JP6857832B2 - Multiple side link control transmissions during the side link control period - Google Patents

Description

The present disclosure relates to a mechanism for allocating radio resources to a transmitting user device to perform multiple direct side link transmissions to one or more receiving user devices through a side link interface during a side link control period. .. In this regard, the present disclosure defines a method of allocation mechanism and a user device to which the allocation mechanism described herein is applied.

<Long Term Evolution (LTE)>
Third-generation mobile communication systems (3Gs) based on WCDMA® wireless access technology are being deployed on a wide scale around the world. High Speed Downlink Packet Access (HSDPA) and Enhanced Uplink (also known as High Speed Uplink Packet Access (HSUPA)) were introduced as the first steps in enhancing, developing and evolving this technology. , Extremely competitive wireless access technology is provided.

In order to meet the ever-increasing demand from users and to be competitive with new wireless access technologies, 3GPP has introduced a new mobile communication system called Long Term Evolution (LTE). LTE is designed to provide the carriers required for high-speed data and media transmission and high-capacity voice support over the next decade. The ability to provide high bitrates is an important strategy in LTE.

The specifications of the work item (WI) related to LTE (Long Term Evolution) are E-UTRA (Evolved UMTS Terrestrial Radio Access (UTRA)) and UTRAN (UMTS Terrestrial Radio Access Network (UTRAN): UMTS Ground. It is called Radio Access Network) and will finally be released as Release 8 (LTE Release 8). LTE systems are packet-based efficient radio access and radio access networks that provide all IP-based functionality at low latency and low cost. In LTE, multiple scalable transmit bandwidths (eg, 1.4 MHz, 3.0 MHz, 5.0 MHz, 10.0 MHz, 15.0 MHz) are used to achieve flexible system deployment using a given frequency band. , And 20.0 MHz). Radio access based on OFDM (Orthogonal Frequency Division Multiplexing) is adopted for the downlink. This is because such radio access is inherently less susceptible to multipath interference (MPI) due to its low symbol rate, uses cyclic prefixes (CP), and supports a variety of transmit bandwidth configurations. Because it is possible. For the uplink, wireless access based on SC-FDMA (Single-Carrier Frequency Division Multiple Access) is adopted. This is because, considering that the transmission output of the user equipment (UE) is limited, it is prioritized to provide a wide coverage area rather than improving the peak data rate. In LTE Release 8/9, a number of major packet radio access technologies (eg MIMO (Multiple Input Multioutput) Channel Transmission Technology) have been adopted to achieve a highly efficient control signaling structure.

<LTE architecture>
FIG. 1 shows the overall architecture of LTE. The E-UTRAN consists of an eNodeB, which terminates the E-UTRA user plane (PDCP / RLC / MAC / PHY) and control plane (RRC) protocols towards the user equipment (UE). eNodeB (eNB) is a physical (PHY) layer, medium access control (MAC) layer, wireless link control (RLC) layer, and packet data control protocol (PDCP) layer (these layers are user plane header compression and encryption). Host). The eNB also provides a radio resource control (RRC) function corresponding to the control plane. The eNB provides wireless resource management, admission control, scheduling, negotiated quality of service (QoS) implementation, cell information broadcasting, user plane data and control plane data encryption / decryption, and downlink / uplink. Performs many functions such as compression / decompression of user plane packet headers. A plurality of eNodeBs are connected to each other by an X2 interface.

In addition, a plurality of eNodeBs are EPC (Evolved Packet Core) by S1 interface, more specifically, MME (Mobility Management Entity) by S1-MME, and serving gateway (Mobility Management Entity) by S1-U. It is connected to SGW: Serving Gateway). The S1 interface supports a many-to-many relationship between the MME / serving gateway and the eNodeB. While routing and forwarding user data packets, the SGW acts as a mobility anchor for the user plane during handover between eNodeBs, and also an anchor for mobility between LTE and another 3GPP technology (S4). It terminates the interface and acts as a relay for traffic between the 2G / 3G system and the PDN GW). The SGW terminates the downlink data path for the idle user device and triggers paging when the downlink data arrives at the user device. The SGW manages and stores the context of the user equipment (eg, IP bearer service parameters, or network internal routing information). In addition, the SGW performs replication of user traffic in the case of lawful interception.

The MME is the main control node of the LTE access network. The MME is responsible for tracking and paging procedures (including retransmissions) of user equipment in idle mode. The MME is involved in the bearer activation / deactivation process and also selects the SGW of the user equipment during the initial attachment and during the in-LTE handover with the relocation of the core network (CN) node. Also plays a role in doing so. The MME is responsible for authenticating the user (by interacting with the HSS). Non-Access Stratum (NAS) signaling is terminated in the MME, which also plays a role in generating a temporary ID and assigning it to the user device. The MME checks the authentication of the user equipment to enter the service provider's Public Land Mobile Network (PLMN) and enforces roaming restrictions on the user equipment. The MME is the end point in the network in the encryption / integrity protection of NAS signaling and manages the security key. Legal interception of signaling is also supported by MME. In addition, the MME provides a control plane function for mobility between the LTE access network and the 2G / 3G access network and terminates the S3 interface from the SGSN. In addition, the MME terminates the S6a interface towards the home HSS for roaming user equipment.

<Component carrier structure in LTE>
The downlink component carriers of the 3GPP LTE system are further divided in the time-frequency domain in the so-called subframe. In 3GPP LTE, each subframe is divided into two downlink slots as shown in FIG. 2, where the first downlink slot provides a control channel area (PDCCH area) within the first OFDM symbol. Be prepared. 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 bandwidth of the component carrier. Therefore, each OFDM symbol is composed of several modulation symbols transmitted by its respective subcarriers. In LTE, the transmitted signal in each slot is described by a resource grid of ^{N DL} _RB x N ^RB _sc lines and N ^DL _{symb OFDM symbols.} N ^DL _RB is the number of resource blocks in the bandwidth. The number N ^DL _RB depends on the downlink transmit bandwidth set in the cell ^{and satisfies N min, DL} _RB ≤ N ^DL _RB ≤ N ^{max, DL} _{RB, in} which case N ^{min, DL} _RB = 6 and N ^{max and DL} _RB = 110 are the minimum and maximum downlink bandwidths supported by the specifications of the current version, respectively. ^NRB _sc is the number of subcarriers in one resource block. For sub-frame structure of conventional cyclic ^prefix, which is _{^{N RB sc = 12, N DL}} symb = 7.

Assuming a multi-carrier communication system that uses, for example, OFDM, such as that used in 3GPP Long Term Evolution (LTE), the smallest unit of resources that can be allocated by the scheduler is one "resource block". As illustrated in FIG. 2, the physical resource block (PRB) is a continuous OFDM symbol (for example, 7 OFDM symbols) in the time domain and a continuous subcarrier (for example, 12 subcarriers of component carriers) in the frequency domain. Defined as. Therefore, in 3GPP LTE (Release 8), the physical resource block is composed of resource elements and corresponds to one slot in the time domain and 180 kHz in the frequency domain (more details on the downlink resource grid can be found in, for example, Non-Patent Document 1-6. See Section .2 (available on the 3GPP website and incorporated herein by reference).

One subframe consists of two slots, so there are 14 OFDM symbols in the subframe when the so-called "normal" CP (cyclic prefix) is used, and the so-called "extended" CP There are 12 OFDM symbols in the subframe when used. For technical purposes, the same continuous subcarrier-equivalent time-frequency resource that spans the entire subframe is referred to below as a "resource block pair" or a synonymous "RB pair" or "PRB pair".

The term "component carrier" refers to a combination of several resource blocks in the frequency domain. In LTE, the term "component carrier" is no longer used and instead the terminology is changed to "cell" which means a combination of downlink resources and optionally uplink resources. The link between the carrier frequency of the downlink resource and the carrier frequency of the uplink resource is indicated in the system information transmitted by the downlink resource.

Similar assumptions about the structure of component carriers apply to later releases.

<Carrier aggregation in LTE-A to support wider bandwidth>
At the World Radiocommunication Conference 2007 (WRC-07), the frequency spectrum of IMT-Advanced was determined. Although the overall frequency spectrum for IMT-Advanced has been determined, the actual available frequency bandwidth will vary by region and country. However, following the determination of the outline of the available frequency spectrum, the standardization of wireless interfaces has begun in the 3GPP (3rd Generation Partnership Project). At the 3GPP TSG RAN # 39 meeting, the description of the items to be examined regarding "Further Advancements for E-UTRA (LTE-Advanced)" was approved. This study item covers the technical elements that should be considered in the evolution and development of E-UTRA (for example, to meet the requirements of IMT-Advanced).

The bandwidth that the LTE advanced system can support is 100 MHz, while the LTE system can only support 20 MHz. Today, the lack of radio frequency bands has become a bottleneck in the development of wireless networks, and as a result, it is difficult to find a sufficiently wide frequency band for LTE advanced systems. Therefore, there is an urgent need to find a way to obtain a wider radio frequency band, where a possible answer is the carrier aggregation function.

In carrier aggregation, two or more component carriers are aggregated to support a wider transmit bandwidth of up to 100 MHz. In the LTE-Advanced system, some 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. ..

At the very least, all component carriers can be configured to be LTE Release 8/9 compatible when the bandwidth of the component carriers does not exceed the supported bandwidth of the LTE Release 8/9 cells. Not all component carriers aggregated by the user equipment are necessarily LTE Release 8/9 compatible. Existing mechanisms (eg, burring) can be used to prevent Release 8/9 user equipment from camping on component carriers.

The user device can simultaneously receive or transmit one or more component carriers (corresponding to multiple serving cells) depending on their capabilities. LTE-A release 10 user equipment with receive and / or transmit capabilities for carrier aggregation can receive and / or transmit simultaneously on multiple serving cells, whereas LTE The Release 8/9 user equipment may receive and transmit on only one serving cell if the component carrier structure complies with the Release 8/9 specifications.

Carrier aggregation is supported on both continuous and discontinuous component carriers, with each component carrier up to 110 in the frequency domain (using the 3GPP LTE (Release 8/9) numerology). Limited to one resource block.

Configure 3GPP LTE-A (Release 10) compatible user equipment to aggregate different numbers of component carriers with different bandwidths, possibly uplinks and downlinks, transmitted from the same eNodeB (base station). It is possible to do. The number of downlink component carriers that can be configured depends on the downlink aggregation capability of the user equipment. Conversely, the number of uplink component carriers that can be configured depends on the uplink aggregation capabilities of the user equipment. At this time, it is not possible to set 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 is the same for the uplink and downlink. Component carriers originating from the same eNodeB do not have to provide the same coverage.

The distance between the center frequencies of the continuously aggregated component carriers is a 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 subcarriers at 15 kHz intervals. Depending on the aggregation scenario, n × 300 kHz spacing can be facilitated by inserting a small number of unused subcarriers between successive component carriers.

The effect of aggregating multiple carriers only extends to the MAC layer. The MAC layer requires one HARQ entity for each component carrier to be aggregated, both uplink and downlink. The maximum number of transport blocks per component carrier is one (when SU-MIMO on the uplink is not used). The transport block and its HARQ retransmission (when it occurs) must be mapped to the same component carrier.

When carrier aggregation is set, the mobile terminal has only one RRC connection to the network. When establishing / reestablishing an RRC connection, one cell has security inputs (one ECGI, one PCI, and one ARFCN) and non-access layer (NAS) mobility information (as in LTE release 8/9). Example: TAI) and. After establishing / reestablishing 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 set for each user device. In a configured set of component carriers, the other cells are called secondary cells (SCell), and the carriers of the SCell are the downlink secondary component carrier (DL SCC) and the uplink secondary component carrier (UL SCC). Up to five serving cells (including PCell) can be set for one UE.

The features of the downlink PCell and the uplink PCell are as follows.
• For each SCell, the use of uplink resources by user equipment in addition to downlink resources can be configured (thus, the number of DL SCCs configured is always greater than or equal to the number of UL SCCs and is up. SCell cannot be configured to use only linked resources).
-Downlink PCells, unlike SCells, cannot be deactivated.
-Reestablishment is triggered when Rayleigh fading (RLF) occurs in the downlink PCell, but reestablishment is not triggered even if RLF occurs in the downlink SCell.
-Non-access layer information is acquired from the downlink PCell.
The PCell can only be modified by a handover procedure (ie, security key change and RACH procedure).
-PCell is used for transmission of PUCCH.
-The uplink PCell is used for transmitting the uplink control information of the first layer.
• From a UE perspective, each uplink resource belongs to only one serving cell.

Component carriers can be configured and reconfigured, as well as added and removed by the RRC. Activation and deactivation are done via MAC control elements. During in-LTE handover, the RRC can also add, remove, or reconfigure SCells for use in target cells. When adding a new SCell, dedicated RRC signaling is used to send the SCell system information (necessary for transmission / reception) (similar to the handover in LTE Release 8/9). When SCell is added to one UE, a serving cell index is set for each SCell. The PCell always has a serving cell index of 0.

When a user device is configured to use carrier aggregation, at least a pair of uplink component carriers and downlink component carriers is always active. The downlink component carrier of this pair is sometimes referred to as the "downlink anchor carrier". The same is true for uplinks.

When carrier aggregation is set, user equipment can be scheduled for multiple component carriers at the same time, but only one random access procedure can proceed at the same time. In cross-carrier scheduling, the PDCCH of a component carrier allows the resources of another component carrier to be scheduled. For this purpose, a component carrier identification field (referred to as "CIF") has been introduced into each DCI (Downlink Control Information) format.

