JP2010263462A - Small base station and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow mobiles present in other cells to make them move to femtocells. <P>SOLUTION: As systems for allowing mobile existence in a femtocell C<SB>1</SB>, a competing frequency system, an overlap frequency system, and an interfering wave system are prepared in a femtocell base station 1. The system that allows mobile existence in the femtocell C<SB>1</SB>is selected, according to a situation of radio waves from a macro cell base station. The competing frequency system is a system for emitting radio waves, in the same frequency band as a used frequency band by the macro cell station, while the overlap frequency system is a system for emitting radio waves, having the same bandwidth as that of one frequency band to spread over each of a plurality of used frequency bands. The interfering wave system is a system for emitting interfering waves, along with the radio waves in a frequency band used for communicating with a mobile 2. The present invention is applicable to the femtocell base stations. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a small base station and a communication method, and more particularly, to a small base station and a communication method that can move a mobile station located in another cell to a femto cell.

  In recent years, “femtocells” for covering a narrow range with a radius of several tens of meters, such as in a home or office, as a communicable range have attracted attention.

  “Femtocell” refers to a femtocell base station, which is a base station that emits radio waves at a level that covers such a narrow range, in a broadband line such as an ADSL (Asymmetric Digital Subscriber Line) line or an optical fiber line. Built by connecting to the device.

  Unlike the “macro cell”, which is intended for the general public and is a wide cell with a radius of several hundred meters to several kilometers, the “femto cell” is limited to the residents of the house where the femto cell base station is installed. The communication service is provided to the user.

  For example, when a user who is outdoors makes a voice call using a mobile device located in the macro cell, the voice data is transmitted from the macro cell base station covering the macro cell via the radio access network and the core network. Sent to the communicating mobile device.

  On the other hand, when a user who is indoors makes a voice call using a mobile device located in the femtocell, the voice data is output from the femtocell base station to the modem, broadband line, core network, etc. Is transmitted to the mobile device of the communication partner.

JP 2007-116391 A JP 2007-140829 A JP 2005-175611 A JP 2002-218528 A

  For communication using mobile devices located in the macro cell and communication using mobile devices located in the femto cell, the latter is cheaper and better. In many cases, a good communication quality can be obtained.

  Therefore, if the house where the femtocell is built is in a macrocell covered by a macrocell base station and both the macrocell and femtocell can be used in the house, it is usually better for the user to use the femtocell. Has merit.

  If you are a user who has introduced a femtocell base station and built a femtocell at home, you can go home from wherever you are and enter your home. It is desirable to move to the state where the femtocell is located.

  However, the transition from the macro cell to the femto cell does not occur even if the reception intensity of the radio wave from the femto cell base station is high unless the radio wave from the macro cell base station is sufficiently deteriorated.

  Here, transition between cells will be described.

  The reception status of radio waves in the mobile device is represented by Ec / No, which is the ratio of the received power of radio waves from the desired base station and the received power of other radio waves. Ec / No is a value of 0 dB or less, and is obtained for each cell.

There are, for example, three values S _intrasearch , S _intersearch , and Q _qualmin as values used to determine whether or not to perform cell migration, and are set in each mobile station.

When the Ec / No value of the cell that is currently _{located is} less than Q _qualmin + S _{intrasearch, the mobile} station is receiving from the base stations whose scrambling codes are described in the neighboring cell list Search and move to another base station that emits radio waves in the same frequency band as the radio waves.

  For a mobile station located in a macro cell, a macro cell base station provides a neighbor cell list, which is a list in which scrambling codes used in macro cells in the vicinity are described. The scrambling code is a code assigned to each base station in a CDMA (Code Division Multiple Access) communication system, and is used, for example, for spread modulation and demodulation during communication with a mobile device.

In addition, when the Ec / No value of a cell that is currently _{located is} equal to or lower than Q _qualmin + S _{intersearch, the mobile} station receives from the base stations whose scrambling codes are described in the neighboring cell list. Search for another base station that emits radio waves in a frequency band different from the radio wave that is being transmitted.

In addition, when the Ec / No value of the cell in which the mobile station is currently _{located is} less than Q _qualmin , the mobile station finds the base station found by the search, even if the scrambling code is not described in the neighboring cell list. Move to the cell covered by the station. Q _qualmin represents the minimum quality required.

Transition to a cell covered by a base station whose scrambling code is not described in the neighboring cell list occurs if the Ec / No value of the cell currently in _{service is} less than Q _qualmin , that is, it has not deteriorated sufficiently. There will be no.

Therefore, even when the user enters the home, the transition to the home femtocell does not occur unless the Ec / No value of the macro cell in the area is equal to or lower than Q _qualmin .

  If you remain in the macro cell even after entering your home because you do not meet these conditions, communication using the mobile device will be performed using the macro cell, and there is a femto cell at home. Even if you do not get the benefits.

  The present invention has been made in view of such a situation, and enables a mobile device located in another cell to be transferred to a femto cell.

  The small base station according to the present invention includes a receiving unit that receives radio waves of a predetermined bandwidth emitted by an external base station, and a frequency band that is set as a band that can be used for communication with a mobile device. Detecting means for detecting whether radio waves in a frequency band have been received by the receiving means; and based on a detection result by the detecting means, the predetermined frequency band in the same frequency band as that used by the external base station A first method of emitting radio waves of bandwidth and a second method of emitting radio waves of the predetermined bandwidth so as to straddle each of a plurality of frequency bands used by the external base station A system selection unit that selects one of the systems, and a transmission unit that emits radio waves of the predetermined bandwidth according to the system selected by the system selection unit.

  When the number of radio waves of the predetermined bandwidth that can be simultaneously emitted from the transmission unit is 1, the method selection unit includes a frequency band used by the external base station as one frequency band. The first method can be selected and the second method can be selected when the two frequency bands are adjacent on the frequency axis.

