JP6530284B2 - Wireless communication device, wireless communication method and program - Google Patents

Description

  Embodiments of the present invention relate to a wireless communication apparatus, a wireless communication method, and a program.

  The diversification of the content handled by the portable terminal increases the amount of traffic flowing through the mobile communication network, causing the wireless band to be tight. For this reason, attention has been focused on mobile P2P (Peer To Peer) in which terminals directly communicate with each other without using a mobile communication network. In a system using mobile P2P, for example, by using a wireless LAN (Local Area Network), a local network can be formed between terminals such as a smartphone and a tablet terminal, and files can be shared.

  A system using mobile P2P is characterized in that shared data can be spread over a wide area by distributing files to many terminals and terminals that have finished receiving the files newly distributing files. For this reason, files will be distributed from many terminals, which may lead to a shortage of wireless bands used in the wireless LAN. Also, in the case of a system that guarantees the arrival of data by retransmission, retransmission requests for retransmission of lost data and retransmission data for retransmission requests are frequently occurring when terminals with poor communication quality join the network during data distribution. It causes pressure on the wireless band because it Due to the tightness of these radio bands, there is a problem that the time it takes for the file to be shared to reach all the terminals participating in the network is prolonged.

  To solve this problem, a wireless LAN infrastructure mode is used to construct a network consisting of an access point (AP) and a plurality of stations (STAs), and STAs that have completed data reception receive surrounding wireless states. There is a method of acquiring only STAs that do not have an AP in the surrounding area. In this method, it is possible to reduce the number of APs distributing data and alleviate congestion in the radio band. However, since the handover function is not defined, when the communication quality of the connected AP is poor, there is a problem that it is not possible to switch the connection to the newly appeared AP with better communication quality.

  Also, in a network using a wireless LAN, the communication quality with surrounding APs other than the currently connected AP is obtained from parameters such as the received signal strength from the AP and the time taken by the STA to connect to the AP, A method of searching for an AP with better communication quality has been proposed. However, in a system that shares various files using mobile P2P, the AP that delivers the data and files required by the STA is limited, so even if the connection is switched to an AP with good communication quality, all data will be It is not always possible to shorten the time to receive. For example, when the STA is connected, there is a case where the AP can not receive a part of the file because the AP has delivered or the like, and waiting for redelivery by the AP may prolong the time.

Patent No. 4808202 JP, 2012-75117, A

  An embodiment of the present invention aims to receive a plurality of data in a short time by appropriately switching a communication device as a connection destination to a plurality of communication devices each distributing a plurality of data.

  A wireless communication apparatus as an embodiment of the present invention includes a communication unit, a quality measurement unit, a message processing unit, and a control unit.

  The communication unit receives the data transmitted from a first communication device that sequentially distributes a plurality of data.

  The quality measurement unit measures communication quality with the first communication device.

  The message processing unit acquires first information indicating a distribution status of the plurality of data from a second communication device to an Nth (N is an integer of 2 or more) communication devices that sequentially distribute the plurality of data.

  The control unit determines to switch the connection destination of the communication unit from the first communication device according to the communication quality, and switches the connection destination to the second communication device to the Nth communication device. The second to Nth communication devices are selected from the second to Nth communication devices according to the position of data receivable from the second to Nth communication devices, and the connection destination is switched to the selected communication device. Control.

A figure showing an example of a radio communications system concerning a 1st embodiment. The figure which shows a mode that several packet is produced | generated from a file and it transmits. FIG. 1 is a block diagram of a wireless communication device according to a first embodiment. 5 is a flowchart of the operation of the wireless communication device of FIG. 3; The flowchart following FIG. The flowchart following FIG. 5A. FIG. 5 is a state transition diagram of the wireless communication device of FIG. 3; The figure which shows the example which determines the value of (alpha). The flowchart of the operation example which measures communication quality using the data missing number or the presence or absence of reception of data. FIG. 2 is a block diagram showing an example of a hardware configuration of a wireless communication terminal equipped with the wireless communication device. 6 is a flowchart of the operation of the wireless communication device according to the second embodiment. The flowchart following FIG. 10A. 11 is a flowchart of the operation of the wireless communication device according to the third embodiment. The flowchart following FIG. The flowchart following FIG. 12A. The flowchart of another operation example following FIG. The flowchart following FIG. 13A. The figure which demonstrates the operation | movement which performs a resending request by a block unit. 16 is a flowchart of the operation of the wireless communication device according to the fourth embodiment.

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

First Embodiment
FIG. 1 shows an example of a wireless communication system according to the first embodiment. The present wireless communication system includes two wireless base stations 1 and 2 which are communication devices, and at least one wireless communication device 3. This wireless communication system can be used as a mobile P2P network in which a plurality of wireless base stations and a plurality of terminals are P2P connected to construct a mesh network, as an example. The communication system of the wireless communication system conforms to the IEEE 802.11 standard, but the communication system used in the wireless communication system is not limited to this. The wireless communication device 3 selectively establishes connection with any one wireless base station, and communicates with the connection destination wireless base station. Although one wireless communication device is shown in FIG. 1, the number of wireless communication devices may be two or more. Further, the number of radio base stations is not limited to two, and may be three or more.

  In the present embodiment, the same file is shared among a plurality of wireless base stations. Each wireless base station configures a local network with one or more wireless communication devices connected to the local station, and distributes the file held to the wireless communication devices belonging to the local station. As an example, the networks formed by each wireless base station have the same network identifier (such as ESSID). The file size of the file held by each wireless base station is large, and each wireless base station divides the held file into a plurality of data chunks, creates a packet having data chunks, and delivers it to this packet Add a sequence number for A packet including a sequence number and a data chunk is defined as data. Data (packets) are transmitted by broadcast or multicast. FIG. 2 shows how a plurality of data (packets) are generated from a file and transmitted. The method of dividing each file into a plurality of data chunks by each wireless base station is the same, and it is assumed that the same sequence number is added to packets including the same data chunks. In practice, packets are transmitted with data link layer and physical layer headers added according to the wireless standard used. In the IEEE 802.11 standard, a MAC header is added to a packet to generate a MAC frame, and a physical frame (physical packet) in which a physical header is added to the MAC frame is transmitted. For example, a communication protocol such as UDP / IP may be operated in the upper layer of the MAC layer, and a file exchange protocol may be operated as an application layer in the upper layer.

