KR101568205B1 - Communication system supporting bandwidth aggregation and method for allocating feedback resource thereof - Google Patents

Abstract

The present invention relates to a communication system supporting a plurality of bands and a method of allocating resources and identifying allocated resources, and more particularly, to a method and apparatus for allocating a first feedback channel signal of a first band in a subframe divided into a control region and a data region, Mapping to a resource in a control region; Mapping a second feedback channel signal of a second band to a resource of the data region; And transmitting the subframe in which the first feedback channel signal and the second feedback channel signal are mapped.

Up-Link, Down-Link, Resource, Allocation

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a communication system supporting a plurality of bands, and a feedback resource allocating method thereof.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedback resource allocation method for a communication system supporting a plurality of bands, and a communication system for performing the same. More particularly, the present invention relates to a feedback resource allocation method for a downlink ACK / NACK, and a communication system for performing the same.

In order to meet the high data rate requirement of IMT-Advanced, a wide bandwidth of 20MHz or more is required. However, it is difficult to secure a wide bandwidth of 20 MHz or more in a limited frequency spectrum resource, so it is necessary to collect a bandwidth that is separated from the frequency to provide a new service. It is also necessary to provide new broadband services in a wide bandwidth, including existing bandwidth, to provide compatibility in existing bandwidths already in service. In order to satisfy such a demand, bandwidth aggregation technology which collects a plurality of bandwidth and provide one broadband service is considered in IEEE 802.16m and LTE Advanced systems.

In particular, 3GPP (3rd Generation Partnership Projec) LTE Advanced system should support the following matters. First, LTE Advanced base stations must be able to support existing LTE terminals simultaneously in the same band. Second, the LTE Advanced terminal must be able to access the existing LTE base station. Third, LTE Advanced base stations should be able to support LTE Advanced terminals combining two or more existing LTE bandwidths. Fourth, the downlink and uplink may have different bandwidths. In other words, the LTE Advanced system should be compatible with the existing LTE system and be able to combine and service two or more bands.

In the conventional LTE system, uplink and downlink are associated with 1: 1. Therefore, an ACK / NACK feedback signal for indicating whether decoding of data transmitted through the uplink or downlink is successful and a channel quality information (CQI) feedback signal corresponding to a transmission data channel for determining a transmission mode Can be transmitted using the downlink and uplink bands corresponding to 1: 1. The terminal may directly acquire information on the position of the feedback resource corresponding to each data channel formed between the base station and the terminal, or may acquire the information through a predetermined rule between the base station and the terminal in advance. In this case, only the positions of the feedback resources mapped to the uplink band and the downlink band corresponding to 1: 1 can be confirmed. However, in the case of an LTE Advanced system capable of supporting a plurality of band combining, there is only one corresponding uplink or downlink band.

An LTE Advanced system supporting multiple band combining in more detail is described with reference to FIG. 1 is a diagram illustrating bandwidths of an uplink and a downlink according to a conventional technique.

1, the LTE Advanced system includes at least two uplink bands 100a and 100b and at least one downlink band 150, as shown in FIG. 1 (a) .

The LTE Advanced system includes at least two uplink bands 100a and 100b and at least two downlink bands 150a and 150b as shown in FIG. .

Even if the downlink or uplink due to bandwidth coupling is combined with a plurality of links, as shown in FIGS. 1A and 1B, a bandwidth capable of transmitting ACK / NACK information in a corresponding uplink or downlink, There may be cases where there is only one.

In this case, ACK / NACK feedback for a plurality of uplink bands is enabled by reserving a control channel for ACK / NACK feedback transmission corresponding to each uplink band in a single downlink band. A method of reserving a control channel for feedback in more detail will be described with reference to FIG.

2 is a diagram illustrating a control channel to which ACK / NACK feedback is allocated in the downlink according to the related art.

Here, the control channel will be described on the basis of a subframe structure transmitted in the downlink. In general, a plurality of resource blocks exist in a bandwidth allocated to each base station. One resource block refers to resources included in one subframe and one band. One band may be composed of 12 sub-carriers, and one sub-frame may be composed of 14 OFDM symbol regions (hereinafter referred to as channels). Here, a subframe means a unit for allocating resources based on a time axis, and a band means a unit for allocating resources based on a frequency.

