KR20010009619A - Ofdm/cdma mobile communication system having pilot tone inserting and detecting apparatus - Google Patents

Abstract

PURPOSE: A mobile communication system of OFDM(Orthogonal Frequency Division Multiple)/CDMA(Code Division Multiple Access) with a device for injecting and detecting the pilot tone is provided to restore data correctly by injecting and detecting a pilot carrier in the field of frequency and a pilot symbol in the field of time. CONSTITUTION: A mobile communication system of OFDM(Orthogonal Frequency Division Multiple)/CDMA(Code Division Multiple Access) with a device for injecting and detecting the pilot tone includes an interleaver(100), a series/parallel converter(101), a pilot symbol inserter(102), a pilot carrier inserter(103), a modulator(104), a parallel/series converter(105), a protect section inserter(106), a D/A converter(107) and an up converter(108). The interleaver(100) inputs the spread data and outputs the symbol data by interleaving them. The series/parallel converter(101) outputs the symbol data output from the interleaver(100)by lining up them. The pilot symbol inserter(102) inserts data output lined up into the field of time at regular intervals and outputs them. The pilot carrier inserter(103) inputs OFDM symbol data and outputs them at regular intervals in the frequency field by inserting pilot carrier. OFDM symbol data are input to the modulator(104) and the modulator(104) modulates and outputs OFDM symbol data. The parallel/series converter(105) outputs OFDM converted data by series. The protect section inserter(106) inserts the protect section into the output data and outputs them. The data, in which the protect section is inserted, are converted into analog data through the D/A converter(107) and are transmitted through the up converter(108) and the antenna.

Description

Orthogonal Frequency Division Multiplex / Signal Division Multiple Access Mobile Communication System with Pilot Tone Injection and Detection Device {OFDM / CDMA MOBILE COMMUNICATION SYSTEM HAVING PILOT TONE INSERTING AND DETECTING APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an orthogonal frequency division multiplex (OFDM) / code division multiple access (CDMA) mobile demodulation device. Particularly, the present invention relates to a demodulation device for accurate original data of received data in a receiver. The present invention relates to a device for injecting and detecting a pilot carrier and a pilot symbol.

Recently, as the types of multimedia services are diversified, high-speed data transmission is required, and at the same time, as the demand of consumers for the construction of wireless networks increases, the market of wireless asynchronous transfer mode (WATM) is expanded. As such, there is a demand for the implementation and acquisition of appropriate technologies. Due to the technical requirements for the WATM, the OFDM / TDMA scheme, which has various forms of technology accumulation as a modulation / demodulation technique of data, has become the basis. However, the conventional method has a weak point in terms of frequency utilization, which is a disadvantage of the TDMA method.

Due to this, the OFDM / CDMA scheme has recently been proposed to compensate for the shortcomings of the OFDM / TDMA scheme, and is one of the OFDM / CDMA schemes, which is called Multi-Code Division Multiple Access (MC-CDMA). The new method will be proposed and applied in various forms.

Since the MC-CDMA receiver is sensitive to frequency offset, a good frequency tracking device is needed. Therefore, in implementing the transmitter / receiver of the MC-CDMA, the conventional transmission signal is injected into the transmission signal in various forms for the channel equalization technique of the receiver in various forms or for synchronization. In practice, in such a technique, the conventionally proposed method, in which a pilot symbol having a predetermined time length is injected into a frame of a physical channel or a predetermined signal is placed on an out-band pilot channel, is proposed. Hard. Therefore, it is necessary to model the transmission signal to guarantee the performance of the receiver in a form suitable for system characteristics.

As described above, the conventional orthogonal frequency division multiple / signal division multiple access technique and the orthogonal frequency division modulation technique are used in a mixed system. Therefore, the conventional pilot tone injection is a multiple code orthogonal frequency division multiple / sign division multiple access sensitive to frequency offset. It is difficult to prevent channel degradation occurring at the receiver. In addition, the method of injecting pilot carriers at the same time also has a problem that the performance of the pilot carrier injection method of the conventional orthogonal frequency division modulation transmission method is difficult to guarantee the performance.

Accordingly, an object of the present invention is to inject a pilot tone in a frequency domain into orthogonal frequency division multiple symbol data when transmitting data in an orthogonal frequency division multiple / code division multiple access mobile communication system, and insert and transmit a pilot symbol in a time domain to transmit an orthogonal frequency. The present invention provides a pilot tone injection device of a transmitter for multiplex / code division multiple access mobile communication system.

