KR20130031189A - Transmission/reception apparatus and method for filtered multi-tone system - Google Patents

Abstract

According to the present invention, a signal spreader and a spread spectrum signal for generating spread spectrum signals through spread spectrum of a plurality of symbol mapped signals are mixed with a plurality of subcarriers, and the mixed spread spectrum signal is added to generate a modulated signal. An apparatus and method for transmitting a multicarrier signal including a modulator are provided.

Description

Transmitter and method of FMT system {TRANSMISSION / RECEPTION APPARATUS AND METHOD FOR FILTERED MULTI-TONE SYSTEM}

The present invention relates to an apparatus and method for transmitting and receiving data, and more particularly, to improving characteristics of a peak-to-average power ratio (PAPR) of a transmission signal in a multicarrier communication system. An apparatus and method for

There are various methods for multicarrier transmission, and these multicarrier transmission schemes are generally classified into superimposed multicarrier transmission schemes and non-overlapping multicarrier transmission schemes according to whether or not sub-bands are overlapped in dividing frequency spectrum. have.

Filtered Multi-Tone (FMT) modulation scheme for data transmission in Terrestrial Trunked Radio (TETRA) system in ETSI EN 300 392-2 and VHF data system in Rec.ITU-R M.1842-1. use.

The FMT modulation method transmits a modulated signal using M subcarriers, and the signal transmitted through each subcarrier passes through a pulse shaping filter having a roll-off factor of a. When the transmission symbol rate of data symbols transmitted on each subcarrier is 1 / T and the number of subcarriers is M, the total data symbol transmission rate is M / T. At this time, the interval of the subcarriers is set so that the overlap of the signals transmitted to the subcarriers in consideration of the roll-off factor of the pulse shaping filter.

In other words, unlike Orthogonal Frequency Division Multiplexing (OFDM), the FMT system has a length of a filter over several symbol periods in the time domain. Occurs.

Unlike OFDM, the FMT system does not cause frequency overlap between subchannels by bandpass filtering each subchannel signal. In addition, there is no need to use a cycle prefix, and the use of a small number of guard bands has the advantage of higher frequency efficiency than OFDM. However, the FMT system has a disadvantage of high complexity due to subchannel filtering.

In the multi-carrier transmission system, since a plurality of subcarrier signals are overlapped and transmitted, there is a problem in that PAPR is increased compared to a single frequency system.

According to an aspect of the present invention, there is provided a signal spreader configured to generate spread spectrum signals through spread spectrum of a plurality of symbol-mapped signals; And

And a modulator for mixing the spread spectrum signals with a plurality of subcarriers and adding the mixed spread spectrum signals to generate a modulated signal.

In addition, the signal spreader may be spread by spreading a plurality of symbol-mapped data using a Fast Fourier Transfrom (FFT).

In addition, the signal spreader may be spread by spreading the plurality of symbol-mapped data using a Discrete Fourier Transform (DFT).

Another embodiment of the present invention for solving the above technical problem is a demodulator for demodulating the received multi-carrier signal for each corresponding sub-carrier; And a signal despreader for performing despreading on each of the demodulated subcarrier signals.

The signal despreader may perform inverse spreading on each of the demodulated subcarrier signals by using an inverse fast fourier transform (IFFT).

The signal despreader may perform despreading on each of the demodulated subcarrier signals using an Inverse Discrete Frourier Transform (IDFT).

Another embodiment of the present invention for solving the above technical problem is a signal spreading step of generating spread spectrum signals through the spread spectrum for a plurality of symbol-mapped signals; And a modulator for mixing the spread spectrum signals with a plurality of subcarriers and summing the mixed spread spectrum signals to generate a modulated signal.

In addition, the signal spreading may be performed by spreading the plurality of symbol-mapped data using a fast Fourier transform (FFT).

The signal spreading may be performed by spreading the plurality of symbol-mapped data using a Discrete Fourier Transform (DFT).

A demodulation step of demodulating another received multicarrier signal for each corresponding subcarrier for solving the above technical problem; And a signal despreading step of performing a despreading process on each of the demodulated subcarrier signals.

The despreading of the signal may be performed by performing an inverse spreading process on each of the demodulated subcarrier signals by using an inverse fast Fourier transform (IFFT).

In addition, the signal despreading step may be a step of performing a despreading process on each of the demodulated subcarrier signals using an Inverse Discrete Frourier Transform (IDFT).

In order to reduce the PAPR of a transmission signal in a multi-carrier transmission system, the PAPR reduction reduces the nonlinear signal distortion of the high output power amplifier, thus providing the effect of reducing the in-band interference signal and adjacent channel interference of the multi-carrier system. .

