JP4789613B2 - Wireless communication terminal and communication method - Google Patents

Description

  The present invention relates to a radio communication terminal and a communication method applied to multi-carrier communication using a plurality of carriers.

  In a mobile communication network using code division multiple access (CDMA), 1xEV-DO (1x evolution-data only) that realizes high-speed data communication is provided (for example, Patent Document 1).

In 1xEV-DO, one carrier is assigned to one user (wireless communication terminal). In addition, introduction of a so-called “multi-carrier” (nxEV-DO) that realizes higher-speed data communication by assigning a plurality of carriers (for example, 15 carriers) to one user is also under consideration.
Japanese Patent Laid-Open No. 2002-300644 (page 2-3, FIG. 1)

  In multicarrier, when handoff of a large number of carriers is executed at the same time, there is a problem that the processing load on the radio base station and the radio communication terminal increases.

  On the other hand, since handoff is determined for each carrier based on the received signal strength (RSSI) of each carrier, chaotic handoff may be executed without synchronization between the carriers. Such disordered handoff causes a problem of destabilizing communication quality of a traffic flow transmitted using the carrier.

  Accordingly, the present invention has been made in view of such a situation, and in a multi-carrier mobile communication network, the processing load at the time of handoff is suppressed, and communication quality is deteriorated due to random handoff of a plurality of carriers. An object of the present invention is to provide a wireless communication terminal and a communication method that can prevent the situation from becoming stable.

  In order to solve the problems described above, the present invention has the following features. First, a first feature of the present invention is that at least a first radio base station (for example, the radio base station 100A) and a second radio base station (the radio base station 100D) perform multi-carrier communication using a plurality of carriers. ) And a predetermined number (for example, 4 carriers) of two or more and less than half of the maximum number of carriers that can be set (for example, 15 carriers). A main session setting unit (main session processing unit 205) for setting a main session (for example, main session MS) used for transmission of a predetermined traffic flow (for example, voice data) with the first radio base station; Main session candidates (with the predetermined number of the carriers) with the second radio base station ( For example, when the main session candidate is set by the main session candidate setting unit (sub-session processing unit 207) for setting the main session candidate CDd) and the main session candidate setting unit, the main session is set as the main session candidate. The gist is to include a session switching unit (session switching unit 211) for switching.

  According to such a radio communication terminal, the number of carriers constituting the main session with the radio base station other than the first radio base station in which the main session is set, that is, the second radio base station, and Main session candidates configured by the same number (predetermined number) of carriers are set. Further, the main session is configured by a predetermined number of carriers that is equal to or less than half of the maximum number of carriers that can be set.

  When the main session candidate is set, the main session is switched to the main session candidate.

  For this reason, it is possible to prevent an increase in processing load at the radio base station and the radio communication terminal by performing handoff of a large number of carriers at the same time.

  Furthermore, the traffic flow transmitted by the main session is switched in units of the number of carriers constituting the main session. For this reason, it is possible to prevent the communication quality of the traffic flow from becoming unstable by performing disordered handoff without synchronizing between carriers.

  A second feature of the present invention relates to the first feature of the present invention, wherein the main session candidate setting unit detects an unused carrier that is not used for communication with the second radio base station. In this case, the main purpose is to include the unused carrier in the main session candidate in preference to the in-use carrier used for communication.

  A third feature of the present invention relates to the first or second feature of the present invention, wherein the session switching unit is not used for the predetermined number of communications when there are a plurality of main session candidates. The gist is to select a main session candidate constituted by a carrier with priority over other main session candidates.

  A fourth feature of the present invention according to the first to third features of the present invention is further provided with a reception state measurement unit (communication quality measurement unit 209) for measuring the reception state of the carrier, wherein the session switching unit includes: When there are a plurality of main session candidates, selecting a main session candidate for switching the main session based on the reception state of the carrier included in the main session candidate measured by the reception state measurement unit. The gist.

