JP2005151384A - Communication system using intercom line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To transmit high-speed image information taken by a camera with high image quality stably by using a signal line of an intercom line without being influenced by a noise generated from household electric appliances. <P>SOLUTION: By using two or more carrier signals, transmission data are allotted to each carrier signal and transmitted. For each carrier signal, S/N (ratio of signal and noise) is estimated or measured. In this way, communication is carried out between communication means 5a, 5b, which change the allotting amount of communication data to the carrier according to the estimated or measured value of S/N and perform communication by using a signal line of the intercom system as a communication line. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a communication device that stably transmits image information captured by a camera using a signal line (also referred to as a door phone line or an intercom line) of a door phone system.

  In recent years, the security situation has deteriorated, and suspicious people have suddenly visited homes and committed crimes. For such visits by suspicious individuals, confirmation by an image captured by a camera is very effective in addition to confirmation of a visitor by voice using a door phone. For this reason, doorphone systems equipped with cameras have become widespread. However, in a home that has already introduced a door phone system only for voice calls, it is necessary to perform wiring work to connect a camera to be newly placed outside the house and a monitor to be placed in the house. Since this cost is a heavy burden, image information communication means using an existing signal line has been devised.

In a TV door phone system that replaces an existing door phone for voice calls with a door phone with a camera, it uses a pair of signal lines laid for voice calls and affects the voice information using a communication frequency band different from that of voice. In such a manner, a signal on which image information, control information, and the like are superimposed is transmitted. As such a television door phone system, there is one disclosed in Patent Document 1, for example. In the door phone system described in Patent Document 1, image information from a camera is mixed with audio information, for example, by modulating a high-frequency signal such as 5 MHz by frequency modulation with a deviation width such as ± 0.5 MHz. In this system, image information is separated from audio information and demodulated from the transmitted signal, and is further RF-modulated and transmitted to the television receiver, and the television receiver displays the received image.
JP-A-5-227313

  However, in the prior art, an existing signal line is used to transmit an image, but a problem caused by using an existing signal line has not been sufficiently studied. Existing signal lines are generally non-polar two-wire systems, and are not shielded like coaxial cables, so that noise is easily superimposed on signals to be transmitted. For example, an infinite number of power lines for power supply are installed in the house, and noise generated from home appliances is superimposed on the power lines. In particular, it has been experimentally known that very large noise is generated in a frequency band of 1 MHz or less from an inverter device such as an electric rice cooker or an electromagnetic cooker. In addition, in the band from 1 MHz to 5 MHz, the noise level is slightly smaller than that of 1 MHz or less, but it has been experimentally found that a considerably large noise is generated. Furthermore, in the band of 5 MHz or more, the noise level is somewhat reduced, but it has been experimentally found that a considerably large noise is generated as compared with the background noise. Therefore, when a power line is laid near the signal line, noise is induced in the signal line by noise superimposed on the power line. For this reason, the conventional TV door phone system can transmit images at low speed and with low image quality, but cannot stably transmit high-speed and high-quality images that require noise resistance. In addition, when a door phone system with a new camera is introduced without using an existing door phone, noise is induced in the wired signal line, and high speed and high image quality that also requires noise resistance are required. There is a problem that images cannot be transmitted stably.

  In order to solve the above-mentioned problems, in the present invention, communication means are provided outside and inside the house, both the communication means are connected by a signal line used in the door phone system, and both communication is performed using the signal line as a communication line. Communication is performed between the means, and image information captured by a camera arranged outside the house is transmitted and displayed in real time to the communication means arranged in the house. These communication means use a plurality of carrier signals (also referred to as multi-carriers), assign transmission data to each carrier signal, and perform communication. Each carrier signal has an S / N (signal to noise ratio). Depending on the value, the transmission data allocation amount is changed for communication. Further, the transmission error rate is evaluated for each carrier signal, and communication is performed by changing the transmission data allocation amount according to the evaluated transmission error rate. In addition to the above, communication is performed by an OFDM (Orthogonal Frequency Division Multiplexing) system. Further, these communication means determine whether or not a predetermined S / N can be obtained for the carrier wave signal, and when the determination result is equal to or less than the predetermined S / N, a predetermined difference is determined. Communicate by changing the frequency of the carrier wave to the specified frequency. Furthermore, communication is performed by a spread spectrum communication method in which communication signals are spread over a wider band for communication.

  In the present invention, “outside the house” means the outside of a building such as a house or office, for example, an entrance, a reception desk, etc., and “inside” means the inside of the building, for example, a living room. Also, in apartment houses and buildings such as condominiums and apartments (hereinafter referred to as apartment houses), “outside the house” refers to the common entrance of the apartment house and the individual entrance of each dwelling unit provided in the apartment house. And “in-home” refers to the interior of each dwelling unit, such as a living room. “Door phone” refers to a device or system for communication between a slave unit installed outside the home and a master unit installed in the home, and is called by the name of intercom, TV door phone, intercom, etc. Including those that have been.

  According to the present invention, S / N improvement is achieved by communication using a carrier signal having a high S / N, communication in a frequency band having a high S / N, and spread spectrum communication in which communication is performed by spreading over a wider band than the communication band. Even if noise from home appliances is superimposed on the signal line, it is possible to transmit image information stably using the signal line of the door phone system without being greatly affected by this. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment of the present invention, (1) an embodiment of a communication device that communicates by a multi-carrier method using a signal line of an existing doorphone system, and (2) a communication that uses a signal line of an existing doorphone system. Embodiment of a communication device for performing transmission and transferring transmitted image information to a mobile phone, (3) performing communication using a signal line of an existing door phone system, and recording the transmitted image information with a recorder; In addition, an embodiment of a communication device that records the time at that time with a time recording device, and (4) an embodiment of a new doorphone system will be described.

  FIG. 1 is a diagram showing a system configuration of a communication apparatus that performs 1: 1 communication (communication between one terminal (external communication means) and one terminal (internal communication means)) using an existing door phone system. is there. The camera 1 and the encoder 2 are coaxial cables or cables of general types used for wiring such as Ethernet (registered trademark) or USB (Universal Serial Bus) (hereinafter, these cables are collectively referred to simply as “cables”). ), And the encoder 2 and the outside communication means 5a are also connected by a cable. The outside communication unit 5a and the inside communication unit 5b are connected by a communication line 71 of an existing door phone. The internal configuration of the out-of-home communication unit 5a will be described later, but the internal configuration of the out-of-home communication unit 5a and the in-home communication unit 5b is the same. The home communication means 5b and the monitor are connected by a cable. In addition, a splitter 4a and a splitter 4b are installed between the doorphone master unit 6 and the doorphone slave unit 7 so as not to affect the existing doorphone system. Here, the splitter 4a and the splitter 4b have the same configuration, and pass only in the communication frequency band for transmitting audio information and the like used in the existing door phone system, and pass signals in a higher frequency band than that. It has a function (also referred to as a low-pass filter or a high-frequency cut filter) to prevent it from occurring. The doorphone base unit 6 and the splitter 4a and the doorphone slave unit 7 and the splitter 4b are connected by a line having the same characteristics as the existing communication line 71. Alternatively, when the splitters 4a and 4b are connected to the in-home communication means 5b and the out-of-home communication means 5a, a high-pass filter that passes only the signals in the MHz band used by the in-home communication means 5b and the out-of-home communication means 5a (low A splitter may be configured using a frequency cut filter.

