Method and apparatus for power line communication

Technical Field The present invention relates to a communication device, integrated circuit and communication method that can easily detect signals output from other communication devices that use different communication methods and are connected to a common transmission line while avoiding interference between signals without carrying out relatively onerous modulation and other processes.

Background Art [0002] US 200410208139 A1 relates to carrier management for the needs of the network. In a communication system using the OFDM-TDMA power line, the time slot and carrier frequency are allocated in a way that reallocates the time slots and carrier frequency to increase the efficiency of bandwidth utilization. Information on reallocation is sent between the sending and receiving stations by sending signal maps that specify the reallocation of time and carrier slots.

Several variations have been presented depending on the circumstances of channel usage and prior allocation of time slots and channels.

[0003] According to EP 1 357 718 A2, an OFDM (Orthogonal Frequency Division Multiplexing) transmitter converts a serial data stream into parallel data and segments the parallel data into multiple blocks; introduces interference data into each of the segmented blocks; performs an inverse fast Fourier transform on the respective blocks to generate time-domain signals and determines the phase coefficients for time-domain signals to reduce the PAPR ( Peak to Average Power Ratio).

[0004] Thanks to the current development of communication technology, PLC (Power Line Communication) is gaining popularity. PLC is a technology that performs multi-carrier communication between multiple terminal devices, using power lines installed inside buildings as transmission lines, and uses the OFDM (Orthogonal Frequency Division Multiplexing) system (for example, Japanese patent publication released for public review 2000165304). OFDM is a modulation method for the purposes of multi-carrier data transmission, by means of which many carriers are multiplexed on the frequency axis. OFDM uses FFT (Fast Fourier Transform) or DWT (Discrete Wavelet Transform) to limit the frequency intervals of multiple carriers and accurately arrange multiple carriers in such a way that they partially overlap, but do not interfere with each other. OFDM therefore enables broadband transmission by efficiently using a narrow frequency spectrum.

[0005] For multi-carrier communication, such as power line communication, interference suppression technology has been proposed in such a way that the phase vector flattens the time wave shape to prevent significant peak values ​​from occurring. In such technology, when the time wave shape does not have a significant peak, the phase of each subcarrier is rotated using the standard vector phase vector. However, when a significant peak is detected, the phase vector changes until the phase vector that generates no peak wave is found and the phase of each subcarrier is thus rotated according to the changed phase vector (Denis JG Mestdagh and Paul MP ​​Spruyt, "A Method to Reduce the Probability of Clipping in DMT-Based Transceivers, "IEEE Transactions on Communications, Vol. 44, No. 10, pp. 1234-1238, 1996). This technology for eliminating peak values ​​is crucial when reducing construction difficulties in a multi-carrier power amplifier.

[0006] Usually, when the specification of the same communication method is used, the specification of the communication devices connected to the network is generally common, even when different logical networks are created using a network key or the like. In this way, communication devices can detect (carrier detection) signals sent between different networks, at the physical layer level of communication devices, and it is also possible to avoid interference between signals using CSMA (Carrier Sense Multiple Access) technology, thereby ensuring smooth communication even in the case of relatively close located various networks.

[0007] However, different manufacturers may use different specifications for a communication method, such as a communication protocol, modulation scheme and frequency band. Such communication technology can be used in an environment where many types of communication methods are connected in the same location. For example, users (communication device users) in a multi-family building, such as a block of flats, do not necessarily use communication devices (e.g., modems) from the same manufacturer. In this case, many types of communication devices manufactured independently by many manufacturers can be simultaneously connected to a common power line.

[0008] When many types of communication devices are connected to a common power line, the communication device cannot demodulate the signal sent from another communication device using a different type of communication method. Therefore, such a signal is considered simply a disturbance. Therefore, although many types of communication devices use the same frequency band, even the presence of other communication devices is not recognized. This causes interference between signals transmitted from many types of communication devices, thus causing communication errors. In other words, many types of communication devices sometimes can't coexist on a shared power line.

[0009] On the other hand, when each communication device is configured to perform modulation, signals transmitted from other communication devices may be distinguished. However, modulation processes implemented to allow many types of communication devices to coexist cause the opposite effect of increasing load. Disclosure of Invention [0010] The purpose of the embodiments described below is to provide a communication device, integrated circuit and communication method that can easily detect signals output from other communication devices, even when many types of communication devices using different communication methods are connected to a common line transmission, without carrying out relatively onerous modulation and other processes.

[0011] A first communication device using a power line according to the present invention is defined in claim 1.

[0012] The method of communication according to the present invention is defined in claim 5.

Brief description of the drawings [0013]

Fig. 1 schematically shows a view of the communication configuration according to the first embodiment; Fig. 2 (a) is a perspective view from the front of the modem;

Fig. 2 (b) is a perspective view from the rear of the modem;

Fig. 3 is a block diagram showing the equipment that forms the modem according to the first embodiment.

outside system exemplified character

Fig. 4 shows a functional block diagram of a PLC block

PHY;

Fig. 5 shows the OFDM signal format;

<td>FIG.</td><td>6 shows an spectrum of an OFDM signal;</td>

<td>FIG.</td><td>7 (a) shows the time graph that it uses</td>

<td colspan="2">time division;</td>

<td>FIG.</td><td>7 (b) shows the time chart that it uses</td>

<td>different</td><td>example of time division;</td>

<td>FIG.</td><td>7 (c) shows the time graph he uses</td>

frequency and time division;

Fig. 8 (a) shows an example of attenuation frequency characteristics on a power line;

Fig. 8 (b) shows an example of a noise level characteristic frequency on a power line;

Fig. 9 shows time slots corresponding to request signals transmitted during control periods;

Fig. 10 is a time chart showing the exchange of control signals between modems;

Fig. 11 is a block diagram showing an example of the equipment that forms the modem in accordance with the second embodiment. Fig. 12 (a) is a time chart that uses frequency division;

Fig. 12 (b) is a time chart that uses frequency and time division;

Fig. 13 is a time diagram showing an example of how many modems operate when different request signals are transmitted;

Fig. 14 is a time diagram showing an example of how many modems operate when some communication methods are not synchronized with synchronization signals;

Fig. 15 is a block diagram showing an example of the equipment that forms the modem in accordance with the third embodiment.

Fig. 16 is a functional block diagram of a PLC PHY block of a backup integrated circuit;

Fig. 17 is a time diagram showing an example of how many modems operate in accordance with the third embodiment; Fig. 18 is a flowchart showing a process of detecting a request signal;

Fig. 19 shows time slots corresponding to request signals in accordance with the fourth embodiment;

Fig. 20 is a flowchart showing a process of detecting a request signal in accordance with the fourth embodiment;

Fig. 21 is a time diagram showing an example of how many modems operate in accordance with the fifth embodiment; Fig. 22 is a flowchart showing the process of modifying the phase vector according to the fifth embodiment;

Preferred Mode for Carrying Out the Invention [0014] First to fourth embodiments are described below with reference to Figures 1 to 22.

First embodiment [0015] The first embodiment is described below with reference to Figures 1 to 10.

[0016] Fig. 1 schematically shows a configuration view of the communication system 100 according to the first embodiment. As shown in Fig. 1, the communication system 100 includes a network using power lines 2 as transmission lines. Supply lines 2 include: power transmission cables from the power pole 7 that are provided outdoors; connection cable connected to power transmission cables via transformer 4 and internal wiring in the house 1. Power lines 2, which include power transmission cables, are connected to the electricity distribution board 6 via power lines 2, which include a connection cable. Fiber optic cable 8, which is connected to an ISP (Internet Service Provider) operator (not shown) or the like, is connected to the electricity distribution board 6 via a 10C3 modem that acts as a communication device.

[0017] The power lines 2, which are connected to the electricity distribution board 6, are connected to a plurality of sockets 5 installed in the house 1. Many modems, using different types of communication methods, are connected to the sockets 5 via plugs 3 and power lines 2 (for example, WF cables). Power lines 2 supply commercial AC voltage (e.g. 100 V, 60 Hz (or 50 Hz)) to various electrical devices, although other values ​​than 100 V, 60 Hz can be used. For example, AC 120 V, 60 Hz is used in the United States, and AC 110/220 V, 50 Hz is used in China, etc.

[0018] As shown in Fig. 1, modems 10A1, 10A2 and 10A3 use communication method A; 10B1 and 10B2 modems use communication method B, and 10C1, 10C2 and 10C3 modems use communication method C. All modems are installed in the home 1. Various electrical devices are connected to the appropriate modems via LAN cables

9. In particular, extension phone 109 is connected to the 10A1 modem, and telephones with the display 107 and 107 are connected to the 10A2 and 10A3 modems. Television 102 is connected to a 10B1 modem and server 105 is connected to a 10B2 modem. The portable personal computer (hereinafter simply referred to as PC) 101 is connected to the 10C1 modem and TV 106 is connected to the 10C2 modem.

[0019] In the following description, when no special distinction is required between modems 10A1, 10A2, 10A3, 10B1, 10B2, 10C1, 10C2 and 10C3, all these modems are simply referred to as "modem 10". The modem described in this embodiment is an example of a communication device 10. It is possible to use any device having a communication function other than a modem. For example, electrical devices having a modem function (in particular, various electrical devices 101, 102, 103, ... shown in Figure 1) can also be used.

[0020] In the specification, communication using the power line used only in residential buildings, e.g. houses and multi-family buildings, as well as in other facilities, e.g. factories and buildings, has been defined as "internal communication" and communication using the power line ( covering communication methods used in buildings that use such communication using a power line), used for external power transmission cables and fiber optic cables, was defined as "access communication". In the following, a communication system using home communication is simply referred to as an "internal system" and a communication system using access communication is simply referred to as an "access system". In fig. 1 the communication system, including 10A1, 10A2, 10A3, 10B1 and 10B2 modems, relates to the internal system, and the communication system, including 10C1, 10C2 and 10C3 modems, applies to the access system.