Another object of the present invention is an orthogonal frequency division multiple / signal division multiple access mobile communication system for detecting an inserted pilot tone and a pilot symbol to compensate for data degradation when receiving data in an orthogonal frequency division multiplex / sign division multiple access mobile communication system. A pilot tone detection apparatus of a receiver is provided.

In order to achieve the above object, in the orthogonal frequency division multiplex / code division multiple access mobile communication system, pilot symbols are inserted at regular intervals in a time domain of a plurality of orthogonal frequency code division symbol data parallelized during data transmission. A transmitter for inserting and transmitting the same pilot carrier to each of the orthogonal frequency code division symbol data at a predetermined interval in a frequency domain; receiving the data transmitted from the transmitter to detect the pilot symbol and the pilot carrier; And a receiver for restoring the original data by the pilot carrier.

1 is a block diagram of a transmitter for an orthogonal frequency division multiple access / signal division multiple access mobile communication system according to an embodiment of the present invention;

2 is a block diagram of a receiver of an orthogonal frequency division multiple access / code division multiple access mobile communication system according to an embodiment of the present invention;

3 is a view showing a pilot tone injection method according to a first embodiment of the present invention.

4 is a view showing a pilot tone injection method according to a second embodiment of the present invention.

5 is a diagram illustrating the structure of a pilot symbol and a pilot carrier inserter according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals have the same reference numerals as much as possible even if displayed on different drawings. 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.

1 is a block diagram illustrating a transmitter in an orthogonal frequency division multiple access / signal division multiple access mobile communication system according to an exemplary embodiment of the present invention.

Hereinafter, referring to FIG. 1, the interleaver 100 is a frequency interleaver. The interleaver 100 receives spread data and interleaves the symbol data. The serial / parallel converter 101 parallelizes and outputs symbol data output from the interleaver 100 on a plurality of subcarriers. The pilot symbol inserter 102 inserts and outputs the data paralleled and output (hereinafter, referred to as "OFDM symbol data") at predetermined time intervals in the time domain. This will be described in detail with reference to FIG. 3. In FIG. 3, a pilot symbol is represented by T _{p (n)} . As such, the pilot symbol inserter 102 pops OFDM symbol data at regular time intervals in order to transmit the number of subcarriers and the length of a spreading code equal to the length before pilot symbol insertion in inserting at regular time intervals in the time domain. And inserts a pilot symbol into the punctured OFDM symbol data. In FIG. 3, as an example, a pilot symbol is punctured and inserted into every fourth OFDM symbol data on the time axis. The OFDM symbol data to be inserted here has a real value and an imaginary value of zero.

Detailed configurations of the pilot symbol inserter 102 and the carrier inserter 103 are shown in FIG. Hereinafter, referring to FIG. 5, reference numerals 501 and 502 referred to in FIG. 5 are multiplexers. And 503 and 505 are perforators.

The multiplexer 501 receives the N * A bit in-phase data (Inphase: I component) and N-bit pilot symbols input from the serial / parallel converter 101 and receives N * A bit timing information. The pilot symbol is inserted and output. A is a pilot symbol insertion period, and N is the number of bits of sample data. The multiplexer 501 inserts and outputs a pilot symbol in N * A bit periods. The multiplexer 502 receives data of quadrature components (Q components) of N * A bits output from the serial / parallel converter 101 and pilot symbols of N bits, and receives the N * A bit timing information. The pilot symbol is inserted and output.

The signal output from the multiplexer 501 is input to the puncturer 503. The pilot carrier index and the pilot carrier data of the puncturer 503 receiving the in-phase component data into which the pilot symbol is inserted are input, and the pilot carrier is inserted according to the pilot carrier index and output to the modulator 104. The puncturer 505 receives the data output from the multiplexer 502 and the pilot carrier index and the pilot carrier data in the same way as the puncturer 503 and is output from the multiplexer 502 according to the pilot carrier index. The pilot carrier data is inserted into the data and output to the modulator 104.

The pilot carrier inserter 103 receives OFDM symbol data inserted with pilot symbols in the time domain and inserts and outputs pilot carriers at predetermined frequency intervals in the frequency domain. The pilot carrier is represented by C _{p (k)} in FIGS. 3 and 4, and there are two methods for the pilot carrier injection method as in FIGS. 3 and 4. The first is a method of injecting pilot carriers in a constant frequency interval in the frequency domain as shown in Figure 3, the second is a method of masking and using an orthogonal pilot code in a certain section in the frequency domain as shown in FIG. The advantage of this method is that the number of IFFT subcarriers and the spreading code length can be kept the same without data puncturing in the frequency domain, and at the same time, the pilot carrier information can be detected at the receiver without data loss. The OFDM symbol data into which the pilot symbols and the pilot carriers are inserted is input to the modulator 104. The modulator 104 is an OFDM modulator and performs OFDM modulation on the OFDM symbol data input in parallel. The parallel / serial converter 105 serializes and outputs the OFDM modulated data again. The guard section inserter 106 inserts and outputs a guard section having a predetermined length to the serialized and output data. The data having the guard interval inserted therein is converted into analog data through the D / A converter 107 and transmitted through the up converter 108 and the antenna.