  The out-of-home communication means 5a, the in-home communication means 5b, the camera 1, the encoder 2, and the monitor 3 may be always activated, but are activated by an activation signal from the doorphone master unit 6 in order to reduce power consumption. And Further, the outside communication means 5a, the inside communication means 5b, the camera 1, the encoder 2, and the monitor 3 each have an auto start circuit (a circuit that automatically detects the application of a DC voltage and activates the apparatus). In this case, as will be described in detail later, the doorphone master unit 6 superimposes power on the communication line 71 to supply power, and starts up in accordance with the start of power supply, or combines them to configure a system. May be. When the image information captured by the camera 1 is an image in an analog format such as NTSC system or PAL system, or is digital image information in a format that cannot be decoded by the monitor 3, the image information is transferred to the encoder 2. The encoder 2 encodes the image information into a digital image of an appropriate format such as MPEG1, MPEG2, AVI format, etc., and transfers the encoded image information to the outside communication means 5a. At this time, when the image information captured by the camera 1 has already been encoded into a digital image in a format that can be decoded by the monitor 3, the encoder 2 is unnecessary, and the encoding by the encoder 2 is not performed. The image information is transferred as it is to the outside communication means 5a. Alternatively, the camera 1 and the encoder 2 can be replaced with a single device having both functions. The outside communication means 5a transmits image information to the in-home communication means 5b using the communication line 71 of the existing door phone as a communication line. Further, the in-home communication means 5b transfers the image information to the monitor 3, and the monitor 3 having an image decoding function decodes the encoded image information and displays it on the screen.

  By the way, a communication speed of about several tens of kbps to several hundreds of kbps is sufficient for conventional low-speed and low-quality images, but in order to perform high-speed and high-quality image transmission, a communication speed of 1 Mbps or more is required. . In addition, noise generated from home appliances and the like is superimposed on the power line, and further superimposed on the communication line 71 of the door phone system. Therefore, the outside communication means 5a and the in-home communication means 5b are required to have noise resistance and high communication performance. Is done.

  The out-of-home communication means 5a and the in-home communication means 5b significantly reduce the influence of such noise and enable high-speed communication, and will be described below with reference to FIG. FIG. 2 shows a case where a DC voltage is not superimposed on the communication line 71. The out-of-home communication means 5a and the in-home communication means 5b have the same configuration, and will be described here based on the out-of-home communication means 5a. The monitor 3 is connected to the protocol converter 56 for the home communication means 5b. The out-of-home communication means 5a includes bandpass filters (BP filters) 50 and 60, a reception amplifier 51, a transmission amplifier 59, an analog / digital converter (A / D) 52, and a digital / analog converter (D / D). A) 58, an equalizer 53, a demodulator 54, a modulator 57, an access controller 55, a protocol converter 56, and an AC / DC converter 502.

  The interface between the outside communication means 5a and the external device (camera 1, monitor 3, encoder 2, etc.) is for transmitting data by a standard data transmission method such as Ethernet (registered trademark) or USB. For this purpose, a protocol converter 56 is provided in the out-of-home communication means 5a. When the protocol converter 56 receives data from the encoder 2, the protocol converter 56 converts the data into a communication packet of a predetermined format handled by the outside communication means 5 a. When receiving a communication packet from the protocol converter 56, the access controller 55 outputs this data to the modulator 57. The modulator 57 allocates the data to each carrier based on the data allocation amount information 55b for each carrier that is input separately. This is also called bit allocation. The signal with the data assigned to the carrier wave is converted into an analog signal by the D / A 58, amplified by the transmission amplifier 59, output to the communication line 71 via the BP filter 60, and transmitted to the home communication means 5b. . Further, an AC / DC converter 502 is connected to an outlet 503 to which a commercial AC voltage (for example, AC 100 V / 50 Hz or 60 Hz) is applied, and the AC / DC converter 502 converts the AC voltage into a DC voltage (DC) 501. The DC voltage 501 from the AC / DC converter 502 is supplied as drive power for each circuit of the outside communication means 5a. The AC / DC converter 502 also supplies a DC voltage 501 ′ as a driving power source for the camera 1 and the encoder 2. Power consumption is increased by connecting the outside communication means 5a, the camera 1, and the encoder 2, and power is likely to be insufficient only with the power source used in the existing door phone system. For example, when a battery (for example, a 1.5V battery or a rechargeable storage battery) is used as a driving power source in an existing door phone system, if the power is supplied to the outside communication means 5a, the camera 1, and the encoder 2, The need to replace the battery arises, and the management effort is great. Therefore, using a commercial power source as a driving power source for the outside communication means 5a, the camera 1, and the encoder 2 has an effect of saving the labor of management.

  When a DC voltage is applied to the communication line 71, as shown in FIG. 3, by connecting the BP filters 50 and 60 and the communication line 71 via a coupler 72, a high frequency in the MHz band. It is possible to superimpose a signal related to image information on a signal related to audio information transmitted via the communication line 71 without attenuating the signal. FIG. 4 shows a connection configuration example in the case where the coupler 72 is used. The coupler 72 cuts a DC voltage or an AC voltage with a capacitor, has a high-frequency passing characteristic determined by the inductance of the transformer and the capacitance value of the capacitor, and only the communication signal 5a and the in-home communication means Between 5b. At this time, when a DC voltage is applied to the communication line 71, the DC / DC converter 504 is connected to the communication line 71, and the DC voltage supplied to the communication line in the DC / DC converter 504 is supplied to the communication device 71. Is converted into a DC voltage 501 of the voltage used in step S1, and the DC voltage 501 is supplied as a driving power source for each circuit of the outside communication means 5a. The DC / DC converter 504 also supplies a DC voltage 501 ′ as a driving power source for the camera 1 and the encoder 2. When the voltage applied to the communication line 71 is an AC voltage, the AC / DC converter 502 shown in FIG. 2 is used instead of the DC / DC converter 504, and the AC / DC converter 502 is connected to the outlet 503. It is also possible to connect to the communication line 71 instead and supply the DC voltage 501 from the AC / DC converter 502 as drive power for each circuit of the outside communication means 5a. The AC / DC converter 502 also uses the DC voltage 501 ′ as a driving power source for the camera 1 and the encoder 2.

  In the existing door phone system, a direct current voltage of a battery built in the door phone master unit 6 is supplied as a driving power source, and a direct current voltage is superimposed on the communication line 71 from the battery built in the door phone master unit 6. When supplying as drive power, communication line 71 from the battery built in door phone main unit 6 as drive power for newly connected external communication means 5a, in-home communication means 5b, camera 1, encoder 2, monitor 3, etc. Supplying with the DC voltage superimposed on the battery increases the power consumption, so that battery replacement frequently occurs. This problem of battery replacement can be solved by replacing the battery of the doorphone master unit 6 with the AC / DC converter 502 ′, and as a result, labor for battery replacement can be saved.

  On the other hand, the signal transmitted from the home communication unit 5 b suppresses signals other than the communication band by the BP filter 50, and outputs a signal in the communication band to the reception amplifier 51. The reception amplifier 51 amplifies the reception signal, and a signal converted into a digital signal by the A / D 52 is output to the equalizer 53. The equalizer 53 is for correcting a communication path distortion (also referred to as a transmission path distortion) of the communication line 71, and the signal subjected to the correction process of the communication path distortion in the equalizer 53 is a demodulator 54. Is output. The demodulator 54 extracts the data allocated to each carrier based on the separately input data allocation amount information 55 a for each carrier and outputs the data to the access controller 55. The access controller 55 converts the extracted data into a communication packet of a predetermined format and outputs it to the protocol converter 56. The protocol converter 56 converts the communication packet so that an interface (for example, Ethernet (registered trademark) or USB) with the external device can be obtained, and outputs information to the external device.

