WO2016122112A1

WO2016122112A1 - Method and device for estimating path loss in wireless communication system supporting laa

Info

Publication number: WO2016122112A1
Application number: PCT/KR2015/013598
Authority: WO
Inventors: 박동현; 권기범
Original assignee: 주식회사 아이티엘
Priority date: 2015-01-30
Filing date: 2015-12-11
Publication date: 2016-08-04
Also published as: KR102299242B1; KR20160094079A

Abstract

Provided are a method and a device for estimating path loss in a wireless communication system supporting an LAA. The method for estimating path loss in a wireless communication system comprises the steps of: receiving a radio resource control (RRC) message from a base station by a terminal, for which a carrier aggregation between a serving cell of a licensed band and a serving cell of an unlicensed band is configured; and estimating path loss at the time of uplink transmission through a sub serving cell configured in the unlicensed band, on the basis of information on a path loss reference serving cell included in the RRC message.

Description

Path loss estimation method and apparatus in wireless communication system supporting LAA

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

Cellular is a concept proposed to overcome the limitations of service area, frequency, and subscriber capacity, and it is possible to reuse frequency spatially by dividing mobile service area into several small cells. . However, in a particular area such as a hotspot inside a cell, there is a great demand for communication, and in a particular area such as a cell edge or a coverage hole, reception sensitivity of radio waves may be reduced.

In order to enable communication at hot spots, cell boundaries, and coverage holes, small cells, such as pico cells and femto cells, are included in a macro cell. A micro cell, a remote radio head (RRH), a relay, a repeater, and the like are installed together. Such a network is called a heterogeneous network (HetNet). In a heterogeneous network environment, a macro cell is a large coverage cell, and a small cell such as a femto cell and a pico cell is a small coverage cell.

As the wireless communication traffic surges, even though such small cells are actively used, securing more frequencies is still an urgent problem. Accordingly, based on carrier aggregation (CA), a method of performing wireless communication using not only a licensed band but also frequencies of an unlicensed band such as a WiFi band has been discussed. Here, CA is a technique for efficiently using a fragmented small band, such as using a logically large band by combining a plurality of physically continuous or non-continuous band in the frequency domain This is to make a difference.

In the case where a CA is configured between the serving cell of the licensed band and the serving cell of the unlicensed band, the serving cell set on the unlicensed band can be easily exposed to interference due to the nature of the unlicensed band, thereby providing reliable path-loss. It is impossible to estimate. This causes uplink transmission power control based on inaccurate path loss values, which not only degrades the performance of the entire system but can also cause unnecessary interference.

Therefore, in a recent wireless communication system, there is an urgent need for how to minimize path loss and reliably estimate CA in a situation where a CA is configured between a serving cell of a licensed band and a serving cell of an unlicensed band.

An object of the present invention is to provide a reliable method and apparatus for estimating path loss in a wireless communication system in which carrier aggregation is configured between a serving cell of a licensed band and a serving cell of an unlicensed band.

Another object of the present invention is to provide a method and apparatus for configuring and transmitting information for estimating a path loss for a serving cell of an unlicensed band in a wireless communication system configured with carrier aggregation.

According to an aspect of the present invention, a method for estimating a path loss in a wireless communication system includes a terminal configured with carrier aggregation between a serving cell of a licensed band and a serving cell of an unlicensed band from an eNB to an RRC Receiving a Radio Resource Control) message and estimating a path loss during uplink transmission through a secondary serving cell configured in the unlicensed band based on information on a path loss reference serving cell included in the RRC message. can do.

According to another aspect of the present invention, in the method for estimating a path loss in a wireless communication system, a terminal configured with carrier aggregation between a serving cell of a licensed band and a serving cell of an unlicensed band is selected from among secondary serving cells of the unlicensed band based on channel acquisition. Dynamically selecting one and estimating a path loss during uplink transmission through the secondary serving cell configured in the unlicensed band based on the selected secondary serving cell.

According to another aspect of the present invention, a path loss estimation method in a wireless communication system is a channel environment of a terminal of a terminal based on a signal received from a terminal configured with carrier aggregation between a serving cell of a licensed band and a serving cell of an unlicensed band. Estimating, determining whether to change the path loss reference serving cell of the terminal based on the estimated channel environment, and if the path loss reference serving cell is changed, determining the path loss reference serving cell to the terminal. The method may include transmitting an RRC message indicating a change of.

According to another aspect of the present invention, in a wireless communication system, a terminal configured with carrier aggregation between a licensed band serving cell and an unlicensed band serving cell is included in an RF (Radio Frequency) unit for receiving an RRC message from a base station and the RRC message. Setting a path loss reference serving cell for a secondary serving cell configured in the unlicensed band based on the information on the received path loss reference serving cell and estimating a path loss during uplink transmission through the secondary serving cell configured in the unlicensed band It may include a processor.