When cross-carrier scheduling is not taking place, the link between the uplink component carrier and the downlink component carrier (established by RRC signaling) can identify the uplink component carrier to which the grant applies. The link of the downlink component carrier to the 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, one downlink component carrier can be linked to only one uplink component carrier.

<Uplink access method in LTE>
In uplink transmission, the user terminal needs to transmit with high power efficiency in order to maximize coverage. As the uplink transmission method of E-UTRA, a method that combines single carrier transmission and FDMA with dynamic bandwidth allocation is selected. The main reason for choosing single-carrier transmission is that it has a lower peak-to-average power ratio (PAPR) compared to multicarrier signals (OFDMA), which in turn improves power amplifier efficiency and coverage. This is because (the data rate is higher than the given terminal peak power). At each time interval, NodeB allocates the user a unique time / frequency resource for transmitting user data, which ensures orthogonality within the cell. Orthogonal multiple access on the uplink increases spectral efficiency by eliminating in-cell interference. Interference caused by multipath propagation is dealt with in the base station (NodeB) by inserting a cyclic prefix in the transmission signal.

_{The basic physical resource used to transmit data consists of a frequency resource of size BW grant} over one time interval (eg 0.5 ms subframe) (encoded information bits are this resource). Mapped to). The subframe (also referred to as transmission time interval (TTI)) is the minimum time interval for transmitting user data. However, by concatenating the subframes, it is also possible to allocate the _{frequency resource BW grant to the user for a time longer than 1 TTI.}

<Uplink scheduling method in LTE>
The uplink scheme in LTE allows both scheduled access (ie, controlled by the eNB) and contention-based access.

For scheduled access, the eNB allocates specific frequency resources (ie, time / frequency resources) over a specific time to the UE to transmit uplink data. Some time / frequency resources can be allocated for contention-based access, and the UE can transmit within this time / frequency resource without being initially scheduled by the eNB. One scenario in which a UE makes contention-based access is, for example, random access, that is, when the UE makes its first access to a cell or requests an uplink resource.

For scheduled access, the NodeB scheduler allocates a unique time-frequency resource for the uplink data transmission to the user. More specifically, the scheduler determines:
-UE (s) that allow transmission
-Physical channel resources-Transport format that mobile terminals should use for transmission (Modulation Coding Scheme (MCS))

The allocation information is then signaled to the UE via a scheduling grant sent on the layer 1 / layer 2 control channels. In the following, for the sake of brevity, this channel will be referred to as an uplink grant channel. Therefore, the scheduling grant message contains, as information, the portion of the frequency band that the UE is allowed to use, the validity period of the grant, and the transport format that the UE must use for future uplink transmissions. .. The shortest validity period is one subframe. Grant messages can also include additional information depending on the method selected. Only grants "for each UE" are used as grants granting the right to transmit on the uplink shared channel (UL-SCH) (ie, there is no "for each radio bearer in each UE" grant). Therefore, the UE needs to allocate the allocated resources among the radio bearers according to some rules. Unlike the case of HSUPA, the transport format is not selected on the user equipment side. The eNB determines the transport format based on some information (eg, reported scheduling information and QoS information), and the user equipment must follow the selected transport format. In HSUPA, NodeB allocates the maximum uplink resources and the UE selects the actual transport format for data transmission accordingly.

Since wireless resource scheduling is the most important function in a shared channel access network in determining quality of service (QoS), the uplink scheduling method in LTE is satisfied for the purpose of enabling efficient QoS management. There are some requirements that should be there.
• You should avoid running out of resources for low-priority services.
• Scheduling schemes should support a clear distinction between wireless bearer / service QoS.
-Perform a detailed buffer report (for example, a report for each wireless bearer or a report for each wireless bearer group) in the uplink report so that the eNB scheduler can identify which radio bearer / service data is transmitted. Should be able to.
• Quality should be clearly distinguishable between services of different users.
-It should be possible to provide a minimum bit rate for each wireless bearer.

As can be seen from the set of conditions listed above, one important aspect of LTE scheduling schemes is that operators control the distribution of their total cell capacity among different QoS class wireless bearers. It is to provide a mechanism that can be done. The wireless bearer QoS class is identified by the corresponding SAE bearer QoS profile signaled from the serving gateway to the eNB as described above. An operator can allocate a particular amount of its total cell capacity to the total traffic associated with a particular QoS class radio bearer. The main purpose of adopting this class-based approach is to be able to distinguish the processing of packets according to the QoS class to which the packet belongs.

<Layer 1 / Layer 2 control signaling>
Layer 1 / Layer 2 control signaling is used to inform the scheduled user of the user's allocation status, transport format, and other transmission-related information (eg, HARQ information, transmit power control (TPC) commands). It is sent downlink with the data. The first-layer / second-layer control signaling is multiplexed with the downlink data in the subframe (assuming that the user allocation can change in subframe units). Note that user allocation can also be performed on a TTI (transmission time interval) basis, in which case the TTI length can be a multiple of the subframe. The TTI length can be constant for all users within the service area, different for different users, or even dynamic for each user. Layer 1 / layer 2 control signaling generally only needs to be transmitted once per TTI. In the following, it is assumed that TTI is equal to one subframe without loss of generality.

Layer 1 / Layer 2 control signaling is transmitted over the physical downlink control channel (PDCCH). The PDCCH conveys the message as downlink control information (DCI), which in most cases contains resource allocation and other control information intended for groups of mobile terminals or UEs. In general, several PDCCHs can be transmitted within one subframe.

It should be noted that in 3GPP LTE, the allocation for uplink data transmission (also referred to as uplink scheduling grant or uplink resource allocation) is also transmitted by PDCCH. In addition, 3GPP Release 11 introduces EPDCCH, which performs essentially the same function as PDCCH (ie, conveys layer 1 / layer 2 control signaling), but the details of the transmission method are different from PDCCH. Further details are described in particular in the current versions of Non-Patent Document 1 and Non-Patent Document 2 (incorporated herein by reference). Therefore, most of the items outlined in the background art and embodiments apply to PDCCH and EPDCCH, or other means of transmitting layer 1 / layer control signaling, unless otherwise stated.

Information sent by layer 1 / layer control signaling for the purpose of allocating uplink or downlink radio resources (especially LTE (-A) release 10) can generally be classified into the following items: it can.
-User identification information: Indicates the user to be assigned. This information is generally included in the checksum by masking the CRC with user identification information.
-Resource allocation information: Indicates the resource allocated to the user (eg resource block (RB)). Alternatively, this information is referred to as resource block allocation (RBA). The number of resource blocks (RBs) assigned to users can be dynamic.
-Carrier indicator: The control channel transmitted by the first carrier is used to allocate resources associated with the second carrier (ie, resources associated with the second carrier or resources associated with the second carrier) (ie). Cross-carrier scheduling).
-Modulation / coding method: Determine the modulation method and coding rate to be adopted.
-HARQ information: New data indicator (NDI), redundant version (RV), etc., which are especially useful when retransmitting a data packet or part of it.
− Power control command: Adjusts the transmission power when transmitting the uplink data or control information to be allocated.
− Reference signal information: The applied cyclic shift or orthogonal cover code index used to send or receive the reference signal to be assigned.
-Uplink Allocation Index or Downlink Allocation Index: Used to identify the order of allocation and is especially useful in TDD systems.
− Hopping information: For example, information on whether to apply resource hopping for the purpose of increasing frequency diversity and how to apply it.
-CSI request: Used to trigger the allocated resource to send channel state information.
-Multi-cluster information: Used to indicate and control whether to send in a single cluster (continuous set of resource blocks) or multi-cluster (at least two discontinuous sets of continuous resource blocks). It is a flag. Multi-cluster allocation was introduced with 3GPP LTE- (A) Release 10.

Note that the above list is not exhaustive and, depending on the DCI format used, it may not be necessary to include all of the listed information items in each PDCCH transmission.

Downlink control information takes the form of several formats, which differ in overall size from the information contained in the fields described above. The different DCI formats currently defined in LTE are: Section 5.3.3.1 of Non-Patent Document 3 (current version 12.4.0 is available on the 3GPP website. , Incorporated herein by reference). In addition, further details regarding the DCI format and the specific information transmitted in DCI can be found in the technical standards listed above, or in Section 9.3 of Non-Patent Document 4 (incorporated herein by reference). Please refer to.
-Format 0: DCI format 0 is used to transmit resource grants for PUSCH using single antenna port transmission in uplink transmit mode 1 or 2.
-Format 1: DCI format 1 is used to transmit resource allocations for transmission of single codeword PDSCH (downlink transmission modes 1, 2, 7).
-Format 1A: DCI format 1A has the purpose of compactly signaling resource allocation for single codeword PDSCH transmission and the purpose of assigning a dedicated preamble signature to mobile terminals for contention-free random access. Used for (all send modes).
-Format 1B: DCI format 1B is used to compactly signal resource allocation for PDSCH transmission (downlink transmission mode 6) using closed-loop precoding with rank 1 transmission. The information transmitted is the same as in format 1A, but in addition an indicator of the precoding vector applied to the transmission of the PDSCH is transmitted.
-Format 1C: DCI format 1C is used to transmit PDSCH allocations in a very compact manner. When format 1C is used, PDSCH transmission is constrained to the use of QPSK modulation. This format is used, for example, to signal paging messages and to broadcast system information messages.
-Format 1D: DCI format 1D is used to compactly signal resource allocation for PDSCH transmission using multi-user MIMO. The information transmitted is the same as for format 1B, but instead of one of the indicator bits of the precoding vector, one bit is used to indicate whether a power offset is applied to the data symbol. Exists. This configuration is necessary to indicate whether transmission power is shared between the two user devices. In future versions of LTE, this configuration can be extended to share power among a larger number of user devices.
-Format 2: DCI format 2 is used to transmit resource allocation for PDSCH in the case of closed-loop MIMO operation (transmission mode 4).
-Format 2A: DCI format 2A is used to send resource allocations for PDSCH in the case of open-loop MIMO operation. The information to be transmitted is the same as in the case of format 2, except that when the eNodeB has two transmitting antenna ports, there is no precoding information, and in the case of four antenna ports, it indicates the transmission rank. 2 bits are used for (transmission mode 3).
-Format 2B: Introduced in Release 9 and used to transmit resource allocation for PDSCH in the case of dual layer beamforming (transmission mode 8).
-Format 2C: Introduced in Release 10, used to transmit resource allocation for PDSCH in the case of closed-loop single-user MIMO operation or multi-user MIMO operation (up to 8 layers) (transmission mode 9).
-Format 2D: Introduced in Release 11, used for transmission of up to 8 layers, mainly in CoMP (cooperative multipoint) (transmission mode 10).
-Formats 3 and 3A: DCI formats 3 and 3A are used to send power control commands for PUCCH and PUSCH, each with a 2-bit or 1-bit power adjustment. These DCI formats include individual power control commands for groups of user equipment.
-Format 4: DCI format 4 is used for scheduling PUSCH using closed-loop spatial multiplexing transmission in uplink transmission mode 2.
-Format 5: DCI format 5 is used for scheduling PSCCH (Physical Sidelink Shared Control Channel) and further for scheduling PSCH (Physical Sidelink Shared Channel). Includes several fields of SCI (Side Link Control Information) format 0. The number of information bits in DCI format 5 mapped to a particular search space is less than the payload size of format 0 for scheduling the same serving cell, and the payload size of format 5 includes padding bits added to format 0. 0 is added to format 5 until it is equal to the payload size of format 0.

Sidelink control information is defined in Section 5.4.3 (incorporated herein by reference) of Non-Patent Document 3 (current version 12.4.0), which is a 3GPP technical standard. (Details on side links will be described later).

SCI (side link control information) can convey side link scheduling information for one destination ID. SCI format 0 is defined for use in PSSCH scheduling. The following information is transmitted in SCI format 0.
・ Frequency hopping flag: 1 bit ・ Resource block allocation and hopping resource allocation ・ Time resource pattern: 7 bits ・ Modulation / coding method: 5 bits ・ Timing advance instruction information: 11 bits ・ Group destination ID: 8 bits

Logical Channel Prioritization (LCP) Procedure For uplinks, the process by which the UE creates a MAC PDU to transmit using its allocated radio resources is fully standardized. This process is designed so that the UE meets the QoS of each configured radio bearer in an optimal and consistent manner across different implementations of the UE. The UE must determine the amount of data for each logical channel to include in the new MAC PDU based on the uplink transmit resource grant message signaled on the PDCCH, and if necessary, additional space for MAC control elements. Must be assigned.

When constructing a MAC PDU with data from multiple logical channels, the easiest and most intuitive method is based on absolute priority, in which the space in the MAC PDU is prioritized by the logical channel. Assign to logical channels in descending order of rank. That is, the data from the highest priority logical channel is processed first in the MAC PDU, then the data from the next highest priority logical channel is processed and continued until all the space in the MAC PDU is occupied. .. The absolute priority-based method is quite simple in terms of UE implementation, but can lead to a lack of data resources from lower priority logical channels in some cases. Insufficient resources mean that data from the high priority logical channel cannot send data from the low priority logical channel because it occupies all the space in the MAC PDU.

In LTE, data is transmitted in order of importance, but a preferred bit rate (PBR) is defined for each logical channel in order to avoid resource shortage of data with lower priority. PBR is the minimum data rate guaranteed for a logical channel. At least a small amount of MAC PDU space is allocated to guarantee PBR, even if the logical channel has a low priority. Therefore, the problem of resource shortage can be avoided by using PBR.

