RU2731775C1 - Improved resource allocation for communication between devices (d2d) - Google Patents

Abstract

FIELD: electrical communication engineering.

SUBSTANCE: invention relates to communication. To this end, the process comprises: receiving a temporary resource template (T-RPT) in the control information; determining a data transmission mode based on control information and determining, based on the received T-RPT index, T-RPT in a given set of T-RPT to be used for transmitting data over a forward link, wherein T-RPT is a bitmap which indicates subframes for transmitting data over a forward link in a resource pool; and receiving data transmission on a forward link using said determined T-RPT for said determined data transmission mode.

EFFECT: technical result is improved distribution of radio resources to a transmitting terminal for transmission with direct communication over a direct connection of a communication line.

5 cl, 22 dwg, 5 tbl

Description

TECHNICAL FIELD OF THE PRESENT INVENTION

The present invention relates to methods for allocating radio resources to a transmitting terminal for direct-link transmission over a direct link connection to a receiving terminal. The present invention also provides a transmitting terminal and base station for participating in the methods described herein.

LEVEL OF TECHNOLOGY

Long Term Evolution (LTE)

Third generation (3G) mobile systems based on WCDMA radio access technology are being widely deployed around the world. The first stage in the improvement or development of this technology includes the introduction of High Speed Downlink Packet Access (HSDPA) and Enhanced Uplink, also called High Speed Uplink Packet Access (HSUPA), which provide a highly competitive radio access technology.

In order to be prepared for further increases in user demand and to be competitive with new radio access technologies, 3GPP has implemented a new mobile communication system called Long Term Evolution (LTE). LTE is designed to meet the needs of a cellular operator for high-speed data and media streaming, as well as high-bandwidth voice, for the next decade. The ability to deliver high data rates is a major metric for LTE.

A Long Term Evolution (LTE) Work Element (WI) specification called UMTS Enhanced Universal Terrestrial Radio Access (UTRA) and UMTS Terrestrial Radio Access Network (UTRAN) is finally agreed as Release 8 (LTE Ver. 8). The LTE system is an efficient radio and radio access network that provides full Internet Protocol (IP) -based functionality at low latency and low cost. In LTE, multiple scalable bandwidths are specified as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz to achieve flexible system deployment using a given spectrum. The downlink has adopted an Orthogonal Frequency Division Multiplexing (OFDM) radio access due to its inherent robustness to multipath interference (MPI) due to its low symbol rate, the use of a cyclic prefix (CP), and its compatibility with different bandwidth arrangements ... In the uplink, a single carrier frequency division multiple access (SC-FDMA) radio access was adopted as providing wide area coverage was considered more important than improving the peak data rate given the limited transmit power of the user equipment (UE) ... Many packet radio access methods are in use, including multichannel input-to-multichannel output channel-based transmission methods and rev. 8/9 LTE achieves a highly efficient control signaling structure.

LTE architecture

The general architecture is shown in FIG. 1, and the E-UTRAN architecture is shown in more detail in FIG. 2. The E-UTRAN consists of an eNodeB supporting the end of the user plane protocols (PDCP / RLC / MAC / PHY) and the control plane (RRC) towards the user equipment (UE). The eNodeB (eNB) hosts the physical (PHY), medium access control (MAC), radio link control (RLC), and packet data control protocol (PDCP) layers, which include header compression and user plane encryption. It also provides a radio resource control (RRC) function corresponding to the control plane. It performs a variety of functions, including radio resource control, connection control, scheduling, enforcement of quality of service (QoS) negotiated uplink, cell information transmission, encryption / decryption of user and control plane data, and downstream / user plane packet header compression / decompression. uplink. The eNodeBs are interconnected with each other through their X2 interface.

The eNodeBs are also connected via the S1 interface to the EPC (Evolved Packet Core), more specifically to the MME (Mobility Management Node) via the S1-MME and to the Serving Gateway (SGW) via the S1-U. The S1 interface supports a many-to-many relationship between MMEs / serving gateways and various eNodeBs. The SGW routes and transmits user data packets while acting as a mobility anchor for the user plane during inter-eNodeB handovers and as a mobility anchor between LTE and other 3GPP technologies (terminating the S4 interface and forwarding traffic between 2G / 3G and PDN GW systems ). For the user equipment in the idle state, the SGW terminates the downlink data path and starts paging when the downlink data arrives for the user equipment. It manages and stores user equipment contexts such as IP channel service parameters, internal network routing information. It also replicates user traffic in the event of legitimate message interception.

MME is the key control node for the LTE access network. It is responsible for tracking and paging of the user equipment in standby mode, including retransmissions. He is involved in the channel activation / deactivation process and is also responsible for the selection of the SGW for the user equipment at the initial connection and during the intra-LTE handover involving the removal of the Core Network (CN) node. It is responsible for authenticating the user (by interacting with the HSS). No Access Stratum (NAS) signaling is terminated in the MME and is also responsible for generating and distributing temporary user equipment identifiers. It verifies the permission of the user equipment to be based on the carrier's public land mobile network (PLMN) and enforces the roaming restrictions of the user equipment. The MME is a termination point in the network for encrypting / combining the transmitted information from alteration for NAS signaling and manages security keys. Lawful signal interception is also supported by MME. The MME also provides a control plane function for mobility between LTE and 2G / 3G access networks, with the S3 interface terminating at the MME from the SGSN. The MME also terminates the S6a interface towards the home HSS for the roaming user equipment.

Carrier structure in LTE

поднесущих, как показано также на фиг. 4.The 3GPP LTE downlink carrier is divided in the time-frequency domain into so-called subframes. In 3GPP LTE, each subframe is divided into two downlink slots as shown in FIG. 3, wherein the first downlink slot comprises a control channel area (PDCCH area) in the first OFDM symbols. Each subframe consists of a predetermined number of OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE (release 8)), with each OFDM symbol covering the entire bandwidth of the downlink component. Thus, each of the OFDM symbols consists of a number of modulation symbols transmitted on the corresponding

subcarriers, as also shown in FIG. 4.