1 is a reference diagram for explaining a conventional filtered multi-tone (FMT) system.
Figure 2 shows the spectrum of the output signal in a conventional FMT system.
3 is a block diagram illustrating a transmission apparatus of an FMT system according to an embodiment of the present invention.
4 is a block diagram illustrating an FMT system according to an embodiment of the present invention.
5 is a reference diagram for comparing PAPR characteristics in an FMT transmission system according to an embodiment of the present invention.
6 is a block diagram illustrating a receiving apparatus in the FMT transmission system of the present invention.
7 is a reference diagram for explaining a FMT reception system according to the present invention.
8 is a flowchart illustrating a transmission method in an FMT system according to an embodiment of the present invention.
9 is a flowchart illustrating a reception method in an FMT system according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

The following embodiments are a combination of elements and features of the present invention in a predetermined form. Each component or feature may be considered to be optional unless otherwise stated. Each component or feature may be embodied in a form that is not combined with other components or features. In addition, some of the elements and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

Embodiments of the invention may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

For a hardware implementation, the method according to embodiments of the present invention may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs) , Field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to embodiments of the present invention may be implemented in the form of a module, a procedure or a function for performing the functions or operations described above. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of the specific terms may be modified in other forms without departing from the technical spirit of the present invention.

An FMT transmission system of a conventional multicarrier transmission method will be described with reference to FIG. 1.

The conventional multi-carrier transmission system includes a channel encoder 101, a digital modulator 103, a symbol resource allocator 105, a pulse shaping filter 107 and a transmitter 109.

The channel encoder 101 is used to encode transmission data of a transmitter for error detection and error recovery of data received at the receiver. The number of subcarrier signals is converted into parallel data.

The digital modulator 103 generates a digital modulation symbol by performing digital modulation on a data symbol composed of binary data to be transmitted through a channel. In this case, the digital modulation performed by the digital modulator 103 may include binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), quadrature amplitude modulation (QAM), 16-QAM, and 64-QAM. The digital modulator may be referred to as a symbol mapping unit.

The symbol resource allocator 105 allocates resources in the time-frequency domain in order to transmit the symbol modulated by the digital modulator 103 in a wired or wireless interval.

The pulse shaping filter 107 pulses shaping M subcarriers in each time symbol interval to which symbol resources are allocated by a filter having a predetermined roll-off factor.

The transmitter 109 performs a subcarrier transition process on the output signal passing through the pulse shaping filter, and M signals which have been shifted by the subcarrier are summed at a sample every hour and then subjected to a frequency shift process at a wired / wireless transmission frequency. It is output as a transmitter output signal.

2 shows that the number of subcarriers is 8, the roll-off factor is 0.2, the transmission rate of data symbols transmitted by subcarriers is 2400 Symbol / sec, and the subcarrier frequency interval is 2700khz in the conventional FMT transmission system. In this case, the spectrum of the output signal is shown.

A transmission apparatus in a communication system of a multi-carrier transmission method according to an embodiment of the present invention will be described with reference to FIG. 3. An FMT system according to an embodiment of the present invention is digitally implemented and has a simplified structure of a transmitter and a receiver using a fast Fourier transform or a fast Fourier inverse transform. The multicarrier transmission scheme includes an OFDM scheme and an FMT scheme. The transmission device includes a signal spreader 301 and a modulator 303.

The signal spreader 301 spreads a signal on a plurality of symbol-mapped data.

According to an embodiment of the present invention, the signal spreader may spread the signal using a fast Fourier transform (FFT) on the plurality of symbol-mapped data. That is, the FFT calculating unit performs fast Fourier transform (FFT) to generate N FFT symbols.

According to another embodiment of the present invention, the signal spreader may spread the signal using a discrete Fourier transform on a plurality of symbol-mapped data.

The modulator 303 converts the plurality of symbol-mapped data that has been signal-spread into symbols in the time domain and modulates the corresponding sub-carriers.

An FMT transmission system including a transmission apparatus according to an embodiment of the present invention will be described with reference to FIG. 4. The FMT transmission system includes a channel encoder 401, a digital modulator 403, a symbol resource allocator 405, a signal spreader 407, a pulse shaping filter 409, and a transmitter 411.

The channel encoder 401 encodes the transmission data of the transmitter.

The digital modulator 403 generates a digital modulation symbol by performing digital modulation on a data symbol composed of binary data to be transmitted through a channel.

The symbol resource allocator 405 allocates resources to the time-frequency domain with the modulated symbols.

The signal spreader 407 spreads the signal with respect to the plurality of symbol-mapped data. That is, a signal is spread using a fast Fourier transform (FFT) or a discrete Fourier transform (DFT) on the plurality of symbol-mapped data.

The pulse shaping filter 409 pulse-shapes the plurality of symbol-mapped data (Pulse Shaping).

The transmitter 411 frequency shifts the signal which passed the pulse shaping filter 409, and outputs it.

A graph comparing PAPR characteristics in an FMT transmission system according to an embodiment of the present invention will be described with reference to FIG. 5. In the FMT transmission system, when the data symbol transmission rate is 2400 symbol / sec and the subcarrier frequency interval is 2.7 kHz, the FMT transmission system according to the present invention provides a PAPR reduction effect of about 1.3 dB at 1% of the CCDF. have.

