JP4762499B2 - Medium access control method and power line communication method - Google Patents

Description

  The present invention relates to a medium access control method in a data link layer of an OSI reference model and a power line communication method for performing communication using a power line as a transmission line.

  In recent years, networking has progressed in various technical fields due to advances in communication technology, and various devices in a building are being connected to the network. Since a device can be connected to a network without being routed, a wireless LAN using wireless as a transmission path has recently started to spread. There are IEEE802.11a and IEEE802.11b as communication standards of this wireless LAN. In IEEE802.11a and IEEE802.11b, a so-called CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) method is used for medium access control (MAC) in the data link layer of the OSI (Open Systems Interconnection) reference model. Thus, communication is performed between the master station and the plurality of slave stations by each of the plurality of slave stations communicating with the master station aiming at communication vacancy. For this reason, when communicating data such as a Web Browser (web browser), there is not much problem. However, when streaming data such as voice and video is communicated, audio disturbance and video frames due to communication packet delays. This is a problem because dropping occurs.

  Therefore, IEEE 802.11e having a so-called QoS (Quality of Service) function has been proposed (for example, Non-Patent Document 1). In this IEEE802.11e, a parent station repeatedly transmits a communication frame called a super frame (Super Frame) including a PCF (Point Coordination Function) and a DCF (Distributed Coordination Function) to the network, and the parent station and a plurality of children. Media access control is performed between stations.

  The PCF is a non-contention period of time division multiple access (TDMA) that includes a plurality of time zones for communicating with a slave station in accordance with the number of slave stations that want to communicate. Since each slave station communicates with the master station using a time zone assigned to itself, a collision of communication signals is avoided, and each slave station is guaranteed to communicate with the master station. Therefore, the QoS function is achieved by this PCF, and it is possible to cope with communication of data such as streaming data that requires real-time property. On the other hand, DCF is a contention period in which each slave station communicates with the master station by the CSMA / CA method.

On the other hand, when connecting electrical / electronic devices to a network, power line communication is used because there is no need to lay a new transmission line because existing wiring (power lines) that supply power to the electrical / electronic devices is used. Sometimes it is done. Since power line communication does not require the installation of a new transmission line in this way, there is an advantage that the initial cost associated with the introduction is low and the aesthetics of the building are not impaired. In this power line communication, communication is not guaranteed for all nodes because the wiring is originally intended to supply power. In many cases, so-called CSMA / CA (Carrier Sense Multiple Access with) is used for medium access control. Collision Avoidance) method is adopted. Since it is difficult to ensure QoS simply by adopting this CSMA / CA method as it is, it is conceivable to apply the above superframe method to power line communication in order to ensure QoS.
Antonio Grilo, Mario Nunes, “PERFORMANCE EVALUATION OF IEEE 802.11E”, [online], Proceedings of the 13th IEEE International Symposium in Person Vol I.I. [Search on March 1, 2004], Internet <URL; http: // www. lx. it. pt / pimrc2002 />

  By the way, in the medium access control method using the superframe method according to the background art, even when the slave station does not want to transmit data, the master station continues to repeatedly transmit the superframe periodically. IEEE802.11 has a power management function, but even if it is in the power save mode, the master station continues to repeatedly transmit a superframe periodically. For this reason, it cannot coexist with other medium access control methods, and the communication band cannot be used effectively.

  Further, in power line communication, when a communication signal flows through the power line, it propagates through an unbalanced transmission path, so that a radio wave is radiated from the power line and propagates in the air due to the antenna effect (leakage radio wave). For this reason, when the superframe method is applied to power line communication, since the superframe is continuously transmitted, the radio wave based on the superframe always leaks. This leaked radio wave affects other electrical / electronic devices.

  The present invention has been made in view of the above circumstances, and is a medium access control method capable of effectively utilizing a communication band and suppressing leakage radio waves, and a power line using the medium access control method. An object is to provide a communication method.

In order to achieve the above-mentioned problem, according to one aspect of the present invention, the master station repeats a superframe having a plurality of time zones for communicating with the slave stations according to the number of slave stations that desire communication. A medium access control method for performing medium access control of a master station and a slave station by transmitting to the network is performed after the master station receives a communication signal indicating that data transmission is desired from the slave station. And after the superframe is transmitted a predetermined number of times after the reception of data from the slave station is completed, the transmission of the superframe is terminated.

In the above-mentioned medium access control method, the superframe is a superframe configured for each predetermined unit of the network topology of the network and is nested in correlation with the network topology. Features.

  According to another aspect of the present invention, there is provided a power line communication method for performing communication via a power line by controlling medium access by a predetermined medium access control method, wherein the predetermined medium access control method is the medium access control described above. It is a method.

