KR20160094079A - Method for estimatingpass-loss in wireless communication system supporting licensed assisted access and apparatus using the method - Google Patents

Abstract

Provided are a method and an apparatus for estimating a path loss in a wireless communication system supporting licensed assisted access (LAA). The method for estimating a path loss in a wireless communication system according to the present invention comprises the steps of: a terminal, which has a carrier aggregation between a serving cell in a licensed band and a serving cell in an unlicensed band, receiving a radio resource control (RRC) message from a base station; and estimating a path loss in uplink transmission via a sub-serving cell set in the unlicensed band, based on information on a path loss reference serving cell included in the RRC message. Thereby, the present invention can provide the method for reliably estimating a path loss in a wireless communication system.

Description

[0001] The present invention relates to a method and an apparatus for estimating a path loss in a wireless communication system supporting a wireless access communication (LAA)

The present invention relates to a method and an apparatus for estimating a path-loss in a wireless communication system supporting LAA (Licensed Assisted Access).

Cellular is a proposed concept to overcome the limitations of service area, frequency and capacity of subscriber capacity, and can divide the mobile communication service area into several small cell units so that frequency can be reused spatially . However, in certain areas, such as hotspots inside cells, there is a particularly high demand for communication, and in certain areas such as cell edges or coverage holes, the reception sensitivity of radio waves may be reduced.

For example, a small cell such as a pico cell or a femto cell may be used in a macro cell for the purpose of enabling communication in a hot spot, a cell boundary, a coverage hole, A micro cell, a remote radio head (RRH), a relay, and a repeater are installed together. Such a network is called a heterogeneous network (HetNet). In a heterogeneous network environment, a macro cell is a large cell with a large coverage and a small cell such as a femtocell and a picocell is a small cell.

As wireless communication traffic increases, despite the fact that small cells such as the above are actively utilized, it is still urgent to secure more frequencies. Accordingly, a method of performing wireless communication using unlicensed band frequencies such as a WiFi band as well as a licensed band based on Carrier Aggregation (CA) has been discussed. Here, CA is a technique for efficiently using a fragmented small band, and is a technique of using a physically continuous or non-continuous plurality of bands in the frequency domain to logically use a band of a large band So that the effect can be achieved.

In the case where the CA is configured between the serving cell of the license band and the serving cell of the license-exempted band, the serving cell set on the license-exempt band can be easily exposed to interference due to the characteristics of the license- Estimation may not be possible. This causes uplink transmission power control based on an incorrect path loss value, so that not only the performance of the entire system deteriorates but also unnecessary interference can be caused.

Therefore, in recent wireless communication systems, there is an urgent need for how to minimize the path loss and reliably estimate the CA between the serving cell of the license band and the serving cell of the license-exempt band.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reliable path loss estimation method and apparatus in a wireless communication system in which carrier aggregation is configured between a serving cell in a licensed band and a serving cell in a license-exempted band.

Another aspect of the present invention is to provide a method and apparatus for constructing and transmitting / receiving information for estimating a path loss for a serving cell in an unlicensed band in a wireless communication system in which carrier aggregation is configured.

According to an aspect of the present invention, there is provided a path loss estimation method in a wireless communication system, wherein a terminal having a carrier aggregation between a serving cell in a licensed band and a serving cell in an unlicensed band receives an RRC And a step of estimating a path loss at the time of uplink transmission through a secondary serving cell set in the license-exempt band based on the information about the path loss reference serving cell included in the RRC message can do.

According to another aspect of the present invention, there is provided a method for estimating a path loss in a wireless communication system, the method comprising: determining whether a terminal configured to perform carrier aggregation between a serving cell of a licensed band and a serving cell of a license- And estimating a path loss at the time of uplink transmission through the secondary serving cell set in the license-exempt zone based on the selected secondary serving cell.

According to another aspect of the present invention, there is provided a path loss estimation method in a wireless communication system, which includes: estimating path loss in a channel environment of a terminal of a terminal based on a signal received from a terminal configured to perform carrier aggregation between a serving cell in a license band and a serving cell in a license- Determining whether to change the path loss reference serving cell of the UE based on the estimated channel environment, and determining whether to change the path loss reference serving cell to the UE if the path loss reference serving cell is changed, Lt; RTI ID = 0.0 > RRC < / RTI >

According to another aspect of the present invention, in a wireless communication system, a terminal configured to perform carrier aggregation between a serving cell in a licensed band and a serving cell in an unlicensed band includes a Radio Frequency (RF) unit for receiving an RRC message from a base station, Path loss reference serving cell for a secondary serving cell set in the license-exempt zone and estimating a path loss for uplink transmission through a secondary serving cell set in the license-extinguishing band, based on information on the path loss serving serving cell Processor.

The present invention can reliably estimate the path loss even when the carrier aggregation is configured between the serving cell of the license band and the serving cell of the license-exempted band. In addition, it provides the advantage of ensuring quality of service throughout the network through the license-exempt band by transmitting and receiving information for estimating the path loss for the license-exempted band between the serving cell of the license band and the serving cell of the license-exempt band.

