Improved two-stage trigger procedure

Abstract

To provide a user device to which a cell uplink radio resource via an unlicensed cell is scheduled and a motion method of the user device.SOLUTION: The present invention provides a two-step uplink (UL) transmission order, and a user device receives a second step UL resource scheduling message related to a first step UL resource scheduling message from a radio base station, determines that UL transmission is scheduled in the case where the first step UL resource scheduling message is in active in accordance with the reception, and determines that the first step UL resource scheduling message is in active in the case where another uplink transmission is not triggered on the basis of the determination that the uplink transmission is triggered by another second step UL resource scheduling message within a prior predetermined period of reception of the second step UL resource scheduling message.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present disclosure relates to user equipment and methods of operation of the user equipment in which uplink radio resources are scheduled. [Background technology]

[0002] [Long Term Evolution (LTE)] Third generation mobile communication systems (3G) based on WCDMA radio access technology are being deployed on a wide scale around the world. As a first step in enhancing or evolving this technology, High-Speed ​​Downlink Packet Access (HSDPA) and enhanced uplink (also called High-Speed ​​Uplink Packet Access (HSUPA)) have been introduced, providing a highly competitive radio access technology.

[0003] To meet the ever-increasing demands of users and to ensure competitiveness against new radio access technologies, 3GPP has introduced a new mobile communications system called Long Term Evolution (LTE), which is designed to accommodate carriers' demands for high-speed transmission of data and media, as well as high-capacity voice support, for the next decade.

[0004] The specifications of the Work Item (WI) on Long Term Evolution (LTE), called Evolved UMTS Terrestrial Radio Access (UTRA) (E-UTRA) and Evolved UMTS Terrestrial Radio Access Network (UTRAN), are finally published as Release 8 (LTE Rel. 8). The LTE system is a packet-based efficient radio access and radio access network that provides full IP-based functionality with low latency and low cost. LTE specifies multiple scalable transmission bandwidths (e.g., 1.4 MHz, 3.0 MHz, 5.0 MHz, 10.0 MHz, 15.0 MHz, and 20.0 MHz) to achieve flexible system deployment with a given spectrum. Orthogonal Frequency Division Multiplexing (OFDM)-based radio access is adopted for the downlink. The radio access is suitable for LTE Rel. 8 / 9 because it is inherently less susceptible to multipath interference (MPI) due to its low symbol rate, uses cyclic prefix (CP), and can accommodate various transmission bandwidth configurations. In the uplink, the radio access is based on Single-Carrier Frequency Division Multiple Access (SC-FDMA), because providing a wide coverage area is prioritized over improving the peak data rate, given the limited transmission power of the User Equipment (UE). In LTE Rel. 8 / 9, a number of key packet radio access technologies (e.g., Multiple Input Multiple Output (MIMO) channel transmission technology) are adopted to achieve a highly efficient control signaling structure.

[0005] [LTE Architecture] Figure 1 shows the overall architecture of LTE. E-UTRAN consists of eNodeB, which terminates E-UTRA user plane (PDCP / RLC / MAC / PHY) and control plane (RRC) protocols for User Equipment (UE). The eNodeB (eNB) hosts the physical (PHY), medium access control (MAC), radio link control (RLC) and packet data control protocol (PDCP) layers, which include user plane header compression and encryption functions. The eNB also provides radio resource control (RRC) functions for the control plane. The eNB performs many functions, such as radio resource management, admission control, scheduling, negotiated uplink quality of service (QoS), broadcasting cell information, encryption / decryption of user and control plane data, and compression / decompression of downlink / uplink user plane packet headers. Multiple eNodeBs are connected to each other by the X2 interface.

[0006] The eNodeBs are also connected to the EPC (Evolved Packet Core) by the S1 interface, more specifically to the MME (Mobility Management Entity) by the S1-MME and to the Serving Gateway (SGW) by the S1-U. The S1 interface supports a many-to-many relationship between the MME / Serving Gateway and the eNodeBs. The SGW routes and forwards user data packets while acting as a mobility anchor for the user plane during handovers between eNodeBs and as an anchor for mobility between LTE and other 3GPP technologies (terminating the S4 interface and relaying traffic between 2G / 3G systems and the PDN GW). For idle user equipment, the SGW terminates the downlink data path and triggers paging when downlink data arrives for that user equipment. The SGW manages and stores the user equipment context (e.g., IP bearer service parameters or network internal routing information). Furthermore, the SGW performs duplication of user traffic in case of lawful interception.

[0007] The MME is the main control node of the LTE access network. It is responsible for tracking of idle mode user equipment and paging procedures (including retransmissions). It is involved in the bearer activation / deactivation process and is also responsible for selecting the SGW for the user equipment at initial attach and during intra-LTE handover involving Core Network (CN) node relocation. The MME is responsible for authenticating the user (by interacting with the HSS). Non-Access Stratum (NAS) signaling is terminated in the MME. The MME is also responsible for generating and assigning temporary identities to user equipment. The MME checks the authorization of the user equipment to enter the service provider's Public Land Mobile Network (PLMN) and enforces roaming restrictions for the user equipment. The MME is the termination point in the network for ciphering / integrity protection of the NAS signaling and is responsible for security key management. Lawful interception of signaling is also supported by the MME. The MME also provides the control plane function for mobility between LTE and 2G / 3G access networks, terminating the S3 interface from the SGSN at the MME, and the S6a interface towards the home HSS for roaming user equipment.

[0008] [Component carrier structure in LTE] The downlink component carrier of a 3GPP LTE system is further divided in the time-frequency domain in so-called subframes. In 3GPP LTE, each subframe is divided into two downlink slots as shown in Figure 2. The first downlink slot comprises 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)), each OFDM symbol spanning the entire bandwidth of the component carrier. Each OFDM symbol therefore consists of several modulation symbols transmitted on each subcarrier. In LTE, the transmitted signal in each slot is divided into N DL RB ×N RB sc Book subcarrier and N DL symb It is described by a resource grid of N OFDM symbols. DL RB is the number of resource blocks in the bandwidth. N DL RB depends on the downlink transmission bandwidth configured in the cell, and N min,DL RB ≦N DL RB ≦N max,DL RB Here, N min,DL RB =6 and N max,DL RB N = 110 are the minimum and maximum downlink bandwidths supported by the current version of the specification, respectively. RB sc is the number of subcarriers in one resource block. For the normal cyclic prefix subframe structure, 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 a scheduler is one "resource block". A physical resource block (PRB) is defined as consecutive OFDM symbols in the time domain (e.g., 7 OFDM symbols) and consecutive subcarriers in the frequency domain (e.g., 12 subcarriers of a component carrier), as illustrated in FIG. 2. Thus, in 3GPP LTE (Release 8), a physical resource block consists of resource elements and corresponds to one slot in the time domain and 180 kHz in the frequency domain (for further details on the downlink resource grid, see, for example, Section 6.2 "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)" of 3GPP LTE (available at http: / / www.3gpp.org and incorporated herein by reference).

[0010] A subframe consists of two slots. There are 14 OFDM symbols in a subframe when the so-called "normal" CP (cyclic prefix) is used, and 12 OFDM symbols in a subframe when the so-called "extended" CP is used. For the purpose of terminology, in the following, a time-frequency resource equivalent to the same consecutive subcarriers spread over the entire subframe is called a "resource block pair" or equivalently an "RB pair" or a "PRB pair". The term "Component Carrier" refers to a combination of several resource blocks in the frequency domain. In future releases of LTE, the term "Component Carrier" will no longer be used, and instead the terminology will be changed to "cell" to refer to a combination of downlink and optionally uplink resources. The linking between the carrier frequency of the downlink resources and the carrier frequency of the uplink resources is indicated in the system information transmitted in the downlink resources.

[0011] Similar assumptions regarding the component carrier structure will apply to subsequent releases.

[0012] [Carrier aggregation in LTE-A to support wider bandwidth] The frequency spectrum for IMT-Advanced was decided at the World Radio communication Conference 2007 (WRC-07). Although the overall frequency spectrum for IMT-Advanced has been decided, the actual available frequency bandwidth varies depending on the region or country. However, following the decision on the outline of the available frequency spectrum, standardization of the air interface has begun in the 3rd Generation Partnership Project (3GPP).

