KR100329713B1 - Data Transceiver for Transmitting and Receiving Data and Voice Signal over Telephone Line - Google Patents

Abstract

The configuration is simple and provides a data transceiver capable of transmitting and receiving data at high speed with a remote receiver located at a long distance through a telephone line.

The transceiver encodes the first data signal from the data processing apparatus and transmits the first encoded data signal to the counterpart transceiver through the telephone line 50, receives the second encoded data signal from the counterpart transceiver via the telephone line 50 and the A second data signal corresponding to a second encoded data signal is supplied to the data processing device. The 8B10B encoder 152 encodes the first data signal such that the magnitude of the accumulated DC component of the data signal is reduced. The packet generator 146 adds preambles and separators to encapsulate the first data signal in an Ethernet format. Equalizer 154 equalizes the encapsulated signal to reduce the magnitude of the transmission level of the second bit to a predetermined reduced level if the logical levels of two consecutive data bits are the same. The media access controller 142 controls the media access to facilitate bidirectional data communication.

Description

Data Transceiver for Transmitting and Receiving Data and Voice Signal over Telephone Line}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to communication equipment, and more particularly, to a data transmission and reception apparatus capable of simultaneously transmitting and receiving telephone signals and LAN data through telephone lines installed in each home or office.

Currently, the most common method for high-speed Internet service access is to use a DSL modem or cable modem that transmits and receives data over an already hypothesized two-wire telephone line or coaxial cable, respectively. The modem transmits data by mapping and modulating a data signal with amplitude, frequency, and phase information of a specific carrier signal, and then transmits the modulated signal through a transmission medium. Examples of the modulation technique include quadrature phase-shift keying (QPSK), quadrature amplitude modulation (QAM), and discrete multi-tone (DMT).

However, communication through modems has the disadvantage of being very complicated and requiring a large amount of signal processing when performing modulation operations. Moreover, the system employing such modulation technique needs to have error control or correction function in consideration of signal attenuation and distortion in the transmission medium, and thus requires encoding and retransmission at the physical layer and the link layer, And software becomes complicated.

Therefore, in transmitting data through a short distance telephone line or the like, it is preferable to transmit the data without changing and demodulating as much as possible. In this regard, the prior patent application filed on May 10, 1999 by the inventor (application number: 10-1999-0016665, the name of the invention: LAN data transmission apparatus over a telephone line) and the prior patent application filed as the same ( Application number: 10-1999-0016666, the title of the invention: LAN data transmission device via a telephone line is coupled to the telephone signal without modulating the data signal and transmitted through a telephone line already installed in an apartment or a business building, Meanwhile, a data transmission apparatus for separating a telephone signal and a LAN data signal from a received signal using a low pass filter and a high pass filter, respectively, is described. However, a system employing such a device may have a problem in that it cannot realize a data rate of 1.5 Mbps or more required for providing a multimedia service, and the transmission distance is not long enough.

In order to increase the transmission speed, the present applicant uses a patent application 10-1999-0033098 (name of the invention: a data communication network and a data transmission / reception apparatus over a telephone line) to combine and transmit a telephone signal and a LAN data signal on a 4-wire telephone line. Has been presented. Although the patented system can increase the data rate, especially when the up and down traffic is asymmetric, the data rate can be significantly increased, but the problem of limited transmission distance remains. In addition, since the above system is built on a four-wire telephone line, the time required for installation work in an individual place may be long, and there may be a problem in that the place to be installed may be limited to the place where the four-wire telephone line is installed or hypothesized.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and its technical problem is to provide a data transceiver which is simple in configuration and capable of transmitting and receiving data at high speed with a remote transceiver located at a long distance through a telephone line.

1 is a view showing an example of a data communication network according to the present invention.

FIG. 2 is a diagram illustrating a configuration of any one of the center module and the subscriber modules shown in FIG. 1;

3 is a block diagram of a digital modem within a center module.

4 is a detailed block diagram of the digital receiver shown in FIG.

5 is a block diagram of a digital modem within a subscriber module.

6 illustrates the format of data packets transmitted and received between digital modems of a center module and a subscriber module in a preferred embodiment of the present invention.

FIG. 7 is a view for explaining the concept of 8B10B encoding and 10B8B decoding in the digital modem shown in FIGS. 3 and 5;

8 is a flowchart showing an 8B10B line encoding process.

9 is a flowchart illustrating a 10B8B line decoding process.

10A shows transmission levels of a data bit where O or 1 is discontinuous;

10B shows transmission levels of zero or one consecutive data bit.

10C is a diagram showing a relationship between transmission level, transmission distance, and transmission reliability.

Fig. 10D shows an example of equalization is performed on an 8B10B coded bit string.

11A is a state transition diagram illustrating a state transition occurring in a time division media access controller of a subscriber module.

11B is a state transition diagram showing a state transition occurring in the time division media access controller of the center module.

12A and 12B are views for explaining the operation of the retransmission controller shown in FIGS. 3 and 5.

FIG. 13 is a view for explaining the operation of the transmission data buffer and the reception data buffer shown in FIGS. 3 and 5; FIG.

<Description of the symbols for the main parts of the drawings>

10: switching hub 20: center module

40: private branch exchange 50: telephone line

70A ... 70N: Subscriber System 72A ... 72N: Subscriber Outlet

74A ... 74N: Subscriber Module 76A ... 76N: Subscriber Terminal

78A ... 78N: Telephone

30: switching hub interface port 80: data terminal interface port

32, 82: digital modem

34: first bandpass filter 84: second bandpass filter

36: first low pass filter 86: second low pass filter

38: telephone network interface port 88: telephone interface port

100: network adapter 140: transmission control unit

120: transmit data buffer 130: receive data buffer

150: transmitter 160: receiver

180: integrator 182: sampler

184: symbol detector 186: phase controller

The data transceiver of the present invention for achieving the above technical problem is suitable for installing an Internet subscriber network, for example, over an existing telephone line in an apartment or a business building. In such an Internet subscriber network, a center module and a subscriber module may be provided at the subscriber side ends of the line distribution room (MDF) and the telephone line, respectively, which modules may be implemented by the data transceiver of the present invention. In a preferred embodiment, the center module is connected to the Internet service provider's Internet server via a switching hub and the subscriber module is connected to the subscriber's data terminal. As such, the center module and the subscriber module may transmit and receive LAN data signals and voice signals to each other through a telephone line while being connected to an external data processing device.

