JP2008005307A - Radio link selection controller, radio equipment and radio link selection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To select and use proper radio communication media contributing to the improvement in frequency using efficiency of a whole radio communication system from among a plurality of radio communication media. <P>SOLUTION: This radio link selection controller is provided with a radio communication media monitoring part 5 for monitoring communication for each radio communication media; a frequency time non-use rate calculation part 6 for calculating a frequency time non-use rate excluding the use of its own station for each radio communication media from the monitor result; and a control part 7 for determining which radio communication media's radio link should be used based on the calculated frequency time non-use rate of each radio communication media. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radio link selection control device, a radio device, and a radio link selection method.

In recent years, a technique called cognitive radio communication in which one radio station performs communication using a plurality of radio communication media has been studied. Non-Patent Document 1 discloses mobile IP (Internet) when connecting to a plurality of wireless communication media (for example, a cellular system and a wireless local area network (wireless LAN) system) installed at different locations. A technique for performing seamless media switching by using (Protocol) is described. Non-Patent Document 2 describes wireless communication at the IP layer when a mobile router is mounted on an ITS (Intelligent Transport System) vehicle that connects to and communicates with a plurality of wireless communication media (for example, a cellular system and a wireless LAN system). A technique for switching media is described. Non-Patent Document 3 describes link aggregation in which a plurality of physical lines are aggregated and provided as one logical line. However, the technique described in Non-Patent Document 3 assumes that each line to be aggregated has the same speed, and does not consider a line whose communication quality changes, such as a wireless line. In selecting a wireless communication medium, mutual interference between base stations or QoS (Quality Of Service) is not considered.
Saito, et al., “Development of software for switching between different types of wireless communication media”, B-5-289, IEICE General Conference, 2003 Kashimura, et al. “Implementation of in-vehicle mobile router capable of switching communication media”, B-7-103, IEICE General Conference, 2003 IEEE802.3ad Standard (IEEE Computer Society LAN MAN Standards Committee) Aggregation of Multiple Link Segments, 2000.

  However, according to cognitive radio communication, an improvement in frequency utilization rate per hour (hereinafter referred to as “frequency time utilization rate”) is expected, but in one radio station (radio base station or radio terminal), A radio link selection method for determining which radio communication medium radio link is used is an issue. For example, just because the frequency time utilization rate of a certain wireless communication medium is low, if the use concentrates on the wireless communication medium, the frequency utilization efficiency of the entire wireless communication system deteriorates.

  The present invention has been made in view of such circumstances, and its purpose is to select an appropriate wireless communication medium that contributes to improving the frequency utilization efficiency of the entire wireless communication system from among a plurality of wireless communication media. Another object of the present invention is to provide a radio link selection control device, a radio device, and a radio link selection method that can be used.

  In order to solve the above-described problems, a radio link selection control device according to the present invention monitors communication for each radio communication medium in the radio link selection control device when one radio station uses a plurality of radio communication media. Wireless communication media monitoring means, and from the monitoring results of the wireless communication media monitoring means, for each wireless communication media, frequency time unused rate calculating means for calculating the frequency time unused rate excluding the usage of the own station, Control means for determining which radio communication medium radio link to use based on the frequency time unavailability for each radio communication medium calculated by the frequency time unavailability calculation means, To do.

  In the radio link selection control apparatus according to the present invention, the control means uses a plurality of radio communication media at a ratio corresponding to a frequency time unused rate of each radio communication medium.

  The radio link selection control apparatus according to the present invention includes a transmission success rate measuring unit that measures a transmission success rate for each radio communication medium, and the control unit includes a frequency time unused rate and a transmission success rate of each radio communication medium. The wireless communication medium to be used is determined based on the above.

  In the radio link selection control device according to the present invention, the control means calculates an evaluation value for each radio communication medium from the frequency time unused rate and the transmission success rate of each radio communication medium, and evaluates each radio communication medium. A plurality of wireless communication media are used at a ratio corresponding to the value.

  A wireless device according to the present invention is a wireless device that uses a plurality of wireless communication media, and includes the above-described wireless link selection control device.

  In the radio apparatus according to the present invention, the radio communication medium provided in the upper layer of the data link layer in the radio communication medium and used in units of IP packets or data link layer packets is selected according to the determination of the radio link selection control apparatus. Data link layer packet switch means is provided.