1 shows a wireless communication system to which the present invention is applied.
Figure 2 shows examples of LAA deployment scenarios to which the present invention is applied.
3 is an exemplary diagram illustrating a case where the existing path loss estimation method is applied to a situation where carrier aggregation between the serving cell of the license band and the serving cell of the license-exempted band is configured.
FIG. 4 and FIG. 5 are views showing an example of an interference situation when carrier aggregation between the serving cell in the license band and the serving cell in the license-exempted band is configured.
6 is a diagram illustrating a path loss estimation method according to an embodiment of the present invention.
7 is a flowchart illustrating an operation of a terminal according to an embodiment of the present invention.
8 is a flowchart illustrating an operation of a base station according to an embodiment of the present invention.
9 is a diagram illustrating a path loss estimation method according to another embodiment of the present invention.
10 is a flowchart illustrating an operation of a terminal according to another embodiment of the present invention.
11 is a block diagram illustrating a wireless communication system according to an embodiment of the present invention.

Hereinafter, some embodiments will be described in detail with reference to exemplary drawings. 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 numerals whenever 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.

1 shows a wireless communication system to which the present invention is applied.

The network structure shown in FIG. 1 may be a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS). The E-UMTS system may include LTE (Long Term Evolution), LTE-A (advanced) systems, and the like. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

On the other hand, there is no limitation on a multiple access technique applied to a wireless communication system. (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier FDMA , OFDM-CDMA, and the like can be used.

Referring to FIG. 1, an E-UTRAN includes at least one base station (BS) 20 that provides a control plane and a user plane to a UE. A user equipment (UE) 10 may be fixed or mobile and may be a mobile station, an AMS (advanced MS), a user terminal (UT), a subscriber station (SS) It can be called a term.

The base station 20 generally refers to a station that communicates with the terminal 10 and includes an evolved Node B (eNodeB), a base transceiver system (BTS), an access point, a femto-eNB ), A pico-eNB, a home eNB, a relay, and the like. The base station 20 may provide at least one cell to the terminal. The cell may mean a geographical area where the base station 20 provides communication services, or may refer to a specific frequency band. A cell may denote a downlink frequency resource and an uplink frequency resource. Or a cell may mean a combination of a downlink frequency resource and an optional uplink frequency resource. Also, in general, in case of not considering Carrier Aggregation (CA), uplink and downlink frequency resources always exist in one cell.

An interface for transmitting user traffic or control traffic may be used between the base stations 20. The source BS 21 refers to a base station for which a radio bearer is currently set with the UE 10 and a target BS 22 transmits a radio bearer to the source BS 21, Means a base station to perform a handover in order to set up a radio bearer. The base stations 20 may be interconnected via an X2 interface. The X2 interface is used for exchanging messages between the base stations 20. The base station 20 is connected to an evolved packet system (EPS), more specifically, an MME (Mobility Management Entity) / S-GW (Serving Gateway) 30 via an S1 interface. S1 interface supports many-to-many-relations between the base station 20 and the MME / S-GW 30. The PDN-GW 40 is used to provide packet data service to the MME / S-GW 30.

Hereinafter, downlink refers to communication from the base station 20 to the terminal 10, and uplink refers to communication from the terminal 10 to the base station 20. The downlink is also referred to as a forward link, and the uplink is also referred to as a reverse link. In the downlink, the transmitter may be part of the base station 20, and the receiver may be part of the terminal 10. [ In the uplink, the transmitter may be part of the terminal 10, and the receiver may be part of the base station 20. A TDD (Time Division Duplex) scheme, which is transmitted using different time periods as an uplink transmission scheme and a downlink transmission scheme, may be used in a wireless communication system, or an FDD (Frequency Division Duplex) scheme that is transmitted using different frequencies may be used. Can be used.

On the other hand, Carrier Aggregation (CA) supports a plurality of carriers and is also referred to as spectrum aggregation or bandwidth aggregation. The individual unit carriers tied by the carrier aggregation are referred to as component carriers (CC). Each element carrier is defined as the bandwidth and center frequency. For example, if five elementary carriers are allocated as the granularity of a carrier unit having a bandwidth of 20 MHz, it can support a bandwidth of up to 100 MHz.

Hereinafter, a multiple carrier system includes a system supporting a carrier aggregation (CA). A serving cell may be defined as an element frequency band that can be aggregated by a CA based on a multiple component carrier system. The serving cell includes a primary serving cell (PCell) and a secondary serving cell (SCell). The main serving cell is a single serving cell that provides security input and non-access stratum (NAS) mobility information in a Radio Resource Control (RRC) establishment or re-establishment state. Quot; serving cell ". Depending on the capabilities of the terminal, at least one cell may be configured to form a set of serving cells together with a main serving cell, said at least one cell being referred to as a secondary serving cell. The set of serving cells set for one UE may consist of only one main serving cell or may consist of one main serving cell and at least one secondary serving cell. Each serving cell can be operated in an activated or deactivated state.

Figure 2 shows examples of LAA deployment scenarios to which the present invention is applied.

As the wireless communication traffic surges, it is becoming an urgent problem to secure more frequencies in order to improve the throughput. Accordingly, the WiFi system uses not only the licensed band but also the unlicensed frequency band A method of performing communication is discussed. Wireless communication in the license-exempt band may be provided with the support of the licensed band's communication techniques to facilitate the wireless communication in the license-exempt band.