последовательных символов OFDM во временной области (например, 7 символов OFDM) и

последовательных поднесущих в частотной области, как приведено в качестве примера на фиг. 4 (например, 12 поднесущих для несущей составляющей). В LTE 3GPP (версия 8) физический ресурсный блок состоит из

ресурсных элементов, соответствующих одному интервалу во временной области и 180 кГц в частотной области (дополнительные сведения о ресурсной сетке нисходящей линии связи см., например, в документе 3GPP TS 36.211, «Расширенный универсальный наземный радиодоступ (E-UTRA); Физические каналы и модуляция (версия 8)», раздел 6.2, доступном по адресу http://www.3gpp.org и включенном в настоящий документ путем ссылки).Based on a multi-carrier communication system such as using OFDM such as used in 3GPP Long Term Evolution (LTE), the smallest resource unit that can be assigned by the scheduler is a single “resource block”. A physical resource block (PRB) is defined as

consecutive OFDM symbols in the time domain (e.g., 7 OFDM symbols) and

consecutive subcarriers in the frequency domain, as exemplified in FIG. 4 (for example, 12 subcarriers for the carrier). In 3GPP LTE (version 8), the physical resource block consists of

resource elements corresponding to one slot in the time domain and 180 kHz in the frequency domain (for more information on the downlink resource grid, see, for example, 3GPP TS 36.211, “Enhanced Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (version 8) ”, Section 6.2, available at http://www.3gpp.org and incorporated herein by reference).

последовательным поднесущим, перекрывающим полный подкадр, называются «парой ресурсных блоков», или, что то же, «парой RB» или «парой PRB».One subframe consists of two slots, so there are 14 OFDM subframe symbols using the so-called “normal” cyclic prefix (CP) and 12 OFDM symbols per subframe using the so-called “extended” CP. For the terminology, in what follows, the time-frequency resources are equivalent to the same

consecutive subcarriers spanning a full subframe are referred to as a "resource block pair" or, equivalently, an "RB pair" or "PRB pair".

The term "carrier" refers to a combination of multiple resource blocks in the frequency domain. In future versions of LTE, the term "carrier" is no longer used; instead, the term has been changed to "cell", which refers to a combination of downlink resources and, if necessary, uplink resources. The relationship between the carrier frequency of the downlink resources and the carrier frequency of the uplink resources is indicated in the system information transmitted in the downlink resources.

Similar assumptions for the carrier structure also apply to later versions.

LTE-A carrier aggregation to support wider bandwidth

The spectrum for IMT-Advanced was decided at the 2007 World Radiocommunication Conference (WRC-07). Although it was decided on a common spectrum for IMT-Advanced, the actual available frequency range differs depending on each region or country. Meanwhile, following the decision on the basic principles of available frequency spectrum in the Third Generation Partnership Project (3GPP), standardization of the radio interface has begun. 3GPP TSG RAN Meeting # 39 approved the Study Element Description "Further Enhancements for E-UTRA (LTE-Advanced)". The research element covers the technology components to be considered for the development of E-UTRA, for example to meet the requirements for IMT-Advanced.

The frequency band that the LTE-Advanced system can support is 100 MHz, while the LTE system can only support 20 MHz. Currently, insufficient radio spectrum has become a limiting factor in the development of wireless networks, and as a result, it is difficult to find a spectral band that is wide enough for an LTE-Advanced system. Therefore, it is imperative to find a way to obtain a wider spectral bandwidth, with the possible answer being a carrier aggregation function.

In carrier aggregation, two or more carrier components (carrier components) are aggregated to support wider transmission bands up to 100 MHz. Several cells in the LTE system are aggregated into one wider channel in the LTE-Advanced system, which is wide enough for 100 MHz even if these cells in LTE are in different frequency bands.

All supporting components can be made with the possibility of compatibility with ver. 8/9 LTE at least when the aggregated carrier numbers in the uplink and downlink are the same. Not all load-bearing components aggregated by user equipment may necessarily be compatible with rev. 8/9. To avoid basing user equipment ver. 8/9 on the carrier, existing mechanisms can be used (eg prohibition).

The user equipment can simultaneously receive or transmit one or multiple carrier components (corresponding to multiple serving cells) depending on its capabilities. User equipment LTE ver. 10 with receiving and / or transmitting capabilities for carrier aggregation can simultaneously receive and / or transmit to multiple serving cells, while the user equipment ver. 8/9 LTE can only receive and transmit in one serving cell, provided that the carrier structure complies with the specifications rev. 8/9.

Carrier aggregation is supported for both contiguous and non-contiguous carriers, with each carrier being limited to a maximum of 110 Resource Blocks in the frequency domain using LTE (Release 8/9) 3GPP numerical data.

LTE-A (Release 10) 3GPP UE can be configured to aggregate a different number of carrier components originating from the same eNodeB (base station), and possibly different bands in the uplink and downlink. The number of downlink component carriers that can be configured depends on the downlink aggregation capability of the UE. In turn, the number of uplink component carriers that can be configured depends on the UE's uplink aggregation capability. It may not be possible to configure a mobile terminal with more uplink carriers than downlink carriers.

In a typical TDD deployment, the number of carriers and the bandwidth of each carrier in the uplink and downlink are the same. Carriers originating from the same eNodeB do not have to provide the same coverage.

The spacing between the center frequencies of adjacent aggregated carriers is a multiple of 300 kHz. This is necessary to be compatible with the LTE 100 kHz frequency raster (Release 8/9) 3GPP while preserving the orthogonality of the subcarriers at 15 kHz spacing. Depending on the aggregation scenario, n × 300 kHz spacing can be achieved by introducing a low number of unused subcarriers between adjacent carriers.

Multi-carrier aggregation patterns are only exposed up to the MAC layer. For both the uplink and the downlink, there is one HARQ entity required in the MAC for each aggregated carrier. There is (in the absence of uplink SU-MIMO) no more than one transport block per carrier. The transport block and its potential HARQ retransmissions should be mapped to the same carrier.

