JP2012143005A - Relay station, radio communication terminal, radio communication system, and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure stable communication quality by comprehending a position of a radio communication terminal and to achieve a seamless handover while maintaining radio communication.SOLUTION: A relay station 130 comprises: a position estimation unit 350 which monitors communication quality with a radio communication terminal and estimates a position of the radio communication terminal while communication of the radio communication terminal is relayed; and a connection control unit 352 which switches QoS of the radio communication with the radio communication terminal in accordance with the position of the radio communication terminal, to switch a handover reference.

Description

  The present invention relates to a relay station, a wireless communication system, and a wireless communication method capable of relaying communication between a wireless communication terminal and a base station.

In recent years, wireless communication terminals represented by PHS (Personal Handy phone System) terminals and mobile phones have become widespread, and it has become possible to make calls and obtain information regardless of location or time. Especially in recent years, the amount of available information has been increasing, and high-speed and high-quality wireless communication systems have been introduced to download large amounts of data.

As one of such high-speed digital wireless communication systems, there is an OFDM (Orthogonal Frequency Division Multiplexing) system represented by IEEE 802.11 or WiMAX (for example, Non-Patent Document 1). The OFDM scheme is classified as one of the data multiplexing schemes, and uses a large number of carriers on the unit time axis, and the carrier band is set so that the phase of the signal wave to be modulated is orthogonal between adjacent carriers. This is a method of effectively using the frequency band by overlapping a part. Also, while OFDM assigns subchannels for each individual user in a time division manner, a plurality of users share all subchannels, and OFDMA (Orthogonal Frequency) assigns a subchannel with the highest transmission efficiency for each user. Division
Multiplex Access (Orthogonal Frequency Division Multiple Access) is also provided.

  When the next-generation high-speed wireless communication method such as WiMAX uses a high-frequency band of 2.5 GHz or higher, a communication range (coverage) for one base station in an area where the radio wave condition is bad such as many obstacles. ) Becomes smaller, and a large number of base stations must be provided to cover the entire periphery. Furthermore, when such an area where the communication range of one base station is small is passed by a moving body such as a train or an automobile, handovers that switch base stations as connection destinations frequently occur, resulting in a decrease in communication quality and an increase in power consumption. Invite.

  Therefore, a technique is disclosed in which a relay station that relays between a base station and a wireless communication terminal is fixed in the moving body to stabilize communication power in the moving body. However, such a relay station includes an amplifier and a filter, has only a function of amplifying power while maintaining a signal waveform, and has not been added with a communication control function. Therefore, no consideration has been given to communication quality degradation and wasteful consumption of power consumption.

  As a technology for developing such a relay station, a technology is disclosed in which a relay station is installed in an aircraft and a wireless communication terminal is connected to a base station antenna connected to the ground communication network through the relay station (for example, Patent Document 1). Here, it is possible to communicate with the terrestrial communication network without using a satellite using a terminal owned by the passenger, and it is possible to receive services such as Internet communication and telephone calls while in the aircraft.

JP 2005-159448 A

However, in the above-described relay station in the aircraft, the wireless communication system between the wireless communication terminal and the relay station is different from the wireless communication system between the wireless communication terminal and the base station. It was necessary to prepare a wireless communication system dedicated to the relay station separately between the mobile station and the base station. Therefore, the pre-processing load and equipment cost for performing wireless communication have been increased.

  In addition, the communication connection state was maintained on the premise that the connection with the base station or relay station in the wireless communication terminal was temporarily disconnected due to the fact that the communication had to be disconnected once when getting on and off the aircraft. The handover of the wireless communication terminal that switches the connection destination is not considered.

  Even if a wireless LAN that enables wireless communication in a small space such as a mobile unit is combined with the current wireless communication system and the function is added to the relay station, the wireless communication terminal is connected between the normal base station and the relay station. Wireless communication using different wireless communication methods is forced, and communication information before switching cannot be used at the time of switching, and a new communication path has to be established each time.

  In view of such problems, the present invention is a relay station and a wireless communication system that can ascertain the position of a wireless communication terminal, ensure stable communication quality, and realize seamless handover while maintaining wireless communication. It is an object of the present invention to provide a wireless communication method.

  In order to solve the above problems, a typical configuration of the present invention is a relay station capable of relaying communication between a wireless communication terminal and a base station, and relays communication between the wireless communication terminal and the base station. In this case, the monitoring unit that monitors the communication quality between the wireless communication terminal and the own station, and the wireless communication terminal is controlled so that the wireless communication terminal and the base station communicate without going through the own station according to the monitoring result. A connection control unit. Such a relay station may be further provided with a position estimation unit that is installed in a mobile body on which a person can get on and off and estimates the position of the wireless communication terminal according to the monitoring result of the monitoring unit.

The position estimation unit grasps the position of the wireless communication terminal, particularly whether the mobile body is located inside or outside (getting on or off), and the connection control unit provides a communication state suitable for the wireless communication terminal according to the position. By providing a communication state suitable for a wireless communication terminal in this way, stable QoS (Quality of Service) can be ensured even when staying in the mobile body, and even when the mobile body leaves the mobile body With this QoS, seamless handover can be realized while maintaining wireless communication.

  The position estimation unit can determine that the wireless communication terminal exists in the moving body when the value indicating the communication quality is equal to or higher than the predetermined value and the communication quality is stable within the predetermined fluctuation range.

