KR101655788B1 - Method and apparatus for managing control channel based on user equipment feedback in wireless communication system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for configuring a control channel search region based on a terminal feedback in an OFDM wireless communication system. Particularly, in the case where the control channel is to be selectively scheduled for frequency resources and transmitted, or when frequency division transmission of the control channel is required, it is possible to transmit using a less frequency / time resource than the existing feedbackless control channel transmission method And is multiplexed with a data channel transmitted by frequency selective scheduling. Also, according to the present invention, the present invention can be applied to a control channel for relay transmission and a control channel scheduling for intercell interference coordination, which are configured such that transmission powers between frequency resources are different from each other.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for managing a control channel based on terminal feedback in a wireless communication system,

The present invention relates to a control channel management method and apparatus in an OFDM (Orthogonal Frequency Division Multiplexing) communication system using multiple carriers. In particular, in OFDM systems, And to a method of arranging a region and retrieving a control channel therethrough.

The mobile communication system has been developed to provide voice service while ensuring the user 's activity. Also, as the communication technology develops, the mobile communication system can provide not only voice service but also high-speed data service. However, as the number of user terminals using voice and data services increases, a shortage of resources occurs, and a number of users demanding high-speed services are increasing, so that a more advanced mobile communication system is required.

In response to this demand, LTE (Long Term Evolution) of 3GPP (The Third Generation Partnership Project) is being developed as one of the systems being developed as a next generation mobile communication system. LTE is a technology for implementing high-speed packet-based communication. It is proposed to reduce the number of nodes located on a communication path by simplifying the structure of a network, and to approach wireless protocols as much as possible to a wireless channel.

In a typical communication system including an LTE system, a base station constructs and transmits a control channel so that a terminal can receive without error in a coverage area. For this, the base station configures a control channel so that it can receive regardless of the channel state of the terminal. The base station transmits the control channel through a frequency distribution. At this time, the base station transmits / receives the control channel according to a predetermined rule between the base station and the mobile station. To do so, the base station configures a control channel to be transmitted to a plurality of terminals based on a predetermined protocol, and the terminal demodulates a control channel corresponding to the control channel in the control channel region. In the current LTE system, a search space is configured for control channel demodulation in a terminal. Then, the terminal searches its control channel among the plurality of control channels in the configured search area.

In LTE-A (Long Term Evolution Advanced) systems that transmit and receive data using multiple carriers, the control channel area is insufficient and the interference of the control channel becomes much larger than in the conventional LTE system. This is because the control channel of the terminal receiving the data channel through different carriers in the LTE-A system can be transmitted in one carrier. Therefore, the control channel is insufficient in the LTE-A system, and the interference is very large due to the increase of small cells such as hotzone cell, relay, and femto cell. Therefore, in the LTE-A system, it is necessary to transmit a control channel to a data channel region where transmission power can be controlled.

A control channel control method and an apparatus therefor in the LTE-A system of the present invention comprise a control channel search region for frequency selective transmission using subband CQI feedback of a terminal, thereby reducing the amount of control channel resources and increasing an insufficient control channel region The present invention aims at enhancing control channel reception performance by enabling multiplexing with a data channel capable of interference control.

In order to solve the above-mentioned problems, the present invention provides a control channel transmission method, comprising: receiving subband channel quality information for each terminal to transmit a control channel; determining a unique ID, a subframe number, Constructing at least two search regions by using the feedback channel quality information, and transmitting control channels for each terminal through the at least two search regions.

In the control channel transmission method of the present invention, the step of configuring the at least two search regions comprises the steps of: constructing a distributed frequency search region through the unique ID, the number of subframes, and the amount of the control channel element; ID, the number of the subframe, the amount of the control channel element, and the channel quality information.

According to another aspect of the present invention, there is provided a method for receiving a control channel, the method comprising: determining whether subband channel quality information is transmitted to receive a control channel; and blind demodulating a control channel received in the search region according to whether the channel quality information is transmitted do.

In the control channel receiving method of the present invention, the blind demodulating process may include blind demodulating a control channel in a distributed frequency search region configured for distributed transmission if the channel quality information is not transmitted, And if it is transmitted, constructs a selective frequency search area through the channel quality information, and blind demodulates the control channel in the configured selective frequency search area.

The control channel transmission apparatus of the present invention includes a first search area generator for constructing a distributed frequency search area through a terminal unique ID, a number of subframes, and a control channel element; And a controller for determining a search area to which a control channel is to be transmitted according to whether the channel quality information is transmitted according to whether the channel quality information is transmitted and transmitting the control channel, .

In addition, the control channel transmission apparatus of the present invention includes a PDCCH aggregator configuring a control channel to be transmitted in a distributed frequency search domain or a control channel to be transmitted in a selective frequency search domain, An interleaver for multiplexing a control channel to be transmitted and an RE (Resource Element) mapper for mapping the control channel to a physical resource block (PRB) resource.

In the control channel transmission apparatus of the present invention, the RE mapper maps a control channel to be transmitted through the distributed frequency search region to a physical resource block resource allocated to control channel transmission, Is mapped to a specific physical resource block resource.

The control channel receiving apparatus of the present invention includes a first search area generator for determining a distributed frequency search area through a unique ID, a number of subframes, and a control channel element, A second search region generator for determining a selective frequency search region through the transmitted channel quality information, and a control unit for controlling the control And a deinterleaver for processing the channel.

In the control channel receiving apparatus of the present invention, when the channel quality information is transmitted, the deinterleaver deinterleaves the received control channel if the channel quality information is not transmitted without processing the received control channel .