  According to a fifth aspect of the present invention, there is provided a communication method in which a radio communication terminal executes multi-carrier communication using a plurality of carriers with at least a first radio base station and a second radio base station. A step of setting, with the first radio base station, a main session that is configured by a predetermined number of the carriers that is greater than or equal to the number of carriers that can be set and that is not more than half of the maximum settable number of carriers (step S210). , A step of setting a main session candidate constituted by the predetermined number of the carriers with the second radio base station (step S220), and when the main session candidate is set, the main session is Switching to the main session candidate (steps S230 and S240). And effect.

  A sixth feature of the present invention relates to the fifth feature of the present invention, wherein in the step of setting the main session candidate, an unused carrier that is not used for communication with the second radio base station. In this case, the unused carrier is included in the main session candidate in preference to the in-use carrier used for communication.

  A seventh feature of the present invention relates to the fifth or sixth feature of the present invention. In the step of switching the session, when there are a plurality of main session candidates, the session is not used for the predetermined number of communications. The gist is to select a main session candidate configured by a carrier used in preference to other main session candidates.

  An eighth feature of the present invention relates to the fifth to seventh features of the present invention, further comprising the step of measuring the reception state of the carrier (Step S370), wherein the main session candidate is selected in the step of switching the session. When there are a plurality of the main session candidates, the main session candidate for switching the main session is selected based on the reception state of the carrier included in the main session candidate measured in the step of measuring the reception state. .

  Advantageous Effects of Invention According to the features of the present invention, in a multi-carrier mobile communication network, the processing load at the time of handoff can be suppressed, and wireless communication that can prevent communication quality from becoming unstable due to disordered handoff of a plurality of carriers. A communication terminal and a communication method can be provided.

  Next, an embodiment of the present invention will be described. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones.

  Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Schematic configuration of mobile communication network)
FIG. 1 is a schematic configuration diagram of a mobile communication network 10 including a wireless communication terminal according to the present embodiment.

  The mobile communication network 10 provides high-speed data communication (nxEV-DO) by multicarrier using a plurality of carriers. The data communication includes voice data based on VoIP.

  The mobile communication network 10 includes radio base stations 100A to 100D and a radio communication terminal 200. Note that the numbers of radio base stations and radio communication terminals included in the mobile communication network 10 are not limited to the quantities shown in FIG.

  The radio base station 100A executes communication with the radio communication terminal 200 by multicarrier using a plurality of carriers. The radio base stations 100B to 100D also have the same function as the radio base station 100A.

  The radio communication terminal 200 is a mobile phone terminal capable of executing communication with the radio base stations 100A to 100D using multicarriers. Specifically, the radio communication terminal 200 can execute high-speed data communication conforming to nxEV-DO via the radio base stations 100A to 100D.

(Function block configuration)
FIG. 2 is a functional block configuration diagram of the wireless communication terminal 200. Hereinafter, portions related to the present invention will be mainly described. Therefore, it should be noted that the wireless communication terminal 200 may include a function block (power supply unit or the like) that is not illustrated or omitted in description, which is essential for realizing the function as the wireless communication terminal 200.

  As illustrated in FIG. 2, the wireless communication terminal 200 includes an RF unit 201, a data communication unit 203, a main session processing unit 205, a subsession processing unit 207, a communication quality measurement unit 209, and a session switching unit 211.

  The RF unit 201 receives a plurality of carriers transmitted by the radio base stations 100A to 100D. Further, the RF unit 201 transmits a plurality of carriers toward the radio base stations 100A to 100D.

  Further, the RF unit 201 performs digital modulation (and demodulation) processing of a baseband signal (for example, traffic flow including voice data by VoIP) transmitted by the plurality of carriers, and the data communication unit 203 and the baseband Send and receive signals.

  The data communication unit 203 executes baseband signal processing. Specifically, the data communication unit 203 executes processing related to data communication (for example, IP packetization or reproduction of received data).