  In such a medium access control method, the master station transmits a super frame to the network transmission line as necessary, and terminates transmission as soon as it is no longer necessary. For this reason, communication using another medium access control method can use the time frame during which transmission of this super frame is interrupted, so that it can coexist with other medium access control methods and the communication band is effective. It can be used for. In addition, in such power line communication, this medium access control method is adopted in which superframe transmission is terminated as soon as it is no longer needed, so that leakage radio waves due to superframes can be suppressed.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(Configuration of this embodiment)
FIG. 1 is a diagram illustrating a configuration of a network according to the embodiment. FIG. 2 is a diagram illustrating the configuration of the master station and the slave stations. 2A shows the configuration of the master station, and FIG. 2B shows the configuration of the slave station.

  In FIG. 1, a local area network 201 includes a master station (BST) 1 and a plurality of slave stations (STA) 5, and the master station 1 and the slave stations 5 are connected to each other by a wireless transmission path. To be communicable. The transmission means is, for example, radio waves, microwaves, infrared rays, and laser light. FIG. 1 shows three slave stations 5 including a slave station (STAa) 5-a, a slave station (STAb) 5-b, and a slave station (STAc) 5-c. In addition, when referring generically, it shows with the reference symbol which abbreviate | omitted the suffix, and when referring to an individual structure, it shows with the reference symbol which attached the suffix.

  In the local area network 201, the master station 1 is connected to the external network 202 from the viewpoint of enabling data exchange with the external network. The network 202 is a communication network such as a telephone network, a digital communication network, and a wireless communication network, and data is transmitted using a predetermined communication protocol. The network 202 constitutes the Internet using, for example, Internet protocols such as HTTP (Hyper Text Transfer Protocol), FTP (File Transfer Protocol), and TCP / IP (Transmission Control Protocol / Internet Protocol) as communication protocols.

  The master station 1 is a device that controls transmission to the local area network 201 such as managing transmission rights and transmitting a superframe to the local area network 201 as necessary. For example, as shown in FIG. 2A, the master station 1 includes a master station side communication interface unit 11, a master station side control unit 12, and a master station side storage unit 13.

  The master station side communication interface unit 11 is a circuit that modulates data to be transmitted into a signal format of a communication protocol in the local area network 201 and demodulates a received communication signal into a data format that can be handled by the master station 1.

  The master station side storage unit 13 includes, for example, a nonvolatile storage element such as a ROM (Read Only Memory) or an EEPROM (Electrically Erasable Programmable Read Only Memory), and a volatile storage element such as a RAM (Random Access Memory). It is configured with. The nonvolatile storage element stores various programs for operating the master station 1, information necessary for executing the various programs, and the like. The volatile storage element is a so-called working memory that reads various programs executed by the control unit 12 from the nonvolatile storage element and temporarily stores data during the execution of the various programs. Become. The master station storage unit 13 includes a polling table storage unit (hereinafter abbreviated as “PT storage unit”) 31 that stores a polling table for managing the slave station 5 to which the transmission right is to be given.

  The master station side control unit 12 is configured to include, for example, a microprocessor, and manages transmission rights using a polling table of the PT storage unit 31 and manages superframe transmission based on a program. The master station side control unit 12 functionally includes a superframe management unit (hereinafter abbreviated as “SF management unit”) 21 that manages superframe transmission, and a transmission right management unit 22 that manages transmission rights. And a counter unit 23 for counting the number of times.

  The slave station 5 is a terminal device that transmits and receives data to and from the master station 1. The slave station 5 includes, for example, a slave station side communication interface unit 51, a slave station side control unit 52, and a slave station side storage unit 53, as shown in FIG.

  Similar to the master station side communication interface unit 11, the slave station side communication interface unit 51 modulates the data to be transmitted into a signal format of a communication protocol in the local area network 201, and the slave station 1 can handle the received communication signal. It is a circuit that demodulates the data format.

  The slave station side control unit 52 includes, for example, a microprocessor, and performs communication control of the slave station side communication interface unit 51. The slave station side control unit 52 includes a super frame detection unit (hereinafter abbreviated as “SF detection unit”) 61 that detects the presence or absence of a super frame based on the output of the slave station side communication interface unit 51, and the slave station side. A transmission / reception processing unit 62 that transmits and receives data in the assigned time zone in the superframe using the communication interface unit 51, and a case in which there is data to be transmitted when the superframe does not exist in the local area network 201, A transmission request processing unit 63 that transmits a communication signal (hereinafter, abbreviated as “transmission request signal”) containing information indicating that data transmission is desired is configured.

  The slave station side storage unit 53 includes a nonvolatile storage element that stores various programs for operating the slave station 5 and information necessary for executing the various programs, and a volatile storage that serves as a working memory. It comprises an element.

  Next, the operation of this embodiment will be described.

(Operation of this embodiment)
FIG. 3 is a flowchart showing the operation of the slave station. FIG. 4 is a time chart showing the superframe structure and the communication status between the master station and each slave station in association with each other. 4A shows a superframe structure and a time chart of the master station, FIG. 4B shows a time chart of the slave station a, and FIG. 4C shows a time chart of the slave station b. A chart is shown, and FIG. 4D shows a time chart of the slave station c. FIG. 5 is a flowchart showing the operation of the master station. FIG. 6 is a diagram showing a superframe transmission status in the local net network.