The step of constructing a MAC PDU using PBR consists of two substeps. In the first substep, each logical channel is processed in descending order of priority of the logical channel, but the amount of data from each logical channel included in the MAC PDU is initially set to the PBR value set for that logical channel. Limit to the corresponding amount. After processing all logical channels to their respective PBR values, if there is space left in the MAC PDU, perform the second substep. In the second substep, each logical channel is processed again in descending order of priority. The major difference between the second substep compared to the first substep is that in all the higher priority logical channels, only if there is no more data to send, then each lower priority logical channel has a MAC PDU space. Can be assigned.

The MAC PDU can include not only the MAC SDU from each configured logical channel but also the MAC CE. MAC CE has a higher priority than MAC SDU from the logical channel, except for padding BSR, because MAC CE controls the operation of the MAC layer. Therefore, when constructing a MAC PDU, the MAC CE (if present) is included first and the remaining space is used for the MAC SDU from the logical channel. Then, if additional space remains and it is large enough to contain the BSR, the padding BSR is triggered and included in the MAC PDU. A logical channel prioritization (LCP) procedure is applied each time a new transmission is performed.

Logical channel prioritization is standardized, for example, in Section 5.4.3.1 (incorporated herein by reference) of Non-Patent Document 5 (current version 12.5.0).

The RRC controls the scheduling of uplink data by signaling the following for each logical channel:
-Priority: The higher the priority value, the lower the priority level.)
-Prioritized BitRate: Set the priority bit rate (PBR) -bucketSizeDuration: Set the bucket size period (BSD)

The UE maintains a _{variable B j} for each logical channel j. B _j is initialized to 0 when the associated logical channel is established, and is incremented by the product PBR × TTI time length for each TTI (PBR is the preferred bit rate of the logical channel j). However, the value of B _j can not exceed the bucket size, the value of B _j is larger than the bucket size of logical channel j, the value of B _j is set to the bucket size. The bucket size of the logical channel is equal to PBR (priority bit rate) x BSD (bucket size period), and PBR and BSD are set by the upper layer.

<LTE device-to-device (D2D) neighborhood service (ProSe)>
Neighborhood-based applications and services are a new trend in social technology. Areas identified include commercial services and services related to public safety that are of interest to businesses and users. By introducing the Prose feature into LTE, the 3GPP industry will be able to serve this growing market while at the same time urgently in some public safety communities using LTE in tandem. Can meet various needs.

Device-to-device (D2D) communication is a technical element in LTE Release 12. Device-to-device (D2D) communication technology can increase spectral efficiency in D2D as an underlay for cellular networks. For example, if the cellular network is LTE, all physical channels carrying data use SC-FDMA in D2D signaling. In D2D communication, user devices transmit data signals to each other through direct links that use cellular resources, without going through a radio base station. Throughout the invention, the terms "D2D", "ProSe", and "sidelink" are synonymous.

<D2D communication in LTE>
D2D communication in LTE focuses on two areas: discovery and communication.

In ProSe Direct Discovery, a ProSe-enabled user device sends another (one or more) ProSe-enabled user devices in the vicinity to an E-UTRA direct radio signal via a PC5 interface. It is defined as the procedure used to use and discover. FIG. 3 schematically shows a PC5 interface for direct discovery between devices. FIG. 4 schematically shows a radio protocol stack (AS) for ProSe direct discovery.

In D2D communication, UEs use cellular resources to transmit data signals to each other over direct links without going through a base station (BS). The D2D user communicates directly but remains under the control of the base station (at least when it is within the coverage of the eNB). Therefore, in D2D, system performance can be improved by reusing cellular resources.

It is assumed that D2D operates in the uplink LTE frequency band (in the case of FDD) or in the uplink subframe of the cell providing coverage (in the case of TDD, except when out of coverage). .. Moreover, D2D transmission / reception does not use full duplex in a given carrier. From the point of view of individual user equipment, D2D signal reception and LTE uplink transmission do not use full duplex in a given carrier (ie, D2D signal reception and LTE uplink transmission cannot be performed at the same time).

In D2D communication, when one specific UE 1 is in the role of transmission (transmitting user device or transmitting terminal), UE 1 sends data and another UE 2 (receiving user device) receives it. UE1 and UE2 can exchange the role of transmission and the role of reception. The transmission from the UE 1 can be received by one or more UEs similar to the UE 2.

Regarding the user plane protocol, the consensus part from the viewpoint of D2D communication is shown below (Non-Patent Document 6 (current version 12.0.1), section 9.2.2 (incorporated herein by reference). See also).
・ PDCP:
− 1: MD2D broadcast communication data (ie, IP packet) should be treated as normal user plane data.
− 1: Header compression / decompression in PDCP can be applied to MD2D broadcast communication data.
-D2D broadcast operations related to public safety use U mode for header compression in PDCP.
・ RLC:
− 1: RLC UM is used for MD2D broadcast communication.
-Segmentation and reconstruction is supported by RLC UM in the second tier.
-The receiving UE needs to maintain at least one RLC UM entity per sending peer UE.
-It is not necessary to configure the receiver's RLC UM entity before receiving the first RLC UM data unit.
-Currently, the need for RLC AM or RLC TM in D2D communication to transmit user plane data is not recognized.
・ MAC:
− 1: HARQ feedback is not assumed in MD2D broadcast communication.
-The receiving UE needs to recognize the source ID for the purpose of identifying the RLC UM entity of the receiver.
-The MAC header contains a layer 2 (L2) destination ID that enables packet filtering in the MAC layer.
-The layer 2 (L2) destination ID can be a broadcast address, a group cast address, or a unicast address.
Layer 2 (L2) group cast / unicast: The received RLC UM PDU by the layer 2 (L2) destination ID transmitted in the MAC header, even before it is passed to the RLC entity of the receiver. It can be discarded.
Layer 2 (L2) broadcast: The receiving UE processes all the RLC PDUs received from all the transmitters, reconstructs them, and passes the IP packets to the upper layer.
-The MAC subheader contains an LCID (logical channel ID) (to distinguish between multiple logical channels).
-In D2D, at least multiplexing / demultiplexing, priority processing, and padding are useful.

<Identification information related to ProSe direct communication>
Section 8.3 of Non-Patent Document 7 (current version 12.5.0) defines the following identification information for use in ProSe direct communication.
-SL-RNTI: (SideLink-Radio Network Temporary Identifier) Unique identification information used for scheduling ProSe direct communication-Source layer 2 ID: Sender of data in sidelink ProSe direct communication To identify. The source layer 2 ID is 24 bits long and is used with the ProSe layer 2 destination ID and LCID to identify the RLC UM and PDCP entities in the receiver.
-Destination layer 2 ID: Identify the target person of the data in the side link ProSe direct communication. The destination layer 2 ID has a length of 24 bits and is divided into two bit strings in the MAC layer.
-One bit string is the lowest portion (8 bits) of the destination layer 2 ID and is transferred to the physical layer as the side link control layer 1 ID. It identifies the intended audience for data in side link control and is used to filter packets at the physical layer.
-The second bit string is the uppermost part (16 bits) of the destination layer 2 ID and is transmitted in the MAC header. It is used for packet filtering at the MAC layer.

Non-access layer signaling is required to form the group and set the source layer 2 ID, destination layer 2 ID, and side link control L1 ID in the UE. These identification information is provided by the upper layer or is derived from the identification information provided by the upper layer. For group cast and broadcast, the ProSe UE ID provided by the upper layer is used directly as the source layer 2 ID, and the ProSe layer 2 group ID provided by the upper layer is used directly as the destination layer 2 ID in the MAC layer. Will be done.

<Radio resource allocation in neighborhood services>
From the viewpoint of the transmitting UE, the UE corresponding to the neighboring service (ProSe compatible UE) can operate in the following two modes of resource allocation.

Mode 1 means a method in which the eNB schedules resource allocation, in which case the UE requests a transmit resource from the eNB (or release 10 relay node) and responds to the eNodeB (or release 10 relay node). ) Schedules the resources that the UE uses to send "direct" data and "direct" control information (DCI) (eg, scheduling allocation). The UE needs to be in the RRC_CONNECTED state in order to transmit data. Specifically, the UE sends a D2D scheduling request (D-SR (dedicated scheduling request) or random access) to the eNB, and then sends a buffer status report (BSR) in the usual way (next section "Transmission procedure in D2D communication"). See also). Based on the BSR, the eNB can determine that the UE has data to be transmitted by ProSe direct communication, and can estimate the resources required for the transmission.

Mode 2, on the other hand, means a method in which the UE autonomously selects resources, in which case the UE transmits "direct" data and "direct" control information (ie, SA (scheduling allocation)). Select the resources (time and frequency) for yourself from the resource pool (s). One resource pool is defined, for example, by the contents of SIB18 (ie, by the comTxPoolNormalCommon field), and this particular resource pool is broadcast within the cell and is commonly available to all UEs still in the RRC_IDLE state within that cell. Is. In practice, the eNB can define up to four different instances of this pool (ie, four resource pools for sending SA messages and "direct" data). However, the UE always uses the first resource pool defined in the list, even if it has multiple resource pools configured on it.

Instead, the eNB defines another resource pool and signals it at SIB18 (ie, by using the comTxPoolExpective field), and the UE can use this resource pool in exceptional cases.

Which resource allocation mode the UE uses can be set by the eNB. In addition, which resource allocation mode the UE uses for D2D data communication can also be determined by the RRC state (ie RRC_IDLE or RRC_CONNECTED) and the coverage state of the UE (ie in or out of coverage). it can. If a UE has a serving cell (ie, the UE is in the RRC_CONNECTED state, or is camping on a particular cell in the RRC_IDLE state), the UE is considered to be in coverage.

The following rules regarding resource allocation mode apply to the UE.
• If a UE is out of coverage, it can only use mode 2.
• If a UE is in coverage, it can use mode 1 if it has been configured by the eNB to use mode 1.
• If a UE is in coverage, it can use mode 2 if it has been configured by the eNB to use mode 2.
• In the absence of exception conditions, the UE can change from mode 1 to mode 2 or from mode 2 to mode 1 only if the eNB configures the UE to change modes. If the UE is within coverage, the UE will only use the mode indicated by the eNB configuration, unless one of the exceptional cases occurs.
-For example, while T311 or T301 is running, the UE considers itself to be under exceptional conditions.
• When an exceptional case occurs, the UE is temporarily allowed to use mode 2, even if it is configured to use mode 1.

While within the coverage area of an E-UTRA cell, the UE performs ProSe direct communication transmission on the uplink carrier only on the resources allocated by that cell (even if the carrier's resources are, for example, UICC (general purpose IC card:: UICC)). Even if it is preset in the Universal Integrated Circuit Card).

For UEs in the RRC_IDLE state, the eNB can choose one of the following options:
-The eNB provides a mode 2 transmission resource pool in the SIB (system information block). UEs that are allowed ProSe direct communication use these resources for ProSe direct communication in the RRC_IDLE state.
-The eNB indicates in the SIB that it supports D2D but does not provide resources for ProSe direct communication. The UE needs to enter the RRC_CONNECTED state in order to execute ProSe direct communication transmission.

For UEs in the RRC_CONNECTED state, the following can be done.
-A UE that is in the RRC_CONNECTED state and is permitted to execute ProSe direct communication transmission indicates to the eNB that it wants to execute ProSe direct communication transmission when it is necessary to execute ProSe direct communication transmission.
-The eNB confirms whether the UE in the RRC_CONNECTED state is permitted to transmit ProSe direct communication by using the UE context received from the MME.
-The eNB can set a transmission resource pool of the mode 2 resource allocation method that can be used without restriction for a UE in the RRC_CONNECTED state while the UE is in the RRC_CONCEPTED state by dedicated signaling. Instead, the eNB can use dedicated signaling to set up a mode 2 resource allocation transmission resource pool for a UE in the RRC_CONNECTED state that can be used by that UE only in exceptional cases. , Unless in exceptional cases, the UE follows mode 1.

The resource pool for scheduling allocation when the UE is out of coverage can be set as follows.
-The resource pool used for reception is preset.
-The resource pool used for transmission is preset.

The resource pool for scheduling allocation when the UE is in coverage can be configured as follows:
The resource pool used for reception is set up by the eNB via RRC (in dedicated or broadcast signaling).
The resource pool used for transmission is set by the eNB via RRC when mode 2 resource allocation is used.
-The SCI (side link control information) resource pool (also referred to as the scheduling allocation (SA) resource pool) used for transmission is not recognized by the UE when the mode 1 resource pool is used.
-When mode 1 resource allocation is used, the eNB schedules specific resources for use in transmitting side link control information (scheduling allocation). The specific resource allocated by the eNB is in the resource pool for receiving the SCI provided to the UE.

FIG. 5 shows the use of transmit / receive resources in overlay (LTE) and underlay (D2D) systems.

Whether the UE applies the mode 1 transmission or the mode 2 transmission is basically controlled by the eNodeB. When the UE recognizes a resource capable of transmitting (or receiving) D2D communication, the current state-of-the-art technology uses the corresponding resource only for the corresponding transmission / reception. For example, in FIG. 5, the D2D subframe is used only for the purpose of receiving or transmitting a D2D signal. Since the UE as a D2D device operates in half-duplex mode, it can either receive or transmit a D2D signal at any time. Similarly, the other subframes shown in FIG. 5 can be used for LTE (overlay) transmission and / or reception.

