JP4749840B2 - Communication apparatus and communication method - Google Patents

Description

  The present invention relates to a communication apparatus and a communication method capable of multicast communication with a plurality of communication apparatuses.

  For example, when performing wired data communication at home, office, factory, etc. using a terminal such as a computer, it is usually necessary to lay wiring such as cables and connectors used as transmission paths where necessary Therefore, various constructions must be performed before the start of operation of the communication equipment.

  On the other hand, most of the homes, offices, factories and the like use a commercial power supply, for example, AC 100V (50/60 Hz), so that a power line (electric light line) for supplying this power is in the home, office, Already laid in every part of the factory. Therefore, if these power lines can be used for data communication, it is not necessary to newly provide a special wiring for communication. That is, it is possible to secure a communication path simply by inserting the communication device into a power outlet.

  As a power line communication technique (PLC: Power Line Communication) using such a power line for communication, for example, a technique disclosed in Patent Document 1 is known.

  Further, for example, Patent Document 2 discloses a method for multiple access and transmission in a point-to-multipoint system on a power line network.

JP 2000-165304 A JP-T-2004-531944

  A power line as a transmission line used for power line communication is not stable in communication transmission characteristics. Therefore, a unicast communication method according to the state of the transmission line between communication devices is used. On the other hand, since data communication using a multicarrier communication method such as IPTV (Internet Protocol TV) is expected to spread in the future, it is desired to support multicast communication in power line communication.

  In current power line communication, a broadcast communication method using a modulation method that is sufficiently resistant to transmission path fluctuations is used for control signals and the like. However, there is a situation in which it is difficult to obtain a sufficient transmission rate for data communication in the modulation method used for transmission of such control signals.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a communication device and a communication method capable of efficiently distributing data for multicast communication.

A first aspect of the present invention is a communication device capable of transmitting data to a plurality of receiving side communication devices, and at least receiving information indicating each receiving state from the plurality of receiving side communication devices to be subjected to multicast communication. A reception information acquisition unit for acquiring transmission data, a transmission processing unit for determining a transmission method of transmission data for multicast communication for the plurality of reception side communication devices based on the reception information acquired by the reception information acquisition unit, The transmission processing unit determines a transmission method adapted to a reception state having the worst characteristics among the reception states indicated by the acquired reception information as a transmission method using the multicast communication , and further On the basis of the received information, each receiving side communication when the transmission data is transmitted to the plurality of receiving side communication devices by a transmission method using unicast communication. Calculates the unicast transmission rate for the device and the multicast transmission rate for transmission using the transmission method using the multicast communication, and is the greater of the minimum value of the unicast transmission rate and the multicast transmission rate the transmission scheme, the multicast that determine the transmission method of the transmission data for communication the communication device is intended to be provided.

With this configuration, communication is performed using the transmission method determined based on the reception state in the reception-side communication device, so that data for multicast communication can be distributed efficiently. With this configuration, it is possible to perform multicast communication in which data can be received in all target receiving-side communication devices. With this configuration, since data is transmitted by selecting multicarrier communication and unicast notification, multicast data can be efficiently distributed according to the transmission path state.

The present invention, in the second, a communication apparatus according to the first, between the receiving communication device is intended to multicarrier communication scheme is used, the transmission processing unit, at least one sub For each subcarrier group including a carrier, a modulation scheme adapted to the reception state having the worst characteristics among the reception states indicated by the acquired reception information is assigned.

  With this configuration, in the multicarrier communication system, all of the target receiving communication devices can receive data, and multicast communication can be performed efficiently.

Third , the communication device according to the second , wherein the transmission processing unit calculates a transmission rate of each of the plurality of reception-side communication devices based on the acquired reception information, The distribution of the transmission band allocated to each of the receiving side communication devices is determined so that each of the transmission speeds is equal to or higher than a predetermined speed threshold, and the unicast transmission speed is determined based on the determined distribution. calculate.

  With this configuration, the transmission method is determined on the condition that the transmission rate equal to or higher than the speed threshold is satisfied. For example, the transmission rate required for data distribution for multicast communication is guaranteed, and the efficiency according to the transmission path state is guaranteed. Delivery is possible.

The present invention, in the fourth, a communication device according to the third, the transmission processing section, when determining the transmission method using the multicast communication as the transmission method of the transmission data, multicast communication starts after When the transmission rate of each receiving-side communication device is calculated using the acquired reception information and the retransmission rate, and the transmission rate is less than the speed threshold, The transmission data is multicast-unicast converted and transmission of the transmission data is started using a transmission method using unicast communication.

  With this configuration, when retransmissions frequently occur, data distribution according to the transmission path state can be performed by switching to an appropriate communication method.

The present invention, in the fifth, the first to fourth of a communication apparatus according to any one, the transmission processing unit, the transmission method of the transmission scheme the transmission data using the multicast communication When the transmission rate is determined, the unicast communication is performed with respect to each receiving-side communication device to measure the retransmission rate. When each retransmission rate is a predetermined value or less, the transmission data is transmitted using the determined transmission method. To start.

  With this configuration, multicast data can be efficiently distributed according to the transmission path state by performing multicast communication on the transmission path where retransmissions do not occur frequently.

The present invention, in the sixth, a communication apparatus according to any one of the first to fourth, the transmission processing unit to determine the transmission method using the multicast communication as the transmission method of the transmission data A reception state indicated by the reception information of each reception side communication device by performing unicast communication with respect to each reception side communication device, acquiring reception information of each reception side communication device multiple times from the reception information acquisition unit When the fluctuation range is less than or equal to a predetermined value, transmission of the transmission data is started using the determined transmission method.

  This configuration tends to increase retransmissions when the reception state of the receiving-side communication device is severely changed, so that multicast communication is performed on a transmission path that is assumed to have few retransmissions by observing fluctuations in the reception state. Thus, multicast data can be efficiently distributed according to the transmission path state.

The present invention, in the seventh, there is provided a communication apparatus according to any one of the above first to sixth, wherein the transmission processing unit, using the multicast communication to the plurality of receiving communication device When transmission is performed using a predetermined transmission method, each transmission rate of the receiving-side communication device is calculated based on the acquired reception information, and all the calculated transmission rates are equal to or greater than a predetermined value. For example, the predetermined transmission method is determined as a transmission method of the transmission data.