[0013] The bandwidth that the LTE-Advanced system can support is 100MHz, while the LTE system can only support 20MHz. Today, the lack of radio spectrum has become a bottleneck in the development of wireless networks, and as a result, it is difficult to find a wide enough spectrum band for the LTE-Advanced system. Therefore, it is urgent to find a way to obtain a wider radio spectrum band, and here, the possible answer is the carrier aggregation function.

[0014] In carrier aggregation, two or more component carriers are aggregated in order to support a wider transmission bandwidth of up to 100 MHz. In the LTE-Advanced system, several cells in the LTE system are aggregated into one wider channel, which is wide enough for 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, at least if the bandwidth of the component carriers does not exceed the supported bandwidth of the LTE Rel. 8 / 9 cells. Not all component carriers aggregated by a user equipment are necessarily Rel. 8 / 9 compatible. Existing mechanisms (e.g. barring) may be used to prevent Rel. 8 / 9 user equipment from camping on a component carrier.

[0015] Depending on its capabilities, a user equipment can simultaneously receive or transmit on one or multiple component carriers (corresponding to multiple serving cells). An LTE-A Rel.10 user equipment with receiving and / or transmitting capabilities for carrier aggregation can simultaneously receive and / or transmit on multiple serving cells. In contrast, an LTE Rel.8 / 9 user equipment can receive and transmit on only one serving cell if the component carrier structure follows the Rel.8 / 9 specifications.

[0016] Carrier aggregation is supported for both contiguous and non-contiguous component carriers, with each component carrier limited to a maximum of 110 resource blocks in the frequency domain (using 3GPP LTE (Release 8 / 9) numerology).

[0017] It is possible to configure 3GPP LTE-A (Release 10) compatible user equipment to aggregate different numbers of component carriers originating from the same eNodeB (base station) and possibly with different bandwidths in the uplink and downlink. The number of downlink component carriers that can be configured is determined by the downlink aggregation capability of the UE. Conversely, the number of uplink component carriers that can be configured is determined by the uplink aggregation capability of the UE. Currently, it is not possible to configure a mobile terminal with 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 in the uplink and downlink. Component carriers originating from the same eNodeB do not need to provide the same coverage.

[0018] The spacing of the center frequencies of consecutively 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) while at the same time preserving the orthogonality of the 15 kHz spaced subcarriers. In some aggregation scenarios, the n x 300 kHz spacing can be facilitated by inserting a small number of unused subcarriers between consecutive component carriers.

[0019] The impact of aggregating multiple carriers only reaches up to the MAC layer, where one HARQ entity is required per aggregated component carrier in both uplink and downlink. There is a maximum of one transport block per component carrier (without SU-MIMO in uplink). A transport block and its HARQ retransmissions (if they occur) must 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 RRC connection establishment / re-establishment, 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 RRC connection establishment / re-establishment, the component carrier corresponding to the cell is called downlink primary cell (PCell). In connected state, one downlink PCell (DL PCell) and one uplink PCell (UL PCell) are always configured per user equipment. In the configured set of component carriers, the other cells are called secondary cells (SCell), and the carriers of the SCell are downlink secondary component carriers (DL SCC) and uplink secondary component carriers (UL SCC). Currently, up to five serving cells (including PCell) can be configured for one UE.

[0021] RRC can configure and reconfigure as well as add and remove component carriers. Activation and deactivation is done e.g. via the MAC Control element. In intra-LTE handover, RRC can also add, remove or reconfigure the SCells used in the target cell. When adding a new SCell, separate RRC signaling is used to send the SCell system information required for transmission / reception (similar to handover in Release 8 / 9). When SCells are added to one UE, a serving cell index is configured for each SCell. The serving cell index of the PCell is always 0.

[0022] If a user equipment is configured with carrier aggregation, there is always at least a pair of uplink and downlink component carriers active. The pair of downlink component carriers may also be called "DL anchor carrier". The same applies for the uplink. If carrier aggregation is configured, the user equipment may be scheduled on several component carriers simultaneously, but at most one random access procedure shall be ongoing at any time. With cross-carrier scheduling, the PDCCH of a component carrier can schedule resources on another component carrier. For this purpose, a component carrier identification field called CIF is introduced in each DCI (Downlink Control Information) format.

[0023] According to the link between the uplink and downlink component carriers established by RRC signaling, it is possible to identify the uplink component carrier to which the grant applies in the absence of cross-carrier scheduling. The link of the downlink component carrier to the uplink component carrier does not necessarily have to be one-to-one. In other words, more than one downlink component carrier may link to the same uplink component carrier. Meanwhile, only one downlink component carrier may link to one uplink component carrier.

[0024] [Uplink / Downlink Scheduling] The MAC function in the eNodeB refers to scheduling, whereby the eNB distributes the available radio resources in one cell among the UEs and among the radio bearers of each UE. In principle, the eNodeB allocates downlink and uplink resources to each UE based on the downlink data buffered in the eNodeB and the Buffer Status Report (BSR) received from the UE, respectively. In this process, the eNodeB selects the size of the MAC PDU, taking into account the QoS requirements of each configured radio bearer.

[0025] The usual mode of scheduling is dynamic scheduling with downlink grant / assignment messages (DCI) allocating downlink transmission resources and uplink grant / assignment messages allocating uplink transmission resources. These are transmitted on the Physical Downlink Control Channel (PDCCH) using a Cell Radio Network Temporary Identifier (C-RNTI) that identifies the intended UE. In addition to dynamic scheduling, persistent scheduling is defined, which allows radio resources to be semi-statically configured and assigned to UEs for a period longer than one subframe, without the need for specific downlink or uplink assignment messages on the PDCCH for each subframe. For configuration or reconfiguration of persistent scheduling, RRC signaling specifies the resource allocation intervals during which radio resources are periodically assigned. If the PDCCH is used for configuration or reconfiguration of persistent scheduling, the scheduling messages that apply to persistent scheduling need to be identified from the scheduling messages used for dynamic scheduling. For this purpose, a special scheduling identity known as Semi-Persistent Scheduling C-RNTI (SPS-C-RNTI) is used, which is different for each UE from the C-RNTI used for dynamic scheduling messages.

[0026] L1 / L2 control signaling is transmitted in the downlink together with the data to inform scheduled users of their allocation status, transport format, and other transmission related information (e.g., HARQ information, Transmit Power Control (TPC) commands). L1 / L2 control signaling is multiplexed with the downlink data in a subframe (assuming that user allocation can vary on a subframe-by-subframe basis). Note that user allocation can also be performed on a TTI (Transmission Time Interval) basis, where the TTI length can be an integer multiple of a subframe. The TTI length can be constant for all users in a service area, can be different for different users, or can be dynamic per user. In general, L1 / L2 control signaling only needs to be transmitted once per TTI. In the following, it is assumed, without loss of generality, that the TTI is equal to one subframe.

[0027] L1 / L2 control signaling is transmitted on the Physical Downlink Control Channel (PDCCH). The PDCCH carries messages as Downlink Control Information (DCI). DCI mostly contains resource allocations for groups of mobile terminals or UEs and other control information. In general, multiple PDCCHs can be transmitted within one subframe.

[0028] The downlink control information comes in several formats, which differ in the overall size and the information contained in each field. The various DCI formats currently defined for LTE are detailed in 3GPP TS 2.0, section 5.3.3.1 “Multiplexing and channel coding”, available at http: / / www.3gpp.org and incorporated herein by reference. For more information on DCI formats and the specific information transmitted in the DCI, please refer to the aforementioned technical standards or 3GPP TS 2.0, which is incorporated herein by reference. Other formats may be defined in the future.

[0029] [Layer 1 / Layer 2 control signaling] L1 / L2 control signaling is transmitted in the downlink together with the data to inform scheduled users of their allocation status, transport format, and other transmission related information (e.g., HARQ information, Transmit Power Control (TPC) commands). L1 / L2 control signaling is multiplexed with the downlink data in a subframe (assuming that user allocation can vary on a subframe basis). User allocation can also be performed on a TTI (Transmission Time Interval) basis. Note that in that case, the TTI length can be an integer multiple of a subframe. The TTI length can be constant for all users in a service area, different for different users, or dynamic for each user. In general, L1 / L2 control signaling only needs to be transmitted once per TTI. In the following, without loss of generality, it is assumed that the TTI is equal to one subframe.

