KR20020014472A - Method and apparatus for masking cyclic prefix in mobile communication system - Google Patents

Abstract

PURPOSE: A device for masking a protection section of a mobile communication system is provided to mask protection section data inserted into the protection section by a subscriber orthogonal code, and to insert the masked data into the protection section, so as to perform user classification and frame synchronization in a receiving device. CONSTITUTION: A protection section data extractor(310) extracts information recorded in a predetermined section of a modulation signal as protection section data from an OFDM(Orthogonal Frequency Division Multiplexing)/CDMA modulator. A subscriber orthogonal code generator(314) generates subscriber orthogonal codes for subscriber classification. A multiplier(312) masks the protection section data of the protection section data extractor(310) to a subscriber orthogonal code from the subscriber orthogonal code generator(314). A multiplexer(316) inputs the modulation signal from the OFDM/CDMA modulator and a cyclic masking code of the multiplier(312), and outputs the cyclic masking code to a protection section insert timing.

Description

Protective section masking device and method of mobile communication system {METHOD AND APPARATUS FOR MASKING CYCLIC PREFIX IN MOBILE COMMUNICATION SYSTEM}

The present invention relates to an apparatus for high speed WATM implementation using MC-CDMA for WATM implementation.

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 increases according to the construction of the wireless network, the market of WATM expands, so that the implementation and acquisition of appropriate technologies are It is necessary.

At the same time, various countries have created various types of organizations for WATM standardization and are approaching various ways for macroscopic expansion of standardization for WATM implementation. At the same time, research on the implementation using the OFDM scheme for the implementation of such a high-speed data transmission technology has been actively conducted.

Various technologies have been developed and prepared for practical use in each country for the implementation of WATM. The OFDM / TDMA method, which has accumulated existing technologies in various forms as data modulation / demodulation technology, is the basis. However, the conventional method has a weak point in terms of frequency utilization, which is a disadvantage of the TDMA method, and recently, MC-CDMA method, which is one of OFDM / CDMA methods, has been newly proposed to compensate for such disadvantages. It is expected to be applied.

The biggest problem in the reception of the reverse link of the conventional MC-CDMA system is that the form transmitted from each user is transmitted asynchronously in the reverse direction. As a result, it is difficult to distinguish terminal users from each other. At the same time, in the case of MC-CDMA transmission, the synchronization technique of matching the starting point of the FFT of the receiver has the greatest influence on system demodulation. In the conventional scheme, the reverse data receiver reduces the overall data rate by inserting and transmitting additional information for user identification. At this time, the complexity of the system is increased and the computational amount is increased due to different user classification and FFT synchronization.

1 is a diagram illustrating a configuration of a transmitter using a conventional MC-CDMA scheme. Referring to FIG. 1, a signal interleaved and applied by an interleaver is QPSK modulated by the QPSK modulator 110 and output. The modulated signal is spread by two multipliers 112 and 114 into a Walsh code for channel classification and a PN code for identifying a base station, and then provided to the OFDM / CDMA modulator 116. The OFDM / CDMA modulator 116 performs OFDM / CDMA modulation on the applied signal. The OFDM / CDMA modulated signal is converted into an analog signal by the DAC 120 after the guard interval is inserted by the guard interval inserter 118. The transmission signal converted into the analog signal is modulated into a high frequency signal by the up-converter 122 and then transmitted through the antenna.

The configuration of the transmission signal output by the configuration of FIG. 1 is as shown in FIG. 4A. As shown in FIG. 4A, the conventional transmission signal has a form in which the last predetermined bits of one OFDM / CDMA symbol are inserted into a guard interval.

As described above, when receiving a conventional reverse link, after inserting a guide section for user identification, data called a SYNC BURST is injected, and this additional information insertion reduces the transmission efficiency of data. In addition, since the FFT frame synchronization is obtained again by using the guide interval after demonstrating the user for demodulation at the time of reception, not only the hardware configuration is complicated but also the amount of computation is large.

On the other hand, conventionally, by inserting the information for distinguishing the user into a separate transmission signal and transmitting it, additional hardware must be provided and data transmission efficiency is also lowered.

An object of the present invention for solving the above problems is to provide an apparatus and method for facilitating user identification in a receiver implementation using the MC-CDMA scheme.

Another object of the present invention is to provide an apparatus and method for improving data transmission efficiency by not inserting an additional information amount.

It is still another object of the present invention to provide an apparatus and method for reducing complexity and improving performance in implementing a receiver by simultaneously performing FFT frame synchronization prior to user classification and data reception demodulation.

1 is a view showing the configuration of a transmission apparatus of a conventional mobile communication system.

2 is a diagram illustrating a configuration of a transmission apparatus of a mobile communication system according to an embodiment of the present invention.

3 is a view showing a detailed configuration of the protective section masking portion disclosed in FIG.

4A is a diagram showing a frame configuration of a transmission signal output by a conventional transmission apparatus.

4B is a view showing a frame configuration of a transmission signal output by a transmitting apparatus according to an embodiment of the present invention.