  With this configuration, for example, multicast communication is first performed by a communication method capable of exhibiting a transmission rate sufficient for data communication of multicast communication to be distributed. If the reception state is good, data distribution by multicast communication is performed by the communication method. By doing so, data communication can be performed without performing complicated processing.

The present invention, in the eighth, there is provided a communication apparatus as claimed in any one of the first to seventh, the transmission processing section, when the retransmission from the receiving-side communication apparatus is requested, unicast A transmission method using communication is determined as a transmission method of data for which retransmission is requested.

  With this configuration, data that needs to be retransmitted is transmitted by unicast communication, so that it is transmitted in a communication method that matches the reception state of only the target receiving communication device, so retransmission data is efficiently transmitted be able to.

The ninth aspect of the present invention is the communication apparatus according to the eighth aspect , wherein the transmission processing unit concatenates data requested to be retransmitted within a predetermined period.

  With this configuration, redundant signals to be added to the packet in addition to the data such as the preamble signal and the control signal are reduced in total, so that the use efficiency of the transmission path at the time of retransmission can be improved.

The present invention, in the tenth, there is provided a communication apparatus according to any one of the first to ninth, the transmission processing unit further plurality of receiving communication apparatuses of the group to be multicast communication The transmission data transmission method is determined for each of the subgroups.

  With this configuration, since the transmission method is determined for each subgroup, when there are a large number of receiving side communication devices, for example, multicast communication and unicast communication can be used in combination for each subgroup. Data can be distributed.

The present invention, in the eleventh, a communication apparatus according to any one of the first to tenth, the transmission path for performing communication between the receiving communication device is a power line.

  With this configuration, data for multicast communication can be efficiently distributed in a power line communication system using a power line as a transmission path.

The present invention, in the twelfth, a communication method of transmitting communication device capable of data to a plurality of receiving communication apparatuses, the reception state of each of a plurality of receiving communication device to be at least the multicast communication And a step of determining a transmission method of transmission data for multicast communication for the plurality of receiving-side communication devices based on the acquired reception information. A transmission method adapted to a reception state having the worst characteristics among the reception states indicated by the reception information is determined as a transmission method using the multicast communication , and further, based on the acquired reception information, the plurality of reception sides Unicast transmission rate for each receiving-side communication device when the transmission data is transmitted to the communication device by a transmission method using unicast communication , Calculating a multicast transmission rate in the case of transmitting by the transmission method using the multicast communication, and selecting the larger one of the minimum value of the unicast transmission rate and the multicast transmission rate as the multicast transmission rate. A communication method for determining a transmission method of transmission data for communication is provided.

By this method, communication is performed using the transmission method determined based on the reception state in the reception-side communication device, so that data for multicast communication can be efficiently distributed. Furthermore, the present invention provides, in a thirteenth aspect , a communication device capable of transmitting data to a plurality of receiving communication devices, and at least receiving states from the plurality of receiving communication devices that are targets of multicast communication. A reception information acquisition unit for acquiring reception information, and a transmission process for determining a transmission method of transmission data for multicast communication for the plurality of reception side communication devices based on the reception information acquired by the reception information acquisition unit And the transmission processing unit performs transmission based on the acquired reception information when transmitting to the plurality of receiving side communication devices using a predetermined transmission method using multicast communication. Each transmission speed of the communication apparatus on the side is calculated, and if all the calculated transmission speeds are equal to or higher than a predetermined value, the predetermined transmission method is determined as a transmission method of the transmission data. In which that communication device is provided.

  According to the present invention, it is possible to provide a communication device and a communication method capable of efficiently distributing data for multicast communication.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, as an example of the communication apparatus, a communication apparatus configured as a modem (PLC modem) that uses a power line as a transmission line and performs broadband communication (2 to 30 MHz) of a multicarrier communication method will be described as an example. To do.

  FIG. 1 is a block diagram showing an outline of a communication system according to an embodiment of the present invention. As shown in FIG. 1, the communication system of this embodiment includes a server 500 that distributes data and receiving terminals 600A and 600B that receive data distributed from the server.

  Server 500 and receiving terminals 600A and 600B are connected via power line PL. Communication device 100X, which is an example of a transmission side communication device, is connected between server 500 and power line PL, and communication, which is an example of a reception side communication device, between power line PL and reception terminals 600A and 600B, respectively. Devices 100A and 100B are connected.

  The server 500 and the communication device 100X are connected by a communication line 501 such as a coaxial cable, for example, and communication is performed using a communication method such as Ethernet (registered trademark). Communication device 100X sends data output from server 500 to power line PL, and outputs data received from power line PL to server 500.

  The communication device 100A and the receiving terminal 600A, and the communication device 100B and the receiving terminal 600B are connected by communication lines 601A and 601B such as coaxial cables, respectively, for example, communication such as Ethernet (registered trademark). Communication is performed using a method. Communication devices 100A and 100B output data received from power line PL to receiving terminals 600A and 600B, respectively, and send data output from receiving terminals 600A and 600B to power line PL.

  Note that a path between the communication apparatus 100X and the communication apparatus 100A is a transmission path XA, and a path between the communication apparatus 100X and the communication apparatus 100B is a transmission path XB.

  FIG. 2 is a conceptual diagram illustrating multicast communication and unicast communication. FIG. 2A illustrates unicast communication, and FIG. 2B illustrates multicast communication. Unicast communication is a method in which individual computers perform data communication on a one-to-one basis. Multicast communication is a method in which addresses for identifying individual computers are grouped and data is distributed to a plurality of grouped terminals. is there.

  Here, in the example shown in FIG. 2, a case where the same data is transmitted from the server 500 to the receiving terminals 600A and 600B will be described.

  As shown in FIG. 2A, in the case of performing unicast communication, a data frame of a UC signal [A] that is a unicast signal addressed to receiving terminal 600A and a UC that is a unicast signal addressed to receiving terminal 600B. It is necessary to transmit the data frame of the signal [B] separately.

  On the other hand, as shown in FIG. 2B, when performing multicast communication, only the data frame of the MC signal [AB], which is a multicast signal destined for both of the receiving terminals 600A and 600B, is transmitted. 600A and 600B receive the data frame of the same MC signal [AB].