  In FIG. 3, when data to be transmitted is generated, the slave station side control unit 52 of the slave station 5 uses the SF detection unit 61 to determine whether or not a super frame exists in the local area network 201 (S11). ). In this embodiment, the superframe is an IEEE802.11e superframe, as in the background art. 3 and 5, the super frame is abbreviated as “SF”.

  As a result of the determination, if a super frame exists (is present), the slave station side control unit 52 uses the transmission / reception processing unit 62 to transmit data in the same procedure as in the background art (S15).

  In other words, in FIG. 4, when receiving a beacon indicating the start of a superframe transmitted from the master station 1, the slave station side control unit 52 uses the transmission / reception processing unit 62 to request participation in the PFC. A communication signal (association request frame, hereinafter abbreviated as “ASF”) is transmitted to the master station 1 within a predetermined fixed period (ASF period). When the master station side control unit 12 of the master station 1 receives the ASF within the ASF period (time t0 to time t1), which is the acceptance request acceptance period, it uses the transmission right management unit 22 to request the child who wants to participate in the PFC. The station 5 is registered in the polling table of the PT storage unit 31, for example, in the order of ASF reception. In the example shown in FIG. 4, each slave station 5 of the slave station 5-a, the slave station 5-b, and the slave station 5-c transmits an ASF to the master station 1 to participate in the polling list. The management unit 22 registers the slave station 5-a, the slave station 5-b, and the slave station 5-c in this order in the polling table. The beacon is a communication signal for informing the slave station of information necessary for communication using the superframe, such as the size of the superframe, and synchronization in which the master station 1 and the slave station 5 synchronize in communication. It is also a signal.

  The master station 1 uses the SF management unit 21 to send the slave station 5-a to the slave station 5-a according to the registered contents of the polling table after elapse of a predetermined time (time t1 to time t2) called SIFS (Shortest Inter Frame Space). A communication signal (hereinafter abbreviated as “CF-Poll”) containing information indicating that the station 5-a is given the transmission right is transmitted (time t2). When the slave station 5-a receives this CF-Poll, the slave station 5-a uses the transmission / reception processing unit 62-a to recognize that the transmission right has been given to the local station, and receives the CF-Poll reception completion time (time t3). ) After the elapse of SIFS time (time t3 to time t4), an ACK signal (Acknowledge signal, “CF-ACK” in FIG. 4) is transmitted.

  When receiving the data and the ACK signal from the slave station 5-a, the master station 1 uses the SF management unit 21 to send the SIFS time (time t5 to time t6) to the slave station 5-b according to the registered contents of the polling table. ), A CF-Poll that gives a transmission right to the slave station 5-b is transmitted (time t6). When the slave station 5-b receives this CF-Poll, the slave station 5-b recognizes that the transmission right is given to the own station by using the transmission / reception processing unit 62-b, and receives the CF-Poll reception completion time (time t7). ) After SIFS time (time t7 to time t8) elapses, data is transmitted and an ACK signal is transmitted.

  Further, when receiving data and an ACK signal from the slave station 5-b, the master station 1 uses the SF management unit 21 to send the SIFS time (time t9 to time t10) to the slave station 5-c according to the registered contents of the polling table. ), A CF-Poll that gives a transmission right to the slave station 5-c is transmitted (time t10). When the slave station 5-c receives this CF-Poll, the slave station 5-c recognizes that the transmission right is given to the own station by using the transmission / reception processing unit 62-c, and receives the CF-Poll reception completion time (time t11). ) After the elapse of SIFS time (time t11 to time t12), data is transmitted and an ACK signal is transmitted.

  Then, when the master station 1 receives the data and the ACK signal from the slave station 5-c, it uses the SF management unit 21 to grant the transmission right to all the slave stations 5 registered in the polling table. After the elapse of SIFS time (time t13 to time t14), a communication signal (hereinafter abbreviated as “CF-End”) for terminating the PCF is transmitted to each slave station 5 (time t14).

  When the transmission of the CF-End of the master station 1 and the reception of the CF-End of each slave station 5 are finished (time t15), the PCF is finished and DCF is started, and each slave station 5 is controlled by the CSMA / CA method. Communicate with station 1 competitively.

  In this way, the superframe PCF is provided with a plurality of time zones for communicating with the slave stations in accordance with the number of slave stations 5 that desire communication, and each slave station 5 is assigned to its own station. Communicates with the master station 1 in the specified time zone. In the example shown in FIG. 4, the PCF includes three time zones corresponding to three slave stations 5-a, 5-b, and 5-c desired to communicate, a first time zone from time t2 to time t5, A second time zone from time t6 to time t9 and a third time zone from time t10 to time t13 are prepared. The slave station 5-a communicates with the master station 1 using the first time zone assigned to the own station, and the slave station 5-b uses the second time zone assigned to the own station. 1 and the slave station 5-c communicates with the master station 1 using a third time zone assigned to the slave station 5-c. For this reason, the communication of each slave station 5 is guaranteed, the QoS function is achieved, and the communication of high priority data is guaranteed for each slave station 5. For example, communication of data that requires real-time properties such as streaming data is guaranteed.