  The main session processing unit 205 executes processing related to the main session. The main session is a predetermined number of carriers (for example, 4 carriers) that are two or more and less than half of the maximum settable number of carriers (15 carriers) transmitted and received with a specific wireless base station (for example, wireless base station 100A). Consists of. The predetermined number is set to an appropriate value according to the traffic flow profile (required communication speed, QoS level, etc.) transmitted using the carrier.

  In the present embodiment, a traffic flow (predetermined traffic flow) including a message for communication control, voice data, streaming data with a high QoS level, and the like is transmitted using the main session.

  In the present embodiment, the main session processing unit 205 constitutes a main session setting unit.

  The subsession processing unit 207 executes processing related to the subsession and the main session candidate. A subsession is composed of one or more carriers transmitted and received with a specific radio base station (for example, radio base station 100A).

  In the present embodiment, traffic flows other than traffic flows including communication control messages, voice data, streaming data with a high QoS level, for example, best effort data with a low QoS level, etc. are transmitted using a sub-session. The

  In addition, a subsession is configured by an unused carrier that is not used for communication.

  Further, the sub-session processing unit 207 has the same number (predetermined number) as the number of carriers constituting the main session with the radio base station (second radio base station) other than the radio base station to which the main session is set. Main session candidates configured by the carriers are set. In the present embodiment, the subsession processing unit 207 constitutes a main session candidate setting unit.

  Specifically, the subsession processing unit 207 uses a subsession configured by one or two or more carriers secured with a radio base station other than the radio base station to which the main session is set. To set main session candidates.

  In addition, when the sub-session processing unit 207 detects an unused carrier that is not used for communication between the radio base stations other than the radio base station for which the main session is set, the sub-session processing unit 207 is in use that is used for communication. The unused carrier can be included in the main session candidate in preference to the carrier.

  The communication quality measuring unit 209 measures the received communication quality of the carrier received by the RF unit 201. In the present embodiment, the communication quality measurement unit 209 constitutes a reception state measurement unit that measures the reception state of the carrier received by the RF unit 201.

  Specifically, the communication quality measurement unit 209 measures the received signal strength (RSSI) of the carrier received by the RF unit 201.

  Further, the communication quality measurement unit 209 determines the RSSI (hereinafter referred to as “session RSSI”) as the session based on the RSSI of the carrier included in each session (main session, sub-session, and main session candidate) (1 set) Can be used to calculate.

Session RSSI = RSSIa + α (Ns−1) (1 formula)
Here, RSSIa is the average of the RSSI of an arbitrary carrier included in the session or the RSSI of a carrier included in the session. α is a constant having a predetermined value, and Ns is the number of carriers included in the session.

  In addition, when the number of carriers constituting a subsession is only one, the RSSI of the carrier is used as it is without applying (Equation 1).

  The session switching unit 211 performs switching from the main session to the main session candidate. Specifically, when the main session candidate is set by the sub-session processing unit 207, the session switching unit 211 switches the main session to the main session candidate.

  In addition, when there are a plurality of main session candidates, the session switching unit 211 selects a main session candidate for switching the main session based on a reception state of a carrier included in the main session candidate.

  Specifically, the session switching unit 211 selects a main session candidate for switching the main session based on the RSSI of the carrier constituting the main session candidate measured by the communication quality measuring unit 209.

  The session switching unit 211 can also select a main session candidate for switching the main session based on the session RSSI (see formula 1) of each session (main session, sub-session, and main session candidate).

  Further, when there are a plurality of main session candidates, the session switching unit 211 selects other main session candidates configured by unused carriers that are not used for the same number (predetermined number) of communications as the number of carriers constituting the main session. Can be selected in preference to the main session candidates. A specific method for selecting main session candidates will be described later.

(Operation of wireless communication terminal and wireless base station)
Next, operations of the radio base stations 100A to 100D and the radio communication terminal 200 included in the mobile communication network 10 described above will be described.

