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] The present disclosure relates to a user equipment in which uplink radio resources are scheduled and a method of operating the user equipment.

Background Art

[0002] [Long Term Evolution (LTE)] The third-generation mobile communication system (3G) based on the WCDMA (registered trademark) radio access technology is being deployed on a wide scale worldwide. As a first step in enhancing or evolving this technology, High-Speed Downlink Packet Access (HSDPA) and Enhanced Uplink (also referred to as High-Speed Uplink Packet Access (HSUPA)) have been introduced, thereby providing a highly competitive radio access technology.

[0003] To meet the increasing demands from users and to ensure competitiveness for new radio access technologies, the 3GPP (registered trademark) introduced a new mobile communication system called Long Term Evolution (LTE). LTE is designed to provide carriers required for high-speed transmission of data and media and support for large-capacity voice over the next 10 years.

[0004] The specifications of the work item (WI) related to Long Term Evolution (LTE), which is referred to as Evolved UMTS Terrestrial Radio Access (E-UTRA) and the evolved UTRAN (UMTS Terrestrial Radio Access Network), 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 all IP-based functions with low latency and low cost. In LTE, scalable multiple transmission bandwidths (e.g., 1.4 MHz, 3.0 MHz, 5.0 MHz, 10.0 MHz, 15.0 MHz, and 20.0 MHz) are specified to achieve flexible system deployment using a given spectrum. For the downlink, a radio access based on Orthogonal Frequency Division Multiplexing (OFDM) is adopted. This is because such a radio access is essentially less susceptible to Multipath Interference (MPI) due to its low symbol rate, uses a Cyclic Prefix (CP), and can also support various transmission bandwidth configurations. For the uplink, a radio access based on Single-Carrier Frequency Division Multiple Access (SC-FDMA) is adopted. This is because considering the limited transmission output of the User Equipment (UE), providing a wider coverage area is prioritized over improving the peak data rate. In LTE Rel.8 / 9, many major packet radio access technologies (e.g., Multiple Input Multiple Output (MIMO) channel transmission technology) are adopted, and a highly efficient control signaling structure is achieved.

[0005] [LTE Architecture] Figure 1 shows the overall architecture of LTE. E-UTRAN consists of eNodeBs, and an eNodeB terminates the user plane (PDCP / RLC / MAC / PHY) protocol and the control plane (RRC: Radio Resource Control) protocol of E-UTRA for user equipment (UE). An eNodeB (eNB) hosts the physical (PHY) layer, the medium access control (MAC) layer, the radio link control (RLC) layer, and the packet data control protocol (PDCP) layer (these layers include functions for header compression and encryption of the user plane). The eNB also provides the radio resource control (RRC) function corresponding to the control plane. The eNB performs many functions such as radio resource management, admission control, scheduling, implementation of uplink quality of service (QoS) through negotiation, broadcast of cell information, encryption / decryption of user plane data and control plane data, compression / decompression of downlink / uplink user plane packet headers, etc. Multiple eNodeBs are connected to each other by the X2 interface.

[0006] In addition, multiple eNodeBs are connected to the EPC (Evolved Packet Core) via the S1 interface, more specifically, to the MME (Mobility Management Entity) 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, functions as a user plane mobility anchor during handover between eNodeBs, and further functions as an anchor for mobility between LTE and another 3GPP technology (terminating the S4 interface and relaying traffic between the 2G / 3G system 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 context of the user equipment (e.g., parameters of IP bearer services or internal network routing information). Further, 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. The MME is responsible for the tracking and paging procedures (including retransmission) of idle-mode user equipment. The MME is involved in the bearer activation / deactivation process and also selects the SGW of the user equipment at the first attach and during LTE intra-handover with relocation of core network (CN) nodes. The MME authenticates the user (by interacting with the HSS). The non-access stratum (NAS) signaling is terminated at the MME. The MME also generates and assigns a temporary ID to the user equipment. The MME checks the authentication of the user equipment for entry into the public land mobile network (PLMN) of the service provider and enforces the roaming restrictions of the user equipment. The MME is the network termination point in the encryption / integrity protection of NAS signaling and manages the security keys. Signaling eavesdropping is also supported by the MME. In addition, the MME provides control plane functions for mobility between the LTE access network and 2G / 3G access networks, terminating the S3 interface from the SGSN at the MME. Furthermore, the MME terminates the S6a interface towards 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 Figure 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 extends over 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 a resource grid of N DL RB ×N RB sc subcarriers of this book and N DL symb 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 a normal cyclic prefix subframe structure, N RB sc = 12, N DL symb = 7.

[0009] For example, assuming a multi-carrier communication system that uses OFDM used in 3GPP Long Term Evolution (LTE), the minimum unit of resources that can be allocated by a scheduler is one "resource block". A physical resource block (PRB) is defined as a continuous OFDM symbol in the time domain (e.g., 7 OFDM symbols) and a continuous sub-carrier in the frequency domain (e.g., 12 sub-carriers 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 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] One subframe consists of two slots. When the so-called "normal" CP (Cyclic Prefix) is used, there are 14 OFDM symbols in a subframe, and when the so-called "extended" CP is used, there are 12 OFDM symbols in a subframe. For the purpose of terminology, hereinafter, a time-frequency resource equivalent to the same continuous subcarriers spreading over the entire subframe is referred to as a "resource block pair" or an equivalent "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, and instead, this terminology will be changed to a "cell" that represents a combination of downlink resources and optionally uplink resources. The linking between the carrier frequency of the downlink resource and the carrier frequency of the uplink resource is indicated in the system information transmitted in the downlink resource.

[0011] Similar assumptions regarding the structure of component carriers also apply to subsequent releases.

[0012] [Carrier Aggregation in LTE-A for Support of Wider Bandwidth] The frequency spectrum of IMT-Advanced was determined at the World Radio communication Conference 2007 (WRC-07). Although the overall frequency spectrum for IMT-Advanced has been determined, the actually available frequency bandwidth varies by region or country. However, following the determination of the outline of the available frequency spectrum, the standardization of radio interfaces has started in the 3rd Generation Partnership Project (3GPP).

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

[0014] In carrier aggregation, two or more component carriers are aggregated for the purpose of supporting a wider transmission bandwidth of up to 100 MHz. In an LTE-Advanced system, several cells in an LTE system are aggregated into one wider channel. This channel 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 as long as the bandwidth of at least the component carriers does not exceed the supported bandwidth of an LTE Rel.8 / 9 cell. Not all component carriers aggregated by a user equipment necessarily have to be Rel.8 / 9 compatible. Existing mechanisms (such as barring) may be used to avoid Rel.8 / 9 user equipment camping on a component carrier.