[0021] Fig. 2 (a) is a perspective view from the outside of the front of the modem, and Fig. 2 (b) is a perspective view from the outside of the rear of the modem. Modem 10 has a housing 11 shown in Fig. 2. Indicators 16, such as LEDs (Light Emitting Diode) are located on the front of the housing 11. Power connector 12, modular LAN (Local Area Network) socket 13, such like RJ 45 and the D-sub 15 connector are on the back of the case 11.

Power lines 2, such as a parallel connector cable, are connected to the power connectors 12. The LAN cable 9 is connected to the modular jack 13. The D-sub cable (not shown) is connected to the D-sub 15 connector. [0022] Fig. 3 is a block diagram showing an example of the equipment that forms modem 10 in accordance with the first embodiment. As shown in Figure 3, modem 10 includes a circuit module 20 and a switching controller 50. The switching regulator 50 supplies various voltage levels (e.g. + 1.2V, + 3.3V, + 12V) to the 20 circuit module.

The circuit module 20 includes the main integrated circuit 22, the AFE IC (Analog Front End IC) 23 integrated circuit, the bandpass filter 25, the driver integrated circuit 26, the coupling circuit 27, the bandpass filter 29, the AMP IC 30 integrated circuit , bandpass 31, integrated circuit ADC IC 32 analog converter, memory 33 and Ethernet integrated circuit PHY IC 12. The power connector 12 is connected to the power lines 2 via plug 3 and a socket

5. [0023] The main integrated circuit 22 includes: a CPU (Central Processing Unit) 22A, a PLC MAC block (Media Access Control PLC) 22C and a PLC PHY block (PLC physical layer) 22B. The CPU 22A is equipped with a 32-bit RISC (Reduced Instruction Set Computer) processor. The MAC 22C PLC block controls the MAC layer, and the PHY 22B PLC block controls the PHY layer. AFE IC 23 includes the 23A digital-to-analogue converter (DAC), 23B and 23C regulated gain (VGA) amplifiers, and the 23D to digital analogue converter (ADC). The coupling system 27 includes a coil transformer 27A and coupling capacitors 27B and 27C.

[0024] The circuit module 20 further includes a backup integrated circuit 42, AFE IC 43, a bandpass filter 45, a driver integrated circuit 46 and a bandpass filter 49. The backup integrated circuit 42 includes the PLC MAC 42C block and the PLC PHY block 42B. AFE IC 43 includes the 43A digital-to-analogue converter (DAC), 43B and 43C regulated gain (VGA) amplifiers, and the 43D analog-to-digital converter (ADC).

[0025] The main integrated circuit 22, as with a standard modem, is an electrical circuit (LSI) that performs signal processing, including basic control and modulation / demodulation for data transmission. In other words, main chip 22 modulates the received data that is output from a communication terminal, such as a computer, and outputs as transmitted signal (data) to AFE IC 23. The main integrated circuit 22 also demodulates the transmitted data, which is input via AFE IC 23 from the supply lines 2, and outputs as a received signal (data) to a communication device, such as a PC. The main integrated circuit 22 further outputs a predefined transmission request signal to the redundant integrated circuit 42 prior to data transmission to check whether the power lines 2 can be used.

[0026] The controller chip 26 functions as a switch that blocks / passes transmitted and received signals between the main chip 22 and the power lines 2. In other words, the controller chip 26 acts as an interface between the digital signal processing circuit and the power lines, and the transmission data can be controlled by switching the 26 ON / OFF driver integrated circuit. The controller chip 26 can assume any configuration as long as it has control capabilities to enable / disable data transmission. For example, the controller chip 26 may be equipped with a switch, such as an analog switch, which allows ON / OFF control by an external signal.

[0027] The first signal output unit, the second signal output unit and the phase vector determination unit are respectively provided as the PHY PLC block 42B of the spare circuit block 42. The data transmission range determining unit is provided as the PLC block PHY 22B and the bandpass filters 25 and 29. The data transmission unit is provided as a PLC block PHY 22B and AFE IC 23.

The PHY 42B PLC block is an example of a receiver, a carrier detector and a transmitter. [0028] Fig. 4 is a functional block diagram of a PLC PHY block 42B of a spare circuit 42. First, the phase determination process that uses inverse wavelet transform to modulate a multi-carrier signal will be described with reference to Fig. 4.

[0029] The PHY PLC block 42B, which is visible at the bottom of Fig. 4, includes: a symbol mapping module 406 that maps transmitted data as serial data on a complex coordinate plane; P / S 407 converter that converts serial data to parallel data corresponding to the corresponding multi-carrier subcarriers; phase 408 rotator that rotates each of the parallel data phases; inverse waveguide 410 that performs multi-carrier modulation by performing inverse wavelet transform on parallel data whose phase has been rotated, and a 405 controller that controls phase vectors rotated with a phase rotator 408. A phase vector is a set of values ​​that indicate the phases corresponding to individual subcarrier signals in a multi-carrier signal. A phase vector is a set of values ​​to equalize time wave shape levels to avoid significant peak values. The signal phases of all subcarriers are randomly selected so that time waveform levels do not produce a peak. Accordingly, since the phase of each subcarrier signal is arbitrary, time waveform levels are equalized and therefore no peak values ​​are generated.

[0030] The symbol mapper 406 performs the first modulation in which the transmitted data in the form of bit data is converted into symbol data with all of the M-1 subcarriers mapped in the complex coordinate plane. The S / P 407 converter sequentially converts the serial input data (transmission symbols) generated by the first modulation to be sequentially entered into parallel data corresponding to each of the subcarriers in the multi-carrier signal. The 408 phase rotator then rotates the parallel input data phases. In this case, (2n-1) -th input (n is a positive integer) is considered as the phase-complex component of complex data, while the 2-th input is considered as the orthogonal component (assuming that 1 £ n £ dM / 2-1 ) complex data. The numbers of subcarriers are considered 0 - M - 1. Complex subcarriers are formed from pairs of subcarriers and the phase of each subcarrier is rotated. In this example, the maximum number of parallel data (number of subcarriers) for which the phase has been rotated is M / 2-1. Inverse waveguide 410 performs multi-carrier modulation by means of inverse wavelet transform of parallel data whose phase has been rotated by each subcarrier, generating transmitted signals in multiple carriers. The S / P converter can be used before the symbol mapping module.

[0031] The controller 405 provides a signal that controls the phase vector (hereinafter referred to as "vector control signal" for simplicity) to the phase rotator 408, controlling the phase vector settings and changes. In this example, controller 405 may include a random value generator. The random value generator generates a random value using, for example, the PN ( Pseudo Noise) and provides a random value to the phase rotator 408 as a vector control signal to perform phase rotation for each of its target subcarriers. As random values ​​mentioned above two values ​​are generated: 0 and p (or -1). Optionally, controller 405 may include a cyclic shift marker to generate a vector control signal (phase shift value) for the cyclic shift operation; a vector control signal is supplied to the phase rotator 405; a phase rotation is performed for each of the subcarriers to be used in communication. [0032] As outlined above, since the phases are rotated based on the PN sequence, phase vectors having less time correlation can be set so that the first and second signals can be differentiated with greater accuracy. ą. In particular, the use of the M sequence as a PN sequence allows the determination of phase vectors with consistent autocorrelation (coherent phases), which allows for more accurate distinction. Any sequence can be used to perform phase rotation as long as its autocorrelation is sensitive and the mutual correlation is insensitive. For example, a PN sequence such as the M sequence and the Gold sequence may be used to perform phase rotation.

[0033] Instead of rotating each of the target subcarriers each time, it is also possible to pre-write, on a carrier such as memory, output signals from a phase rotator 408 or inverse waveguide 410, and retrieve the signal from the memory as a specific data signal each time when a vector control signal is generated to output the generated vector control signal as a vector control signal. Optionally, it is also possible to download specific data each time the phase vector is changed, and to output specific data as a vector control signal.

[0034] The following is a description of a phase re-rotation process that uses wavelet transform to modulate a multi-carrier signal. PLC PHY 42B block, which is visible in the upper part of Fig. 4, further comprising: a waveguide 401 that performs multi-carrier demodulation using a wavelet transform of the received signal; a 402 phase rotator that rotates the parallel data phases corresponding to each of the modulated subcarriers, and a P / S 403 converter that converts the parallel data corresponding to each of the subcarriers whose phases have been rotated again to serial data.

[0035] The waveguide 401 demodulates the multi-carrier signal using the wavelet transform of the received signal and generates parallel data corresponding to each of the subcarriers in the multi-carrier. The phase rotator 402 then rotates the data separately again by rotating the parallel input data phases. The P / S 403 converter then converts the parallel input data, which each packet corresponds to each of the subcarriers in many carriers, into serial data to obtain the received data. Changing the order of the phase 402 rotator and P / S 403 converter does not cause difficulties in operation.

[0036] The controller 405 controls the settings and changes of the phase vector by supplying the vector control signal to the phase rotator 402. As in the above-described phase determination process, the controller 405 includes a random value generator that generates a random value, for example using a PN (Pseudo Noise) and provides the generated random value as a vector control signal to a phase rotator 402 to invert each of the target subcarriers. As random values ​​mentioned above, two values ​​are generated: 0 and p. Optionally, the controller 405 may include a cyclic shift marker to generate a vector control signal (phase shift value) for the cyclic shift operation; the vector control signal is supplied to the phase rotator 402 and phase rotation is performed on each of the subcarriers for use in communication. Therefore, such a cyclic shift operation allows a large number of subcarriers to undergo phase rotation at a relatively low load.

