KR101607328B1 - Method of transmitting control information in multi-carrier system - Google Patents

Abstract

A method of transmitting control information in a multi-carrier system is provided. The method includes the steps of transmitting a primary identifier for detecting a primary control region transmitted via a primary carrier and transmitting a primary identifier for detecting an auxiliary control region transmitted via the primary carrier And transmitting a secondary identifier. By clearly distinguishing the primary carrier from the secondary carrier, it is possible to efficiently transmit the control information at the physical layer level related to the transmission of the auxiliary carrier, and to reduce the overhead due to transmission of the control information of the auxiliary carrier have.

Description

[0001] METHOD OF TRANSMITTING CONTROL INFORMATION IN MULTI-CARRIER SYSTEM [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to a method of transmitting control information in a multi-carrier system.

Background of the Invention [0002] Wireless communication systems are widely deployed to provide various types of communication services such as voice and data. Generally, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access) systems.

SC-FDMA has almost the same complexity as OFDMA, but has a lower peak-to-average power ratio (PAPR) due to the single carrier property. Since the low PAPR is advantageous for the UE in terms of transmission power efficiency, the SC-FDMA is a 3GPP (3rd Generation Partnership Project) TS 36.211 V8.6.0 (2009-03) "Technical Specification Group Radio Access Network (UTRAN), Physical channels and modulation (Release 8) "in 3GPP LTE (Long Term Evolution).

In a typical wireless communication system, although a bandwidth between an uplink and a downlink is set to be different from each other, only one carrier is mainly considered. In 3GPP LTE, the number of carriers constituting the uplink and the downlink is one, and the bandwidths of the uplink and the downlink are symmetrical to each other. However, there is a disadvantage in that the frequency allocation of a large bandwidth is not easy except for a few regions globally, and a non-continuously fragmented small band can not be efficiently used. On the other hand, a multi-carrier system is a system in which a plurality of uplink carriers and a plurality of downlink carriers are used, and effectively suppresses intersymbol interference in a channel environment in which inter symbol interference (ISI) exists. can do.

In order to operate the wireless communication system, various physical layer level control signaling between the base station and the terminal is required. For example, modulation and coding scheme (MCS), resource allocation, ACK (Acknowledgment) / NACK (Not-Acknowledgment) information for performing hybrid automatic repeat request (HARQ) And a CQI (Channel Quality Indicator) indicating a downlink channel quality.

However, in a multi-carrier system, control information used for demodulation or decoding of data such as MCS and resource allocation information may differ from one carrier to another. In this case, separate control information must be transmitted for each subcarrier. These control information may be transmitted on the corresponding carrier wave, but in some cases, control information necessary for demodulation or decoding of a specific carrier may not be transmitted through the specific carrier wave in some cases. In this case, control information necessary for demodulating or decoding the specific carrier wave must be transmitted through another carrier wave. For example, a first carrier may be established between the base station and the terminal, and control information of the remaining carrier (s) may be transmitted via the first carrier.

In this case, a method for distinguishing control information associated with each carrier is required. For this purpose, it is necessary to newly define a format of control information related to demodulation or decoding of a carrier wave.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of transmitting control information in a multi-carrier system that facilitates the identification of carriers and provides an optimal control information format.

According to an aspect of the present invention, there is provided a method of transmitting control information in a multi-carrier system. The method includes the steps of transmitting a primary identifier for detecting a primary control region transmitted via a primary carrier and transmitting a primary identifier for detecting an auxiliary control region transmitted via the primary carrier And transmitting a secondary identifier. The scheduling information included in the sub-control region is information related to scheduling of data transmitted through a secondary carrier belonging to a frequency band different from the main carrier.

According to another aspect of the present invention, there is provided a method of transmitting control information in a multi-carrier system. The method includes transmitting identification information for detecting a control region of a main carrier, transmitting the masking scheduling information through a control region of a main carrier, Transmitting downlink data through an auxiliary carrier wave belonging to a frequency band different from a carrier wave or receiving uplink data.

