes a method for solving this problem by using a random access channel.

  The random access channel will be described later with reference to FIG.

  The above communication system can reduce interference only when there is an unregistered mobile station receiving interference.

  FIG. 5 is a functional block diagram of the unregistered mobile station of the femto base station according to the first embodiment.

  The unregistered mobile station 50 according to the first embodiment receives a radio signal transmitted from an unregistered femto base station and a radio signal transmitted from a communicating macro base station, and relates to the received radio signal. Information (interference reduction request in this embodiment) is transmitted to the femto base station.

  As illustrated in FIG. 5, the unregistered mobile station 50 according to the first embodiment includes an antenna 51, a reception unit 52, a measurement unit 53, an interference determination unit 54, and a transmission unit 55.

  The antenna 51 transmits a radio signal output from the transmitter 55 to the macro base station and the femto base station using radio waves as media, and receives signals transmitted from the macro base station and femto base stations using radio waves as media. The wireless signal is output to the receiving unit 52.

  The receiving unit 52 receives a radio signal transmitted from the macro base station and the femto base station via the antenna 51, and outputs the received radio signal to the measuring unit 53.

  The measurement unit 53 measures the received power of each of the signal received from the macro base station and the signal received from the femto base station.

  Here, as a method for measuring received power, a method using a pilot signal transmitted from a base station is generally known.

  The base station constantly transmits a signal pattern that is unique at least between neighboring cells as a pilot signal. As a cell-specific pilot signal pattern, for example, a long-period pseudo-random number or a sequence orthogonal between cells is used. The mobile station can estimate the received power in which the interference from other cells and the influence of noise are suppressed by removing the pilot signal from the base station for which the received power is to be measured by correlation calculation and averaging it.

  The measurement unit 53 measures the received power from each base station by the above-described processing for the radio signal input from the reception unit 52 and inputs it to the interference determination unit 54.

  Here, the received power of each radio signal received from the macro base station and the femto base station is measured, but the received power of either the macro base station or the femto base station may be measured. The error correction rate and S / N ratio of the received signal from the macro base station may be measured.

  The interference determination unit 54 determines the interference level of the radio signal received from the macro base station based on the measurement result input from the measurement unit 53. For example, when the reception power of the radio signal of the femto base station is larger than the reception power of the radio signal of the macro base station, the interference determination unit 54 determines that the radio signal transmitted by the femto base station is interference. judge.

  However, the determination method is not limited to the above determination method. For example, when the received power of the macro base station is equal to or lower than a threshold value, it may be determined that the interference level is high, or an error correction rate, S / N ratio, or the like may be used.

  Then, the interference determination unit 54 outputs an interference reduction request to the transmission unit 55 according to the interference level received from the macro base station. That is, when it is determined that the radio signal transmitted by the femto base station causes interference, an interference reduction request that requests to reduce the interference is output to the transmission unit 55.

  The transmission unit 55 transmits the interference reduction request input from the interference determination unit 54 to the femto base station via the antenna. Here, the transmission unit 55 transmits the interference reduction request to the femto base station using a channel used for transmission of the interference reduction request determined in advance in the femto base station. For example, the interference reduction request is transmitted using a part of the random access channel.

  In the present embodiment, the unregistered mobile station transmits information on the radio signal to the femto base station via the antenna. However, the radio signal is transmitted to the macro base station communicating with the mobile station. May be transmitted to the femto base station via the host station.

  FIG. 6 is a hardware configuration diagram of the unregistered mobile station according to the first embodiment.

  As illustrated in FIG. 6, the mobile station 60 includes an antenna 601, an RF unit 602, a baseband function unit 603, and a CPU 604. Furthermore, the RF unit 602 includes a duplexer 605, a down converter 606, an ADC 607, a DAC 612, and an up converter 613. The baseband function unit 603 includes a demodulator 608, a decoder 609, and an encoding unit. 610 and a modulator 611.

  The antenna 601 transmits a transmission signal output from the RF unit 602 to the macro base station and the femto base station using radio waves as a medium, and receives a signal transmitted from the macro base station and the femto base station using radio waves as a medium. The received signal is output to the RF unit 602.

  An RF (Radio Frequency) unit 602 converts data to be transmitted by a predetermined communication method into a high-frequency signal and transmits it from the antenna 601, or converts a high-frequency signal input from the antenna 601 into a data signal. . Note that the processing in the RF unit 602 is realized by the duplexer 605, the down converter 606, the ADC 607, the DAC 612, and the up converter 613.

  The duplexer 605 is for sharing a single transmission / reception antenna, and electrically separates the transmission path and the reception path.

  When a signal is input, the down-converter 606 converts the input radio wave into an intermediate frequency that is easy to process. The converted intermediate frequency radio signal is output to the ADC 607.

  An ADC (Analog to Digital Converter) 607 is an analog-digital converter, which converts an input analog signal into a digital signal and outputs a received signal to the baseband function unit 603.

  A DAC (Digital to Analog Converter) 612 is a digital-analog converter, which converts the modulation signal input from the baseband function unit 603 into an analog signal and outputs the analog signal to the up-converter 613.

  The up-converter 613 raises the input modulated wave to a target frequency and outputs it to the duplexer 605.

  The baseband function unit 603 demodulates and decodes the signal input from the RF unit 602 and outputs the demodulated signal to the CPU 604. Further, the data signal input from the CPU 604 is encoded and modulated and output to the RF unit 602. Note that the baseband function unit 603 in this embodiment includes a demodulator 608, a decoder 609, an encoder 610, and a modulator 611, and the receiving unit 52 in FIG. The transmission unit 55 in FIG. 5 is realized by an encoder 610 and a modulator 611.

  The demodulator 608 restores the modulated signal that is the received signal input from the RF unit 602, and outputs it to the decoder 609 as demodulated data. Demodulation is performed corresponding to each modulation method.

  The decoder 609 decodes the encoded data signal that is the demodulated data input from the demodulator 608 and outputs the decoded data signal to the CPU 604 as decoded data.

  A CPU (Central Processing Unit) 604 is an example of a configuration that controls various functional units, and executes various application units and controls various functional units and reads / writes data to / from a memory. Note that the functions of the measurement unit 53 and the interference determination unit 54 in FIG. 5 in the present embodiment are realized by the CPU 604.

  The encoder 610 encodes the signal input from the CPU 604 according to a predetermined rule, and outputs the encoded signal to the modulator 611 as encoded data. The modulator 611 digitally modulates the encoded data input from the encoder 610 and outputs the result to the RF unit 602.

  FIG. 7 is a functional block diagram of the femto base station according to the first embodiment.

  The femto base station according to the first embodiment receives information on a radio signal received by an unregistered mobile station, and intermittently transmits a radio signal transmitted by the femto base station based on the information on the radio signal.

  As illustrated in FIG. 7, the femto base station 70 according to the first embodiment includes an antenna 71, a reception unit 72, a random access function unit 73, a timing determination unit 74, and a transmission unit 75. Further, the random access function unit 73 includes a channel determination unit 76 and a request determination unit 77, and the timing determination unit 74 includes a timer 78.

  The antenna 71 transmits a radio signal output from the transmission unit 75 to a registered mobile station and an unregistered mobile station using a radio wave as a medium, and a radio signal transmitted from the registered mobile station and an unregistered mobile station using a radio wave as a medium. And outputs the received radio signal to the receiving unit 72.

  The receiving unit 72 receives radio signals from the registered mobile station and the unregistered mobile station via the antenna 71, and outputs the received radio signal to the random access function unit 73.

