Improved two-stage trigger procedure

Abstract

To provide an improved integrated circuit involved in scheduling uplink transmission executed by a user equipment.SOLUTION: In a communication system, user equipment receives a second stage uplink resource scheduling message associated with s first stage uplink resource scheduling message received from a wireless base station, indicating uplink radio resources that UE is capable of using for executing uplink transmission via unlicensed cells. The first stage uplink resource scheduling message is determined to be valid on the basis of whether the uplink transmission was triggered by a separate second-stage uplink resource scheduling message within a predetermined period prior to receiving the second-stage uplink resource scheduling message. Thereafter, the UE executes the uplink transmission.SELECTED DRAWING: Figure 10

Description

[Technical Field] 【0001】 This disclosure relates to user equipment on which uplink wireless resources are scheduled and to a method for operating user equipment. [Background technology] 【0002】 [Long-Term Evolution (LTE)] Third-generation mobile communication systems (3G), based on WCDMA® wireless access technology, are being deployed on a large scale worldwide. As the first step in enhancing and developing this technology, High-Speed ​​Downlink Packet Access (HSDPA) and Enhanced Uplink (also known as High-Speed ​​Uplink Packet Access (HSUPA)) have been introduced, providing highly competitive wireless access technologies. 【0003】 To meet the ever-increasing demand from users and to ensure competitiveness in new wireless access technologies, 3GPP® has introduced a new mobile communications system called Long-Term Evolution (LTE). LTE is designed to provide the carriers required for high-speed data and media transmission and high-capacity voice support over the next decade. 【0004】 The specifications for the Work Item (WI) concerning Long-Term Evolution (LTE), referred to as E-UTRA (Evolved UMTS Terrestrial Radio Access (UTRA)) and Evolved UTRAN (UMTS Terrestrial Radio Access Network), will ultimately be published as Release 8 (LTE Rel.8). The LTE system is a packet-based, efficient radio access and radio access network that provides all IP-based functionality with low latency and low cost. LTE specifies scalable multiple transmit bandwidths (e.g., 1.4MHz, 3.0MHz, 5.0MHz, 10.0MHz, 15.0MHz, and 20.0MHz) to achieve flexible system deployment using a given spectrum. The downlink employs radio access based on Orthogonal Frequency Division Multiplexing (OFDM). This is because such wireless access is inherently less susceptible to multipath interference (MPI) due to its low symbol rate, uses cyclic prefixes (CP), and can accommodate various transmission bandwidth configurations. The uplink employs wireless access based on Single-Carrier Frequency Division Multiple Access (SC-FDMA). This is because, given the limited transmit power of user equipment (UE), providing a wide coverage area takes precedence over increasing the peak data rate. LTE Rel.8 / 9 employs numerous key packet wireless access technologies (e.g., Multiple Input Multiple Output (MIMO) channel transmission technology) to achieve a highly efficient control signaling structure. 【0005】 [LTE Architecture] Figure 1 shows the overall architecture of LTE. E-UTRAN consists of eNodeBs, which terminate the E-UTRAN user plane (PDCP / RLC / MAC / PHY) protocols and control plane (RRC: Radio Resource Control) protocols for user equipment (UE). The eNodeB (eNB) hosts the physical (PHY) layer, medium access control (MAC) layer, radio link control (RLC) layer, and packet data control protocol (PDCP) layer (these layers include functions for user plane header compression and encryption). The eNB also provides radio resource control (RRC) functions corresponding to the control plane. The eNB performs many functions, including radio resource management, admission control, scheduling, negotiated uplink quality of service (QoS) implementation, cell information broadcasting, encryption / decryption of user plane data and control plane data, and compression / decompression of downlink / uplink user plane packet headers. Multiple eNodeBs are connected to each other by X2 interfaces. 【0006】 Furthermore, multiple eNodeBs are connected to the Evolved Packet Core (EPC) via the S1 interface, more specifically to the Mobility Management Entity (MME) via S1-MME, and to the Serving Gateway (SGW) via S1-U. The S1 interface supports a many-to-many relationship between the MME / Serving Gateway and the eNodeB. The SGW routes and forwards user data packets, acts as a mobility anchor for the user plane during handovers between eNodeBs, and also acts as an anchor for mobility between LTE and other 3GPP technologies (terminating the S4 interface and relaying traffic between the 2G / 3G system and the PDN GW). For idle user devices, the SGW terminates the downlink data path and triggers paging when downlink data arrives for that user device. The SGW manages and stores the context of user devices (e.g., parameters for IP bearer services or internal network routing information). Furthermore, SGW performs replication of user traffic in the case of lawful interception. 【0007】 The MME is the primary control node of the LTE access network. The MME is responsible for tracking and paging (including retransmission) user devices in idle mode. The MME participates in the bearer activation / deactivation process and also selects the SGW for user devices during initial attachment and during LTE handovers involving Core Network (CN) node relocation. The MME authenticates users (by interacting with the HSS). Non-Access Stratum (NAS) signaling is terminated at the MME. The MME also generates and assigns temporary IDs to user devices. The MME checks the authentication of user devices for accessing the service provider's Public Land Mobile Network (PLMN) and enforces roaming restrictions on user devices. The MME is the network endpoint for encryption / integrity protection of NAS signaling and manages security keys. Legitimate interception of signaling is also supported by the MME. Furthermore, the MME provides control plane functionality for mobility between the LTE access network and the 2G / 3G access network, and terminates the S3 interface from the SGSN at the MME. In addition, the MME terminates the S6a interface to the home HSS for roaming user equipment. 【0008】 [Component Carrier Structure in LTE] The downlink component carrier of the 3GPP LTE system is further divided in the time-frequency domain in a so-called subframe. In 3GPP LTE, each subframe is divided into two downlink slots as shown in FIG. 2. The first downlink slot includes a control channel region (PDCCH region) within the first OFDM symbol. Each subframe consists of a given number of OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE (Release 8)), and each OFDM symbol spreads across the entire bandwidth of the component carrier. Thus, each of the OFDM symbols consists of several modulation symbols transmitted on each subcarrier. In LTE, the transmission signal in each slot is described by an N DL RB ×N RB sc resource grid of this number of subcarriers and N DL symb number of OFDM symbols. N DL RB is the number of resource blocks in the bandwidth. N DL RB depends on the downlink transmission bandwidth set in the cell, and N min,DL RB ≦N DL RB ≦N max,DL RB is satisfied. Here, N min,DL RB = 6 and N max,DL RB = 110 are the minimum downlink bandwidth and the maximum downlink bandwidth supported by the current version of the specification, respectively. N RB sc is the number of subcarriers in one resource block. In the case of the subframe structure with a normal cyclic prefix, N RB sc = 12, N DL symb = 7. 【0009】 For example, assuming a multi-carrier communication system using OFDM as used in 3GPP Long-Term Evolution (LTE), the smallest unit of resources that can be allocated by the scheduler is a single “resource block.” A Physical Resource Block (PRB) is defined as a sequence of OFDM symbols in the time domain (e.g., seven OFDM symbols) and a sequence of subcarriers in the frequency domain (e.g., twelve subcarriers of a component carrier), as illustrated in Figure 2. Thus, in 3GPP LTE (Release 8), a physical resource block consists of resource elements corresponding to one slot in the time domain and 180 kHz in the frequency domain (for further details regarding the downlink resource grid, see, for example, Section 6.2 of Non-Patent Document 1, “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)” (available at http: / / www.3gpp.org and incorporated herein by reference)). 【0010】 A subframe consists of two slots. When a so-called "normal" CP (cyclic prefix) is used, there are 14 OFDM symbols within the subframe; when a so-called "extended" CP is used, there are 12 OFDM symbols within the subframe. For the sake of technical terms, the same continuous subcarrier and equivalent time-frequency resources spanning the entire subframe are referred to as a "resource block pair," or equivalently, an "RB pair" or "PRB pair." The term "component carrier" represents a combination of several resource blocks in the frequency domain. In future releases of LTE, the term "component carrier" will no longer be used; instead, the technical term will be changed to "cell," which represents a combination of downlink resources and, optionally, uplink resources. The linking between the carrier frequencies of the downlink resources and the uplink resources is indicated in the system information transmitted on the downlink resources. 【0011】 Similar assumptions regarding the structure of component carriers will apply to subsequent releases. 【0012】 [Carrier aggregation in LTE-A for wider bandwidth support] The frequency spectrum for IMT-Advanced was determined at the World Radio Communication Conference 2007 (WRC-07). While the overall frequency spectrum for IMT-Advanced has been determined, the actually usable frequency bandwidth will vary by region or country. However, following the determination of the outline of the usable frequency spectrum, standardization of the radio interface has begun in the 3rd Generation Partnership Project (3GPP). 【0013】 The LTE Advanced System can support a bandwidth of 100 MHz, while the LTE System can only support 20 MHz. Today, the lack of radio spectrum is a bottleneck in wireless network development, and as a result, it is difficult to find a sufficiently wide spectrum bandwidth for the LTE Advanced System. Therefore, finding a way to obtain a wider radio spectrum bandwidth is urgent, and in this regard, a possible answer is carrier aggregation. 