[0037] In a first embodiment, the OFDM signal is used as a data signal or a control signal (described later). Fig. 5 shows the OFDM signal format. Fig. 6 shows the spectrum of an OFDM signal; The OFDM signal is configured in the same way as the preamble signal, which is usually used for carrier detection and synchronization processes. The preamble signal includes pre-defined data. For example, controller 405 enters, as pre-defined data, a series of the same values ​​for each subcarrier (e.g., signal in the form 1,1,1, ··· for each subcarrier) into a phase rotator 408; rotates each of the subcarriers with a suitable phase vector and generates a time signal using a frequency-time transform in an inverted waveguide 410. For example, a multi-tone signal with a symbol length of about 100 ms (e.g. 56 waves) is used as the current OFDM signal.

[0038] Although the above descriptions relate to the case where the phase vector is rotated by means of a wavelet transform, other transformation methods, such as Fourier transform, can also be used. The phase determination and re-rotation processes of the PHY 22B PLC block are the same as for the PHY 42B PLC block, so their descriptions will be omitted.

[0039] Fig. 7 (a) shows a time chart that uses time division, Fig. 7 (b) shows a time chart that uses another example of time division, and Fig. 7 (c) shows a time chart that uses frequency division and time.

[0040] In a first embodiment, the frequency bands on the power lines 2 are divided, as shown in Fig. 7, into the control signal band BW1 and the data signal band BW2. The BW1 control signal band is the band for transmitting the control signal. The control signal is used to control communication between modems 10 and includes an SS synchronization signal and an RS request signal, wherein the SS synchronization signal indicates the synchronization control for each modem 10, and the RS request signal means that each modem 10 starts data transmission. The RS request signal is an example of the first signal and the SS synchronization signal is an example of the second signal.

[0041] The BW2 data signal band is the band for transmitting the data signal. The data signal contains various information, such as video, voice and text data, which are specified in the packet data block. When the frequency band used for power line communication is, for example, between 2 and 30 MHz, the 2-3 MHz frequency band is allocated as the BW1 control signal band, and the 3-30 MHz frequency band is allocated as the BW2 data signal band. Although any frequency band can be selected as the BW1 control signal bandwidth, lower frequencies reduce the sampling frequency, thus allowing the modem to be configured using a simple circuit.

[0042] Fig. 8 (a) shows an example of attenuation-frequency characteristics on a power line, and Fig. 8 (b) shows an example of noise level and frequency on a power line characteristics. As shown in Fig. 8 (a), signal attenuation is high in the frequency band

2-3 MHz, which translates into higher noise levels, as shown in Figure 8 (b). To achieve a high transmission rate, it is preferable that the communication uses the widest possible frequency band. However, as described above, simultaneously with the attenuation level, the noise level in the 2-3 MHz band increases, and thus the S / N (signal-to-noise ratio) decreases, affecting the high transmission speed to a limited extent . Thus, the reduction in transmission speed can be kept to a minimum by allocating the 2-3 MHz frequency band only for negotiation as the BW1 control signal band. This also allows the use of a relatively high frequency band for data transmission, which improves the efficiency of data transmission.

[0043] In the following, a specific control operation implemented by the PLC PHY block 42B of the backup integrated circuit 42 shown in Fig. 3 is described, wherein the control operation allows multiple modems 10 to coexist on common power lines 2.

[0044] In a first embodiment, two or more different types of phase vectors that use the same properties (e.g., sampling frequency and symbol length) of the control signal are used as the control signal common to many types of modems 10. For example, different types of phase vectors, such as the phase vector used solely for the needs of the SS synchronization signal and the phase vector used exclusively for the needs of the RS request signal, are used as needed to control many types of modems.

[0045] In particular, the PHY PLC block 42B of the standby integrated circuit 42 sends a predefined signal to the controller integrated circuit 26 so that the controller integrated circuit 26 blocks data transmission in the main integrated circuit 22. When the controller integrated circuit 26 is turned OFF, the PLC block PHY 42B outputs the SS synchronization signal via AFE IC 43, band pass filter 45, and driver integrated circuit 46.

The SS synchronization signal is applied to the AC power supply via the coupling system 27 and output to the power lines 2 via the power connector 12, plug 3 and socket 5. The SS synchronization signal is set to be output during each predefined time interval, and the block The PHY 42B PLC repeatedly outputs the SS synchronization signal in each predefined cycle. [0046] As shown in Fig. 7 (a), a modem PHY PLC block 42B

10B1 (see Fig. 1), which uses communication method B, outputs the synchronization signal SS at time t1, t9, t11, t20, t30, ···. As described earlier, since two or more types of phase vectors are used, each modem 10 stores, in its predefined memory (not shown), data (two values, i.e. 0 and for each subcarrier) associated with the control signal phase vectors, such as an SS synchronization signal and an RS request signal. Thus, the PHY PLC block 42B of each modem 10 retrieves data associated with phase vectors from its own memory and detects the SS synchronization signal after performing the phase rotation process described earlier in the phase rotator 402 and controller 405. By detecting the SS synchronization signal, each modem 10 sets control periods T1, T2, T3, T4, ···, each of which defines a previously defined cycle (for example, order ms) as one cycle. As described earlier, the period for transmitting the control signal is referred to as the "control period Tc".

[0047] Fig. 9 shows time slots corresponding to request signals transmitted during the control period Tc; The PLC PHY block 42B of each modem 10 is configured to output the RS request signal after a period corresponding to its own communication method based on where the SS synchronization signal was detected. The phase rotator 408 and controller 405 perform the previously described phase determination process in such a way that the phase vector of the RS request signal is different from the phase vector of the SS synchronization signal.

[0048] As shown for example in Fig. 9, it is assumed that modem 10B1 outputs an SS synchronization signal between times

The T18 that correspond are determined during t1 and t2. In this case, modems 10A1, 10A2 and 10A3, which use communication method A, output the request signal RS after the time elapsed between times t1 to t2. Modems 10B1 and 10B2, which use the B communication method, output the RS request signal after a time elapsed from the times t1 to t3. The 10C1 and 10C2 modems, which use the C communication method, output the RS request signal after a time elapsed from times t1 to t4. In other words, time slots T12, T13, T14, · communication methods A, B, C, · control period Tc. Setting a period for each time slot does not require the intervals to be equal.

[0049] Each modem 10 stores in its pre-defined memory data associated with the phase vector of the RS request signal. Thus, as with the SS synchronization signal, each modem 10 fetches from its memory data associated with the phase vector and detects the RS request signal after performing the phase rotation process in the phase rotator 402 and controller 405. The request signal RS, as previously described, is determined by the phase rotator 408 in such a way that its phase vector is different from the phase vector of the SS synchronization signal. Thus, each modem 10 can distinguish the RS request signal from the SS synchronization signal based on the differences in their phase vectors.

[0050] When the same phase vector is used for the SS synchronization signal and the RS request signal, and when carrier detection is performed using signals output from the waveguide 401, for example using inter-carrier correlation and frequency-correlation distribution, it is possible it becomes receiving both signals, which makes it impossible to determine whether the SS synchronization signal or RS request signal was sent. However, the power line communication device supports the 405 controller to perform carrier discovery using the phase vector for the SS synchronization signal and to perform carrier discovery using the phase vector for the RS request signal. In this way, two different phase vectors are used for two different signals, and thus it becomes impossible to perform carrier detection simultaneously for multiple signals in the frequency domain. This makes it possible to distinguish between the SS synchronization signal and the RS request signal, which allows each modem to confirm what the control signal means. [0051] Each modem 10 stores in its pre-defined memory (not shown) data related to the correlation between the time slot and the communication method. Based on the correlation, it is possible to detect in which time slot the RS request signal is output during one control period Tc, and thus to learn the number of communication modes (namely the number of types of communication modes) of modems that reported the initiation of data transmission.

As stated above, since each RS request signal is output in respective time slots T12, T13, ---, T18, it is possible to avoid interference between the RS request signals. As a result, each modem 10 can reliably detect RS request signals output from other modems 10. When the correlation between the time slot and the communication method has been previously defined, the order of outputting the RS request signal is not limited to A®B®C® ···, but can be modified if required. The time slots T12, T13, ···, T18 do not have to have equal intervals.

[0053] Furthermore, when a control signal is output to each of the time slots during the control period Tc, any functional meaning is possible for each slot. For example, it is possible to use a specific time slot during the Tc control period (e.g., T18 time slot) as a special time slot that allows multiple modems to coexist by using the frequency domain.

[0054] The following is a description of an example of a specific operation performed by modem 10 according to the first embodiment with reference to Figures 1, 3, 7 (a), 9 and

10. Fig. 10 is a time chart showing exchange of control signals between modems 10. In this example, modem 10B1, which uses communication method B, outputs synchronization signals. The descriptions provided apply only to the transmission of control signals from the 10A1, 10B1 and 10C1 modems to facilitate the understanding of the embodiment.

[0055] As shown in Figs. 7 (a), 9 and 10, the modem 10B1 outputs 2 sync signals SS at supply time t1. The PLC block PHY 42B of each modem 10 monitors the status of all time slots, i.e. T12, T13, ···, T18 during the control period Tc, and therefore other 10A1 and 10C1 modems detect SS synchronization signals output from the 10B1 modem. In this case, it is assumed that the video signal signal is captured by the internal telephone

109 (see Fig. 1) is forwarded to the 10A1 modem via a LAN cable 9. The 10A1 modem outputs 2 RS request signals during t2 to output the received video image signal to a telephone with a display 103 (see Fig. 1) via 10A2 modem. Other 10B1 and 10C1 modems detect RS request signals output from 10A1 modem. The RS request signal and SS synchronization signal transmitted to the 10A2 modem are not shown in Figure 10.