The Layer 2 structure with carrier aggregation enabled is shown in FIG. 5 and FIG. 6 for the downlink and uplink, respectively.

When carrier aggregation is configured, the mobile terminal has only one RRC connection to the network. When establishing / re-establishing an RRC connection, one cell provides secure entry (one ECGI, one PCI and one ARFCN) and non-access stratum mobility information (eg, TAI) similar to ver. 8/9 LTE. After establishing / re-establishing an RRC connection, the carrier component corresponding to this cell is called the downlink primary cell (PCell). There is always one and only one downlink PCell (DL PCell) and one uplink PCell (UL PCell) configured for each user equipment in the connected state. Within the configured carrier set, other cells are referred to as secondary cells (SCell); wherein the SCells are a downlink secondary carrier (DL SCC) and an uplink secondary carrier (UL SCC).

Configuration and reconfiguration, as well as addition and deletion of carriers, can be performed by RRC. Activation and deactivation are carried out through the control elements of the MAC. In an intra-LTE handover, RRC can also add, delete, or reconfigure SCell for use in the target cell. When a new SCell is added, the dedicated RRC signaling is used to send system information about the SCell, where the information is needed for transmission / reception (similar to Ver. 8/9 for handover).

When configuring user equipment with carrier aggregation, there is one uplink and downlink carrier pair that is always active. The downlink carrier from this pair may also be referred to as the "DL anchor carrier". The same is true for the uplink.

When carrier aggregation is configured, the user equipment can be scheduled across multiple carriers at the same time, but no more than one random access procedure can be performed at any given time. Inter-carrier scheduling allows a carrier PDCCH to schedule resources on a different carrier. For this purpose, a carrier identification field called CIF is introduced into the corresponding DCI formats.

The communication between the carriers of the uplink and the downlink allows identification of the carrier of the uplink for which the grant is applied in the absence of scheduling between carriers. The relationship of the downlink carriers to the uplink carrier does not need to be one-to-one. In other words, more than one downlink carrier may associate with the same uplink carrier. At the same time, the downlink carrier can only associate with one uplink carrier.

RRC LTE states

LTE is based on only two basic states: "RRC_IDLE" and "RRC_CONNECTED".

In RRC_IDLE, the radio is not active, but the ID is assigned and monitored by the network. In particular, the mobile terminal in RRC_IDLE performs cell selection and reselection — in other words, it decides which cell to base on. The cell (re) selection process takes into account the priority of each applicable frequency of each applicable radio access technology (RAT), the quality of the radio link, and the state of the cell (i.e., whether the cell is locked or reserved). The RRC_IDLE mobile terminal monitors the paging channel to detect incoming calls and also obtains system information. The system information mainly consists of parameters by which the E-UTRAN can control the (re) cell selection process, as well as how the mobile terminal accesses the network. RRC specifies control signaling applicable to the mobile terminal in RRC_IDLE, namely paging and system information. The behavior of the mobile terminal in RRC_IDLE is specified in more detail, for example, in TS 36.304, Chapter 4 "Understanding Idle Mode", which is incorporated herein by reference.

In RRC_CONNECTED, the mobile terminal has an active radio communication operation with contexts in the eNodeB. E-UTRAN allocates radio resources to the mobile terminal to facilitate the transmission of (unicast) data over shared data channels. To support this operation, the mobile terminal monitors the associated control channel, which is used to indicate the dynamic allocation of shared transmission resources in time and frequency. The mobile terminal provides the network with reports on the status of its buffer and the quality of the downlink, as well as measurement information about the neighboring network to allow the E-UTRAN to select the most suitable cell for the mobile terminal. These measurement reports include cells using other frequencies or RATs. The UE also receives system information consisting mainly of information required to use the transmission channels. To extend its battery life, the UE in RRC_CONNECTED may be configured using a discontinuous receive cycle (DRX). RRC is the protocol over which the E-UTRAN controls the behavior of the UE in RRC_CONNECTED.

The various functions of a mobile terminal in and including RRC for connected mode are described in 3GPP TS36.331, Chapter 4 Functions, which is incorporated herein by reference. Uplink access scheme for LTE

Uplink transmission requires transmission by an energy efficient user terminal to maximize coverage. Single carrier transmission combined with dynamic bandwidth allocation FDMA was selected as the extended UTRA uplink transmission scheme. The main reason for preferring single carrier transmission is the lower peak-to-average power ratio (PAPR) versus multi-carrier signals (OFDMA) and the corresponding improved power amplifier efficiency and the expected improved coverage (higher data rates for a given peak terminal power ). During each slot, the Node B assigns a unique time-frequency resource to users to transmit user data, thereby ensuring intra-cell orthogonality. Uplink orthogonal access promises increased spectral efficiency by eliminating intra-cell interference. Multipath interference is handled at the base station (Node B) by introducing a cyclic prefix into the transmitted signal.

The basic physical resource used for data transmission consists of a frequency resource of BW _grant size for one time interval, for example, a 0.5 ms subframe to which the coded information bits are mapped. It should be noted that a subframe, also called a transmission time interval (TTI), is the smallest time interval for the transmission of user data. However, it is possible to assign a frequency resource BW _grant for a longer period of time than one TTI to a user by concatenating subframes.

UL scheduling scheme for LTE

The uplink scheme allows both scheduled access, ie, eNB controlled, and contention-based access.

In the case of scheduled access, the UE is allocated a specific frequency resource for a specific time (i.e., time-frequency resource) for uplink data transmission. However, some time-frequency resources may be allocated for contention-based access. Within these time-frequency resources, UEs may transmit without being first scheduled. One scenario in which the UE performs contention-based access is, for example, random access, ie, when the UE performs an initial cell access or to request uplink resources.

For scheduled access, the Node B scheduler assigns a unique time-frequency resource to the user for uplink data transmission. Specifically, the scheduler defines:

- which (which) UE is allowed to transmit,

- what are the resources of the physical channel (frequency),

- a transmission format (Modulation Code Scheme (MCS)) to be used by the mobile terminal for transmission.