【0014】 In carrier aggregation, two or more component carriers are aggregated to support a wider transmit bandwidth of up to 100 MHz. In LTE-Advanced systems, several cells in an LTE system are aggregated into a single wider channel. This channel is sufficiently wide to 100 MHz, even if these cells in LTE are in different frequency bands. All component carriers can be configured to be LTE Rel. 8 / 9 compatible, provided that the bandwidth of at least the component carriers does not exceed the supported bandwidth of the LTE Rel. 8 / 9 cells. Not all component carriers aggregated by user equipment necessarily need to be Rel. 8 / 9 compatible. Existing mechanisms (e.g., burring) may be used to avoid Rel. 8 / 9 user equipment camping on component carriers. 【0015】 Depending on its capabilities, a user device can simultaneously receive or transmit one or more component carriers (corresponding to multiple serving cells). LTE-A Rel.10 user devices with receive and / or transmit capabilities for carrier aggregation can simultaneously receive and / or transmit on multiple serving cells. In contrast, LTE Rel.8 / 9 user devices can receive and transmit on only one serving cell if the component carrier structure conforms to the Rel.8 / 9 specifications. 【0016】 Carrier aggregation is supported in both contiguous component carriers and non - contiguous component carriers, and each component carrier is limited to a maximum of 110 resource blocks in the frequency domain (using the numerology of 3GPP LTE (Release 8 / 9)). 【0017】 It is possible to configure a 3GPP LTE - A (Release 10) - compatible user equipment to aggregate a different number of component carriers with different bandwidths, optionally in the uplink and downlink, from the same eNodeB (base station). The number of configurable downlink component carriers is determined by the downlink aggregation capability of the UE. Conversely, the number of configurable uplink component carriers is determined by the uplink aggregation capability of the UE. At present, it is not possible to configure a mobile terminal such that there are more uplink component carriers than downlink component carriers. In a typical TDD deployment, the number of component carriers and the bandwidth of each component carrier are the same for the uplink and the downlink. Component carriers transmitted from the same eNodeB do not need to provide the same coverage. 【0018】 The interval between the center frequencies of continuously aggregated component carriers shall be an integer multiple of 300 kHz. This is to maintain compatibility with the 100 kHz frequency raster of 3GPP LTE (Release 8 / 9) and at the same time maintain the orthogonality of the 15 kHz - spaced sub - carriers. Depending on the aggregation scenario, it is possible to facilitate an interval of n×300 kHz by inserting a small number of unused sub - carriers between consecutive component carriers. 【0019】 The impact of aggregating multiple carriers only reaches the MAC layer. At the MAC layer, one HARQ entity is required for each component carrier to be aggregated in both the uplink and downlink. The transport block per component carrier is at most one (when not using SU-MIMO in the uplink). The transport block and its HARQ retransmission (when it occurs) need to be mapped to the same component carrier. 【0020】 When carrier aggregation is configured, the mobile terminal has only one RRC connection with the network. In the establishment / re-establishment of the RRC connection, similar to LTE Rel.8 / 9, one cell provides security inputs (one ECGI, one PCI, and one ARFCN) and non-access stratum (NAS) mobility information (e.g., TAI). After the establishment / re-establishment of the RRC connection, the component carrier corresponding to that cell is referred to as the downlink primary cell (PCell). In the connected state, one downlink PCell (DL PCell) and one uplink PCell (UL PCell) are always configured per user equipment. In the set of configured component carriers, other cells are called secondary cells (SCells), and the carriers of the SCells are downlink secondary component carriers (DL SCCs) and uplink secondary component carriers (UL SCCs). For one UE, currently, a maximum of five serving cells (including the PCell) can be configured. 【0021】 The RRC can configure and reconfigure component carriers, as well as add and remove them. Activation and deactivation are performed, for example, via the MAC control element. In LTE handovers, the RRC can also add, remove, or reconfigure SCells to be used in the target cell. When adding a new SCell, separate RRC signaling is used to send the SCell's system information required for transmission / reception (similar to handovers in release 8 / 9). When a SCell is added to a UE, each SCell is assigned a serving cell index. The serving cell index of a PCell is always 0. 【0022】 If carrier aggregation is configured for user equipment, there is always at least one active uplink and downlink component carrier. The pair of downlink component carriers is sometimes referred to as the "DL anchor carrier." The same applies to uplinks. When carrier aggregation is configured, user equipment may be scheduled on multiple component carriers simultaneously, but there should always be at most one continuous random access procedure. Cross-carrier scheduling allows a component carrier's PDCCH to schedule resources on another component carrier. For this reason, each DCI (Downlink Control Information) format includes a component carrier identification field called CIF. 【0023】 Links between uplink and downlink component carriers established by RRC signaling can identify uplink component carriers to which grants are applied when cross-carrier scheduling does not exist. Links between downlink component carriers and uplink component carriers do not necessarily have to be one-to-one. In other words, two or more downlink component carriers can link to the same uplink component carrier. Conversely, only one downlink component carrier can link to a single uplink component carrier. 【0024】 [Uplink / Downlink Scheduling] The MAC function in eNodeB refers to scheduling, which allows eNB to distribute available radio resources within a single cell among UEs and among the radio bearers of each UE. In principle, eNodeB allocates downlink and uplink resources to each UE based on downlink data buffered in eNodeB and buffer status reports (BSRs) received from UEs, respectively. In this process, eNodeB selects the size of the MAC PDU considering the QoS requirements of each configured radio bearer. 【0025】 The typical scheduling mode is dynamic scheduling using downlink grant / allocation messages (DCIs) to allocate downlink transmit resources and uplink grant / allocation messages to allocate uplink transmit resources. These are transmitted over the physical downlink control channel (PDCCH) using a Cell Radio Network Temporary Identifier (C-RNTI) to identify the intended UE. In addition to dynamic scheduling, persistent scheduling is also specified, which allows for the quasi-static configuration of radio resources and their allocation to UEs over periods longer than one subframe, without requiring a specific downlink allocation or uplink grant message on the PDCCH for each subframe. When setting or resetting persistent scheduling, RRC signaling specifies the resource allocation interval over which radio resources are periodically allocated. When the PDCCH is used to set or reset persistent scheduling, it is necessary to identify the scheduling messages applicable to persistent scheduling from the scheduling messages used for dynamic scheduling. For this reason, a special scheduling identifier known as semi-persistent scheduling C-RNTI (SPS-C-RNTI) is used, which differs from the C-RNTI used for dynamic scheduling messages and is specific to each UE. 【0026】 L1 / L2 control signaling is transmitted downlink along with data to inform scheduled users of their user assignment status, transport format, and other transmission-related information (e.g., HARQ information, Transmit Power Control (TPC) commands). The L1 / L2 control signaling is multiplexed with downlink data within subframes (assuming user assignments can vary on a subframe basis). User assignments can also be performed on a TTI (Transmission Time Interval) basis, in which case the TTI length can be an integer multiple of the subframe. The TTI length may be constant for all users within the service area, may vary for different users, or may be dynamic per user. Generally, L1 / L2 control signaling only needs to be transmitted once per TTI. Below, without loss of generality, we assume that the TTI is equal to one subframe. 【0027】 L1 / L2 control signaling is transmitted over the Physical Downlink Control Channel (PDCCH). The PDCCH carries messages as Downlink Control Information (DCI). DCI typically includes resource allocation and other control information for a group of mobile terminals or UEs. Generally, multiple PDCCHs can be transmitted within a single subframe. 【0028】 Downlink control information takes the form of several formats, which differ in their overall size and the information contained in each field. The various DCI formats currently specified for LTE are described in detail in Section 5.3.3.1, “Multiplexing and channel coding,” of Non-Patent Document 2 (available at http: / / www.3gpp.org and incorporated herein by reference). For more detailed information on DCI formats and specific information transmitted in DCI, please refer to the aforementioned technical standards or Non-Patent Document 3, incorporated herein by reference. In the future, other formats may be specified. 【0029】 [Layer 1 / Layer 2 control signaling] L1 / L2 control signaling is transmitted downlink along with data to inform scheduled users of their user assignment status, transport format, and other transmission-related information (e.g., HARQ information, Transmit Power Control (TPC) commands). The L1 / L2 control signaling is multiplexed with downlink data within subframes (assuming user assignments can vary on a subframe basis). User assignment can also be performed on a TTI (Transmission Time Interval) basis. In this case, note that the TTI length can be an integer multiple of the subframe. The TTI length may be constant for all users within the service area, may vary for different users, or may be dynamic per user. Generally, L1 / L2 control signaling only needs to be transmitted once per TTI. Below, without loss of generality, we assume that the TTI is equal to one subframe. 【0030】 L1 / L2 control signaling is transmitted over the Physical Downlink Control Channel (PDCCH). The PDCCH carries messages as Downlink Control Information (DCI). DCI typically includes resource allocation and other control information for a group of mobile terminals or UEs. Generally, multiple PDCCHs can be transmitted within a single subframe. 