(1) Subsession Switching Operation First, subsession switching operation will be described. FIG. 3 is a sub-session switching operation sequence diagram.

  As illustrated in FIG. 3, in step S10, the radio communication terminal 200 sets a subsession configured with two carriers (2X) with the radio base station 100B.

  Note that, as described above, a subsession is composed of one or more carriers, and best effort data having a low QoS level is transmitted using the subsession. In addition, a subsession is configured by an unused carrier that is not used for communication.

  In step S20, the radio communication terminal 200 transmits, to the radio base station 100A, a RouteUpdate message with the radio base station 100A as a candidate for handoff as the carrier RSSI transmitted by the radio base station 100A increases. .

  In step S30, the radio base station 100A performs radio communication with a TCA (Traffic Channel Assignment) message including channel information necessary for the radio communication terminal 200 to perform communication with the radio base station 100A based on the received RouteUpdate message. Transmit to terminal 200.

  In step S40, the radio communication terminal 200 transmits a ReversePilot signal to the radio base station 100A.

  In step S50, the radio base station 100A transmits an RTCACK message including information related to RTC (reverse traffic channel) to the radio communication terminal 200 based on the received ReversePilot signal.

  In step S60, the radio communication terminal 200 performs T-CH (traffic channel) setting based on the received TCA message and RTCACK message, and sends a TrafficChannelComplete message indicating that the setting is completed to the radio base station 100A. Send.

  In step S70 and step S80, the radio communication terminal 200 switches the DRC (date rate control) Cover to the radio base station 100A when the RSSI of the carrier transmitted by the radio base station 100A is further increased. The wireless base station 100A and the wireless base station 100B are notified that the handoff of the carrier included in the sub-session set with the wireless base station 100B is executed.

  Here, it is assumed that one carrier included in the subsession is a target of handoff.

  In step S90, the radio communication terminal 200 newly sets a subsession constituted by one carrier (1X) with the radio base station 100A.

  In step S100, the radio communication terminal 200 reduces the number of carriers included in the sub-session set with the radio base station 100B from two to one.

  The sub-session switching (handoff) described above can be executed at any time without any particular restriction.

(2) Main Session Switching Operation Next, the main session switching operation will be described. FIG. 4 is a main session switching operation sequence diagram. The main session switching operation is also substantially the same as the sub-session switching operation described above.

  As shown in FIG. 4, in step S210, the radio communication terminal 200 performs a main session composed of, for example, four carriers (4X) with the radio base station 100A (first radio base station). Set. In the main session, as described above, a traffic flow including a communication control message, voice data, streaming data with a high QoS level, and the like is transmitted.

  In step S220, the radio communication terminal 200 sets a main session candidate configured with, for example, four carriers (4X) with the radio base station 100B (second radio base station).

  As described above, the main session candidates are the same as the number of carriers constituting the main session with the radio base station (radio base station 100B) other than the radio base station 100A to which the main session is set (radio base station 100B). 4X) carriers.

  In step S230 and step S240, the radio communication terminal 200 switches the main session to a main session candidate, similarly to the sub-session described above.

  As a result, the radio communication terminal 200 sets a main session composed of four carriers (4X) with the radio base station 100B. Also, the radio communication terminal 200 sets a session with the radio base station 100A that has become unused by switching the main session as a main session candidate.

  Note that the QoS control parameters of the traffic flow transmitted by the main session are taken over from the radio base station 100A to the radio base station 100B in the processes of steps S230 and S240.

  In addition, the switching timing of step S230 and S240 is not limited to this.

(3) Detailed switching operation flow of main session in wireless communication terminal Next, a detailed switching operation flow executed in the wireless communication terminal 200 to execute the above-described switching of the main session will be described. FIG. 5 is a detailed switching operation flow of the main session in the wireless communication terminal 200.

  As shown in FIG. 5, in step S310, the radio communication terminal 200 determines whether or not a main session candidate is set.