By clearly distinguishing the primary carrier from the secondary carrier, it is possible to efficiently transmit the control information at the physical layer level related to the transmission of the auxiliary carrier, and to reduce the overhead due to transmission of the control information of the auxiliary carrier have.

The following description is to be understood as illustrative and non-limiting, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access And can be used in various wireless access systems. CDMA may be implemented in radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. The TDMA may be implemented in a wireless technology such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in wireless technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) is a part of E-UMTS (Evolved UMTS) using E-UTRA, adopting OFDMA in downlink and SC-FDMA in uplink. LTE-A (Advanced) is the evolution of 3GPP LTE.

The basic wireless communication system, the structure of the radio frame, the control channel, and the format of the control information related to the transmission of the control information will be described with reference to the transmission method of the control information according to the present invention. Although the description of the 3GPP system is taken as an example, the present invention is not limited to the 3GPP system, but is only a difference in terminology used in each standard. The structure of the IEEE 802.16 system, the frame structure, As shown in FIG.

1 shows a wireless communication system.

Referring to FIG. 1, a wireless communication system 10 includes at least one base station 11 (BS). Each base station 11 provides a communication service to a specific geographical area (generally called a cell) 15a, 15b, 15c. The cell may again be divided into multiple regions (referred to as sectors). A user equipment (UE) 12 may be fixed or mobile and may be a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA) A wireless modem, a handheld device, and the like. The base station 11 generally refers to a fixed station that communicates with the terminal 12 and may be referred to by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point have.

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

2 shows a structure of a radio frame in 3GPP LTE. A radio frame is composed of 10 subframes, and one subframe is composed of two slots. The time taken for one subframe to be transmitted is referred to as a transmission time interval (TTI). For example, the length of one subframe may be 1 ms and the length of one slot may be 0.5 ms.

One slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain and a plurality of RBs (resource blocks) in a frequency domain. The OFDM symbol is used to represent one symbol period because 3GPP LTE uses OFDMA in the downlink and may be called another name according to the multiple access scheme. For example, when SC-FDMA is used in an uplink multiple access scheme, it may be referred to as an SC-FDMA symbol. A resource block includes a plurality of consecutive subcarriers in one slot in a resource allocation unit.

The structure of the radio frame is merely an example, and the number of subframes included in a radio frame, the number of slots included in a subframe, and the number of OFDM symbols included in a slot can be variously changed.

3 shows a structure of a downlink sub-frame. The subframe includes two slots in the time domain. A maximum of 3 OFDM symbols preceding a first slot in a subframe are control regions to which control channels are allocated, and the remaining OFDM symbols are data regions to which a physical downlink shared channel (PDSCH) is allocated. In IEEE 802.16e, the control region is called a DL-MAP and the data region is called a burst.

The downlink control channels included in the control region include a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), and a Physical Hybrid-ARQ Indicator Channel (PHICH). The PCFICH transmitted in the first OFDM symbol of the subframe carries information on the number of OFDM symbols (i.e., the size of the control region) used for transmission of the control channels in the subframe. The control information transmitted through the PDCCH is referred to as downlink control information (DCI). The following table shows the DCI according to the DCI format.

DCI format 0 indicates uplink resource allocation information, DCI formats 1 and 2 indicate downlink resource allocation information, and DCI formats 3 and 3A indicate uplink TPC (transmit power control) commands for arbitrary UE groups .

The following table shows inforamtion elements included in the DCI format 0 which is uplink resource allocation information (or uplink grant). Each information element is described in Section 5.3.3.1 of 3GPP TS 36.212 V8.6.0 (2009-03) "Technical Specification Group Radio Access Network (E-UTRA), Multiplexing and channel coding (Release 8) can do.

Hereinafter, DCI, DL-MAP, and UL-MAP are unified into scheduling information. The scheduling information indicates MCS, uplink resource allocation information, downlink resource allocation information, and uplink transmission power control commands for certain UE groups.

We now describe a multi-carrier system.