The control channel transmission apparatus of the present invention further includes a blind demodulator for blind demodulating the control channel processed through the deinterleaver.

According to the present invention, in the OFDM system, a frequency selective search region can be configured using only existing subband CQI feedback without additional channels. Therefore, in the LTE-A system in which the control channel region is lacking, an additional control channel region can be secured to solve the lack of the control channel. In the LTE-A system, the base station transmits the control channel through the preferred frequency resource of the terminal, thereby reducing the amount of resources required for the control channel transmission. In addition, the transmission power between frequency resources is multiplexed with the data channel used for controlling inter-cell interference, so that the interference of the control channel can be reduced. It can also be used with a terminal, relay system where the control channel has to multiplex with the data channel.

1 is a diagram illustrating a downlink frame structure according to the present invention.
2 is a diagram illustrating a control channel structure according to the present invention.
3 is a diagram illustrating an apparatus for configuring a control channel search area according to the present invention.
4 is a diagram illustrating a control channel region included in a downlink according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating an apparatus for configuring a search region of a control channel according to an embodiment of the present invention. Referring to FIG.
6 is a diagram illustrating a process of transmitting / receiving a control channel through a search region of a subframe according to an embodiment of the present invention.
FIG. 7 illustrates a method of constructing a search region for each terminal in a subframe according to an embodiment of the present invention.
8 illustrates a time relationship between a BS and a UE according to an embodiment of the present invention.
9 is a flowchart illustrating a transmission process of a base station according to an embodiment of the present invention.
10 is a flowchart illustrating a process of receiving a terminal according to an embodiment of the present invention.
11 is a block diagram of a base station according to an embodiment of the present invention.
12 is a block diagram of a terminal according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same components are denoted by the same reference numerals as possible in the accompanying drawings. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted.

Also, the terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor is not limited to the concept of terms in order to describe his invention in the best way. It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be properly defined.

Hereinafter, the LTE system and the LTE-Advanced system are described as an example, but the present invention can be applied to other wireless communication systems to which base station scheduling is applied without adding or subtracting it.

Hereinafter, channels and resources used for LTE-A use will be referred to as E (extension) -channel or E-resource. Also, a method of using a distributed frequency search region, which is a search region for transmitting a control channel by distributing frequencies, is called a type I method, and a selective frequency search region, which is a search region for transmitting a channel channel through a proposed selected frequency, Method.

The OFDM Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme transmits data using a multi-carrier, that is, a multi-carrier. More specifically, the OFDM transmission scheme is a scheme for parallelizing symbol streams input in a serial manner, and for each of them, a plurality of mutually orthogonal multicarriers, that is, a plurality of sub-carrier channels (Multi Carrier Modulation) scheme.

The system using this multicarrier modulation scheme was first applied to the military high frequency radio in the late 1950s. The OFDM scheme that overlaps a plurality of orthogonal subcarriers has been developed since the 1970s. However, since the implementation of orthogonal modulation between the multicarriers is a difficult problem, there is a limitation in actual system application. However, in 1971, Weinstein et al. Developed a technique of OFDM using DFT (Discrete Fourier Transform) using OFDM. In addition, as a method of inserting Cyclic Prefix (CP) symbols into a guard interval is known, the adverse effect of the system on multipath and delay spread in the OFDM scheme is further reduced.

As a result of this technological advance, the OFDM scheme can be applied to a digital audio broadcasting (DAB), a digital video broadcasting (DVB), a wireless local area network (WLAN) and a wireless asynchronous transmission mode Transfer Mode, WATM). In other words, the OFDM scheme is not widely used due to its hardware complexity. Recently, a variety of digital signal processing techniques including Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT) It has become feasible.

The OFDM scheme is similar to the conventional Frequency Division Multiplexing (FDM) scheme. However, the OFDM scheme maintains orthogonality among a plurality of tones and transmits the orthogonality, thereby achieving optimal transmission efficiency in high-speed data transmission. The OFDM scheme is also characterized in that it has good frequency utilization efficiency and is resistant to multi-path fading, thereby achieving optimal transmission efficiency in high-speed data transmission.

Another advantage of the OFDM scheme is that frequency use is efficient because it uses frequency spectra superimposed. In addition, the OFDM scheme is robust against frequency selective fading and multipath fading, and the effect of inter symbol interference (ISI) can be reduced by using the guard interval. The OFDM scheme can be used to easily design an equalizer structure in hardware, and has the advantage of being strong against impulse noise, so that it is being utilized in a communication system structure.

Factors that hinder high-speed, high-quality data services in wireless communications are largely due to the channel environment. In this case, the channel environment may include a Doppler effect due to a power change, a shadowing, a terminal movement, and a frequent rate change of a received signal caused by a fading phenomenon other than white Gaussian noise (AWGN) , Other users, and interference due to multi-path signals. Therefore, in order to support high-speed and high-quality data service in wireless communication, it is necessary to effectively overcome obstacles to channel environment.

In the OFDM scheme, a modulated signal is located in a two-dimensional resource composed of time and frequency. The resources on the time axis are distinguished by different OFDM symbols and they are orthogonal to each other. And the resources on the frequency axis are distinguished by different tones, which are also orthogonal to each other. That is, in the OFDM scheme, a specific OFDM symbol can be indicated on the time axis and a specific tone can be specified on the frequency axis, which is referred to as a resource element (RE). Different REs have characteristics that are orthogonal to one another even though they pass through a frequency selective channel. Therefore, signals transmitted in different REs can be received at the receiving side without mutual interference.