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

[0016] Carrier aggregation is supported in both continuous component carriers and discontinuous 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 different numbers of component carriers with different bandwidths, possibly 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 to have 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 downlink. Component carriers transmitted from the same eNodeB do not need to provide the same coverage.<UNK>

[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) while maintaining the orthogonality of the 15 kHz spaced subcarriers. Depending on the aggregation scenario, it is possible to facilitate an interval of n×300 kHz by inserting a small number of unused subcarriers between consecutive component carriers.

[0019] The impact of aggregating multiple carriers only reaches the MAC layer. In the MAC layer, for both the uplink and the downlink, one HARQ entity is required for each component carrier to be aggregated. The number of transport blocks per component carrier is at most one (when SU-MIMO is not used 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] In addition to configuring and reconfiguring component carriers, RRC can also perform addition and deletion. Activation and deactivation are performed, for example, via MAC control elements. In an intra-LTE handover, RRC can also add, delete, or reconfigure SCell to be used in the target cell. When adding a new SCell, individual RRC signaling is used to transmit the system information of the SCell required for transmission / reception (similar to the handover in Release 8 / 9). When an SCell is added to a UE, a serving cell index is set for each SCell. The serving cell index of the PCell is always 0.

[0022] When carrier aggregation is configured for a user equipment, there is always at least one pair of uplink and downlink component carriers that are active. The pair of downlink component carriers may be referred to as "DL anchor carrier". The same applies to the uplink. When carrier aggregation is configured, the user equipment may be scheduled simultaneously on multiple component carriers, but it is assumed that there is at most one ongoing random access procedure. According to cross-carrier scheduling, the PDCCH of a component carrier can schedule resources on another component carrier. Therefore, in each DCI (downlink control information) format, a component carrier identification field called CIF is introduced.

[0023] According to the link between the uplink and downlink component carriers established by RRC signaling, it is possible to identify an uplink component carrier to which a grant is applied when cross-carrier scheduling does not exist. The link from a downlink component carrier to an uplink component carrier does not necessarily have to be one-to-one. In other words, two or more downlink component carriers can be linked to the same uplink component carrier. On the other hand, only one downlink component carrier can be linked 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 UEs and between 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 considering the QoS requirements of each configured radio bearer.

[0025] The general scheduling mode is dynamic scheduling by a downlink grant / assignment message (DCI) that allocates downlink transmission resources and an uplink grant / assignment message that allocates 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 enables the quasi-static setting of radio resources and the allocation to a UE over a period longer than one subframe, obviating the need for a specific downlink assignment message or uplink grant message on the PDCCH for each subframe. In the case of setting or re-setting persistent scheduling, RRC signaling specifies the resource allocation interval in which radio resources are periodically allocated. When PDCCH is used for setting or re-setting persistent scheduling, it is necessary to identify the scheduling message applicable to persistent scheduling from the scheduling messages used for dynamic scheduling. For this purpose, special scheduling identification information known as the semi-persistent scheduling C-RNTI (SPS-C-RNTI) is used, which is different for each UE from the C-RNTI used for messages of dynamic scheduling.

[0026] For the purpose of notifying the user to be scheduled of the user's allocation status, transport format, and other transmission-related information (e.g., HARQ information, transmit power control (TPC) commands), L1 / L2 control signaling is transmitted in the downlink together with data. The L1 / L2 control signaling is multiplexed with the downlink data within a subframe (assuming that the user allocation can change on a subframe-by-subframe basis). Note that the user allocation 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 be different for different users, or may be dynamic for each user. Generally, the L1 / L2 control signaling may be transmitted once per TTI. Hereinafter, without loss of generality, it is assumed that the TTI is equal to one subframe.

[0027] The L1 / L2 control signaling is transmitted on the physical downlink control channel (PDCCH). The PDCCH conveys a message as downlink control information (DCI). The DCI generally contains resource allocation and other control information for a mobile terminal or a group of UEs. Generally, multiple PDCCHs can be transmitted within one subframe.

[0028] Downlink control information takes several formats, which differ in overall size and the information contained in each field. The various DCI formats currently defined 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 detailed information on DCI formats and the specific information transmitted in DCI, refer to the aforementioned technical standard or Non-Patent Document 3 incorporated herein by reference. In the future, there may be other formats defined.

[0029] [Layer 1 / Layer 2 control signaling] For the purpose of notifying the user to be scheduled of the user's allocation status, transport format, and other transmission-related information (e.g., HARQ information, Transmit Power Control (TPC) command), L1 / L2 control signaling is transmitted on the downlink together with data. L1 / L2 control signaling is multiplexed with downlink data within a subframe (assuming that the user allocation can change on a subframe-by-subframe basis). It is also possible to perform user allocation on a TTI (Transmission Time Interval) basis. In that 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 be different for different users, or may be dynamic for each user. Generally, L1 / L2 control signaling may be transmitted once per TTI. Hereinafter, 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 conveys a message as Downlink Control Information (DCI). DCI typically includes resource allocation for a mobile terminal or a group of UEs and other control information. Generally, multiple PDCCHs can be transmitted within one subframe.

[0031] In 3GPP LTE, note that the allocation for uplink data transmission, also referred to as uplink scheduling grant or uplink resource allocation, is also transmitted on the PDCCH. Furthermore, in 3GPP Release 11, an EPDCCH was introduced that basically serves the same function as the PDCCH. That is, although the detailed transmission method is different from that of the PDCCH, L1 / L2 control signaling is carried. Further details can be found in the current versions of Non-Patent Document 1 and Non-Patent Document 4, which are hereby incorporated by reference. As a result, most of the 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, the information sent by L1 / L2 control signaling for the purpose of allocating uplink radio resources or downlink radio resources (especially in LTE(-A) Release 10) can be classified 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)) allocated to the user. Alternatively, this information is referred to as Resource Block Assignment (RBA). Note that the number of RBs allocated to the user can be dynamic. - Carrier indicator: Used when the control channel transmitted on the first carrier allocates resources related to the 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 a new data indicator (NDI: New Data Indicator) and / or redundancy version (RV: Redundancy Version), which is particularly useful when retransmitting a data packet or a part thereof. - Power control command: Adjusts the transmission power when transmitting uplink data or control information to be allocated. - Reference signal information: Applied cyclic shift and / or orthogonal cover code (OCC) index used for transmitting or receiving the reference signal to be allocated, etc. - Uplink allocation index or downlink allocation index: Used to identify the order of allocation and is particularly useful in a TDD system. - Hopping information: For example, information indicating whether to apply resource hopping for the purpose of increasing frequency diversity and how to apply it. - 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 to perform transmission in a single cluster (a continuous set of RBs) or in a multi-cluster (at least two discontinuous sets of continuous RBs). Multi-cluster allocation was introduced in 3GPP LTE-(A) Release 10.