  When the main session candidate is set (YES in step S310), in step S320, the wireless communication terminal 200 analyzes the main session candidate. Specifically, the process of step S330 and step S340 is performed.

  On the other hand, when the main session candidate is not set (NO in step S310), the wireless communication terminal 200 ends the process.

  In step S330, the radio communication terminal 200 configures the main session candidate and acquires the number of unused carriers that are not used for communication.

  In step S340, the radio communication terminal 200 acquires the received signal strength (RSSI) of each carrier constituting the main session candidate.

  In step S350, when there are a plurality of main session candidates, radio communication terminal 200 repeats the processing from step S320.

  In step S360, the radio communication terminal 200 determines the number of main session candidates whose number of unused carriers acquired in step S330 is equal to or greater than the number of carriers constituting the main session.

  When the number of main session candidates that satisfy the determination condition in step S360 is two or more, in step S370, the wireless communication terminal 200 selects the main session candidate having the strongest RSSI.

  Specifically, the wireless communication terminal 200 selects a main session candidate having the strongest session RSSI (see formula 1).

  Note that the session RSSI calculation using (Equation 1) is applied up to the number of carriers constituting the main session. For the RSSI of carriers exceeding the number of carriers, (Equation 1) is not applied. For example, the main session candidate is calculated based on the average of the session RSSI calculated by (Equation 1) and the RSSI of carriers exceeding the number of carriers. Session RSSI can be obtained.

  When the main session candidate satisfying the determination condition of step S360 is 1, in step S380, the radio communication terminal 200 selects the main session candidate.

  In step S390, the wireless communication terminal 200 switches the main session to the main session candidate selected in step S370 or step S380.

  When the main session candidate satisfying the determination condition of step S360 is 0, in step S400, the radio communication terminal 200 selects the main session candidate having the strongest RSSI among the main session candidates that do not satisfy the determination condition. The main session candidate is selected by the same process as in step S370.

  In step S410, the radio communication terminal 200 performs switching of the traffic flow transmitted using the carrier constituting the selected main session candidate.

  Specifically, the radio communication terminal 200 switches the traffic flow to another radio base station that is different from the radio base station that transmits the carrier constituting the main session candidate.

  In step S420, the radio communication terminal 200 determines whether the number of unused carriers in the main session candidate is equal to or greater than the number of carriers constituting the main session.

  When the number of unused carriers is equal to or greater than the number of carriers constituting the main session (YES in step S420), in step S430, radio communication terminal 200 switches the main session to the main session candidate.

  If the number of unused carriers does not exceed the number of carriers constituting the main session (NO in step S420), radio communication terminal 200 ends the process.

(3) Operation Example Next, a specific operation example of the wireless communication terminal 200 will be described. Here, it is assumed that the radio base stations 100A to 100D and the radio communication terminal 200 can transmit and receive a maximum of 15 carriers (15X). In the following description, the same or similar parts are denoted by the same or similar reference numerals, and the description of the same or similar parts will be omitted as appropriate.

(3.1) Operation example 1
6A and 6B are diagrams illustrating an operation example 1 of the wireless communication terminal 200. FIG. In FIG. 6A, the radio communication terminal 200 sets the main session MS constituted by four carriers (4X) as the radio base station 100A.

  In addition, the radio communication terminal 200 sets a sub-session SSa configured by 11 carriers (11X) as the radio base station 100A. The subsession is used for transmission of best effort data having a low QoS level. Alternatively, the subsession may be configured with unused carriers.

  Here, when radio communication terminal 200 moves away from radio base station 100A, the session setting state changes to the state shown in FIG. 6B.

  Specifically, some of the carriers constituting the subsession SSa are switched to another radio base station. Specifically, the two carriers (2X) are switched to the sub session SSb with the radio base station 100B and the sub session SSc with the radio base station 100C, respectively. Further, the three carriers (3X) are switched to the sub session SSd with the radio base station 100D.

  As a result, the number of carriers in the subsession SSa with the radio base station 100A is reduced to 4 (4X).