Referring to FIG. 2, one subframe 200a and 200b are divided into control areas 210a and 210b and data areas 220a and 220b. The control areas 210a and 210b include at least one channel for transmitting control information. In more detail, the channel includes a physical downlink control channel (PDCCH) 230a and 230b for transmitting resource allocation information on resources allocated to a plurality of terminals, and a downlink sub- And a PHICH (Physical Hybrid-ARQ Indicator Channel) 240a, 240b, 250a, 250b for transmitting ACK / NACK as a response signal. 2, the control areas 210a and 210b include first PHICH channels 240a and 240b for the first ACK / NACK to be transmitted on the first uplink, And a second PHICH channel 250a, 250b for a second ACK / NACK to be transmitted on the link.

In general, only a part of the resources corresponding to the second PHICH channels 250a and 250b are often used for ACK / NACK feedback. In this case, there is a problem that resources other than the resources selected for the ACK / NACK feedback are wasted among the resources of the second PHICH channels 250a and 250b. 2, only 2, 4 and 8 among 1 to 10 resources constituting the second PHICH channels 250a and 250b in the control areas 210a and 210b are used for PHICH transmission I suppose. Then, the resources other than the resources 2, 4 and 8 of the second PHICH channels 250a and 250b located in the control areas 210a and 210b are transmitted on the uplink without information being included. Also, since the second PHICH channels 250a and 250b are located in the l control areas 210a and 210b, the number of channels allocated to the data areas 220a and 220b is reduced. Also, among the resources of the second PHICH channels 250a and 250b, remaining resources not including control information can not be used for transmitting data, resulting in resource waste.

In order to solve the above problems, the present invention provides a feedback resource allocation method for a communication system supporting a plurality of bands and a mobile communication terminal for performing the same.

According to an aspect of the present invention, there is provided a method for allocating a feedback resource, the method comprising: mapping a first feedback channel signal of a first band to a resource of the control region in a subframe divided into a control region and a data region; ; Mapping a second feedback channel signal of a second band to a resource of the data region; And transmitting the subframe in which the first feedback channel signal and the second feedback channel signal are mapped.

According to another aspect of the present invention, there is provided a feedback resource allocation communication system for mapping a first feedback channel signal of a first band to a resource of a control region in a subframe divided into a control region and a data region, A base station for transmitting the subframe by mapping a second feedback channel signal of a second band to resources of the data region; If the received subframe is a subframe transmitted through the first band, a first feedback channel signal mapped to the control region of the subframe is checked. If the received subframe is a subframe transmitted through the second band A second feedback channel signal mapped to a data area of the subframe and transmitting a feedback signal to the base station through a channel identified through the first or second feedback channel signal.

According to the present invention, an ACK / NACK feedback resource of data transmitted on a plurality of uplinks can be efficiently transmitted in a single downlink band. And the resources can be effectively allocated in the downlink band. Also, since the ACK / NACK feedback resource corresponding to each transmission data channel can be confirmed without any separate information on the location of the ACK / NACK feedback resource, the overhead of the control message can be reduced.

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

3 is a diagram illustrating a base station transmitter structure of an LTE Advanced system for allocating feedback resources according to the present invention.

Referring to FIG. 3, the controller 310 controls the symbol generator 320 to generate signals of downlink physical channels. The controller 310 controls the mapper 330 to map the signals generated by the symbol generator 320.

The symbol generator 320 includes a first PHICH symbol generator 323, a second PHICH symbol generator 325, a PDCCH symbol generator 327, and a PDSCH symbol generator 329.

The first PHICH symbol generator 323 generates a first PHICH signal that is a first feedback channel signal including information of a first feedback channel allocated for a feedback signal indicating whether decoding of data transmitted in the first uplink band is successful . The second PHICH symbol generator 325 generates a second PHICH signal which is a second feedback channel signal including information of a second feedback channel allocated for a feedback signal to be transmitted in a second uplink band. The PDCCH symbol generator 327 generates a PDCCH signal transmitted through a downlink control channel (PDCCH). The PDSCH symbol generator 329 generates a PDSCH signal transmitted through a Physical Downlink Shared Channel (PDSCH). Although not shown in the figure, the symbol generator 320 further includes a BCH symbol generator and an SCH symbol generator. The BCH symbol generator generates a signal of system information transmitted through a BCH (Broadcasting Channel). An SCH (Synchronization Channel) symbol generator generates a signal of a synchronization signal transmitted through a synchronization channel.

The mapper 330 maps the signal generated by the symbol generator 320 under the control of the controller 310. Here, among the signals, the PHICH signal may be mapped to each resource through the following Equation (1).

는 PHICH group을 의미한다. 그리고

는 PHICH의 시퀀 스를 의미한다.

는 상향 링크 패킷이 점유하고 있는 자원의 가장 낮은 자원 인덱스를 의미한다.

