WO2006014026A2

WO2006014026A2 - Transmission apparatus and communication system using the same

Info

Publication number: WO2006014026A2
Application number: PCT/JP2005/014794
Authority: WO
Inventors: Tomiya Miyazaki
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2004-08-05
Filing date: 2005-08-05
Publication date: 2006-02-09
Also published as: WO2006014026A3; JP2006050306A

Abstract

Since a coding controller 9, 10 controls a code determinator 8 in such a manner that an error correcting code set by the code determinator 8 is changed and the changed error correcting code is set in response to a degree of an error detected by a decoder 65, the error correction as to the communication data RD can be carried out without excessively increasing the error correcting capability of the error correcting code. As a result, even in such a case that the communication status as to the communication data RD is not stable due to impedance loss and noise which are generated from electric appliances connected to a power line, for example, in a power line communication, lowering of the communication speed can be suppressed as much as possible, while reliability of the communication may be maintained.

Description

DESCRIPTION

TRANSMISSION APPARATUS AND COMMUNICATION SYSTEM USING

THE SAME

The present invention relates to a transmission apparatus for transmitting/receiving communication data, and for error-correcting the communication data based upon an error correction code, and relates to a communication system using this communication apparatus . More specifically, the present invention is directed to a communication apparatus and a communication system, by which even in such a case that a communication status as to communication data is not stable, while reliability of communications is maintained, lowering of communication speeds can be suppressed as much as possible .

Very recently, since so-called "broadband" communication systems have been realized in accordance with such communication systems as wireless LANs (Local Area Networks) and ADSLs (Asymmetric Digital Subscriber Lines) , high-speed communications have been progressed. In addition to these communication systems, power line communications capable ofutilizingpower lines as network transmission paths have been proposed in, for instance, Japanese Laid-open Patent Application No. 2000-165304. In communication apparatus using such power line communications, in order to realize high communication speeds and also to improve reliability of communications, error correcting codes known as convolution codes and Reed-Solomon codes havebeen employed as error corrections of communication data.

However, when communication speeds are increased, errors of communication data are increased. Thus, there is a drawback that reliability of communications is lowered. In such a case, there is one method that error correcting capability of an error correcting code is increased as high as possible. However, if the error correcting capability of this error correcting code is merely increased in such a case that errors are increased/decreased, so that communication statuses are not stable, then the error correcting capability may become excessively high when the communication statuses are recovered. As a result, there is another problem that communication speeds are unnecessarily lowered. For example, in power line communications, there are some possibilities that communication statuses are brought into unstable conditions, because of impedance losses and noise produced from electric appliances which are connected to power lines. Such communication apparatus have been therefore desired by which lowering of communication speeds can be suppressed as much as possible while reliability of communications can be maintained even under such communication statuses.

A problem to be solved the present invention is such that when a communication status as to communication data is not stable, if an error correction code having high error correction capability is employed, then a communication speed is unnecessarily lowered.

The present invention owns such a major feature that a coding controller controls a code determinator in such a manner that a set error correcting code is changed in response to a degree of an error detected by a decoder, and then, the changed error correcting code is set.

In a communication apparatus of the present invention, since the error correcting code is changed to be set in correspondence with the error degree of the communication data, the error correction as to the communication data can be carried out without excessively increasing the error correcting capability of the error correcting code. As a result, even in such a case that the error number is changed, so that the communication condition is not stable, lowering of the communication speed can be suppressed as much as possible, while the communication reliability may be maintained.

<Brief Description of the Drawings> Fig. 1 is an explanatory diagram for schematically explaining a home-use network using a communication apparatus .

Fig. 2 is a perspective view for showing an outer appearance of a front surface of the communication apparatus .

Fig. 3 is a perspective view for representing an outer appearance of a rear surface of the communication apparatus .

Fig. 4 is a block diagram for indicating one example of hardware of a PLC adaptor.

Fig.5 is a functional block diagram for representing a PLC adapter according to an embodiment mode 1 of the present invention.

Fig. 6 is a functional block diagram for indicating an error correcting encoder of a transmitter in the embodiment mode. 1.

Fig. 7 is a functional block diagram for showing an error correcting decoder of a receiver in the embodiment mode 1.

Fig. 8 is a flow chart for indicating one example of communication operations executed by the PLC adaptor.

Fig. 9 is a functional block diagram for indicating an error correcting encoder of a transmitter in an embodiment mode 2 of the present invention.

Fig. 10 is a functional block diagram for showing an error correcting decoder of receiver in the embodiment mode 2.

Fig. 11 is a functional block diagram for indicating a communication apparatus according to an embodiment mode 3 of the present invention.

Fig. 12 is a block diagram for indicating a communication system according to an embodiment mode 4 of the present invention.

First invention which has been made to solve the above-describedproblemis featuredby such a transmission apparatus (1) for transmitting/receiving communication data (SD, RD), and for performing an error correction of the communication data (SD, RD) based upon an error correcting code, comprising: a code determinator (8, 57,67) for setting the error correcting code; an encoder (51) for adding a redundant bit based upon the error correcting code set by the code determinator (8, 57, 67) to the communication data (SD) ; atransmitter (5) for transmitting the communication data (SD) to which the redundant bit has been added by the encoder (51); a receiver (6) for receiving the transmitted communication data (RD) ; a decoder (65) for detecting an error of the communication data (RD) receivedby the receiver (6) based upon the error correcting code set by the code determinator (8, 57, 67), and for correcting the detected error; and a coding controller (9, 10) for controlling the code determinator (8, 57, 67) in such a manner that the error correcting code set by the code determinator (8, 57, 67) is changed and the changed error correcting code is set in response to a degree (for example, error number) of the error detected by the decoder (65) .

With employment of this arrangement, since the error correcting code is changed to be set in correspondence with the error degree of the communication data, the error correction as to the communication data can be carried out without excessiv.ely increasing the error correcting capability of the error correcting code. As a result, even in such a case that the error number is changed, so that the communication condition is not stable, lowering of the communication speed can be suppressed as much as possible, while the communication reliability may be maintained.