2 is a block diagram of a receiver of an orthogonal frequency division multiple access / code division multiple access mobile communication system according to an embodiment of the present invention. Hereinafter, an operation of a receiver by inserting a pilot symbol and a pilot carrier will be described with reference to FIG. 2.

First, the signal transmitted from the transmitter is received as analog data through the antenna of the receiver and the down converter 110. The A / D converter 111 receives the analog data, receives a predetermined clock, and converts the analog data into digital data and outputs the data. The first multiplier 112 multiplies the data output from the A / D converter 111 by a predetermined frequency synchronization signal and outputs the multiplied signal. The guard interval remover 113 receives a predetermined window timing and removes the guard interval from the data output from the first multiplier 112 and outputs the guard interval. The demodulator receives OFDM data from which the guard interval is removed and performs OFDM demodulation to output OFDM symbol data. The deinterleaver 115 is a frequency deinterleaver and deinterleaves the OFDM symbol data to output spread data. The symbol extractor 121 receives the deinterleaved spread data and detects and outputs two pilot tones, that is, a pilot symbol and a pilot carrier, which are reference signals from the spread data. The channel estimator 123 receives a pilot symbol from the symbol extractor 123, determines a channel degradation according to a channel state, and outputs a channel degradation compensation value for compensating for the channel degradation. The frequency synchronizer 122 receives a pilot symbol and a pilot carrier from the symbol extractor 121, generates a local oscillation frequency for frequency synchronization, and outputs the generated local oscillation frequency to the summator 112. The frame / time synchronizer 124 receives a pilot symbol from the symbol extractor 121 to correct an A / D converting offset of the A / D converter 111 (hereinafter, referred to as a “converting clock”). Output). In addition, the frame / time synchronizer 124 determines a timing start point of the FFT window to output the guard interval remover 113 to remove the guard interval from the guard interval remover 113.

The second multiplier 116 multiplies the spread data by the compensation value output from the channel estimator 123 and outputs spread data whose frequency offset is corrected. The despreader 125 despreads and outputs the spread data output from the second multiplier 116. The inverted data is restored to the original data through the demapper 117, the error corrector 118, the external interleaver 119, and the RS decoder 120.

As described above, according to the present invention, by inserting and transmitting a pilot symbol and a pilot carrier in an orthogonal frequency division multiplex / code division multiple access transmitter, an accurate frequency offset correction and an inverse of an accurate frequency offset in an orthogonal frequency division multiplex / sign division multiple access receiver sensitive to frequency offset There is an advantage in that the window timing synchronization and frequency error correction of the spreading and fast Fourier transform can be accurately performed.

Claims (11)