  In this way, in unicast communication, it is necessary to perform transmission using bands separately for receiving terminal 600A and receiving terminal 600B. On the other hand, in multicast communication, it is only necessary to transmit the same data frame to the receiving terminals 600A and 600B. Therefore, it is sufficient to use a band for transmission to one receiving terminal. That is, as is clear from comparison between FIG. 2A and FIG. 2B, when multicast communication is used, data transmission to the two receiving terminals 600A and 600B uses unicast communication. Compared to half the time.

  Therefore, when data is transmitted from the server 500 to the two receiving terminals 600A and 600B, the entire transmission capacity between the server 500 and the receiving terminals 600A and 600B when performing multicast communication is unicast communication. Half of the transmission capacity will be enough. Thus, by using multicast communication, when distributing the same data to a plurality of computers, the load on the server and the network can be reduced.

  By the way, the power line PL has an unstable transmission path state, and its characteristics fluctuate depending on time and distance. 3A and 3B are diagrams illustrating an example of transmission path characteristics in the power line. FIG. 3A illustrates transmission path characteristics of the transmission path XA, and FIG. 3B illustrates transmission path characteristics of the transmission path XB. FIG. 4 is a diagram illustrating an example of noise characteristics in the power line. FIG. 4A illustrates the noise characteristics of the transmission path XA, and FIG. 4B illustrates the noise characteristics of the transmission path XB. Further, FIG. 5 is a diagram illustrating an example of noise characteristics of a received signal in a communication device on the receiving side, FIG. 5A is a communication device 100A, and FIG. 5B is an average CINR of received signals in the communication device 100B. is there.

  As shown in FIGS. 3A and 3B, the transmission path XA and the transmission path XB have different impulse responses, gain frequency characteristics, and group delay (group delay) frequency characteristics. Also, as shown in FIGS. 4A and 4B, the transmission path XA and the transmission path XB have different noise characteristics.

  Thus, since the transmission path characteristics (frequency characteristics and noise characteristics) differ depending on the transmission path, as shown in FIGS. 5A and 5B, the CINR of the received signal in the communication devices 100A and 100B Received signal characteristics such as (Carrier to Interference and Noise Ratio) also differ.

  In multicast communication, data is transmitted to a plurality of receiving communication devices in one data frame to be transmitted. Therefore, data cannot be received correctly by the receiving communication device connected to a transmission path having a poor transmission path state, or conversely. If data is transmitted using a transmission system that is resistant to noise, the transmission capacity may be reduced more than necessary, and efficient transmission may not be possible.

  Therefore, in the communication device 100A according to the embodiment of the present invention, the reception information indicating each reception state is acquired from at least the communication devices 100A and 100B of the group to be subjected to multicast communication, and based on the reception state indicated by the reception information. Thus, the transmission method of transmission data for multicast communication for the communication devices 100A and 100B is determined. Therefore, data for multicast communication can be efficiently distributed according to the transmission path state of each transmission path. Here, in this embodiment, the transmission method includes all data transmission methods for the communication device on the receiving side, and includes communication methods such as broadcast communication, multicast communication, and unicast communication, modulation method, multiplexing method, and the like.

  6 is a block diagram showing a schematic configuration of a communication apparatus according to an embodiment of the present invention, FIG. 7 is a block diagram showing a schematic configuration of a receiving unit in the communication apparatus according to the embodiment of the present invention, and FIG. 8 is an implementation of the present invention. It is a block diagram which shows schematic structure of the transmission part in the communication apparatus which concerns on a form.

  As illustrated in FIG. 7, the communication device 100 </ b> X includes a reception unit 10 that functions as an example of a reception information acquisition unit, a transmission unit 20, and a transmission processing unit 30. The communication device 100 </ b> A includes a receiving unit 10, a transmitting unit 20, a CNR measuring device 50, and a transmission path estimator 60. Although not shown, it is assumed that a communication device 100B having the same configuration as the communication device 100A is connected to the communication device 100X, as in FIG.

  In the communication device 100X and the communication device 100A, as illustrated in FIG. 7, the receiving unit 10 includes an A / D converter 11 that converts an input analog signal into a digital signal, and a Fourier transformer (FFT) or a wavelet converter. (DWT) or the like, a multicarrier converter 12 for performing desired time-frequency conversion, an equalizer 13 for correcting a received signal so as to cancel the influence of the transmission path, and converting parallel data into serial data A P / S converter 14 and a demapper 15 that converts the mapped symbol data into bit data that is a received signal.

  In the communication device 100X and the communication device 100A, as illustrated in FIG. 8, the transmission unit 20 converts the bit data, which is a transmission signal, into symbol data and performs symbol mapping, and converts serial data into parallel data. Output from the S / P converter 22, the inverse multi-carrier converter 23 that performs desired frequency-time conversion, such as an inverse Fourier transformer (IFFT) and an inverse wavelet transformer (IDWT), and the output from the inverse multi-carrier converter 23 And a D / A converter 24 for converting the converted digital signal into an analog signal.

  In communication apparatus 100A, CNR measuring device 50 measures the carrier-to-noise ratio (hereinafter referred to as CNR) of each subcarrier from the output of equalizer 13 of receiving section 10. The transmission path estimator 60 determines a modulation method to be used for each subcarrier from the noise level of the received signal measured by the CNR measuring device 50, and outputs a value indicating the modulation method to the transmission unit 20 as a tone map. The transmission unit 20 transmits the input tone map to the communication device 100X. Note that the transmission path estimator 60 does not necessarily have to determine the modulation scheme for each subcarrier, and may divide the subcarriers to be used into a plurality of groups and determine the modulation scheme for each subcarrier group. Good.

  In the communication device 100X, the transmission processing unit 30 includes a transmission rate calculator 31, a tone map synthesizer 32, a transmission method determiner 33, and a multicast-unicast converter (hereinafter referred to as MC-UC converter) 34. Based on the reception information acquired by the receiving unit 10, the transmission method of transmission data for multicast communication for the communication devices 100A and 100B on the receiving side is determined.