The present invention can reliably estimate path loss even when carrier aggregation is configured between a serving cell of a licensed band and a serving cell of an unlicensed band. In addition, by transmitting and receiving information for estimating a path loss for the unlicensed band between the serving cell of the licensed band and the serving cell of the unlicensed band, it provides an advantage of guaranteeing the overall quality of service through the unlicensed band.

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

2 shows examples of a LAA deployment scenario to which the present invention is applied.

3 is an exemplary diagram illustrating a case where an existing path loss estimation method is applied to a situation in which carrier aggregation between a serving cell of a licensed band and a serving cell of an unlicensed band is configured.

4 and 5 are diagrams illustrating an example of an interference situation when carrier aggregation between a serving cell of a licensed band and a serving cell of an unlicensed band is configured.

6 illustrates a path loss estimation method according to an embodiment of the present invention.

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

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

9 illustrates a path loss estimation method according to another embodiment of the present invention.

10 is a flowchart illustrating the 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 the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the embodiments of the present specification, when it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present specification, the detailed description thereof will be omitted.

In addition, the present specification describes a wireless communication network, the operation performed in the wireless communication network is performed in the process of controlling the network and transmitting data in the system (for example, the base station) that is in charge of the wireless communication network, or the corresponding wireless Work may be done at the terminal coupled to the network.

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 a Long Term Evolution (LTE), an LTE-A (Advanced) system, 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 the multiple access scheme applied to the wireless communication system. Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA (SC-FDMA), OFDM-FDMA, OFDM-TDMA For example, various multiple access schemes such as OFDM-CDMA may be used.

Referring to FIG. 1, the E-UTRAN includes at least one base station (BS) 20 that provides a control plane and a user plane to the terminal. The UE 10 may be fixed or mobile and may have other mobile stations, advanced MSs (AMS), user terminals (UTs), subscriber stations (SSs), wireless devices (Wireless Devices), and the like. It may be called a term.

The base station 20 generally refers to a station communicating with the terminal 10, and includes an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and a femto-eNB. ), A pico base station (pico-eNB), a home base station (Home eNB), relay (relay) may be called other terms. The base station 20 may provide at least one cell to the terminal. The cell may mean a geographic area where the base station 20 provides a communication service or may mean a specific frequency band. The cell may mean a downlink frequency resource and an uplink frequency resource. Alternatively, the cell may mean a combination of a downlink frequency resource and an optional uplink frequency resource. Also, in general, when carrier aggregation (CA) is not considered, uplink and downlink frequency resources always exist in pairs in one cell.

An interface for transmitting user traffic or control traffic may be used between the base stations 20. The source base station (Source BS) 21 refers to a base station in which a radio bearer is currently set up with the terminal 10, and the target base station (Target BS, 22) means that the terminal 10 disconnects the radio bearer from the source base station 21 and renews it. It means a base station to be handed over to establish a radio bearer. The base stations 20 may be connected to each other through an X2 interface. The X2 interface is used to send and receive messages between the base stations 20. In addition, the base station 20 is connected to an evolved packet system (EPS), more specifically, a mobility management entity (MME) / serving gateway (S-GW) 30 through an S1 interface. The S1 interface supports a many-to-many-relation between base station 20 and MME / S-GW 30. The PDN-GW 40 is used to provide packet data services to the MME / S-GW 30.

Hereinafter, downlink means communication from the base station 20 to the terminal 10, and uplink means communication from the terminal 10 to the base station 20. The downlink is also called a forward link, and the uplink is also called a reverse link. In downlink, the transmitter may be part of the base station 20 and the receiver may be part of the terminal 10. In uplink, the transmitter may be part of the terminal 10 and the receiver may be part of the base station 20. In the wireless communication system, a time division duplex (TDD) scheme using different times may be used as an uplink transmission and a downlink transmission scheme, or a frequency division duplex (FDD) scheme using different frequencies may be used. Can be used.

Meanwhile, carrier aggregation (CA) supports a plurality of carriers and is also referred to as spectrum aggregation or bandwidth aggregation. Individual unit carriers bound by carrier aggregation are called component carriers (CC). Each component carrier is defined by a bandwidth and a center frequency. For example, if five component carriers are allocated as granularity in a carrier unit having a 20 MHz bandwidth, a bandwidth of up to 100 MHz may be supported.

Hereinafter, a multiple carrier system includes a system supporting carrier aggregation (CA). A serving cell may be defined as an element frequency band that may 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 primary serving cell is one that provides security input and non-access stratum (NAS) mobility information in a radio resource control (RRC) connection or re-establishment state. It means a serving cell. According to the capabilities of the terminal, at least one cell may be configured to form a set of serving cells together with the main serving cell, wherein the at least one cell is called a secondary serving cell. The set of serving cells configured for one terminal may consist of only one main serving cell or one main serving cell and at least one secondary serving cell. Each serving cell may be operated in an activated or deactivated state.