Second invention which has been made to solve the above-described problem is featured by that the coding controller (9, 10) controls the code determinator (8, 57, 67) in such a manner that a data length of the redundant bit based upon the error correcting code set by the code determinator (8, 57, 67) is changed, and the changed data length of the redundant bit is set.

With employment of the above-described arrangement, the data length of the redundant bit is changed based upon the error correcting code, so that the error correction can be carried out in the very fine mode. As a result, since the error correction can be carried out in the high efficiency, a waste of the error correcting capability can be reduced, and lowering of the communication speed can be further suppressed.

Third invention which has been made to solve the above-described problem is featured by that the coding controller (9, 11) controls the code determinator (8, 57, 67) in such a manner that the system of the error correcting code set by the code determinator (8, 57, 67) is changed into a different error correcting code system (for example, Reed-Solomon code is changed into Turbo code) and the changed error correcting code system is set .

With employment of this arrangement,, since the system of the error correcting code is changed/set to the different system (for instance, Reed-Solomon code is changed into Turbo code), even when the sort of the occurring error (for instance, random error, burst error, and byte error) is changed, this communication apparatus can select such an error correcting code system which is suitable for the error sort, and thus, can furthermore improve reliability of the communication.

Fourth invention which has been made to solve the above-described problem is featured by that the transmitter (5) transmits the communication data (SD) to which the redundant bit has been added via a power line (2) ; and the receiver (6) receives the transmitted communication data (RD) via the power line (2) .

With employment of this arrangement, even in such a case that the communication status is not stable due to impedance loss and noise which are generated from electric appliances connected to the power line, the error correcting code is changed/set in response to the error degree of the communication data. As a result, lowering of the communication speed can be suppressed as much as possiblewhile reliabilityof thepower line communication may be maintained.

Fifth invention which has been made to solve the above-described problem is featured by that the transmitter (5) includes a wavelet inverse transformer (52) for performing a wavelet inverse transformation with respect to the communication data (SD) to which the redundant bit has been added by the encoder (51), and for transmitting the wavelet-inverse-transformed communication data (RD) ; and the receiver (6) includes a wavelet transformer (64) for performing a wavelet transformation with respect to the transmitted communication data (RD) , and for receiving the wavelet-transformed communication data.

With employment of this arrangement, since the communication apparatus transmits and receives the communication data by utilizing the wavelet transformation, the communication apparatus no longer performs the complex calculation in the Fourier transformation, so that the circuit scale of the communication apparatus can be reduced.

Sixth invention which has been made to solve the above-described problem is featured by that the communication apparatus (1) is further comprised of: a communication status checker (9) for checking a communication status (for example, S/N ratio) as to the communication data (RD) received by the receiver (6); and a communication status output unit (9) for outputting the communication status as to the communication data (RD) checked by the communication status checker (9) to a predetermined user interface (for example, 11) .

With employment of this arrangement, since the communication status as to the communication data is outputtedtoapredetermineduser interface (for instance, display and speaker), the user of the communication apparatus can grasp the communication status as to the communication data. As a consequence, for instance, in the case that the error correcting capability is not sufficientlyhighwith respect to the communication status, since the user utilizes a noise-free appliance, and/or changes communication plugs, the communication can be maintained.

Seventh invention which has been made to solve the above-described problem is featured by such a communication system (700) comprising: a communication apparatus (1) and a server (703) , which are connected to a network (701) , in which the communication apparatus (1) is further comprised of: a communication status informer (9) for informing the communication status as to the communication data (RD) checked by the communication status checker (9) to the server (703) .

With employment of this arrangement, since the server receives the communication status as tot he reception data from the communication apparatus, the manager of the server can provide the following services in the case that the error correcting capability is not sufficientlyhighwith respect to the communication status by establishing a cooperation with, for example, a service management firm, and thus, the communication by the communication system can maintain the communication. As to these services, themanager changes communicationplugs, or utilizes a noise-free appliance.

Eighth invention which has been made to solve the above-described problem is featured by such a reception apparatus (1) for receiving communication data (SD, RD) , and for performing an error correction of the communication data (SD, RD) based upon an error correcting code, comprising: a code determinator for (8, 67) setting the error correcting code; a receiver (6) for receiving the transmitted communication data (RD); a decoder (65) for detecting an error of the communication data (RD) receivedby the receiver (6) based upon the error correcting code set by the code determinator (8, 67), and for correcting the detected error; and a coding controller (9, 10) for controlling the code determinator (8, 67) in such a manner that the error correcting code set by the code determinator (8, 67) is changed and the changed error correcting code is set in response to a degree (for example, error number) of the error detected by the decoder (65) .

With employment of this arrangement, even when the communication status is not stable, such a communication apparatus can be provided by which lowering of the communication speed can be suppressed as much as possible, while the reliability of the communication can be maintained.

Next, embodiment modes of the present invention will now be described with reference to Fig. 1 to Fig. 12.

It should be understood that reference numerals shown in brackets merely indicate relevant elements in the drawings in order to readily understand the present invention for the sake of convenience. Therefore, the above description are not limited only to the descriptions represented in the drawings, and thus, the technical scope of the present invention must not be interpreted based upon the descriptions of these reference numerals.

Fig. 1 is an explanatory diagram for schematically showing a home-use network 600 with employment of a communication apparatus 1. The home-use network 600 corresponds to a LAN (Local Area Network) constructed in a home. It should be noted that the LAN need not be always constructed inside a home, but may be arranged inside an office, and a facility (hospital, school etc.) . The home-use network 600 contains a power line 2 of a commercial power supply. Various sorts of domestic electric appliances 3 have been connected via a communication apparatus 1 to the power line 2. In Fig. 1, a television 3A, a personal computer (will be referred to as a "PC" hereinafter) 3B, an inverter illumination 3C, and the like have been connected to the power line 2 as the domestic electric appliances 3.

