JP2008177875A - Communication system and communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably repeat data transmission using a power line transmission path between bridge devices. <P>SOLUTION: The bride device is so composed as to perform communication between access points by a composite bridge function using both a radio transmission path and the power line transmission path. Namely, since divided transmission data are alternately distributed and transmitted to a first radio transmission path and the power line transmission path in a first composite bridge device, a communication speed becomes higher compared to the case that only either of transmission paths is used. Therefore, the device is suitable, for example, for the down-loading of large capacity data from a server to a radio communication terminal, or applications requiring isochronous nature such as moving image streaming, etc. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication system and a communication device that perform relay to a data transmission destination using a plurality of bridge devices, and more particularly, to a communication system and a communication device that relay data transmission between bridge devices using a power line transmission line.

  In recent years, information providing services constructed on a wide area network represented by the Internet have been actively used, and there are many opportunities to download large-capacity data files and video stream distribution. As a general form of enjoying this type of service in the home, a bridge device such as a router is connected to the Internet through broadband wired communication such as ADSL (Asynchronous Digital Subscriber Line), etc., and laid in the home It is conceivable to transfer data from a bridge device to an information terminal such as a personal computer (PC) via a LAN.

  Recently, the wireless LAN has been rapidly promoted. In this case, the bridge device that mediates with the external network functions as a wireless LAN access point in the home. FIG. 13 schematically shows an example of the system configuration. In the illustrated example, the bridge device 103 includes a network interface function for connecting to the server 101 via the wired transmission path 102, a wireless LAN access point function for the wireless terminals 105 and 106 such as a PC, a wired transmission path 102, and the like. A protocol conversion function between the wireless transmission paths 104 is provided.

  Currently, the systems mainly used in home wireless LANs are IEEE802.11a using a 5.2 GHz band as a carrier frequency and IEEE802.11b / g using a 2.4 GHz band. For example, in IEEE802.11a / g, an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, which is one of multicarrier schemes, is adopted as a standard for wireless LANs. In the OFDM modulation scheme, transmission data is distributed and transmitted to a plurality of carriers in which frequencies orthogonal to each other are set. Being orthogonal to each other means that the peak point of the spectrum of an arbitrary subcarrier always coincides with the zero point of the spectrum of another subcarrier. Therefore, since transmission data is distributed and transmitted to a plurality of carriers having different frequencies, the bandwidth of each carrier is narrow, the frequency utilization efficiency is very high, and it is strong against frequency selective fading interference.

  Wireless LANs have low transmission output due to regulations related to radio waves and avoidance of interference with other systems, and communication between rooms is limited due to limited communication distances and poor ability to cross walls. There is a problem that can not be. For this reason, as shown in FIG. 14, the bridge device 203 connected to the server 201 via the wired transmission path 202 is further relayed to the terminal wireless communication terminals 207 and 208 by another wireless bridge device 205. Possible forms. That is, the wireless bridge devices 203 and 205 perform inter-access point communication (WDS: Wireless Distribution System).

  According to the communication between access points, the wireless communication terminals 207 and 208 expand the service area using the roaming function, but at that time, it is not necessary to install a LAN cable for connecting the access points. For example, when there are a plurality of access points with a wired network in the same wireless network, the access points perform communication between the access points so that the wireless terminal communicates with only one of the access points. Proposals have been made for wireless communication systems that access respective wired networks via access points (see, for example, Patent Document 1).

  In the communication system shown in FIG. 14, the two wireless transmission paths 204 and 206 relayed by the wireless bridge device 205 may be the same wireless LAN standard or different wireless LAN standards. When the wireless transmission paths 204 and 206 are operated in different frequency bands, the wireless transmission paths 204 and 206 are independent transmission paths, so that they do not interfere with each other even if transmission operations are performed simultaneously. There is little decrease in throughput due to the relay of the wireless bridge device 205. On the other hand, the wireless bridge device 205 simultaneously performs transmission and reception in the frequency bands used by the wireless transmission paths 204 and 206, so two types of transceivers are required. Further, since transmission and reception are performed simultaneously on two frequency channels, a high-accuracy filter is required to avoid interference between adjacent channels, and the equipment becomes more expensive.

  On the other hand, when operating in the same frequency band as the wireless transmission paths 204 and 206, the wireless bridge device 205 only needs to be equipped with one transmitter / receiver. However, when the wireless transmission paths 204 and 206 use the same frequency channel, it is necessary to avoid mutual interference, and the wireless transmission path 206 cannot be used when the wireless transmission path 204 is in use. For this reason, the throughput of the entire system is simply less than half. In addition, a normal wireless LAN includes a random back-off mechanism that randomly shifts the transmission time, and data is transmitted simultaneously from multiple terminals to prevent a collision, but the exact same The possibility of starting transmission in time cannot be excluded. Therefore, the throughput further decreases due to a collision between data transmission from the wireless bridge device 203 to the wireless bridge device 205 and data transmission from the wireless bridge device 205 to the wireless communication terminal 207 or 208.

  By the way, IEEE802.11a and IEEE802.11g (described above), which are typical wireless LAN standards, have a data transmission rate of up to 54 Mbps in the physical layer, a maximum of less than 30 Mbps in the MAC (Media Access Control) layer, and TCP (Transport Control Protocol). The effective speed of transmission is about 20 Mbps at the maximum. However, with the increase in the amount of data information handled in the world, it is thought that a communication method for realizing a higher transmission speed is necessary. In addition, the radio communication technology generally has a problem that it is easily affected by interference with other systems using the same frequency channel.

  On the other hand, a device having a communication function that receives power supply through a power line superimposes a communication signal on the power line and communicates with another device having a similar function through the power line (PLC: Power Line Communication) is known. According to power line communication, communication can be performed between devices as long as the rooms are provided with AC outlets, and the location of the counterpart device is not limited. A communication system using power line communication can realize high-speed communication of 100 Mbps or more without using a new communication line by using an existing power line.

  FIG. 15 shows a configuration example of a communication system in which a part of a wired transmission path between the server 301 and a communication terminal 307 such as a PC is replaced with a power line transmission path 304 by a set of PLC bridge devices 303. In the illustrated example, the PLC bridge device 303 includes a network interface function that connects to the server 301 via a wired transmission path 302, and a PLC interface function. The PLC bridge device 303 is connected to the other PCL bridge device 305 via a power line 304. The PLC bridge device 305 relays to a terminal information terminal 307 such as a PC via a wired transmission path 306.

  In the example illustrated in FIG. 15, the wired transmission path 302 or 306 is a wired LAN represented by, for example, Ethernet (registered trademark). For example, a proposal has been made for a method of connecting a packet received at the edge of a PLC network by a PLC MAC bridge so that the packet can efficiently pass between a PLC LAN and a network technology device different from the PLC LAN. (For example, see Patent Document 2).

  Further, as shown in FIG. 16, it is possible to replace the communication between access points in the communication system shown in FIG. 14 with a power line transmission path from the wireless LAN. For example, a communication system in which communication between access points is configured with a power line transmission path has been proposed (see, for example, Patent Document 3). According to such a communication system, when constructing a new local area network for connecting access points, wiring work can be eliminated, the installation location of the communication device is not limited, and the aesthetics deteriorate due to the installation. Can be prevented.

  However, a communication system using power line communication differs in behavior depending on the structure of the house where the communication is performed, and is also affected by noise caused by life rhythm (such as noise caused by plugging / unplugging or using a dryer). There is a problem that it is easy.

