KR100474890B1 - Method for transmitting data in LAS-CDMA(large-area synchronized code-division multiple access) system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method in a mobile communication system. In particular, the present invention relates to a LAS (LAS) adapted to be suitable for transmitting data according to a transmission channel environment in an LAS-code division multiple access (LAS-CDMA) system. The present invention relates to a data transmission method in a code division multiple access system. In the LAS system, a data transmission method uses an IFW (FW) suitable for a channel environment of the transmitter and the receiver by measuring a signal-to-noise ratio (SIR) and a delay spread of the pilot signal at the receiver receiving the pilot signal transmitted from the transmitter. And a second step of transmitting data to the receiver by applying an LS code having an IFW interval selected by the transmitter to the receiver.

Description

Method for transmitting data in LAS-CDMA (large-area synchronized code-division multiple access) system}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method in a mobile communication system. In particular, the present invention relates to data transmission in an LAS code division multiple access (LAS-CDMA) system so as to be suitable for improving transmission efficiency by transmitting data. The present invention relates to a data transmission method in a mobile communication system.

Large-Area Synchronized Code-Division Multiple Access (LAS-CDMA) system is a PN sequence and Walsh (hereinafter referred to as CDMA) system used in Code Division Multiple Access (CDMA) system. In the LAS-CDMA system, LA code is used to distinguish cells and sectors, and LS code is used for signal spreading. Is given.

Among them, the LS code serves as a PN sequence and Walsh code in the existing CDMA system. That is, it has a signal spreading function and a user classification or channel classification function.

Here, the signal spread in the LAS-CDMA system is spread by multiplying the LS code of several chip lengths by one bit or symbol like the PN sequence in the CDMA system. Channel division uses orthogonal properties between LS codes. That is, the orthogonality between users and channels can be maintained by assigning LS codes to users or channels that need to be distinguished.

Hereinafter, a general LAS code division multiple access system will be described with reference to the accompanying drawings.

1 is a diagram for explaining an LS code in a typical LAS code division multiple access (LAS-CDMA) system.

LS codes are directly proportional to the number of codes along their length, like Walsh codes. For example, if the LS code length is 16 chips, the total number of LS codes that can be used is 16. As shown in FIG. 1, the total number of codes according to the code length can be allocated up to 128 users or 128 channels if the LS code having a length of 128 chips is used.

FIG. 2 is a diagram illustrating a state in which different codes are shifted by an arbitrary chip in a typical LAS code division multiple access (LAS-CDMA) system, and FIGS. 3A and 3B are typical LAS code division multiple access (LAS-CDMA) systems. FIG. 4 illustrates an IFW (Interference Free Window) in autocorrelation value and cross-correlation value of LS code in a system. FIG. 4 simultaneously displays IFWs having different sizes in a typical LAS code division multiple access (LAS-CDMA) system. The figure shows the change in the overall IFW when sending.

When the LS code has no phase difference, autocorrelation is maximized, and cross correlation between LS codes is zero. That is, there is a characteristic that the cross-correlation value between LS codes in a case where there is no phase difference (synchronization SYNC is correct) becomes zero. This characteristic is the same as that of Walsh code.

The LS code has a section where there is no interference called an IFW (Interference Free Window). That is, the LS code has a characteristic that the autocorrelation value and the cross correlation value of the code become zero in the IFW section.

Here, the correlation value can be obtained when there is a shift by an arbitrary k chip as shown in FIG. 2, where the autocorrelation value has the maximum autocorrelation value when there is no phase difference. The LS code also has the maximum autocorrelation value when there is no phase difference. That is, as shown in FIGS. 3A and 3B, the autocorrelation value becomes zero at the phase difference of up to n chips before and after the phase difference is zero with respect to zero. In addition, the cross-correlation value becomes 0 similarly in the section which has a phase difference of -n-n. In this case, the LS code has an IFW section of [-n, n].

The number of codes having an IFW interval and an IFW is limited, and the number of LS codes is determined by the code length and the IFW value. If the code length is 128 chips, the total LS codes are 128, but not all codes have the same IFW interval.