Fig. 2 is a perceptive view for showing an outer appearance of a front surface of the communication apparatus 1. Fig.3isaperspectiveviewforrepresenting an outer appearance of a rear surface of the communication apparatus 1. The communication apparatus 1 according to an embodiment mode of the present invention corresponds to a modem as indicated in Fig. 2 and Fig. 3. The communication apparatus 1 has contained a housing 101. As shown in Fig. 3, a light emitting unit 105 constituted by an LED (Light Emitting Diode), and a display unit 11 have been provided on a front surface of the housing 101.

As represented in Fig. 3, a power supply connector 102, a LAN-purpose modular jack 103 such as RJ45, and a D-sub connector 104 have been provided on a rear surface of the housing 101. As indicated in Fig. 3, a parallel cable 108 is connected to the power supply connector 102. A LAN cable 109 is connected to the modular jack 103. AD-sub cable (notshown) is connectedto the Dsub connector 104.

It should be also noted that although the modem of Fig. 2 and Fig. 3 has been indicated as one example of the communication apparatus 1, this communication apparatus 1 may be alternatively realized by a mobile communication terminal, for example, a portable telephone and a PDA (Personal Digital Assistant) if a communication function is equipped with such a mobile communication terminal, namely this communication apparatus 1 need not be always realized by the modem. Alternatively, the communication apparatus 1 may be realized by an electric appliance containing a modem, while this electric appliance corresponds to such a domestic electric appliance as a DVD recorder, and a set-top box. As previously explained, the communication apparatus 1 according to this embodiment mode corresponds to such a modem which performs a communication by using the power line 2 as a transferpath (namely, power line communication, PLC: Power Line Communication) . It should be understood that this modem will be referred to as a "PLC adaptor" hereinafter.

Fig. 4 is a block diagram for indicating one example of hardware of the PLC adaptor 1. As indicated in Fig. 4, the PLC adaptor 1 has contained a circuit module 200, a switching power supply 300, and the switch 11. The switching power supply 300 applies various sorts of voltages (for instance, +1.2 V, +3.3 V, and +12 V) to the circuit module 200. In this circuit module 200, a main IC 201, an AFE • IC (Analog Front End • IC) 202, a bandpass filter 55, a driver IC 15, a coupler 206, another bandpass filter 61, an AMP (Amplifier) • IC 208, another bandpass filter 21, an ADC (A/D converter) • IC 22, a transmitter memory 10, and an Ethernet PHY • IC 212 have been provided. The power supply connector 102 is connected via a plug 400 and a plug socket 500 to the power line 2.

The main IC 201 hasbeen constituted byaCPU (Central Processing Unit) 9, a PLC • MAC (Power Line Communication • Media Access Control layer) block 201C, and a PLC • PHY (Power Line Communication • Physical layer) block 201B. The CPU 9 has mounted thereon a 32-bit RISC (Reduced Instruction Set Computer) processor. The PLC • MAC block 201C manages MAC layers as to a transmission signal and a reception signal whereas the PLC ^• PHY block 210B manages PHY layers as to a transmission signal and a reception signal. The AFE • IC 202 has been constituted by a D/A converter (DAC) 53, an A/D converter (ADC) 63, amplifiers 54, and gain controller 62. The coupler 206 has been arranged by a coil transformer 7, and coupling-purpose capacitors 206A and 206B. The transmitter memory 10 may be constituted by such a memory as a ROM (Read-OnlyMemory) and a RAM (Random Access Memory) .

(EMBODIMENT MODE 1)

Fig. 5 is a functional block diagram for indicating the PLC adapter according to an embodiment mode 1 of the present invention. As previously explained with reference to Fig. 1, the PLC adaptor 1 has been connected via the parallel cable 108 to the power line 2, and has been connected via the LAN cable 109 to the television 3A. In other words, the PLC adaptor 1 relays the power line 2 to the television 3A. These household appliances to which the PLC adaptor has been connected constitute a home communication network via the power line 2 by way of the power line communication. The household appliances are not limited only to the example shown in Fig. 1, but contain a DVD recorder, a set-top box, and the like. It should also be noted that the power line 2 which is employed in the power line communication need not be always a power line of a commercial power supply, but may be realized by a power line of a DC power supply by which AC 100 V has been converted into a DC voltage.

The PLC adaptor 1 contains a transmitter 5, a receiver 6, a coupler 7, a controller 8, a CPU 9, a transmitter memory 10, and the switch 11. As shown in an upper broken line frame of Fig. 5, the transmitter 5 contains an error correcting encoder 51, a wavelet inverse transmitter 52, a D/A converter 53, an amplifier 54, and a bandpass filter 55. As indicated in a lower broken line frame of Fig. 5, the receiver 6 contains a bandpass filter 61, a gain controller , an A/D converter 63, a wavelet transformer 64, and an error correcting decoder 65. It should also be noted that the controller 8, the error correcting encoder 51, the wavelet inverse transformer 52, -the wavelet transformer 64, and the error correcting decoder 65 may be operated by that the PLC-PHY block 201B of the main IC 201 shown in Fig. 4 functions.

Fig. 6 is a functional block diagram for indicating an internal arrangement of the error correcting encoder 51 of the transmitter 5 according to the embodiment mode 1. As indicatedwithin a broken line frame of this drawing, the error correcting encoder 51 contains a transmitting selector 57 and RS (Reed-Solomon) encoders. The Reed-Solomon encoders are constructed of a first Reed-Solomon encoder 58 and a second Reed-Solomon encoder 59.

Fig. 7 is a functional block diagram for indicating an internal arrangement of the error correcting decoder 65 of the receiver 6 according to the embodiment mode 1. As indicatedwithin abroken line frame of this drawing, the error correcting decoder 65 contains a receiving selector 67 and RS (Reed-Solomon) decoders. The Reed-Solomon decoders are constructed of a first Reed-Solomon decoder 68 and a second Reed-Solomon decoder 69.