  The method selection means includes the first method, the second method, and an interference having all or some of a plurality of frequency bands that can be used for communication with the mobile device. When any one of the third methods for emitting waves is selected and the transmission unit selects the third method by the method selection unit, the interference wave, the mobile device, Radio waves in any one of a plurality of frequency bands that can be used for communication can be emitted.

  The method selection means can select the third method when a plurality of frequency bands used by the external base station are separated on the frequency axis.

  When the number of radio waves of the predetermined bandwidth that can be simultaneously emitted from the transmission unit is 2, the frequency band used by the external base station is separated on the frequency axis in the method selection unit When there are two frequency bands, the first method can be selected, and the transmission unit can emit radio waves having the predetermined bandwidth in the same frequency band as the two frequency bands.

  The method selection means further causes the transmission means to select the second method when the frequency bands used by the external base station are three frequency bands adjacent on the frequency axis. Can emit radio waves of the predetermined bandwidth so as to straddle one adjacent two frequency bands and the other two frequency bands of the three frequency bands.

  The method selection means further includes three frequency bands used by the external base station: two frequency bands adjacent on the frequency axis, and one frequency band separated from the two frequency bands. When there are two frequency bands, a method combining the first method and the second method is selected, and the transmitting means has one radio wave having the predetermined bandwidth so as to straddle the two frequency bands. And the radio wave having the predetermined bandwidth in the same frequency band as the one frequency band apart from the two frequency bands can be emitted.

  The communication method of the present invention receives a radio wave of a predetermined bandwidth emitted by an external base station, and in which frequency band of a plurality of frequency bands set as bands that can be used for communication with a mobile device A first method for emitting radio waves of the predetermined bandwidth in the same frequency band as the frequency band used by the external base station based on the detection result And any one of the second methods for emitting radio waves of the predetermined bandwidth so as to straddle each of the plurality of frequency bands used by the external base station, and the selected method And emitting a radio wave of the predetermined bandwidth according to

  In the small base station or the communication method of the present invention, a radio wave having a predetermined bandwidth emitted by an external base station is received, and a plurality of frequency bands set as bands that can be used for communication with a mobile device are selected. It is detected which frequency band radio waves are received. Further, based on the detection result, a first method for emitting radio waves of the predetermined bandwidth in the same frequency band as the frequency band used by the external base station, and used by the external base station One of the second methods for emitting radio waves of the predetermined bandwidth is selected so as to straddle each of a plurality of frequency bands, and the radio waves of the predetermined bandwidth are emitted according to the selected method Is done.

  ADVANTAGE OF THE INVENTION According to this invention, the moving apparatus currently located in another cell can be moved to a femto cell.

It is a figure which shows the structural example of the communication system which concerns on one Embodiment of this invention. It is a figure which shows the example of the frequency band of an electromagnetic wave. It is a figure which shows the example of a competition frequency system. It is a figure which shows the example of an overlap frequency system. It is a figure which shows the other example of an overlap frequency system. It is a figure which shows the example of an interference wave system. It is a figure which shows the other example of a jamming wave system. It is a block diagram which shows the structural example of a femtocell base station. It is a block diagram which shows the function structural example of a femtocell base station. It is a figure which shows the example of selection of a visiting system. It is a flowchart explaining the located area assist process of a femtocell base station. It is a figure which shows the other example of a competition frequency system. It is a figure which shows the other example of an overlap frequency system. It is a figure which shows the example of the located area system which combined the competition frequency system and the overlap frequency system.

  FIG. 1 is a diagram illustrating a configuration example of a communication system according to an embodiment of the present invention.

In the example of FIG. 1, a femtocell base station 1 is installed in a premises such as a house or an office building, and a femtocell C ₁ is formed by the femtocell base station 1. The femtocell C ₁ is a cell that covers the range of the premises where the femtocell base station 1 having a radius of several meters or several tens of meters is installed as a communicable range.

A modem (not shown) is connected to the femtocell base station 1 via a LAN (Local Area Network) cable or the like. A modem is a home device of a broadband line composed of an ADSL line or an optical fiber line. The femtocell base station 1 is connected to a network such as the Internet via a LAN cable, a modem, and a broadband line. When the mobile device 2 shown in FIG. 1 is located in the femtocell C ₁ , the mobile device 2 Relays communications such as voice data.

  The mobile device 2 is a terminal such as a mobile phone that supports CDMA communication. In the example of FIG. 1, only one mobile device is shown, but the femtocell base station 1 can simultaneously relay communication by a predetermined number of mobile devices such as a maximum of four.

Further, in the example of FIG. 1, outside the building in which the femtocell base station 1 is installed, the macrocell base station 3 is installed is a base station that manages the macro cell C _2. Is shown by the size of the same level as the femtocell C ₁ in the example of FIG. 1, the macrocell C ₂ is wider cell than the femtocell C _1. In the mobile device 2, not only radio waves from the femtocell base station 1 but also radio waves from the macrocell base station 3 can be received.

  Although FIG. 1 shows only the macro cell base station 3 as the macro cell base station, a macro cell base station other than the macro cell base station 3 is also provided outside the building where the femto cell base station 1 is installed. Radio waves from each macrocell base station also reach the mobile device 2.

  FIG. 2 is a diagram illustrating an example of a frequency band of radio waves used in the communication system of FIG. The horizontal axis in FIG. 2 represents frequency, and the vertical axis represents radio wave intensity.

  In a CDMA communication system, the entire frequency band assigned to a communication company is divided into a predetermined number of bands, and which frequency band radio waves are used is set in each macro cell base station. The mobile device performs radio communication by selecting the frequency of the radio wave to be transmitted / received in accordance with the frequency band of the radio wave of the macro cell in which it is located.