The allocation information is signaled to the UE by a scheduling grant sent on the L1 / L2 control channel. For simplicity, this channel is hereinafter referred to as the uplink grant channel. The scheduling grant message contains at least information about which portion of the frequency band the UE is allowed to use, the grant validity period, and the transmission format that the UE should use for the upcoming uplink transmission. The smallest validity period is one subframe. Additional information may also be included in the permission message, depending on the selected scheme. Only per UE grants are used to grant UL-SCH transmission rights (ie, there are no per UE per RB grants). Therefore, the UE needs to distribute the allocated resources among the radio channels according to some rules. Unlike HSUPA, there is no UE-based transmission format selection. The eNB selects a transmission format based on some information, such as reported scheduling information and QoS information, and the UE should follow the selected transmission format. In HSUPA, the Node B assigns the maximum uplink resource and the UE selects the actual transmission format for data transmissions accordingly.

Since radio resource scheduling is the most important function in a shared channel access network for determining Quality of Service, there are a number of requirements that must be met by the UL scheduling scheme for LTE in order to enable efficient QoS management.

- Lack of low priority services should be avoided.

- A clear differentiation of QoS for radio channels / services should be supported by a scheduling scheme.

- UL reporting should allow granular buffered reports (eg, per radio channel or per radio channel group) to allow the eNB scheduler to identify for which radio channel / service the data should be sent.

- It should be possible to create clear QoS differentiation between different user services.

- It should be possible to provide a minimum transmission rate for each radio channel.

As can be seen from the above list, one important aspect of the LTE scheduling scheme is to provide mechanisms by which an operator can control the partitioning of their aggregated cell capacity between radio channels of different QoS classes. The QoS class of the radio channel is identified by the QoS profile of the corresponding SAE channel signaled from the AGW to the eNB, as described above. The operator can then allocate a certain amount of aggregated cell capacity to aggregated traffic associated with radio channels of a certain QoS class. The main purpose of using such a class-based approach is to be able to differentiate packet processing based on the QoS class to which they belong.

Information structure of the (broadcast) system

In 3GPP terminology, the (broadcast) system information is also denoted as BCCH information, that is, it denotes information transmitted on the broadcast control channel (which is a logical channel) of the radio cell to which the UE is connected (active state) or attached (idle state).

Typically, system information includes a service information block (MIB) and multiple system information blocks (SIB). The MIB contains management information for each block of system information. The control information associated with the corresponding SIB may have the following structure. The corresponding control information associated with the SIB may indicate the position of the SIB in the transport channel (e.g., the position in the time-frequency plane for an OFDM radio access, i.e., the specific resource blocks assigned to transmit the corresponding SIB) on which it is transmitted. relative to the overall clock frequency. In addition, the SIB retry period may be specified. This retry period indicates the frequency with which the corresponding SIB is transmitted. The control information may also include a timer value for a timer-based update mechanism, or alternatively a tag value for a tag-based update of the SIB information.

The table below shows an overview of the classification and types of system information blocks in the standard UMTS system, as defined in 3GPP TS 25.331, Radio Resource Control (RRC), version 12.2.0, section 8.1.1, incorporated herein by links. System information is also defined for LTE systems and can be found in TS 36.331 in. 12.2.0 subclause 6.3.1, incorporated herein by reference.

As explained in more detail in the following sections, device-to-device (D2D) technology is expected to be implemented for LTE Ver.12 Among other things, 3GPP standardization is currently in the process of defining SystemInformationBlock Type 18 to contain some information related to forward communication and ProSe discovery. The following definition of SIB18 is taken from the currently discussed change request r2-143565 for TS 36.331, covering the current agreements for ProSe, which is nevertheless not yet fully decided and therefore is only subject to review. as an example.

SystemInformationBlockType18 Information Item

Field descriptions SystemInformationBlockType18 commIdleTxPool
Indicates the resources by which the UE is allowed to perform feedforward transmissions while in RRC_IDLE. discInterFreqList
Indicates adjacent frequencies on which direct detection notification is provided. discIdleTxPool
Indicates the resources by which the UE is allowed to send forward discovery notifications while in RRC_IDLE.

As seen from the above system information, the commIdleTxPool field, which includes the commSA-TxResourcePoolCommon subfields, indicates shared resources that any UE that accepts SIB18 and is still idle can use (concurrently). In other words, the network operator can usually define radio resources for all UEs, which, however, can only be used when the UE is still idle. As will be discussed below, these radio resources, defined by commIdleTxPool, are classified as Mode 2 resources for autonomous use by various UEs.

Buffer Status Reporting

The buffer status reporting procedure is used to provide the serving eNB with information on the amount of data available for transmission in the UL buffers to the UE. RRC manages BSR reporting by configuring two timers, periodicBSR-Timer and retxBSR-Timer, and, for each logical channel, by the optional logicalChannelGroup signaling that allocates logical channels to the LCG. Additional information on buffer status reporting can be found in 3GPP TS 36.321 clause 5.4.5, incorporated herein by reference.

Proximity services (ProSe) between devices (D2D) LTE

Proximity apps and services are a newly emerging socio-technological trend. These areas include services related to commercial services and public safety that could be of interest to operators and users. The introduction of Proximity Services (ProSe) capability in LTE would enable the 3GPP industry to serve this emerging market and at the same time serve the pressing needs of several public safety communities that are together actively tuned in to LTE.

Communication between devices (D2D) is a technology component for Ver. 12 LTE. Device-to-device (D2D) technology enables D2D to increase spectral efficiency as the basis for the cellular network. For example, if the cellular network is LTE, all data-carrying physical channels use SC-FDMA for D2D signaling.

D2D to LTE connectivity

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

In D2D communication, UEs transmit data signals to each other over a forward link using cellular resources instead of transmission through a base station (BS). D2D users communicate directly while remaining under the control of the BS, ie at least while in the coverage area of the eNB. Therefore, D2D can improve system performance by reusing cellular resources.

