KR101412290B1 - Method for transmitting scheduling request signal and control information - Google Patents

Abstract

A method for transmitting a scheduling request signal in a wireless communication system includes generating a control channel on a subframe including a first slot and a second slot, and transmitting an ACK / NACK signal and a scheduling request signal through the control channel The ACK / NACK signal is transmitted in different phases in the first slot and the second slot, and the phase difference according to the slot of the ACK / NACK signal expresses the presence or absence of the scheduling request signal. Since there is no need to allocate a separate radio resource for the scheduling request signal, it is possible to reduce the waste of limited radio resources and to transmit the scheduling request signal with little influence on other control information, thereby increasing the transmission efficiency of the control information .

Description

[0001] The present invention relates to a scheduling request signal transmission method and a control information transmission method in a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to wireless communication, and more particularly, to a method for transmitting a scheduling request signal and control information.

A 3rd Generation Partnership Project (3GPP) mobile communication system based on WCDMA (Wideband Code Division Multiple Access) wireless access technology is widely deployed all over the world. HSDPA (High Speed Downlink Packet Access), which can be defined as the first evolutionary phase of WCDMA, provides 3GPP with highly competitive wireless access technology in the mid-term future. However, since the development of wireless access technology that continues to increase and compete with the requirements and expectations of users and operators continues, development of new technologies in 3GPP is required for future competitiveness.

One of the systems considered in the third generation and later systems is an Orthogonal Frequency Division Multiplexing (OFDM) system capable of attenuating inter-symbol interference effects with low complexity. The OFDM converts data symbols input in series into N parallel data symbols, and transmits the data symbols on separate N subcarriers. The subcarriers maintain orthogonality at the frequency dimension. Each orthogonal channel experiences mutually independent frequency selective fading, and the interval of transmitted symbols becomes longer, so that inter-symbol interference can be minimized. Orthogonal frequency division multiple access (OFDMA) refers to a multiple access method in which a part of subcarriers available in a system using OFDM as a modulation scheme is independently provided to each user to realize multiple access. OFDMA provides a frequency resource called a subcarrier to each user, and each frequency resource is provided independently to a plurality of users and is not overlapped with each other. Consequently, frequency resources are allocated mutually exclusively for each user.

Meanwhile, in order to implement various transmission or reception techniques for high-speed packet transmission, it is indispensable to transmit control information for time, space and frequency domain. A channel for transmitting control information is called a control channel. A physical layer channel for transmitting control information from a base station to a mobile station is referred to as a physical downlink control channel (PDCCH), and a physical layer channel for transmitting control information from a mobile station to a base station is referred to as a physical uplink control channel ; PUCCH). The control information transmitted through the uplink control channel includes ACK (Acknowledgment) / NACK (Negative-Acknowledgment) signals for downlink data transmission, CQI (Channel Quality Indicator) indicating downlink channel quality, A scheduling request signal for a plurality of antennas, and a multiple input multiple output (MIMO) control signal, which is information related to multiple antennas.

The scheduling request signal is a message for requesting the Node B to allocate radio resources for uplink data or downlink data transmission. When a base station receives a scheduling request signal from a mobile station, the base station allocates radio resources to the mobile station. The scheduling request signal is arbitrarily transmitted according to the needs of the UE. Assigning a separate radio resource for such a scheduling request signal causes a waste of limited radio resources.

There is a need for a method capable of transmitting a scheduling request signal without unnecessary waste of radio resources.

SUMMARY OF THE INVENTION The present invention provides a control information transmission method capable of efficiently transmitting a scheduling request signal.

According to an aspect of the present invention, a method for transmitting a scheduling request signal in a wireless communication system includes generating a control channel on a subframe including a first slot and a second slot, and generating an ACK / NACK signal and a scheduling Wherein the ACK / NACK signal is transmitted in different phases in the first slot and the second slot, and the phase difference according to the slot of the ACK / NACK signal indicates whether or not a scheduling request signal exists Express.

According to another aspect of the present invention, a method for transmitting control information in a wireless communication system includes transmitting first control information through a first slot, and transmitting the first control information through a second slot by converting a phase of the first control information And multiplexes the second control information with a phase difference of the first control information.