As wireless communication traffic surges, securing more frequencies is urgently needed to improve throughput. Accordingly, the wireless system utilizes the frequencies of the licensed band as well as the unlicensed band that the WiFi system is using. Methods of conducting communication are under discussion. In order to smoothly support wireless communication in the unlicensed band, wireless communication in the unlicensed band may be provided with the support of the communication technique of the licensed band.

Hereinafter referred to as License Assisted Access (LAA) supports CA operation for one or more secondary serving cells operating in an unlicensed band or unlicensed spectrum based on the assistance of a primary serving cell operating in a licensed band or spectrum. A wireless communication scheme is shown. In other words, LAA is a technology that binds a licensed band and an unlicensed band to one using a CA as an anchor and a licensed band as an anchor. In this case, the licensed band may be used as the primary serving cell and the unlicensed band may be used as the secondary serving cell. In addition, the unlicensed band may be activated only through the CA and may not perform LTE communication alone. The terminal accesses the network through the licensed band to use the service, and the base station combines the licensed band and the unlicensed band into the CA through an RRC resetting process according to circumstances, thereby offloading the traffic of the licensed band to the unlicensed band. You can.

As an example, various LAA deployment scenarios are shown in FIG. 2. 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 licensed carrier F1 (frequency 1) and a small cell using an unlicensed carrier F3 are connected by carrier aggregation (CA). Scenario 2 is a case where the small cell # 1 using the licensed carrier F2 and the small cell # 2 using the unlicensed carrier F3 are connected by carrier aggregation in addition to the macro cell coverage. Scenario 3 is a case where there is a macro cell using a licensed carrier F1 and a small cell # 1, and the small cell # 1 is connected to the carrier aggregation through F1 and F2 carrier by additionally using an unlicensed carrier F3. Scenario 4 is a situation where there is a macro cell using a licensed carrier F1, a small cell # 1 using a licensed carrier F2 and an unlicensed carrier F3. In this case, carrier aggregation may be set using F1, F2, and F3. If dual-connectivity is set using F1 and F2, carrier aggregation may be additionally set using F2 and F3.

As in the above scenarios, when a CA is configured between a serving cell of a licensed band and a serving cell of an unlicensed band, that is, in a LAA situation, each serving cell in the licensed band and the unlicensed band has a time alignment group (TAG) according to the band in which it is located. : Timing Advance Group). The TAG is a group including serving cell (s) using the same time forward value and the same timing reference or the timing reference cell including the timing reference among uplink configured serving cells. The TAG is divided into a primary timing alignment group (P-TAG) and a secondary timing alignment group (S-TAG). The P-TAG is a TAG including a primary serving cell, and the S-TAG is a TAG composed of only secondary serving cells. The primary serving cell may be configured only on the licensed band.

If an uplink component carrier (UL SCC) of a secondary serving cell belongs to a P-TAG in a wireless communication system, the base station uses RRC signaling to downlink component carrier (DL PCC) of the primary serving cell or UL of the secondary serving cell. The UE provides a configuration of a path-loss reference serving cell for the UL SCC among DL SCCs having an SCC and SIB2 (System Information Block 2) linkage. All secondary serving cells (eg, secondary serving cells belonging to the S-TAG) without this configuration estimate path loss based on the DL CC having the corresponding UL CC and SIB2 connection. The UL PCC always estimates the path loss based on the DL PCC. Here, the SIB2 is information provided to allow the terminal to access the cell and includes an 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 some heterogeneous network (HetNet) environments, reliable path loss estimation is not possible on DL SCCs of small cells that may be strongly interfered with from macro cells. . In this case, by using the RRC signaling, terminals in the small cell can estimate the path loss of the UL SCC based on the DL PCC, thereby enabling more reliable path loss estimation.

On the other hand, the wireless communication system currently supports CA between up to five CCs, but in the 5 GHz band where LAA is being considered, a greater number of CCs (eg, up to 32 CCs) may be used. CA may be considered. Currently, a local area network (LAN) system such as WiFi can provide 80 MHz and 160 MHz bands, and thus a wireless communication system such as LTE also needs to provide a similar or higher frequency concatenation. In addition, since the wireless communication system may additionally provide one or more carriers to the existing band even in the licensed 3.5 GHz band, it is necessary to provide a function capable of concatenating five or more component carriers at least in downlink.

However, the overhead on the primary serving cell on which the Physical Uplink Control CHannel (PUCCH) is transmitted may become even larger in the situation of configuring CA between a large number of carriers as well as the present. Accordingly, in order to solve this problem, PUCCH transmission on a secondary serving cell may be considered. This is not only an overhead problem, but in a situation in which a remote radio head (RRH) as in Scenario 4 is considered, the utilization of RRH is distributed depending on the main serving cell without depending on the operation of changing the main serving cell. You can.

