KR20080079630A - Method and apparatus for transmitting different control channels'bits - Google Patents

Abstract

A bit transmission method of different control channels is provided to perform modulation by binding bits of different control channels, or to perform an encoding process by binding the bits, and to send the bound bits, thereby allocating the same frequency, time, and code resources to two pieces of information. A base station performs a CRC(Cyclic Redundancy Check) function after receiving packet data(510) from a mobile station to check whether an error exists, and if so, the base station generates an NACK bit, and if not, the base station generates an ACK bit. The base station detects reception strength of the packet data to generate a power control symbol, and transmits a symbol(520) for combining the ACK/NACK bits with the power control symbol to a downlink.

Description

{Method and Apparatus for Transmitting different control channels'bits}

The present invention relates to a method of transmitting a 1-bit type control channel in a cellular system, and more particularly, to an 1-bit type control channel in a cellular system, an ACK used as a response to a hybrid automatic retransmit reGuest (HARQ) packet data. / NACK bit, power control bit for performing power control, scheduling request bit transmitted by the mobile station to request scheduling from the base station, grant bit for grant purpose for granting scheduling to the mobile station by the base station It relates to a bit transmission method of different control channels such as (grant bit).

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 Communication Research and Development. [Task Management Number: 2005-S-404-13, Project Name: 3G Evolution Wireless Transmission Technology Development ].

In the 4th generation mobile communication system requiring large data transmission such as WLAN, wireless broadcasting, and DMB, Orthogonal Frequency Division Multiplex Access (OFDMA) for transmitting broadband high speed data is referred to as 'OFDMA'. The method is used.

In a mobile communication system using an OFDMA scheme (hereinafter, referred to as an "OFDMA system"), a base station transmits a data packet to a mobile terminal is called downlink or downlink, and the data packet transmitted from the base station is called a downlink packet. .

When the downlink packet is transmitted from the base station to the mobile terminal, the mobile terminal should check whether the received downlink packet is an error. If an error is detected, the base station requests retransmission of the downlink packet. This method is called an automatic retransmission request and is called an 'ARQ (Automatic Repeat reQuest)'.

That is, the base station transmits a downlink packet to the mobile terminal by applying an ARQ method for requesting a response to the error. As such, the downlink packet to which the ARQ scheme transmitted from the base station to the mobile terminal is applied is called an 'ARQ packet'. Recently, in order to improve throughput in an OFDMA system, HARQ technology, which controls errors by combining retransmission requests based on ARQ and forward error correction requests made in a physical layer, has been introduced. .

HARQ is a slight variation of the existing ARQ, and shows good performance in wireless networks. The downlink packet to which the HARQ scheme transmitted from the base station to the mobile terminal is applied is called a 'HARQ packet'.

1 is a diagram schematically illustrating an OFDMA system for transmitting a response to a general HARQ packet.

In an OFDMA system, a base station receives uplink packet data from a plurality of mobile stations located in a corresponding cell. In addition, the base station receiving the transmitted packet data transmits a response regarding whether the packet is an error through the downlink.

Typically, the base station transmits an ACK response indicating that there is no error to the mobile station when there is no error in the received packet, and transmits a NACK response when there is an error in the packet. In addition, the mobile station may be configured to transmit a NACK signal to the mobile station indicating that an error has occurred only when an error is found from the packet received at the base station, or to transmit an ACK signal to the mobile station only when reception is successful without an error.

The mobile station determines that an error has occurred in the transmitted packet and retransmits the packet if a response indicating that there is no error is not transmitted from the base station or a response indicating that an error has occurred is transmitted within a predetermined time set in advance. Here, the response indicating that there is no error transmitted from the base station to the mobile station is called 'ACK', the response indicating that an error is called 'NACK', and an uplink response channel for transmitting a signal indicating ACK or NACK Is called an ACK channel.

For example, in the case of VoIP, VoIP packets are transmitted in uplink and downlink. In this case, HARQ is introduced in both directions. In particular, in the uplink, power control is introduced to minimize interference between users or other cells. In this case, the downlink transmits an ACK / NACK bit and a power control bit for the uplink packet data. At this time, there is a need for a method of simultaneously transmitting different control channel information such as K / NACK bit and power control bit.

As another example, a mobile station may need to transmit ACK / NACK bits in uplink as a response to downlink packet data, and at the same time, may need to transmit a scheduling request bit to a base station.

As described above, there is a need for a method and a method of efficiently transmitting two or more control channel bits to be transmitted simultaneously for different purposes using the same resource, that is, frequency, time, and code resources.

