JP5086176B2 - Mobile communication terminal and wireless communication method - Google Patents

Description

  The present invention relates to a portable communication terminal and a wireless communication method capable of performing wireless communication through a plurality of networks.

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

  As one of such networks for transmitting information between nodes such as mobile communication terminals (also referred to as network media and wireless communication methods), CDMA (Code Division Multiple Access) and WiMAX (Worldwide Interoperability for Microwave) Access).

  CDMA is a scheme in which a plurality of signals are multiplied by different codes, and all signals are combined and transmitted using a single frequency. On the other hand, WiMAX is one of communication systems using an OFDMA (Orthogonal Frequency Division Multiplex Access) system (for example, Non-Patent Document 1), and the OFDM system is one of data multiplexing systems. The frequency band is effectively used by superimposing a part of the carrier band so that the phase of the signal wave to be modulated is orthogonal between adjacent carriers, using multiple carrier waves on the unit time axis It is a method.

  Not only the case where such a network is used alone but also a further increase in speed can be achieved by using a plurality of networks in parallel. With such a configuration, a plurality of packets generated from one data can be distributed and transmitted to each network, and the transfer rate or bandwidth is the sum of the cases of each network alone.

Patent Document 1 discloses a technique for selecting one network by excluding a network that is not suitable for using an application in an environment where a plurality of networks can be used (for example, Patent Document 1). .
JP 2006-60579 A "Mobile WiMAX? Part I: A Technical Overview and Performance Evaluation" Prepared on Behalf of the WiMAX Forum, February 21, 2006, http://www.intel.com/netcomms/technologies/wimax/WiMAX_Overview_v2.pdf

  In a normally used communication protocol, the link layer of a mobile communication terminal receives a packet from the network, and if a packet that should be received is missing, the link layer makes a retransmission request for the missing packet. Thus, complete data is reproduced by complementing the retransmitted packet. Further, as described above, even when packets are received in parallel through a plurality of networks, a packet loss determination is made by a common link layer, and a retransmission request is made.

  However, when a plurality of networks are used as one data link, packets to be transmitted are sequentially distributed to the plurality of networks and are transmitted independently, so that the packet reception timing is asynchronous. Therefore, it is determined that the packet is missing before the packet arrives, and a problem arises in that a retransmission of the packet is requested. This is due to differences in data transfer methods, communication bandwidths, changes in communication quality, etc. in multiple networks.

  For example, packets to be transmitted on the transmission side are distributed to each network in the order of serial numbers assigned according to the reproduction time. As described above, when the packets arranged in time series at the time of distribution are also different in network, a difference occurs in reception time due to a difference in transmission unit (frame) or the like. Therefore, depending on the network, there may occur a phenomenon in which a packet is distributed and transmitted first, but is received later.

  In the above case, since the link layer determines that the packet is missing and the original packet arrives after making a retransmission request, the retransmission request and the corresponding retransmission packet are wasted. In this way, if the packet loss from a plurality of networks is determined independently of each other, unnecessary retransmission requests and reception of unnecessary retransmission-compatible packets are executed.

  Such a problem can be solved by extending the waiting time until it is determined that the packet is missing. However, since the held packet cannot be used until the missing judgment is completed, simply extending the waiting time is not possible. This will result in the loss of real-time performance.

  In view of such a problem, the present invention deletes useless retransmission requests while maintaining real-time performance, even when a plurality of networks are used as one data link, by using an appropriate waiting time for packet loss determination. An object of the present invention is to provide a portable communication terminal and a wireless communication method capable of performing efficient wireless communication.

  In order to solve the above problems, a typical configuration of the present invention is a mobile communication terminal that can be connected to a plurality of networks, a holding unit that holds packets received from a plurality of networks, and a plurality of networks. A loss determination unit that determines whether or not a packet held in the holding unit is missing after a predetermined waiting time determined according to the frame time, and a retransmission that requests retransmission of the lost packet when the loss determination unit determines that there is a loss And a request unit.

  A packet received with a delay due to a time lag in data transfer between a plurality of networks should not be regarded as a missing packet. Therefore, in the present invention, considering the frame time in the network, that is, the time from when a packet is allocated until the packet is actually transmitted, the retransmission request is suppressed until reception of a predetermined amount of packets is completed. Thus, it is possible to delete a useless retransmission request while maintaining real-time performance and perform efficient wireless communication.