【0031】 In 3GPP LTE, it should be noted that allocations for uplink data transmission, also known as uplink scheduling grants or uplink resource allocations, are transmitted over the PDCCH. Furthermore, 3GPP Release 11 introduced the EPDCCH, which fulfills essentially the same function as the PDCCH; that is, it carries L1 / L2 control signaling, although the detailed transmission method differs from that of the PDCCH. Further details can be found in the current versions of Non-Patent Documents 1 and 4, which are incorporated herein by reference. Consequently, most items outlined in the background art and embodiments apply to the PDCCH and EPDCCH, or other means of carrying L1 / L2 control signaling, unless otherwise noted. 【0032】 Generally, information transmitted via L1 / L2 control signaling for the purpose of allocating uplink or downlink radio resources (especially in LTE(-A) Release 10) can be classified into the following categories: - User Identity: Indicates the user to whom the assignment is to be made. This information is usually included in the checksum by masking the CRC with the user identity. - Resource Allocation Information: This indicates the resources (e.g., resource blocks (RBs)) that a user is allocated. Alternatively, this information is called Resource Block Assignment (RBA). The number of RBs allocated to a user can be dynamic. - Carrier indicator: Used when a control channel transmitted on the first carrier allocates resources related to the second carrier (i.e., resources on the second carrier or resources related to the second carrier) (cross-carrier scheduling). - Modulation and coding scheme: Determine the modulation scheme and coding rate to be adopted. - HARQ information: New Data Indicator (NDI) and / or Redundancy Version (RV), etc., which are particularly useful when retransmitting data packets or parts thereof. - Power control command: Adjusts the transmit power when transmitting data or control information on the assigned uplink. - Reference signal information: Applicable cyclic shift and / or orthogonal cover code (OCC) index used to transmit or receive the assigned reference signal, etc. - Uplink allocation index or downlink allocation index: Used to identify the order of allocations, and is particularly useful in TDD systems. - Hopping information: For example, information indicating whether and how to apply resource hopping to increase frequency diversity. - CSI request: Used to trigger the transmission of Channel State Information on the allocated resource. - Multi-cluster information: This flag is used to indicate and control whether to transmit using a single cluster (a contiguous set of RBs) or a multi-cluster (at least two discontinuous sets of contiguous RBs). Multi-cluster assignment was introduced in 3GPP LTE-(A) Release 10. 【0033】 Please note that the above list is not exhaustive, and depending on the DCI format used, it may not be necessary to include all of the aforementioned information items in each PDCCH transmission. 【0034】 Downlink control information takes the form of several formats, which differ in their overall size and the information contained in the fields described above. Below is a list of some of the DCI formats currently defined for LTE. For more detailed information, see Non-Patent Literature 5, in particular Section 5.3.3.1 “DCI formats”, which is incorporated herein by reference. - Format 0: DCI Format 0 is used for transmitting resource grants in PUSCH and uses single antenna port transmission in uplink transmission mode 1 or 2. - Format 1: DCI Format 1 is used for transmitting resource allocations in single codeword PDSCH transmissions (downlink transmission modes 1, 2, and 7). - Format 1A: DCI Format 1A is used for compact signaling of resource allocation for single codeword PDSCH transmissions and for assigning individual preamble signatures to mobile terminals for contention-free random access (for all transmission modes). - Format 1B: DCI Format 1B is used for compact signaling of resource allocation in PDSCH transmissions using closed-loop precoding for rank 1 transmissions (downlink transmission mode 6). The transmitted information is the same as in Format 1A, but in addition, an indicator of the precoding vector is applied to the PDSCH transmission. - Format 1C: DCI Format 1C is used for very compact transmissions of PDSCH assignments. When Format 1C is used, PDSCH transmissions are limited to the use of QPSK modulation. This is used, for example, for signaling paging messages and broadcast system information messages. - Format 1D: DCI Format 1D is used for compact signaling of resource allocation in PDSCH transmissions using multi-user MIMO. The transmitted information is the same as Format 1B, except that one of the pre-coding vector indicator bits is replaced by a single bit indicating whether a power offset is applied to the data symbol. This feature is necessary to indicate whether the transmit power is shared between two UEs. This may be extended to cases of power sharing between more UEs in future versions of LTE. - Format 2: DCI Format 2 is used to transmit PDSCH resource allocations related to closed-loop MIMO operation (transmit mode 4). - Format 2A: DCI Format 2A is used to transmit resource allocations for PDSCH related to open-loop MIMO operation. The transmitted information is the same as Format 2, except that if the eNodeB has two transmit antenna ports, there is no precoding information, and if there are four antenna ports, two bits are used to indicate the transmit rank (transmit mode 3). - Format 2B: Introduced in Release 9, used for transmitting PDSCH resource allocations related to dual-layer beamforming (transmission mode 8). - Format 2C: This format was introduced in Release 10 and is used to transmit PDSCH resource allocations for closed-loop single-user or multi-user MIMO operation with up to 8 layers (transmission mode 9). - Format 2D: This format was introduced in Release 11 and is used for transmitting up to 8 layers, primarily for COMP (Cooperative Multipoint) (transmission mode 10). - Formats 3 and 3A: DCI formats 3 and 3A are used to transmit PUCCH and PUSCH power control commands with 2 bits or 1 bit of power adjustment, respectively. These DCI formats include individual power control commands for groups of UEs. - Format 4: DCI Format 4 is used for scheduling PUSCH using closed-loop spatial multiplexing transmission in uplink transmission mode 2. - Format 5: DCI Format 5 is used for scheduling PSCCH (Physical Sidelink Control Channel) and includes multiple SCI Format 0 fields used for scheduling PSSCH (Physical Sidelink Shared Control Channel). If the number of information bits of DCI Format 5 mapped to a given search space is smaller than the payload size of Format 0 scheduling the same serving cell, zeros shall be added to Format 5 until the payload size, including the padding bits added to Format 0, becomes equal to the payload size of Format 0. 【0035】 [Unlicensed LTE band - License-Assisted Access (LAA)] In September 2014, 3GPP launched a new research project on LTE operation over unlicensed spectrum. The reason for extending LTE into unlicensed bands is the increasing demand for wireless broadband data, coupled with the constraints of licensed bands. Therefore, cellular operators are increasingly considering unlicensed spectrum as a complementary tool to expand service delivery. One advantage of LTE in unlicensed bands compared to reliance on other radio access technologies (RATs) such as Wi-Fi is that the complementarity of the LTE platform with unlicensed spectrum access allows operators and suppliers to utilize existing or planned investments in LTE / EPC hardware for their wireless core network. 【0036】 However, since coexistence with other radio access technologies (RATs) in the unlicensed spectrum, such as Wi-Fi, is essential, it must be considered that the quality of unlicensed spectrum access and licensed spectrum access cannot be matched. Therefore, at least initially, LTE operation in the unlicensed band should be considered a complement to LTE on the licensed spectrum, rather than a standalone operation in the unlicensed spectrum. Based on this assumption, 3GPP established the term License-Assisted Access (LAA) for LTE operation in the unlicensed band in conjunction with at least one licensed band. However, this does not exclude future independent operation of LTE on the unlicensed spectrum, i.e., without assistance from licensed cells. Enhanced Licensed Assisted Access (eLAA) is an extension of LAA and similarly utilizes the unlicensed spectrum, especially in the uplink. Efficiently using the unlicensed spectrum as a complement to the licensed spectrum has the potential to bring significant value to service providers and the wireless industry as a whole. To fully utilize the benefits of LTE operation in the unlicensed spectrum, it is most important to define a complete UL access scheme in addition to the already defined DL access scheme. 【0037】 The general LAA method currently planned in 3GPP will utilize the already implemented Rel.12 Carrier Aggregation (CA) framework as much as possible, but the aforementioned CA framework configuration will include a so-called primary cell (PCell) carrier and one or more secondary cell (SCell) carriers. CA generally supports both cell self-scheduling (scheduling information and user data are transmitted on the same component carrier) and cross-carrier scheduling between cells (scheduling information for PDCCH / EPDCCH and user data for PDSCH / PUSCH are transmitted on different component carriers). 【0038】 Figure 4 shows a very basic scenario including a licensed PCell, a licensed SCell1, and various unlicensed SCell2, 3, and 4 (exemplified as small cells). The transmit / receive network nodes for the unlicensed SCell2, 3, and 4 can be remote radio heads managed by the eNB, or nodes attached to the network but not managed by the eNB. For simplicity, the connections of these nodes to the eNB or network are not explicitly shown in the figure. 【0039】 Currently, the basic approach assuming 3GPP involves PCell operating in the licensed band while one or more SCells operate in the unlicensed band. One advantage of this method is that PCell can be used for reliable transmission of control messages and user data that require high quality of service (QoS), such as voice or video. However, SCells in the unlicensed spectrum may experience some degree of QoS degradation due to the need for coexistence with other RATs, depending on the scenario. 