KR100390582B1 - Line code transmission using pulse width bit inversion - Google Patents

Abstract

The present invention provides a line encoding transmitter, comprising: a multilevel level converter for converting an input serial signal into a multilevel level signal having two or more amplitude levels; A multilevel level / pulse width converter for converting the multilevel level signal converted by the multilevel level converter into a binary signal by pulse width modulation; And a bit inverter for alternately bit inverting the binary signal pulse-width modulated by the multi-level level / pulse width converter alternately at regular intervals.

As a result, the signal converted to the multilevel level in the line coding scheme can be transmitted on the basis of a binary signal without being directly transmitted through the line, but the transmission bandwidth can be reduced. In the present invention, since the transmission bandwidth is transmitted as described above, Since the demand of such a circuit can be greatly reduced, and since it is transmitted by binarization, only a level of "0" and "1" needs to be determined at the receiving end, so that a longer distance can be transmitted than multi-level transmission. As a result, since the transmission distance is increased, there is an advantage that low overall line cost can be achieved.

Description

Transmitter and receiver using pulse width bit inversion and transmitter and line coding method using same {LINE CODE TRANSMISSION USING PULSE WIDTH BIT INVERSION}

The present invention relates to a line encoding transmission apparatus, a receiving apparatus, a transmission apparatus using the same, and a line encoding method, and more particularly, to a line encoding transmission apparatus using a pulse width bit inversion, a receiving apparatus, and a transmission apparatus and a line encoding method using the same.

In transmission, interconnection, and storage systems, line code coding is used to increase the efficiency of the line by increasing the bandwidth efficiency when transmitting data over a wired line.

With the explosive growth of high-speed Internet subscribers, line-coded transmission equipment such as Digital Subsriber Line (DSL) line equipment and Integrated Services Digital Network (ISDN) equipment has become widespread. As a line coding method widely used in such a line coding transmission equipment, there is a 2B1Q (2 Binary 1 Quaternary) coding method.

The 2B1Q coding method is a type of multi-level modulation that reduces the bandwidth by half by transmitting two bits in four levels of symbols to avoid an increase in bandwidth. The 2B1Q coding method is a standard line coding method defined in T1.601 in the ANSI standard, and is widely used for transmission equipment using telephone lines such as ISDN or digital subscriber line devices.

For reference, the 2B1Q coding method will be described with reference to FIG. 1.

1 is a diagram for describing a 2B1Q line coding method.

As shown, the input bit string is represented by one of two levels, with two bits grouped together. That is, the "00" bit is represented by 0 level, the "01" bit by 1 level, the "10" bit by 2 levels, and the "11" bit by 3 levels.

As a complement to the 2B1Q line coding scheme, there is a carrierless amplitude modulation phase modulation (CAP) scheme. The CAP method is a kind of digital modulation that transmits after processing to have more amplitude levels. Of course, 2B1Q line coding may be processed like 4B1Q or 6B1Q. That is, 4B1Q expresses 16 levels by grouping 4 bits and 6B1Q expresses 64 levels by grouping 6 bits.

However, this multilevel level line coding method is fundamentally not suitable for a system for transmitting data through a wire. A digital subscriber line transmission device or an integrated information communication network transmission device transmits a signal through a wire. In general, when a bandwidth of a transmitted signal is widened, a transmission reach is shortened. In other words, as the data transmission rate increases, the bandwidth becomes wider, which results in a shorter transmission distance. In other words, a subscriber within a short transmission distance can receive a lot of data within the same time, and a subscriber located at a long distance receives a relatively small amount of data.

In order to represent more bits in one symbol, the efficiency of the wireline is degraded due to a problem in the wireline itself. That is, a wireline, in particular, a telephone line, like a wireless, changes in characteristics and echoes, which are inevitable in wired transmission, occur. In the case of transmitting the multilevel signal, distortion of the signal due to reflection and attenuation occurs. Therefore, the greater the number of amplitude levels, the more efficient the bandwidth can be. However, a deterioration factor of the system itself is generated and additional techniques are required to compensate for this. As a result, in order to compensate for such signal distortion and attenuation, a very complex algorithm such as an equalizer or an echo canceller has to be introduced, and the cost of equipment increases due to such a complex algorithm. That is, in the multilevel level modulation method, since the transmitted signal has a plurality of levels, it is restricted to long distance transmission, and the equipment itself becomes complicated.