However, in a LAA situation, the serving cell set on the unlicensed band may be easily exposed to interference due to the nature of the unlicensed band. This makes it impossible to estimate a reliable path-loss. It causes uplink transmit power control based on incorrect path loss values, which not only degrades the performance of the entire system but can also cause unnecessary interference. Therefore, there is a need for a method for reliably estimating path loss in a situation where a CA is configured between a serving cell of a licensed band and a serving cell of an unlicensed band.

For example, in FIG. 3, a primary serving cell (PCell) and two secondary serving cells (SCell # 1 and SCell # 2) are configured in a licensed band (L-band), and three subbands are provided in an unlicensed band (U-band). The case where the serving cells SCell # 3, SCell # 4 and SCell # 5 are configured is shown. In this case, since the licensed band and the unlicensed band are inter-bands, a plurality of TAGs (Multiple-TAGs) need to be set in the terminal. Therefore, as shown in FIG. 3, the P-TAG including the serving cells on the licensed band (PCell, SCell # 1, and SCell # 2) and the S including the serving cells (SCell # 3, SCell # 4, and SCell # 5) on the unlicensed band. -TAG can be set.

In such a situation, DL SCCs (DL CCs of SCell # 3, SCell # 4 and SCell # 5) set on the unlicensed band are more than DL SCCs (DL CCs of SCell # 1 and SCell # 2) set on the licensed band. Easily exposed to interference In addition, a DL SCC (DL of SCell # 1 and SCell # 2) in which a path loss reference serving cell of an UL SCC (UL CC of SCell # 1 and SCell # 2) set on a licensed band due to interference in a specific environment is connected to SIB2. In the situation of changing from the CC to the main serving cell, it is obvious that the DL SCCs (DL CCs of SCell # 3, SCell # 4 and SCell # 5) on the unlicensed band are in a worse channel environment. For example, secondary serving cells on the unlicensed band may be exposed to interference as shown in FIG. 4.

4 illustrates an example in which a carrier configured between a serving cell and a serving cell of an unlicensed band (hereinafter referred to as a LAA terminal) experiences interference from a hidden node. The unlicensed band allows a base station or a terminal to acquire a channel access opportunity based on competition. There may be various methods of accessing a channel based on contention, and a channel access mechanism for an unlicensed band according to the present invention includes the following.

The channel access mechanism according to the present invention provides opportunistic channel access. To this end, a wireless communication device such as a base station or an access point (AP) may perform a clear channel assessment (CCA) or extended clear channel assessment (ECCA) before using a corresponding channel. This is to avoid the case where other LAA base stations (eNBs) and Wireless Local Area Network (WLAN) systems simultaneously transmit on the same channel. Here, CCA or ECCA is a procedure for determining whether the channel is occupied or unoccupied, that is, whether the channel is busy or idle by performing an energy scan or detection on the channel. Such a channel access mechanism may be referred to as 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 energy measured in the channel. LBT may be performed frame-based or load-based. For LBT, parameters such as CCA, Extended CCA, channel occupancy time, idle period, CCA energy detection threshold may be defined. A wireless communication device using an unlicensed band may perform (E) CCA at the end of an idle period before starting transmission on an operating channel. That is, the wireless communication device can grasp the occupancy state of the channel by performing (E) CCA for the (E) CCA execution time within the idle period. If the wireless communication device correctly receives the packet intended for the device on the channel occupied by the previous CCA, if it has not exceeded the maximum channel occupancy time, the wireless communication device does not perform (E) CCA again. (E.g., ACK and Block ACK frames) may be transmitted.

However, as shown in FIG. 4, when the base station (LAA operator # 1) and the WLAN AP operating as LAAs are physically spaced from each other, the two nodes (LAA operator # 1 and the WLAN AP) perform LBTs at the same time. The same channel may be obtained, and downlink transmission may be performed to the first terminal UE1 and the second terminal UE2 on the unlicensed band, respectively. In this case, it is very likely that the first terminal UE1 continuously experiences strong interference from the WLAN AP. This is also the case when ordinary users who are not coordinated by the LAA operator install WLAN AP or use Bluetooth.

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

Meanwhile, as illustrated in FIG. 5, in a WLAN system such as WiFi, data transmission / reception may be performed by concatenating a band having a maximum size of 160 MHz. On the other hand, wireless communication systems such as LTE systems define all physical layer operations based on fixed system bandwidth information. In addition, since the interval of the center carriers on the unlicensed band in the wireless communication system is 5 MHz, the overlapping is partially overlapped with each other due to inaccurate noise interference (NI) and inaccurate radio resource management (RRM). Resource occupancy may occur between different nodes, causing interference. Accordingly, the present specification provides a reliable path loss estimation method in the following various interference situations as follows.