The technical problem to be achieved by the present invention is to assign the same frequency, time, code resources to the two pieces of information by performing the modulation by combining the bits of the different control channels together or by encoding them together.

The technical problem to be achieved by the present invention is to reduce the complexity of the transmitter and the receiver by simplifying the resource management procedure of the transmitter, and by performing the demodulation of different channels at the same time.

In order to solve the above technical problem, a method of transmitting different control channel information using the same resource proposed in the present invention includes control channel information in a wireless communication system including a base station transmitting a response to packet data received from a mobile station. In the method for transmitting a packet comprising the step of binding and modulating different control channel information for the mobile station in response to the packet data received by the base station and transmitting the response to the packet data to the mobile station that transmitted the packet data Characterized in that.

The different control channel information may include a combination of ACK / NACK information, power control information, scheduling request information, and grant information.

In addition, according to the information included in the different control channel information, characterized in that the modulation through the Quadrature Phase Shift Keying (QPSK) or Quadrature Amplitute Modulation (QAM) modulation scheme.

Further, when the different control channel information is ACK / NACK information and power control information, the modulation is performed by varying an interval between constellation points for the ACK / NACK information and the power control information.

In addition, the Euclidian distance of the ACK / NACK information (Euclidian distance) is characterized in that the modulation is larger than the Euclidean distance of the power control information.

In addition, it characterized in that to generate a repetition code (repetition code) for repeatedly placing the possible combination of different control channel information.

In addition, a bi-orthogonal code is generated for a possible combination of different control channel information.

In addition, the modulation symbols modulated by combining the different control channel information for the mobile station that has transmitted the packet data in the wireless communication system by multiplexing by CDM, FDM or TDM characterized in that for transmitting to the mobile stations.

In order to solve the above technical problem, a base station transmitting different control channel information by using the same resource proposed by the present invention is a base station transmitting a response to packet data received from a mobile station in a wireless communication system, which is received at a base station. In response to the received packet data, different control channel information is bundled, modulated, and transmitted to the mobile station which has transmitted the packet data.

In addition, when the different control channel information is ACK / NACK information and power control information, the NACK bit is received when an error is found by receiving packet data from the mobile station and performing a cyclic redundancy check (CRC) check on the packet data. When the error is not found, the ACK / NACK information generating the ACK bit and the reception strength of the packet data are detected, the power control information generating the power control symbol of the packet data is bundled, modulated, and transmitted to the mobile station. do.

In order to solve the above technical problem, a mobile station that transmits packet data suitable for different control channel information received through the same resource proposed by the present invention may transmit packet data to a base station in a wireless communication system. After receiving the response to the packet data from the base station after transmitting the different control channel information from the response, characterized in that for transmitting the packet data according to the information contained in the different control channel information.

When the different control channel information is ACK / NACK information and power control information, after receiving the packet data from the base station after transmitting the packet data, the ACK / NACK information and the power control information are received in the response. Extract and retransmit the previously sent packet data according to the information included in the ACK / ANCK information, or transmit the next packet data of the previously sent packet data, and according to the information included in the power control information, It is characterized by transmitting by adjusting the transmission power.

As described above, when one user needs to simultaneously transmit two control channels having different purposes in a cellular system, the same resources, that is, frequency, time, and code resources may be simultaneously used, but the bits of the two channels may be bundled and modulated and transmitted. have.

In addition, resource management can be efficiently performed at the transmitter, and the receiver can reduce the complexity of the receiver since the same channel estimation result can be used when coherent demodulation of the two channels.

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

An example of uplink VoIP as a packet data transmission method according to an embodiment of the present invention will be described.

In order to minimize packet errors in the cellular data transmission of the cellular system, introduction of a HARQ (Hybrid Automatic Retransmit reGuest) is essential. In this case, the ACK or NACK bit is transmitted on the link (opposite link) that receives the packet data. The ACK is transmitted when no error occurs in the received packet, and the NACK is transmitted when an error occurs. If a NACK is received, the packet is retransmitted. If an ACK is received, the next packet is transmitted. This is called HARQ.

When the packet data is transmitted in the uplink of the cellular system, uplink power control is performed to reduce the effect on other cells and to minimize the packet error rate. In this case, power control information for the uplink packet transmission power control is performed. It is transmitted in downlink.

The present invention simultaneously modulates or encodes different types of control channel information such as ACK / NACK bits, power control bits, scheduling request bits, grant bits for scheduling permission, etc. using the same resources (eg, frequency, time, code). It relates to a method to perform the transmission.