JP 2004-222136 A JP 2005-39814 A JP 2002-374189 A

  An object of the present invention is to provide an excellent communication system and communication apparatus capable of suitably performing relaying to a data transmission destination using a plurality of bridge devices.

  It is a further object of the present invention to provide an excellent communication system and communication device that can suitably relay data transmission between bridge devices using a power line transmission line.

The present invention has been made in view of the above problems, and is a communication system for performing data transmission from a data transmission source server to a data reception destination wireless communication terminal,
A first composite bridge device connected to the server via a wired transmission path, transferring transmission data on the wired transmission path to a composite medium composed of a first wireless transmission path and a power line transmission path, and relaying data transmission;
A second composite bridge device that relays data transmission by transferring transmission data on the composite media to the wireless communication terminal via a second wireless transmission path;
It is a communication system characterized by comprising.

  However, “system” here refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter whether or not (hereinafter the same).

  In a wireless LAN system, a service area provided to a wireless communication terminal can be expanded using a roaming function based on communication between access points. When the access point on the wireless communication terminal side relays data transmission by communication between access points, if the wireless transmission line between the access points and the wireless transmission line between the wireless communication terminals are operated in the same frequency band, the device configuration The price can be kept low.

  However, it is necessary to avoid interference between two adjacent wireless transmission paths relayed by the access point, and while using one wireless transmission path, the other wireless transmission path must wait for transmission operation, Throughput decreases. Moreover, even if an attempt is made to prevent a collision with a random back-off mechanism, the possibility of a collision cannot be completely eliminated. Also, inter-access point communication using wireless communication is not good at crossing rooms.

  On the other hand, there is a technique for performing communication between access points through a power line transmission line. A communication system using power line communication can realize high-speed communication of 100 Mbps or more without using a new communication line by using an existing power line. However, the power line transmission path has a problem that it is easily affected by noise caused by life rhythm.

  Therefore, in the communication system according to the present invention, the bridge device is configured to perform communication between access points by a composite bridge function using both the wireless transmission line and the power line transmission line. That is, in the first composite bridge device, the divided transmission data is alternately distributed and transmitted to the first wireless transmission line and the power line transmission line, so that compared with the case where only one of the transmission lines is used, communication is performed. Speed increases. Therefore, it is suitable for applications that require isochronous properties such as downloading large-capacity data and moving image streaming from a server to a wireless communication terminal.

  As described above, even when communication between access points is performed using the composite medium including the first wireless transmission line and the power line transmission line, it is necessary to avoid interference between the adjacent first wireless transmission line and the second wireless transmission line. When one wireless transmission path is in use, the other wireless transmission path must wait for a transmission operation. For this reason, the composite bridge devices perform transmission between access points by allocating transmission data to the first wireless transmission line and the power line transmission line so that the throughput to the wireless communication terminal as the data transmission destination is maximized. This is very important.

  Therefore, in the communication system according to the present invention, the throughput of the entire system is maximized based on the maximum throughput when it is assumed that each of the first and second wireless transmission lines and the power line transmission line is transmitted alone. For this reason, the distribution of transmission data is calculated.

  In this case, it is assumed that the effective throughputs W1, W2, and P possessed by each of the first and second wireless transmission lines and the power line transmission line are known in advance, and each transmission line transmits data at the maximum throughput. Is assumed to be performed.

  In the first composite bridge device, first, the unit transmission time is determined based on the ratio of time division allocation to the first wireless transmission path and the second wireless transmission path (however, the amount of transmission data on the power line transmission path is determined). The amount of data that can be transmitted on the second wireless transmission path during a unit transmission time is obtained.

  Further, it is necessary to transmit the data on the second radio transmission line during the unit transmission time in consideration of the data amount obtained by adding the transmission data quantity on the first radio transmission line per unit transmission time and the transmission data quantity on the power line transmission line. Find a certain amount of data.

  Next, based on the amount of data obtained from each viewpoint, the maximum value of the amount of data that can be transmitted on the second wireless transmission path during the unit transmission time is obtained, and this is set as the maximum throughput of the entire communication system. Then, the first and second composite bridge devices perform time division allocation of unit transmission times to the first and second radio transmission paths at a ratio that realizes the maximum throughput, and between the composite bridge devices and the second Wireless data transmission from the composite bridge device to the wireless communication device.

  However, assigning the unit transmission time to the use of the first and second wireless transmission lines in time division is effective only when the throughput of the second wireless transmission line is larger than the throughput of the power line transmission line. On the contrary, when the throughput of the power transmission path is larger than the throughput of the second wireless transmission path, the unit transmission time is also allocated to the first wireless transmission path in a time-sharing manner, and the second wireless transmission path is increased accordingly. Therefore, the throughput of the entire communication system simply decreases.

  Therefore, in the latter case, it is considered preferable to assign all unit transmission times to the second wireless transmission line and perform data transmission corresponding to the throughput of the second wireless transmission line on the power line transmission line.

  As described above, in order to perform transmission between access points by allocating transmission data to the first wireless transmission line and the power line transmission line, the first composite bridge device uses the first and second wireless transmission lines and the power line transmission. It is necessary to know in advance the effective throughput each road has.

  However, the first composite bridge device does not include a means for knowing by itself the effective throughput of the second wireless transmission path that connects the second composite bridge device and the wireless communication terminal that is the data reception destination. Therefore, the second composite bridge device notifies the information on the throughput of the second wireless transmission path as control data included in the packet transmitted via the first wireless transmission path or the power transmission path. good.

  Specifically, the second composite bridge device periodically notifies information related to the throughput of the second wireless transmission path as control data in an arbitrary format to be transmitted to the first composite bridge device. Alternatively, information regarding the throughput of the second wireless transmission path is included in a beacon periodically notified by the second composite bridge device as a wireless LAN access point, so that notification is made periodically. Alternatively, information on the throughput of the second wireless transmission path is included in the control packet such as ACK / NACK for the data packet transmitted from the first composite bridge device via the first wireless transmission path or the power line transmission path. By including it, it will be notified.

  ADVANTAGE OF THE INVENTION According to this invention, the outstanding communication system and communication apparatus which can relay data transmission suitably using a power line transmission line between bridge | bridging apparatuses can be provided.

  Further, according to the present invention, an excellent communication system in which a plurality of bridge devices can perform inter-access point communication using both a radio transmission line and a power line transmission line, and can preferably perform relaying to a data transmission destination. A communication device can be provided.

  Further, according to the present invention, it is possible to perform communication between access points by allocating transmission data to the wireless transmission line and the power line transmission line between the bridge devices so that the throughput to the data transmission destination is maximized. A communication system and a communication device can be provided.

  In addition, according to the present invention, when the wireless transmission path between the bridge devices and the wireless transmission path with the wireless communication terminal relayed by the bridge device are operated in the same frequency band, the adjacent wireless relayed by the bridge device. Inter-access point communication can be performed by allocating transmission data between the wireless transmission line and the power line transmission line between the bridge devices so that the throughput to the data transmission destination is maximized while avoiding interference between the transmission lines. An excellent communication system and communication apparatus can be provided.

  In the communication system according to the present invention, in the first and second composite bridge devices that relay a composite medium between a server that is a data transmission source and a wireless communication terminal that is a data reception destination, considering the throughput of each medium. Since the amount of data transmitted to the first wireless transmission path is controlled, higher throughput can be realized as the entire system.