  The radio apparatus according to the present invention is characterized in that a radio communication medium to be used by the own radio apparatus is selected from available radio communication media candidates selected for each radio base station.

  The radio link selection method according to the present invention is a radio link selection method when one radio station uses a plurality of radio communication media, the process of monitoring communication for each radio communication medium, and from the monitoring result, The wireless link of which wireless communication media is calculated based on the process of calculating the frequency time unused rate excluding the use of the own station for each wireless communication medium and the calculated frequency time unused rate for each wireless communication medium. And determining whether to use.

  The radio link selection method according to the present invention further includes a step of measuring a transmission success rate for each radio communication medium, and which radio communication medium is selected based on the frequency time unused rate and the transmission success rate of each radio communication medium. It is characterized by deciding whether to use.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to select and use the suitable radio | wireless communication medium which contributes to the improvement of the frequency utilization efficiency of the whole radio | wireless communications system from several radio | wireless communication media.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an overall configuration of a wireless communication system according to an embodiment of the present invention. In FIG. 1, a radio base station 1 and a radio terminal 2 correspond to a plurality of radio communication media. In the example of FIG. 1, four wireless communication media A, B, C, and D are supported, and wireless base stations are provided by the wireless links 101A, 101B, 101C, and 101D of the wireless communication media A, B, C, and D, respectively. Wireless communication between 1 and the wireless terminal 2 is possible. The radio base station 1 is connected to the backbone network 3. The backbone network 3 relays communications between the wireless base stations 1 located at various places, and connects communications with external networks (such as the Internet).

  Examples of the wireless communication medium include a cellular system and a wireless LAN system.

[First Embodiment]
FIG. 2 is a block diagram showing a configuration of the radio link selection control device 4 according to the first embodiment of the present invention. The radio link selection control device 4 is provided in the radio base station 1 or the radio terminal 2.

  In FIG. 2, the wireless communication media monitoring unit 5 monitors communication for each wireless communication medium. The frequency time unused rate calculation unit 6 calculates the frequency time unused rate for each wireless communication medium from the monitoring result of the wireless communication media monitoring unit 5. The control unit 7 determines which radio communication medium to use on the basis of the frequency time unused rate for each radio communication medium calculated by the frequency time unused rate calculating unit 6.

  An operation according to this embodiment will be described.

  The wireless communication media monitoring unit 5 receives a wireless signal of each wireless communication medium and performs reception processing of packets communicated with each wireless communication medium. Thereby, a packet for each wireless communication medium is received. The wireless communication media monitoring unit 5 records the occupation time of each received packet for each wireless communication media. Occupancy time refers to the time that a packet occupies the frequency of the wireless communication medium.

  The frequency time unused rate calculation unit 6 calculates the frequency time unused rate for each wireless communication medium based on the occupation time recorded by the wireless communication media monitoring unit 5. Here, a method for calculating the frequency time unused rate will be described.

FIG. 3 is a conceptual diagram for explaining a method of calculating a frequency time unused rate according to the present embodiment. FIG. 3 shows a frequency utilization state regarding a certain wireless communication medium. In the present embodiment, the frequency time unused rate Y is calculated from the occupied time b of each received packet for each monitoring period a for the wireless communication medium to be calculated. The calculation formula of the frequency time unused rate Y is expressed by the following formula.
Y = {1- (Σb) / a}

  However, the calculation of the frequency time unavailability is performed excluding received packets related to transmission of communication packets from the own station. For example, FIG. 4 is a sequence diagram of packet communication of the IEEE (Institute of Electrical and Electronic Engineers) wireless LAN standard “IEEE802.11”. In the IEEE802.11 standard, a DATA packet as a communication packet is delivered in a series of procedures using four types of packets (RTS, CTS, DATA, ACK). Packets (RTS, CTS, ACK) other than DATA packets are control packets for DATA packet delivery. At this time, frequency packets that are not used in frequency time are excluded from received packets that are control packets for delivery of DATA packets transmitted from the local station, that is, CTS packets and ACK packets addressed to the local station, from among the packets received by the local station. Calculate the rate.