In fact, in the wired system, when the line coding is performed by 3B1Q or 4B1Q, satisfactory transmission efficiency cannot be obtained due to signal distortion and reflection in the wireline. This is because technically, 3B1Q or 4B1Q line coding is not impossible, and although implementation is possible, desired transmission efficiency could not be obtained due to distortion of multilevel signal.

For reference, it can be understood that the performance of the system becomes weaker as the number of signal levels increases. When a signal has a signal-to-noise ratio (S / N), increasing the number of levels of that signal means that the signal-to-noise ratio decreases in the relative signal. Therefore, the multilevel signal becomes sensitive to distortion and noise. Basically, the signal with the most noise or distortion resistance is a binary signal.

Therefore, in the line coding scheme, the signal converted to the multilevel level is transmitted on a binary signal basis without being directly transmitted through the line. At this time, if the transmission bandwidth can be reduced, considerable efficiency can be expected.

Accordingly, an object of the present invention is to use a pulse width bit inversion, which transmits a signal converted to a multilevel level on a binary signal basis without transmitting it as it is, but reduces transmission bandwidth, thereby increasing transmission distance and lowering equipment cost. A transmitter, a receiver, and a transmitter and a line encoding method using the same are provided.

According to an aspect of the present invention, there is provided a line encoding transmission apparatus comprising: a multilevel level converter for converting an input serial signal into a multilevel level signal having two or more amplitude levels; A multivalue level / pulse width converter configured to pulse modulate the multilevel level signal into a binary signal; And a bit inverter for alternately bit inverting the pulse width modulated binary signal at regular intervals.

In addition, the present invention provides a line encoding receiver, comprising: a signal level determiner for determining a level of an input signal as "0" or "1"; A sync pattern tracker for tracking a sync pattern of the input signal; A bit inverter for inverting bits of the input signal alternately every predetermined period to restore two or more pulse width conditions to a pulse width modulated signal; A pulse width / multilevel level converter for restoring two or more amplitude levels into a multivalue level signal according to the pulse width width of each period of the pulse width modulated signal; And a multilevel level / binary signal converter for restoring the multilevel level signal to the original serial signal.

The present invention provides a line encoding transmission apparatus, comprising: an error correction encoder for error correction encoding an input higher layer signal, a multilevel level converter for converting the error correction encoded signal into a multilevel level signal having two or more amplitude levels; A transmitter comprising a multilevel level / pulse width converter for pulse width modulating the multilevel level signal into a binary signal, and a bit inverter for alternately bit inverting the pulse width modulated binary signal at regular intervals; A transformer for transmitting the bit inverted binary signal through a telephone line and receiving a signal through the telephone line; A signal level determiner that determines the level of the received signal as "0" or "1", a sync pattern tracker that tracks the sync pattern of the received signal, and inverts the bits of the received signal alternately at regular intervals, thereby providing two or more signals. A bit inverter for restoring a pulse width modulated signal having a pulse width condition, a pulse width / multilevel level converter for restoring a multivalue level signal having two or more amplitude levels according to the pulse width width of each period of the pulse width modulated signal, A receiver comprising a multilevel level / binary signal converter for restoring a multilevel level signal to an original serial signal, and an error correction decoder for error correction decoding the received signal restored to the original serial signal; And an upper layer unit configured to perform communication with a network port, input an error correction decoded signal from the error correction decoder, and output the upper layer signal to the error correction encoder.

In addition, the present invention provides a line encoding method, comprising: a first step of converting a serial signal to be transmitted into a multilevel signal having two or more amplitude levels; A second step of converting the multilevel signal into a binary signal by pulse width modulation; And a third step of alternately bit-inverting the pulse width modulated binary signal at regular intervals and transmitting the wired transmission medium.

1 is a diagram for explaining a 2B1Q line coding scheme.

2 is an example for showing that the number of transitions of the signal is reduced when the bit is inverted alternately every digital period.