In FIG. 6, as in the situation of FIG. 3, a main serving cell (PCell) and two secondary serving cells (SCell # 1 and SCell # 2) are configured in a licensed band (L-band) and in an unlicensed band (U-band). In the case where three secondary serving cells (SCell # 3, SCell # 4, and SCell # 5) are configured, a situation in which the DL CC of the secondary serving cell # 3 on the unlicensed band receives strong interference is illustrated. Here, it is assumed that all secondary serving cells on the unlicensed band are included in the S-TAG.

In this case, the UE may perform the secondary serving in the DL CC of the secondary serving cell # 3 on the unlicensed band in which the path loss reference serving cell for the UL CC of the secondary serving cell # 3 on the unlicensed band is connected to SIB2 for a more reliable path loss estimation. It is possible to change to a DL CC of another secondary serving cell (SCell # 4 or SCell # 5) in an unlicensed band in an interference environment less than the DL CC of cell # 3. In this case, the terminal may perform more accurate power control for uplink transmission on the unlicensed band, thereby improving overall system performance.

To this end, the base station may transmit path-loss reference linking information for the secondary serving cell (s) configured on the unlicensed 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 when the path is lost among the secondary serving cells set on the unlicensed band, and may include an index of the secondary serving cell to be used for estimating the path loss. For example, the path loss reference connection information may be delivered by using a pathloss reference linking parameter included in an information element (IE) of an uplink power control dedicated SCell.

Based on the path loss reference connection information, the UE determines S-TAGs belonging to the S-TAG, except for a sub-serving cell corresponding to the uplink (SIB2-linkage) or a sub-serving cell corresponding to the uplink. One of the secondary serving cells corresponding to the index of the secondary serving cell indicated by RRC signaling among other secondary serving cells in the TAG may be applied as a path loss reference serving cell.

Meanwhile, as another example, if a secondary serving cell carrying a PUCCH (that is, a secondary serving cell capable of PUCCH transmission) is configured in a secondary serving cell belonging to an S-TAG, a DL having an SIB2 connection with a secondary serving cell carrying the PUCCH One of the CCs may be configured as a path loss reference serving cell by RRC signaling. That is, when a DL CC of a specific secondary serving cell on an unlicensed band is subjected to strong interference, if a secondary serving cell carrying a PUCCH is configured in a secondary serving cell belonging to an S-TAG, the DL CC of the secondary serving cell carrying the PUCCH is It can be used to estimate the path loss of a DL CC in strong interference situations.

For example, the path loss estimation value PL _c estimated by the terminal with respect to the serving cell c may be calculated by Equation 1 below.

Equation 1

Here, the 'referenceSignalPower' value is a value provided from the upper layer. The upper layer filtering setting is based on the reference serving cell, and the RSRP (Reference Signal Received Power) value is measured based on the reference serving cell.

Hereinafter, a method of estimating a path loss by a LAA terminal will be described with reference to FIG. 7.

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

When the terminal receives the RRC message from the base station (S710), based on the information on the path loss reference serving cell included in the RRC message, the secondary serving cell (configured to belong to the S-TAG) set in the unlicensed band The path loss is estimated at the time of uplink transmission (S720). The path loss reference connection information may be information about a secondary serving cell to be referred to when a path is lost among secondary serving cells set on an unlicensed band, and may include an index of the secondary serving cell. Here, the secondary serving cell to be referred to when the path is lost may be a secondary serving cell different from the secondary serving cell used for the uplink transmission among the serving cells of the unlicensed band.

For example, in a situation where a specific secondary serving cell on an unlicensed band is subjected to strong interference, the UE may perform DL serving based on the path loss reference connection information for a DL CC to be referred for uplink transmission through the specific secondary serving cell. The path loss of the specific secondary serving cell can be estimated by the DL CC of another secondary serving cell in the S-TAG to which the cell belongs.

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

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

Referring to FIG. 8, the base station reports a status report, a sounding reference signal (SRS), and a PRACH from a terminal to a channel already set such as channel state information (CSI), reference signal received power (RSRP), and reference signal received quality (RSRQ). An uplink signal such as a physical random access channel may be received. In this case, the base station may estimate (inferred) the channel environment of the corresponding terminal based on the received signal (S810). here, The RSRP value is defined as a value [W] that averages the power distribution of the REs transmitted by the CRS (or DRS) transmitted within the frequency bandwidth considered in the channel measurement. The RSRQ value is defined as N × RSRP / (E-UTRA carrier RSSI), and the RSSI value represents an average value of all received powers in the measured frequency bandwidth. The CSI considers the ratio of the power of the original signal to the power of the interference signal through downlink / uplink RSs (eg CRS, CSI-RS, SRS, etc.) and corresponding channel values (RI, PMI, CQI) corresponding thereto. This value is taken into account for scheduling.