A physical channel is a channel of a physical layer for transmitting a modulation symbol modulating one or more encoded bit streams. In an Orthogonal Frequency Division Multiple Access (OFDMA) system, a plurality of physical channels are configured and transmitted according to the use of an information sequence to be transmitted or a receiver. Then, a rule is set as a rule between a transmitter and a receiver to which one physical channel is to be allocated to which RE, and the rule is referred to as mapping or mapping.

The LTE system is a typical system in which the above-described OFDM system is applied to the downlink, and a single carrier-frequency division multiple access (SC-FDMA) system is applied in the uplink. In addition, the LTE-A system is a system in which LTE systems are extended to multiple bands, and relays are applied.

1 is a diagram illustrating a downlink frame structure according to the present invention. Here, the downlink frame structure is also supported for compatibility in the LTE-A system.

Referring to FIG. 1, an entire LTE transmission bandwidth 101 includes a plurality of resource blocks (RBs) 103. Each RB 103 is composed of 14 OFDM symbols or 12 OFDM symbols arranged in 12 axes and time axes arranged on the frequency axis and is a basic unit of resource allocation called a subframe 105 . One subframe 105 has a length of 1 ms and is composed of two slots 107.

A reference signal (RS) 121 is a signal transmitted to a terminal for channel estimation, which is transmitted in a promised signal between a base station and a terminal, and is a signal transmitted from an antenna port. If the number of antenna ports is 1 or more, it means that a multi-antenna is used. Although the absolute positions of the RBs 103 on which the RSs 121 are arranged on the frequency axis are set differently for each cell, the relative spacing between the RSs 121 remains constant. That is, the RS 121 of the same antenna port maintains six RB 103 intervals. Here, the reason why the absolute position of the RS 121 is set differently for each cell is to avoid inter-cell collision of the RS 121. There are a total of eight RSs 121 in one RB 103 and one subframe 105 in the case of antenna ports 0 and 1. In the case of antenna ports 2 and 3 A total of four RSs 121 exist in one RB 103 and the subframe 105. Therefore, in case of using four antennas, the accuracy of channel estimation using antenna ports 2 and 3 is less accurate than that of antenna ports 0 and 1.

The control channel signal is located at the head of the subframe 105 on the time axis. In FIG. 1, reference numeral 111 denotes an area where a control channel signal can be located. The control channel signal may be transmitted over L OFDM symbols located at the head of the subframe 105. Where L may have a value of 1, 2, or 3. L = 3, a method of transmitting a control channel will be described. When L is 3, only one OFDM symbol at the head is used for control channel signal transmission (L = 1) and the remaining 13 OFDM symbols are used for transmission of control channel signals in a single OFDM symbol because the amount of control channels is small It is used for data channel signal transmission. In this case, the value of L is used as basic information for demapping the allocated control channel resources in the control channel receiving operation, and if it is not received, the control channel can not be recovered.

The reason for placing the control channel signal at the head of the subframe 105 is that the UE first receives the control channel signal, checks whether the data channel signal transmitted to the UE is transmitted, and determines whether to perform the data channel receiving operation It is for this reason. Therefore, if there is no data channel signal transmitted to the terminal, the terminal does not need to receive the data channel signal. In this way, the terminal can save the power consumed in the data channel signal receiving operation. Also, since the control channel at the head is received faster than the data channel, the scheduling relay is reduced.

(Physical Control Format Indicator Channel), PHICH (Physical Hybrid ARQ Indicator Channel), PDCCH (Packet Data Control Channel), and the like are defined as the downlink control channels defined in the LTE system. (Resource Element Group) unit 123 composed of a plurality of resource elements.

The PCFICH is a physical channel for transmitting CCFI (Control Channel Format Indicator) information. The CCFI is 2-bit information for indicating the number of symbols L occupied by the control channel in the subframe 105. [ The terminal must first receive the CCFI to know and receive the number of symbols assigned to the control channel. Therefore, the PCFICH is a channel that all terminals must first receive in the subframe 105, except when downlink resources are fixedly allocated to the terminals. Also, the terminal can not know L before receiving the PCFICH. Therefore, the PCFICH must be transmitted in the first OFDM symbol. Thus, the PCFICH channel is divided into 16 subcarriers and transmitted over the entire band.

The PHICH is a physical channel for transmitting downlink ACK / NACK signals. The terminal receiving the PHICH is a terminal that is in the process of transmitting data in the uplink. Therefore, the number of PHICHs is proportional to the number of terminals in data transmission on the uplink. PHICH is transmitted in the first OFDM symbol (LPHICH = 1) or transmitted over three OFDM symbols (LPHICH = 3). All terminals can know PHICH configuration information (amount of used channel, LPHICH) through PBCH (Primary Broadcast Channel) when initially accessing a cell. The PHICH is also transmitted at the designated location for each cell in the same manner as the PCFICH. Therefore, the terminal can receive the PHICH control channel through the obtained PBCH information when the terminal is connected to the cell regardless of other control channel information.

The PDCCH is a physical channel for transmitting data channel allocation information or power control information. The PDCCH is set to have a different channel coding rate according to the channel state of the receiving terminal. Since the PDCCH uses quadrature phase shift keying (QPSK) as a modulation scheme, it is necessary to change the amount of resources used by one PDCCH in order to change the channel coding rate. Therefore, a high channel coding rate is applied to a terminal having a good channel state, and the amount of resources used can be reduced. On the other hand, even if the amount of resources allocated to a terminal having a bad channel state increases, a PDCCH can be received by applying a high channel coding rate. The amount of resources consumed by the individual PDCCHs is determined by a unit called a control channel element (hereinafter referred to as "CCE"). The CCE is composed of a plurality of resource element groups (REGs) 113. And the REG of the PDCCH is distributed in the entire PDCCH region as indicated by reference numeral 113. [ In other words, the REG is placed in the control channel resource after going through the interleaver to ensure diversity. Here, the diversity transmission of the control channel is performed because the channel information of all terminals in the cell can not be known, so that the coding rate is increased and transmitted over the entire band to guarantee the reception performance of the terminal.