<Transmission procedure in D2D communication>
The procedure for transmitting D2D data differs depending on the resource allocation mode. As mentioned above, in mode 1, the eNB explicitly schedules the resources for communicating the scheduling allocation and D2D data after the corresponding request from the UE. Specifically, the eNB can notify the UE that D2D communication is basically permitted but the mode 2 resource (that is, the resource pool) is not provided. This notification can be performed, for example, by exchanging the D2D communication Interest Indication by the UE and the corresponding response, the D2D Communication Response. In this case, the above-mentioned correspondence can be performed. An exemplary ProcessComcomcomm information element that does not include comTxPoolNormalCommon, i.e., a UE wishing to initiate direct communication, including transmission, must request resource allocation from E-UTRAN for each transmission. Therefore, in such a case, the UE must request the resource for each of the individual transmissions, and the series of steps of the request / allocation procedure in the case of this mode 1 resource allocation is illustrated below.
-Step 1 The UE sends an SR (Scheduling Request) to the eNB via PUCCH.
-Step 2 The eNB grants the uplink resource (for the UE to send a BSR (buffer status report)) via the PDCCH scrambled by C-RNTI.
-Step 3 The UE sends a D2D BSR indicating the state of the buffer via the PUSCH.
-Step 4 The eNB allocates D2D resources (for the UE to send data) via the PDCCH scrambled by SL-RNTI.
− Step 5 The D2D transmitting UE transmits SA (scheduling allocation) / D2D data according to the grant received in step 4.

Scheduling allocation (SA) (also referred to as SCI (side link control information)) provides control information (eg, a pointer to a time-frequency resource for transmitting the corresponding D2D data, a modulation / coding method, a group destination ID). A compact (low payload) message that contains. The SCI conveys sidelink scheduling information for one (ProSE) destination ID. The content of the SA (SCI) basically follows the grant received in step 4 above. The contents of the D2D grant and SA (ie, the contents of the SCI) are, in particular, 5.4 of Non-Patent Document 3 (current version 12.4.0), which defines the SCI format 0 described above in the Background Techniques section. It is defined in Section 3 (incorporated herein by reference).

On the other hand, in the case of mode 2 resource allocation, steps 1 to 4 above are basically unnecessary, and the UE sets and provides resources for transmitting SA and D2D data by the eNB (eNB). Autonomously select from one or more transmit resource pools.

FIG. 6 schematically shows scheduling allocation and transmission of D2D data in the case of two UEs (UE-A and UE-B). The resources for sending scheduling quotas are periodic, and the resources used for sending D2D data are indicated by the corresponding scheduling quotas.

FIG. 7 shows the D2D communication timing of mode 2 (autonomous scheduling) during one SA / data period (also known as the SC period (side link control period)). FIG. 8 shows the D2D communication timing of mode 1 (eNB schedules allocation) during one SA / data period. The SC period is a time frame consisting of scheduling allocations and transmission of their corresponding data.

As can be seen from FIG. 7, after the SA offset time, the UE uses the transmit pool resource (SA_Mode2_Tx_pool) for scheduling allocation in mode 2 to transmit the scheduling allocation. After the first transmission of SA, the same SA message is retransmitted, eg, three times. The UE then performs D2D data transmission (ie, more specifically the time resource pattern of transmission) after some configured offset (Mode2data_offset) from the first subframe of the SA resource pool (given by SA_offset). That is, it starts (using the T-RPT bitmap / pattern).

A single D2D data transmission of a MAC PDU consists of its first transmission and several retransmissions. In the illustration of FIG. 7 (and FIG. 8), it is assumed that three retransmissions (ie, second, third, and fourth transmissions of the same MAC PDU) are performed. The mode 2 T-RPT bitmap (transmission time resource pattern (T-RPT)) is basically a MAC PDU transmission (first transmission) and its retransmission (second, third, and fourth transmission). Define the timing of transmission).

During one SA / data period, the UE can transmit multiple transport blocks (only one per subframe (TTI), i.e. sequentially), but only to one ProSe destination group. In addition, the retransmission of one transport block must be completed before the first transmission of the next transport block begins, i.e. only one HARQ process is used to transmit multiple transport blocks. Will be done.

As is clear from FIG. 8, in the resource allocation mode (mode 1) scheduled by the eNB, the D2D data transmission (ie, more specifically the T-RPT pattern / bitmap) is in the SA resource pool. It is started in the next UL subframe after the last iteration of SA transmission. As already described in FIG. 7, the mode 1 T-RPT bitmap (transmission time resource pattern (T-RPT)) is basically a MAC PDU transmission (first transmission) and its retransmission (transmission). The timing of the second, third, and fourth transmissions) is defined.

<ProSe network architecture and ProSe entities>
FIG. 9 illustrates a high level of exemplary architecture for non-roaming, including different ProSe applications in UE A and UE B, as well as ProSe application servers and ProSe functions in the network. An example of the architecture of FIG. 9 is taken from Section 4.2 “Architectural Reference Model” of Non-Patent Document 8 (incorporated herein by reference).

These functional entities are presented and described in detail in Section 4.4, “Functional Entities” of Non-Patent Document 8 (incorporated herein by reference). The ProSe function is a logical function used for network-related operations required for ProSe, and plays a different role in each of the features of ProSe. The ProSe function is part of 3GPP's EPC (Evolved Packet Core) and provides all related network services such as authorization, authentication, and data processing related to nearby services.

In ProSe direct discovery and direct communication, the UE can obtain unique ProSe UE identification information, other configuration information, and authentication from the ProSe function through the PC3 reference point. Although multiple ProSe functions can be deployed in the network, one ProSe function is shown for ease of explanation. The ProSe function has three main sub-functions that perform different roles according to the characteristics of the ProSe, namely the Direct Provision Function (DPF), the Direct Discovery Name Management Function, and the EPC level. It consists of a discovery function (EPC-level Discovery Function). The DPF is used to provide the UE with the necessary parameters for the purpose of using ProSe direct discovery and ProSe direct communication.

As used in this context, the term "UE" means, for example, a ProSe-enabled UE that supports the following ProSe features:
-Prose control information is exchanged between the ProSe compatible UE and the ProSe function through the PC3 reference point.
-Procedure for open ProSe direct discovery of another ProSe-enabled UE through the PC5 reference point.
-Procedure for one-to-many ProSe direct communication through the PC5 reference point.
ProSe UE-Procedure for operating as a network repeater. The remote UE communicates with the ProSe UE-network repeater through the PC5 reference point. The ProSe UE-network repeater uses Layer 3 packet forwarding.
• Control information is exchanged between ProSe UEs through the PC5 reference point, for example for UE-network repeater detection and ProSe direct discovery.
-Prose control information is exchanged between another ProSe-compatible UE and the ProSe function through the PC3 reference point. In the case of a ProSe UE-network repeater, the remote UE sends this control information through the PC5 user plane to be relayed to the ProSe function through the LTE-Uu interface.
-Set parameters (including, for example, IP address, ProSe layer 2 group ID, group security material, and radio resource parameters). These parameters can be preset in the UE or, if within coverage, can be provided to the ProSe function in the network by signaling through the PC3 reference point.

The ProSe application server supports the storage of the EPC ProSe user ID and the ProSe function ID, and the mapping between the application layer user ID and the EPC ProSe user ID. The ProSe application server (AS) is an entity outside the scope of 3GPP. The ProSe application in the UE communicates with the ProSe AS via the application layer reference point PC1. The ProSe AS is connected to the 3GPP network via the PC2 reference point.

<UE coverage status in D2D>
As already mentioned earlier, the resource allocation method in D2D communication depends not only on the RRC state (ie, RRC_IDLE and RRC_CONNECTED), but also on the coverage state of the UE (ie, in-coverage, out-of-coverage). If the UE has a serving cell (ie, the UE is in the RRC_CONNECTED state, or the UE is camping on the cell in the RRC_IDLE state), the UE is considered to be in coverage.

The two coverage states mentioned so far (ie, in-cover (IC) and out-of-cover (OOC)) are further divided into sub-states in D2D. FIG. 10 shows four types of states to which a D2D UE can be associated, and these states can be summarized as follows.
State 1: UE1 has uplink coverage and downlink coverage. In this state, the network controls each D2D communication session. Further, the network sets whether the UE 1 should use the resource allocation mode 1 or the resource allocation mode 2.
State 2: UE2 has downlink coverage but no uplink coverage (ie DL coverage only). The network broadcasts (competition-based) resource pools. In this state, the transmitting UE selects the resources used for SA and data from the resource pool set by the network. In such a state, only resource allocation in mode 2 for D2D communication is possible.
State 3: UE3 has no uplink and downlink coverage, so UE3 is considered out of coverage (OOC). However, the UE 3 is also within the coverage of some UEs (eg, UE1) that are themselves within the coverage of the cell, i.e. these UEs can also be referred to as CP relay UEs. Therefore, the area of the UE in the state 3 in FIG. 10 can be referred to as a CP UE relay coverage area. The UE in this state 3 is also referred to as an OOC (out of coverage) state 3 UE. In this state, the UE receives some information specific to the cell, which is sent by the eNB (SIB) and is sent by the CP UE relay UE within the coverage of the cell via PD2DSCH in OOC state 3 Transferred to UE. Network-controlled (competition-based) resource pools are signaled by PD2DSP.
State 4: UE4 is out of coverage and does not receive PD2DSP from another UE within the coverage of the cell. In this state (also referred to as state 4 OOC (out of coverage)), the transmitting UE selects a resource to use for data transmission from a preset (competition-based) resource pool.

The reason for distinguishing between the state 3 OOC and the state 4 OOC is mainly to avoid possible interference between the D2D transmission from the out-of-coverage device and the legacy E-UTRA transmission. Generally, a D2D capable UE has a D2D SA and a preconfigured resource pool for data transmission for use when out of coverage. When these out-of-coverage UEs use these preconfigured resource pools to transmit at cell boundaries, interference between their D2D transmissions and legacy transmissions within coverage adversely affects intra-cell communication. May affect.

If the D2D-enabled UEs in coverage transfer the D2D resource pool settings to these out-of-coverage devices near cell boundaries, the out-of-coverage UEs send their transmissions to those resources specified by eNodeB. It can be limited and thus minimize interference with legacy transmissions within coverage. Therefore, RAN1 has introduced a mechanism by which UEs in coverage transfer resource pool information and other settings related to D2D to devices just outside the coverage area (UEs in state 3).

A physical D2D synchronization channel (PD2DSP) is used to convey this information about the in-cover D2D resource pool to nearby UEs in the network, thus coordinating resource pools within the vicinity of the network.

<LCP procedure for D2D (side link) logical channel>
The LCP (logical channel prioritization) procedure in D2D differs from the LCP procedure shown above for "normal" LTE data. The following information is taken from Section 5.14.1.3.1 of Non-Patent Document 5, which describes LCP in ProSe, which is incorporated herein by reference in its entirety.

The UE performs the following logical channel prioritization procedure when a new transmission is performed.
• The UE (eg MAC entity) allocates resources to the sidelink logical channel according to the following rules:
-If the entire RLC SDU (or partially transmitted SDU) fits in the remaining resources, the UE should not split the SDU (or partially transmitted SDU).
-The UE maximizes the size of the segment to fill the grant as much as possible when splitting the RLC SDU from the sidelink logical channel.
-UE should maximize data transmission.
-If the UE has data in a transmittable state and is given a sidelink grant size equal to or greater than 10 bytes, the UE does not transmit only padding.
Note: The above rule means that the order in which sidelink logical channels are processed is left to the UE implementation.

Generally, MAC entities consider only logical channels that have the same source Layer 2 ID and destination Layer 2 ID pair in one PDU, that is, MAC entities in the UE have the same ProSe destination group in one PDU. Only consider logical channels of (ie, having the same destination group ID). The UE selects the ProSe destination group during the LCP procedure. Further, in Release 12, the D2D transmitting UE can only transmit data to one ProSe destination group during one SA / data period.

All D2D (sidelink) logical channels (eg STCH (Sidelink Traffic CHannel)) are assigned to the same logical channel group (LCG) (ie, LCG with LCGID set to "11") (non). See Section 5.14.1.4, “Buffer Status Reporting” of Patent Document 5). In Release 12, there is no prioritization mechanism for D2D (sidelink) logical channels / groups. In essence, all sidelink logical channels have the same priority from the UE's point of view, i.e. the order in which the sidelink logical channels are processed is left to the UE implementation.

Release 13 considers a more sophisticated prioritization mechanism, in which each side-link logical channel is associated with a logical channel priority (also referred to as PPPP (ProSe per packet priority)). Be done. The UE selects the ProSe destination group of the given side link grant based on this logical channel priority (that is, the highest priority logical channel determines the ProSe destination group) and belongs to the selected ProSe destination group. Allocate more resources (in descending order of priority) to logical channels.

For illustration purposes only, consider the following exemplary scenario. That is, three ProSe logical channels LCH # 1, LCH # 2, and LCH # 3 have been established in the user equipment, and all three are associated with the same ProSe LCG (eg, "11"). Illustratively, it is assumed that LCH # 1 and LCH # 2 are assigned to ProSe destination group 1 and LCH # 3 is assigned to ProSe destination group 2. This scenario is shown in FIG.

<Buffer status report in ProSe>
Buffer status reporting has also been adapted to ProSe, and is currently in Release 12 of Non-Patent Document 5 (Version 12.5.0), Section 5.14.1.4, “Buffer Status Reporting” ( Incorporated herein by reference).