D2D is assumed to operate in the LTE uplink spectrum (in the case of FDD) or uplink subframes of the cell providing the coverage (in the case of TDD - except when out of coverage). In addition, D2D transmit / receive does not use full duplex on a given carrier. From the standpoint of an individual UE, on a given carrier, D2D signal reception and LTE uplink transmission do not use full duplex, i.e., simultaneous D2D signal reception and LTE uplink transmission are not possible.

In D2D communication, when one particular UE1 performs the transmitting role (transmitting user equipment or transmitting terminal), UE1 sends data and another UE2 (receiving user equipment) receives it. UE1 and UE2 can exchange their transmit and receive roles. The transmission from UE1 can be received by one or more UEs like UE2.

With regard to user plane protocols, part of the agreement from a D2D communication perspective is presented below (see also 3GPP TS 36.843 vers. 12.0.0 section 9.2.2, incorporated herein by reference).

1. PDCP:

- Broadcast data 1: M D2D (ie, IP packets) should be treated as normal user plane data.

- Header compression / decompression in PDCP is applicable for broadcast 1: M D2D.

- Mode U is used for header compression in PDCP for D2D broadcast mode for public safety;

- RLC:

- RLC UM is used for broadcast communication 1: M D2D.

- Segmentation and reassembly is provided by RLC UM over L2.

- The receiving UE needs to support at least one RLC UM entity per transmitting peer UE.

- The RLC UM receiver entity does not need to be configured before receiving the first UM RLC data block.

- So far, no need for RLC AM or RLC TM has been identified for D2D communications for user plane data transmission.

- MAC:

- No feedback is assumed for broadcast 1: M D2D.

- The receiving UE needs to know the source identifier (ID) to identify the receiver UM RLC entity.

- The MAC header contains an L2 target identifier that allows packets to be dropped at the MAC layer.

- The L2 target ID can be a broadcast, multicast, or point-to-point address.

- Group / point-to-point L2: The L2 target identifier contained in the MAC header would allow the received RLC UM PDU to be discarded before being sent to the RLC receiver entity.

- Broadcast L2: The receiving UE would process all received RLC PDUs from all transmitters and pursue the goal of reassembling and transmitting IP packets to the upper layers.

- The MAC sub-header contains different LCIDs (to distinguish multiple logical elements).

- At least multiplexing / demultiplexing, priority processing and padding are appropriate for D2D.

Radio resource allocation

From the point of view of the transmitting UE, the Proximity Service Activated UE (ProSe Activated UE) can operate in two modes for resource allocation:

Mode 1 refers to scheduling eNB resource allocation, in which the UE requests transmission resources from the eNB (or a Version 10 transit node) and the eNodeB (or a Version 10 transit node) in turn schedules the exact resources used by the UE for direct data transmission and direct control information (for example, scheduling assignments). The UE needs to be RRC_CONNECTED in order to transmit data. Specifically, the UE sends a scheduling request (D-SR or random access) to the eNB following the Buffer Status Report (BSR) in the usual manner (see also the next section “Transmission Procedure for D2D Communication”). Based on the BSR, the eNB can determine that the UE has data for ProSe feedforward transmission and can estimate the resources required for transmission.

On the other hand, Mode 2 refers to resource selection of an autonomous UE, in which the UE independently selects resources (time and frequency) from resource pools for transmitting immediate data and immediate control information. One resource pool is defined, for example, by the content of SIB18 (as presented in the previous section), namely the commIdleTxPool field, where this particular resource pool is broadcast in the cell and then publicly available to all UEs in the cell, still in RRC_Idle state. Alternatively, or in addition, another resource pool may be defined by the eNB and specifically allocated to the UE, namely by using the commTxResourcePool field. Although not yet finally decided, the corresponding ProSe information element is currently being standardized for TS 36.331 in accordance with the change request r2-143565. Therefore, the following definition should be considered as an example only:

Information element ProseCommConfig

Field descriptions ProseCommConfig commSA-RxResourcePoolDedicated
Indicates a pool of resources that the UE should monitor in order to receive scheduling assignments for Prose communication. commTxResourcePool
If enabled, the UE is allowed to use the specified resources under normal or exceptional conditions depending oncommTxPoolUse... If not enabled, or when the conditions for use are not met, a UE that wishes to initiate direct communications involving transmissions should request the E-UTRAN to assign resources for each individual transmission, as specified in 36.321 [6]. commSA-TxResourcePoolDedicated
Indicates TBC. commData-TxResourcePoolDedicated
Indicates TBC.

This ProSeCommConfig information element may be part of the network response sent by the eNB in response to a corresponding UE request that assumes D2D communication. For example, as illustrated in FIG. 16, the UE may transmit an indication of interest in D2D communication to the eNB in case the UE wishes to perform D2D communication. The D2D communication response (eg, as part of the RRCCommunicationReconfiguration) may, for example, include the aforementioned ProseCommConfig information element.

In addition, the preconfigured radio resources available to a UE that is outside the coverage area of an eNB cell for D2D SA or data transmission may also be classified as Mode 2 resources.

Which resource allocation mode the UE will use is configured by the eNB, as explained above. In addition, which resource allocation mode the UE will use to transmit D2D data may also depend on the RRC state, i.e., RRC_IDLE or RRC_CONNECTED, and the UE's coverage state, i.e., in coverage, out of coverage. ... A UE is considered to be in coverage if it has a serving cell (i.e., the UE is RRC_CONNECTED or cell-based in RRC_IDLE).

As agreed to date (see change request to TS 36.300 in R2-143672, resource allocation section), the following rules apply to the UE with respect to the resource allocation mode:

- If the UE is out of coverage, it can use Mode 2;

- If the UE is in the coverage area, it can use Mode 1 if the eNB configures it accordingly;

- If the UE is in the coverage area, it can use Mode 2 if the eNB configures it accordingly;

- When there are no exceptional conditions, the UE may switch from Mode 1 to Mode 2 or vice versa if configured by the eNB to do so. If the UE is in the coverage area, it uses only the mode specified by the eNB configuration, unless one of the exceptional cases occurs;

- the UE considers itself to be in an exceptional condition, for example, when performing T311 or T301;

- When an exceptional case occurs, the UE is allowed to temporarily use Mode 2 even if it is configured to use Mode 1.