【0040】 The LAA has agreed to focus on the 5GHz unlicensed band. Therefore, one of the most important issues is coexistence with Wi-Fi (IEEE 802.11) systems operating in these unlicensed bands. To ensure fair coexistence between LTE and other technologies such as Wi-Fi, and to support fairness among different LTE operators in the same unlicensed band, LTE channel access in the unlicensed band must be complied with by specific sets of regulatory rules, which may be determined in part by region and specific frequency band. A comprehensive description of the regulatory requirements for operation in the 5GHz unlicensed band across all regions is provided in Non-Patent Document 6 (incorporated herein by reference) and Non-Patent Document 7. Depending on the region and band, regulatory requirements to be considered when designing LAA procedures include Dynamic Frequency Selection (DFS), Transmit Power Control (TPC), Listen Before Talk (LBT), and discontinuous transmission with limited maximum transmit duration. The goal of 3GPP is to establish a single global framework for LAA, which essentially means that all requirements for various regions and frequency bands in the 5GHz range must be taken into account in the system design. 【0041】 For example, in Europe, specific limits on nominal channel bandwidth are set, as is evident from Section 4.3 of Non-Patent Document 8 (incorporated herein by reference). The nominal channel bandwidth is the widest frequency band, including the guard band allocated to a single channel. The occupied channel bandwidth is the bandwidth containing 99% of the signal power. A device can operate simultaneously on one or more adjacent or non-adjacent channels. 【0042】 The Listen Before Talk (LBT) procedure is defined as a mechanism by which an instrument applies a Clear Channel Assessment (CCA) check before using a channel. CCA determines channel occupancy or clearing by using at least energy sensing to determine the presence or absence of other signals on the channel. Current European and Japanese regulations require the use of LBT in the unlicensed band. Aside from regulatory requirements, LBT-mediated carrier sensing is considered an essential feature for fair and friendly operation in the unlicensed spectrum within a single global solution framework, as it represents one method for the equitable sharing of the unlicensed spectrum. 【0043】 In the unlicensed spectrum, channel availability is not always guaranteed. Furthermore, certain regions, such as Europe and Japan, prohibit continuous transmission in the unlicensed spectrum and impose limits on the maximum duration of transmission bursts. Therefore, discontinuous transmission with limited maximum transmission duration is a necessary function of LAA. DFS is required in certain regions and bands to detect interference from radar systems and avoid co-channel operation with these systems. The intention is further to achieve a more uniform load across the spectrum. DFS operation and corresponding requirements are associated with the master-slave principle. The master is supposed to detect radar interference, but radar detection can be performed by relying on another device associated with the master. 【0044】 In most areas, operation on the 5GHz unlicensed band is limited to lower transmit power levels than operation on the licensed band, resulting in a smaller coverage area. Even if licensed and unlicensed carriers transmit at the same power, it is generally expected that unlicensed carriers in the 5GHz band will support a smaller coverage area than licensed cells in the 2GHz band due to increased signal path loss and shadowing effects. Another requirement specific to certain regions and bands is the use of TPC to mitigate the average level of interference that may occur if other devices are operating on the same unlicensed band. 【0045】 Further information can be found in Non-Patent Document 8, which is incorporated herein by reference. 【0046】 In accordance with European regulations concerning LBTs, a device must perform a Clear Channel Assessment (CCA) before occupying a radio channel for data transmission. Transmission on an unlicensed channel can only begin after detecting, for example, that the channel is free based on energy detection. Specifically, the device must observe the channel for a certain minimum time during the CCA (e.g., 20 μs in Europe (see Section 4.8.3 of Non-Patent Document 8)). A channel is considered occupied if the detected energy level exceeds the CCA's set threshold (e.g., -73 dBm / MHz in Europe (see Section 4.8.3 of Non-Patent Document 8)). Conversely, if the detected power level falls below the CCA's set threshold, the channel is considered free. If the channel is determined to be occupied, no transmission on the channel will occur during the next fixed frame period. Once the channel is classified as free, the device can transmit immediately. This limits the maximum transmission duration and facilitates fair resource sharing with other devices operating on the same bandwidth. 【0047】 Energy detection in CCA is performed across the entire channel bandwidth (for example, 20 MHz in the 5 GHz unlicensed band). This means that the received power levels of all subcarriers of the LTE OFDM symbol within the channel contribute to the energy level evaluated by the device performing the CCA. 【0048】 In addition to the CCA described above, if the equipment is classified as Load-Based Equipment (LBE) in accordance with Section 4.9.2.2 of Non-Patent Document 8, which is incorporated herein by reference, the application of an additional Extended CCA (ECCA) may be required. The ECCA includes another CCA observation time over a duration obtained by multiplying the random coefficient N by the CCA observation time slot. N defines the number of clear idle slots, which is the total idle period that must be observed before the start of transmission. 【0049】 Furthermore, the total time that equipment transmits on a given carrier without reassessing channel availability (i.e., LBT / CCA) is defined as channel occupancy time (see Section 4.8.3.1 of Non-Patent Document 8). The channel occupancy time is in the range of 1 ms to 10 ms. However, as currently stipulated in Europe, the maximum channel occupancy time can be, for example, 4 ms. In addition, there is a minimum idle time during which the UE cannot transmit after transmission in an unlicensed cell, and this minimum idle time is at least 5% of the channel occupancy time. At the end of the idle period, the UE can perform a new CCA, etc. This transmission behavior is schematically shown in Figure 5, which is derived from Non-Patent Document 8 (Figure 2 "Example of timing for Frame Based Equipment"). 【0050】 Figure 6 shows the timing between Wi-Fi transmission and LAA UE transmission on a specific frequency band (unlicensed cell). As can be seen from Figure 5, after a Wi-Fi burst, at least a CCA gap is required before the eNB "reserves" the unlicensed cell, for example by sending a reservation signal to the next subframe boundary. The actual LAA DL burst then begins. This is also true for LTE UE, which reserves a subframe by sending a reservation signal to initiate the actual LAA UL burst after successfully performing the CCA. 【0051】 [Uplink scheduling in unlicensed cells] For eLAA, DCI formats 0A, 0B, 4A, and 4B are provided to support single-subframe and multi-subframe grants, as well as uplink transmission (PUSCH) for each single and multi-antenna port. • DCI Format 0A: Single subframe, single antenna port • DCI Format 0B: Multiple subframes, single antenna port • DCI Format 4A: Single subframe, multiple antenna ports • DCI Format 4B: Multiple subframes, multiple antenna ports Details of these DCI formats can be found in sections 5.3.3.1.1A, 5.3.3.1.1B, 5.3.3.1.8A, and 5.3.3.1.8B of Non-Patent Document 5, which is incorporated herein by reference. 【0052】 Any of these DCI formats (i.e., uplink grants) can be either a single-stage grant or part of a two-stage grant. In current exemplary embodiments in LTE (see Non-Patent Document 5), this is reflected by a one-bit field called "PUSCH Trigger A," which distinguishes whether the received uplink grant is for "non-trigger scheduling" (i.e., a single-stage uplink grant) when the bit value is 0, or for "trigger scheduling" (i.e., a two-stage uplink grant) when the bit value is 1. This is controllable by the eNB, which is the radio network entity responsible for scheduling radio resources to the UE. 【0053】 In the two-stage uplink scheduling procedure, one uplink transmission must be scheduled based on the reception of two distinct messages ("Trigger A" and "Trigger B") by the UE in a specific manner. 【0054】 The trigger A message can be any of the above uplink grants (i.e., DCI formats 0A, 0B, 4A, or 4B). With respect to this two-stage grant, the four DCI formats include the following data fields, as currently defined in Non-Patent Document 5. 【0055】 "PUSCH trigger A (1 bit): As specified in Section 8.0 of [3], a value of 0 indicates non-trigger scheduling, and a value of 1 indicates trigger scheduling." - Timing offset (4 bits): As defined in [3]. - If the trigger scheduling flag is set to 0, - This field indicates the absolute timing offset of the PUSCH transmission. - Otherwise, - The first two bits of this field indicate the relative timing offset of the PUSCH transmission. - The last two bits of this field indicate the time window in which scheduling of PUSCH via trigger scheduling is effective. 【0056】 Furthermore, the DCI format available for trigger A messages includes standard data fields indicating the radio resources scheduled for uplink transmission, such as the "Resource Block Allocation" field, the "Modulation / Encoding Scheme" field, and the "HARQ Process Number" field. In addition, DCI formats 0A, 0B, 4A, and 4B (in particular, DCI CRC) can be scrambled with UE-specific identification information (such as C-RNTI) to ensure that the corresponding uplink grant is addressed to a specific UE. 【0057】 The trigger B message has DCI format 1C as currently specified in section 5.3.3.1.4 of Non-Patent Document 5, which is incorporated herein by reference. DCI format 1C as currently specified in the technical standards used within the scope of unlicensed carrier transmissions, including a two-stage grant procedure, is as follows: 【0058】 "Other than that" - LAA subframe setting (4 bits): As defined in section 13A of [3]. - Uplink transmit duration and offset specification (5 bits): As defined in Section 13A of [3]. This field applies only to UEs for which uplink transmit is configured on the LAA SCell. - PUSCH trigger B (1 bit): Defined in section 8.0 of [3]. This field applies only to UEs configured to uplink transmit on the LAA SCell. - Reservation information bits are added until the size equals that of Format 1C, which is used for very compact scheduling of a single PDSCH codeword. 