[0033] Note that the above list does not cover everything, 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 several formats, which differ in overall size and the information contained in the fields described above. Some of the currently defined DCI formats for LTE are listed below. For more detailed information, see, in particular, section 5.3.3.1, “DCI formats” of Non-Patent Document 5, which is hereby incorporated by reference into this specification. - Format 0: DCI format 0 is used for transmitting resource grants for 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 for single-codeword PDSCH transmission (downlink transmission modes 1, 2, and 7). - Format 1A: DCI format 1A is used for compact signaling of resource allocations for single-codeword PDSCH transmission 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 allocations for PDSCH transmission using closed-loop precoding for rank 1 transmission (downlink transmission mode 6). The information transmitted is the same as that of 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 transmission of PDSCH allocations. 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 using multi-user MIMO. The information transmitted is the same as that in Format 1B, but instead of one of the bits of the precoding vector indicator, there is a single bit indicating whether a power offset is applied to the data symbols. This feature is necessary to indicate whether the transmission power is shared between two UEs. This may be extended to cases of power sharing among more UEs in future versions of LTE. - Format 2: DCI Format 2 is used for transmission of resource allocation of PDSCH related to closed-loop MIMO operation (transmission mode 4). - Format 2A: DCI Format 2A is used for transmission of resource allocation of PDSCH related to open-loop MIMO operation. The information transmitted is the same as that in Format 2, but there is no precoding information when the eNodeB has two transmit antenna ports, and two bits are used to indicate the transmission rank when there are four antenna ports (transmission mode 3). - Format 2B: Introduced in Release 9, it is used for transmission of resource allocation of PDSCH related to dual-layer beamforming (transmission mode 8). - Format 2C: A format introduced in Release 10, it is used for transmission of resource allocation of PDSCH related to closed-loop single-user or multi-user MIMO operation with up to 8 layers (transmission mode 9). - Format 2D: A format introduced in Release 11, it is used for transmission with up to 8 layers and is mainly used for COMP (Cooperative Multipoint) (transmission mode 10). - Formats 3 and 3A: DCI Formats 3 and 3A are used for transmission of 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 UE groups. - Format 4: DCI Format 4 is used for the scheduling of PUSCH using closed-loop spatial multiplexing transmission in uplink transmission mode 2. - Format 5: DCI Format 5 is used for the scheduling of PSCCH (Physical Sidelink Control Channel) and includes multiple SCI Format 0 fields used for the scheduling of PSSCH (Physical Sidelink Shared Channel). When the number of information bits of DCI Format 5 mapped to a given search space is smaller than the payload size of Format 0 that schedules the same serving cell, zeros shall be added to Format 5 until the payload size becomes equal to the payload size of Format 0 including the padding bits added to Format 0.

[0035] [Unlicensed Band LTE-Licensed Assisted Access (LAA)] In September 2014, 3GPP initiated a new research item on LTE operation in unlicensed spectrum. The reason for extending LTE to the unlicensed band is that the demand for wireless broadband data is increasing steadily along with the limited amount of licensed band. Therefore, cellular operators are considering the unlicensed spectrum more as a complementary tool for expanding service provision. One advantage of LTE in the unlicensed band compared to reliance on other radio access technologies (RATs) such as Wi-Fi is that by complementing the LTE platform with unlicensed spectrum access, operators and suppliers can utilize existing or planned investments in LTE / EPC hardware for the radio core network.

[0036] However, since coexistence with other radio access technologies (RATs) in unlicensed spectra such as Wi-Fi is essential, it is necessary to consider that the quality of unlicensed spectrum access and licensed spectrum access may not match. Therefore, at least initially, LTE operation in the unlicensed band is considered not as a standalone operation in the unlicensed spectrum, but as a complement to LTE on the licensed spectrum. Based on this assumption, 3GPP established the term Licensed Assisted Access (LAA) for LTE operation in the unlicensed band in conjunction with at least one licensed band. However, future standalone operation of LTE without assistance from the licensed spectrum, i.e., on the unlicensed spectrum, is not excluded. Extended Licensed Assisted Access (eLAA) is an extension of LAA that also utilizes the unlicensed spectrum, particularly in the uplink. Efficient use of the unlicensed spectrum as a complement to the licensed spectrum can bring significant value to service providers and thus to the wireless industry as a whole. To fully benefit from LTE operation in the unlicensed spectrum, in addition to the already defined DL access method, it is most important to define a complete UL access method.

[0037] In the general LAA approach currently planned in 3GPP, the already implemented Rel.12 carrier aggregation (CA) framework is utilized as much as possible. The aforementioned CA framework configuration includes a so-called primary cell (PCell) carrier and one or more secondary cell (SCell) carriers. CA generally supports both intra-cell self-scheduling (where scheduling information and user data are transmitted on the same component carrier) and inter-cell cross-carrier scheduling (where scheduling information regarding PDCCH / EPDCCH and user data regarding 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 (illustrated as small cells). As the transmission / reception network nodes for the unlicensed SCell2, 3, and 4, it is possible to have a remote radio head managed by the eNB, or a node that is attached to the network but not managed by the eNB. For simplicity, in the figure, the connection of these nodes to the eNB or the network is not explicitly shown.

[0039] Currently, as a basic approach assuming 3GPP, the PCell operates in a licensed band while one or more SCells operate in an unlicensed band. One advantage of this method is that the PCell can be used to reliably transmit control messages and user data that require high service quality (QoS), such as voice or video. However, for SCells in the unlicensed spectrum, depending on the scenario, there may be a certain degree of QoS degradation due to the indispensability of coexistence with other RATs.