  When the mobile body leaves the mobile body, the radio quality is greatly deteriorated because the metal covering the mobile body becomes a barrier for shielding radio waves. In addition, if the mobile body further moves after going out of the mobile body, the distance between the relay station and the wireless communication terminal is increased, so that the communication quality is further deteriorated. Therefore, the presence of the wireless communication terminal in the moving body can be determined when the value indicating the communication quality is equal to or higher than the predetermined value and the communication quality is stable within the predetermined fluctuation range. It can be judged that it exists. In addition, since the position estimation unit can determine not only the inside and outside of the mobile body but also the switching time point, the wireless communication terminal can prompt the wireless communication terminal to perform a handover before the handover is difficult to perform the handover. Thus, seamless handover can be more reliably realized while maintaining wireless communication.

  The connection control unit may cause the QoS with high communication quality to be selected when the wireless communication terminal exists in the moving body, and the QoS with high mobility when the wireless communication terminal exists outside the moving body.

In the mobile body, there is no barrier to wireless communication, and there is almost no change in the distance between the relay station and the wireless communication terminal in a small space such as the mobile body, so the communication environment is very good. Therefore, when the wireless communication terminal exists in the mobile body, QoS with high communication quality can be selected and power consumption can be reduced. Since the communication quality is not guaranteed outside the mobile body, it is necessary to select a QoS with high mobility and cancel the reduction in power consumption.

  The connection control unit may instruct suppression of handover when the wireless communication terminal exists in the moving body, and may instruct handover to a base station other than the own station when the wireless communication terminal exists outside the moving body.

  As described above, since a good communication environment with the relay station is formed in the mobile body, even if a base station with a good communication quality temporarily exists, it should not be handed over in a dark manner. Further, outside the mobile body, wireless communication with a relay station that is likely to increase in distance should not be maintained indefinitely. Therefore, when the wireless communication terminal is present in the mobile body, the handover is suppressed by measures such as increasing the handover threshold, and when the wireless communication terminal is present outside the mobile body, the threshold is lowered and other base stations other than the relay station are provided. Wireless communication is shifted.

  The connection control unit may instruct a handover to a base station in which the local station is performing wireless communication when the wireless communication terminal exists outside the moving body.

  The relay station selects an arbitrary base station as the optimum wireless communication destination. Therefore, there is a high possibility that the base station with which the relay station wirelessly communicates is the optimum wireless communication destination for the wireless communication terminal that has existed in the vicinity of the relay station until just before. The relay station provides the wireless communication terminal with information on this base station that has good wireless communication with itself, so that the wireless communication terminal can establish wireless communication with the base station at an early stage.

  The relay station may further include a terminal function unit that functions as a radio communication terminal for the base station, and a base station function unit that functions as a base station for the radio communication terminal.

  With this configuration, the relay station functions as a wireless communication terminal when connecting to the base station, and can handle the relay station like the wireless communication terminal.

  The terminal function unit may perform wireless communication with the base station by a wireless communication method used between the base station and the wireless communication terminal.

  With this configuration, it is not necessary to newly prepare a wireless communication method between the relay station and the base station, and the processing load and equipment cost of the wireless communication terminal can be reduced. In addition, since the terminal function unit of the relay station is placed in the same situation as the wireless communication terminal in the mobile body, it is possible to infer communication quality and the like on behalf of the wireless communication terminal and to transmit the information to the wireless communication terminal It becomes.

  Another exemplary configuration of the present invention is a wireless communication system including a wireless communication terminal, a base station that performs wireless communication with the wireless communication terminal, and a relay station that can relay communication between the wireless communication terminal and the base station. The radio communication terminal includes a terminal radio communication unit that establishes radio communication with a base station or a relay station, and a handover request unit that requests a handover according to a handover standard from the relay station. When relaying communication between a communication terminal and a base station, a monitoring unit that monitors communication quality between the wireless communication terminal and the local station, and a position that estimates the position of the wireless communication terminal according to the monitoring result of the monitoring unit An estimation unit and a connection control unit that switches a QoS of radio communication with the radio communication terminal according to a position of the radio communication terminal and switches a handover reference of the radio communication terminal, and the base station is a radio communication terminal Depending on the handover request, characterized in that it comprises a base station communication section for performing a handover of the relay station and the own station.

Another typical configuration of the present invention is to perform wireless communication using a wireless communication terminal, a base station that performs wireless communication with the wireless communication terminal, and a relay station that can relay communication between the wireless communication terminal and the base station. A wireless communication method to be executed, wherein the wireless communication terminal establishes wireless communication with the relay station, the relay station monitors the communication quality of the wireless communication terminal and estimates the position of the wireless communication terminal, According to the position of the radio communication terminal, the QoS of radio communication with the radio communication terminal is switched, and the handover standard of the radio communication terminal is switched. The radio communication terminal is directed to the instructed base station according to the handover standard from the relay station. The base station executes handover from the relay station to the own station in response to the handover request from the radio communication terminal.

  The above-described components based on the technical idea of the relay station and the description thereof can be applied to the wireless communication system and the wireless communication method.

  As described above, according to the relay station of the present invention, it is possible to grasp the position of the wireless communication terminal to ensure stable communication quality and to realize seamless handover while maintaining wireless communication.