  The transmission rate calculator 31 calculates the transmission rate in each of the transmission paths XA and XB based on the tone map transmitted from the receiving side communication devices 100A and 100B. The transmission rate may be calculated directly based on the tone map, but it is preferable to calculate the rate excluding redundant signals such as frame configuration and control signals.

  The tone map synthesizer 32 synthesizes the tone maps transmitted from the communication devices 100A and 100B. As a combining method, in the tone map transmitted from the communication devices 100A and 100B, the modulation method (multilevel) is compared for each communication device for each subcarrier, and the lowest modulation method is adopted. It is not necessary to fix the modulation scheme after adopting the lowest modulation scheme. For example, when the retransmission rate is lower than a predetermined value, the multi-level can be increased.

  For example, if 2PAM (Pulse Amplitude Modulation) is specified for subcarrier number 100 in the tone map from communication apparatus 100A, and 8PAM is specified for subcarrier number 100 in the tone map from communication apparatus 100B, the subcarrier of the composite tone map The number 100 is set to 2PAM. Further, when 8 PAM (Pulse Amplitude Modulation) is specified in subcarrier number 150 in the tone map from communication apparatus 100A, and 2 PAM is specified in subcarrier number 150 in the tone map from communication apparatus 100B, the subcarrier of the composite tone map The number 150 is set to 2PAM. In this way, a synthetic tone map is generated.

  As in such a synthetic tone map, by assigning a transmission scheme such as a modulation scheme adapted to the reception state with the worst characteristics among the reception states acquired in each subcarrier (or subcarrier group), it becomes a target. Both receiving-side communication devices 100A and 100B can receive data and perform multicast communication efficiently according to the reception state.

  The transmission method determiner 33 determines a transmission method for transmission data for multicast communication based on the transmission rate calculated by the transmission rate calculator 31 and the synthesized tone map output by the tone map synthesizer 32.

  The MC-UC converter 34 converts multicast communication data (multicast signal) into unicast communication data (unicast signal) as needed based on an instruction from the transmission method determiner 33.

  The operation of the communication system configured as described above will be described. FIG. 9 is a diagram showing a processing procedure of transmission path estimation in the receiving-side communication apparatus according to the embodiment of the present invention.

  As shown in FIG. 9, in the communication apparatuses 100A and 100B on the receiving side, first, the CNR measuring device 50 measures the CNR of each subcarrier from the output of the equalizer 13 of the receiving unit 10 (step S901). Next, the transmission path estimator 60 compares the CNR value of each subcarrier measured by the CNR measuring device 50 with a threshold value, and determines the modulation method to be used for each subcarrier (step S902). Then, the transmission path estimator 60 generates a value representing the modulation scheme determined for each subcarrier as a tone map, and transmits the generated tone map to the communication device 100X via the transmission unit 20 (step S903).

  FIG. 10 is a diagram showing a first example of a processing procedure for determining a transmission method in the transmission-side communication apparatus according to the embodiment of the present invention. This process is a process for determining which of multicast communication and unicast communication is suitable for transmission. First, the outline of the processing of FIG. 10 will be described.

  For example, it is assumed that the transmission speeds of the transmission paths XA and XB obtained from the communication devices 100A and 100B are 50 Mbps. In this case, in the multicast communication using the composite tone map, as described with reference to FIG. 2B, there is no need to transmit separate data frames for each receiving apparatus, so that the communication apparatuses 100A and 100B have an error at a maximum of 50 Mbps. (In the following description, “data can be transmitted without error” at a predetermined transmission rate is expressed as “service can be received” at that transmission rate). However, in unicast communication in which transmission data for multicast is multicast-unicast converted (hereinafter referred to as MC-UC conversion), as described with reference to FIG. 2A, separate data frames are transmitted for each receiving apparatus. Therefore, if the distribution of the transmission band allocated to each of the communication devices 100A and 100B is 1: 1 (= 25 Mbps: 25 Mbps), both the communication devices 100A and 100B can receive a service of a maximum of 25 Mbps.

  Next, it is assumed that the transmission speeds of the transmission paths XA and XB obtained from the communication devices 100A and 100B are 50 Mbps and 30 Mbps. In this case, in multicast communication using the composite tone map, the communication devices 100A and 100B can receive a service at a maximum of 30 Mbps. However, in the unicast communication in which the transmission data for multicast is MC-UC converted, assuming that the time during which the transmission path can be used for each of the communication devices 100A and 100B is half, the communication device 100A has a maximum of 25 Mbps and the communication device 100B has a maximum of Service at 15 (= 25 Mbps × 30/50) Mbps can be received. In this case, the total capacity is a maximum of 40 MBps, which is larger than the multicast communication using the synthetic tone map.

  However, if the bandwidth required for multicast communication is 20 Mbps, the receiving terminal 600B connected to the communication device 100B cannot receive the service itself. In a real environment, a band used for multicasting may be set in advance in the service itself (for example, 4 Mbps or more for streaming reproduction by MPEG2). Here, a bandwidth required for multicast is referred to as a required bandwidth, and the required bandwidth is described as 20 Mbps.

  When the transmission path XA is set to 20 Mbps, the transmission path XB is 18 Mbps (= 30 Mbps × 30/50). As described above, when any one of the transmission paths (in this case, the transmission path XA) is set to a band required for multicast, the distribution of the transmission band (20 Mbps) allocated to each of the communication devices 100A and 100B is 4: 6 (= 20 Mbps: 30 Mbps). Even in this case, since the transmission path XB is less than 20 Mbps, a multicast service requiring 20 Mbps cannot be received. As described above, in the case of MC-UC conversion, the total capacity is often larger than that of the composite tone map, but as a result, it is often difficult to simultaneously provide a multicast service to a plurality of receiving terminals 600A and 600B. .

  Therefore, in MC-UC conversion, a transmission band allocated to each of a plurality of receiving-side communication apparatuses so as to be equal to or higher than a target value (for example, a speed threshold necessary for performing a multicast service) in all transmission paths. Determine the distribution of For example, first, the transmission band is set to be equally distributed to each communication device, each transmission rate is obtained, and if these transmission rates all satisfy the necessary bandwidth, the transmission band assigned to each communication device. Are equally distributed. And when there is a communication device whose transmission rate is less than the required bandwidth, each communication device whose transmission rate is equal to or higher than the required bandwidth is reset to the distribution so that the transmission rate is equal to the required bandwidth. The distribution of the transmission band allocated to the communication device is determined.