  The predetermined waiting time may be an interval at which the frame completion timings of the plurality of networks substantially coincide.

  By confirming packet loss at intervals at which frame completion timings substantially match, the time difference between the end of frames between networks can be filled to some extent, and wasteful retransmission requests can be reduced.

  When it is determined that there is a loss, the missing determination unit may determine again the presence or absence of a missing packet by adding further added packets after a predetermined time.

  As described above, when the predetermined waiting time is determined in units of intervals at which the frame completion timings substantially coincide with each other, it may occur that an erroneous packet loss determination is made. Here, only when it is determined that there is a loss, the missing determination unit further receives a frame from one of the networks, and again determines whether there is a packet that is considered to be missing in that frame, and then finally loses the frame. Results are shown. With this configuration, it is possible to prevent missing determinations and to quickly correct missing determinations without a retransmission request even if there is an erroneous determination.

  The predetermined waiting time may be a time corresponding to the least common multiple of the frame times of each of the plurality of networks.

  When the time corresponding to the least common multiple of the frame time has elapsed, the frame endings of each network are aligned, so the time lag of the packet to be received is absorbed, and it is possible to reliably delete useless retransmission requests while maintaining real-time performance. It becomes possible.

  Another exemplary configuration of the present invention is a wireless communication method for receiving packets in parallel from a plurality of networks, holding packets received from a plurality of networks, and according to the frame time of each of the plurality of networks. It is characterized by determining whether or not there is a missing packet held after a predetermined predetermined waiting time, and when it is determined that there is a missing packet, a retransmission of the missing packet is requested.

  The above-described components based on the technical idea of the mobile communication terminal and the description thereof can also be applied to the wireless communication method.

  As described above, according to the present invention, even when a plurality of networks are used as a single data link, unnecessary retransmission requests are deleted while maintaining real-time performance with an appropriate waiting time for packet loss determination. Thus, efficient wireless communication can be performed.

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

  When a plurality of networks are used as one data link, packets distributed to each of the plurality of networks are received at different timings according to the frame time of each network. Under such circumstances, conventionally, a phenomenon has occurred in which a serial number of a packet from one network is referred to and an unreachable packet is determined to be missing in the other network. The object of the present embodiment is to delete unnecessary retransmission requests due to such a determination of missing errors and to perform efficient wireless communication. Hereinafter, in order to facilitate understanding of the present embodiment, the entire wireless communication system will be described first, and then the specific configuration of the mobile communication terminal will be described.

(Wireless communication system 100)
FIG. 1 is an explanatory diagram showing a schematic connection relationship of the wireless communication system 100. The wireless communication system 100 includes a mobile communication terminal 110, a base station 120 (120A, 120B), a router 130, a communication network 140 including an ISDN (Integrated Services Digital Network) line, the Internet, a dedicated line, and the like. And an application server 150.

  The mobile communication terminal 110 is a mobile phone, a PHS terminal, a notebook personal computer, a PDA (Personal Digital Assistant), a digital camera, a music player, a car navigation system, a portable TV, a game device, a DVD player, a remote controller, etc. The user can receive various services from a service provider having the application server 150 or the like using the portable communication terminal 110. Detailed configuration will be described later.

  The base station 120 establishes wireless communication with the mobile communication terminal 110 through the network, and controls calls with other mobile communication terminals of the mobile communication terminal 110, data communication through the communication network 140, and the like. Here, in particular, base station 120A establishes wireless communication by CDMA, and base station 120B establishes wireless communication by WiMAX. In the present embodiment, CDMA and WiMAX are cited as networks in this way, but the present invention is not limited to such cases, and various networks such as WLAN (Wireless Local Area Network), PHS MoU (Memorandum of Understanding), LTE (Long Term Evolution), etc. It is also possible to use a network.

  The router 130 collects the data input from the mobile communication terminal 110 through the two networks and transmits the data to the application server 150 (as one data link), and also transmits the data from the application server 150 to the two networks. Sort at an appropriate transfer rate. Further, when the transfer rate or frame time changes due to the change of the modulation method, the packet distribution is adaptively changed accordingly.