  Further, in the first and second composite bridge apparatuses, the throughput of the first wireless transmission path and the power line transmission path as the composite media to be relayed and the second wireless transmission path as the connection medium to the data transmission destination are frequently set. As a result, it is possible to achieve higher throughput as a whole system while following the communication quality of each medium that changes every moment.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

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

  The present invention relates to a communication system that relays data transmission between bridge devices using a power line transmission line. A communication system using power line communication differs in behavior depending on the structure of a house that performs communication, and is easily affected by noise caused by life rhythm. Therefore, in one embodiment of the present invention, the bridge device is configured to perform communication between access points by a composite bridge function that relays using a composite medium including a wireless transmission path and a power line transmission path.

  For example, in Japanese Patent Laid-Open No. 2006-109022, which has already been assigned to the present applicant, both wireless transmission lines and power line transmission lines are used in combination, and communication states are established by combining or selecting the respective transmission lines. Proposals have been made for hybrid communication systems that achieve efficient transmission while complementing both communication qualities with the corresponding transmission form.

  FIG. 1 schematically shows a communication system configuration according to an embodiment of the present invention. The system shown in the figure has a configuration example in which each PLC bridge device in the communication system shown in FIG. 16 is replaced with composite bridge devices 403 and 406 each having a wireless LAN interface together with a PLC interface. In addition, although there is no restriction | limiting in particular about the specific frequency of a wireless transmission path, when following standard wireless LAN standards, such as IEEE802.11a / g, it is possible to use a 2.4 GHz band or a 5 GHz band, On the other hand, in a transmission line using a power line, a short wave band, that is, a frequency band of 3 MHz to 30 MHz is generally used. In the present embodiment, it is assumed that an OFDM modulation scheme is used in each transmission path from the viewpoint that multipath countermeasures and partial interference removal to other systems are easy.

  In FIG. 1, one composite bridge apparatus 403 is connected to a server 401 via a wired transmission path 402 such as Ethernet (registered trademark), and the other composite bridge apparatus 406 is connected to a wireless transmission path 404 and a power line transmission path. 405 is connected via a hybrid transmission line using both of them, and communication between access points is performed. The other composite bridge device 406 is connected to a wireless terminal such as a PC at the end via a wireless transmission line 407. Relay to 408.

  In the communication system shown in FIG. 1, for example, in a residence, a composite bridge device 403 having a connection point with the Internet is installed on the first floor, and a composite bridge device 406 is installed on the second floor. It can be applied to a configuration that allows Internet connection.

  In the communication system shown in the figure, when data is transmitted from the server 401 to the wireless communication terminal 408, the data is first transmitted to the composite bridge device 403 through a wired transmission path 402 such as Ethernet (registered trademark).

  In the composite bridge device 403, when the received data is transferred to the composite bridge device 406, either the wireless transmission line 404 or the power line transmission line 405 is selected, or the transmission data is divided and both the media are divided. Sort and transmit. The composite bridge device 406 transmits the received data to the wireless communication terminal 408 via the wireless transmission path 407.

  In FIG. 2, a transmission packet is transmitted to each medium of a wireless transmission line and a power line transmission line when communication between access points is performed between the composite bridge apparatus 403 and the composite bridge apparatus 406 that relays between the server 401 and the wireless communication terminal 408. It shows the state of sorting and transmitting.

In the figure, D ₁ , D ₂ , D ₃ ,... Are transmission packets, and the subscript numbers indicate the order in the original transmission stream. As shown in the figure, since the divided transmission data is alternately distributed and transmitted to the wireless transmission line 404 and the power line transmission line 405, the communication speed is faster than when only one of the transmission lines is used. . Therefore, for example, it is suitable for applications that require isochronous properties such as downloading large-capacity data and moving image streaming from the server 401 to the wireless communication terminal 408.

  In the communication system shown in FIG. 1, the server 401 connected to the wired transmission path 402 such as Ethernet (registered trademark) is configured by, for example, a general personal computer that operates a server application. Description is omitted. The wireless communication terminal 408 connected to the composite bridge device 406 via a wireless transmission path 407 such as a wireless LAN may be a terminal station that can communicate with a base station such as an access point, and thus description thereof is omitted. Hereinafter, the configuration of the composite bridge device 406 that bridges between the composite medium including the wireless transmission path 404 and the power line transmission path 405 and the general wireless transmission path 407 will be described with reference to FIG.

  The composite bridge device 406 includes an antenna 11 for a wireless transmission path 404, a changeover switch (SW) 12, an RF reception unit 13 and an RF transmission unit 14, a power amplifier 15, and a plug 21 for a power line 405. A power cord 22, a coupler 23, a changeover switch (SW) 24, a PLC receiver 25, a PLC transmitter 26, and a power amplifier 27 are provided in the wireless transmission path 404 with the other composite bridge device 403. Transmission / reception and transmission / reception in the power line transmission path 405 can be performed simultaneously.

  The antenna 11 is used for transmitting and receiving a high-frequency signal in a radio frequency band such as 2.4 GHz. The changeover switch 12 switches between the RF receiving unit 13 and the RF transmitting unit 14 in the radio frequency band and connects to the antenna 11. The changeover switch 24 switches the PLC receiving unit 25 and the PLC transmitting unit 26 in the short wave band that propagates through the power line 405 to connect to the coupler 23. The plug 21 is a plug of the power cord 22 connected to a power line outlet. The coupler 23 is a coupler for coupling a shortwave signal and a power line.

  The RF receiving unit 13 and the PLC receiving unit 25 receive, demodulate, and decode signals in the radio frequency band and the short wave band, respectively. Further, the RF transmission unit 14 and the PLC transmission unit 26 perform encoding and modulation in order to transmit signals in the radio frequency band and the short wave band, respectively. Power amplifiers 15 and 27 are connected to the output units of the RF transmission unit 14 and the PLC transmission unit 26, respectively, and amplify the transmission signal.

  The composite bridge device 406 includes an antenna 31 for the wireless transmission path 407, a changeover switch (SW) 32, an RF receiver 33 and an RF transmitter 34, and a power amplifier 35, and is connected to the wireless communication terminal 408. Thus, transmission / reception is performed in the wireless transmission path 407. Communication operations in the RF receiver 33 and the RF transmitter 34 are the same as those of the RF receiver 13 and the RF transmitter 14.

  The composite bridge device 403 side also includes circuit function modules for RF transmission / reception and PLC transmission / reception similar to those of the composite bridge device 406. The composite bridge device 403 transmits / receives to / from the server 401 through a wired transmission path 402 such as Ethernet (registered trademark) instead of wirelessly, but a well-known technique can be applied to the configuration of the wired interface and the like. Therefore, explanation is omitted.

  FIG. 4 illustrates an internal configuration example of the PLC receiving unit 25 of the composite bridge device 406 illustrated in FIG. The illustrated PLC receiving unit 25 assumes an OFDM system, and includes a down converter 251, an orthogonal demodulator 252, a discrete Fourier transformer (DFT) 253, a differential decoder 254, a demapping circuit 255, an error, and the like. A correction circuit 256 is provided, and is configured to convert a short-wave high-frequency signal received by the coupler 23 into an intermediate signal for demodulation and decoding.

  The down-converter 251 converts a short wave signal into an intermediate signal in a predetermined intermediate frequency band. The quadrature demodulator 252 performs quadrature detection on the intermediate signal converted by the down converter 251, and uses an in-phase signal (I signal) that is in phase with the intermediate signal and a quadrature signal (Q signal) that is a quadrature component of the intermediate signal. The baseband signal is extracted. The discrete Fourier transformer 253 performs fast Fourier transform on the baseband signal extracted by the orthogonal demodulator 252 in an effective symbol period excluding the guard period, and demodulates complex data for each subcarrier. The differential decoder 254 is used in, for example, a PSK (Phase Shift Keying) system, and differentially decodes complex data demodulated by the discrete Fourier transformer 213. The demapping circuit 255 demaps the complex data decoded by the differential decoder 254 and extracts data symbols. The error correction circuit 256 corrects data by Viterbi decoding or the like. The data thus obtained is output to the physical layer interface 41 of the communication control unit 40.