는 DCI(Down link Channel) 포맷 0에서 DMRS(Demodulation Reference Signal) 필드를 위해 매핑된 사이클 쉬프트를 의미한다.

는 상위 계층들에 의해 설정된 PHICH 그룹들의 넘버를 의미한다.

는 PHICH 변조(modulation)을 위해 사용되는 확산 계수(spreading factor)를 의미한다.

는 TDD(Time Division Duplex) 상향 링크/하향 링크 구성(configuration)이 0이면 1을 다른 경우에는 0을 의미한다. here

Means PHICH group. And

Means a sequence of PHICHs.

Indicates the lowest resource index of the resource occupied by the UL packet.

Means a cyclic shift mapped for a demodulation reference signal (DMRS) field in a downlink channel (DCI) format 0.

Indicates the number of the PHICH groups set by upper layers.

Quot; means a spreading factor used for PHICH modulation.

Means 1 if the TDD (Time Division Duplex) uplink / downlink configuration is 0, and 0 otherwise.

In other words, the BS maps a PHICH signal for ACK / NACK feedback to a position corresponding to an index value of an uplink resource occupied by a signal transmitted from each terminal. The base station transmits the decoding result for the corresponding data to the terminal using the mapped PHICH signal corresponding to the index value of the uplink resource. Also, the UE can confirm the location and transmission pattern of the ACK / NACK resource to be transmitted to the base station indirectly by using Equation (1) without receiving the information on the ACK / NACK transmission position.

Through this equation, the mapper 330 maps the PHICH signal to a position corresponding to the index value of the uplink resource occupied by the packet transmitted from each terminal. The location where the PHICH signal is mapped will be described in more detail with reference to FIGS. 4A and 4B.

4A and 4B are views showing resources allocated to PHICH subcarrier symbols according to two embodiments of the present invention, respectively.

First, referring to FIG. 4A, the first PHICH signal 430a is mapped in the control region 410a. And the second PHICH signal 450a is mapped in the data area 420b. At this time, the area of the resource to which the second PHICH signal is mapped in the data area 420b can be previously agreed between the BS and the MS. Alternatively, the area of the resource to which the second PHICH signal is mapped in the data area 420b is not promised in advance between the BS and the MS, and the BS periodically transmits information on the area of the resource to which the second PHICH signal is mapped in the data area, And may be included in a broadcast channel or a control area transmitted to the terminal. In this case, the MS can determine the region of the resource to which the second PHICH signal is mapped in the data region through the mapping information included in the received broadcast channel or the control region.

The region of the resource to which the second PHICH signal is mapped is divided into a plurality of PHICH groups, and each PHICH group is divided into several PHICH sequences. For example, if one PHICH group is defined as a resource corresponding to N subcarriers for one subframe time, and the second PHICH is composed of a total of M PHICH groups, the region of the resource to which the second PHICH signal is mapped is N subcarriers for the number of subframe periods. The resources in each PHICH group are multiplexed into orthogonal codes and divided into L PHICH sequences. Therefore, in this case, it is possible to transmit a second PHICH signal for a maximum of N * M * L terminals.

A method of mapping the second PHICH signal of each terminal within the transmission resources of the second PHICH is as follows. First, the PHICH group and the PHICH sequence for each terminal are obtained by a calculation method determined from the index value of the resource transmitted from the terminal. At this time, the same method as in Equation (1) may be used. Next, the second PHICH signal of the terminal is mapped to a transmission resource corresponding to the PHICH group and the PHICH sequence of each terminal within the transmission resource of the second PHICH.

A region where the second PHICH signal can not be mapped in the data areas 420a and 420b is used for data transmission. Even if the second PHICH signal can be mapped, the resources 460a and 460b, which are not actually mapped, Lt; / RTI > Since the base station performs the second PHICH mapping, the base station can identify the resource to which the second PHICH is not mapped and use it for data transmission. Since the terminal always receives the resource used for data transmission from the base station, the base station may perform data transmission according to the designation.

Referring to FIG. 4B, the first PHICH signal is mapped in the control region 410a as shown in FIG. 4A. And the second PHICH signal 450a is mapped in the data area 420b. However, unlike FIG. 4A, the second PHICH signal corresponding to each terminal is notified by using separate control information 430a in the control region 410a. Accordingly, the terminal receives the first PHICH signal in the control area 410a. Then, the UE receives the allocation information for the resource location to which the second PHICH signal is allocated in the control domain 410a, and then receives the second PHICH signal from the resource corresponding to the second PHICH allocation information.