3 is a block diagram of a transmitter according to the present invention;

Figure 4 is a waveform diagram for explaining the operation of the transmitter according to the present invention.

5 is a block diagram of a receiver according to the present invention;

6 is a block diagram of a digital subscriber line equipment in accordance with the present invention.

7 is a flowchart of line coding according to the present invention.

Disclosure of Invention In the present invention, a technique of encoding a pulse width bit inversion method having excellent frequency distribution characteristics while solving a problem of multi-level line coding, that is, a signal distortion caused by a deterioration factor of a transmission line itself is disclosed. do.

The signal transmitted by multi-level line coding is in the form of an analog signal having a plurality of signal levels. The present invention converts such a change in amplitude into a change in pulse width to binarize the multi-level signal to be transmitted. In addition, the binarization signal converted into the pulse width is alternately bit-inverted every predetermined period, thereby reducing the number of transitions of the clock, that is, reducing transmission bandwidth to improve transmission efficiency.

As a result, the present invention converts the multi-level line coded signals, which are widely used in the line coding scheme, to binary level but reduces the transmission bandwidth and transmits them, thereby ensuring stable transmission over a long distance while ensuring high transmission efficiency. The signal can be processed, and the line coding transmission / reception equipment can be easily implemented without the need of an equalizer or an echo canceller.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As described above, the present invention converts a multi-level signal to be transmitted by converting the pulse width into a binary signal, and inverts the binary signal alternately at predetermined intervals to reduce the transmission bandwidth of the binary signal. Due to this, the number of transitions of the binary signal is greatly reduced, which will be described with reference to FIG. 2.

2 is an example for showing that the number of transitions of the signal decreases when the digital signal is bit-inverted alternately every predetermined period.

The digital signal is a square wave consisting of rising and falling edges. For the clock signal ⓐ, once per period t is normal and bit inverted the next time (i.e., if the digital signal is inverted alternately every period t), as shown, the number of clock transitions is 8 to 4 circuits. You can see it shrinks.

Although FIG. 2 has been described on the assumption that the clock signal is alternately bit-inverted every period t, it can be seen that the number of transitions is reduced for any digital signal.

3 is a block diagram of a transmitter according to the present invention.

The N-value multi-level level converter 301 processes input serial data and outputs multi-level level data having N amplitude levels. The N-value multi-value level / pulse width converter 303 processes the multi-level level data having the N amplitude levels and outputs a pulse width modulated signal having N pulse width conditions. The bit inverter 305 alternately bit inverts the pulse width modulated signal at regular intervals. The bit inverted pulse width modulated signal is transmitted via a wired transmission medium.

4 is a waveform diagram illustrating the operation of the transmitter according to the present invention.

Here, it is assumed that the N-value multilevel level converter 301 is a 2B1Q code converter. Of course, the N-value multilevel converter 301 may be a 3B1Q code converter, a 3B1Q converter, or the like. Hereinafter, a description will be given with reference to FIGS. 3 and 4.

The N-value multi-value level converter 301 converts the data (2) having four levels with respect to the serial data (binary data) 1 inputted in the period T. At this time, the N-value multi-value level converter 301 binds two bits of serial data ① so that the "00" bit is at "0" level, the "01" bit is at "1" level, and the "10" bit is "2". The "level" and "11" bits convert the amplitude to the "3" level. When serial data ① is converted into multilevel level data ②, one period of data increases to 2T. The increase in the period of data to 2T means that the bandwidth is reduced by half.

The N-value multilevel level / pulse width converter 303 converts the multilevel level data ② having the four amplitude levels into a pulse width modulated signal ③ having four pulse width conditions. That is, the N-value multi-value level / pulse width converter 303 is a signal that occupies three pulses of data of "3" level, and a signal of two pulses of data of "2" level is a signal of "1" level. Data is converted into a signal occupying one pulse and data of the "0" level is converted into a signal occupying zero pulse. At this time, the period of the signal converted into the pulse width is 1.5T. The period of the signal 1.5T means that the bandwidth is increased compared to the case of simple amplitude modulation (quad level amplitude modulation). The number of transitions of the data is 28 times.