[0056] Modems 10B1 and 10B2, which use communication method B, as well as modems 10C1, 10C2 and 10C3, which using communication method C, do not perform data transmission between times t3 and t9, and therefore do not output the RS request signal as shown in Fig. 7 (a) and 9. As the 10A1 modem monitors for RS request signal in time slots T12, T13, ---, T18 and detects the lack of the RS request signal, the 10A1 modem performs data transmission using the next entire control period Tc (T2). [0057] When modem 10B1 outputs 2 SS synchronization signals to power lines at time t9, modem main chip 22 of modem 10A1 (see Fig. 3) outputs a transmission request signal to backup circuit 42 (see Fig. 3). Upon receipt of the transmission request signal, the back-up integrated circuit 42 sends a predefined signal to the controller integrated circuit 26 and allows forwarding of transmitted and received signals. In this state, modem 10A1, as shown in Fig. 10, sends to DS10A2 a data signal DS video signal that was received from extension telephone 109.

[0058] After receiving the DS data signal, the 10A2 modem sends the ACK signal (confirmatory response) to the 10A1 modem. After receiving the ACK signal, the 10A1 modem sends another DS data signal. The 10A2 modem sends the received DS data signal to the phone 103 via LAN 9. As a result, the video image captured by the extension phone 109 is displayed on the display of the phone 103. As stated earlier, as the data transmission is carried out in the BW2 data signal band, the data transmission using the internal communication method A is, as shown in Fig. 7 (a), carried out in the frequency band 3-30 MHz during the control period Tc ( T2).

[0059] At time t9, it is assumed that the user supports TV 102 (see Fig. 1) to replay the moving image data that is stored on the server 105 (see Fig. 1). TV 102 then sends the moving image data request signal to the 10B1 modem via a LAN cable 9. After receiving the 10B1 modem signal, as shown in Fig. 7 (a), it outputs an RS request signal to the power lines at t10

2. During the check period Tc (T2) between times t9 and t10, other modems 10 do not output an RS request signal. As a result, the 10B1 modem detects the lack of an RS request signal from the other 10 modems and thus performs data transmission using the next entire control period Tc (T3). At t11, the 10B1 modem outputs the SS synchronization signal and then sends the moving image data request signal to the server 105 via the 10B2 modem. After receiving the request signal, server 105 sends the DS video signal data signal to modem 10B1, after which the moving image stored on the server 105 is displayed on the TV 102. In other words, data transmission using the internal communication method B is implemented, as shown in Fig. 7 (a) in the 3-30 MHz frequency band during the Tc (T3) control period, as in the case of communication method A.

[0060] Next, it is assumed that PC 101 (see Fig. 1) sends to the ISP (not shown) a request signal for example HTML (Hyper Text Markup Language) data.

After receiving the request signal from PC 101 and detecting the SS synchronization signal output during t11, the 10C1 modem outputs the RS request signal to power lines 2 during t14.

As the other 10 modems do not output the RS request signal, the 10C1 modem performs data transmission using the next control period Tc (T4). After the 10C1 modem sends the request signal to the 10C3 modem, the 10C3 modem requests a World Wide Web server (not shown) for the ISP Internet operator to send HTML data via fiber optic cable 8 (see Fig. 1). After receiving the HTML data, the 10C3 modem sends the HTML data to PC 101 via a 10C1 modem, after which the HTML data is displayed on the PC 101. In other words, data transmission using the C access method is implemented, as shown in Fig. 7 (a) , in the 3-30 MHz frequency band during the Tc (T4) control period, as in the case of communication method A and B.

[0061] At t20, the 10B1 modem outputs an SS synchronization signal. However, during the control period Tc (T4), none of the modems 10 outputs the RS request signal. Therefore, no data transmission is carried out during the Tc control period since t30. The 10B1 modem outputs the SS synchronization signal during each control period Tc. When any modem 10 outputs the RS request signal, one of the modems 10B1 performs data transmission using the next control period Tc.

[0062] As described above, in the first embodiment, different phase vectors are used for the SS synchronization signal and the RS request signal. Therefore, each modem 10 can easily detect an RS request signal derived from another modem 10 based on the SS synchronization signal without performing relatively burdensome modulation and other processes. This allows many types of modems 10, using different communication methods on shared power lines 2, to easily coexist. In particular, in the case of communication using a power line, which has a large amount of correlation noise on the time axis, each communication device can perform data transmission while avoiding interference between signals.

[0063] In the first embodiment described above, descriptions have been provided for the case in which the number of timeslots is 8, as shown in Fig. 9. However, the number need not be 8 and can be arbitrary as long as it is 2 or more. In addition, descriptions have been provided for the case where each time slot is pre-allocated to the appropriate communication method. However, the appropriate correlation does not require prior definition. When the modem has been recently installed in the network, for example, it is possible to monitor the status of the RS request output signal and when a free time slot is detected (e.g. when a time slot in which it is detected that no RS request signal is output during a predefined period), the detected time slot can be used.

[0064] In the first embodiment described above, a case is presented in which data transmission is carried out using one communication method during one control process Tc. However, data transmission can also be accomplished using multiple communication methods during one control period Tc.

[0065] Descriptions have been made with reference to Fig. 7 (b) for the case in which data transmission is carried out by using time division, using a variety of communication methods during the control period Tc. The operations between times t1 and t11 in Fig. 7 (b) are the same as those described in Fig. 7 (a), and therefore their descriptions are omitted. The 10A1 modem outputs the RS request signal at t12, and the 10B1 modem outputs the RS request signal at t13. Each modem 10 detects based on the RS request signal detected during one control period Tc the number of communication modes of the modems 10 that perform data transmission. In particular, modems 10A1 and 10B1 detect an RS request signal in time slot T12 corresponding to communication method A (see Fig. 9) and an RS request signal in time slot T13 corresponding to communication method B. On the other hand, the 10A1 and 10B1 modems detect the lack of an RS request signal in other time slots T14, T15, ···, T18. As a result, modems 10A1 and 10B1 detect that the number of communication methods is two, i.e. communication methods A and B.

[0066] PLC PHY 22B of each modem 10 divides, based on the number of communication methods, the time domains during the control period Tc for data transmission. In this example, the order of the split time domains is determined as the A® B communication methods. Therefore, the PHY PLC 22B of the 10A1 modem sets its time domain in such a way that data transmission takes place between times t20 and t21. In turn, PLC PHY 22B of modem 10B1 sets its time domain in such a way that data transmission is carried out between times t21 and t30. As a result, data transmission using communication method A and data transmission using communication method B are performed based on the division of time during the control period Tc (T4) as shown in Fig. 7 (b).

[0067] Hereinafter, with reference to Fig. 7 (c), a case in which data transmission is carried out by using frequency division, using multiple methods of communication during one control period Tc. In Fig. 7 (c) the operations between times t1 and t11 are the same as those described in Fig. 7 (a) and their descriptions are therefore omitted. The 10B1 modem outputs the RS request signal at t13, and the 10C1 modem outputs the RS request signal at t14. In turn, during the control period Tc (T4), other modems 10 do not output the RS request signal. As a result, the 10B1 and 10C1 modems detect that the number of communication methods is two, i.e. they are communication methods B and C.

[0068] The PLC PHY 22B of each modem 10 divides, based on the number of communication methods, the frequency domain during the control period Tc for data transmission.

In this example, the internal system is set in the high frequency band in the BW2 data band and the access system is set in the low frequency band in the BW2 band. As a result, the PLC PHY 22B of modem 10B1 sets its frequency domain in such a way that the data transmission is carried out in the high frequency band in the BW2 data band through the bandpass filters 25 and 29. In turn, the PLC PHY 22B of the 10C1 modem sets its frequency domain in such a way that data transmission is carried out in the low frequency band in the BW2 data band via bandpass filters 25 and 29. As a result, data transmission using communication method B and data transmission using using the communication method C are implemented based on frequency division during the control period Tc (T4) as shown in Fig. 7 (c). When it comes to a system such as an access system with a long transmission line, the components in the high frequency band have relatively high attenuation. Therefore, the entire frequency spectrum can be effectively used by allocating the access system to the low frequency band.

[0069] As described earlier, at least one of the time domain and frequency domain for the purpose of data transmission is determined based on the number of communication methods, and the data transmission is performed using the established domain. Therefore, each modem 10 can perform data transmission while avoiding interference between data signals.

Second embodiment [0070] The second embodiment is described below with reference to Figures 1, 2 and 11 to 14.

[0071] The communication system 100 according to the second embodiment is the same as that described in the first embodiment, and therefore its descriptions will be omitted. The communication device according to the second embodiment is the same modem 10 as described in the first embodiment, and therefore its description will be omitted.

[0072] Fig. 11 is a block diagram showing an example of the equipment that forms the modem 10 according to the second embodiment. Modem 10, as shown in Fig. 11, does not have a backup integrated circuit 42, which is shown in Fig. 3. Modem 10, as shown in Fig. 11, also does not have AFE IC 43, bandpass filters 45 and 49, and the driver integrated circuit 46 (hereinafter referred to as the "AFE circuit", which is shown in Figure 3). In other words, modem 10 has the same components as described in the first embodiment except for the removed redundant integrated circuit 42 and AFE circuit, so their descriptions will be omitted here. The main integrated circuit 22 of Fig. 11 also has the function of a spare integrated circuit 42 of Fig. 3. Therefore, the PLC block PHY 22B of the main integrated circuit 22 has the corresponding components shown in Fig. 4, and therefore their descriptions will be omitted here.

[0073] The following is an example of a specific operation of modem 10 according to the second embodiment with respect to Figs. 11 and 12. Fig. 12 (a) is a time chart that uses frequency division, and Fig. 12 (b) is a chart time, which uses frequency and time division.

