KR20000019060A - Convolutional coding perforator for digital communication and method thereof - Google Patents

Abstract

PURPOSE: A convolutional coding perforator for digital communication and methode thereof is provided to improve a timing for an input of information bit and an output of symbol by using a FIFO memory. CONSTITUTION: The convolutional coding perforator for digital communication and methode thereof comprises: a FIFO memory(210) for outputting a received information bit from a data source if a read signal is activated; a convolutional coder(220) for performing a convolutional coding for the information bit to a symbol if a coding signal is activated; a symbol selector(230) for exchanging each bit of the symbol to each other if an exchange signal is activated; a latch(240) for outputting the exchanged symbol to a punched convolutional coding output signal; and a controller(250) for generating a useful signal to represent the read signal, the coding signal, the exchange signal, the renewed signal, and the punched convolutional coding output signal.

Description

Weaving coding punching device and method for digital communication

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system using a digital modulation scheme. In particular, in order to change a data rate of a convolutional coding signal, information bits are encoded into symbols and then encoded. A method and apparatus for puncturing any bits in a symbol.

In order to cope with errors in transmission, digital communication systems represent data bits to be transmitted in k-bit strings, i.e. symbols. Convolutional Coding converts an input of one bit of information into a symbol of two or three bits. When transmitting each bit of the converted symbol, the digital communication system uses only 1/2 or 1/3 of the power used to transmit one bit of the original information. Therefore, the convolutional encoder transmits symbols without increasing the overall power, so that errors in information transmission can be reduced.

However, when the symbol rate is different from that required by the communication channel, it is essential to drill a few bits among the symbols of the plurality of bits. The symbol puncturer converts the ratio of information bits and symbolized bits, that is, code rates, to 9/16, 5/8, 3/4, 7/8, and the like instead of 1/2. For example, if a convolutional encoder of code rate 1/2 converts 9 bits of information bits into 18 bits of symbols, the symbol puncturer removes 2 bits of the 18 bits of symbols, leaving only 16 bits of symbols.

Conventional digital communication systems perform symbol puncturing using a microprocessor or a digital signal processor (DSP). However, the related art causes an overload of a microprocessor or a digital signal processing processor, and requires a separate circuit for maintaining a signal while the processor stores and transmits transmission data. In addition, if symbol puncturing is performed in the processor, the processor must also perform convolutional encoding, and thus the processor must perform many operations.

1 is a block diagram of a convolutional coding perforation system according to the prior art. As shown, a convolutional encoder 110 for encoding information bits into symbols by a data clock, and a symbol puncturer 120 for puncturing arbitrary bits from the symbols by a symbol clock. The symbol puncturer 120 has coding rates of 3/4 and 7/8, and outputs the punctured convolutional coded output signals C0 and C1 and a symbol clock.

In the convolutional coding puncture system operating as described above, since the convolutional encoder and the symbol puncturer use different clocks, the encoder and the puncturer must accurately synchronize the input and output. If the synchronization is not correct, the transmission data is repeated or lost. In addition, since the convolutional coding puncture system has a fixed code rate (3/4 and 7/8), there is a problem that a separate symbol puncturer must be used to operate at different code rates.

U.S. Patent No. 5,668,820, "Digital communication system having a punctured convolutional coding system and method" and U.S. Patent No. 5,633,881, "Trellis encoder and decoder based upon punctured rate 1/2 convolutional codes" Although a circuit capable of processing the puncture has been disclosed, the above problem has not been solved.

The present invention was devised to solve the problems of the prior art operating as described above, and convolutional encoding puncturing for digital communication using a dedicated circuit capable of convolutional encoding and symbol puncturing information bits without using a processor. It is an object to provide an apparatus and method.

Another object of the present invention is to provide a convolutional encoding perforation apparatus and method for digital communication, in which a function of convolutionally encoding and receiving input information bits and synchronizing the encoded symbols with one clock signal is synchronized. do.