  Hereinafter, the sequence number for data distribution is called a sequence number. The sequence number represents the position of each data in the plurality of data transmitted from the wireless base station. For example, this sequence number is defined separately from the sequence number described in the frame in wireless communication conforming to the IEEE 802.11 standard. In addition, as long as the position of each data can be specified among a plurality of data transmitted from the wireless base station, a method that does not use a sequence number is also possible. For example, when a time slot is assigned to each of a plurality of data transmitted from the wireless base station and data is transmitted in the time slot, data can be specified from each time slot. Therefore, in this case, it can be said that the time slot represents the position of data.

  FIG. 3 is a block diagram of the wireless communication apparatus according to the first embodiment. The wireless communication apparatus includes an antenna 101, a wireless interface (wireless IF) 102 which is a communication unit, a quality measurement unit 103, a message processing unit 104, a control unit 105, and a storage unit 106.

  The wireless IF 102 transmits and receives wireless signals to and from a wireless base station. The wireless IF 102 transmits and receives frames to and from a wireless base station according to a wireless communication standard such as the IEEE 802.11 standard. The types of frames include, for example, management frames such as broadcast frames (beacon frames), control frames such as data frames, and delivery confirmation responses. The operation of the wireless IF 102 is controlled by the control unit 105 in which an application or the like operates. The wireless IF 102 detects the presence of a wireless base station by receiving a notification frame periodically transmitted by the wireless base station. The broadcast frame includes, as an example, an identifier of a wireless base station, an identifier of a local network, information indicating a delivery status of data, and the like. It may further include an identifier of the file to be delivered. The identifier of the wireless base station corresponds to the BSSID or MAC address of the IEEE 802.11 standard as an example, and the identifier of the local network corresponds to the ESSID or SSID. The wireless communication apparatus transmits the search request frame to the wireless base station and detects the presence of the wireless base station by receiving the search response frame, in addition to detecting the presence of the wireless base station by receiving the broadcast frame. It is also good. The search response frame includes the same content as the broadcast frame.

  The quality measurement unit 103 measures communication quality with the connected wireless base station based on a wireless signal or the like received by the wireless IF 102. The radio signal used to measure the communication quality may be a signal of a notification frame (notification signal) or a signal of a data frame including a packet (data signal). The signal used to measure the communication quality may be another signal as long as it is a signal transmitted from the wireless base station. Also, as described later, in the process of receiving data distributed from the radio base station, communication quality may be measured based on the number of missing data and the like.

  The message processing unit 104 extracts and processes the message (frame body portion) in the frame received from the wireless base station. If it is a data frame, data (data chunk, sequence number, etc.) is extracted and stored in the storage unit 106. If it is a notification frame, the identifier of the radio base station, the network identifier, and information indicating the distribution status of data are extracted and stored in the storage unit 106. If the broadcast frame includes a file identifier, the file identifier may also be stored in the storage unit 106. The storage unit 106 may be a memory or a storage. The memory may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as MRAM or NAND. The storage may be any device that permanently stores data, such as an HDD or an SSD.

  The control unit 105 controls connection with the radio base station and the quality measurement unit 103 based on the message extracted by the message processing unit. For example, depending on the communication quality with the wireless base station, it is determined whether to maintain the connection with the current wireless base station to be connected or to switch the connection destination to another wireless base station. When switching to another wireless base station, it is determined which wireless base station is to be switched according to the distribution status of data by the other wireless base station, the communication quality with the other wireless base station, and the like. The control unit 105 controls the wireless IF 102 according to the determination result, and connects to another wireless base station. After completing reception of the file (plurality of data) distributed from the wireless base station, the control unit 105 determines whether or not there is a wireless base station in the vicinity. Distribution of data may be performed. Such may occur depending on the movement of the surrounding radio base station or the movement of the radio communication device. The control unit 105 and the wireless IF 102 also have functions as a file distribution server and a wireless base station.

  FIG. 4 is a flowchart of the operation of the wireless communication apparatus of FIG. 5A and 5B are flowcharts subsequent to FIG. FIG. 6 is a state transition diagram of the wireless communication apparatus of FIG. The wireless communication apparatus has a standby state A1, a data reception state A2, a reception completion state A3, a reception quality check state A4, a radio base station search state A5, and a switching processing state A6.

  The wireless communication device initially exists in the standby state (standby state A1). The radio base station periodically transmits a broadcast frame including a radio base local identifier, a local network identifier, and the like. The identifier of the wireless base station corresponds to the BSSID or MAC address of the IEEE 802.11 standard as an example, and the identifier of the local network corresponds to the ESSID or SSID. The wireless communication device detects the presence of the wireless base station by receiving the notification frame. Alternatively, the wireless communication apparatus may detect the presence of the wireless base station by transmitting the search request frame and receiving the search response frame.

  The wireless communication apparatus performs an association process with the wireless base station, and when connecting to the wireless base station succeeds, the wireless communication apparatus participates in a local network formed by the wireless base station (data reception state A2). Before the association process, an authentication process may be performed. The wireless communication apparatus sequentially receives a plurality of data transmitted from the wireless base station based on the application for file exchange (S11).

  It is checked whether the sequence number included in the received data is continuous with the sequence number included in the previously received data. If the sequence numbers are consecutive, the wireless communication device determines whether all data has been received. If all the data has been received (YES in S11), that is, if acquisition of the file has been completed, the process ends (reception complete state A3).