[0074] First, descriptions of the example of operation shown in Fig. 12 (a) will be provided. In this example, the operation is different from that described in the first embodiment. The same frequency band is used as the shared frequency band BW1, BW21, BW2 for transmitting the control signal and performing data transmission. When the frequency band for communication using power lines is for example between 2 and 30 MHz, the shared frequency band BW1, BW2 is set between 2 and 30 MHz. The shared frequency band BW1, BW2 can be modified to be different from the frequency band to be used.

[0075] At t41, the PHY PLC block 22B of modem 10B1 outputs the SS synchronization signal to the power lines 2 via the band pass filter 23, the SS synchronization signal being determined in the shared frequency band BW1, BW2. At t42, the PHY PLC block 22B of modem 10A1 outputs the RS request signal using a bandpass filter 25, as in the case of the SS synchronization signal, the RS request signal being set in the shared frequency band BW1, BW2. At t43, the PHY PLC block 22B of modem 10B1, as in the case of modem 10A1, outputs a request signal RS which is determined in the shared frequency band BW1, BW2.

[0076] In the second embodiment, as in the first embodiment, the period between two adjacent SS synchronization signals is set as one cycle. However, as shown in Fig. 12, one cycle is divided into the control period Tc (T21) and the subsequent data period Td. In other words, the control signal and the data signal are time-divided as opposed to the first embodiment. In addition, as shown in the example shown in Fig. 12 (a), the data period Td is divided in terms of time into many data periods T22, T23, T24, [0077] In particular, modem 10A1 performs data transmission between times t49 and t50 in the shared frequency band BW1, BW2 during the first data period T22 and modem 10B1 performs data transmission between times t50 and t51 in the shared frequency band BW1, BW2. Modem 10A1 performs data transmission between times t51 and t52 during the second data period T23, and modem 10B1 performs data transmission between times t52 and t53. Modem 10A1 performs data transmission between times t53 and t54 during the third data period T24, and modem 10B1 performs data transmission between times t54 and t55.

[0078] As described above, in the second embodiment, the same frequency band is used to transmit the control signal and to perform data transmission.

[0079] Therefore, as shown in Fig. 3 in a first embodiment, the circuits of the backup integrated circuit 42 and AFE can be omitted. This configuration avoids large-scale circuit modification, which means that many modems 10 can coexist on shared power lines 2.

[0080] Although the time division has been described in the second embodiment described above, it is also possible to use frequency division. Time division and frequency division can also be combined. The case where time division and frequency division are combined is described below with reference to Fig. 12 (b).

[0081] For example, when each modem 10 detects an RS request signal only from an internal system during the control period Tc, data transmission is performed using a time split between different communication methods as in Fig. 12 (a). Then, as shown in fig. 12 (b) when each modem 10 detects communication methods A, B and C, RS request signals from the internal and access system, internal communication methods A and B implement data transmission by using time division, and the access communication method C implements data transmission by using frequency division. In this case, the 10A1 and 10B1 modems, using the internal system, perform data transmission by narrowing the 2-30 MHz frequency band, used to send control signals to, for example, the 3-30 MHz frequency band in such a way that data transmission can be carried out in such a narrowed frequency band. In turn, the 10C1 modem, using the access system, performs data transmission in the free 2-3 MHz frequency band. In this case, since different frequency bands are used for transmitting control signals and DS data signals, each modem 10 may have the equipment configuration shown in Figure 3.

[0082] Furthermore, Fig. 12 (b) is only an example of a combination of time division and frequency division, and it is possible to use another combination. For example, when there are many ways of communication that use an access system, data transmission can be accomplished using a time division between communication methods using the access system. It is also possible to use time division as a multi-access method for the needs of the internal and access system, while using frequency division in each of the internal and access systems. In addition, it is possible to determine whether to use time division or frequency division as the communication method based on which time slot is to be used.

[0083] Furthermore, in the second embodiment described previously, the descriptions have been provided for the case in which all control signals are transmitted in the same frequency band. However, it is also possible to use different frequency bands to transmit different control signals. FIG. 13 is a time diagram showing an example of how many modems 10 operate when different request signals are transmitted; In this case, the control signal using the internal system uses the 2-30 MHz frequency band, and the control signal using the access system uses the 2-3 MHz frequency band. Internal data transmission uses the 3-30 MHz frequency band, which is different from the band used to send control signals. In turn, access data transmission uses the 2-3 MHz frequency band, which is the same as the band used to send control signals. In this way (for example for reducing the size of the circuit), a communication method that uses a narrow frequency band can result in the size of the circuit not being large.

[0084] In the first and second embodiments described previously, a case has been described in which all communication methods are synchronized with SS synchronization signals. However, you can also synchronize some communication methods. Fig. 14 is a time diagram showing an example of how many modems 10 operate when some communication methods are out of sync with synchronization signals;

[0085] In the example of Fig. 14, it is necessary to send / receive an RS request signal not synchronized with the SS synchronization signal. Other communication methods require the detection of the request signal carrier RS ​​of the communication method C, wherein the RS request signal is transmitted / received asynchronously relative to the SS synchronization signal. When the carrier is detected, it is necessary to narrow down the frequency band used for the SS synchronization signal and RS request signal in such a way that both signals do not interfere with the C communication method. The communication method synchronized with the SS synchronization signal can recognize which communication method uses the power lines 2 and in what form in each time slot.

[0086] It is possible to recognize asynchronous communication methods with others by receiving asynchronous request signals. However, considering the situation of the transmission line as shown in Fig. 8 (b), there may be a case where it is impossible to determine whether the RS request signal, which is in a wide band for the purpose of the communication method (which may be in the receive mode), appears to be concentrated in the lower frequency band affected properties of the transmission line, whether the RS request signal is initially set only in the lower frequency band. To prevent this, the phase vector of the RS request signal for synchronous coexistence and the phase vector of the RS request signal for asynchronous coexistence are set to be different, so that it becomes possible to determine whether it is a RS request signal in a wide band or an RS request signal in the initially narrow band. It is still impossible to determine, using the asynchronous communication method, the communication method synchronized with the synchronization signal SS. However, asynchronous communication methods can coexist by using a coexisting method that uses frequency division, even when a synchronous communication method cannot be recognized.

[0087] For transmission lines used as power lines 2, even when the wideband RS request signal and the narrowband RS request signal cannot be distinguished, it is described that both signals can be distinguished by using different phase vectors. However, it is possible to distinguish both signals by determining whether RS ​​request signals are detected synchronously with respect to synchronous and asynchronous types.

[0088] In the first and second embodiments described above, the SS synchronization signal may be generated in any form as long as it is output multiple times during a predefined period. For example, commercial AC voltage (or current) on power lines 2 can be used to generate an SS synchronization signal. In this case, for example, zero crossing of AC commercial voltage is detected, and the SS synchronization signal (e.g., pulse wave shape formed from a square wave) is generated using a point at which zero crossing is detected as a reference time. When commercial AC voltage is, for example, 100 V, 60 Hz, the SS synchronization signal is generated at 60 Hz as the reference frequency. In this case, the zero crossing circuit, which includes a comparator or the like, and is connected (directly or indirectly) to supply lines 2, can be installed in modem 10 shown in Figures 3 or 11. The average value of multiple reference times denoting the passage through zero can be used for reference time. A fixed reference time can be set even if the zero crossing changes.

[0089] In the first and second embodiments described previously, case reports have been provided in which the 10B1 modem, which uses communication method B, outputs an SS synchronization signal. However, it is also possible that modems 10, which use communication methods A and C, output the SS synchronization signal if at least one modem 10 outputs the SS synchronization signal. Modem 10, which outputs the SS synchronization signal, can be set to fixed or variable mode; in addition, when the variable mode has been selected, it can be set manually or automatically.

[0090] For example, in the fixed mode setting, modem 10 using a particular communication method can be set as the default to output the SS synchronization signal. In the case of variable mode setting, the user can provide modem 10 with an interface (e.g. switch) which can control whether SS synchronization signal is output. On the other hand, in the case of automatic variable setting, modem 10 searches (listens) for the SS synchronization signal (or request signal) during at least one control period Tc. When an SS synchronization signal is detected, modem 10 does not output the SS synchronization signal alone. On the other hand, when no SS synchronization signal is detected, modem 10 outputs the SS synchronization signal. In this way, priority is given to the SS synchronization signal sent from modem 10 that has already communicated using power lines on power lines 2. Therefore, even when modem 10 is disconnected from power lines 2, one of the other modems 10 automatically outputs SS synchronization signal.

[0091] In the first and second embodiments described previously, descriptions are provided for the case in which the phase vectors of the SS synchronization signal and the RS request signal are different, but the phase vectors of the RS request signals are the same. However, it is also possible to set different phase vectors for RS request signals depending on each of the different communication methods. For example, when transmitting the complete signal (complete signal), a new other phase vector may be used for the complete signal. This allows you to create a more flexible environment in which modems 10 can coexist. In other words, each modem 10 can identify each other even when RS request signals are output in any way (namely, regardless of time slots). This reduces the time required to derive the RS request signal (namely the control signal Tc) and improves the performance of the RS request signal transmission.

Third Embodiment [0092] A third embodiment is described below with reference to Figures 15 to 17.

[0093] The communication system 100 according to the third embodiment is the same as that described in the first embodiment, and therefore its descriptions will be omitted. As shown in Fig. 2, the communication device according to the third embodiment is the same as the modem 10 according to the first embodiment, and therefore its descriptions will be omitted.

[0094] Fig. 15 is a block diagram showing an example of equipment that forms modem 10 in accordance with the third embodiment. In the circuit configuration shown in Fig. 15, the zero crossing circuit 63 is provided in the modem 10 shown in Fig. 3. The circuit configuration shown in Fig. 15 is the same as that described in Fig. 3, except for the zero crossing circuit 63 and the PLC block PHY 42D (described later) in the reserve integrated circuit 42.