License assisted access (LAA) refers to the operation of CA operations on one or more secondary serving cells operating in the license-exempt band or license-exempt spectrum, based on the assistance of the primary serving cell operating in the licensed band or spectrum. And the like. In other words, the LAA is a technology that bundles the license and license-exempt bands together using the CA as an anchor for the LTE licensed band. In this case, the license band is used as the main serving cell and the license-exempt band can be used as the secondary serving cell. Also, the license-exempt band is activated only through the CA, and may not perform LTE communication by itself. The terminal accesses the network by using the license band and uses the service, and the base station combines the licensed band and the license-exempted band with the CA through the RRC reset process to offload the license band traffic to the license- .

2, various LAA deployment scenarios are shown. In each scenario, the number of licensed carriers and unlicensed carriers may be one or more, respectively. Scenario 1 is a case where a macro cell using a license carrier F1 (frequency 1) and a small cell using a license-exempt carrier F3 are connected to a CA (carrier aggregation). Scenario 2 is a case where small cell # 1 using F2, which is a license carrier, and small cell # 2 using F3, which is a license-exempt carrier, are connected to carrier aggregation in addition to macro cell coverage. Scenario 3 is a case where there is a macro cell and a small cell # 1 using a license carrier F1 and the small cell # 1 is connected to a carrier aggregation through F1 and F2 carriers by additionally using a license-exempt carrier F3. Scenario 4 is a situation where there is a macro cell using F1, a license carrier, and a small cell # 1 using F2, a license carrier, and F3, a license-exempt carrier. In this case, the carrier aggregation can be set using F1, F2 and F3. If dual-connectivity is set up using F1 and F2, you can further configure the carrier aggregation using F2 and F3.

In the case where a CA is configured between a serving cell of a license band and a serving cell of a license-exempted band in the LAA situation, that is, in a case where a time alignment group TAG : Timing Advance Group). The TAG is a group comprising serving cell (s) using a timing reference cell that includes the same time advance value or the same timing reference or the timing reference among the uplink configured serving cells. The TAG is divided into a primary Timing Advance Group (P-TAG) and a secondary Timing Advance Group (S-TAG). P-TAG is a TAG including a main serving cell, and S-TAG is a TAG composed only of secondary serving cells. The main serving cell may only be configured on the license band.

If the uplink component carrier (UL SCC) of the secondary serving cell belongs to the P-TAG in the wireless communication system, the base station transmits the downlink component carrier (DL PCC) of the primary serving cell or the UL SCC and a System Information Block 2 (SIB2) linkage to the UE for the path-loss reference serving cell for the UL SCC. A serving cell (e.g., serving cells belonging to S-TAG) that does not have this setting estimates the path loss based on the DL CC having the corresponding UL CC and SIB2 connection. UL PCC always estimates path loss based on DL PCC. Herein, the SIB2 is information that the UE provides to the cell, and includes uplink cell bandwidth, a random-access parameter, and parameters related to uplink power control.

The reason for introducing such RRC signaling for UL SCC is that, in a heterogeneous network (HetNet) environment, reliable path loss estimation may not be possible on a small-cell DL SCC that may receive strong interference from a macrocell . In this case, the UEs in the small cell can estimate the UL SCC path loss based on the DL PCC using the RRC signaling, thereby making it possible to more reliably estimate the path loss.

Meanwhile, in the current wireless communication system, CA between up to 5 elementary carriers is supported. However, in the 5 GHz band in which LAA is considered, a larger number of elementary carriers (for example, up to 32 elementary carriers) CA can be considered. In the case of a wireless local area network (LAN) system such as WiFi, 80 MHz and 160 MHz bands can be provided. Therefore, a wireless communication system such as LTE also needs to provide concatenation of similar or more frequencies. In addition, since the wireless communication system can additionally provide one or more carriers to the existing band even in the 3.5 GHz band, which is the license band, it is necessary to provide a function to concatenate at least five element carriers in the downlink at least.

However, the overhead on the main serving cell on which the Physical Uplink Control CHannel (PUCCH) is transmitted may become even larger in a situation where a CA is formed between a larger number of carriers as well as the present. Therefore, PUCCH transmission on the secondary serving cell can be considered to solve this problem. This is because, in a situation where not only the overhead problem but also the RRH (Remote Radio Head) as in the scenario 4 is considered, the overhead is concentrated in the main serving cell without depending on the operation of changing the main serving cell, .

However, in the LAA situation, the serving cell set on the license-exempt band can be easily exposed to interference due to the nature of the license-exempt band. This makes reliable path-loss estimation impossible. This causes the uplink transmission power control based on the incorrect path loss value, so that not only the performance of the entire system deteriorates, but also unnecessary interference can be caused. Therefore, there is a need for a method that can reliably estimate the path loss in a situation where a CA is configured between the serving cell of the license band and the serving cell of the license-exempted band.

3 is an exemplary diagram illustrating a case where the existing path loss estimation method is applied to a situation where carrier aggregation between the serving cell of the license band and the serving cell of the license-exempted band is configured.

For example, in FIG. 3, a main serving cell (PCell) and two secondary serving cells (SCell # 1 and SCell # 2) are configured in a licensed band (L- And the serving cells SCell # 3, SCell # 4 and SCell # 5 are configured. In this case, since the license band and the license-exempt band are inter-band, a plurality of TAGs (Multiple TAGs) need to be set for the terminal. Therefore, as shown in FIG. 3, the P-TAG including the serving cells (PCell, SCell # 1 and SCell # 2) on the license band and the S-cell including the serving cells (SCell # 3, SCell # 4 and SCell # -TAG can be set.