  FIG. 5 shows a flowchart of a frequency time unavailability calculation procedure taking the IEEE802.11 standard packet communication sequence shown in FIG. 4 as an example. In FIG. 5, in step S1, a packet is received. In step S2, it is determined whether the received packet is a CTS packet or an ACK packet. If it is a CTS packet or an ACK packet, the process proceeds to step S3. On the other hand, if it is neither a CTS packet nor an ACK packet, the process proceeds to step S5.

  In step S3, it is determined whether the received CTS packet or ACK packet is addressed to the own station. If it is addressed to the own station, the process proceeds to step S4. On the other hand, if it is not addressed to the own station, the process proceeds to step S5.

  In step S4, the received CTS packet or ACK packet is excluded from the received packets subject to frequency time unavailability calculation targets.

  In step S5, the frequency time unavailability is calculated from the received packet which is the frequency time unavailability calculation target based on the occupied time.

  As a result, for each wireless communication medium, the frequency time unused rate excluding the use of the own station can be obtained. This is very effective in evaluating the frequency time unavailability of each wireless communication medium on the assumption that the local station uses it, since the usage of the local station becomes redundant.

  The control unit 7 selects the wireless communication medium having the highest frequency time unused rate for each monitoring period a from the frequency time unused rate for each wireless communication medium calculated by the frequency time unused rate calculating unit 6. The control unit 7 controls the communication of the local station so that communication is performed using the wireless link of the selected wireless communication medium.

  A plurality of wireless communication media may be used at a ratio corresponding to the frequency time unused rate of each wireless communication media. For example, it is assumed that the frequency time unused rates of the wireless communication media A, B, C, and D are R1, R2, R3, and R4, respectively. At this time, packets are transmitted to the wireless communication media A, B, C, and D at a ratio of R1, R2, R3, and R4.

  According to the first embodiment described above, the frequency time unused rate of each wireless communication medium is calculated by excluding the usage amount of the own station, and the frequency time unused rate of each wireless communication medium excluding the usage amount of the own station. Based on the above, the wireless communication medium used by the local station is determined. As a result, the wireless communication medium to be used is determined based on the frequency time unused rate from which redundant use of the local station is eliminated, so that an appropriate wireless communication medium is selected and the frequency utilization efficiency of the entire wireless communication system is selected. It can contribute to improvement.

[Second Embodiment]
FIG. 6 is a block diagram showing a configuration of a radio link selection control device 4a according to the second embodiment of the present invention. In FIG. 6, the frequency time unavailability calculating unit 6 is the same as that of the first embodiment shown in FIG.

  In the second embodiment, the transmission success rate measuring unit 8 is provided to measure the transmission success rate for each wireless communication medium, and determine which wireless communication medium to use in consideration of the transmission success rate of each wireless communication medium. .

  In addition to the function of the wireless communication media monitoring unit 5 of the first embodiment, the wireless communication media monitoring unit 5a monitors the success or failure of packet transmission from the own station for each wireless communication media. For example, in FIG. 4, when an ACK packet is received, the packet transmission is successful. On the other hand, when an ACK packet is not received, the packet transmission is failed.

  The transmission success rate measuring unit 8 measures the success rate of packet transmission from the own station for each wireless communication medium. For the wireless communication media that the local station is communicating with, the packet transmission success rate is calculated from the monitoring result of packet transmission success / failure by the wireless communication media monitoring unit 5a.

  For wireless communication media in which the local station is not communicating, measurement is performed by periodically transmitting measurement packets from the local station. Specifically, the local station periodically transmits a measurement packet to each wireless communication medium that the local station is not communicating with. The measurement packet receiving station measures the reception success rate for each transmission source of the measurement packet, and reports the reception success rate of the measurement result to the transmission source of the measurement packet. For this report, a measurement packet transmitted from the station that measured the reception success rate to the report destination may be used. As a result, the local station uses the reception success rate reported from the other station as the packet transmission success rate from the local station.

The control unit 7a determines a wireless communication medium to be used for each monitoring period a based on the frequency time unused rate and the transmission success rate for each wireless communication medium. For the determination, an evaluation value Ya obtained by the following equation is used.
Ya = (frequency time unused rate) + β × (transmission success rate)
However, β is a constant satisfying 0 <β ≦ 1.

  The control unit 7a selects the wireless communication medium having the maximum evaluation value Ya. The control unit 7a controls communication of the local station so that communication is performed using the wireless link of the selected wireless communication medium.

