KR100968223B1 - Apparatus and Method for communicating ACK/NAK control information in wireless communication systems - Google Patents

Abstract

The present invention relates to a technique for efficiently transmitting and receiving ACK / NAK control information transmitted from a terminal to a base station to inform a base station whether the terminal successfully demodulated data in a wireless communication system. Assigning a mutual orthogonal code sequence to each of a frequency axis and a time axis of the block; Generating first and second signal groups each having a group of N signals orthogonal to each other and orthogonal to each other on a time axis of the resource block, wherein the signal groups overlap at least one signal; Transmitting an overlapping first signal group and a second signal group to a base station; And a method for transmitting ACK / NAK control information to distinguish a terminal using the same ACK / NAK resource, characterized in that it comprises the step of transmitting a control signal to the base station. Also, a corresponding reception method and a transmission / reception apparatus are also provided.

OFDM, ACK / NAK, Multiple Access, Interorthogonal Sequence, CDM, FDM

Description

APPARATUS AND METHOD FOR COMMUNICATION ACK / NAK CONTROL INFORMATION IN WIRELESS COMMUNICATION SYSTEMS}

The present invention proposes a method of using code division multiplexing (CDM) to distinguish users when multiple users use the ACK / NAK channel together in a wireless communication system. In particular, a method of distinguishing signals of a plurality of terminals from each other using a spreading code using both a frequency axis and a time axis is provided.

The present invention also relates to a method for transmitting an ACK / NAK signal for data received in a mobile communication system.

The present invention is derived from the research conducted as part of the IT new growth engine core technology development project of the Ministry of Information and Communication and the Ministry of Information and Telecommunications Research and Development. ].

Currently, 3GPP is actively working on standardization of technology that can replace the existing 3G-WCDMA radio access technology. On the technical side of modulation and demodulation, E-UTRA / UTRAN (Evolved Universal Terrestrial Radio Access) uses Orthogonal Frequency Division Multiple Access (OFDMA) for downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) radio access technology for uplink. The UMTS Terrestrial Radio Access Network (UMTS) system is being standardized.

In particular, a method of efficiently transmitting and receiving an uplink control channel has been proposed in various ways. The uplink control channel refers to a physical layer channel for transmitting control information related to downlink control information or control information related to uplink transmission.

In a wireless communication system, a receiver sends an ACK signal when the received data is successfully demodulated and a NAK signal when the demodulation fails. The ACK / NAK signal is represented by one bit per codeword. The ACK / NAK signal must be able to be transmitted simultaneously by multiple users using a given time and frequency resource.

Such multiplexing techniques include frequency division multiplexing (FDM) and code division multiplexing (CDM).

FDM means that different users use different time / frequency resources, and CDM allows different users to distinguish different users on the receiving side by using the same time / frequency resources but multiplying and transmitting a specific orthogonal code. To ensure that

In the uplink, a Zadoff-Chu sequence having a good PAPR (Peak to Average Power Ratio) characteristic is used as a mutual orthogonal code. In such a sequence, orthogonality can be created between users by performing a cyclic delay instead of multiplying a specific code in the frequency domain.

The uplink ACK / NAK signal is for the UE to inform the base station of the successful reception (ACK or NAK) for downlink data transmission, and one bit is required for each codeword used for downlink data transmission. Do.

1 shows an example of a time / frequency resource used by a terminal for uplink ACK / NAK signaling considered in a 3GPP LTE system.

As shown in FIG. 1, a resource used for one control channel is composed of two resource blocks separated from each other. That is, frequency hopping is performed. These two resource blocks each occupy N sub-carriers on the frequency axis and occupy seven OFDM symbols corresponding to slots on the time axis. One slot has a time length of 0.5 ms.

A plurality of terminals may use one control channel in common. That is, as illustrated in FIG. 1, several terminals may use the control channel A or B together. At this time, in order to distinguish a plurality of different terminals using the same control channel, each terminal is pre-assigned a specific code sequence. That is, each terminal generates a signal spread on the frequency and time axis using the assigned specific code sequence and transmits it to the base station.

2 shows a code sequence and a symbol transmitted to each sub-frequency in an ACK / NAK channel occupying N sub-frequency on the frequency axis and 7 OFDM symbols on the time axis.

When using a CDM to distinguish signals of a plurality of terminals, as shown in FIG. 2, a structure in which sequences and symbols are mapped to respective time / frequency resources may be considered. In order to distinguish the plurality of terminal signals from each other, a sequence is applied to the frequency axis and the time axis, respectively. In FIG. 2, a reference signal is required for channel estimation and a signal previously determined by the terminal and the base station is transmitted.