  The random access function unit 73 determines whether or not an interference reduction request is included in the radio signal input from the reception unit 72. If the interference reduction request is included, the random access function unit 73 determines that the interference reduction request is a timing determination unit. Output to 74. At this time, the random access function unit 73 determines whether the interference reduction request is included in the channel by monitoring a random access channel for interference reduction request described later, and when the interference reduction request is included. The interference reduction request is output to the timing determination unit 74. The function in the random access function unit 73 is realized by a channel determination unit 76 and a request determination unit 77 described later.

  The channel determination unit 76 determines a channel to be used when an unregistered mobile station transmits an interference reduction request. In this embodiment, the channel determination unit 76 determines a channel to be used when an unregistered mobile station transmits an interference reduction request from random access channels that can be arbitrarily accessed by the mobile station. Then, the channel determination unit 76 includes the determined channel as broadcast information in the broadcast information or the like, and transmits it to the unregistered mobile station via the transmission unit 75 and the antenna 71. Further, the channel determination unit 76 outputs the channel information to the request determination unit 77.

  The request determination unit 77 determines whether or not an interference reduction request from an unregistered mobile station is included in the received radio signal by monitoring the channel indicated by the channel information input from the channel determination unit 76. When the interference reduction request is included, the interference reduction request is output to the timing determination unit 74.

  When an interference reduction request is input from the request determination unit 77, the timing determination unit 74 determines the timing for stopping the radio signal transmitted by the femto base station. That is, when an interference reduction request is input from the request determination unit 77 of the random access function unit 73, the timing for stopping the radio signal transmitted to the registered mobile station is determined, and the determined timing is output to the transmission unit 75 as timing information. To do. The transmission stop timing may be determined from, for example, a number uniquely assigned to each cell. However, since it is not desirable to stop transmission of information essential for cell maintenance, for example, broadcast information and the like, it is preferable to exclude the timing for transmitting broadcast information and the like that are known in advance from the transmission stop timing.

  The transmission unit 75 transmits a radio signal to the registered mobile station via the antenna 71 at a timing other than the timing indicated by the timing information input from the timing determination unit 74. That is, for the timing input from the timing determination unit 74, communication by intermittent transmission is realized by stopping the transmission of the radio signal. Here, regarding the transmission stop timing, among the control information other than the user data, information that is essential for maintaining the cell and cannot be stopped from transmission does not have to be a target of transmission stop.

  In addition, the transmission unit 75 transmits the channel information input from the channel determination unit 76 to the unregistered mobile station via the antenna 71 using broadcast information or the like. By transmitting the channel information to the unregistered mobile station, it is possible to notify the unregistered mobile station of the interference reduction request channel.

  Further, when an interference reduction request is input from the channel determination unit 76, the timing determination unit 74 outputs a control signal to the timer 78, and the timer 78 receives the timing information from the transmission unit 75. Measure the elapsed time from When the preset elapsed time is reached, the transmission unit 75 stops intermittent transmission and transmits a radio signal to the registered mobile station via the antenna 71 as usual.

  FIG. 8 is a hardware configuration diagram of the femto base station in the first embodiment.

  As shown in FIG. 8, the femto base station 80 includes an antenna 801, an RF unit 802, and a baseband function unit 803. Further, the RF unit 802 includes a duplexer 804, a down-conversion 805, an ADC 806, a DAC 812, and an up-converter 813. The baseband function unit 803 includes a demodulator 807, a decoder 808, and a layer 2 function. A unit 809, an encoder 810, and a modulator 811.

  The antenna 801 transmits a transmission signal output from the RF unit 802 to a registered mobile station and an unregistered mobile station using a radio wave as a medium, and transmits a signal transmitted from the registered mobile station and an unregistered mobile station using a radio wave as a medium. The received radio signal is received and output to the RF unit 802.

  The RF unit 802 converts data to be transmitted by a predetermined communication method into a high-frequency signal and transmits it from the antenna 801, or converts a high-frequency signal input from the antenna 801 into a data signal. Note that the processing in the RF unit 802 is realized by the duplexer 804, the down-conversion 805, the ADC 806, the DAC 812, and the up-converter 813.

  The duplexer 804 is for sharing a single transmission / reception antenna, and electrically separates the transmission path and the reception path.

  When a signal is input, the down-conversion 805 outputs the signal to the ADC 806 after down-converting to a baseband signal using a local signal or the like.

  The ADC 806 is an analog-digital converter, which converts an input analog signal into a digital signal and outputs a reception signal to the baseband function unit 803.

  The DAC 812 is a digital-analog converter, which converts the modulation signal input from the baseband function unit 803 from an analog signal to a digital signal and outputs the digital signal to the up-converter 813.

  The up-converter 813 generates a carrier band signal by multiplying the input signal by a carrier wave, and outputs the signal to the duplexer 804.

  The baseband function unit 803 demodulates and decodes the signal input from the RF unit 802 and outputs it to the core network. Further, the data signal input from the core network is encoded and modulated and output to the RF unit 802. The baseband function unit 803 includes a demodulator 807, a decoder 808, a layer function unit 809, an encoder 810, and a modulator 811. The receiving unit 72 in FIG. 7 includes a demodulator 807 and a decoder 808. The transmitter 75 shown in FIG. 7 is realized by an encoder 810 and a modulator 811.

  The demodulator 807 restores the modulated signal that is the received signal input from the RF unit 802 and outputs the demodulated data to the decoder 808 as demodulated data. Demodulation is performed corresponding to each modulation method.

  The decoder 808 decodes the encoded data signal that is the demodulated data input from the demodulator 807 and outputs the decoded data signal to the layer 2 function unit 809 as decoded data.

  The layer 2 function unit 809 performs packetization of the decoded data input from the decoder 808 and transmits it to the core network. Also, error correction or the like of the data signal input from the core network is executed and output to the encoder 810. The layer 2 function unit 809 is realized by a CPU.

  The encoder 810 encodes the signal input from the layer 2 function unit 809 according to a predetermined rule, and outputs the encoded data to the modulator 811 as encoded data. The modulator 811 digitally modulates the encoded data input from the encoder 810 and outputs it to the RF unit 802.

  The CPU 814 is an example of a configuration that controls various functional units, and executes various application units and controls various functional units and reads / writes data to / from a memory. It also controls packet processing and call processing. The CPU 814 implements the functions of the random access function unit 73 and the timing determination unit 74 in FIG.

  FIG. 9 is a diagram illustrating an example of channels determined by the channel determination unit in the femto base station according to the first embodiment.

  Here, the superiority of using the random access channel when notifying the interference reduction request will be described.

  When a mobile station performs initial access for establishing a radio link, re-establishment of the radio link, handover that requires uplink synchronization, etc., the mobile station transmits a random access preamble to the base station. Send. A channel used when transmitting the random access preamble is a random access channel.

  The random access preamble includes a signature that is a signal pattern representing information. By preparing dozens of types of signatures and selecting and using them, several bits of information can be expressed. Currently, in EUTRA, 6-bit information is transmitted from a mobile station to a base station using a signature. For these 6 bits, 64 kinds of preambles of 2 6 are prepared. This 6-bit information is called a preamble ID.

  Of the 6-bit preamble ID, a random ID is assigned to 5 bits, and information indicating the amount of information necessary for the random access request is assigned to the remaining 1 bit.

  That is, there is no information for identifying a mobile station in a random access preamble transmitted using a random access channel. For the femto base station, the signal is transmitted from a registered mobile station or transmitted from an unregistered mobile station. It is not possible to recognize whether the signal is correct.

  Utilizing this fact, the present invention notifies the interference reduction request using a random access channel.