  The access controller 55 outputs the data allocation amount information 55a and 55b to the demodulator 54 and the modulator 57. The data allocation amount indicated by this information is not always constant, and the remote communication means 5a and the in-home communication unit 5 Training (also referred to as learning) for communication characteristics between the communication means 5b is performed and S / N is estimated (referred to as measurement or determination) for each carrier wave, or a transmission error rate during communication is evaluated, and these results are Accordingly, the data allocation amount is changed for each carrier or for all carriers. Further, the data allocation amount may be changed by using both S / N estimation and transmission error rate evaluation. In this way, the communication characteristics (transmission error and S / N) of the communication line 71 are dynamically evaluated between the out-of-home communication means 5a and the in-home communication means 5b, and the modulation / demodulation processing is changed (data allocation) based on the result. By changing the amount), it becomes possible to communicate so as not to cause a transmission error. This point will be described in detail below.

  As shown in FIG. 5, the intensity of noise superimposed on the communication line 71 is higher at lower frequencies, and is not so high at high frequencies, for example, 5 MHz or higher. Assuming that data is transmitted from the in-home communication means 5b to the out-of-home communication means 5a, even if the strength (power) of the transmission signal transmitted from the in-home communication means 5b to the communication line 71 is constant as shown in FIG. Since the transmission characteristic of the line 71 has frequency dependence, the strength of the signal received by the outside communication means 5a decreases and fluctuates as the frequency increases. This is due to attenuation of the communication signal due to the inductance of the communication line and the capacitance between the forward path and the return path of the communication line, reflection at the end point of the communication line 71, and the like. For stable communication of image information (communication speed is about 1 Mbps or more), it is necessary to set the S / N, which is the ratio of received signal and noise (difference in dB expression), to a predetermined value or more. Therefore, when evaluating the attenuation of the received signal in the high frequency band, it is desirable to use a frequency band of 30 MHz or less as the communication band. In addition, as a rule of EMI (electromagnetic interference), a radiation electric field is determined to be 30 dBμV / m or less at a point 10 m away from 30 MHz or more. Therefore, by limiting the frequency band to be used in this way, it is possible to suppress the radiation field to the outside, that is, radiation noise. The equalizer 53 is necessary for correcting the channel distortion of the communication line 71 and correctly restoring the data when demodulating. In this method, communication path distortion is evaluated using a preamble signal in communication, and correction is performed using the evaluation result. Without this equalizer 53, data cannot be restored due to the influence of channel distortion, that is, a transmission error occurs. This point will also be described later.

Taking a case where a plurality of carriers (multi-carriers) are used in the use band as carriers, an example of a mechanism for evaluating the S / N and changing the data allocation amount will be described below.
FIG. 6 shows a multicarrier spectrum. A plurality of carriers in the band Δf are allocated to the used band, but it is general that a predetermined band is provided between the carriers in order to prevent the adjacent carriers from overlapping with each other. Each carrier wave is assigned a bit of predetermined transmission data. As shown in FIG. 7, OFDM (orthogonal frequency division multiplexing), which is a special case of multicarrier, arranges each carrier so that the power of the other carrier becomes zero at the peak point of the carrier. When the band is Δf, orthogonality is maintained by inverse Fourier transform at time 1 / (Δf / 2). For this reason, unlike general multicarriers, signals can be restored even if the carriers overlap, and the bandwidth used can be narrower than general multicarriers, and the frequency utilization efficiency is higher than general multicarriers. Yes. Note that OFDM is a type of multicarrier.

As a method of communication using a carrier wave, a method of communication using a plurality of carrier waves as described above (referred to as a multi-carrier communication method) and a method of communication using a single carrier wave (also referred to as a single carrier) (single carrier) All of them transmit data by assigning data (bits) to a carrier wave (carrier). Here, when data is allocated to a carrier wave and transmitted, the data allocation amount is limited by the S / N for each carrier.
The multi-carrier communication system is a system in which a plurality of narrow-band carriers are provided within a used band for communication. For this reason, if the noise level of a specific frequency is high among the noises superimposed on the communication line 71, the S / N of the carrier that matches the frequency of the noise becomes lower than the other carriers, and the data to that carrier The allocation amount only becomes lower, and a high data allocation amount can be maintained for all carriers. As a result, it is possible to ensure a high transmission rate. As described above, since the multi-carrier communication method performs communication using a plurality of carriers, the data allocation amount is only low for a specific carrier wave having a low S / N.
On the other hand, in the single carrier communication method, even if the noise level of a specific frequency is only high, there is only one carrier, so the amount of data assigned to that carrier is low, In comparison, the transmission speed is considerably reduced.
Therefore, in order to realize a transmission rate of 1 Mbps or more, the multicarrier communication method is more suitable than the single carrier communication method.

A plurality of waveforms (with different amplitude and phase) are used for each carrier (carrier), and data (bits) is assigned to this waveform for transmission. This is called modulation, and the data allocation amount (also referred to as bit allocation amount) is limited by the S / N for each carrier, and the relationship is as shown in FIG. For example, if the transmission error rate is set to 1/10 ⁵ , the S / N needs to be about 32 dB, about 26 dB, about 20 dB, about 14 dB, and about 10 dB in 256 QAM, 64 QAM, 16 QAM, QPSK, and BPSK, respectively. is there. 256QAM can be assigned 8 bits, 64QAM is 6 bits, 16QAM is 4 bits, QPSK is 2 bits, BPSK is 1 bit, and if S / N is less than about 10 dB, Do not assign. QAM is called Quadrature Amplitude Modulation, QPSK is called Quadrature Phase Shift Keying, BPSK is called Binary Phase Shift Keying, QAM is amplitude modulation, and QPSK and BPSK are phase modulation. In the above example, 128 QAM, 32 QAM, etc. are not shown, but there are other QAMs. By adding an error correction function, the transmission error rate can be reduced from 1/10 ⁵ to 1/10 ⁷ . Therefore, in this case, for example, if the transmission rate is 1 Mbps, an error occurs probabilistically once every 10 seconds, and the transmission frame in which the error has occurred is retransmitted and stable without any problem. Communication is possible.

[Estimated evaluation of S / N]
Next, the evaluation of S / N will be described with reference to FIG. FIG. 9 is a processing flow diagram for S / N evaluation at regular intervals. Training data for evaluating S / N is transmitted from the out-of-home communication means 5a to the in-home communication means 5b to obtain the S / N. An example of calculation is shown. Note that the same processing flow is performed when the S / N is calculated by transmitting training data for evaluating the S / N from the in-home communication unit 5b to the out-of-home communication unit 5a. When normal data is transmitted from the out-of-home communication means 5a, the procedure from Step 1 to Step 5 is performed, and the processing for S / N evaluation is performed by interrupt processing. Here, as an interrupt process, an interrupt process that starts at a predetermined time is taken as an example. The process shown in FIG. 9 is performed by the access controller 55.
In normal data transmission, the access controller 55 first creates packet data in the communication device based on the data fetched from the protocol converter 56 in step 1. Next, in step 2, the created packet data is output to the modulator 57. As a result, the data is modulated, and the modulated data is output to the home communication means 5b. On the other hand, for the data transmitted from the home communication means 5b, the packet data from the demodulator 54 is taken in as shown in step 3. In step 4, a CRC (Cycle Redundancy Check) is evaluated to detect transmission errors. In step 5, if there is a transmission error, a re-transmission request is made to the home communication means 5b. If there is no transmission error, the fetched data is output to the protocol converter 56.