While in the coverage area of an E-UTRA cell, the UE performs ProSe point-to-point transmission on the UL carrier only on the resources assigned by that cell, even if the resources of that carrier are preconfigured in, for example, UICC (Universal Integrated Circuit Card).

For UEs in RRC_IDLE, the eNB may choose one of the following options:

- The eNB can provide a pool of Mode 2 transmission resources in the SIB. UEs that are allowed for direct ProSe communication use these resources for direct ProSe communication in RRC_IDLE;

- The eNB may indicate in the SIB that it supports D2D, but does not provide resources for direct ProSe communication. UEs must enter RRC_CONNECTED to perform ProSe feedforward transmission.

For UE in RRC_CONNECTED:

- The UE in RRC_CONNECTED, which is allowed to perform ProSe forward link transmission, indicates to the eNB that it wishes to perform ProSe forward link transmission when it needs to perform ProSe forward link transmission;

- the eNB checks if the UE in RRC_CONNECTED is allowed for ProSe feedforward transmission using the UE context received from the MME;

- The eNB can configure the UE to RRC_CONNECTED by dedicated signaling with a Mode 2 resource allocation transmission resource pool that can be used without restriction when the UE is RRC_CONNECTED. Alternatively, the eNB may configure the UE to RRC_CONNECTED by dedicated signaling with a Mode 2 resource allocation transmission resource pool that is allowed to be used by the UE only in exceptional cases and rely on Mode 1 otherwise.

This behavior of the UE with respect to resource allocation is illustrated in a simplified manner in accordance with the state diagrams in FIG. 7 and 8. FIG. 7 refers to the case in which the UE is in the RRC_IDLE state and distinguishes between being in coverage and out of coverage. It should be noted that a UE that is out of coverage and in RRC_IDLE can use resource allocation in Mode 2. There are no exceptions at the time specified for the UE in RRC_IDLE. On the other hand, FIG. 8 refers to the case in which the UEs are in the RRC_CONNECTED state and distinguishes between being in coverage and out of coverage. It is clear that a connected UE, in an exceptional case, can use resource allocation in Mode 2.

FIG. 9 illustrates transmission / reception resource utilization for an upper layer (LTE) and a lower layer (D2D) system.

Basically, the eNodeB controls whether the UE can apply a Mode 1 or Mode 2 transmission. Once the UE knows its resources in which it can transmit (or receive) a D2D message, in the state of the art it uses the corresponding resources only for the corresponding transmission. / reception. For example, in FIG. 9 D2D subframes will only be used for receiving or transmitting D2D signals. Since the UE as a D2D device can operate in half duplex mode, it can either receive or transmit D2D signals at any time. Likewise, the other subframes illustrated in FIG. 9 can be used for LTE (upper layer) transmission and / or reception.

Transfer Procedure for D2D Communication

The D2D data transfer procedure differs depending on the resource allocation mode. As described above for Mode 1, the eNB explicitly schedules resources for scheduling and D2D data transmission assignments upon appropriate request from the UE. In particular, the UE can inform the eNB that D2D communication is generally allowed, but that Mode 2 resources (i.e., resource pool) are not provided; this may be accomplished, for example, by exchanging an indication of interest in D2D communication by the UE and a corresponding response to D2D communication, as illustrated in FIG. 16, where the corresponding example ProseCommConfig information element mentioned above will not include commTxREsourcePool, which means that a UE that wishes to initiate direct communication involving transmissions must request the E-UTRAN to allocate resources for each individual transmission. Therefore, in such a case, the UE must request resources for each individual transmission, and below the various steps of the request / grant procedure are listed by way of example for a given Mode 1 resource allocation:

- Step 1: UE sends SR (scheduling request) to the eNB on PUCCH;

- Stage 2: the eNB provides the UL resource (for the UE to send the BSR) on the PDCCH, scrambling with C-RNTI;

- Step 3: UE sends D2D BSR indicating buffer status on PUSCH;

- Step 4: The eNB provides a D2D resource (for the UE to send data) on the PDCCH, with D2D-RNTI scrambling.

- Step 5: D2D Tx UE transmits SA / D2D data according to the grant obtained in step 4.

A scheduling assignment (SA) is a compact (low payload) message containing control information such as pointer (s) to time-frequency resources for the respective D2D data transmissions. The SA content is largely in line with the permission taken in the above Step 4. The details of the D2D permission and SA content have not yet been established, but as a working assumption for SA content, the following agreements have been reached:

- The frequency resource is specified in the resource allocation Type 0 UL ver. 8 (5-13 bits depending on the system bandwidth)

- 1-bit frequency switching indicator (according to Ver. 8)

- It should be noted that some reinterpretation of indexing should be defined such that the switchover does not use different PRBs outside the configured resource pool for Mode 2.

- Only single-cluster resource allocations are allowed

- it follows from the above that if there are gaps in the resource pool in the frequency domain, the resource allocation will not close the gap

- RV indicator in SA is missing

RV template for data: {0, 2, 3, 1}.

On the other hand, for resource allocation in Mode 2, the above steps 1-4 are generally unnecessary and the UE autonomously selects resources for SA transmission and D2D data from the resource pool (s) configured and provided by the eNB.

FIG. 10 illustrates by way of example the transmission of a scheduling assignment and D2D data for two UEs, a UE-A and a UE-B, wherein the resources for sending the scheduling assignments are periodic and the resources used for the D2D data transmission are indicated by the corresponding scheduling assignment.

Resource pool for D2D scheduling and data assignment

The resource pool for Scheduling Assignment (SA) and D2D data when the UE is out of coverage can be configured as follows:

- The resource pool used to receive the SA is pre-configured.

- The resource pool used for SA transmission is pre-configured.

