KR20080097112A - Method of transmitting control region format information - Google Patents

Abstract

A method for transmitting control region format information is provided to reduce the overhead of a control channel having restricted radio resources. A method for transmitting control information for a sub frame which is made of a plurality of OFDM symbols and a plurality of subcarriers and is divided into a control area and data area comprises the following steps of: transmitting the first sub frame(the sub frame for unicast) having a control area of the variable size or the second sub frame having a control area of the fixed size; and transmitting the control area format information(the subframe for multicast) which informs the size of the control area used for the sub frame as indicating the size of the control area of the first sub frame or the second sub frame.

Description

Method of transmitting control region format information

The present invention relates to wireless communication, and more particularly, to a method of transmitting control region format information for a subframe.

In a mobile communication system, generally, one base station provides a service to a plurality of terminals. The base station schedules user data for a plurality of terminals, and sends the user data together with the control information containing scheduling information to the terminal. The channel on which the control information is carried is called a control channel, and the channel on which user data is carried is called a data channel. The terminal searches for the control channel to find its own control information, and processes its data using the control information.

The control information includes resource allocation information, which is information on a structure in which radio resources used for downlink or uplink are allocated, information on whether a group communication method is unicast, broadcast, or multicast, and whether transmission information is retransmitted. Multiple Input Multiple Output (MIMO) control such as Acknowledgment (ACK) / Negative-Acknowledgement (NACK) signal, Channel Quality Indicator (CQI) indicating downlink channel quality, as well as Precoding Matrix Index (PMI) and Rank Indicator (RI) There can be many different types of information.

The base station transmits control information to the terminal through a downlink control channel. The size of the control information may be variable. That is, since different control information may be required for each terminal, the size of the control information may be different for each terminal, and the size of control information required for the same terminal may vary according to time or frequency.

Group communication methods may be divided into unicast, broadcast and multicast transmissions according to the number of transmitters and receivers participating in the communication. Unicast transmission is a method in which one transmitter transmits data to one receiver. Broadcast transmission is a method in which one transmitter transmits data to all receivers on a network. Multicast transmission is a method in which one transmitter transmits data to a receiver belonging to a specific group on a network. That is, the unicast transmission method transmits data in point-to-point, and the broadcast and multicast transmission methods transmit data in point-to-multipoint.

Since the control information varies according to the group communication method, the amount of control information increases accordingly. When the amount of control information transmitted through the control channel increases, it may cause excessive overhead on the control channel having limited radio resources. Therefore, a method for efficiently transmitting control information is required.

An object of the present invention is to provide a method for configuring and transmitting information on the size of a control region of a subframe, which is control information on a subframe, and information on a group communication method, into one control region format information.

According to an aspect of the present invention, a method of transmitting control information for a subframe including a plurality of OFDM symbols and a plurality of subcarriers and divided into a control region and a data region is provided. The method includes transmitting a first subframe having a control region of a variable size or a second subframe having a control region of a fixed size, and controlling the size of the control region of the first subframe or the second subframe. The method may include transmitting control region format information indicating a size of a control region used for a subframe.

According to another aspect of the present invention, a method of transmitting control region format information for a subframe is provided. The method includes transmitting a subframe consisting of a plurality of OFDM symbols and a plurality of subcarriers and divided into a control region and a data region, and indicating whether the subframe is a unicast subframe or a multicast subframe. And simultaneously transmitting control region format information indicating the size of the control region included in the subframe.

It is possible to reduce overhead of a control channel having limited radio resources by configuring and transmitting information on the size of the control region of the subframe, which is control information on the subframe, and information on the group communication method, as one control region format information. .

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present embodiment is not limited to the embodiments disclosed below, but will be implemented in various forms, and only this embodiment is intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. Shapes of the elements in the drawings may be exaggerated parts to emphasize a more clear description, elements denoted by the same reference numerals in the drawings means the same element.

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

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

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

Multiple access schemes for downlink and uplink transmission may be different. For example, downlink may use Orthogonal Frequency Division Multiple Access (OFDMA) and uplink may use Single Carrier-Frequency Division Multiple Access (SC-FDMA).