The (D2D) sidelink buffer status reporting procedure is used to provide the serving eNB with information about the amount of sidelink data in the sidelink buffer in the UE that is ready for transmission. The RRC controls side-link BSR reporting by setting two timers, Periodic-ProseBSR-Timer and RetxProseBSR-Timer. Each sidelink logical channel (STCH) is assigned to an LCG whose LCGID is set to "11" and belongs to the ProSe destination group.

The sidelink buffer status report (BSR) is triggered when some specific event occurs (as detailed in Section 5.14.1.4 of Non-Patent Document 5).

Further, Section 6.1.3.1a (incorporated herein by reference) of Non-Patent Document 5 (Version 12.5.0) describes the ProSe BSR MAC control element and its corresponding content. , Is defined as follows. The MAC control element of the ProSe buffer status report (BSR) consists of one group index field, one LCG ID field, and one corresponding buffer size field per reported D2D destination group. More specifically, the following fields are defined for each included ProSe destination group.
-Group index: The group index field identifies the ProSe destination group. The length of this field is 4 bits. The value is set in the index of the destination identification information reported in the destinationInfoList.
LCG ID: The logical channel group ID field identifies the group of logical channels (s) for which buffer status is reported. The length of the field is 2 bits and is set to "11".
Buffer size: The buffer size field identifies the total amount of data available across all logical channels of the ProSe destination group after all MAC PDUs for TTI have been built. The amount of data is indicated by the number of bytes.
-R: It is a reserved bit and is set to "0".

FIG. 11 shows the MAC control elements of ProSe BSR in the case of even N (the number of ProSe destination groups) (cited from Section 6.1.3.1a of Non-Patent Document 5).

As described above, transmission methods in inter-device communication differ from conventional LTE methods, including the use of ProSe destination groups to identify possible content of data. Some of the currently defined mechanisms are quite inefficient.

3GPP TS 36.211, “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)” 3GPP TS 36.213 3GPP TS 36.212, “Multiplexing and channel coding” LTE --The UMTS Long Term Evolution --From Theory to Practice, Edited by Stefanie Sesia, Issam Toufik, Matthew Baker 3GPP TS 36.321 3GPP TR 36.843 3GPP TS 36.300 TS 23.303 v.12.4.0 3GPP TS 36.331

An exemplary embodiment that does not limit the invention is for a transmitting user device to perform multiple direct side link (SL) transmissions to one or more receiving user devices through a side link interface. Provides an improved way of allocating radio resources. The independent claims provide exemplary embodiments that do not limit the invention. An advantageous embodiment is the subject of the dependent claims.

According to some aspects, the sender user, in particular, in a scenario (but not limited to) in which data destined for multiple sidelink destination groups can be transmitted in the sender user device. The execution of direct communication transmission by the device is improved.

In one general first aspect, the techniques disclosed herein are multiple direct sidelink (SL) transmissions to one or more receiving user devices through an SL interface in a communication system. Provides a sender user device, which allocates radio resources to perform. Allocation of radio resources during the side link control (SC) period is limited by the maximum number of SL processes configured on the transmitting user equipment during the SC period. The processor of the transmitting user equipment acquires multiple SL grants for the next SC period, and among the acquired SL grants, the most recently acquired specific number before the start of the next SC period. It is configured to select SL grants, and the number of SL grants selected does not exceed the maximum number of SL processes set for one SC period. In addition, the processor may perform multiple SL processes in the next SC period, each of which is a different SL grant out of a selected number of SL grants for allocating radio resources within the next SC period. It is configured to be associated so that it can be associated with. In addition, the processor will perform one of the plurality of SL transmissions to one or more of the receiving user devices for each of the plurality of SL processes within the next SC period. Radio resources are configured to allocate according to the selected SL grant to which each SL process is associated. Each of the plurality of SL transmissions includes transmission of at least one side link control information (SCI) and at least one data transmission through the SL interface.

In one general second aspect, the techniques disclosed herein are multiple direct sidelink (SL) transmissions to one or more receiving user devices through an SL interface in a communication system. Provides a sender user device, which allocates radio resources to perform. Allocation of radio resources during the side link control (SC) period is limited by the maximum number of SL processes configured on the transmitting user equipment during the SC period. The processor is configured to acquire multiple sidelink (SL) grants in different subframes prior to the start of the next SC period for the next SC period, in this case an association scheme. ) Is applied to each of the acquired SL grants to be associated with one of the maximum number of SL processes based on the subframe from which the SL grant is acquired, and in the association scheme, the maximum number of SLs. Each process is associated with an SL grant from a set of different subframes, and each subframe in the set is offset from each other by a predefined number of subframes. In addition, the processor associates each of the multiple maximum SL processes with one SL grant, which was acquired in each set of multiple different subframes and most recently acquired prior to the start of the next SC period. It is configured as follows. In addition, the processor will perform one of the plurality of SL transmissions to one or more of the receiving user devices for each of the plurality of SL processes within the next SC period. Radio resources are configured to allocate according to the SL grant associated with each SL process. Each of the plurality of SL transmissions includes transmission of at least one side link control information (SCI) and at least one data transmission through the SL interface.

In one general third aspect, the techniques disclosed herein are to one or more receiving user devices through the SL interface within a side link control (SC) period in a communication system. Provided is a transmitting user device, which allocates radio resources for performing a plurality of direct side link (SL) transmissions. The processor of the transmitting user device is configured to autonomously select SL grants for multiple SL transmissions from different resource pools, and each resource pool is configured for SL transmission within the communication system. The pool is available. The processor is configured to associate different SL processes with SL grants selected from different configured resource pools for each of the multiple SL transmissions. In addition, the processor provides a separate logical channel prioritization (LCP) procedure, which only considers logical channels to different destination group IDs for each of the multiple SL processes with associated SL grants. It is configured to run. In addition, the processor provides radio resources for each of the multiple SL processes to perform multiple SL transmissions within the same SC period according to the autonomously selected SL grant to which each SL process is associated. It is configured to be assigned. Each of the plurality of SL transmissions includes transmission of at least one side link control information (SCI) and at least one data transmission through the SL interface.

In one general fourth aspect, the techniques disclosed herein include a plurality of direct sides of a transmitting user device to one or more receiving user devices through an SL interface in a communication system. Provides a method of allocating radio resources to perform link (SL) transmission. Allocation of radio resources during the side link control (SC) period is limited by the maximum number of SL processes configured on the transmitting user equipment during the SC period. Multiple SL grants will be acquired for the next SC period. Of the acquired SL grants, a certain number of SL grants acquired most recently before the start of the next SC period is selected, and the number of selected SL grants is for one SC period. Do not exceed the maximum number of SL processes that have been set. The plurality of SL processes in the next SC period are then associated with each of the plurality of SL processes in a different SL grant out of a selected number of SL grants for allocating radio resources in the next SC period. To associate. Then, for each of the plurality of SL processes, a radio resource within the next SC period for executing one of the plurality of SL transmissions to one of one or a plurality of receiving user devices is provided. , Each SL process is assigned according to the associated selected SL grant. Each of the plurality of SL transmissions includes transmission of at least one side link control information (SCI) and at least one data transmission through the SL interface.

In one general fifth aspect, the techniques disclosed herein include a plurality of direct sides of a transmitting user device to one or more receiving user devices through an SL interface in a communication system. Provides a method of allocating radio resources to perform link (SL) transmission. Allocation of radio resources during the side link control (SC) period is limited by the maximum number of SL processes configured on the transmitting user equipment during the SC period. For the next SC period, obtain multiple sidelink (SL) grants in different subframes prior to the start of the next SC period, in this case by applying the association method, each SL grant obtained. Is associated with one of the maximum number of SL processes based on the subframe from which the SL grant is obtained, and in the association scheme, each of the maximum number of SL processes is from a set of multiple different subframes. Associated with the SL grant, each subframe in the set is offset from each other by a predefined number of subframes. Each of the plurality of maximum SL processes is then associated with one SL grant acquired in each set of multiple different subframes and most recently acquired prior to the start of the next SC period. Then, for each of the plurality of SL processes, a radio resource within the next SC period for executing one of the plurality of SL transmissions to one of one or a plurality of receiving user devices is provided. , Each SL process is assigned according to the associated SL grant. Each of the plurality of SL transmissions includes transmission of at least one side link control information (SCI) and at least one data transmission through the SL interface.

In one general sixth aspect, the technique disclosed herein allows a transmitting user device to receive one or more units through an SL interface within a side link control (SC) period in a communication system. Provided is a method of allocating radio resources for performing a plurality of direct side link (SL) transmissions to a side user device. SL grants for multiple SL transmissions are autonomously selected from different resource pools, and each resource pool is configured and enabled for SL transmission within the communication system. It then associates different SL processes with SL grants selected from different configured resource pools for each of the plurality of SL transmissions. A separate logical channel prioritization (LCP) procedure, which only considers logical channels to different destination group IDs, is then performed for each of the plurality of SL processes with associated SL grants. Finally, for each of the plurality of SL processes, radio resources for performing multiple SL transmissions are allocated within the same SC period according to the autonomously selected SL grant to which each SL process is associated. Each of the plurality of SL transmissions includes transmission of at least one side link control information (SCI) and at least one data transmission through the SL interface.

Further benefits and advantages of the disclosed embodiments will be apparent from the specification and drawings. These benefits and / or benefits can be provided individually by the various embodiments and features of the content disclosed herein and in the drawings, and all to obtain one or more of these benefits and / or benefits. There is no need to provide.

These general and specific aspects can be implemented using a system, method, computer program, or any combination thereof.

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

An exemplary architecture of a 3GPP LTE system is shown. An exemplary downlink resource grid of subframe downlink slots as defined in 3GPP LTE (Release 8/9) is shown. The PC5 interface for direct discovery between devices is shown schematically. The radio protocol stack for ProSe direct discovery is outlined. Shows the use of transmit / receive resources in overlay (LTE) and underlay (D2D) systems. It shows the scheduling allocation (SA) and the transmission of D2D data for two UEs. It shows the D2D communication timing in mode 2 that the UE autonomously schedules. The D2D communication timing in the scheduling mode 1 scheduled by the eNB is shown. An exemplary architectural model of ProSe in a non-roaming scenario is shown. It shows cell coverage for four different states to which a D2D UE can be associated. Shows the MAC control elements for ProSe buffer status reporting as defined in the standard. The correspondence between the ProSe logical channel, the ProSe LCG, and the ProSe destination group in an exemplary scenario is shown. It shows the D2D communication timing in two D2D transmissions scheduled by eNB according to the first variation of the first embodiment. The second variation of the first embodiment shows the D2D communication timing in the two D2D transmissions scheduled by the eNB.

A user device (UE), mobile station, mobile node, or user terminal is a physical entity within a communication system. A user device can have several functional elements, including an interface that allows itself to communicate within the communication system, for example, with another user device via a medium. Similarly, evolved NodeBs (eNBs), base stations, network nodes, or network terminals include several interfaces that allow them to communicate with, for example, user equipment over the same medium within a communication system. It has a functional element.

The term "radio resource" in the present context, the time for the user equipment and / or evolved NodeB is used as a communication medium as described above - frequency resources (e.g., resource elements (RE) or resource blocks ( It is used to mean a physical radio resource such as RB)) in a broad sense.

The term "(direct) sidelink (SL) transmission" broadly means direct communication between two user devices (ie, not via evolutionary NodeB (eNB)) in the context of this specification. It is used as a thing to do. Sidelink communication is established between the two user devices exchanging sidelink transmissions. The term "(direct) side link communication" is used herein synonymously with device-to-device (D2D) communication or ProSe communication.

Further, the direct side link transmission is performed through the "side link (SL) interface", and the "side link (SL) interface" is defined herein as broadly meaning the function of the user device that provides the side link transmission. A term used in the context of. In 3GPP LTE terminology, the sidelink interface is a PC5 interface as described in the Background Technology section.

The term "sidelink (SL) process" is used in the context of the present specification to broadly mean a process set up in a user device that can be associated with a sidelink grant. Such a sidelink process is described as being configured for a corresponding user device that provides the ability to associate SL grants with the sidelink process on a SC period basis. In 3GPP LTE terminology, the sidelink process is maintained by the sidelink HARQ entity in the MAC entity for transmission over the sidelink shared channel (SL-SCH), as described in the Background Technology section.

However, in the context of this specification, the sidelink process is not limited to this point. Instead, the sidelink process may only be involved in the memory area within the user equipment where the associated sidelink grant or sidelink grant information is stored and maintained. Such a memory area is managed by the user device, for example, the user device associates (or stores) the newly received side link grant information with the memory area, or deletes the previously associated side link grant information. Initializes (or erases) the memory area (re) for the purpose of

The term "sidelink control (SC) period" is used in the context of the present specification to broadly mean the period during which a user device performs a sidelink transmission. Each sidelink transmission includes at least one scheduling assignment (sidelink control information) transmission and at least one corresponding data transmission. In other words, the "side link control period" can also be regarded as the period during which the side link grant is valid. In 3GPP LTE terminology, a "side link control period" is an SA / data period, or SC (side link control) period.

The term "ProSe destination group" or "sidelink destination group" means, for example, one source layer 2 ID and destination layer 2 ID pair as defined in 3GPP LTE terminology throughout the specification. It is used as a thing.

The expressions "get (sidelink) grant", "receive (sidelink) grant", and similar expressions allow the user device to get / receive (sidelink) grant from the evolved NodeB that is responsible for it. It means to do (that is, the function of mode 1) in a broad sense. Conversely, the expression "autonomously select a (sidelink) grant" and similar expressions allow the UE to identify the (sidelink) grant itself, i.e. the grant's resources are appropriate (s). It means that it autonomously selects from a large transmission resource pool (that is, a mode 2 function) (that is, the UE internally receives a grant).