  Based on this distribution, the transmission rate in each transmission path is calculated as a unicast transmission rate (hereinafter referred to as UC rate). Then, the minimum value of the UC rates is compared with the multicast transmission rate (hereinafter referred to as the MC rate) when transmitting by multicast communication using the composite tone map, and the faster one is used.

  Hereinafter, the procedure of the above processing will be described. First, the transmission rate calculator 31 calculates the transmission rate in each transmission path XA, XB based on the tone map acquired from each communication device 100A, 100B via the receiving unit 10 (step S1001).

  Next, when the transmission method determiner 33 performs unicast communication with respect to each of the communication devices 100A and 100B based on the transmission rate calculated in step S1001, the transmission rate in each of the transmission paths XA and XB is determined. The distribution of the bandwidth of the transmission path to be transmitted to each communication device 100A, 100B is set so as to be equal to or greater than the target value (step S1002).

  Then, the transmission method determiner 33 calculates the transmission rate of each transmission path as the UC rate from the distribution set in step S1002 (step S1003).

  The tone map synthesizer 32 synthesizes the tone maps transmitted from the communication devices 100A and 100B to generate a synthesized tone map. Then, the transmission method determiner 33 calculates the MC speed when multicast communication is performed using the composite tone map (step S1004).

  Then, the calculated MC speed is compared with the minimum speed of the UC speed (step S1005). If the MC speed is equal to or higher than the minimum speed of the UC speed (YES in step S1005), the multicast speed output from the server 500 is used. The transmission data is sent to the power line PL via the transmission unit 20 using the synthetic tone map. In this way, data is distributed to receiving terminals 600A and 600B via communication devices 100A and 100B using multicast communication.

  On the other hand, if the minimum UC speed is lower than the MC speed (NO in step S1005), the multicast transmission data output from server 500 is MC-UC converted by MC-UC converter 34, and in step S1002. Based on the set distribution, the data is sent to the power line PL via the transmission unit 20. In this way, data is distributed to receiving terminals 600A and 600B via communication devices 100A and 100B using unicast communication.

  As described above, since multicast transmission and unicast communication are selected to transmit data, multicast data can be efficiently distributed according to the transmission path state. In addition, as a criterion for the determination, a transmission method is determined on the condition that the transmission rate equal to or higher than a speed threshold such as a target value is satisfied. For example, after guaranteeing the transmission rate necessary for data distribution for multicast communication, Efficient distribution according to the transmission path state can be performed.

  FIG. 11 is a diagram showing a second example of a processing procedure for determining a transmission method in the transmission-side communication apparatus according to the embodiment of the present invention. This process is a process of determining whether each transmission path is a transmission path suitable for multicast communication from the viewpoint of a retransmission rate when multicast communication is selected by the process of FIG.

  When unicast communication is performed in each transmission path, if the retransmission rate is large, there is a high possibility that the retransmission rate will be high even if multicast communication is performed using the composite tone map. And if retransmissions occur frequently in multicast communication, the transmission efficiency may eventually deteriorate compared to the case where unicast communication is performed. Therefore, in this process, the retransmission rate in each transmission path is obtained in advance, and multicast communication or unicast communication is selected.

  As shown in FIG. 11, when multicast communication is selected in step S1006 of FIG. 10 (step S1101), the transmission method determiner 33 determines unicast communication, and each communication device via the MC-UC converter 34 Unicast communication is performed with respect to 100A and 100B (step S1102).

  Then, the transmission method determiner 33 calculates a retransmission rate based on the retransmission request transmitted from the communication devices 100A and 100B (step S1103) and compares it with a predetermined threshold (for example, 10%) (step S1104). The transmission method determiner 33 selects multicast communication if the retransmission rate is less than or equal to the threshold (YES in step S1104), and performs unicast communication if the retransmission rate is greater than the threshold (NO in step S1104). select. In this way, by performing multicast communication on a transmission path where retransmissions do not occur frequently, multicast data can be efficiently distributed according to the transmission path state.

  Instead of actually measuring the retransmission rate, the retransmission rate in communication between the communication apparatuses may be estimated by observing the tone map a plurality of times and measuring the variation thereof. For example, the communication devices 100A and 100B transmit the tone map a plurality of times within the cycle of the commercial power supply frequency or within a half cycle thereof, and if the fluctuation range is equal to or less than a predetermined value, multicast communication is performed. Perform communication by performing unicast conversion. An error rate may be used instead of the retransmission rate.

  Since the retransmission tends to increase when the reception state fluctuation in the receiving side communication device is severe, by performing multicast communication on the transmission line that is assumed to have few retransmissions by observing the fluctuation of the reception state, the transmission line Multicast data can be efficiently distributed according to the state.

  FIG. 12 is a diagram illustrating a third example of a processing procedure for determining a transmission method in the transmission-side communication apparatus according to the embodiment of the present invention. This process is a process of switching the transmission method when retransmission frequently occurs after multicast communication is selected by the process of FIG. 10 and multicast communication is actually started.

  As shown in FIG. 12, when multicast communication is started (step S1201), the transmission method determiner 33 calculates a retransmission rate based on a retransmission request transmitted from each communication device 100A, 100B (step S1202). As the transmission rate, a transmission rate considering the retransmission rate is calculated for each of the transmission paths XA and XB (step S1203). Then, the transmission method determiner 33 compares each of the transmission rates with a predetermined value (step S1204), and if greater than the predetermined value (NO in step S1204), returns to step S1202, and transmits the transmission paths XA and XB. If any of the speeds is equal to or lower than the predetermined value (YES in step S1204), the mode is switched to unicast communication (step S1205).

  In this way, when retransmissions occur frequently, data distribution according to the transmission path state can be performed by switching to an appropriate transmission method.

  Instead of measuring the retransmission rate after the start of multicast communication, the actual transmission rate including the retransmission rate may be measured by actually communicating at the time of speed measurement in the processing of FIG.

  FIG. 13 is a diagram showing a fourth example of the processing procedure for determining the transmission method in the transmission-side communication apparatus according to the embodiment of the present invention.