[0040] LAA has agreed to focus on the unlicensed bands at 5 GHz. Therefore, one of the most important issues is coexistence with Wi-Fi (IEEE 802.11) systems operating in these unlicensed bands. In addition to fair coexistence with other technologies such as LTE and Wi-Fi, in order to support fairness among different LTE operators in the same unlicensed band, depending on the region and specific frequency bands, a specific set of regulatory rules that may be partly determined by the region and specific frequency bands are required to comply with LTE channel access in the unlicensed band. For a comprehensive description of the regulatory requirements for all regions in the case of operation in the 5 GHz unlicensed band, in addition to Non-Patent Document 6 (incorporated herein by reference), it is described in Non-Patent Document 7. Depending on the region and band, the regulatory requirements to be considered in the design of the LAA procedure include dynamic frequency selection (DFS), transmit power control (TPC), listen before talk (LBT), and discontinuous transmission with a limited maximum transmission duration. The objective of 3GPP is to target a single global framework for LAA, which basically means that all requirements regarding various regions and bands at 5 GHz need to be considered in the system design.

[0041] For example, in Europe, specific restrictions on the nominal channel bandwidth are set, as is clear 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 assigned to a single channel. The occupied channel bandwidth is the bandwidth that includes 99% of the power of the signal. The device can operate simultaneously in one or more adjacent or non-adjacent channels.

[0042] The Listen Before Talk (LBT) procedure is defined as a mechanism for a device to apply a Clear Channel Assessment (CCA) check before using a channel. In CCA, at least energy detection is used 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 way for fair sharing of the unlicensed spectrum, and thus is considered an essential feature for fair and friendly operation in the unlicensed spectrum in a single global solution framework.

[0043] In the unlicensed spectrum, channel availability is not always guaranteed. Also, in certain regions such as Europe and Japan, continuous transmission in the unlicensed spectrum is prohibited, and a limit is set on the maximum duration of a transmission burst. Therefore, discontinuous transmission with a limited maximum transmission duration is a necessary function of LAA. To detect interference from radar systems and avoid co-channel operation with these systems, Dynamic Frequency Selection (DFS) is required in certain regions and bands. The intention is further to achieve a load closer to uniform in the spectrum. DFS operation and the corresponding requirements are associated with the master-slave principle. The master is assumed to detect radar interference, but it is possible to perform radar detection relying on another device associated with the master.

[0044] In most regions, operation on the 5GHz unlicensed band is restricted to lower transmission power levels than operation on the licensed band, resulting in a smaller coverage area. Even if the licensed carrier and the unlicensed carrier transmit at the same power, typically, due to increased path loss and shadowing effects of the signal, the unlicensed carrier in the 5GHz band is expected to support a smaller coverage area than the licensed cell in the 2GHz band. As another requirement for a specific region and band, there is the use of TPC to suppress the average level of interference that occurs when other devices operate in the same unlicensed band.

[0045] Detailed information can be found in Non-Patent Document 8, which is hereby incorporated by reference into this specification.

[0046] The device needs to perform a Clear Channel Assessment (CCA) before occupying the wireless channel for data transmission in accordance with European regulations regarding LBT. For example, transmission on the unlicensed channel can only be started after detecting that the channel is idle based on energy detection. In particular, the device needs to observe the channel for a certain minimum time (e.g., 20μs in the case of Europe, see Section 4.8.3 of Non-Patent Document 8) during CCA. The channel is considered to be occupied if the detected energy level exceeds the set threshold of CCA (e.g., -73dBm / MHz in the case of Europe, see Section 4.8.3 of Non-Patent Document 8). Conversely, if the detected power level is below the set threshold of CCA, it is considered to be idle. If the channel is determined to be occupied, transmission on the channel in the next fixed frame period shall not be performed. When the channel is classified as idle, the device can transmit immediately. This restricts 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 across the entire channel bandwidth (e.g., 20 MHz in the 5 GHz unlicensed band). This means that the received power levels of all subcarriers of the LTE OFDM symbols within the channel contribute to the energy level evaluated by the device that performs CCA.

[0048] In addition to the above-mentioned CCA, when the device is classified as a load-based equipment (LBE) according to the description in Section 4.9.2.2 of Non-Patent Document 8 incorporated herein by reference, another extended CCA (ECCA) may be required. ECCA includes another CCA observation time over a duration obtained by multiplying the CCA observation time slot by a random coefficient N. N defines the number of clear idle slots that is the total idle period to be observed before the start of transmission.

[0049] Furthermore, the total time for the device to transmit on a given carrier without re-evaluating the channel availability (i.e., LBT / CCA) is defined as the channel occupancy time (see Section 4.8.3.1 of Non-Patent Document 8). The channel occupancy time ranges from 1 ms to 10 ms. However, as currently defined in Europe, the maximum channel occupancy time can also be, for example, 4 ms. Additionally, there is also a minimum idle time after which the UE cannot transmit 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 or the like. This transmission behavior is schematically shown in FIG. 5, which is derived from Non-Patent Document 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 specific frequency band (unlicensed cell). As can be seen from Figure 5, at least a CCA gap is required after a Wi-Fi burst before the eNB "reserves" the unlicensed cell by transmitting a reservation signal until, for example, the next subframe boundary. Thereafter, the actual LAA DL burst starts. This also applies to an LTE UE that reserves a subframe by transmitting a reservation signal after successful execution of CCA and starting the actual LAA UL burst.

[0051] [Uplink Scheduling in Unlicensed Cell] For eLAA, DCI formats 0A, 0B, 4A, and 4B are provided to support single subframe and multiple subframe grants as well as uplink transmissions (PUSCH) for each single and multiple antenna ports. · 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 a current exemplary embodiment in LTE (see Non-Patent Document 5), it is reflected by a 1-bit field "PUSCH Trigger A" that distinguishes whether the received uplink grant is for "non-triggered scheduling" (i.e., single-stage uplink grant) when the bit value is 0, or for "triggered scheduling" (i.e., two-stage uplink grant) when the bit value is 1. This is controllable by the eNB, which is a radio network entity responsible for scheduling radio resources for the UE.

[0053] In the two-stage uplink scheduling procedure, it is necessary to schedule one uplink transmission by the UE receiving two separate messages ("Trigger A" and "Trigger B") in a specific manner.

