JP2010004458A - Handover control device, handover control method, handover control program, and wireless communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a handover control method determining a handover destination, wherein a connection status is continuously excellent even in the environment where radio waves are unstable, on the basis of a score (switching evaluation value) derived from radio wave environments and previous connection times, in a wireless communication system. <P>SOLUTION: A handover control apparatus, which determines a handover destination, is provided with: a wireless communication measuring means for measuring wireless communication statuses of a plurality of base stations; a connection time measuring means for measuring a connection time of each of the base stations to be connected; a switching evaluation value calculating means for calculating a switching evaluation value of each of the base stations on the basis of the wireless communication status measurement results of the base stations and the connection times with the base stations; a switching evaluation value control means for holding the switching evaluation value calculated by the switching evaluation value calculating means for each base station; and a handover destination determining means for determining a base station of the handover destination on the basis of the switching evaluation values of the base stations held by the switching evaluation value control means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a handover control device, a handover control method, a handover control program, and a wireless communication device. For example, WiMAX (registered trademark: IEEE802.16e standardization standard technology) communication and WiFi (registered trademark: IEEE802.11 standardization standard technology). In communication, when the radio wave environment deteriorates, the present invention can be applied to a wireless communication apparatus that switches connection to another base station.

  In general, handover (hereinafter also referred to as HO) for switching a connection to another base station is a technique for switching a connection from a currently connected base station to a base station that provides a better communication environment due to fluctuations in the radio wave environment. It is.

  For example, in Patent Document 1, when a mobile phone registers a location in a base station, the FER value is measured with respect to a FER (frame error rate) reference value transferred from the base station, and the measurement result is the FER. When the reference value is equal to or greater than the reference value and the RSSI (Received Signal Strength Index) is equal to or less than the reference value, the mobile phone determines that the mobile phone is used in a weak electric field region, and performs a handover process for switching the connection to another base station. The technique to be performed is described.

JP 2000-050337 A

  However, in cases where base stations that can be connected from wireless terminals all provide the same level of communication environment, and both are weak and easily cause handover due to environmental fluctuations. In this case, the wireless terminal frequently performs handover, and each time the communication is disconnected.

  In particular, if the terminal is fixed and cannot move in a direction where the radio wave environment is better, a phenomenon in which handover is continuously repeated is likely to occur, and the influence becomes remarkable.

  Therefore, in a wireless communication system, a handover control apparatus capable of continuously determining a handover destination having a good connection state even in an environment where radio waves are unstable, based on a radio wave environment and a score derived from a previous connection time There is a need for a handover control method, a handover control program, and a wireless communication apparatus.

  In order to solve such a problem, a handover control apparatus according to a first aspect of the present invention provides a handover control apparatus for determining a handover destination, wherein: (1) wireless communication measurement means for measuring wireless communication states of a plurality of base stations; 2) Connection time measuring means for measuring the connection time with each base station to be connected, and (3) Switching of each base station based on the wireless communication state measurement result of each base station and the connection time with each base station Switching evaluation value calculation means for obtaining an evaluation value, (4) switching evaluation value control means for holding the switching evaluation value obtained by the switching evaluation value calculation means for each base station, and (5) holding by the switching evaluation value control means. And handover destination determining means for determining a handover destination base station based on the switching evaluation value of each base station.

  A handover control method according to a second aspect of the present invention is the handover control method of a handover control apparatus for determining a handover destination, wherein: (1) a wireless communication measurement unit measures a wireless communication state of a plurality of base stations; (2) a connection time measuring step in which the connection time measuring means measures the connection time with each base station to be connected; and (3) a switching evaluation value calculating means is a wireless communication state measurement result of each base station and each base station. A switching evaluation value calculation step for obtaining a switching evaluation value of each base station based on the connection time with the station, and (4) the switching evaluation value control means determines the switching evaluation value obtained by the switching evaluation value calculation means as described above. A switching evaluation value control step to be held for each base station; and (5) a handover destination determination unit based on a switching evaluation value of each base station held by the switching evaluation value control unit. And having a handover destination determination step of determining.