  A plurality of wireless communication media may be used at a ratio corresponding to the evaluation value Ya of each wireless communication media. For example, it is assumed that the evaluation values Ya of the wireless communication media A, B, C, and D are Ya1, Ya2, Ya3, and Ya4, respectively. At this time, packets are transmitted to the wireless communication media A, B, C, and D at the ratio of Ya1, Ya2, Ya3, and Ya4.

  According to the second embodiment described above, the wireless communication media to be used is determined in consideration of the transmission success rate of each wireless communication medium. Thereby, there is no problem in the own station, but the communication partner station can be prevented from using a wireless communication medium having a problem due to the influence of interference or fading. As a result, the communication quality of cognitive radio communication can be improved.

Next, a wireless device according to a first embodiment of the present invention will be described.
FIG. 7 is a block diagram illustrating a configuration of the wireless base station 1 according to the first embodiment illustrated in FIG. 1. FIG. 8 is a block diagram illustrating a configuration of the wireless terminal 2 illustrated in FIG. 1 according to the first embodiment. In FIG. 7 and FIG. 8, the same reference numerals are assigned to the corresponding parts.

  The wireless base station 1 and the wireless terminal 2 include wireless modules 11A, 11B, 11C, and 11D of wireless communication media A, B, C, and D, a packet switch 12, a control unit 15, an upper layer unit 16, and a data link. A layer portion 17 and a PHY (physical) layer portion 18 are provided. In addition, the wireless terminal 2 includes an application layer and transport layer processing unit 20. In the following description, unless otherwise limited, each unit will be described without distinguishing between the radio base station 1 and the radio terminal 2.

  The wireless modules 11A, 11B, 11C, and 11D (hereinafter referred to as “wireless module 11” unless otherwise distinguished) are functions of the PHY layer and the data link layer corresponding to the respective wireless communication media A, B, C, and D. Have Examples of the function of the data link layer include MAC (Medium Access Control) and LLC (Logical Link Control). The wireless module 11 transmits and receives data link layer packets to and from the packet switch 12. The wireless module 11 performs wireless transmission and wireless reception of data link layer packets.

  The packet switch 12 has a data link layer packet switching function. The packet switch 12 has a buffer 13 provided corresponding to each wireless module 11. The buffer 13 buffers the data link layer packet transmitted / received to / from the wireless module 11. The packet switch 12 includes a conversion unit 14 that performs mutual conversion between the data link layer packet and the IP packet. The packet switch 12 transmits and receives IP packets to and from the upper layer unit 16.

  The control unit 15 controls the packet switch 12. The upper layer unit 16 has a network control function such as an IP layer or an access network routing layer.

  The radio base station 1 includes a data link layer unit 17 and a PHY layer unit 18 having functions of a data link layer and a PHY layer for connecting to the backbone network 3. In the wireless terminal 2, a processing unit 20 having functions of an application layer and a transport layer, a data link layer unit 17 having a function of a data link layer and a PHY layer for connecting to a wired LAN port, and a PHY layer A portion 18 is provided.

  The packet switch 12 converts the IP packet received from the upper layer unit 16 into a data link layer packet by the conversion unit 14 and outputs the data link layer packet to the wireless module 11 designated by the control unit 15. In the case of single connection communication, the control unit 15 designates the output destination wireless module 11 as the packet switch 12 in units of data link layer packets. On the other hand, in the case of communication with a plurality of connections, the output destination wireless module 11 is designated to the packet switch 12 in units of IP packets. The output destination of one data link layer packet may be one wireless module 11 or a plurality of wireless modules 11. The packet switch 12 has a function of copying and outputting the same data link layer packet to the plurality of wireless modules 11.

  The packet switch 12 converts the data link layer packet received from each wireless module 11 into an IP packet by the conversion unit 14 and outputs the IP packet to the upper layer unit 16.

  Further, the packet switch 12 discards the data link layer packet stored in the buffer 13 in accordance with an instruction from the control unit 15. Further, the packet switch 12 notifies the control unit 15 of the buffering status of each buffer 13.

  At the time of transmission, the wireless module 11 converts the data link layer packet received from the packet switch 12 into a unique format of its own wireless communication medium and wirelessly transmits it. Further, at the time of reception, the data link layer packet of the specific format received wirelessly is converted into a data link layer packet of the common format and output to the packet switch 12.