Since there is no need to allocate a separate radio resource for the scheduling request signal, it is possible to reduce the waste of limited radio resources and to transmit the scheduling request signal with little influence on other control information, thereby increasing the transmission efficiency of the control information .

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station (BS) 20. The terminal 10 may be fixed or mobile and may be referred to by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, The base station 20 generally refers to a fixed station that communicates with the terminal 10 and may be referred to in other terms such as a Node-B, a Base Transceiver System (BTS), an Access Point Can be called. One base station 20 may have more than one cell.

Hereinafter, downlink refers to communication from the base station 20 to the terminal 10, and uplink refers to communication from the terminal 10 to the base station 20. In the downlink, the transmitter may be part of the base station 20, and the receiver may be part of the terminal 10. [ In the uplink, the transmitter may be part of the terminal 10, and the receiver may be part of the base station 20.

There are no restrictions on multiple access schemes applied to wireless communication systems. Such as CDMA (Code Division Multiple Access), TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access), SC-FDMA (Single-Carrier FDMA), and Orthogonal Frequency Division Multiple Access (OFDMA) . Multiple access schemes for downlink and uplink transmissions may be different. For example, the downlink may use OFDMA and the uplink may use SC-FDMA.

2 is a block diagram illustrating a transmitter according to an embodiment of the present invention.

2, the transmitter 100 includes a transmit processor 110, a DFT unit 120 for performing a Discrete Fourier Transform (DFT), an IFFT unit 130 for performing an Inverse Fast Fourier Transform (IFFT) . The DFT unit 120 performs DFT on the data processed by the transmission processor 110 to output a frequency domain symbol. The data input to the DFT unit 120 may be control information and / or user data. The IFFT unit 130 performs IFFT on the input frequency-domain symbols and outputs a transmit signal. The transmitted signal becomes a time domain signal and is transmitted via the transmit antenna 190. The time-domain symbols output through the IFFT unit 130 are also referred to as an SC-FDMA (Single Carrier-Frequency Division Multiple Access) symbol in that an OFDM (Orthogonal Frequency Division Multiplexing) symbol or a DFT spread IFFT is applied. A method of spreading symbols by performing DFT on the front end of the IFFT unit 130 is referred to as SC-FDMA. This is advantageous for lowering the Peak-to-Average Power Ratio (PAPR) as compared to OFDM.

Herein, the SC-FDMA transmission is described, but there is no limit to the multiple access scheme to which the present invention is applied. For example, various multiplexing schemes such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Single-Carrier FDMA (SC-FDMA), and Orthogonal Frequency Division Multiple Access Connection technique.

The uplink and downlink multiple access schemes may be different in a wireless communication system. For example, the uplink may use SC-FDMA and the downlink may use OFDMA.

3 shows an example of a sub-frame. It may be an uplink sub-frame in which SC-FDMA is used.

Referring to FIG. 3, one subframe may include two slots. One slot may comprise a plurality of OFDM symbols in the time domain and at least one subcarrier in the frequency domain. A slot is a unit for allocating radio resources in the time domain. For example, one slot may comprise 7 or 6 OFDM symbols.

A subframe of the SC-FDMA structure can be divided into two parts, a control region and a data region. Since the control region and the data region use different frequency bands, they are FDM (Frequency Division Multiplexing). Control information is stored in the control area, and user data is stored in the data area. The control area and the data area may be composed of one sub-frame. A physical layer channel through which a UE transmits control information to a Node B using a control region is called a Physical Uplink Control Channel (PUCCH).

The control information may include various types such as an ACK / NAK signal, a channel quality indicator (CQI), a scheduling request signal, a Precoding Matrix Index (PMI), and a Rank Indicator (RI). Only the control information can be placed in the control area. User data and control information may be stored together in the data area. That is, when the terminal transmits only the control information, the control information can be transmitted through the control domain. When the terminal transmits the user data and the control information, the control information is transmitted through the control domain or the user data and control information are multiplexed And transmit it through the data area.

