KR100743361B1 - A Transmitting and Receiving Method using the Multi-Carrier Transmit Diversity based on Space Time SpreadingSTS for Mobile Communication Systems - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a multiple transmission frequency diversity transmission and reception method using a space-time spreading method in a mobile communication system.

2. The technical problem to be solved by the invention

The present invention processes a space-time encoded data signal in a space-time spreading (STS) scheme as a frequency pair (f1 and f2, f2 and f3, f3 and f1) instead of one frequency. STS diversity gain and new frequency diversity gain are obtained by transmitting each through an antenna, and thereby detecting fading and propagation paths that are independent of each other and transmitting data signals through the reverse process of the transmitting end in the received signals. The present invention aims to provide a multi-transmission frequency diversity transmission / reception method using a space-time spreading (STS) method and a computer-readable recording medium recording a program for realizing the method in a mobile communication system.

3. Summary of the Solution of the Invention

A diversity transmission method applied to a diversity transmission apparatus of a mobile communication system, comprising: a first step of demultiplexing a channel coded and interleaved user data signal into a predetermined number of data signals; A second step of dividing each user data signal demultiplexed in the first step into space block coding to divide the data stream into as many data streams as the number of transmit antennas; Spreading each of the divided data streams with a Walsh code, and then copying each of the spread data streams by a predetermined number; And multiply each of the spread data streams by a different transmission frequency for each of the spread data streams, and then combine and Walsh cover the respective data streams by which the different transmission frequencies are multiplied. A fourth step of transmitting.

4. Important uses of the invention

The present invention is used for diversity transmission and reception in a mobile communication system.

Mobile communication system, diversity, diversity transmission, multiple transmission frequency, STS, space-time spreading method.

Description

A Transmitting and Receiving Method using the Multi-Carrier Transmit Diversity based on Space Time Spreading (STS) for Mobile Communication Systems}             

1 is a block diagram of an embodiment of a multiple transmission frequency diversity transmission apparatus using a space-time spreading (STS) scheme in a mobile communication system according to the present invention.

2 is a configuration diagram of an apparatus for receiving multiple transmission frequency diversity using a space-time spreading (STS) scheme in a mobile communication system according to the present invention.

3 is a flowchart illustrating a method for transmitting / receiving multiple transmission frequency diversity using a space-time spreading (STS) scheme in a mobile communication system according to the present invention.

4 is an explanatory diagram of the performance of the multiple transmission frequency diversity transmission and reception method according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity transmission / reception method in a mobile communication system, and in particular, a space-time encoded data signal in a space-time spreading (STS) scheme instead of one frequency, instead of one frequency. , f2 and f3, f3 and f1) are transmitted through a plurality of antennas, respectively, and because of this, they undergo independent fading and propagation paths and detect data signals transmitted through the reverse process of the transmitter in the received signals. In the mobile communication system to obtain the STS diversity gain and the new frequency diversity gain, a multi-transmission frequency diversity transmission / reception method using a space-time spreading (STS) method and a computer for recording the program for realizing the method are provided. The present invention relates to a readable recording medium.

In a wireless channel environment that suffers from fading severely, such as mobile communication, the power of a received signal changes rapidly in time, and various diversity techniques can be used to reduce the effects of such fading.

In IS-95, a standard adopted by cellular and PCS, the diversity effect is obtained by using two receiving antennas at a base station in uplink connected from a terminal station to a base station. A method for improving downlink performance through the applied transmit diversity scheme is being considered.

In the current cdma2000, an orthogonal transmit diversity (OTD) method and a space time spread (STS) method are selectively used in a direct spread (DS) method and a multi-carrier (MC) method.                         

Currently, in IS-95, the diversity effect is obtained by using two receiving antennas at the base station in the uplink accessing from the terminal station to the base station. However, these receiving antennas have major problems in terms of cost, size, and power with the terminal station. do.

Therefore, the diversity scheme is more effective for the base station than the terminal station. However, in the downlink, it is difficult for the receiving side to install two receiving antennas in the terminal station. The path is not independent and it is difficult to expect a performance improvement.

For the above reason, a transmission diversity scheme for transmitting a transmission antenna by installing a transmission antenna in a base station rather than having two reception antennas in a terminal station has recently been developed for the IMT2000 system and is known to have a significant performance improvement.