In the example of FIG. 2, 2150 to 2170 MHz is allocated as the downlink frequency band, and the frequency band of the 20 MHz bandwidth is divided into four frequency bands of F ₁ , F ₂ , F ₃ , and F ₄ , each 5 MHz. It has been. A certain frequency band is allocated to each macro cell base station, such that a certain macro cell base station uses the frequency band F ₁ and a certain macro cell base station uses a plurality of frequency bands F _{2 and} F ₃ .

As shown in FIG. 2, the center frequency f ₁ of the frequency band F ₁ is 2152.6MHz, the center frequency f ₂ of the frequency band F ₂ are 2157.6MHz, the center frequency f ₃ of the frequency band F ₃ 2162.4MHz, frequency The center frequency f ₄ of the band F ₄ is 2167.4 MHz.

The bandwidth of the frequency bands F _{1 to} F ₄ is 5 MHz, but radio waves having a bandwidth of 3.84 MHz (3840 kHz) are emitted from each macrocell base station with f _{1 to} f ₄ as the center frequency.

Similarly, the femtocell base station 1 emits radio waves in any one of the four frequency bands F ₁ , F ₂ , F ₃ , and F ₄ and moves within the femtocell C _1. Communicate with the machine. The fact that the femtocell base station 1 emits radio waves in a plurality of frequency bands will be described later.

  Radio waves from each base station received by the mobile device 2 in FIG. 1 including radio waves from the femtocell base station 1 and the macrocell base station 3 are expressed as shown in FIG. The intensity of each radio wave is determined by the distance from the base station to the mobile device 2, the shielding between the base station and the mobile device 2, and the like.

The femtocell base station 1 that communicates with the mobile device 2 using the frequency bands F ₁ , F ₂ , F ₃ , and F ₄ having a bandwidth of 5 MHz as described above includes the mobile device 2 located in the macro cell. Is provided to assist in moving to the femtocell C ₁ .

If the Ec / No of the macro cell in which the mobile device 2 is _located deteriorates, for example, below the Q _qualmin described above, the mobile device 2 is shifted to another cell. If the radio wave from the femtocell base station 1 is received by the mobile device 2 when the radio wave of the macro cell in the area has deteriorated, the mobile device 2 can be transferred to the femtocell C ₁ .

  The located area assist function is a function of causing the mobile device 2 to receive the radio wave emitted by the femtocell base station 1 itself while deteriorating the radio wave of the macro cell.

For example, three methods, a competitive frequency method, an overlap frequency method, and an interference wave method, are prepared as methods for causing the femtocell C ₁ to be in the service area.

The femtocell base station 1 selects which location system the mobile device 2 is located in the femtocell C _{1 according} to the state of radio waves from the macrocell base station detected by the operation in the listening mode.

The listening mode is a mode in which a radio wave emitted by an external base station such as a macro cell base station is received and the status of the received radio wave is detected. For example, which frequency band of the frequency bands F ₁ , F ₂ , F ₃ , and F ₄ the received radio wave is, that is, which frequency band is used by an external base station. In addition, the intensity (electric power) of radio waves is detected.

By the operation in the listening mode, in the femtocell base station 1, the frequency and intensity of radio waves from an external base station that can be received at the installation position of the femtocell base station 1 are observed as shown in FIG. Based on the observation result, the location method is appropriately selected from the competing frequency method, the overlap frequency method, and the interference wave method, and the mobile device 2 is located in the femtocell C ₁ by the selected location method. Is done.

  Here, each location system will be described.

  FIG. 3 is a diagram illustrating an example of a competitive frequency method.

Competition computing frequency system is a system for serving the mobile station 2 to the femto cell C ₁ by emitting a radio wave of the same frequency band as the frequency band used by the macrocell base station. The intensity of the radio wave emitted by the femtocell base station 1 is higher than the reception intensity of the radio wave from the macro base station.

When the operation in the listening mode receives radio waves in the frequency band F ₃ as radio waves from a certain macrocell base station and detects that one frequency band has been used, as shown in FIG. 3A, the femtocell base Station 1 selects the competing frequency scheme.

In this case, the femtocell base station 1 emits a radio wave having the same frequency band F ₃ as the used frequency band as shown in FIG. 3B and having a higher intensity than the radio wave intensity from the macrocell base station. .

In the example of FIGS. 3A and 3B, the strength of the radio wave from the macro cell base station at the installation position of the femtocell base station 1 is p ₁ , and the strength at which the mobile device 2 receives the radio wave emitted by the femtocell base station 1. Is p ₂ higher than p ₁ .

  FIG. 3C is a diagram in which the radio wave from the macro cell base station shown in FIG. 3A and the radio wave emitted by the femtocell base station 1 shown in FIG. 3B are overlapped.

Since the femtocell C ₁ has a relatively narrow range such as a radius of several meters to several tens of meters, radio waves from the macrocell base station are received in substantially the same manner at the installation position of the femtocell base station 1 and the position of the mobile device 2. Is done.

  In the mobile device 2, radio waves from the macrocell base station and radio waves from the femtocell base station 1 are received in the form shown in FIG. 3C.

When the radio wave from the macro cell base station and the radio wave from the femto cell base station 1 are received in a state as shown in FIG. 3C, the radio waves from the macro cell base station deteriorate in the mobile device 2 located in the macro cell. And move to the femtocell C ₁ capable of receiving radio waves with high intensity. When the radio wave from the macro cell base station is masked by the radio wave from the femtocell base station 1, the Ec / No of the macro cell becomes Q _qualmin or less.

When the mobile device 2 is located in the femtocell C ₁ , the femtocell base station 1 communicates with the mobile device 2 using the frequency band F ₃ .