  As a device configuration of the wireless base station 1, the wireless module 11 may be mounted in the device, or the wireless module 11 is extended between the wireless modules 11 using a communication line such as an optical fiber cable, and the wireless module 11 is placed at a plurality of points. It may be distributed.

  The upper layer unit 16 notifies the control unit 15 of information on the input / output IP packet. Examples of the IP packet information to be notified include address information (destination IP address, transmission source IP address, TCP (Transmission Control Protocol) port address, etc.), connection type (single connection, multiple connections), and communication quality for an IP flow. Request (transmission speed, QoS, etc.). Examples of QoS requests include unconditional priority, delay quality priority, and best effort. A request for communication quality for an IP flow is generated from an application involving IP packet communication, for example. The request content of the communication quality for the IP flow can be known by referring to the “Priority identifier” included in the IP packet. In addition, for each IP address of the wireless terminal 2, a communication quality request content (priority etc.) for the IP flow may be determined in advance.

  The control unit 15 associates the IP flow with the data link layer packet based on the address information notified from the upper layer unit 16. The control unit 15 instructs the packet switch 12 on how to integrate the data link layer packets input from the wireless module 11 based on the connection type notified from the upper layer unit 16. Specifically, in the case of single connection communication, it is instructed to integrate the data link layer packet as a single IP flow, whereas in the case of multiple connection communication, the data link layer packet is IP flow unit. Instruct them to integrate. The packet switch 12 converts the data link layer packet into an IP packet according to the instruction.

  In the first embodiment, the wireless module 11 includes a wireless communication media monitoring unit of the wireless link selection control device according to the present embodiment, and monitors communication of its own wireless communication media. The control unit 15 includes a frequency time unused rate calculation unit of the radio link selection control device according to the present embodiment, and calculates a frequency time unused rate for each radio communication medium from the monitoring result of the radio module 11. In addition, the control unit 15 includes a control unit of the radio link selection control device according to the present embodiment, and determines which radio communication medium radio link is used based on the frequency time unused rate for each radio communication medium. To do.

  In addition, a transmission success rate measurement unit of the radio link selection control device according to the present embodiment is provided, and the control unit 15 determines a radio communication medium to be used in consideration of a transmission success rate for each radio communication medium. Also good.

  According to the first embodiment, a data link layer packet switch that selects a wireless communication medium to be used in units of IP packets or data link layer packets is provided above a data link layer (MAC, LLC, etc.) in the wireless communication medium. . Further, based on the frequency time unused rate of each wireless communication medium, it is determined which wireless communication medium is to be used, and the data link layer packet switch is controlled. The frequency time unused rate is a frequency time unused rate excluding the usage of the own station. Thereby, a radio link of an appropriate radio communication medium is selected, which can contribute to an improvement in frequency use efficiency of the entire radio communication system.

  Note that the radio link selection control device according to the present embodiment may be provided in either one of the radio base station 1 and the radio terminal 2 or in both. When the wireless device is provided in either one of the wireless base station 1 and the wireless terminal 2, the wireless communication medium to be used is designated to the wireless device that is not provided from the wireless device that is provided. When both the radio base station 1 and the radio terminal 2 are provided, the radio base station 1 adopts a radio communication media selection by either radio apparatus, but the radio base station 1 comprehensively determines and uses the radio communication media. It is preferable to select media.

Next, a second embodiment of the wireless device according to the present invention will be described.
FIG. 9 is a block diagram showing the configuration of Embodiment 2 of the wireless communication system according to the present invention. FIG. 9 shows only the configuration related to the radio base station 1. Also, in FIG. 9, the same reference numerals are given to portions corresponding to the respective portions in FIG. 7, and the description thereof is omitted.

  In the second embodiment, a host control unit 30 shown in FIG. 9 is provided. The host control unit 30 is connected to each radio base station 1 via a communication line. The upper control unit 30 controls each radio base station 1. Hereinafter, differences from the first embodiment will be mainly described.

The upper control unit 30 selects candidates for wireless communication media to be used in each wireless base station 1.
The upper control unit 30 has an interface with the control unit 15 in each radio base station 1. The host control unit 30 receives notifications such as the radio environment status and the buffering status of the packet switch 12 from the control unit 15 in each radio base station 1. Examples of the wireless environment status include (a) communication quality for each wireless terminal 2, (b) presence information of the wireless terminal 2, (c) usage status for each wireless module 11, and (d) subordinates for each wireless module 11. A list of wireless terminals 2 can be given. Based on the information notified from each radio base station 1, the upper control unit 30 selects a radio communication media candidate to be used in each radio base station 1 and notifies the control unit 15 in each radio base station 1. The control unit 15 selects a wireless communication medium from the notified candidates.