The 3GPP LTE system supports a case where the downlink bandwidth and the uplink bandwidth are set differently, but this assumes a single carrier. This means that the 3GPP LTE supports only the case where the downlink bandwidth and the uplink bandwidth are different in a situation where one carrier is defined for the downlink and the uplink, respectively. For example, the 3GPP LTE system supports a maximum of 20 MHz and supports only one carrier on the uplink and the downlink although the uplink bandwidth and the downlink bandwidth may be different.

The size (i.e. bandwidth) of the multi-carriers may be different. For example, assuming that five carriers are used for a 70 MHz band configuration, a 5 MHz carrier (carrier # 0) +20 MHz carrier (carrier # 1) +20 MHz carrier (carrier # 2) +20 MHz carrier (carrier # 3) + 5MHz carrier (carrier # 4).

4 is a diagram illustrating the configuration of a multi-carrier according to the present invention.

Referring to FIG. 4, the primary carrier and the secondary carrier occupy different frequency bands. The main carrier transmits the control area and the data area. The control region transmitted through the main carrier includes a primary control region 10 and a secondary control region 20. The main control area is a control area including control information used for detecting the data area 11 transmitted via the main carrier. On the other hand, the auxiliary control area means a control area including control information for detecting the data area 21 transmitted through the auxiliary carrier.

The reason why the auxiliary control area 20 is transmitted through the main carrier is that the auxiliary carrier may not transmit a separate control area due to the characteristics of the multi-carrier system. In this case, the control information for detecting the data area 21 of the auxiliary carrier must be transmitted through the auxiliary control area 20 of the main carrier. Therefore, the terminal having allocated the auxiliary carrier band needs to detect the auxiliary control area 20 transmitted first through the main carrier.

In this way, when the sub control area is transmitted through the main carrier, the control information of the sub control area can be configured in the same format as the control information of the main control area. The format of the control information may be the various DCI formats described above.

On the other hand, since the main control area and the auxiliary control area are distinguished from each other in the main carrier, the UE needs a method of distinguishing these control areas. These control areas are distinguished by identification information (ID) for each carrier. The ID corresponding to the main carrier is referred to as primary-ID (P-ID), and the ID corresponding to the auxiliary carrier is referred to as secondary-ID (S-ID). The terminal may be assigned only a P-ID or an S-ID, or both P-IDs and a plurality of S-IDs.

If the terminal has been assigned a P-ID, the terminal can detect the main control region using the assigned P-ID. On the other hand, if the terminal has been assigned an S-ID, the terminal can detect the sub-control region using the assigned S-ID. If the terminal has been allocated a plurality of S-IDs, the terminal can detect a plurality of corresponding sub-control regions using a plurality of allocated S-IDs.

The P-ID and the S-ID may be collectively allocated when the UE initially accesses the cell, and may be dynamically allocated or released as needed. However, the dynamic assignment or release of the ID is performed only for the S-ID. In particular, the S-ID is assigned when activating the corresponding auxiliary carrier, and the S-ID is released when deactivating the corresponding auxiliary carrier.

The P-ID and the S-ID may be C-RNTI in 3GPP LTE, and station ID in IEEE 802.16e or IEEE 802.16m. Hereinafter, the case where the P-ID and the S-ID are C-RNTIs will be described as an example.

5 is a flowchart illustrating a method of configuring a main control area or an auxiliary control area by using a base station.

Referring to FIG. 5, in step S110, the BS attaches a cyclic redundancy check (CRC) to the scheduling information to be transmitted to the UE. The control field may be a PDCCH or a DL-MAP or a UL-MAP. The CRC is masked with a unique identifier (referred to as a Radio Network Temporary Identifier (RNTI)) according to the owner or use of the control area. The unique identifier of the UE, for example, the C-RNTI (Cell-RNTI), may be masked in the CRC if it is a control domain for a particular UE.

In step S120, the CRC-added scheduling information is channel-coded to generate coded data. In step S130, rate mathing is performed. In step S140, the coded data is modulated to generate modulation symbols. In step S150, the modulation symbols are mapped to physical resource elements.

In order for the UE to receive the downlink data, the UE must first detect the main control area and the auxiliary control area configured as described above. The terminal monitors a plurality of control areas in each subframe. Here, monitoring means that the terminal attempts to decode each of the control regions according to the format of the control region. In the control region allocated in the subframe, the BS does not provide information on where the corresponding control region is located to the UE. The terminal monitors a set of control region candidates in a subframe to find its control region. This is called blind decoding.