  That is, the radio wave for degrading the radio wave from the macrocell base station is used as it is as a radio wave for communicating with the mobile device 2. This makes it possible to efficiently perform assistance and communication in the area.

As described above, according to the competitive frequency system, the same frequency band is selected by competing with the frequency band used by the macrocell base station, and radio waves in the selected frequency band are emitted, so that the mobile device 2 is made femto. The cell C ₁ can be located.

  FIG. 4 is a diagram illustrating an example of the overlap frequency method.

The overlap frequency method is a method in which the mobile device 2 is located in the femtocell C ₁ by emitting radio waves with a bandwidth of 3.84 MHz so as to straddle each of a plurality of frequency bands used by the macrocell base station. It is. The intensity of the radio wave emitted by the femtocell base station 1 is higher than the reception intensity of the radio wave from the macro base station.

By the operation in the listening mode, as shown in FIG. 4A, the radio wave of the frequency band F _{3 and} the radio wave of the frequency band F ₄ are received as radio waves from the macro cell base station, and two adjacent frequency bands on the frequency axis are used. When it is detected that the transmission has been completed, the femtocell base station 1 selects the overlap frequency method.

In this case, the femtocell base station 1 selects, as shown in FIG. 4B, a frequency f _3.5 is the center frequency intermediate frequency f ₃ and f ₄ of the used frequency band as the center frequency. Center frequency f _3.5 is 2164.9MHz.

Further, the femtocell base station 1 is a radio bandwidth 3.84MHz having a center frequency f _3.5, to emit radio waves of higher strength than the strength of the radio waves from the macro cell base station. In the example of FIGS. 4A and 4B, the strength of the radio wave from the macro cell base station at the installation position of the femtocell base station 1 and the mobile device 2 is p ₁₁ , and the radio wave emitted by the femtocell base station 1 is transmitted to the mobile device 2. The received intensity is p ₁₂ higher than p ₁₁ .

  FIG. 4C is a diagram in which radio waves from the macro cell base station shown in FIG. 4A and radio waves emitted by the femtocell base station 1 shown in FIG. 4B are superimposed.

When the radio wave from the macro cell base station and the radio wave from the femto cell base station 1 are received in the state as shown in FIG. 4C, the radio waves from the macro cell base station deteriorate in the mobile device 2 located in the macro cell. And move to the femtocell C ₁ capable of receiving radio waves with high intensity. In the example of FIG. 4C, when the radio wave from the macro cell base station interferes with the radio wave from the femtocell base station 1, the Ec / No of both macro cells becomes Q _qualmin or less.

If the mobile station 2 is located in the femto cell C _1, the femtocell base station 1 communicates with the mobile station 2 using the frequency band of the bandwidth of 3.84MHz having a center frequency of f _3.5.

  That is, even in the overlap frequency method, the radio wave for degrading the radio wave from the macrocell base station is used as it is as a radio wave for communicating with the mobile device 2. This makes it possible to efficiently perform assistance and communication in the area.

In the communication system of FIG. 1, communication is basically performed using any one of the frequency bands F ₁ , F ₂ , F ₃ , and F ₄ , but the center frequency of each frequency band is used as a reference. As described above, it is also possible to select a center frequency at intervals of 200 kHz and perform communication using a frequency band having a bandwidth of 3.84 MHz. When the femtocell base station 1 emits a radio wave having a bandwidth of 3.84 MHz with a frequency f _3.5 as the center frequency, the mobile device 2 adjusts the center frequency of the received radio wave to the frequency f _3.5 and a band of 3.84 MHz. Communicate using a wide range of radio waves.

Thus, according to the overlap frequency method, the mobile device 2 is located in the femtocell C ₁ by emitting radio waves having frequency bands that straddle a plurality of frequency bands used by the macrocell base station. It becomes possible to make it.

  FIG. 5 is a diagram illustrating another example of the overlap frequency method.

By the operation in the listening mode, as shown in FIG. 5A, the radio wave of the frequency band F _{3 and} the radio wave of the frequency band F ₄ are received as radio waves from the macro cell base station, and two adjacent frequency bands on the frequency axis are used. When it is detected that it has been completed, the femtocell base station 1 selects the overlap frequency method as described with reference to FIG. In the example of FIG. 4, the intensity of the radio waves in the frequency bands F ₃ and F ₄ is assumed to be p ₁₁ , but in the example of FIG. 5, the intensity of the radio wave in the frequency band F ₃ is p ₂₁ and the frequency The intensity of the radio wave in the band F ₄ is p ₂₂ higher than p ₂₁ .

In this case, the femtocell base station 1 is slightly in the frequency band of the higher-frequency radio wave having a frequency between the center frequencies f ₃ and f ₄ of the used frequency band as shown in FIG. 5B. The frequency f _3.8 that is the selected frequency is selected as the center frequency. The center frequency f _3.8 is 2166.4 MHz.

The femtocell base station 1 emits a radio wave having a bandwidth of 3.84 MHz with the frequency f _3.8 as the center frequency and higher than the radio wave intensity from the macro cell base station. In the example of FIG. 5B, the intensity of the femtocell base station 1 receives the mobile station 2 is a radio wave to be emitted is higher p ₂₃ than p _21, p _22.

  FIG. 5C is a diagram in which the radio wave from the macro cell base station shown in FIG. 5A and the radio wave emitted by the femtocell base station 1 shown in FIG. 5B are overlapped.

When the radio wave from the macro cell base station and the radio wave from the femto cell base station 1 are received in a state as shown in FIG. 5C, the radio wave from the macro cell base station deteriorates in the mobile device 2 located in the macro cell. And move to the femtocell C ₁ capable of receiving radio waves with high intensity.