  Here, when the slave station 5 cannot transmit all the data to be transmitted in the time zone assigned to the PCF of one superframe, it transmits by the DCF following the PCF or the next superframe. Transmit in the time zone assigned to the PCF of the frame. Thus, the master station 1 continues to transmit the superframe until there is no data to be transmitted in each slave station 5, but some of the slave stations 5 should be transmitted before the other slave stations 5. May disappear. In such a case, the slave station 5 having no data to transmit returns only the ACK signal to the master station 1 when receiving the CF-Poll from the master station 1.

  Returning to FIG. 3, if the result of determination in step S11 is that there is no superframe in the local area network 201 (none), the slave station side controller 52 of the slave station 5 sets the transmission request processor 63 to Then, medium access control is performed by the CSMA / CA method, and a transmission request signal is transmitted to the master station 1 to request data transmission (S12). As is well known, the CSMA / CA system transmits data after confirming that a node to which data is to be transmitted continues for a predetermined time or longer and there is no communication signal on the transmission path, and receives an ACK signal from the receiving side. In this method, it is confirmed that the data has been correctly transmitted by reception, and when the ACK signal is not received, the data is retransmitted. The predetermined time, which is the waiting time, is a time obtained by adding a random length of time to the minimum time, and a situation in which a plurality of nodes connected to the transmission path transmit at the same time after the previous communication has occurred. It is time to prevent.

  Then, the slave station side control unit 52 repeats the determination as to whether or not the master station 1 has resumed super frame transmission (S13). In the present embodiment, the slave station side control unit 52 uses the SF detection unit 61 to repeat the determination of whether or not a beacon indicating the start of a superframe has been received.

  In FIG. 5, for example, when the master station side control unit 12 of the master station 1 is arranged and activated in the local area network 201, the master station side control unit 12 is in a reception standby state waiting for reception of a transmission request signal (S31). When the request signal is received, the management of the transmission right by the superframe is started using the SF management unit 21 (S32), and the transmission of the superframe is started (S33).

  Returning to FIG. 3, when the slave station side control unit 52 of the slave station 5 determines that the transmission of the SF is started (restarted) in the process S <b> 13, the slave station side controller 52 transmits the ASF within the ASF period as described above. Data is transmitted using the time zone assigned to the station (S14). When the slave station side control unit 52 has transmitted all the data, the slave station side controller 52 keeps silent or notifies the master station 1 that there is no data to be transmitted to the slave station 5, or a communication signal indicating that all data has been transmitted. To the master station 1. In the present embodiment, the slave station side control unit 52 uses the transmission / reception processing unit 62 to return only the ACK signal in response to the reception of CF-Poll transmitted from the master station 1 in the PCF.

  Returning to FIG. 5, the master station side control unit 12 of the master station 1 uses the SF management unit 21 to finish receiving data from all the slave stations 5 registered in the polling table of the PT storage unit 31. Whether or not (S34). This determination is made in the superframe according to the present embodiment based on whether or not only ACK signals have been received from all the slave stations 5 for the CF-Poll in the PCF. If it is determined that only the ACK signal is received from all the slave stations 5, it is determined that all the slave stations 5 registered in the polling table of the PT storage unit 31 have no data to be transmitted in the slave station 5, It is determined that the reception of data from the slave station 5 has been completed.

  As a result of the determination, if the data reception has not ended (No), the master station side control unit 12 transmits a superframe using the SF management unit 21 (S40), and executes the process S34. That is, the master station 1 continues to transmit the superframe continuously while the data reception is not completed. On the other hand, when the reception of the data is completed as a result of the determination (Yes), the master station side control unit 12 initializes the count variable to “0” by using the counter unit 23, and Counting of the number of transmissions is started (S35). The count variable is a variable for counting the number of superframe transmissions.

  Using the SF management unit 21, the master station side control unit 12 transmits a super frame to the local area network 201 and counts up the count variable (S36). Next, the master station side control unit 12 determines whether or not there is a transmission request from the slave station 5 in the transmission request reception time zone (S37). This determination is made based on whether or not the ASF is received from the slave station 5 within the ASF period in the superframe in the present embodiment. When the master station 1 receives the ASF from the slave station 5, it determines that there is a transmission request. Note that it may be determined that there is a transmission request also when a transmission request signal is received.

  As a result of the determination, if there is a transmission request (present), the master station side control unit 12 uses the SF management unit 21 to send the slave station 5 that has requested transmission to the polling table of the PT storage unit 31 as described above. Is communicated with the slave station 5 using the superframe PCF and DCF (S41), and the process returns to the process S34.