(3.2) Operation example 2
7A and 7B are diagrams illustrating an operation example 2 of the wireless communication terminal 200. FIG. FIGS. 7A and 7B show an operation example when the radio communication terminal 200 switches the main session MS to the radio base station 100D.

  In FIG. 7A, the radio communication terminal 200 sets the main session candidate CDd constituted by four carriers (4X) as the radio base station 100D.

  Specifically, FIG. 7A shows a state where the radio communication terminal 200 has moved further away from the radio base station 100A from the state shown in FIG. 6B.

  Comparing FIG. 6 (b) and FIG. 7 (a), the number of carriers constituting a session that is further switched from the radio base station 100A to another radio base station and set with the radio base stations 100B to 100D. Has increased further.

  In particular, when the number of carriers in the subsession SSd shown in FIG. 6B is increased to four (4X), the number of carriers becomes the same as that of the main session MS. When the number of carriers becomes the same as the number of main sessions MS, the subsession SSd is set as the main session candidate CDd.

  Here, when radio communication terminal 200 further moves in a direction away from radio base station 100A, the session setting state changes to the state shown in FIG. 7B.

  Specifically, the radio communication terminal 200 switches the main session MS to the radio base station 100D. Further, the radio communication terminal 200 is configured by five carriers (5X) by a carrier that has been unused by switching the main session MS to the radio base station 100D and a carrier that has constituted the sub-session SSa. The main session candidate CDa to be performed is set as the radio base station 100A.

(3.3) Operation example 3
8A and 8B are diagrams illustrating an operation example 3 of the wireless communication terminal 200. FIG. FIGS. 8A and 8B show an operation example when there are a plurality of main session candidates.

  Specifically, as shown in FIG. 8A, a main session candidate CDc with the radio base station 100C and a main session candidate CDd with the radio base station 100D are set as the radio communication terminal 200.

  Here, the main session candidate CDc is assumed to be composed of four unused carriers. On the other hand, the main session candidate CDd is composed of five carriers, but it is assumed that two carriers (2X) are being used for communication (in-use carriers). That is, there are three (3X) unused carriers that constitute the main session candidate CDd.

  In this case, as illustrated in FIG. 8B, the radio communication terminal 200 switches the main session MS to the main session candidate CDc.

  That is, the number of carriers (5X) of the main session candidate CDd is larger than the number of carriers (4X) of the main session candidate CDc, but the number of unused carriers (4X) constituting the main session candidate CDc is not used for the main session candidate CDd. Since there are more than the number of used carriers (3X), the main session candidate CDc is selected.

(3.4) Operation example 4
9A and 9B are diagrams illustrating an operation example 4 of the wireless communication terminal 200. FIG. FIGS. 9A and 9B show an operation example when the number of unused carriers constituting the main session candidate is less than the number of carriers constituting the main session MS.

  As shown in FIG. 9A, the main session candidate CDd is composed of six carriers, but it is assumed that three carriers (3X) are being used for communication (in-use carriers). That is, there are three (3X) unused carriers that constitute the main session candidate CDd.

  Further, although the subsession SSc is composed of three carriers, it is assumed that one carrier (1X) is being used for communication (in-use carrier).

  In this case, as shown in FIG. 9B, the traffic flow transmitted by the carrier constituting the main session candidate CDd is switched to the carrier constituting the sub-session SSc.

  As a result, in the sub-session SSc, two carriers (2X) are in use for communication. In addition, the number of unused carriers constituting the main session candidate CDd increases from three (3X) to four. The radio communication terminal 200 switches the main session MS to the main session candidate CDd having four unused carriers (4X), that is, the number of carriers increased to the same number as the main session MS.

(3.5) Operation example 5
10A to 10C are diagrams illustrating an operation example 5 of the wireless communication terminal 200. FIGS. 10A to 10C show an operation example when the number of carriers constituting the main session MS exceeds half of the maximum settable number of carriers (15X), specifically, eight. .