【0059】 As described above, when used as part of a two-stage grant procedure, the trigger B message (DCI format 1C) is typically not addressed to a specific UE, but rather DCI format 1C, and in particular its CRC, can be scrambled by the use of shared identification information by the eNB (in this case, CC-RNTI (Common Control RNTI) (see Non-Patent Document 9 incorporated herein by reference), which is an RNTI used in situations where common control PDCCH information is provided). 【0060】 The cross-reference "[3]" in the above citation of Non-Patent Document 5 represents Non-Patent Document 4, all of which are incorporated herein by reference, since at least paragraphs 8.0 and 13 relate to two-stage grants. 【0061】 In particular, paragraph 8 of Non-Patent Document 4 specifies in more detail the timing and method of performing uplink transmission (i.e., PUSCH) for LAA SCell. 【0062】 "For a serving cell that is an LAA SCell, the UE is, - In subframe n targeting the UE, in response to the detection of a PDCCH / EPDCCH where the "PUSCH trigger A" field is set to "0" in DCI format 0A / 0B / 4A / 4B, or - In the most recent subframe from subframe nv targeting the UE, detection of PDCCH / EPDCCH with the "PUSCH trigger A" field set to "1" in DCI format 0A / 0B / 4A / 4B, and in subframe n, in response to the detection of PDCCH with the DCI CRC scrambled by CC-RNTI and the "PUSCH trigger B" field set to "1", - PDCCH / EPDCCH and HARQ process ID mod(n HARQ_ID +i,N HARQIn accordance with the subframe n+l+k+i (i=0, 1, ..., N-1), the corresponding PUSCH transmission shall be performed, subject to the channel access procedure described in Section 15.2.1. Here, - For DCI formats 0A / 4A, N=1, and the value of N is determined by the "Number of scheduled subframes" field in the corresponding DCI format 0B / 4B. - The UE is configured to have a maximum value of N set by the high-level layer parameter maxNumberOfSchedSubframes-Format0B for DCI format 0B and maxNumberOfSchedSubframes-Format4B for DCI format 4B. - The value of k is determined by the scheduling delay field in the corresponding DCI0A / 0B / 4A / 4B, according to Table 8.2d if the "PUSCH Trigger A" field is set to "0", and according to Table 8.2e otherwise. - n HARQ_ID The value of is determined by the HARQ process number field in the corresponding DCI format 0A / 0B / 4A / 4B, N HARQ = 16 - If the "PUSCH Trigger A" field is set to "0" in the corresponding DCI format 0A / 0B / 4A / 4B, - l=4, - Otherwise, - The value of l is the UL offset determined by the "UL setting for LAA" field in the corresponding DCI, where the CRC is scrambled by CC-RNTI according to the procedure in Section 13A and the "PUSCH Trigger B" field is set to "1". - The value of v is determined by the effective duration field in the corresponding PDCCH / EPDCCH in DCI format 0A / 0B / 4A / 4B, where the "PUSCH Trigger A" field is set to "1", according to Table 8.2f. - The minimum value of l+k supported by UE is included in UE-EUTRA-Capability. [Table 1] [Table 2] [Table 3] " 【0063】 As described above, the current 3GPP technical standard specifies in more detail how to implement the two-stage grant procedure. However, it should be noted that the above-mentioned standardized two-stage grant procedure is subject to change and improvement, and may change in the future. As a result, the above-mentioned implementation of the two-stage grant procedure in the current 3GPP technical standard is merely an exemplary implementation, and many of the details are not considered important to the present invention. 【0064】 Nevertheless, for the purposes of this invention, we assume that the fundamental concepts behind the two-stage grant procedure remain the same as described above. In particular, we will explain the fundamental concepts with respect to Figure 7, which illustrates the function of a two-stage grant, including the sending and receiving of DCIs containing Trigger A and Trigger B messages. For the following illustrative description, we assume that the illustrated subframes are numbered by acquiring the subframe in which Trigger B (i.e., the second-stage uplink scheduling message) is received as reference subframe n, and that preceding and succeeding subframes are numbered accordingly. Furthermore, we assume that the Trigger A message is received in subframe n-3, defining a time window of length v in which the two-stage grant procedure can be effectively executed. In other words, the time window is considered to define the period in which the Trigger B message is received and, based on the transmission parameters indicated by Trigger A and / or Trigger B messages, the corresponding uplink transmission can actually be triggered. 【0065】 The time window length v can be exemplified in the trigger A message, as shown above by the last two bits of the timing offset field of DCI format 0A, 0B, 4A, 4B in Table 8.2f of Non-Patent Literature 5 and Non-Patent Literature 4. 【0066】 If a trigger B message is received in subframe n, the UE will determine whether the associated trigger A message was received by the UE within a time window of length v (starting immediately before the reception of the trigger B message, i.e., in the range of n-1 to nv). In the illustrated scenario, the trigger A scheduling message is received in subframe n-3 and thus within the time window, triggering an uplink transmission at the UE. Then, with a specific transmission timing offset, the uplink transmission (i.e., PUSCH) is performed at subframe n+ offset. The UE may also perform the uplink transmission using, for example, specified radio resources and modulation / coding schemes, based on the information received in the trigger A and trigger B messages. 【0067】 In this invention, the exact PUSCH timing offset is not important. For example, as currently standardized in Non-Patent Literature 4, the PUSCH timing offset is "l + k + i". Here, parameter l is defined by the trigger B message (see the "Uplink Transmit Duration and Offset Specification" field in DCI format 1C, Table 13A-2 of Non-Patent Literature 5 and Non-Patent Literature 4), and parameter k is defined by the trigger a message (see the first two bits of the "Timing Offset" field in any of DCI formats 0A, 0B, 4A, and 4B, Table 8.2e of Non-Patent Literature 5 and Non-Patent Literature 4). Parameter i is applicable when multiple uplink subframes are scheduled by a two-stage uplink scheduling procedure, in which case it moves from 0 to (number of allowed subframes - 1) (otherwise it remains 0). More details can be derived from paragraph 8 cited above in Non-Patent Literature 4. However, the PUSCH timing offset for executing uplink transmissions according to this two-stage uplink scheduling procedure may be defined differently or predetermined. 【0068】 As mentioned above, 3GPP specifies a two-stage scheduling procedure for uplink transmissions in unlicensed cells. However, this two-stage scheduling procedure can be further improved. [Prior art documents] [Non-patent literature] 【0069】 [Non-Patent Document 1] 3GPP TS 36.211, current version 12.6.0 [Non-Patent Document 2] 3GPP TS 36.212, current version v12.6.0 [Non-Patent Document 3] LTE - The UMTS Long Term Evolution - From Theory to Practice, Edited by Stefanie Sesia, Issam Toufik, Matthew Baker, Chapter 9.3 [Non-Patent Document 4] 3GPP TS 36.213 [Non-Patent Document 5] 3GPP TS 36.212 v14.0.0 [Non-Patent Document 6] R1-144348, “Regulatory Requirements for Unlicensed Spectrum”, Alcatel-Lucent et al., RAN1#78bis, Sep. 2014 [Non-Patent Document 7] 3GPP Technical Report 36.889, current version 13.0.0 [Non-Patent Document 8] the European standard ETSI EN 301 893, current version 1.8.1 [Non-Patent Document 9] 3GPP TS 36.321 v14.0.0 [Overview of the project] [Problems that the invention aims to solve] 【0070】 Non-limiting and exemplary embodiments provide improved methods and user equipment for scheduling uplink transmissions performed by user equipment. 【0071】 The independent claims provide non-limiting and exemplary embodiments. Advantageous embodiments are subject to the dependent claims. [Means for solving the problem] 【0072】 In one general embodiment, a user device on which uplink radio resources are scheduled is described. The cell is configured for communication between the user device and a radio base station responsible for scheduling uplink radio resources on at least one cell. The user device includes a receiver that receives a first-stage uplink resource scheduling message from the radio base station indicating the uplink radio resources available to the user device for performing uplink transmissions through the scheduled cell. The receiver further receives a second-stage uplink resource scheduling message from the radio base station, which is associated with the first-stage uplink resource scheduling message. The user device further includes a processor that determines whether the first-stage uplink resource scheduling message is valid. If the processor receives the second-stage uplink resource scheduling message, it determines that an uplink transmission has been scheduled if the processor has determined that the first-stage uplink resource scheduling message is valid. Thus, the determination of whether the first-stage uplink resource scheduling message is valid is based on a determination of whether an uplink transmission was triggered by another second-stage uplink resource scheduling message within a predetermined period prior to the reception of the second-stage uplink resource scheduling message. This user device further includes a transmitter that performs uplink transmissions via a scheduled cell if the processor determines that the uplink transmission is scheduled. The cell could be, for example, an unlicensed cell in the context of 3GPP LTE Release 14, or another cell that supports two-stage scheduling. 