When the mobile device 2 is located in the femtocell C ₁ , the femtocell base station 1 communicates with the mobile device 2 using a frequency band having a bandwidth of 3.84 MHz with the frequency f _3.8 as the center frequency. Also in this case, the radio wave for degrading the radio wave from the macro cell base station is used as it is as a radio wave for communicating with the mobile device 2.

The frequency f _3.8 spans both the used frequency bands F ₃ and F ₄ with a frequency band of 3.84 MHz, and the amount of interference with the radio wave in the frequency band F _{3 and} the radio wave in the frequency band F ₄ from the macrocell base station. Is selected by searching for a frequency that maximizes.

Of the radio waves femtocell base station 1 is fired, a portion which enters the frequency band F ₃ will give interference to radio waves from the macro cell base station that exists in a frequency band F _3. Further, a portion which enters the frequency band F ₄ will give interference to radio waves from the macro cell base station that exists in a frequency band F _4.

If the center frequency of the radio wave emitted by the femtocell base station 1 is set to the frequency f ₄ , the radio wave in the frequency band F ₄ , which is the stronger radio wave, may be intensively degraded. The possibility that the mobile device 2 moves to the macro cell using the frequency band F ₃ remains. The mobile device 2 receives radio waves in the frequency band F _{3 in} addition to radio waves in the frequency band F ₄ .

In order to shift to the femtocell C ₁ more reliably, the radio wave in the frequency band F ₃ also needs to be deteriorated. Therefore, a part of the radio wave emitted by the femtocell base station 1 enters the frequency band F ₃ . Need to be.

  FIG. 6 is a diagram illustrating an example of an interference wave system.

Disturbance method, the frequency band _{F 1, F 2, F 3} , F 4 in the entire area or a disturbance wave having a frequency of some band, the frequency band F ₁ to be used for communication with the mobile station 2,, F ₂ , F ₃ , and F ₄ , the mobile device 2 is located in the femtocell C ₁ by being emitted together with radio waves in any frequency band. The intensity of the interference wave emitted by the femtocell base station 1 is higher than the reception intensity of the radio wave from the macro base station.

Depending on the operation in the listening mode, when radio waves of three or more frequency bands such as F ₁ , F ₂ , F ₃ are received as radio waves from the macro cell base station, or radio waves of two frequency bands, _When receiving radio waves in a frequency band separated on the frequency axis such as ₁ and F ₃ , the femtocell base station 1 selects the interference wave system.

  When the macro cell base station uses more than two frequency bands or frequency bands that are separated on the frequency axis, the above-described overlap method cannot degrade radio waves from all macro cell base stations. The wave method is selected.

In this case, the femtocell base station 1, as shown in FIG. 6A, emits radio waves as a radio wave to be used for example the frequency band F ₃ for communication with the mobile station 2. In FIG. 6A, the intensity of the radio wave in the frequency band F ₃ is p ₃₁ , and the intensity of the radio waves in the frequency bands F ₁ , F ₂ , F ₄ is p ₃₂ lower than p ₃₁ . Actually, a radio wave having a predetermined intensity is detected in this way even in a frequency band not used for communication.

Further, as shown in FIG. 6B, the femtocell base station 1 emits radio waves having frequency bands over the entire frequency bands F ₁ , F ₂ , F ₃ , and F ₄ as interference waves, for example. The intensity of the interference wave is p ₃₃ which is lower than the intensity p _{31 and} higher than p ₃₂ .

Radio waves of the frequency band F ₃ modulates the RF signal of the data to be transmitted, a radio wave output by up-converting the modulated signal. On the other hand, the interference wave is a white noise signal emitted as a radio wave in a frequency band over the entire frequency bands F ₁ , F ₂ , F ₃ , and F ₄ . The white noise signal is a signal generated by a dedicated generator.

  6C is a diagram in which the radio wave used for the communication shown in FIG. 6A and the jamming wave shown in FIG. 6B are overlapped.

When the radio wave from the femtocell base station 1 is received in a state as shown in FIG. 6C, the mobile device 2 located in the macro cell detects that the radio wave from the macro cell base station has deteriorated, The process shifts to a femtocell C ₁ that can receive radio waves with high intensity.

In the example of FIG. 6C, the radio wave in the frequency band F _{1 and} the radio wave in the frequency band F ₃ from the macro cell base station indicated by dotted lines are masked by the interference wave component of the radio wave from the femtocell base station 1, Ec / No is less than Q _qualmin .

When the mobile device 2 is located in the femtocell C ₁ , the femtocell base station 1 communicates with the mobile device 2 using the frequency band F ₃ .

Thus, according to the interference wave method, the radio wave emitted by the macrocell base station can be degraded by the interference wave, and the mobile device 2 is located in the femtocell C ₁ by the radio wave emitted separately from the interference wave. Communication.

  The interference wave method can be used when there is only one used frequency band as shown in FIG. 3A or when there are a plurality of used frequency bands as shown in FIG. 4A. Since unnecessary radio waves that are not actually used for communication are emitted, the priority is lower than that of the competitive frequency method and the overlap method.

  By selecting the competitive frequency method and the overlap method preferentially over the interference wave method, it is possible to suppress the emission of unnecessary radio waves.

Further, at the timing when mobile station 2 is located in the femto cell C _1, the firing of the interference wave may be stopped. This also makes it possible to suppress the emission of unnecessary radio waves.

  FIG. 7 is a diagram illustrating another example of an interference wave system.

  In the example of FIG. 6, the white noise signal is used as a signal from which an interference wave is generated. However, a dummy signal may be used as a signal from which an interference wave is generated. The dummy signal is a signal composed of a sequence of bits that do not appear in the transmitted / received data, such as a value of all 0s and a value of all 1s.