For example, if the terminal has been assigned a P-ID and an S-ID, the terminal blind decodes the control region using the P-ID and performs blind decoding again using the S-ID. If the CRC error is not detected by demasking its P-ID and S-ID in the corresponding control region, the UE succeeds in detecting the control region having its own DCI.

If the control region is successfully detected, the UE reads the downlink scheduling information on the control region. And receives the downlink data on the data area using the downlink resource allocation in the downlink scheduling information. If the terminal detects the control region with the P-ID, the terminal receives the downlink data on the data region transmitted through the main carrier. If the terminal detects the control region with the S-ID, the terminal receives the downlink data on the data region transmitted via the auxiliary carrier. Meanwhile, in order to transmit uplink data, the UE reads uplink scheduling information on the PDCCH. The UE transmits uplink data on the data area using uplink resource allocation in uplink scheduling information.

6 is a flowchart illustrating a method of transmitting control information according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the BS transmits a P-ID and an S-ID to the MS (S200). P-ID is identification information for detecting a main control area transmitted through a main carrier, and S-ID is identification information for detecting an auxiliary control area transmitted via a main carrier. The main control area includes scheduling information necessary for reading a data area (hereinafter referred to as a main data area) transmitted via the main carrier. On the other hand, the auxiliary control area includes scheduling information necessary for reading a data area (hereinafter referred to as an auxiliary data area) transmitted through the auxiliary carrier. In a multi-carrier system, the main carrier and the auxiliary carrier belong to different frequency bands. The P-ID and the S-ID may be a C-RNTI or a station ID. The scheduling information includes MCS for modulating and coding data on a data area and resource allocation information indicating a resource block on which data is loaded.

The S-ID may be plural. This means that a plurality of carriers can be allocated to one terminal. Therefore, a terminal that has been allocated a plurality of S-IDs can receive auxiliary carriers of different frequency bands using respective S-IDs. For example, it is assumed that the first S-ID corresponds to the first auxiliary carrier and the second S-ID corresponds to the second auxiliary carrier. The terminal receives the first auxiliary carrier wave from the first auxiliary control region detected using the first S-ID. And. The terminal receives the second auxiliary carrier from the second auxiliary control region detected using the second S-ID.

The terminal detects a main control area and an auxiliary control area (S210). The method of detecting the control area can be performed by blind decoding as described above. The terminal in which the control region is detected can acquire the scheduling information.

The UE receives the downlink data from the base station on the main data area or the auxiliary data area using the obtained scheduling information (S220), and transmits the uplink data to the base station (S230). According to this method, data on the auxiliary carrier wave can be efficiently received even if the control area is not transmitted on the auxiliary carrier wave.

However, if a plurality of S-IDs are assigned to the terminal, the terminal must blind-decode the control region using all S-IDs. This can increase the complexity of the terminal and reduce the transmission rate. Therefore, it is desirable to minimize blind decoding, and a representative S-ID representative of a plurality of S-IDs can be used for this purpose. Hereinafter, the representative S-ID will be described.

7 is a flowchart illustrating a method of transmitting control information according to another example of the present invention.

Referring to FIG. 7, the base station transmits a P-ID and a representative S-ID to the terminal (S300). Even if a plurality of auxiliary carriers are allocated to the terminal, the base station transmits only one representative S-ID without transmitting the S-IDs of all the auxiliary carriers. This is to reduce not only the signaling overhead but also the burden of blind decoding of the terminal. Hereinafter, it is assumed that the base station allocates two auxiliary carriers from among five auxiliary carriers in total.