For example, for an LS code of length 128, 16 codes with [-7,7], 16 codes with [-3,3], 32 codes with [-1,1] and [0,0] It has 64 codes.

By using such an LS code, interference caused by signals of other users and interference caused by multipaths can be significantly reduced. That is, the signal-to-interference ratio (SIR) is improved because the correlation value becomes 0 (interference is 0) for multipath by its own transmission signal, multipath by another user, or multipath signals received in IFW interval. This results in a substantial increase in transmission efficiency. In addition, since the cross-correlation value of the LS code becomes 0 in the [-n, n] section, the cross-correlation value becomes 0 even in a situation where it is not perfectly synchronized with another user's signal.

However, if the IFW transmits a small code and the IFW large code at the same time, the whole IFW becomes equal to the small IFW. For example, when the code having IFW of [-3, 3] and the code having IFW of [0, 0] are simultaneously sent, the IFW becomes [0, 0] as shown in FIG. That is, there is no IFW section.

FIG. 5 is a diagram for explaining a data transmission frame in a typical LAS code division multiple access (LAS-CDMA) system.

As shown in FIG. 5, the physical structure of the data transmission frame of the LAS-CDMA system is composed of one header and nine subframes (subframes 0 to 8) that transmit user data in one frame of 20 ms. One subframe consists of 17 time slots, of which the first time slot (time slot 0) is used as a pilot. One time slot consists of an 8-chip gap (4 chips + 4 chips) and 128 LS chips (LS Coded Data 64 chips + LS Coded Data 64 chips) with no data transmitted at 136 chips. Coded data is sent.

The conventional CDMA system measures the received SNR at the receiver to determine how much transmission rate it can receive at the present time and informs the transmitter. Then, the transmitting end can predict the quality of the current communication channel and accordingly determine the transmission transmission rate and transmit.

At this time, there are the following methods to change the transmission rate required by the user at the transmitting end.

First, if the communication environment is good, use a transmission method that enables high-speed data transmission such as quadrature amplifier modulation (QAM). Otherwise, phase shift modulation (PSK: You can select a transmission method such as Phase Shift Keying).

Next, there is a method of efficiently using a limited radio channel by changing a coding rate according to a channel environment. By using coding, this method reduces redundancy by giving redundancy to information data.

In other words, we use a method that reduces data rate by using strong coding, which increases redundancy and decreases the coding rate in very poor channels, while reducing redundancy and improves the coding rate for a better channel environment. Applies how the data rate is increased.

In a typical LAS-CDMA system, the received signal-to-interference ratio (SIR) or error rate is used to analyze the user's communication environment.

That is, the LAS-CDMA system increases the efficiency of the system by minimizing the interference of the multipath signal between the magnetic signal and the signal of another user due to the characteristic of the LS code. Therefore, if the receiver decides only the transmission rate by applying the simple signal-to-interference ratio (SIR) or the error rate, the characteristics of LAS-CDMA cannot be used sufficiently.

In addition, there is a problem in that the number of codes that can be used is larger as the characteristic of the LS code, the larger the interval of the signal interference, that is, the IFW interval.

The data transmission of such a general LAS-CDMA system has the following problems.

At the receiver, the signal-to-interference ratio (SIR) or error rate is very good and requires a high transmission speed, but when multipath is long, many LS codes are allocated to users who require high-speed transmission. The overall IFW length of the code can be shortened.

However, the current LAS-CDMA scheme requires high speed regardless of the length of the IFW. Therefore, if a large number of LS codes are transmitted, the receiver may increase the interference due to multipath.

This problem is to assign a code having an arbitrary IFW to the user in the situation that the channel status of the receiving end is not known. That is, the LS code according to the IFW could not be efficiently allocated to a plurality of users.