PHICH applies Code Domain Multiplexing (CDM) technique to multiplex multiple ACK / NACK signals. In one REG, eight PHICH signals are code-multiplexed into four real and imaginary parts, respectively, and are arranged such that they are repeatedly arranged as many as the number of NPHICHs in order to obtain frequency diversity gain, and are arranged so as to be separated as much as possible on the frequency axis. Therefore, if NPHICH REGs are used, 8 or fewer PHICH signals can be constructed. To configure more than eight PHICH signals, another NPHICH REG must be used.

After the resource and allocation of PCFICH and PHICH are determined, the scheduler sets the L value. Based on this value, the physical control channel is mapped to the REG of the allocated control channel, and interleaving is performed to obtain the frequency diversity gain. Interleaving is performed for the total REG of the subframe determined by L, in REG units of the control channel. The interleaver output of the control channel can prevent inter-cell interference due to the use of the same interleaver among the cells, and at the same time, the REGs of the control channels allocated to one or more symbols are moved away from the frequency axis So that diversity gain can be obtained. Also, the interleaver output of the control channel ensures that the REGs constituting the same channel can be evenly distributed among the symbols for each channel.

Recently, development of LTE-A (LTE Advanced) system with advanced LTE system is under development. In the LTE-A system, studies are being conducted using a hot zone cell, a femto cell, and a relay cell in order to increase the capacity in the cell.

2 is a diagram illustrating a control channel structure according to the present invention.

The basic unit of PDCCH allocation is a CCE (control channel element) 201, and the basic unit of resource allocation is REG 203. [ REG 203 is composed of four REs consecutively except for the same symbol on the time axis and RS on the frequency axis. The REG 203 is used as a unit for allocating resources and a multiplexing unit for multiplexing each control channel. The resource to which the control channel is transmitted constitutes a CCE and is mapped to the control channel of the terminal to be scheduled. Each terminal has unique allocation areas 205, 207, and 209 in the entire CCE area 201, which is referred to as a search space. The search area is configured for each terminal through the unique ID of each terminal, the amount of the entire CCE resources, and the currently scheduled subframe number. At this time, the search areas 205, 207, and 209 of each terminal are configured by using a random number generator capable of indicating an area different for each subframe without overlapping or overlapping. In more detail, once a terminal is connected to one cell, the base station managing the cell assigns a unique ID to the connected terminal. The terminal receiving the unique ID can immediately reproduce the same area as the search area reproduced by the base station. The search area thus reproduced is configured differently for each terminal, and is changed every subframe.

For example, reference numeral 205 denotes a search area allocated to the user terminal 1, reference numeral 207 denotes a search area allocated to the user terminal 3, and reference numeral 209 denotes a search area allocated to the user terminal 2. The search area of the user terminal 1 and the search area of the reference number 207 may overlap or overlap with each other as in the search area of the reference number 205 and the search area of the reference number 207, It is possible to prevent overlapping of the search areas in different search areas.

The base station allocates the PDCCH by selecting an appropriate amount of resources according to the channel state of each terminal in each search area. This is called an aggregation level, and PDCCH can be 1, 2, 4, or 8 levels. Also, the CCEs of the PDCCHs arranged at this time are consecutively arranged to perform the blind demodulation when the PDCCH is received for each terminal. In FIG. 2, reference numeral 203 denotes a control channel to be transmitted to the user terminal 1, reference numeral 215 denotes a user terminal 2, and reference numeral 213 denotes a control channel to be transmitted to the user terminal 3. The reason for this is that the channel state of the user terminal 2 is better than that of the other terminals in comparison with the control channel transmitted at the reference number 215 to the other terminals.

The control channels allocated in units of CCEs are interleaved 217 in REG units for distributed transmission in the entire band, and cyclic shift 223 is performed in order to reduce inter-cell interference. Next, a resource mapping 227 is performed. One CCE is composed of 9 REGs, and each REG is multiplexed with a REG of another CCE and mapped to the control channel region 231. [

The control channel thus interleaved and transmitted is divided into four RE units on the physical channel as indicated by reference numeral 229, and is scattered over the entire bandwidth. Then, the terminal receives the control channel through the de-interleaving process 233 and performs blind demodulation according to each coding rate for the search area of each terminal. Reference numeral 237 denotes a case where blind demodulation is performed on the search area of the user terminal 1. [ According to each aggregation level, the user terminal 1 attempts to receive the PDCCH to receive its control channel for reference numbers 239, 241, 243, and 245.

When the next subframe is transmitted, the user terminal 3 can be placed in the search area of reference numeral 247, the user terminal 2 in the search area of reference numeral 249, and the user terminal 1 in the search area of the reference numeral 251. [ Here, reference numeral 253 denotes the next subframe.

3 is a diagram illustrating an apparatus for configuring a control channel search area according to the present invention.

Reference numeral 313 denotes a control channel search area generator of the base station, and reference numeral 329 denotes a control channel search area generator of the terminal.