It should be noted that the controller 8, the transmitting selector 57, and the receiving selector 67 may function as one example of a code setting unit. The error correcting encoder 51 may function as one example of a code determinator. The error correcting decoder 65 may function as one example of a decode determinator. The controller 9 and the transmitter memory 10 may function as one example of a coding controller.

With employment of the above-described arrangements, communication operations executed by the PLC adaptor 1 will now be described with reference to Fig. 1 through Fig. 8. Fig. 8 is a flow chart for describing one example of the communication operations executed by the PLC adaptor 1.

While mode information "MI" has been previously stored in the transmitter memory 10 of the PLC adaptor 1, the mode information "MI" indicates a setting condition (will be referred to as "mode" hereinafter) of an error correcting code (will be described later) . As the modes of the error correcting code, two sorts of modes have been prepared. In the below-mentioned descriptions, such a mode whose error correcting capability is low will be referred to as a "normal mode"; such a mode whose error correcting capability is high will be referred to as a "enhancing mode"; mode information MI indicative of the normal mode will be referred to as "MIL"; and also mode information MI indicative of the enhancing mode will be referred to as "MIH. " In this case, it is so assumed that the mode information MIL has been stored as a default in the transmitter memory 10.

As the error correcting code, the Reed-Solomon coding system has been set. In the normal mode, RS (255, 239) is used by the first Reed-Solomon encoder 58 (see Fig. 6) of the error correcting encoder 51 and the first Reed-Solomon decoder 68 (see Fig. 7) of the error correctingdecoder 65. On the otherhand, in the enhancing mode, RS (255, 15) is used by the second Reed-Solomon encoder 59 (see Fig. 6) of the error correcting encoder 51 and the second Reed-Solomon decoder 69 (see Fig. 7) of the error correcting decoder 65.

In order to perform a communication operation, firstly, the controller 8 reads out the mode information MIL which has been stored in the transmitter memory 10, and then, outputs the read mode information MIL to both the error correcting encoder 51 of the transmitter 5, and the error correcting decoder 65 of the receiver 6. Upon receipt of the mode informationMIL, the transmitting selector 57 of the error correcting encoder 51 selects the first RS (Reed-Solomon) encoder 58 shown in Fig. 6 as the Reed-Solomon encoder, and also, the receiving selector 67 of the error correcting decoder 65 selects the first RS (Reed-Solomon) decoder 68 indicated in Fig. 7 as an Reed-Solomon decoder. This process operation is carried out by all of the PLC adaptors 1 shown in Fig. 1, and thus, an error correcting code is set to the normal mode (step SlOl of Fig. 8) .

In the case that a transmission operation is carried out under this condition, as shown in Fig.5, the television 3A outputs transmission data "SD" to the PLC adaptor 1. The transmission data "SD" is entered via the controller 9 to the error correcting encoder 51 of the transmitter 5. As previously explained, since the error correcting encoder 51 uses RS (255, 239) in the normal mode, the first Reed-Solomon encoder 58 selectedbythe transmitting selector 57 constructs such a data block having a code length of 255 bytes so as to encode the transmission data SD (step S102 of Fig. 8) . This data block is produced by adding a parity bit (redundant bit) whose data length is made of 16 bytes to the transmission data SD having 239 bytes.

The error correcting encoder 51 encodes the transmission data SD which has been coded, and the wavelet inverse transformer 52 performs a wavelet inverse transformation with respect to the encoded transmission data SD so as to produce transmission data SD of a digital signal. The D/A converter 53 converts the produced digital transmission data SD into an analog signal of this transmission data SD, and the amplifier 54 amplifies the transmission data SD which has been converted into the analog signal thereof. The bandpass filter 55 derives a necessary signal component from the amplified transmission data SD, and then, outputs this transmission data SD via the coupler 7 to the power line 2. In other words, the transmission data SD outputted from the television 3A is superimposed on the voltage of the power line 2, and the superimposed transmission data SD is transmitted to, for example, the PC 3B shown in Fig. 1 (step S103 of Fig. 8) .

It shouldalso be understood that as the transforming method between the time domain and the frequency domain, the wavelet transforming method has been indicated. However, the present invention need not be always limited only to the wavelet transformingmethod, but, for example, the Fourier transforming method may be employed. Although the OFDM (Orthogonal Frequency Division Multiplex) modulating method has been described as the modulatingmethod, thepresent invention is not especially limited thereto. For example, the spread spectrum modulating method may be alternatively used as the modulating method. On the other hand, in the case that a receiving operation is carried out, for instance, the PC 3B shown in Fig. 1 executes the process operation of the step S102 of Fig. 8, and thus, outputs transmission data SD to the power line 2 in a similar manner to the step S103 of Fig. 8. The transmission data SD is transmitted via the PLC adaptor 1 connected to the PC 3B and the power line 2 to the PLC adaptor 1 connected to the television 3A. The receiver 6 of the PLC adaptor 1 connected to the television 3A receives the transmitted transmission data SD via the coupler 7 as reception data "RD", as indicated in Fig. 5 (step S104 of Fig. 8) . The bandpass filter 61 of the receiver 6 derives a necessary signal component from the received reception data RD, and the gain controller 62 ampIifies such a reception data RD fromwhich the necessary signal component has been derived. The A/D converter 63 converts the amplified reception data RD from an analog signal into a digital signal, and then, the wavelet transformer 64 wavelet-transforms the reception data RD which has been converted into the digital signal.

The error correcting decoder 65 demodulates the reception data RD which has been wavelet-transformed, and decodes the demodulated reception data RD. In other words, the error correcting decoder 65 uses RS (255, 239) in the normal mode in a similar manner to the error correcting encoder 51. As a result, the first Reed-Solomon encoder 68 selectedbythe receiving selector 67 detects an error from the demodulated reception data RD, and corrects the detected error. As a consequence, the errors may be corrected up to 8 bytes in maximum within 255 bytes of the code length.