[0030] L1 / L2 control signaling is transmitted on the Physical Downlink Control Channel (PDCCH). The PDCCH carries messages as Downlink Control Information (DCI). DCI mostly contains resource allocations for groups of mobile terminals or UEs and other control information. In general, multiple PDCCHs can be transmitted within one subframe.

[0031] It should be noted that in 3GPP LTE, allocations for uplink data transmission, also referred to as uplink scheduling grants or uplink resource allocations, are also transmitted on the PDCCH. Furthermore, 3GPP Release 11 introduced the EPDCCH, which fulfills essentially the same functions as the PDCCH, i.e., it carries L1 / L2 control signaling, although the detailed transmission method is different from the PDCCH. Further details can be found in the current versions of 3GPP LTE RFC111 and 3GPP LTE RFC111, which are incorporated herein by reference. As a result, most items outlined in the Background and the Embodiments apply to the PDCCH and EPDCCH, or other means of carrying L1 / L2 control signaling, unless otherwise stated.

[0032] Generally, the information sent in L1 / L2 control signaling for the purpose of allocating uplink or downlink radio resources (particularly in LTE(-A) Release 10) can be categorized into the following items: - User Identity: Indicates the user to whom the allocation is made. This information is usually included in the checksum by masking the CRC with the user identity. Resource Allocation Information: indicates the resources (e.g., Resource Blocks (RBs)) to which a user is assigned. Alternatively, this information is called Resource Block Assignment (RBA). Note that the number of RBs to which a user is assigned can be dynamic. Carrier indicator: Used when a control channel transmitted on a first carrier allocates resources related to a second carrier (i.e. resources of the second carrier or resources related to the second carrier) (cross-carrier scheduling). - Modulation and coding scheme: Determines the modulation method and coding rate to be adopted. - HARQ information: such as New Data Indicator (NDI) and / or Redundancy Version (RV), which are particularly useful when retransmitting a data packet or parts of it. - Power control command: adjusts the transmission power of the assigned uplink data or control information transmission. Reference signal information: the applied cyclic shift and / or orthogonal cover code (OCC) index used for transmitting or receiving the assigned reference signal. - Uplink or Downlink Allocation Index: Used to identify the order of allocations, especially useful in TDD systems. - Hopping information: Information indicating whether and how resource hopping is applied, for example, for the purpose of increasing frequency diversity. - CSI Request: Used to trigger the transmission of Channel State Information in the allocated resources. - Multi-cluster information: A flag used to indicate and control whether transmission is to be performed in a single cluster (a contiguous set of RBs) or in multiple clusters (at least two discontinuous sets of contiguous RBs). Multi-cluster allocation is introduced in 3GPP LTE-(A) Release 10.

[0033] It should be noted that the above list is not exhaustive and that depending on the DCI format used, not all of the above information items need to be included in each PDCCH transmission.

[0034] The downlink control information comes in several formats, which differ in their overall size and in the information contained in the above mentioned fields. Below we list some DCI formats currently defined for LTE. More detailed information can be found in 3GPP TS 2.0, especially in section 5.3.3.1 “DCI formats”, which is incorporated herein by reference. - Format 0: DCI format 0 is used for transmitting resource grants for the PUSCH and uses a single antenna port transmission in uplink transmission mode 1 or 2. - Format 1: DCI Format 1 is used for transmitting resource allocations for 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 transmission and for allocation of dedicated 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 for PDSCH transmission with closed-loop precoding for rank-1 transmission (downlink transmission mode 6). The transmitted information is the same as in Format 1A, but in addition an indicator of the precoding vector applied to the PDSCH transmission. - Format 1C: DCI Format 1C is used for very compact transmission of PDSCH assignments. When Format 1C is used, PDSCH transmission is restricted 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 for PDSCH transmission with multi-user MIMO. The transmitted information is the same as in Format 1B, but instead of one of the bits of the precoding vector indicator there is a single bit indicating if a power offset is applied to the data symbols. This feature is necessary to indicate if the transmission power is shared between two UEs or not. This may be extended to the case of power sharing between more UEs in future versions of LTE. - Format 2: DCI format 2 is used for transmitting resource allocations of the PDSCH for closed-loop MIMO operation (transmission mode 4). - Format 2A: DCI Format 2A is used to transmit PDSCH resource allocation for open-loop MIMO operation. The transmitted information is the same as in Format 2, except that there is no precoding information if the eNodeB has two transmit antenna ports, and two bits are used to indicate the transmission rank in the case of four antenna ports (transmission mode 3). - Format 2B: Introduced in Release 9 and used for transmitting PDSCH resource allocation for dual layer beamforming (transmission mode 8). - Format 2C: Format introduced in Release 10 and used for transmission of PDSCH resource allocations for closed-loop single-user or multi-user MIMO operation up to 8 layers (transmission mode 9). - Format 2D: Format introduced in Release 11, used for transmission of up to 8 layers, mainly used for COMP (Cooperative Multipoint) (transmission mode 10). - Formats 3 and 3A: DCI formats 3 and 3A are used for transmitting power control commands for PUCCH and PUSCH with 2-bit or 1-bit power adjustment, respectively. These DCI formats contain individual power control commands for UEs. - Format 4: DCI format 4 is used for scheduling of PUSCH with closed-loop spatial multiplexing transmission in uplink transmission mode 2. - Format 5: DCI Format 5 is used for scheduling the PSCCH (Physical Sidelink Control Channel) and contains multiple SCI Format 0 fields used for scheduling the 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 appended to Format 5 until the payload size is equal to the payload size of Format 0 including the padding bits appended to Format 0.

[0035] [Unlicensed LTE - Licensed Assisted Access (LAA)] In September 2014, 3GPP started a new study item on LTE operation over unlicensed spectrum. The reason for extending LTE into unlicensed spectrum is the ever-increasing demand for wireless broadband data combined with a constrained amount of licensed spectrum. Therefore, cellular operators are increasingly considering unlicensed spectrum as a complementary tool to expand their service offerings. One advantage of LTE in unlicensed spectrum compared to relying on other radio access technologies (RATs) such as Wi-Fi is that complementing the LTE platform with unlicensed spectrum access allows operators and suppliers to utilize existing or planned investments in LTE / EPC hardware for the wireless core network.

[0036] However, it must be taken into account that there can be no consistency in quality between unlicensed and licensed spectrum access, since coexistence with other radio access technologies (RATs) in unlicensed spectrum, such as Wi-Fi, is essential. Therefore, at least initially, LTE operation in unlicensed bands is considered as a complement to LTE on licensed spectrum, rather than as a standalone operation in unlicensed spectrum. Based on this assumption, 3GPP has established the term Licensed Assisted Access (LAA) for LTE operation in unlicensed bands together with at least one licensed band. However, future standalone operation of LTE on unlicensed spectrum, i.e. without assistance from licensed cells, is not excluded. Enhanced Licensed Assisted Access (eLAA) is an extension of LAA, which also utilizes unlicensed spectrum, especially in the uplink. An efficient use of unlicensed spectrum as a complement to licensed spectrum could bring significant value to service providers and thus to the wireless industry as a whole. To exploit the full benefits of LTE operation in unlicensed spectrum, it is of utmost importance to specify a complete UL access scheme in addition to the already specified DL access scheme.

[0037] A typical LAA approach currently planned in 3GPP utilizes as much as possible the already specified Rel.12 Carrier Aggregation (CA) framework, but with a so-called Primary Cell (PCell) carrier and one or more Secondary Cell (SCell) carriers in said CA framework configuration. 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] A very basic scenario involving a licensed PCell, a licensed SCell1, and various unlicensed SCells 2, 3, and 4 (illustrated as small cells) is shown in Figure 4. The transmitting / receiving network nodes for unlicensed SCells 2, 3, and 4 can be remote radio heads managed by the eNB, or they can be nodes attached to the network but not managed by the eNB. For simplicity, the connection of these nodes to the eNB or the network is not explicitly shown in the figure.

