KR100633989B1 - Trellis coded modulation encoder using a convolutional encoder - Google Patents

Abstract

The present invention relates to a TCM encoder using a convolutional encoder.

The present invention relates to a convolutional coder for convolutionally encoding a coded bit signal of one bit out of five bits of input data and outputting a convolutional signal of two bits; First and second 8PSK modulators for mapping a convolutional signal of the convolutional encoder and two unsigned bit signals of input data to 8 phase shift keying (8PSK) according to a system clock; And a multiplexer which is driven by a multiplex clock and selectively outputs 8PSK modulated outputs of the first and second 8PSK modulators as modulated signals having a coding rate of 5/6.

Therefore, in the wireless communication system such as mobile communication, satellite communication, etc., which uses the Trellis Coded Modulation (TCM) method to correct an error caused by a channel environment when transmitting a radio signal, the TCM encoder inputs 5 input data. Convolutionally encodes only the least significant bit (LSB) into two bits after input, and modulates 8PSK (8 Phase Shift Keying) by combining the unsigned bit signals with each other and then doubles the frequency of the system clock. By selectively outputting the 8PSK modulated signal at, by outputting two modulated signals for each I and Q channel when five information bits are input according to a system clock, the coding rate is increased. The addition of an element has the effect of enabling high-speed data transfer.

Description

TCMIS coder using convolutional encoder {TRELLIS CODED MODULATION ENCODER USING A CONVOLUTIONAL ENCODER}             

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing the configuration of a TCM encoder using a convolutional encoder having a conventional coding rate of 2/3.

Figure 2 is a block diagram showing the configuration of a TCM encoder using the present invention convolutional encoder.

Figures 3a to 3d is a signal flow diagram showing the flow of each signal according to the system clock and multiplexer clock in the TCM coder using the convolutional encoder of the present invention.

4 is a signal diagram showing a mapping example of a first and a second 8PSK modulator in a TCM encoder using a convolutional encoder of the present invention.

*** Description of the symbols for the main parts of the drawings ***

20: Convolutional Coder 21: First 8PSK Modulator

22: second 8PSK modulator 23: multiplexer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system. In particular, in a wireless communication system such as mobile communication and satellite communication, which uses a Trellis Coded Modulation (TCM) scheme to correct an error caused by a channel environment during transmission of a wireless signal, Receives 5 bits of input data from the encoder, convolutionally encodes only the least significant bit (LSB) into 2 bits, and modulates 8 Phase Shift Keying (8PSK) by combining the unsigned bit signals with each other. By selectively outputting the 8PSK modulated signal in a multiplexer having a double frequency, the modulation rate is increased by outputting two modulation signals for each I and Q channel when five information bits are input according to a system clock. Under good circumstances, a convolutional encoder can be used to enable high-speed data transfer with simple addition of simple components. It relates to a used TCM encoder.

The Enhanced General Packet Radio Service (EGPRS) system is a GSM-based communication system that increases data transmission capability by using packet switched transmission, and uses Enhanced Data Rate for GSM Evolution (EDGE) technology.

That is, using 8PSK (8 Phase Shift Keying) modulation method for packet data channels in addition to GMSK (Gaussian Minimum Shift Keying) modulation method commonly used in GSM, non-copying such as file copying and the use of Internet browsers. In addition to real-time data transmission services, it also enables real-time packet-switched services in the transmission of voice and video images.

Meanwhile, in a wireless communication system such as mobile communication or satellite communication, an error correcting code method for correcting an error occurring in a channel when a wireless signal is transmitted and received, and when an error occurs in a channel after adding an additional symbol to the wireless signal, The Forward Error Correction (FEC) scheme, which detects or corrects channel errors using algebraic properties at the receiving end, is mainly used.

The FEC method can be divided into a block code and a convolution code. A convolution coder using a convolution code uses a method of encoding based on a correlation between a current input and a past input. As an encoder, it is effective to correct a random error.

In addition, additional information for error correction is added to data that is error corrected and encoded by the convolutional encoder, and thus the amount of data that can be transmitted per limited bandwidth is reduced. Therefore, the encoding and modulation are performed separately. By combining, the Trellis Coded Modulation (TCM) scheme is used as a transmission method that can obtain a large code gain without reducing the data rate or increasing the bandwidth.