Hereinafter, a method of simultaneously transmitting ACK / NACK bits and power control bits through the same resource will be described. In the present specification, if a technology for simultaneously transmitting two different types of control channel information through the same resource, it is within the scope of the present invention irrespective of the type of control channel information. If you have it, you can easily understand it. The ACK or NACK bit for HARQ and the power control bit for power control are modulated or bundled together using the same resources, that is, frequency, time, and code resources, to perform encoding.

For example, when 1 bit is assigned as a bit for the ACK or NACK and 1 bit as the bit for the power control, the 2 bits are combined to perform 4QAM or quadrature phase shift keying (QPSK) modulation. For example. In the case of 4QAM or QPSK modulation, the length between constellation points may be different during transmission to change the error rate of the ACK / NACK bit and the power control bit when demodulating at the receiving end. In general, the error rate of the ACK / NACK bit should be 10 ^-3 or less, but the error rate of the power control bit needs only to be maintained at 10 ^-1 to 10 ^-2 .

FIG. 2 is a diagram illustrating a method of varying an error rate of an ACK / NACK bit and a power control bit at a mobile station receiving end by varying a length between constellation points according to an exemplary embodiment of the present invention.

In FIG. 2, the front portion b ₀ of (b ₀ b ₁ ) represents an ACK / NACK bit, and the rear portion b ₁ represents a power control bit. As a result, Euclidian distances 200 and 220 for distinguishing 0s and 1s of the ACK / NACK bits from the transmitting end are Euclidian distances 210 and 230 for distinguishing 0s and 1s of the power control bits. In this case, the error rate of the ACK / NACK bit can be lower than the error rate of the power control bit at the receiving end.

Even when the method of the present invention is used for combining uplink ACK / NACK bits and scheduling request bits, it can be combined and transmitted using QPSK as described above, and the error rate and scheduling request bits of the ACK / NACK bits are received at the receiving end. In order to different the error rate of the Euclidian distance (Euclidian distance) can be transmitted differently as described above.

As described above, in the case of performing modulation by combining two different types of channels as described above, the receiver may demodulate using the same channel estimation result when coherent demodulation, thereby reducing the complexity of the demodulator.

In the method of the present invention, the 4QAM or QPSK modulated symbols may be repeatedly transmitted several times to minimize errors. That is, it may be transmitted by repetition coding. Assuming that b ₀ and b ₁ are ACK / NACK bits and other control bits, respectively, four possible repetition codes are generated for four possible combinations of b ₀ and b ₁ , for example, having a length of eight. For example, how to create a repetition code.

The repetition code is grouped by two elements and transmitted in QPSK or 4QAM modulation as in the example of FIG. 2, and the number of modulation symbols is 1/2 of the length of the repetition code. On the other hand, modulation symbols for other users in the cell are transmitted multiplexed to the CDM, FDM or TDM. This will be described in detail later.

As another example, when 1 bit is allocated as a bit for ACK or NACK and 1 bit as the bit for the other control, a method of performing bi-orthogonal coding on the 2 bits is given.

That is, assuming that b ₀ and b ₁ are the ACK / NACK bits and the power control bits, respectively, four possible bi-orthogonal codes are generated for four possible combinations of b ₀ and b ₁ . An example is how to make a bi-orthogonal code of length 8.

The bi-orthogonal code is transmitted by QPSK or 4QAM modulation for each element, and the number of modulation symbols is 1/2 of the length of the bi-orthogonal code. Symbols between different users in a cell are transmitted multiplexed with CDM, FDM or TDM. This will be described in detail later.

FIG. 3 is a diagram illustrating modulation symbols of 6QAM modulated orthogonal type ACK / NACK bits and power control bits according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating modulation symbols of 6QAM (or non-uniform 6PSK) having a rectangular type of ACK / NACK bits and power control bits according to an exemplary embodiment of the present invention.

On the other hand, the power control information may further include information that the mobile station to "hold" in addition to "up" and "down" the power when transmitting the VoIP packet.

There are six possible cases in this case. That is, since the power control symbol has three kinds of information (0: up, 1: down, h: hold), the total number of ACK / NACK bits and power control symbols is six.

That is, assuming that b ₀ and b ₁ are ACK / NACK bits and power control symbols, respectively, the combination of b ₀ b ₁ becomes {00, 0h, 01, 10, 1h, 11}. In this case, the two symbols may be bundled to perform a 6QAM modulation of a rectangular type as shown in FIG. 3 or a 6QAM (or non-uniform 6PSK) modulation of a circular type as shown in FIG. 3.