  Note that the number of carriers constituting the main session MS is preferably equal to or less than half of the maximum number of carriers that can be set. This operation example relates to a countermeasure when the number of carriers constituting the main session MS exceeds half of the maximum settable number of carriers.

  As shown in FIG. 10 (a), when the number of carriers constituting the main session is eight that exceeds half of the maximum number of carriers that can be set (15X), the main session is composed of four carriers (4X). The main session MS1 is divided into a main session MS2 and a main session MS2.

  Next, when the radio communication terminal 200 moves in a direction away from the radio base station 100A, the main session MS1 is switched to the main session candidate CDd as shown in FIG. 10B.

  Further, by switching the main session MS1 to the main session candidate CDd, a main session candidate CDa constituted by five carriers (5X) is set.

  In the state shown in FIG. 10 (b), the radio communication terminal 200 moves from the radio base station 100A to the radio base station 100D for three of the five (5X) carriers constituting the main session candidate CDa. Perform a handoff.

  When the handoff is executed, the number of carriers constituting the subsession SSd becomes four, and the subsession SSd is set as a main session candidate (not shown). Next, the main session MS2 is switched to the main session candidate.

  As a result, as shown in FIG. 10C, a main session MS1 and a main session MS2 are set between the radio communication terminal 200 and the radio base station 100D.

(Action / Effect)
According to the present embodiment described above, the main session is established with a radio base station (second radio base station) other than the specific radio base station (first radio base station) for which the main session is set. A main session candidate configured by the same number (predetermined number) of carriers as the number of carriers configuring is set. Further, the main session is configured by a predetermined number of carriers (for example, 4X) which is equal to or less than half the maximum number of carriers that can be set (15X).

  When the main session candidate is set, the main session is switched to the main session candidate.

  For this reason, it is possible to prevent an increase in processing load on the radio base stations 100A to 100D and the radio communication terminal 200 by performing handoff of a large number of carriers at the same time.

  Furthermore, the traffic flow transmitted by the main session is switched in units of the number of carriers constituting the main session. For this reason, it is possible to prevent the communication quality of the traffic flow from becoming unstable by performing disordered handoff without synchronizing between carriers.

  According to the present embodiment, when an unused carrier is detected, the unused carrier can be included in the main session candidate in preference to the in-use carrier used for communication. In addition, when there are a plurality of main session candidates, the main session candidates configured by the number of unused carriers (predetermined number) constituting the main session are selected with priority over the other main session candidates.

For this reason, the main session candidate that can be immediately provided for switching of the main session can be set more reliably without affecting the traffic flow transmitted using the main session candidate.

  Furthermore, according to the present embodiment, when there are a plurality of main session candidates, the main session candidate for switching the main session is selected based on the reception state of the carrier included in the main session candidate. For this reason, stable communication quality can be ensured even after switching of the main session.

  Moreover, in this embodiment, session RSSI is calculated using (1 type | formula). According to (Equation 1), main session candidates with a large number of carriers are easily selected, and switching of traffic flows transmitted using sub-sessions (and main session candidates) to other radio base stations is reduced. can do.

(Other embodiments)
As described above, the content of the present invention has been disclosed through one embodiment of the present invention. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the wireless communication terminal 200 has been described as a mobile phone terminal. However, the wireless communication terminal 200 may be of a card type that can be mounted on a personal computer, a PDA, or the like. Further, the function of the wireless communication terminal 200 according to the present invention can also be provided as a wireless communication module.