【0073】 In response to the above, in a general alternative embodiment, the technology disclosed herein features a method for operating user equipment on which uplink radio resources are scheduled. An unlicensed cell is configured for communication between the user equipment and a radio base station responsible for scheduling uplink radio resources on at least one unlicensed cell. The method includes the step of receiving a first-stage uplink resource scheduling message from the radio base station indicating uplink radio resources available to the user equipment for performing uplink transmissions over the unlicensed cell. The method further includes the step of receiving a second-stage uplink resource scheduling message from the radio base station associated with the first-stage uplink resource scheduling message. The method further includes the step of determining whether the first-stage uplink resource scheduling message is valid. If the method has received the second-stage uplink resource scheduling message, it further includes the step of determining that an uplink transmission has been scheduled, provided that the first-stage uplink resource scheduling message was determined to be valid. Thus, the determination of whether the first-stage uplink resource scheduling message is valid is based on a determination of whether an uplink transmission was triggered by another second-stage uplink resource scheduling message within a predetermined period prior to the receipt of the second-stage uplink resource scheduling message. This method further includes the step of performing the uplink transmission via an unlicensed cell if it is determined that the uplink transmission is scheduled. 【0074】 Other benefits and advantages of the embodiments of the disclosure will become apparent from this specification and the drawings. These benefits and / or advantages may be provided individually by the various embodiments and features of the disclosure in this specification and the drawings, and not all of them are required to be provided in order to obtain one or more of them. 【0075】 These general and specific embodiments may be implemented using user equipment and methods, as well as combinations of user equipment and methods. 【0076】 The exemplary embodiments will be described in more detail below with reference to the attached drawings. [Brief explanation of the drawing] 【0077】 [Figure 1] This diagram shows a conceptual architecture of a 3GPP LTE system. [Figure 2] This diagram shows an example downlink resource grid of subframe downlink slots as defined in 3GPP LTE (Rel.8 / 9). [Figure 3] This diagram shows an example uplink resource grid of subframe uplink slots as defined in 3GPP LTE. [Figure 4] This diagram illustrates an exemplary LAA scenario involving multiple licensed and unlicensed cells. [Figure 5] This diagram illustrates the transmission behavior of LAA transmission. [Figure 6] This diagram shows the timing between Wi-Fi transmission and LAA UE downlink burst in an unlicensed cell. [Figure 7] This diagram illustrates the two-step uplink scheduling procedure provided for uplink transmission via an unlicensed cell. [Figure 8] This diagram illustrates multiple triggers for uplink transmission in a multi-UE environment. [Figure 9] This figure illustrates the prevention of multiple triggers for uplink transmission in a multi-UE environment, according to a first implementation form of one embodiment. [Figure 10] This is a diagram illustrating a two-stage uplink transmission procedure according to the first implementation form of the embodiment. [Figure 11]This figure illustrates the prevention of multiple triggers for uplink transmission in a multi-UE environment, according to a second implementation of the embodiment. [Figure 12] This is a diagram illustrating a two-stage uplink transmission procedure according to a second implementation of the embodiment. [Modes for carrying out the invention] 【0078】 A mobile station, mobile node, user terminal, or user equipment is a physical entity within a communication network. A single node may have multiple functional entities. A functional entity represents a software or hardware module that implements and / or provides a predetermined set of functions to a node or other functional entities in the network. A node may have one or more interfaces connecting it to communication equipment or media that enable communication. Similarly, a network entity may have logical interfaces connecting its functional entities to communication equipment or media that enable communication with other functional entities or corresponding nodes. 【0079】 In a set of claims and in this application, the term “wireless resource” shall be broadly understood to refer to a physical wireless resource such as a time-frequency wireless resource. 【0080】 In a set of claims and in this application, the terms “unlicensed cell” or “unlicensed carrier” shall be broadly understood as a cell / carrier operating in an unlicensed frequency band of a specific frequency bandwidth. Correspondingly, in a set of claims and in this application, the terms “licensed cell” or “licensed carrier” shall be broadly understood as a cell / carrier operating in a licensed frequency band of a specific frequency bandwidth. For illustrative purposes, these terms shall be understood in the context of 3GPP Release 12 / 13 and the License Assist Access work item. 【0081】 Figure 8 shows the UEs belonging to UE group #1, the UEs belonging to UE group #2, and eNodeB. 【0082】 Assume that trigger A, a first-stage uplink resource scheduling message, is sent from eNodeB to the UE of group #1 in subframe n-2. In this example, the valid time window for trigger A sent to the UE of group #1 is 5 subframes. Therefore, information regarding the valid time window is provided by trigger A itself. 【0083】 It is further assumed that trigger B, a second-stage uplink resource scheduling message, is sent from eNodeB in subframe n. Trigger B is received by both UEs in groups #1 and #2, but eNodeB sends trigger B with the same intent as the second-stage uplink resource scheduling message for trigger A (as a first-stage uplink resource scheduling message) that was sent to the UEs in group #1 in subframe n-2. In this illustrative case, it is assumed that the UEs in group #2 have not received any trigger A within the corresponding valid time window prior to trigger B. Upon receiving trigger B, all UEs capable of receiving trigger B (generally including the UEs in groups #1 and #2) must check whether they have received trigger A within the corresponding valid time window. Therefore, in this example, the UEs in group #1 check whether they received trigger A up to 5 subframes earlier (in this case, between subframes n-5 and n-1). Since trigger A was received in subframe n-2, which is within the valid time window, the UE in group #1 will later trigger an uplink transmission. 【0084】 Since the UE in group #2 did not receive trigger A, trigger B, which was received in subframe n, does not trigger an uplink transmission by the UE in group #2. 【0085】 As is further evident from Figure 8, the UE of group #2 receives trigger A in subframe n+1. In this exemplary case, the valid time window for trigger A sent to the UE of group #2 is 3 subframes. As further shown in this figure, eNodeB sends a second trigger B (in subframe n+3). The second trigger B is also received by both the UEs of group #1 and #2, but eNodeB sends the second trigger B with the same intent as the second-stage uplink resource scheduling message for trigger A (as a first-stage uplink resource scheduling message) sent to the UE of group #2 in subframe n+1. Upon receiving trigger B, the UE of group #2 checks whether trigger A was received up to 3 subframes earlier (in this case, between subframes n and n+2). Since the corresponding trigger A was received in subframe n+1, which is within the valid time window, the UE of group #2 will subsequently trigger an uplink transmission. 【0086】 However, since the second trigger B is also received by the UE of group #1 in subframe n+3, the UE of group #1 will check again whether trigger A was received up to 5 subframes earlier (in this case, between subframes n-2 and n+2). Considering that the UE of group #1 received trigger A in subframe n-2, i.e., within the valid time window of the received trigger A, the UE of group #1 will trigger its second uplink transmission again, but this triggered second uplink transmission is intended to be executed by the UE of group #2 only, and not by the UE of group #1, by eNodeB. According to this exemplary scenario shown in Figure 8, if the second trigger B is received in subframe n+2 (instead of being received in subframe n+3), a triggered second uplink transmission will also occur, which will be executed by the UE of group #1. However, considering the exemplary valid time window of 5 subframes for the UE of group #1, if the second trigger B is received in subframe n+4 or later, no multiple triggers for uplink transmissions will occur. 【0087】 Overall, multiple triggers for such uplink transmissions are undesirable in a multi-UE environment. Firstly, such undesirable uplink transmissions risk interference with other transmissions in the corresponding subframes. Secondly, such multiple triggers can imply UL transmission collisions. If a UE in group #1 is triggered to transmit UL by trigger B in subframe n, trigger A indicates that the corresponding UL transmission will continue across four subframes, and this corresponding UL transmission will occur, exemplifyingly, in subframes n+2 to n+5. Similarly, if the same UE in group #1 is triggered to transmit UL again by trigger B in subframe n+3, the same trigger A indicates that the corresponding UL transmission will continue across four subframes, and this corresponding UL transmission will occur, exemplifyingly, in subframes n+5 to n+8. Therefore, as illustrated, these two triggers result in a collision in subframe n+5, but it is unclear whether the data is transmitted as a result of the first trigger B or the second trigger B. Even if the transmission resources are identical in both cases, the corresponding data will generally contain different transport blocks or packets. Such conflicts should be avoided as they can lead to misunderstandings between the UE and the eNodeB. 【0088】 The inventors have conceived of the following exemplary embodiments to alleviate one or more of the problems described above. 【0089】 The broad specifications provided by the 3GPP standard, and partially described in the background section, enable various specific implementations of the embodiment, and certain important features are added to the various implementations of this embodiment, as described below. This embodiment may be conveniently used in mobile communication systems such as the 3GPP LTE-A (Release 10 / 11 / 12 / 13 and later) communication systems described in the background section, but is not limited to use in these specific exemplary communication networks. 【0090】 It should be understood that the above description is not intended to limit the scope of this disclosure, but merely to provide examples of embodiments for a deeper understanding of this disclosure. Those skilled in the art will recognize that the general principles of this disclosure outlined in the set of claims and the description provided in the summary section of this specification can be applied to different scenarios in ways not explicitly stated below. Some assumptions have been made for illustrative and explanatory purposes, but these should not unduly limit the scope of the embodiments described below. 