FIG. 7B is a diagram illustrating an interference wave emitted by modulating a dummy signal and emitting the modulated signal as a radio wave in a frequency band covering the entire frequency bands F ₁ , F ₂ , F ₃ , and F ₄ . FIG. 7C is a diagram in which the radio wave used for communication shown in FIG. 7A and the radio wave shown in FIG. 7B are overlapped.

Also by this, the radio wave of the frequency band F _{1 and} the radio wave of the frequency band F ₃ from the macro cell base station indicated by the dotted line in FIG. 7C are masked by the interference wave component of the radio wave from the femtocell base station 1 and deteriorated. It becomes possible to make it.

Processing of the femtocell base station 1 that causes the mobile device 2 to be located in the femtocell C ₁ using the above-described three located areas will be described later.

[Configuration Example of Femtocell Base Station 1]
FIG. 8 is a block diagram illustrating a hardware configuration example of the femtocell base station 1.

  As shown in FIG. 8, the femtocell base station 1 includes a network communication unit 21, a control unit 22, a wireless communication unit 23, an antenna 24, and an interference signal generation unit 25.

  The network communication unit 21 is a network interface, and communicates with a server or the like connected to the network via a modem according to a predetermined protocol such as TCP / IP (Transmission Control Protocol / Internet Protocol) or UDP (User Datagram Protocol). Do.

The network communication unit 21 outputs voice data transmitted from a call session control function (CSCF), which is a server having a function as an exchange, and transferred from a modem, to the wireless communication unit 23, while from the wireless communication unit 23. The supplied voice data from the mobile device 2 located in the femtocell C ₁ is output to the modem and transmitted to the CSCF.

  The control unit 22 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and executes a predetermined program to control the overall operation of the femtocell base station 1.

  For example, the control unit 22 performs an operation in the listening mode, and detects the state of radio waves from the macro cell base station based on the signal supplied from the wireless communication unit 23. In addition, the control unit 22 selects a location method and controls the wireless communication unit 23 and the interference signal generation unit 25 to emit radio waves according to the location method.

The wireless communication unit 23 performs wireless communication with the mobile device 2 located in the femtocell C ₁ by a method such as W-CDMA or CDMA2000. The wireless communication unit 23 includes a transmission unit 31 and a reception unit 32.

The transmission unit 31 emits radio waves with a predetermined intensity such as an antenna power of 20 mW or less from the antenna 24 according to control by the control unit 22, and transmits predetermined data such as voice data supplied from the network communication unit 21 to the femtocell C. It is transmitted to the mobile device 2 located in ₁ .

  In addition, the transmission unit 31 emits an interference wave from the antenna 24 based on the interference signal supplied from the interference signal generation unit 25.

  The receiving unit 32 outputs a signal obtained in response to reception of radio waves by the antenna 24 to the control unit 22 when operating in the listening mode. The receiving unit 32 receives predetermined data such as voice data transmitted from the mobile device 2 based on the signal supplied from the antenna 24 and outputs the received data to the network communication unit 21.

  The interference signal generation unit 25 generates an interference signal including a white noise signal and a dummy signal according to control by the control unit 22 and outputs the interference signal to the wireless communication unit 23.

Further, the interference signal generation unit 25 stops the generation of the interference signal according to the control by the control unit 22 and ends the emission of the interference wave. A request for location registration is transmitted from the mobile device 2 that has moved to the femtocell C ₁ . For example, the emission of the jamming wave is stopped in response to the request being transmitted from the mobile device 2.

  The location registration process is a process of registering in which cell each mobile station is located in an HSS (Home Subscriber Server) connected to a core network or the like. The HSS is a device that is connected to a core network or the like, and is a server that manages in which cell each mobile device is located and provides the managed information to the CSCF as appropriate.

  The emission of the interference wave may be stopped at a timing when a predetermined time has elapsed since the start of the emission of the interference wave.

  FIG. 9 is a block diagram illustrating a functional configuration example of the femtocell base station 1.

  As shown in FIG. 9, in the control unit 22 of the femtocell base station 1, a detection unit 41 and a visiting area selection unit 42 are realized. At least a part of the functional units shown in FIG. 9 is realized by a predetermined program being executed by the CPU in the control unit 22.

  Based on the signal supplied from the reception unit 32 of the wireless communication unit 23, the detection unit 41 detects the reception status of radio waves from the macrocell base station as shown in FIGS. 3A and 4A.

The detection unit 41 includes information indicating which frequency band of the frequency bands F ₁ , F ₂ , F ₃ , and F ₄ is used by the macro cell base station, and information indicating the reception intensity. It outputs to the service area selection unit 42.

  The visiting system selection unit 42 selects a visiting system based on the information supplied from the detection unit 41.

  FIG. 10 is a diagram collectively showing the above-mentioned selection method of the visiting system.

  As shown in FIG. 10, when the frequency band used by the macrocell base station is one frequency band, the located system selection unit 42 selects the competitive frequency system.

  When the frequency band used by the macrocell base station is two frequency bands and they are adjacent on the frequency axis, the in-zone method selection unit 42 selects the overlapping frequency method, and the frequency band If it is far away, select the jamming method.

  When the frequency band used by the macrocell base station is three or four frequency bands, the located area selection unit 42 selects an interference wave system.

When the femtocell base station 1 can only emit radio waves in any one of the frequency bands F ₁ , F ₂ , F ₃ , and F _{4 at} the same time, the in-zone method selection unit 42 does this. The location method is selected.

  The selection pattern of the visiting system is not limited to that shown in FIG. Assuming that a radio wave having a predetermined bandwidth such as 3.84 MHz is one radio wave, the pattern for selecting the location system is changed as appropriate according to the number of radio waves that can be emitted by the femtocell base station 1.

  When the competing frequency system is selected, the located system selection unit 42 outputs information indicating the center frequency or frequency band of the emitted radio wave and information indicating the intensity of the radio wave to the transmission unit 31.