  Here, the configuration in which the PLC receiving unit 25 receives and processes a short-wave band signal has been described, but the RF receiving unit 13 also uses a similar configuration to convert a radio signal such as a 2.4 GHz band received by the antenna 11 into an intermediate signal. Convert, demodulate and decode.

  FIG. 5 illustrates an internal configuration example of the PLC transmission unit 26 of the composite bridge device 406 illustrated in FIG. 3. The illustrated PLC transmission unit 26 assumes an OFDM system, and includes an error correction encoding circuit 261, a map circuit 262, a differential encoder 263, an inverse discrete Fourier transformer (IDFT) 264, and orthogonal modulation. 265 and an up-converter 266, and is configured to encode and modulate data from the physical layer interface 41 to convert it into a high frequency signal and output it to the plug 21.

  The error correction encoding circuit 261 performs encoding using a convolutional code or the like according to the bit rate. The map circuit 262 maps the data error-coded by the error correction coding circuit 261 to complex data symbols. The differential encoder 263 differentially encodes the complex data symbols mapped by the map circuit 262 and assigns complex data for each subcarrier. The inverse discrete Fourier transformer 264 modulates the complex data differentially encoded by the differential encoder 263 by inverse Fourier transform, and outputs baseband signals (I signal and Q signal). The quadrature modulator 265 performs quadrature modulation on the baseband signal to generate an intermediate signal in a predetermined intermediate frequency band. The up-converter 266 converts the intermediate signal generated by the quadrature modulator 265 into a short-waveband signal and outputs it to the plug 21.

  Although the PLC transmission unit 26 has been described here, the RF transmission unit 14 also has the same configuration, and encodes and modulates data from the physical layer interface 31 to convert it into a radio signal such as a 2.4 GHz band. 11 is output.

  FIG. 6 shows a functional configuration of the data transmission control function in the composite media including the wireless transmission path 404 and the power line transmission path 405 in the communication control unit 40 of the composite bridge apparatus 406 shown in FIG. One composite bridge device 403 also has a similar data transmission control function.

  The data transmission control function shown in the figure includes a data distribution unit 441 that distributes data held in the data buffer 442, a distribution control unit A 410 that controls data distribution in the wireless transmission path 404, and data distribution in the power line transmission path 405. A distribution control unit B420 for controlling is provided.

  The distribution control unit A410 includes a carrier sense unit A411, a response determination unit A412, a counter A413, and a data output unit A415.

  The carrier sense unit A411 reports the availability of the wireless transmission path 404 to the data output unit A415, the response determination unit A412 and the data distribution unit 441.

  If the carrier sensing unit A411 reports that the wireless transmission path 404 is not free, the data output unit A415 outputs data only as a result of not outputting data if the power line transmission line 405 is free. Transmission will be performed. In this case, when data transmission on the power line transmission path 405 is started, control is performed so that data transfer on the wireless transmission path 404 is not performed even if it is found that the wireless transmission path 404 is free thereafter. It is desirable. This is to avoid complication of control due to a shift in data transmission timing in the wireless transmission path 404.

  In addition, the response determination unit A412 and the data distributor 431 can perform control related to the next data transmission without waiting for an actual response when the carrier sense unit A411 reports that the wireless transmission path 404 is not free. .

  The response determination unit A412 determines a response to the previous data transmission on the wireless transmission path 404, and supplies the result to the data distribution unit 441, the counter A413, and the counter B423.

  The counter A 413 includes a success counter A and a failure counter A (both not shown). The success counter A counts the number of consecutive times when the wireless transmission path 404 has succeeded in receiving a response to data transmission. On the other hand, the failure counter A counts the number of consecutive times when reception of transmission data on the wireless transmission path 404 fails continuously.

  The counter A 413 is supplied with response determination results from both the response determination unit A 412 and the response determination unit B 422, so that the communication state in one of the transmission paths 404 or 405 deteriorates so that a response cannot be received. Even in such a case, if a response can be received on at least one of the transmission paths 404 or 405, the reception status of data in all frequency bands can be recognized.

  The distribution control unit B420 also controls data distribution in the power line transmission path 405 with the same configuration as the distribution control unit A430.

  The data distribution unit 441 extracts transmission data from the data buffer 442 and sequentially distributes the transmission data to the data output unit A 415 and the data output unit B 425. However, the data transmission mode in the wireless transmission line 404 or the power line transmission line 405 is switched according to the state of the counter A 413 as follows.

  Specifically, when the composite bridge device 403 and the composite bridge device 406 perform inter-access point communication for data transmission in the downlink direction from the server 401 to the wireless communication terminal 408, a communication control unit on the composite bridge device 403 side In the data transmission control function 40, the communication quality of each of the wireless transmission path 404 or the power line transmission path 405 is checked based on the count value of the failure counter A or the success counter A, and the wireless transmission path 404 or the power line transmission path 405 Either medium is selected, or the transmission data is divided and distributed to both media for transmission (see FIG. 2).

  FIG. 7 shows a functional configuration of the data reception control function in the composite media including the wireless transmission path 404 and the power line transmission path 405 in the communication control unit 40 of the composite bridge apparatus 406 shown in FIG. One composite bridge device 403 also has a similar data transmission control function.

  The illustrated data reception control function includes a data merging unit 471 that merges data received in each frequency band and holds the data in the data buffer 472, and a merge control unit A480 that controls data merging of received packets in the wireless transmission path 404. , A merge control unit B490 for controlling data merge in the power line transmission line 405 is provided.

  The merge control unit A480 includes a data determination unit A481 and a response output unit A482. The merge control unit B490 includes a data determination unit B491 and a response output unit B492.

  The data discriminating unit A481 discriminates the data reception state in the wireless transmission path 404 and supplies the result to the data merging unit 471 and the response output units A482 and B492. The data discriminating unit B491 discriminates the data reception state in the power line transmission path 405 and supplies the result to the data merging unit 471 and the response output units A482 and B492.

  The response output unit A482 combines the determination result of the data reception state in the wireless transmission path 404 by the data determination unit A481 and the determination result of the data reception state in the power line transmission line 405 by the data determination unit B491 together with the response in the wireless transmission path 404. Output as. Further, the response output unit B492 combines the determination result of the data reception state in the wireless transmission path 404 by the data determination unit A481 and the determination result of the data reception state in the power line transmission line 405 by the data determination unit B491, in the power line transmission line 405. Output as a response. That is, the response in each transmission path 404 and 405 includes the determination result of the data reception state in all the transmission paths 404 and 405.

  For example, when the composite bridge device 403 and the composite bridge device 406 perform inter-access point communication for downlink data transmission from the server 401 to the wireless communication terminal 408, the composite bridge device 406 The content of the response described above is included in a control packet such as ACK / NACK for a data packet transmitted in the downstream direction from the terminal.

  FIG. 8 shows a frame configuration example of a data packet used in the communication system according to the present embodiment. The illustrated packet is used when the composite bridge device 403 and the composite bridge device 406 perform communication between access points, and includes a physical layer header 610, a MAC header 620, and a payload 630.

  The physical layer header 610 is a PLCP frame header that transmits information in the PLCP (Physical Layer Convergence Protocol) sublayer as a physical layer, and includes fields indicating a transmission rate, a modulation method, a length of the PLCP frame, and the like. . The MAC header 620 is a header of a MAC frame that conveys information in the MAC sublayer, and includes fields indicating the type of frame and the transmission / reception address of the frame. The payload 630 is a MAC frame payload and includes data 631 and a CRC 632.