  According to a third aspect of the present invention, there is provided a handover control program for determining a handover destination, comprising: (1) wireless communication measuring means for measuring wireless communication states of a plurality of base stations; A connection time measuring means for measuring a connection time with a station; (3) a switching evaluation value for obtaining a switching evaluation value of each base station based on a wireless communication state measurement result of each base station and a connection time with each base station; (4) switching evaluation value control means for holding the switching evaluation value obtained by the switching evaluation value calculating means for each base station, (5) switching evaluation value of each base station held by the switching evaluation value control means Based on the above, it is made to function as a handover destination determination means for determining a handover destination base station.

  A radio communication apparatus according to a fourth aspect of the present invention includes the handover control apparatus according to the first aspect of the present invention.

  According to the present invention, in a wireless communication system, based on a radio wave environment and a score (switching evaluation value) derived from a previous connection time, a handover destination having a good connection state continuously even in an environment where the radio wave is unstable. Can be determined.

(A) First Embodiment Hereinafter, a first embodiment of a handover control device, a handover control method, a handover control program, and a wireless communication device of the present invention will be described with reference to the drawings.

(A-1) Configuration of First Embodiment FIG. 1 is an overall configuration diagram showing an overall configuration of a wireless communication system 9A according to the first embodiment.

  In FIG. 1, a wireless communication system 9A according to the first embodiment exemplifies a wireless communication system that employs WiMAX as a wireless communication method. The wireless communication system is not particularly limited, and can be widely applied to systems that employ handover, such as WiFi and mobile communication systems.

  As shown in FIG. 1, the wireless communication system 9A according to the first embodiment includes a plurality of WiMAX base stations 1-1 to 1-n (n is a positive integer) connected to the IP network 101, and a fixed number. And at least a WiMAX terminal 2 installed in the network. The numbers of WiMAX base stations and WiMAX terminals are not particularly limited.

  The IP network 101 is a network whose communication protocol is IP (Internet Protocol), but the communication protocol is not particularly limited and can be widely applied.

  The WiMAX base stations 1 (1-1 to 1-n) are base stations that perform wireless communication with the connected WiMAX terminals 2. FIG. 2 is a block diagram showing an internal configuration of the WiMAX base station 1. As shown in FIG. 2, the WiMAX base station 1 includes a radio control unit 11, a reception unit 12, and a transmission unit 13.

  The wireless control unit 11 is a unit that controls wireless communication with the WiMAX terminal 2 in accordance with a predetermined communication control method (WiMAX in this embodiment).

  The receiving means 12 receives signals from the connected WiMAX terminal 2 under the control of the wireless control means 11 and performs various receiving processes.

  The transmission unit 13 transmits a transmission signal to the connected WiMAX terminal 2 under the control of the wireless control unit 11.

  The WiMAX terminal 2 is a terminal that performs wireless communication with the WiMAX base station 1, and includes a wireless communication apparatus having the handover control apparatus of the present invention. In the first embodiment, the case where it is fixedly installed is illustrated, but it can also be applied as a mobile terminal.

  FIG. 3 is a block diagram illustrating an internal configuration of the WiMAX terminal 2 according to the first embodiment. As illustrated in FIG. 3, the WiMAX terminal 2 includes a wireless reception unit 201, a wireless measurement unit 202, a connection time measurement unit 203, a HO score calculation unit 204, a HO score control unit 205, a timer 206, a HO score DB 207, and a HO determination unit. 208, a message creation unit 209, and a wireless transmission unit 210.

  The wireless reception unit 201 captures a wireless signal by a predetermined wireless control method (WiMAX in this embodiment) and performs various reception processes.

  The wireless measurement unit 202 measures a radio wave state related to wireless communication, and includes a received signal level (RSSI: Received Signal Strength Indication) of a wireless signal received by the wireless reception unit 201 and a carrier level to interference / noise ratio ( CINR (Carrier to Interference and Noise Ratio) is measured. The wireless measurement unit 202 gives the measured RSSI and CINR to the HO score calculation unit 204.