  On the other hand, if the result of the determination is that there is no transmission request (none), the master station side control unit 12 determines whether or not the counter unit 23 has counted out (S38). As a result of the determination, if the count-out has not been performed (No), the master station-side control unit 12 returns the process to step S36. If the count-out has been performed (Yes), the master station-side control unit 12 has By stopping the transmission of the superframe to the local area network 201, the transmission right management by the superframe is interrupted (S39), and the process returns to the process S31. That is, until the counter unit 23 counts out, even after data reception is completed, the superframe is periodically transmitted to the local area network a predetermined number of times, and transmission right management by the superframe cycle is continued. When the counter unit 23 counts out, superframe transmission is stopped, and transmission right management by the superframe cycle is interrupted until a transmission request signal is received.

  It should be noted that the number of times until the counter unit 23 counts out is appropriately set to, for example, 2, 3, or 5, and the superframe is only this number of times after the data reception from the slave station 5 is completed. It is transmitted periodically and repeatedly. If this number is large, the slave station 5 can immediately transmit data by transmitting an ASF within the ASF period of the superframe without transmitting a transmission request signal, while the superframe cycle is interrupted. Will be pressed. For this reason, the number of times is appropriately designed, for example, in consideration of a balance between the communication frequency of the slave station 5 and the efficient use of the communication band and the leaked radio wave due to the superframe. In this embodiment, it is set to twice.

  For example, in FIG. 6, when the slave station (STAa) 5-a desires to transmit data while the transmission right management by the superframe cycle is interrupted, first, in steps S11 and S12, The station 5-a transmits a transmission request signal to the local area network 201 by the CSMA / CA method. The master station (BST) 1 that has received this transmission request signal through steps S31 to S34 and step S40 resumes superframe transmission in order to resume management of transmission rights in the superframe cycle. That is, in the superframe method of this embodiment, a beacon is transmitted. The master station 1 receives the ASF transmitted as necessary from the slave station 5 that has received the beacon, registers the slave station 5 that has transmitted the ASF in the polling table, assigns a time zone to the PCF, and Send a poll. Then, by processing S13 and processing S14, the slave station 5-a receives the CF-Poll, and transmits data using the time zone assigned to the local station in the superframe PCF.

  When the data transmission is completed, the master station 1 stores only the data for managing the transmission right until the counter unit 23 starts counting the superframe and counts it out. An empty super frame with no data is transmitted to the local area network 201. If there is no transmission request from the slave station 5 during this period, super frame transmission is stopped and transmission right management by the super frame cycle is interrupted.

  Then, when data to be transmitted is generated to the slave station (STAc) 5-c, the slave station 5-c transmits a transmission request signal to the local area network 201 by the CSMA / CA method through the processes S11 and S12. The master station 1 that has received the transmission request signal through the processing S31 to S34 and the processing S40 starts transmission of a super frame, and receives the ASF from the slave station 5-c, whereby the slave station 5-c is added to the polling table. , Assign a time zone to the PCF, and send CF-Poll. Then, the slave station 5-c receives the CF-Poll through the processes S13 and S14, and transmits data using the time zone assigned to the own station in the PCF.

  When the data transmission is completed, the master station 1 transmits an empty superframe to the local area network 201 until the counter unit 23 starts counting the superframe and counts out by the processes S35 to S39. When there is no transmission request from the station 5, the transmission of the superframe is stopped, and the transmission right management by the superframe cycle is interrupted.

  As described above, in the medium access control using the superframe method according to the present embodiment, the master station 1 normally suspends superframe transmission, interrupts the management of transmission rights by the superframe cycle, and sends a transmission request from the slave station 5. Wait for the signal to resume superframe transmission. For this reason, communication using another medium access control method can use the interruption period during which transmission of the superframe is interrupted, so that it can coexist with other medium access control methods, and communication bandwidth is effective. It can be used for. In addition, since the superframe is transmitted a predetermined number of times after the transmission of the actual data from the slave station 5, the slave station 5 that intends to transmit data during this time is immediately given a transmission right and transmits the data. Can do. Furthermore, by applying such medium access control using superframes to power line communication, transmission of superframes is terminated as soon as they are no longer needed, so that leakage radio waves due to superframes can be suppressed.

  In the above description, when there is data to be transmitted from the master station 1 to the slave station 5, if the transmission right by the superframe cycle is managed, the superframe to be transmitted is used or the transmission right by the superframe cycle is used. The master station 1 embeds the data to be transmitted in the CF-Poll in the PCF and transmits it using the superframe in which transmission is resumed when the management of the communication is interrupted, or competes by the CSMA / CA method in the DCF The data is transmitted to the slave station 5 through communication.

  Next, a case where medium access control using such a superframe is applied to power line communication will be described.