  In the present embodiment, the MAC header 620 in the packet includes fields of usage status 621, order 622, and CRC 623.

  The usage status 621 is a field indicating the usage status of each frequency band when this frame is transmitted, and 1 bit is allocated to each transmission path constituting the composite medium. For example, when the first bit is “0”, the wireless transmission path 404 is unused, and when the first bit is “1”, the wireless transmission path 404 is used. Similarly, when the second bit is “0”, it indicates that the power line transmission line 405 is not used, and when it is “1”, it indicates that the power line transmission line 405 is used. As a result, the receiving units 13 and 25 that have received the frame can know whether or not there is a frame transmitted simultaneously on the other transmission path.

  The order 622 is a field indicating the order relation (packet serial number) of data transmitted at the same time. For example, if two data are distributed at the same time, it indicates that the data is the first half when “0”. , “1” indicates the latter half of the data. CRC (Cyclic Redundancy Code) 623 is a cyclic redundancy check code for detecting a data error in the MAC header 620.

  At the time of frame transmission, the data distribution unit 441 of the communication control unit 40 generates the usage status 621 and the order 622 and adds them to the MAC header 620. On the other hand, on the frame receiving side, the data merging unit 471 of the communication control unit 40 stores the data in the data buffer 472 according to the order 622.

  For example, when the composite bridge apparatus 403 and the composite bridge apparatus 406 perform inter-access point communication for data transmission in the downlink direction from the server 401 to the wireless communication terminal 408, as shown in FIG. Distribution of transmission data to paths 404 and 405, that is, distribution of packets is performed. FIG. 9 shows a state in which the data to be transferred is divided into two, distributed to the transmission packets on the transmission paths 404 and 405, and transmitted. In the illustrated example, the transfer data 601 is 1512 bytes, the data included in the data packet 602 is 504 bytes in the first half of the transfer data 601, and the data included in the data packet 603 is 1008 in the second half of the transfer data 601. It is a byte.

  FIG. 10 shows a frame configuration example of a control packet used for returning a response in the communication system according to the present embodiment. The illustrated response packet is, for example, returned from the terminal station that has received the data packet to the data transmission source base station, and includes a physical layer header 640, a MAC header 650, and a payload 660. A physical layer header 640 is a header of a PLCP frame that conveys information in the PLCP sublayer. The MAC header 650 is a MAC frame header that transmits information in the MAC sublayer, similar to the physical layer header 610 and the MAC header 620 of the data packet shown in FIG.

  The illustrated response packet includes the status 661 and CRC 662 fields in the payload 660. A state 661 is a field indicating the reception state of distributed data. CRC 662 is a cyclic redundancy check code for detecting data errors in the MAC header 650 and the payload 660.

  The state 661 includes all reception states relating to data that has been distributed and transmitted simultaneously. Therefore, for example, even a response packet in the wireless transmission path 404 includes the reception state of the power line transmission path 405 as well as the wireless transmission path 404. For this reason, the state 661 includes information corresponding to the number of distributed data, and when the data is distributed and transmitted in two, the field is composed of, for example, 2 bits, and the first bit is the first half. The reception state of the second part can be indicated, and the reception state of the latter half part can be indicated by 2 bits. That is, the first bit is “0” when the first half is successfully received, and the first bit is “1” when the first half is unsuccessful. Similarly, the second bit is “0” when the second half is successfully received, and the second bit is “1” when the second half is unsuccessfully received.

  The response packet state 661 is generated by the response output units A452 and B462 based on the determination results in the data determination units A451 and B461 of the communication control unit 40 on the composite bridge device 406 side that has received the data packet. The response packet is returned to the composite bridge device 403 that is the data transmission source, and the state 661 is determined by the response determination units A412 and B422 in the composite bridge device 403.

  Subsequently, a data transmission operation in the communication system according to the present embodiment will be described.

  In the communication system shown in FIG. 1, when the composite bridge device 403 transfers received data to the composite bridge device 406, either the wireless transmission path 404 or the power line transmission path 405 is selected, or the transmission data Is divided and distributed to both media for transmission. The composite bridge device 406 transmits the received data to the wireless communication terminal 408 via the wireless transmission path 407.

  When the composite bridge device 403 selects one of the media and transfers data to the composite bridge device 406, the data is transmitted to the composite bridge device 406 according to the communication status of the wireless transmission path 404 and the power line transmission path 405. Higher throughput can be obtained in the transmission path up to the wireless communication terminal 408.

  For example, the composite bridge device 403 alternately selects the wireless transmission line 404 and the power line transmission line 405 if the communication qualities of the transmission lines 404 and 405 are approximately the same. Further, if the communication quality of the power line transmission path 405 is better, the number of times of selecting the power line transmission path 405 as the medium is increased (or data is transmitted using only the power line transmission path 405). Dynamically change the media used.

  There are various methods for obtaining the communication quality of each medium. For example, when the wireless transmission path 404 uses a general wireless LAN system, the composite bridge device 403 receives an ACK (Acknowledge) packet returned from the composite bridge device 406 that is a transmission destination when transmitting a data packet. Communication quality can be determined based on the electric field strength. In the case of the power line transmission path 405, the communication quality can be determined based on the number of retransmissions when transmission fails.

  The wireless transmission path 404 between the composite bridge apparatuses 403 and 406 and the wireless transmission path 407 between the bridge apparatus 406 and the wireless communication terminal 408 may be the same wireless LAN standard or different wireless LAN standards. In the present embodiment, in consideration of reduction in device cost, the two wireless transmission paths 404 and 407 bridged by the composite bridge device 406 are operated in the same frequency band.

  As described above, the composite bridge device 403 operates to adjust the ratio of transmission data distributed to each medium according to the communication quality in each of the wireless transmission path 404 and the power line transmission path 405. However, when the wireless transmission paths 404 and 407 use the same frequency channel, there is a restriction that the wireless transmission path 404 and the wireless transmission path 407 cannot transmit data at the same time.

  That is, when the wireless transmission paths 404 and 407 use the same frequency channel, it is necessary to avoid mutual interference. When data transmission is performed irregularly, an interference avoidance operation based on carrier detection is necessary. In isochronous communication or the like, it is necessary to reserve a bandwidth in a time division manner for the adjacent wireless transmission paths 404 and 407 in a unit transmission cycle.

  In any case, since the wireless transmission path 407 cannot be used when the wireless transmission path 404 is being used, the throughput is simply reduced to half or less. For this reason, between the composite bridge devices 403 and 406, the transmission data is allocated to the wireless transmission line 404 and the power line transmission line 405 so that the throughput to the wireless communication terminal 408 as the data transmission destination is maximized. Intercommunication is important.

  For example, even if the communication quality of the wireless transmission line 404 is significantly better than that of the power line transmission line 405, if a large amount of data is transmitted on the wireless transmission line 404, the wireless communication terminal 408 is transmitted on the subsequent wireless transmission line 407. It becomes impossible to secure a sufficient band for data transmission (that is, data transmission time). As a result, even if the throughput is improved between the composite bridge devices 403 and 406, transmission data stays in the composite bridge device 406, which causes a reduction in throughput of the entire communication system.