The same numbers were assigned to the same components, so their descriptions were omitted.

[0095] The zero crossing circuit 63 includes diodes connected in bridge circuit 63a, resistors 63b and 63c, power supply

DC 63e and 63d comparator. Bridge-connected diodes 63a are connected to resistor 63b, and resistor 63b is connected in series with another resistor 63c. These two resistors, 63b and 63c, are connected in parallel with the input terminal at one end, which was provided in the 63d comparator. The positive pole of the DC 63e power supply is connected to the input terminal at the other end, which was provided in the 63d comparator. The PLC MAC 42C block in the backup integrated circuit 42 is connected to the output terminal of the comparator

63d.

[0096] Fig. 16 is a functional block diagram of a PLC PHY block 42D of a spare circuit 42. A PHY PLC block 42D performs a Fast Fourier Transform as a time-frequency transform. In other words, the PHY 42D PLC block includes the FFT 411 transducer and the IFFT (Inverse Fourier Transform) 420 transducer instead of the wavelet transducer 401 and the inverted waveguide 410, which is shown in figure 4. In the functional block shown in Fig. 16, the components in common with those of Fig. 4 are assigned the same numbers, so their descriptions will be omitted here. The time-frequency transform need not be an FFT transform, but it can also be a wavelet transform described in the first and second embodiments.

[0097] The following is an example of a specific operation of modem 10 according to the third embodiment in relation to Figs. 15 to 17. Fig. 17 is a time diagram showing an example of how many modems 10 are operating in accordance with the third embodiment. The operation shown in Fig. 17 is different from that shown in Fig. 14 only in that synchronization is carried out according to commercial AC voltage and the RS request signals have different phase vectors. In Fig. 17, joint operations with those in Fig. 14 are assigned the same numbers, and therefore their descriptions are omitted. The commercial AC voltage shown in Fig. 17 means "voltage" on a vertical scale for easier understanding. The following is a description of the case where commercial AC voltage is indicated on a time chart, as shown in Figure 17. Also, in Figure 17, 60 Hz is indicated as commercial AC voltage, but other voltage values, e.g. 50 Hz , can also be used.

[0098] In this example, each modem 10A1, 10A2, 10B1, 10B2, ··· has a predefined phase vector set differently depending on the frequency band used for the RS request signal. The A and B communication methods use the entire frequency band

2-30 MHz (from 2-30 MHz). The C communication method uses the 2-16 MHz frequency band (from 2-30 MHz). Any frequency band can be used to send the RS request signal.

[0099] Each modem 10 is intended for transmitting the RS request signal and performing data transmission, using as a reference: the zero crossing point (voltage is 0V AC) of the commercial AC voltage in the zero crossing circuit 63. In this case, the 2AC cycle is treated as one cycle from the zero crossing of the commercial AC voltage, and the time slots to output the RS request signal are set starting from the zero crossing, in the order of communication methods A, B and C.

[0100] At t42, the zero crossing circuit 63 of modem 10A1 detects the zero crossing ZC of commercial AC voltage. When ZC zero crossing is detected, controller 405 from the PHY 42D PLC block of the 10A1 modem retrieves the data associated with the phase vector from memory 33. The data associated with the phase vector indicates the phase vector PV1. In particular, PV1 includes rotation degree coefficients, which are formed from two values, i.e. 0 and p, corresponding to each subcarrier or phase shift value for cyclic displacement of the subcarriers using these coefficients. The phase rotator 408 of the PLC PHY 42D block inverts the phase vector of each of the subcarriers forming the multi-carrier signal using the PV1 phase vector. The IFFT 420 of the PHY 42D PLC block performs an IFFT transform on a multi-carrier signal whose phase has been rotated to generate an RS request signal. The IFFT 420 transducer outputs the generated RS request signal to power lines 2 via AFE IC 43, band pass filter 45, driver chip 46, coupling system 27, power connector 12 and plug 3.

[0101] As with the 10A1 modem, the 10B1 modem detects the zero crossing of ZC in the zero crossing circuit at time t42. When ZC zero crossing is detected, controller 405 from the PHY 42D PLC block of the 10B1 modem retrieves the data associated with the phase vector from memory 33. As communication methods A and B use the same frequency band to transmit the RS request signal, data associated with the downloaded vector phase indicate the phase vector

PV1, like the 10A1 modem. The phase rotator 408 of the PLC block PHY 42D rotates, based on the information collected related to the phase vector, the phase vector of each subcarrier forming the multi-carrier signal, using the phase vector PV1, as in the case of the 10A1 modem. The IFFT 420 of the PHY 42D PLC block performs an IFFT transform on a multi-carrier signal whose phase has been rotated to generate an RS request signal. At t43, the IFFT 420 transducer outputs the generated RS signal to power lines 2, using zero crossing as a reference point, in the time slot set for communication method B.

[0102] As with the 10A1 modem, the 10C1 modem detects the zero crossing of the ZC in the zero crossing circuit at time t42. After ZC zero crossing detection, the PHY 42D PLC block 405 of the 10C1 modem retrieves from the memory 33 data associated with the phase vector, indicating the phase vector PV2, which is different from the phase vector PV1, because the communication method C uses a frequency band other than communication methods A and B for transmitting the RS request signal. The phase rotator 408 of the PLC block PHY 42D rotates the phase of each subcarrier, creating a multi-carrier signal, using the PV2 phase vector, based on the data associated with the downloaded phase vector, unlike the 10A1 and 10B1 modems. The IFFT 420 of the PHY 42D PLC block performs an IFFT transform on a multi-carrier signal whose phase has been rotated to generate an RS request signal. At t44, the IFFT 420 transducer outputs the generated RS request signal to power lines 2, using the detected zero crossing as a reference point, in the time slot determined for communication method C.

[0103] The following describes the RS request signal detection process implemented by modem 10 with reference to FIGS. 16 to 18. FIG. 18 is a flowchart showing the RS request signal detection process. The FFT transducer 411 of the PLC PHY block 42D of modem 10 performs an FFT transform on the received signal (step S11). The controller 405 of the PLC block PHY 42D retrieves from the memory 33 data associated with the phase vector PV1. The phase rotator 402 of the PLC block PHY 42D rotates the phase of each subcarrier by reference to data associated with the phase vector PV1 and multiplying the received signal transformed by the FFT by the phase vector PV1 (step S12).

[0104] The controller 405 of the PLC block PHY 42D performs quadrant determination on subcarriers whose phases have been rotated (step S13) as detailed below. In this example, it is assumed that 512 subcarriers are used, and the phase vectors on the send and receive side are many factors that indicate the degrees of rotation (for example, p, 0, p, p, ···, 0) corresponding to the number of subcarriers 1, 2,3,4, ···, 512.

[0105] The RS request signal includes known transmitted data as known data, such as a preamble. The data transmitted corresponds to the number of subcarriers 1,2,3,4, ···, 512. Although the known transmitted data can be any, in this example all data is set to "1". "1" means (1, 0) in the complex coordinate plane. Therefore, known data have the form 1,1,1,1, ···, 1 and correspond to the numbers of subcarriers 1,2,3,4, ···, 512. The 408 phase rotator on the transmission side multiplies the known data 1,1,1,1, ···, 1 by phase vectors (p, 0, p, ρ, ···, 0), and outputs RS request signals in the form -1 , 1, -1.1, ··· 1 as data transmitted to power lines 2.

[0106] The phase rotator 402 on the receiving side multiplies the transmitted data -1, 1, -1, -1, ···, 1 by the coefficients (p, 0, p, π, ···, 0), all transmitted data is included in each subcarrier of the transmitted RS request signal. As a result, known data in the form of transmitted data

1,1,1,1, ···, 1, are rotated again. The 405 controller determines whether the transmitted data indicated by the subcarriers whose phases have been rotated are known data, such as a preamble. In this case, the 405 controller sums up the transmitted data and compares it with the previously defined Th1 threshold. For example, when the Th1 threshold is "258" and the transmitted data is probably correct, the combined SUM is "512 (= 1 + 1 + 1 + 1 + ··· + 1)". Thus, controller 405 determines that the SUM integration value has exceeded the Th1 threshold (step S13: YES). After determining that the SUM combined value has exceeded the Th1 threshold, controller 405 determines that the carrier with the phase vector PV1 has been detected (step S14) and terminates the process. In other words, the received signal is a multi-carrier signal whose phase vector is PV1. On the other hand, when the combined SUM value did not exceed the Th1 threshold, the controller 405 determines that the combined SUM value did not exceed the Th1 threshold (step S13: NO).

[0107] After determining that the combined SUM value has not exceeded the Th1 threshold, controller 405 retrieves from memory 33 data associated with the phase vector PV2. The phase rotator 402 of the PLC PHY block 42D multiplies the received signal transformed using FFT by the phase vector PV2 and rotates the phase of each subcarrier (step S15). The controller 405 of the PLC block PHY 42D performs a quadrant determination on subcarriers whose phases have been rotated (step S16), as in the case of step 13. After determining that the combined SUM value has exceeded the Th2 threshold (step S16: Yes), the controller 405 determines that the carrier with the phase vector PV2 has been detected (step S18), thereby interrupting the process. In other words, the received signal is a multi-carrier signal whose phase vector is PV2. The quadrant determination is described in detail below.

In turn, after determining that the SUM integration value has not exceeded the Th2 threshold (step S16: No), the controller 405 determines that the received signal has neither the phase vector PV1 nor PV2 (i.e. the signal is a multi-carrier signal whose the phase vector is different from PV1 and PV2 (or is noise) (step S17) and determines that no carrier with the PV1 and PV2 phase vectors (step S18) has been detected, thus interrupting the process. It is also possible to carry out steps 15 and 16 before steps 12 and 13 in Fig. 18. The phase vector need not necessarily have two types, i.e. PV1 and PV2, but may have three types or more.