The base station estimates the channel using the reference signal and uses the channel estimation result for demodulation of the ACK / NAK symbols transmitted by the control signal. Each time / frequency resource transmits one symbol obtained by multiplying two symbols or three symbols.

와 시간축 시퀀스 심볼

를 곱하여 얻어진다. 컨트롤 시그날이 실리는 시간/주파수 자원은 주파수 축 시퀀스 심볼

, 시간축 시퀀스 심볼

, ACK/NAK 심볼

를 곱하여 얻어진다. 도 2에서

는 주파수축 k번째 부주파수 (subcarrier)에 적용되는 길이가

, 기본 인덱스가 m, cyclic delay 인덱스가 q인 Zadoff-Chu 시퀀스를 표시하며 아래 (수학식 1)과 같이 표현된다. That is, the time / frequency resource on which the reference signal is carried is a frequency axis sequence symbol.

And timebase sequence symbols

Is obtained by multiplying The time / frequency resource on which the control signal is carried is a frequency axis sequence symbol.

, Time base sequence symbol

, ACK / NAK symbol

Is obtained by multiplying In Figure 2

Is the length applied to the kth subcarrier of the frequency axis.

For example, the Zadoff-Chu sequence with the default index m and the cyclic delay index q is represented by Equation 1 below.

로 표현된다. 레퍼런스 시그날에 적용된 시퀀스는

로 표현된다.On the time base, one sequence is applied to each of the reference and control signals. That is, the sequence applied to the control signal in FIG.

It is expressed as The sequence applied to the reference signal

It is expressed as

Currently, 3GPP LTE considers a structure having three reference signals per slot for an uplink ACK / NAK channel. A Zadoff-Chu sequence is used as a frequency axis to distinguish terminals, and a Discrete Fourier Transformation (DFT) vector, a Walsh-Hadamard sequence, and a Zadoff-Chu sequence may be used as the time axis.

The present invention relates to a technique for efficiently transmitting and receiving ACK / NAK control information sent by the terminal to the base station to inform the base station whether the terminal successfully demodulated data in a wireless communication system.

The present invention shows a scheme in which multiple users can use the same ACK / NAK resources together using a code division multiple access (CDMA) scheme.

A method of transmitting ACK / NAK control information to distinguish a terminal using the same ACK / NAK resources in a wireless communication system in order to achieve the above technical problem, the frequency axis and time axis of the resource block used by the terminal Assigning each orthogonal code sequence to a; Generating first and second signal groups each having a group of N signals orthogonal to each other and orthogonal to each other on a time axis of the resource block, wherein the signal groups overlap at least one signal; Transmitting an overlapping first signal group and a second signal group to a base station; And transmitting the control signal to the base station.

Preferably, the resource block occupies seven symbols corresponding to slots on a time axis, and the first and second signal groups include two signals R0, R1, and R1 and R2, respectively. do.

Preferably, each of the R0, R1 and R2 signals is arranged in the slot so as not to be adjacent to each other.

Preferably, the R0, R1 and R2 are arranged in the slot such that all are adjacent to each other.

Preferably, the first and second signal groups include four signals (R0, R1, R2, R3 and R3, R4, R5, R6), respectively.

Preferably, the four signals R0, R1, R2, and R3 are arranged on the time axis of the resource block so that they are not adjacent to each other.

Preferably, the four signals R0, R1, R2 and R3 are arranged on the time axis of the resource block so that they are adjacent to each other.

Preferably, the orthogonal code sequence is any one of a Zadoff-Chu, a Discrete Fourier Transformation (DFT) vector, and a Walsh-Hadamard sequence.

In addition, to achieve the above technical problem, there is provided a method for receiving ACK / NAK control information to distinguish a terminal using the same ACK / NAK resources in a wireless communication system, the method is mutually on the time axis in the resource block Receiving a first and a second signal group comprising a group of neighboring orthogonal N signals, wherein the signal groups include at least one signal and overlap the first and second signal groups; Obtaining N reference signals for each of the N terminals by applying the despreading to each of the N signals included therein; And channel estimation of the N received control signals through the obtained N reference signals.

Preferably, when the first and the second signal group includes two signals R0, R1, R1, and R2, respectively, two reference signal acquisitions and two control signal channel estimations are performed for one group per terminal. Characterized in that made.