The bit inverter 305 alternately bit inverts the pulse width modulation signal with the four pulse width conditions (3), and alternately bit inverts every 1.5T periods in FIG. Output the signal ④. That is, the first period is normal, the second period is bit inverted, and the third period is normal, starting from an arbitrary starting point. However, looking at the data waveform (4) of the bit inverted pulse width modulated signal, it can be seen that the effective transmission bandwidth is reduced by 20 transition times.

In the description of FIG. 4, it can be seen that the present invention can reduce transmission bandwidth while converting and transmitting multilevel-level line coded signals into binary data. In this case, the decrease in the number of transitions of the data depends on the pattern of the data to be transmitted. Since the pattern of the data to be transmitted is random, the rate of decrease in the number of transitions of the clock also varies slightly depending on the situation. The reason why this reduction in bandwidth cannot be accurately represented numerically is also because of the random pattern of data. The transmitter of the pulse width conversion bit inversion method as shown in FIG. 3 has an advantage that can be simply implemented using a digital logic circuit.

5 is a block diagram of a receiver according to the present invention. Hereinafter, a description will be given with reference to FIGS. 3 to 4. However, since the processing operation of the receiver of FIG. 5 is the reverse order of the processing operation of the transmitter of FIG. 4, it will be briefly described.

Since the pulse width bit inversion signal ④ input to the receiver has been transmitted through the wire line, the signal becomes a signal added with distortion and noise. However, since the pulse width bit inversion signal (4) is a binary signal, the signal level determiner 501 simply determines whether the input signal is a "1" level or a "0" level. Next, the sync pattern tracker 503 extracts clock information and the like for the received signal to track the sync pattern and establish sync.

The bit inverter 505 inverts the bits alternately input every predetermined period (period of 1.5T in FIG. 4) according to a predetermined convention with the transmitter (see FIG. 3), and has a pulse width modulation signal having N pulse width conditions. Outputs (③). Next, the pulse width / N-value multivalue level converter 507 converts the multivalue level data ② having N amplitude levels according to the width of the pulse width modulated signal ③ according to the width of the pulse width modulated signal ③.

The N-value multi-value level / binary converter 509 restores the multi-value level data (2) having the N amplitude levels to the original serial data (1).

6 is a block diagram of a digital subscriber line equipment according to the present invention.

Hereinafter, a description will be given with reference to FIGS. 3 to 5.

In FIG. 6, operations of the transmitter 620 excluding the error correction encoder 607 and operations of the receiver 610 except the error correction decoder 603 have been described in detail with reference to FIGS. 3 to 5. Omit.

The upper layer interface unit 605 performs an interface with a higher layer such as Ethernet or V.35.

The error correction encoder 607 performs error correction encoding on the data received from the upper layer 605 so that the receiver can perform error correction. In addition, the error correction decoder 603 performs decoding for error correction on the data input from the receiver 610. Transformer 601 transmits a signal via a telephone line.

7 is a flowchart of line coding according to the present invention.

Hereinafter, a description will be given with reference to FIGS. 3 to 6.

When serial data (see ①) to be transmitted from the error correction encoder 607 is input to the N-value multi-value level converter 301 (701), the N-value multi-value level converter 301 receives the input serial data (see 1). Is converted to an N-value multivalue level having N amplitude levels (see 2).

When the step 703 is completed, the N-value multi-value level / pulse width converter 303 processes the multi-level level data (see ②) having the N amplitude levels to generate a pulse width modulated signal having N pulse width conditions (③). In this case, the pulse width modulated signal ③ becomes binarized data, thereby increasing the transmission bandwidth.

The bit inverter 305 inverts the pulse width modulation signal ③ alternately at regular intervals (step 707). That is, the first period is normal and the second period is a bit based on an arbitrary starting point. Invert, and the third cycle is treated as normal. In this case, the period is a period (1.5T in the example of FIG. 4) of the target signal ③ to be bit inverted.

The pulse width modulated signal ④ alternately bit inverted every predetermined period output from the bit inverter 305 is transmitted through a wired transmission medium (eg, a telephone line). (709) Bit inverting alternately every predetermined period. Since the pulse width modulated signal? Is reduced in the number of data transitions, the transmission bandwidth is reduced and the transmission efficiency is increased.