Another object of the present invention is to provide a convolutional encoding puncturing apparatus and method for digital communication using a first input first output (FIFO) buffering input information bits.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention and the accompanying drawings.

1 is a block diagram of a convolutional coding perforation system according to the United States patent.

2 is a block diagram of a convolutional coding punching device according to the present invention.

3 is an exemplary diagram of a convolutional encoder configuration applied to the present invention.

4 is a timing diagram showing an example of a method of generating a punched convolutional coded output signal generated by a clock and a control signal;

5 is an embodiment of a symbol puncturing rule applied to the present invention.

6 is a flowchart illustrating a convolutional coding puncturing method according to the present invention.

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

110: convolutional encoder 120: symbol puncturer

210: first-in, first-out memory 260: data source

220: convolutional encoder 230: symbol selector

240: latch 250: controller

270: Clock Generator 310: Repository

320: exclusive-OR device 1: clock period

2: symbol period

In a communication system using a digital modulation scheme, a preferred embodiment of a convolutional encoding and puncturing apparatus for digital communication according to the present invention, which is designed to achieve the above object,

A first-in first-out memory for outputting information bits input from a data source when a read signal is activated;

A convolutional encoder for convolutionally encoding the information bits transferred from the first-in, first-out memory into symbols when the encoded signal is activated;

A symbol selector for exchanging each bit of a symbol transmitted from the convolutional encoder with each other when the exchange signal is activated;

A latch for outputting the exchanged symbol as a punctured convolutional coded output signal when the update signals for each bit of the symbol are activated;

And a controller for generating an available signal indicating that a read signal, an encoded signal, an exchange signal, an update signal, and a punctured convolutional coded output signal are output.

According to a preferred embodiment of a convolutional coding puncturing method for digital communication according to the present invention, in a communication system using a digital modulation scheme,

Inputting information bits to the first-in, first-out memory by the convolutional encoder when the read signal is activated;

Convolutional encoding the input information bits into symbols of 2 bits or 3 bits when the encoded signal is activated;

A symbol selector exchanging each bit of the symbol with each other when an exchange signal is activated;

A latch outputting the convolutional coded symbol or the exchanged symbol as a punctured convolutional coded output signal when an update signal is activated;

The controller activating an available signal indicating that the punctured convolutional coded output signal is output.

In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The convolutional coding apparatus and method according to the present invention perform convolutional coding and symbol puncturing without a processor. In addition, convolutional coding and symbol puncturing are performed by one clock, and a first-in first-out memory is used to remove timing constraints on input of information bits and output of symbols. 2 is a block diagram of a convolutional encoding punching device according to the present invention. Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention.

The convolutional coding puncturing apparatus according to the present invention includes a first-in first-out memory 210 that outputs information bits input from a data source 260 by a read signal, and an information signal transferred from the first-in first-out memory. a convolutional encoder 220 convolutionally encoding the symbol by an encoding signal, a symbol selector 230 for exchanging each bit of the symbol transmitted from the convolutional encoder by an exchange signal, and update the exchanged symbol by an update signal ( a latch 240 for puncturing, storing and outputting the punctured convolutional coded output signal and generating an available signal indicating that the read signal and the encoded signal, the exchange signal, the update signal, and the punctured convolutional coded output signal are output. Controller 250. The first-in first-out memory 210, the convolutional encoder 220, and the latch 240 are synchronized with one clock generated by the clock generator 270. However, when the first-in, first-out memory 210 is configured asynchronously, the first-in, first-out memory is not provided with a clock.

The first-in, first-out memory 210 receives and stores information bits from the data source 260. When the read signal generated from the controller 250 is activated, the first-in first-out memory outputs the stored information bits one bit in the order of first input. The output information bits are input to the convolutional encoder 220. When the first-in, first-out memory is full of information bits, the first-in, first-out memory activates an empty / full signal. The data source 260 does not transfer information bits to the first-in, first-out memory when the empty / full signal is activated.