The transmission diversity scheme currently in progress in cdma 2000 is divided into direct spread (DS) and multi-carrier (MC) methods using orthogonal transmit diversity (OTD) and space time spread (STS). It is selectively adopted in accordance with.

In the multi-carrier (MC) scheme, a conventional technique using space-time spreading (STS) transmission diversity is to demultiplex channel-coded and interleaved signals to reduce fading. These signals are space block coded with a space-time spreading (STS) technique. For example, assuming two data signals, Y ₁₁ and Y _12, the signals transmitted to each antenna are shown in Table 1 below.

        Antenna 1            Antenna 2   Time t Y ₁₁ Y ₁₂   Time t + T -Y ₁₂ * Y ₁₁ *

Here, "*" points to a conjugate complex number.

By transmitting to two independent antennas on each transmission frequency, the receiver could only receive the transmission signal at the transmitted transmission frequency. This transmit diversity effect is based on a non-selective channel environment where the channel is constant at each transmission frequency. Although the spatial and temporal diversity gains of the independent antennas can be obtained, there is a problem in that the frequency diversity gains cannot be brought in a frequency selective channel environment such as a case where a fading occurs rapidly at the transmission frequency of each antenna.

The present invention has been made to solve the above-described problem, and the frequency-paired data signal in the space-time spreading (STS) method, rather than one frequency pair (f1 and f2, f2 and f3, f3 and f1) are transmitted through a plurality of antennas, respectively, and are thus subjected to independent fading and propagation paths to detect data signals transmitted through the reverse process of the transmitting end in the received signals. An object of the present invention is to provide a multiple transmission frequency diversity transmission and reception method using a space-time spreading (STS) method in a mobile communication system, and a computer-readable recording medium recording a program for realizing the method.

According to an aspect of the present invention, a diversity transmission method applied to a diversity transmission apparatus of a mobile communication system includes demultiplexing a channel coded and interleaved user data signal into a predetermined number of data signals. A first step of making; A second step of dividing each user data signal demultiplexed in the first step into space block coding to divide the data stream into as many data streams as the number of transmit antennas; Spreading each of the divided data streams with a Walsh code, and then copying each of the spread data streams by a predetermined number; And multiply each of the spread data streams by a different transmission frequency for each of the spread data streams, and then combine and Walsh cover the respective data streams by which the different transmission frequencies are multiplied. A fourth step of transmitting.
Meanwhile, the present invention provides a diversity reception method applied to a diversity reception apparatus of a mobile communication system for receiving and processing a signal transmitted according to a multiple transmission frequency diversity transmission method using a space-time spreading method, through an antenna. Performing a Walsh uncovering operation using a plurality of Walsh codes different from each other on the received data signal; After detecting the transmission data signal for each transmission frequency by uncovering each of the Walsh uncovered data signals in the first step with different transmission frequency pairs used at the transmitting side, the detected transmission data is detected. Frequency combining the signals; And a third step of multiplexing the frequency-coupled data signals, deinterleaving the channelized data signal, and channel decoding to restore the original data signal transmitted from the transmitter.

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Meanwhile, the present invention provides demultiplexing of a channel coded and interleaved user data signal into a predetermined number of data signals in a diversity transmission apparatus having a processor for multiple transmission frequency diversity transmission using a space-time spreading scheme. a first function of demultiplexing; A second function of dividing each user data signal demultiplexed in the first function into space block coding and splitting the data stream into as many data streams as the number of transmit antennas; A third function of spreading each of the divided data streams with a Walsh code, and then copying each of the spread data streams by a predetermined number; And multiply each of the spread data streams by a different transmission frequency for each of the spread data streams, and then combine and Walsh cover the respective data streams by which the different transmission frequencies are multiplied. A computer readable recording medium having recorded thereon a program for realizing a fourth function of transmission is provided.