  An interrupt process for S / N evaluation is performed in a state where such a normal data communication process is performed. In this interrupt process, first, training data prepared in advance is output to the modulator 57 in step 6. As a result, the training data is modulated and transmitted to the home communication means 5b. On the other hand, the in-home communication means 5b receives the training data in step 10, and calculates the S / N for each carrier wave in step 11. This calculation will be described later. Further, in step 12, the carrier number and the bit allocation amount are converted into packet data as a pair and output to the modulator. The carrier number and the bit allocation amount are paired and called bit allocation information. As a result, the bit allocation information (carrier number and bit allocation amount) is transmitted from the in-home communication unit 5b to the out-of-home communication unit 5a. Further, the bit allocation information table is rewritten in order to update the bit allocation information of the home communication means 5b itself, which is the local station. This bit allocation information is used when the data transmitted from the outside communication means 5a is demodulated by the demodulator of the inside communication means 5b. Thereafter, the out-of-home communication means 5a receives the bit allocation information transmitted from the in-home communication means 5b in step 7, and rewrites the bit allocation information table in step 8. When this process is completed, in step 9, an ACK (acknowledgement) indicating the completion of rewriting of the bit allocation information table is transmitted. In-home communication means 5b receives ACK in step 13 and ends the process. When this processing is completed, the training information is transmitted from the in-home communication means 5b to the out-of-home communication means 5a, and the S / N for the transmission from the in-home communication means 5b to the out-of-home communication means 5a is evaluated. This is not necessary if the S / N of the communication line is symmetric, but is effective when the S / N is not symmetric. For example, when the noise source is near the outside communication means 5a, the noise on the outside communication means 5a side is stronger than the noise on the inside communication means 5b. Therefore, since the S / N in the out-of-home communication means 5a becomes low, when data is transmitted from the in-home communication means 5b to the out-of-home communication means 5a, it is necessary to lower the bits allocated to each carrier according to the S / N. Occurs. When there is a difference in S / N between the communication devices as described above, bi-directional S / N evaluation is performed, and the bit allocation information obtained as a result is stored in each access controller 55 and modulated. It is desirable to use it corresponding to demodulation.

  Although it is necessary to distinguish between transmitting training data and normal data, this can be realized by configuring a transmission format as shown in FIG. This transmission format includes a preamble signal, a header, data, and a CRC, and the header indicates training information or normal data information. If the header indicates training information, training data is included in the data. If the header indicates data information, normal data is included in the data.

  As training data, there are 256QAM, 64QAM, QPSK, and the like. Here, in order to facilitate understanding, QPSK will be described as an example. The preamble signal is used for symbol synchronization. QPSK is a modulation method in which 2 bits are assigned to each carrier wave, and the signal point arrangement is as shown in FIG. In FIG. 11, the I axis indicates the in-phase component of the signal, and the Q axis indicates the quadrature component of the signal. For example, the data assignment to the signal point indicates data “00” at the signal point in the first quadrant, data “01” at the signal point in the second quadrant, data “11” at the signal point in the third quadrant, and the fourth. Data “10” is represented by signal points in the quadrant. Therefore, it is possible to evaluate the S / N more accurately by transmitting data in all quadrants. If not strict, appropriate data consisting of 2 bits may be used. For example, it may be composed of data in the first quadrant and the third quadrant and may be “00” and “11”, or may be all data in the first quadrant and may be “00”.

  “00”, “01”, “11”, and “10” are set as the training data in FIG. In this case, in FIG. 1, as the bit allocation information output from the access controller 55 to the modulator 57, it is output that 2-bit allocation (QPSK) is performed for each carrier wave. Thus, the modulator 57 transmits 2-bit training data by assigning 2 bits to each carrier by QPSK modulation. In the case of training, since the purpose is to evaluate the S / N of each carrier, QPSK modulation is performed on all carriers and data is transmitted. Then, since it is determined in advance that transmission is performed by QPSK modulation at the time of training, the reception side demodulates by QPSK. In QPSK, the amplitude is constant for any signal point, only the phase is different, and the demodulation process is simple. However, training may be performed using 256 QAM, 64 QAM, or the like.

Now, the S / N is evaluated as follows. In the case of QPSK, if there is no noise and no attenuation on the communication line, the signal points upon demodulation are as shown in FIG. However, there is noise on the communication line and it also attenuates. Since the attenuation is corrected by the equalizer 53 of FIG. 1, the demodulated signal is basically restored around the true value in the signal point arrangement. In FIG. 12, the range indicated by a circle is the position of the signal point after demodulation. The distance from the origin to the true value is the signal strength S, and the distance from the true value to the demodulated signal point position is the noise strength N. Therefore, S / N can be obtained by calculating the ratio between the two.
Here, since the modulation method is determined in advance in the training, it is possible to store in advance in the communication device where the true value is. As described above, there is a method using an average value in addition to a method for calculating S / N using a true value. This is a method of calculating an average of signal point positions after demodulation, using this result as S as the distance from the origin, and setting N as the distance from the signal point position after each demodulation. In any method, in order to evaluate (estimate or measure) noise more accurately, it is necessary to transmit training data a plurality of times for each carrier wave.

[Transmission error rate evaluation]
Next, a method for performing training at an event will be described. The process for this is shown in FIG. The difference from the method shown in FIG. 9 is that training is not performed at regular intervals, but is performed when normal data transmission is performed and many transmission errors occur. . Therefore, based on the CRC error check result in step 4 shown in FIG. 13, the error occurrence frequency within a predetermined time is calculated in step 5, and this result exceeds a predetermined value. Conduct training. The training is achieved by performing Step 6 to Step 13 as in FIG. When this training is completed, normal data communication is performed.
In this example, training from the out-of-home communication unit 5a to the in-home communication unit 5b is shown based on a transmission error that occurs when data is transmitted from the in-home communication unit 5b to the out-of-home communication unit 5a. Training from the in-home communication means 5b to the out-of-home communication means 5a is performed in the same manner based on a transmission error that occurs during data transmission from the out-of-home communication means 5a to the in-home communication means 5b.

In this way, training is performed according to the transmission error rate (event-driven training), that is, training is performed when the S / N deteriorates, so that training is performed at regular intervals. The characteristic that transmission efficiency becomes high is acquired.

  Further, when this event-driven training and training at regular intervals are used in combination, the transmission efficiency is further improved. In other words, it is possible to train when the S / N deteriorates due to event-driven training, and when the S / N improves, it is possible to allocate data in a high S / N state by training for a certain period of time. The transmission speed can be further increased. Only event-driven training results in only data allocation determined by the training when it deteriorates, so the transmission speed cannot be improved. However, this problem can be solved by using both methods together. For this purpose, event-driven training may be performed by the processing shown in FIG. 13 by the access controller, and training at regular intervals may be performed by interrupt processing.

[OFDM communication]
In addition to the above, there is a frequency at which sufficient S / N cannot be secured by performing communication between the out-of-home communication means 5a and the in-home communication means 5b using a multi-carrier communication method including OFDM, so that data allocation is possible. Even if there is a carrier that cannot be used, if the S / N of other frequencies is high, a large amount of data can be allocated to the carriers of these frequencies, and a sufficient communication speed of 1 Mbps or more can be ensured as a whole. Furthermore, since OFDM has high frequency use efficiency, it is possible to ensure the same communication speed in a narrower band than a general multicarrier communication system. For this reason, although the S / N varies depending on the frequency due to noise, even if the change of the S / N is over a certain frequency range, it is easy to set a frequency band having a relatively high S / N as a use frequency band in OFDM. There is a feature.

[Single carrier S / N evaluation]
Next, the S / N evaluation when a single carrier is used will be described.
In order to achieve the same transmission rate as a multicarrier using a single carrier, it is necessary to widen the band of the single carrier. By widening the band of a single carrier, the transmission speed can be increased. Since the modulation method is the same as that of multi-carrier, the training shown in FIGS. 9 and 13 can be applied as it is. The S / N evaluation is also as shown in FIG.