That is, the center module converts the downlink LAN data signal from the switching hub according to the channel characteristics of the telephone line, and then combines the converted downlink data signal with the downlink signal and transmits the combined downlink signal to the subscriber module. In addition, the center module recovers the uplink LAN data signal and the uplink phone signal from the combined uplink signal and transmits the uplink data signal to the switching hub. Meanwhile, the subscriber module converts the uplink LAN data signal from the subscriber station according to the channel characteristics of the telephone line, and then combines the converted uplink data signal with the uplink signal to transmit the combined uplink signal to the center module. In addition, the subscriber module restores the downlink LAN signal and the downlink signal from the combined downlink signal and transmits the downlink LAN data signal to the subscriber station.

More generally, the transceiver receives a first data signal and a first voice signal from a data processing device and a voice communication device, respectively, and combines the first coded data signal corresponding to the first data signal with the first voice signal to be combined. The signal is transmitted to the opposite transceiver through the telephone line. The transceiver may receive a second coded data signal and a second voice signal from the counterpart transceiver through the telephone line, and transmit the second data signal and the second voice signal corresponding to the second coded data signal to the data processing apparatus. Supply to the voice communication device.

The transceiver includes a data interface port, a voice interface port, data processing means, a bandpass filter, and a lowpass filter. The data interface port provides an electrical interface for receiving the first data signal from a data processing device and for supplying the second data signal to the data processing device. The voice interface port provides an electrical interface for receiving a first voice signal from the voice communication device and for supplying a second voice signal to the voice communication device. Data processing means encodes the first data signal to generate the first encoded data signal such that the magnitude of the DC component of the first data signal is reduced, and accepts and decodes the second encoded data signal to restore the second data signal. do. A bandpass filter is disposed between the data processing means and the telephone line, and transmits the first encoded data signal from the data processing means through the telephone line and selectively receives the second encoded data signal from the received signals received through the telephone line. Pass it and supply it to the said data processing means. The low pass filter is disposed between the voice interface port and the telephone line, and transmits the first voice signal from the voice interface port through the telephone line and selectively passes the second voice signal among the received signals received through the telephone line. Supply to the port.

The data processing means comprises a network adapter, an encoder and a decoder. The network adapter receives the first data signal from the data processing device and transmits the second data signal to the data processing device in accordance with a predetermined network protocol. The encoder encodes the first data signal input through the network adapter to generate the first encoded data signal. The decoder decodes the second coded data signal received through a bandpass filter to reconstruct the second data signal.

In a preferred embodiment, the coder encodes the first data signal every m-bits according to a predetermined encoding rule such that the magnitude of the DC component of the first encoded data signal is smaller than the magnitude of the accumulated DC component of the first data signal. The codeword is coded with n-bits (m <n). In this case, the m-bit first data signal is divided into upper i-bits and lower j-bits, the upper i-bit data is encoded into k-bit data according to a first encoding rule, and the lower j-bit data is second And encoded into l-bit data according to any one of third encoding rules, and the k-bit data and the l-bit data are contiguous to form the n-bit codeword. Where i + j = m and k + l = n. The selection of the second or third coding rule is made according to the DC component of the k-bit data. The decoder decodes every n-bit of the second coded data signal into an m-bit of second data signal according to a predetermined decoding rule opposite to the coding rule.

Preferably, the data processing means includes a first buffer, a packet generation unit, a packet release unit, and a second buffer. The first buffer buffers the first data signal from the network adapter. The packet generation unit configures a first data packet including a control sequence for media access control with respect to the first data signal in order to transmit the first data signal in packet units. The packet release unit receives the second data packet output by the decoder and includes the second data signal to release the packet. The second buffer buffers the second data signal and supplies the buffered second data signal to the network adapter.

The data processing means may include a media access controller for controlling a media access and allocating a band for the first and second data signals to facilitate bidirectional data communication through a telephone line, and an error occurs in a second data packet. In this case, a retransmission controller for requesting retransmission of the second data packet to the counterpart transceiver and an encoder and a bandpass filter are disposed, and when two consecutive data bits have the same logical level, the size of the transmission level of the second bit is determined. It is further desirable to include an equalizer for reducing to the reduced level. The control sequence of packets at least optionally includes a test vector for determining the reduced level. The medium access controller controls the equalizer to send the test vectors at different levels and determines the magnitude of the reduced level based on the line characteristic information fed back from the opposite transceiver for the test vector.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 shows an example of a data communication network according to the present invention. The data communication network includes a switching hub 10, a center module 20, and a plurality of subscriber systems 70A to 70N, and is suitable for implementing an internet subscriber network. The data communication network of FIG. 1 may be constructed in units of buildings or aisles in a multi-unit house such as an apartment, or in a building or office unit in a business building. When implemented in an apartment, the switching hub 10 and the center module 20 are located in the line distribution room (MDF) of each apartment agreement line distribution box or management office. On the other hand, when built in a business building, the switching hub 10 and the center module 20 is located in the circuit distribution room (MDF) or communication room of the building or circuit distribution box of each floor.

In the preferred embodiment of the present invention, the switching hub 10 and the center module 20 may be installed and managed by an internet service network operator. The switching hub 10 is connected to a server of an Internet service network operator through a dedicated line, and transmits and receives data traffic according to the TCP / IP protocol or the Ethernet protocol. The switching hub 10 forwards the downlink data traffic received from the Internet via the center module 20 to the corresponding subscriber system 70A,..., 70N. In addition, the switching hub 10 receives upstream data traffic from the subscriber systems 70A, ..., 70N through the center module 20, regenerates the signal level, and sends it to the Internet server.

The center module 20 has a plurality of RJ-45 and RJ-11 ports on the front side. The center module 20 is connected to the switching hub 10 via a plurality of UTP cables connected to the RJ-45 ports, and connected to the plurality of subscriber systems via telephone lines 50 connected to the RJ-11 ports. 70A, ..., 70N). In addition, the center module 20 is connected to the public communication network directly or via a private branch exchange 40 through a 37-pin connector provided on the back. The center module 20 synthesizes the data signal received through the switching hub 10 and the telephone signal received from the telecommunication network and delivers the received signal to the corresponding subscriber system through the telephone line 50. In addition, the center module 20 separates a data signal and a telephone signal among the signals received through the respective telephone lines 50 from each of the plurality of subscriber systems 70A, ..., 70N, and the dual data signal is a switching hub. (10) and telephone signals to the exchanges of public telecommunications networks.