  Further, since the random access channel is a channel reserved in advance in the base station, a new radio resource is not secured. That is, the interference reduction request can be notified without using the radio resource that the registered mobile station should occupy.

  The random access channel 90 is a channel that the mobile station can transmit to the base station at an arbitrary timing, and is a channel used for establishing an uplink.

  The channel determination unit 76 determines the normal channel 91 and the interference reduction request channel 92 among the random access channels 90 described above, and outputs the determined interference reduction request channel 92 to the request determination unit 77 as channel information. .

  The normal channel 91 is a channel used for uplink establishment, and the interference reduction request channel 92 is a channel for an unregistered mobile station to transmit an interference reduction request.

  The unregistered mobile station transmits an interference reduction request to the femto base station using the interference reduction request channel 92 included in the channel information received from the femto base station.

  The femto base station determines whether or not an interference reduction request is included in a radio signal received from an unregistered mobile station by monitoring the interference reduction request channel 92 determined by the channel determination unit 76.

  FIG. 10 is a flowchart showing processing and operations when the unregistered mobile station of the femto base station determines the interference level in the first embodiment.

The receiving unit 52 in the unregistered mobile station 50 outputs the radio signal transmitted from the macro base station and the radio signal transmitted from the femto base station to the measuring unit 53. (S100)
The measurement unit 53 measures the reception power of the radio signal transmitted from the macro base station and the radio signal transmitted from the femto base station input from the reception unit 52, and outputs the measurement result to the interference determination unit 54.

The interference determination unit 54 calculates the difference between the reception power (P0) of the radio signal of the macro base station measured by the measurement unit 53 and the reception power (Pf) of the radio signal of the femto base station. Is too large, the interference level of the radio signal received from the macro base station is high, so that it is determined that the interference is received from the femto base station. When the calculation result is smaller than the threshold value T, it is determined that no interference is received from the femto base station because the interference level of the radio signal received from the macro base station is small. (S101)
In step S101, when the interference determination unit 54 determines that no interference is received, the interference determination in the unregistered mobile station is terminated. (S103)
In step S <b> 101, when the interference determination unit 54 determines that interference has occurred, an interference reduction request is output to the transmission unit 55. The transmission unit 55 transmits the interference reduction request to the femto base station receiving the interference using the interference reduction request channel based on the channel information received from the femto base station. (S102)
When the transmission unit 55 transmits the interference reduction request to the femto base station, the interference determination in the unregistered mobile station is terminated. (S103)
According to the above flow, only when there is an unregistered mobile station receiving interference, the femto base station can be requested to reduce interference.

  FIG. 11 is a flowchart showing processing and operation of the random access function unit of the femto base station in the first embodiment.

When receiving the radio signal from the mobile station, the receiving unit 71 of the femto base station outputs the radio signal to the random access function unit 73. (S110)
When a radio signal is input from the reception unit 71, the determination unit 77 in the random access function unit 73 receives a radio signal by monitoring an interference reduction request channel based on channel information input from the channel determination unit 76. It is determined whether an interference reduction request is included in the signal. (S111)
If it is determined in step S111 that the interference reduction request is not included, the processing / operation in the random access function unit is terminated. (S113)
If it is determined in step S111 that the interference reduction request is included, the determination unit 77 in the random access function unit 73 outputs the interference reduction request to the timing determination unit 74. (S112)
When the random access function unit 73 outputs an interference reduction request to the timing determination unit 74, the processing / operation in the random access function unit 73 is terminated. (S113)
With the above flow, the femto base station can determine whether or not an interference reduction request is notified from an unregistered mobile station.

  FIG. 12 is a flowchart showing the processing / operation of the timing determination unit of the femto base station in the first embodiment.

When the signal is input from the random access function unit 73 (S120), the timing determination unit 74 determines whether the signal is an interference reduction request. (S121)
If it is an interference reduction request, the timer 78 in the timing determination unit 74 starts measuring time. If the timer 78 has already started measuring time, the timer 78 is initialized and the measurement is started again. (S122)
Here, the timer is initialized, for example, when a new interference reduction request is notified during measurement, but when it is not initialized, a new interference reduction request is notified. Regardless, the timer is not expired while the interference reduction for the new interference reduction request is not sufficient.

The timing determination unit 74 determines the timing for stopping the transmission of the radio signal transmitted to the registered mobile station together with the measurement start of the timer 78, and outputs the determined transmission stop timing to the transmission unit 75 as timing information. (S123)
Here, the transmission unit 75 performs intermittent transmission based on the timing information input from the timing determination unit 74.

The timer 78 measures the time during which a radio signal is transmitted at a timing other than the timing indicated by the timing information determined in step S123, that is, the time during which intermittent transmission is performed at this timing. (S124)
The timer 78 determines whether or not a predetermined time has elapsed. (S125)
When it is determined in S125 that the predetermined time has elapsed, the timing determination unit 74 sets an invalid value as timing information as the transmission stop timing (S126), and outputs timing information that is an invalid value to the transmission unit 75. . (S127)
Note that, when the timing information input from the timing determination unit 74 is an invalid value, the transmission unit 75 determines that a predetermined time has elapsed since the start of intermittent transmission, and stops the intermittent transmission.

The timing determination unit 74 ends the processing / operation by outputting timing information that is an invalid value to the transmission unit 75. (S128)
Through the above flow, the femto base station performs interference reduction by intermittent transmission.

  According to the first embodiment, the fem base station can reduce interference with an unregistered mobile station by performing interference reduction.

  If the femto base station does not receive an interference reduction request, the femto base station does not perform interference reduction, and can use all radio resources and provide communication at the optimum throughput at that time. Become. That is, radio resources can be used effectively.

  Further, by adopting intermittent transmission as an interference reduction technique, it is possible to reduce interference without reviving the dead zone.

  Another advantage of adopting intermittent transmission as interference reduction technology is that it can reduce the interference without excessive power reduction even for unregistered mobile stations that cannot directly communicate and request how much power to reduce. Can be implemented. Furthermore, since the femto base station can notify the mobile station under its own control of the timing of intermittent transmission, when the femto base station has stopped transmitting radio signals, the mobile stations under the femto base station also Since it can be suspended, the mobile station and the femto base station can save power.

  In the first embodiment, the femto base station performs interference reduction when receiving one interference reduction request from an unregistered mobile station. However, a threshold is provided, and an interference reduction request equal to or greater than the threshold is provided. If received, interference reduction may be performed. In this way, interference reduction can be performed only when interference is caused to many unregistered mobile stations without unnecessarily reducing throughput for the registered mobile stations of the femto base station. .

Second Embodiment
In the second embodiment, when the femto base station receives information related to a radio signal, use of at least a part of the frequency band corresponding to the information related to the received radio signal among the frequency bands used to transmit the radio signal To stop.

  That is, in the second embodiment, the radio signal transmitted by the femto base station is controlled so that intermittent transmission is performed in the frequency direction based on information on the radio signal. The second embodiment is different from the first embodiment in that intermittent transmission is performed in the frequency direction, not in the time direction.

  In the second embodiment, as in the first embodiment, the interference reduction request is an example of information on the radio signal. However, the information on the radio signal is not limited to the interference reduction request. Information indicating the presence or absence of power or interference may be used.

  A communication system according to the second embodiment will be described with reference to FIGS.

  Here, a functional block diagram of the unregistered mobile station (FIG. 5), a hardware configuration diagram of the unregistered mobile station (FIG. 6), a hardware configuration diagram of the femto base station (FIG. 8), and an example of an interference reduction request channel (FIG. 9), the flowchart (FIG. 10) showing the processing / operation when the unregistered mobile station determines the interference level is the same as in the first embodiment.