  The connection time measurement unit 203 measures the connection time with the currently connected WiMAX base station 1 and gives the connection time to the HO score calculation unit 204 and the HO score control unit 205.

  The HO score calculation unit 204 calculates a HO score (switching evaluation value) based on the RSSI and CINR received from the wireless measurement unit 202 and the connection time with the WiMAX base station 1 received from the connection time measurement unit 203. Is. Further, the HO score calculation unit 204 calculates the HO score every time HO occurs in the WiMAX terminal 2 and records the HO score of the calculation result in the HO score DB 207. Thereby, the total value during the collection period of the HO score is recorded in the HO score DB 207.

  Here, the HO score is a score reflecting a wireless communication state with each WiMAX base station 1 and a connection time within a predetermined time, and is an index for determining execution of handover.

The HO score calculation part 204 calculates | requires the method of calculating | requiring a HO score based on following formula (1). Here, A is an arbitrary coefficient larger than 1, and time (connection) is a connection time in which a single WiMAX base station 1 is connected continuously.

  Equation (1) is derived by multiplying the length of the connection time with the WiMAX base station 1 by an exponential function of time in order to largely reflect it in the score, and multiplying it by RSSI_Score and CINR_Score.

  Equation (1) is a derivation formula for the HO score for each WiMAX base station 1 connected to the currently connected WiMAX base station 1, and this is stored for each WiMAX base station 1 in the HO score DB 207. The total value of HO scores within the collection period can be totaled.

  When receiving the RSSI from the wireless measurement unit 202, the HO score calculation unit 204 obtains an RSSI_score corresponding to the RSSI while referring to a preset RSSI score calculation table.

  Further, when receiving the CINR from the wireless measurement unit 202, the HO score calculation unit 204 obtains a CINR_score corresponding to the CINR while referring to a preset CINR score calculation table.

  4 is an example of an RSSI score calculation table for calculating RSSI_score, and FIG. 5 is an example of a CINR calculation table for calculating CINR_score.

  The RSSI score calculation table shown in FIG. 4 associates the RSSI average value with the RSSI_score, and is set so that the RSSI_score increases as the RSSI average value decreases.

  The CINR score calculation table shown in FIG. 5 associates the CINR average value with the CINR_score, and is set so that the CINR_score increases as the CINR average value increases.

  The HO score control unit 205 controls writing and erasing of the HO score calculated by the HO calculation unit 204 in the HO score DB 207.

  The HO score control unit 205 manages the collection time of the HO score of each WiMAX base station 1 using the timer 206. The collection time is a time for collecting the HO score for each WiMAX base station 1, and the handover process is performed using the HO scores collected within the collection time. This collection time can be arbitrarily set or changed.

  Further, when receiving the continuous connection time with the WiMAX base station 1 measured by the connection time measuring unit 203, the HO score control unit 205 records and holds the continuous connection time.

  FIG. 6 is an explanatory diagram for explaining the record keeping of the continuous connection time with the currently connected WiMAX base station 1. As illustrated in FIG. 6, the HO score control unit 205 records and holds the continuous connection time with the WiMAX base station 1 acquired from the connection time measurement unit 203.

  Further, the HO score control unit 205 refers to the recording result of the continuous connection time with the currently connected WiMAX base station 1, and when there is a continuous connection time continuously below the threshold, the HO score The information held in the DB 207 is cleared. Thereby, the connection switching of the WiMAX base station 1 can be performed according to a change in the radio wave environment.

  In the first embodiment, it is determined that there is a continuous connection time that is equal to or less than the threshold, but the present invention is not limited to this. As another determination method, it may be detected that the connection times that are equal to or less than the threshold value are not consecutive and the connection times that are equal to or less than the threshold value among the predetermined number of times are found.

  The timer 206 provides a timer time for timing to the HO score control unit 205.

  The HO score DB 207 records and holds the HO score of the WiMAX base station 1 under the control of the HO control unit 205.

  FIG. 7 is an explanatory diagram for explaining the recording of the HO score of each WiMAX base station 1 held in the HO score DB 207. As shown in FIG. 7, the HO score DB 207 holds the HO score for each WiMAX base station 1.