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

Alternatively, CSI or path loss may be directly measured based on the SRS and PRACH signals. For example, the base station may evaluate and estimate a channel environment of the corresponding terminal by calculating a difference value between a predetermined SRS transmission power and the power of the SRS signal received by the base station.

This is because carriers in the unlicensed band for the LAA may use channel reciprocity like the TDD carrier. If the BLER (Block-Error Rate) value of the PUSCH (Physical Uplink Shared Channel) received from the UE is based on a target value (this is a preset value, it is applied as a parameter applied for base station / terminal implementation). It can be used, which is a value that can be adjusted in consideration of the service, which can be set by the service provider (network operator) in consideration of the network environment for the service). It can be determined that such a problem is caused by wrong power control, and the main cause is that wrong path loss estimation is performed at the terminal side.

Therefore, the base station may change the reference serving cell for estimating the path loss performed by the terminal based on the path loss measured based on the SRS and PRACH signals. That is, the base station determines that the path loss estimation of the terminal is unreliable and can change the reference serving cell for the path loss estimation to another reference serving cell.

The base station compares the CSI, RSRP and RSRQ values reported from the terminal, the CSI measured by the base station directly based on the uplink SRS and PRACH, the path loss value, and the BLER of the PUSCH. These factors can be used to determine if the original signal is weak.

On the other hand, the base station is based on the channel information (CSI, RSRP, RSRQ) reported from the terminal and all or some bad value based on the value directly estimated by the base station uplink signal (SRS / PRACH) from the terminal If reported, the path loss reference serving cell may be changed. When 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 base station corresponding serving cell (S830), and the RRC indicating a change of the path loss reference serving cell for the corresponding serving cell. The message is transmitted to the terminal (S840).

The path loss channel estimation method described with reference to FIGS. 6 to 8 may be usefully used in a situation where the channel environment has little change. However, in situations where the channel environment is changing (fast), there is a need to change the path loss reference serving cell more adaptively and dynamically.

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

As an example, as shown in FIG. 9, the path loss reference serving cell for the UL SCC on the unlicensed band set to S-TAG may be dynamically selected. That is, the path loss estimation for the set UL CC (UL CC of SCell # 3) may be dynamically changed based on the secondary serving cell of the (licensed) licensed band selected through (C) CCA after performing LBT.

In the wireless communication system, the path loss is estimated even for the deactivated serving cell. If a specific serving cell occupies a channel after performing LBT at a specific time through physical layer signaling in the LAA, it may be changed to an "on" or "busy" state, otherwise it is an "off" or "Idle" state. The serving cell of may also be in an "on" state. In order to cope with such a possibility, the terminal always needs to prepare for uplink transmission by estimating a path loss even for a deactivated serving cell.

9 is described in terms of secondary serving cell # 3 (UL SCC # 3) (ie, path loss estimation for uplink transmission of secondary serving cell # 3). As shown, when the sub-licensed cell # 3 of the unlicensed band is occupied after performing the LBT at the time t1 and becomes “on”, the channel estimation for the UL SCC of the sub-serving cell # 3 is performed at the time t1. It may be performed based on the DL SCC of the secondary serving cell # 3 having the UL SCC of 3 and the SIB2 connection. If 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 uplink transmission through the secondary serving cell # 3. Based on the channel estimation for the UL SCC of the secondary serving cell # 3 may be performed.

In addition, when two serving cells SCell # 3 and SCell # 5 are in an “on” state as in time t3, there may be two choices in terms of UL SCC # 3. These are the secondary serving cell # 3 (DL SCC # 3) and the secondary serving cell # 5 having the UL SCC # 3 and the SIB2 connection. If a plurality of DL CCs are turned “on”, a path for one UL CC is performed. As a lost reference serving cell, a DL CC (ie, secondary serving cell # 3 in FIG. 9) having an SIB2 connection with a corresponding UL CC (UL SCC # 3) may be selected with the highest priority.

On the other hand, although not shown in Figure 9, if there is no DL CC having an SIB2 connection to the UL CC, a plurality of DL CCs in the S-TAG of the unlicensed band is a secondary serving cell index is small May have a higher priority. That is, if DL SCC # 4 and DL SCC # 5 are "on" at time t3, DL SCC # 4 may be selected as a path loss reference serving cell for UL SCC # 3.

Or, if a DL CC having an SIB2 connection with respect to a UL CC is not "on" and a plurality of DL CCs are "on" in an S-TAG of an unlicensed band, a serving cell configured for RRC signaling has a higher priority. Can have. Alternatively, information about the priority for all serving cells in the S-TAG may be indicated by RRC signaling.