On the other hand, the present invention, in order to receive the signal transmitted according to the multi-frequency diversity transmission method using the space-time spreading method, the diversity receiving apparatus having a processor, the data signal received through the antenna to each other A first function of performing Walsh uncovering using another plurality of Walsh codes; After detecting the transmission data signal for each transmission frequency by uncovering each of the Walsh uncovered data signals in the first function with different transmission frequency pairs used at the transmitting side, the detected transmission data is detected. A second function of frequency combining the signals; And a program for realizing a third function of multiplexing the frequency-coupled data signals, deinterleaving the channelized data signal, channel decoding, and restoring the original data signal transmitted from a transmission apparatus. Provides a recording medium that can be read by
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

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1 is a configuration diagram of an apparatus for transmitting a multi-frequency diversity diversity using a space-time spreading (STS) scheme in a mobile communication system according to the present invention, and shows a diver using a time-space spreading scheme in a frequency selective channel environment. A city transmitting apparatus.

After the data signal X of each user having a bit interval T _b is transmitted by the channel coding unit 100 at a code rate of 1/3, and interleaved by the interleaver 102 again, The demultiplexer 104 is demultiplexed into three complex data streams Y ₁ , Y ₂ , and Y ₃ , respectively.

The time-space spreader 108 of the transmit diversity unit 106 is used to generate two data signals Y ₁ , Y ₂ , and Y ₃ by a space block coder 110. It is divided into data streams. In other words, Y ₁ is divided into Y ₁₁ and Y ₁₂ , Y ₂ is divided into Y ₂₁ and Y ₂₂ , and Y ₃ is divided into Y ₃₁ and Y ₃₂ with half the data rate.

Based on the space block coding described above, each data signal is time-space spread (STS) and then spread to a Walsh code (i.e., Y ₁₁ is W ₁ and Y ₁₂ is W _2). (112, 114) and combine the respective data signals (116, 118) spread with their different Walsh codes.

After spreading the different Walsh codes, the combined data signals are multiplied by different transmission frequency pairs (for example, f ₁ , f _2, etc.) instead of one frequency, and then separated by Walsh covering. And transmit to the antenna (130,138).

That is, the data signals spread by the copiers 120 and 122 to the different Walsh codes are copied, and each of the copied data signals is multiplied by different transmission frequencies (124 and 126), and the different transmissions are performed. After combining the respective data signals multiplied by the frequency (125, 136), it is separated through the Walsh covering (Walsh covering) and transmitted to the antenna (130, 138). Here, specific processes of "116", "118", 125 ", and" 136 "are shown in Equation 1 below.

For example, if three transmission frequencies (f ₁ , f ₂ , f ₃ ) are used, three Walsh codes may exist, w ₁ between the transmission frequencies f ₁ , f ₂ , and f _2. , the f ₃ w ₂ between, allocates f _3, f ₁ w ₃ between each.

If we assume two transmit antennas, the signal sent to each antenna is the same signal is sent to the same antenna through two different frequencies, and the signals are separated through Walsh covering. .

The data signal s ₁₁ (t) transmitted from the antenna 1 may be expressed as Equation 1 below.

Similarly, the data signal s ₁₂ (t) transmitted from the antenna 2 may be expressed as Equation 2 below.

Here, P _i denotes the transmission power of the user, W ₁ , W ₂ is a spread Walsh code (doubled) as shown in the following equation (3).

And w _i (t) represents a Walsh code assigned to transmission frequencies f ₁ and f ₂ .

On the other hand, the data signals s ₂₁ (t), s ₂₂ (t), s ₃₁ (t), and s ₃₂ (t) are also transmitted in the same manner as described above (142, 144).

Finally, the signal transmitted through antenna 1 is the combined signal of s ₁₁ (t), s ₂₁ (t), and s ₃₁ (t), and the signal transmitted through antenna 2 is s ₁₂ (t), s ₂₂ (t), and s ₃₂ (t) are combined signals (140).

2 is a configuration diagram of an apparatus for receiving multiple transmission frequency diversity using a space-time spreading (STS) scheme in a mobile communication system according to the present invention, and shows a diver using a time-space spreading scheme in a frequency selective channel environment. It relates to a city receiving device.

A method for detecting a transmission signal by the STS diversity method according to the present invention. The method of detecting at a receiving end is received by one antenna through independent fading for each transmitting antenna and a frequency selective radio channel environment by L multipath propagation. Signals are separated by multiplying Walsh uncovering and multiplying each transmission frequency to detect the transmission signal in the same manner as the conventional STS receiver.