1 is a block diagram showing a schematic configuration of a wireless communication system. It is the functional block diagram which showed the hardware constitutions of the PHS terminal. It is the perspective view which showed the external appearance of the PHS terminal. It is the block diagram which showed the schematic structure of the base station. It is the block diagram which showed the schematic structure of the relay station. It is explanatory drawing which showed the positional relationship when a PHS terminal exists in a moving body. It is explanatory drawing which showed the positional relationship when a PHS terminal detaches | leaves out of a moving body. It is explanatory drawing which showed the image of the data transfer by mobile IP. It is explanatory drawing for demonstrating the registration process of a relay station. FIG. 6 is an explanatory diagram for explaining handover processing of a relay station. It is explanatory drawing for demonstrating the radio | wireless establishment process with the relay station in a PHS terminal. It is explanatory drawing for demonstrating the leaving process from the relay station in a PHS terminal.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  A wireless communication terminal represented by a PHS terminal, a mobile phone, or the like constructs a broadband wireless communication system with a plurality of base stations arranged at predetermined intervals, and other PHS terminals and communication networks are connected through this wireless communication system. Communicate with the above server. In the present embodiment, QoS maintenance and handover reference setting in a wireless communication system including such a wireless communication terminal will be described.

Here, in order to facilitate understanding of the present embodiment, the schematic configuration of the wireless communication system will be described first, and then the specific operation of the wireless communication terminal will be described. In addition, although a PHS terminal is cited here as a wireless communication terminal, the present invention is not limited to such a case. A mobile phone, a notebook personal computer, a PDA (Personal Digital Assistant), a digital camera, a music player, a car navigation system, a portable TV, Various electronic devices capable of wireless communication such as game devices, DVD players, and remote controllers can also be used as wireless communication terminals. In addition, the moving body indicates a vehicle on which a person can get on and off, such as an automobile, a bus, a train (train), a ship, and an aircraft.

(Wireless communication system 100)
FIG. 1 is a block diagram illustrating a schematic configuration of a wireless communication system 100. The wireless communication system 100 includes a PHS terminal 110 (110A, 110B), a base station 120 (120A, 120B), a relay station 130, an ISDN (Integrated Services Digital Network) line, the Internet, a dedicated line, and the like. Communication network 140 and relay server 150
It is comprised including.

  In such a wireless communication system 100, when a user connects a communication line from his / her PHS terminal 110A to another PHS terminal 110B, the PHS terminal 110A makes a wireless connection request to the base station 120A within the communicable range. . The base station 120A that has received the wireless connection request requests the relay server 150 to establish a communication connection with the communication partner via the communication network 140, and the relay server 150 refers to the location registration information of the other PHS terminal 110B, and so on. The base station 120B within the wireless communication range of the PHS terminal 110B is selected to secure a communication path between the base station 120A and the base station 120B, and communication between the PHS terminal 110A and the PHS terminal 110B is established.

  At this time, when the user gets on, for example, a train as the moving body 160, the PHS terminal 110A switches to indirect communication via the relay station 130 instead of directly with the base station 120A. The relay station 130 is fixed to the moving body 160 and moves together with the moving body 160, and makes the moving body a communicable area. The PHS terminal 110A and the relay station 130 possessed by the user who has entered the moving body move together without any change in the positional relationship, and block between the two unless an operation such as searching for an empty seat occurs. Since there is no barrier, stable wireless communication can be ensured. Therefore, the PHS terminal 110 </ b> A can maintain communication with another PHS terminal 110 </ b> B via the relay station 130 regardless of the movement of the moving body 160. Hereinafter, the PHS terminal 110, the base station 120, and the relay station 130 that are components of the wireless communication system 100 will be described individually.

(PHS terminal 110)
FIG. 2 is a functional block diagram showing a hardware configuration of the PHS terminal 110, and FIG. 3 is a perspective view showing an appearance of the PHS terminal 110. As shown in FIG. The PHS terminal 110 includes a terminal control unit 210, a terminal memory 212, a display unit 214, an operation unit 216, a voice input unit 218, a voice output unit 220, and a terminal wireless communication unit 222. .

  The terminal control unit 210 manages and controls the entire PHS terminal 110 using a semiconductor integrated circuit including a central processing unit (CPU). The terminal control unit 210 also performs a call function, a mail transmission / reception function, an imaging function, a music playback function, and a TV viewing function using the program in the terminal memory 212. In addition, the terminal control unit 210 also functions as a handover request unit 230 that requests a handover according to a handover standard from the relay station 130. The terminal memory 212 includes a ROM, a RAM, an EEPROM, a nonvolatile RAM, a flash memory, an HDD, and the like, and stores a program processed by the terminal control unit 210, audio data, and the like.

  The display unit 214 includes a liquid crystal display, an EL (Electro Luminescence), etc., and is stored in the terminal memory 212 or provided from an application relay server (not shown) via the communication network 140. GUI (Graphical User Interface) can be displayed. The operation unit 216 includes switches such as a keyboard, a cross key, and a joystick, and receives a user operation input.

  The voice input unit 218 includes voice recognition means such as a microphone, and converts a user voice input during a call into an electrical signal that can be processed in the PHS terminal 110. The voice output unit 220 includes a speaker, and converts the voice signal of the other party received by the PHS terminal 110 into voice and outputs the voice. Further, a ring tone, an operation sound of the operation unit 216, an alarm sound, etc. can be output.