  As shown in FIG. 13, the transmission method determiner 33 performs multicast or unicast communication using a fixed tone map (step S1301). Here, a predetermined transmission method such as a multi-value level used for the fixed tone map is determined depending on, for example, a target value in multicast communication. If high speed is necessary, 8PAM or 64QAM is used. If low speed is acceptable, 2PAM or QPSK may be used. Further, the error correction capability may be changed according to the target value. In other words, more robust error correction can be used at low speeds.

  Then, the transmission rate calculator 31 calculates the transmission rate on each of the transmission paths XA and XB when communication is performed using the fixed tone map (step S1302), and the transmission method determiner 33 calculates all the calculated transmission rates. The transmission speed in the transmission path is compared with a predetermined value (step S1303).

  If the transmission rate calculated in step S1302 is equal to or greater than a predetermined value (YES in step S1303), the transmission method determination unit starts multicarrier communication using the fixed tone map (step S1304). On the other hand, if at least one of the transmission rates calculated in step S1302 is less than the predetermined value (NO in step S1303), multicast / unicast communication determination processing is performed (step S1305). Note that step S1305 is processing of steps S1001 to S1007 shown in FIG.

  Thus, for example, a transmission method using multicast communication is first performed by a method such as a modulation method capable of exhibiting a transmission rate sufficient for data communication of the distributed multicast communication. If the reception state is good, the transmission method is used. By performing data distribution, data communication can be performed without performing complicated processing.

  Next, a data retransmission method when a retransmission request is generated will be described. FIG. 14 is an explanatory diagram showing a first example of a retransmission data transmission method in the transmission-side communication apparatus according to the embodiment of the present invention. As shown in FIG. 14, in this example, the communication device on the transmission side transmits retransmission data by unicast communication every time a retransmission request is received.

  For example, when the communication device 100X on the transmission side transmits the MC signal (2) and a response to the transmission cannot be obtained or a negative response (NACK) indicating that the communication device 100X has not correctly received from the reception device has been received, The same data as the MC signal (2) is transmitted as the UC signal (1) by unicast communication.

  As a result, data that needs to be retransmitted is transmitted by unicast communication, so that it is transmitted in a transmission method that matches the reception status of only the target receiving communication device. Can do.

  FIG. 15 is an explanatory diagram illustrating a second example of a retransmission data transmission method in the transmission-side communication apparatus according to the embodiment of the present invention. As shown in FIG. 15, in this example, the transmission method determiner 33 of the transmission processing unit 30 concatenates data requested to be retransmitted within a predetermined period and transmits the data by unicast communication.

  For example, the transmission method determiner 33 transmits the MC signal (1) to the MC signal (4) regardless of the response during the period from when the MC signal (1) is transmitted to the MC signal (4). Thereafter, a negative response NACK is transmitted, the data corresponding to the MC signal (2) and the MC signal (4) requested to be retransmitted are connected, and the UC signal (1) and the UC signal (2) are transmitted at a time. Since the redundant signal added to the packet other than the data such as the preamble signal and the control signal is reduced in total, the utilization efficiency of the transmission path at the time of retransmission can be improved.

  Even in normal multicast communication or unicast communication, it is preferable to link data such as Ethernet (registered trademark) packets (up to about 1500 bytes per packet) as much as possible in order to increase transmission efficiency.

  As described above, if retransmissions occur frequently, the transmission efficiency is degraded by the amount of retransmissions, and the efficiency is further degraded by redundant signals. Therefore, the tone map synthesizer 32 may change the threshold value used when generating the synthesized tone map to a safe and error-free one, and the error correction used by the transmission method determiner 33 is resistant to errors. You may change to a certain method.

  Further, in the communication apparatuses 100A and 100B on the receiving side, the transmission path estimation for multicast may be performed differently from that for unicast communication. In that case, the threshold for determining the modulation scheme has a margin more than that for unicast communication, and the tone map is generated using the threshold, and more powerful error correction is used. Also good. The multicast transmission path estimation may be performed when a multicast communication request is made or may be determined together with the unicast communication transmission path estimation.

  FIG. 16 is a block diagram showing another example of the outline of the communication system according to the embodiment of the present invention. When the number of communication devices in the group to be used for multicast communication is large, when multicast communication is not possible, or when unicast communication is performed for all communication devices, the overall transmission efficiency increases extremely. It will end up. Therefore, in this example, the communication devices of the group to be subjected to multicast communication are further divided into a plurality of subgroups, and the transmission method of transmission data is determined for each subgroup.

  As shown in FIG. 16, there are communication devices 100A, 100B, 100C, 100D, 100E, and 100F of a group that is a target of multicast communication. At this time, the transmission method determination unit of the communication device 100X, for example, includes a subgroup in which two communication devices are paired (the communication device 100A and the communication device 100B are subgroups SG1, the communication device 100C and the communication device 100D are subgroups SG2). Then, the communication device 100E and the communication device 100F are set to the subgroup SG3).

  Then, the processing shown in FIGS. 10 to 13 is performed for each of the subgroups SG1, SG2, and SG3. For example, the transmission method determination unit 33 determines whether multicast communication / unicast communication is performed for two communication devices in each subgroup, and unicast communication is performed for a subgroup for which unicast communication is selected. decide. In addition, it is determined whether multicast communication / unicast communication is performed between subgroups for which multicast communication is selected (for example, every two), and if unicast communication is selected, those subgroups are changed to unicast communication. decide.

  As described above, since the transmission method is determined for each subgroup, when there are a large number of receiving side communication devices, for example, multicast communication and unicast communication can be used together for each subgroup. Data can be distributed.

  Note that the transmission method determiner 33 uses the parameters that can directly or indirectly represent the transmission path state, such as the speed, retransmission rate, average CNR, and error rate, for the transmission method determiner 33. It is preferable to set the communication devices using the path to the same subgroup.

  In the above description, the tone map has been described as an example of the reception information indicating the reception state transmitted from the communication devices 100A and 100B on the reception side to the communication device 100X on the transmission side, but the CNR and the signal-to-noise ratio (Signal to Noise Ratio) are described. : SNR) noise characteristics, received electric field strength, ITU-T SG15 G. Any information indicating the reception state of the communication device on the receiving side, such as B & G defined in the 992.1 recommendation, may be used.