[0109] In this case, it is assumed, for example, that the power line transmission state has deteriorated and the gain in the 16-30 MHz frequency band has decreased. In this case, the RS request signals output from the 10A1 and 10B1 modems are characterized by a higher S / N subcarrier ratio that is transmitted in the 16 MHz or higher frequency band. This makes it difficult to distinguish RS request signals output from 10A1 and 10B1 modems from RS request signals output from 10C1 modem. However, since different phase vectors are set for modems 10A1, 10B1 and 10C1, the RS request signals can be easily distinguished when the modem 10 performs the previously described RS request detection process.

[0110] As described above, in the third embodiment, the different phase vectors are used in accordance with the frequency bands used for the RS request signal. As a result, it becomes possible to distinguish RS request signals even when the power line transmission status is deteriorating. Fourth Embodiment [0111] The communication system 100 according to the fourth embodiment is the same as that described in the first embodiment, and therefore its descriptions will be omitted. The communication device according to the fourth embodiment is the same as the modem 10 according to the first embodiment in Fig. 2, and therefore its descriptions will be omitted. The configuration of the modem 10 circuit according to the fourth embodiment is the same as in Figs. 15 and 16, and therefore its descriptions will be omitted. [0112] The following is an example of a specific operation of modem 10 according to the fourth embodiment with reference to Figs. 19 and 20. Figs. 19 shows the time slots corresponding to the request signals according to the fourth embodiment, and FIG. 20 is a flowchart showing the process of detecting the request signal according to the fourth embodiment. Fig. 19 illustrates the extended control period Tc shown in Fig. 17. In a fourth embodiment, which differs from the third embodiment, different phase vectors have been set for the respective time slots T11, T12, ···, T17. It is also possible that different phase vectors will be used for different frequency bands and different time slots. The number of time slots is arbitrary as long as it is two or more.

[0113] Detailed descriptions will be given below. It is assumed that various electrical devices (not shown) are properly connected to sockets 5 to which 10A1 and 10B1 modems are connected. In this case, which is affected by electrical devices (e.g. impedance change), commercial AC2 AC voltage at sockets 5 to which 10A1 and 10B1 modems are connected causes time delays relative to commercial AC1 AC voltage at sockets 5 to which they are connected other 10C1 modems, ···. Fig. 19 (a) shows the waveform of commercial AC1 AC voltage in sockets to which other 10C1 ··· modems are connected, and Fig. 19 (b) shows the waveform of commercial AC2 AC voltage in the outlets to which 10A1 and 10B1 modems are connected. Commercial AC2 alternating voltage as shown in Fig. 19 (a) and (b) is delayed by TD time compared to commercial AC1 alternating voltage.

[0114] In this case, when the 10A1 modem outputs the RSa request signal, the zero crossing circuit 63 detects the zero crossing of the ZC of the commercial AC2 voltage. Commercial AC2 AC voltage is only delayed by TD time compared to commercial AC1 AC voltage. Thus, modem 10A1 outputs the RS request signal at time t421, which is delayed only by time TD relative to time t42.

[0115] When modem 10B1 outputs a request signal RSb, the zero crossing circuit 63 detects at t421 the zero crossing of the ZC commercial AC voltage AC, as with the 10A1 modem. After detecting the zero ZC transition, the 10B1 modem outputs the RSb request signal at t431, which is only delayed by TD time relative to t43.

[0116] At this stage, modem 10C1 has performed the RS request signal detection process shown in Fig. 20, and detects RS and RSb request signals. The following describes the carrier detection process in the T12 time slot with reference to Fig. 20.

[0117] The FFT transducer 411 of the PHY PLC block 42D of the 10C1 modem performs an FFT transform on the received signal (step S21). Then PLC PHY 42D retrieves from the memory 33 data associated with the phase vector as slot data corresponding to the time slot T12. Memory 33 stores data associated with different phase vectors, corresponding to time slots T11, T12, T13, ···. In this example, the phase vector PV1 is determined for communication method A and the phase vector PV2 is determined for communication method B. Memory 33 stores data associated with the phase vectors PV1 and PV2, corresponding to the time slots T11 and T12.

[0118] PLC PHY block 42D outputs current slot data in the zero crossing circuit 63 (step S22). In particular, the 10C1 modem recognizes, based on commercial AC1 AC voltage in the zero crossing circuit 63, that the zero crossing of ZC takes place at t42. Each modem 10 includes a counter (not shown) and stores data indicating the duration of time slots. Thus, each modem 10 can determine how many time slots occur between the current time slot and the ZC zero crossing using the time since zero ZC and the time slot width.

[0119] For example, at time t43, the PHY PLC block 42D of the 10C1 modem recognizes that the time elapsed since passing through zero ZC is the time slot duration and determines that the current time slot is "T12". As a result, the controller 405 of the PLC block PHY 42D retrieves from the memory 33 data associated with the phase vector PV2, corresponding to the time slot T12.

[0120] Then the phase rotator 402 of the PHY PLC block 42D multiplies the received signal transformed using FFT by the phase vector PV2 to rotate the phase of each subcarrier (step S23). The phase 405 rotator of the PLC PHY 42D block performs quadrant determination on each of the subcarriers whose phases have been rotated (stage S24), as in stages 13 and 15

<td>described in Fig. 18.</td><td>Steps S25</td><td>and S26 are the same as</td>

<td>stages S14 (or S17)</td><td>and S18,</td><td>and therefore their descriptions remained</td>

<td>omitted.</td><td></td><td></td>

<td>[0121] In the gap</td><td>time</td><td>T12 two phase vectors</td>

request signals RSa and RSb are output as shown in Fig. 19 (a). However, as described above, the 10C1 modem rotates the subcarrier phases using the PV2 phase vector and thus only detects the RSb request signal.

[0122] As described above, in the fourth embodiment, each modem 10 rotates the subcarrier phases of the request signal RS output in the time slot by means of a phase vector corresponding to the time slot. This enables reliable detection of RS request signals output in each time slot, even when there is a time difference between AC voltages.

[0123] In the fourth embodiment described above, descriptions are provided for the case in which the different phase vectors have been established for time slots

Τ11, Τ12, ···, Τ17. However, it is not necessary to set different phase vectors for the respective time slots. Phase vectors can be reliably distinguished when phase vectors having different degrees of rotation (e.g., PV1 and PV2) are set at least for adjacent time slots (e.g., T11 and T12).

Fifth Embodiment [0124] The communication system 100 according to the fifth embodiment is the same as that described in the first embodiment, and therefore its descriptions will be omitted. The communication device according to the fifth embodiment is the modem 10 described in the first embodiment, and therefore its descriptions will be omitted. The configuration of the modem 10 circuit according to the fifth embodiment is the same as in Figs. 15 and 16, and therefore its descriptions will be omitted.

[0125] The following is an example of a specific operation of modem 10 in accordance with the fifth embodiment in relation to Figs. 21 and 22. Fig. 21 is a time diagram showing an example of how many modems 10 are operating in accordance with the fifth embodiment. Fig. 22 is a flowchart showing the process of modifying the phase vector according to the fifth embodiment; The process of detecting the RS request signal is the same as described with reference to Fig. twenty in a fourth embodiment.

[0126] Below is a description of the phase vector modification process implemented by modem 10A1. Modem 10A1 looks for the RS request signal during the control period Tc (step S31). For example, it is assumed that the controller 405 (see Fig. 16) of the PHY PLC block 42D of the 10A1 modem detects the zero crossing ZC in the zero crossing circuit 63 (see Fig. 15) at time t81 shown in Fig. 21. The controller 405 determines whether the RS request signal is output between times t81 and t82. The carrier detection method is the same as that shown in Fig. 18, and therefore its descriptions will be omitted.

[0127] In a fifth embodiment, each time slot during the control period Tc is allocated to communication methods in the order of "C", "A" and "B". When data transmission is carried out by means of communication methods A, B, ···, the data period Td is divided in terms of time into communication methods A, B, ···. When data transmission is carried out by communication methods A, B, ··· and C, the 16-30 MHz frequency band is allocated to communication methods A, B, ···, and the 2-16 MHz frequency band is allocated to communication method C , thus sharing the frequency band used for communications using power lines. The memory 33 of each modem 10 stores data including these time slot allocations, wherein the multiple access scheme is used when the RS request signal is output.

[0128] Modem 10A1 determines whether the required channel has a gap (step S32). The channel must be at least one of the frequency time bands and in this example the frequency band is used. When the 10A1 modem wants to use the 2-30 MHz frequency band and when the RS request signal is not output between t81 and t82, the PHY 42D PLC block 405 of the 10A1 modem determines that the required channel has a gap (step S32: Yes) because the communication method C does not perform data transmission during the next Td data period (between times t84 and t86) and terminates the process.

[0129] Therefore, the 10A1 modem performs data transmission using the 2-30 MHz frequency band without performing the phase vector modification process at t84. In this case, as the 10B1 modem outputs the RS request signal during t83, the 10A1 modem detects the RS request signal output from the 10B1 modem, and the 10A1 and 10B1 modems alternately perform data transmission during the Td data period.

[0130] Furthermore, in Fig. 21, the duration of the control period Tc and the data period Td are equal to two cycles of commercial AC voltage. However, it is arbitrary if it is greater than 1/6 cycle of commercial AC voltage. In particular, it is preferred that 1/2 cycle is used for a single phase and 1/6 or more cycles are used for three phases. This is because it eliminates the need to determine whether commercial AC voltage is increasing or decreasing, even when the commercial AC voltage waveform is inverted by reversing the direction of placement of a pair of plug ends.