The terminal wireless communication unit 222 performs wireless communication with the base station 120 or the relay station 130 in the communication network 140. Various wireless communication methods such as a TDMS (Time Division Multiple Access) method, an OFDM method, and an OFDMA method can be applied to the terminal wireless communication unit 222.

(Base station 120)
FIG. 4 is a block diagram illustrating a schematic configuration of the base station 120. The base station 120 includes a base station control unit 250, a base station memory 252, a base station wireless communication unit 254, and a base station wired communication unit 256.

  The base station control unit 250 manages and controls the entire base station 120 using a semiconductor integrated circuit including a central processing unit (CPU). The base station memory 252 includes a ROM, a RAM, an EEPROM, a nonvolatile RAM, a flash memory, an HDD, and the like, and stores a program processed by the base station control unit 250.

  The base station wireless communication unit 254 establishes wireless communication with the PHS terminal 110 or the relay station 130 using, for example, the OFDMA method, and adaptively changes the modulation method according to the communication state with the PHS terminal 110 or the relay station 130. (Adaptive modulation). In addition, the base station radio communication unit 254 executes handover between the relay station 130 and the own station in response to a handover request from the PHS terminal 110. The base station wired communication unit 256 can be connected to various servers including the relay server 150 via the communication network 140.

(Relay station 130)
FIG. 5 is a block diagram showing a schematic configuration of relay station 130. The relay station 130 includes a relay station control unit 310, a relay station memory 312 and a relay station wireless communication unit 314.

  The relay station control unit 310 manages and controls the entire relay station 130 by a semiconductor integrated circuit including a central processing unit (CPU). The relay station memory 312 includes a ROM, a RAM, an EEPROM, a nonvolatile RAM, a flash memory, an HDD, and the like, and stores a program processed by the relay station control unit 310. The relay station wireless communication unit 314 is connected to the PHS terminal 110 and the base station 120 and relays between the PHS terminal 110 and the base station 120. The relay station wireless communication unit 314 includes a monitoring unit 348, a position estimation unit 350, a connection control unit 352, a terminal function unit 354, a base station function unit 356, a position registration information control unit 358, a channel information control unit 360, authentication information. It functions as the control unit 362.

  The monitoring unit 348 monitors communication quality with the PHS terminal 110 when the relay station 130 is relaying communication with the PHS terminal 110.

The position estimation unit 350 estimates the position of the PHS terminal 110, particularly whether or not it exists in the moving body, according to the monitoring result of the monitoring unit 348. Here, communication quality includes electric field strength, SNR (Signal
to noise ratio) and BER (Bit Error Rate).

FIG. 6 is an explanatory diagram showing a positional relationship when the PHS terminal 110 exists in the moving body. The position estimation unit 350 constantly transmits (broadcasts) a weak quantitative signal into the moving body, and the PHS terminal 110 transmits from the relay station 130 through a radio wave intensity measurement command such as a report request command from the relay station 130. The radio field intensity of the determined quantitative signal is measured at predetermined time intervals, and is returned to the relay station 130 as the radio field intensity information.

  The position estimation unit 350 determines that the PHS terminal 110 exists in the moving body when the radio wave intensity information from the PHS terminal 110 exceeds a predetermined amount and is stable within a predetermined fluctuation range. The mobile body 160 is often covered with a metal that shields radio waves, and the communication quality differs significantly between the inside and outside of the mobile body. In addition, since there is no change in the distance between the PHS terminal 110 and the relay station 130 or the spatial positional relationship in the mobile body, stable communication can be performed with low power. Therefore, the position estimation unit 350 can estimate that the PHS terminal 110 exists in the moving body because the communication quality is high and stable.

  Here, the position estimation unit 350 estimates the distance by measuring the radio field intensity of the quantitative signal. However, the position estimation unit 350 is not limited to this, and if the transmission power of the PHS terminal 110 can be grasped, the transmission power and It is also possible to derive power degradation from the radio wave intensity of the received signal and estimate the distance, or to measure the propagation delay of the radio wave forward path with the PHS terminal 110 and estimate the distance.

  FIG. 7 is an explanatory diagram showing the positional relationship when the PHS terminal 110 leaves the moving body. When the user of the PHS terminal 110 goes out of the moving body from the moving body, the radio quality is greatly deteriorated because the metal covering the moving body 160 becomes a barrier for shielding radio waves. Further, after moving out of the moving body, if the moving body 160 further moves as indicated by the white arrow, the distance between the relay station 130 and the PHS terminal 110 increases, so that the communication quality further deteriorates. Therefore, the value indicating the communication quality is equal to or less than the predetermined value or the communication quality deviates outside the predetermined fluctuation range, and the position estimation unit 350 determines that the PHS terminal 110 exists outside the moving body.

  In addition, since the position estimation unit 350 can determine not only the inside and outside of the mobile body but also the switching time point, before the PHS terminal 110 and the relay station 130 are separated so as to make handover difficult, a connection control unit described later By 352, it is possible to prompt the PHS terminal 110 to perform a handover. With this configuration, it is possible to avoid the problem that communication is temporarily disconnected before the handover is performed due to the movement of the mobile body 160, and the initial setting such as the location registration of the PHS terminal 110 must be set again. In this way, seamless handover can be reliably realized while maintaining wireless communication.