  The HO determination unit 208 performs a handover process based on the measurement result acquired from the wireless measurement unit 202. The HO determination unit 208 performs, for example, a normal handover process standardized by IEEE 802.16e or a handover process using the HO score according to the first embodiment as the handover process.

  The HO determination unit 208 performs a routine handover process when the WiMAX terminal 2 is in the initial activation state or when the collection result of the HO score is not held in the HO score DB. In addition, when the HO score DB 207 holds the collection result of the HO score, the HO determination unit 208 performs handover of the highest HO score among the HO scores of the WiMAX base station 1 held in the HO score DB 207. It is to be judged first.

  The message creation unit 209 creates a connection request message to the WiMAX base station 1 having the highest HO score determined by the HO determination unit 208.

  The wireless transmission unit 210 wirelessly transmits a transmission signal. The wireless transmission unit 210 wirelessly transmits the message created by the message creation unit 209.

(A-2) Operation of the First Embodiment Next, the operation of the handover control process in the wireless communication system 9A of the first embodiment will be described with reference to the drawings.

  Hereinafter, for convenience of explanation, a case where there are two WiMAX base stations that can be connected to the WiMAX terminal 2 will be described as an example, and will be denoted as WiMAX base stations 1-1 and 1-2.

  First, the overall operation of the initial connection process of the WiMAX terminal 2 with the WiMAX base station 1 will be described.

  When the WiMAX terminal 2 is fixedly installed in the initial state, the WiMAX terminal 2 is connected to the one having a better radio wave environment with the connectable WiMAX base stations 1-1 and 1-2.

  At this time, the WiMAX terminal 2 is connected to the connectable WiMAX base station 1, and is connected to the WiMAX base station 1-1 having a good radio wave environment among the WiMAX base stations 1-1 and 1-2.

  In addition, within a predetermined collection time (for example, 1 day, 12 hours, 60 minutes, etc.), the WiMAX terminal 2 operates a normal handover process standardized by IEEE 802.16e. During this collection time, the WiMAX terminal 2 monitors the connection status of the wireless communication with each WiMAX base station 1-1 and 1-2 and, as will be described later, each WiMAX base station 1-1 and Collect HO score of 1-2.

  When the predetermined collection time ends, the HO scores of the WiMAX base stations 1-1 and 1-2 collected during the collection time are recorded in the HO score DB 207 of the WiMAX terminal 2. Then, with reference to the HO score of each WiMAX base station 1-1 and 1-2 held in the HO score DB 207 at the time of handover, the handover process is performed so as to connect to the WiMAX base station 1-1 having the highest HO score. . As a result, it is possible to prevent connection to an inappropriate WiMAX base station due to instantaneous wireless environment deterioration, and to prevent communication deterioration due to frequent switching of WiMAX base stations.

  Next, HO score creation processing and initialization processing in the WiMAX terminal 2 will be described with reference to the drawings. FIG. 8 is a flowchart showing HO score creation processing and initialization processing in the WiMAX terminal 2.

  First, when the WiMAX terminal 2 is activated (step S301), the HO score is initialized (step S102), the collection of the HO score is started (step S103), and each WiMAX base station until the HO score collection time ends. A HO score of 1 is collected (step S104).

  The wireless measurement unit 202 measures the RSSI and CINR of the wireless signal received by the wireless reception unit 201, and provides the RSSI and CINR to the HO score calculation unit 204. The normal handover process is performed within the collection time, and the RSSI and CINR of the received radio wave are measured every time the handover is switched to the WiMAX base station 1-1 or 1-2 as the handover destination.

  The connection time measuring unit 203 measures the connection time with the WiMAX base stations 1-1 and 1-2 that are handover destinations, and provides the measurement time to the HO score calculation unit 204 and the HO score control unit 205.

  Upon receiving the RSSI and CINR of the radio signal from the radio measurement unit 202, the HO score calculation unit 204 refers to the RSSI score calculation table and the CINR score calculation table and calculates RSSI_score and CINR_score corresponding to the acquired RSSI and CINR. To do.