  FIG. 2 is an explanatory diagram for explaining the operation of the router 130. Here, a box 160 with a number indicates a packet, and the number indicates a sequence number of the packet. Hereinafter, each packet is referred to as, for example, the first packet using the numbers.

  Data transmitted from the application server 150 is packetized in the router 130 and distributed to each network as shown in FIG. Although such a distribution procedure depends on the implementation of the router 130, in the present embodiment, in order to facilitate understanding, an odd packet is distributed to the base station 120A, that is, the CDMA network, and an even packet is distributed to the base station 120B, that is, the WiMAX network. .

  Assuming that four packets can be included in each frame in CDMA, a frame 170 that can be transmitted is generated at the time of FIG. 2A in which eight packets are distributed, and the mobile communication terminal 110 as shown in FIG. Sent to. Also, in WiMAX, if six packets can be included in each frame, a frame 172 that can be transmitted at the time of FIG. 2B is generated and transmitted to the mobile communication terminal 110 later as shown in FIG. The

  As can be understood with reference to FIG. 2, even if the packets are evenly distributed to each network, if the frame time for each network is different, for example, the seventh packet as shown in FIG. After reaching the mobile communication terminal 110, the arrival order such as the arrival of the second packet as shown in FIG. Such a problem is solved by the mobile communication terminal 110 described later.

  The application server 150 is connected to the mobile communication terminal 110 through the communication network 140 and provides various services such as data transfer in response to a request from the mobile communication terminal 110.

(Mobile communication terminal 110)
3 is a functional block diagram showing a hardware configuration of the mobile communication terminal 110, and FIG. 4 is a perspective view illustrating a mobile phone as the mobile communication terminal 110. As shown in FIG. The mobile communication terminal 110 includes a terminal control unit 210, a terminal memory 212, a display unit 214, an operation unit 216, a voice input unit 218, a voice output unit 220, and a terminal wireless communication unit 222. The

  The terminal control unit 210 manages and controls the entire mobile communication terminal 110 using a semiconductor integrated circuit including a central processing unit (CPU), and uses a program stored in the terminal memory 212 to make a call function, mail transmission / reception function, imaging function, and music playback. It also performs functions and TV viewing functions. The terminal memory 212 includes a ROM, a RAM, an EEPROM, a nonvolatile RAM, a flash memory, an HDD, and the like, and stores a program processed by the terminal control unit 210, communication data, and the like.

  The display unit 214 is composed of a liquid crystal display, EL (Electro Luminescence), etc., and is stored in the terminal memory 212 or provided from the application server 150 via the communication network 140 or provided from another Web server. Web content, application GUI (Graphical User Interface), and the like can be displayed.

  The operation unit 216 includes a movable switch such as a keyboard, a cross key, and a joystick, and accepts a user operation input.

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

  The terminal wireless communication unit 222 establishes wireless communication with the base station 120 through a network such as CDMA or WiMAX in a common link layer, and performs voice communication with a communication partner or data communication with the application server 150. In addition, two networks as communication targets can be fixedly allocated as CDMA as voice communication and WiMAX as data communication, for example.

  The terminal wireless communication unit 222 described above functions as the network control unit 250 (250A, 250B), the network resource management unit 252, the holding unit 254, the lack determination unit 256, the protocol stack unit 258, and the retransmission request unit 260.

  The network control unit 250 performs communication with each network. Here, the network control unit 250A establishes communication by CDMA, and the network control unit 250B establishes communication by WiMAX. Then, the packet is extracted from each received frame and transferred to the holding unit 254.

  The network resource management unit 252 performs resource allocation of the network control unit 250 according to the communication quality requested by the host application. For example, when there is a request for data communication at a transfer rate of 6 Mbps from an upper application, 6 Mbps is realized by assigning transfer rates of 2.4 Mbps and 3.6 Mbps to CDMA and WiMAX, respectively. The frame time of each network determined by such transfer rate assignment is transmitted to the loss determination unit 256.

  The holding unit 254 functions as a buffer that temporarily holds packets received from a plurality of networks.

  The missing determination unit 256 calculates a predetermined waiting time according to the frame time derived from the transfer speed (bandwidth) and frame length of each of the plurality of networks, and the target held by the holding unit 254 after the calculated predetermined waiting time. Determine if there are any missing packets.