When the coded signal generated by the controller 250 is activated, the convolutional encoder 220 converts one bit of information into a symbol of 2 bits or 3 bits. A convolutional encoder with a code rate of 1/2 converts one bit of information into a 2-bit symbol, and a convolutional encoder with a code rate of 1/3 converts one bit of information into a symbol of three bits. The convolutional encoder shown in Fig. 2 has a code rate of 1/2 and thus outputs symbols of C0 and C1. 3 illustrates an example of a convolutional encoder configuration applied to the present invention. As shown, a plurality of reservoirs 310 storing the input information bits and any number of exclusive OR elements 320 that sum the information bits input to the information bits stored in any of the reservoirs. The reservoir is composed of flip-flops. The number of reservoirs, the number of exclusive OR elements, and the combination of the reservoirs and exclusive OR elements may vary. The convolutional encoder shown in Fig. 3 has a coding rate of 1/2 and a constraint length of 7, and converts one bit of information D into symbols C0 and C1. 3, generator polynomials for symbols C0 and C1 g ₀ (x) Wow g ₁ (x) Is the same as Equation 1.

g ₀ (x) = 1 + x ² + x ³ + x ⁵ + x ⁶

g ₁ (x) = 1 + x + x ² + x ³ + x ⁶

The convolutional coded symbols C0 and C1 are input to the symbol selector 230.

When the exchange signal generated by the controller 250 is activated, the symbol selector 230 exchanges each bit C0 and C1 of the symbol with each other. If the exchange signal is not activated, the symbol selector 230 bypasses symbols C0 and C1 without exchanging them. The exchanged or bypassed symbols are input to latch 240.

The latch 240 stores the input symbols C0 and C1 and outputs a C0 output or a C1 output when the C0 update signal or C1 update signal generated by the controller 250 is activated. Since the holding period 2 of the symbol delivered by the selector is constant, the update signal determines the bit to be removed. The latch holds the symbol until the update signal is activated, and outputs the punctured convolutional coded output signals C0 and C1. That is, by the update signal, the latch can simultaneously puncture and store the symbol.

The controller 250 generates a control signal such as a read signal, an encoded signal, an exchange signal, and an update signal according to an information bit generation rate, a symbol transmission rate, and a punctured convolutional coded output signal. The clock generator 270 provides one clock to the first-in, first-out memory 210, the convolutional encoder 220, and the latch 240. However, if the first-in, first-out memory is configured asynchronously, the clock generator does not provide a clock to the first-in, first-out memory. The frequency of the clock is determined according to the symbol rate of the symbol generated by the convolutional encoder 220. If the symbol rates vary, the clock frequency is a common multiple of the various symbol rates. For example, if the bit rate of one bit of a symbol is 8, 16, 32, 64, 128 kbps, the least common multiple is 128 kbps. Therefore, the clock frequency is 128, 256, 384 ... kHz.

The controller activates various control signals, and each device (first in, first out memory, convolutional encoder, symbol selector, latch) operates in accordance with the control signal, and consequently, the convolutional encoding punching device performs convolutional encoding and symbol puncturing. In order to satisfy the required symbol rate and coding rate, the controller must activate each control signal correctly. 4 is a timing diagram illustrating an example of a method of generating a punched convolutional coded output signal generated by a clock and a control signal.

The read signal is activated during the first or second clock period (1) of the symbol transmission period, which is the time at which one symbol is maintained. The coded signal is also activated in the clock cycle in which the read signal is activated or in the next clock cycle. When the first-in, first-out memory 210 operates asynchronously, the read signal and the coded signal are activated in the same clock period. Therefore, FIG. 4A illustrates a read signal and a coded signal for a convolutional coded puncture apparatus using the asynchronous first-in, first-out memory 210. As shown, the read signal and the coded signal are activated with a certain period (2). In the case of a convolutional coded puncture apparatus using a synchronous first-in, first-out memory, the controller activates the coded signal in the next clock period of the clock period in which the read signal is activated.