There is no limitation on the multiple access scheme applied to the wireless communication system. Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Single-Carrier FDMA (SC-FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or other known modulation techniques. It can be based on the same multiple access techniques. These modulation techniques demodulate signals received from multiple users of a communication system to increase the capacity of the communication system. For clarity, the following description will be made of an OFDMA-based wireless communication system.

Orthogonal Frequency Division Multiplexing (OFDM) uses multiple orthogonal subcarriers. OFDM uses orthogonality between inverse fast fourier transforms (IFFTs) and fast fourier transforms (FFTs). At the transmitter, data is sent by performing an IFFT. The receiver performs FFT on the received signal to recover the original data. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers. According to OFDM, the complexity of the receiver can be reduced in a frequency selective fading environment of a wideband channel, and the spectral efficiency can be improved through selective scheduling in the frequency domain by using different channel characteristics between subcarriers. . Orthogonal Frequency Division Multiple Access (OFDMA) is a multiple access scheme based on OFDM. According to OFDMA, the efficiency of radio resources can be improved by assigning different subcarriers to multiple users.

2 shows an example of a radio frame structure.

Referring to FIG. 2, a radio frame may consist of 10 subframes, and one subframe may include two slots. The basic unit of data transmission is a subframe unit, and downlink or uplink scheduling is performed on a subframe basis. One slot may include a plurality of OFDM symbols in the time domain and at least one subcarrier in the frequency domain. One slot may include 7 or 6 OFDM symbols.

The structure of the radio frame is only an example, and the number of subframes included in the radio frame or the number of slots included in the subframe, the number of OFDM symbols included in the slot, and the number of subcarriers may be variously changed.

3 shows an example of a subframe structure.

Referring to FIG. 3, a subframe may be divided into two parts, a control area and a data area. The control area is an area for transmitting only control signals and is allocated to the control channel. The data area is an area for transmitting data and is allocated to a data channel. The control channel is a channel for transmitting a control signal, and the data channel is a channel for transmitting user data or user data and a control signal. The control channel and the data channel may consist of one subframe. The control signal is a signal other than user data, and may include various types such as an ACK (Acknowledgement) / NACK (Negative-Acknowledgement) signal, a channel quality indicator (CQI), a precoding matrix index (PMI), and a rank indicator (RI).

The control area is located at the beginning of the subframe, and the data area is located at the end of the control area. However, this is only an example and the arrangement of the control region and the data region on the subframe is not limited. Positions of the control area and the data area may be interchanged, and are not necessarily limited to the illustrated form.

Each slot per subframe may include seven OFDM symbols in the time domain from one UE perspective. Therefore, when one subframe consists of two slots, one subframe may consist of a total of 14 OFDM symbols. When a control signal and data are transmitted through at least one OFDM symbol in one subframe, the first three OFDM symbols may transmit a control signal and the remaining 11 OFDM symbols may transmit user data. The number of OFDM symbols for transmitting control signals and data on one subframe may be variously set.

One OFDM symbol in the frequency domain may include at least one subcarrier. One subcarrier and one OFDM symbol are also called a resource element. In the case of downlink, the number of subcarriers included in one OFDM symbol is different for each terminal. For example, in the FDMA system, the number of subcarriers included in one OFDM symbol is the number of subcarriers corresponding to the frequency bandwidth allocated to the terminal.

4 shows an example of a group communication method.

Referring to FIG. 4, the base station 130 transmits a signal to each terminal 140a, 140b, 140c, 140d. The base station 130 may transmit multiple transmission signals simultaneously through broadcast, multicast and / or unicast transmission. Broadcast transmissions are sent to all users in a particular area (eg, cells and / or sectors), multicast transmissions are sent to specific groups of users, and unicast transmissions are sent to specific users. All terminals 140a, 140b, 140c, 140d in the cell may receive broadcast signals. In addition, the terminals 140b and 140c belonging to a specific group may receive a multicast signal. Specific terminals 140c and 140d may receive unicast signals for themselves. If this is indicated from the viewpoint of the terminal, each terminal 140a, 140b, 140c, 140d may receive a signal necessary for itself. The first terminal 140a receives only a broadcast signal. The second terminal 140b receives a broadcast signal and a multicast signal. The third terminal 140c receives a broadcast signal, a multicast signal, and a unicast signal. The fourth terminal 140d receives the broadcast signal and the unicast signal.