When there is no data to be sent together with the control signal, the transmitter modulates the control signal in the SC-FDMA format and transmits it. A scheme of transmitting a control signal in the control domain may be a frequency division multiplexing (FDM) scheme or a code division multiplexing (CDM) scheme between terminals.

A slot allocated to each terminal is frequency hopped on a subframe. One of the two slots allocated to one terminal may be allocated to one frequency band and the remaining one may be staggered to the other frequency band. A frequency diversity gain can be obtained by transmitting one control channel for a UE through slots allocated to different frequency bands.

In order to clarify the description, it is assumed that one slot is composed of 7 OFDM symbols, and one subframe including 2 slots includes 14 OFDM symbols in total. The number of OFDM symbols included in one subframe or the number of OFDM symbols included in one slot is only an example and the technical idea of the present invention is not limited thereto.

FIG. 4 illustrates a method of loading control information in a control channel in order to transmit control information according to an embodiment of the present invention.

Referring to FIG. 4, it is assumed that an uplink control channel (PUCCH) is allocated to the UE for transmission of control information. The uplink control channel includes a first slot and a second slot. The first slot and the second slot may occupy different frequency bands for frequency diversity. A reference signal (RS) is put on three consecutive OFDM symbols in the middle part of seven OFDM symbols included in one slot, and control information is put on the remaining four OFDM symbols. The number and location of the symbols used in the reference signal may vary depending on the control channel and the number and position of the symbols for the associated control information may be changed accordingly.

When the data symbols of the first control information (C) that the mobile station wants to send that x _0, UE x ₀ for the second control information (D) to the mapping shown in Table 1 with respect to the first slot and a second slot You can transfer more.

Control
Information OFDM symbols index 1st Slot 2nd Slot C ₀ C ₁ C ₂ C ₃ C ₄ C ₅ C ₆ C ₇ C ₈ C ₉ C ₁₀ C ₁₁ C ₁₂ C ₁₃ C x ₀ x ₀ One One One x ₀ x ₀ x ₀ x ₀ One One One x ₀ x ₀ C + D x ₀ x ₀ One One One x ₀ x ₀ -x ₀ -x ₀ One One One -x ₀ -x ₀

To transmit 1-bit first control information, the first control information is modulated by BPSK (Binary Phase Shift Keying) to generate a data symbol x _0. To transmit 2-bit first control information, a Quadrature Phase Shift Keying) to generate the data symbol x ₀ .

The data symbols are arranged as shown in Table 1 according to the OFDM symbols of the subframe.

In the case of transmitting only the first control information (C), when the data symbol of the first slot and the data symbol of the second slot are transmitted in the same phase and the first control information and the second control information are transmitted together (C + D Converts the data symbols of the first slot and the data symbols of the second slot into different phases and transmits them.

In the case of transmitting only the first control information (C), the data symbols of the first slot and the data symbols of the second slot are arranged in the same phase. That is, the data symbols of the first slot and the data symbols of the second slot are arranged in the same phase as {x ₀ , x ₀ , 1, 1, 1, x ₀ , x ₀ }. When the first control information and the second control information are multiplexed and transmitted, (C + D), the phase of the data symbol of the slot of either the first slot or the second slot is converted. That is, the data symbols of the first slot and the data symbols of the second slot are arranged in different phases. For example, the data symbols in the first slot, _{{x 0, x 0, 1} , 1, 1, x 0, x 0} as shown in the array, and by the second slot, converting the phase of the data symbols {-x ₀ , -x ₀ , 1, 1, 1, -x ₀ , -x ₀ }. When expressing such an arrangement as _{c i, c i = x i} (i = 0,1,5,6), c i = -x i (i = 7,8,12,13), c i = 1 (i = 2, 3, 4, 9, 10, 11).

When transmitting control information in a pre-allocated band, frequency-domain spreading and time-domain spreading are applied to increase the number of multiplexable terminals or control channels. Data symbols arranged according to an OFDM symbol are spread in a frequency domain by a sequence carried on each OFDM symbol. The sequence may be an orthogonal sequence having excellent correlation characteristics. The orthogonal sequence may be an orthogonal sequence having a length of 12 to spread the data symbols to 12 consecutive subcarriers in the frequency domain. As an example of the orthogonal sequence, a Zadoff-Chu (ZC) sequence, which is one of the CAZAC (Constant Amplitude Zero Auto-Correlation) sequences, can be used.