【0091】 Furthermore, as mentioned above, the following embodiments may be implemented in a 3GPP LTE-A (Rel.12 / 13 or later) environment. Various embodiments primarily allow for improvements to the uplink transmission method. However, other functions (i.e., functions that are not changed by the various embodiments) may be exactly the same as those described in the background art section, or they may be changed without affecting the various embodiments. For example, functions and procedures that define the method of actually performing uplink transmission (e.g., splitting, modulation, coding, beamforming, multiplexing) and scheduling (PDCCH, DCI, cross-carrier scheduling, self-scheduling) or the method of performing normal uplink transmission timing using timing advance procedures (e.g., initial timing advance, timing advance update command). 【0092】 The following describes in detail a general embodiment that solves the above problem, using the following exemplary scenario, which is designed to facilitate the explanation of the principles of this embodiment. However, these principles are also applicable to other scenarios, some of which are explicitly stated below. 【0093】 The UE initiates two-stage uplink resource scheduling. Specifically, resource scheduling is initiated by the unlicensed cell's first-stage uplink resource scheduling message (trigger A), which is received by the UE's receiver. Subsequently, the unlicensed cell's second-stage uplink resource scheduling message (trigger B) is received by the UE's receiver. 【0094】 Subsequently, the UE's processor determines whether the first-stage uplink resource scheduling message (trigger A) is valid during the first-stage uplink resource scheduling message verification. This determination of the validity of the first-stage uplink resource scheduling message (trigger A) is based on whether an uplink transmission was triggered by another second-stage uplink resource scheduling message (trigger B) within a predetermined period prior to the receipt of the second-stage uplink resource scheduling message (trigger B). 【0095】 Subsequently, if a second-stage uplink resource scheduling message (trigger B) is received, and the processor determines that the first-stage uplink resource scheduling message (trigger A) is valid, the processor determines that an uplink transmission has been scheduled. 【0096】 Finally, if the processor determines that an uplink transmission is scheduled, the UE's transmitter will perform the uplink transmission via the unlicensed cell. 【0097】 The main principle of the present invention described above is advantageous because it prevents multiple uplink transmission triggers in a multi-UE environment. Since there is no risk of a second uplink transmission being unintentionally triggered by a specific UE that has already triggered an uplink transmission in the past within the valid time window due to trigger B targeting a different UE, eNodeB can send a new trigger A directly to a different UE immediately after sending trigger B, even within a predetermined period / valid time window. 【0098】 This method significantly improves user / cell throughput. Furthermore, by avoiding multiple uplink transmission triggers, the long verification time indicated by trigger A can be used more efficiently, thereby reducing the overhead of the required trigger A. 【0099】 Furthermore, a false alarm from the second trigger B following a correct first trigger B within the verification time / effective time window will not result in an incorrect PUSCH transmission. This is advantageous as it avoids error cases caused by false alarm trigger B. 【0100】 Figure 9 shows a first implementation of an embodiment in which multiple triggers for uplink transmission in a multi-UE environment are prevented. 【0101】 Figure 9 essentially illustrates the situation described above with respect to Figure 8 regarding the reception of triggers in UEs of groups #1 and #2. As previously mentioned, the UE of group #1 receives trigger B in subframe n+3. To avoid a second trigger for uplink transmission (which may occur in the conventional system described in relation to Figure 8), the UE of group #1 checks whether another trigger B has already triggered an uplink transmission within a predetermined period prior to the reception of trigger B received in subframe n+3. This predetermined period is preferably the valid time window specified in the trigger A message. In this example, the predetermined period is a valid time window of length 5 subframes (as already explained in relation to Figure 8, where trigger A notifies the UE of the number of subframes (v=5) indicating the valid time window). 【0102】 Therefore, the UE of group #1 checks whether another trigger B triggered an uplink transmission within the period of 5 subframes preceding subframe n+3. In particular, the UE of group #1 checks whether another trigger B triggered an uplink transmission between subframes n-2 and n+2. As shown in Figure 8, the uplink transmission has already been triggered by trigger B received in subframe n. Therefore, in order to avoid multiple triggers of uplink transmissions within the valid time window of trigger A, in this example, for any trigger B after the first trigger B received in subframe n, the UE creates a valid time window between subframes n-2 and n+2, and ignores the trigger A received in subframe n-2, which would otherwise allow another uplink transmission to be triggered by trigger B received in subframe n+3. In particular, by ignoring the trigger A received in subframe n-2, a valid time window is never found before the reception of trigger B in subframe n+3, thus avoiding the trigger of an uplink transmission by trigger B received in subframe n+3. Furthermore, when a past uplink transmission triggered within the valid time window of such trigger A is found, the expression "ignore trigger A" means that trigger A, received in subframe n-2, is "not considered" in relation to trigger B, which was received in subframe n+3. 【0103】 As a result, as shown in Figure 9, in subframe n+3, no undesirable second / multiple uplink transmissions are triggered by the UE of group #1. Therefore, in this case, only the UE of group #2 triggers an uplink transmission due to trigger B received in subframe n+3. This solution avoids / prevents multiple triggers in a multi-UE environment. 【0104】 Figure 10 is a diagram of a two-stage uplink transmission procedure relating to the first implementation form of the embodiment already described in relation to Figure 9. 【0105】 In step S101, the UE (either one of the UEs in group #1 or #2) initiates two-stage uplink resource scheduling. Specifically, resource scheduling is initiated by the first-stage uplink resource scheduling message from the unlicensed cell, which the UE receives in step S102. Subsequently, in step S103, the UE receives the second-stage uplink resource scheduling message from the unlicensed cell. 【0106】 The first-stage uplink resource scheduling message verification consists of step S104, in which a determination is made as to whether an uplink transmission has already been triggered by another second-stage uplink resource scheduling message within a period T prior to the reception of the second-stage uplink resource scheduling message. Thus, "period T" corresponds to the "predetermined period prior to the reception of the second-stage uplink resource scheduling message" as reflected in the claims, as well as the "effective time window" shown in Figures 8 and 9. 【0107】 If it is determined that another uplink transmission has already been performed within period T (yes in step S104), the process proceeds to step S102 and waits for the first-stage uplink resource scheduling message in the next cycle. 【0108】 However, if it is determined in step S104 that no other uplink transmissions have been performed within the period T (i.e., "No" in step S104), the process proceeds to step S105, where it is determined that the first-stage uplink resource scheduling message is valid. 【0109】 Because the first-stage uplink resource scheduling message is valid, the process proceeds to step S106, where the uplink transmission is scheduled. Then, in step S107, the uplink transmission is actually executed. 【0110】 Figure 11 shows a second implementation of an embodiment in which multiple triggers for uplink transmissions in a multi-UE environment are prevented. The second implementation is an alternative to the first implementation, but instead of simply ignoring trigger A as described in the first embodiment, it disables trigger A, thereby avoiding multiple triggers for uplink transmissions by the same UE within the effective time window of trigger A. 【0111】 Referring to the scenario in Figure 9, the second trigger B is received by the UE of group #1 in subframe n+3. As an alternative to the first implementation of this embodiment, in the second implementation of this embodiment shown in Figure 11, in response to the receipt of trigger B in subframe n, the UE of group #1 can actively disable trigger A (received in subframe n-2) (disabling can also be done in subframe n+1 or n+2, but must be done before the interpretation / analysis / consideration of the second trigger B in subframe n+3). Therefore, the second trigger B received in subframe n+3 cannot trigger an uplink transmission by the UE of group #1 because there is no longer an effective time window for trigger A. In other words, in the second implementation of the embodiment, trigger A is actively deactivated / disabled in response to the receipt of the first trigger B that has already triggered an uplink transmission (or at least prior to the receipt of the next trigger B). In this way, by actively disabling / deactivating trigger A, the effective time window for trigger A is removed, preventing multiple unintended uplink transmissions from being triggered by the UE in group #1. 【0112】 In general, the second implementation of the embodiment (related to Figure 11) differs from the first implementation (related to Figures 9 and 10) in that, instead of simply ignoring trigger A in response to the reception of the second trigger B (ignoring the effective time window of trigger A) as shown in Figure 9, trigger A is disabled in response to the uplink transmission triggered by trigger B (removing the effective time window of trigger A). 【0113】 Actively "disabling / deactivating Trigger A" may be achieved, for example, by toggling a specific bit in a field associated with disabling / deactivating the first-stage uplink transmission resource scheduling message (Trigger A). 