[Change method of carrier frequency]
Next, a method for changing the carrier frequency based on the S / N evaluation result will be described.
Although FIG. 9 and FIG. 13 show that the data allocation amount is changed, instead of changing the data allocation amount, the frequency of the carrier wave is changed to a frequency band in which the S / N is equal to or higher (also referred to as a shift). It is also possible to do. In this case, the carrier frequency change information is output from the access controller 55 to the modulator 57 and the demodulator 54 instead of the data allocation amount information 55a and 55b shown in FIG. Note that S / N measurement is performed in advance, and it is determined which frequency band to change to. In this system, in the case of a single carrier, since there is one carrier wave, this change process is easy. However, the use band of communication needs to be a sufficiently wide band so that the frequency can be changed.

  As described above, even when noise from a home appliance is superimposed on a signal due to communication using a carrier signal with a high S / N or communication in a frequency band with a high S / N, the signal is not greatly affected by this. Thus, it is possible to stably transmit image information captured by the camera 1 using an existing signal line.

[Spread spectrum communication system]
A communication apparatus that performs communication using the spread spectrum communication method will be described with reference to FIG.
FIG. 14 shows an embodiment to which a spread spectrum communication system is applied.
The embodiment shown in FIG. 14 is different from the embodiment shown in FIG. 1 in the part related to the modulator 57 and the demodulator 54, and the other parts are the same.
In the multicarrier scheme including OFDM described above, the bit allocation change processing is performed for each carrier. However, in the spread spectrum communication scheme, such processing is not performed, and instead, the baseband bandwidth is increased to a wider bandwidth. Communication is performed by spreading, and the data is restored by compressing the band to the baseband band at the time of demodulation. This spread spectrum communication method can increase the S / N with respect to communication under the situation where random noise is superimposed on the communication path, enables stable communication, and noise (frequency selectivity in a specific frequency band). This is suitable for communication when the level of noise is high.

  Next, the difference between the spread spectrum communication system shown in FIG. 14 and the system shown in FIG. 1 will be described. In the case of a spread spectrum communication system, the modulator 57 is also called a primary modulator, and amplitude modulation, frequency modulation, phase modulation (BPSK, QPSK) used in normal transmission, 16QAM, 64QAM that modulates phase and amplitude simultaneously. Various modulation schemes such as 256QAM are employed.

The output signal (primary modulated signal) of the modulator 57 is input to the spread spectrum modulator 63. The spread spectrum modulator 63 multiplies the first-order modulated signal with a special waveform called a PN (Pseudorandom Noise) sequence output from the spread code generator 64 and outputs the product to the D / A 58. This processing can be realized by an analog processing circuit, and in this case, the D / A 58 is unnecessary.
Through these processes, the spread-modulated signal is transmitted from the out-of-home communication means 5a to the in-home communication means 5b. The bandwidth after the spread modulation is the sum of the bandwidth of the primary modulation and that of the PN sequence. Usually, since the magnification of the band spread is large, the bandwidth of the PN sequence substantially becomes the bandwidth of the spread signal. Accordingly, the use band (PN sequence band) needs to be wider than the primary modulation bandwidth (baseband bandwidth), and the spreading factor (PN sequence bandwidth / primary modulation bandwidth) is 5. Although it is desirable to make it more than double, it is desirable to make it at least 10 times when the noise level of home appliances is relatively high. In order to transmit high-quality images, a transmission speed of 1 Mbps is required at least. Therefore, the baseband bandwidth is required to be at least 1 MHz, and a bandwidth of 10 MHz or more, which is 10 times the bandwidth, is used. As necessary. In addition, as shown in FIG. 5, it is effective to use 5 MHz or more based on the measurement result. That is, it is effective to use a band of 5 MHz or more and at least 10 MHz as a use band.

On the other hand, demodulation is processed as follows.
The output signal of A / D 52 is output to timing / synchronization circuit 61 and spread spectrum despreader 62. In the spread spectrum despreader 62, the same PN sequence as that used on the transmission side is multiplied again to restore the primary modulation signal. This process is also called bandwidth compression. By this band compression, S is improved in S / N, and N of frequency selective noise such as inverter noise of an electromagnetic cooker is suppressed. For this reason, the S / N in the demodulating process in the demodulator 54 is sufficiently high, and the original signal can be restored without being affected by noise on the communication path. Note that the timing / synchronization circuit 61 is used for the purpose of obtaining synchronization for multiplying the PN sequence by the spread spectrum despreader 62 again. Further, when the timing / synchronization circuit 61 and the spread spectrum despreader 62 are realized by analog circuits, the A / D 52 is not necessary.

  As described above, training is performed to determine the bit allocation amount necessary for the multi-carrier communication method by communicating between the outside communication unit 5a and the in-home communication unit 5b using the spread spectrum communication method. Since it is not necessary to carry out, it is possible to have a feature that there is no temporary interruption of image transmission.

[Two-way communication by time division]
By keeping the communication direction between the out-of-home communication means 5a and the in-home communication means 5b constant, it is not necessary to switch the communication direction and the frequency band can be used to the maximum, so that high-speed and stable communication is possible. However, in order to improve the function of the communication device, the communication direction between the out-of-home communication means 5a and the in-home communication means 5b is not always constant. For example, even if an image captured by the camera 1 is transmitted from the out-of-home communication unit 5a to the in-home communication unit 5b, a control response such as a confirmation response to the transmission of image information and a training signal is transmitted from the in-home communication unit 5b. It may be transmitted to the communication means 5a. Alternatively, control information such as on / off command of camera 1 and zoom, head swing command, etc., or a person who cannot speak loudly displays a message to the visitor from the home communication means 5b to the outside communication means 5a Thus, it is also possible to transmit text information for displaying a telop to respond. In this way, bidirectional communication (in this case, the direction from the outside communication means 5a to the in-home communication means 5b) and the down direction (here, from the in-home communication means 5b to the outside communication means 5a) is performed. There are several methods for realizing this, such as a frequency division method and a time division method.

In the frequency division method, communication is performed by dividing a frequency band to be used and allocating predetermined frequency bands set in advance in the upstream and downstream directions.
In the method using time division, the uplink and downlink communication directions are alternately switched every predetermined time set in advance.
Such bi-directional communication can be realized by adding a function for switching the uplink direction and the downlink direction to the access controller 55 shown in FIGS. 2, 3, and 14.

Here, a method for realizing bidirectional communication by time division will be described.
As shown in FIG. 15, it is assumed that time t1 to time t2 are assigned to uplink transmission, and time t2 to time t3 are assigned to downlink transmission. At this time, communication is performed using all frequency bands that can be used in the upstream and downstream directions. Here, the time td1 (= t2-t1) is set to a predetermined time, and similarly, the time td2 (= t3-t2) is set to a predetermined time. In this way, when transmission in the downlink direction is completed, transmission is continued in the uplink direction for a time td1 between time t3 and time t4, and transmission in the downlink direction is performed for a time td2 from time t4 to time t5. It is possible to transmit alternately. Therefore, if the rule for starting communication is determined, the times td1 and td2 may be set in advance, so that a control signal for switching between the uplink direction and the downlink direction is not necessary. This communication start rule is, for example, a method in which a signal is transmitted only during a predetermined time td3 (= t1-t0) set in advance in the downlink direction. Alternatively, a method of transmitting a predetermined waveform signal may be used.

  In addition, the frequency division method is easily affected by noise (also referred to as colored noise) in a specific frequency band generated from an inverter device or the like. For example, when colored noise occurs over the entire frequency band allocated in the upstream direction, the transmission speed of the upstream communication decreases, or in the worst case, the upstream direction becomes incapable of communication. Communication is not possible. However, the method using time division has a feature that it is less susceptible to colored noise than the method using frequency division because the communication direction is switched by time division using all available frequency bands.