Referring to FIG. 6, a reception apparatus in a transmission system of the FMT method according to an embodiment of the present invention will be described. The receiving device includes a signal despreader 601 and a demodulator 603.

The signal despreader 601 performs despreading on each received subcarrier signal.

The demodulator 603 demodulates the multicarrier signal on which the despreading process has been performed for each corresponding subcarrier.

According to an embodiment of the present invention, the signal despreader 603 despreads each demodulated subcarrier signal by using an inverse fast Fourier transform or an inverse discrete fourier transform. Perform the process.

A receiving apparatus in a transmission system of an FMT scheme according to an embodiment of the present invention will be described with reference to FIG. 7.

The receiving unit 701 receives a signal transmitted from the transmitting device.

The multi-phase filter 703 generates M parallel signals based on the signal received by the receiver 701.

The signal spreader 705 performs a spreading process on the M signals by using a fast Fourier transform (FFT) or a discrete Fourier transform (DFT).

The parallel signal processor 707 performs a fast Fourier inverse transform (IFFT) when the signal spreader performs the fast Fourier transform (FFT) on the M parallel signals subjected to the signal spreading process, and performs a discrete Fourier transform (DFT). If performed, the Discrete Fourier Inverse Transform (IDFT) is performed to process the parallel signals.

The symbol resource extractor 709 extracts a symbol resource from a signal processed by the parallel signal processor 707.

The symbol demapping unit 711 modulates binary data symbols with respect to the digitally modulated signal.

The channel decoder 713 transmits higher layer data by decoding the data of the receiver.

A transmission method in a transmission system of the FMT method according to an embodiment of the present invention will be described with reference to FIG. 8. In the FMT transmission system, the same contents as the transmitting apparatus are replaced with the above description.

In step S101, signal spreading is performed on a plurality of symbol-mapped data.

According to an embodiment of the present invention, signal spreading may be performed by spreading a signal on a plurality of symbol-mapped data using a Fast Fourier Transform (FFT) or a Discrete Fourier Transform. have.

In step S103, a plurality of symbol-mapped data that has been spread is converted into symbols in the time domain and modulated to a corresponding sub-carrier.

A reception method in a transmission system of the FMT method according to an embodiment of the present invention will be described with reference to FIG. 9. In the FMT transmission system, the same contents as the reception apparatus are replaced with the above description.

Step S201 demodulates the received multicarrier signal for each corresponding subcarrier with respect to the plurality of symbol-mapped data.

In step S203, a despreading process is performed on each demodulated subcarrier signal.

Embodiments according to the present invention can be written as a computer program. Codes and code segments constituting this computer program can be easily inferred by a computer programmer in the art. In addition, the computer program is stored in a computer readable medium (Computer Readable Media), and the embodiment is implemented by being read and executed by a computer. The information storage medium includes a magnetic recording medium, an optical recording medium and a carrier wave medium.

The present invention has been described above with reference to preferred embodiments. It will be understood by those skilled in the art that the present invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof. Therefore, the above-described embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is shown not in the above description but in the claims, and all differences within the scope should be construed as being included in the present invention.

Claims (12)

A signal spreader configured to generate spread spectrum signals through spread spectrum of the plurality of symbol mapped signals; And
And a modulator for mixing the spread spectrum signals with a plurality of subcarriers and adding the mixed spread spectrum signals to generate a modulated signal. The method of claim 1, wherein the signal spreader
And spreading a plurality of symbol-mapped data using fast Fourier transform (FFT). The method of claim 1, wherein the signal spreader
And spreading a plurality of symbol-mapped data by using a discrete Fourier transform (DFT). A demodulator for demodulating the received multicarrier signal for each corresponding subcarrier; And
And a signal despreader which despreads each demodulated subcarrier signal. The method of claim 4, wherein the signal despreading unit
And a despreading process for each of the demodulated subcarrier signals using an inverse fast fourier transform (IFFT). The method of claim 4, wherein the signal despreading unit
And a despreading process for each of the demodulated subcarrier signals using an Inverse Discrete Fourier Transform (IDFT). A signal spreading step of generating spread spectrum signals through spread spectrum for a plurality of symbol mapped signals; And
And a modulator for mixing the spread spectrum signals with a plurality of subcarriers and adding the mixed spread spectrum signals to generate a modulated signal. The method of claim 7, wherein the signal spreading step
And spreading the plurality of symbol-mapped data using fast Fourier transform (FFT). The method of claim 7, wherein the signal spreading step
And spreading the plurality of symbol-mapped data using discrete Fourier transform (DFT). Demodulating the received multi-carrier signal for each corresponding subcarrier; And
And a signal despreading step of performing a despreading process on each of the demodulated subcarrier signals. The method of claim 10, wherein the signal despreading step
And performing a despreading process on each of the demodulated subcarrier signals by using an inverse fast fourier transform (IFFT). The method of claim 10, wherein the signal despreading step
And performing a despreading process on each of the demodulated subcarrier signals using an inverse discrete Frourier transform (IDFT).

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