  In addition, when the overlapping frequency method is selected, the location method selection unit 42 selects the center frequency of the radio wave to be emitted as described with reference to FIG. 5C, information indicating the selected center frequency, Information indicating the intensity of the signal is output to the transmitter 31.

  When the jamming wave method is selected, the located mode selection unit 42 instructs the jamming signal generation unit 25 to emit a jamming wave having a predetermined intensity. In addition, the located system selection unit 42 includes information representing the center frequency or frequency band of the radio wave used for communication with the mobile device 2 that emits the jamming wave, and information representing the radio wave used for communication and the intensity of the jamming wave. To the transmitter 31.

[Operation of femtocell base station 1]
Here, with reference to the flowchart of FIG. 11, the location assistance processing of the femtocell base station 1 will be described.

  This process is triggered by the activation in the listening mode. The femtocell base station 1 operates in the listening mode at a predetermined timing such as once a day.

  In step S <b> 1, the detection unit 41 detects the reception status of radio waves from the macrocell base station based on the signal supplied from the wireless communication unit 23.

  In step S <b> 2, the located area selection unit 42 selects the located area method as described with reference to FIG. 10 based on the information supplied from the detection unit 41.

  In step S3, the transmission unit 31 emits radio waves according to the selected location method.

  For example, when the competitive frequency method is selected, the transmission unit 31 uses the information supplied from the located method selection unit 42 to obtain a predetermined intensity in the same frequency band as the frequency band used by the macrocell base station. The radio wave is emitted.

  When the overlap frequency method is selected, the transmission unit 31 spans each of a plurality of frequency bands used by the macrocell base station based on the information supplied from the located method selection unit 42. A radio wave of a predetermined intensity with a bandwidth of 3.84MHz is emitted.

  When the jamming wave method is selected, the transmission unit 31 emits a jamming wave based on the jamming signal supplied from the jamming signal generation unit 25 and moves based on the information supplied from the located mode selection unit 42. A radio wave of a predetermined frequency band used for communication with the machine 2 is emitted.

Thereafter, the processing is terminated, and communication is performed between the mobile device 2 located in the femtocell C ₁ and the femtocell base station 1.

Through the above processing, the mobile device 2 located in another cell can be transferred to the femtocell C ₁ .

In addition, the operation in the listening mode is repeatedly performed at a predetermined timing such as once a day, so that even if the configuration of the macro cell is changed, the mobile device 2 can be operated in response to the change. The femtocell C ₁ can be located.

[Modification]
In the above description, it is assumed that one of the visiting systems is selected from the three systems of the competing frequency system, the overlap frequency system, and the jamming wave system. You may make it select from one system.

  In this case, when the frequency band used by the macrocell base station is one frequency band, the competitive frequency system is selected, and in other cases, the interference wave system is selected.

  A description will be given of selection of a location method when the femtocell base station 1 can simultaneously emit radio waves of two frequency bands.

  FIG. 12 is a diagram illustrating another example of the competitive frequency method.

When it is detected by the operation in the listening mode that two frequency bands of frequency bands F ₁ and F ₃ that are separated from each other on the frequency axis are used as shown in FIG. 12A, the femtocell base station 1 selects the competition frequency method.

In this case, the femtocell base station 1 emits radio waves in the frequency band F ₁ and radio waves in the frequency band F ₃ so as to compete with each used radio wave as shown in FIG. 12B. The intensity of the radio wave emitted by the femtocell base station 1 is higher than the reception intensity of the radio wave from the macrocell base station.

Thus, as shown in FIG. 12C, the radio waves femtocell base station 1 is fired, it is possible to degrade the radio waves from both the macrocell base station, it is serving the mobile station 2 to the femto cell C ₁ It becomes possible.

Communication is performed with the mobile device 2 located in the femtocell C _{1 using one} of the frequency bands F ₁ and F ₃ .

  FIG. 13 is a diagram illustrating another example of the overlap frequency method.

When it is detected by the operation in the listening mode that _three frequency bands F ₂ , F ₃ and F ₄ adjacent on the frequency axis are used as shown in FIG. 13A, the femtocell base station 1 selects the overlap frequency method.

In this case, the femtocell base station 1, as shown in FIG. 13B, the frequency f _2.5 is an intermediate frequency center frequency f ₂ and f ₃ of the used frequency band, the center frequency f ₃ and f ₄ intermediate selecting a frequency f _3.5 a frequency as the center frequency.

Further, the femtocell base station 1 emits a radio wave having a bandwidth of 3.84 MHz with the frequency f _2.5 as the center frequency and a radio wave with a bandwidth of 3.84 MHz having the frequency f _3.5 as the center frequency. The strength of the radio wave emitted by the femtocell base station 1 is higher than the strength of the radio wave from the macrocell base station.

Thus, as shown in FIG. 13C, the radio waves femtocell base station 1 is fired, it is possible to degrade the radio waves from three macrocell base station, it is serving the mobile station 2 to the femto cell C ₁ It becomes possible.

Between the mobile station 2 located in the femtocell C ₁ , a frequency band with a bandwidth of 3.84 MHz with the frequency f _2.5 as the center frequency and a frequency band with a bandwidth of 3.84 MHz with the frequency f _3.5 as the center frequency. Communication is performed using any one of the frequency bands.

  FIG. 14 is a diagram illustrating an example of a visited system combining a competitive frequency system and an overlapping frequency system.

When it is detected by the operation in the listening mode that the _three frequency bands of the frequency band F ₁ and the adjacent frequency bands F ₃ and F ₄ on the frequency axis are used as shown in FIG. 14A, The femtocell base station 1 selects a serving system that combines the competitive frequency system and the overlapping frequency system.