  FIG. 13 is a schematic diagram showing a communication system according to the second embodiment.

  As illustrated in FIG. 13, the communication system according to the second embodiment is realized in a communication system in which the unregistered mobile station 133 of the femto base station 132 communicates with the macro base station 131.

  The mobile station 133 is an unregistered mobile station that communicates with the macro base station 131 and does not communicate with the femto base station 132. The mobile station 134 is a registered mobile station that performs communication with the femto base station 132.

  Hereinafter, an outline of the communication system will be described.

  When it is determined that the unregistered mobile station 133 is receiving interference from the femto base station 132, the unregistered mobile station 133 transmits an interference reduction request to the femto base station 132 using the random access channel.

  When the femto base station 132 receives the interference reduction request from the unregistered mobile station 133, the femto base station 132 determines a frequency band to stop using, and performs radio signal transmission outside the determined frequency band to perform intermittent transmission in the frequency direction. Run.

  FIG. 14 is a functional block diagram of a femto base station according to the second embodiment.

  When the femto base station according to the second embodiment receives information on a radio signal, the femto base station uses at least a part of the frequency band used for transmitting the radio signal according to the information on the received radio signal. To stop.

  As illustrated in FIG. 14, the femto base station 140 according to the second embodiment includes an antenna 141, a reception unit 142, a random access function unit 143, a frequency determination unit 144, and a transmission unit 145. Furthermore, the random access function unit 143 includes a channel determination unit 146 and a request determination unit 147, and the frequency determination unit 144 includes a timer 148.

  Note that functional units (antenna 141, receiving unit 142, random access functional unit 143) similar to those in the first embodiment will not be described.

  When an interference reduction request is input from the request determination unit 147, the frequency determination unit 144 determines a frequency band to stop using from among the frequency bands used by the femto base station 140 for transmitting radio signals, The determined frequency band is output to the transmission unit 145 as frequency information. The function of the frequency determination unit 144 is realized by the CPU 814 in FIG.

  The transmission stop frequency band is determined by, for example, a method of generating from a unique number assigned to the own cell or a method of selecting from a band that is most unnecessary for the registered mobile station currently communicating. Also good. However, since it is not desirable to stop transmission of information essential for cell maintenance, for example, broadcast information and the like, it is preferable to exclude a frequency band for transmitting previously known broadcast information from the transmission stop frequency band.

  The transmission unit 145 transmits a radio signal to the registered mobile station via the antenna 141, except for the frequency band indicated by the frequency information input from the frequency determination unit 144. That is, for the frequency band indicated by the frequency information input from the frequency determination unit 144, intermittent transmission in the frequency direction is realized by stopping the transmission of the radio signal. The function of the transmission unit 145 is realized by the encoder 810 and the modulation unit 811 in FIG.

  Further, when an interference reduction request is input from the random access function unit 143, the frequency determination unit 144 outputs a control signal to the timer 148, and the timer 148 outputs the frequency information to the transmission unit 145. Measure the elapsed time since then.

  Then, when the elapsed time set in advance is reached, the transmission unit 145 stops the intermittent transmission and transmits a radio signal to the registered mobile station via the antenna 141 as usual.

  FIG. 15 is a flowchart illustrating a processing / operation flow of the random access function unit of the femto base station according to the second embodiment.

When receiving the radio signal from the unregistered mobile station, the receiving unit 142 of the femto base station outputs it to the random access function unit 143. (S150)
When a wireless signal is input from the receiving unit 142, the request determining unit 147 in the random access function unit 143 monitors the interference reduction request channel based on the channel information input from the channel determining unit 146, thereby receiving the wireless signal. It is determined whether an interference reduction request is included in the signal. (S151)
If it is determined in step S151 that the interference reduction request is not included, the processing / operation in the random access function unit is terminated. (S153)
If it is determined in step S151 that an interference reduction request is included, the request determination unit 147 in the random access function unit 143 outputs the interference reduction request to the frequency determination unit 144. (S152)
When the random access function unit 143 outputs an interference reduction request to the frequency determination unit 144, the processing / operation in the random access function unit 143 ends. (S153)
Through the above flow, the femto base station confirms whether an interference reduction request is notified from the unregistered mobile station.

  FIG. 16 is a flowchart showing the processing and operation of the frequency determination unit of the femto base station in the second embodiment.

When the frequency determination unit 144 receives a signal from the random access function unit 143 (S160), the frequency determination unit 144 determines whether the signal includes an interference reduction request. (S161)
When the interference reduction request is included, the timer 148 in the frequency determination unit 144 starts measuring elapsed time. If the timer 148 has already started measuring the elapsed time, the timer 148 is initialized and the measurement is started again. (S162)
Here, the reason for initializing the timer is the same as in the first embodiment.

The frequency determination unit 144 determines the frequency band in which the transmission of the radio signal transmitted to the registered mobile station is stopped when the timer 148 starts measurement, and outputs the transmission stop frequency band as frequency information to the transmission unit 145. (S163)
Here, the transmission unit 145 performs intermittent transmission in the frequency direction based on the frequency information input from the frequency determination unit 145.

The timer 148 measures the time during which a radio signal is transmitted outside the frequency band based on the frequency information determined in step S163, that is, the time during which intermittent transmission is performed after the use of the frequency band is stopped. (S164)
The timer 148 determines whether or not a predetermined time has elapsed. (S165)
If it is determined in S165 that the predetermined time has elapsed, the frequency determination unit 144 sets an invalid value in the frequency information as the transmission stop frequency band (S166), and outputs the frequency information that is an invalid value to the transmission unit 145. To do. (S167)
In addition, when the frequency information input from the frequency determination unit 144 is an invalid value, the transmission unit 145 determines that a predetermined time has elapsed since the start of intermittent transmission, and stops the intermittent transmission.

The frequency determination unit 144 outputs the frequency information that is an invalid value to the transmission unit 145, thereby ending the processing / operation. (S168)
By the above flow, the femto base station can execute intermittent transmission in the frequency direction when an interference reduction request is notified from an unregistered mobile station.

  According to the second embodiment, since the femto base station performs interference reduction by providing a transmission stop frequency band, the femto base station can perform voice communication even when there is an unregistered mobile station that is receiving interference. It is possible to reduce interference without affecting a call of a registered mobile station that is preferably a communication path such as a call that is narrow and continuous.

  In the first embodiment, intermittent transmission is performed in the time direction. In the second embodiment, intermittent transmission is performed in the frequency direction. However, intermittent transmission may be performed in both the time direction and the frequency direction.

  By doing so, interference reduction can be more reliably performed.

<Third Embodiment>
In the third embodiment, an unregistered mobile station transmits information on a radio signal including a frequency band requesting to stop transmission to the femto base station according to the interference level from the femto base station. Determines a frequency band that the femto base station stops using based on the received stop request frequency information, and transmits a radio signal in a frequency other than the determined frequency band.

  That is, in the third embodiment, control is performed so that the femto base station performs intermittent transmission in the frequency band notified from the unregistered mobile station receiving interference. Further, the third embodiment differs from the second embodiment in that the unregistered mobile station determines the transmission stop frequency instead of the femto base station.

  In the third embodiment, as in the first embodiment, the interference reduction request is an example of information related to the radio signal. However, the information related to the radio signal is not limited to the interference reduction request. For example, reception of a macro base station Information indicating the presence or absence of power or interference may be used.

  In the third embodiment, the unregistered mobile station determines the transmission stop frequency band, but is not limited to the frequency band. For example, the transmission stop timing may be determined and notified to the femto base station.