  The connection control unit 352 switches the QoS of wireless communication of the PHS terminal 110 according to the position of the PHS terminal 110, and switches the handover reference of the PHS terminal 110.

  Regarding the QoS, the connection control unit 352 causes the PHS terminal 110 to select a QoS with high communication quality as wireless communication with the PHS terminal 110 while the position estimation unit 350 estimates that the PHS terminal 110 exists in the moving body. When the position estimation unit 350 estimates that the object exists outside the moving body, the QoS having high mobility is selected. Here, QoS indicates the quality of service including communication speed, modulation method, and output voltage, and can be arbitrarily adjusted according to communication quality.

  For example, in a mobile body, as described above, there is no barrier to wireless communication, and there is almost no change in the distance between the relay station 130 and the PHS terminal 110 in a small space such as the mobile body 160, so the communication environment is extremely Good for. Therefore, as shown in FIG. 6, when the PHS terminal 110 is present in the moving body, it is possible to select QoS with high communication quality and reduce power consumption. In addition, since the communication quality is not guaranteed when moving outside the moving body as shown in FIG. 7, the connection control unit 352 must select a QoS with high mobility and cancel the reduction in power consumption.

  Regarding the handover criteria, the connection control unit 352 instructs to suppress handover when the PHS terminal 110 exists in the moving body, and performs handover to the base station 120 other than the own station when the PHS terminal 110 exists outside the moving body. Instruct. In the conventional wireless communication system, the request for handover is limited to the PHS terminal 110, but in the next-generation high-speed wireless communication system such as WiMAX, the handover request can be executed bidirectionally. Therefore, it is possible to request handover from the connection control unit 352 to the PHS terminal 110.

  As described above, since a good communication environment with the relay station 130 is formed in the mobile body, even if the base station 120 having a good communication quality temporarily exists, it should not be handed over in a dark manner. Further, outside the moving body, wireless communication with the relay station 130 that is likely to increase in distance should not be maintained indefinitely. Therefore, when the PHS terminal 110 exists inside the moving body as shown in FIG. 6, the handover is suppressed by measures such as increasing the threshold value of the handover, and when it exists outside the moving body as shown in FIG. And the wireless communication is transferred to another base station 120 other than the relay station 130.

  The connection control unit 352 not only instructs the handover to the base station 120 other than the local station when the PHS terminal 110 exists outside the mobile body, but also performs the handover to the base station 120 on which the local station is performing wireless communication. You may instruct.

  The relay station 130 selects an arbitrary base station 120 as an optimal wireless communication destination. Therefore, the PHS terminal 110 that has existed in the vicinity of the relay station 130 until just before is highly likely that the base station 120 with which the relay station 130 communicates wirelessly becomes the optimum wireless communication destination. The relay station 130 provides the PHS terminal 110 with information on the base station 120 that has good wireless communication with the local station, so that the PHS terminal 110 can establish wireless communication with the base station 120 at an early stage. .

  Furthermore, the connection control unit 352 can adaptively change the modulation method according to the communication state with the PHS terminal 110 (adaptive modulation).

  As described above, the position estimation unit 350 grasps the position of the PHS terminal 110, particularly whether it is located inside or outside (getting on and off) of the moving body, and the connection control unit 352 determines whether the PHS terminal 110 is in accordance with the position. Provide suitable communication status. By providing a communication state suitable for the PHS terminal 110 in this way, stable QoS can be secured even when staying in the mobile body, and wireless communication can be performed with appropriate QoS switched even when the mobile body leaves the mobile body. Seamless handover can be realized while maintaining communication.

  The terminal function unit 354 functions as the PHS terminal 110 with respect to the base station 120. As shown in FIG. 5, the relay station 130 includes, for example, four terminal function units 354 and each independently connects to the base station 120. The four terminal function units 354 can be connected to one base station 120 or to a plurality of base stations 120, respectively. The four terminal function units 354 can accommodate, for example, about 40 PHS terminals 110, which is ten times as large. This is because the communication of a plurality of PHS terminals 110 can be divided and allowed in the time direction and the band direction with the resources of one terminal function unit 354. Therefore, the wireless communication system 100 can be applied not only to voice communication using data communication and VoIP (Voice over Internet Protocol) but also to voice communication that requires real-time communication.

As will be described later in detail, the terminal function unit 354 sequentially switches the handover points of the plurality of terminal function units 354 without superimposing even if a handover of the relay station 130 to the base station 120 occurs. Accordingly, even if one terminal function unit 354 is disconnected from the wireless communication at the time of switching, the wireless communication between the other terminal function unit 354 and the base station 120 is not interrupted. Communication can be maintained, and seamless handover is possible.

  In addition, the terminal function unit 354 performs wireless communication with the base station 120 by a wireless communication scheme used between the base station 120 and the PHS terminal 110, here, WiMAX. Such a wireless communication system is composed of a MAC physical layer specialized for relay stations within a standard range.

  With this configuration, it is not necessary to newly prepare a wireless communication method between the relay station 130 and the base station 120, and the processing load and equipment cost of the PHS terminal 110 can be reduced. Further, since the terminal function unit 354 of the relay station 130 is placed in a situation equivalent to that of the PHS terminal 110 in the mobile body, the communication quality is estimated on behalf of the PHS terminal 110 and the information is transmitted to the PHS terminal 110. Is possible.