Each subscriber system 70A, ..., 70N is installed in each floor of each subscriber's home or business building. In the following description, for the sake of brevity, the description will be given mainly on the case where the subscriber systems 70A, ..., 70N of the present invention are installed in homes. Subscriber system 70A includes subscriber outlet 72A and subscriber module 74A, to which subscriber equipment such as subscriber terminal 76A and telephone 78A may be connected. The subscriber outlet 72A can be installed in a wall or the like of a home in a manner similar to a conventional telephone outlet, and a user can connect the subscriber terminal 76A and the telephone 78A to the telephone line 50 through the subscriber module 74A. To make it possible. Subscriber module 74A has at least one RJ-45 and RJ-11 port to connect subscriber terminal 76A and telephone 78A, respectively. In combination with the subscriber receptacle 72A, the subscriber module 74A synthesizes the uplink data signal from the subscriber terminal 76A and the uplink signal from the telephone 78A and loads it on the telephone line, and also receives through the telephone line. The downlink data signal and the downlink signal are separated and provided to the subscriber station 76A and the telephone 78A, respectively. The second to Nth subscriber systems 70B-70N may be configured similarly to the first subscriber system 70A.

FIG. 2 is a circuit diagram showing the configuration of the center module 20 and the subscriber module (for example 74A) shown in FIG.

The center module 20 includes a switching hub interface port 30, a digital modem 32, a first bandpass filter 34, a first lowpass filter 36 and a telephone network interface port 38. The switching hub interface port 30 is implemented as an RJ-45 port and is connected to the switching hub 10 shown in FIG. 1 through a telephone line or a coaxial cable and a transmission medium. The digital modem 32 converts the downlink data received from the switching hub 10 into a form suitable for transmission over the telephone line, and transmits it to the subscriber module 74A, and the uplink digital signal from the data signal received from the subscriber module 74A. The data is recovered and transmitted to the switching hub 10. The first bandpass filter 34 selectively transmits only the data signal among the signals received from the subscriber module 74A to the digital modem 32. The first low pass filter 36 selectively transmits only the voice signal among the signals received from the subscriber module 74A to the telephone network interface port 38. The telephone network interface port 38 is implemented as an RJ-11 port and is connected to a switch of a public telecommunication network.

Subscriber module 74A includes a data terminal interface port 80, a digital modem 82, a second bandpass filter 84, a second lowpass filter 86, and a telephone interface port 88. The data terminal interface port 80 is implemented as an RJ-45 port and is connected to the subscriber terminal 76A shown in FIG. The digital modem 82 converts the upstream data received from the subscriber terminal 76A into a form suitable for transmission over the telephone line, and transmits the data to the center module 20, and the downlink digital data from the data signal received from the center module 20 is transmitted. The data is recovered and transmitted to the subscriber station 76A. The second band pass filter 84 selectively transmits only the data signal among the signals received from the center module 20 to the digital modem 82. The second low pass filter 86 selectively transmits only the voice signal among the signals received from the center module 20 to the telephone interface port 88. The telephone interface port 88 is implemented with an RJ-11 port and is connected to the telephone 78A shown in FIG. On the other hand, in the preferred embodiment, subscriber outlet 72A only provides a connection to the telephone line of subscriber module 74A, as shown, and remains transparent for data transmission.

In FIG. 2, the downlink data from the switching hub 10 is converted by the digital modem 32 to be suitable for transmission over the telephone line and then synthesized with the voice signal and transmitted to the subscriber module 74A. Among the synthesized downlink signals, the high frequency band data signal is selected by the second band pass filter 84 and then restored by the digital modem 82 to be supplied to the subscriber station 76A, and the low frequency band voice signal is supplied to the second signal. It is selected by the low pass filter 86 and supplied to the telephone 78A. On the other hand, the upstream data from the subscriber terminal 76A is converted by the digital modem 82 to be suitable for transmission over the telephone line, and then synthesized with the voice signal and transmitted to the center module 20. Among the synthesized uplink signals, the high frequency band data signal is selected by the first bandpass filter 34 and then restored by the digital modem 32 to be supplied to the switching hub 10, and the low frequency band audio signal is provided. It is selected by the low pass filter 36 and supplied to the exchange of the public communication network.

FIG. 3 specifically shows the digital modem 32 in the center module 30 shown in FIG. 2. The digital modem 32 includes a network adapter 100, a transmission data buffer 120, a reception data buffer 130, a transmission control unit 140, a transmission unit 150, and a reception unit 160. In the preferred embodiment, the digital modem 32 is manufactured and implemented in the form of an ASIC in one-chip.

The network adapter 100 transmits and receives data to and from the switching hub 10 according to the Ethernet protocol and performs a medium access control (MAC) associated therewith, and the Ethernet controller 102 to the switching hub 10. And a network interface 104 suitable for interfacing with the physical medium connecting the center module 20. The Ethernet controller 102 transmits and receives data with the switching hub 10 while performing a carrier sense multiple access with collision detection (CSMA / CD) protocol defined in the IEEE802.3x standard to prevent data loss due to a collision. The network interface 104 may include a medium independent interface (MII), a media attachment unit (MAU), a general purpose serial interface (GPSI), and an attachment unit to enable communication between the switching hub 10 and the center module 20. And at least one of an interface such as an external address detection interface (EADI).

The transmission data buffer 120 temporarily stores and buffers downlink data received from the switching hub 10 and the packet is released, thereby smoothly receiving data from the switching hub 10 and transmitting data to the subscriber station 76A. To make it possible. The reception data buffer 130 temporarily stores and buffers upstream data received from the subscriber station 76A, thereby facilitating data reception from the subscriber station 76A and data transmission to the switching hub 10.

The transmitter 150 includes an 8B10B encoder 152, an equalizer 154, and an amplifier 156. The 8B10B encoder 152 encodes the downlink data in such a manner as to remove or reduce the direct current (DC) component of the downlink data signal, thereby preventing interference between the downlink data signal and the voice signal during transmission over the telephone line 50. It can be minimized. Equalizer 154 converts the level of the downlink data signal to match the characteristics and length of telephone line 50 to increase the transmission reliability of the system. The amplifier 156 amplifies the signal equalized by the equalizer 154 and outputs the signal to the telephone line 50. The specific operations of the 8B10B encoder 152 and equalizer 154 will be described later.