  A communication system according to the third embodiment will be described with reference to FIGS.

  Here, the hardware configuration diagram of the unregistered mobile station (FIG. 6), the hardware configuration diagram of the femto base station (FIG. 8), and the flowchart (FIG. 8) showing the processing and operation when the unregistered mobile station determines the interference level. 10) is the same as in the first and second embodiments.

  FIG. 17 is a schematic diagram showing a communication system according to the third embodiment.

  As shown in FIG. 17, the communication system according to the third embodiment is realized in a communication system in which the unregistered mobile station 173 of the femto base station 172 communicates with the macro base station 171.

  The mobile station 173 is an unregistered mobile station that does not communicate with the femto base station 172, and the mobile station 174 is a registered mobile station that performs communication with the femto base station 172.

  Hereinafter, an outline of the communication system will be described.

  If the unregistered mobile station 173 determines that interference is received from the femto base station 172, the unregistered mobile station 173 transmits an interference reduction request to the femto base station 172 using a random access channel. Furthermore, in order to reduce interference, the unregistered mobile station 173 transmits the frequency band for which transmission stop is requested as stop request frequency information.

  When the femto base station 172 receives the interference reduction request and stop request frequency information from the mobile station 173, the femto base station 172 stops the transmission of the radio signal in the frequency band corresponding to the stop request frequency information.

  FIG. 18 is a functional block diagram of an unregistered mobile station according to the third embodiment.

  The non-registered mobile station according to the third embodiment indicates a frequency band requesting the femto base station to reduce interference and stop transmission when it is determined that the radio signal transmitted by the femto base station causes interference. Send stop request frequency information.

  As illustrated in FIG. 18, the unregistered mobile station 180 includes an antenna 181, a reception unit 182, a measurement unit 183, an interference determination unit 184, a stop request frequency determination unit 185, and a transmission unit 186. The receiving unit 182 is realized by the demodulator 608 and the decoder 609, the measuring unit 183, the interference determining unit 184, and the stop request frequency determining unit 185 are realized by the CPU 604, and the transmitting unit 186 is an encoder 610 and a modulator 611. (See FIG. 6).

  The functional units (antenna 181, receiving unit 182, measuring unit 183, interference determining unit 184) similar to those in the first and second embodiments are the same as those in FIG.

  The measurement unit 183 measures the reception power of each of the signal received from the macro base station and the signal received from the femto base station via the antenna 181 and the reception unit 182 for each frequency band (for each channel), and the measurement result is interfered The result is output to the determination unit 184. At this time, the measurement unit 183 receives a pilot signal (known signal) from the base station and measures an SIR (Signal-to-Interference Ratio) of the received signal. Since the pilot signal is transmitted over the entire band, the quality of each band can be measured.

  The interference determination unit 184 determines the interference level of the radio signal received from the macro base station based on the measurement result input from the measurement unit 183.

  For example, when the reception power of the radio signal of the femto base station is larger than the reception power of the radio signal of the macro base station, the interference determination unit 184 increases the interference level of the radio signal transmitted by the macro base station, It is determined that there is interference from the base station.

  When the interference determination unit 184 determines that the radio signal transmitted by the femto base station causes interference, the interference determination unit 184 sends the interference reduction request and the received power for each frequency band of the radio signal received from the macro base station to the stop request frequency determination unit 185. Output.

  The stop request frequency determining unit 185 determines the frequency band with the lowest received power among the input received power for each frequency band as the frequency band requesting transmission stop, and determines the determined frequency band as stop request frequency information. And output to the transmitter 186 together with the interference reduction request.

  In the present embodiment, the frequency band with the lowest received power is an example of stop request frequency information, but the present invention is not limited to this. For example, two frequency bands, the frequency band with the lowest received power and the frequency band with the second lowest received power, may be included in the stop request frequency information.

  The transmission unit 186 transmits the interference reduction request to the femto base station through the antenna 181 in association with the stop request frequency information. Here, the transmission unit 185 transmits the interference reduction request and stop request frequency information to the femto base station using the channel determined in advance in the femto base station. For example, an interference reduction request is transmitted using a channel in which stop request frequency information and a frequency band are associated with each other among random access channels. The channel for transmitting the interference reduction request and stop request frequency information will be described later with reference to FIG.

  In this embodiment, the unregistered mobile station transmits the interference reduction request and stop request frequency band information to the femto base station via the antenna. However, the macro base station that is communicating with the mobile station May be transmitted to the femto base station via an upper station.

  FIG. 19 is a functional block diagram of a femto base station according to the third embodiment.

  When the femto base station according to the third embodiment determines that the received radio signal includes information on the radio signal, the femto base station, based on the frequency band notified in association with the interference reduction request, The frequency band to be stopped is determined from the frequency bands used by the femto base station for wireless signal transmission, and intermittent transmission is performed by transmitting the wireless signal outside the determined frequency band.

  As illustrated in FIG. 19, the femto base station 190 according to the third embodiment includes an antenna 191, a receiving unit 192, a random access function unit 193, a frequency detecting unit 194, and a transmitting unit 195. Further, the random access function unit 193 includes a channel determination unit 196 and a determination unit 197, and the frequency detection unit 194 includes a timer 198. The receiving unit 192 is realized by the demodulator 807 and the decoder 808, the random access function unit 193 and the frequency detecting unit 194 are realized by the CPU 814, and the transmitting unit 195 is realized by the encoder 810 and the modulator 811 ( (See FIG. 8).

  Note that description of the functional units (antenna 191 and receiving unit 192) similar to those in the first embodiment is omitted.

  The random access function unit 193 monitors the random access channel for interference reduction request, and when the interference reduction request is included in the channel, the random access function unit 193 receives reception channel information indicating the channel that has received the interference reduction request and the interference reduction request. It outputs to the frequency detection part 194. Further, the function in the random access function unit 193 is realized by a channel determination unit 196 and a request determination unit 197 described later.

  The channel determination unit 196 uses a channel used when the unregistered mobile station transmits an interference reduction request among the channels used for random access, and a frequency used for communication between the unregistered mobile station and the macro base station. The channel association is determined, and the unregistered mobile station is notified to the unregistered mobile station using the broadcast information or the like, using the determined channel and frequency-channel association as channel information via the transmission unit 195 and the antenna 191. Send to.

  Further, the channel determination unit 196 outputs the channel information to the request determination unit 197 and the frequency detection unit 194. The request determination unit 197 determines whether or not an interference reduction request is included in the radio signal received from the unregistered mobile station by monitoring a channel based on the channel information input from the channel determination unit 196. When the reduction request is included, the interference reduction request and the reception channel information are output to the frequency detection unit 194.

  When an interference reduction request is input from the request determination unit 197, the frequency detection unit 194 compares the reception channel information input from the request determination unit 197 with the channel information input from the channel determination unit 196, and stops the radio signal The frequency band to be detected is detected, and the detected frequency band is output to the transmission unit 195 as frequency information. In addition, the frequency band for stopping the radio signal is detected by comparing the reception channel information input from the request determination unit 197 with the channel information input from the channel determination unit 196, and the frequency band corresponding to the channel indicated by the reception channel information. Is detected as a transmission stop frequency band.

  The transmission unit 195 transmits a radio signal to the mobile station via the antenna 191 outside the frequency band indicated by the frequency information input from the frequency detection unit 194. That is, intermittent transmission is realized by stopping the transmission of the radio signal in the frequency band indicated by the frequency information input from the frequency detection unit 194.