[0054] As the Trigger A message, any of the above uplink grants (i.e., DCI formats 0A, 0B, 4A, or 4B) is possible. Regarding 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 defined in Section 8.0 of [3], a value of 0 indicates non-triggered scheduling, and a value of 1 indicates triggered scheduling. - Timing offset (4 bits): As defined in [3]. - When the flag for triggered scheduling is set to 0, - This field indicates the absolute timing offset of PUSCH transmission. - Otherwise, - The first two bits of this field indicate the relative timing offset of PUSCH transmission. - The last two bits of this field indicate the time window during which PUSCH scheduling by trigger scheduling is valid.

[0056] In addition, the DCI formats available for the trigger A message include normal data fields indicating the radio resources scheduled for uplink transmission, such as the "resource block allocation" field, the "modulation and coding scheme" field, and the "HARQ process number" field. Further, DCI formats 0A, 0B, 4A, and 4B (especially DCI CRC) can be scrambled by UE-specific identification information (such as C-RNTI) so that the corresponding uplink grant can be addressed to a specific UE.

[0057] The trigger B message has a DCI format 1C as currently defined in Section 5.3.3.1.4 of Non-Patent Document 5 incorporated herein by reference. The DCI format 1C currently defined in the technical standard used within the scope of unlicensed carrier transmission including a two-step grant procedure is as follows.

[0058] "Otherwise - LAA subframe configuration (4 bits): Specified in Section 13A of [3]. - Uplink transmission duration and offset specification (5 bits): Specified in Section 13A of [3]. This field only applies to UEs with uplink transmission configured on the LAA SCell. - PUSCH trigger B (1 bit): Specified in Section 8.0 of [3]. This field only applies to UEs with uplink transmission configured on the LAA SCell. - Reserved information bits are added until it is equal to the size of format 1C used for very compact scheduling of one PDSCH codeword.

[0059] As described above, the trigger B message (DCI format 1C) when used as part of the two-stage grant procedure is typically not addressed to a specific UE, but rather the DCI format 1C, in particular its CRC, can be scrambled by the use of shared identification information by the eNB (in this case, the CC-RNTI (common control RNTI) which is the RNTI used in the situation providing common control PDCCH information (see Non-Patent Document 9 incorporated herein by reference)).

[0060] The cross-reference "[3]" in the above citation of Non-Patent Document 5 represents Non-Patent Document 4, and since at least Sections 8.0 and 13 thereof are related to the two-stage grant, all of it is incorporated herein by reference.

[0061] In particular, Section 8 of Non-Patent Document 4 more specifically defines the execution timing and method of uplink transmission (i.e., PUSCH) for the LAA SCell.

[0062] "For the serving cell that is an LAA SCell, the UE - in subframe n targeted at the UE, in response to the detection of PDCCH / EPDCCH in which the "PUSCH trigger A" field is set to "0" in DCI format 0A / 0B / 4A / 4B, or - in the most recent subframe from subframe n-v targeted at the UE, in response to the detection of PDCCH / EPDCCH in which the "PUSCH trigger A" field is set to "1" in DCI format 0A / 0B / 4A / 4B and the detection of PDCCH in which the DCI CRC is scrambled by the CC-RNTI and the "PUSCH trigger B" field is set to "1" in subframe n, - PDCCH / EPDCCH and HARQ process ID mod(n HARQ_ID +i,N HARQIn accordance with , in subframe n + l + k + i (i = 0, 1, ···, N - 1), the corresponding PUSCH transmission is performed on the condition of the channel access procedure described in Section 15.2.1. Here, - In the case of 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. - For the UE, the maximum value of N is set by the higher layer parameter maxNumberOfSchedSubframes-Format0B in the case of DCI format 0B and the higher layer parameter maxNumberOfSchedSubframes-Format4B in the case of 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 when 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, and N HARQ = 16. - When 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 configuration for LAA" field in the corresponding DCI in which the CRC is scrambled by the 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 of DCI format 0A / 0B / 4A / 4B in which the "PUSCH trigger A" field is set to "1" according to Table 8.2f, - The minimum value of l + k supported by the 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 execute the two-stage grant procedure. However, it should be noted that the above-mentioned provisions of the two-stage grant procedure currently standardized are still subject to continuous changes and improvements, and may change in the future. As a result, the above-cited implementation form of the two-stage grant procedure according to the current 3GPP technical standard is only an exemplary implementation form, and many details are considered not important for the present invention.

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

[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 formats 0A, 0B, 4A, and 4B in Non-Patent Document 5 and Table 8.2f of Non-Patent Document 4.

[0066] When the trigger B message is received in subframe n, the UE determines whether the related trigger A message has been received by the UE within the time window of length v (starting immediately before the reception of the trigger B message, i.e., in the range of n-1 to n-v). In the illustrated scenario, since the trigger A scheduling message has been received within subframe n-3 and thus within the time window, uplink transmission is triggered in the UE. Then, with a specific transmission timing offset, uplink transmission (i.e., PUSCH) is performed in subframe n + offset. The UE may perform uplink transmission in accordance with the information received in the trigger A message and the trigger B message, for example, using the specified radio resources and modulation and coding schemes.

[0067] In the present invention, an exact PUSCH timing offset is not important. As an example, as currently standardized in Non-Patent Document 4, the PUSCH timing offset is "l + k + i". Here, parameter l is defined by a trigger B message (see the "uplink transmission duration and offset specification" field of DCI format 1C in Table 13A-2 of Non-Patent Document 5 and Non-Patent Document 4), and parameter k is defined by a trigger a message (see the first 2 bits of the "timing offset" field in any of DCI formats 0A, 0B, 4A, and 4B in Table 8.2e of Non-Patent Document 5 and Non-Patent Document 4). Parameter i is applicable when a plurality of uplink subframes are scheduled by a two-stage uplink scheduling procedure. In this case, it moves from 0 to (the number of permitted subframes - 1) (otherwise it remains 0). More specifically, it can be derived from the above-cited item 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 defined differently or may be predetermined.

[0068] As described above, 3GPP has defined a two-stage scheduling procedure for uplink transmission in an unlicensed cell. However, this two-stage scheduling procedure can be further improved.

Prior Art Documents

Non-Patent Documents

[0069]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

[0070] Non - limiting and exemplary embodiments provide an improved method and user equipment involved in the scheduling of uplink transmissions performed by a user equipment.