  Any method can be used to determine whether all data has been received. For example, when the file size is notified in advance from the wireless base station, and the total size of the data chunks reaches the notified file size, it may be determined that all the data has been received. Alternatively, when the wireless base station sets a flag to the last data and the wireless communication device detects this flag, it may determine that all the data has been received. The reception completion of the file may be determined by a method other than that described here.

  If the reception of all the data has not been completed, it is determined whether there is a loss of sequence number, that is, there is a loss of data (YES in S12). If the sequence numbers are not consecutive, it is determined that there is a dropout. If a loss of data is detected, the wireless communication device transitions to the reception quality check state A4.

  The wireless communication device having transitioned to the reception quality investigation state A4 investigates the communication quality with the connected wireless base station (communication quality investigation) (S101 in FIG. 5A). The communication quality with the connected wireless base station is referred to as a first communication quality. The first communication quality is, as an example, a received signal strength indicator (RSSI) of a wireless signal received from a wireless base station, a received power, and a signal noise power ratio (SNR). Alternatively, the number of data lost by the wireless communication device within a predetermined time period or a value based thereon may be used. The first communication quality is an indicator that the higher the numerical value, the better the communication quality in the case of received signal strength, received power, signal-to-noise power ratio, etc., and the smaller the number of lost data, the better the communication quality. Use Here, it is assumed that the value of the first communication quality is larger as the communication quality is better. However, the first communication quality may be defined such that the value of the first communication quality decreases as the communication quality is better.

  If the first communication quality is equal to or higher than the first threshold (YES in S101), it is determined that the communication quality with the connected radio base station is good. In this case, a frame (a retransmission request frame) for requesting retransmission of the missing data is transmitted (S102), the state is shifted to the data reception state A2, and the process returns to the flow of FIG. If data is lost, a retransmission request for the lost data is sent to the radio base station. The transmission of the retransmission request may be broadcast or multicast transmission, or may be unicast transmission for the currently connected radio base station.

  On the other hand, when the first communication quality is less than the first threshold, it is determined that the communication quality with the connected radio base station is inferior, and the state transitions to the radio base station search state A5.

  The wireless communication device that has transitioned to the wireless base station search state A5 attempts to receive a broadcast frame transmitted from another wireless base station for a certain period of time (S103), and receives the broadcast frame, whereby wireless base stations existing in the surrounding area Detect (surrounding base station). At this time, only the wireless base station transmitting the broadcast frame including the identifier of the local network (that is, the same network identifier as the connected wireless base station) is detected as the surrounding base station. Alternatively, a list storing an identifier (such as BSSID) of a wireless base station that may appear in the local network in advance is compared with the identifier of the wireless base station described in the received broadcast frame, and the same identifier If it is included in the list, the radio base station may be detected as a surrounding base station. Furthermore, only the wireless base station which has notified the same file identifier as the connected wireless base station may be detected. If there is a premise that a plurality of wireless base stations belonging to the same network identifier are transmitting the same file, processing using such a file identifier is unnecessary. The above list may be stored in advance in the storage unit 106 of the wireless communication apparatus. As long as it is possible to identify whether the target radio base station belongs to the local network, methods other than those described here are also possible.

  Here, the broadcast frame transmitted from the wireless base station includes information indicating the distribution status of data. The information indicating the delivery status of the data is information that can identify how far the radio base station has delivered data of the sequence number up to now. Here, among the sequence numbers transmitted before the broadcast frame, the largest sequence number is indicated. However, the information indicating the delivery status of data is not limited to this. For example, the sequence number next to the largest sequence number among the sequence numbers transmitted before the broadcast frame (the smallest and untransmitted (not retransmission) sequence numbers among the sequence numbers scheduled to be transmitted after the broadcast frame) And other values may be represented.

  The wireless communication device that has received the notification frame from the surrounding wireless base station measures the second communication quality from the received signal of the notification frame. Then, the list (surrounding base station storage list) stores an entry including identifiers (BSSID etc.) of surrounding radio base stations, reception time of broadcast frame, second communication quality, and information indicating data distribution status etc. Do. The second communication quality may be the same as or different from the first communication quality.

  If the surrounding base station storage list is empty after a predetermined time has elapsed, that is, if none of the surrounding radio base stations can be detected (YES in S104), the radio communication device searches for the radio base station searching state A5. The process ends and transitions to the data reception state A2 (return to the process of the flow in FIG. 4).

  On the other hand, if there is one or more entries of surrounding wireless base stations in the surrounding base station preservation list, that is, if one or more surrounding wireless base stations are detected (NO in S104), wireless communication The apparatus selects one entry from the list (S105). Based on the distribution status of data in the selected entry, it is checked whether the wireless base station (peripheral base station) indicated by the entry can receive the data requested by the wireless communication apparatus (can it be received in time for data reception) (S106). The data desired by the wireless communication device is data missing from the wireless communication device, and it is determined whether it is possible to receive data having the smallest sequence number.

Here, if the following inequality is satisfied, it is determined that the data requested by the wireless communication device is in time for (or likely to be in time for) reception by the surrounding base station from now on.

  The minimum missing sequence number is the minimum value of the sequence number of data that the wireless communication device has missed. The minimum dropout sequence number can be identified by sequentially checking the data received by the wireless communication apparatus from the smallest one with the smallest sequence number of the data, and confirming the place where the sequence number becomes discontinuous for the first time.

  α is a constant set in advance, and is an integer of 0 or more. α is a margin in consideration of the processing delay from when the surrounding base station notifies the information indicating the data distribution status to when the wireless communication device receives the information. In the process (S104) of waiting for a fixed time in the radio base station search state A5, the delivery status (sequence number) indicated by the information notified by the notification frame from the neighboring base stations and the actual reception by first connecting to the neighboring base stations It may be different from the data sequence number. At this time, it is possible to correct the difference by adjusting the value of α.