[0039] Currently, the basic approach envisaged by 3GPP is for the PCell to operate in licensed bands while one or more SCells operate in unlicensed bands. One advantage of this approach is that the PCell can be used for reliable transmission of control messages and user data that require high quality of service (QoS), e.g. voice or video, while the SCell in unlicensed spectrum may suffer some degradation in QoS due to the necessity for coexistence with other RATs, depending on the scenario.

[0040] It has been agreed that the LAA will focus on the 5 GHz unlicensed spectrum. Therefore, one of the most important issues is the coexistence with Wi-Fi (IEEE 802.11) systems operating in these unlicensed spectrum. To support fair coexistence between LTE and other technologies such as Wi-Fi, as well as fairness between different LTE operators in the same unlicensed spectrum, LTE channel access in unlicensed spectrum needs to be adhered to by a specific set of regulatory rules that may depend in part on the region and the specific frequency band. A comprehensive description of the regulatory requirements for all regions in the case of operation in the 5 GHz unlicensed spectrum is given in 3GPP TS 2011-01-13, which is incorporated herein by reference, as well as in 3GPP TS 2011-01-13, which is incorporated herein by reference. Depending on the region and band, the regulatory requirements to be considered when designing the LAA procedure include Dynamic Frequency Selection (DFS), Transmit Power Control (TPC), Listen Before Talk (LBT), and discontinuous transmission with limited maximum transmission duration. 3GPP's aim is to target a single global framework for LAA, which basically means that all the requirements for the various regions and bands of 5 GHz need to be taken into account in the system design.

[0041] For example, in Europe, certain limits for the nominal channel bandwidth are set, evident from section 4.3 of IEEE 802.11b, incorporated herein by reference. The nominal channel bandwidth is the widest frequency band, including guard bands, allocated to a single channel. The occupied channel bandwidth is the bandwidth that contains 99% of the power of the signal. A device can operate simultaneously on one or multiple adjacent or non-adjacent channels.

[0042] The Listen-Before-Talk (LBT) procedure is specified as a mechanism by which equipment applies a Clear Channel Assessment (CCA) check before using a channel. CCA utilizes at least energy detection to determine the presence or absence of other signals on the channel, thereby determining whether the channel is occupied or clear, respectively. Current European and Japanese regulations require the use of LBT in unlicensed bands. Apart from regulatory requirements, carrier sensing via LBT is one method for fair sharing of unlicensed spectrum, and therefore is considered an essential feature for fair and friendly operation in unlicensed spectrum in a single global solution framework.

[0043] In unlicensed spectrum, channel availability is not always guaranteed. Also, certain regions, such as Europe and Japan, prohibit continuous transmission in unlicensed spectrum and impose limits on the maximum duration of a transmission burst. Discontinuous transmission with a limited maximum transmission duration is therefore a necessary feature 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 near-uniform loading of the spectrum. DFS operation and the corresponding requirements are associated with the master-slave principle. The master shall detect radar interference but can rely on another device associated with the master to perform radar detection.

[0044] In most regions, operation on the 5 GHz 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 typically expected that an unlicensed carrier in the 5 GHz band will support a smaller coverage area than a licensed cell in the 2 GHz band due to increased signal path loss and shadowing effects. Another requirement for certain regions and bands is the use of TPC to limit the average level of interference that other devices may experience when operating in the same unlicensed band.

[0045] Further information can be found in Non-Patent Document 8, which is incorporated herein by reference.

[0046] According to the European regulations on LBT, a device must perform a clear channel assessment (CCA) before occupying a radio channel with data transmission. Only after detecting that the channel is free, for example based on energy detection, can the device start transmitting on an unlicensed channel. In particular, the device must observe the channel for a certain minimum time during CCA (e.g., 20 μs for Europe (see 3GPP TS 8.110.110, section 4.8.3)). The channel is considered occupied if the detected energy level exceeds the set threshold for CCA (e.g., −73 dBm / MHz for Europe (see 3GPP TS 8.110.110, section 4.8.3)). Conversely, if the detected power level is below the set threshold for CCA, the channel is considered free. If the channel is determined to be occupied, no transmissions on the channel shall be made in the next fixed frame period. Once the channel is classified as free, the device may transmit immediately. This limits the maximum transmission duration and facilitates fair resource sharing with other devices operating on the same band.

[0047] The energy detection of CCA is performed over the entire channel bandwidth (e.g., 20 MHz in the 5 GHz unlicensed band), which means that the received power levels of all subcarriers of an LTE OFDM symbol in the channel contribute to the energy level evaluated at the device performing CCA.

[0048] In addition to the above CCA, another Enhanced CCA (ECCA) may be required if the equipment is classified as Load Based Equipment (LBE) as described in 3GPP TS 21.2006-01011, section 4.9.2.2, which is incorporated herein by reference. The ECCA includes another CCA observation time with a duration of the random factor N multiplied by the CCA observation time slot. N defines the number of clear idle slots that is the total idle period that needs to be observed before starting transmission.

[0049] Furthermore, the total time that an equipment transmits on a given carrier without re-evaluating the channel availability (i.e. LBT / CCA) is specified as the channel occupation time (see section 4.8.3.1 of 3GPP TS 8.1003). The channel occupation time shall be in the range of 1 ms to 10 ms. However, as currently specified in Europe, a maximum channel occupation time can be, for example, 4 ms. Furthermore, there is also a minimum idle time during which the UE cannot transmit after a transmission in an unlicensed cell, which is at least 5% of the channel occupation time. At the end of the idle period, the UE can perform a new CCA etc. This transmission behavior is shown diagrammatically in Fig. 5, which comes from 3GPP TS 8 (Fig. 2 "Example of timing for Frame Based Equipment").

[0050] Figure 6 shows the timing between Wi-Fi transmission and LAA UE transmission on a particular frequency band (unlicensed cell). As can be seen from Figure 5, after the Wi-Fi burst, at least a CCA gap is required before the eNB can "reserve" the unlicensed cell, for example by transmitting a reservation signal until the next subframe boundary. Then the actual LAA DL burst starts. This will be equally true for an LTE UE that reserves the subframe after successfully performing CCA by transmitting a reservation signal to start the actual LAA UL burst.

[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 and uplink transmission (PUSCH) of single and multiple antenna ports, respectively. 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 3GPP TS 2.0, which is incorporated herein by reference.

[0052] Any of these DCI formats (i.e. uplink grants) can be either a one-stage grant or part of a two-stage grant. In a current exemplary implementation in LTE (see Non-Patent Document 5), this is reflected by the "PUSCH Trigger A" field, which is a one-bit field that distinguishes whether the received uplink grant is for "non-triggered scheduling" (i.e. one-stage uplink grant) if the bit value is 0, or for "triggered scheduling" (i.e. two-stage uplink grant) if the bit value is 1. This is controllable by the eNB, the radio network entity responsible for scheduling radio resources for UEs.

[0053] In a two-stage uplink scheduling procedure, one uplink transmission needs to be scheduled upon receipt by the UE of two separate messages ("Trigger A" and "Trigger B") 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). For this two-stage grant, the four DCI formats contain the following data fields as currently specified in 3GPP TS 2.0:

[0055] "PUSCH Trigger A (1 bit): A value of 0 indicates non-triggered scheduling and a value of 1 indicates triggered scheduling, as specified in Section 8.0 of [3]. - Timing Offset (4 bits): as specified 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 during which scheduling of the PUSCH by triggered scheduling is valid."

[0056] In addition, the DCI formats available for the Trigger A message include the usual data fields indicating the radio resources scheduled for uplink transmission, such as the "resource block allocation" field, the "modulation and coding scheme" field, the "HARQ process number" field, etc. Furthermore, DCI formats 0A, 0B, 4A, and 4B (especially the DCI CRC) can be scrambled with a UE-specific identity (e.g., C-RNTI) so that the corresponding uplink grant is addressed to a specific UE.