  Thereby, the candidate of the radio | wireless module 11 which can be utilized of each radio base station 1 is selected after the mutual interference between base stations is considered.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.

1 is a block diagram showing an overall configuration of a wireless communication system according to an embodiment of the present invention. It is a block diagram which shows the structure of the radio link selection control apparatus 4 which concerns on 1st Embodiment of this invention. It is a conceptual diagram for demonstrating the calculation method of the frequency time unavailability based on 1st Embodiment of this invention. It is a sequence diagram of packet communication of IEEE802.11 standard. It is a flowchart of the calculation procedure of the frequency time unavailability based on 1st Embodiment of this invention. It is a block diagram which shows the structure of the radio link selection control apparatus 4a which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of Example 1 of the radio | wireless apparatus (radio base station 1) which concerns on this invention. It is a block diagram which shows the structure of Example 1 of the radio | wireless apparatus (radio | wireless terminal 2) which concerns on this invention. It is a block diagram which shows the structure of Example 2 of the radio | wireless communications system which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wireless base station (wireless apparatus), 2 ... Wireless terminal (wireless apparatus), 4, 4a ... Wireless link selection control apparatus, 5, 5a ... Wireless communication media monitoring part, 6 ... Frequency time unused rate calculation part, 7 , 7a ... control unit, 8 ... transmission success rate measurement unit, 11 ... wireless module, 12 ... packet switch, 13 ... buffer, 14 ... conversion unit, 15 ... control unit, 16 ... upper layer unit, 17 ... data link layer unit , 18 ... PHY (physical) layer unit, 20 ... application layer and transport layer processing unit, 30 ... upper control unit

Claims (9)

In a radio link selection control device when one radio station uses a plurality of radio communication media,
Wireless communication medium monitoring means for monitoring communication for each wireless communication medium;
From the monitoring result of the wireless communication media monitoring means, for each wireless communication medium, a frequency time unused rate calculating means for calculating a frequency time unused rate excluding the usage of the own station,
Control means for determining which radio communication medium radio link is to be used based on the frequency time unavailability ratio for each radio communication medium calculated by the frequency time unavailability calculating means;
A radio link selection control device comprising:   The radio link selection control apparatus according to claim 1, wherein the control means uses a plurality of radio communication media at a ratio corresponding to a frequency time unused rate of each radio communication media. A transmission success rate measuring means for measuring a transmission success rate for each wireless communication medium;
The radio link selection control apparatus according to claim 1, wherein the control means determines which radio communication medium to use based on a frequency time unused rate and a transmission success rate of each radio communication medium. The control means includes
From the frequency time unused rate and transmission success rate of each wireless communication media, calculate the evaluation value for each wireless communication media,
The radio link selection control apparatus according to claim 3, wherein a plurality of radio communication media are used at a ratio corresponding to an evaluation value of each radio communication media. In a wireless device using multiple wireless communication media,
A radio apparatus comprising the radio link selection control apparatus according to any one of claims 1 to 4.   Data link layer packet switch means is provided above the data link layer in the wireless communication medium and selects a wireless communication medium to be used in units of IP packets or data link layer packets according to the determination of the wireless link selection control device. The wireless device according to claim 5.   The radio apparatus according to claim 5 or 6, wherein a radio communication medium to be used in the own radio apparatus is selected from available radio communication media candidates selected for each radio base station. A radio link selection method when one radio station uses a plurality of radio communication media,
A process of monitoring communication for each wireless communication medium;
From the monitoring result, for each wireless communication medium, a process of calculating a frequency time unused rate excluding the usage of the own station;
Determining which radio communication medium radio link to use based on the calculated frequency time unavailability for each radio communication medium;
A method of selecting a radio link, comprising: Further comprising measuring a transmission success rate for each wireless communication medium,
The radio link selection method according to claim 8, wherein which radio communication medium is to be used is determined based on a frequency time unused rate and a transmission success rate of each radio communication medium.

Images