- The resource pool used to receive D2D data is pre-configured.

- The resource pool used for D2D data transfer is pre-configured.

The resource pool for Scheduling Assignment (SA) and D2D data when the UE is in coverage can be configured as follows:

- The resource pool used to receive the SA is configured by the eNB via RRC in dedicated or broadcast signaling.

- The resource pool used for SA transmission is configured by the eNB via RRC if Mode 2 resource allocation is used.

- The SA resource pool used for transmission is unknown to the UE if Mode 1 resource allocation is used.

- The eNB schedules specific resource (s) for use in transmitting the Scheduling Assignment if Mode 1 resource allocation is used. The specific resource assigned by the eNB is within the resource pool for receiving the Scheduling Assignment that is provided to the UE.

UE Coverage States for D2D

As already mentioned above (see, for example, Figs. 7 and 8), the way of allocating resources for D2D communication depends - in addition to the RRC state, i.e., RRC_IDLE and RRC_CONNECTED, also on the UE coverage state, i.e., in coverage area, outside the coverage area. A UE is considered to be in coverage if it has a serving cell (i.e., the UE is RRC_CONNECTED or cell-based in RRC_IDLE).

The two coverage states referred to so far, ie, in-area (IC) and out-of-area (OOC), are further divided into substates for D2D. FIG. 11 shows four different states with which a D2D UE can be associated and which can be summarized as follows:

- State 1 : UE1 has uplink and downlink coverage. In this state, the network manages every D2D communication. In addition, the network configures whether UE1 should use mode 1 or mode 2 resource allocation.

- State 2 : UE2 has downlink coverage but no uplink, i. E. only covered in DL. The network broadcasts a (contention-based) resource pool. In this state, the transmitting UE selects resources used for SAs and data from a network-configured resource pool; in this state, resource allocation is only possible in accordance with Mode 2 for D2D communication.

- State 3 : Since UE3 has no uplink and downlink coverage, UE3 is, strictly speaking, already considered to be out of coverage (OOC). However, UE3 is in the coverage area of some UEs that themselves (e.g. UE1) are in the coverage area of the cell, i.e., these UEs may also be referred to as CP relay UEs, hence the UE region in state 3 in FIG. 11 may be referred to as a UE relay coverage area CP. UEs in this state 3 are also referred to as UEs in state 3 OOC. In this state, the UEs receive some cell specific information that is sent to the eNB (SIB) and forwarded by the UE with the UE CP relaying in the cell coverage area via PD2DSCH to various UEs in the OOC state 3. The network-controlled (contention-based) resource pool is signaled by PD2DSCH.

- State 4 : UE4 is out of coverage and does not receive PD2DSCH from other UEs that are in cell coverage. In this state, also referred to as state 4 OBS, the transmitting UE selects the resources used for data transmission from a pre-configured resource pool.

The reason for distinguishing between OOS state 3 and OOS state 4 is mainly to eliminate the potentially strong interference between D2D transmissions from out-of-coverage devices and standard E-UTRA transmissions. Typically, D2D-capable UEs have a pre-configured resource pool (s) to carry different SAs and D2D data for use when out of coverage. If said out-of-area UEs are transmitting in said pre-configured resource pools near cell boundaries, then interference between D2D transmissions and standard coverage transmissions may adversely affect communication within the cell. If D2D-activated UEs within coverage area forwarded the D2D resource pool configuration to specified out-of-coverage devices near the cell boundary, then out-of-coverage UEs can restrict their transmissions to resources specified by eNode B, and therefore minimize interference in standard transmissions in the coverage area. Thus, RAN1 introduced a mechanism whereby in-coverage UEs forward resource pool information and other D2D-related configurations to said devices just outside of the coverage area (UE state 3).

The Physical D2D Synchronization Channel (PD2DSCH) is used to convey this information about in-coverage D2D resource pools to UEs in the network proximity such that the resource pools within the network proximity match. However, the detailed content of PD2DSCH has not yet been set.

D2D detection

Direct ProSe Discovery (Proximity Based Services) is defined as the procedure used by a ProSe enabled UE to discover another ProSe enabled UE (s) in its vicinity using E-UTRA direct radio signals via the PC5 interface. FIG. 12 schematically illustrates a PC5 interface for direct discovery between devices.

The upper layer handles the permission to notify and control the detection information. To this end, the UEs must exchange predefined signals called acquisition signals. By periodically checking the discovery signals, the UE maintains a UE proximity list to establish a communication link as needed. Detection signals must be reliably detected, even under low signal-to-noise ratio (SNR) conditions. To enable periodic transmission of acquisition signals, resources for acquisition signals must be assigned.

There are two types of direct ProSe detection: open and limited. Open is a case where there is no explicit grant that is needed from the UE being discovered, while limited discovery is only done when there is an explicit grant from the UE being discovered.

Forward Discovery ProSe may be an autonomous service activator in a discovery UE that invokes the discovery UE to use information from the discovered UE for some applications. For example, the information sent by direct ProSe detection could be “find a taxi nearby”, “find a café for me”, “find the nearest police station for me”, etc. Through direct ProSe discovery, the discovery UE can obtain the necessary information. In addition, depending on the information received, ProSe direct detection can be used for subsequent actions in the communication system, such as initiating ProSe direct detection.

ProSe direct detection models

ProSe direct detection is based on several detection models. An overview is given below. Models for direct ProSe detection are defined in more detail in 3GPP TS 23.303 V12.1.0 section 5.3, which is incorporated herein by reference.

Model A ("I am here)

Model A is also referred to as "I am here" because the notifying UE broadcasts information about itself, such as ProSe application identifiers or ProSe UE identifiers in a discovery message, thereby identifying itself and informing other parties of the communication system that it is available.

Consistent with Model A, two roles are defined for ProSe-activated UEs that participate in direct ProSe discovery. The UE activated by ProSe can serve as a notification UE and a monitoring UE. the notifying UE advertises some information that can be used by various nearby UEs that have permission to discover. The monitoring UE monitors some information of interest in the vicinity of the notifying UEs.