The subframe structure may be different according to the group communication method. For example, since a unicast subframe and a multicast subframe may have different cyclic prefixes, the receiver must know whether the subframe received from the transmitter is a unicast subframe or a multicast subframe. .

5 is an example of a method of configuring control region format information according to the present invention.

Referring to FIG. 5, a unicast subframe is a subframe having a structure necessary for unicast transmission, and a multicast subframe is a subframe having a structure necessary for multicast transmission. The unicast subframe has a control area of variable size, and the multicast subframe has a control area of fixed size. The first to third states are states of unicast subframes, and the fourth state is states of multicast subframes. The control region is allocated in OFDM symbol units, and it is assumed that the maximum number of OFDM symbols allocated to the control region is three.

Since the size of the control region of the unicast subframe is variable, the unicast subframe may have various states according to the size of the control region. The first state is a case where the control region has one OFDM symbol, the second state is a case where the control region has two OFDM symbols, and the third state is a case where the control region has three OFDM symbols. That is, the unicast subframe may have as many states as the maximum number of OFDM symbols allocated to the control region.

On the other hand, the size of the control region of the multicast subframe is fixed. Therefore, the subframe for multicast has only one state, unlike the subframe for unicast. The number of OFDM symbols allocated to the control region of the multicast subframe is determined to be within a predetermined number. The subframe in the fourth state represents a multicast subframe having a control region fixed with two OFDM symbols.

The subframe transmitted by the base station or the terminal belongs to one of the subframes of the first to fourth states. Information indicating the state of such a subframe is called control region format information. That is, the control region format information is the control information for the subframe, and together indicates the size of the control region included in the subframe and information about the group communication method of the subframe.

Since the control region format information is control information for a subframe to be transmitted, the control region format information may be transmitted through a physical dedicated control channel (hereinafter referred to as PDCCH). Alternatively, the control region format information may be transmitted through a physical control format indicator channel (PCFICH). The PCFICH is a channel indicating the size of the control region included in the subframe.

Table 1 shows an example in which the subframes of the four states of FIG. 5 correspond to 2-bit control region format information.

State of the subframe Group communication method Size of control area Control Area Format Information First state Unicast 1 OFDM symbol 00 Second state Unicast 2 OFDM symbols 01 Third state Unicast 3 OFDM symbols 10 4th state Multicast 2 OFDM symbols 11

Referring to Table 1, the subframes of the first to third states are all unicast subframes, and since the size of the control region is variable within three OFDM symbols, the control region format information that may indicate three cases is determined. I need a quantity. On the other hand, the subframe of the fourth state is a multicast subframe, and since the size of the control region is fixed to two OFDM symbols, an amount of control region format information indicating one case is required.

Therefore, the amount of control region format information that can represent the total number of four cases is required, and since all four cases can be represented as two bits, the control region format information requires two bits. If the control region format information is 00, the subframe of the first state; if the control region format information is 01; the subframe of the second state; if the control region format information is 10, the subframe of the third state; 11 indicates a subframe of the fourth state.

As simple control region format information, information on the size of the control region of the subframe and the group communication method of the subframe can be transmitted, thereby reducing overhead due to excessive control information. The maximum size of the control area and the group communication method may be combined in various ways. The size of the control area may be three or more OFDM symbols, and the group communication method may include broadcast. The number of bits required for the format information can also vary. In addition, even in a multicast subframe, the number of fixed OFDM symbols may vary depending on the system.

6 is another example of a method of configuring control region format information according to the present invention.

Referring to FIG. 6, the first to fourth states are examples of configuring control region format information for a subframe. The group communication method is either unicast or multicast, and the control region is allocated in the subcarrier unit in the frequency band or in the OFDM symbol unit in the time domain. The control region may occupy part or all of the frequency band evenly divided into a predetermined number of subcarriers.

Since the size of the control region of the unicast subframe is variable, the unicast subframe may have various states according to the size of the control region. That is, the total subcarrier is divided into three and the state varies depending on the number of subcarriers occupied by the control region. The first state is a case where the control region occupies one third of the total subcarriers on three OFDM symbols, and the second state is a case where the control region occupies two thirds of the total subcarriers on three OFDM symbols. The state occupies all subcarriers on three OFDM symbols.