In other words, if a specific serving cell c belongs to a TAG that does not include the primary serving cell and a channel is obtained through (E) CCA on the serving cell c, the terminal always refers to the serving cell c for path loss estimation. Can be used as a serving cell. Otherwise, if the serving cell c belongs to a TAG that does not include the main serving cell and the channel is not obtained through (E) CCA on the serving cell c and the channel is obtained on another serving cell in the same TAG, the terminal A serving cell obtained with a channel can always be used as a path loss reference serving cell.

If there are a plurality of serving cells from which channels are acquired, a serving cell having the smallest secondary serving cell index may be used as a path loss reference serving cell. This is because the last distinguishable element is the serving cell index (sub-serving cell index) if the channel state of the plurality of serving cells in which the channel is obtained is the same state. Alternatively, if there are a plurality of serving cells from which channels are obtained, the serving cell selected based on the priority indicated by the RRC signaling may be used as the path loss reference serving cell.

Referring to FIG. 10, if at least one secondary serving cell is configured on an unlicensed band based on LAA configuration information, the terminal sets at least one secondary serving cell on the unlicensed band to S-TAG and is set to S-TAG. The path loss reference serving cell for the UL SCC on the band may be dynamically selected (S1010). The path loss of the secondary serving cell in the unlicensed band may 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 an unlicensed band, the UE may preferentially use a serving cell including a DL CC connected to SIB2 to the specific 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 a path loss reference serving cell. If there are a plurality of secondary serving cells from which the channel is obtained, 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 RRC signaling. Can be.

Referring to FIG. 11, a wireless communication system supporting 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 1110, a processor 1120, and a memory 1130. The memory 1130 is connected to the processor 1120 and stores various information for driving the processor 1120. The RF unit 1110 is connected to the processor 1120 to transmit and / or receive a radio signal. 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 a path loss reference serving cell, and the like, and provide the information to the processor 1120 according to a request of the processor 1120.

The processor 1120 implements the functions, processes, and / or methods proposed herein. Specifically, the processor 1120 allows the steps according to FIGS. 3 and / or 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 a path loss reference serving cell for the secondary serving cell configured in the unlicensed band based on the information on the path loss reference serving cell included in the RRC message. For example, the setting unit 1121 may determine a path loss of a secondary serving cell set in the unlicensed band based on path loss reference connection information included in an information element of an uplink power control dedicated SCell in the RRC message. The index of the reference serving cell can be checked.

The estimator 1122 estimates a path loss during uplink transmission through the secondary serving cell set in the unlicensed band using the path loss reference serving cell. For this purpose, the estimator 1122 may use Equation 1 below.

As an embodiment, when the setting unit 1121 receives the RRC message from the base station 1200, the setting unit 1121 uses the path loss reference serving cell included in the RRC message to estimate the path loss of the secondary serving cell configured on the unlicensed band. Set to cell. The path loss reference serving cell may be a secondary serving cell to be referred to when a path is lost among secondary serving cells configured on an unlicensed band. The RRC message may include an index of the path loss reference serving cell.

For example, when a specific secondary serving cell on an unlicensed band is subjected to strong interference, the setting unit 1121 may determine a DL CC to be referred for uplink transmission through the specific secondary serving cell as the path loss reference connection information. Based on the sub serving cell may be set to the DL CC of the other secondary serving cell in the S-TAG. However, if the secondary serving cell carrying the PUCCH is configured 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 for the PUCCH may be transmitted to the terminal through the RRC signaling, the estimator 1122 is a secondary serving cell carrying the PUCCH in a situation that a particular secondary serving cell is subjected to strong interference. DL CC may be used to estimate a path loss of the specific secondary serving cell.

On the other hand, in another embodiment, the setting unit 1121 dynamically selects a path loss reference serving cell for the UL SCC on the unlicensed band set to S-TAG, depending on whether the channel is obtained through (e) CCA of the unlicensed band and thus the path loss. It can be set as a reference serving cell. In this case, the estimator 1122 may dynamically perform path loss estimation for uplink transmission through the unlicensed band based on the secondary serving cell of the unlicensed band set as the path loss reference serving cell. For example, the estimator 1122 always loses the path of the particular serving cell if the particular serving cell belongs to a TAG that does not include the primary serving cell and the channel is obtained through (E) CCA on the specific serving cell. Can be used as a reference serving cell for estimation. However, if the specific serving cell belongs to a TAG that does not include the main serving cell and the channel is not obtained through (E) CCA on the specific serving cell and the channel is obtained on another serving cell in the same TAG, the estimator 1122 may always use a serving cell from which a channel is obtained as a path loss reference serving cell. In this case, if there are a plurality of serving cells in which channels are acquired, the serving cell having the smallest secondary serving cell index is used as the path loss reference serving cell, or the path loss is selected based on the priority indicated by the RRC signaling. Can be used as a reference serving cell.