Reference numerals 301 and 317 are input values required for the search area generator in the base station and the terminal. The input value may be the unique IDs 303 and 319 of the terminal, the slot indexes 305 and 321, and the CCE amounts 307 and 323. The unique IDs 303 and 309 of the terminal are generated in the base station 313 and are transmitted (315) to the terminal upon initial connection, and the ID of the terminal once connected is not changed. The slot indexes 305 and 321 indicate which of the slots constituting the subframe. Here, the value obtained by dividing the slot indexes 305 and 321 by 2 is the number of the subframe. The slot indexes 305 and 321 are learned during the initial access of the terminal to the cell. The amount of CCEs 307 and 323 is the amount of CCE, which is the control channel resource used in the current subframe. The amounts of CCEs 307 and 323 vary depending on the L value of PCFICH. For example, when L is 1, 2, or 3, the amount of CCEs 307 and 323 has one of three L values, and is determined by receiving the PCFICH of the current subframe and demodulating the L value.

The base station and the terminal generate a search area having the same value using the input values 302 and 317. Hashing function generators 309 and 325, which are random number generators, are used for this purpose. The hashing function generators 309 and 325 generate a random value of the same value using the same initial value. Accordingly, since random values are generated using unique IDs for respective terminals, different search areas can be assured for different terminals. The slot index value, i.e., the number of subframes, is used to prevent a control channel from being allocated due to redundancy of a search area that may possibly be generated at the next scheduling transmission time.

4 is a diagram illustrating a control channel region included in a downlink according to an embodiment of the present invention.

In the LTE-A system, the E-PDCCH can be transmitted in two forms. This is because the data channel PDSCH can be transmitted in two forms. For example, the PDSCH may be transmitted over a distributed resource over the entire bandwidth, such as reference numeral 417, or may be transmitted over all resources allocated to a certain region, such as 421. [ A method of transmitting a PDSCH through a resource located in a predetermined area is called a frequency selective transmission method. In the LTE-A system, in order to prevent the decrease of the control channel performance due to the lack of the control channel and the increase of the interference, a method of multiplexing the data channel and transmitting the control channel is considered. In the LTE-A subframe, as shown in reference numeral 419, the RB uses a DRS (Dedicate reference signal) in addition to a common reference signal (CRS) 423. Reference numeral 425 denotes a DRS added in the LTE- It is.

The LTE-A terminal receives the E-PDCCH and the PDSCH using the added DRS. Reference numeral 427 shows an example in which the E-PDCCH is mapped in the RB. Here, it is assumed that the CCE of one E-PDCCH is allocated to three symbol resources in the RB and transmitted over two RBs. However, the present invention can be applied regardless of the number of symbols occupied by one CCE of the E-PDCCH and the number of RBs occupied.

FIG. 5 illustrates an apparatus for configuring a search region of a control channel according to an embodiment of the present invention.

Reference numeral 521 denotes an apparatus for generating a search region in a base station, and Figure 547 shows an apparatus for generating a search region in a terminal. The terminal always uses a search region for distributed transmission as described in FIG. 3, and the frequency selective search region proposed in the present invention is a terminal in which frequency selective transmission is extended while insufficient control channel resources are extended, To apply.

The search area generated from the search area generator, which is the hashing function generator of the reference numeral 517 and the reference numeral 539, is always present as the input value of the reference numeral 513 and the reference numeral 529. A search area always present is called a distributed frequency search area. This is because the terminal always reports one channel estimate to the base station over the entire bandwidth. In addition, when reporting the frequency-selective channel estimation value, only when the channel state of the UE is advantageous for frequency-selective channel estimation, it is instructed to transmit the CQI channel quality indicator at the upper part. Accordingly, when the BS instructs the corresponding terminal to transmit the subband CQI value, the terminal transmits the CQI value of reference numeral 527 to the BS through the corresponding channel (523).

The base station receives the information and uses the information of the reference number 501 to configure the search area so that the control channel can be transmitted in a frequency region preferred by the terminal. A search area configured using CQI is referred to as a selective frequency search area. Accordingly, the MS constructs a frequency selective search area in the same manner as the BS using the information of the preferred frequency region reported to the BS.

That is, the distributed frequency search area is a structure that does not require feedback from the terminal, and the selective frequency search area requires a feedback of the terminal. Also, since the preferred frequency region of the terminal has better channel characteristics than that of the distributed transmission using the entire band, transmission is possible using less resources. Accordingly, the base station may feed back the preferred frequency region of the terminal and selectively transmit the control channel through the selective frequency search region corresponding to the preferred frequency region, as in the present invention.

When only frequency selective transmission is performed, a reporting error and an error may occur. Therefore, the existing search area is maintained as shown in FIG. 5, and a search area based on terminal feedback can be further configured. Therefore, when there is no reporting error of the base station, the base station transmits the control channel in the frequency selective region and transmits the control channel through the existing search region when a problem occurs in the transmission. In this case, there is an advantage that the distributed transmission and the frequency selective control channel transmission can be dynamically switched. Equation (1) represents an input / output relationship of the distributed frequency search region.

[Equation 1]

Type I search space = f (n _RNTI , n _s , N _{CCE, k} )

Here, nRNTI represents the unique ID of the UE, ns represents the number of subframes, NCCE represents k, and k represents the number of CCEs of the kth subframe.

Equation (2) represents an input / output relationship of the selective frequency search region configured based on the feedback of the terminal.

&Quot; (2) "

Type II search space = f (S _kP , n _RNTI , n _s , N _{CCE, k} )

Where Sk-p represents the preferred subband of the terminal received in the k-Pth subframe. The P subframe represents the time taken by the base station to apply to the scheduling after the subbands transmit CQIs in the subframe. P takes 8 subframes of time and can be changed in the upper part according to the system.

A terminal that has not fed back the CQI of a subframe performs blind demodulation for a distributed control channel transmission in a distributed frequency search region that is a type I search region. The terminal that fed back the CQI of the subframe performs the distributed control channel blind demodulation in the type I search region and the frequency selective control channel blind demodulation in the selective frequency search region which is the type II search region.