An example of determining the value of α is shown below. As shown in FIG. 7, a reception time t1 of a broadcast frame including information representing a data distribution status, a time t2 at which reception waiting of a broadcast frame transmitted from a neighboring base station is started, and reception of a broadcast frame is attempted. Based on the said fixed time P which is a period, the elapsed time L from the reception time t1 of the alerting | reporting flame | frame to the waiting completion of the said fixed time P is calculated. Then, the value of α is calculated by the following equation.

  In the above equation (2), the transmission rate is the bit rate of the physical layer. For example, assuming wireless communication with a guard interval of 800 ns and a bandwidth of 20 MHz according to the IEEE 802.11n standard, one of 6.5 Mbps to 65 Mbps is used. The transmission rate can be obtained from the most recently received data frame. More specifically, the transmission rate can be specified from the MCS (Medulation and Coding Scheme) described in the physical header of the data frame.

  By using the above equation (2), the maximum number of data that can be received during the elapsed time L is grasped, and it is predicted how much the base station advances the sequence number during the elapsed time L. By this, it is possible to set an appropriate α for each surrounding base station. Therefore, the possibility of finding a wireless base station where the wireless communication apparatus can receive data of the minimum missing sequence number is increased.

  If the wireless communication device determines that reception of the data of the minimum missing sequence number distributed from the surrounding base station is possible (reception is possible) (YES in S107), that is, the sequence of data that can be received first when connected If it is determined that the number is smaller than the minimum missing sequence number, it is checked whether the second communication quality with the surrounding base station satisfies a predetermined condition (S108). Here, the larger the value of the second communication quality, the better the quality, and it is confirmed whether the second communication quality is equal to or higher than the second threshold.

  If the second communication quality is equal to or higher than the second threshold, an expected reception value is calculated (S109), and an entry including the identifier of the surrounding base station and the expected reception value is stored in the connection candidate list (S110) . The base stations around the entry registered in the connection candidate list are called connection candidate base stations.

  Here, the expected reception value is a value obtained by subtracting the sequence number of the largest data transmitted by the surrounding base station before the broadcast frame and α from the smallest missing sequence number (from the left side to the right side of equation (1) Result of subtracting The expected reception value corresponds to the length of time until the wireless communication device switches the connection to the surrounding base station and receives the data of the minimum missing sequence number. It shows that the smaller the expected reception value is, the faster the data of the minimum missing sequence number can be received when connecting. In other words, the surrounding base station with the smaller reception estimation value can start receiving data of the sequence number closest to the minimum missing sequence number when connected. Since it is determined that the wireless communication device will be in time for receiving the data of the minimum missing sequence number distributed by the surrounding base station, the reception prediction value becomes a value of 0 or more.

  The order of the process of determining whether the data of the minimum missing sequence number is received (S107) and the process of determining whether the second communication quality is equal to or more than the second threshold (S108) may be interchanged.

  Investigate all surrounding base stations registered in the surrounding base station storage list (S105), and after examining all surrounding base stations, if the connection candidate list is empty (YES in S111), transition to data reception state A2 (Return to the process of the flow in FIG. 4).

  When an entry of one or more connection candidate base stations is registered in the connection candidate list (NO in S111), the connection with the connected radio base station is disconnected (S112). Then, in the connection candidate list, a connection candidate base station with a small reception expected value is preferentially selected, and connection is attempted to the selected connection candidate base station (at step S112). Specifically, an association process is performed with a connection candidate base station, and an authentication process is performed prior to that as necessary. If the connection with the connection candidate base station fails (NO in S113), connection is attempted to the connection candidate base station of the next priority. If the connection with the connection candidate base station is successful (YES in S113), the state transitions to the data reception state A2 (return to the processing of the flow in FIG. 4). If connection with all connection candidate base stations registered in the connection candidate list fails, the original radio base station is connected again, and the state transits to the data reception state A2.

  As a case where connection with the connection candidate base station fails, for example, when the radio wave environment suddenly deteriorates, when the load of the connection candidate base station is high (for example, the number of accommodated wireless communication devices is at the upper limit). And if the authentication process fails. However, of course there are cases where connection fails in any of the examples other than those listed here.

  By the above procedure, the wireless communication apparatus can shorten the time until receiving the data of the minimum missing sequence number after switching of the connection destination, and can communicate with the wireless base station with suitable communication quality even after switching. Therefore, missing data can be acquired efficiently, and the time to complete reception of all data can be shortened.

  FIG. 8A is a flowchart of an operation example of measuring the communication quality with the wireless communication base station being connected using the number of missing data from the wireless base station being connected in step S101 of FIG. 5A. Show.

  The wireless communication apparatus calculates the number of missing data up to the data of the N-th previous sequence number from the sequence number of the data received most recently (S201). N is an integer of 1 or more, and it is necessary to change the value according to the desired communication quality. If the data loss number is less than the third threshold (NO in S202), it is determined that the communication quality is good (S206), and the process proceeds to step S202 in FIG. 5A. If the data loss number is equal to or greater than the threshold, data reception is continued for a certain period of time from the time when the data loss number is determined to be equal to or greater than the third threshold (S203). The number of missing data is calculated from the sequence number of the data received during the fixed time (at S203), and if the number of missing data is less than the fourth threshold (NO at S204), it is judged that the communication quality is good. (NO of S206), it progresses to step S202 of FIG. 5A. If the number of missing data is equal to or greater than the fourth threshold (YES in S204), the communication quality is determined to be inferior (S205), and transition to a neighboring base station search state A5 is made (proceed to step S103 in FIG. 5A).