  Moreover, although the case where the transmission rate calculator 31 of the communication device 100X on the transmission side calculates the transmission rate of each transmission path has been described, even if the transmission rate is calculated after the transmission channel is estimated in the communication devices 100A to 100F on the reception side. Good.

  Next, a specific configuration example of the communication devices 100X and 100A to 100F according to the above-described embodiment is shown as the communication device 100. FIG. 17 is an external perspective view showing the front of the communication apparatus according to the embodiment of the present invention, and FIG. 18 is an external perspective view showing the back of the communication apparatus according to the embodiment of the present invention.

  The communication device 100 has a housing 101. As shown in FIG. 17, a display unit 105 such as an LED is provided on the front surface of the housing 101. As shown in FIG. 18, a power connector 102, a modular jack 103 for LAN (Local Area Network) such as RJ45, and a Dsub connector 104 are provided on the rear surface of the housing 101. As shown in FIG. 18, an AC power cord C such as a parallel cable is connected to the power connector 102. A LAN cable (not shown) is connected to the modular jack 103. A Dsub cable (not shown) is connected to the Dsub connector 104. Note that the modem of FIGS. 17 and 18 is shown as an example of the communication device. However, the present invention is not limited to this, and the communication device may be an electric device (for example, a home appliance such as a television) provided with the modem. Good.

  FIG. 19 is a block diagram illustrating an example of hardware of the communication device according to the embodiment of the present invention. As shown in FIG. 19, the communication device 100 includes a circuit module 200 and a switching power supply 300. The switching power supply 300 supplies +1.2 V, +3.3 V, and +12 V to the circuit module 200.

  The circuit module 200 includes a main IC (Integrated Circuit) 201, an AFE IC (Analog Front End IC) 202, a low-pass filter (LPF) 203, a driver IC 205, a coupler 206, a band-pass filter (BPF) 207, and an AMP (amplifier) IC 209. , An ADC (AD conversion) IC 210, a memory 211, and an Ethernet (registered trademark) physical layer IC (PHYIC) 212 are provided.

  The main IC 201 includes a CPU (Central Processing Unit) 201a, a PLC / MAC (Power Line Communication / Media Access Control) block 201b, and a PLC / PHY (Power Line Communication / Physical layer) block 201c. The AFE IC 202 includes a D / A converter (DAC) block 202a, an A / D converter (ADC) block 202b, and a variable amplifier (VGA) block 202c. The coupler 206 includes a coil transformer 206a and a capacitor 206b.

  In the main IC 201, the PLC / MAC block 201b has the function of the transmission processing unit 30, and the PLC / PHY block 201c includes the multicarrier converter 12, the equalizer 13, the P / S converter 14, the demapper 15, and the symbol mapper. 21, S / P converter 22, inverse multicarrier converter 23, CNR measuring device 50, and transmission path estimator 60.

  In the AFEIC 202, the DAC block 202a has the function of the D / A converter 24, the ADC block 202b has the function of the A / D converter 12, and the VGA block 202c has the function of the AGC circuit 11.

  In the embodiment of the present invention, as an example of the communication apparatus, a communication apparatus that uses a power line as a transmission line and performs broadband communication (2 to 30 MHz) of a multicarrier communication system has been described as an example. The communication apparatus is not limited to the multicarrier communication system, and may perform a single carrier communication system or a spread spectrum system. In addition, as long as power line communication via a service outlet is used for setting with an external communication device, other transmission paths used for normal communication are not limited to power lines. For example, a transmission line such as a coaxial cable, a TEL line, a speaker line, or a harness may be used.

  INDUSTRIAL APPLICABILITY The communication apparatus and communication method of the present invention have an effect that data distribution for multicast communication can be efficiently performed, and are useful for power line communication apparatuses and the like.

The block diagram which shows the outline | summary of the communication system which concerns on embodiment of this invention Conceptual diagram explaining multicast communication and unicast communication The figure which shows an example of the transmission line characteristic in a power line Diagram showing an example of noise characteristics in power lines The figure which shows an example of the received signal characteristic in the communication apparatus of the receiving side The block diagram which shows schematic structure of the communication apparatus which concerns on embodiment of this invention. The block diagram which shows schematic structure of the receiving part in the communication apparatus which concerns on embodiment of this invention. The block diagram which shows schematic structure of the transmission part in the communication apparatus which concerns on embodiment of this invention. The figure which shows the process sequence of the transmission line estimation in the receiving side communication apparatus which concerns on embodiment of this invention. The figure which shows the 1st example of the process sequence of the transmission system determination in the transmission side communication apparatus which concerns on embodiment of this invention. The figure which shows the 2nd example of the process sequence of the transmission system determination in the transmission side communication apparatus which concerns on embodiment of this invention. The figure which shows the 3rd example of the process sequence of the transmission system determination in the transmission side communication apparatus which concerns on embodiment of this invention. The figure which shows the 4th example of the process sequence of the transmission system determination in the transmission side communication apparatus which concerns on embodiment of this invention. Explanatory drawing which shows the 1st example of the transmission method of the retransmission data in the transmission side communication apparatus which concerns on embodiment of this invention. Explanatory drawing which shows the 2nd example of the transmission method of the retransmission data in the transmission side communication apparatus which concerns on embodiment of this invention. The block diagram which shows the other example of the outline | summary of the communication system which concerns on embodiment of this invention 1 is an external perspective view showing a front surface of a communication apparatus according to an embodiment of the present invention. 1 is an external perspective view showing a back surface of a communication device according to an embodiment of the present invention. The block diagram which shows an example of the hardware of the communication apparatus which concerns on embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Receiving part 11 A / D converter 12 Multicarrier converter 13 Equalizer 14 P / S converter 15 Demapper 20 Transmitting part 21 Symbol mapper 22 S / P converter 23 Inverse multicarrier converter 24 D / A converter DESCRIPTION OF SYMBOLS 30 Transmission processing part 31 Transmission speed calculator 32 Tone map synthesizer 33 Transmission method determiner 34 MC-UC converter 50 CNR measuring device 60 Transmission path estimator 100,100A-100F, 100X Communication apparatus 101 Case 102 Power supply connector 103 Modular jack 104 Dsub connector 105 Display unit 200 Circuit module 201 Main integrated circuit 201a CPU
201b PLC / MAC block 201c PLC / PHY block 202 AFE integrated circuit 202a DA conversion block 202b AD conversion block 202c Variable gain amplification block 203 Low pass filter 205 Driver integrated circuit 206 Coupler 206a Coil transformer 206b Capacitor 207 Band pass filter 209 Amplifier 210 AD conversion Integrated circuit 211 Memory 212 Ethernet (registered trademark) physical layer integrated circuit 300 Switching power supply 500 Server 600A, 600B Receiving terminal C AC power cord A Power adapter OL Wall outlet PL Power line