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

FIG. 2 is a diagram illustrating the configuration of a transmitter according to an embodiment of the present invention, in which a user of a reverse receiver is injected by injecting a cyclic masking code in place of a guard interval injected as a protection scheme for multipath interference in a conventional OFDM transmitter. It shows a configuration that allows for differentiation. In other words, a transmitter has been proposed for masking and transmitting information inserted into a protection section as information for user identification without injecting additional information for user identification into a transmission terminal of a conventional reverse receiver. At this time, the most important thing to consider is to maintain the nature of the cyclic prefix of protection from the original multipath interference.

The configuration of the transmitter according to the embodiment of the present invention is contrasted with the configuration of the conventional transmitter in the configuration including the protective section masking unit 218 as shown in FIG. The guard period masking unit 218 masks a predetermined code for user identification in inserting bits of a predetermined period of an OFDM / CDMA symbol output from the OFDM / CDMA modulator 216 into the guard period.

Therefore, by using the cyclic masking code, the present invention simultaneously performs frame synchronization for obtaining user identification and the start of the FFT frame in the reverse receiver, thereby simplifying the circuit and reducing the amount of computation.

The detailed configuration of the above-described protective section masking unit 218 is as shown in FIG. Referring to FIG. 3, the guard interval data extractor 310 extracts guard interval data from an output signal from the OFDM / CDMA modulator 216. Subscriber orthogonal code generator 314 generates an orthogonal code for distinguishing subscribers. The multiplier 312 masks and outputs the guard interval data from the guard interval data extracting unit 310 with the subscriber identification code from the subscriber quadrature code generator 314. The multiplexer (MUX) 316 inputs a modulation signal from the OFDM / CDMA modulator 216 and a cyclic masking code from the multiplier 312. Therefore, the cyclic masking code is output at a timing corresponding to the protection interval, and the modulation signal is output at other timings. The timing corresponding to the guard period (Cyclic Prefix On Time) is provided by a controller (not shown) that controls the overall operation of the transmitter. Here, masking is not a concept of spreading, but refers to an operation of applying a user code to protection interval data once more by operating a code generator at the same rate as each symbol rate.

The configuration of the transmission signal output by the above operation is as shown in FIG. 4B. As shown in FIG. 4B, it can be seen that information of a predetermined region of one OFDM / CDMA symbol is copied, and the copied information is masked by a user identification code and inserted into a guard interval.

Meanwhile, as described above, the receiver of the base station receiving the transmission signal in which the information masked by the user identification code is inserted into the protection interval not only performs frame synchronization by reverse operation of the operation of the above-described transmitter but also simultaneously distinguishes users. Will be performed. That is, the reception apparatus of the base station acquires codes used by the users to distinguish the users, and then detects the data of the guide section among the received data at the front end of the FFT and then masks the received data in order to distinguish the users. When the reverse masking is performed, the absolute value is obtained by subtracting the reception size of the reverse masked data and the copied guard interval data by using the property that the energy value is greatest when despreading to its own code due to the property of the orthogonal code. Find the value. The above-described process is performed for each unit sample while moving for N samples corresponding to one OFDM symbol. At the same time, size the window section and do so over several guard intervals.

For example, if the length of an OFDM symbol is N, after receiving data of 2N + G, matching filtering is performed to obtain initial guide interval data, reverse mask the N user codes simultaneously, and obtain a sum thereof. Then, for each user code, check which code's matching filter output value is large while shifting the guard interval.

At this time, the transition region of the protection section calculates the maximum value while calculating the output of the matching filter in parallel by N + G (protection section). The code that provides the output corresponding to the maximum value obtained is the user code. If the shift value is ni, and if MAX (ni) -G / 2≤Wn≤MAX (ni) + G / 2 based on ni, then Wn is the observation function region. Correlate the copied original received signal of the despread data while moving, and estimate Wn which provides the largest value among them as the starting point of the FFT window.

As described above, the present invention masks the protection section data inserted into the protection section by the subscriber orthogonal code and inserts the protection section data into the protection section, so that the receiving apparatus can perform operations for frame synchronization and user synchronization at the same time, thereby simplifying hardware and calculating amount. The effect of reducing this can be obtained.

Claims (2)

In the device for inserting the protective section of the transmission device constituting the mobile communication system, A guard interval data extracting section for extracting information recorded in a predetermined section of the modulation signal from the OFDM / CDMA modulation section as guard interval data; A subscriber orthogonal code generator for generating a subscriber orthogonal code for distinguishing subscribers, A multiplier for masking guard interval data from the guard interval data extractor with a subscriber orthogonal code from the subscriber orthogonal code generator; And a multiplexer for inputting a modulation signal from the OFDM / CDMA modulator and a cyclic masking code from the multiplier, and outputting the cycling masking code at a guard interval insertion timing. In the method for inserting the protective section of the transmission device constituting the mobile communication system, Extracting information recorded in a predetermined section of the modulation signal from the OFDM / CDMA modulator as guard interval data; Generating a subscriber orthogonal code to distinguish between subscribers, Outputting a cyclic masking code by masking the guard interval data with the subscriber orthogonal code; And inputting a modulated signal from the OFDM / CDMA modulator and the cyclic masking code, and outputting the cycling masking code at a guard interval insertion timing.