[0057] The Trigger B message has DCI format 1C, as currently specified in clause 5.3.3.1.4 of 3GPP TS 2013-01016, which is incorporated herein by reference. DCI format 1C, as currently specified in technical standards used within the scope of unlicensed carrier transmission including the two-stage grant procedure, is as follows:

[0058] "Other than that - LAA Subframe Configuration (4 bits): as specified in Clause 13A of [3]. - Uplink Transmission Duration and Offset Designation (5 bits): as specified in Clause 13A of [3]. This field is only applicable for UEs configured for uplink transmission on the LAA SCell. - PUSCH Trigger B (1 bit): as specified in Clause 8.0 of [3]. This field is only applicable for UEs configured for uplink transmission on the LAA SCell. - Reservation information bits are added until the size is equal to that of format 1C, which allows very compact scheduling of one PDSCH codeword."

[0059] As mentioned above, the Trigger B message (DCI format 1C) when used as part of a two-stage grant procedure is typically not addressed to a specific UE, but rather the DCI format 1C, and in particular its CRC, can be scrambled by the eNB through the use of a shared identity (in this case the CC-RNTI (Common Control RNTI) (see 3GPP TSE 2013-11062, which is incorporated herein by reference), which is the RNTI used in the context of providing common control PDCCH information).

[0060] The cross-reference "[3]" in the above citation of Non-Patent Document 5 refers to Non-Patent Document 4, the entire contents of which are incorporated herein by reference, since at least Sections 8.0 and 13 are relevant to Two-Stage Grants.

[0061] In particular, section 8 of Non-Patent Document 4 specifies in more detail the timing and method of performing uplink transmission (i.e., PUSCH) for the LAA SCell.

[0062] For a serving cell that is an LAA SCell, the UE - upon detection of a PDCCH / EPDCCH with DCI format 0A / 0B / 4A / 4B and the "PUSCH trigger A" field set to "0" in subframe n intended for the UE, or - in response to detection of a PDCCH / EPDCCH with DCI format 0A / 0B / 4A / 4B and with the "PUSCH trigger A" field set to "1" in the most recent subframe from subframe nv for the UE and detection of a PDCCH with DCI CRC scrambled by the CC-RNTI and with the "PUSCH trigger B" field set to "1" in subframe n, - PDCCH / EPDCCH and HARQ process ID mod(n HARQ_ID +i,N HARQ), subject to the channel access procedure described in clause 15.2.1, in subframe n+l+k+i, i=0,1,...,N-1, where: - For DCI format 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. - In the UE, the maximum value of N is configured by the high layer parameter maxNumberOfSchedSubframes-Format0B for DCI format 0B and by the high layer parameter 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", otherwise according to Table 8.2e. -n HARQ_ID The value of N is determined by the HARQ process number field in the corresponding DCI format 0A / 0B / 4A / 4B. 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 settings for LAA" field in the corresponding DCI with CRC scrambled by the CC-RNTI according to the procedure of clause 13A and with the "PUSCH trigger B" field set to "1", - the value of v is determined by the validity duration field in the corresponding PDCCH / EPDCCH of DCI format 0A / 0B / 4A / 4B with the "PUSCH trigger A" field set to "1" according to Table 8.2f; - The minimum value of l+k that the UE supports 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 the two-phase grant procedure is performed. However, it should be noted that the above-mentioned currently standardized two-phase grant procedure specification may be changed in the future due to continuous changes and improvements. As a result, the above-cited implementation of the two-phase grant procedure according to the current 3GPP technical standard is only one exemplary implementation, and many details are considered to be immaterial to the present invention.

[0064] Nevertheless, for the present invention, it is assumed that the basic concept behind the two-phase grant procedure remains the same as described above. In particular, the basic concept is described with respect to Fig. 7, which illustrates the two-phase grant function including the transmission and reception of DCI including Trigger A and Trigger B messages. For the following exemplary description, it is assumed that the illustrated subframes are numbered by taking the subframe in which Trigger B (i.e., the second stage uplink scheduling message) is received at the UE as the reference subframe n, and the preceding and subsequent subframes are numbered accordingly. It is further assumed that the Trigger A message is received at subframe n-3, defining a time window of length v during which the two-phase grant procedure can be validly performed. In other words, the time window is considered to define a period during which the Trigger B message may be received and actually trigger a corresponding uplink transmission based on the transmission parameters indicated by the Trigger A and / or Trigger B messages.

[0065] The time window length v can be exemplarily indicated in the Trigger A message as illustrated above by the last two bits of the timing offset field for DCI formats 0A, 0B, 4A, 4B in Non-Patent Document 5 and Table 8.2f in Non-Patent Document 4.

[0066] If a Trigger B message is received in subframe n, the UE shall determine whether an associated Trigger A message has been received by the UE within a time window of length v (starting immediately before receipt of the Trigger B message, i.e. ranging from 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, thus triggering an uplink transmission at the UE. Then, an uplink transmission (i.e. PUSCH) is performed in subframe n+offset with a specific transmission timing offset. The UE may perform the uplink transmission according to the information received in the Trigger A and Trigger B messages, e.g. using specified radio resources and modulation and coding schemes.

[0067] In the present invention, the exact PUSCH timing offset is not important. By way of example, as currently standardized in Non-Patent Document 4, the PUSCH timing offset is "l+k+i", where the parameter l is specified by the Trigger B message (see the "Uplink Transmission Duration and Offset Specification" field of DCI format 1C in Non-Patent Document 5 and Table 13A-2 of Non-Patent Document 4) and the parameter k is specified by the Trigger a message (see the first two bits of the "Timing Offset" field of any of DCI formats 0A, 0B, 4A, and 4B in Non-Patent Document 5 and Table 8.2e of Non-Patent Document 4). The parameter i is applicable when multiple uplink subframes are scheduled by a two-stage uplink scheduling procedure, in which case it runs from 0 to (number of allowed subframes - 1) (it remains 0 otherwise). More details can be derived from the above-cited section 8 of Non-Patent Document 4. However, the PUSCH timing offset for performing uplink transmission according to this two-stage uplink scheduling procedure may be specified differently or may be 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 Summary of the Invention [Problem to be solved by the invention]

[0070] The non-limiting and exemplary embodiments provide improved methods and user equipment involved in scheduling of uplink transmissions performed by the user equipment.

[0071] The independent claims provide non-limiting exemplary embodiments. Advantageous embodiments are the subject of the dependent claims. [Means for solving the problem]

[0072] According to one general aspect, a user equipment for which uplink radio resources are scheduled is described. The cells are configured for communication between the user equipment and a radio base station responsible for scheduling uplink radio resources on at least one cell. The user equipment comprises a receiver for receiving a first stage uplink resource scheduling message from the radio base station indicating uplink radio resources available to the user equipment for performing an uplink transmission via the scheduled cell. The receiver further receives a second stage uplink resource scheduling message from the radio base station associated with the first stage uplink resource scheduling message. The user equipment further comprises a processor for determining whether the first stage uplink resource scheduling message is valid. When the second stage uplink resource scheduling message is received, the processor determines that the uplink transmission is scheduled if the processor determines 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 as to whether the uplink transmission has been triggered by another second stage uplink resource scheduling message within a predefined period prior to receiving the second stage uplink resource scheduling message. The user equipment further comprises a transmitter for performing an uplink transmission via a scheduled cell, which may be, for example, an unlicensed cell in the context of 3GPP LTE Release 14, or another cell in which two-stage scheduling is supported, if the processor determines that the uplink transmission is scheduled.

[0073] Correspondingly, in another general aspect, the disclosed technology features a method of operating a user equipment in which uplink radio resources are scheduled. The 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 receiving a first stage uplink resource scheduling message from the radio base station indicating uplink radio resources available to the user equipment for performing an uplink transmission via the unlicensed cell. The method further includes receiving a second stage uplink resource scheduling message from the radio base station, the second stage uplink resource scheduling message being associated with the first stage uplink resource scheduling message. The method further includes determining whether the first stage uplink resource scheduling message is valid. When the second stage uplink resource scheduling message is received, the method further includes determining that the uplink transmission has been scheduled if it is 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 as to whether the uplink transmission has been triggered by another second stage uplink resource scheduling message within a predetermined time period prior to receiving the second stage uplink resource scheduling message. The method further includes performing the uplink transmission via the unlicensed cell if it is determined that the uplink transmission is scheduled.