The receiver 160 includes a digital receiver 162 for detecting a symbol in the received signal and a 10B8B decoder 164 for recovering uplink data by decoding the detected symbol. Referring to FIG. 4, the digital receiver 162 includes a digital integrator 180, a sampler 182, a symbol detector 184, and a phase controller 186. The digital integrator 180 integrates the received signal so that sampling can be performed while minimizing the influence of noise introduced into the signal on the telephone line 50. Sampler 182 samples the integrated signal level, and symbol detector 184 detects the symbol at the sampled signal level. On the other hand, phase controller 186 determines the timing for sampling at the sampled signal level so that the detected symbols can be accurately synchronized.

The transmission control unit 140 includes a time division media access controller 142, a retransmission controller 144, a packet generation unit 146, and a packet release unit 148. The time division media access controller 142 transmits and receives a media access control frame for data flow control with a counterpart controller in the digital modem 82 of the subscriber module 74A so as to allocate up and down bands to facilitate bidirectional data transmission. . The retransmission controller 144 enables retransmission of data when a packet error occurs on the line 50. That is, the retransmission controller 144 of the center module 20 requests data retransmission to the subscriber module 74A when a packet error occurs during reception of an uplink data packet, and receives a data retransmission request from the subscriber module 74A. In this case, the downlink data packet can be retransmitted from the buffer 120 through the transmitter 150. The packet generation unit 146 encapsulates the Ethernet packet by generating a packet by adding a preamble and various delimiters to the downlink data of the Ethernet format in the transmission data buffer 120. The packet release unit 148 restores the uplink data of the Ethernet format by removing the preamble and various delimiters from the uplink data packet in the reception data buffer 120.

FIG. 5 specifically shows the digital modem 82 in the subscriber module 74A shown in FIG. As shown, the digital modem 82 in subscriber module 74A has a configuration similar to that of digital modem 32 in center module 20. That digital modem 32 transmits the downlink data packet and receives the uplink data packet, while digital modem 82 transmits the uplink data packet and receives the downlink data packet; The two digital modems 32 and 82 operate the same, except that the digital modem 82 is coupled to the subscriber terminal 76A. Therefore, detailed description of the modem shown in FIG. 5 will be omitted.

6 shows the format of a data packet transmitted and received between the digital modems 32 and 82 of the center module 20 and the subscriber module 74A in the preferred embodiment. The data packet includes a preamble (200) for synchronization of the phase controller 186 on the receiving side, a start delimiter (SOF) 202 indicating the start of the packet, a control sequence 204 for media access control, an uplink or The downlink data includes client data 206 encoded, a CRC 208 for error detection and correction, and an end delimiter (EOF) 210 indicating the end of the packet. The preamble 200 has a pattern in which a predetermined bit string is repeated, and synchronizes the reception phase controller 186. The control sequence 204 includes information on the data buffers 120 and / or 130, transmission / reception error indication information, transmission permission indication information, and the like, for band allocation and error control.

On the other hand, in order to simultaneously transmit audio signals and data via telephone lines, it is preferable that the low frequency component of 4 kHz or less is included in the data signal as much as possible. In a preferred embodiment, the digital modems 32 and 82 encode data by 8B10B line coding combining 5B6B coding and 3B4B coding, thereby reducing the low frequency components included in the transmitted signal.

FIG. 7 is a diagram for describing a concept of 8B10B encoding performed by the 8B10B encoder 152 shown in FIGS. 3 and 5. In the preferred embodiment, the 8B10B encoder 152 encodes only the client data excluding the preamble and the separator among the data packets of FIG. 6. Every 8 bits of data are divided into upper 5 bits and lower 3 bits, and then encoded into 6 bits and 4 bits, respectively. The upper 5 bits are encoded according to the encoding table I, and the lower 3 bits are encoded by any one of the encoding tables IIA and IIB. The 6 bit codewords in the encoding table I are prepared to minimize the DC component. Each of the 4-bit codewords in the encoding table IIA is prepared such that the DC component has a negative value, and each of the 4-bit codewords in the encoding table IIB is prepared so that the DC component has a positive value.

Each time the lower 3 bits are encoded, either one of the two encoding tables IIA and IIB is selected so that the accumulated DC component DC _i converges to zero. That is, the lower 3 bits are encoded according to encoding table IIA when the accumulated DC component DC _i is positive, and encoded according to encoding table IIB when the accumulated DC component DC _i is negative. Accordingly, the accumulated DC component DC _i continuously converges to zero. In addition, this data processing result is equivalent to the high-pass filtering of the data, the low frequency component of less than 4kHz in the data signal is significantly reduced and it is possible to sufficiently eliminate the interference between the data signal and the voice signal.

Referring to FIG. 8, the 8B10B line encoding process will be described in more detail. First, after dividing 8-bit data into upper 5 bits and lower 3 bits (step 250), the upper 5 bits are encoded using a 6-bit codeword according to encoding table I (step 252). The DC component DC of the 6-bit codeword is calculated, and the accumulated DC component DC _i up to the present is calculated by adding it to the accumulated DC component DC _i-1 up to the previous data transmission (254 and _th ). 256 steps). Next, it is determined whether the DC _i value is negative (step 258). If the cumulative DC component DC _i is nonnegative (DC _i ≥ 0), the lower 3 bits are encoded by the 4-bit codeword 4B + according to Table IIA (step 260). On the other hand, when the DC component is negative (DC _i <0), the lower 3 bits are encoded by the 4-bit codeword 4B- in accordance with Table IIB (step 262). Finally, 10-bit encoded data is generated by concatenating the 6-bit codeword and the 3-bit codeword (step 264).

The decoding process in the 10B8B decoder 164 is as follows. Referring to FIG. 9, first, 10 bits of data are divided into upper 6 bits and lower 4 bits (step 270), and the upper 6 bits are decoded into 5 bits of data according to Table I (step 272). And the top 6, and calculates the DC component (DC) of the bit, in addition to this, the cumulative DC components (DC _i-1) to the previously received data calculating cumulative DC component (DC _i) to the current (first 274 and second 276 step). Next, it is determined whether the DC _i value is negative (step 278). If the cumulative DC component DC _i is not negative (DC _i ? 0), the lower 4 bits are decoded according to the table IIA (step 280). On the other hand, when the DC component is negative (DC _i <0), the lower 4 bits are decoded according to the table IIB (step 282). Finally, the 8-bit original signal is restored by connecting the 5-bit data and the 3-bit data (step 284).