  Further, the HO score calculation unit 204 calculates the HO score by substituting the connection time acquired from the connection time measurement unit 203, RSSI_score, and CINR_score into the equation (1).

  The HO score control unit 205 holds the connection time acquired from the connection time measurement unit 203 for each WiMAX base station 1 and manages the continuous connection time with each WiMAX base station 1. Further, the HO score control unit 205 causes the HO score DB 207 to record the HO score obtained by the HO score calculation unit 204 for each WiMAX base station 1. As a result, the total HO score of each WiMAX base station 1 collected within the collection time can be recorded.

  When the collection time ends, the WiMAX terminal 2 determines a handover destination using the HO score of each WiMAX base station 1 recorded in the HO score DB 207 (step S105). The operation of the handover process using this HO score will be described later.

  When the number of surrounding WiMAX base stations 1 that can be connected fluctuates and fluctuates, the HO score control unit 205 of the WiMAX terminal 2 returns to step S102, initializes the HO score, and again for each WiMAX base station 1 in the collection period. HO score collection processing is performed (step S106). On the other hand, when there is no change in the number of WiMAX base stations 1, a handover process using the HO score is performed as it is.

  Regarding the detection of the fluctuation of the WiMAX base station 1, the HO score control unit 205 detects the fluctuation by receiving a control signal from the newly added WiMAX base station, or refers to the HO score DB 207 or the like to check the HO score. The control unit 205 manages the connectable WiMAX base station 1, and a method of detecting by receiving a control signal from a device other than the managed WiMAX base station can be applied.

  Further, the HO score control unit 205 holds the connection time with the WiMAX base station 1-1, and there is a continuous connection time continuously equal to or less than the threshold with reference to the past predetermined number of connection times. It is determined whether or not. If connection times equal to or less than the threshold are continuously present, the process returns to step S102, and the HO score control unit 205 initializes the HO score, and again collects the HO score of each WiMAX base station 1 in the collection period. On the other hand, if not, the handover process is continued using the HO score.

  In this way, the continuous connection time of the connected WiMAX base station 1-1 can be monitored, and a change in the radio wave environment can be detected quickly, and the optimal WiMAX base station with a high HO score in the environment. 1 can be established.

  Further, the HO control unit 207 initializes the HO score every predetermined time. In other words, when the HO reset timer reaches 0, the HO control unit 207 initializes the HO score held in the HO score DB 207 (steps S108 and S102). Thereby, the HO score can be reviewed periodically.

  Next, the operation of the handover process in the WiMAX terminal 2 will be described with reference to the drawings. FIG. 9 is a flowchart showing the operation of the handover process in the WiMAX terminal 2.

  The HO determination unit 208 of the WiMAX terminal 2 determines whether or not to perform handover based on the measurement result of the received radio wave by the wireless measurement unit 202. Then, the handover determining unit 208 activates a handover condition (step S201).

  The HO score control unit 205 determines whether or not the connection time is being measured (step S202). If the connection time is being measured, the recording of the connection time is ended (step S203). On the other hand, when the connection time is not being measured, the process proceeds to step S204.

  Next, it is determined whether or not the HO score of each WiMAX base station 1 is recorded in the HO score DB 207 (step S204). If not recorded, normal handover processing is performed (steps S210 and S211).

  On the other hand, when it is recorded in the HO score DB, the HO score control unit 205 refers to the past predetermined number of continuous connection times and determines whether or not there is a continuous connection time equal to or less than the threshold ( Step S205).

  If the continuous connection time equal to or less than the threshold is continuously present, the HO score control unit 205 initializes the HO score (step S209) and causes normal handover processing to be performed (step S210).

  On the other hand, when the continuous connection time below the threshold does not exist continuously, the HO determination unit 208 selects the WiMAX base station 1-1 having the highest HO score among the HO scores recorded in the HO score DB 207. It judges that it is a handover destination, and makes a connection request to this WiMAX base station 1-1 (step S206). That is, the message creation unit 209 creates a handover connection request message for the WiMAX base station 1-1 determined by the HO determination unit 208, and the wireless transmission unit 210 wirelessly transmits the connection request message.