Even in this case, the error rate of the ACK / NACK bit is changed by varying the Euclidian distance of 0 and 1 of the ACK / NACK bit and the Euclidian distance between 0 and h or h and 1 or 0 and 1 of the power control symbol. Can be lower than the error rate of the power control symbol.

As shown in FIG. 4, when the circular type 6QAM (or non-uniform 6PSK) is used, the energy of each constellation point is the same, so that the peak-to-average power ratio and peak-to-average power ratio are PAPR. It may be better than 6QAM of the orthogonal type of FIG.

When the transmitter uses MIMO (Multi-Input Multi-Output), an ACK / NACK channel sent by one user may include 2 bits. In this case, when combined with the bits of the control channel other than the ACK / NACK channel bits, that is, the transmission power control (TPC) bits or the scheduling bits, the transmission may be combined with 8PSK or 8QAM. Such a method also does not depart from the scope of the present invention.

The M-QAM or M-PSK symbol may be repeatedly transmitted several times to minimize errors. That is, it may be transmitted by repetition coding. Assuming b ₀ and b ₁ are ACK / NACK bits and power control symbols, respectively, six possible repetition codes for six possible combinations of b ₀ and b ₁ (assuming M is 6) As an example, how to make a repetition code of length 8 is generated.

The repetition code is grouped by two elements for each element and transmitted after being modulated by 6QAM (or 6QPSK) as shown in FIG. 3 or 4, and the number of modulation symbols is 1/2 of the length of the repetition code. do. Meanwhile, modulation symbols for other users in the cell are multiplexed with CDM, FDM or TDM and transmitted. This will be described in detail later.

5 is a diagram illustrating a method for transmitting packet data between a base station and a mobile station using HARQ according to an embodiment of the present invention.

The base station checks the Cyclic Redundancy Check (CRC) after receiving the packet data 510 from the mobile station and generates a NACK bit if there is an error, otherwise generates an ACK bit, and detects the reception strength of the packet data to generate the power. After generating the control symbol, a symbol 520 (called a combined symbol) combining the ACK / NACK bit and the power control symbol is transmitted in downlink.

After transmitting the packet data 510, the mobile station receives the combined symbol 520 from the base station, extracts an ACK / NACK bit and a power control symbol, and transmits the next packet data 511 different from the previously sent packet if the ACK. In this case, the packet data 512, which is the same as the packet previously sent or further added with redundancy, is retransmitted.

In addition, when the power control symbol means "up", the power of the sending packet is increased by a predetermined difference 504 from the most recently transmitted power, and when the power control symbol 523 is "down", If the power control pawns 522 and 524 are " hold ", the power is lowered by the preset difference 505 and sent to the same power as the most recently transmitted power. 515).

Coupling symbols of different control channels for one user may be multiplexed with CDM, FDM or TDM as mentioned above when distinguishing between different users. That is, in a cellular system, multiple users must be multiplexed. The method of the present invention can use CDM, FDM, or TDM as multiplexing of the combined symbols between different users.

FIG. 6 is a diagram illustrating a method of melplexing a combined symbol by a CDM scheme in an OFDMA or DFT spread OFDMA transmission system according to an embodiment of the present invention.

In FIG. 6, when N is defined as the number of OFDM symbols for transmitting the combined symbols and M is defined as the number of subcarriers, in the example of FIG. 6, a total of 4 (= N × M) time-frequency resources transmit the combined symbols. Can be used for

In FIG. 6, reference numeral 600 denotes an OFDM symbol period, and 610 denotes an OFDM subcarrier bandwidth. In the example of FIG. 6, when using different orthogonal code sequences, for example, a Hadamard code having a length of 4, the combined symbols of four mobile stations can be multiplexed with the CDM. Hadamard code is one example, and the use of other kinds of code does not depart from the scope of the present invention.

FIG. 7 is a diagram illustrating a method in which a combined symbol is repeatedly transmitted in a frequency domain in order to obtain a frequency diversity gain when a combined symbol is multiplexed into another user's CDM in an OFDM scheme according to an embodiment of the present invention.

In the case of using repetition coding as shown in Equation 1 or 3, each symbol may be transmitted as far as possible on a frequency to obtain a frequency diversity gain in an OFDM system. In FIG. 7, an example is given only when there are two mobile stations. In FIG. 7, S _j and S _k are modulated joint symbols transmitted to the j and k th mobile stations, respectively, and C ^(j) and C ^(k) denote code sequences used to code multiplex the j and k th mobile stations, respectively. it means. As such, when using CDM, there is an advantage of reducing interference between neighbor cells compared to TDM or FDM.