  The base station function unit 356 functions as a base station for the PHS terminal 110. As shown in FIG. 5, the base station function unit 356 is basically composed of one unit, and is responsible for communication with all the PHS terminals 110 in the mobile body. Moreover, when it applies to a space large to some extent, such as a ship and an aircraft, it can also comprise in multiple. With this base station function unit 356, one or a plurality of PHS terminals 110 in the moving body can be maintained as if they were connected to the base station 120, although they are actually connected to the relay station 130. it can.

  The location registration information control unit 358 manages the MAC address, IP address, and location registration information of the PHS terminal 110 connected to the base station function unit 356. Also, in this embodiment, the relay station 130 uses a mobile communication system so that the wireless communication system from the PHS terminal 110 is the same regardless of whether the connection destination with the PHS terminal 110 is the base station 120 or the relay station 130. It functions as an IP foreign agent.

  FIG. 8 is an explanatory diagram showing an image of data transfer by mobile IP. In FIG. 8A, the PHS terminal 110 communicates directly with the base station 120. Here, the PHS terminal 110 transfers the IP data encapsulated by the mobile IP to the home agent 370. In FIG. 8B, the PHS terminal 110 is connected to the base station 120 via the relay station 130. Here, the PHS terminal 110 performs the same transfer to the relay station 130 as in FIG. 8A, but an FA address that identifies the foreign agent is used between the relay station 130 and the base station 120. Accordingly, the encapsulated FA address and IP data are transferred between the relay station 130 and the base station 120 and between the base station 120 and the home agent 370. The location registration information control unit 358 also manages the FA address of the relay station 130 as described above.

  Further, since the relay station 130 is also assumed to move with respect to the relay server 150 in the same manner as the PHS terminal 110, the position of the relay station 130 is also registered in the relay server 150. Therefore, the PHS terminal 110 connected to the base station 120 via the relay station 130 is registered as a lower terminal of the relay station 130 with respect to the base station 120.

  The channel information control unit 360 controls the QoS between the PHS terminal 110 and the base station function unit 356 according to the communication quality between the terminal function unit 354 and the base station 120 so that the QoS can be maintained. Also controls.

The authentication information control unit 362 functions as an authentication (AAA: Authentication, Authorization, Accounting) server for the base station function unit 356 and transfers authentication information to the PHS terminal 110.

(Wireless communication method)
Next, a wireless communication method for performing wireless communication using the PHS terminal 110, the base station 120, and the relay station 130 will be described in detail. Here, the operation of the relay station 130 includes (1) registration of the relay station 130, (2) handover of the relay station 130, (3) radio establishment with the relay station 130 in the PHS terminal 110, and (4) in the PHS terminal 110. The explanation will be divided into separation from the relay station 130.

  FIG. 9 is an explanatory diagram for explaining (1) the registration process of the relay station 130. In particular, FIG. 9A shows a positional relationship between the relay station 130 and the base station 120, and FIG. 9B shows a sequence diagram showing registration processing of the relay station 130.

  First, the connection control unit 352 of the relay station 130 makes an activation request to each terminal function unit 354 (354A, 354B) in the relay station (S400), and each terminal function unit 354A, 254B executes carrier sense, Establishes wireless communication independently of the base station 120 with high communication quality (S402).

When the wireless communication with the base station 120 is established, each terminal function unit 354A, 354B transmits a completion notification to the connection control unit 352 (S404). The connection control unit 352 transmits the MAC address, IP address, and base station processing capability (Capabilitiy) included in the completion notification to the location registration information control unit 358 (S406). It transmits to the authentication information control part 362 (S408). Such connection information is periodically notified from each terminal function unit 354 to the connection control unit 352 (S410), and the relay station 130 is handed over according to the contents.

  FIG. 10 is an explanatory diagram for explaining (2) the handover process of the relay station 130. In particular, FIG. 10A shows a positional relationship between the relay station 130 and the base station 120, and FIG. 10B shows a sequence diagram showing a handover process of the relay station 130.

  The relay station 130 communicates with the base station 120A through the terminal function units 354A and 354B (S450). The connection control unit 352 receives periodic notification of connection information from the terminal function unit 354 (S452), and when it becomes difficult to maintain communication with the currently connected base station 120A due to the movement of the relay station 130, the connection control unit 352 Unit 352 attempts to perform handover to another base station 120B. At the time of such a handover, the terminal function units 354A and 354B are not switched at a time, but are switched sequentially at different timings.

  First, the connection control unit 352 issues a handover instruction to only one terminal function unit 354A of the two terminal function units 354A and 354B connected to the base station 120A (S454), and the terminal function unit 354A A handover request is made to 120A (S456).

  The base station 120A that has received the handover request notifies terminal information to the switching destination base station 120B via the relay server 150 (S458), and returns a handover response to the terminal function unit 354A (S460). The terminal function unit 354A issues a connection request to the base station 120B as a new connection destination (S462), and the communication connection between the terminal function unit 354A and the base station 120B is established with the connection response (S464) (S466). . The terminal function unit 354A notifies the connection control unit 352 that the handover has been completed (S468).

When the handover of the terminal function unit 354A is completed, the connection control unit 352 subsequently makes a handover request to the terminal function unit 354B. Since this handover operation is substantially the same as the processing (S454 to S468) of the terminal function unit 354A except that the target is the terminal function unit 354B, the description thereof is omitted here.