  Further, when an interference reduction request is input from the random access function unit 193, the frequency detection unit 194 outputs a control signal to the timer 198, and the timer 198 outputs the frequency information to the transmission unit 195. Measure the elapsed time since then. When the preset elapsed time is reached, the transmission unit 195 stops intermittent transmission and transmits a radio signal to the mobile station via the antenna 191 as usual.

  FIG. 20 is a diagram illustrating an example of channels determined by the stop request frequency determining unit of the unregistered mobile station according to the third embodiment.

  FIG. 20 shows received power for each band of the macro base station measured by the measurement unit 183. As shown in FIG. 20, the vertical axis represents received power 201 and the horizontal axis represents frequency 202.

  In the case of the graph of FIG. 20, the reception quality is lowest in the hatched frequency band 203. Therefore, the stop request frequency determination unit 185 determines the frequency band for which transmission stop is requested as the frequency band 203 and outputs the frequency band 203 to the transmission unit 186 as stop request frequency information.

  FIG. 21 is an example of a frequency band corresponding to a channel used for transmission of an interference reduction request determined by the channel determination unit 196 of the third embodiment.

  As shown in FIG. 21, among the random access channels, channels 211 to 214 are allocated to the interference reduction request channel.

  Channel 211 is associated with frequency band 0-24 [kHz], channel 212 is frequency band 25-49 [kHz], channel 213 is frequency band 50-74 [kHz], and channel 214 is frequency band 75-100 [kHz]. ], Respectively.

  In addition, the unregistered mobile station transmits the interference reduction request to the femto base station using the channel corresponding to the stop request frequency information, so that the unregistered mobile station transmits the frequency band requesting the transmission stop to the femto base. It is possible to notify the station of the interference reduction request and the stop request frequency information at the same time.

  For example, it is assumed that an unregistered mobile station transmits an interference reduction request to the femto base station using the channel 212. The femto base station that has received the interference reduction request stops transmission of the radio signal in the frequency band of the frequency band 25 to 49 [Hz] associated with the channel 212 and performs intermittent transmission.

  FIG. 22 is a flowchart showing a processing / operation flow of the random access function unit of the femto base station according to the third embodiment.

Receiving unit 192 of femto base station 190 outputs a radio signal from the unregistered mobile station to random access function unit 193. (S220)
When a radio signal is input from the reception unit 192, the determination unit 197 in the random access function unit 193 executes the following flow for each interference reduction request channel based on channel information. (S221)
For example, assuming that the channels indicated by the channel information are channels 211 to 214 as shown in FIG. 21, the channel information indicating the channels 211 to 214 is input from the channel determination unit 196.

The determination unit 197 determines whether or not an interference reduction request is included in the channel 211 among the channels based on the channel information input from the channel determination unit 196. (S222)
If it is determined in step S222 that no interference reduction request is included in the channel 211, the process returns to step S221 to execute the flow of the channel 212. (S224)
If it is determined in step S222 that the channel 211 includes an interference reduction request, the determination unit 197 in the random access function unit 193 receives the frequency detection unit 194 indicating that the channel 211 has received the interference reduction request. Output channel information and interference reduction request. (S223)
Next, the determination unit 197 returns to step S221 and executes the flow of the channel 212. (S224)
When the random access function unit 193 ends the determination of the channels 211 to 214 and outputs the reception channel information for each channel to the frequency detection unit 194, the processing / operation in the random access function unit 143 ends. (S225)
Through the above flow, the femto base station can confirm whether the interference reduction request is notified from the mobile station.

  FIG. 23 is a flowchart illustrating processing and operation of the frequency detection unit of the femto base station according to the third embodiment.

When a signal is input from the random access function unit 193 (S230), the frequency detection unit 194 determines whether there is an interference reduction request for the signal. (S231)
When there is an interference reduction request, the timer 198 in the frequency detection unit 194 starts measuring elapsed time. If the timer 198 has already started to measure the elapsed time, the timer 198 is initialized and the measurement is started again. (S232)
The frequency detection unit 194 compares the reception channel information with the channel information when the timer 198 starts measurement, and stops the transmission of the radio signal transmitted to the registered mobile station in the frequency band corresponding to the channel indicated by the reception channel information. The band is determined, and the transmission stop frequency band is output to the transmission unit 195 as frequency information. (S233)
Here, the transmission unit 195 performs intermittent transmission based on the frequency information input from the frequency detection unit 194.

The timer 198 measures the time during which a radio signal is transmitted outside the frequency band based on the frequency information determined in step S163, that is, the time during which intermittent transmission is performed in the frequency band. (S234)
The timer 198 determines whether or not a predetermined time has elapsed. (S235)
If it is determined in S165 that the predetermined time has elapsed, the frequency detection unit 194 sets an invalid value as frequency information as a transmission stop frequency band (S236), and outputs frequency information that is an invalid value to the transmission unit 195. To do. (S237)
Note that, when the frequency information input from the frequency detection unit 194 is an invalid value, the transmission unit 195 determines that a predetermined time has elapsed since the start of intermittent transmission, and stops the intermittent transmission.

The frequency detection unit 194 ends the processing / operation by outputting frequency information that is an invalid value to the transmission unit 195. (S238)
With the above flow, the femto base station can determine the frequency band in which the transmission of the radio signal is stopped.

According to the third embodiment, it is possible to select an optimal frequency band for stopping transmission for an unregistered mobile station, and it is possible to improve communication efficiency.
<Fourth embodiment>
In the fourth embodiment, when the femto base station performs communication by intermittent transmission, the femto base station further transmits timing information indicating the timing to stop transmission of the radio signal, and the unregistered mobile station receives the timing received from the femto base station. Information is transmitted to the macro base station, and the macro base station controls the radio signal transmitted by the macro base station based on the timing information received from the mobile station.

  That is, in the fourth embodiment, the macro base station communicates with the mobile station using radio resources that are not used when the femto base station performs interference reduction. The fourth embodiment is different from the first to third embodiments in that the transmission stop timing is also notified to the macro base station with which the unregistered mobile station is communicating.

  In the fourth embodiment, as in the first embodiment, the interference reduction request is an example of information on the radio signal. However, the information on the radio signal is not limited to the interference reduction request. For example, the reception of the macro base station Information indicating the presence or absence of power or interference may be used.

  In the fourth embodiment, the macro base station communicates with the mobile station at a timing when the femto base station is not communicating. However, the macro base station is not limited to the timing, and is not used by the femto base station, for example. If there is a frequency band, communication with the mobile station may be performed using the frequency band.

  A communication system according to the fourth embodiment will be described with reference to FIGS.

  Here, a hardware configuration diagram of an unregistered mobile station (FIG. 6), a hardware configuration diagram of a femto base station (FIG. 8), an example of an interference reduction request channel (FIG. 9), and an unregistered mobile station having an interference level The flowchart (FIG. 10) showing the processing / operation at the time of determination, the flowchart (FIG. 11) showing the processing / operation of the random access function unit, and the flowchart (FIG. 12) showing the processing / operation of the timing determination unit of the femto base station This is the same as in the first embodiment.

  FIG. 24 is a schematic diagram showing a communication system according to the fourth embodiment.

  As shown in FIG. 24, the communication system according to the fourth embodiment is realized in a communication system in which the unregistered mobile station 243 of the femto base station 242 communicates with the macro base station 241.

  The mobile station 243 is an unregistered mobile station for the femto base station 242, and the mobile station 244 is a registered mobile station for the femto base station 242.

  Hereinafter, an outline of the communication system will be described.

  If the unregistered mobile station 243 determines that interference is received from the femto base station 242, it transmits an interference reduction request to the femto base station 242 using the random access channel.