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

[0072] According to one general aspect, a user equipment for which uplink radio resources are scheduled is described. A cell is 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 includes a receiver that receives from the radio base station a first-stage uplink resource scheduling message indicating uplink radio resources available for use by the user equipment to perform uplink transmission via the scheduled cell. The receiver further receives from the radio base station a second-stage uplink resource scheduling message associated with the first-stage uplink resource scheduling message. The user equipment further includes a processor that determines whether the first-stage uplink resource scheduling message is valid. When the processor receives the second-stage uplink resource scheduling message and determines that the first-stage uplink resource scheduling message is valid, the processor determines that uplink transmission is scheduled. Thereby, the determination of whether the first-stage uplink resource scheduling message is valid is based on a determination as to whether uplink transmission has been 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. When the processor determines that uplink transmission is scheduled, the user equipment further includes a transmitter that performs uplink transmission via the scheduled cell. The cell can be, for example, an unlicensed cell in the context of 3GPP LTE Release 14, or another cell that supports two-stage scheduling.

[0073] Correspondingly, in another general aspect, the technology disclosed herein features a method of operating a user equipment in 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 receiving, from the radio base station, a first-stage uplink resource scheduling message indicating uplink radio resources available for the user equipment to use for performing uplink transmission via the unlicensed cell. The method further includes receiving, from the radio base station, a second-stage uplink resource scheduling message associated with the first-stage uplink resource scheduling message. The method further includes determining whether the first-stage uplink resource scheduling message is valid. The method further includes, when the second-stage uplink resource scheduling message is received and when it is determined that the first-stage uplink resource scheduling message is valid, determining that uplink transmission has been scheduled. Thereby, the determination of whether the first-stage uplink resource scheduling message is valid is based on a determination as to whether uplink transmission has been 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. The method further includes performing uplink transmission via the unlicensed cell when it is determined that uplink transmission has been scheduled.

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

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

[0076] Hereinafter, exemplary embodiments will be described in more detail with reference to the accompanying drawings.

Brief Description of the Drawings

[0077]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0078] A mobile station, mobile node, user terminal, or user equipment is a physical entity within a communication network. One node may have multiple functional entities. A functional entity represents a software or hardware module that implements a predetermined set of functions and / or provides services to other functional entities of the node or network. The 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 a logical interface that connects the functional entity to communication facilities or media that enable communication with other functional entities or corresponding nodes.

[0079] The term "radio resource" used in a set of claims and in the present application is to be broadly understood as representing a physical radio resource such as a time-frequency radio resource.

[0080] The term "unlicensed cell" or "unlicensed carrier" used in a set of claims and in the present application is to be broadly understood as a cell / carrier operating in an unlicensed frequency band of a specific frequency bandwidth. Correspondingly, the term "licensed cell" or "licensed carrier" used in a set of claims and in the present application is to be broadly understood as a cell / carrier operating in a licensed frequency band of a specific frequency bandwidth. By way of example, these terms are to be understood in the context of 3GPP Release 12 / 13 and the Licensed-Assisted Access work item.

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

[0082] Assume that trigger A, which is the first-stage uplink resource scheduling message, is transmitted from the eNodeB to the UE of group #1 in subframe n-2. In this exemplary case, the valid time window of trigger A transmitted to the UE of group #1 is 5 subframes. Therefore, the information regarding the valid time window is given by trigger A itself.

[0083] Further assume that trigger B, which is the second-stage uplink resource scheduling message, is transmitted from the eNodeB in subframe n. Trigger B is received by both UEs of groups #1 and #2, and the eNodeB transmits trigger B with the same intention as the second-stage uplink resource scheduling message for trigger A (as the first-stage uplink resource scheduling message) that has been transmitted to the UE of group #1 in subframe n-2. In this exemplary case, assume that the UE of group #2 has not received any trigger A within the corresponding valid time window before trigger B. In response to the reception of trigger B, all UEs capable of receiving trigger B (generally including the UEs of group #1 and group #2) need to check whether they have received trigger A within the corresponding valid time window. Therefore, in this example, the UE of group #1 checks whether it has received trigger A up to 5 subframes earlier (in this case, in subframes n-5 to n-1). Since trigger A has been received in subframe n-2 within the valid time window, the UE of group #1 will trigger an uplink transmission later.

[0084] Since the UE of group #2 has not received trigger A, the trigger B received in subframe n does not trigger an uplink transmission by the UE of group #2.

[0085] As is further apparent from FIG. 8, the UEs in group #2 receive trigger A in subframe n+1. In this exemplary case, the valid time window of trigger A transmitted to the UEs in group #2 is three subframes. As further shown in this 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 in groups #1 and #2. However, the eNodeB transmits the second trigger B with the same intention as the second uplink resource scheduling message for trigger A (as the first stage uplink resource scheduling message) transmitted to the UEs in group #2 in subframe n+1. In response to the reception of trigger B, the UEs in 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 has been received in subframe n+1 within the valid time window, the UEs in group #2 will trigger an uplink transmission later.

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

[0087] Overall, such multiple triggers for uplink transmission are undesirable in a multi-UE environment. As a first reason, such undesirable uplink transmission bears the risk of causing interference with other transmissions in the corresponding subframe. As a second reason, such multiple triggers may imply a collision of UL transmissions. When a UE in Group #1 is triggered to perform UL transmission by Trigger B in subframe n, the corresponding UL transmission is shown to continue over four subframes as triggered by Trigger A, and this corresponding UL transmission occurs, for example, in subframes n+2 to n+5. When the same UE in Group #1 is triggered again to perform UL transmission by Trigger B in subframe n+3, the corresponding UL transmission is also shown to continue over four subframes as triggered by the same Trigger A, and this corresponding UL transmission occurs, for example, in subframes n+5 to n+8. Thus, as shown, a collision occurs in subframe n+5 due to these two triggers, but it is not clear whether the 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 generally include different transport blocks or packets. Such a collision should be avoided because it may cause a misunderstanding between the UE and the eNodeB.

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

[0089] In the broad specifications given by the 3GPP standards and partly described in the background art section, specific implementations of various embodiments are realized, and as described below regarding the various implementations of this embodiment, specific important features are added thereto. This embodiment may be conveniently used, for example, in a mobile communication system such as the 3GPP LTE-A (Release 10 / 11 / 12 / 13 and later) communication system described in the background art 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 the present disclosure, but is merely an example of embodiments 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 the set of claims and the description in the summary section of this specification can be applied to different scenarios in ways not explicitly described below. For purposes of illustration and explanation, some assumptions are introduced, but these are not intended to unduly limit the scope of the following embodiments.