The kth element c (k) of the ZC sequence with index M can be expressed as:

Where N is the length of the ZC sequence, index M is a natural number less than or equal to N, and M and N are relatively prime.

It is possible to distinguish each terminal by applying a ZC sequence having different circular shift values. The number of available cyclic shifts may vary depending on the delay spread of the channel.

The data symbols spread in the frequency domain are spread to the time domain again after performing the IFFT. The data symbols are spread in the time domain through spreading codes of length 4 [W (0) W (1) W (2) W (3)] for 4 OFDM symbols. Also, the reference signal is also spread through a spreading code [W _RS (0) W _RS (1) W _RS (2)] of length 3. The spreading code of length 4 is W ₁ = [+ 1 +1 +1 +1], W ₂ = [+ 1 -1 +1 -1] and W ₃ = [+ 1 +1 -1 -1] , W ₄ = [+ 1 -1 -1 +1] may be used. Spreading codes of length 3 is W _RS1 = orthogonal sequences [1, 1, 1], W RS2 = [1 e j2π / 3 e j4π / 3], W RS3 = [1 e j4π / 3 e j2π / 3] a Can be used. The orthogonal sequence used is merely illustrative and not limiting. Various other orthogonal sequences having excellent correlation characteristics can be used.

If the UE transmits the data symbols of the control information in different slots, the BS can recognize that the second control information is present. The first control information may be control information that the terminal must frequently transmit to the base station or periodically transmit. The second control information may be control information that is transmitted aperiodically according to need. The ACK / NACK signal, the channel quality indication (CQI) reporting the channel state, the precoding matrix indication (PMI) reported by the multi-antenna system, the rank indication (RI) . There is a scheduling request signal in control information that is transmitted aperiodically as needed. If control information transmitted non-periodically using control information transmitted periodically is multiplexed and transmitted, a scheduling gain can be obtained since no additional resource allocation is required.

Here, it is exemplified that the phase of the data symbol of the first slot is different from that of the data symbol of the second slot in the case of multiplexing and transmitting the first control information and the second control information (C + D) (C + D) in the case of transmitting the first control information and the second control information together in the phase (C + D) in which the data symbol of the first slot and the data symbol of the second slot are transmitted differently, The data symbols of one slot and the data symbols of the second slot can be transmitted in the same manner.

Table 2 below shows an example of transmitting an ACK / NACK signal and a Scheduling Request (SR).

Control
Information OFDM symbols 1st Slot 2nd Slot C ₀ C ₁ C ₂ C ₃ C ₄ C ₅ C ₆ C ₇ C ₈ C ₉ C ₁₀ C ₁₁ C ₁₂ C ₁₃ ACK One One One One One One One One One One One One One One NACK -One -One One One One -One -One -One -One One One One -One -One ACK + SR One One One One One One One -One -One One One One -One -One NACK + SR -One -One One One One -One -One One One One One One One One

Assume that the data symbol of the ACK signal is 1 and the data symbol of the NACK signal is -1. When the ACK / NACK signal is 1 bit and modulated with BPSK, the case where the data symbol is 1 and -1 means that the signal constellation has an opposite position.

In the case of transmitting only the ACK signal (ACK), ACK signals of the same phase are transmitted through the first slot and the second slot. NACK signal is transmitted through the first slot and the second slot, NACK signals of the same phase are transmitted through the first slot and the second slot. That is, when transmitting only the ACK signal or transmitting only the NACK signal, the phase of the data symbol carried in the first slot and the phase of the data symbol carried in the second slot are equal to each other.

When the ACK signal and the scheduling request signal are transmitted together (ACK + SR), ACK signals of different phases are transmitted through the first slot and the second slot. At this time, the phase of the reference signal is transmitted as it is in both the first slot and the second slot. The phase of the ACK signal may be transmitted as it is in the first slot and the phase of the ACK signal may be transmitted in the second slot. Alternatively, the phase of the ACK signal may be converted and transmitted in the first slot, and the phase of the ACK signal may be directly transmitted in the second slot.