  When the WiMAX terminal 2 is connected to the WiMAX base station 1-1 (step S207), the HO score control unit 205 starts recording the continuous connection time with the WiMAX base station 1-1 (step S208). The handover process is terminated (step S211).

  When connection with the WiMAX base station 1-1 is not possible, normal handover processing is performed. Thereby, the disconnection state with the WiMAX base station 1 is avoided.

(A-3) Effect of the First Embodiment As described above, according to the first embodiment, the WiMAX terminal gives the HO score to each WiMAX base station based on the radio wave condition and the connection time. By calculating and determining the handover destination according to the superiority or inferiority of the HO score of each WiMAX base station at the time of handover, the radio wave condition is continuously avoided while avoiding the phenomenon of repeated handovers even in an unstable radio wave environment. It is possible to connect to a WiMAX base station with good quality.

(B) Second Embodiment Next, a handover control apparatus, method and program, and a wireless communication control apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

(B-1) Configuration and Operation of Second Embodiment FIG. 10 is an overall configuration diagram showing an overall configuration of a wireless communication system 9B according to the second embodiment.

  In FIG. 10, the wireless communication system 9 </ b> B according to the second embodiment includes a plurality of WiMAX base stations 1-1 to 1-n connected to the IP network 101 and a WiMAX terminal 3.

  FIG. 11 is a block diagram illustrating an internal configuration of the WiMAX terminal 3 according to the second embodiment. As shown in FIG. 11, the WiMAX terminal 3 according to the second embodiment includes a radio reception unit 301, a radio measurement unit 302, a connection time measurement unit 303, a HO score calculation unit 304, a HO score control unit 305, a timer 306, and a HO. A score DB 307, a HO determination unit 308, a message creation unit 309, a wireless transmission unit 310, and a communication time measurement unit 311 are included.

  The second embodiment is different from the first embodiment in the function related to the handover process in the WiMAX terminal 3. Specifically, the first embodiment uses the wireless connection time with the WiMAX base station 1 as the connection time, whereas the second embodiment uses the actual communication time as the connection time. Is calculated.

  Hereinafter, the functional configuration of the handover process of the WiMAX terminal 2 that is characteristic of the second embodiment will be described, and details of the functional configuration already described in the first embodiment will be omitted.

  The communication time measurement unit 311 measures continuous communication time with one WiMAX base station 1 that is continuously connected, and the measured communication time is sent to the HO score calculation unit 304 and the HO score control unit 305. Give.

  Thereby, the communication frequency in one continuous connection period with a certain WiMAX base station 1 can be calculated | required.

  Here, as the communication frequency within one continuous connection period, the communication time with the WiMAX base station 1 and the data amount (packet amount) can be used. In the second embodiment, a case where the communication time measured by the communication time measurement unit 311 is used is illustrated.

  The communication time measured by the communication time measuring unit 311 is a time when radio waves are transmitted / received to / from one WiMAX base station 1 that is specifically continuously connected.

  For example, when transmitting / receiving a communication packet, the communication time measuring unit 311 can determine the communication time by observing the time required for packet transmission / reception of the wireless reception unit 301 or the wireless transmission unit 310.

  Further, for example, as a method for measuring the packet transmission / reception time by the communication time measuring unit 311, the number of packets transmitted / received this time is measured, the time required for transmission / reception of one packet is provided, the number of packets transmitted this time is measured, and the number of packets The communication time may be obtained by multiplying the time required for transmission / reception of one packet by.

  FIG. 12 is a communication time management table by the communication time measuring unit 311. As shown in FIG. 12, the total time of communication during one continuous connection time is recorded.

  In this embodiment, the communication time measurement unit 311 measures the communication time. However, the communication time measurement unit 311 measures the amount of data (packets) transmitted / received to / from the WiMAX base station 1. Also good.