  In the above-described embodiment, the reception signal strength (RSSI) is used as the carrier reception state. However, for example, a CIR (signal power to interference power ratio) or a bit error rate may be used.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

1 is a schematic configuration diagram of a mobile communication network including a wireless communication terminal according to an embodiment of the present invention. It is a functional block block diagram of the radio | wireless communication terminal which concerns on embodiment of this invention. FIG. 5 is a switching operation sequence diagram of a subsession according to the embodiment of the present invention. It is a switching operation sequence diagram of the main session concerning the embodiment of the present invention. 5 is a detailed switching operation flow of the main session in the wireless communication terminal according to the embodiment of the present invention. It is a figure which shows the specific operation example (operation example 1) of the radio | wireless communication terminal which concerns on embodiment of this invention. It is a figure which shows the specific operation example (operation example 2) of the radio | wireless communication terminal which concerns on embodiment of this invention. It is a figure which shows the specific operation example (operation example 3) of the radio | wireless communication terminal which concerns on embodiment of this invention. It is a figure which shows the specific operation example (operation example 4) of the radio | wireless communication terminal which concerns on embodiment of this invention. It is a figure which shows the specific operation example (operation example 5) of the radio | wireless communication terminal which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Mobile communication network, 100A-100D ... Wireless base station, 200 ... Wireless communication terminal, 201 ... RF part, 203 ... Data communication part, 205 ... Main session processing part, 207 ... Subsession processing part, 209 ... Communication quality Measurement unit 211 ... Session switching unit, CDa, CDc, CDd ... Main session candidate, MS, MS1, MS2 ... Main session, SSa-SSd ... Sub-session

Claims (4)

A wireless communication terminal that performs multi-carrier communication using a plurality of carriers with at least a first wireless base station and a second wireless base station,
A main session setting unit configured to set, as the first radio base station, a main session that is configured by a predetermined number of the carriers that is two or more and less than or equal to half of the maximum number of carriers that can be set; ,
A main session candidate setting unit that sets main session candidates configured with the predetermined number of carriers with the second radio base station;
A session switching unit that switches the main session to the main session candidate when the main session candidate setting unit sets the main session candidate;
When the main session candidate setting unit detects an unused carrier that is not used for communication with the second radio base station, the main session candidate setting unit gives priority to the unused carrier that is used for communication. A wireless communication terminal including a used carrier in the main session candidate. A wireless communication terminal that performs multi-carrier communication using a plurality of carriers with at least a first wireless base station and a second wireless base station,
A main session setting unit configured to set, as the first radio base station, a main session that is configured by a predetermined number of the carriers that is two or more and less than or equal to half of the maximum number of carriers that can be set; ,
A main session candidate setting unit that sets main session candidates configured with the predetermined number of carriers with the second radio base station;
A session switching unit that switches the main session to the main session candidate when the main session candidate setting unit sets the main session candidate;
When there are a plurality of main session candidates, the session switching unit selects a main session candidate configured by an unused carrier that is not used for the predetermined number of communications in preference to other main session candidates. Wireless communication terminal. A wireless communication terminal is a communication method for executing communication by multicarrier using a plurality of carriers with at least a first wireless base station and a second wireless base station,
A main session configured with a predetermined number of carriers that is two or more and less than or equal to half of the maximum settable number of carriers and used for transmission of a predetermined traffic flow is set with the first radio base station;
Setting main session candidates configured with the predetermined number of carriers with the second radio base station;
When the main session candidate is set, the main session is switched to the main session candidate, and
In the step of setting the main session candidate, when an unused carrier that is not used for communication is detected with the second radio base station, it is given priority over the used carrier that is used for communication. A communication method for including the unused carrier in the main session candidate. A wireless communication terminal is a communication method for executing communication by multicarrier using a plurality of carriers with at least a first wireless base station and a second wireless base station,
A main session configured with a predetermined number of carriers that is two or more and less than or equal to half of the maximum settable number of carriers and used for transmission of a predetermined traffic flow is set with the first radio base station;
Setting main session candidates configured with the predetermined number of carriers with the second radio base station;
When the main session candidate is set, the main session is switched to the main session candidate, and
In the step of switching the sessions, when there are a plurality of main session candidates, the main session candidates configured by unused carriers not used for the predetermined number of communications are selected with priority over other main session candidates. Communication method.

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