[0091] Furthermore, as described above, the following embodiments may be implemented in an environment of 3GPP LTE-A (since Rel. 12 / 13). According to various embodiments, mainly, the uplink transmission method can be improved. However, for other functions (i.e., functions that do not change according to various embodiments), they may be exactly the same as those described in the background art section, or may be changed without affecting various embodiments. For example, the actual execution of uplink transmission (e.g., splitting, modulation, coding, beamforming, multiplexing) and the methods of scheduling (PDCCH, DCI, cross-carrier scheduling, self-scheduling) or the execution of normal uplink transmission timing using timing advance procedures (e.g., initial timing advance, timing advance update command).

[0092] Hereinafter, a general embodiment for solving the above problem will be described in detail. For this description, the following exemplary scenarios devised to easily explain the principles of this embodiment will be used. However, these principles are also applicable to other scenarios, and some of them will be explicitly described below.

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

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

[0095] Thereafter, when the 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, the processor determines that uplink transmission has been scheduled.

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

[0097] According to the main principle of the present invention described above, it is convenient because it is possible to prevent a plurality of uplink transmission triggers in a multi-UE environment. By trigger B for different UEs, there is no risk that a second uplink transmission by a specific UE that has already triggered an uplink transmission in the past within the effective time window is unintentionally triggered. Therefore, even within a predetermined period / effective time window, the eNodeB can directly transmit a new trigger A to a different UE immediately after transmitting trigger B.

[0098] By this means, it is possible to significantly improve the throughput of the user / cell. Furthermore, by avoiding a plurality of uplink transmission triggers, the long verification time indicated by trigger A can be used more efficiently, so that the overhead of the necessary trigger A can be reduced.

[0099] Also, there will be no incorrect PUSCH transmission due to a false alarm of the second trigger B after the correct first trigger B within the verification time / effective time window. Thus, it is convenient because error cases due to the false alarm trigger B are avoided.

[0100] FIG. 9 shows a first implementation form of an embodiment in which a plurality of triggers for uplink transmission in a multi-UE environment are prevented.

[0101] Figure 9 basically shows the situation described above with respect to FIG. 8 regarding the reception of triggers in the UEs of group #1 and #2. As described above, the UEs of group #1 receive trigger B in subframe n+3. To avoid a second trigger for uplink transmission (which may occur in the conventional system described with respect to FIG. 8), the UEs of group #1 check whether another trigger B has already triggered 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 with respect to FIG. 8 where trigger A notifies the UE about the number of subframes (v = 5) indicating the valid time window).

[0102] Therefore, the UE in Group #1 checks whether another Trigger B triggered an uplink transmission within a period of 5 subframes prior to subframe n+3. Specifically, the UE in Group #1 checks whether another Trigger B triggered an uplink transmission between subframes n-2 and n+2. As shown in FIG. 8, the uplink transmission has already been triggered by the Trigger B received in subframe n. Therefore, in order to avoid multiple triggers for uplink transmission 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 generates a valid time window between subframes n-2 and n+2 and ignores the Trigger A received in subframe n-2 that enables another uplink transmission trigger by the Trigger B received in subframe n+3. Specifically, by ignoring the Trigger A received in subframe n-2, since no valid time window will be found before the reception of the Trigger B in subframe n+3, the trigger for uplink transmission by the Trigger B received in subframe n+3 can be avoided. Note that the expression "ignore Trigger A" when a past uplink transmission triggered within the valid time window of such Trigger A is found means that the Trigger A received in subframe n-2 is "not considered" for the Trigger B received in subframe n+3.

[0103] As a result, as shown in FIG. 9, in subframe n+3, an unwanted second / multiple uplink transmissions will not be triggered by the UE in Group #1. Therefore, in this case, only the UE in Group #2 is triggered to perform an uplink transmission by the Trigger B received in subframe n+3. By this solution, multiple triggers in a multi-UE environment are avoided / prevented.

[0104] FIG. 10 is a diagram of a two-stage uplink transmission procedure according to a first implementation form of the embodiment already described above with respect to FIG. 9.

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

[0106] The first-stage uplink resource scheduling message verification consists of step S104, where a determination is made as to whether uplink transmission has 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, the "period T" corresponds to the "predetermined period prior to the reception of the second-stage uplink resource scheduling message" reflected in the claims, and also corresponds to the "valid time window" shown in FIGS. 8 and 9.

[0107] If it is determined that another uplink transmission has been executed within the 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 transmission has been executed within the period T ( "No" in step S104), the process proceeds to step S105 and it is determined that the first-stage uplink resource scheduling message is valid.

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

[0110] FIG. 11 shows a second implementation form of an embodiment in which a plurality of triggers for uplink transmission in a multi-UE environment are prevented. The second implementation form is an alternative to the first implementation form. Instead of simply ignoring trigger A described in the first embodiment, by invalidating trigger A, a plurality of triggers for uplink transmission by the same UE within the valid time window of trigger A are avoided.

[0111] Referring 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 form of this embodiment, in the second implementation form of this embodiment according to FIG. 11, in response to the reception of trigger B in subframe n, the UE of group #1 may actively invalidate trigger A (received in subframe n-2) (the invalidation 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 uplink transmission by the UE of group #1 because the valid time window of trigger A no longer exists. In other words, in the second implementation form of the embodiment, trigger A is actively released / invalidated in response to the reception of the first trigger B for which uplink transmission has been triggered (or at least prior to the reception of the next trigger B). In this way, by actively invalidating / releasing trigger A, by removing the valid time window of trigger A, unintended multiple uplink transmissions are no longer triggered by the UE of group #1.

[0112] Note that, generally in the second implementation form of the embodiment (relating to FIG. 11), instead of simply ignoring trigger A in response to the reception of the second trigger B (ignoring the valid time window of trigger A) as shown in FIG. 9, trigger A is deactivated (the valid time window of trigger A is removed) in response to the uplink transmission triggered by trigger B, which is different from the first implementation form (relating to FIGS. 9 and 10).

[0113] Actively "deactivating / releasing trigger A" may be achieved, for example, by switching specific bits of a field associated with the deactivation / release of 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 the second implementation form of the embodiment already described above with respect to FIG. 11.

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

[0116] The first-stage uplink resource scheduling message verification consists of step S108. Here, 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 and waits for the first-stage uplink resource scheduling message in the next cycle, or proceeds to step S103 and waits for the second-stage uplink resource scheduling message.

