KR20160109228A - Method and apparatus for configuring epdcch subframe in unlicensed carrier - Google Patents

Abstract

Disclosed are a method and an apparatus for setting an EPDCCH sub-frame in an unlicensed carrier. Therefore, the method can efficiently transmit an EPDCCH on the unlicensed carrier in which an LAA system operates.

Description

METHOD AND APPARATUS FOR CONFIGURING EPDCCH SUBFRAME IN UNLICENSED CARRIER BACKGROUND OF THE INVENTION < RTI ID = 0.0 > [0001] <

The present invention relates to wireless communication, and more particularly, to a method and apparatus for setting an EPDCCH subframe in a license-exempt band.

In the LAA system using the license-exempt band channel, both the eNB and the UE can not know when the channel can be acquired and the data can be transmitted or received. Therefore, there is a problem that efficient EPDCCH transmission and monitoring operations can not be performed in an unlicensed carrier environment which is turned on / off with subframe or OFDM symbol level together with LBT operation using existing semi-static EPDCCH subframe setting information and transmission methods.

In the LTE-A system, we are considering LAA technology that can perform CA with an existing licensed carrier in unlicensed carrier. The present invention proposes a new EPDCCH transmission method that can be transmitted on an unlicensed carrier.

In particular, a new method for what subframes should be utilized in the license-exempt band for EPDCCH transmission is required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wireless communication method and apparatus based on LAA.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for setting an EPDCCH subframe in an unlicensed carrier.

Method and apparatus for setting an EPDCCH subframe in a license-exempt band

The EPDCCH transmission can be efficiently provided on the license-exempted band where the LAA system operates through the method proposed in the present invention.

FIGS. 1A and 1B illustrate examples of the start and end of Tx data / control transmission in a partial subframe on an LBE-LBT based u-carrier.
2 shows a conditional EPDCCH monitoring operation (Alt 2) within an EPDCCH subframe according to the present invention.
3 shows an operation according to the first embodiment.
FIG. 4 shows examples (LAA with LBE-LBT) capable of PDSCH transmission with a larger TBS size.
5 shows an example having a 5 ms frame period in the FBE-LBT based LAA system.
FIG. 6 shows an example (4 ms maximum occupancy time) of a new bitmap indicating method for setting an EPDCCH subframe in the LBE-LBT LAA system.
FIG. 7 shows an example (5ms frame period) in which an EPDCCH subframe is set through a new bitmap in an LAA system based on an FBE-LBT.
8 shows an operational flow diagram of the FBE-LBT-based LAA system.
9 is a flowchart of the operation according to the third embodiment.
10 is an example of an operation flow chart according to the fourth embodiment.
11 is another example of the operation flow chart according to the fourth embodiment.

Hereinafter, the contents related to the present invention will be described in detail with reference to exemplary drawings and embodiments, together with the contents of the present invention. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear.

In addition, the present invention will be described with respect to a wireless communication network. The work performed in the wireless communication network may be performed in a process of controlling a network and transmitting data by a system (e.g., a base station) Work can be done at a terminal connected to the network.

In the present invention, the following embodiments are proposed.

Example 1. The base station and the terminal performing the LAA always perform EPDCCH transmission and monitoring only in the occupied subframes after the LBT operation without using the EPDCCH subframe setting based on the RRC signaling.

In other words, EPDCCH monitoring is not performed in a subframe that is not occupied. Also, in the exceptional situation proposed according to the present invention, the UE does not perform EPDCCH monitoring even in the occupied subframe.

Example 2. The new RRC signaling is introduced in consideration of the maximum channel occupancy time to set up the EPDCCH subframe. The new RRC setting is valid only for the subframes occupied after performing the LBT. For this purpose, the bitmap according to the present invention can be repeatedly applied whenever a channel is occupied by a transmitting node.

Example 3. In order to adaptively use EPDCCH in the license - exempt band, we propose a method of setting up EPDCCH subframe through dynamic signaling.

Example 4. We propose a new EPDCCH monitoring subframe selection method based on RRC signaling.

Here, it is apparent that the present invention is not limited to the concept of the above-mentioned embodiments.

EPDCCH transmission method in LAA environment

1. How to set EPDCCH monitoring subframe in LAA system

The partial subframe on the u-carrier considered in the LAA system can transmit EPDCCH (PDSCH) at various positions. The OFDM symbol index can transmit the EPDCCH at a certain position in one subframe or can transmit at a limited OFDM symbol index (or candidate symbol index) according to the time occupied by the channel according to the LBT performance. For example, FIG. 1A and FIG. 1B show an example where downlink channels / signals are transmitted after channel occupation based on candidate points of limited OFDM symbol indexes and channel occupancy signals transmitted to occupy corresponding channels, Show examples at the time.