While the communication operation is carried out in the above-described manner, it is so assumed that, for instance, since noise is produced from the inverter light 3C shown in Fig. 1 (otherwise, impedance loss is changed due to change in total number of household appliances which are connected to power line 2) , an error number of the reception data RD exceeds 8 bytes. While the controller 9monitors the error number of the reception data RD detected by the error correcting decoder 65, in the case that the error number is reached to 8 bytes, the mode of the error correction code has been set in such a manner that this mode is changed from the normal mode to the enhancing mode .

As a consequence, in the case that the error number is not reached to 8 bytes ("NO" in step S106 of Fig. 8), the receiving process operation of the controller 9 is returned to the previous step S105 of Fig. 8 in which the controller 9 directly detects an error number. When, the controller 8 detects that the error number is reached to 8 bytes ("YES" in step S106 of Fig. 8), the controller 9 updates themode informationMI stored in the transmitter memory 10 from the mode information MIL which indicates the normal mode to the mode informationMIHwhich indicates the enhancing mode, and then, stores the updated mode informationMIH. When the mode informationMIH is updated and stored, as shown in Fig. 1, the controller 8 outputs the mode information MIH stored in the transmitter memory 10 to both the error correcting encoder 51 of the transmitter 5, and the error correcting decoder 65 of the receiver 6. Whenthemode informationMIH is received, the transmitting selector 57 of the error correcting encoder 51 switches the RS (Reed-Solomon) encoder from the first Reed-Solomon encoder 58 to the second Reed-Solomon encoder 59, and also, the receiving selector 67 of the error correcting decoder 65 switches the RS (Reed-Solomon) decoder from the first Reed-Solomon decoder 68 to the secondReed-Solomondecoder 69. Inother words, the error correcting code is changed fromthe normal mode to the enhancing mode (step S107 of Fig. 8) .

When the error correcting code is changed/set to the enhancing mode, in the transmission operation, the error correcting encoder 51 of the transmitter 5 encodes the transmission data SD in the enhancing mode (step S108 of Fig. 8) . That is to say, since the error correcting encoder 51 uses RS (255, 15) in the enhancing mode, the second Reed-Solomon encoder 59 selected by the transmitting selector 57 constructs such a data block having a code length of 255 bytes so as to encode the transmission data SD. This data block is produced by adding a parity bit (redundant bit) whose data length is made of 240 bytes to the transmission data SD having 15 bytes. The transmitter 5 performs a process operation similar to that of the normal mode as to the encoded transmission data SD, and then, outputs the processed transmission data SD to the power line 2 (step S103 of Fig. 8) .

On the other hand, in the receiving operation, when the receiver 6 receives the reception data RD from another household appliance, this receiver 6 executes a process operation similar to that of the normal mode as to the received reception data RD so as to decode this processed reception data RD. That is to say, since the error correcting decoder 65 of the receiver 6 uses RS (255, 15) , the second Reed-Solomon decoder 69 switched by the receiving selector 67 detects an error from the reception data RD so as to correct the detected error. As a consequence, the maximum error number which can be corrected within the code length of 255 bytes is increased from 8 bytes to 120 bytes. Within such a range that the errors do not exceed 120 bytes, these errors may be corrected, and thus, the communication may be maintained. It shouldbe noted that in this case, since the transmission data SD is decreased from 239 bytes to 15 bytes within the code length of 255 bytes, the communication speed is lowered by the reduced data bytes.

In the case that the communication operation is carried out in the enhancing mode in the above-described manner, and then, the noise generated from another household appliance is again decreased, so that the error number of the reception data RD becomes smaller than 8 bytes, the controller 9 detects such a fact that the error numberbecomes smaller than 8 bytes in such amanner similar to the step S106 of Fig. 8, and this controller 8 updates the mode information MI stored in the transmitter memory 10 from the mode information MIH indicative of the enhancing mode to the mode information MIL indicative of the normal mode, and then, stores the updated mode information MIL into the transmitter memory 10. As a consequence, the transmitting selector 57 of the error correcting encoder 51 switches the RS (Reed-Solomon) encoder from the second Reed-Solomon encoder 59 to the first Reed-Solomon encoder 58, and also, the receiving selector 67 of the error correcting decoder 65 switches the RS (Reed-Solomon) decoder fromthe secondReed-Solomon decoder 69 to the first Reed-Solomon decoder 68. In other words, similar to the step S107 of Fig. 8, the error correcting code is again changed from the enhancing mode to the normal mode, and the changed error correcting code is set.

As a consequence, although the correctable maximum error number is decreased from 120 bytes to 8 bytes, as previously explained, since the noise generated from another household appliance has been decreased, the communication can be maintained without any problem. Also, since the error correcting code is changed to the normal mode and the changed error correcting code is set, the transmission data SD is again increased from 15 bytes to the 239 bytes, so that the communication speed can be recovered.

As previously described, since the error correcting code is changed to be set in correspondence with the error number of the reception data RD, the error correction as to the reception data RD can be carried out without excessively increasing the error correcting capability of the error correcting code. As a result, even in such a case that the error number is changed, so that the communication condition (for instance, S/N ratio) is not stable as explained in, for example, the power line communication, lowering of the communication speed can be suppressed as much as possible, while the communication reliability may be maintained.

Also, the data length of the redundant bit is changed in order that the error correcting code is changed/set, so that the error correction can be carried out in the very fine mode. As a result, since the error correction can be carried out in the high efficiency, a waste of the error correcting capability can be reduced, and lowering of the communication speed can be further suppressed.

It should also be understood that the above-explained embodiment mode 1 has exemplified such a case that the error correcting code is changed in correspondence with the error number of the reception data RD and the changed error correcting code is set. Alternatively, if the error correcting code is changed/set in response to such a parameter indicative of an error degree, then the present invention is not always limited only to the above-described error number, but may be modified. For example, the error correcting code may be alternatively changed/set in response to an error rate of the reception data RD.