[0117] In step S108, if it is determined that the first-stage uplink resource scheduling message has not been invalidated (No in step S108), the process proceeds to step S105 regarding the determination that the first-stage uplink resource scheduling message is valid. Thereafter, since the first-stage uplink resource scheduling message is valid, the process proceeds to step S106 regarding the uplink transmission being scheduled. Thereafter, in step S107, the uplink transmission is actually executed. Thereafter, the process proceeds to step S109 regarding the first-stage uplink resource scheduling message being invalidated. Thereafter, the process proceeds to step S102 and waits for the first-stage uplink resource scheduling message in the next cycle, or proceeds to step S103 and waits for the second-stage uplink resource scheduling message.

[0118] For example, if the second-stage uplink resource scheduling message is received after the invalidation of the first-stage uplink resource scheduling message (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 to step S102 or step S103 again without executing the uplink transmission.

[0119] Such a procedure as described above reflects the specific behavior shown in FIG. 11. Since Trigger A has been deactivated when the first Trigger B triggers uplink transmission, another uplink transmission will not be started by the second Trigger B in subframe n+3.

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

[0121] According to another embodiment realized in the environment of item 8.0 of Non-Patent Document 4, it is proposed to stipulate the following in the standard.

[0122] For a serving cell that is an LAA SCell, the UE · In subframe n for the UE, in response to the detection of PDCCH / EPDCCH in which the "PUSCH Trigger A" field is set to "0" in DCI format 0A / 0B / 4A / 4B, or · In the most recent subframe from subframe n-v for a UE not triggered by the "PUSCH Trigger B" field set to "1" in subframes n-v+1 and n-1, in response to the detection of PDCCH / EPDCCH in which the "PUSCH Trigger A" field is set to "1" in DCI format 0A / 0B / 4A / 4B, and in subframe n, in response to the detection of PDCCH in which the DCI CRC is scrambled by CC-RNTI and the "PUSCH Trigger B" field is set to "1", Perform the corresponding PUSCH transmission in subframe n + l + k + i (i = 0, 1, ···, N - 1) according to PDCCH / EPDCCH and [···], on condition that the channel access procedure described in Section 15.2.1 is satisfied.

[0123] [Hardware and Software Implementations of the Present Disclosure] Other exemplary embodiments relate to the implementation of the various embodiments described above by the use of hardware, software, or software in cooperation 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 execute the methods described herein, and corresponding entities such as a receiver, a transmitter, a processor, etc. are appropriately involved in these methods.

[0124] It is further recognized that the various embodiments can be implemented or executed using a computer device (processor). The computer 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, etc. Also, the various embodiments may be executed or embodied by a combination of these devices. In particular, each functional block used in the description of each of the above embodiments can be realized by an LSI as an integrated circuit. These may be formed individually as chips, or one chip may be formed to include part or all of the functional blocks. These may have their data input / outputs connected. Here, depending on the degree of integration, the LSI may also be referred to as an IC, a system LSI, a super LSI, or an ultra super LSI. However, the technology for implementing the integrated circuit is not limited to LSI, and it may be realized by using discrete circuits or general-purpose processors. Also, a field programmable gate array (FPGA) that can be programmed after the manufacture of the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells disposed inside the LSI may be used.

[0125] Furthermore, various embodiments may be implemented by software modules that are executed by a processor or directly executed in hardware. Also, a combination of software modules and hardware implementations is considered possible. The software modules may be stored in any type of computer-readable storage medium, such as, for example, RAM, EPROM, EEPROM, flash memory, registers, hard disk, CD-ROM, DVD, etc. It should be further noted that the individual features of the various embodiments may be the subject of another embodiment, individually or in any combination.

[0126] It will be apparent to those skilled in the art that many variations and / or modifications of the present disclosure are possible as shown in the specific embodiments. Therefore, this embodiment should be considered illustrative in all respects and not restrictive at all.

Claims

1. An integrated circuit for controlling a radio base station, the integrated circuit comprising: A transmitter that transmits to the user equipment a first-stage uplink resource scheduling message indicating uplink radio resources available to the user equipment for performing uplink transmission by the user equipment via an unlicensed cell, and that transmits to the user equipment a second-stage uplink resource scheduling message associated with the first-stage uplink resource scheduling message; The first-stage uplink resource scheduling message is considered valid if uplink transmission has not 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 receiving circuit that performs uplink reception via the unlicensed cell when the first-stage uplink resource scheduling message is valid; An integrated circuit comprising the above.

2. If uplink transmission has been triggered by the other 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 invalidated; The first-stage uplink resource scheduling message is considered valid if the first-stage uplink resource scheduling message has not been invalidated; The integrated circuit 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 equipment that receive the second-stage uplink resource scheduling message; Optionally, the first-stage uplink resource scheduling message is addressed to the user equipment by user equipment-specific identification information employed in the transmission of the first-stage uplink resource scheduling message, and the user equipment-specific identification information is configurable; Optionally, the second-stage uplink resource scheduling message is commonly addressed to a plurality of user equipments that receive the second-stage uplink resource scheduling message by shared identification information employed in the transmission of the second-stage uplink resource scheduling message, the shared identification information being predefined and common to the plurality of user equipments. The integrated circuit according to claim 1.

4. The first-stage uplink resource scheduling message designates the predetermined period that can be considered in conjunction with the second-stage uplink resource scheduling message transmitted as the first-stage uplink resource scheduling message. Optionally, when the second-stage uplink resource scheduling message is transmitted within the designated predetermined period after the transmission of the first-stage uplink resource scheduling message, the first-stage uplink resource scheduling message is considered in conjunction with the second-stage uplink resource scheduling message. The integrated circuit according to claim 1.

5. The first-stage uplink resource scheduling message further designates a first time offset to be considered when performing the uplink transmission, and the second-stage uplink resource scheduling message designates a second time offset to be considered when performing the uplink transmission. Optionally, in response to the transmission of the second-stage uplink resource scheduling message, the receiving circuit performs the uplink reception at least after the sum of the first and second time offsets. The integrated circuit according to claim 1.

6. The first-stage uplink resource scheduling message is the DCI message of 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 for two-stage uplink resource scheduling. Optionally, the second-stage uplink resource scheduling message is the DCI message of format 1C including a second-stage flag indicating that the downlink control information (DCI) message is the second uplink resource scheduling message for two-stage uplink resource scheduling. The integrated circuit according to claim 1.

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