Hereinafter, the "Partial subframe" in the present invention occupies a channel in a first subframe occupying a channel and outputs a Tx data / control signal transmission start point 110 as shown in the first and last subframes in FIGS. 1A and 1B, Or the end point 130 where the channel occupation for transmission of the Tx data / control signal ends according to the maximum time that the channel can be occupied is defined as a subframe occurring in the middle of the subframe other than the subframe boundary.

On the other hand, " Regular subframe " is defined as a subframe in which the start and end of transmission of Tx data / control signals are always performed in the subframe boundary 120.

Here, it is assumed that the Tx data / control signals include at least one of a PDCCH / PDSCH / EPDCCH or a signal including a PDCCH, a PDSCH or a PDSCH and an EPDCCH, a PDSCH, or an EPDCCH in the case of DL. On the other hand, in the UL case, a guard period for uplink / downlink conversion can be additionally considered in the sections required for performing the LBT. However, a method for determining the start and end points of transmission of the UL Tx data / Is assumed to be the same as the case in which only the consideration is given.

As shown in FIGS. 1A and 1B, a transmitting node on a u-carrier may acquire a channel through an LBT operation and may transmit a channel occupancy signal to occupy the channel before transmitting the data / control channel. After transmitting the channel occupancy signal, the base station (defined as the transmitting node) can determine whether to transmit the EPDCCH on the subframe set or determined as the EPDCCH transmission subframe among the occupied subframes. From the terminal point of view, the EPDCCH is always monitored in the subframe set and determined as the EPDCCH transmission subframe. However, since it is determined whether or not the EPDCCH is transmitted by the actual base station, the UE can perform EPDCCH decoding on the base station (EPDCCH transmission or non-transmission).

In this regard, the present invention proposes how to set an EPDCCH subframe through a method in a license-exempt frequency environment through the following methods.

Example 1. The base station and the terminal performing the LAA always perform the EPDCCH transmission and monitoring only in the occupied subframes after the LBT without using the EPDCCH subframe setting based on the RRC signaling. Naturally, EPDCCH monitoring is not performed in a subframe that is not occupied. However, in the following exceptional cases, the UE does not perform monitoring even if it is an occupied subframe.

In addition, an exceptional situation in which EPDCCH monitoring is not performed among the occupied subframes is as follows. Hereinafter, an exceptional situation to be mentioned is effectively applicable in all the embodiments proposed according to the present invention.

A. Exception regarding EPDCCH monitoring of LAA system based on LBE-LBT

i. The LAA system based on the LBE-LBT does not always monitor the EPDCCH within the partial subframe. In this example, the EPDCCH transmission is not performed on the partial subframe. (Only when transmission of the Tx data / control signal at the subframe boundary is started / ended) or

ii. The LAA system based on the LBE-LBT does not monitor the EPDCCH only when a certain number of OFDM symbols (for example, three system BW => 10 PRBs) are used for EPDCCH transmission in the partial subframe. (When Tx data / control signal transmission starts / ends at any OFDM symbol boundary in a subframe) or

iii. In order to transmit DRS (Discovery RS) for channel measurement (e.g., CSI, RRM) without data scheduling, the UE does not monitor the EPDCCH in a subframe occupying a channel. or

One. Additional explanation for the above case: Since the mapping pattern of the DRS signal (eg CRS, PSS / SSS, CSI-RS) is not transmitted in consecutive time or the entire occupied channel, May be required to maintain continuous DRS transmissions. Otherwise, DRAs may not be able to transmit all of the DRS occasions by surrounding LAA or WiFi nodes, and neighboring nodes may occupy the channel.

iv. If short control signaling (SCS) is supported, the UE does not monitor the EPDCCH in a subframe that occupies a channel and transmits a signal without performing a CCA like SCS.

Here, the DRS (Discovery RS) is a reference signal transmitted by the small cell eNBs performing on / off operations for the purpose of channel quality evaluation (e.g., RRM, CSI, etc.) , And may be transmitted within subframes (DRS occasions) that can periodically transmit DRS through a combination of PSS / SSS and CSI-RS (configuration required).

In addition, SCS is capable of transmitting signals on license-free channels without CCA operation within a maximum 5% of the observation time of 50 ms, according to EU regulations. If the corresponding rule (operation) is allowed in the LTE for the SCS, a particular type of RS may be transmitted within the corresponding duty cycle.