The currently standardized transmission methods used for D2D communication (mode 1 related (ie, scheduled by eNB) and mode 2 related (autonomously selected) transmission methods) are both. It is explained in the background technology section.

At present, a UE can have only one (valid) sidelink grant (SL grant) per sidelink control period (SC period). Therefore, at present, the UE is configured with only one SL process associated with the same grant. Even if the eNB issues several grants to the UE in mode 1, the UE considers only the one most recently (ie, last) received grant to be a valid SL grant for that SC period. In particular, the SL process overwrites the previously received (s) SL grants, so the SL process is only associated with the most recently received SL grant.

Therefore, since only one SL grant is available per SC period, the UE can only transmit one scheduling allocation (SA) per SC period (ie, side link control information (SCI)). Further, the transmitting UE can transmit data to only one or a plurality of receiving UEs in one ProSe destination group per scheduling allocation (SA) (that is, scheduling control information (SCI)).

More specifically, the sending UE has the same source layer 2 ID and destination layer 2 ID pair in the (one or more) MAC packet data units (PDUs) associated with one SCI. Consider only logical channels. This D2D transmission method, which is currently standardized, causes some inconveniences.

If the UE has data to more than one ProSe destination group in its own (s) buffers, the sender UE should only send data to one ProSe destination group per SC period. Limited to. Therefore, the data in the remaining ProSe destination groups (s) are delayed by at least one additional SC period. In other words, the transmission of scheduling allocation (SA) (ie, side link control information (SCI)) can indicate only one ProSe destination group, and the corresponding data transmission is limited to only the same ProSe destination group.

Depending on the set SC period and the number of SC periods required to transmit all the data to one ProSe destination group, the delay may be large, resulting in poor sidelink communication characteristics. This is also true for sufficient radio resources capable of transmitting more data than the ProSe destination group processed first.

Further, the transmitting UE can only inefficiently utilize the D2D transmission resources allocated by the evolved NodeB (eNB) for data transmission. The evolved NodeB (eNB) may allocate more D2D transmit resources (by SL grant) than the transmitting UE needs. However, since it is limited to only one ProSe destination group, for example, if sufficient data for that one ProSe destination group is not in the UE's buffer, the sending UE will utilize all the allocated radio resources. Can not do it. This situation can occur, for example, when the buffer state information signaled to the eNB by the sending UE is inaccurate or out of date. In this case, some of the allocated radio resources remain unused, because these resources cannot be used for the purpose of transmitting data from another ProSe destination group within the same SC period.

The inventor has conceived the following exemplary embodiments for the purpose of alleviating the problems described above.

Some of these exemplary embodiments are implemented within the broad specification given by the 3GPP standard, some of which are described in the Background Techniques section, and are of particular importance to the various implementations. Is added as described below. It should be noted that these embodiments can be advantageously used in mobile communication systems such as 3GPP LTE-A (Release 10/11/12/13) described in the Background Technology section, for example. Note that is not limited to use in this particular exemplary communication network.

The following description should be understood not as limiting the scope of the present disclosure, but merely as 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 disclosure described in the claims can be applied to various scenarios in ways not expressly described herein. Let's do it. Therefore, the following scenarios are envisioned for the purpose of explaining various embodiments, and the embodiments are not limited to such scenarios.

First Embodiment In the following, the first embodiment for solving the above problems will be described in detail. The implementation form of the first embodiment will be described with reference to FIG. Some assumptions are made for illustration purposes, but these assumptions do not limit the scope of the embodiments.

First, a user device (ProSe-compatible UE) capable of executing ProSe communication (that is, direct D2D transmission between UEs without going through eNodeB) is assumed. Further, the UE shall have data in a transmittable state with a plurality of sidelink destination groups (ie, ProSe destination groups) as destinations, provided that the improved direct sidelink transmission according to this first embodiment. The mechanism also applies when the UE is in a state where only one sidelink destination group of data can be transmitted.

The first embodiment improves direct sidelink transmission by introducing the concept that sidelink grants can be assigned one-to-one to the (plural) sidelink processes within the UE. In other words, the UE can handle multiple sidelink grants by running a sidelink process corresponding to each sidelink grant. The sidelink process can be addressed by the use of the corresponding identification information (hereinafter exemplarily referred to as the sidelink process ID).

In today's standardized mobile communication systems, the UE has one valid sidelink grant per sidelink control (SC) period (previously received (s) sidelink grants are overwritten and most recently. Sidelink grants) are only allowed to be used, whereas the first embodiment allows UEs to have more than one valid sidelink grant per same SC period. By doing so, D2D communication is improved.

In other words, according to the first embodiment, the sender UE is allowed to have one valid sidelink grant per sidelink process, and thus the sender UE is configured with multiple sidelink processes. Can have the same number of valid sidelink grants for the SC period. Therefore, in the UE, its sidelink communication capability is limited by the maximum number of sidelink processes.

Secondly, it is assumed that the user equipment of this embodiment is set with the maximum number of side link processes. This maximum number of SL processes can be implementation specific and is therefore preset in the user equipment. The maximum number can also be unique to the UE, so the UE is set by an evolved NodeB that is within its coverage. Alternatively, this number can be network-specific, thus setting the same maximum number of sidelink processes for all UEs in the same network. UE-specific or network-specific configuration mechanisms may require RRC signaling.

In particular, side-link transmissions are direct transmissions from one (sender) UE to one or more (receiver) UEs, but the same maximum number for all UEs involved in such side-link transmissions. Sidelink process does not need to be configured.

Instead, the transmitting UE can be configured with a maximum number of SL processes that is greater than the maximum number of one or more receiving UEs that are the destinations of the side-link transmission of the transmitting UE. Further, all SL transmissions from the transmitting UE may be received by one or a plurality of receiving UEs in the side link destination group. In this regard, a sufficient number of sidelink processes are configured not only for the transmitting UE but also for one or more receiving UEs.

However, for the purpose of simplifying the configuration of the sending and receiving UEs, it is assumed that the maximum number of sidelink processes is network specific. For example, the maximum number of sidelink processes can be m = {2,4,8}, and in the following example, m = 2 (2) sidelink processes are set for each UE in the communication system. The case where it is. Thus, such an exemplary UE can handle two different sidelink grants at the same time (thus the UE has two valid (also referred to as "configured") sidelink grants available during the SC period. Has).

Overall, the UE has already standardized the D2D transmission behavior of each sidelink process with a corresponding sidelink grant within the same SC period to perform the D2D transmission, eg, described in the Background Techniques section. Perform according to each concept. Specifically, the UE determines one sidelink destination group for each sidelink grant available to it (ie, for each sidelink process) and destinations the determined sidelink destination group. Generate the corresponding transport block containing the data. Radio resources for D2D transmission are allocated according to their respective sidelink grants. The UE identifies the sidelink destination group for each sidelink grant available to it (ie, for each sidelink process) and the corresponding radio resource allocated for D2D transmission. It generates link control information and performs D2D transmission of side link control information and corresponding data to each side link grant (process) using the assigned radio resources of each side link grant.

Details of these steps for performing D2D transmission are omitted here and instead refer to the corresponding parts of the Background Techniques section of the present application.

The above-mentioned principles underlying the first embodiment offer various advantages. In this regard, already established procedures can be reused without modification. For example, the same SCI format 0 can be used to transmit sidelink control information, because no additional information needs to be conveyed. Moreover, since the D2D transmission of each side-link process remains unchanged compared to the currently standardized D2D transmission, the receiving UE is a D2D performed in one side-link process according to the first embodiment. There is no distinction between transmission and D2D transmission performed according to current standards (there is no need to actually distinguish). Therefore, it is not necessary to adapt the behavior of the UE on the receiving side.

Furthermore, in the first embodiment, it is possible to transmit more data within the SC period, thus increasing the data rate of D2D transmission.

In addition to this, in the first embodiment, data destined for several sidelink destination groups will be sent to the same SC period, for example by selecting different sidelink destination groups for each of the various sidelink processes. It is possible to send within. Therefore, it is possible to avoid a resource shortage of a specific side link destination group.

So far, we have generally assumed that the UE has some sidelink grants available and have not paid attention to how the UE first acquired these sidelink grants. .. This point will be described in more detail below.

First Variation In the first variation, the transmitting UE, in this first embodiment, has multiple sidelink grants for at least some of the maximum number of sidelink processes configured on it. get. These plurality of side link grants are signaled by the evolved NodeB (eg, via PDCCH) by applying a standardized signaling scheme, which the UE receives.

The transmitting UE selects a specific number of sidelink grants from the plurality of acquired sidelink grants. The number of sidelink grants selected by the UE can be, for example, n = {2,4,8), and in the illustrated example, the UE selects n = 2 (2) sidelink grants. The case where it is configured as follows is shown. In other words, the sending UE does not store or maintain all of the sidelink grants acquired by the UE after being signaled by the evolved NodeB, but stores or maintains only a certain number of sidelink grants.

In particular, the transmitting UE selects a specific number of recently acquired sidelink grants prior to the start of the sidelink control period from among the plurality of acquired sidelink grants. Assuming that the sidelink control period begins in a particular subframe, the transmitting UE selects a plurality of last acquired sidelink grants prior to that particular subframe.

However, this does not mean that the transmitting UE can only select that particular number of sidelink grants at the beginning of the sidelink control period. Instead, the UE of the sidelink grants by associating each of the multiple sidelink processes with (alternately) (again) the more recently acquired sidelink grants (eg, by overwriting the memory areas involved). This choice can be achieved.

Therefore, each time the UE acquires a newer sidelink grant, the newly acquired sidelink grant can be assigned to the sidelink process having the oldest sidelink grant among the multiple sidelink processes. , This causes a certain number of the most recent sidelink grants to be selected by the UE at the beginning of the sidelink control period. In this regard, the UE can alternate a plurality of sidelink processes when assigning the most recently acquired sidelink grants to the sidelink processes.

Next, the example shown in FIG. 13 will be referred to. In this example, the UE is set with the number n = 2 (2) of sidelink grants to be selected and the maximum number m = 2 (2) of sidelink processes. The UE acquires the side link grant in the subframe N until the start of the side link control period (to be exact, up to four subframes before the start of the side link control period (subframe N-4)).

The first sidelink grant obtained (eg in subframe N-13) is associated with the first sidelink process of the sidelink processes with m = 2 (2) set (eg in subframe N-13). The next acquired sidelink grant (in N-11) is associated with the second sidelink process of these two configured sidelink processes. In other words, the sidelink grant is periodically associated with the configured sidelink process.

When additional sidelink grants are acquired (eg in subframe N-8), the UE recognizes that it is set to select only n = 2 (2) sidelink grants. Thus, the UE subsequently (or periodically) transfers its newly acquired sidelink grant to the first sidelink process of the sidelink processes with m = 2 (2) set. Associate (again). In other words, the sidelink grant acquired in subframe N-13 and previously associated with the (also) first sidelink process of the two configured sidelink processes is overwritten.

In particular, this periodic association to the configured sidelink process depends on the number of sidelink grants selected (n = 2) and is the maximum number of sidelink processes configured on the UE (m = 2). It does not depend on 2). Furthermore, the number of sidelink grants selected (n = 2) must not exceed the maximum number of sidelink processes set (m = 2) (n <= m).

Finally, when an additional sidelink grant is acquired by the UE (eg in subframe N-6), this sidelink grant is the second of the sidelink processes with m = 2 (2) set. Is reassociated with the sidelink process. Therefore, the sidelink grant acquired in subframe N-11 and previously associated with the (also) second sidelink process of the two configured sidelink processes is overwritten.

In summary, by applying the behavior described above, the sending UE acquires multiple sidelink grants at the beginning of the sidelink control period (more precisely, four subframes before the start). , A certain number of sidelink grants most recently acquired prior to the start of that sidelink control period have been selected. In addition, each of the n = 2 (2) selected sidelink grants is associated with a different sidelink process of the m = 2 (2) configured sidelink processes.

In a favorable implementation, the sender UE acquires this new sidelink grant before associating it with the corresponding one of the configured sidelink processes. Determines if the sidelink grant that has been made matches another sidelink grant that is already associated with another one of the configured sidelink processes. If it matches another sidelink grant and the two acquired sidelink grants point to the same radio resource for multiple sidelink transmissions (ie leading to a radio resource conflict), a new receive Discard the same sidelink grant that was created (ie, do not associate the newly acquired sidelink grant with the corresponding sidelink process). This maintains a periodic association with the configured sidelink process.

Although the mechanisms described above are simple, these mechanisms take advantage of the above behavior to eliminate interference and distortion in the medium (ie PDCCH) used by the evolved NodeB to signal sidelink grants to the transmitting UE. It can be suppressed, which is advantageous.

Traditionally, evolved NodeBs address interference and distortion (eg, in PDCCH) by signaling the same sidelink grant to the transmitting UE multiple times. The UE only acquires sidelink grants that are unaffected by interference or distortion. Therefore, each time the same sidelink grant is repeatedly signaled by the evolved NodeB, the probability that the sidelink grant is normally acquired in the transmitting UE is improved. The conventional transmitting UE overwrites the SL grant each time the SL grant is successfully acquired. This approach is simple and robust as long as the same sidelink grant is signaled.