  FIG. 5 is an explanatory diagram showing an example of the operation of the missing determination unit 256. Here, the representation of the packet follows FIG. For example, it is assumed that the CDMA frame time is 4 msec and the WiMAX frame time is 6 msec. Then, as shown in FIG. 2, it is assumed that a frame including an odd-numbered packet via CDMA is received from the base station 120A and a frame including an even-numbered packet via WiMAX is received from the base station 120B. Here, the frame time indicates a unit time in which the physical layer in each network (CDMA, WiMAX) processes data.

  For example, at the time shown in FIG. 5A, the frame 310 via CDMA and the frame 312 via WiMAX have already been received and held in the holding unit 254. Here, the 10th and 12th packets exist, but since the frame 314 has not yet arrived, the 9th and 11th packets are determined to be missing packets.

  In this embodiment, the apparatus waits for a predetermined waiting time determined according to the frame time of different networks, for example, a time corresponding to the least common multiple of each frame time. Therefore, in the example of FIG. 5, the predetermined waiting time is 12 msec. When a packet group for each time corresponding to the least common multiple is set as one processing unit and a missing packet is determined for a packet received during that time, as shown in FIG. 314, 316, and 318 are received and the end of the frames 316 and 318 of each network are aligned, so that the packet time lag is absorbed.

  In this way, by considering the frame time in the network, that is, the interval from when a packet is distributed until the packet is actually transmitted, by suppressing the retransmission request until reception of a predetermined amount of packets is completed, It is possible to delete unnecessary retransmission requests while maintaining real-time performance and perform efficient wireless communication.

  The predetermined waiting time may be an interval at which the frame completion timings of the plurality of networks substantially coincide.

  FIG. 6 is an explanatory diagram showing another example of the operation of the lack determination unit 256. Here too, the packet representation follows FIG. In FIG. 6, for example, it is assumed that the CDMA frame time is 3 msec and the WiMAX frame time is 16 msec. In FIG. 6, as in FIG. 5, it is assumed that a frame including an odd number packet from the base station 120 </ b> A through CDMA and a frame including an even number packet from the base station 120 </ b> B through WiMAX are received.

  Even under the above conditions, if the time corresponding to the least common multiple is calculated as in FIG. 5, 3 × 16 = 48 msec is consumed. The protocol stack unit 258, which will be described later, cannot use the packet of the holding unit 254 until the deletion determination by the deletion determination unit 256 is completed. Therefore, if a time corresponding to the least common multiple is simply used, the real-time property is lost. There is a case. However, in terms of the relationship between 3 msec and 16 msec, even if the lack is determined at 16 msec with a long frame time, as shown in FIG. 6, the difference d between the frames is 1 msec, which is at most 2 msec.

  In this way, even if the frame completion timing is not perfectly matched, by confirming packet loss at substantially matching intervals, the time difference between the end of frames between networks can be filled to some extent, which is useless. It is possible to remarkably reduce retransmission requests.

  In addition, even if it is determined that there is a loss once, the loss determination unit 256 may determine again the presence or absence of the loss by adding a further added packet after a predetermined time.

  FIG. 7 is an explanatory diagram showing another example of the operation of the lack determination unit 256. Such an operation can be described as a continuation of FIG. For example, in the situation of FIG. 6, the loss determination unit 256 determines whether or not a packet is lost after a predetermined waiting time of 16 msec, and determines that the 31st packet is lost. At this time, the missing determination unit 256 does not immediately issue a retransmission request, and further waits for one frame 320 on the network side (CDMA side) where the end of the frame does not overlap the predetermined waiting time. When the number of packets are secured in the holding unit 254, the 31st packet of the one frame 320 is added to the packet group that is a processing unit, and the added packet group 322 is determined to be missing.

  In this way, only when it is determined that there is a loss, the loss determination unit 256 further receives a frame from one of the networks, determines again whether or not there is a packet regarded as a loss in that frame, and then finally Show missing results. With this configuration, it is possible to prevent missing misjudgments, and even if there is a misjudgment, without a retransmission request, and without waiting for a time corresponding to the least common multiple, maintain a high real-time property and quickly make a missing decision It becomes possible to correct.