It should also be understood that the above-explained embodiment mode 1 has exemplified such a case that the error number of 8 bytes is employed as the threshold value. However, the present invention is not always limited only to 8 bytes, but may be applied to an arbitrary byte number. Moreover, there is no need that only one threshold value is employed, but a plurality of threshold values may be alternatively employed. For instance, while a plurality of threshold values have been set, a redundant bit may be alternatively changed in a stepwise manner. In this alternative case, a plurality of Reed-Solomon encoders of the error correcting encoder 51, and a plurality of Reed-Solomon decoders of the error correcting decoder 65 may be provided, the total numbers of which are equal to a total number of threshold values (in case that three pieces of threshold values are provided, three sets of Reed-Solomon encoders and Reed-Solomon decoders are employed) . As a result, the error correction may be carried out in a further fine mode, and also, the efficiency of the error correction may be furthermore improved.

Also, the error correcting code may be changed/set in response to not only an error degree of reception data RD, but also a transmission condition of the power line 2. As this transmission condition, the following conditions may be conceived, namely, an S/N ratio, a CNR

(Carrier Noise Radio) , and a CINR

(Carrier-to-Interference-plus-noise Ratio) in each of sub-carriers. In a power line communication, either a CNR or a CINR is measured when a transmission path prediction is carried out. As a result, the error correcting code may be changed/set, while the measured CNR, or the measured CINR is utilized.

It should also be noted that although the above-described embodiment mode 1 has described the Reed-Solomon code system as the error correcting code system, the present invention is not limited only to this Reed-Solomon code system, but may employ any of the following error correction systems, for instance, a BCH

(Bose Chaudhuri Hocquenghem) code, a convolution code, a Turbo code, a trellis code, and the like.

It should also be understood that in the above-described embodiment mode 1, the PLC adaptor 1 has been described as one example of the communication apparatus 1. Alternatively, if such an apparatus having a transmission function is available, then any type of apparatus may be used. For example, a semiconductor element equipped with the communication function may be alternatively employed. Further, any electric appliances (personal computer, printer, copy machine, telephone, facsimile etc.) having the communication functions may be alternatively employed. It should also be noted that domestic electric appliances (namely, so-called "network domestic electric appliances" such as television and DVD [Digital Versatile Disk] recorder) equipped with the communication function may be involved by such electric appliances. Since the above-explained various structural modes are utilized, user friendly commercial products may be provided to users.

Further, the above-explained embodiment mode 1 has described the communication apparatus for transmitting/receiving the communication data. However, the present invention is not always limited only to the communication apparatus, but maybe applied to a reception apparatus .

(EMBODIMENT MODE 2)

Next, a communication apparatus according to an embodiment mode 2 of the present invention will now be described. In the communication apparatus of this embodiment mode 2, only internal arrangements of both an error correcting encoder 51 and an error correcting decoder 65 are different from those of the embodiment mode 1. It should be understood that the same reference numerals of the embodiment mode 1 will be employed as those for denoting the same, or similar structural element of this embodiment mode 2.

Fig. 9 is a functional block diagram for indicating an internal arrangement of the error correcting encoder 51 employed in the transmitter 5 according to the embodiment 2. As shown in a broken line frame of this drawing, the error correcting encoder 51 contains a transmitting selector 57, a first RS (Reed-Solomon) encoder 58, and a Turbo encoder 70.

Fig. 10 is a functional block diagram for indicating an internal arrangement of the error correcting decoder 65 employed in the receiver 6 according to the embodiment 2. As shown in a broken line frame of this drawing, the error correcting decoder 65 contains a receiving selector 67, a first RS (Reed-Solomon) decoder 68, and a Turbo decoder 71.

Referring now to Fig. 5, Fig. 9, and Fig. 10, communication operations executed by the PLC adaptor 1 having the above-explained arrangement according to the embodiment mode 2 will be described. It should also be noted that as to the communication operations performed by the PLC adaptor 1 according to the embodiment mode 2, since only an error correcting code system thereof is different from that of the communication operations explained in Fig. 8, only different points of the communication operations will be explained.

Similar to the above-explained embodiment mode 1, as to modes of error correcting codes, two sorts of modes (normal mode and enhancing mode) have been prepared. As to the error correcting codes, both a Reed-Solomon code system and a Turbo code system have been set, which is different from the embodiment mode 1. In the normal mode, the Reed-Solomon code and RS (255, 239) are used by both a first Reed-Solomon encoder 58 of the error correcting encoder 51 and a first Reed-Solomon decoder 68 of the error correcting decoder 65. On the other hand, in the enhancing mode, the Turbo code is used by both a Turbo encoder 70 of the error correcting encoder 51 and a Turbo decoder 71 of the error correcting decoder 65. It should also be noted that as to the error correcting code system, the present invention is not limited only to the above-explained combined system, but 3 sorts, or more sorts of error correcting code systems may be alternatively combined with each other.

In the normal mode, since RS (255, 239) is used in a similar manner to the embodiment mode 1, explanations as to communication operation thereof are omitted. It is now assumed that while the communication operation is carried in the normal mode, for example, a random error (otherwise, burst error) happens to occur, so that an error number of reception data RD is reached to 8 bytes. The controller 9 updates the mode information MI stored in the transmitter memory 10 from the mode information MIL to the mode information MIH in a similar manner to that of the embodiment mode 1. Then, the transmitting selector 57 of the error correcting encoder 51 switches the encoder from the first Reed-Solomon encoder 58 to the Turbo encoder 70, and also, the receiving selector 67 of the error correcting decoder 65 switches the decoder fromthe first Reed-Solomon decoder 68 to the Turbo decoder 71. That is to say, the system of the error correcting code is changed/set from the Reed-Solomon code to the Turbo code.