  When the handover of the terminal function units 354A and 354B is completed, the connection control unit 352 transmits the connection information at that time to the location registration information control unit 358 and the authentication information control unit 362 (S470).

  As described above, in the handover of the relay station 130 in the present embodiment, all the terminal function units 354 do not perform the handover at the same time and are shifted in timing, so that the communication as the whole relay station 130 is not interrupted. Stable wireless communication is possible.

  FIG. 11 is an explanatory diagram for explaining (3) wireless establishment processing with the relay station 130 in the PHS terminal 110. In particular, FIG. 11A shows a positional relationship among the relay station 130, the base station 120, and the PHS terminal 110, and FIG. 11B shows a sequence diagram showing a wireless establishment process with the relay station 130 in the PHS terminal 110. .

  The PHS terminal 110 has already established wireless communication with the base station 120 (S500). At this time, the base station 120 notifies the PHS terminal 110 of the base station function unit 356 of the relay station 130 belonging to the own station as an adjacent base station 120 (S502). The PHS terminal 110 acquires broadcast information transmitted from the base station function unit 356 based on the information (S504), and prepares for handover. The PHS terminal 110 can determine the handover timing based on the neighbor information from the base station 120, and can perform a smooth handover into the moving body.

  The PHS terminal 110 performs carrier sense to the relay station 130 through broadcast information from the base station function unit 356, and makes a handover request to the base station 120 if the electric field strength from the base station function unit 356 is equal to or greater than a predetermined value. (S506). At this time, since the target relay station 130 performs communication in a limited space such as a mobile object, the predetermined value can be set to a value higher than the threshold value for the normal base station 120.

  Upon receiving a handover request from the PHS terminal 110, the base station 120 instructs the relay server 150 to perform handover, and when the relay server 150 is confirmed, the handover request is sent to the connection control unit 352 through the terminal function unit 354 of the relay station 130. Is transmitted (S508). Then, the connection control unit 352 waits for a connection request from the PHS terminal 110 to arrive at the base station function unit 356 (S510).

  In response to the handover response (S512) from the base station 120, the PHS terminal 110 makes a connection request to the connection control unit 352 through the base station function unit 356 of the relay station 130 (S514), and the connection control unit 352 A preparation completion response is made (S516). In response to the preparation completion response, the base station function unit 356 makes a channel reservation request to the channel information control unit 360 (S518), and the channel information control unit 360 executes channel reservation in the terminal function unit 354 (S520). . In this way, wireless communication between the PHS terminal 110 and the relay station 130 and between the relay station 130 and the base station 120 is established (S522), and the PHS terminal 110 can perform wireless communication similar to the normal base station 120.

  Then, when the position estimation unit 350 confirms that the PHS terminal 110 exists in the moving body, the connection control unit 352 selects QoS with high communication quality, reduces power consumption, and further performs handover of the PHS terminal 110. The threshold is increased to suppress handover (S524).

FIG. 12 is an explanatory diagram for explaining (4) the process of leaving the relay station in the PHS terminal. In particular, FIG. 12A shows a positional relationship among the relay station 130, the base station 120, and the PHS terminal 110, and FIG. 12B shows a sequence diagram showing a leaving process from the relay station in the PHS terminal.

  The PHS terminal 110 has already established wireless communication with the relay station 130, and the relay station 130 has established wireless communication with the base station 120 (S550). At this time, the position estimation unit 350 causes the base station function unit 356 to transmit a weak quantitative signal (S552), and the PHS terminal 110 measures the radio field intensity of the quantitative signal transmitted from the relay station 130 at predetermined time intervals. (S554), the radio wave strength information is returned to the relay station 130 (S556). The radio wave intensity information is analyzed by the position estimation unit 350 (S558).

  Here, when the position estimation unit 350 determines that the radio wave intensity indicated in the radio wave intensity information is equal to or less than a predetermined value or the radio wave intensity deviates from a predetermined fluctuation range, it is considered that the radio wave intensity has significantly deteriorated, that is, Assuming that the PHS terminal 110 has left the mobile body 160, the PHS terminal 110 is notified to the connection control unit 352 (S560). The connection control unit 352 makes a handover request to the PHS terminal 110 through the base station function unit 356 (S562). At this time, the handover request prompts the mobile station to make a handover to the base station 120 with which wireless communication is established as a candidate, selects a QoS with high mobility, and returns power consumption to normal. Here, when making a handover request, the base station 120 that establishes wireless communication with the own station is used as a handover candidate. However, the present invention is not limited to this, and it is possible to request that another base station be selected. It is also possible to request the PHS terminal 110 to select a handover destination base station.

  In addition, when the PHS terminal 110 and the relay station 130 are communicating, the base station 120 and the PHS terminal 110 communicate with each other as a handover criterion when the relay station 130 requests the PHS terminal 110 to perform a handover. In some cases, it may be different from the handover criterion when handing over to another base station. Further, when the PHS terminal 110 and the base station 120 are communicating, the handover criterion for performing handover to another base station is that the PHS terminal 110 and the base station 120 are communicating. It may be different from the handover criterion when handing over to 130.

  In addition, the connection control unit 352 transmits information on the PHS terminal 110 necessary for handover to the base station 120 in parallel (S564). The base station 120 receives the handover request from the relay station 130, instructs the relay server 150 to perform handover, obtains confirmation from the relay server 150, and enters a state of waiting for a connection request from the PHS terminal 110 (S566).