Preferably, when the first and second signal groups include four signals R0, R1, R2, and R3, four reference signals are acquired and four control signal channel estimations are performed for one group for each terminal. It features.

In addition, in order to achieve the above technical problem, a mutual orthogonal code sequence allocator for allocating an orthogonal code sequence to each frequency and time axis of a resource block used by a terminal to distinguish N terminals sharing a control channel ; A signal group generation unit generating first and second signal groups each having N signals orthogonal to each other and being orthogonal to each other on a time axis in the resource block, wherein the signal groups overlap at least one signal; A reference signal transmitter for transmitting the overlapping first signal group and the second signal group to a base station; And a control signal transmission unit for transmitting the control signal to the base station.

In addition, in order to achieve the above technical problem, a reference signal receiver for receiving a first and a second signal group having N signals orthogonal to each other on a time axis in a resource block used by a terminal in a wireless communication system as a group ; A control signal receiver for receiving a control signal; A reference signal obtaining unit which obtains N reference signals for each of N terminals by applying despreading to N signals included in the first and second signal groups, respectively; And a channel estimator configured to estimate a channel of the control signal received through the control signal receiver through the obtained N reference signals. The apparatus for receiving ACK / NAK control information is provided in a wireless communication system.

The present invention can increase efficiency in transmitting and receiving ACK / NAK control information sent from the terminal to the base station to inform the base station whether the terminal successfully demodulated the data in the wireless communication system.

Hereinafter, a method and apparatus for transmitting and receiving ACK / NAK control information in a wireless communication system according to the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to a client's or operator's intention or custom. Therefore, the definition should be based on the contents throughout this specification.

3 to 5 show a slot structure of an ACK / NAK channel including three reference signals per slot.

3, 4, and 5 are slot structures considered in the present invention, one slot has three reference signals and four control signals.

In order to distinguish the signals of the multiple terminals, the receiving side should be able to distinguish the reference signals for each terminal by receiving the reference signals transmitted by the multiple terminals, and at the same time receive the control signals transmitted by the multiple terminals and distinguish the control signals for each terminal. It should be possible.

As described above, a CDM method using both frequency and time base resources can be used to distinguish signals.

개일 때, 시퀀스의 길이가

이고 시퀀스들 간에 상호 직교를 만족하는

개의 시퀀스를 만들 수 있다. i번째 시퀀스를 행 벡터

라고 표현할 때 상호직교는 다음과 같은 의미이다.The time base sequence used for time base CDM uses an orthogonal sequence. Total number of consecutive OFDM symbols on the time base

, The length of the sequence

Satisfying orthogonality between sequences

You can create a sequence of dogs. i-th sequence of row vector

In this regard, mutual orthogonal means:

이다. here,

to be.

In theory, since the total number of frequency axis resources is M and three reference signals are shown in FIGS. 3 to 5, the total M × 3 reference signals can be distinguished as CDMs.

In the case of the control signal, since the total number of frequency axis resources is M and four control signals are shown in FIGS. 3 to 5, total M × 4 control signals can be distinguished as CDMs.

However, since each UE must transmit at least one reference signal to demodulate the control signal using the BS, the total number of distinguishable terminals becomes M × 3. In this case, we use an orthogonal sequence with a spreading factor of 3 for the reference signal and an orthogonal sequence with a SF of 4 for the control signal. This method can distinguish three terminals using the same ZC (Zadoff-Chu) sequence by using an orthogonal sequence of length 3 for the entire reference signal and an orthogonal sequence of length 4 for the control signal. However, there is a problem in that the orthogonality of the sequences used for the reference signal and the control signal is broken when the actual terminal speed is high.

In particular, in the case of control signals, the four control signals are significantly separated from each other on the time axis, making them more sensitive to speed. That is, in the case of a terminal having a high speed orthogonality is not guaranteed. When the orthogonality is broken, performance of the terminal signals is poor because the terminal signals cannot be distinguished.

In order to solve this problem, the present invention proposes a method of reducing the number of distinguishable terminals to M × 2.

In the following embodiment, two UEs UE0 and UE1 assigned the same ZC sequence are distinguished using different time base Walsh-Hadamard sequences. All of the time axis sequences described in Tables 1 and 2 can be applied to FIGS. 3 to 5.

Sequence to distinguish reference signals R ₀ R ₁ R ₂ UE0 One One One UE1 -One One -One

Sequence for distinguishing control signals
C ₀ C ₁ C ₂ C ₃ UE0 One One One One UE1 One -One One -One

The characteristic of the above method is that both the reference signal and the control signal use Walsh-Hadamard sequence of length 2. In particular, the method used in the reference signal of Table 1 is designed to improve the quality of channel estimation at the receiver.