The second PHICH allocation information transmitted in the control region 410a may be transmitted in the same manner as the PDCCH, which is data channel allocation information. And the User ID used in the second PHICH allocation information is a value commonly applied to terminals to which spectrum aggregation is applied. The user ID uses a predetermined value in the terminal or a value transmitted through a broadcast channel periodically transmitted from the base station. The length of the ACK / NACK resource allocation message for the second uplink is determined to be a length that must be always decoded regardless of the MIMO mode of the MS among the resource allocation messages of the existing system. For example, the length may be the DCI length or format 0 / 1A length corresponding to the common search space for 3GPP LTE-Advanced.

The ACK / NACK resource allocation message includes a bitmap of a resource to which a second PHICH signal is mapped in the data area, information on the total number of ACK / NACK subchannels (PHICH groups), or an ACK / NACK number (number of PHICH sequences). And information on which subchannel ACK / NACK is transmitted among ACK / NACK channels to which the PHICH signal is mapped is designated when a channel is allocated for the corresponding uplink data.

The transmitter of the base station having such a configuration generates a PHICH signal corresponding to a plurality of uplink bands. When the generated signal is mapped, the transmitter maps the first PHICH signal to the channel located in the control region. The transmitter also maps the second PHICH signal to the resource of the channel located in the data area. The transmitter maps the PDCCH signal to the resources of the remaining channels in the control domain. Then, the transmitter maps the PDSCH signal to the remaining resources except the resource to which the PHICH signal is mapped in the data area.

The base station transmits the signal-mapped subframe to the terminal. The receiving terminal decodes the received sub-frame and verifies the signal mapped to the sub-frame. The terminal may transmit a feedback signal to the base station, which is an ACK / NACK signal indicating whether the decoding is successful for each signal. The method of identifying a resource between the BS and the MS will be described generally with reference to FIGS. 5 to 6. FIG.

5 is a flowchart illustrating a method of identifying resources between communication systems according to an embodiment of the present invention. 6 is a flowchart illustrating a resource mapping method according to an embodiment of the present invention.

5 to 6, in step 510, the BS generates a signal to be mapped to each resource of a subframe to be transmitted to the MS. Then, the BS maps the signal generated in step 520 to each resource of the subframe. A method of mapping a signal to a subframe will be described with reference to FIG. Referring to FIG. 6, in step 610, the BS maps a first PHICH signal, which is a first feedback channel signal of a first band, to a resource located in a control region of a subframe. The base station maps the second PHICH signal, which is the second feedback channel signal of the second band, to the resource located in the data area of the subframe. Although not shown in the drawing, the PDCCH signal including the control information is mapped to the control area, and the PDSCH signal including the data is mapped to the data area.

5, the base station codes the signal-mapped sub-frame into a packet, and transmits the coded sub-frame to the mobile station in step 530. In step 540, the terminal decodes the signal mapped to the received sub-frame. The terminal then checks the decoded signal. Next, the MS transmits an ACK / NACK to the BS according to the signal confirmed in step 550. A method of transmitting a ACK / NACK according to a resource after confirming a resource of a subframe will be described in detail with reference to FIG. 7 to FIG. 9. FIG.

Next, a method of confirming the PHICH signal in the terminal and transmitting the ACK / NACK will be described with reference to FIG. 7 to FIG.

7 is a flowchart illustrating a method of transmitting an ACK / NACK according to the present invention.

Referring to FIG. 7, if a subframe is received from a base station in step 710, the terminal checks a band in which the subframe was received in step 720. The mobile station checks the PHICH signal in the control region or the data region according to the band identified in Step 730. A process of confirming the PHICH signal will be described later with reference to FIG. 7 to FIG. Next, the MS transmits an ACK / NACK feedback signal to the BS using the channel identified through the PHICH signal confirmed in step 740.

The method of confirming the PHICH signal according to the confirmed band may be an indirect confirmation method or a direct confirmation method. The indirect confirmation method is a method of confirming the location of a resource to which the PHICH signal promised in advance is mapped between the BS and the MS. A direct confirmation method is a method in which a terminal checks a PCCCH signal located in a control region and confirms a location of a resource to which a PHICH signal is mapped. These processes will be described in detail with reference to FIGS. 8 to 9. FIG.

8 is a method for confirming the PHICH according to the embodiment of the present invention.