On the other hand, the size of the control region of the multicast subframe is fixed. Therefore, the subframe for multicast has only one state, unlike the subframe for unicast. The subframe in the fourth state is a subframe for multicast and has a control region fixed with two OFDM symbols.

Table 2 shows an example in which the subframes in the four states of FIG. 6 are mapped to 2-bit control region format information.

State of the subframe Group communication method Size of control area Control Area Format Information First state Unicast One-third of the total carrier 00 Second state Unicast Two-thirds of the total carrier 01 Third state Unicast General Carrier 10 4th state Multicast 2 OFDM symbols 11

Referring to Table 2, the subframes of the first to third states are all unicast subframes, and since the number of subcarriers allocated to the control region is variable, the amount of control region format information that can represent three cases is increased. need. On the other hand, the subframe of the fourth state is a multicast subframe, and since the size of the control region is fixed to two OFDM symbols, an amount of control region format information indicating one case is required.

Therefore, the amount of control region format information that can represent the total number of four cases is required, and since all four cases can be represented as two bits, the control region format information requires two bits. If the control region format information is 00, the subframe of the first state; if the control region format information is 01; the subframe of the second state; if the control region format information is 10, the subframe of the third state; 11 indicates a subframe of the fourth state.

The size of the control region may occupy some or all of the usable subcarriers by dividing the usable total subcarriers evenly or evenly, and may include broadcast in the group communication scheme. Accordingly, the number of states can be increased or decreased, so the number of bits used as format information of the control region can be increased or decreased.

7 is a flowchart of a method for transmitting control region format information according to the present invention.

Referring to FIG. 7, a subframe is generated (S210). A transmitter for transmitting a subframe first generates a subframe including a control region and a data region to which a predetermined radio resource is allocated. The subframe includes a plurality of OFDM symbols and a plurality of subcarriers, and the control region includes at least one or more OFDM symbols and at least one subcarrier.

The control region format information is transmitted (S220). The receiver receiving the subframe needs to know the size occupied by the control region and the data region on the subframe, and also needs to know the information about the group communication method indicating whether the received subframe is for unicast or multicast. Therefore, the transmitter should inform the receiver of control region format information, which is control information regarding the size of the control region and the group communication method.

Since the control region format information is control information for a subframe to be transmitted, the control region format information may be transmitted through a physical dedicated control channel (hereinafter referred to as PDCCH). Alternatively, the control region format information may be transmitted through a physical control format indicator channel (PCFICH). The PCFICH is a channel indicating the size of the control region included in the subframe.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

1 is a block diagram illustrating a wireless communication system.

2 shows an example of a radio frame structure.

3 shows an example of a subframe structure.

4 shows an example of a group communication method.

5 is an example of a method of configuring control region format information according to the present invention.

6 is another example of a method of configuring control region format information according to the present invention.

7 is a flowchart of a method for transmitting control region format information according to the present invention.

Claims (10)

In the method for transmitting control information for a subframe consisting of a plurality of OFDM symbols and a plurality of subcarriers and divided into a control region and a data region, Transmitting a first subframe having a control size of a variable size or a second subframe having a control size of a fixed size; And And transmitting control region format information indicating the size of the control region of the first subframe or the second subframe and indicating the size of the control region used for the subframe. The method of claim 1, Wherein the variable size is a variable number of OFDM symbols occupied by the control region. The method of claim 1, Wherein the variable size is a variable number of subcarriers occupied by the control region. The method of claim 1, Wherein the fixed size is a fixed number of OFDM symbols occupied by the control region. The method of claim 1, And the first subframe is a subframe for unicast. The method of claim 1, And the second subframe is a subframe for multicast. The method of claim 1, The control region format information is transmitted through a physical dedicated control channel (PDCCH). The method of claim 1, The control region format information is transmitted through a physical control format indication channel (PCFICH). Transmitting a subframe consisting of a plurality of OFDM symbols and a plurality of subcarriers and divided into a control region and a data region; And And indicating whether the subframe is a unicast subframe or a multicast subframe and transmitting control region format information indicating a size of a control region included in the subframe. The method of claim 9, When the subframe is a unicast subframe, the size of the control region included in the subframe is variable, and when the subframe is a multicast subframe, the size of the control region included in the subframe is fixed. .

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