Meanwhile, in the subframe for monitoring the EPDCCH transmission according to the present invention, a new terminal operation can be considered as follows.

Alt 1. The current terminal operation does not perform USS PDCCH monitoring in the set EPDCCH subframe but performs CSS PDCCH monitoring and USS EPDCCH monitoring. In the above i-ii, other operations on the partial subframe are proposed based on the current terminal operation. On the other hand, with a new monitoring operation, the UE may consider monitoring both USS PDSCH and USS EPDCCH in occupied subframes through LBT performance of the transmitting node. In this case, the number of blind decodings for each PDCCH and EPDCCH may need to be limited within the maximum value currently considered.

Here, the CSS (Common Search Space) refers to a resource space in which all terminals can monitor PDCCH for the purpose of transmitting common information to all terminals in a cell. Transmits the scrambled PDCCH for the purpose of SI / Paging / Random Access / MCCH change notification / TPC / eIMTA signaling as well as data scheduling through the CSS space and transmits the information to all or a plurality of associated terminals in the cell A control channel (PDCCH) is transmitted. The CSS uses a common location for all terminals in the cell.

Meanwhile, USS (UE Specific Search Space) is a resource space to which a specific control channel (PDCCH or EPDCCH) is transmitted to one UE, and is mainly used for data scheduling purposes. The USS determines a location of a resource space that can transmit a control channel at a UE-specific location based on parameters such as RNTI and Cell ID of the UE.

The reasons for monitoring all of the USS PDCCH / EPDCCH in the EPDCCH subframe are that the UE needs to perform decoding both on the PDSCH having the EPDCCH reception and the large TBS indicated by it as shown in the following example, Lt; RTI ID = 0.0 > UL < / RTI > subframe license-free frequency). In this case, the BS can perform the scheduling through the USS PDCCH in order to transmit the PDSCH having the larger TBS even in the actual EPDCCH subframe in every subframe. As another example, if there are a small number of UEs in the cell and the UEs are scheduled using only the EPDCCH, there may be no PDCCH transmission in the existing PDCCH area (CRS transmission is performed in this case as well). Therefore, PDCCH transmission may be required in order to prevent the other transmission node from acquiring the channel once acquired. Of course, there may be a method of transmitting a specific signal on an empty OFDM symbol as another way to maintain the occupied channel. The particular signal may be a channel occupancy signal (e.g., an improved form of CRS, PSS / SSS, CSI-RS).

Herein, as an example, the channel occupancy signal is distributed throughout the cell, and the RE distribution on the frequency axis for the CRS antenna port 0 is repeated so that there is no empty OFDM symbol index in order to continuously occupy the channel, It is repeatedly transmitted on the index. In the case of PSS / SSS, it is repeatedly mapped to distribute to all PRBs to avoid being located only in the 6PRB of the center of the frequency band unlike the CRS, or the PSS / SSS sequence allocated on the current frequency axis is mapped onto the entire PRB Can be extended.

In addition, Embodiment 1 of the present invention can operate as shown in FIG.

Alt 2. Basically, it is considered to monitor PDCCH / EPDCCH in all of the EPDCCH subframe, but it is possible to determine whether to perform EPDCCH monitoring by comparing the size of the PDSCH TBS with a predetermined threshold value through a predetermined layer signaling. In this manner, the UE can reduce the time required to decode the EPDCCH on the EPDCCH subframe. This can prevent processing delay of the UE and will not affect the PDSCH decoding time requirement (time required to decode the PDSCH scheduled on one subframe) currently defined in RAN4. Here, the EPDCCH subframe means a subframe in which the UE must monitor the EPDCCH. Therefore, the EPDCCH is monitored conditionally on the EPDCCH subframe.

1. In this case, although the UE is once an EPDCCH monitoring subframe, the UE first determines the TBS size of the scheduled PDSCH through PDCCH monitoring on the USS, and if the size of the PDSCH TBS is greater than a specific threshold Threhold # 1 And / or does not perform EPDCCH monitoring at the set threshold value Threhold # 2. In such a case, the BS assumes that all DCI information on the USS to be provided to the UE is transmitted to the PDCCH USS domain, and the UE also performs monitoring in the domain. Otherwise, the UE monitors both the PDCCH / EPDCCH USS region. In this manner, the UE can reduce the time required to decode the EPDCCH on the EPDCCH subframe.