  Further, in order to avoid interference between the wireless transmission path 404 and the wireless transmission path 407 bridged by one composite bridge apparatus 406 in this way, only the power line transmission path 406 is used between the composite bridge apparatuses 403 and 406. If communication between access points is attempted, the throughput of the entire communication system depends only on the communication quality of the power line transmission path 405. In this case, the feature of the composite media that the divided transmission data is alternately distributed and transmitted to the wireless transmission path 404 and the power line transmission path 405 to increase the communication speed cannot be fully utilized. Of course, when noise due to life rhythm occurs on the power line transmission line 405, the wireless transmission line 404 cannot compensate for this, and the communication speed and communication quality are extremely poor.

  Therefore, in the following, in the communication system shown in FIG. 1, a data transmission method for maximizing the throughput of the entire system while simultaneously using wireless inter-access point communication and power line transmission between the composite bridge apparatuses 403 and 406 Consider.

  In this embodiment, distribution of transmission data for maximizing the throughput of the entire system based on the maximum throughput when it is assumed that each of the wireless transmission paths 404 and 407 and the power line transmission path 405 is transmitted alone. Is calculated. The distribution of data here refers to the ratio of the transmission data received from the server 401 to the wireless transmission path 404 and the power line transmission path 405 in the composite bridge device 403, and the unit transmission time for each wireless transmission path 404 and 407 in time division. It means the ratio to share with.

  Here, it is assumed that both the wireless transmission paths 404 and 407 use a wireless LAN standard such as IEEE802.11a. It is assumed that the effective throughput of each transmission path 404, 405, 407 is known in advance. That is, W1 [Mbps] is set for the wireless transmission path 404, W2 [Mbps] is set for the wireless transmission path 407, and P [Mbps] is set for the power line transmission path 405. In the following description, the amounts of data sent in one second through the wireless transmission path 404 and the wireless transmission path 407 are set to DATAw1 and DATAw2, respectively.

  First, consider the amount of data transmitted from the composite bridge device 403 to the other composite bridge device 406 via the wireless transmission path 404 per second. A maximum of W1 [Mbyte] can be transmitted in one second. However, if the wireless transmission path 404 occupies all of one second, the band for using the wireless transmission path 407 is eliminated, so that transmission data stays in the composite bridge device 406. As a result, the throughput of the communication system as a whole is reduced.

  Therefore, the amount of data transmitted from the composite bridge device 403 per second is limited to DATAw1 [bytes] (provided that DATAw1 <W1). In this case, the required time tw1 [sec] for transmitting the data amount of DATAw1 at the effective throughput W1 on the wireless transmission path 404 is expressed by the following equation (1).

  In this case, since the time for using the wireless transmission line 404 in one second is limited to tw1 [sec] (where 0 <tw1 <1), the remaining tw2 as shown in the following equation (2). (= 1−tw1) [sec] can be assigned to the time when the composite bridge device 406 transfers the data received from the composite bridge device 403 to the wireless communication terminal 408 through the wireless transmission path 407.

  In addition, since the power line transmission line 405 has no problem of interference with other transmission lines, data transmission can be performed using all of one second. Therefore, the composite bridge device 403 can transmit data of P [Mbyte] at maximum in one second using the power line transmission path 405.

  Next, consider the data amount DATAw2 transmitted from the composite bridge device 406 to the wireless communication terminal 408 via the wireless transmission path 407 in one second.

  Since the maximum throughput of the wireless transmission path 407 is W2 [Mbps], the data amount DATAw2 that can be transmitted using tw2 [sec] allocated to use of the wireless transmission path 407 in one second is expressed by the following equation (3 )

  On the other hand, the composite bridge device 407 needs to transmit the amount of data transmitted using both the wireless transmission path 404 and the power line transmission path 405 per second via the wireless transmission path 407 in the same manner. That is, the amount of data DATAw2 sent per second on the wireless transmission path 407 is equal to the sum of the transmission data amounts DATAw1 and P of the wireless transmission path 404 and the power line transmission path 405 for one second. Holds.

  Here, the horizontal axis represents the data amount DATAw1 transmitted on the wireless transmission path 404 per second and the horizontal axis represents the data amount DATAw2 transmitted on the wireless transmission path 407 per second. When the straight lines represented by 4) are drawn on the graph, they are as shown in FIG.

  The above equation (3) represents the maximum amount of data that can be transmitted on the wireless transmission path 407 per second, which is determined based on the ratio obtained by time-sharing the wireless transmission path 404 and the wireless transmission path 407 for 1 second (however, (The transmission data amount of the power line transmission line 405 is not taken into consideration), and actually the inequality shown in the following expression (3 ′) is obtained.

  Further, the above equation (4) is determined based on the total amount of data transmitted using both the wireless transmission path 404 and the power line transmission path 405, and is the maximum that can be transmitted on the wireless transmission path 407 per second. This represents the amount of data (however, the ratio of 1-second time division between the wireless transmission path 404 and the wireless transmission path 407 is not considered), and is actually an inequality represented by the following expression (4 ′).

  Therefore, the values that DATAw1 and DATAw2 can take when actually transmitting are within the area drawn with diagonal lines in FIG. Regarding the data transmission for one second, the maximum value of the transmission data amount in the wireless transmission path 407 is the maximum throughput of the entire system. That is, at the intersection (DATAw1, DATAw2) = (B, A) of two straight lines represented by the above equations (3) and (4) in FIG. 11, B [Mbyte] on the wireless transmission line 404 per second, Although only P [Mbyte] is transmitted on the power line transmission line 405, A = B + P [Mbyte] is the maximum throughput in the entire system.

  The maximum throughput of the system is determined by solving the simultaneous linear equations consisting of the above equations (3) and (4). Regarding the transmission data amount DATAw1 for one second of the wireless transmission path 404 when realizing this maximum throughput, the following equation (8) is obtained.

  Further, the maximum value DATAw2 of the transmission data amount per second of the wireless transmission path 407 corresponding to the maximum throughput of the system is expressed by the following equation (9).

  Then, DATAw1 and DATAw2 represented by the equations (8) and (9) are substituted into the above equations (1) and (2), respectively, at a ratio of tw1: tw2 and wirelessly transmitted for 1 second to the wireless transmission line 404. If the path 407 is allocated in a time division manner, the maximum throughput of the system can be realized.

  As described above, in this embodiment, the composite bridge device 403 that relays data between the server 401 that is the data transmission source and the wireless communication terminal 408 that is the data reception destination using the composite media performs wireless transmission in consideration of the throughput of each medium. Since the amount of data transmitted to the path 404 is controlled, higher throughput can be realized as the entire system.

  In the above description, for the sake of convenience, the amount of transmission data per second in each transmission path is calculated. However, this is the amount of data per unit transmission time, which can be referred to as throughput.

  However, the transmission data amounts DATAw1 and DATAw2 per second of the wireless transmission paths 404 and 407 for realizing the maximum throughput of the communication system represented by the above formulas (8) and (9) are the values of the wireless transmission path 407. It is assumed that the throughput W2 is larger than the throughput of the power line transmission path 405 (that is, W2> P). This can be understood intuitively from FIG.

  When the throughput W2 of the wireless transmission path 407 is smaller than the throughput of the power line transmission path 405 (ie, W2 <P), the horizontal axis represents the amount of data DATAw1 transmitted on the wireless transmission path 404 per second and With the amount of data DATAw2 transmitted on the wireless transmission path 407 as the horizontal axis, the straight lines represented by the equations (3) and (4) are drawn on the graph, respectively, as shown in FIG. Then, the area drawn with diagonal lines in the figure is a value that DATAw1 and DATAw2 can take when actually transmitting.