  Instead of performing data reception for a certain period of time in step S203, a certain number of data may be received. When the fixed number of data has been received, the number of missing data is counted while the fixed number of data is received. If the number of lost data is less than the fourth threshold, the communication quality is judged to be good, and if it is equal to or more than the fourth threshold, the communication quality is judged to be poor.

  According to the above procedure, it is determined that the communication quality is poor due to a temporary factor, since the number of missing data up to the data of the Nth previous sequence number is obtained from the sequence number of the data received most recently. It can prevent. For example, when the mobile passes between the wireless base station and the wireless communication apparatus, the communication quality may temporarily deteriorate, but also in this case, when the communication quality is improved due to the passage of time by the above method. It can be judged that the communication quality is good.

  In addition, even when the number of missing data is equal to or greater than the third threshold, data reception is continued for a certain period of time in step S203, and if the number of missing data is not the fourth threshold, the communication quality is determined to be good. When a temporary burst error as a cause occurs, it can be prevented that the communication quality is judged to be inferior. This is because when burst errors occur due to fading, the communication quality may improve over time. Of course, if the state of low communication quality continues intermittently, it is determined in step S205 that the communication quality is poor.

  As a modification of the operation flow of FIG. 8A, when it is determined in step S202 that the number of missing data is equal to or more than the third threshold, it may be determined that the communication quality is inferior (S205). That is, a configuration in which steps S203 and S204 are omitted is also possible.

  FIG. 8B shows a flowchart of another operation example of measuring the communication quality with the wireless communication base station being connected in step S101 of FIG. 5A. This operation can also be applied to the case where data has not been received even after connection to a wireless base station.

  The wireless communication apparatus starts a timer and waits for a predetermined time (S211). If a predetermined number of data are received during standby (YES in S212), it is determined that the communication quality is good (S213). The predetermined number may be one or more than one. If the number of data received during standby does not reach the predetermined number (NO in S212), it is determined that the communication quality is inferior (S214).

  FIG. 9 is a block diagram showing an example of a hardware configuration of a wireless communication terminal equipped with the wireless communication apparatus according to an embodiment of the present invention. The wireless communication terminal includes a processor 351, a memory 352, a storage 353, a network interface 354, an input device 355 and an output device 356, which are connected via a bus 357.

  The processor 351 reads out the program from the storage 353, develops it in the memory 352, and executes it, whereby the functions of the quality measurement unit 103, the message processing unit 104, and the control unit 105 are realized. Some of the functions of the wireless IF 102 may be performed by the processor 351.

  The memory 352 temporarily stores instructions executed by the processor 351, various data used by the processor 351, and the like. The memory 352 may be a volatile memory such as SRAM or DRAM, or a non-volatile memory such as NAND or MRAM. The storage 353 is a storage device for permanently storing programs, data and the like, and is, for example, an HDD or an SSD. The memory 352, the storage 353, or both of them correspond to the storage unit 106 of FIG. 3 and stores data or information etc. received from the radio base station and data or information etc. to be transmitted to the radio base station. The memory 352, the storage 353 or both may be provided in the wireless communication terminal or may be externally connected to the wireless communication terminal.

  The network interface 354 is an interface for performing wireless or wired communication, and corresponds to the wireless IF 102 in FIG. The network interface 354 is, for example, a baseband integrated circuit that performs header processing, modulation and demodulation, etc. of the data link layer and physical layer such as MAC layer, an AD converter circuit, a DA converter circuit, and an RF integrated circuit that performs analog processing etc. May be provided. Analog processing includes frequency conversion between baseband and radio frequency, band control, amplification processing and the like. A processor such as a CPU may be disposed in the network interface 354. When using TCP / IP or the like, processing such as TCP / IP may be performed by the CPU on the network interface 354, or may be performed by the processor 351 connected to the bus 357. Although only one network interface is shown here, a plurality of network interfaces such as a wireless network interface and a wired network interface may be mounted. The network interface 354 may be controlled by the processor 351, and the network interface 354 may directly access the memory 352 by DMA (Direct Memory Access).

  The input device 355 is an input interface for inputting an instruction or information of a keyboard, a touch panel, a mouse or the like. The output device 356 is a display device such as a liquid crystal panel or an electronic ink panel.

  The wireless communication terminal in FIG. 9 may be any device as long as it can communicate with a wireless base station. For example, a mobile terminal, a tablet, a smartphone, a wearable device, a game device, a network storage device, a monitor, a digital audio player, a web camera It may be a video camera, a projector, a navigation system, a set top box, a gateway, a printer server, a router, a portable device, a hand-held device, etc.

  As described above, according to the present embodiment, the wireless communication apparatus can switch the connection destination to a wireless base station having a short communication quality and a short time until receiving the missing data of the minimum missing sequence number after switching. Therefore, the wireless communication device can efficiently receive the missing data, and can shorten the time to finish receiving the file (all data).

Second Embodiment
10A and 10B show flowcharts of the operation of the wireless communication apparatus according to the second embodiment. The same or corresponding steps as in the flowcharts of FIG. 5A and FIG. The block diagram of the wireless communication apparatus of the present embodiment is the same as that of the first embodiment.

  Steps S101 to S105 are the same as the flowchart of FIG. 5A. If it is determined in step S105 that all entries in the surrounding base station storage list have not been examined, the process proceeds to step S251. In step S251, the wireless communication apparatus selects an unselected entry from the surrounding base station storage list, and information indicating the second communication quality and data distribution status included in the selected entry (here, the surrounding base station broadcasts a notification frame) The reception expectation value is calculated using the maximum sequence number transmitted before (1).

  The expected reception value means that by switching the connection to the surrounding radio base station, some data of the data (missing data) desired by the wireless communication apparatus can be received after switching (in time for reception) and by the surrounding radio base station It is a value to evaluate how quickly the delivery of the file (all data) is completed.