And when such efficient code assignment is not made, if a user has LS codes with a wide range of IFWs because a certain user has a lot of interference due to multipath of other users and its range is large, the system already has a wide range of IFWs. If the codes with 하였다 are allocated to a user with good channel conditions without much interference, a significant capacity reduction is shown for the system. Therefore, there is a need for a method of allocating a code having an appropriate IFW interval to a user by analyzing the channel environment of the user in advance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and is a mobile communication system capable of increasing transmission efficiency by transmitting data according to a transmission channel environment in an LAS code division multiple access (LAS-CDMA) system. To provide a data transmission method in.

According to a feature of the present invention for achieving the above object, the receiving end receiving the pilot signal transmitted from the transmitting end to measure the signal-to-noise ratio (SIR) and delay spread of the pilot signal suitable for the channel environment of the transmitting end and the receiving end And a second step of selecting an IFW interval and a second step of transmitting data to the receiver by applying an LS code having an IFW interval selected by the transmitter.

Preferably, the step of transmitting data to the receiving end by applying the LS code, the transmitting end, the step of transmitting the signal-to-noise ratio and the selected IFW interval to the transmitting end, and the LS having the IFW interval in the transmitting end Selecting a code and transmitting the selected LS code information to the receiving end before transmitting the data by applying the LS code from the transmitting end to the receiving end.

Hereinafter, a configuration and an operation according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

6 is a diagram illustrating a data transmission method in an LAS code division multiple access (LAS-CDMA) system according to a first embodiment of the present invention.

The data transmission method in the LAS code division multiple access system according to the first embodiment of the present invention is for allocating a code having an appropriate IFW to a user by grasping the environment of a transmission channel in advance in the LAS-CDMA system. As described above, the transmitter of the LAS-CDMA system transmits a pilot signal to the receiver in order to determine the state of the transmission channel (S11).

The receiver uses the pilot signal to measure the strength of a received signal such as SIR, finds the received signal delayed by multipath, and obtains a delay spread of the signals (S12).

Then, the IFW suitable for the channel situation is selected using the SIR and the delay spread (S13), and the SIR is transmitted to the transmitting end together with the SIR (S14).

The transmitting end selects the LS code having the selected (suitable) IFW using this information (S15).

The transmitter transmits data by applying the selected LS code (S17), and informs the receiver of the selected LS code information (S16).

The receiving end receives the data by applying the LS code (S18).

FIG. 7 is a diagram illustrating a data transmission method in an LAS code division multiple access (LAS-CDMA) system according to a second embodiment of the present invention.

In the LAS code division multiple access system according to the second embodiment of the present invention, a data transmission method does not transmit SIR and IFW from a receiver to a transmitter, but calculates the transmission rate and LS code by calculating the SIR and IFW in advance at the receiver. By using the method of transmitting this to the transmitting end, the transmitting end transmits a pilot signal to the receiving end to determine the state of the transmission channel (S21).

The receiver uses the pilot signal to measure the strength of a received signal such as SIR, finds the received signal delayed by multipath, and obtains a delay spread of these signals (S22).

Next, the IFW suitable for the channel situation is selected using the SIR and the delay spread (S23), and the transmission rate and the LS code are determined using the IFW together with the SIR (S24).

Subsequently, the receiving end requests the transmitting end to transmit data according to the transmission rate and LS code information determined in the previous step (S24) using the SIR and the IFW (S25).

The transmitting end determines the transmission rate and the LS code to be transmitted to the receiving end according to the transmission rate and LS code information determined by the receiving end (S26).

Subsequently, the transmitting end transmits the selected LS code information to the receiving end (S27), and the transmitting end transmits data to the receiving end by applying the selected LS code (S28). The receiving end receives the data (S29).

8 is a diagram illustrating a data transmission method in an LAS code division multiple access (LAS-CDMA) system according to a third embodiment of the present invention.

In the LAS code division multiple access system according to the third embodiment of the present invention, a data transmission method of a transmitting end and a receiving end pre-determines the type of LS codes used according to the transmission speed, and stores the same in advance, and has a SIR and an IWF at the receiving end. In order to use the method of determining only the transmission to the transmitting end, the transmitting end transmits a pilot signal to the receiving end to determine the state of the transmission channel (S31).

The receiver uses the pilot signal to measure the strength of a received signal such as SIR, finds the received signal delayed by multipath, and obtains a delay spread of these signals (S32).