Referring to FIG. 8, in step 810, the terminal determines whether a subframe has been transmitted from a base station through a first uplink (UL) band. If the subframe transmitted in the first uplink has been received, the terminal checks the resource to which the first PHICH signal is mapped in the control region of the subframe in step 820. [ On the other hand, if the identified subframe is a subframe transmitted in a band other than the first uplink, the terminal checks resources mapped to the second PHICH signal in the data area of the subframe in step 830. When the location of the resource resource to which the PHICH signal is mapped is confirmed, the MS can transmit an ACK / NACK feedback signal to the BS according to the PHICH signal.

9 is a method for confirming the PHICH according to another embodiment of the present invention.

Referring to FIG. 9, in step 910, the terminal determines whether a subframe transmitted in a first uplink (UL) band has been received. If the subframe of the first uplink band is received, the terminal checks resources mapped to the first PHICH signal in the control region of the subframe in step 920. [ On the other hand, if the subframe transmitted in the second uplink band other than the first uplink band is received, the terminal transmits the second PHICH signal in the data area through the PDCCH, which is allocation information of the control region in the subframe, Check the resources. Then, the MS confirms the second PHICH signal in the resource identified in step 940. When the location of the PHICH resource is confirmed, the mobile station can transmit an ACK / NACK feedback signal to the base station according to the confirmed PHICH.

Up to now, a method of mapping a PHICH signal for ACK / NACK transmission or checking a mapped PHICH signal in two uplink bands and one downlink band has been described. In addition, a method of mapping a PHICH signal for ACK / NACK transmission in two uplink bands and one downlink band, or a method of checking a mapped PHICH signal can be similarly applied. That is, in a communication system having a plurality of bands, a first PHICH signal, which is a first feedback channel signal corresponding to a first band, is allocated to a control region and a second band And maps the second PHICH signal, which is the second feedback channel signal, to the resource located in the data area. The location of the resource to which the first or second PHICH signal, the first or second feedback channel signal, is mapped may be a predetermined location between the MS and the BS. Also, when a subframe is received, the UE or the BS can confirm the location of the resource to which the second feedback channel signal is mapped in the data region through the PDDCH mapped to the control region. The UE may check the second feedback channel signal mapped to the identified resource and transmit the ACK / NACK feedback signal to the base station or the UE.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. 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.

1 is a diagram illustrating a bandwidth of an uplink and a downlink according to a conventional technique.

2 is a diagram illustrating a control channel to which feedback is assigned in the downlink according to the prior art;

3 is a diagram illustrating a base station transmitter structure of an LTE Advanced system for allocating feedback resources according to the present invention;

4A and 4B are diagrams illustrating resources allocated a PHICH signal according to an embodiment of the present invention;

5 is a flowchart illustrating a method of identifying resources between communication systems according to an embodiment of the present invention.

6 is a flowchart illustrating a resource mapping method according to an embodiment of the present invention.

7 is a flowchart illustrating a method of transmitting ACK / NACK according to the present invention.

8 illustrates a method for identifying a PHICH according to an embodiment of the present invention.

9 illustrates a method for identifying a PHICH according to another embodiment of the present invention.

Claims (7)

A feedback resource allocation method in a communication system supporting a plurality of bands, Mapping a feedback channel signal of a first band to a resource of the control region in a subframe divided into a control region and a data region; Mapping a feedback channel signal of a second band to a resource of the data region; And transmitting the subframe in which the feedback channel signal of the first band and the feedback channel signal of the second band are mapped. The method of claim 1, wherein the feedback channel signals of the first and second bands (PHICH) signal of the first and second bands. A method for identifying a feedback resource in a communication system supporting a plurality of bands, Checking a feedback channel signal of a first band in the control region in a subframe divided into a control region and a data region; And checking a feedback channel signal of a second band in the resource of the data region. 4. The method of claim 3, wherein the step of verifying the feedback channel signal of the second band comprises: Checking a position of a resource to which a feedback channel signal of a second band is mapped in the data region using assignment information mapped to the control region; And checking the feedback channel signal of the second band at the identified position. Mapping a first feedback channel signal of a first band to resources of the control region in a subframe divided into a control region and a data region and mapping a second feedback channel signal of a second band to resources of the data region, A base station for transmitting a sub-frame; And a terminal for confirming a feedback channel signal of a first band in the control region and a feedback channel signal of a second band in resources of the data region in the subframe. 6. The method of claim 5, Wherein the control unit checks the position of the resource to which the second feedback channel signal is mapped in the data area using the allocation information mapped to the control region and verifies the second feedback channel signal at the identified position. Assigned communication system. 6. The method of claim 5, wherein the first and second feedback channel signals And a first and a second physical hybrid ARQ indicator channel (PHICH) signal.

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