  The communication time measuring unit 311 can set the type of protocol to be observed in advance, such as SIP (Session Initiation Protocol), UDP (User Datagram Protocol), or HTTP (Hyper Text Transfer Protocol). As a result, the communication time measuring unit 311 can observe the number of packets configured with a specific protocol among the packets transmitted and received by the wireless reception unit 301 and the wireless transmission 310, and can obtain the connection time.

  Thus, by acquiring the amount of transmitted / received data (packets) as the connection time, it is possible to easily select a station having a high tendency to perform communication using a specific protocol as the HO destination.

  The HO score calculation unit 304 calculates the HO score of each WiMAX base station 1 every time it connects to each WiMAX base station 1.

  As in the first embodiment, the HO score calculation unit 304 acquires the radio waves RSSI and CINR from the radio measurement unit 302 and calculates RSSI_score and CINR_score. Further, the HO score calculation unit 304 acquires the measurement time from the connection time measurement unit 303. The RSSI_score and CINR_score calculation methods can be the same as those in the first embodiment.

  Further, the HO score calculation unit 304 acquires the communication time with the WiMAX base station 1 from the communication time measurement unit 311.

Here, the HO score calculation unit 304 calculates the HO score using, for example, Expression (2). A is an arbitrary coefficient larger than 1, and time (connection) is a connection time in which a single WiMAX base station 1 is connected continuously. B is an arbitrary coefficient greater than 1, and time (communication) is a total time of communication times communicated within the same connection time.

  Equation (2) is derived by multiplying the length of the connection time with the WiMAX base station 1 and the length of the communication time as an exponential function of time for greatly reflecting the score, and multiplying it by RSSI_Score and CINR_Score.

  As a result, it is possible to avoid connection with a WiMAX base station that can be connected but cannot communicate due to some cause on the radio or an upper network. In addition, by introducing the connection time required for transmission / reception of radio waves into the HO score, it is possible to easily select the WiMAX base station 1 having a high tendency to perform wireless communication as a handover destination.

  Equation (2) is a derivation formula for the HO score for each WiMAX base station 1 connected to the currently connected WiMAX base station 1, and this is stored for each WiMAX base station 1 in the HO score DB 307. The total value of HO scores within the collection period can be totaled.

  The HO score DB 307 records and holds the HO score of the WiMAX base station 1 under the control of the HO control unit 305.

  FIG. 13 is an explanatory diagram for explaining the recording of the HO score of each WiMAX base station 1 held in the HO score DB 307. As illustrated in FIG. 13, the HO score DB 307 holds the HO score for each WiMAX base station 1.

(B-2) Effect of the Second Embodiment As described above, according to the second embodiment, the WiMAX terminal adds a function for adding the communication time to the HO score, so that something is added to the wireless network or the upper NW. It is possible to calculate an appropriate HO score even when there is a cause and connection is established but communication is not possible.

(C) Other Embodiments The handover control process described in the first to third embodiments has exemplified the case of performing wireless communication by WiMAX, but can be widely applied to wireless communication devices having a handover function.

  The handover control processing described in the first to third embodiments is realized by software processing in the wireless communication apparatus. For example, in a wireless communication apparatus including a CPU, ROM, RAM, EEPROM, etc., the CPU reads out a processing program stored in the ROM and executes it to execute the handover process described in the first to third embodiments. Realized.

1 is an overall configuration diagram of a wireless communication system according to a first embodiment. It is an internal block diagram of a WiMAX base station. It is a block diagram which shows the internal structure of the WiMAX terminal of 1st Embodiment. It is explanatory drawing explaining the RSSI score calculation table of 1st Embodiment. It is explanatory drawing explaining the CINR score calculation table of 1st Embodiment. It is explanatory drawing explaining the table which records the connection time of 1st Embodiment. It is explanatory drawing explaining the table which records the HO score of each WiMAX base station of 1st Embodiment. 3 is a flowchart illustrating handover creation processing and initialization according to the first embodiment. It is a flowchart which shows the operation | movement of the hand-over process of 1st Embodiment. It is a whole block diagram of the radio | wireless communications system of 2nd Embodiment. It is a block diagram which shows the internal structure of the WiMAX terminal of 2nd Embodiment. It is explanatory drawing explaining the table which records the communication time of 2nd Embodiment. It is explanatory drawing explaining the table which records the HO score of each WiMAX base station of 2nd Embodiment.