[Connection form when signal lines have branches]
When a doorphone terminal (home communication means) is installed on each of the first and second floors of a house, or a doorphone terminal (home communication means) is installed in a room in each dwelling unit of a housing complex. When a terminal (external communication means) is shared by each dwelling unit, etc., the signal line of the door phone is branched and a terminal (in-home communication means) is connected to each of the branched signal lines. In such a case, as shown in FIG. 16, the home communication means 5b and 5b ′ may be connected to the doorphone master units 6 and 6 ′ in the same manner. By connecting in this way, 1: N communication (communication between one terminal (external communication means) and a plurality of terminals (internal communication means)) becomes possible. At this time, between the respective communication means, the access controller 55 shown in FIGS. 2, 3, and 14 switches the communication direction by time division, so that communication signals overlap and communication collision occurs. Can be avoided. Alternatively, when a communication collision occurs according to a CSMA / CD (Carrier Sense Multiple Access / Collision Detection) method, the transmission may be performed again after a random time.

In addition, apartment buildings often have a common entrance for security reasons, and visitors to the apartment are confirmed at the common entrance before admission to the apartment is permitted. In such a case, as shown in FIG. 17, when the common entrance and the door phone terminal in each dwelling unit share one signal line, the visitor uses the room number input terminal 8 as the target dwelling unit. The number is entered, and the resident of the entered unit number will respond. For example, when the target dwelling unit is dwelling unit 1, a call is started between door phone master unit 6 and door phone sub unit 7, and at the same time, outside communication unit 5a communicates with in-home communication unit 5b. Communication is started and an image captured by the camera 1 is transmitted. The resident of the dwelling unit 1 confirms the image displayed on the monitor 3 and permits the visitor to enter. At this time, the communication between the out-of-home communication means 5a and 5b ends. The operations of the out-of-home communication means 5a and the in-home communication means 5b at this time are the same as described above.
Next, when the visitor arrives at the entrance 1 for each dwelling unit (entrance of the dwelling unit 1), the doorphone slave unit 7 'makes a call with the doorphone master unit 6, but at the same time, the outside communication means 5a' is connected to the in-home communication means 5b. Start communication. An image captured by the camera 1 ′ is transmitted from the outside communication unit 5 a ′ to the in-home communication unit 5 b and displayed on the monitor 3. The operations of the out-of-home communication means 5a 'and the in-home communication means 5b at this time are the same as described above. If it can be determined that the camera 1 installed at the common entrance is sufficiently secure, the camera 1 ', the encoder 2', the outside communication means 5a ', etc. at the entrance 1 for each dwelling unit are not required. good.
In the case of the connection configuration as shown in FIG. 17, for example, the out-of-home communication means 5a and the in-home communication means 5b can communicate with the out-of-home communication means 5a and the in-home communication means 5b at the same time. . That is, it is possible to perform N: M communication (communication between a plurality of terminals (external communication means) and a plurality of terminals (internal communication means)).

  In addition, FIG. 18 shows a connection form in which each dwelling unit is wired separately without sharing a signal line. In this case, the changeover switch 9 is provided, and the signal line to which the changeover switch 9 is connected is switched in accordance with the dwelling unit number input at the dwelling unit number input terminal 8. For example, when the dwelling unit number 1 is input, the changeover switch connects the signal line 71 and the signal line 71 ′ and does not connect to the signal line 71 ″. The operation of the communication device after connection is the same as when the signal line is shared by each dwelling unit. In the case of such a connection configuration, for example, N: 1 communication is possible because the outside communication means 5a and the in-home communication means 5b communicate, and the outside communication means 5a ′ and the in-home communication means 5b can communicate. (Communication between a plurality of terminals (external communication means) and one terminal (in-home communication means)).

FIG. 19 is a system configuration diagram showing the second embodiment of the present invention. Although the basic configuration is the same as that of FIG. 1 described in the first embodiment, a compression code / decoder 81 and a transfer device 82 are added to the monitor 3 instead of the monitor 3.
In the second embodiment, the procedure for transmitting the image information captured by the camera 1 from the outside communication means 5a to the inside communication means 5b is the same as that in the first embodiment, but the outside communication means 5a The device 2 and the decoder 203 are connected. Two external devices are connected to the out-of-home communication means 5a, but it is only necessary to cope with the protocol converter 56 so that a plurality of external devices can be connected. The camera 1 and the microphone 201 are connected to the encoder 2, and the speaker 202 is connected to the decoder 203. The home communication means 5b is connected to a compression code / decoder 81 instead of the monitor 3, and the home communication means 5b transfers the transmitted image information to the compression code / decoder 81. Here, the home communication means 5b and the compression code / decoder 81 are connected by Ethernet (registered trademark) or USB. The camera 1, the encoder 2, the outside communication means 5a, the in-home communication means 5b, the compression encoder / decoder 81, and the transfer device 82 may be always activated, but may cause an increase in power consumption. It may be activated by an activation signal from the machine 6. Alternatively, if the in-home communication means 5b, the out-of-home communication means 5a, etc. have an auto-start circuit (a circuit that automatically detects the application of a DC voltage and activates the device), a trigger from the doorphone slave unit 7 By the signal (button push), the intercom base unit 6 detects the signal and superimposes a DC voltage on the communication line 71. As a result, communication may be started between the in-home communication unit 5b and the out-of-home communication unit 5a.

  The compression encoder / decoder 81 has a function of compressing and encoding the MPEG1, MPEG2, and AVI formats, which are the formats of the transmitted image information, into the MPEG4 format. Forward. Similarly, the compression encoder / decoder 81 and the transfer device 82 are connected by Ethernet (registered trademark) or USB. The transfer device 82 has a function of connecting to the Internet by a communication function such as ADSL (Asymmetric Digital Subscriber Line), and the transfer device 82 has an IP (Internet Protocol) address or telephone number set in advance or Image information is transferred to address information having a function of specifying a mobile phone such as an e-mail address. At this time, by connecting the microphone 201 to the encoder 2, the voice of the visitor is collected by the microphone 201 without passing through the door phone slave unit 7, and encoded by the encoder 2 into a digital signal to be combined with the image information. To the mobile phone. The voice of the resident who responds with the mobile phone is transferred from the transfer device 82 to the compression encoder / decoder 81, and the compression encoding / decoder 81 decodes the compression encoding. 5a, transferred to the decoder 203, and the decoder 203 decodes the digital signal into an analog signal and then allows the speaker 202 to utter. Thus, even when the user is away from home by having the function of transferring to the mobile phone, there is an effect that it is possible to respond to visitors to the home. In addition, although the person who responds with a mobile telephone was demonstrated as a resident here, the person who responds with a mobile telephone is not restricted to a resident. In addition, by compressing the image information into the MPEG4 format in the compression encoder 81, the image information can be compressed into an image with a bit rate of about 5 kbps at the minimum, and can be received even by a current digital mobile phone with a communication speed of 9.6 kbps. It becomes possible. Furthermore, since the mobile phone does not have a large screen, the transmission information can be reduced and the image information can be efficiently transferred by compressing the MPEG4 format. The compression encoder / decoder 81 and the transfer device 82 can be replaced with a single device having both functions. Further, the home communication means 5b has a function of switching the input / output interface between the home communication means 5b and the compression code / decoder 81, so that the monitor 3 and the compression code / decoder 81 can be connected simultaneously. .

Next, FIG. 20 is a system configuration diagram showing a third embodiment of the present invention.
The basic configuration of the system according to the third embodiment is the same as that shown in FIG. 1 described in the first embodiment, except that a recorder 91 is installed instead of the monitor 3 and a time recording device 92 for recording time stamps. Has been added.