On the receiver side, two signals are used to allow despreading. That is, when despreading is applied to R ₀ and R ₁ that are orthogonal to each other at the receiving side, one reference signal may be obtained for each terminal UE0 and UE1. The reference signal thus obtained is used for channel estimation of two control signals with C ₀ and C ₁ applied to each other orthogonally.

In addition, when despreading is applied to R ₁ and R ₂ , which are guaranteed orthogonality, one reference signal may be obtained for each UE UE and UE1. This reference signal is used to estimate the channel of the two control signals with C ₂ and C ₃ applied.

That is, two reference signals per slot can be extracted for each terminal, thereby improving channel estimation quality. In particular, when the terminal moves at high speed, it is easy to estimate a channel change over time in a slot. In particular, the structure of FIGS. 3 and 4 will perform better than FIG. 5 in terms of channel estimation.

6 shows a reference signal generation method in the case of applying a ZC sequence in the pre-DFT step in the SC-FDMA system.

Signal generation is done in blocks. 6 shows a method of generating one reference block. After multiplying the ZC sequence of N symbols by the time-base sequence symbol, DFT (Discrete Fourier Transform) is applied to the N symbols obtained. N symbols obtained as a result of the DFT are allocated to N sub-frequency. Next, an Inverse Fast Fourier Transform (IFFT) is performed.

7 shows a control signal generation method in the case of applying the ZC sequence in the pre-DFT step in the SC-FDMA system. Signal generation is done in blocks. 7 shows a method of generating one control block. A Discrete Fourier Transform (DFT) is applied to N symbols obtained by multiplying a ZC sequence of N symbols by a time axis sequence symbol and an ACK / NAK symbol. N symbols obtained as a result of the DFT are allocated to N sub-frequency. Then perform Inverse Fast Fourier Transform (IFFT).

8 shows an apparatus for transmitting ACK / NAK control information in a wireless communication system according to the present invention.

The ACK / NAK control information transmitter 800 first includes a code sequence allocator 810. The code sequence allocator 810 allocates a mutually orthogonal code sequence to the frequency and time axis of the resource block used by the terminal to distinguish N (N is even) terminals that share one control channel.

The signal group generator 820 generates first and second signal groups each having N signals that are orthogonal to each other and orthogonal to each other on a time axis in the resource block. The signal groups are characterized by including at least one signal in an overlapping manner.

In order to transmit the signal, a reference signal transmitter 830 is first required. The reference signal transmitter 830 transmits the overlapping first signal group and the second signal group to the base station.

Finally, the ACK / NAK control information transmitter 800 includes a control signal transmitter 840 for transmitting a control signal to the base station. The control signal is transmitted to the base station through the control signal transmitter 840.

Although not shown, the signal group and control signal transmission may be performed through one signal transmitter.

9 illustrates an ACK / NAK control information receiving apparatus 900 in a wireless communication system according to the present invention.

The ACK / NAK control information receiving apparatus 900 receives first and second signal groups each having N signals orthogonal to one another on a time axis in a resource block used by a terminal in a wireless communication system. The reference signal receiver 910 is included.

In this case, each signal group may include two signals or may include four signals, and each signal group includes at least one overlapping signal. The two or in some cases the four signals are orthogonal to each other as described above.

The control signal receiver 920 receives a control signal. Similarly, the reference signal and the control signal may be made through one signal receiver.

The reference signal acquirer 930 applies despreading to each of the N signals included in the received first and second signal groups. Through the spreading, N reference signals are obtained for each N terminals.

Now we need channel estimation. The channel estimator 940 estimates a channel of the control signal received through the control signal receiver through the obtained N reference signals.

The invention can also be embodied as computer readable code on a computer readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, which are also implemented in the form of carrier waves (for example, transmission over the Internet). Include.

The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

As described above, the present invention has been described based on the preferred embodiments, but these embodiments are intended to illustrate the present invention, not to limit the present invention, so that those skilled in the art to which the present invention pertains can practice the above without departing from the technical spirit of the present invention. Various changes, modifications or adjustments to the example will be possible. Therefore, the protection scope of the present invention will be limited only by the appended claims, and should be construed as including all changes, modifications or adjustments.

Figure 1 shows the position in the frequency-time resource space of the control channel considered in the uplink of the 3GPP LTE system.