Therefore, in FIG. 7, it is combined in the form of S _j C ^(j) + S _k C ^(k) and repeats in the frequency domain (700-A to 730-A) using a repetition coding method of length 8. Indicates the type of transmission.

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, optimal embodiments have been disclosed in the drawings and the specification. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not intended to limit the scope of the present invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a diagram schematically illustrating an OFDMA system for transmitting a response to a general HARQ packet.

FIG. 2 is a diagram illustrating a method of varying an error rate of an ACK / NACK bit and a power control bit at a mobile station receiving end by varying a length between constellation points according to an exemplary embodiment of the present invention.

FIG. 3 is a diagram illustrating modulation symbols of 6QAM modulated orthogonal type ACK / NACK bits and power control bits according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating modulation symbols of 6QAM (or non-uniform 6PSK) having a rectangular type of ACK / NACK bits and power control bits according to an exemplary embodiment of the present invention.

5 is a diagram illustrating a method for transmitting packet data between a base station and a mobile station using HARQ according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a method of melplexing a combined symbol by a CDM scheme in an OFDMA or DFT spread OFDMA transmission system according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a method in which a combined symbol is repeatedly transmitted in a frequency domain in order to obtain a frequency diversity gain when a combined symbol is multiplexed into another user's CDM in an OFDM scheme according to an embodiment of the present invention.

Claims (12)

A method of transmitting control channel information in a wireless communication system including a base station transmitting a response to packet data received from a mobile station, the method comprising: Binding and modulating different control channel information for the mobile station in response to the packet data received at the base station; And And transmitting a response to the packet data to a mobile station that has transmitted the packet data. The method of claim 1, The different control channel information is a combination of ACK / NACK information, power control information, scheduling request information, grant (Grant) information, characterized in that for transmitting different control channel information using the same resource. The method of claim 1, A method of transmitting different control channel information using the same resource, characterized in that the modulation is performed through Quadrature Phase Shift Keying (QPSK) or Quadrature Amplitute Modulation (QAM) modulation according to the information included in the different control channel information. . The method of claim 1, When the different control channel information is ACK / NACK information and power control information, the same resource may be modulated by varying an interval between constellation points for the ACK / NACK information and the power control information. Method for transmitting different control channel information. The method of claim 4, wherein And controlling the Euclidian distance of the ACK / NACK information to be larger than the Euclidean distance of the power control information to modulate different control channel information using the same resource. The method of claim 1, And generating a repetition code for repeatedly arranging the possible combinations of different control channel information. The method of claim 1, And generating bi-orthogonal codes for the possible combinations of different control channel information. The method of claim 1, The modulation symbols modulated by binding the different control channel information for the mobile stations transmitting the packet data in the wireless communication system are multiplexed by CDM, FDM or TDM and transmitted to the mobile stations by using the same resource. How to send other control channel information. A base station for transmitting a response to packet data received from a mobile station on a wireless communication system, A base station for transmitting different control channel information using the same resource, characterized in that to bind and modulate different control channel information in response to the packet data received from the base station to the mobile station that transmitted the packet data. The method of claim 9, When the different control channel information is ACK / NACK information and power control information, when receiving an packet data from the mobile station and an error is found through a cyclic redundancy check (CRC) check on the packet data, an NACK bit is returned. Is not found, the ACK / NACK information generating the ACK bit and the reception strength of the packet data are detected, the power control information generating the power control symbol of the packet data is bundled, modulated, and transmitted to the mobile station. A base station for transmitting different control channel information using the same resource. A mobile station for transmitting packet data to a base station on a wireless communication system, Receiving packet response from the base station after transmitting the packet data, extracting different control channel information from the response, and transmitting the packet data according to the information included in the different control channel information again; A mobile station transmitting packet data suitable for different control channel information received through the same resource. The method of claim 11, When the different control channel information is ACK / NACK information and power control information, after receiving the response to the packet data from the base station after transmitting the packet data, the ACK / NACK information and power control information are extracted from the response. Retransmit the previously sent packet data according to the information included in the ACK / ANCK information or transmit the next packet data of the previously sent packet data, And transmitting the packet data suitable for different control channel information received through the same resource, characterized in that the transmission power of the transmitted packet data is adjusted and transmitted according to the information included in the power control information.

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