Claims (13)

A communication device capable of transmitting data to a plurality of receiving communication devices,
A reception information acquisition unit that acquires reception information indicating each reception state from at least a plurality of reception-side communication devices that are targets of multicast communication;
A transmission processing unit for determining a transmission method of transmission data for multicast communication for the plurality of receiving-side communication devices based on the reception information acquired by the reception information acquisition unit;
The transmission processing unit determines a transmission method adapted to a reception state having the worst characteristics among the reception states indicated by the acquired reception information as a transmission method using the multicast communication , and further, the acquired reception information Based on the unicast transmission rate for each receiving communication device when the transmission data is transmitted to the plurality of receiving communication devices using a transmission method using unicast communication, and the multicast communication is used. A multicast transmission rate in the case of transmitting by a transmission method is calculated, and the transmission method for transmission data for multicast communication is selected as the larger one of the minimum value of the unicast transmission rate and the multicast transmission rate. Communication device determined as a method . The communication device according to claim 1,
A multicarrier communication system is used between the receiving side communication device and
The transmission apparatus assigns a modulation scheme adapted to a reception state with the worst characteristics among reception states indicated by the acquired reception information for each subcarrier group including at least one subcarrier. The communication device according to claim 2 ,
The transmission processing unit calculates a transmission rate of each of the plurality of reception side communication devices based on the acquired reception information, and allocates a transmission band allocated to each of the reception side communication devices to each of the transmissions. A communication apparatus that determines a speed to be equal to or higher than a predetermined speed threshold and calculates the unicast transmission speed based on the determined distribution. The communication device according to claim 3 ,
The transmission processing unit, when determining a transmission method using the multicast communication as a transmission method of the transmission data, measures a retransmission rate after the start of multicast communication, and uses the acquired reception information and the retransmission rate. A transmission method using unicast communication by calculating the transmission speed of each receiving-side communication device and, when the transmission speed is less than the speed threshold, converting the transmission data from multicast to unicast A communication device that starts transmission of the transmission data using the communication device. A communications device as claimed in any one of claims 1 to 4,
When the transmission processing unit determines a transmission method using the multicast communication as a transmission method of the transmission data, the transmission processing unit performs a unicast communication with each receiving-side communication device to measure a retransmission rate. A communication device that starts transmission of the transmission data by using the determined transmission method when it is equal to or less than a predetermined value. A communications device as claimed in any one of claims 1 to 4,
When the transmission processing unit determines the transmission method using the multicast communication as the transmission method of the transmission data, the transmission processing unit performs unicast communication with respect to each reception side communication device, and receives each reception side from the reception information acquisition unit. When the reception information of the communication device is acquired a plurality of times and the fluctuation range of the reception state indicated by the reception information of each of the reception side communication devices is equal to or less than a predetermined value, the transmission data is transmitted using the determined transmission method. The communication device to start. The communication device according to any one of claims 1 to 6 ,
The transmission processing unit transmits each of the reception side communication devices based on the acquired reception information when transmitting to the plurality of reception side communication devices using a predetermined transmission method using multicast communication. A communication apparatus that calculates a transmission rate of the transmission data and determines the predetermined transmission method as a transmission method of the transmission data if all the calculated transmission rates are equal to or greater than a predetermined value. The communication device according to any one of claims 1 to 7,
When the retransmission is requested from the receiving communication device, the transmission processing unit determines a transmission method using unicast communication as a transmission method of data for which retransmission is requested. The communication device according to claim 8 ,
The transmission processing unit is a communication device that connects data requested to be retransmitted within a predetermined period. A communications device as claimed in any one of claims 1 to 9,
The transmission processing unit is a communication device that further divides a receiving-side communication device of a group to be subjected to multicast communication into a plurality of subgroups and determines a transmission method of the transmission data for each of the subgroups. A communications device as claimed in any one of claims 1 to 10,
A communication device in which a transmission line for communicating with the receiving communication device is a power line. A communication method of a communication device capable of transmitting data to a plurality of receiving side communication devices,
Obtaining reception information indicating each reception state from at least a plurality of receiving side communication devices to be subjected to multicast communication; and
Determining a transmission method of transmission data for multicast communication for the plurality of receiving communication devices based on the acquired reception information, and
A transmission method adapted to a reception state having the worst characteristics among the reception states indicated by the acquired reception information is determined as a transmission method using the multicast communication, and the plurality of the transmission methods are determined based on the acquired reception information. Unicast transmission rate for each receiving side communication device when transmitting the transmission data to a receiving side communication device using a transmission method using unicast communication, and the transmission method using multicast communication. Communication method for calculating the multicast transmission rate in the case, and determining the larger transmission method of the minimum value of the unicast transmission rate and the multicast transmission rate as the transmission method of the transmission data for the multicast communication . A communication device capable of transmitting data to a plurality of receiving communication devices,
A reception information acquisition unit that acquires reception information indicating each reception state from at least a plurality of reception-side communication devices that are targets of multicast communication;
A transmission processing unit for determining a transmission method of transmission data for multicast communication for the plurality of receiving-side communication devices based on the reception information acquired by the reception information acquisition unit;
The transmission processing unit transmits each of the reception side communication devices based on the acquired reception information when transmitting to the plurality of reception side communication devices using a predetermined transmission method using multicast communication. A communication apparatus that calculates a transmission rate of the transmission data and determines the predetermined transmission method as a transmission method of the transmission data if all the calculated transmission rates are equal to or greater than a predetermined value.

Images