[0131] Durations need not be equally divided for the purpose of splitting data transmission data. For example, one duration can be longer than the other. Although in Fig. 21 data transmission is carried out three times in one way of communication during one Td data period, the number of data transmissions carried out is arbitrary.

[0132] At t86, modem 10A1 starts the process described in Fig. 22 and again looks for the request signal RS (step S31). At the same time, the 10A1 modem determines whether the required channel (frequency band) has a gap (step S32). The controller 405 of the PLC block PHY 42D of the 10A1 modem determines whether the RS request signal is output between time t86 and t87. As shown in fig. 21, as modem 10C1 outputs a request signal RS, controller 405 determines whether the required channel has a gap, because the communication method C performs data transmission during the next data period Td between times t84 and t86 (step S32: No).

[0133] The controller 405 of the PHY PLC block 42D of modem 10A1 modifies the phase vector corresponding to the channel (frequency band) (step S32). In this example, memory 33 stores data associated with the PV1 phase vector that corresponds to the 2-30 MHz frequency band and data related to the PV2 phase vector that corresponds to the 16-30 MHz frequency band. In addition, the PV1 phase vector is set for the 10A1 modem as a phase vector between the times t81 and t87.

[0134] The communication method C performs data transmission (because the frequency band 2-16 MHz cannot be used) during the next data period Td (between times t86 and t89), the controller 405 of the PLC block PHY 42D of modem 10A1 retrieves 33 related data from memory with a phase vector corresponding to the 16-30 MHz frequency band. In other words, the controller 405 retrieves from the memory 33 data associated with the phase vector PV2, and the phase vector 408 of the PLC block PHY 42D of modem 10A1 modifies the phase vector on PV2 (step S32). The phase vector modification process has been described in detail in the fourth embodiment, and therefore its descriptions will be omitted.

[0135] After the phase vector change, the IFFT transducer 420 of the PHY 42D PLC block of the 10A1 modem performs an IFFT transform on subcarriers whose phase vectors have been rotated using PV2 to generate the transmitted signal. The PLC PHY 42D block of the 10A1 modem cuts the 2-16 MHz frequency band from the transmitted signal using a 45 band pass filter. The transmitted signal in the 16-30 MHz frequency band is output as a request signal RS to the power lines 2 via the controller chip 46, the coupler 27, the power connector 12 and the plug 3. The 10A1 modem outputs the RS request signal between times t87 and t88 (stage S33) and interrupts the process. The 10B1 modem performs the same process, so its descriptions are omitted. Therefore, during the Td data period, beginning with t89, the 10C1 modem performs data transmission in the 2-16 MHz frequency band, and the 10A1 and 10B1 modems perform data transmission in the 16-30 MHz frequency band.

[0136] As the 10A1 modem modifies the phase vector according to the frequency band for the RS request signal, other 10B1, 10C1, ··· modems can easily determine the frequency band used for the RS request signal even when the transmission line condition has deteriorated. The same results can be obtained when any other modem 10 differentiates the RS request signal.

[0137] As described above, in the fifth embodiment, the phase vector is modified according to the frequency band used for the RS request signal. Thus, the frequency band used for the RS request signal can be seamlessly determined despite changes in the transmission line condition. As a result, the phase vector can be recognized without problems, even when the transmission line condition has deteriorated.

[0138] In the third to fifth embodiments described previously, case reports have been provided in which the request signal RS is output synchronously relative to the zero crossing as a reference point. However, this synchronization does not have to refer to the zero crossing point. For example, synchronization can be arbitrary as long as commercial AC voltage reaches a predefined value (e.g. 10V) and starts at the detected time point.

[0139] In the first to fifth embodiments described previously, descriptions have been provided for the power line as an example of a transmission line that performs transmission of a control signal and data. However, it is possible to use a line other than the power line. For example, both wireless connections and cables can be used as transmission lines. For example, with a wired transmission line, you can use various cables, such as coaxial cable, telephone line, and speaker cable.

[0140] In the first to fifth embodiments described above, the modification of the phase vector has been referred to as "rotating the subcarrier phase". This is the same as rotating the signal point on the complex coordinate plane. In addition, the "phase vector" defined in the specification is a set of values ​​indicating the degree of rotation by which the signal point of each subcarrier is rotated on the complex coordinate plane, each subcarrier forming a multi-carrier signal, such as an OFDM signal. The "phase vector" is therefore a combination of values ​​for the purpose of equalizing the time waves of a multi-carrier signal (eliminating the peak value on the time axis). The phase vector has two types, i.e. a constant value which is a combination of predefined values ​​and a variable value which is a combination of different values ​​according to predefined conditions. Such predefined conditions include cyclic shift and random value. In addition, the phase vector is also referred to as the "carrier phase". In this case, the fixed value is referred to as the "deterministic carrier phase" and the variable value is referred to as the "random carrier phase". The RS request signal described earlier is also referred to as the Commonly Distributed Coordination Function (CDFC) signal.

[0141] The first to fifth embodiments described previously were described separately. However, these embodiments can also be combined as needed.

[0142] The communication device and communication method of the present invention are useful in communication using power lines in particular in multi-family housing, such as apartment blocks, due to their communication capabilities while avoiding interference between signals when many communication devices using different communication methods are connected to one common transmission line.

[0143] It should be noted that the above examples are provided for the purpose of explanation only and are not intended to limit the present invention in any way. While the present invention has been described with reference to exemplary embodiments, it is understood that the words that have been used herein are words of description and illustration, not words of limitation. Changes may be made within the scope of the appended claims in their current form and with changes, without departing from the scope and keynote of the present invention in its aspects. Although the present invention has been described herein with reference to specific constructions, materials and embodiments, the present invention is not intended to be limited to the details disclosed herein, instead the present invention relates to all functionally equivalent constructions, methods and applications as in the appended claims.

[0144] The present invention is not limited to the embodiments described previously, and various variations and modifications are possible without departing from the scope of the present invention. Application in industry [0145] The present invention can easily detect signals derived from other communication devices that use different communication methods and are connected to a common transmission line, while avoiding interference between signals without performing relatively burdensome modulation and other processes.

The following is a list of further examples of the invention: [0146] 1 A communication device that can connect to a power line connected to at least the first communication device and the second communication device, wherein the first communication device can perform data transmission with said first communication device and the second communication device cannot carry out data transfer with said communication device, said communication device comprising:

a receiver for receiving a signal from a second communication device;

a carrier detector for detecting predefined data in a signal;

a channel determination unit for determining at least one of the frequency time bands used for the first communication device when the carrier detector detects predefined data, wherein the time and frequency band used for the needs of the first device for communication are different from the time and frequency band used for the needs of the second device for communication and the transmitter for performing data transmission with the first device for communication in at least one of the time and frequency band used for the first device for communication.

A device for communication with the features of embodiment 1, wherein the signal is a multi-carrier signal including many sub-carriers.

A device for communication with the features of embodiment 2, including in addition:

a phase rotator for rotating the phase of many of the subcarriers using a phase vector, wherein the phase vector represents a predefined degree of rotation, the carrier detector detecting predefined data in a multi-carrier signal including many of the subcarriers whose phase is rotated using the phase vector.

The communication device with the features of embodiment 3, wherein the receiver further receives a multi-carrier signal from the first communication device, and the phase vector used by the first communication device is different from the phase vector used by the second communication device.

A communication device with the features of embodiment 4, wherein the frequency band used by the first communication device is different from the frequency band used by the second communication device.

A communication device with features of embodiment 4, wherein there is a PN sequence relationship between the phase vector used by the first communication device and the phase vector used by the second communication device.

A device for communication with the features of embodiment 6, wherein the PN sequence is an M sequence.

An apparatus for communication with the features of embodiment 3, wherein the receiver further receives the synchronization signal, and the phase vector corresponding to the synchronization signal is different from the phase vector corresponding to the multi-carrier signal.

A device for communicating with the features of embodiment 8, wherein the frequency band of the synchronization signal is different from the frequency band of the multi-carrier signal.

A device for communication with the features of embodiment 8, wherein there is a relationship of the PN sequence between the phase vector corresponding to the synchronization signal and the phase vector corresponding to the multi-carrier signal.

A communication device with the features of embodiment 10, wherein the PN sequence is an M sequence.

A device for communication with the features of embodiment 3, wherein the receiver further receives the synchronization signal and the multi-carrier signal is output at a predefined time based on the synchronization signal.

A device for communication with the features of embodiment 1, further comprising:

a time point detector for detecting a time point at which the alternating voltage transmitted to the power line obtains a predefined value and the multi-carrier signal is output at a predefined time based on the time point.

An integrated circuit that can connect to a power line connected to at least the first communication device and the second communication device, wherein the first communication device can perform data transfer using said integrated circuit, and the second communication device cannot perform data transfer using using said integrated circuit, the integrated circuit comprising:

a receiver for receiving a signal from a second communication device;

a carrier detector for detecting predefined data in a signal;

a channel determining unit for determining at least one of the time and frequency band used for the first communication device when the carrier detector detects predefined data, wherein the time and frequency band used for the first communication device are different from the time and frequency band used for the needs of the second communication device;

a transmitter for performing data transmission using the first communication device in at least one of the time and frequency band used for the needs of the first communication device.

A method of communication for controlling data transfer, which is implemented by a device for communication via a power line connected to at least the first communication device and a second device for communication, wherein the first device for communication can perform data transfer with said device for communication, and the second device for communication cannot carry out data transmission with the said communication device, wherein said method of communication includes:

receiving a signal from a second communication device; detecting predefined data in the signal; determining at least one of the time and frequency bands used for the first communication device when the carrier detector detects pre-defined data, wherein the time and frequency band used for the first communication device are different from the time and frequency band used for the second communication device and performing data transmission using the first communication device in at least one of the time and frequency band used for the first device for communication.

Panasonic Corporation

Proxy:

EP 2 309 656