  As can be seen from FIG. 12, in this case, when one second is allocated to the radio transmission lines 404 and 407 in a time-sharing manner, the amount of transmission data decreases according to the time allocated to the radio transmission path 407, so that Throughput of the entire communication system decreases. For this reason, all data for 1 second is used for data transmission on the wireless transmission path 407 without time division (that is, DATAw1 = 0 [byte]), and on the power line transmission path 405, data equivalent to the throughput W2 of the wireless transmission path 407 is used. It is preferable to perform transmission.

  Next, an actual data transmission method when the maximum throughput to be transmitted on each medium is determined as described above will be described with reference to FIG.

  It is assumed that the throughput of the wireless transmission path 404 is calculated as B and the throughput of the power line transmission path 405 is calculated as P using the above equation (8). At this time, when the composite bridge device 403 receives data from the server 401, it selects either the wireless transmission path 404 or the power line transmission path 405, or divides the data to be transferred and both of these media. Will be transmitted after being sorted.

  When selecting one of the media, the composite bridge device 403 can perform data transmission to obtain the maximum throughput by selecting the media according to the calculated ratio of the throughputs B and P.

  On the other hand, when dividing the data to be transferred, the data is divided in accordance with the similarly calculated ratio of the throughputs B and P and distributed to the transmission packets of the respective media, thereby similarly performing data transmission for obtaining the maximum throughput. be able to.

  In order to distribute the transmission data to the wireless transmission line 404 and the power line transmission line 405 according to the above formulas (8) and (9) and perform communication between access points, each transmission line 404, 405, 407 has an effective throughput that is independent of each other. Need to be known in advance. Therefore, a method for calculating the throughput of each transmission path will be described below.

  For example, if the wireless transmission paths 404 and 407 are IEEE802.11g, an OFDM modulation scheme is adopted, and subcarrier modulation schemes are BPSK (Binary Phase Shift Keying), QPSK (Quadrature Amplitude Modulation), 16QAM (Quadrature Amplitude Modulation). 64QAM is defined. Then, if the communication environment is good, a subcarrier modulation scheme that provides a high throughput such as 64QAM is applied, while in a poor communication environment, the subcarrier modulation scheme is dynamically switched to a low throughput subcarrier modulation scheme such as BPSK. Adaptive modulation based on the communication environment can be performed.

  Here, the composite bridge apparatuses 403 and 406 can calculate the logical throughput according to the definition of the modulation method and the specification of the MAC (Media Access Control) layer protocol (the provisions regarding the physical layer level of IEEE802.11g). (Shown in the table below). Further, by measuring the error rate during actual transmission and taking it into consideration for the logical throughput, a more accurate throughput at a certain point in time can be calculated.

  In order to calculate the throughput of each medium at a certain point in time, information on the modulation scheme used at the time of actual transmission is required. In the communication system shown in FIG. 1, it is the composite bridge device 403 and the composite bridge device 406 that can know the throughput of the wireless transmission line 404 and the power line transmission line 405. Further, the composite bridge device 406 and the wireless communication terminal 408 can know the throughput of the wireless transmission path 407. In other words, the composite bridge device 403 cannot directly know the throughput of the wireless transmission path 407.

  However, in order to realize data transmission distribution on the composite medium so as to maximize the throughput of the entire system by the method described with reference to FIGS. 11 and 12, the wireless transmission path 404 is used in the composite bridge device 403. It is necessary to know all the throughputs of the power line transmission line 405 and the wireless transmission line 407.

  Therefore, a means for notifying the composite bridge apparatus 403 of information regarding the throughput of the wireless transmission path 407 recognized by the composite bridge apparatus 406 or a means for acquiring the information by the composite bridge apparatus 403 is necessary. This type of means can be configured using a medium such as the wireless transmission line 404 or the power line transmission line 405 connecting the composite bridge apparatuses 403 and 406.

  For example, information regarding the throughput of the wireless transmission path 407 is periodically notified as control data of an arbitrary format transmitted from the composite bridge device 406 to the composite bridge device 403.

  Further, as another method of notifying the composite bridge device 403 of information related to the throughput of the wireless transmission path 407, it relates to the throughput of the wireless transmission path 407 in the beacon that the composite bridge device 406 periodically notifies as an access point of the wireless LAN. By including the information, information regarding the throughput of the wireless transmission path 407 is periodically notified.

  Further, as yet another method for notifying the composite bridge device 403 of information on the throughput of the wireless transmission path 407, an ACK / data for a data packet transmitted from the composite bridge apparatus 403 via the wireless transmission path 404 or the power line transmission path 405 is used. By including information regarding the throughput of the wireless transmission path 407 in a control packet such as NACK, information regarding the throughput of the wireless transmission path 407 is notified.

  As described above, in the communication system according to the present embodiment, in the composite bridge devices 403 and 406 that relay the composite data between the server 401 that is the data transmission source and the wireless communication terminal 408 that is the data reception destination, Since the amount of data transmitted to the wireless transmission path 404 is controlled in consideration of the throughput of each medium, a higher throughput can be realized as the entire system.

  Further, in the composite bridge apparatuses 403 and 406, by frequently measuring the throughput of the wireless transmission path 404 and the power line transmission path 405 as composite media to be relayed and the wireless transmission path 407 as a connection medium to the data transmission destination, While following the communication quality of each medium that changes from moment to moment, higher throughput can be realized as a whole system.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  In the present specification, the description has focused on an embodiment having a system configuration in which composite bridge devices are connected to each other by composite media including a wireless transmission line such as a wireless LAN and a power line transmission line such as a PLC. Is not necessarily limited to this. The present invention can be similarly applied to various communication systems composed of wireless media other than the wireless LAN and composite media including combinations of wired transmission paths other than the PLC.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram schematically showing a communication system configuration according to an embodiment of the present invention. FIG. 2 shows that transmission packets are distributed to each medium of a wireless transmission line and a power line transmission line when communication between access points is performed between the composite bridge apparatus 403 and the composite bridge apparatus 406 that relays between the server 401 and the wireless communication terminal 408. FIG. FIG. 3 is a diagram showing the configuration of the composite bridge device 406. FIG. 4 is a diagram illustrating an internal configuration example of the PLC receiving unit 25 of the composite bridge device 406 illustrated in FIG. 3. FIG. 5 is a diagram illustrating an internal configuration example of the PLC transmission unit 26 of the composite bridge device 406 illustrated in FIG. 3. FIG. 6 is a diagram illustrating a functional configuration of a data transmission control function in the composite media including the wireless transmission path 404 and the power line transmission path 405 in the communication control unit 40 of the composite bridge apparatus 406 illustrated in FIG. FIG. 7 is a diagram illustrating a functional configuration of a data reception control function in the composite media including the wireless transmission path 404 and the power line transmission path 405 in the communication control unit 40 of the composite bridge apparatus 406 illustrated in FIG. FIG. 8 is a diagram showing a frame configuration example of a data packet used in the communication system according to the present invention. FIG. 9 is a diagram showing a state in which the data to be transferred is divided into two parts, distributed to the transmission packets on the transmission paths 404 and 405, and transmitted. FIG. 10 is a diagram showing a frame configuration example of a control packet used for returning a response in the communication system according to the present invention. FIG. 11 shows the amount of data DATAw1 transmitted on the wireless transmission path 404 per second on the horizontal axis and the amount of data DATAw2 transmitted on the wireless transmission path 407 per second on the horizontal axis. It is the figure which showed the relationship (however, when W2> P). FIG. 12 shows the amount of data DATAw1 transmitted on the wireless transmission path 404 per second on the horizontal axis and the amount of data DATAw2 transmitted on the wireless transmission path 407 per second on the horizontal axis. It is the figure which showed the relationship (however, when W2 <P). FIG. 13 is a diagram illustrating a configuration example of a communication system in which a bridge device that mediates with an external network operates as an access point of a wireless LAN indoors. FIG. 14 is a diagram illustrating a configuration example of a communication system using communication between access points. FIG. 15 is a diagram illustrating a configuration example of a communication system in which a part of a wired transmission path is replaced with a power line transmission path. FIG. 16 is a diagram illustrating a configuration example of a communication system in which communication between access points in the communication system illustrated in FIG. 14 is replaced from a wireless LAN to a power line transmission path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Antenna 12 ... Changeover switch 13 ... RF receiver 14 ... RF transmitter 15 ... Power amplifier 21 ... Plug 22 ... Power cord 23 ... Coupler 24 ... Changeover switch 25 ... PLC receiver 26 ... PLC transmitter 27 ... Power amplifier DESCRIPTION OF SYMBOLS 31 ... Antenna 32 ... Changeover switch 33 ... RF receiving part 34 ... RF transmission part 35 ... Power amplifier 40 ... Communication control part 41 ... Physical layer interface 251 ... Down converter 252 ... Orthogonal demodulator 253 ... Discrete Fourier transformer 254 ... Differential Decoder 255 ... Demap circuit 256 ... Error correction circuit 261 ... Error correction encoder circuit 262 ... Map circuit 263 ... Differential encoder 264 ... Inverse discrete Fourier transformer 265 ... Orthogonal modulator 266 ... Upconverter 401 ... Server 402 ... Wired transmission line 403 ... Composite bridge device 404 ... Wireless transmission path 405 ... Power line transmission path 406 ... Composite bridge device 407 ... Wireless transmission path 408 ... Wireless communication terminal 410 ... Distribution controller A
411 ... Career sense part A
412 ... Response determination unit A
413 ... Counter A
415 ... Data output part A
420: Distribution control unit B
421 ... Career sense part B
422 ... Response discrimination unit B
423 ... Counter B
425 ... Data output part B
441 ... Data distribution unit 442 ... Data buffer 471 ... Data merging unit 472 ... Data buffer 480 ... Merge control unit A
481... Data discrimination unit A
482 ... Response output unit A
490 ... Merge control unit B
491... Data discrimination unit B
492 ... Response output unit B