In this situation, the DL SCCs (SCC # 3, SCell # 4, and SCC # 5 DL CC) set on the license-exempt zone are set to the DL SCCs (DL CC of SCell # 1 and SCell # 2) It is easily exposed to interference. In addition, the path loss reference serving cell of the UL SCC (SCC # 1 and SCC # 2 UL CC) set on the license band due to interference in a specific environment is connected to the DL SCC (SCell # 1 and SCell # 2 CC) to the main serving cell, it is clear that the DL SCCs (SCC # 3, SCell # 4 and SCC # 5 DL CC) on the license-exempt band are in a poor channel environment. As an example, the serving cells on the license-exempt band may be exposed to interference as shown in FIG. 4 below.

FIGS. 4 and 5 are diagrams illustrating an example of an interference situation when carrier aggregation between the serving cell in the license band and the serving cell in the license-exempted band is configured.

FIG. 4 shows a case where a terminal (hereinafter referred to as a LAA terminal) configured to perform carrier aggregation between a serving cell and a serving cell in a license-exempted band experiences interference from a hidden node. The license-exempt band allows the base station or terminal to acquire channel access opportunities based on contention. There are various ways of accessing a channel based on contention, and a channel access mechanism for a license-exempt band according to the present invention includes the following.

The channel access mechanism according to the present invention provides opportunistic channel access. For this purpose, a wireless communication device such as a base station or an access point (AP) can perform a clear channel assessment (CCA) or an extended clear channel assessment (ECCA) before using the corresponding channel. This is to avoid cases where other LAA base stations (eNBs) and Wireless Local Area Network (WLAN) systems transmit simultaneously on the same channel. Here, the CCA or ECCA is a procedure for determining whether the corresponding channel is occupied or unoccupied, that is, whether the corresponding channel is busy or idle, through energy scanning or detection of the corresponding channel. Such a channel access mechanism may be called Listen Before Talk (LBT) or Carrier Sense (CS).

Under the LBT protocol, the wireless communication device determines whether the channel is available for transmission based on the measured energy in the channel. The LBT can be performed on a frame basis or a load basis. Parameters may be defined for the LBT such as CCA, Extended CCA, channel occupancy time, idle period, and CCA energy detection threshold. A wireless communication device using the license-exempt band may perform (E) CCA at the end of the idle period before starting transmission on the operating channel. That is, the wireless communication apparatus can determine the occupation state of the channel by performing (E) CCA by (E) CCA execution time within the idle period. If the wireless communication device correctly receives a packet intended for the device on the channel occupied by the previous CCA and does not exceed the maximum channel occupation time, the wireless communication device does not perform the CCA again, (E.g., ACK and Block ACK frames).

However, as shown in FIG. 4, when the base station (LAA operator # 1) operating as the LAA and the WLAN AP are physically separated from each other, the two nodes (LAA operator # 1 and WLAN AP) And can perform downlink transmission to the first terminal UE1 and the second terminal UE2 on the license-exempt band, respectively. In this case, it is very likely that the first terminal UE1 will continuously experience strong interference from the WLAN AP. This is also true for non-coordinated users who are not coordinated by the LAA operator to install a WLAN AP or use Bluetooth or the like.

In addition, a wireless communication system (e.g., LTE) transmits / receives control / data information in a fixed format (e.g., a subframe / radio frame) unlike a wireless LAN system. Thus, different network operators can perform LAA deployment that is not synchronized with each other. Therefore, interference may occur between each other due to unadjusted LAA base stations installed by different network operators.

Meanwhile, as shown in FIG. 5, a WLAN system such as WiFi can concatenate bands having a maximum size of 160 MHz to perform data transmission and reception. On the other hand, wireless communication systems such as LTE systems define all physical layer operations based on fixed system bandwidth information. In addition, in the wireless communication system, since the interval of the center carriers on the license-exempted band is 5 MHz, they partially overlap each other due to incorrect NI (Noise Interference) estimation and inaccurate radio resource management (RRM) Resource occupancy may occur between different nodes, causing interference. Therefore, in the present specification, a reliable path loss estimation method is provided as follows even in the various interference situations as described above.

6 is a diagram illustrating a path loss estimation method according to an embodiment of the present invention.

6, a main serving cell (PCell) and two secondary serving cells (SCell # 1 and SCell # 2) are configured in a license band (L-band) There is shown a situation in which the DL CC of the secondary serving cell # 3 on the license-exempted band is subjected to strong interference when three secondary serving cells SCell # 3, SCell # 4 and SCell # 5 are configured. Here, it is assumed that all the secondary serving cells on the license-exempt band are included in the S-TAG.

In this case, in order to more reliably estimate path loss, the path loss reference serving cell for the UL CC of the secondary serving cell # 3 on the license-exempt band is referred to as the secondary serving cell of the secondary cell # 3 on the license- To the DL CC of another secondary serving cell (SCell # 4 or SCell # 5) in the license-exempt band in an interference environment less than the DL CC of cell # 3. In this case, the UE can perform more accurate power control for uplink transmission on the license-exempt band, thereby improving the overall system performance.