FIG. 1 is a block diagram showing the configuration of a TCM encoder (TCM Encoder) using a convolutional encoder having a conventional coding rate of 2/3. As shown therein, data input from the convolutional encoder 10 is shown. When the coded bit signal E1 is received and convolutionally encoded and output as two output signals C1 and C2, the 8-phase shift keying (8PSK) modulator 11 is input according to the system clock signal CLK. The unsigned bit signal NE of the data and the output signals C1 and C2 of the convolutional encoder 10 are combined to be output as I and Q signals modulated to be trellis coded.

In this case, a wireless communication system using a convolutional encoder 10 having a coding rate of 2/3 in an abnormal channel environment is useful because it can reduce the data error rate generated in the transmission of a radio signal, but in a good channel environment, a small coding rate Due to this, there is a problem in that channel resources are wasted because more data cannot be transmitted.

Accordingly, the present invention has been proposed to solve the above-described problems, such as mobile communication, satellite communication, etc. using a Trellis Coded Modulation (TCM) scheme to correct an error caused by a channel environment when transmitting a radio signal. In a wireless communication system, the TCM encoder receives input data as 5 bits and convolutionally encodes only the least significant bit (LSB) into 2 bits, and then combines the unsigned bit signals with 8 phase shift keying (PSK) modulation. Then, by selectively outputting the 8PSK modulated signal in a multiplexer having a frequency twice as large as the system clock, when 5 information bits are input according to the system clock, two modulated signals for each I and Q channel are output and encoded. The purpose is to provide a device for increasing the rate.

According to an aspect of the present invention, there is provided a convolutional coder for convolutionally encoding a coded bit signal of one bit among five bits of input data and outputting a convolutional signal of two bits; First and second 8PSK modulators for mapping a convolutional signal of the convolutional encoder and two unsigned bit signals of input data to 8 phase shift keying (8PSK) according to a system clock; And a multiplexer which is driven by a multiplex clock and selectively outputs 8PSK modulated outputs of the first and second 8PSK modulators as modulated signals having a code rate of 5/6.

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram showing the configuration of a TCM encoder using the convolutional encoder of the present invention. As shown in FIG. 2, two bits of the 5-bit input data are convolutionally encoded by convolutional coding of a 1-bit encoded bit signal E1. A convolution encoder 20 outputting the convolution signals enout1 and enout2; 8PSK (8 Phase Shift) by mapping a second convolutional signal enout2 of the convolutional encoder 20 and two bit unsigned bit signals NE1 and NE2 of the input data according to a system clock CLK. A first 8PSK modulator 21 for modulating with Keying); A second 8PSK modulator for mapping the first convolutional signal enout1 of the convolutional encoder 20 and unsigned bit signals NE3 and NE4 of the input data to modulate 8PSK according to a system clock CLK (22); 8PSK modulated outputs I ₁ , Q ₁ , I ₂ , and Q of the first and second 8PSK modulators 21 and 22, driven by a multiplexer clock CLK1 having a predetermined frequency, according to the selection signal MUX_SEL. ₂ ) and a multiplexer 23 for outputting the modulated signals I and Q having a code rate of 5/6.

The present invention can be applied to a wireless communication system, such as mobile communication, satellite communication using the Trellis Coded Modulation (TCM) method in order to correct an error caused by a channel environment when transmitting a wireless signal, the wireless communication to which the present invention is applied The system design a TCM encoder with a code rate of 5/6 using the 8PSK modulation scheme with the simple addition of simple components, enabling high-speed data transmission in a good channel environment compared to the conventional TCM coders with a code rate of 2/3. do.

That is, according to the present invention, the TCM encoder receives the input data as 5 bits and divides the least significant bit (LSB) into a bit signal E1 that is encoded, and divides the remaining bit strings into uncoded bit signals NE1 to NE4. After encoding the encoded bit signal E1 into two bits in the convolutional encoder 20, combining the encoded bit signal E1 with the uncoded bit signals NE1 to NE4 and performing 8PSK modulation, and then having a double speed of the system clock CLK. Multiplexer 23 selectively outputs the 8PSK modulated signals I ₁ , Q ₁ , I ₂ , and Q ₂ , so that when each of the five information bits E1, NE1 to NE4 is input, 2 for each I and Q channel. Output modulation signals.