B. Exception regarding EPDCCH monitoring of LAA system based on FBE-LBT

i. Since there is no partial subframe, EPDCCH monitoring is always performed in the occupied subframes. In the FBA-LBT-based LAA system, a method based on the bitmap shown in FIG. 5 is expected to be more efficient.

Example 2. The new RRC signaling is introduced in consideration of the maximum channel occupancy time to set up the EPDCCH subframe. The new RRC setting is valid only for the subframes occupied after performing the LBT. The bitmap is repeated every time the channel is occupied by the transmitting node. Also, exceptions that do not perform EPDCCH monitoring mentioned in Embodiment 1 above are equally applicable in Embodiment 2. [

A. LAA system based on LBE-LBT

i. Alt 1. The bitmap length of the corresponding RRC signaling is based on the largest possible maximum channel occupancy time value. That is, according to current European LBE regulations, "<= (13/32) × q ms" maximum occupancy time can be defined, and according to Japanese regulations, 4 ms is always defined as maximum occupancy time. According to European regulations, the maximum channel occupancy depends on the q value, which can be chosen by the equipment manufacturer between [4 ... 32]. The q value may be selected randomly or one value may be selected. Therefore, if you are designing an LAA that performs LBE-LBT by European regulations, you must determine the bitmap based on the maximum value. Therefore, the EPDCCH subframe can be indicated in the occupied subframe using the value 13 + 1 = 14 bits. The reason for adding 1 bit here is due to the presence of a partial subframe (see FIG. 6).

ii. Alt 2. The bitmap length of the corresponding RRC signaling is selected based on the determined maximum channel occupation time. The length of the bitmap may be determined according to the maximum channel occupation time of different lengths for each region. For example, 4 + 1 = 5 bits in Japan, and 14 bits in Europe, while in other regions it can be determined to be an arbitrary length.

6, if the partial subframe does not exist, that is, when the Tx data / control transmission is performed directly on the subframe boundary, since the last subframe is not the actual occupied subframe, The base station and the terminal do not perform EPDCCH transmission and monitoring. This is an example that can occur because the above bitmap is applied repeatedly.

Hereinafter, for the purpose of the present invention, RRC signaling will be described as follows.

Existing RRC signaling Vs New RRC signaling comparison

- Existing RRC signaling (40 bits (FDD), 20 bits (TDD # 1-5), 70 bits (TDD # 0), 60 bits (TDD # 1)

 > After the LBT is performed, the EPDCCH subframe exists in the random subframe within the occupied subframes

- New RRC signaling (up to max. Channel occupancy time in LBE / FBE, (1 to 13 bits)):

 > After performing the LBT, the EPDCCH subframe is present in the intended subframe within the occupied subframes

New RRC signaling Advantages:

- The EPDCCH subframe setting can be avoided in subframes with limited resources that can be utilized for EPDCCH transmission such as partial subframes. This is because more PRBs and ALs (ECCE / EREG) are required to maintain the same EPDCCH link performance as in regular subframes. This will adversely affect the efficiency of the PDSCH transmission. Also, since the EPDCCH capacity is limited on the partial subframe, the PDSCH transmission efficiency will be adversely affected as the number of UEs with the EPDCCH set in the same subframe increases. Therefore, it is possible to provide the base station equipment manufacturer with full flexibility to set the EPDCCH on the preferred subframe (e.g., regular subframe) through the proposed RRC signaling.

  > This problem is expected to be less favorable in cases where more frequent partial subframes appear in LAA systems based on short maximum channel occupancy times, especially during specified times.

- There may be uncertainty when using SCS-transmitted subframes and existing RRC signaling if short control signals (provisions that can be transmitted without CCA operation within a maximum of 5% of observation time of 50 ms) are allowed, The same uncertainty can be avoided through new RRC signaling.

- For example, a new terminal operation may be required if the same subframe is set to an EPDCCH subframe by an existing RRC signaling in order to transmit an SCS within 2.5 subframes of 5% within 50 ms. In another example, a new terminal operation definition may be required if the subframe is set as an EPDCCH subframe by existing RRC signaling in a subframe occupied by a channel only for CSI / RRM measurement purpose. However, a new terminal operation definition may be required through the new RRC signaling according to the present invention It is not necessary to define a separate terminal operation.

- Of course, even if the difference in the number of EPDCCH subframes within the occupied subframe is not large during the long-term time, it is possible to set the correct number of EPDCCH subframes within the occupied subframe at a given time.

- In addition, the inefficient bitmap length of existing bitmap signaling used in existing eICIC and EPDCCH can be significantly reduced.