For this, the base station may transmit path-loss reference linking information for the secondary serving cell (s) set on the license-exempt band to the terminal through RRC signaling. The path loss reference connection information may be information on a secondary serving cell to be referred to in case of a path loss among the secondary serving cells set on the license-exempt band, and may include an index of a secondary serving cell to be used for estimating path loss. For example, the path loss reference connection information may be transmitted using a pathlossReferenceLinking parameter included in an information element (IE) of an uplink power control dedicated secondary serving cell (UplinkPowerControlDedicatedSCell).

The terminal transmits S-TIB-related sub-serving cells corresponding to the corresponding uplink (SIB2-linkage) or sub-serving cell corresponding to the uplink based on the path loss reference connection information, One of the secondary serving cells corresponding to the index of the secondary serving cell indicated by the RRC signaling among other serving cells in the TAG may be applied as the path loss reference serving cell

On the other hand, if a secondary serving cell (i.e., a PUCCH-capable secondary serving cell) carrying a PUCCH is set in the secondary serving cell belonging to the S-TAG, the secondary serving cell carrying the PUCCH and the DL One of the CCs may be set as a path loss reference serving cell by RRC signaling. That is, if the DL CC of a specific sub-serving cell on the license-exempted band is strongly interfered and the secondary serving cell carrying the PUCCH is set in the secondary serving cell belonging to the S-TAG, the DL CC of the secondary serving cell carrying the PUCCH Can be used to estimate the pathloss of the DL CC in strong interference situations.

For example, the path loss estimation value PL _c estimated by the UE with respect to the serving cell c can be calculated as shown in Equation (1).

Here, the value of 'referenceSignalPower' is the value provided by the upper layer. The upper layer filtering setting is based on a reference serving cell, and the RSRP (reference signal received power) value is a value measured based on a reference serving cell.

Hereinafter, a method for estimating the path loss by the LAA terminal will be described with reference to FIG.

7 is a flowchart illustrating an operation of a terminal according to an embodiment of the present invention.

The terminal may configure at least one secondary serving cell on the license-exempt band based on configuration information (hereinafter referred to as LAA configuration information) about the serving cell of the license-exempt band. For example, the LAA configuration information may be transmitted from the base station to the terminal through the main serving cell of the license band, and may be transmitted through the RRC message. Here, the RRC message may be an RRC connection reconfiguration message.

Upon receiving the RRC message from the base station (S710), the UE transmits a secondary serving cell (set to belong to the S-TAG) set in the license-exempt band based on the information on the path loss reference serving cell included in the RRC message (Step S720). The path loss reference connection information may be information on a secondary serving cell to be referred to in case of path loss among the secondary serving cells set on the license-exempt band, and may include an index of the secondary serving cell. Here, the secondary serving cell to be referred to in the path loss may be a secondary serving cell different from the secondary serving cell used for the uplink transmission among the serving cells of the license-exempt band.

For example, when a specific sub-serving cell on a license-exempted band is subject to intensive interference, the UE may allocate a DL CC to be referred to for uplink transmission through the specific sub-serving cell to the serving sub- The path loss of the specific sub-serving cell can be estimated by DL CC of another sub-serving cell in the S-TAG to which the cell belongs.

However, if a secondary serving cell carrying a PUCCH is set in the secondary serving cell belonging to the S-TAG, the secondary serving cell carrying the PUCCH may be set as a path loss reference serving cell by RRC signaling. In this case, the UE can use the DL CC of the secondary serving cell carrying the PUCCH to estimate the path loss of the particular serving cell in a situation where a particular serving cell is subject to strong interference.

Hereinafter, the process of determining the path loss reference serving cell by the base station for uplink transmission through the serving cell included in the S-TAG in the license-exempt band will be described in more detail.

8 is a flowchart illustrating an operation of a base station according to an embodiment of the present invention.

Referring to FIG. 8, a BS transmits a state report, a SRS (sounding reference signal), a PRACH (preamble), or the like to a preset channel such as CSI (Channel State Information), RSRP (Physical Random Access Channel) or the like. In this case, the base station can estimate (approximate) the channel environment of the corresponding terminal based on the received signal (S810). here, The RSRP value is defined as a value ([W]) obtained by averaging the power distribution of the REs to which the CRS (or DRS) transmitted in the frequency bandwidth considered as the channel measurement is transmitted. The RSRQ value is defined as N x RSRP / (E-UTRA carrier RSSI), and the RSSI value represents an average value of all the received powers in the frequency bandwidth to be measured. The CSI calculates appropriate channel values (RI, PMI, CQI) considering the ratio of the power of the original signal and the power of the interference signal through the downlink / uplink RSs (e.g., CRS, CSI- And then takes into account scheduling.

Thereafter, the base station may determine whether to change the path loss reference serving cell of the corresponding terminal based on the estimated channel environment of the corresponding terminal (S820). For example, the BS may estimate the interference condition of the UE based on the CSI value or determine the channel based on the RSRP / RSRQ value. For example, the base station can evaluate the quality of the original signal through the ratio of the RSRP / RSRQ value to the power of the original signal and other signals including interference and noise.