When the NACK signal and the scheduling request signal are transmitted together (NACK + SR), NACK signals of different phases are transmitted through the first slot and the second slot. At this time, the phase of the reference signal is transmitted as it is in both the first slot and the second slot. The phase of the NACK signal may be transmitted as it is in the first slot and the phase of the NACK signal may be transmitted in the second slot. Alternatively, the phase of the NACK signal may be converted and transmitted in the first slot, and the phase of the NACK signal may be transmitted as it is in the second slot. That is, when the ACK signal and the scheduling request signal are transmitted together or the NACK signal and the scheduling request signal are transmitted together, the data symbols carried in the first slot and the data symbols carried in the second slot are loaded in different states.

The scheduling request signal is a signal for the UE to request the uplink radio resource allocation to the base station, and is a kind of advance information exchange for data exchange. In order for the UE to transmit uplink data to the Node B, radio resources must be allocated through a scheduling request signal. When the UE requests scheduling through a scheduling request signal, the Node B allocates a radio resource for uplink data transmission and notifies the UE of the scheduling request signal. Since the scheduling request signal can indicate whether or not the allocation of the radio resources is requested based on only the presence or absence of the signal, it can be sufficiently represented by 1 bit and the existence of the scheduling request signal can be expressed by whether the phase of the ACK / NACK signal according to the slot changes.

If the phase of the reference signal is modulated to distinguish whether the first control information and the second control information are multiplexed, the control signal transmitted by fading that can change the phase of the signal may not be clearly distinguished have. Table 3 shows an example of a case where the ACK / NACK signal and the scheduling request signal together by modulating the phase of the reference signal.

Control
Information OFDM symbols 1st Slot 2nd Slot C ₀ C ₁ C ₂ C ₃ C ₄ C ₅ C ₆ C ₇ C ₈ C ₉ C ₁₀ C ₁₁ C ₁₂ C ₁₃ ACK One One One One One One One One One One One One One One NACK -One -One One One One -One -One -One -One One One One -One -One ACK + SR One One -One -One -One One One One One -One -One -One One One NACK + SR -One -One -One -One -One -One -One -One -One -One -One -One -One -One

Assume that the data symbol of the ACK signal is 1 and the data symbol of the NACK signal is -1. An ACK signal or a NACK signal is transmitted in the same manner as in Table 2. ACK signal and a scheduling request signal are transmitted together (ACK + SR) or when a NACK signal and a scheduling request signal are transmitted together (NACK + SR), the phase of the reference signal is converted to indicate that there is a scheduling request signal. If the phase of the control information changes due to fading during transmission, the base station can not distinguish 'ACK' from 'NACK + SR', and can not distinguish 'NACK' and 'ACK + SR' from each other. For example, when the ACK signal is inverted in phase (equal to -1 for each OFDM symbol) during transmission, the NACK signal and the scheduling request signal are transmitted together (NACK + SR) The base station mistakes the 'ACK' signal as the 'NACK + SR' signal. When the ACK signal and the scheduling request signal are multiplexed and transmitted (ACK + SR) when the NACK signal is inverted in phase during transmission, the base station receives the NACK signal as the ACK + SR signal .

According to the proposed method, if the phases of the control information are transmitted differently according to the slots while the phase of the reference signal is maintained in the first slot and the second slot, even if the phase of the control information changes during transmission, There is no need to worry about it. The base station can distinguish whether it is an ACK signal or a NACK signal based on a reference signal, and can confirm whether or not a scheduling request signal exists due to a phase change depending on a slot. For example, if the ACK signal and the scheduling request signal are transmitted together (ACK + SR) in Table 2, even if the phase of the signal changes during transmission, the base station confirms that the phase of the reference signal is negative, It can be seen that this has been changed. The base station can know that the received signal is an ACK signal. Since the phases of the first slot and the second slot are different from each other, the base station can know that there is a scheduling request signal.

