KR19980039215A - Broadcasting system using spread band method - Google Patents

Abstract

The present invention relates to a broadcast system using a spread spectrum method that allows a simple receiver to be configured by spreading and modulating a complex orthogonal spreading code that satisfies an orthogonal property. A plurality of mapping means for performing a function, a plurality of spreading modulation means for spread-band modulating a signal passed through the plurality of mapping means, an adding means for adding up the signals passed through the spreading modulation means, and a result signal of the adding means. A matching means for matching a carrier, a carrier modulating means for carrier modulating a signal passing through the matching means, a transmission means for amplifying the carrier modulated signal, and a receiving means for performing despreading modulation. do.

Description

Broadcasting system using spread band method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast system using a spread spectrum method that can form a simple receiver by spreading and modulating a spread spectrum modulated signal with a complex orthogonal spreading code satisfying orthogonality. The spread spectrum modulation scheme is used instead of the orthogonal frequency division modulation (OFDM) scheme.

At present, the broadcasting system is changing to digital broadcasting to improve the quality of analog frequency modulation (FM) and TV broadcasting and also for efficient frequency management. As a practical example, in Europe, orthogonal frequency division multiplexing (OFDM) is used. Audio and television broadcasting systems are implemented.

In principle, OFDM signaling is the same as MCM (multi carrier modulation).

Hereinafter, a conventional MCM transmission method will be described with reference to the drawings.

1 is a block diagram of a transmission stage using a conventional MCM transmission scheme.

Referring to FIG. 1, a transmission stage using an MCM transmission scheme includes a plurality of two-dimensional mappers 11 performing mapping functions of a plurality of parallel data capable of transmitting mN bits of information for T seconds, and the mapper 11. The modulator 12 modulates the data mapped by the subcarrier to satisfy the mutual orthogonal condition, the adder 13 summing the contents of the plurality of modulators 12, and the contents of the adder 13. A matching filter 14, a carrier modulator 15 for carrier modulating the contents of the filter 14, and a high frequency amplifier 16 for amplifying and transmitting the carrier modulator to the outside.

The operation of the transmitter using the MCM transmission scheme configured as described above is as follows.

First, in order to transmit mN bits of information for T seconds, the transmission path is divided into N parallel data transmission paths each capable of transmitting mN bits of information for T seconds through a serial-to-parallel 1: N serial-to-parallel conversion.

The data passing through the parallel data transmission path is subjected to the plurality of two-dimensional mappers 11 appropriate to the data of each path, and then modulated by the modulator 12 to subcarriers satisfying mutual orthogonal conditions. Then, the adder 13 adds all the path data and transmits the data.

The conventional MCM transmission scheme as described above requires a large number of oscillators for generating each subcarrier, and thus, hardware implementation is very complicated.

In addition, the data modulated by each subcarrier undergoes an appropriate filtering process to eliminate cross talk, respectively, further increasing the complexity of hardware configuration.

However, since the data of each path in the configuration of FIG. 1 may be regarded as Fourier coefficients of corresponding subcarrier frequencies, the inverse fast fourier transform (IFFT) may be used without using each subcarrier generating oscillator and filter. By implementing the transmitter, the hardware implementation of the transmitter is greatly simplified, and the receiver uses fast fourier transform (FFT), which has the opposite function, to restore the data of each parallel path.

However, the above-described method has a disadvantage in that the configuration of the receiver is very complicated since the FFT is proposed to have a very large value in the application of the actual system.

For example, in order to receive a European audio DAB signal (1536 x 1536), an FFT implementation is required, and at least 22 log2 (11) multipliers are required to implement the receiver. This is very complicated, and the performance is changed by the number of quantization bits and the peak ratio of the receiver FFT, it is difficult to comprehensively determine the various parameters to obtain the desired performance.

Accordingly, the present invention provides a broadcast system using a spread spectrum method that can form a simple receiver by spreading and modulating the spread spectrum with a complex orthogonal spreading code that satisfies the orthogonality. to provide.

1 is a block diagram of a transmission stage using a conventional MCM transmission scheme,

2 is a block diagram of a broadcasting system using a spread spectrum method according to an embodiment of the present invention,

3 is a block diagram of a transmission stage using a spread spectrum modulation method according to an embodiment of the present invention,

4 is a block diagram of a receiving end according to an embodiment of the present invention.

The broadcast system using the spread spectrum method provided by the present invention comprises a transmitting means for transmitting a signal modulated by spreading modulation and a receiving means for despreading the spread-modulated signal by the transmitting means to restore data. This simplifies the receiver implementation.

Hereinafter, the present invention will be described in detail with reference to the drawings.

2 is a block diagram of a broadcast system using a spread spectrum method according to an embodiment of the present invention, FIG. 3 is a block diagram of a transmission stage using a spread spectrum modulation method according to an embodiment of the present invention, and FIG. A configuration diagram of a receiving end according to an embodiment of the present invention. Referring to FIG. 2, the broadcast system of the present invention has a spread modulation transmitter 20 that transmits a signal modulated by spread modulation, and a reverse recovery function by despreading a spread modulated signal by the transmission means. It consists of a spread demodulation receiver 30.