  In the first embodiment, only surrounding wireless base stations that satisfy the equation (1), that is, only the surrounding wireless base stations that can receive all the missing data after switching the connection destination, are selected as connection candidate base stations. On the other hand, in the second embodiment, the connection candidate base station is selected by using the early completion of distribution as an indicator of selection while allowing not all of the missing data to be received in time. Increase the number of As a result, even if connection to any of the surrounding radio base stations is not in time for reception of part of the missing data, it is possible to preferentially connect to the radio base station whose delivery is completed earlier. With regard to missing data that has not been received in time, after the completion of delivery, it may wait to start delivery again to obtain missing data. By connecting to a surrounding radio base station whose delivery is completed early, it is possible to accelerate acquisition of missing data. Alternatively, missing data may be acquired by transmitting a retransmission request frame to the switched radio base station.

Hereinafter, an example of calculation of the expected reception value will be shown. Using the second communication quality, the largest sequence number most recently distributed by the surrounding radio base station (the sequence number notified in the notification frame), and the sequence number of the missing data in the radio communication apparatus, the following equation The expected reception value is calculated in (3).

  f (x) increases as the number of data that can be received after switching the connection destination (that is, in time for reception) increases, and as distribution progresses (the largest sequence number distributed most recently) increases. . Further, f (x) becomes smaller as the number of receivable data decreases, and becomes smaller as distribution is later (as the maximum sequence number distributed most recently is smaller). f (x) may be any form of equation that may be a monotonically increasing function with respect to the number of receivable data and a monotonically increasing function with respect to the delivery advance. Below, the specific example of f (x) is shown.

右辺の第１項である「欠落データ数−接続後に受信不可な欠落データ数」は、接続後に受信可能なデータ数に対応する。接続後に受信可能なデータ数が多いほど、右辺の第１項の値が大きくなり、接続後に受信可能なデータ数が少ないほど、右辺の第１項の値が小さくなる。換言すれば、接続後に受信不可な欠落データ数が少ないほど、右辺の第１項の値が大きくなり、接続後に受信不可な欠落データ数が多いほど、右辺の第１項の値が小さくなる。

The first term on the right side, “the number of missing data−the number of missing data that can not be received after connection”, corresponds to the number of data that can be received after the connection. The larger the number of data that can be received after connection, the larger the value of the first term on the right side, and the smaller the number of data that can be received after connection, the smaller the value of the first term on the right side. In other words, the value of the first term of the right side increases as the number of unreceivable missing data after connection decreases, and the value of the first term of the right side decreases as the number of unreceivable missing data after connection increases.

  Further, the value of Xp + α, which is the second term of the right side, becomes larger as the peripheral base station to which the distribution progresses, and the value of the second term of the right side becomes smaller as the peripheral base station whose distribution progresses later. The form of f (x) is not limited to Formula (4), and may be an exponential function or a linear function.

  Here, α is a preset constant of 0 or more, and may be determined by the same method as α in equation (3).

βは、受信期待値の大きさを制御する値である。βが大きくなるほど、受信可能なデータ数が増加することによる、受信期待値の増加量が大きくなる。αは、予め設定する定数であり、式（３）のαと同じ方法で決定してもよい。 Another example of f (x) is shown in equation (5).

β is a value that controls the magnitude of the expected reception value. The larger the β, the larger the increase in expected reception value due to the increase in the number of receivable data. α is a constant set in advance, and may be determined in the same manner as α in equation (3).

ａは受信期待値の大きさを制御する値である。ａが大きくなるほど、受信可能なデータ数が増加することによる受信期待値の増加量が大きくなる。αは、予め設定する定数であり、式（３）のαと同じ方法で決定してもよい。ｂは、予め設定する定数である。 A further example of f (x) is shown in equation (6).

a is a value for controlling the magnitude of the expected reception value. The larger the value a, the larger the increase in expected reception value due to the increase in the number of receivable data. α is a constant set in advance, and may be determined in the same manner as α in equation (3). b is a constant set in advance.

ｇ（ｘ）は、通信品質を評価する関数である。ｇ（ｘ）の具体例を以下に示す。

Up to this point, the reception expectation value has been calculated focusing on the number of data that can be received by the wireless communication apparatus, etc. However, the reception expectation value may be calculated using the second communication quality. In this case, the expected reception value can be calculated, for example, by the following equation (7).

g (x) is a function for evaluating communication quality. Specific examples of g (x) are shown below.

  The higher the second communication quality, the larger the value of g (x). f (x) is the same as that of the formula (3) described above. Therefore, the reception expectation value is obtained by calculating the value according to the number of receivable data and the progress of distribution by f (x) and weighting this with g (x). In the case of g (x) = 1, the equation (7) matches the aforementioned (3). In addition, the unit of the value of Formula (8) changes with kinds of 2nd communication quality. For example, when RSSI is used as the second communication quality, there are two ways, a true value and a decibel value.

  After obtaining the expected reception value in step S251 of FIG. 10A, it is determined whether the expected reception value is equal to or greater than the fifth threshold (S252). When the expected reception value is equal to or higher than the fifth threshold and the second communication quality with the neighboring base stations is equal to or higher than the second threshold (step S108), the identifier of the neighboring radio base station and the reception expectation in the connection candidate list An entry including a value etc. is added (S253). The order of the process of determining whether the expected reception value is the fifth threshold or more and the process of determining whether the second communication quality is the second threshold or more may be interchanged.

  After the investigation of all surrounding base stations registered in the surrounding base station storage list, if the connection candidate list is empty (YES in S111), the state transitions to the data reception state A2 (return to the processing of the flow in FIG. 4). When one or more connection candidate base stations are registered in the connection candidate list (NO in S111), the connection with the connected radio base station is disconnected. In the connection candidate list, a connection candidate base station with a large reception expectation value is preferentially tried to connect (S112). If the connection with the connection candidate base station is successful, the state transitions to the data reception state A2 (return to the processing of the flow in FIG. 4). If connection with all connection candidate base stations registered in the connection candidate list fails, the original radio base station is connected again, and the state transits to the data reception state A2.