Meanwhile, the base station 1200 includes a radio frequency unit 1210, a processor 1220, and a memory 1230. The memory 1230 is connected to the processor 1220 and stores various information for driving the processor 1220. The RF unit 1210 is connected to the processor 1220 and transmits and / or receives a radio signal. The processor 1220 implements the functions, processes, and / or methods proposed herein. In the above-described embodiment, the operation of the base station 1200 may be implemented by the processor 1220. The processor 1220 generates an RRC message published herein and performs an (E) CCA for an unlicensed band to obtain a channel.

For example, the processor 1220 may include a determiner 1221 and a generator 1222. The determination unit 1221 determines a channel environment of the terminal 1100 based on a status report on a predetermined channel such as CSI, RSRP, RSRQ, etc. received from the terminal 1100, and determines an uplink signal such as SRS and PRACH. Based on this, the channel environment of the terminal 1100 may be directly estimated. Then, it may be determined whether to change the path loss reference serving cell of the terminal based on the estimated channel environment of the terminal.

For example, when the block error rate BLER of the PUSCH received from the UE 1100 is continuously received at a value lower than a target value, the determination unit 1221 indicates that the UE has sent an incorrect path loss estimation value. You can judge. In this case, the generation unit 1222 may generate an RRC message indicating change of the reference serving cell for the path loss estimation performed by the terminal 1100.

On the other hand, as another example, the determination unit 1221 compares the value directly estimated based on the channel information (CSI, RSRP, RSRQ) reported from the terminal 1100 and the uplink signal (SRS / PRACH) from the terminal 1100. Does not reach a certain threshold from the terminal (1100) The path loss reference serving cell may be changed only for the serving cell whose 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 card, storage medium and / or other storage device. The RF unit may include a baseband circuit for processing a radio signal. When the present embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

Claims

A path-loss estimation method in a wireless communication system,

Receiving a radio resource control (RRC) message from a base station by a terminal configured with carrier aggregation between a serving cell of a licensed band and a serving cell of an unlicensed band; And

Estimating a path loss during uplink transmission through the secondary serving cell configured in the unlicensed band based on the information on the path loss reference serving cell included in the RRC message.

Path loss estimation method comprising a.
The method of claim 1,

Information about the path loss reference serving cell,

And the index of the secondary serving cell to be used for the estimation of the path loss among the secondary serving cells set in the unlicensed band.
The method of claim 2,

The secondary serving cell to be used for the estimation of the path loss,

And a secondary serving cell different from the secondary serving cell used for the uplink transmission among the serving cells configured in the unlicensed band.
The method of claim 2,

The secondary serving cell to be used for the estimation of the path loss,

Path loss estimation method characterized in that the secondary serving cell capable of transmitting the PUCCH (Physical Uplink Control Channel).
A path-loss estimation method in a wireless communication system,

Dynamically selecting one of the secondary serving cells of the unlicensed band based on channel acquisition by a terminal configured with carrier aggregation between a serving cell of a licensed band and a serving cell of an unlicensed band; And

Estimating a path loss during uplink transmission through the secondary serving cell configured in the unlicensed band based on the selected secondary serving cell

Path loss estimation method comprising a.
The method of claim 5,

The selecting step,

If there is a serving cell including a downlink component carrier connected to the secondary serving cell used for the uplink transmission, selecting a serving cell including the downlink component carrier first; Loss Estimation Method.
The method of claim 5,

The selecting step,

When there are a plurality of secondary serving cells in which channels are acquired among the serving cells of the unlicensed band, the secondary serving cell having the smallest secondary serving cell index is selected as a path loss reference serving cell or indicated by RRC (Radio Resource Control) signaling. Selecting a path loss reference serving cell based on the priorities.
A path-loss estimation method in a wireless communication system,

Estimating a channel environment of a terminal of the terminal based on a signal received from a terminal configured with carrier aggregation between a serving cell of a licensed band and a serving cell of an unlicensed band;

Determining whether to change a path loss reference serving cell of the terminal based on the estimated channel environment; And

If a change of the path loss reference serving cell is determined, transmitting a radio resource control (RRC) message indicating a change of the path loss reference serving cell to the terminal;

Path loss estimation method comprising a.
The method of claim 8,

The estimating step,

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 determining the path loss.
A terminal in which carrier aggregation is configured between a serving cell of a licensed band and a serving cell of an unlicensed band in a wireless communication system,

A radio frequency (RF) unit for receiving a radio resource control (RRC) message from a base station; And

When setting a path loss reference serving cell for a secondary serving cell configured in the unlicensed band based on the information on the path loss reference serving cell included in the RRC message, and performing uplink transmission through the secondary serving cell configured in the unlicensed band Processor to estimate path loss

Terminal comprising a.