[0074] Other benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings, and these benefits and / or advantages may be achieved individually by the various embodiments and features of the disclosure in the specification and drawings, and need not all be provided to obtain one or more of them.

[0075] These general and specific aspects may be implemented using user equipment and methods, and combinations of user equipment and methods.

[0076] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0077] [Figure 1] FIG. 1 illustrates an example architecture of a 3GPP LTE system. [Diagram 2] FIG. 1 illustrates an example downlink resource grid of a downlink slot of a subframe defined in 3GPP LTE (Rel. 8 / 9). [Diagram 3] FIG. 2 illustrates an example uplink resource grid of uplink slots of a subframe defined in 3GPP LTE. [Figure 4] A diagram showing an example LAA scenario involving multiple licensed and unlicensed cells. [Diagram 5] A diagram showing the transmission behavior of LAA transmission. [Figure 6] A diagram showing the timing between Wi-Fi transmission and LAA UE downlink burst in an unlicensed cell. [Figure 7] A diagram illustrating an exemplary two-stage uplink scheduling procedure provided for uplink transmission via an unlicensed cell. [Figure 8] FIG. 1 illustrates multiple triggers for uplink transmission in a multi-UE environment. [Figure 9] A diagram illustrating prevention of multiple triggers of uplink transmission in a multi-UE environment according to a first implementation form of one embodiment. [Figure 10] FIG. 1 is a diagram of a two-stage uplink transmission procedure according to a first implementation form of an embodiment. [Figure 11]FIG. 11 illustrates the prevention of multiple triggers of uplink transmission in a multi-UE environment according to a second implementation of an embodiment. [Figure 12] FIG. 11 is a diagram of a two-stage uplink transmission procedure according to a second implementation of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] A mobile station, mobile node, user terminal, or user equipment is a physical entity in a communication network. A node may have multiple functional entities. A functional entity represents a software or hardware module that implements and / or provides a given set of functions to other functional entities of the node or the network. A node may have one or more interfaces that connect the node to communication facilities or media that enable communication. Similarly, a network entity may have logical interfaces that connect a functional entity to communication facilities or media that enable communication with other functional entities or corresponding nodes.

[0079] The term "radio resource" as used in the claims and in this application is intended to be broadly understood as referring to physical radio resources, such as time-frequency radio resources.

[0080] The term "unlicensed cell" or "unlicensed carrier" as used in the set of claims and in this application shall be broadly understood as a cell / carrier operating in an unlicensed spectrum of a particular frequency bandwidth. Correspondingly, the term "licensed cell" or "licensed carrier" as used in the set of claims and in this application shall be broadly understood as a cell / carrier operating in a licensed spectrum of a particular frequency bandwidth. By way of example, these terms shall be understood in the context of 3GPP Release 12 / 13 and Licensed Assisted Access Work Items.

[0081] FIG. 8 shows UEs belonging to UE group #1, UEs belonging to UE group #2, and an eNodeB.

[0082] Assume that the first stage uplink resource scheduling message, Trigger A, is transmitted from the eNodeB to the UEs of Group #1 in subframe n-2. In this exemplary case, the valid time window of Trigger A transmitted to the UEs of Group #1 is 5 subframes. Thus, the information about the valid time window is given by Trigger A itself.

[0083] It is further assumed that a second stage uplink resource scheduling message, Trigger B, is transmitted from the eNodeB in subframe n. Trigger B is received by both group #1 and #2 UEs, but the eNodeB transmits Trigger B with the same intent as the second stage uplink resource scheduling message for Trigger A (as the first stage uplink resource scheduling message) already transmitted to the group #1 UEs in subframe n-2. In this exemplary case, it is assumed that the group #2 UEs have not received any Trigger A within the corresponding valid time window before Trigger B. Upon receiving Trigger B, all UEs capable of receiving Trigger B (which generally includes the group #1 and group #2 UEs) need to check whether they have received Trigger A within the corresponding valid time window. Thus, in this example, the group #1 UEs check whether they have received Trigger A up to 5 subframes earlier (in this case, in subframe n-5 to subframe n-1). Since Trigger A is received in subframe n-2, which is within the valid time window, the UEs in Group #1 will trigger their uplink transmission later.

[0084] Because Trigger A has not been received by the UEs of Group #2, Trigger B received in subframe n will not trigger an uplink transmission by the UEs of Group #2.

[0085] As is further evident from FIG. 8, the UEs of group #2 receive trigger A in subframe n+1. In this exemplary case, the valid time window for trigger A transmitted to the UEs of group #2 is three subframes. As further illustrated in the figure, a second trigger B is transmitted from the eNodeB (in subframe n+3). The second trigger B is also received by both the UEs of groups #1 and #2, but the eNodeB transmits the second trigger B with the same intent as the second stage uplink resource scheduling message for trigger A (as the first stage uplink resource scheduling message) transmitted to the UEs of group #2 in subframe n+1. In response to receiving trigger B, the UEs of group #2 check whether they have received trigger A up to three subframes earlier (in this case, in subframes n to n+2). Since the corresponding trigger A is received in subframe n+1, which is within the valid time window, the UEs of group #2 will trigger their uplink transmission later.

[0086] However, since the second trigger B is also received by the group #1 UE in subframe n+3, the group #1 UE will check again whether it has received the trigger A up to 5 subframes earlier (in this case in subframe n-2 to subframe n+2). Considering that the group #1 UE received the trigger A in subframe n-2, i.e. within the valid time window of the reception trigger A, the group #1 UE will re-trigger its second uplink transmission, which is intended by the eNodeB to be performed only by the group #2 UE and not by the group #1 UE. According to this exemplary scenario shown in FIG. 8, if the second trigger B is received in subframe n+2 (instead of receiving it in subframe n+3), a triggered second uplink transmission performed by the group #1 UE will also occur. However, considering the exemplary valid time window of 5 subframes for the group #1 UE, if the second trigger B is received after subframe n+4, multiple triggering of the uplink transmission will not occur.

[0087] Overall, such multiple triggers of uplink transmissions are undesirable in a multi-UE environment. First, such undesirable uplink transmissions run the risk of causing interference with other transmissions in the corresponding subframes. Second, such multiple triggers may imply collisions of UL transmissions. If a UE in group #1 is triggered to transmit an UL transmission in subframe n by trigger B, the corresponding UL transmission is shown by trigger A to last for four subframes, but this corresponding UL transmission occurs in subframes n+2 to n+5 as an example. If the same UE in group #1 is triggered to transmit an UL transmission again in subframe n+3 by trigger B, the corresponding UL transmission is shown by the same trigger A to last for four subframes, but this corresponding UL transmission occurs in subframes n+5 to n+8 as an example. Thus, as shown, these two triggers cause a collision in subframe n+5, but it is not clear whether data is transmitted as a result of the first trigger B or the second trigger B. Even if the transmission resources are the same in both cases, the corresponding data will typically contain different transport blocks or packets. Such collisions should be avoided as they may lead to misunderstandings between the UE and the eNodeB.

[0088] The inventors have conceived the following exemplary embodiments that alleviate one or more of the above-described problems.

[0089] Specific implementations of the various embodiments are intended to be realised in the broad specifications given by the 3GPP standards and partly described in the Background section, to which certain important features are added as described below with respect to the various implementations of the present embodiments, which may be advantageously adapted for use in mobile communication systems, such as the 3GPP LTE-A (Release 10 / 11 / 12 / 13 and beyond) communication systems described in the Background section, but are not limited to use in these particular exemplary communication networks.

[0090] It should be understood that the above description is not intended to limit the scope of the present disclosure, but is merely an example of an embodiment for a deeper understanding of the present disclosure. Those skilled in the art will recognize that the general principles of the present disclosure outlined in a set of claims and the description given in the summary section of this specification can be applied to different scenarios in a manner not explicitly stated below. For the purposes of illustration and explanation, some assumptions are introduced, which should not unduly limit the scope of the following embodiments.