  As described above, according to the present embodiment, by switching the connection to a surrounding wireless base station having a high reception expectation value, while receiving as many missing data as possible, it is possible to shorten the time until the reception of the file (all data) is finished. It becomes possible. Even when missing data that can not be received after connection switching is acquired by redistributing files, it is possible to select a surrounding base station for which file delivery is completed early, so file reception is completed early. it can.

Third Embodiment
In the first and second embodiments, when there is no neighboring wireless base station to which switching is performed, retransmission of missing data occurs frequently, and the wireless band becomes tight, in order to connect again to the original wireless base station with poor communication quality. there is a possibility. Therefore, the third embodiment is characterized by suppressing a retransmission request for missing data to the original wireless base station when reconnecting to the original wireless base station without the switching destination wireless base station being present. I assume.

  FIG. 11 is a flowchart of the operation of the wireless communication apparatus according to the third embodiment, which adds step S301 before step S101 in FIG. 4. FIGS. 12A and 12B are a flowchart following FIG. 11, and step S302 is added between steps S101 and S102 of FIG. 5A, and further step S303 is performed after YES of step S104, YES of S111 and YES of S112. It is added.

  In FIG. 11, when the wireless communication apparatus in the standby state A1 transitions to the data reception state A2, True is set in the retransmission request flag (S301). The wireless communication device detects the loss of data in step S12, and determines whether the retransmission request flag is True (step S101 in FIG. 12A) if the first communication quality at that time is equal to or higher than the first threshold (YES in S101 of FIG. 12A) (step S302). If True, a retransmission request is transmitted to the connected radio base station (S102 in FIG. 12A).

  If it is determined in step S104 that there is no neighboring base station (NO in S104), False is set in the retransmission request flag (S303). Also, in the case where it is determined that the connection candidate list is empty in step S111 (YES in S111), or in the case where it is determined that the connection with all connection candidate base stations has failed in step S112 (YES in S112) , False is set in the retransmission request flag.

  The setting example of the retransmission request flag described above is an example, and another method may be used. For example, the first communication quality with the original radio base station is measured at an arbitrary timing or a predetermined timing, and False is set if the first communication quality is less than the threshold, True is set if the first communication quality is greater than the threshold. May be Alternatively, the radio signal for measuring the first communication quality may be a signal of a frame including data or may be a broadcast signal. Alternatively, when the number of transmissions of the retransmission request to the same wireless base station becomes equal to or more than the threshold, False may be set in the retransmission request flag. If the number of missing data from the same wireless base station becomes equal to or greater than a threshold, False may be set in the retransmission request flag. The number of missing data may be the number of data of the missing data for which a retransmission request has been made. The plurality of methods described herein may be combined. Alternatively, one or more of the methods described herein may be combined with step S302 or S303 of FIG. 12A.

  Steps S302 and S303 in FIGS. 12A and 12B can be added to the same parts in the flowchart of FIGS. 10A and 10B in the second embodiment. A flowchart in this case is shown in FIGS. 13A and 13B. The operations in steps S302 and S303 are the same as those in FIGS. 12A and 12B, and thus the description thereof is omitted.

  As described above, according to the present embodiment, it is possible to alleviate the congestion of the wireless band by suppressing the transmission of the retransmission request according to the first communication quality with the wireless communication device. Thus, it is possible to shorten the time until another wireless communication device finishes receiving all data.

Fourth Embodiment
In the first to third embodiments, the first communication quality measured with the connected radio base station is measured each time a data loss (a loss of sequence number) is detected, and the first communication quality measured. In response to the request (S12 in FIG. 4, S101 in FIG. 5A, S102, etc.). As another example, as shown in FIG. 14, a plurality of data transmitted from the radio base station is divided into a plurality of sections (blocks) at a predetermined number from the top, and a period (block period) corresponding to each block At the end, check if missing data occurred in the block. If there is missing data, the first communication quality is measured, and a retransmission request is made for the missing data according to the measured first communication quality.

  As an operation example in this case, as shown in FIG. 15, step S13 may be added between steps S11 and S12 of the flowchart of FIG. The flowchart following FIG. 15 is the same as the flowchart (FIG. 5A and FIG. 5B, FIG. 10A and FIG. 10B, FIG. 12A and FIG. 12B, or FIG. 13A and FIG. 13B etc.) described in each of the embodiments described above. .

  In step S13 of FIG. 15, the wireless communication apparatus determines whether the current blocking period has been completed. For example, when the range of the sequence number is previously determined for each block, the current block period is detected by detecting the sequence number at the end of the current block or the data sequence number included in the blocks after the next block. You can judge the completion of the If the current block period is completed, it is detected whether there is a missing sequence number in the block (S12). If there is a drop, the state changes to the reception quality check state A4, and the operations of the first to third embodiments (FIGS. 5A and 5B, FIGS. 10A and 10B, FIGS. 12A and 12B, or FIGS. 13A and 13 13 B etc.). If there is no missing sequence number in the block, the process returns to step S11. By thus making a retransmission request in block units, it is possible to ensure the integrity of data in block units.

  The terms used in this embodiment should be interpreted broadly. For example, the term "processor" may encompass a general purpose processor, a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a controller, a microcontroller, a state machine, and the like. Depending on the context, "processor" may refer to an application specific integrated circuit, field programmable gate array (FPGA), programmable logic circuit (PLD), etc. "Processor" may refer to a combination of processing devices such as multiple microprocessors, a combination of DSP and microprocessor, one or more microprocessors that cooperate with a DSP core.