In the Orthogonal Frequency Division Multiple / Code Division Multiple Access mobile communication system, Transmitter inserts pilot symbols at regular intervals in the time domain of the parallelized orthogonal frequency code division symbol data in data transmission, and inserts and transmits the same pilot carriers at predetermined intervals in each of the orthogonal frequency code division symbol data in the frequency domain Wow, Orthogonal frequency having a pilot tone injection and detection device comprising a receiver for receiving the data transmitted from the transmitter to detect the pilot symbol and the pilot carrier, and restore the original data by the pilot symbol and pilot carrier Split multiple / sign split multiple access mobile communication system. The apparatus of claim 1, wherein the transmitter comprises a pilot symbol inserter for inserting pilot symbols at regular intervals in the time domain into orthogonal frequency division symbol data input from a serial / parallel converter. Orthogonal frequency division multiple / signal division multiple access mobile communication system. 3. The pilot tone injection method of claim 2, further comprising a pilot tone inserter for inserting a pilot carrier at regular intervals in a frequency domain and outputting orthogonal frequency division symbol data output from the pilot symbol inserter to a modulator. Orthogonal Frequency Division Multiplex / Code Division Multiple Access mobile communication system having a detection device. 3. The pilot tone injection and detection apparatus of claim 2, wherein the pilot symbol inserter inserts and punctures a predetermined interval in the time domain to equalize the number of subcarriers and the spreading code length before pilot symbol insertion. Orthogonal frequency division multiplexing / signal division multiple access mobile communication system. 4. The pilot tone injection and detection apparatus of claim 3, wherein the pilot carrier inserter inserts and punctures at a predetermined interval in the frequency domain to equalize the number of subcarriers and the spreading code length before pilot carrier insertion. Orthogonal frequency division multiplexing / signal division multiple access mobile communication system. 3. The method of claim 2, further comprising a pilot tone inserter for inserting a pilot carrier by masking an orthogonal frequency division symbol data output from the pilot symbol inserter at a predetermined interval of a frequency domain and inserting a pilot carrier. An orthogonal frequency division multiplexing / signal division multiple access mobile communication system having a pilot tone injection and detection device. The method of claim 1 wherein the receiver is An analog / digital converter that receives analog data, receives a predetermined clock, and converts the data into digital data; A first multiplier configured to receive the digital data and a predetermined local oscillation frequency, multiply them, and output the signals in synchronization with each other; A guard interval eliminator for receiving a predetermined window timing signal and removing a guard interval from data output from the first multiplier; A demodulator for receiving orthogonal frequency division demodulation and outputting orthogonal frequency division symbol data by receiving the data from which the guard interval is removed; A second multiplier configured to receive the orthogonal frequency division symbol data and a predetermined frequency offset estimate and correct and output a frequency offset of the orthogonal frequency division symbol data; A symbol extractor for detecting a pilot symbol and a pilot carrier from the data output from the demodulator; A frequency synchronizer which receives a pilot symbol and a pilot carrier from the symbol extractor, determines a local oscillation frequency for frequency synchronization, and outputs the first oscillator to the first multiplier; A channel estimator which receives a pilot symbol from the symbol extractor, calculates a channel degradation estimate according to a channel state, and outputs the estimated channel degradation value to the second multiplier; Pilot tone injection and receiving the pilot symbol from the symbol extractor and outputs the converting clock to the analog / digital converter, the fast Fourier transform window timing to output to the guard interval eliminator characterized in that the pilot tone injection and Orthogonal Frequency Division Multiplex / Code Division Multiple Access mobile communication system having a detection device. Orthogonal frequency division multiple access / code division multiple access mobile communication comprising an interleaver for interleaving predetermined data, a serial / parallel converter for converting the interleaved data into parallel data, and a modulator for receiving orthogonal frequency division modulation by receiving predetermined data. In the transmitter of the system, A pilot symbol inserter for inserting pilot symbols at regular intervals into the data input from the serial / parallel converter; Orthogonal frequency division multiplex / code division multiple access mobile communication having a pilot tone injector characterized in that the pilot carrier inserter for inserting the pilot carrier at a predetermined interval and then outputs the data output from the pilot symbol inserter system. The orthogonal frequency division multiplexing apparatus of claim 8, wherein the pilot symbol inserter inserts pilot symbols at regular intervals in the time domain into orthogonal frequency division symbol data inputted from a serial / parallel converter. Code Division Multiple Access Mobile Communication System. 10. The mobile communication system according to claim 9, wherein the pilot carrier inserter inserts the pilot carrier in the time domain. In the receiver of an orthogonal frequency division multiplex / code division multiple access mobile communication system for transmitting data including pilot symbols and pilot carriers, An analog / digital converter that receives analog data, receives a predetermined clock, and converts the data into digital data; A first multiplier configured to receive the digital data and a predetermined local oscillation frequency, multiply them, and output the signals in synchronization with each other; A guard interval eliminator for receiving a predetermined window timing signal and removing a guard interval from data output from the first multiplier; A demodulator for receiving orthogonal frequency division demodulation and outputting orthogonal frequency division symbol data by receiving the data from which the guard interval is removed; A second multiplier configured to receive the orthogonal frequency division symbol data and a predetermined frequency offset estimate and correct and output a frequency offset of the orthogonal frequency division symbol data; A symbol extractor for detecting a pilot symbol and a pilot carrier from the data output from the demodulator; A frequency synchronizer which receives a pilot symbol and a pilot carrier from the symbol extractor, determines a local oscillation frequency for frequency synchronization, and outputs the first oscillator to the first multiplier; A channel estimator which receives a pilot symbol from the symbol extractor, calculates a channel degradation estimate according to a channel state, and outputs the estimated channel degradation value to the second multiplier; Quadrature frequency division having a pilot tone detection device comprising a frame / time synchronizer for receiving a pilot symbol from the symbol extractor and outputting a converting clock to the analog / digital converter and outputting a window timing to the guard interval remover Multiple / Code Division Multiple Access Mobile Communication System.