Explanation of symbols

  1-1 to 1-n ... WiMAX base station, 2 and 3 ... WiMAX terminals, 201 and 301 ... radio receiver, 202 and 302 ... radio measurement unit, 203 and 303 ... connection time measurement unit, 204 and 304 ... HO score Calculation unit, 205 and 305 ... HO score control unit, 206 and 306 ... Timer, 207 and 307 ... HO score DB, 208 and 308 ... HO judgment unit, 209 and 309 ... Message creation unit, 210 and 310 ... Wireless transmission unit, 311: Communication time measuring unit.

Claims (11)

In a handover control device that determines a handover destination,
Wireless communication measuring means for measuring wireless communication states of a plurality of base stations;
A connection time measuring means for measuring a connection time with each of the base stations to be connected;
Based on the wireless communication state measurement result of each base station and the connection time with each base station, a switching evaluation value calculation means for obtaining a switching evaluation value of each base station,
Switching evaluation value control means for holding the switching evaluation value obtained by the switching evaluation value calculation means for each base station;
A handover control apparatus comprising: a handover destination determining unit that determines a handover destination base station based on the switching evaluation value of each base station held by the switching evaluation value control unit. Further comprising communication frequency measuring means for measuring the communication frequency with each of the base stations to be connected,
The switching evaluation value calculation means calculates the switching evaluation value of each base station based on the wireless communication state measurement result of each base station, the connection time with each base station, and the communication frequency of each base station. The handover control apparatus according to claim 1, wherein the handover control apparatus is obtained.   The handover control apparatus according to claim 1 or 2, wherein the switching evaluation value calculation means obtains the switching evaluation value so that the degree of contribution of the length of connection time with each base station increases.   The handover control apparatus according to claim 2 or 3, wherein the switching evaluation value calculation unit obtains the switching evaluation value so that a contribution degree of a communication frequency with each base station is high.   The handover control apparatus according to any one of claims 1 to 4, wherein the switching evaluation value control means holds switching evaluation values of the base stations collected within a predetermined collection time.   When the switching evaluation value control means holds the continuous connection time with the currently connected base station and has a continuous connection time that is equal to or less than a threshold value in the past predetermined number of times, the switching evaluation value of each base station is again The handover control apparatus according to claim 1, wherein values are collected.   The handover control apparatus according to claim 1, wherein the switching evaluation value control means periodically collects the switching evaluation values of the base stations.   The handover control apparatus according to claim 1, wherein the handover destination determination unit determines the base station having the highest switching evaluation value as a handover destination. In a handover control method of a handover control apparatus for determining a handover destination,
A wireless communication measuring means for measuring wireless communication states of a plurality of base stations;
A connection time measuring means for measuring a connection time with each of the base stations to be connected; and
A switching evaluation value calculating means for determining a switching evaluation value of each base station based on a wireless communication state measurement result of each base station and a connection time with each base station;
A switching evaluation value control means for holding the switching evaluation value obtained by the switching evaluation value calculation means for each base station;
A handover destination determining unit that determines a handover destination base station based on the switching evaluation value of each base station held by the switching evaluation value control unit; Method. In a handover control program for determining a handover destination,
Computer
Wireless communication measuring means for measuring wireless communication states of a plurality of base stations;
A connection time measuring means for measuring a connection time with each of the base stations to be connected;
Based on the wireless communication state measurement result of each base station and the connection time with each base station, a switching evaluation value calculation means for obtaining a switching evaluation value of each base station,
Switching evaluation value control means for holding the switching evaluation value obtained by the switching evaluation value calculation means for each base station;
A handover control program that functions as a handover destination determination unit that determines a handover destination base station based on a switching evaluation value of each base station held by the switching evaluation value control unit.   A wireless communication apparatus comprising the handover control apparatus according to claim 1.

Images