  As another example, the term "memory" may encompass any electronic component capable of storing electronic information. “Memory” means random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable PROM (EEPROM), non-volatile It may refer to random access memory (NVRAM), flash memory, magnetic or optical data storage, which can be read by a processor. If the processor reads and / or writes information to the memory, the memory can be said to be in electrical communication with the processor. The memory may be integrated into the processor, and again, the memory may be said to be in electrical communication with the processor.

  Also, the term "storage" may encompass any device capable of storing data permanently, using magnetic technology, optical technology, or non-volatile memory. For example, the storage may be an HDD, an optical disk, an SSD or the like.

  The present invention is not limited to the above embodiment as it is, and at the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention. In addition, various inventions can be formed by appropriate combinations of a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components in different embodiments may be combined as appropriate.

1: Wireless base station (communication device)
2: Radio base station (communication device)
3: wireless communication device 101: antenna 102: wireless interface 103: quality measurement unit 104: message processing unit 105: control unit 106: storage unit 351: processor 352: memory 353: storage 354: network interface 355: input device 356: output Device 357: Bus

Claims (16)

A communication unit connected to a first communication device for sequentially distributing a plurality of data including a sequence number, and for receiving the data from the first communication device ;
A quality measurement unit that measures communication quality with the first communication device;
Information for specifying a sequence number of data that has been distributed from the second communication device to the Nth communication device from the second communication device to the Nth (N is an integer of 2 or more) communication devices that sequentially distribute the plurality of data A message processing unit for acquiring first information including
A control unit that switches the connection destination of the communication unit according to the communication quality ;
The control unit is a communication to which the connection of the communication unit is to be switched among the second to Nth communication devices based on the first information and a sequence number of data received from the first communication device. Select a device Wireless communication device. The control unit detects a loss of the data,
Identifying the communication device is before the first sequence number of the data sequence number and the lack of data that can be received from the second communication device to N-th communication apparatus after switching the connection destination of the communication unit, from the specified communication apparatus, a wireless communication apparatus according to claim 1 for selecting a communication apparatus as a transfer destination connection of the communication unit. The wireless communication apparatus according to claim 2, wherein the control unit selects the communication device in which the first receivable sequence number of the data is closest to the missing data sequence number . The control unit detects a loss of the data,
Wherein, among the data the missing claim 1 based on the number of available receive data after switching a connection destination of the communication unit selects a communication device serving as the transfer destination connection of the communication unit The wireless communication device according to. The wireless communication apparatus according to claim 4, selected the higher the communication device number of receivable data is often preferentially the communication unit of the connection destination after E replacement Ri off. The wireless communication according to claim 4 or 5, wherein the control unit selects the communication device of the switching destination based on a sequence number of data which can be received first from each of the second to Nth communication devices. apparatus. Wherein, the wireless communication apparatus according to claim 6, wherein the first receivable of the data of the sequence number is less communication device as preferentially selected. The quality measuring unit measures communication quality with the second to Nth communication devices,
Wherein the control unit is configured based on the communication quality between the second to N communication device, in any one of claims 1 to 7 to select a communication device serving as the transfer destination connection of the communication unit A wireless communication device as described. The control unit selects a communication device in which the communication quality between the second to Nth communication devices satisfies a predetermined condition, and the communication unit determines that there is no communication device satisfying the predetermined condition. 9. The wireless communication device according to claim 8 , controlling to receive the data from the first communication device and not making a retransmission request even if the data is lost. The control unit selects one or more candidates of the communication device of the switching destination, and controls to reconnect to the first communication device when connection to all the candidates of the selected communication device fails. The wireless communication device according to any one of claims 1 to 9 , wherein the wireless communication device receives the data from the first communication device and does not request retransmission even if the data is lost. The quality measurement unit determines, as the communication quality with the first communication device, received signal strength, received power, signal-to-noise power ratio, and predetermined time of a wireless signal received from the first communication device. The wireless communication apparatus according to any one of claims 1 to 10 , wherein at least one of the number of missing data is measured. The quality measurement unit may use, as communication quality between the second to Nth communication devices, received signal strength, received power, signal-to-noise power ratio of wireless signals received from the second to Nth communication devices. the wireless communication apparatus according to claim 8 or 9 for measuring at least one of. A storage unit for storing the plurality of data received by the communication unit;
Wherein the control unit detects whether there is a communication device for distributing the plurality of data around, if not the communication apparatus is present in the surrounding of claims 1 to 12 for distributing the plurality of data The wireless communication device according to any one of the preceding claims. The wireless communication apparatus according to any one of claims 1 to 13 , wherein distribution of the plurality of data is performed by multicast or broadcast. A wireless communication method performed by a wireless communication device, the method comprising:
A communication step of connecting to the first communication apparatus for sequentially delivering a plurality of data including a sequence number, receiving the data from the first communication device,
A quality measurement step of measuring communication quality with the first communication device;
Information for specifying a sequence number of data that has been distributed from the second communication device to the Nth communication device from the second communication device to the Nth (N is an integer of 2 or more) communication devices that sequentially distribute the plurality of data An acquisition step of acquiring first information including
A control step of switching the connection destination of the wireless communication device according to the communication quality
The control step is a switching destination of the connection of the wireless communication device among the second to Nth communication devices based on the first information and a sequence number of data already received from the first communication device. A wireless communication method for selecting a communication device. A program for causing a computer in a wireless communication device to execute the program,
A step of connecting to the first communication apparatus for sequentially delivering a plurality of data including a sequence number, receiving the data from the first communication device,
Measuring the quality of communication with the first communication device;
Information for specifying a sequence number of data that has been distributed from the second communication device to the Nth communication device from the second communication device to the Nth (N is an integer of 2 or more) communication devices that sequentially distribute the plurality of data Obtaining first information including
Controlling the computer to execute the control step of switching the connection destination of the wireless communication device according to the communication quality ;
The control step is a switching destination of the connection of the wireless communication device among the second to Nth communication devices based on the first information and a sequence number of data already received from the first communication device. Program to select the communication device.

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