  In this third embodiment, the procedure for transmitting the image information captured by the camera 1 from the outside communication means 5a to the in-home communication means 5b is the same as that in the first embodiment, but the in-home communication means 5b is replaced with the monitor 3 instead. Is connected to the recorder 91, and the home communication means 5 b transfers the transmitted image information to the recorder 91. Here, the home communication means 5b and the recorder 91 are connected by Ethernet (registered trademark) or USB. The camera 1, the encoder 2, the out-of-home communication means 5a, the in-home communication means 5b, the compression encoder 81, and the transfer device 82 may be activated at all times, but may cause an increase in power consumption. It may be activated by an activation signal from. Alternatively, if the in-home communication means 5b, the out-of-home communication means 5a, etc. have an auto-start circuit (a circuit that automatically detects the application of a DC voltage and activates the device), a trigger from the doorphone slave unit 7 By the signal (button push), the intercom base unit 6 detects the signal and superimposes a DC voltage on the communication line 71. As a result, communication may be started between the in-home communication unit 5b and the out-of-home communication unit 5a, and recording by the recorder 91 and the time recording device 92 may be started.

  The recorder 91 has a function of recording the transmitted image information. When the resident is absent, the recorder 91 automatically records the visitor image so that the resident can return the visitor after returning home. Can be confirmed. The image information is recorded while being encoded, but the image information decoded using a decoder may be recorded. At this time, the recording time can be set in advance, for example, 10 minutes. Also, a time recording device 92 is connected to the home communication means 5b, and the time recording device 92 has a function of automatically recording the time when the image is transmitted to the home communication means 5b. By recording the time when the visitor visited, the time when the visitor visited after returning home when the resident was absent can be confirmed. It is also possible to confirm the time when the image is reproduced by simultaneously overwriting the time information on the image recorded by the recorder. Here, the recorder 91 and the time recording device 92 are connected by Ethernet (registered trademark) or USB. Note that the recorder 91 and the time recording device 92 can be used independently, but using both in combination is more effective because the time when the image was recorded can be known. Further, by providing the camera 1 with a microphone, the voice of the visitor is collected by the microphone of the camera 1 without passing through the door phone slave unit 7 and transferred to the recorder 91 together with the image information. By recording together, it is also possible to record the visitor's business as audio information.

Next, FIGS. 21A to 21C are system configuration diagrams showing the fourth embodiment of the present invention.
In addition, in the newly installed door phone system, when noise is easily superimposed on the signal line as in the existing door phone system, the communication device is not only the signal line of the existing door phone system but also the signal line of the newly installed door phone system. In the same way, it is possible to realize high-speed and high-quality communication. In this case, as shown in FIG. 21A, the monitor door phone 101 disposed in the house includes a home communication means 1011, a monitor with a speaker 1012 (with a monitor, a speaker, and a decoder), a microphone 1013, an encoder 1014, and a response switch 1015. The camera doorphone 102 installed outside the home incorporates an out-of-home communication means 1021, a camera 1022 with a microphone (containing a camera, a microphone, and an encoder), a speaker 1023, a decoder 1024, and a doorphone switch 1025. Here, the out-of-home communication means 1021 and the in-home communication means 1011 have basically the same configuration as the out-of-home communication means 5a and the in-home communication means 5b described in FIG. The camera with microphone 1022 has a function to encode and multiplex the audio information collected by the microphone and the image information captured by the camera with an encoder, and the monitor with speaker 1012 decodes the audio information and the image information with a decoder. The audio information is reproduced by a speaker and the image information is displayed on a monitor. The in-home communication means 1011 is connected to the monitor with speaker 1012, the encoder 1014, and the response switch 1015, but it is only necessary to support the protocol converter 56 so that a plurality of external devices can be connected. The same applies to the out-of-home communication means 1021. The monitor door phone 101 and the camera door phone 102 are connected by a communication line 71. Here, the communication line 71 may be a line having characteristics equivalent to those used in an existing door phone system, or a coaxial cable. The door phone switch 1025 generates a signal when the visitor presses the door phone switch 1025, for example, and the signal is transmitted from the outside communication means 1021 to the in-home communication means 1011 and is always activated. It has a function of generating a specific pattern of sound from the 1012 speaker in the house and notifying the resident of the arrival of the visitor. The response switch 1015 generates a signal for starting the microphone 1013, for example, when the resident presses the response switch 1015. Alternatively, a signal for activating the camera 1022 with a microphone of the camera door phone 102 is generated, and the signal is transmitted from the in-home communication unit 1011 to the out-of-home communication unit 1021 and further transmitted to the camera 1022 with a microphone. It has functions such as starting up. Image information picked up by the camera 1022 with microphone of the camera doorphone 102 and collected sound information are transmitted from the outside communication means 1021 to the in-home communication means 1011 of the monitor doorphone 101 and transferred to the monitor 1012 with speaker. Audio information collected by the microphone 1013 is transmitted from the in-home communication unit 1011 to the out-of-home communication unit 1021 of the camera door phone 102 through the encoder 1014, and transferred to the speaker 1023 through the decoder 1024. The monitor door phone 101 is connected to an outlet 503. The monitor door phone 101 converts an AC voltage (for example, AC 100V) supplied from the outlet 503 into a DC voltage by an AC / DC converter, and serves as a drive power source for each circuit of the monitor door phone 101. Supply. The monitor door phone 101 superimposes the DC voltage converted by the AC / DC converter on the communication line 71, and the camera door phone 102 converts the DC voltage superimposed on the communication line 71 by the DC / DC converter, and the camera door phone 102. Is supplied as drive power for each circuit. Note that, when the monitor door phone 101 has a built-in battery, connection to the outlet 503 is not necessary, but connecting to the outlet 503 has an effect of omitting management work such as battery replacement.

  FIG. 21B shows a connection configuration when image information is transferred to the mobile phone in the newly installed door phone system. Basically, it is the same as FIG. 21A, but further includes a compression code / decoder 1016, a transfer device 1017, and a transfer switch 1018. When the transfer switch 1018 is set to OFF, FIG. 21B operates in the same manner as FIG. 21A. However, when the transfer switch 1018 is set to ON, the compression code / decoder 1016 and transfer device 1017 of FIG. It works basically the same as Specifically, in the case of ON setting, when the door phone switch 1025 is pressed, an activation signal generated by the door phone switch 1025 is transmitted from the outside communication unit 1021 to the inside communication unit 1011 and is compressed from the inside communication unit 1011. The data is sent to the decoder 1016 and the transfer device 1017, and the compression code / decoder 1016 and the transfer device 1017 are activated. The image and audio information captured by the camera with microphone 1022 are transferred to the outside communication means 1021 and then transmitted from the outside communication means 1021 to the in-home communication means 1211 using the communication line 71 as a communication line. After being compressed at 1016, it is transferred from the transfer device 1017 to the mobile phone of the resident who is away. The voice of the resident who responds with the cellular phone is transmitted to the outside communication means 1021 from the in-home communication means 1011 after the compression code is decoded by the compression code / decoder 1016 through the transfer device 1017, and the decoder Decoded at 1024 and reproduced from the speaker 1023. As described with reference to FIG. 19, the person who responds with the mobile phone is not limited to the resident.