  When the femto base station 242 receives the interference reduction request from the unregistered mobile station 243, the femto base station 242 stops transmitting the radio signal at a constant period. Further, the femto base station 242 includes the timing information indicating the timing of stopping the transmission of the radio signal in the broadcast information and transmits it to the unregistered mobile station 243.

  The unregistered mobile station 243 that has received the timing information from the femto base station 242 transmits the received timing information to the communicating macro base station 241. The macro base station 241 performs communication scheduling in accordance with the timing indicated by the received timing information, and performs communication with the mobile station 243 according to the scheduling.

  FIG. 25 is a functional block diagram of an unregistered mobile station according to the fourth embodiment.

  As shown in FIG. 25, the unregistered mobile station 250 of the femto base station of the fourth embodiment includes an antenna 251, a receiving unit 252, a broadcast information searching unit 253, a control information generating unit 254, a transmitting unit 255, Is provided. The receiving unit 251 is realized by the demodulator 608 and the decoder 609, the broadcast information searching unit 253 and the control information generating unit 254 are realized by the CPU 604, and the transmitting unit 255 is realized by the encoder 610 and the modulator 611. (See FIG. 6).

  Note that description of the functional units (antenna 251 and receiving unit 252) similar to those of the first embodiment is omitted.

  The broadcast information search unit 253 searches for timing information included in the broadcast information when the radio signal input from the reception unit 252 is broadcast information received from the femto base station, and uses the timing information as a control information generation unit. Output to H.254.

  Based on the timing information input from the broadcast information search unit 253, the control information generation unit 254 generates radio resource control information that is transmitted to the macro base station with which the mobile station is communicating. The radio resource control information is information including timing information at which the femto base station has stopped transmitting radio signals to the macro base station, and the macro base station includes timing information included in the radio resource control information. By performing communication scheduling at the timing indicated by, radio resources can be effectively used. The control information generation unit 254 outputs the generated radio resource control information to the transmission unit 255, and the transmission unit 255 transmits the radio resource control information to the macro base station via the antenna 251.

  FIG. 26 is a functional block diagram of a femto base station according to the fourth embodiment.

  As shown in FIG. 26, the femto base station of the fourth embodiment includes an antenna 261, a receiving unit 262, a random access function unit 263, a timing determining unit 264, a broadcast information generating unit 265, a transmitting unit 266, Is provided. The random access function unit includes a channel determination unit 267 and a request determination unit 268, and the timing determination unit 264 includes a timer.

  Here, the reception unit 262 is realized by a demodulator 807 and a decoder 808, the random access function unit 263, the timing determination unit 264, and the broadcast information generation unit 265 are realized by the CPU 814, and the transmission unit 266 is modulated by the encoder 810 and modulation. This is realized by the device 811 (see FIG. 8).

  Note that descriptions of the same function units (antenna 261, reception unit 262, random access function unit 263, channel determination unit 267, request determination unit 268) as in the first embodiment are omitted.

  When an interference reduction request is input from the request determination unit 268, the timing determination unit 264 determines a timing for stopping the radio signal, and notifies the notification information generation unit 265 and the transmission unit 266 as the determined timing as timing information. . The transmission stop timing may be determined from, for example, a number uniquely assigned to each cell. However, since it is not desirable to stop transmission of information essential for cell maintenance, for example, broadcast information and the like, it is preferable to exclude the timing for transmitting broadcast information and the like that are known in advance from the transmission stop timing.

  The notification information generation unit 265 generates notification information including the timing information input from the timing determination unit 264 and outputs the notification information to the transmission unit 266.

  The transmission unit 266 transmits a radio signal to the registered mobile station via the antenna 261 other than the timing indicated by the timing information input from the timing determination unit 264. That is, the timing indicated by the timing information input from the timing determination unit 264 realizes intermittent transmission by stopping the transmission of the radio signal. Furthermore, the transmission unit 266 transmits the broadcast information input from the broadcast information generation unit 265 to the unregistered mobile station via the antenna 261.

  Further, when an interference reduction request is input from the random access function unit 263, the timing determination unit 264 outputs a control signal to the timer 269, and the timing determination unit 264 outputs timing information to the transmission unit 266. Measure the elapsed time since then. When the preset elapsed time is reached, the transmission unit 266 stops intermittent transmission and transmits a radio signal to the registered mobile station via the antenna 261 as usual.

  Here, the timing information is notified only to the unregistered mobile station by the broadcast information. However, as can be seen from the fact that the timing information is the broadcast information, the timing information is also transmitted to the registered mobile station of the femto base station. Can be sent. By receiving the timing information, the registered mobile station can also be suspended at the timing when the femto base station stops transmitting the radio signal.

  FIG. 27 is a functional block diagram of the macro base station according to the fourth embodiment.

  As illustrated in FIG. 27, the macro base station 270 of the fourth embodiment includes an antenna 271, a reception unit 272, a control function unit 273, and a transmission unit 274.

  The antenna 271 transmits a transmission signal output from the transmission unit 274 to the mobile station using a radio wave as a medium, receives a signal transmitted from the mobile station using the radio wave as a medium, and outputs a reception signal to the reception unit 272. To do.

  The receiving unit 272 receives a radio signal from the mobile station via the antenna 271 and performs demodulation and decoding.

  When the reception signal input from the reception unit 272 includes radio resource control information, the control function unit 273 outputs timing information included in the radio resource control information to the transmission unit 274.

  The transmission unit 274 transmits a radio signal to the mobile station via the antenna 271 at the timing indicated by the timing information input from the control function unit 273. That is, since the transmission unit 275 communicates with the mobile station at the timing when the femto base station stops transmission, radio resources can be used effectively.

  According to the fourth embodiment, it is possible to efficiently use vacant radio resources while the femto base station intermittently transmits, so that it is possible to improve communication efficiency.

<Fifth Embodiment>
In the fifth embodiment, when the femto base station determines that the received radio signal includes information related to the radio signal, the femto base station determines the timing to stop the radio signal transmitted by itself and communicates with the femto base station. A downlink data signal and an uplink scheduling signal are transmitted to a registered mobile station at a timing other than the determined timing, an uplink data signal is transmitted to the femto base station based on the received scheduling signal, and the femto base station The feedback for the received uplink data signal is transmitted at a timing other than the determined timing.

  That is, in the fifth embodiment, the femto base station performs intermittent transmission of the downlink data signal and the uplink scheduling signal only when there is an unregistered mobile station that is receiving interference. Further, the registered mobile station transmits an uplink data signal to the femto base station based on the scheduling signal, and the femto base station transmits an uplink feedback signal for the uplink data signal at a timing other than the timing. Further, the fifth embodiment is different from the first embodiment in that not only the downlink data signal but also the uplink scheduling signal and the uplink feedback signal are intermittently transmitted.

  A communication system according to the second embodiment will be described with reference to FIGS. 28 to 29.

  Here, a functional block diagram of the unregistered mobile station (FIG. 5), a hardware configuration diagram of the unregistered mobile station (FIG. 6), a functional block diagram of the femto base station (FIG. 7), and a hardware configuration diagram of the femto base station (FIG. 8), an example of an interference reduction request channel (FIG. 9), a flowchart (FIG. 10) showing processing / operation when an unregistered mobile station determines an interference level, and processing / operation of a random access function unit The flowchart (FIG. 11) and the flowchart (FIG. 12) showing the processing / operation of the timing determination unit of the femto base station are the same as those in the first embodiment.

  FIG. 28 is a schematic diagram of a communication system according to the fifth embodiment.

  As shown in FIG. 28, the communication system according to the fifth embodiment is realized in a communication system in which the unregistered mobile station 283 of the femto base station 282 communicates with the macro base station 281.