4 (b) and 4 (c) show symbols C0 and C1 generated by the convolutional encoder by the coded signals. As shown, the convolutional coder generates convolutionally coded symbols periodically, and generates the next symbol if the coded signal is activated at the time when the clock signal is applied.

The exchange signal shown in (D) is activated when C0 and C1 need to be exchanged. The C0 and C1 update signals shown in (e) and (f) are activated at the next clock cycle and the next clock cycle, respectively. The latch outputs a punctured C0 (Fig. 4A) when the C0 update signal is activated, and outputs a punctured C1 signal (A) in Fig. 4 when the C1 update signal is activated. The available signal shown in (i) is always activated in the same clock period within the symbol period. Therefore, the available signal is used as a reference signal for symbol transmission.

When the coding rate of the convolutional coding punching device operated as described above is i / s, each control signal is repeated with a certain period of " (time required for transmitting one symbol) × s / 2 ". For example, when the code rate is 5/8 and one symbol is held for 1/64000 seconds (= 15.625 ms), each control signal is "(1/64000 seconds) x 8/2" = 62.5 ms It is repeated with a cycle of.

5 illustrates an embodiment of a symbol puncturing rule applied to the present invention. 5 is a symbol puncturing rule required when information bits of 80 kbps (symbol per second) should be transmitted. (A) shows 5-bit information D (0), D (1), D (2), D (3), and D (4) stored in the FIFO 210. When 5 bits of information are input at a rate of 80 kbps, the convolutional encoder 220 encodes 5 bits of information into a symbol of 10 bits. (B) denotes 10-bit symbols C0 (0), C1 (0), C0 (1), C1 (1), C0 (2), C1 (2), C0 (3) and C1 ( 3), C0 (4) and C1 (4) are shown. The convolutional encoder encodes the information bits D (x) into symbols C0 (x) and C1 (x). When two bits are to be punctured from the 10-bit symbol encoded as described above, it is assumed that C0 (2) and C1 (4) are punctured in this example. (C) is 8-bit symbols C0 (0), C1 (0), C0 (1), C1 (1), C1 (2), C0 (3), C1 (3), C0 (4) is shown. Since 8-bit symbols are transmitted in pairs of 2 bits, the punctured symbols are transmitted at a rate of 64ksps.

6 is a flowchart illustrating a convolutional coding puncturing method according to the present invention.

In step S110, when a read signal is generated, the convolutional encoder receives an information bit. In operation S120, when the encoded signal is generated, the convolutional encoder convolutionally encodes the information bits into symbols of two or three bits (for example, C0 and C1). In step s130, when an exchange signal is generated, the symbol selector exchanges bits of the symbol with each other (for example, C0, C1 to C1, C0). In step S140, when an update signal is generated, the latch outputs the exchanged signal as a punctured symbol. In step S150, the convolutional encoding puncturing apparatus generates an available signal to inform that the punctured symbol is ready.

The present invention can be variously modified and can take various forms and only the specific embodiments thereof are described in the detailed description of the invention. It is to be understood, however, that the present invention is not limited to the specific forms mentioned in the detailed description of the invention, but rather includes all modifications, equivalents, and substitutions within the spirit and scope of the invention as defined by the appended claims. It should be understood to do.

In the present invention operating as described above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present apparatus and method convolutionally encodes and symbol punctures information bits without using a processor, thereby reducing the weighted load by the processor of the digital communication system performing convolutional encoding and symbol puncturing.

Since the convolutional coding and the symbol puncturing are synchronized with one clock signal, the present apparatus and method can easily design a convolutional coding puncturing apparatus having a desired coding rate by applying a synchronous circuit design technique. Prevent malfunction. In addition, since only one clock generator is used, it is easy to implement as an application specific integrated circuit (ASIC).

The apparatus and method facilitates timing for input of information bits and output of symbols by using a first-in first-out memory that buffers input information bits. Since the present apparatus and method generate an available signal according to the symbol rate, the transmission rate of the punctured symbol can be known accurately.