  Next, FIG. 21C shows a connection configuration when image information is recorded in the newly installed door phone system. Basically the same as FIG. 21A, but additionally a recording switch 1019, a recorder 10191, and a time recording device 10192 are added. When the recording switch 1019 is set to OFF, FIG. 21C operates in the same manner as FIG. 21A. However, when the recording switch 1019 is set to ON, the recorder 10191 and the time recording device 10192 of FIG. 21C are those described in FIG. And basically works the same way. Note that the recorder 10191 and the time recording device 10192 may start recording automatically, for example, at the same time as the doorphone switch 1025 is pressed, or start recording when the response switch 1015 is pressed. May be. When the door phone switch 1025 is pressed, the activation signal for this purpose is transmitted from the outside communication means 1021 to the in-home communication means 1011 and sent to the recorder 10191 and the time recording device 10192. Alternatively, when the response switch is pressed, the activation signal is transferred to the home communication means 1011 and similarly sent to the recorder 10191 and the time recording device 10192. At this time, the image information picked up by the camera with microphone 1022 and the collected voice information are encoded by the encoder and then transferred to the outside communication means 1021, and from the outside communication means 1021 to the inside communication means 1011. It is transmitted, transferred to the recorder 10191, and recorded with time information. Alternatively, the image information and audio information may be transferred from the home communication means 1011 to the decoder of the monitor 1012 with speaker, decoded by the decoder, transferred to the recorder 10191, and recorded together with the time information.

  If communication means are added to the existing doorphone system later, multiple devices will be installed, which may cause problems such as poor appearance and insufficient space. By combining the two into one device, it is possible to solve these problems. Further, if the existing communication line can be used, new cabling is not necessary, and the wiring cost can be reduced.

  As described above, according to the present invention, even when noise from home appliances or the like is superimposed on a communication line, the high-speed and high-quality image captured by the camera using the signal line of the door phone system as the communication line is not greatly affected by this. It becomes possible to transmit image information stably.

It is explanatory drawing which showed 1st embodiment of this invention. It is explanatory drawing which showed the internal structure of the outside communication means 5a. It is explanatory drawing which showed the internal structure of the outside communication means 5a provided with the coupler 72. FIG. It is a figure explaining the example of a connection structure of the coupler. It is a figure explaining a communication characteristic. It is a figure explaining the spectrum of a general multicarrier. It is a figure explaining the spectrum of OFDM. It is a figure explaining the transmission error characteristic under Gaussian noise. It is a processing flow figure for S / N evaluation for every fixed time. It is a figure explaining a transmission format. It is a figure explaining the signal point arrangement | positioning of QPSK. It is a figure explaining S / N evaluation of QPSK. It is a processing flowchart for S / N evaluation by event drive. It is a figure explaining the internal structure of the outside communication means 5a to which the spread spectrum communication system is applied. It is a figure explaining the transmission time allocation of an up direction and a down direction. It is explanatory drawing which showed the connection form of the communication apparatus when there is a branch in a signal line. It is explanatory drawing which showed the connection form of the communication apparatus in case a signal line is shared in an apartment house. It is explanatory drawing which showed the connection form of the communication apparatus in case the signal line is wired separately in an apartment house. It is explanatory drawing which showed the 2nd Embodiment of this invention. It is explanatory drawing which showed the 3rd Embodiment of this invention. In the 4th Embodiment of this invention, it is explanatory drawing which shows the connection structure of the newly installed door phone system. It is explanatory drawing which shows the connection structure in the case of transferring image information to a mobile telephone in the new door phone system in the 4th Embodiment of this invention. It is explanatory drawing which shows the connection structure in the case of recording image information in the newly installed door phone system in the 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera 2 Encoder 3 Monitor 4a, 4b Splitter 5a Out-of-home communication means 5b In-home communication means 6 Doorphone parent machine 7 Doorphone child machine 8 Room number input terminal 9 Changeover switch 50 BP filter 51 Reception amplifier 52 Analog / digital converter 53 etc. 54 demodulator 55 access controller 56 protocol converter 57 modulator 58 digital / analog converter 59 transmission amplifier 60 BP filter 61 timing / synchronization circuit 62 spread spectrum despreader 63 spread spectrum modulator 64 spread code generator 71 communication Line 72 Coupler 81 Compression encoder / decoder 82 Transfer device 91 Recorder 92 Time recording device 101 Monitor door phone 102 Camera door phone 201 Microphone 202 Speaker 203 Decoder 501 DC voltage 502 AC / DC converter 503 Outlet 504 DC / DC converter 1011 In-home communication means 1012 Monitor with speaker 1013 Microphone 1014 Encoder 1015 Response switch 1016 Compression encoder / decoder 1017 Transfer device 1018 Transfer switch 1019 Recording switch 10191 Recorder 10192 Time recording device 1021 Outside communication device 1021 1022 Camera with microphone 1023 Speaker 1024 Decoder 1025 Door phone switch

Claims (12)

An out-of-home communication means arranged outside the house, and an in-home communication means arranged inside the house,
The out-of-home communication means and the in-home communication means are connected by a signal line connecting a door phone master unit and a door phone slave unit, and each carrier signal is transmitted to the carrier signal using a plurality of carrier signals with the signal line as a communication line. The transmission data is allocated and communicated, and for each carrier signal, the S / N, which is the ratio of signal to noise, is estimated or measured, and each carrier wave is determined according to the estimated or measured S / N value. A communication apparatus for performing communication by changing a transmission data allocation amount to a signal. An out-of-home communication means arranged outside the house, and an in-home communication means arranged inside the house,
The out-of-home communication means and the in-home communication means are connected by a signal line connecting a door phone master unit and a door phone slave unit, and each carrier signal is transmitted to the carrier signal using a plurality of carrier signals with the signal line as a communication line. The transmission data is allocated and communicated. The transmission error rate is evaluated for each carrier signal, and the transmission data allocation amount to each carrier signal is changed according to the evaluated transmission error rate. A communication device characterized by   The communication apparatus according to claim 1, wherein the out-of-home communication unit and the in-home communication unit perform communication by an orthogonal frequency division multiplexing method.   The out-of-home communication means and the in-home communication means use at least one carrier signal of the plurality of carrier signals to allocate transmission data to the carrier signal and communicate with the carrier signal. If the determination result is equal to or lower than a predetermined S / N, the frequency of the carrier signal is changed to a predetermined frequency different from the carrier signal before the determination. The communication apparatus according to claim 1, wherein communication is performed. An out-of-home communication means arranged outside the house, and an in-home communication means arranged inside the house,
The out-of-home communication means and the in-home communication means are connected by a signal line connecting the door phone master unit and the door phone slave unit, and the signal line is used as a communication line to communicate a communication signal over a wide band. A communication apparatus that performs communication by a spread spectrum system.   The communication apparatus according to any one of claims 1 to 5, wherein the outside communication unit and the in-home communication unit perform communication using a signal line of an existing door phone system as a communication line.   The communication apparatus according to any one of claims 1 to 5, wherein the outside communication unit and the in-house communication unit perform communication using a frequency of at least 1 MHz and at most 30 MHz.   The communication apparatus according to any one of claims 1 to 5, wherein the outside communication unit and the in-house communication unit perform communication using a frequency of at least 5 MHz to 30 MHz.   The communication according to any one of claims 1 to 5, wherein the out-of-home communication unit and the in-home communication unit perform communication by switching a communication direction by time division in bidirectional communication. apparatus.   The communication device connects the out-of-home communication means or the in-home communication means to a branched signal line when the signal line has a branch, and connects the three or more out-of-home communication means and the in-home communication means. The communication apparatus according to claim 1, wherein communication is performed between the communication apparatuses.   The outside communication unit includes a camera that captures an image, transmits the image captured by the camera to the home communication unit, and the home communication unit includes a monitor that displays the received image. The communication apparatus according to any one of claims 1 to 6.   12. The communication apparatus according to claim 11, wherein the in-home communication means includes a transfer device having a function of transferring image information to a mobile phone.

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