  The mobile station 283 is an unregistered mobile station for the femto base station 282, and the mobile station 284 is a registered mobile station for the femto base station 282.

  Hereinafter, an outline of the operation of the communication system in the fifth embodiment will be described.

  If the unregistered mobile station 283 determines that the interference is received from the femto base station 282, the unregistered mobile station 283 requests the femto base station 282 to reduce the interference. At this time, the interference reduction request is notified to the femto base station 282 using the random access channel.

  When the femto base station 282 receives the interference reduction request from the unregistered mobile station 283, the femto base station 282 stops transmission of the downlink data signal at a constant period. Further, the femto base station 2 stops transmission of the downlink signal that is the uplink scheduling signal at the same period as the period in which the transmission of the downlink data signal is stopped.

  The registered mobile station 284 transmits an uplink data signal to the femto base station 282 based on the uplink scheduling signal received from the femto base station 282. That is, here, the transmission of the uplink data signal is stopped based on the uplink scheduling signal whose transmission is stopped at the timing, and therefore, the channel corresponding to the timing in the uplink data signal is stopped. Further, the mobile station 284 also stops transmission of the uplink feedback signal at this timing, and transmits it to the femto base station 284.

  FIG. 29 is an example of a channel that performs transmission stop in the communication system according to the fifth embodiment.

  As shown in FIG. 29, the downlink data signal stops signal transmission at timing (4).

  The uplink scheduling signal is a downlink signal that instructs the mobile station at which timing to transmit the uplink data signal. In the present embodiment, transmission is stopped at timing (4) as in the case of downlink data.

  The uplink feedback signal is a downlink signal that the base station feeds back to the mobile station whether or not reception of uplink data has been successful at the base station. In the present embodiment, transmission of an upstream data signal is stopped in advance such that the transmission stop timing of this upstream feedback signal becomes the transmission stop timing. That is, by scheduling the uplink data signal at timing (−3) to be stopped by the uplink scheduling signal, the signal at timing (−4) that is an uplink feedback signal corresponding to the uplink data signal at timing (−3). It becomes possible to stop sending.

  The uplink data signal is an uplink signal transmitted from the mobile station to the base station, and signal transmission at timing (−3) is stopped according to an instruction of the downlink scheduling signal. Furthermore, the signal corresponding to the timing (4) at which the uplink scheduling signal itself stops transmission is also stopped.

According to the fifth embodiment, when intermittent transmission is performed, the downlink data signal, uplink scheduling signal, and uplink feedback signal of the femto base station can be intermittently transmitted, so that further interference reduction is performed for unregistered mobile stations. I can do it.

21, 32, 42, 70, 80, 132, 140, 172, 190, 242, 260, 282 Femto base station 22 Femtocell 23, 34, 44, 134, 174, 244, 284 Registered mobile station 24, 33, 43 , 50, 60, 133, 173, 180, 243, 283 Unregistered mobile stations 31, 41, 131, 171, 241, 270, 281 Macro base stations 51, 601, 71, 801, 141, 181, 191, 251 261, 271 Antenna 52, 72, 142, 182, 192, 252, 262, 272 Receiver 53, 183 Measuring unit 54, 184 Interference determination unit 55, 75, 145, 186, 255, 266, 274 Transmitter 602, 802 RF unit 603, 803 Baseband function unit 604 CPU
605, 804 Duplexer 606, 805 Down converter 607, 806 ADC
608, 807 Demodulator 609, 808 Decoder 610, 810 Encoder 611, 811 Modulator 612, 812 DAC
613, 813 Up-converter 73, 143, 193, 263 Random access function unit 74, 264 Timing determination unit 76, 146, 196, 267 Channel determination unit 77, 147, 197, 268 Request determination unit 78, 148, 198, 269 Timer 809 Layer 2 function unit 814 CPU
90 Random Access Channel 91 Normal Channel 92 Interference Reduction Request Channel 144 Frequency Determination Unit 185 Stop Request Frequency Determination Unit 194 Frequency Detection Unit 201 Reception Quality 202 Frequency 203, 211, 212, 213, 214 Channel 253 Broadcast Information Search Unit 254, 265 Control information generation unit 273 Control function unit

Claims (10)

In a communication system in which a mobile station not registered in the first base station communicates with the second base station,
The mobile station
A receiver that receives a radio signal transmitted by the first base station and a radio signal transmitted by the second base station;
A transmitter for transmitting received signal information related to the received radio signal;
With
The first base station is
A receiving unit for receiving the received signal information transmitted by the mobile station;
Based on the received signal information, a transmitter that intermittently transmits a radio signal;
A communication system comprising: The transmission unit of the first base station transmits information on the intermittent transmission to the mobile station,
The receiver of the mobile station receives information on the intermittent transmission transmitted by the first base station,
The transmitter of the mobile station transmits the received information regarding the intermittent transmission to the second base station,
The second base station is
A receiver for receiving information on the intermittent transmission transmitted by the mobile station;
A transmitter that transmits a radio signal using a radio resource according to the received information regarding the intermittent transmission;
The communication system according to claim 1, further comprising: The mobile station
An interference determination unit for determining the interference level of the received radio signal;
Further comprising
The communication system according to claim 1 or 2, wherein the transmission unit of the mobile station transmits the received signal information according to the determined interference level. The transmission unit of the first base station stops transmission of a radio signal at a timing corresponding to the received reception signal information, and transmits information on the timing as information on the intermittent transmission. The communication system according to 1 to 3. The transmission unit of the first base station stops use of at least a part of the frequency according to the received signal information received from the frequency band used by the local station for transmitting the radio signal, and relates to the intermittent transmission. The communication system according to any one of claims 1 to 4, wherein information on the stopped frequency is transmitted as information. The first base station is
A channel determining unit that determines a channel to be used when the mobile station transmits the received signal information;
A request determination unit that determines whether the received signal information has been received by monitoring the determined channel;
Further comprising
The transmission unit of the first base station transmits channel information indicating the determined channel to the mobile station,
A receiving unit of the mobile station receives the channel information transmitted by the first base station;
The communication system according to any one of claims 1 to 5, wherein the transmitter of the mobile station transmits the received signal information using a channel based on the received channel information. In a communication system in which a mobile station not registered in the first base station communicates with the second base station,
The mobile station
A receiver that receives a radio signal transmitted by the first base station and a radio signal transmitted by the second base station;
A transmitter for transmitting received signal information related to the received radio signal;
With
The first base station is
A receiving unit for receiving the received signal information transmitted by the mobile station;
When receiving the received signal information from a plurality of mobile stations, based on the received signal information, a transmission unit that controls a radio signal transmitted by the own station;
A communication system comprising: In a mobile station that is not registered with the first base station and communicates with the second base station,
A receiver that receives a radio signal transmitted by the first base station and a radio signal transmitted by the second base station;
When requesting intermittent transmission based on the received radio signal, a transmission unit that transmits received signal information related to the received radio signal;
A mobile station characterized by that. In base stations that do not communicate with unregistered mobile stations,
A receiving unit that receives received signal information related to a radio signal received by the unregistered mobile station;
Based on the received signal information received, a transmitter that intermittently transmits a radio signal;
A base station comprising: In a communication method in which a mobile station not registered in the first base station communicates with the second base station,
The mobile station
Receiving a radio signal transmitted by the first base station and a radio signal transmitted by the second base station;
Send received signal information about the received radio signal,
The first base station is
Receiving the received signal information transmitted by the mobile station;
A wireless signal is intermittently transmitted based on the received signal information.

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