As described above, in the line coding scheme, the present invention enables long-distance transmission by binarizing and transmitting a multilevel signal. In this case, an increase in bandwidth occurs in the process of binarizing a signal in the form of a pulse width, but in order to overcome this, the transmission bandwidth is reduced by reducing the number of transitions of data by inverting bits alternately at regular intervals. In addition, since the signal in the wired transmission section has the form of a binary signal, there is an advantage that the line encoding transmission apparatus and the transmission method become very simple. In addition, when a signal of the multilevel level coding method is transmitted as it is conventionally, an equalizer including a complex algorithm must be used to remove the signal distortion and distinguish the multilevel level signal, and a powerful echo canceller is used to remove the echo signal component. Was required. However, since the present invention transmits in the form of a binary signal as described above, it is possible to greatly reduce the requirements of such a circuit, and since it is transmitted in binary, the receiver side only needs to determine levels of "0" and "1". It can transmit longer distance than that. As a result, since the transmission distance is increased, there is an advantage that low overall line cost can be achieved.

Claims (8)

A multilevel level converter for converting an input serial signal into a multilevel level signal having two or more amplitude levels; A multilevel level / pulse width converter for converting the multilevel level signal converted by the multilevel level converter into a binary signal by pulse width modulation; And And a bit inverter for alternately inverting the binary signal pulse-width modulated by the multi-level level / pulse width converter alternately at predetermined intervals. The method according to claim 1, The constant period is, And a period of the pulse width modulated signal. A signal level determiner for determining a level of the input signal as "0" or "1"; A synchronization pattern tracker for establishing synchronization by tracking a synchronization pattern of a signal whose level is determined by the signal level determiner; A bit inverter, alternately at regular intervals, inverting the bits of the signal whose synchronization has been established by the sync pattern tracker to restore two or more pulse width conditions to a pulse width modulated signal; A pulse width / multilevel level converter for restoring two or more amplitude levels into a multilevel level signal according to the pulse width width of each period of the pulse width modulated signal by the bit inverter; And And a multilevel level / binary signal converter for restoring the multilevel level signal recovered by the pulse width / multilevel level converter to the original serial signal. The method according to claim 3, The constant period is, And a period of the pulse width modulated signal. An error correction encoder for error correction encoding the input higher layer signal; A multilevel level converter for converting the error correction coded signal into a multilevel level signal having two or more amplitude levels; A multilevel level / pulse width converter for converting the multilevel level signal converted by the multilevel level converter into a binary signal by pulse width modulation; A bit inverter for alternately bit inverting the binary signal pulse-width modulated by the multilevel level / pulse width converter alternately at regular intervals; A transformer for transmitting a binary signal inverted by the bit inverter through a telephone line and receiving a signal through the telephone line; A signal level determiner for determining a level of the received signal received by the transformer as "0" or "1"; A sync pattern tracker for establishing sync by tracking the sync pattern of the signal level determined by the signal level determiner; A bit inverter, alternately at regular intervals, inverting the bits of the signal whose synchronization has been established by the sync pattern tracker to restore two or more pulse width conditions to a pulse width modulated signal; A pulse width / multi-level level converter for restoring two or more amplitude levels into a multi-value level signal according to the pulse width width of each period of the pulse width modulated signal restored by the bit inverter; A multilevel level / binary signal converter for restoring the multilevel level signal restored by the pulse width / multilevel level converter to an original serial signal; An error correction decoder for error correcting and decoding the received signal restored to the original serial signal by the multi-level level / binary signal converter; And And an upper layer interface unit which receives the error correction decoded signal from the error correction decoder and transmits the received signal to the upper layer, and transmits the signal received from the upper layer to the error correction encoder. . The method according to claim 5, The constant period is, And a period of the pulse width modulated signal. In the line encoding method for transmitting a signal through a telephone line, Converting a serial signal to be transmitted into a multilevel signal having two or more amplitude levels; A second step of converting the multilevel signal into a binary signal by pulse width modulation; And And a third step of alternately bit inverting the pulse width modulated binary signal at regular intervals. The method of claim 7, wherein The constant period is, And a period of the pulse width modulated signal.