  When the loss determination unit 256 does not detect a packet loss, the protocol stack unit 258 acquires a packet group from the holding unit 254 as a single processing unit and stacks it so that it can be used by a higher-level application. At this time, packet rearrangement may be performed.

  The retransmission request unit 260 selects a stable network having a higher communication quality from the two networks when the loss determination unit 256 detects the loss, and determines that the packet is determined to be lost via the network. Send a resend request.

  As described above, according to the mobile communication terminal 110 described above, even when a plurality of networks are used as a single data link, a useless retransmission request is deleted while maintaining real-time performance by an appropriate waiting time for packet loss determination. Thus, efficient wireless communication can be performed.

(Wireless communication method)
Next, a wireless communication method for receiving packets in parallel from a plurality of networks will be described.

  FIG. 8 is a sequence diagram showing the overall flow of the wireless communication method. Here, packets are acquired from the base stations 120A and 120B through a plurality of networks. Specifically, first, the mobile communication terminal 110 receives and holds the first, third, fifth, and seventh packets from the base station 120A (S400), and the second, fourth, sixth, eighth, and tenth from the base station 120B. The 12th packet is received and held (S402). Similarly, the 9, 11, 13, and 15th packets from the base station 120A are received and held (S404), and the 17, 19, 21, and 23 packets from the base station 120A are received at different times. (S406), and receive and hold the No. 14, 16, 18, 20, 22, and 24 packets from the base station 120B (S408).

  At this time, when a predetermined waiting time for executing the omission determination elapses, the omission determination unit 256 determines the presence or absence of the omission of the packet held in the holding unit 254 (S410). If it is determined that there is a missing packet (number packet), the retransmission request unit 260 selects a network with higher communication quality, here WiMAX, and requests the base station 120B to retransmit the missing packet number 21 (S412). .

  In response to the retransmission request, the base station 120B retransmits the 21st packet (S414), and when the packet is complemented, the target packet group is transmitted to the protocol stack unit 258 (S416).

  Also in such a wireless communication method, it is possible to perform efficient wireless communication by deleting a useless retransmission request while maintaining real-time performance with an appropriate standby time for packet loss determination.

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

  For example, in the above-described embodiment, a plurality of different networks have been described. However, if there are a plurality of communication paths, the same network is connected to different base stations, or the network and the base station are different from each other. The present embodiment can be applied even when the time slots are different as in OFDM.

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

  The present invention can be used for a portable communication terminal and a wireless communication method capable of wireless communication through a plurality of networks.

It is explanatory drawing which showed the rough connection relation of the radio | wireless communications system. It is explanatory drawing for demonstrating operation | movement of a router. It is the functional block diagram which showed the hardware constitutions of the mobile communication terminal. It is the perspective view which illustrated the mobile phone as a portable communication terminal. It is explanatory drawing which showed the operation example of the missing determination part. It is explanatory drawing which showed the other operation example of the missing determination part. It is explanatory drawing which showed the other operation example of the missing determination part. It is the sequence diagram which showed the whole flow of the radio | wireless communication method.

Explanation of symbols

110 ... mobile communication terminal 254 ... holding unit 256 ... missing determination unit 260 ... retransmission request unit

Claims (5)

A mobile communication terminal that can be connected to multiple networks,
A holding unit for holding packets received from the plurality of networks;
A missing determination unit that determines whether there is a missing packet held in the holding unit after a predetermined waiting time determined according to the frame time of each of the plurality of networks;
If the missing determination unit determines that there is a loss, a retransmission request unit that requests retransmission of the lost packet;
A mobile communication terminal comprising:   The mobile communication terminal according to claim 1, wherein the predetermined waiting time is an interval at which frame completion timings of the plurality of networks substantially coincide with each other.   3. The mobile communication terminal according to claim 2, wherein, when it is determined that there is a loss, the loss determination unit determines again whether or not there is a loss by adding a further added packet after a predetermined time.   The mobile communication terminal according to claim 2, wherein the predetermined waiting time is a time corresponding to a least common multiple of a frame time of each of the plurality of networks. A wireless communication method for receiving packets in parallel from a plurality of networks,
Holding packets received from the plurality of networks;
Determining whether or not the held packet is lost after a predetermined waiting time determined according to the frame time of each of the plurality of networks;
A wireless communication method characterized by requesting retransmission of a lost packet when it is determined that a packet is missing.

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