6 is a diagram illustrating a process of transmitting / receiving a control channel through a search region of a subframe according to an embodiment of the present invention.

Referring to FIG. 6, a terminal having two search regions has two virtual CCE regions 601 and 603. Reference numeral 603 denotes an area constituted by CCEs included in PRB (Physical Resource Block) resources pre-allocated by the system for E-PDCCH transmission. The base station transmits a candidate of the PRB to which the E-PDCCH can be transmitted through the upper signaling to the terminal, and the terminal performs CCE indexing based on the received region. The area of reference numeral 601, which is another virtual CCE area, is a CCE area configured by using the PRB of the area in which the terminal feeds back the subband CQI. The terminal performs CCE indexing based on the area of reference numeral 601. In other words, the base station possesses a common CCE region for one distributed transmission and N unique CCE regions for each terminal performing subband CQI feedback. The terminal also has two areas, a common CCE area and a dedicated CCE area using the subbands that it has fed back, using the PRB informed by the base station. And a terminal without subband feedback has only one common CCE region. The search area is a candidate area that is actually transmitted to the terminal in the common CCE area and the dedicated CCE area. The actual control channel is transmitted in the common CCE area and a part of the dedicated CCE area, and the terminal receives the control channel by performing blind demodulation in the method of configuring the CCE area and its search area if it knows the search area.

For example, in FIG. 6, it is assumed that the user terminal 1 and the user terminal 3 hold only the common CCE region without subband CQI feedback, and the user terminal 2 also holds the dedicated CCE region by performing subband CQI feedback.

Reference numeral 605 denotes a search area in the common CCE area of the user terminal 1, and reference numeral 607 denotes a search area of the user terminal 3. The user terminal 2 has a reference area 609 in the common CCE area and a reference area 615 in the dedicated CCE area as search areas. The base station allocates the control channel of each terminal based on the search area of each terminal. If the PRB is fed back to the dedicated CCE region of the user terminal 2, the user terminal 2 immediately performs RE mapping to the PRB as indicated by reference numeral 627. [ This is because the base station transmits the control channel directly through the search area corresponding to the frequency resource designated by the terminal. However, in the case of a control channel transmitted in the common E-PDCCH region, an interleaving process is required as indicated by reference numeral 619. The interleaving process is performed so that one control channel is distributed to a plurality of PRBs. Assuming that the control channel also obtains the same dispersion effect as the existing LTE data channel, the control channel composed of one CCE has the diversity effect of diversity order 2. And a control channel composed of two or more CCEs is transmitted when diversity order 4 has a dispersing effect. The interleaving of the control channel may also include a cyclic shift process in the process. This is to prevent interference that may occur when the candidates of the E-PDCCH transmission PRBs assigned to the adjacent cell are the same or similar. The interleaved control channel is mapped to the PRB as indicated by reference numeral 623. At this time, the control channel is not transmitted over the entire CCE region as indicated by reference numeral 603, and the portion where the control channel is not transmitted can be utilized for data channel transmission of other terminals. Therefore, in the case of the user terminal 2, the base station configures the control channel in the frequency selective control channel region configured through the dedicated CCE region, and distributes the control channel to the remaining terminals through the remaining region. After the transmission, the user terminal 1 and the user terminal 3 perform blind demodulation of their control channel in the search area defined as shown in FIG. 3, and in the case of the user terminal 2, And performs blind demodulation in the area of reference numeral 635 to receive the control channel.

The additional control channel search area causes the terminal to increase the number of blind demodulations. The increase of the number of blind demodulation is not a problem when the demodulation performance of the terminal is guaranteed, but causes a problem of increasing the false alarm in the system. Here, the false alarm includes a problem of attempting to transmit data that the terminal itself has received the control channel, and a problem of not receiving its control channel despite the transmission of its control channel, even though the terminal is not its own control channel do. Such a terminal causes a high false alarm as the number of times of blind demodulation of the terminal increases, which causes a deterioration of system performance. Therefore, there is a need for a method that does not increase the blind demodulation frequency of the terminal even if the type II search range increases. There may be a method of adjusting the aggregation level by decreasing the number of blind demodulation and a method of decreasing the search area of type I.

First, we explain how to adjust the aggregation level. In the case of frequency selective transmission, a high aggregation level is not necessary because the channel is transmitted in a good region. Therefore, if the terminal needs to perform demodulation on two areas, type II area performs only aggregation level 1 and 2, and type I area performs level 4 and 8 only.

The method of reducing the search area of type I is as follows. The maximum size of the current search area is 16 CCEs. If the size of the search area is reduced to half, the number of blind decoding times is also reduced to half. Although the allocation area is decreased due to a decrease in the search area, the terminal does not increase the blocking probability since it has acquired an additional type II area. In this case, the blocking probability means a probability that the search area of each terminal overlaps and the control channel can not be allocated. If the length of the search area is reduced, there is a high probability that the overlapping search area between the terminals will increase. However, it is possible to prevent this because the type II area is added to the terminal.

FIG. 7 illustrates a method of constructing a search region for each terminal in a subframe according to an embodiment of the present invention.

The base station can configure all or a portion of the CQI of the preferred subband transmitted by the terminal as a search area. A search area may be configured as a whole area, or a control channel may be allocated when the preferred subband area is overlapped. 703, 705, 707, 709, 711, and 713 are part of a subband 701 that divides the entire band when the subband 701 is present in the system, And 4 CCEs, respectively. Reference numeral 717 denotes a case where the user terminal 1 prefers the subbands 1, 3, 8, and 6 and the priority of the preference is determined according to the order. Reference numeral 719 denotes a case in which the user terminal 2 prefers subbands 1, 12, and 3. 15, and the priority of the preference is determined according to the order. Finally, reference numeral 721 denotes a case in which the user terminal 3 prefers subbands 1, 6, 3 and 8, and the priority of the preference is determined according to the order. The priorities of preferences for each user terminal were fed back to the base station.