[0091] Furthermore, as mentioned above, the following embodiments may be implemented in a 3GPP LTE-A (Rel.12 / 13 and later) environment. Various embodiments may mainly improve the uplink transmission scheme. However, other features (i.e. features that are not changed by the various embodiments) may be exactly the same as described in the background section or may be changed without affecting the various embodiments. For example, features and procedures that define how the actual uplink transmission is performed (e.g., segmentation, modulation, coding, beamforming, multiplexing) and how scheduling (PDCCH, DCI, cross-carrier scheduling, self-scheduling) or how normal uplink transmission timing is performed using timing advance procedures (e.g., initial timing advance, timing advance update command).

[0092] A general embodiment that solves the above problems is described in detail below using the following exemplary scenario designed to facilitate illustrating the principles of the embodiment, although these principles are also applicable to other scenarios, some of which are explicitly described below.

[0093] The UE initiates two-stage uplink resource scheduling. In particular, resource scheduling is initiated by a first-stage uplink resource scheduling message (Trigger A) of the unlicensed cell, which is received by the receiver of the UE. Then, a second-stage uplink resource scheduling message (Trigger B) of the unlicensed cell is received by the receiver of the UE.

[0094] Then, in the first stage uplink resource scheduling message verification, the processor of the UE determines whether the first stage uplink resource scheduling message (Trigger A) is valid, whereby the determination of the validity of the first stage uplink resource scheduling message (Trigger A) is based on a determination as to whether an uplink transmission has been triggered by another second stage uplink resource scheduling message (Trigger B) within a predetermined period prior to receiving the second stage uplink resource scheduling message (Trigger B).

[0095] Thereafter, when a second stage uplink resource scheduling message (Trigger B) is received, if the processor determines that the first stage uplink resource scheduling message (Trigger A) is valid, then the processor determines that the uplink transmission is scheduled.

[0096] Finally, if the processor determines that an uplink transmission is scheduled, the transmitter of the UE performs the uplink transmission via the unlicensed cell.

[0097] According to the above-mentioned main principle of the present invention, it is advantageous to prevent multiple uplink transmission triggers in a multi-UE environment: the eNodeB can directly send a new trigger A to a different UE immediately after sending trigger B, even within a predefined period / valid time window, since there is no risk that trigger B intended for a different UE will unintentionally trigger a second uplink transmission by a particular UE that has already triggered an uplink transmission before within the valid time window.

[0098] By this measure, user / cell throughput can be significantly improved, and furthermore, by avoiding multiple uplink transmission triggers, the required Trigger A overhead can be reduced since the long verification time implied by Trigger A can be used more efficiently.

[0099] Also, a false alarm of a second trigger B after a correct first trigger B within the validation time / valid time window will not result in an erroneous PUSCH transmission, which advantageously avoids error cases due to false alarm trigger B.

[0100] FIG. 9 illustrates a first implementation of an embodiment in which multiple triggering of uplink transmissions in a multi-UE environment is prevented.

[0101] Figure 9 basically illustrates the situation described above with respect to Figure 8 for the reception of triggers at the UEs of groups #1 and #2. As before, the UEs of group #1 receive trigger B in subframe n+3. To avoid a second trigger of an uplink transmission (which may occur in the conventional system described with respect to Figure 8), the UEs of group #1 check whether another trigger B has already triggered an uplink transmission within a predefined period prior to the reception of trigger B received in subframe n+3. This predefined period is preferably the valid time window specified in the trigger A message. In this example, the predefined period is a valid time window of length 5 subframes (as already described with respect to Figure 8 where trigger A informs the UE of the number of subframes (v=5) that indicates the valid time window).

[0102] Then, the UEs of group #1 check whether another trigger B has triggered an uplink transmission within the period of 5 subframes prior to subframe n+3. In particular, the UEs of group #1 check whether another trigger B has triggered an uplink transmission between subframes n-2 and n+2. As shown in FIG. 8, an uplink transmission has already been triggered by a trigger B received in subframe n. So, in order to avoid multiple triggers of an uplink transmission within the valid time window of a trigger A, in this example, for any trigger B after the first trigger B received in subframe n, the UE generates a valid time window between subframes n-2 and n+2 and ignores a trigger A received in subframe n-2 that allows another uplink transmission to be triggered by a trigger B received in subframe n+3. In particular, by ignoring a trigger A received in subframe n-2, a valid time window is not found before the reception of a trigger B in subframe n+3, so that an uplink transmission to be triggered by a trigger B received in subframe n+3 can be avoided. Note that the expression "ignoring trigger A" when a previous triggered uplink transmission is found within the valid time window of such trigger A means that trigger A received in subframe n-2 is "not taken into account" with respect to trigger B received in subframe n+3.

[0103] As a result, no undesired second / multiple uplink transmissions are triggered by the UEs of group #1 in subframe n+3, as shown in Figure 9. Therefore, in this case, only the UEs of group #2 trigger uplink transmissions due to Trigger B received in subframe n+3. This solution avoids / prevents multiple triggers in a multi-UE environment.

[0104] FIG. 10 is a diagram of a two-stage uplink transmission procedure according to a first implementation of the embodiment already described above with respect to FIG.

[0105] In step S101, a UE (either one of the UEs in group #1 or #2) initiates two-stage uplink resource scheduling. In particular, resource scheduling is initiated by a first-stage uplink resource scheduling message of an unlicensed cell, which is received by the UE in step S102. Then, in step S103, the UE receives a second-stage uplink resource scheduling message of the unlicensed cell.

[0106] The first stage uplink resource scheduling message verification comprises step S104, in which a determination is made as to whether an uplink transmission has been triggered by another second stage uplink resource scheduling message within a period T prior to receipt of the second stage uplink resource scheduling message, whereby "period T" corresponds to the "predetermined period prior to receipt of the second stage uplink resource scheduling message" reflected in the claims, as well as the "valid time window" shown in Figures 8 and 9.

[0107] If it is determined that another uplink transmission has been performed within the period T (YES in step S104), the process proceeds to step S102 to wait for a first stage uplink resource scheduling message in the next cycle.

[0108] However, if it is determined in step S104 that no other uplink transmission is being performed within the period T ("No" in step S104), the process proceeds to step S105, where the first stage uplink resource scheduling message is determined to be valid.

[0109] Since the first stage uplink resource scheduling message is valid, the process proceeds to step S106, where the uplink transmission is scheduled, and then in step S107, the uplink transmission is actually performed.

[0110] 11 illustrates a second implementation of the embodiment in which multiple triggering of uplink transmissions in a multi-UE environment is prevented. The second implementation is an alternative to the first implementation, but instead of simply ignoring trigger A as described in the first embodiment, multiple triggering of uplink transmissions by the same UE within the valid time window of trigger A is avoided by disabling trigger A.

[0111] With reference to the scenario of FIG. 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 according to FIG. 11, the UE of group #1 may actively disable the trigger A (received in subframe n-2) in response to the reception of the trigger B in subframe n (the disablement can also be performed in subframe n+1 or n+2, but it needs to be performed 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 in the UE of group #1, since the valid time window of the trigger A does not exist anymore. In other words, in the second implementation of the embodiment, the trigger A is actively deactivated / disabled in response to the reception of the first trigger B that has already triggered an uplink transmission (or at least prior to the reception of the next trigger B). In this way, by actively disabling / clearing Trigger A, the valid time window of Trigger A is eliminated, thereby preventing unintended multiple uplink transmissions from being triggered by UEs in Group #1.

[0112] It should be noted that, overall, the second implementation of the embodiment (according to FIG. 11 ) generally differs from the first implementation (according to FIGS. 9 and 10 ) by disabling Trigger A (removing the valid time window of Trigger A) in response to an uplink transmission triggered by Trigger B, instead of simply ignoring Trigger A (ignoring the valid time window of Trigger A) in response to receiving a second Trigger B as shown in FIG. 9 .

[0113] Actively "disabling / deactivating Trigger A" may be achieved, for example, by toggling a specific bit in a field associated with deactivation / deactivation in the first stage uplink transmission resource scheduling message (Trigger A).

[0114] FIG. 12 is a diagram of a two-stage uplink transmission procedure according to a second implementation of the embodiment already described above with respect to FIG.