Alternatively, the CSI or path loss can be measured directly based on the SRS, PRACH signal. For example, the base station can estimate and estimate the channel environment of the UE by calculating the difference between the preset SRS transmission power and the power of the SRS signal received by the base station.

This is because carriers in the license-exempt band for LAA can use channel reciprocity like TDD carrier. If a value of a BLER (Block-Error Rate) of a Physical Uplink Shared Channel (PUSCH) received from a mobile station is used as a reference value (this is a preset value, This value can be adjusted in consideration of the service, which can be adjusted by considering the network environment for the service by the corresponding service provider (network operator). If the service is consistently poorly received, It can be judged that such a problem is caused by the erroneous power control, and the main reason is that the wrong path loss estimation is performed on the terminal side.

Therefore, the BS can change the reference serving cell for the path loss estimation performed by the UE based on the path loss measured based on the SRS and PRACH signals. That is, the BS may determine that the path loss estimation of the UE is unreliable, and change the reference serving cell for path loss estimation to another reference serving cell.

The BS compares the CSI, RSRP, and RSRQ values reported from the MS, the CSI directly measured based on the uplink SRS and the PRACH, the path loss value, and the BLER of the PUSCH, thereby determining whether the current interference condition is severe or the path loss It is possible to determine whether or not the power of the original signal is weak.

On the other hand, if the base station determines that the channel information (CSI, RSRP, RSRQ) reported from the UE and the base station are all or some of the bad values based on the directly estimated values based on the uplink signals (SRS / PRACH) The path loss reference serving cell may be changed if reported. If the change of the path loss reference serving cell is determined, the RRC signaling is triggered to change the path loss reference serving cell of the serving cell of the base station (S830), and the RRC Message to the terminal (S840).

9 is a diagram illustrating a path loss estimation method according to another embodiment of the present invention.

The path loss channel estimation method described with reference to FIGS. 6 to 8 can be usefully used in a situation where the channel environment changes little. However, it is necessary to change the path loss reference serving cell more adaptively and dynamically in a situation where a change in the channel environment is large (fast).

The LAA will consider how to effectively select multiple channels (carriers) on the license-exempt band to be set to S-TAG. That is, this means that a carrier is dynamically selected in a plurality of serving cells set as a base station from the viewpoint of one terminal, and thus selected secondary serving cell can be considered for the path loss estimation for UL CC.

For example, as shown in FIG. 9, the path loss reference serving cell for the UL SCC on the license-exempt band set to S-TAG may be dynamically selected. That is, the path loss estimation for the established UL CC (UL CC of SCell # 3) can be dynamically changed based on the (serving) cell of the license-exempt band selected (obtained) after the LBT execution (e) CCA.

In the wireless communication system, the path loss is estimated also for the deactivated serving cell. If the LAA can change its state to "on" or "busy" state when a specific serving cell occupies a channel after LBT execution at a specific point in the LAA, the state of "off" or "Idle" Quot; on "state. In order to cope with this possibility, the UE must always prepare the uplink transmission by estimating the path loss for the inactive serving cell.

In FIG. 9, it is described in view of the secondary serving cell # 3 (UL SCC # 3) (that is, the path loss estimation for uplink transmission of the secondary serving cell # 3). As shown, when the secondary serving cell # 3 of the license-exempted band is occupied after the LBT execution and becomes the "on" state at time t1, the channel estimation for the UL SCC of the secondary serving cell # 3 < / RTI > of the serving cell # 3 with UL SCC and SIB2 connection. When the secondary serving cell # 3 is not occupied at the time t2 and the secondary serving cell # 4 is occupied, the DL SCC of the secondary serving cell # 4 in the "on" state is prepared to prepare for the uplink transmission through the secondary serving cell # The channel estimation for the UL SCC of the serving cell # 3 can be performed.

Additionally, if the two serving cells SCell # 3 and SCell # 5 are in the "on" state as at the time t3, there can be two choices in the UL SCC # 3 view. And a secondary serving cell # 3 (DL SCC # 3) and a secondary serving cell # 5 having UL SCC # 3 and SIB2 connection. If a plurality of DL CCs are in the "on" state, The DL CC having the UL CC (UL SCC # 3) and the SIB2 connection as the loss reference serving cell (i.e., the serving cell # 3 in FIG. 9) can be selected with the highest priority.

On the other hand, although not shown in FIG. 9, if there is no DL CC with SIB2 connection to the UL CC and a plurality of DL CCs are " on " within the S-TAG in the license- It can have a higher priority. That is, if DL SCC # 4 and DL SCC # 5 are "on" at time t3, DL SCC # 4 can be selected as a path loss reference serving cell for UL SCC # 3.

Alternatively, if the DL CC having the SIB2 connection to the UL CC is not "on" and the plurality of DL CCs are "on" within the S-TAG of the license-exempt band, the serving cell set to RRC signaling has a higher priority Lt; / RTI > Alternatively, information on the priority for all serving cells in the S-TAG may be indicated by RRC signaling.

In other words, if a particular serving cell c belongs to a TAG that does not include a main serving cell and a channel is obtained via (E) CCA on the serving cell c, the UE always refers to the serving cell c as a reference It can be used as a serving cell. Otherwise, if the serving cell c belongs to a TAG that does not include a main serving cell and a channel has not been acquired via (E) CCA on that serving cell c and a channel has been acquired on another serving cell in the same TAG, The serving cell in which the channel is always acquired can be used as the path loss reference serving cell.