That is, in consideration of independent fading for each antenna in the transmission channel and frequency selective channel environment by L multiple propagation, the receiving device received with one antenna 200 transmits the i th signal transmitted from each antenna to a different transmission frequency. The user data is first separated by Walsh uncovering from the reception diversity unit 204 (206), and then separated through the transmission frequency (208, 210), thereby transmitting the signal in the same manner as the conventional STS receiver. Can be detected. That is, the received signal for the transmission frequency f ₁ can be represented as follows.

Here, h _{1, f 1, k} (t) and h _2, f ₁ , k (t) indicate the complex channel value experienced by the k- th at the transmission frequency f ₁ of each antenna, and n (t) indicates white noise.

_f1,k(t)과

_f1,k(t) 을 가지고 상관기의 출력값이 전송 주파수 f₁에 대해서 다음의 (수학식 5)와 같은 STS 수신방법으로 검출된다.
In the STS receiving unit 212, the channel value predicted by the channel estimator 202.

_{f1, k} (t) and

_{With f1, k} (t), the output of the correlator is detected for the transmission frequency f ₁ by the STS receiving method as shown in Equation 5 below.

As above, the output value of the k- th STS receiver for the transmission frequency f ₂ is expressed by Equation 6 below.

Therefore, the signal received here is not only for the existing spatial and temporal diversity gains, but also for the fading experienced at different frequencies per same antenna through the frequency combining process by the frequency combiner 214, as shown in Equation 7 below. By considering the impact, the frequency diversity gain can also be brought.

       Meanwhile, data detection for other transmission frequencies may also be detected in the same manner as described above (222 and 224). The frequency-coupled data signals are then multiplexed by the multiplexer 216, deinterleaved by a deinterleaver 218, and then channel decoded by the channel decoder 220. The process recovers the signal transmitted from the transmitter.

3 is a flowchart illustrating a method for transmitting / receiving multiple transmission frequency diversity using a space-time spreading (STS) scheme in a mobile communication system according to the present invention.

First, the transmission process 300 will be briefly described as follows.

In the multi-frequency STS transmit diversity method, a new multi-transmit frequency STS transmit diversity is improved by the frequency diversity gain together with the existing space-time coding gain in a real mobile communication environment in which multipath components exist. will be.

That is, the user data signals input to the transmitting apparatus (301), the channel coding (302) and the interleaving (303) in the STS scheme of the multiple transmission frequency are demultiplexed (304), and the same method as in the conventional STS. Space block coding is performed (305).

Subsequently, the space-time spread 306 user signals are copied through the space block coding, and each copied signal is multiplied by a different transmission frequency and transmitted through an antenna (307). Here, signals transmitted through different frequencies for each antenna are distinguished through Walsh coverings.

In a wireless channel environment that suffers severe fading, such as mobile communication, the power of a received signal is drastically changed in time, and Gaussian noise is added to be received by the receiver (310 and 311).

Hereinafter, the reception process 320 will be described briefly as follows.

The receiver detects the corresponding transmission signal for each antenna by performing uncovering again with Walsh and the transmitted frequency (321).

The frequency-coupled data signals through the frequency combining process 323 are further multiplexed (324), deinterleaved (325), and then transmitted through a channel decoding process (328) by a channel decoder (transmitter). In step 328, the data signal transmitted is recovered.

Therefore, the reception method of the present invention can detect the same data signal transmitted at different transmission frequency per same antenna through the frequency combining process, compared to the conventional method of receiving one frequency per antenna.                     

4 is an explanatory diagram of the performance of the multiple transmission frequency diversity transmission and reception method according to the present invention.

The results in the figure are taken into account when the speed of the terminal in the frequency selective channel is 3km / h and 120km / h through the simulation.

As shown in the figure, the present invention exhibits lower performance than the conventional MC STS in a frequency non-selective environment in which one channel path is considered, but as the channel environment becomes more severe (that is, the channel path increases and the speed of the terminal is increased). As is increased, the performance is improved compared to the conventional MC STS.