Next, an operation of the equalizer 154 of the transmitter 150 shown in FIGS. 3 and 5 will be described with reference to FIGS. 10A to 10D. In general, the transmission characteristics of the telephone line vary depending on the media characteristics, the line connection state and the distance, and the transmission characteristics affect the error rate of the received data. The error rate of the received data is also influenced by the DC component balance of the transmitted data. The imbalance of the DC component is increased when a plurality of data bits having the same sign are transmitted in succession. In the present invention, the equalizer 154 reduces the DC component imbalance by adjusting the transmission level of data when a plurality of data bits having the same sign are transmitted consecutively. In particular, the equalizer 154 adaptively adjusts the transmission level in accordance with the line characteristics, thereby making it possible to stably transmit data.

As shown in Fig. 10A, when the sign of one of the transmission data bits is different from the sign of the previous data bit, the equalizer 154 sets the transmission data bits to the level of V _{peak when} the transmission data bits are '1'. If it is 0, it transmits at the level of -V _peak . On the other hand, as shown in Fig. 10B, when the sign of the transmission data bit is the same as the sign of the previous data bit, the equalizer 154 sets the transmission data bit to the level of V _{i when} the transmission data bit is '1'. In case of '0', it transmits at the level of -V _i . The magnitude (V _i ) of the level used when transmitting continuous '1' or '0' is smaller than the magnitude (V _peak ) of the level used when transmitting discontinuous data, and thus the DC component of the continuous data. This can be reduced.

As shown in Figure 10c, transmission reliability is the magnitude (V _i) as a function of the transmission distance of the transmission level. Therefore, the size (V _i) of the transmission level of the serial data is preferably determined in consideration of the addition, the transmission distance and line characteristics.

Since the equalizer 154 on the transmitting side does not know the line characteristics and the transmission distance, the time division media access controller 142 on the transmitting side sends a plurality of test vectors having different levels to the receiving side through the equalizer 154. . The time division media access controller 142 of the receiving side determines the characteristics of the transmission line based on the received test vectors, and feeds back characteristic information of the transmission line to the transmitting side. In this way, the transmitter is able to determine the optimal transmission level (V _i) to the line. If the packet error of the received data increases above a certain reference value, it is desirable to determine the transmission level again according to the above procedure. Fig. 10D shows an example in which equalization is performed on an 8B10B coded bit string.

On the other hand, since data must be transmitted in both directions through the telephone line, it is necessary to control the medium connection between the center module 20 and the subscriber module 74a. In the present invention, the bidirectional transmission is implemented through a time division scheme, and in particular, the subscriber module becomes a master to control the medium access. 11A and 11B are state diagrams illustrating the operation of time division media access controllers 142 in subscriber module 74a and center module 20, respectively. A media access control process will be described with reference to FIGS. 11A and 11B.

Referring to FIG. 11A, the subscriber module 74A has five states, namely, a line search state S10, a standby state S12, a reception state S14, a control packet transmission state S16, and a data packet transmission state ( It is in the state of any one of S18). Under the state in which the line is not connected, the subscriber module 74A searches whether the center module 20 is connected in the line search state S10. In the track search state S10, the time division media access controller 142 of the subscriber module 74A changes the state of the equalizer 154 to repeatedly perform the test vector transmission and the response packet reception. The receiver 160 controls the receiver 160 and selects an equalizer condition suitable for a line state according to the number of response packets received. When connected to the center module 20, the subscriber module 74A sends a line establishment packet to the center module 20, and enters the link connection state (step 300). On the other hand, if the line search fails, the subscriber module 74A enters the standby state S12 (step 302). After the waiting time expires, the subscriber module 74A enters the track search state S10 again and searches for the center module 20 again (step 304).

Referring to FIG. 11B, the center module 20 has five states, namely, a waiting state S20, a response packet transmission state S22, a reception state S24, a control packet transmission state S26, and a data packet transmission state. It is in the state of any one of (S28). Under the condition that the line is not connected, the center module 20 waits for a test vector packet from the subscriber module 74A in the waiting state S10. If the test vector packet arrives correctly, the center module 20 enters the response packet transmission state S22 in step 350 and sends the response packet to the subscriber module 74A. When the subscriber module 74A checks the line state and sends a line setup packet, the center module 20 sets the transmission equalizer 154 therein and enters the link connection state (step 352). . On the other hand, if the line setup packet is not received for a predetermined time, the center module 20 enters the standby state (S20) again (step 354).

When the link is in the connected state, the subscriber module 74A and the center module 20 move between the reception states S14 and S24, the control packet transmission states S16 and S26, and the data packet transmission states S18 and S28. It will work.

In the reception state S14, the subscriber module 74A waits for the delimiter of the downlink packet when the downlink packet comes from the center module 20, and according to the presence or absence of uplink data to be transmitted, the data packet transmission state S18 or the control packet. Transition to the transmission state S16 (step 306 or 310). When the downlink packet does not come from the center module 20, the subscriber module 74A transitions to the data packet transmission state S18 or waits for a predetermined time and then to the control packet transmission state S16 (306). Or step 310). In such cases, if there is uplink data to be sent, the subscriber module 74A sends an uplink data packet in the data packet transmission state S18 and then transitions to the reception state S14 (step 312). If there is no uplink data to send, the subscriber module 74A transfers the uplink control packet in the control packet transmission state S16 and then transitions to the reception state S14 (step 308). On the other hand, if the packet error is excessive or the constant packet reception time expires, the subscriber module 74A returns to the standby state S12 (step 314).

In the reception state S24, the center module 20 waits for an end delimiter of the upstream packet when the upstream packet comes from the subscriber module 74A and then transitions to the data packet transmission state S28 or the control packet transmission state S26. (Step 356 or 360). That is, if there is downlink data to be sent, the center module 20 transitions to the data packet transmission state S28 and transmits the downlink data packet. If there is no packet, the center module 20 transitions to the control packet transmission state S26. Downlink packet is transmitted. After transmitting the packet, the center module 20 transitions back to the reception state S24 and waits for the packet from the subscriber module 74A (step 358 or 362). On the other hand, if the packet error is excessive or the predetermined packet reception time expires, the center module 20 returns to the standby state S20 again (step 364).

12A and 12B are diagrams for explaining the operation of the retransmission controller 144 of the digital modem according to the present invention. The retransmission controller 144 prevents errors in the data packet due to impulse noise or crosstalk on the telephone line, thereby preventing the error on the line from being transmitted to a higher layer and stably transmitting multimedia data. As shown, subscriber module 74a or center module 20 waits for a response packet from the receiving side after transmitting one data packet. The control sequence 204 of the response packet transmitted by the receiving side includes an acknowledgment bit ACK (i) indicating whether the i-th transmitted packet 'data packet (i)' is transmitted correctly. If acknowledgment bit ACK (i) is' 1 ', the sender transmits the next packet' data packet (i + 1) .If acknowledgment bit ACK (i) is 0 or no response packet is received, The already transmitted packet 'data packet (i)' will be transmitted again.