Claims (21)

In a communication system using a digital modulation method, A first-in first-out memory for outputting information bits input from a data source when a read signal is activated; A convolutional encoder for convolutionally encoding the information bits transferred from the first-in, first-out memory into symbols when the encoded signal is activated; A symbol selector for exchanging each bit of a symbol transmitted from the convolutional encoder with each other when the exchange signal is activated; A latch for outputting the exchanged symbol as a punctured convolutional coded output signal when the update signals for each bit of the symbol are activated; And a controller for generating a usable signal indicating that a read signal and a coded signal, an exchange signal, an update signal, and a punctured convolutional coded output signal are output. The convolutional encoding puncturing apparatus of claim 1, wherein the read signal is activated during a first or second clock period in a symbol transmission period that is a time at which the one symbol is maintained. The convolutional coding puncturing apparatus for digital communication according to claim 1, wherein the first-in, first-out memory is configured synchronously. The convolutional encoding puncturing apparatus for digital communication according to claim 1 or 3, wherein the first-in first-out memory, the convolutional encoder, and the latch are synchronized with one clock. The convolutional encoding puncturing apparatus of claim 4, wherein the encoded signal is activated in a first clock period after a clock period in which the read signal is activated. The convolutional encoding puncture apparatus for digital communication according to claim 2, wherein the first-in, first-out memory is configured asynchronously. 7. The convolutional encoding puncture apparatus for digital communication according to claim 1 or 6, wherein the convolutional encoder and the latch are synchronized with one clock. The convolutional encoding puncturing apparatus of claim 7, wherein the encoded signal is activated in the same clock period as the clock period in which the read signal is activated. The method of claim 1, wherein the exchange signal, A convolutional encoding puncturing apparatus for digital communication, activated according to a puncturing rule of a symbol. The convolutional encoding puncturing apparatus of claim 1, wherein the update signals are activated in sequence in a subsequent clock period after a clock period in which the encoded signal is activated. 11. The convolutional encoding puncturing apparatus of claim 1 or 10, wherein the available signal is activated in a first clock period after the last update signal is activated. The convolutional encoding puncturing apparatus of claim 1, wherein the controller activates the read signal, the encoded signal, the exchange signal, and the update signals according to the occurrence rate of the information bit and the transmission rate of the punctured convolutional coded output signal. . The convolutional encoding puncturing apparatus of claim 5 or 8, wherein a period of the clock is a common multiple of a transmission rate of the punctured symbol. The convolutional encoding puncturing apparatus for digital communication according to claim 1, wherein the read signal, the encoded signal, the exchange signal, the update signal, and the available signal are repeated with a constant period. The method according to claim 1 or 14, wherein the coding rate of the convolutional coding apparatus is i / s. And the constant period is "(time required to transmit one symbol) x s / 2". In a communication system using a digital modulation method, Inputting information bits to the first-in, first-out memory by the convolutional encoder when the read signal is activated; Convolutional encoding the input information bits into symbols of 2 bits or 3 bits when the encoded signal is activated; A symbol selector exchanging each bit of the symbol with each other when an exchange signal is activated; A latch outputting the convolutional coded symbol or the exchanged symbol as a punctured convolutional coded output signal when an update signal is activated; And a controller activating an available signal indicating that the punctured convolutional coded output signal is output. 17. The method of claim 16, wherein the read signal is activated during a first or second clock period within a symbol transmission period during which the one symbol is maintained. 18. The convolution of claim 16 or 17, wherein the encoded signal is activated at a first clock period after a clock period in which the read signal is activated or at a clock period equal to a clock period in which the read signal is activated. Coding method. The convolutional coding puncturing method according to claim 16, wherein the exchange signal is activated according to a puncturing rule of a symbol. 17. The method of claim 16, wherein the update signals are activated in order in each subsequent clock period after the clock period in which the coded signal is activated. 21. The method of claim 16 or 20, wherein the available signal is activated in a first clock period after the last update signal is activated.