Claims (13)

A communication system for transmitting data from a data transmission source server to a data reception destination wireless communication terminal,
A first composite bridge device connected to the server via a wired transmission path, transferring transmission data on the wired transmission path to a composite medium composed of a first wireless transmission path and a power line transmission path, and relaying data transmission;
A second composite bridge device that relays data transmission by transferring transmission data on the composite media to the wireless communication terminal via a second wireless transmission path;
A communication system comprising: The first wireless transmission line and the second wireless transmission line use the same frequency band,
The first or second composite bridge device uses a unit transmission time by time-sharing the first radio transmission path and the second radio transmission path,
The communication system according to claim 1. The effective throughput of each of the first and second wireless transmission lines and the power line transmission line is known in advance, and data transmission is performed at the maximum throughput in each transmission line.
First transmission data that can be transmitted on the second wireless transmission path during the unit transmission time, determined based on the ratio of unit transmission time allocated to the first wireless transmission path and the second wireless transmission path in a time-sharing manner First transmission data amount calculation means for determining the amount;
Considering a data amount that is the sum of the transmission data amount on the first wireless transmission path per unit transmission time and the transmission data amount on the power line transmission line, it is necessary to transmit on the second wireless transmission path in the unit transmission time. 2nd transmission data amount calculation means for obtaining the transmission data amount of 2,
Maximum throughput calculating means for obtaining, as a maximum throughput of the entire communication system, a maximum value of the amount of data that can be transmitted on the second wireless transmission path during a unit transmission time based on the first and second transmission data amounts. ,
The first and second composite bridge devices allocate a unit transmission time to the use of the first and second radio transmission paths in a time-sharing manner at a ratio that realizes the maximum throughput.
The communication system according to claim 2. When the throughput of the power line transmission path is larger than the throughput of the second wireless transmission path, the first composite bridge device allocates all unit transmission time to the second wireless transmission path, and the power line Data transmission corresponding to the throughput of the second wireless transmission path is performed on the transmission path.
The communication system according to claim 2. The second composite bridge device notifies information about the throughput of the second wireless transmission path as control data included in a packet transmitted via the first wireless transmission path or the power transmission path.
The communication system according to claim 3. A communication device connected to a composite bridge device via a composite medium comprising a first wireless transmission line and a power line transmission line,
Transmission data acquisition means for acquiring transmission data for transmitting the data received by the composite bridge device via the composite media to the wireless communication terminal via a second wireless transmission path;
Transmission data distribution means for distributing transmission data to the composite bridge device to the first wireless transmission line and the power line transmission line;
Wireless communication means for communicating with the composite bridge device via the first wireless transmission path;
Power line communication means for communicating with the composite bridge device via the power line transmission line;
A communication apparatus comprising: Server connection means for connecting to a server that provides data to be transmitted to the wireless communication terminal,
The transmission data acquisition means acquires transmission data for transmission to the wireless communication terminal from the server via the server connection means.
The communication apparatus according to claim 6. The first wireless transmission line and the second wireless transmission line use the same frequency band,
The transmission data distribution means uses transmission data to the composite bridge device for the first wireless transmission so that a unit transmission time is used in a time-sharing manner in the first wireless transmission path and the second wireless transmission path. Distributing to the transmission line and the power line transmission line,
The communication apparatus according to claim 6. The apparatus further comprises a throughput acquisition means for acquiring information on the throughput of each of the first wireless transmission path, the power transmission path, and the second wireless transmission path,
The transmission data distribution unit is configured to transmit transmission data to the composite bridge device based on each throughput of the first wireless transmission path, the power transmission path, and the second wireless transmission path. Each of the power line and the power line transmission line,
The communication apparatus according to claim 6. The throughput acquisition means is configured to determine the throughput of the first wireless transmission path and the power transmission path based on an error rate when actually transmitting with the composite bridge device using the wireless communication means and the power line communication means. Get information about the
The communication apparatus according to claim 9. The throughput acquisition means acquires information on the throughput of the second wireless transmission path as control data included in a packet transmitted from the composite bridge device via the first wireless transmission path or the power transmission path. To
The communication apparatus according to claim 9. The transmission data distribution means includes
First transmission data that can be transmitted on the second wireless transmission path during the unit transmission time, determined based on the ratio of unit transmission time allocated to the first wireless transmission path and the second wireless transmission path in a time-sharing manner First transmission data amount calculation means for determining the amount;
Considering a data amount that is the sum of the transmission data amount on the first wireless transmission path per unit transmission time and the transmission data amount on the power line transmission line, it is necessary to transmit on the second wireless transmission path in the unit transmission time. 2nd transmission data amount calculation means for obtaining the transmission data amount of 2,
Based on the first and second transmission data amounts, comprising a maximum throughput calculating means for obtaining the maximum value of the data amount that can be transmitted on the second wireless transmission path in unit transmission time as the maximum throughput of the entire communication system,
A unit transmission time is allocated to use of the first and second radio transmission lines in a time-sharing manner at a ratio that realizes the maximum throughput.
The communication apparatus according to claim 9. When the throughput of the power line transmission path is larger than the throughput of the second radio transmission path, the transmission data distribution means allocates all unit transmission time to the second radio transmission path, and the power line transmission path For the transmission data corresponding to the throughput of the second wireless transmission path,
The communication apparatus according to claim 9.

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