FIG. 13 is a diagram for describing operations of the transmission data buffer 120 and the reception data buffer 130 illustrated in FIGS. 3 and 5. As described above, the transmit data buffer 120 buffers data received via the network interface 104 and the Ethernet controller 102 from the switching hub 10 or subscriber terminal 76A, and receives the receive data buffer 130. ) Buffers data to be sent to switching hub 10 or subscriber terminal 76A via Ethernet controller 102 and network interface 104. The network interface 104 may employ any one or more of a variety of interfaces, and is particularly preferably configured to support general-purpose Ethernet standards such as 10Base-T and 100Base-T as defined in IEEE 802.3x. While the Ethernet transmission rate is 10 Mbps or 100 Mbps while the digital modems 32 and 82 operate at high speed, data transmission and reception speeds between the digital modems 32 and 82 and the switching hub 10 or the subscriber station 76A may be different. have. In this case, the Ethernet controller 102 performs traffic control using a back-pressure or a PAUSE packet defined in IEEE 802.3 so that the data buffers 120 and 130 do not overflow.

The above description illustrates a preferred embodiment of the present invention, and the present invention is not limited thereto and may be variously modified. For example, although not shown in Figs. 3 and 5, digital modems 32 and 82 are non-e.g. EEPROM or flash memory for storing program code for driving time division media access controller 142 and retransmission controller 144. A volatile memory can be provided. In addition, the digital modems 32 and 82 may further include volatile memory such as DRAM in addition to the buffers 120 and 130. This memory facilitates packet generation and release, and may store the control sequence 204 obtained in the received packet for reference by the time division media access controller 142 and the retransmission controller 144. In addition, the digital modems 32 and 82 may include a main controller for controlling the overall operation.

In the preferred embodiment, 8B10B encoding is performed only on the client data in the transport packet. In another embodiment of the present invention, encoding may be performed on the entire packet including the preamble and the separator. On the other hand, mBnB encoding may be generally performed instead of 8B10B encoding of data. In performing 8B10B encoding, instead of combining 5B6B encoding and 3B4B encoding, two types of 4B5B encoding may be combined or 6B7B encoding and 2B3B encoding may be combined. In addition, instead of encoding data after generating the packet, the packet may be generated after encoding first.

In the above description, for the purpose of simplicity, the packet generation unit 146 generates a packet for data in the transmission data buffer 120. However, in the preferred embodiment, the packet generation unit 146 actually generates a packet for data input to the transmission data buffer 120 or data output from the transmission data buffer 120. In each of these cases, the packet releasing unit 148 releases the packet for data output from the reception data buffer 130 or data input to the reception data buffer 130, respectively. In another embodiment of the present invention, the packet generator 146 may be arranged between the encoder 152 and the equalizer 154 to generate a packet for the encoded data signal, and thus the packet release unit 148. ) May be disposed between the digital receiver 162 and the decoder 164.

Although the filter for selectively passing the data signal in the digital modems 32 and 82 is referred to as a 'bandpass filter', a high pass filter may actually be used instead of the bandpass filter. Therefore, in the present specification including the claims to be described later, the term 'band pass filter' should be understood as a concept including a 'high pass filter'. Meanwhile, although the Ethernet protocol is described as being used for the communication between the switching hub 10 and the center module 20 and the communication between the subscriber module 74A and the subscriber terminal 76A, other network protocols may be used. On the other hand, in another embodiment in which the preferred embodiment is modified, either the encoder 152 or the equalizer 154 may be omitted in the digital modems 32 and 82. If encoder 152 is omitted, decoder 164 will also be omitted.

As described above, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. Therefore, the above-described embodiments are to be understood as illustrative in all respects and not as restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

As described above, the data transceiver of the present invention can transmit and receive, for example, high-speed data of 1.5 Mbps or more with the other party with high reliability through a telephone line. Since the data is encoded so that the accumulated DC component DC _i converges to 0, and the transmission level of the continuous data is adjusted so as to reduce the imbalance of the DC component, the distance from the opposite transceiver is 1, for example. Even when it is far beyond kM, communication with the other party's transceiver can be performed stably. Since data is transmitted without being modulated by the usual modulation scheme, data processing in the layer above the link layer is simplified and the configuration of the transceiver is very simple. In particular, according to the preferred embodiment, since the digital modem is manufactured and implemented in the form of a single-chip ASIC, the configuration of the digital modem and the transceiver as a whole becomes simpler.

Transceivers like these make it easy to build Internet subscriber networks in business buildings, apartment complexes, malls, hotels, etc., by using existing telephone lines. Since the time division media access controller in the digital modem dynamically allocates up and down channels, i.e., time slots, according to up and down traffic, the Internet subscriber network according to the present invention can provide a multimedia Internet service suitable for a data transmission / reception pattern of each user. .

Claims (34)