[0115] In step S101, a UE (either one of the UEs in group #1 or #2) initiates two-stage uplink resource scheduling. In particular, resource scheduling is initiated by a first-stage uplink resource scheduling message of an unlicensed cell, which is received by the UE in step S102. Then, in step S103, the UE receives a second-stage uplink resource scheduling message of the unlicensed cell.

[0116] The first stage uplink resource scheduling message verification consists of step S108, in which 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 (step S108: YES), the process proceeds to step S102 to wait for a first stage uplink resource scheduling message in the next cycle, or proceeds to step S103 to wait for a second stage uplink resource scheduling message.

[0117] If it is determined in step S108 that the first stage uplink resource scheduling message is not disabled (step S108: No), the process proceeds to step S105, which relates to determining that the first stage uplink resource scheduling message is valid. Then, since the first stage uplink resource scheduling message is valid, the process proceeds to step S106, which relates to the uplink transmission being scheduled. Then, in step S107, the uplink transmission is actually performed. Then, the process proceeds to step S109, which relates to the first stage uplink resource scheduling message being disabled. Then, the process proceeds to step S102, which involves waiting for the first stage uplink resource scheduling message in the next cycle, or to step S103, which involves waiting 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 is invalidated (step S109), the process proceeds from step S103 to step S108. Since the first-stage uplink resource scheduling message is determined to be invalid in step S108, the process proceeds again to step S102 or step S103 without performing uplink transmission.

[0119] This above procedure reflects the particular behavior shown in FIG. 11, where a second trigger B in subframe n+3 will not initiate another uplink transmission because trigger A has been disabled when the first trigger B triggered an uplink transmission.

[0120] In the above description of the embodiment, the two-stage uplink radio resource scheduling is described for a cell of a communication system, and such two-stage uplink radio resource scheduling is not only possible for an unlicensed cell or a licensed cell, but also for any cell that supports two-stage uplink radio resource scheduling.

[0121] According to another embodiment implemented in the context of section 8.0 of 3GPP TS 2.0, it is proposed to specify in the standard:

[0122] For a serving cell that is an LAA SCell, the UE upon detection of a PDCCH / EPDCCH with DCI format 0A / 0B / 4A / 4B and the "PUSCH trigger A" field set to "0" in subframe n intended for the UE, or in response to detection of a PDCCH / EPDCCH with DCI format 0A / 0B / 4A / 4B and with the "PUSCH trigger A" field set to "1" in the latest subframe from subframe nv for UEs that are not triggered by the "PUSCH trigger B" field set to "1" in subframe n-v+1 and subframe n-1, and detection of a PDCCH with DCI CRC scrambled with CC-RNTI and with the "PUSCH trigger B" field set to "1" in subframe n, The corresponding PUSCH transmission shall be performed in subframe n+l+k+i (i = 0, 1, ···, N-1) according to the PDCCH / EPDCCH and [···], subject to the channel access procedure described in clause 15.2.1.

[0123] Hardware and Software Implementations of the Disclosure Other exemplary embodiments relate to the implementation of the above-mentioned various embodiments by using hardware, software, or software in conjunction with hardware. In this regard, a user terminal (mobile terminal) and an eNodeB (base station) are provided. The user terminal and the base station are configured to perform the methods described herein, with corresponding entities such as receivers, transmitters, processors, etc. participating in these methods accordingly.

[0124] It is further recognized that the various embodiments may be implemented or performed using a computing device (processor). The computing device or processor may be, for example, a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic devices. The various embodiments may also be performed or embodied by a combination of these devices. In particular, each functional block used in the description of each of the above-mentioned embodiments can be realized by an LSI as an integrated circuit. These may be formed as individual chips, or a single chip may be formed to include some or all of the functional blocks. These may have data inputs and outputs coupled thereto. Here, the LSI may be referred to as an IC, a system LSI, a very large scale LSI, or an ultra-large scale LSI depending on the degree of integration. However, the technology for implementing the integrated circuit is not limited to the LSI, and may be realized by using individual circuits or a general-purpose processor. Also, a field programmable gate array (FPGA) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells arranged inside the LSI may be used.

[0125] Furthermore, the various embodiments may be implemented by means of software modules, executed by a processor or directly in hardware. A combination of software modules and hardware implementation is also conceivable. The software modules may be stored on any kind of computer-readable storage medium, for example a RAM, an EPROM, an EEPROM, a flash memory, a register, a hard disk, a CD-ROM, a DVD, etc. It is further noted that individual features of the various embodiments may also be the subject of other embodiments, either individually or in any combination.

[0126] Many variations and / or modifications of the present disclosure as illustrated in the specific embodiments will be apparent to those skilled in the art, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A radio base station, a transmitter configured to transmit to the user equipment a first stage uplink resource scheduling message indicating uplink radio resources available to the user equipment for performing uplink transmissions by the user equipment via unlicensed cells, the transmitter configured to transmit to the user equipment a second stage uplink resource scheduling message related to the first stage uplink resource scheduling message; the first stage uplink resource scheduling message is deemed valid if no uplink transmission has been triggered by another second stage uplink resource scheduling message within a predetermined period prior to transmission of the second stage uplink resource scheduling message; a receiver that performs uplink reception via the unlicensed cell if the first stage uplink resource scheduling message is valid; A wireless base station comprising:

2. if an uplink transmission is triggered by another second stage uplink resource scheduling message within the predetermined period prior to transmission of the second stage uplink resource scheduling message, the first stage uplink resource scheduling message is disabled; If the first stage uplink resource scheduling message is not invalidated, the first stage uplink resource scheduling message is considered to be valid. The radio base station according to claim 1.

3. the first stage uplink resource scheduling message is addressed to the user equipment, and the second stage uplink resource scheduling message is commonly addressed to a plurality of user equipments receiving the second stage uplink resource scheduling message; Optionally, the first stage uplink resource scheduling message is addressed to the user equipment by a user equipment specific identity employed in the transmission of the first stage uplink resource scheduling message, and the user equipment specific identity is configurable; Optionally, the second stage uplink resource scheduling message is commonly addressed to a plurality of user equipments receiving the second stage uplink resource scheduling message by a shared identity adopted in the transmission of the second stage uplink resource scheduling message, the shared identity being predefined and common to a plurality of user equipments. The radio base station according to claim 1.

4. the first stage uplink resource scheduling message specifies the predetermined period during which the first stage uplink resource scheduling message can be considered in conjunction with the transmitted second stage uplink resource scheduling message; Optionally, if the second stage uplink resource scheduling message is transmitted within the specified predetermined period after transmission of the first stage uplink resource scheduling message, the first stage uplink resource scheduling message is taken into account in conjunction with the second stage uplink resource scheduling message. The radio base station according to claim 1.

5. the first stage uplink resource scheduling message further specifies a first time offset to be taken into account when performing the uplink transmission, and the second stage uplink resource scheduling message specifies a second time offset to be taken into account when performing the uplink transmission; Optionally, said receiver performs said uplink reception after at least a sum of said first and second time offsets in response to transmission of said second stage uplink resource scheduling message. The radio base station according to claim 1.

6. the first stage uplink resource scheduling message is a downlink control information (DCI) message of format 0A, 0B, 4A, or 4B, each including a first stage flag indicating that the DCI message is a first uplink resource scheduling message of a two-stage uplink resource scheduling; Optionally, the second stage uplink resource scheduling message is a downlink control information (DCI) message of Format 1C including a second stage flag indicating that the DCI message is a second uplink resource scheduling message of a two-stage uplink resource scheduling. The radio base station according to claim 1.

7. 1. A method of operating a radio base station, comprising the steps of: transmitting a first stage uplink resource scheduling message to the user equipment indicating uplink radio resources available to the user equipment for performing uplink transmissions by the user equipment via the unlicensed cell; transmitting a second stage uplink resource scheduling message associated with the first stage uplink resource scheduling message to the user equipment; if no uplink transmission has been triggered by another second stage uplink resource scheduling message within a predetermined period prior to receipt of the second stage uplink resource scheduling message, the first stage uplink resource scheduling message is deemed valid; performing uplink reception via the unlicensed cell if the first stage uplink resource scheduling message is determined to be valid; A method comprising:

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