Since the phase of the first control information is changed according to the slot to indicate the second control information, there is no need to allocate additional resources for transmission of the second control information and does not affect the transmission efficiency of the first control information. Also, there is no need to change the coding rate or the modulation scheme or separately use a CDM (Code Division Multiplex) code for additional control information in a limited radio resource.

5 illustrates a method of loading control information in a control channel in order to transmit control information according to another embodiment of the present invention.

Referring to FIG. 5, it is a case of multiplexing a scheduling request signal (SR) in an ACK / NACK signal. An ACK / NACK signal is carried in the first slot and the second slot of the control channel allocated to the UE. When transmitting only the ACK signal or the NACK signal, the phases of the ACK / NACK signals carried in the first slot and the second slot are equally set. That is, ACK / NACK signals of the same phase are transmitted through the first slot and the second slot.

When ACK / NACK signals and a scheduling request signal are transmitted together (ACK / NACK + SR), ACK / NACK signals carried in the first and second slots are loaded in different phases. That is, ACK / NACK signals of different phases are transmitted through the first slot and the second slot.

The ACK / NACK signal input to the first slot (or the second slot) is spread in the frequency domain by the orthogonal sequence. A ZC sequence of length 12 may be used for frequency domain spreading. The ACK / NACK signal is spread in time domain by another type of orthogonal sequence W after performing IFFT. On the other hand, the time by the reference signal (RS) is mapped to the OFDM symbol index 2, 3 and 4 (or 9,10,11) of OFDM symbols, it performs an orthogonal sequence as IFFT and other types of orthogonal sequence (W _RS) that is Lt; / RTI >

In the case of multiplexing the scheduling request signal in the ACK / NACK signal, the ACK / NACK signal is directly input to the first slot and the ACK / NACK signal is converted into the second slot. However, The ACK / NACK signal may be input to the second slot and the ACK / NACK signal may be directly input to the second slot.

Hereinabove, the phase of the ACK / NACK signal is converted according to the slot and the scheduling request signal is transmitted together. However, according to the proposed method, phases of various control information can be converted and various control information can be transmitted together. For example, a CQI may be transmitted in a different phase through a plurality of slots to indicate a scheduling request signal or an ACK / NACK signal. The number of slots included in the control channel is not limited, and the number of bits of the second control information that can be expressed by converting the phase of the first control information according to the number of slots Can be increased.

All of the functions described above may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), etc. according to software or program code or the like coded to perform the function. The design, development and implementation of the above code will be apparent to those skilled in the art based on the description of the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. You will understand. Therefore, it is intended that the present invention covers all embodiments falling within the scope of the following claims, rather than being limited to the above-described embodiments.

1 is a block diagram illustrating a wireless communication system.

2 is a block diagram illustrating a transmitter according to an embodiment of the present invention.

3 shows an example of a sub-frame.

FIG. 4 illustrates a method of loading control information in a control channel in order to transmit control information according to an embodiment of the present invention.

5 illustrates a method of loading control information in a control channel in order to transmit control information according to another embodiment of the present invention.

Claims (6)

A method for transmitting a scheduling request signal to a base station in a wireless communication system, The terminal generating a control channel on a subframe including a first slot and a second slot; And And transmitting, by the UE, an ACK / NACK signal and a scheduling request signal to the Node B through the control channel, wherein the ACK / NACK signal is transmitted in different phases in the first slot and the second slot, And a phase difference according to a slot of the ACK / NACK signal represents the presence or absence of the scheduling request signal. The method of claim 1, wherein the first slot and the second slot occupy different frequency bands. The method of claim 1, wherein reference signals are transmitted in the same phase through the first slot and the second slot, respectively. The method of claim 1, wherein the control channel is a Physical Uplink Control Channel (PUCCH). A method for a terminal to transmit control information to a base station in a wireless communication system, The terminal transmitting first control information through a first slot; And And transmitting the first control information through a second slot by converting the phase of the first control information, The second control information is multiplexed based on information on the phase difference between the phase information of the first control information transmitted in the first slot and the first control information transmitted in the second slot, The first control information is control information periodically transmitted to the base station by the terminal And the second control information is control information that the terminal periodically transmits to the base station. 6. The method of claim 5, wherein the first slot and the second slot are temporally continuous.

Images