A telephone line 50 receives a first data signal and a first voice signal from a data processing device and a voice communication device, respectively, and combines the first coded data signal corresponding to the first data signal and the first voice signal. Transmits a second coded data signal and a second voice signal to the other transceiver through the telephone line 50 from the other transceiver and transmits a second data signal and the second voice signal corresponding to the second coded data signal. A data and voice transceiver for supplying the data to the data processing device and the voice communication device, respectively, A data interface port (30, 80) for receiving said first data signal from said data processing device and for supplying said second data signal to said data processing device; Voice interface ports (38, 88) for receiving said first voice signal from said voice communication device and for supplying said second voice signal to said voice communication device; Data for encoding the first data signal to generate the first encoded data signal such that the magnitude of the DC component of the first data signal is reduced, and for receiving and decoding the second encoded data signal to restore the second data signal. Processing means 32, 82; Disposed between the data processing means 32 and 82 and the telephone line 50, transmitting the first encoded data signal from the data processing means 32 and 82 through the telephone line 50, and Band pass filters (34, 84) for selectively passing the second coded data signal among the received signals received through (50) to supply to the data processing means (32, 82); And Disposed between the voice interface ports 38 and 88 and the telephone line 50, and transmits the first voice signal from the voice interface ports 38 and 88 through the telephone line 50 and the telephone line ( A low pass filter (36, 86) for selectively passing the second voice signal among the received signals received through 50) and supplying the second voice signal to the voice interface ports (38, 88); Data and voice transceiver comprising a. The method of claim 1, wherein said data processing means A network adapter for receiving a first data signal from the data processing device and transmitting the second data signal to the data processing device in accordance with a predetermined network protocol; An encoder for encoding the first data signal input through the network adapter to generate the first encoded data signal; And A decoder which decodes the second coded data signal received through the bandpass filter and restores the second data signal; Including; The encoder encodes the first data signal of every m-bits as a codeword of n-bits (m <n) according to a predetermined encoding rule so that the magnitude of the DC component of the first coded data signal is kept small. And the decoder decodes the every n-bit second encoded data signal into an m-bit second data signal according to a predetermined decoding rule opposite to the encoding rule. The method of claim 2, wherein the encoder divides the m-bit first data signal into upper i-bits and lower j-bits, and encodes upper i-bit data into k-bit data according to a first encoding rule. Encode lower j-bit data into l-bit data according to any one of second and third encoding rules, and concatenate the k-bit data and the l-bit data to form the n-bit codeword. (Where i + j = m, k + l = n), wherein the data and voice transceiver selects one of the second and third coding rules according to the DC component of the k-bit data. The method of claim 2, wherein said data processing means A packet generation unit constituting a first data packet of a predetermined format with respect to the first data signal to transmit the first encoded data signal in packet units; And A packet release unit for receiving a second data packet output by the decoder and including the second data signal to release the packet; Data and voice transceiver further comprising. The method of claim 2, wherein said data processing means A first buffer for buffering the first data signal from the network adapter and for supplying a buffered first data signal to the encoder; And A second buffer for buffering the second data signal and for supplying a buffered second data signal to the network adapter; Data and voice transceiver further comprising. The method of claim 5, wherein said data processing means A packet generation unit disposed in front of the first buffer and configured to output a first data packet having a predetermined format with respect to the first data signal to the first buffer; And A packet release unit disposed at a rear end of the second buffer, and configured to release the second data packet from the second buffer and output the second data signal; Data and voice transceiver further comprising. The method of claim 5, wherein said data processing means A packet generator disposed between the first buffer and the encoder and configured to output a first data packet of a predetermined format to the encoder by the first data signal from the first buffer; And A packet release unit disposed between the decoder and the second buffer, and configured to release a second data packet from the decoder and output the second data signal to the second buffer; Data and voice transceiver further comprising. The method of claim 5, wherein said data processing means A packet generator disposed at a rear end of the encoder, configured to output a first encoded data packet having a predetermined format with respect to the first encoded data signal; And A packet release unit disposed in front of the decoder and configured to receive and release a second encoded data packet and output the second encoded data signal to the decoder; Data and voice transceiver further comprising. 9. The method according to any one of claims 6 to 8, wherein said data processing means A medium access controller for controlling a medium access based on a control sequence included in the packets and allocating a band for the first and second encoded data signals to facilitate bidirectional data communication through the telephone line; And A retransmission controller for requesting retransmission of the second data packet to the counterpart transceiver when an error occurs in the second data packet; Data and voice transceiver further comprising. 10. The apparatus according to claim 9, wherein said data processing means Disposed between the encoder and the bandpass filter and configured to reduce a magnitude of a transmission level of at least some of the bits having the same logical level to a predetermined reduced level when the logical levels of two or more consecutive data bits are the same. Equalizer; Data and voice transceiver further comprising. The method of claim 10, wherein the control sequence comprises at least optionally a test vector for determining the reduced level, And the medium access controller controls the equalizer to send the test vectors at different levels, and determines the magnitude of the reduced level based on the line characteristic information fed back from the opposite transceiver for the test vector. Receives the first data signal and the first voice signal from the data processing device and the voice communication device, respectively, and combines the first modified data signal corresponding to the first data signal and the first voice signal to provide a combined signal to the telephone line 50 Transmits the second modified data signal and the second voice signal through the telephone line 50 through the telephone line 50 and transmits the second modified data signal and the second data signal corresponding to the second modified data signal. A data and voice transceiver for supplying two voice signals to the data processing device and the voice communication device, respectively. A data interface port (30, 80) for receiving said first data signal from said data processing device and for supplying said second data signal to said data processing device; Voice interface ports (38, 88) for receiving said first voice signal from said voice communication device and for supplying said second voice signal to said voice communication device; Data processing means (32, 82) for equalizing the first data signal over a telephone line to output the first modified data signal; Disposed between the data processing means 32, 82 and the telephone line 50, transmitting the first modified data signal from the data processing means 32, 82 through the telephone line 50 and the telephone line A band pass filter (34, 84) for selectively transmitting the second modified data signal among the received signals received through (50) to the data processing means (32, 82); And Disposed between the voice interface ports 38 and 88 and the telephone line 50, and transmits the first voice signal from the voice interface ports 38 and 88 through the telephone line 50 and the telephone line ( A low pass filter (36, 86) for selectively transmitting the second voice signal to the voice interface ports (38, 88) among the received signals received through 50); Including; The data processing means 32, 82 A network adapter (100) for receiving a first data signal from the data processing device and transmitting the second data signal to the data processing device in accordance with a predetermined network protocol; And When the logical levels of two or more consecutive data bits are the same, the first inputted through the network adapter 100 to reduce the size of a transmission level of at least some of the same bits to a predetermined reduced level. An equalizer 154 for equalizing one data signal and outputting an equalized signal as the first modified data signal; Data and voice transceiver comprising a. 13. The apparatus according to claim 12, wherein said data processing means A packet generation unit constituting a first data packet of a predetermined format with respect to the first data signal to transmit the first modified data signal in a packet unit; Receiving circuitry for accepting the second modified data signal and restoring a second data packet; And A packet