In this case, the femtocell base station 1 emits radio waves in the frequency band F ₁ so as to compete with radio waves in the used frequency band F ₁ as shown in FIG. 14B. The intensity of the radio wave emitted by the femtocell base station 1 is higher than the reception intensity of the radio wave from the macrocell base station.

Further, the femtocell base station 1, as shown in FIG. 14B, and select the center frequency f _3.5 is the center frequency intermediate frequency f ₃ and f ₄ of the used frequency band, bandwidth of 3.84MHz Which emits a radio wave having a strength higher than that of the radio wave from the macrocell base station.

Thus, as shown in FIG. 14C, the radio waves femtocell base station 1 is fired, it is possible to degrade the radio waves from three macrocell base station, it is serving the mobile station 2 to the femto cell C ₁ It becomes possible.

Between the mobile station 2 located in the femtocell C ₁ , any _one of the frequency band F ₁ and the frequency band having a bandwidth of 3.84 MHz centered on the frequency f _3.5 is used. Communication takes place.

When the femtocell base station 1 can simultaneously emit radio waves of two frequency bands, there are three used frequency bands, and one frequency band is separated from the other two adjacent frequency bands on the frequency axis. Even when the mobile station 2 is in the femtocell C ₁ , the mobile station 2 can be located in the femtocell C ₁ by the visiting area method that combines the competitive frequency method and the overlapping frequency method.

  When the femtocell base station 1 can emit radio waves of two frequency bands at the same time, the competing frequency method is selected when two frequency bands that are separated from each other on the frequency axis have been used. When the three adjacent frequency bands are used, the overlap frequency method is selected, and the two adjacent frequency bands on the frequency axis and one frequency band that is separated from the two frequency bands are selected. In addition, when the three frequency bands are already used, the in-range method combining the competing frequency method and the overlap frequency method is selected. Will be selected.

  As described above, the selection pattern of the in-zone method can be changed according to the number of frequency bands in which the femtocell base station 1 can simultaneously emit radio waves.

  In the above description, the case where the mobile station is assisted in the CDMA communication system has been described. However, the above-described location assistance is a communication system that communicates with a mobile station using a plurality of frequency bands. It can also be applied to other communication systems.

  In place of the femtocell base station 1, a base station for forming a small cell called “picocell” or “microcell” is provided, and the base station assists the cell managed by itself as described above. May be performed. The small base station is a base station that forms a small cell such as a femto cell, a pico cell, or a micro cell.

  The embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

  1 femtocell base station, 2 mobile station, 21 network communication unit, 22 control unit, 23 wireless communication unit, 24 antenna, 25 jamming wave generation unit, 31 transmission unit, 32 reception unit

Claims (8)

Receiving means for receiving radio waves of a predetermined bandwidth emitted by an external base station;
Detecting means for detecting which frequency band of a plurality of frequency bands set as bands usable for communication with a mobile device is received by the receiving means;
A first method for emitting radio waves of the predetermined bandwidth in the same frequency band as the frequency band used by the external base station based on a detection result by the detection means; and used by the external base station A method selecting means for selecting any one of the second methods for emitting radio waves of the predetermined bandwidth so as to straddle each of the plurality of frequency bands being performed;
A small-sized base station comprising: transmission means for emitting radio waves of the predetermined bandwidth according to the method selected by the method selection means. When the number of radio waves of the predetermined bandwidth that can be simultaneously emitted from the transmission means is 1,
The method selection means selects the first method when the frequency band used by the external base station is one frequency band, and when the two frequency bands are adjacent on the frequency axis, The small base station according to claim 1, wherein the second method is selected. The method selection means includes the first method, the second method, and a jamming wave having frequencies in all or some of a plurality of frequency bands that can be used for communication with the mobile device. Select one of the third methods to fire
When the third method is selected by the method selecting unit, the transmitting unit is configured to receive the jamming wave and a radio wave in any one of a plurality of frequency bands usable for communication with the mobile device. The small base station according to claim 1 or 2. The small base station according to claim 3, wherein the method selection means selects the third method when a plurality of frequency bands used by the external base station are separated on the frequency axis. When the number of radio waves of the predetermined bandwidth that can be simultaneously emitted from the transmission means is 2,
The method selection means selects the first method when the frequency band used by the external base station is two frequency bands separated on the frequency axis,
The small base station according to claim 1, wherein the transmission unit emits radio waves having the predetermined bandwidth in the same frequency band as the two frequency bands. The method selection means further selects the second method when the frequency band used by the external base station is three frequency bands adjacent on the frequency axis,
The said transmission means emits the electromagnetic wave of the said predetermined | prescribed bandwidth so that it may straddle one adjacent two frequency bands and the other two frequency bands among the three frequency bands, respectively. Small base station. The method selection means further includes three frequency bands used by the external base station: two frequency bands adjacent on the frequency axis and one frequency band separated from the two frequency bands. When it is a frequency band, select a method that combines the first method and the second method,
The transmitting means emits one radio wave of the predetermined bandwidth so as to straddle the two frequency bands, and the predetermined bandwidth of the same frequency band as the one frequency band apart from the two frequency bands. The small base station according to claim 5 or 6, which emits radio waves. Receive radio waves of a predetermined bandwidth emitted by an external base station,
Detecting which frequency band of a plurality of frequency bands set as bands usable for communication with a mobile device is received by the receiving means,
A first method for emitting radio waves of the predetermined bandwidth in the same frequency band as the frequency band used by the external base station based on a detection result; and a plurality of methods used by the external base station Selecting one of the second methods of emitting radio waves of the predetermined bandwidth so as to straddle each of the frequency bands of,
A communication method for a small base station, comprising: emitting a radio wave of the predetermined bandwidth according to a selected method.

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