  In power line communication, since the power line is used, firstly, the transmission environment is affected by noise generated by the electric / electronic device connected to the power line and the decrease in impedance of the power line due to the connection of the electric / electronic device. Deteriorates, the communication error rate increases, and in some cases, communication is impossible. The transmission environment changes dynamically depending on the connection status (plug / unplug) of the electrical / electronic device to the power line and the operating status of the electrical / electronic device. As a result, the availability of communication also changes dynamically. End up. Second, since the power line is generally branched from the distribution board to each outlet, the actual wiring length of the power line may become long even if the slave stations that communicate with each other can be seen. . For this reason, as a result of an increase in the attenuation amount of the transmission / reception signal, a sufficient strength (reception level) for reception cannot be obtained and communication is impossible. Further, thirdly, since power is generally supplied by a single-phase three-wire system including one neutral line N and two voltage lines L1 and L2 having a potential difference of 100 V from the neutral line N, the power line is divided. The branch from the panel to each outlet is 100V between the neutral line N and the voltage line L1, 100V between the neutral line N and the voltage line L2, and between the voltage line L1 and the voltage line L2. It is connected by any one of three combinations of 200V. For this reason, the slave stations connected to the outlet may be connected to different phases, and as a result, communication becomes impossible. For this reason, in power line communication, a relay station that relays communication signals is often arranged in a network.

  FIG. 7 is a diagram illustrating a network configuration in the case of power line communication according to the embodiment. In FIG. 7, the network 203 in the case of power line communication includes a master station (BST) 1, a plurality of slave stations (STA) 5, and one or a plurality of relay stations (RPT) 6. In the local area network 201, the master station 1 is connected to the external network 202 from the viewpoint of enabling data exchange with an external network.

  FIG. 7 includes a slave station (STAaa) 5-aa, a slave station (STAab) 5-ab, a slave station (STAac) 5-ac, a slave station (STAba) 5-ba, a slave station (STAbb) 5-bb, Slave station (STAbc) 5-bc, Slave station (STAca) 5-ca, Slave station (STAcb) 5-cb, Slave station (STAcc) 5-cc, Slave station (STAda) 5-da, Slave station (STAdb) 12 slave stations 5 of 5-db and slave station (STAdc) 5-dc are shown, and relay station (RPTa) 6-a, relay station (RPTb) 6-b, and relay station (RPTc) 6-c Three relay stations 6 are shown.

  The master station 1, the slave station 5, and the relay station 6 are divided into three slave stations 5-aa, a slave station 5-ab, a slave station 5-ac, and two relay stations 6-a and 6 The relay station 6-b is connected via a power line, and the relay station 6-a is connected to three slave stations 5-ba, a slave station 5-bb, and a slave station 5-bc via a power line. Three slave stations 5-da, a slave station 5-db, a slave station 5-dc, and one relay station 6-c are connected to the station 6-b through a power line, respectively. Each of the slave stations 5-ca, the slave station 5-cb, and the slave station 5-cc are connected via a power line, and constitute a tree structure having the master station 1 as a root as a network topology. The relay station 6-a, the slave station 5-ba, the slave station 5-bb, and the slave station 5-bc constitute a sub-network 301, and the relay station 6-c, the slave station 5-ca, and the slave station 5-bc. cb and the slave station 5-cc constitute a subnetwork 303, and the relay station 6-b, the slave station 5-da, the slave station 5-db, the slave station 5-dc, and the subnetwork 303 constitute a subnetwork 302. To do.

  In the master station 1 and the slave station 5, the master station side communication interface unit 11 and the slave station side communication interface unit 51 correspond to power line communication, but the configuration is the same as that described above with reference to FIG. Since there is, explanation is omitted.

  The relay station 6 is a node that relays communication signals between the master station 1 and the slave station 5 or another relay station 6. The relay station 6 operates in the same manner as the master station 1 with respect to the slave station 5 and the relay station 6 (downstream relay station 6) in the subnetwork. That is, when the relay station 6 receives a transmission request signal from within the subnetwork, the relay station 6 manages the transmission right of the slave station 5 and the relay station 6 within the subnetwork by transmitting a superframe within the subnetwork. When the communication with the slave station 5 and the relay station 6 is completed, the superframe transmission is interrupted after transmitting the superframe a predetermined number of times. The relay station 6 operates in the same manner as the slave station 5 with respect to the master station 1 and the upstream relay station 6. That is, when data to be transmitted to the master station 1 is received from the slave station 5 and the relay station 6 in the sub-network, it is detected whether or not a super frame is transmitted from the master station 1 and the upstream relay station 6. When the transmission of the superframe is interrupted, the transmission request signal is transmitted to the master station 1 and the upstream relay station 6, and when the transmission of the superframe is resumed, the time zone allocated to the own station Send data using.

  Therefore, the relay station 6 includes a relay-station-side communication interface unit (not shown) for the sub-network and a relay-station-side communication interface unit for the outside of the sub-network, similar to the master-station-side communication interface unit 11 and the slave-station-side communication interface unit 51. (Not shown), a relay station side control unit (not shown) for the same subnetwork as the master station side control unit 12, and a relay station side control unit for the outside the subnetwork (not shown) similar to the slave station side control unit 52 1), a first relay station side storage unit (not shown) for the relay station side control unit for in-subnetwork similar to the master station side storage unit 13, and the same outside of the subnetwork as for the slave station side storage unit 53 And a second relay station side storage unit (not shown) for the relay station side control unit.

  In the tree structure having the parent station 1 as a root, the parent station 1 side is referred to as an upstream side, and the terminal side of the tree structure is referred to as a downstream side.