Next, the IFW suitable for the channel situation is selected using the SIR and the delay spread (S33).

Subsequently, the transmission rate is determined by comparing the predetermined rate table with the SIR and IFW (S34).

Next, the receiving end requests the transmitting end to transmit data according to the transmission rate determined in the previous step (step S34) and the transmission rate according to the LS code information using the SIR and the IFW (S35).

The transmitting end selects the LS code according to the transmission rate determined by the receiving end (S36).

Subsequently, the transmitting end transmits the selected LS code information to the receiving end (S37), and the transmitting end transmits data to the receiving end by applying the selected LS code (S38). The receiving end receives data (S39).

As described above, the data transmission method in the LAS-CDMA system of the present invention analyzes the channel environment of the user in advance and allocates a code having an appropriate IFW interval to the user, thereby solving the code shortage problem according to the IFW interval length. Receiving end receives relatively little interference because it can guarantee proper IFW duration to user, and thus, transmitting end can transmit data through relatively low transmission power, which can improve the channel capacity of system. .

1 is a diagram for explaining an LS code in a typical LAS code division multiple access (LAS-CDMA) system.

2 is a view showing a state in which different codes are shifted by an arbitrary chip in a typical LAS code division multiple access (LAS-CDMA) system.

3A and 3B are diagrams for explaining IFW in autocorrelation values and cross-correlation values of LS codes in a typical LAS code division multiple access (LAS-CDMA) system.

4 is a view for explaining the change in the overall IFW when simultaneously sending different size IFW in a typical LAS code division multiple access (LAS-CDMA) system

5 is a diagram illustrating a data transmission frame in a typical LAS code division multiple access (LAS-CDMA) system.

6 is a diagram illustrating a data transmission method in an LAS code division multiple access (LAS-CDMA) system according to a first embodiment of the present invention.

7 is a diagram illustrating a data transmission method in an LAS code division multiple access (LAS-CDMA) system according to a second embodiment of the present invention.

8 is a diagram illustrating a data transmission method in an LAS code division multiple access (LAS-CDMA) system according to a third embodiment of the present invention.

Claims (4)

Receiving a pilot signal transmitted from a transmitter to measure a signal-to-noise ratio (SIR) and a delay spread of the pilot signal and selecting an IFW (Interference Free Window) section suitable for the channel environment of the transmitter and the receiver; And a second step of transmitting the data to the receiving end by applying the LS code having the IFW interval selected by the receiving end to the receiving end. The method of claim 1, wherein the transmitting end transmits data to the receiving end by applying the LS code. Transmitting, by the receiver, the signal to noise ratio and the selected IFW interval to the transmitter; Selecting an LS code having the IFW interval at the transmitting end; And transmitting the selected LS code information from the transmitting end to the receiving end before transmitting the data by applying the LS code from the transmitting end to the receiving end. Transmission method. The method of claim 1, wherein the transmitting end transmits data to the receiving end by applying the LS code. Determining a transmission rate and an LS code by using the signal-to-noise ratio and IFW at the receiving end; Requesting the transmitting end to transmit data according to the transmission rate and LS code information determined using the signal-to-noise ratio and the IFW; Determining, by the transmitting end, a transmission rate and an LS code to be transmitted to the receiving end according to the transmission rate and LS code information sent from the receiving end; And transmitting the selected LS code information from the transmitting end to the receiving end before transmitting the data by applying the LS code from the transmitting end to the receiving end. Transmission method. The method of claim 1, wherein the transmitting end transmits data to the receiving end by applying the LS code. Determining a transmission rate suitable for the channel environment by comparing the signal-to-noise ratio and the IFW with a preset transmission rate table at the receiving end; Requesting, by the receiving end, a transmitting end to transmit data according to the determined transmission rate; Selecting, by the transmitting end, an LS code according to a transmission rate determined and sent by the receiving end; And transmitting the selected LS code information from the transmitting end to the receiving end before transmitting the data by applying the LS code from the transmitting end to the receiving end. Transmission method.