Meanwhile, as shown in the signal flow diagram of FIG. 3A, the convolution encoder 20 convolutionally encodes a coded bit signal E1 corresponding to the least significant bit LSB of the input data according to the system clock CLK, thereby performing 2-bit convolution. The first convolutional signal enout1 is 8PSK modulated in combination with the unsigned bit signals NE3 and NE4, and the second convolutional signal enout2 is an unsigned bit signal. 8PSK modulated in combination with (NE1, NE2).

That is, as shown in FIG. 3B, the second convolution signal enout2 of the convolutional encoder 20 and the 2-bit unsigned bit signal NE1 of the first 8PSK modulator 21 according to the system clock CLK are input. , NE2) to output 8PSK modulated outputs I ₁ and Q ₁ modulated to 8PSK, and the convolutional encoder according to the system clock CLK in the second 8PSK modulator 22 as shown in FIG. 3C. The first convolutional signal enout1 of (20) and the 2 bit unsigned bit signals NE3 and NE4 of the input data are mapped to output 8PSK modulated outputs I ₂ and Q ₂ modulated to 8PSK.

Here, the first and second 8PSK modulators 21 and 22 map so that the least significant bit LSB of the mapped bit stream repeats the values '0' and '1' as shown in FIG. 4, and FIGS. 3B and 3C. The number displayed inside each 8PSK modulated output (I ₁ , Q ₁ , I ₂ , Q ₂ ) is an arbitrary output value of each signal.

Then, the 8PSK modulation outputs I ₁ , Q ₁ , I ₂ , and Q _{2 of} the first and second 8PSK modulators 21 and 22 are input to the multiplexer 23, and the multiplex clock having a predetermined frequency ( In the multiplexer 23 driven by CLK1, the 8PSK modulation outputs I ₁ , Q ₁ , I ₂ , and Q ₂ are selected according to the selection signal MUX_SEL, and the modulation signals I and Q having a coding rate of 5/6. Will be printed.

For example, when the multiplexer clock CLK1 having a frequency twice as large as the system clock CLK in the multiplexer 23 becomes a falling edge, as shown in FIG. 3D, the selection of the 'high' state is performed. By selecting the 8PSK modulated outputs I ₁ and Q ₁ from the signal MUX_SEL and the 8PSK modulated outputs I ₂ and Q ₂ from the selection signal MUX_SEL in the 'low' state, the system is selected. When five information bits E1, NE1 to NE4 are input in accordance with the clock CLK, two modulation signals are output for each of the I and Q channels, thereby obtaining a TCM encoder effect having a coding rate of 5/6.

As described above, the present invention provides a wireless communication system using a Trellis Coded Modulation (TCM) scheme to correct an error caused by a channel environment during transmission of a radio signal. Receives 5 bits of input data and convolutionally encodes only the least significant bit (LSB) into 2 bits, then modulates 8 Phase Shift Keying (8PSK) by combining the unsigned bit signals with each other. By selectively outputting the 8PSK modulated signal in a multiplexer having a frequency, when two information bits are input according to a system clock, two modulated signals are output for each I and Q channel to increase the coding rate, thereby providing a good channel condition. Under the circumstances, there is an effect that high-speed data transmission is possible by simply adding components.

Claims (3)

A convolution encoder for convolutionally encoding the encoded bit signal of one bit among the 5-bit input data and outputting it as a 2-bit convolution signal; First and second 8PSK modulators for mapping a convolutional signal of the convolutional encoder and two unsigned bit signals of input data to 8 phase shift keying (8PSK) according to a system clock; And a multiplexer driven by a multiplex clock to selectively output 8PSK modulated outputs of the first and second 8PSK modulators as modulated signals having a coding rate of 5/6. . The TCM encoder of claim 1, wherein the encoded bit signal is a least significant bit (LSB) of 5-bit input data. The TCM encoder according to claim 1, wherein the multiplex clock has a frequency twice that of a system clock.

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