release unit which releases the second data packet and restores the second data signal; Data and voice transceiver further comprising. The method of claim 13, wherein said data processing means A medium access controller for controlling a medium access based on a control sequence included in the packets and allocating a band for the first and second modified data signals to facilitate bidirectional data communication through the telephone line; And A retransmission controller for requesting retransmission of the second data packet to the counterpart transceiver when an error occurs in the second data packet; Data and voice transceiver further comprising. The method of claim 14, wherein the control sequence of the packet comprises at least optionally a test vector for determining the reduced level, And the medium access controller controls the equalizer to send the test vectors at different levels, and determines the magnitude of the reduced level based on the line characteristic information fed back from the opposite transceiver for the test vector. A telephone line 50 receives a first data signal and a first voice signal from a data processing device and a voice communication device, respectively, and combines the first coded data signal corresponding to the first data signal and the first voice signal. Transmits a second coded data signal and a second voice signal to the other side transceiver through the telephone line 50 from the other side transceiver and transmits a second data signal and the second voice signal corresponding to the second coded data signal. Is suitable for use in data and voice transceivers that respectively supply the data processing device and the voice communication device, A network adapter (100) for receiving a first data signal from the data processing device and providing the second data signal to the data processing device in accordance with a predetermined network protocol; An encoder 152 that encodes the first data signal to generate and output the first encoded data signal such that the magnitude of the DC component of the first data signal is reduced; And A decoder (164) for decoding the second coded data signal to restore the second data signal; And a signal processing device for allowing interference between the first encoded data signal and the first speech signal to be reduced. The method of claim 16, The encoder encodes the first data signal of every m-bits as a codeword of n-bits (m <n) according to a predetermined encoding rule so that the magnitude of the DC component of the first coded data signal is kept small. And the decoder decodes every n-bit of the first encoded data signal into an m-bit first data signal according to a predetermined decoding rule opposite to the encoding rule. 18. The apparatus of claim 17, wherein the encoder divides the m-bit first data signal into upper i-bits and lower j-bits, and encodes upper i-bit data into k-bit data according to a first encoding rule. Encode lower j-bit data into l-bit data according to any one of second and third encoding rules, and concatenate the k-bit data and the l-bit data to form the n-bit codeword. (Where i + j = m, k + l = n), wherein the signal processing apparatus selects one of the second and third encoding rules according to the DC component of the k-bit data. The method of claim 16, A packet generation unit constituting a first data packet of a predetermined format with respect to the first data signal to transmit the first encoded data signal in packet units; And A packet release unit which receives a second data packet including the second encoded data signal and releases the packet; Signal processing device further comprising. The method of claim 16, A first buffer for buffering the first data signal from the network adapter and for supplying a buffered first data signal to the encoder; And A second buffer for buffering the second data signal and for supplying a buffered second data signal to the network adapter; Signal processing device further comprising. The method of claim 20, A packet generation unit disposed in front of the first buffer and configured to output a first data packet having a predetermined format with respect to the first data signal to the first buffer; And A packet release unit disposed at a rear end of the second buffer, and configured to release the second data packet from the second buffer and output the second data signal; Signal processing device further comprising. The method of claim 20, A packet generator disposed between the first buffer and the encoder and configured to output a first data packet of a predetermined format to the encoder by the first data signal from the first buffer; And A packet release unit disposed between the decoder and the second buffer, and configured to release a second data packet from the decoder and output the second data signal to the second buffer; Signal processing device further comprising. The method of claim 20, A packet generator disposed at a rear end of the encoder, configured to output a first encoded data packet having a predetermined format with respect to the first encoded data signal; And A packet release unit disposed in front of the decoder and configured to receive and release a second encoded data packet and output the second encoded data signal to the decoder; Signal processing device further comprising. The method according to any one of claims 19 to 23, A medium access controller for controlling a medium access based on a control sequence included in the packets and allocating a band for the first and second encoded data signals to facilitate bidirectional data communication through the telephone line; And A retransmission controller for requesting retransmission of the second data packet to the counterpart transceiver when an error occurs in the second data packet; Signal processing device further comprising. The method of claim 24, An equalizer connected to an output terminal of the encoder and for reducing a magnitude of a transmission level of at least some of the bits having the same logical level to a predetermined reduced level when the logical levels of two or more consecutive data bits are the same; Signal processing device further comprising. The method of claim 25, wherein the control sequence at least optionally comprises a test vector for determining the reduced level, And the medium access controller controls the equalizer to transmit the test vectors at different levels, and determines the magnitude of the reduced level based on the line characteristic information fed back from the opposite transceiver for the test vector. A transceiver for combining a coded data signal corresponding to a transmission data signal and the voice signal and transmitting the combined signal to a counterpart transceiver through a telephone line, (a) encoding the transmission data signal to generate an encoded data signal such that the magnitude of the DC component of the transmission data signal is reduced; And (b) combining the encoded data signal and the speech signal and transmitting the combined signal to the counterpart transceiver; Signal transmission method comprising a. The method of claim 27, wherein step (a) (a1) dividing every m-bits of the transmitted data signal into upper i-bits and lower j-bits, where i + j = m; (a2) Upper i-bit data is encoded into k-bit data according to a predetermined first encoding rule, and lower j-bit data is converted into l-bit data according to any one of the predetermined second and third encoding rules. Encoding; And (a3) concatenating the k-bit data and the l-bit data to generate an n bit codeword, where k + l = n; Including; In the step (a2), one of the second and third encoding rules is selected according to the DC component of the k-bit data. The method of claim 27, wherein step (a) (a1) encoding the transmission data signal to generate an encoded data signal; (a2) constructing an encoded data packet by including a control sequence for media access control in the encoded data; Signal transmission method comprising a. The method of claim 27, wherein step (a) (a1) constructing a data packet including the transmission data signal and a control sequence for medium access control; And (a2) encoding at least the data signal portion of the data packet to generate the encoded data signal; Signal transmission method comprising a. The method of claim 27, wherein step (b) Equalizing the encoded data signal to reduce the magnitude of a transmission level of at least some of the data bits having the same logical level to a predetermined reduced level if the logical levels of two or more consecutive data bits are the same; Further comprising a signal transmission method for combining the equalized signal and the voice signal. 32. The method of claim 31, wherein step (b) (b1) transmitting a predetermined test vector to the counterpart transceiver; (b2) receiving a response signal fed back to the test vector from the counterpart transceiver; And (b3) determining the magnitude of the attenuated level based on the response signal; Signal transmission method further comprising. A transceiver for combining a coded data signal and an audio signal corresponding to a transmission data signal and transmitting the combined signal to a counterpart transceiver through a telephone line, (a) if the logical levels of two or more consecutive data bits of the transmission data signal are the same, the data signal is reduced to reduce the magnitude of the transmission level of at least some of the data bits having the same logical level to a predetermined reduced level. Equalizing; And (b) combining the equalized data signal and the voice signal in step (a) and transmitting the combined signal to the counterpart transceiver; Signal transmission method comprising a. The method of claim 33, wherein step (a) (a1) transmitting a predetermined test vector to the counterpart transceiver; (a2) receiving a response signal fed back to the test vector from the counterpart transceiver; And (a3) determining the magnitude of the attenuated level based on the response signal; Signal transmission method further comprising.