  For example, the slave stations 5-aa, 5-ab, and 5-ac that can directly communicate with the master station 1 operate in the same manner as the slave stations 5-a and 5-c described above, so that the master station 1 to communicate.

  Also, for example, in the slave stations 5-ba, 5-bb, 5-bc that can communicate indirectly with the master station 1 via the relay station 6-a, the transmission right management by the superframe cycle is suspended. When these slave stations 5-ba, 5-bb, 5-bc, for example, the slave station 5-bb wants to transmit data, first, the slave station 5-bb transmits a transmission request signal by the CSMA / CA method. Is transmitted to the sub-network 301. Receiving this transmission request signal, the relay station 6-a resumes superframe transmission in order to resume transmission right management by the superframe cycle. The relay station 6-a registers the slave station 5 that has transmitted the ASF in the polling table by receiving the ASF transmitted as necessary from the slave station 5 that has received the beacon, and assigns a time zone to the PCF. Send CF-Poll. Then, the slave station 5-bb receives the CF-Poll and transmits data using the time zone assigned to the own station in the PCF of the superframe. On the other hand, when data is received from the slave station 5 in the sub-network 301 while the transmission right management by the superframe cycle is interrupted, the relay station 6-a sends a transmission request signal by the CSMA / CA method. Transmit to the local area network 203. Receiving this transmission request signal, the master station 1 resumes superframe transmission in order to resume transmission right management by the superframe cycle. The master station 1 receives the ASF transmitted from the relay station 6-a that has received the beacon and the slave stations 5-aa, 5-ab, and 5-ac as necessary, thereby transmitting the relay station 6 that has transmitted the ASF. The slave station 5 is registered in the polling table, the time zone is assigned to the PCF, and the CF-Poll is transmitted. The relay station 6-a receives the CF-Poll and transmits data using the time zone assigned to the own station in the superframe PCF.

  When the transmission of data in the slave station 5 in the subnetwork 301 is completed, the relay station 6-a transmits an empty superframe to the subnetwork 301 until the counter unit 23 starts counting the superframe and counts out. During this time, if there is no transmission request from the slave station 5 in the sub-network 301, the superframe transmission is stopped, and the transmission right management by the superframe cycle is interrupted.

  Also, for example, in the slave stations 5-ca, 5-cb, 5-cc that can communicate indirectly with the master station 1 via the relay station 6-c and the relay station 6-b, the transmission right is managed by the superframe cycle. If the slave stations 5-ca, 5-cb, 5-cc, for example, the slave station 5-cc, wants to transmit data while the slave station 5-cc is interrupted, first, the slave station 5-cc A transmission request signal is transmitted to the subnetwork 303 by the CA method. The relay station 6-c that has received this transmission request signal resumes superframe transmission in order to resume transmission right management in the superframe cycle. The relay station 6-c receives the ASF transmitted from the slave stations 5-ca, 5-cb, and 5-cc that have received the beacon as necessary, thereby making the polling table indicate the slave station 5 that has transmitted the ASF. Register, assign time zone to PCF, and send CF-Poll. Then, the slave station 5-cc receives the CF-Poll and transmits data using the time zone assigned to the own station in the PCF of the superframe. On the other hand, when data is received from the slave station 5 in the subnetwork 303 while the transmission right management by the superframe cycle is interrupted, the relay station 6-c transmits a transmission request signal by the CSMA / CA method. Transmit to sub-network 302. The relay station 6-b that has received this transmission request signal resumes superframe transmission in order to resume transmission right management by the superframe cycle. The relay station 6-b receives the ASF transmitted from the relay station 6-c and the slave stations 5-da, 5-db, and 5-dc that have received the beacon as necessary, thereby transmitting the ASF. The station 6-c and the slave station 5 are registered in the polling table, a time zone is assigned to the PCF, and CF-Poll is transmitted. Then, the relay station 6-c receives the CF-Poll and transmits data using the time zone assigned to the own station in the PCF of the superframe. The relay station 6-b that has received data from the relay station 6-c relays the data to the master station 1 by operating in the same manner. By operating in this way, the data transmitted by the slave station 5-cc is relayed by the relay station 6-c and the relay station 6-b and transmitted to the master station 1.

  When the transmission of data in the slave station 5 in the subnetwork 303 is completed, the relay station 6-c transmits an empty superframe to the subnetwork 303 until the counter unit 23 starts counting the superframe and counts out. During this time, if there is no transmission request from the slave station 5 in the sub-network 303, the transmission of the superframe is stopped, and the management of the transmission right by the superframe cycle is interrupted.

  As described above, when the medium access control by the superframe method in the present embodiment is applied to the power line communication, in addition to coexistence with other medium access control methods and effective use of the communication band, the superframe will be used as soon as it becomes unnecessary. Therefore, leakage of radio waves due to the superframe can be suppressed.