If a plurality of serving cells are acquired, the serving cell having the smallest serving cell index can be used as the path loss reference serving cell. This is because, if the channel states of the plurality of serving cells in which the channel is acquired are the same, the element that can be finally distinguished is the serving cell index (secondary serving cell index). Or if the serving cell has a plurality of channels, the selected serving cell may be used as a path loss reference serving cell based on the priority indicated by RRC signaling.

10 is a flowchart illustrating an operation of a terminal according to another embodiment of the present invention.

Referring to FIG. 10, if at least one secondary serving cell is configured on a license-exempt band based on LAA configuration information, the UE sets at least one secondary serving cell on the license-exempt band to S-TAG, The path loss reference serving cell for the UL SCC on the band may be dynamically selected (S1010). The path loss for the serving cell on the license-exempt band can be estimated based on the selected path loss reference serving cell (S1020).

For example, if a channel is acquired in a specific secondary serving cell on the license-exempt band, the UE may preferentially use the serving cell containing the DL CC connected to SIB2 in the particular secondary serving cell as a reference serving cell for path loss estimation . However, if the channel is not acquired on the specific secondary serving cell and the channel is acquired on another secondary serving cell in the same TAG, the terminal may use the other secondary serving cell as the path loss reference serving cell. If the number of the secondary serving cell is plural, the secondary serving cell having the smallest secondary serving cell index is used as the path loss reference serving cell, or the path loss reference serving cell is selected based on the priority indicated by the RRC signaling .

11 is a block diagram illustrating a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 11, a wireless communication system supporting the LAA according to the present invention includes at least one terminal 1100 and at least one base station 1200.

Each terminal 1100 includes an RF unit (radio frequency unit) 1110, a processor 1120, and a memory 1130. The memory 1130 is coupled to the processor 1120 and stores various information for driving the processor 1120. [ The RF unit 1110 is coupled to the processor 1120 to transmit and / or receive wireless signals. For example, the RF unit 1110 may receive an RRC message from the base station 1200 and transmit an uplink signal such as CSI, RSRP, RSRQ, SRS, and PRACH to the base station 1200.

The memory 1130 may store LAA configuration information, information about path loss reference serving cells, etc., in accordance with the present disclosure, and may provide the information to the processor 1120 according to the requirements of the processor 1120.

Processor 1120 implements the functions, processes and / or methods suggested herein. Specifically, the processor 1120 causes the steps according to FIG. 3 and / or FIG. 10 to be performed. For example, the processor 1120 may include a setting unit 1121 and an estimating unit 1122. [

The setting unit 1121 sets up a path loss reference serving cell for a secondary serving cell set in the license-exempt zone based on the information on the path loss reference serving cell included in the RRC message. For example, the setting unit 1121 may set path loss reference connection information included in the information element of the uplink power control dedicated sub-serving cell (Uplink Power Controlled SCS) in the RRC message, The index of the reference serving cell can be confirmed.

The estimation unit 1122 estimates a path loss at the time of uplink transmission through the secondary serving cell set in the license-exempt band using the path loss reference serving cell. For this, the estimating unit 1122 can use Equation (1).

In one embodiment, when the RRC message is received from the base station 1200, the setting unit 1121 sets a path loss reference serving cell included in the RRC message to a serving cell for use in path loss estimation of a secondary serving cell set on a license- Cell. The path loss reference serving cell may be a secondary serving cell to be referred to in case of path loss among the secondary serving cells set on the license-exempt band. The RRC message may include an index of the path loss reference serving cell.

For example, when the specific sub-serving cell on the license-exempted band is subject to strong interference, the setting unit 1121 sets the DL CC to be referred to for uplink transmission through the specific sub- Based on the DL CC of another sub-serving cell in the S-TAG to which the secondary serving cell belongs. However, if a secondary serving cell for carrying a PUCCH is set in the secondary serving cell belonging to the S-TAG, the setting unit 1121 may set the secondary serving cell carrying the PUCCH as a path loss reference serving cell. In this case, the information on the secondary serving cell that is the PUCCH may be transmitted to the UE through the RRC signaling, and the estimation unit 1122 may determine that the secondary serving cell, which carries the PUCCH, Can be used to estimate the path loss of the particular serving cell.

In another embodiment, the setting unit 1121 may dynamically select a path loss reference serving cell for the UL SCC on the license-exempted band set to the S-TAG according to whether the channel is acquired through the (e) CCA of the license- And can be set as a reference serving cell. In this case, the estimation unit 1122 can dynamically perform the path loss estimation for uplink transmission through the license-exempt band based on the secondary serving cell of the license-exempted band set as the path loss reference serving cell. For example, if the particular serving cell belongs to a TAG that does not include a main serving cell and the channel is obtained via (E) CCA on the particular serving cell, It can be used as a reference serving cell for estimation. However, if the particular serving cell belongs to a TAG that does not include a main serving cell and a channel is not acquired via (E) CCA on the particular serving cell and a channel is acquired on another serving cell in the same TAG, The serving cell 1122 may always use the serving cell for which the channel was acquired as a path loss reference serving cell. At this time, if a plurality of serving cells are acquired, the serving cell having the smallest serving cell index may be used as the path loss reference serving cell, or a selected serving cell based on the priority indicated by the RRC signaling may be used as the path loss It can be used as a reference serving cell.