- Here, the ECCE is a physical resource component constituting one EPDCCH and can allocate one EPDCCH using one or a plurality of ECCE resources. The EREG is an element constituting one ECCE, and the number of EREGs constituting one ECCE is determined according to subframe characteristics (e.g., normal or special subframe) or CP type.

Meanwhile, the existing bitmap is a signaling method of setting the ABS subframe to be set when the eICIC is performed. Although the unnecessary long bitmap is used to minimize the influence on the UL HARQ operation, the proposed signaling is more efficient in size and higher Flexibility can be provided.

B. The FBE-LBT-based LAA system (see FIG. 7)

i. Alt 1. The bitmap length of the corresponding RRC signaling is based on the largest possible maximum channel occupancy time value. For example, according to European regulations, the value may be 10. This is because the channel occupation time is fixed to 1 to 10 ms. The EPDCCH subframe can be set through a bitmap with a maximum length of 10 based on the largest 10 ms. The bitmap thus set is used repeatedly each time the channel is occupied.

ii. Alt 2. The length of the bitmap of the corresponding RRC signaling can be determined to be the same value as the predetermined frame period instead of the bitmap having the maximum length. For example, if the frame period is 10ms, the bitmap length of the corresponding RRC signaling may also be 10 bits.

The flowchart shown in Fig. 8 can be proposed in connection with the above-described embodiment.

Example 3. An EPDCCH subframe indication method using dynamic signaling in order to adaptively use EPDCCH in a license-exempt band

A. A method of adding a new field in the DCI format transmitted via the PDCCH and instructing it

i. (UE), and then instructs the UE whether the new DCI with enabling configuration (PDCCH) monitors additional EPDCCH after decoding the PDCCH. This is to confirm the EPDCCH monitoring through the PDCCH without utilizing the RRC signaling utilizing the existing bitmap. For example, 0: only PDCCH monitoring and 1: additional EPDCCH monitoring through a new 1 bit field (EPDCCH monitoring indicator) of the DCI field in the PDCCH.

B. Dynamic EPDCCH Monitoring Sub-frame Indication Method Using Channel Occupancy Signal

i. After the LBT is performed, the base station provides the intended occupancy time (K ms) through the channel occupancy signal transmitted to occupy the channel. This is equal to or less than the maximum occupied sub time (M ms) (K = <M). This does not force the base station to occupy the channel for the maximum occupancy time after performing the LBT, and if the LAA base station does not need to occupy the channel for the maximum occupancy time, You may. In this case, the UEs having the EPDCCH set can monitor the EPDCCH only for the corresponding subframes for Kms.

ii. In addition, it can also indicate whether to monitor EPDCCH during on time occupied by the channel occupancy signal (on / off instruction).

The flowchart of FIG. 9 can be proposed in connection with the above-described embodiment.

Example 4. If there is a subframe pointing to the EPDCCH subframe by the RRC signaling among the subframes occupied by the LBT, the terminal performs the EPDCCH monitoring only in that subframe.

A subframe that requires semi-static EPDCCH monitoring by RRC signaling can be set up as follows.

"The IE MeasSubframePattern is used to specify a subframe pattern. The first / leftmost bit corresponds to the subframe # 0 of the radio frame satisfying SFN mod x = 0, where SFN is the PCN and x is the size of the bit string divided by 10. "1" represents the corresponding subframe is used. "

MeasSubframePattern information element

- ASN1START

MeasSubframePattern-r10 :: = CHOICE {
subframePatternFDD-r10 BIT STRING (SIZE (40)),
subframePatternTDD-r10 CHOICE {
subframeConfig1-5-r10 BIT STRING (SIZE (20)),
subframeConfig0-r10 BIT STRING (SIZE (70)),
subframeConfig6-r10 BIT STRING (SIZE (60)),
...
},
...
}

- ASN1STOP

Therefore, even if the EPDCCH subframe is indicated by the RRC signaling, the UE performs EPDCCH monitoring only when the corresponding subframe is occupied by the LBT. However, as mentioned above, even in situations where the above conditions are met, additional EPDCCH monitoring may not be performed under exceptional circumstances. The exception is the situation mentioned above.

That is, after the LBT, the UE performs EPDCCH monitoring for the occupied subframe, the subframe indicated by the existing EPDCCH signaling, and the subframe corresponding to the exceptional subframe.

The flowchart shown in Fig. 10 can be proposed in connection with the above-described embodiment.

As another example, a flowchart as shown in FIG. 11 can be proposed.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (1)

Method and apparatus for setting an EPDCCH subframe in a license-exempt band

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