  The PHS terminal 110 acquires broadcast information transmitted from the base station 120 (S568) and prepares for handover. The PHS terminal 110 performs carrier sense to the base station 120 through this broadcast information. If the electric field strength from the base station 120 is equal to or greater than a predetermined value, the base station 120 is used as a handover destination and a handover response is returned to the relay station 130. (S570).

  The PHS terminal 110 transmits a connection request to the base station 120 (S572). In response to the connection request from the PHS terminal 110, the base station 120 returns a connection response to the PHS terminal 110 (S574). Thus, wireless communication between the PHS terminal 110 and the base station 120 is established (S576). In response to the handover response, the base station function unit 356 makes a channel release request to the channel information control unit 360 (S578), and the channel information control unit 360 releases the channel in the terminal function unit 354 (S580).

Even in such a wireless communication method, it is possible to grasp the position of the PHS terminal 110 to ensure stable communication quality and to realize seamless handover while maintaining wireless communication.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  In the above-described embodiment, the wireless communication terminal has been described using a PHS terminal or the like, but is not necessarily limited to a PHS terminal. For example, it is possible to construct this wireless communication system by high-speed digital wireless communication (for example, WiMAX, next-generation PHS, etc.) using the OFDM method or OFDMA method. In this case, the wireless communication terminal or relay station uses the OFDM method. And a communication function corresponding to the OFDMA system.

  Note that each step in the wireless communication method of the present specification does not necessarily have to be processed in time series in the order described as a sequence diagram, and may include processing in parallel or by a subroutine.

  The present invention can be used for a relay station, a wireless communication system, and a wireless communication method capable of relaying communication between a wireless communication terminal and a base station.

110 ... PHS terminal (wireless communication terminal)
DESCRIPTION OF SYMBOLS 120 ... Base station 130 ... Relay station 160 ... Mobile body 350 ... Location estimation part 352 ... Connection control part 354 ... Terminal function part 356 ... Base station function part 358 ... Location registration information control part 360 ... Channel information control part 362 ... Authentication information Control unit

Claims (10)

A relay station capable of relaying communication between a wireless communication terminal and a base station,
When relaying communication between the wireless communication terminal and the base station, a monitoring unit that monitors communication quality between the wireless communication terminal and the own station;
In accordance with the monitored result, a connection control unit that controls the wireless communication terminal so that the wireless communication terminal and the base station communicate without going through the own station;
A relay station comprising: The relay station is installed on a mobile body on which a person can get on and off,
The relay station according to claim 1, further comprising a position estimation unit that estimates a position of the wireless communication terminal according to a monitoring result of the monitoring unit.   The position estimating unit determines that the wireless communication terminal exists in the moving body when a value indicating the communication quality is equal to or greater than a predetermined value and the communication quality is stable within a predetermined fluctuation range. The relay station according to claim 2.   The connection control unit causes a QoS having a high communication quality to be selected when the wireless communication terminal exists in the mobile body, and a QoS having a high mobility when the wireless communication terminal exists outside the mobile body. The relay station according to claim 2 or 3.   The connection control unit instructs to suppress handover when the wireless communication terminal exists in the mobile body, and instructs handover to a base station other than the local station when the wireless communication terminal exists outside the mobile body. The relay station according to any one of claims 1 to 4.   6. The relay station according to claim 5, wherein the connection control unit instructs a handover to a base station in which the local station is performing wireless communication when the wireless communication terminal is outside the mobile body. A terminal function unit that functions as a wireless communication terminal for the base station;
A base station function unit that functions as a base station for the wireless communication terminal;
The relay station according to claim 1, further comprising:   The relay station according to claim 7, wherein the terminal function unit performs wireless communication with the base station by a wireless communication method used between the base station and a wireless communication terminal. A wireless communication system comprising a wireless communication terminal, a base station that performs wireless communication with the wireless communication terminal, and a relay station that can relay communication between the wireless communication terminal and the base station,
The wireless communication terminal is
A terminal wireless communication unit for establishing wireless communication with the base station or relay station;
A handover request unit for requesting a handover according to a handover criterion from the relay station;
With
The relay station is
When relaying communication between the wireless communication terminal and the base station, a monitoring unit that monitors communication quality between the wireless communication terminal and the own station;
A position estimation unit that estimates a position of the wireless communication terminal according to a monitoring result of the monitoring unit;
A connection control unit that switches QoS of wireless communication with the wireless communication terminal according to a position of the wireless communication terminal, and switches a handover reference of the wireless communication terminal;
With
The base station
A radio communication system comprising a base station radio communication unit that executes a handover between the relay station and the own station in response to a handover request from the radio communication terminal. A wireless communication method for performing wireless communication using a wireless communication terminal, a base station that performs wireless communication with the wireless communication terminal, and a relay station that can relay communication between the wireless communication terminal and the base station. ,
The wireless communication terminal establishes wireless communication with the relay station;
The relay station monitors the communication quality of the wireless communication terminal and estimates the position of the wireless communication terminal;
The relay station, depending on the position of the wireless communication terminal, switch the QoS of wireless communication with the wireless communication terminal, switch the handover reference of the wireless communication terminal,
The radio communication terminal executes a handover request to the instructed base station according to a handover standard from the relay station,
The base station performs a handover from the relay station to the own station in response to a handover request from the radio communication terminal.