Different sidelinks between the sending UE and one or more receiving UEs Behavior is not clear when applying this approach to different sidelink grants that indicate radio resources for transmission. .. Further, the evolved NodeB does not recognize which of the different sidelink grants is successfully acquired by the transmitting UE and which sidelink grant is not successfully acquired. In other words, the evolved NodeB cannot assess whether one or another of the different sidelink grants needs to be retransmitted before the start of the SC period.

The transmitting UE in the first variation assumes that different (plural) different side link grants are repeatedly signaled, and when a plurality of side link grants are normally acquired, the side of the acquired side link grants is obtained. Select a certain number of side link grants most recently acquired prior to the start of the link period. In addition, a sidelink grant (and therefore for the next SC period) is acquired by the UE prior to the next SC period.

This approach is advantageous for the following reasons: That is, if the UE successfully acquires all the sidelink grants signaled by the evolved NodeB, then as a result of selecting a certain number of the most recently acquired sidelink grants, the sender UE ( Different sidelink grants (s) are offered. Thus, the transmitting UE can perform multiple (different) sidelink transmissions to one or more receiving UEs.

Also, if the UE successfully acquires only that particular number of last sidelink grants signaled by the evolved NodeB, it will also select the most recently acquired grant to its sender UE. ) Different grants are offered. Therefore, as long as that particular number of signaled sidelink grants is successfully obtained by the sending UE, all but that particular number of signaled sidelink grants are normal. It does not have to be acquired in.

However, for example, if the last grant of the sidelink grants signaled by the evolved NodeB is not successfully (at all) acquired by the UE, the UE will successfully acquire other than the last sidelink grant that was not successfully acquired. Select a certain number of acquired sidelink grants. Again, as will be clear from the discussion below, the transmitting UE will eventually acquire a certain number of different sidelink grants.

Assuming that different sidelink grants are signaled repeatedly, even in this case, the repeated signaling by the evolved NodeB ensures that the selected number of sidelink grants are different. , The transmitting UE successfully obtains (s) different sidelink grants, so the transmitting UE uses these sidelink grants to multiple (different) to one or more receiving UEs. Sidelink transmission can be performed.

Furthermore, one of the sidelink grants signaled between the first and last by the evolved NodeB is the most recently acquired by the sending UE, even if it is not successfully acquired (ie, not) by the UE. If the evolved NodeB signals an extra number of different sidelink grants (“preliminary” sidelink grants) within the range of multiple sidelink grants that are made, then the most recently received specific number of sides. As a result of selecting a link grant, different side link grants are also obtained. In other words, by increasing the cycle in which different sidelink grants are iteratively signaled by the evolved NodeB for the number of sidelink grants acquired by the sending UE, at least the most recently acquired sidelink grant is the UE. It can be ensured that it is acquired normally.

In summary, choosing a certain number of sidelink grants most recently acquired by the sending UE loses the advantage of well eliminating interference and distortion as part of the traditional approach. A mechanism is provided that allows a UE to perform multiple (different) sidelink transmissions to one or more receiving UEs without the need for it.

Furthermore, this approach does not require the sidelink grant to include identifying information to associate the acquired sidelink grant with one of the maximum number of sidelink processes configured on the sending UE. In that respect, it is advantageous. Therefore, by individually associating the acquired sidelink grants with the corresponding processes of the maximum number of sidelink processes, the information (and therefore size) of each signaled sidelink grant is kept to a minimum. be able to.

The number of sidelink grants selected by the UE must not exceed the maximum number of sidelink processes configured on the UE for that sidelink control period. This allows all sidelink grants selected by the UE to be associated with a different one of the selected number of sidelink processes in order to allocate radio resources within the sidelink control period. it can. The UE is responsible for each of the multiple sidelink transmissions to one or more receiving UEs in each of the sidelink processes associated with one different sidelink grant of the selected sidelink grants. To perform one transmission, the sidelink grant allocates radio resources within the received sidelink control period according to the associated sidelink grant.

According to an exemplary implementation, the number of sidelink grants selected by the UE matches the maximum number of sidelink processes (UE is configured with up to this maximum number of sidelink processes for the sidelink period). Will be). This allows all configured maximum number of sidelink processes to be associated with a different one of the selected number of sidelink grants for allocating radio resources within the sidelink control period. ..

An exemplary implementation that applies the above principles of the first variation involves the following changes to the relevant 3GPP technical standard in Non-Patent Document 5 (current version 12.7.0). For the sake of brevity, only the relevant sections are listed below, but all other sections of this Non-Patent Document 5 are also incorporated herein by reference.

5.14 SL-SCH data transmission 5.14.1 SL-SCH data transmission 5.14.1.1 SL grant reception and SCI transmission In order to transmit on SL-SCH, the MAC entity uses a side link grant. Must have. A MAC entity can have up to x sidelink grants. Sidelink grants are selected as follows:
-The MAC entity is configured to dynamically receive sidelink grants on the PDCCH or EPDCCH, with more data available on the STCH (Sidelink Traffic Channel) than can be transmitted during the current SC period. If so, the MAC entity shall:
-Using the received side link grant, the set of subframes in which the SCI is transmitted and the first transport block is transmitted is determined according to Section 14.2.1 of [2] (Non-Patent Document 2). To do.
-The sidelink grant receives the last x sidelink grants received up to 4 subframes (including the 4th previous subframe) before the first subframe of the first available SC period. Considered as a set sidelink grant that exists in the subframe that starts at the beginning of the first available SC period that starts after at least 4 subframes after the subframe that was set, and exists in the same SC period, set before Overwrite the sidelink grant (if available).
-Clear the set side link grant at the end of the corresponding SC period.
-Rather, the MAC entity is configured by the upper layers to transmit using a pool of resources as described in Section 5.10.4 of [8] (Non-Patent Document 9). If more data is available in STCH than can be transmitted within the current SC period and the MAC entity does not have a configured sidelink grant, the MAC entity shall: ..
-Randomly select a side link grant from the resource pool set by the upper layer. The random function is such that each of the allowed options [2] can be selected with equal probability.
-Using the selected side link grant, the set of subframes in which the SCI is transmitted and the first transport block is transmitted is determined according to Section 14.2.1 of [2] (Non-Patent Document 2). To do.
-The selected sidelink grant is combined with the configured sidelink grant that is present in the subframe starting at the beginning of the first available SC period, where the sidelink grant begins at least four subframes after the selected subframe. I reckon.
-Clear the set side link grant at the end of the corresponding SC period.
Note: After the set side link grant is cleared, it is not possible to retransmit with SL-SCH.

The MAC entity shall do the following for each subframe:
-If the MAC entity has a configured sidelink grant that resides within its subframe
-If the configured side link grant supports SCI transmission,
-Instruct the physical layer to send the SCI corresponding to the configured side link grant.
-Otherwise, if the configured sidelink grant corresponds to the transmission of the first transport block,
-Pass the configured sidelink grant and associated HARQ information to the sidelink HARQ entity for that subframe.

5.14.1.2 Sidelink HARQ operation 5.14.1.2.1 Sidelink HARQ entity There is one sidelink HARQ entity in the MAC entity for transmission on SL-SCH, and the sidelink HARQ entity. Maintains one X sidelink process.

For each subframe of SL-SCH, the sidelink HARQ entity shall:
− If a sidelink grant for the sidelink process is shown and SL data is ready to be transmitted
-Get the MAC PDU from the "Multiplexing and assembly" entity.
-Pass MAC PDU and sidelink grant and HARQ information to the sidelink process.
− Instruct the sidelink process to trigger a new transmission.
− Otherwise, if the subframe corresponds to a retransmission opportunity in the sidelink process
− Instruct the sidelink process to trigger a retransmission.
Note: Resources for retransmission opportunities are specified in Section 14.2.1 of [2] (Non-Patent Document 2).

According to the alternative implementation, a sidelink grant receive window associated with the SC period is introduced, which means the period during which the received sidelink grant is considered for the corresponding SC period. The sidelink grant reception window associated with the SC period n starts at subframe y-3 (subframe y means the first subframe of SC period n-1 (previous SC period)) and SC period n. It ends only 4 subframes before the first subframe of. For the first variation, the UE considers the last x sidelink grants (if available) received in the sidelink grant reception window to be sidelink grants configured for the corresponding SC period. ..

Second Variation In the second variation, the transmitting UE, in this first embodiment, has a plurality of sidelink grants for at least some of the maximum number of sidelink processes configured on it. To get. These plurality of side link grants are signaled by the evolved NodeB (eg, via PDCCH) by applying a standardized signaling scheme, which the UE receives.

Importantly in this second variation, sidelink grants are acquired in different subframes prior to the start of the sidelink control period (exactly four subframes before the start). In other words, the sending UE is of the maximum number of sidelink processes configured (see, eg, m = {2,4,8} above), depending on the subframe when the sidelink grant is acquired. It (potentially) behaves differently when assigning a sidelink grant to one.

In particular, in this second variation, as in the previous variation, the UE selects (and) a certain number of n sidelink grants that correspond to a subset of the maximum number of m sidelink processes that have been set. Therefore, it cannot be associated). Further, the UE associates a maximum of several m acquired sidelink grants among the plurality of acquired sidelink grants with a corresponding maximum number of m sidelink processes set in the transmitting UE. It is configured as follows. Obviously, for this behavior, the UE actually needs to get up to a few meters of sidelink grants.

As mentioned above, the subframe when a sidelink grant is acquired determines in the sending UE the sidelink process to which that sidelink grant is associated. More specifically, because multiple sidelink grants are signaled and therefore acquired in different subframes prior to the start of the sidelink control period (more precisely, before the four subframes before the start). Subframes allow unique allocation to associate each of the created sidelink grants with one of the maximum number of sidelink processes configured.

The sending UE applies an association method to associate the acquired sidelink grant with one of the maximum number of configured sidelink processes. This association method is defined as follows. That is, each of the maximum number of SL processes is associated with a sidelink grant from a set of different subframes, and each of the subframes in the corresponding set is a predefined number (eg o) of subframes. Only offset from each other.

In other words, each set of different subframes from which a sidelink grant is acquired defines an association for these sidelink grants with one of the configured sidelink processes. The sets of subframes are separate from each other because each set contains different subframes. In addition, the subframes in each set are offset from each other. This allows successive subframes to associate the sidelink grants acquired within them with a different one of the maximum number of configured sidelink processes. In other words, multiple sidelink grants associated with different sidelink processes are interleaved and have synchronized timing.

In summary, by applying an association scheme to each subframe when the sending UE gets a sidelink grant, the sending UE has the maximum number (eg, by overwriting the memory area involved). One of the sidelink processes can be (again) associated with the most recently acquired sidelink grant. In this regard, each of the maximum number of configured sidelink processes was acquired in each set of different subframes and most recently acquired before the start of the next sidelink control period. Associated with ,.

Next, the example shown in FIG. 14 will be referred to. In this example, the UE is configured with a maximum number of m = 2 (2) sidelink processes, and the offset between different subframes in the set is a predefined number of o = 2 (2) subs. It is assumed that it corresponds to the frame. This example shall not be construed to limit the underlying concept, as it is possible, for example, to offset o = {2,4,8}, as will be clear from the following. The UE acquires the side link grant until the start of the subframe N of the side link control period (to be exact, up to four subframes (N-4) before the start of the side link control period).

As is clear from the top, the offset between different subframes in the set (eg o = 2) matches or this maximum of the maximum number of sidelink processes configured (eg m = 2). It can be larger than the number (this leaves the intermediate subframes unassigned to one or another of the maximum number of sidelink processes).

Furthermore, by defining the offset between different subframes in the set (eg o = 2) and the maximum number of sidelink processes set (eg m = 2) to match, the sidelink grant The medium for signaling (eg, PDCCH) is most efficiently used, whereas if the offset is greater than the maximum number, the transmitting UE will reduce the monitoring of the same medium, which will result in the transmitting side. The battery efficiency of the UE is improved.

In addition to the illustrated example, the association scheme is such that the first set of multiple different subframes (subframes N-14, N-12) with respect to the first of the sidelink processes with a maximum of several m = 2. , N-10, N-8, N-6, N-4). In this association method, for the second process of the side link process having a maximum number of m = 2, a second set of a plurality of different subframes (subframes N-13, N-11, N-9) , N-7, N-5 are included). For each set, the different subframes are offset from each other by a predefined number o = 2 (2) of subframes.

For example, the first sidelink grant acquired by the UE in subframe N-13 is associated with the second of the sidelink processes with m = 2 (2) set, because the UE is on top. By applying the association scheme described in, this sidelink grant is required to be obtained in subframes that belong to a second set of multiple different subframes, so the UE is therefore required to have the maximum number of this sidelink grant. This is because it is assumed that it is associated with the second process of the side link process of m = 2.

Then, for example, an additional sidelink grant acquired by the UE in subframe N-11 is also associated with the second of the two configured sidelink processes, because this sidelink grant is also a subframe. This is because it is acquired in the subframe belonging to the second set of. The UE will take the newly acquired sidelink grant (eg in N-11) to the second of the sidelink processes with m = 2 (2), regardless of the previous sidelink grant. Associate (again) with the process of. In other words, the sidelink grant previously associated with the (also) second process of the two configured sidelink processes acquired in subframe N-13 is overwritten.

Then, for example, another sidelink grant acquired by the UE in subframe N-8 is associated with the first of the sidelink processes with m = 2 (2) set, because the UE is. By applying the association scheme described above, we want this sidelink grant to be acquired in subframes that belong to the first set of different subframes, so the UE will have this sidelink grant up to a few meters. This is because it is assumed that it is associated with the first process of the = 2 sidelink processes.