When the error correcting code system is changed/set to the Turbo code system, in the transmitter 5, the Turbo encoder 70 of the error correcting encoder 51 encodes transmission data SD by using the Turbo code. Also, in the receiver 6, the Turbo decoder 71 of the error correcting decoder 65 decodes reception data RD by using the Turbo code.

A Turbo code corresponds to such a code capable of improving error correction capability rather than that of a Reed-Solomon code in such a manner that a gap is narrowed up to a theoretical restriction (namely, Shannon's restriction) by combining a simple separation code with a soft in/out decoder having an interleaver which is operated in a repetitive manner. As a result, this Turbo code can correct any sorts of errors, namely a random error and a burst error.

As a consequence, even when any sort of errors happen to occur, namely, any of the random error and the burst error happens to occur, the Turbo decoder 71 may detect an error fromthe received reception dataRD andmay correct the detected error, so that the communication can be maintained without any problem.

As previously explained, since the error correcting code system is changed/set in the communication apparatus of the embodiment mode 2, even when the sort of the occurring error (for instance, random error, burst error, and byte error) is changed, this communication apparatus can select such an error correcting code system which is suitable for the error sort, and thus, can furthermore improve reliability of the communication.

(EMBODIMENT MODE 3)

Next, a description is made of a communication apparatus according to an embodiment mode 3 of the present invention. Fig. 11 is a functional block diagram for indicating an internal arrangement of the communication apparatus according to the embodiment mode 3. Similar to the embodiment mode 1, the communication apparatus of this embodiment mode 3 corresponds to, for instance, a PLC adaptor 1. The PLC adaptor 1 contains a display unit 11 which is connected to a controller 9. As to the displayunit 11, if auser of this PLC adaptor 1 can visually recognize displayed information, then any of display unit modes may be employed, for instance, a liquid crystal display and an organic EL (Electro-Luminescence) display may be employed. It should be understood that structural elements of this communication apparatus except for the display unit 11 are similar to those of the communication apparatus shown in Fig. 1 according to the embodiment mode 1, and the same reference numerals of Fig. 1 will be employed as those for denoting these similar structural elements, and therefore, explanations thereof are omitted, Also, the controller 9 may function as one example of the communication status checker, the communication status output unit, andthe communication status informer.

Referring now to Fig. 16, communication operations executed by the PLC adaptor 1 with employment of the above-explained arrangement according to the embodiment mode 3 will be described.

While the controller 9 monitors a communication status (for example, S/N ratio) as to reception data RD based upon the reception data RD which is outputted from the error correcting decoder 65 of the receiver 6, the controller 9 produces image data which represents this monitored communication status. The display unit 11 displays thereon the produced image data under a predetermined display mode (for instance, numeral value, or gauge) . For instance, it is so assumedthat noise is generated from another household apparatus, and then, an error number of reception data RD is approximated to the correctable maximum error number. Since the display unit 11 displays thereon such an image data indicative of the deteriorated communication status, the user of the PLC adaptor 1 views the deteriorated communication status displayed on the display unit 11, so that this user can recognize that there is nomargin as to the error correcting capabilitywith respect to the deteriorated communication status.

As previously explained, in the communication apparatus according to the embodiment mode 3, since the user of the communication apparatus can grasp the communication status as to the reception data RD via the display unit 11, the user changes communication plugs, or utilizes a noise-free appliance in order that the error number of the reception RD does not exceed the correctable maximum error number, so that the communication can be maintained.

The above-explained embodiment mode 3 has exemplified such an example that the communication status is displayed. Alternatively, the communication apparatus of this embodiment mode 3 may simply display the communication status, but also may output an alarm by way of an image, or voice in the case that, for example, an error number of reception data RD is approximated to the correctable maximum error number. As a result, the communication apparatus may quickly inform that there is no margin in the error correcting capability with respect to the communication status. Also, the modes of the error correcting codes may be alternatively displayed in combinationwith the communication status, for instance, the normal mode is displayed in "LOW", and the enhancing mode is displayed in "HIGH." In addition, as one example of a user interface for outputting a communication status, the display unit 11 has been indicated. Alternatively, the communication status neednot be necessariIydisplayed as the image, but the communication status may be produced from a speaker as voice.

It should also be noted that the above-explained embodiment mode 3 has exemplified such a case that the communication status is displayed on the display unit 11 equipped in the own PLC adaptor 1. Alternatively, this communication status need not be always displayed on the display unit 11 employed in the own PLC adaptor 1, but the communication status may be displayed via a network to another communication apparatus (for example, mobile communication apparatus such as portable telephone and PHS) .

(EMBODIMENT MODE 4)

Next, a description is made of a communication system according to an embodiment mode 4 of the present invention. Fig. 12 is a block diagram for indicating a communication system 700 as the embodiment mode 4. As indicated in Fig. 12, the communication system 700 contains both a server 703 and a homegateway 702 which have been connected to a network 701 such as the Internet connected network, and also, contains a communication apparatus 1 which has been connected to the homegateway 702. It should be understood that an arrangement of the communication apparatus 1 is the same arrangement as the above-described PLC adaptor 1 shown in Fig. 5, and explanations thereof are omitted. Also, each of the server 703 and the homegateway 702 is equipped with an IC (Integrated Circuit) which constitutes a CPU (Central ProcessingUnit) , a memory, and a modem. The memory is constituted by a ROM and a RAM, which store thereinto predetermined information. The modem converts a digital signal into an analog signal.

Referring now to Fig. 12, communication operations executed by the communication system 700 with employment of the above-described arrangement will be described.

A controller 9 (not shown) of the communication apparatus 1 monitors a communication status as to reception data RD similar to that of the above-described embodiment mode 3. The controller 9 transmits the monitored communication status via the homegateway 702 and the network 701 to the server 703.

For instance, it is so assumedthat noise is generated from another household apparatus, and then, an error number of reception data RD is approximated to the correctable maximum error number. The controller 9 transmits the deteriorated communication status to the server 703, and thus, a manager of this server 703 can recognize that there is no margin as to the error correcting capabilitywith respect to the deteriorated communication status based upon the transmitted communication status.