That is, in case of undergoing frequency selective channel fading as in a wireless channel environment such as real mobile communication, the received signal is received by the receiver through a combination technique such as MRC or EGC, and the received signal has the spatial and temporal diversity gain of the STS technique. In a channel-selective real channel environment where the channel environment is severely changed due to multiple propagation, such as downtown, there is an advantage in that the frequency transmission diversity effect can be brought together.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited by the drawings.

As described above, the present invention provides a frequency diversity gain as well as a conventional spatial and temporal diversity gain in a frequency selective channel environment by multiple propagation such as a real wireless mobile communication channel environment through a transmission diversity scheme using a multiple transmission frequency STS scheme. As a result, it is possible to implement transmission diversity suitable for a channel environment such as downtown with improved performance.

That is, the present invention has a gain of more than 3dB of Eb / No compared to the case where the base station does not use transmit diversity, which means that the subscriber capacity is increased by 30% or more, significantly lowering the investment cost per subscriber and significantly increasing the profitability. There is an effect that can be improved. In addition, the present invention has an effect of improving the profitability by increasing the subscriber capacity without increasing the cost through the performance improvement of about 1dB in the actual operating propagation environment compared to the existing STS scheme.

Claims (6)

delete In the diversity transmission method applied to the diversity transmission apparatus of a mobile communication system, A first step of demultiplexing the channel coded and interleaved user data signal into a predetermined number of data signals; A second step of dividing each user data signal demultiplexed in the first step into space block coding to divide the data stream into as many data streams as the number of transmit antennas; Spreading each of the divided data streams with a Walsh code, and then copying each of the spread data streams by a predetermined number; And Each spread data stream is multiplied by a different transmission frequency to each of the spread data streams, and then the respective data streams multiplied by the different transmission frequencies are combined, Walsh covered, and transmitted through a transmission antenna. 4th step Multiple transmission frequency diversity transmission method using a space-time spreading method in a mobile communication system comprising a. The method of claim 2, The Walsh covering process of the fourth step, For each transmission frequency pair used in the modulation process, Walsh covering is performed using different Walsh codes, and multiple transmission frequency divers using a space-time spreading method in a mobile communication system. City transmission method. A diversity reception method applied to a diversity reception apparatus of a mobile communication system for receiving and processing a signal transmitted according to a multiple transmission frequency diversity transmission scheme using a space-time spreading scheme, A first step of performing Walsh uncovering using a plurality of Walsh codes different from each other on a data signal received through an antenna; After detecting the transmission data signal for each transmission frequency by uncovering each of the Walsh uncovered data signals in the first step with different transmission frequency pairs used at the transmitting side, the detected transmission data is detected. Frequency combining the signals; And A third step of multiplexing the frequency-coupled data signals, deinterleaving the channelized data signal, and channel decoding to restore the original data signal transmitted from a transmitter; Multiple frequency diversity reception method using a space-time spreading method in a mobile communication system comprising a. In the diversity transmission apparatus having a processor for multiple transmission frequency diversity transmission using a space-time spreading scheme, A first function of demultiplexing the channel coded and interleaved user data signal into a predetermined number of data signals; A second function of dividing each user data signal demultiplexed in the first function into space block coding and splitting the data stream into as many data streams as the number of transmit antennas; A third function of spreading each of the divided data streams with a Walsh code, and then copying each of the spread data streams by a predetermined number; And Each spread data stream is multiplied by a different transmission frequency to each of the spread data streams, and then the respective data streams multiplied by the different transmission frequencies are combined, Walsh covered, and transmitted through a transmission antenna. 4th function to A computer-readable recording medium having recorded thereon a program for realizing this. In order to receive and process a signal transmitted according to a multi-frequency diversity transmission scheme using a space-time spreading scheme, a diversity receiver including a processor includes: A first function of performing Walsh uncovering using a plurality of Walsh codes different from each other on a data signal received through an antenna; After detecting the transmission data signal for each transmission frequency by uncovering each of the Walsh uncovered data signals in the first function with different transmission frequency pairs used at the transmitting side, the detected transmission data is detected. A second function of frequency combining the signals; And A third function of multiplexing the frequency-coupled data signals, deinterleaving the channelized data signal, and channel decoding to restore an original data signal transmitted from a transmission apparatus A computer-readable recording medium having recorded thereon a program for realizing this.

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