【0114】 Figure 12 is a diagram of a two-stage uplink transmission procedure relating to a second implementation of the embodiment already described in relation to Figure 11. 【0115】 In step S101, the UE (either one of the UEs in group #1 or #2) initiates two-stage uplink resource scheduling. Specifically, resource scheduling is initiated by the first-stage uplink resource scheduling message from the unlicensed cell, which is received by the UE in step S102. Subsequently, in step S103, the UE receives the second-stage uplink resource scheduling message from the unlicensed cell. 【0116】 The first-stage uplink resource scheduling message verification consists of step S108, where a determination is made as to whether the first-stage uplink resource scheduling message has been invalidated. If it is determined that the first-stage uplink resource scheduling message has been invalidated (yes in step S108), the process proceeds to step S102 to wait for the first-stage uplink resource scheduling message in the next cycle, or proceeds to step S103 to wait for the second-stage uplink resource scheduling message. 【0117】 If, in step S108, it is determined that the first-stage uplink resource scheduling message is not invalid (the answer in step S108 is "no"), the process proceeds to step S105, which determines that the first-stage uplink resource scheduling message is valid. Subsequently, because the first-stage uplink resource scheduling message is valid, the process proceeds to step S106, which determines that an uplink transmission is scheduled. Subsequently, in step S107, the uplink transmission is actually performed. Subsequently, the process proceeds to step S109, which determines that the first-stage uplink resource scheduling message is invalid. Subsequently, the process proceeds to step S102, which waits for the first-stage uplink resource scheduling message in the next cycle, or to step S103, which waits for the second-stage uplink resource scheduling message. 【0118】 For example, if a second-stage uplink resource scheduling message is received after the first-stage uplink resource scheduling message has been invalidated (step S109), the process proceeds from step S103 to step S108. In step S108, since the first-stage uplink resource scheduling message is determined to be invalid, the process proceeds again to step S102 or step S103 without performing an uplink transmission. 【0119】 The procedure described above reflects the specific behavior shown in Figure 11, where, since trigger A is deactivated when the first trigger B triggers an uplink transmission, another uplink transmission will not be initiated by the second trigger B in subframe n+3. 【0120】 In the above description of the embodiment, two-stage uplink wireless resource scheduling was described with respect to the cell of the communication system. Such two-stage uplink wireless resource scheduling is possible not only for unlicensed or licensed cells, but also for any cell that supports two-stage uplink wireless resource scheduling. 【0121】 According to another embodiment implemented in the environment of Section 8.0 of Non-Patent Document 4, it is proposed that the standard specify the following: 【0122】 For a serving cell that is an LAA SCell, the UE is: • In subframe n targeting the UE, in response to the detection of a PDCCH / EPDCCH where the "PUSCH trigger A" field is set to "0" in DCI format 0A / 0B / 4A / 4B, or In subframes n-v+1 and n-1, for UEs not triggered by the "PUSCH Trigger B" field set to "1", the detection of PDCCH / EPDCCHs with the "PUSCH Trigger A" field set to "1" in DCI format 0A / 0B / 4A / 4B is performed in the most recent subframe from subframe nv, and in subframe n, the detection of PDCCHs with the DCI CRC scrambled by CC-RNTI and the "PUSCH Trigger B" field set to "1" is performed accordingly. In accordance with PDCCH / EPDCCH and [...], a corresponding PUSCH transmission shall be performed in subframe n+l+k+i (i=0, 1, ..., N-1), subject to the channel access procedure described in Section 15.2.1. 【0123】 [Hardware and software implementations of this disclosure] Other exemplary embodiments relate to implementations of the various embodiments described above using hardware, software, or software in conjunction with hardware. In this regard, user terminals (mobile terminals) and eNodeBs (base stations) are provided. The user terminals and base stations are configured to perform the methods described herein, with corresponding entities such as receivers, transmitters, and processors participating in these methods as appropriate. 【0124】 It is also recognized that various embodiments can be implemented or executed using computer devices (processors). These computer devices or processors may include, for example, general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices. Furthermore, various embodiments may be implemented or embodied by combinations of these devices. In particular, each functional block used in the description of the embodiments above can be realized by an LSI as an integrated circuit. These may be formed individually as chips, or a single chip may be formed to include some or all of the functional blocks. These may have data input / output connections. Here, LSIs may also be referred to as ICs, system LSIs, ultra-LSIs, or ultra-ultra-LSIs, depending on their level of integration. However, the technology for implementing integrated circuits is not limited to LSIs and may be implemented using discrete circuits or general-purpose processors. Furthermore, a programmable FPGA (field-programmable gate array) or a reconfigurable processor capable of reconfiguring the connections and settings of circuit cells disposed inside the LSI may be used after the LSI is manufactured. 【0125】 Furthermore, various embodiments may be implemented by software modules that are executed by a processor or directly in hardware. Combinations of software modules and hardware implementations are also possible. Software modules may be stored in any type of computer-readable storage medium, such as RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROMs, DVDs, etc. It should be further noted that individual features of various embodiments, individually or in any combination, may be the subject of other embodiments. 【0126】 As will be obvious to those skilled in the art, many modifications and / or improvements of this disclosure are possible, as shown in certain embodiments. Therefore, these embodiments should be considered in all respects to be illustrative and not limiting in any way.

Claims

[Claim 1] An integrated circuit for controlling a wireless base station, wherein the integrated circuit is A transmitter that transmits a first-stage uplink resource scheduling message to a user device indicating the uplink radio resources available to the user device for performing uplink transmission via an unlicensed cell, comprising a transmitting circuit that transmits a second-stage uplink resource scheduling message associated with the first-stage uplink resource scheduling message to the user device, If no uplink transmission has been triggered by another second-stage uplink resource scheduling message within a predetermined period prior to the transmission of the second-stage uplink resource scheduling message, the first-stage uplink resource scheduling message is deemed valid. If the first-stage uplink resource scheduling message is valid, a receiving circuit that performs uplink reception via the unlicensed cell, An integrated circuit equipped with [a specific feature / feature]. [Claim 2] If an uplink transmission is triggered by another second-stage uplink resource scheduling message within the predetermined period prior to the transmission of the second-stage uplink resource scheduling message, the first-stage uplink resource scheduling message is invalidated. If the first-stage uplink resource scheduling message is not disabled, the first-stage uplink resource scheduling message is considered to be enabled. The integrated circuit according to claim 1. [Claim 3] The first-stage uplink resource scheduling message is addressed to the user device, and the second-stage uplink resource scheduling message is commonly addressed to multiple user devices that receive the second-stage uplink resource scheduling message. Optionally, the first-stage uplink resource scheduling message is addressed to the user device using user device-specific identification information adopted in the transmission of the first-stage uplink resource scheduling message, and the user device-specific identification information is configurable. Optionally, the second-stage uplink resource scheduling message is addressed in common to multiple user devices receiving the second-stage uplink resource scheduling message by the shared identification information used in the transmission of the second-stage uplink resource scheduling message, and the shared identification information is predetermined and common to multiple user devices. The integrated circuit according to claim 1. [Claim 4] The first-stage uplink resource scheduling message specifies a predetermined period that can be considered together with the second-stage uplink resource scheduling message that has been transmitted. Optionally, if the second-stage uplink resource scheduling message is sent within the specified predetermined period after the first-stage uplink resource scheduling message is sent, the first-stage uplink resource scheduling message is considered together with the second-stage uplink resource scheduling message. The integrated circuit according to claim 1. [Claim 5] The first-stage uplink resource scheduling message further specifies a first time offset to be considered when performing the uplink transmission, and the second-stage uplink resource scheduling message specifies a second time offset to be considered when performing the uplink transmission. Optionally, the receiving circuit performs the uplink reception at least after the sum of the first and second time offsets in response to the transmission of the second-stage uplink resource scheduling message. The integrated circuit according to claim 1. [Claim 6] The first-stage uplink resource scheduling message is a DCI message in format 0A, 0B, 4A, or 4B, each including a first-stage flag indicating that the downlink control information (DCI) message is the first uplink resource scheduling message of the two-stage uplink resource scheduling. Optionally, the second-stage uplink resource scheduling message is a DCI message in format 1C that includes a second-stage flag indicating that the downlink control information (DCI) message is the second uplink resource scheduling message of the two-stage uplink resource scheduling. The integrated circuit according to claim 1.

Images