Aspreviouslyexplained, in the communication system of the embodiment mode 4, since the server 703 receives the communication status as to the reception data RD from the communication apparatus 1, the manager of the server 703 can provide the following services in the case that the error correcting capability is not sufficiently high with respect to the communication status by establishing a cooperation with, for example, a service management firm, and thus, the communication by the communication system 700 can maintain the communication. As to these services, the manager changes communication plugs, or utilizes a noise-free appliance.

It should be noted that the above-explained embodiment mode 4 has exemplified such a case that the communication status with respect to a single set of the communication apparatus 1. Alternatively, a communication status corresponding to each of plural sets of the communication apparatus 1 may be managed. For instance, the server 703 may alternatively manage such information indicative of respective communication statuses in correspondence with such fixed information as customer information, a serial number, and shipping counting information in the communication apparatus 1. In accordance with this alternative management, the manager of the server 703 may alternatively provide very precise services with respect to the respective users of these plural communication apparatus 1 by being cooperated with the service management firm.

Although the arrangement of Fig.7 has been disclosed as one example of the communication system 700 in the above-explained embodiment mode 4, the present invention is not limited only to the arrangement. For instance, the communication apparatus 1 may be directly connected to the network 701 without via the homegateway 702. Also, as to the network, if the communication apparatus 1 can be freely connected thereto, then the present invention neednot be limited only to the Internet connectednetwork. For instance, an unified digital communication network such as ISDN (Integrated Services Digital Network), an international public network, a cable modem network, a DSL (Digital Subscriber Line) modem network, an FTTH (Fiber to the Home), or such an intranet network which has been individually constituted within an enterprise may be employed as the above-explained network. Furthermore, as to the Internet connected network, if an IP (Internet Protocol) layer in an OSI (Open System Interconnection) can be provided, then either an open type broadband network or an intranet network which has been individually constituted within an enterprise may be employed. Also, no specific restriction is required for a physical layer, a data link layer, and a network layer.

Further, as to the connecting means between the communication apparatus 1 and the network 701 in the communication system 700, if the communication apparatus 1 may be connected to the network 701 by employing at least one of a power line, a copper wire, a twisted wire, a coaxial cable, a wireless line, Ethernet (registered trademark) , a telephone line, and the like, then any of these connecting means may be employed, and both sorts of physical layers of interfaces and total quantities thereof are not limited.

This application is based on and claims the benefit ofpriorityof Japanese PatentApplicationNo.2004-229238 filed on August 5, 2004, the content of which is incorporated herein by reference in its entirely. <Industrial Applicability>

The inventive idea of the present invention can be applied to the communication apparatus, the reception apparatus, the communication method, and the communication system, which perform the error correction of the communication data based upon the error correcting code. Even in such a case that the communication status as to the communication data is not stable, lowering of the communication speed can be suppressed as such as possible, while the reliability of the communication can be maintained.

Claims

1. A transmission apparatus for transmitting/receiving communication data, and for performing an error correction of the communication data based upon an error correcting code, comprising: a code determinator, setting the error correcting code; an encoder, adding a redundant bit based upon the error correcting code set by the code determinator to the communication data; a transmitter, transmitting the communication data to which the redundant bit has been added by the encoder; a receiver, receiving the transmitted communication data; a decoder, detecting an error of the communication data received by the receiver based upon the error correcting code set by the code determinator, and for correcting the detected error; and a coding controller, controlling the code determinator in such a manner that the error correcting code set by the code determinator is changed in response to a degree of the error detected by the decoder and the changed error correcting code is set.

2. The communication apparatus according to claim 1, wherein the coding controller controls the code determinator in such a manner that a data length of the redundant bit based upon the error correcting code set by the code determinator is changed, and the changed data length of the redundant bit is set.

3. The communication apparatus according to claim 1, wherein: the codingcontroller controls the code determinator in such a manner that the system of the error correcting code set by the code determinator is changed into a different error correcting code system and the changed error correcting code system is set.

4. The communication apparatus according to claim 1, wherein: the transmitter transmits the communication data to which the redundant bit has been added via a power line; and the receiver receives the transmitted communication data via the power line.

5. The communication apparatus, according to claim 1, wherein: the transmitter includes a wavelet inverse transformer for performing a wavelet inverse transformation with respect to the communication data to which the redundant bit has been added by the encoder, and for transmitting the wavelet-inverse-transformed communication data; and the receiver includes a wavelet transformer for performing a wavelet transformation with respect to the transmitted communication data, and for receiving the wavelet-transformed communication data.

6. The communication apparatus as claimed in claim 1, further comprising: a communication status checker, checking a communication status as to the communication data received by the receiver; and a communication status output unit, outputting the communication status as to the communication data checked by the communication status checker to a predetermined user interface.

7. A communication system, comprising: the communication apparatus recited in claim 6 and a server, which are connected to a network; wherein: the communication apparatus is further comprised of: a communication status informer for informing the communication status as to the communication data checked by the communication status checker to the server.

8. A reception apparatus for receiving communication data, and for performing an error correction of the communication data based upon an error correcting code, comprising: a code determinator for setting the error correcting code; a receiver for receiving the transmitted communication data; a decoder for detecting an error of the communication data received by the receiver based upon the error correcting code set by the code determinator, and for correcting the detected error; and a coding controller for controlling the code determinator in such a manner that the error correcting code set by the code determinator is changed in response to a degree of the error detected by the decoder and the changed error correcting code is set.

9. A communication method for transmitting/receiving communicationdata, and forperforming anerror correction of the communication data based upon an error correcting code, wherein: the error correcting code is set; a redundant bit based upon the set error correcting code is added to the communication data; the communication data to which the redundant bit has been added is transmitted; the transmitted communication data is received; an error of the received communication data is detected based upon the set error correcting code, and the detected error is corrected; and the set error correcting code is changed in response to degree of the detected error and the changed error correcting code is set.