Finally, for example, an additional sidelink grant acquired by the UE in subframe N-6 is also associated with the first of the two configured sidelink processes, because this sidelink grant is also in the subframe. This is because it is acquired in the subframe belonging to the first set. The sidelink grant previously associated with the (also) first process of the two configured sidelink processes acquired in subframe N-8 is overwritten.

In summary, the sending UE acquires multiple sidelink grants by applying the behavior described above, and at the beginning of the associated sidelink control period (more precisely, only four subframes from the start). Previously), each of the multiple sidelink processes with a maximum of several m = 2 was acquired in each set of multiple different subframes and the most recently acquired side prior to the start of the next sidelink control period. Associated with the link grant.

The transmitting UE is a radio resource within the next side link control period for performing one of the multiple side link transmissions to one or more receiving user devices for each of the plurality of SL processes. Are assigned according to the sidelink grant to which each sidelink process is associated.

According to an exemplary implementation associated with a first variation or a second variation, the transmitting UE has a sidelink grant for one (ie, the next) sidelink control period of that sidelink control period. Acquire only 4 subframes before the start. This provides the evolved NodeB with accurate information on when the most recent sidelink grant can be obtained by the UE. In other words, the evolved NodeB can pre-plan the appropriate signaling of sidelink grants.

In a further exemplary implementation associated with the first variation or the second variation, each of the plurality of sidelink processes is reinitialized (or reinitialized) prior to the start of its (ie, next) sidelink control period. It is then possible to associate the sidelink process with a later (ie, next) sidelink control period. Assuming that the sidelink grant can be obtained 4 subframes before the start of the sidelink control period, then as soon as possible (ie, 3 subframes before the start of the sidelink control period), multiple The sidelink process is reinitialized. This allows the acquired sidelink grant to be associated with the sidelink process as soon as possible for a later (ie, next) sidelink control period, which means It is particularly advantageous in the second variation, but is not limited to this.

According to yet another exemplary implementation associated with the first variation and the second variation, the sending UE associates each of the selected sidelink grants with a different one of the plurality of sidelink processes. Then perform a logical channel prioritization (LCP) procedure for each associated sidelink process. After each of the LCP procedures identifies a different ProSe destination group, each of the plurality of sidelink transmissions can be made to be performed to one or more different receiving UEs.

An exemplary implementation that applies the above principles of the second variation involves the following changes to the relevant 3GPP technical standard in Non-Patent Document 5 (current version 12.7.0). For the sake of brevity, only the relevant sections are listed below, but all other sections of this Non-Patent Document 5 are also incorporated herein by reference.

5.14 SL-SCH data transmission 5.14.1 SL-SCH data transmission 5.14.1.1 SL grant reception and SCI transmission In order to transmit on SL-SCH, the MAC entity uses a side link grant. Must have. A MAC entity can have up to x sidelink grants. Sidelink grants are selected as follows:
-The MAC entity is configured to dynamically receive sidelink grants on the PDCCH or EPDCCH, with more data available on the STCH (Sidelink Traffic Channel) than can be transmitted during the current SC period. If so, the MAC entity shall:
-Using the received side link grant, the set of subframes in which the SCI is transmitted and the first transport block is transmitted is determined according to Section 14.2.1 of [2] (Non-Patent Document 2). To do.
− Received sidelink grants are configured sidelinks that are present in the subframe starting at the beginning of the first available SC period, which begins at least four subframes after the received subframe. Considers a grant and overwrites the previously set sidelink grant (if available) that was received only X subframes before the received subframe and existed within the same SC period. To do.
-Clear the set side link grant at the end of the corresponding SC period.
-Rather, the MAC entity is configured by the upper layers to transmit using a pool of resources as described in Section 5.10.4 of [8] (Non-Patent Document 9). If more data is available in STCH than can be transmitted within the current SC period and the MAC entity does not have a configured sidelink grant, the MAC entity shall: ..
-Randomly select a side link grant from the resource pool set by the upper layer. The random function is such that each of the permitted options [2] (Non-Patent Document 2) can be selected with equal probability.
-Using the selected side link grant, the set of subframes in which the SCI is transmitted and the first transport block is transmitted is determined according to Section 14.2.1 of [2] (Non-Patent Document 2). To do.
-The selected sidelink grant is combined with the configured sidelink grant that is present in the subframe starting at the beginning of the first available SC period, where the sidelink grant begins at least four subframes after the selected subframe. I reckon.
-Clear the set side link grant at the end of the corresponding SC period.
Note: After the set side link grant is cleared, it is not possible to retransmit with SL-SCH.

The MAC entity shall do the following for each subframe:
-If the MAC entity has a configured sidelink grant that resides within its subframe
-If the configured side link grant supports SCI transmission,
-Instruct the physical layer to send the SCI corresponding to the configured side link grant.
-Otherwise, if the configured sidelink grant corresponds to the transmission of the first transport block,
-Pass the configured sidelink grant and associated HARQ information to the sidelink HARQ entity for that subframe.

5.14.1.2 Sidelink HARQ operation 5.14.1.2.1 Sidelink HARQ entity There is one sidelink HARQ entity in the MAC entity for transmission on SL-SCH, and the sidelink HARQ entity. Maintains one X sidelink process.

For each subframe of SL-SCH, the sidelink HARQ entity shall:
− If a sidelink grant for the sidelink process is shown and SL data is ready to be transmitted
− Get the MAC PDU from the Multiplexing and Assembly entity.
-Pass MAC PDU and sidelink grant and HARQ information to the sidelink process.
− Instruct the sidelink process to trigger a new transmission.
− Otherwise, if the subframe corresponds to a retransmission opportunity in the sidelink process
− Instruct the sidelink process to trigger a retransmission.
Note: Resources for retransmission opportunities are specified in Section 14.2.1 of [2] (Non-Patent Document 2).

According to another implementation, if a sidelink grant is received within this TTI at a given TTI, the UE identifies the sidelink process with which the sidelink grant is associated. The sidelink grant received in subframe n overrides the sidelink grant received in subframe n-X, where X means a predefined integer value.

Second Embodiment In the following, a second embodiment for solving the above problems will be described in detail. This embodiment specifically focuses on (but is not limited to) multiple sidelink transmissions in the mode 2 resource allocation mode. Further in this regard, the communication system allocates radio resources to perform multiple direct side link (SL) transmissions to one or more receiving user devices through the SL interface within the side link control (SC) period. The mechanism that makes this possible has been devised.

More specifically, the transmitting UE autonomously selects multiple SL grants for SL transmission from different resource pools, and each resource pool is configured and enabled for SL transmission within the communication system. There is. In addition, the UE must associate different SL processes with SL grants selected from different configured resource pools for each of the multiple SL transmissions.

The sending UE performs a separate logical channel prioritization (LCP) procedure for each of the multiple SL processes with associated SL grants, which logical to the different destination group IDs. Only consider the channel. Thus, the UE allocates radio resources to each of the plurality of SL processes according to an autonomously selected SL grant with which each SL process is associated within the same or overlapping SC periods.

Thereby, the transmitting UE can be configured to execute a plurality of SL transmissions within the same side link control period, and each of the plurality of SL transmissions has one or a plurality of receiving UEs as destinations. To do. In addition, the MAC is restricted to allow only SL transmissions to different ProSe destination groups within the same SC period or overlapping SC periods (when the transmitting UE performs SL transmissions in different transmission resource pools). This is advantageous because there is no need for additional mechanisms to reorder the transport blocks (TB) within the layer. In other words, in this embodiment ProSe communication is forced to be passed in the correct order.

According to an exemplary implementation, the transmitting UE further determines, for each subframe within the SC period, whether the allocated radio resource is allocated for multiple SL transmissions within the same subframe. Specifically, since ProSe communication is performed by applying the single carrier frequency division multiple access (SC-FDMA) method in the uplink band, as will be clarified from the following, a plurality of SL transmissions have single carrier characteristics. Must be met.

As is clear from the SC-FDMA system, the transmitting UE can only perform the transmission of one transport block (TB) per transmission time interval (TTI). However, radio resources autonomously selected for multiple SL transmissions within the same SC period may not meet this characteristic. In other words, radio resources cannot be allocated for the same plurality of SL transmissions.

If the transmitting UE determines that the allocated radio resources are not properly arranged (that is, does not satisfy the single carrier characteristics described above) for each transmission time interval, the priority rank of the logical channel for SL transmission is ranked. The transmission of each SCI and / or data of the lower SL process can be skipped, or the UE can skip the transmission of each SCI and / or data of the SL process associated with the lower rank resource pool. Can be done.

The priority of the logical channel targets the data transmission portion of the SL transmission. Further, the rank of the resource pool also establishes the priority of the data transmission portion of the SL transmission. Furthermore, skipping individual transmissions generally has little effect on system performance, as many retransmissions are performed by each resource pool as described above.

In summary, in this advantageous implementation, when performing multiple SL transmissions (each SL transmission destined for one or more receiving UEs) within the same SC period, multiple SL transmissions SC-FDMA compatibility is enforced by the transmitting UE. This avoids defining compatibility between SL grants that are autonomously selected from different resource pools.

As a result of the SL grant issued by the eNB, when the allocated radio resources are allocated for a plurality of SL transmissions in the same subframe within the SC period, the resource allocation mode controlled by the eNB Note that it may be necessary to skip some of the respective SCI and / or data transmissions also in (Mode 1).

<Implementation of this disclosure by hardware and software>
Another exemplary embodiment relates to implementing the various embodiments described above using hardware, software, or software that works with the hardware. In this regard, a user terminal (mobile terminal) and an eNodeB (base station) are provided. User terminals and base stations are configured to perform the methods described herein and include corresponding entities (receivers, transmitters, processors, etc.) that are appropriately involved in these methods.

Various embodiments are further recognized as being able to be implemented or performed using a computing device (processor). Computing devices or processors include, for example, general purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices. Various embodiments can also be implemented or embodied by a combination of these devices. In particular, each functional block used in the description of each embodiment described above can be implemented by an LSI as an integrated circuit. These functional blocks can be formed individually as chips, or one chip can be formed so as to include a part or all of the functional blocks. These chips can include a data input / output unit that is coupled to them. LSIs are also referred to as ICs, system LSIs, super LSIs, or ultra LSIs, depending on the degree of integration. However, the technique for implementing an integrated circuit is not limited to LSI, and can be achieved by using a dedicated circuit or a general-purpose processor. Further, an FPGA (field programmable gate array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reset the connection and setting of the circuit cells arranged inside the LSI can also be used.

In addition, various embodiments may also be implemented by software modules. These software modules are executed by the processor or directly in the hardware. It is also possible to combine software modules and hardware implementations. The software module can be stored in any kind of computer-readable storage medium, such as RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROMs, DVDs, and the like. Furthermore, it should be noted that the individual features of a plurality of different embodiments can be the subject of another embodiment individually or in any combination.

Those skilled in the art will appreciate that the disclosure presented in a specific embodiment may be modified and / or modified in various ways without departing from the broadly defined concept or scope of the invention. Will be done. Therefore, the embodiments presented herein are considered exemplary in all respects and are not intended to limit the invention.

Claims (7)

An integrated circuit for controlling the transmission-side user equipment to allocate the radio resources to perform a plurality of direct-side link (SL) sent to one or multiple receiving user equipment via SL interface in a communication system,
The control
For the next side link control (SC) period, receiving a plurality of side links (SL) grant in different sub-frames before the start of the next side link control (SC) period, the receiver is related By applying the attachment method, each of the received SL grants is associated with one of a plurality of maximum SL processes based on the subframe in which the SL grant is received, and side link control is performed. the allocation of radio resources in the (SC) period, in the side link control (SC) period, is limited by the maximum number of SL process configured on the sending user equipment,
Prior Symbol associated method, wherein the respective maximum number of SL process is associated with SL grants from a set of a plurality of different sub-frames, each of the sub-frame in said set, to each other by the number of subframes is defined The number of subframes that are offset and defined as said offset is greater than the maximum number of said SL processes.
Each of the plurality of maximum SL processes is received in each set of a plurality of different subframes and is the last SL grant received prior to the start of the next side link control (SC) period. Association,
Wherein for each of the plurality of SL processes, for performing one of the plurality of SL transmission of one or the one of multiple receiving user equipment, said next side link control (SC) allocates a radio resource in time, according to the previous SL S L process the SL grant to which each is associated,
Each of the plurality of SL transmissions, including the transmission of at least one side link control information (SCI) and at least one data transmission through the SL interface, is performed.
Including that
Integrated circuit. The integrated circuit according to claim 1, wherein the defined number of subframes matches the maximum number of SL processes set in the transmitting user equipment. The integrated circuit of claim 1, wherein the SL grant for the next side link control (SC) period is received only before the four subframes before the start of the side link control (SC) period. Each of the plurality of SL processes can be reinitialized prior to the start of the side link control (SC) period, after which the SL process can be assigned to the SL grant for the next side link control (SC) period. The integrated circuit according to claim 1. The integrated circuit of claim 4, wherein each of the plurality of SL processes is reinitialized three subframes before the start of the side link control (SC) period. The integrated circuit of claim 1, wherein a logical channel prioritization (LCP) procedure is performed for each of the plurality of SL processes associated with the SL grant. Executing each of the plurality of LCP procedure, including one or identifying different destination group ID is used to perform a plurality of SL transmissions to multiple receiving user equipment, wherein Item 6. The integrated circuit according to item 6.

Images