The base station 1200 includes an RF unit (radio frequency unit) 1210, a processor 1220, and a memory 1230. The memory 1230 is coupled to the processor 1220 to store various information for driving the processor 1220. RF section 1210 is coupled to processor 1220 to transmit and / or receive wireless signals. Processor 1220 implements the functions, processes, and / or methods suggested herein. The operation of base station 1200 in the above described embodiments may be implemented by processor 1220. [ The processor 1220 generates the posted RRC message and performs the (E) CCA for the license-exempt band to obtain the channel.

For example, the processor 1220 may include a determination unit 1221 and a generation unit 1222. The determination unit 1221 determines the channel environment of the UE 1100 based on the status report about the established channel such as CSI, RSRP, and RSRQ received from the UE 1100 and transmits the uplink signals such as SRS and PRACH The channel environment of the UE 1100 can be estimated directly. Then, it is possible to determine whether to change the path loss reference serving cell of the corresponding UE based on the estimated channel environment of the corresponding UE.

For example, when the block error rate (BLER) of the PUSCH received from the AT 1100 is continuously received at a value lower than the target value, the determination unit 1221 determines that the terminal has sent an incorrect path loss estimation value It can be judged. In this case, the generator 1222 can generate an RRC message instructing the terminal 1100 to change the reference serving cell for path loss estimation.

On the other hand, the determination unit 1221 compares the directly estimated values based on the channel information (CSI, RSRP, RSRQ) reported from the UE 1100 and the uplink signal (SRS / PRACH) (1100) that does not reach a predetermined reference value (Threshold) The path loss reference serving cell may be changed only for the serving cell for which the value is reported.

The above-described processor may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, and / or a data processing device. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices. The RF unit may include a baseband circuit for processing the radio signal. When the present embodiment is implemented in software, the above-described technique may be implemented by a module (process, function, etc.) that performs the above-described function. The module is stored in memory and can be executed by the processor. The memory may be internal or external to the processor and may be coupled to the processor by any of a variety of well known means.

Claims (10)

A method for estimating a path-loss in a wireless communication system,
The method comprising: receiving a radio resource control (RRC) message from a base station, the mobile station having a carrier aggregation between a serving cell in a licensed band and a serving cell in an unlicensed band; And
Estimating a path loss at the time of uplink transmission through a secondary serving cell set in the license-exempt band based on the information about the path loss reference serving cell included in the RRC message
/ RTI > The method according to claim 1,
The information on the path loss reference serving cell may include,
And an index of a secondary serving cell to be used for estimation of the path loss among the secondary serving cells set in the license-exempt zone. 3. The method of claim 2,
A secondary serving cell to be used for the estimation of the pathloss includes:
Wherein the serving cell is a secondary serving cell different from a secondary serving cell used for the uplink transmission among the serving cells set in the license-exempt band. 3. The method of claim 2,
A secondary serving cell to be used for the estimation of the pathloss includes:
And a PUCCH (Physical Uplink Control Channel). A method for estimating a path-loss in a wireless communication system,
Dynamically selecting one of the sub-serving cells of the license-exempted band based on whether the terminal configured to perform carrier aggregation between a serving cell in a licensed band and a serving cell in an unlicensed band receives a channel; And
Estimating a path loss at the time of uplink transmission through a secondary serving cell set in the license-exempt band based on the selected secondary serving cell
/ RTI > 6. The method of claim 5,
Wherein the selecting comprises:
And a step of preferentially selecting a serving cell including the downlink component carrier if there is a serving cell including a downlink component carrier connected to a secondary serving cell used for the uplink transmission, Loss estimation method. 6. The method of claim 5,
Wherein the selecting comprises:
In the case where there are a plurality of secondary serving cells in which the channel of the license-exempted serving cell is acquired, the secondary serving cell having the smallest serving cell index is selected as a path loss reference serving cell, And selecting a path loss reference serving cell based on the determined priority. A method for estimating a path-loss in a wireless communication system,
Estimating a channel environment of a terminal of the terminal based on a signal received from a terminal configured to perform carrier aggregation between a serving cell in a licensed band and a serving cell in an unlicensed band;
Determining whether to change a path loss reference serving cell of the UE based on the estimated channel environment; And
When a change in the path loss reference serving cell is determined, transmitting a Radio Resource Control (RRC) message instructing the UE to change the path loss reference serving cell
/ RTI > 9. The method of claim 8,
Wherein the estimating step comprises:
A reliability of a path loss value received from the terminal based on at least one of a path loss value received from the terminal, a path loss value measured based on an uplink signal received from the terminal, and an error rate of a block received from the terminal And estimating the path loss based on the estimated path loss. In a wireless communication system, in a terminal configured with carrier aggregation between a serving cell in a licensed band and a serving cell in an unlicensed band,
An RF (Radio Frequency) unit for receiving an RRC (Radio Resource Control) message from a base station; And
Setting up a path loss reference serving cell for a secondary serving cell set in the license-exempt zone based on information on a path loss reference serving cell included in the RRC message, and setting up a path loss reference serving cell for the uplink transmission through the secondary serving cell The path loss estimating processor
.

Images