2 shows a code sequence and a symbol transmitted at each subfrequency in an ACK / NAK channel occupying N subfrequency on the frequency axis and occupying 7 OFDM symbols on the time axis.

3 shows slot structure A of an ACK / NAK channel including three reference signals per slot.

4 shows a slot structure B of an ACK / NAK channel including three reference signals per slot.

5 shows a slot structure C of an ACK / NAK channel including three reference signals per slot.

6 is a block diagram illustrating reference signal generation of an ACK / NAK channel.

7 is a block diagram illustrating control signal generation of an ACK / NAK channel.

8 shows an apparatus for transmitting ACK / NAK control information in a wireless communication system according to the present invention.

9 illustrates an ACK / NAK control information receiving apparatus 900 in a wireless communication system according to the present invention.

Claims (13)

A method of transmitting ACK / NAK control information to distinguish a terminal using the same ACK / NAK resources in a wireless communication system, Allocating an orthogonal code sequence to each of a frequency axis and a time axis of a resource block used by the terminal; Generating first and second signal groups each having a group of N signals orthogonal to each other and orthogonal to each other on a time axis of the resource block, wherein the signal groups include at least one signal overlapping each other; Transmitting the overlapping first signal group and the second signal group to a base station; And Transmitting ACK / NAK control information to distinguish a terminal using the same ACK / NAK resource, characterized in that it comprises transmitting a control signal to a base station. The method of claim 1, wherein the resource block occupies seven symbols corresponding to slots on a time axis, and the first and second signal groups each include two signals R0, R1, and R1 and R2. A method of transmitting ACK / NAK control information to distinguish the terminal using the same ACK / NAK resources in a wireless communication system, characterized in that. The method of claim 2, wherein the R0, R1 and R2 signals are arranged in the slots so as not to be adjacent to each other ACK / NAK control to distinguish the terminal using the same ACK / NAK resources in a wireless communication system How to send information. The method according to claim 2, wherein the R0, R1 and R2 are arranged in the slot so that all of them are adjacent to each other, ACK / NAK control information to distinguish the terminal using the same ACK / NAK resources in a wireless communication system How to send. delete delete delete The UE of claim 1, wherein the mutual orthogonal code sequence is any one of a Zadoff-Chu, a Discrete Fourier Transformation (DFT) vector, and a Walsh-Hadamard sequence. Method of transmitting ACK / NAK control information to distinguish. In the method for receiving ACK / NAK control information to distinguish the terminal using the same ACK / NAK resources in a wireless communication system, Receiving first and second signal groups each having a group of N signals orthogonal to each other and orthogonal to each other on a time axis in a resource block, wherein the signal groups include at least one signal overlapping each other; Obtaining N reference signals for each N terminals by applying despreading to each of N signals included in the first and second signal groups; And ACK / NAK control information for distinguishing terminals using the same ACK / NAK resources in the wireless communication system, characterized in that the channel estimation of the N received control signals through the obtained N reference signals; How to receive it. 10. The method of claim 9, wherein when the first and second signal groups include two signals R0, R1, and R1 and R2, respectively, two reference signals and two control signals are acquired for one group per terminal. A method of receiving ACK / NAK control information to distinguish a terminal using the same ACK / NAK resources in a wireless communication system characterized in that the channel estimation is made. delete An apparatus for transmitting ACK / NAK control information to distinguish a terminal using the same ACK / NAK resources in a wireless communication system, An orthogonal code sequence allocator for allocating an orthogonal code sequence to a frequency and time axis of the resource block; A signal group generation unit generating first and second signal groups each having N signals orthogonal to each other and being orthogonal to each other on a time axis in the resource block, wherein the signal groups overlap at least one signal; A reference signal transmitter for transmitting the overlapping first signal group and the second signal group to a base station; And An apparatus for transmitting ACK / NAK control information to distinguish the terminal using the same ACK / NAK resources in a wireless communication system comprising a control signal transmitting unit for transmitting a control signal to the base station. An apparatus for receiving ACK / NAK control information in a wireless communication system, A reference signal receiver configured to receive first and second signal groups each having N signals orthogonal to each other and being orthogonal to each other on a time axis in a resource block used by the terminal; A control signal receiver for receiving a control signal; A reference signal acquisition unit for obtaining N reference signals for each of N terminals by applying despreading to N signals included in the first and second signal groups, respectively; And And a channel estimator configured to estimate a channel of the control signal received through the control signal receiving unit through the obtained N reference signals.

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