When all the subbands fed back by the base station and the terminal are determined as the search regions, the subbands 1 and 3 are preferred overlap regions of all terminals. In this case, if the preferences of the terminals are not changed, the base station will mainly allocate control channels of all terminals to subbands 1 and 3. Accordingly, if there is a terminal to which a control channel is preferentially allocated by the base station, the remaining terminals can not use the region, and must return to the type I region. This problem also occurs in type II. In order to solve this problem, it is necessary to move the search area in subframe units.

For this purpose, the base station can use a method of dividing the pitched subbands from the terminal with respect to a maximum of eight CCEs and changing the search area configured in the terminal for each subframe. In reference numeral 723, subbands 1 and 3 (729) originally belong to the search area of all terminals, but are determined to be the search area of the user terminal 1 in order to prevent blocking probability. The base station then allows the user terminal 1 to use subbands 6 and 8 (737) at reference numeral 725 at the next scheduling timing. In the next scheduling timing, subbands 1 and 3 (735) are allocated to the search area of the user terminal 3 as indicated by reference numeral 725, . Since subbands 1 and 3 (735) are also set as the search area of the user terminal 2 at the reference numeral 725, at the next scheduling timing, the base station transmits subbands 1 and 3 (739) as shown in reference numeral 727 Subbands 6 and 8 (741) are set as a search area of the user terminal 3, and subbands 12 and 15 (743) are set as a search area of the user terminal 2. As shown in FIG.

8 illustrates a time relationship between a BS and a UE according to an embodiment of the present invention.

Referring to FIG. 8, a base station (eNodeB) 801 and a terminal (UE) 803 transmit scheduling information using a type I search area and transmit the data channel accordingly. In step 805, the BS determines whether the terminal should change the sub-band CQI transmission time 817 or the transmission mode 819, and transmits the signal to the terminal through higher signaling. In step 807, the MS receives the subband CQI feedback transmission 809 from the BS in the nth subframe and transmits the subband CQI from the n + 4th through the PUSCH. The base station receives the signal of the terminal, and informs the terminal whether the signal received through the PHICH channel is normally received in step 811. At this time, if the base station does not normally receive the signal, the terminal performs feedback retransmission, and additional time is generated accordingly.

In step 821, the mobile station checks whether the sub-band CQI information transmitted from the base station is normally received. In step 823, the mobile station receives a scheduling signal including a search area of type II. Through these processes, the base station can transmit the control channel to the type II search area 813 as well as the type I search area.

9 is a flowchart illustrating a transmission process of a base station according to an embodiment of the present invention.

Referring to FIG. 9, in step 903, the base station prepares to transmit scheduling information for scheduling a mobile station. In step 905, the base station determines whether the terminal can perform subband CQI feedback. If the CQI feedback is available in step 907, the base station instructs the terminal requiring subband CQI feedback in step 911 to perform subband CQI feedback through upper signaling. The indication of feedback also includes an indication of feedback for control channel transmission in the next subframe other than the scheduling of the current subframe.

In step 913, the terminal receives the CQI for the M subbands. In step 915, the BS transmits an Ack / Nack acknowledgment message to the MS to determine whether CQI information has been received. When the terminal transmits CQI information on the PUSCH, the terminal responds using the PHICH channel, which is an ACK / NACK channel.

In step 917, the BS configures a type II control channel search area using the subband CQI information. The base station allocates and transmits scheduling information in step 919 using the type I and type II search regions, which are configured search regions. In step 921, the base station determines whether there is next scheduling information, and in step 925, the terminal determines whether subband CQI feedback is possible. The base station determines whether to transmit the next control channel by using both type I and type II or only the search area of type I as described in step 931, as described in step 919, and performs scheduling. On the other hand, if there is no next scheduling information in step 921, the base station discontinues transmission of the control channel in step 933 if there is no more information to schedule in the terminal. In the above process, the transmission process of the data channel transmitted after the control channel transmission is omitted. However, when the control channel region of type I is used, the data channel uses distributed transmission. When the control channel region of type II is used, Lt; / RTI >

10 is a flowchart illustrating a process of receiving a terminal according to an embodiment of the present invention.

Referring to FIG. 10, in step 1003, the terminal prepares to receive scheduling information. In step 1005, the terminal determines whether the state of the feedback transmission mode is the subband CQI feedback state. If it is not the subband CQI feedback mode as in step 1007, the terminal blind demodulates the scheduling information only in the type I domain in step 1011. [ On the other hand, if the mobile station is in the subband feedback mode as in step 1009, the mobile station blind demodulates the scheduling information in the area of type I in step 1015. In step 1017, the terminal constructs a type II search area using the subband CQI region fed back by itself. In step 1019, the terminal blind demodulates the scheduling information in the type II search area. In step 1021, the UE receives the data channel using the demodulated scheduling information.

11 is a block diagram of a base station according to an embodiment of the present invention.