The terminal detects the main control area and the auxiliary control area using the P-ID and the representative S-ID (S310). The terminal blind decodes the sub control area using the representative S-ID, and acquires the representative scheduling information included in the sub control area when the sub control area is detected. The representative scheduling information includes an auxiliary carrier indicator indicating the two auxiliary carriers. As an example, the auxiliary carrier indicator may be bitmap information. An auxiliary carrier at a position corresponding to a bit of 1 is allocated to the terminal, and an auxiliary carrier at a position corresponding to bit 0 is not allocated to the terminal. For example, assume that five auxiliary carriers are mapped to five bits. When the auxiliary carrier indicator is 01010, the 1 st, 3 rd and 5 th auxiliary carrier corresponding to 0 are not allocated to the terminal, and the 2 nd and 4 th auxiliary carrier corresponding to 1 are allocated to the terminal.

Meanwhile, the representative scheduling information may include a difference value. This difference is information indicating whether the MCS or resource allocation information applied to the reference auxiliary carrier is different from that applied to the other auxiliary carrier. For example, assume that the number of bits used for MCS is 10, the first MCS is applied to the first subcarrier, and the second MCS is applied to the second subcarrier. If the first MCS is the reference and the difference value from the second MCS is 3, the difference value can be represented by only 2 bits, in which case 7 bits can be saved. Therefore, the representative scheduling information includes only the first MCS and the difference value between the first MCS and the second MCS.

The MS receives the downlink data using the scheduling information and the representative scheduling information obtained in the detected main control region (S320), and transmits the uplink data (S330). In this manner, only one representative S-ID is used without transmitting the S-ID corresponding to all the auxiliary carriers, and if the difference value is used, the overhead due to transmission of the control information can be reduced.

Even if the representative S-ID is used, since there is a burden of decoding rather than blind decoding using only the P-ID, the control region can be detected using only the P-ID below. That is, the base station allocates only the P-ID to the terminal. However, when only P-ID is used, a field indicating information of a plurality of auxiliary carriers must be added to the scheduling information. The field includes the auxiliary carrier indicator and the difference value as described above. The auxiliary carrier indicator may again be bitmap information.

The present invention may be implemented in hardware, software, or a combination thereof. (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microprocessor, and the like, which are designed to perform the above- , Other electronic units, or a combination thereof. In software implementation, it may be implemented as a module that performs the above-described functions. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

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 shows a wireless communication system.

2 shows a structure of a radio frame in 3GPP LTE.

3 shows a structure of a downlink sub-frame.

4 is a diagram illustrating the configuration of a multi-carrier according to the present invention.

5 is a flowchart illustrating a method of configuring a main control area or an auxiliary control area by using a base station.

6 is a flowchart illustrating a method of transmitting control information according to an exemplary embodiment of the present invention.

7 is a flowchart illustrating a method of transmitting control information according to another example of the present invention.

Claims (13)

A method for monitoring control information in a multi-carrier system, A terminal determines a control region of a primary carrier based on its C-RNTI (Cell-Radio Network Temporary Identifier) and an identifier of a secondary carrier to detect a control channel among a plurality of carriers, Wherein the plurality of carriers include the main carrier and the auxiliary carrier, the main carrier and the auxiliary carrier have different frequency bands, and the identifier of the auxiliary carrier is allocated when the auxiliary carrier is activated; And Performing a blind decoding for detecting a control channel having information for scheduling a data area of the auxiliary carrier in the control area of the determined main carrier, Wherein the control channel having information for scheduling the data region of the auxiliary carrier is not detected in the control region of the auxiliary carrier. delete delete The method according to claim 1, Wherein the control channel includes a physical downlink control channel (PDCCH). A terminal for a multi-carrier system, An RF (Radio Frequency) unit for transmitting or receiving a radio signal; And And a processor coupled to the RF unit, Determining a control region of a primary carrier based on a Cell-Radio Network Temporary Identifier (C-RNTI) of the UE and an identifier of a secondary carrier among a plurality of carriers to detect a control channel, The main carrier and the auxiliary carrier have different frequency bands and the identifier of the auxiliary carrier is allocated when the auxiliary carrier is activated, Performing blind decoding to detect a control channel having scheduling information for the auxiliary carrier in a control region of the determined main carrier, Wherein the control channel having information for scheduling the data area of the auxiliary carrier is not detected in the control area of the auxiliary carrier  Terminal. delete delete delete delete delete delete delete delete

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