Referring to FIG. 3, the spreading modulation transmitter 20 includes a plurality of two-dimensional mappers 21 that perform a mapping function of a plurality of parallel data capable of transmitting mN bits of information for T seconds, and the plurality of two-dimensional images. A plurality of spreading modulators 22 for spread-band modulating a signal passed through the mapper 21, an adder 23 for adding up the signals passed through the spreading modulator 22, and a signal added by the adder 23 A matching filter 24, a carrier modulator 25 for carrier modulating a signal passing through the filter 24, and a high frequency amplifier 26 for amplifying the carrier modulated signal.

The operation of the spread modulation transmitter 20 of the present invention configured as described above is as follows.

In order to transmit the information rate of mN bits for T seconds, the transmission path is first divided into N parallel data transmission paths each capable of transmitting mN bits of information for T seconds through a 1: N serial-to-parallel conversion, similar to the OFDM scheme. After passing through the 2D mapper 21 suitable for the data of the path, C _i (C ₁ ), which is a complex orthogonal spreading code having a chip ratio N / T satisfying orthogonality in the spread modulator 22. After spread-band modulation by ˜C _n) , the N signals of each path spread by the adder 23 are combined and transmitted.

In this case, since the transmission signal transmits mN bits of data in the N / T band, the transmission signal has the same transmission efficiency as that of the OFDM scheme.

Referring to FIG. 3, the despread demodulation receiver 30 transposes an antenna 31, a noise synthesizer 32 for synthesizing noise to a signal received from the antenna, and a signal passed through the noise synthesizer 32. A preamplifier 33 for amplifying, a carrier demodulator 34 for carrier demodulating the signal amplified by the preamplifier 33, a filter 35 for matching the carrier demodulated signal in the carrier demodulator 34, A sample value determiner (T / N) 36 having a signal matched by the filter 35 and obtaining sample values on a predetermined time basis, and a disturbance element that removes the disturbing element from the result of the sample value determiner 36; 37 therein, a despread demodulator 38 for despreading and demodulating by multiplying a predetermined number of sample values determined by the sample value determiner 36, and a two-dimensional demapper 39 for restoring the despread signal. It consists of.

The operation of the receiving end 30 of the present invention configured as described above is as follows.

The signal received through the antenna 31 is passed through the pre-amplifier 33 after the noise is synthesized in the noise synthesizer 32, the carrier demodulated in the carrier demodulator 34, and then through the matched filter 35, The sample value determiner 36 obtains a sample value at every T / N time point.

The sample number sequence obtained by the sample value determiner 36 is multiplied by a desired spreading code to despread, and then the data is restored through the two-dimensional demapper 39.

In general, the receiving end should obtain a desired quality performance regardless of the amount of data to be transmitted.In case of the OFDM scheme, when a large amount of data is transmitted in the N / T band, that is, when the m value becomes large, that is, only by increasing the transmission power, Quality performance can be obtained at the receiving end.

However, in the scheme of the present invention, no matter how large the reception power is, the performance of the receiver is determined solely by the processing gain (= N / m), and may not be suitable as a broadcasting system if this value is not large enough.

Therefore, in order to solve this problem, the interference canceller 37 is attached to the receiving end so that the reception performance can maintain the desired broadcast quality. For the interference canceller 37, Azang, Verdu, etc.

The environment of broadcasting system is synchronous transmission environment, so it can be easily implemented.

Unlike the OFDM scheme, the present invention does not require complicated multiplier processing, thereby simplifying the device configuration and processing the transmission signal as a pure binary digital signal, thereby being extremely sensitive to quantization and peak ratio. It has the advantage of not showing performance. In addition, since it includes a frequency diversity effect in itself, there is an advantage that it can cope with the fading environment very firmly.

An object of the present invention is to provide a broadcast system using a spread spectrum method that can form a simple receiver by spreading and modulating a spread spectrum modulated signal with a complex orthogonal spreading code satisfying orthogonality.

Claims (3)

And a transmitting means for transmitting a signal modulated by spreading modulation, and a receiving means for despreading the spread-modulated signal by the transmitting means to restore data. The method of claim 1, wherein the transmitting means comprises: a plurality of two-dimensional mapping units for performing a mapping function of a plurality of parallel data capable of transmitting a predetermined amount of information for a predetermined time, and spread-band modulation of a signal passed through the plurality of mapping means; A plurality of spreading modulators, an adder for adding up all the signals passed through the spreading modulation means, a matched filter for matching the resultant signal of the adding means, a carrier modulator for carrier modulating the signals passed through the matching means; And a high frequency amplifier for amplifying the carrier modulated signal. The signal receiving apparatus of claim 1, wherein the receiving unit comprises: a noise synthesizer for receiving a signal received from an antenna and synthesizing noise, a preamplifying unit for preamplifying a signal passed through the noise combining unit, and a signal amplified by the preamplifying unit. A sample value determination unit having a carrier demodulation unit for performing carrier demodulation, a matching filtration unit for matching the carrier demodulated signal in the carrier demodulation means, a signal matched in the matching means, and obtaining sample values in units of time; An interference elimination unit for removing an interference factor from the result of the sample value determining means, a despreader for despreading by multiplying a sample code sequence determined by the sample value determining means by a predetermined code, and a restoration unit for restoring the despread signal. Broadcast system using a spread spectrum method, characterized in that configured.