Referring to FIG. 11, a base station performs scheduling for a current subframe transmission in a control unit 1113 managing the scheduling. The Type I search area generator 1109 configures a type I search area using a terminal ID 1101, a number 1103 of subframes, and a CCE size 1105. The type II search area generator 1111 transmits a type II search area together with a terminal ID 1101, a subframe number 1103 and a CCE size 1105 as well as a CQI 1107 which is a preferred subband index transmitted by the terminal . The base station control unit 1113 determines to which search region the control channel is to be transmitted to one terminal. When the search area to which the control channel of each terminal is to be transmitted is determined, the base station controller 1113 configures the PDCCH of the terminal using the type I in the type I PDCCH aggregator 1115. The base station control unit 1113 controls the interleaver 1119 to multiplex the PDCCH of the configured UE. The PDCCH using the type II search area is configured in the type II PDCCH aggregator 1117. Next, the control channel that has passed through the interleaver 1119 through the RE mapper 1121 is mapped over the PRB resources allocated to the control channel transmission, and the control channels that are not mapped to the specific PRB area are mapped.

12 is a block diagram of a terminal according to an embodiment of the present invention.

Referring to FIG. 12, when a control channel region is received, the terminal uses a terminal ID 1201, a subframe number 1203, and a CCE size 1205 to control the type I search region generator 1209 in a control channel And determines a search area for demodulation. Then, the terminal determines the type II search region using the upper M subband index 1207, which is further fed back to the CQI by the type II search region generator 1211. Next, the control unit 1213 of the terminal demaps the control channel signal received through the RE demapper 1215. The controller 1213 of the terminal determines whether the subband CQI feedback is transmitted, and performs PDCCH blind demodulation.

In other words, if the subband CQI feedback is not transmitted, the controller 1213 deinterleaves the demap control channel signal through the deinterleaver 1219. Then, the controller 1213 performs blind demodulation of the deinterleaved control channel signal through the type I PDCCH blind demodulator 1221 on the PDCCH allocated to the type I. Here, the UE can confirm the scheduling information 1223 through blind demodulation.

When the terminal transmits subband CQI feedback, the terminal does not go through the deinterleaver 1219 and obtains the scheduling information 1223 through the type II PDCCH blind demodulator 1217. [ The UE recognizes the scheduling information of the data channel using the obtained scheduling information 1223, and demodulates it through the receiver (1225).

The embodiments of the present invention disclosed in the present specification and drawings are merely illustrative examples of the present invention and are not intended to limit the scope of the present invention in order to facilitate understanding of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

Claims (10)

A method for managing a control channel of a base station in a wireless communication system,
Checking channel quality information of a subband for each terminal to transmit a control channel;
Configuring at least two search regions according to whether the channel quality information is received based on the result of the check;
And transmitting the control channel for each terminal through the at least two search regions,
Wherein the step of constructing the at least two search regions comprises:
If the channel quality information is not received, constructing a distributed frequency search region through a unique ID, a number of subframes, and an amount of a control channel element,
If the channel quality information is received, constructing a selective frequency search region through the unique ID, the number of subframes, the amount of the control channel element, and the channel quality information. delete A method for managing a control channel of a terminal in a wireless communication system,
Determining whether to transmit channel quality information for a subband to receive a control channel,
And blind demodulating control channels received in different search areas according to whether the channel quality information is transmitted,
The blind demodulation may include:
Performing blind demodulation on the control channel in a distributed frequency search region configured for distributed transmission if the channel quality information is not transmitted;
If the channel quality information is transmitted, constructing an optional frequency search region through the channel quality information and blind demodulating the control channel in the configured selective frequency search region. delete A first search area generator configured to form a distributed frequency search area through the terminal unique ID, the number of subframes, and the amount of the control channel element;
A second search region generator for constructing a selective frequency search region through the terminal unique ID, the number of subframes, the amount of the control channel element, and the channel quality information transmitted from the terminal,
And a control unit for determining a search region to which a control channel is to be transmitted for each terminal according to whether the channel quality information is received and transmitting a control channel through the determined search region,
Wherein,
If the channel quality information is not received, constructs a distributed frequency search area through the terminal unique ID, the number of subframes, and the amount of the control channel element,
Wherein when the channel quality information is received, a selective frequency search region is configured through the terminal unique ID, the number of subframes, the amount of the control channel element, and the channel quality information. 6. The method of claim 5,
A PDCCH aggregator configuring a control channel to be transmitted in the distributed frequency search domain or a control channel to be transmitted in the selective frequency search domain;
An interleaver for multiplexing a control channel to be transmitted in the distributed frequency search region among the configured control channels;
Further comprising an RE (Resource Element) mapper for mapping the control channel to a physical resource block (PRB) resource. 7. The method of claim 6, wherein the RE mapper
Wherein a control channel to be transmitted through the distributed frequency search region is mapped to a physical resource block resource allocated to a control channel transmission and a control channel to be transmitted through the selective frequency search region is mapped to a specific physical resource block resource Control channel transmission device. A first search area generator for determining a distributed frequency search area through a unique ID, a number of subframes, and a control channel element amount;
A second search region generator for determining a selective frequency search region through the unique ID, the number of subframes, the amount of the control channel element, and the channel quality information transmitted to the base station;
And a deinterleaver for processing the control channel received in the distributed frequency search region or the selective frequency search region according to whether the channel quality information is transmitted,
Wherein the control channel comprises:
If the channel quality information is not transmitted, blind demodulated in a distributed frequency search area configured for distributed transmission,
And when the channel quality information is transmitted, blind demodulation is performed in the selective frequency search area configured through the channel quality information. 9. The apparatus of claim 8, wherein the deinterleaver
Wherein the control channel deinterleaver performs the deinterleaving of the received control channel if the channel quality information is not transmitted without processing the received control channel when the channel quality information is transmitted. 10. The method of claim 9,
And a blind demodulator for performing blind demodulation on the control channel processed through the deinterleaver.

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