  In the above-described embodiment, the super station is configured to transmit the superframe a predetermined number of times after the transmission of the actual data from the slave station 5 from the viewpoint of enabling the slave station 5 to transmit the data quickly. However, from the viewpoint of further utilizing the communication band and suppressing the leaked radio wave, transmission of the superframe may be interrupted as soon as the transmission of the actual data from the slave station 5 is completed.

  The relay station 6 according to the above-described embodiment operates in the same manner as the master station 1 with respect to the slave station 5 and the relay station 6 (downstream relay station 6) in the subnetwork. The upstream relay station 6 is a regenerative relay station that operates in the same manner as the slave station 5. However, after the communication signals from the slave station 5 and the relay station 6 in the subnetwork are amplified, the master station 1 and An amplification relay station that transmits to the upstream relay station 6 and amplifies the communication signal from the master station 1 and the upstream relay station 6 and then transmits the amplified signal to the slave station 5 and the relay station 6 in the subnetwork may be used. .

  In the above-described embodiment, the super frame is configured to include the PCF and the DCF. However, the super frame may be a PCF-only super frame.

  Furthermore, the downlink time zone for performing downlink (Down-Link) communication, the uplink time zone for performing uplink (Up-Link) communication, and the slave station 5 request the start of transmission. A superframe consisting of a transmission request reception time zone for requesting transmission in each case is configured for each predetermined unit of the network topology, and a superframe in which these are nested in correlation with the network topology It may be used. Here, the downlink is communication from the upstream side to the downstream side, that is, communication from the master station 1 to the slave station 5 and the relay station 6, and the uplink is communication from the downstream side to the upstream side, that is, Communication from the slave station 5 and the relay station 6 to the master station 1.

  FIG. 8 is a diagram showing the structure of another super frame. For example, in the local area network 203 having a tree structure shown in FIG. 7, as shown in FIG. 8, first, three slave stations 5-ca, slave stations 5-cb, and slave stations connected to the relay station 6-c are connected. A super frame (SF of RPT-c) of the relay station 6-c is configured for 5-cc. Nesting the superframe of this relay station 6-c, the relay station 6-c connected to the relay station 6-b and the three slave stations 5-da, the slave station 5-db, and the slave station 5-dc Therefore, a super frame (SF of RPT-b) of the relay station 6-b is formed, and three slave stations 5-ba, slave stations 5-bb, and slave stations 5 connected to the relay station 6-a are formed. A superframe (SF of RPT-a) of the relay station 6-a is configured for -bc. Then, the superframe of the relay station 6-a and the superframe of the relay station 6-b are nested, and the relay station 6-a, the relay station 6-b, and the three slave stations 5 connected to the master station 1 are nested. A super frame (SF of BST) of the master station 1 is configured for -aa, the slave station 5-ab, and the slave station 5-ac.

  When the slave station 5 transmits data in the superframe having such a structure, the superframe of the relay station 6 positioned immediately above the network topology with respect to the slave station 5 in the superframe cycle flowing in the network. The transmission request is requested in the transmission request reception time zone, and this sequentially reaches the master station 1 by going back in the superframe nesting structure. The master station 1 that has received the request for transmission request registers the request for transmission in the managed polling table, and assigns a time zone for the slave station 5 to transmit to the uplink time zone in the superframe. The slave station 5 transmits data to the master station using the allocated uplink time zone.

It is a figure which shows the structure of the network which concerns on embodiment. It is a figure which shows the structure of a master station and a slave station. It is a flowchart which shows operation | movement of a sub_station | mobile_unit. 3 is a time chart showing the superframe structure and the communication status between the master station and each slave station in association with each other. It is a flowchart which shows operation | movement of a master station. It is a figure which shows the transmission condition of the super frame in a local net network. It is a figure which shows the structure of the network in the case of the power line communication which concerns on embodiment. It is a figure which shows the structure of another super frame.

Explanation of symbols

1 master station 5 slave station 6 relay station 11 master station side communication interface unit 12 master station side control unit 13 master station side storage unit 21 superframe management unit 22 transmission right management unit 23 counter unit 31 polling table storage unit 51 slave station side Communication interface unit 52 Slave station side control unit 53 Slave station side storage unit 61 Super frame detection unit 62 Transmission / reception processing unit 63 Transmission request processing unit 201, 203 Local area network 202 Networks 301, 302, 303 Subnetwork

Claims (3)

A medium that performs medium access control of the master station and the slave station by repeatedly transmitting a super frame having a plurality of time zones for communicating with the slave station in accordance with the number of slave stations that desire communication. In the access control method,
The master station transmits the super frame to the network after receiving a communication signal indicating that data transmission is desired from the slave station, and transmits the super frame a predetermined number of times after reception of data from the slave station is completed. A medium access control method comprising: terminating transmission of the superframe after transmission. The medium according to claim 1 , wherein the superframe is a superframe constructed by correlating the superframe configured for each predetermined unit of the network topology of the network with the network topology. Access control method. In a power line communication method of performing communication via a power line by controlling medium access by a predetermined medium access control method,
The power access communication method according to claim 1, wherein the predetermined medium access control method is the medium access control method according to claim 1.

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