In this Model A, the notifying UE broadcasts discovery messages at predetermined discovery intervals, and the monitoring UEs that are interested in these messages read them and process them.

Model B ("who is there?" / "Are you listening?")

This model defines two roles for different ProSe activated UEs that participate in direct ProSe discovery:

- Discoverer UE: A UE that transmits a request containing some information about what is of interest to the finder;

- Discoverable UE: A UE that receives the request message may respond with some information related to the discovery request.

Model B is equivalent to "who is there" / "are you listening" since the discoverer UE transmits information about other UEs from which it would like to receive responses. The information transmitted can, for example, be about the ProSe application identifier corresponding to the group. Group members can respond to the mentioned information transmitted.

In accordance with this Model B, two roles are defined for the different ProSe-activated UEs that participate in direct ProSe discovery: the Discoverer UE and the Discoverable UE. The UE-finder transmits a request containing some information about what is of interest to the finder. On the other hand, the UE being discovered receives the request message and may respond with some information related to the discovery UE's request.

The content of the discovery information is transparent to the access layer (AS), which does not know the content of the discovery information. Thus, in the access layer, no distinction is made between the various ProSe direct detection models and the ProSe direct detection types. ProSe ensures that only valid discovery information is sent to the AS for notification.

The UE can participate in the notification and monitoring of discovery information in both the RRC_IDLE state and the RRC_CONNECTED state for each eNB configuration. The UE notifies and monitors its discovery information based on the half-duplex restrictions.

Detection types

FIG. 13 illustrates a diagram showing IDLE and CONNECTED modes when receiving discovery resources on D2D communication and in relation to resource allocation procedure.

D2D communications can be either a managed network, where the operator regulates the switches between direct transmission (D2D) and traditional cellular links, or direct links can be controlled by devices without operator control. D2D allows you to combine infrastructure mode and ad-hoc communication.

Generally, device discovery needs to be done periodically. In addition, D2D devices use the discovery message signaling protocol to perform device discovery. For example, a D2D activated UE may transmit its discovery message, and another D2D activated UE receives this discovery message and may use this information to establish a link. An advantage of a hybrid network is that if the D2D devices are also within the communication range of the network infrastructure, network entities like eNBs can further facilitate the transmission or configuration of discovery messages. The coordination / control performed by the eNB when transmitting or configuring discovery messages is also important to ensure that D2D message transmission does not interfere with cellular traffic controlled by the eNB. In addition, even if some of the devices are outside the range of the network coverage, the devices in the coverage area can contribute to a special detection protocol.

At least the following two types of detection procedures are defined for the purpose of defining terminology used later in the description.

- Type 1 : A resource allocation procedure in which resources for notification of discovery information are allocated in a non-UE-specific manner, further characterized in that:

- The eNB provides one (multiple) UEs with a resource pool configuration used to notify discovery information. The configuration can be signaled in the SIB.

- The UE autonomously selects the radio resource (s) from the specified resource pool and notifies the discovery information.

- The UE may notify the acquisition information on a randomly selected acquisition resource during each acquisition period.

- Type 2 : A resource allocation procedure in which resources for notification of discovery information are allocated in a UE-specific manner, further characterized in that:

- The UE in RRC_CONNECTED may request resource (s) to notify discovery information from the eNB via RRC. The eNB assigns resource (s) via RRC.

- Resources are assigned within a resource pool that is configured in different UEs for monitoring.

Resources - in accordance with a Type 2 procedure - for example, are assigned semi-permanently to carry an acquisition signal.

In the case where the UEs are in RRC_IDLE mode, the eNB can choose one of the following options:

- The eNB may provide a Type 1 resource pool for advertising discovery information in the SIB. UEs that are allowed ProSe direct discovery use these resources to advertise discovery information in RRC_IDLE.

- The eNB may indicate in the SIB that it supports D2D, but does not provide resources to advertise discovery information. UEs must enter RRC Connected to request D2D resources to notify discovery information.

For various UEs in the RRC_CONNECTED state, the UE that is allowed to perform ProSe forward discovery notification indicates to the eNB that it wants to perform D2D discovery notification. The eNB then checks whether the ProSe direct discovery notification is enabled by the UE using the UE context received from the MME. The eNB may configure the UE to use the Type 1 resource pool or Type 2 dedicated resources to notify the discovery information via dedicated RRC signaling (or not use the resource). The resources allocated by the eNB are valid until a) the eNB unconfigures the resource (s) with RRC signaling or b) the UE enters IDLE.

Receiving UEs in RRC_IDLE and RRC_CONNECTED monitor both Type 1 and Type 2 discovery resource pools as they are granted. The eNB provides a resource pool configuration used to control discovery information in the SIB. The SIB may contain discovery resources that are also used for notification in neighboring cells.

Radio protocol architecture

FIG. 14 schematically illustrates a radio protocol (AS) stack for direct ProSe detection.

The AS layer is interfaced with the upper layer (ProSe protocol). Accordingly, the MAC layer receives discovery information from the upper layer (ProSe Protocol). Therefore, the IP layer is not used to convey discovery information. In addition, the AS layer performs a scheduling function according to which the MAC layer determines the radio resource used to notify the acquisition information received from the upper layer. In addition, the AS layer performs an acquisition PDU generation function, according to which the MAC layer creates a MAC PDU containing acquisition information and sends the MAC PDU to the physical layer for transmission in the designated radio resource. No MAC header is added.

In the UE, the RRC protocol reports the discovery resource pools to the MAC. The RRC also reports a dedicated Type 2 resource for transmission to the MAC. There is no need for a MAC header. The MAC header for discovery does not contain any fields on which to filter in Layer 2. Filtering the discovery message at the MAC layer does not appear to save processing or energy compared to performing high layer filtering based on ID UE ProSe or ProSe Application identifier. The MAC receiver forwards all received acquisition messages to the upper layers. The MAC will only transmit correctly received messages to the upper layers.

It is assumed below that L1 (PHY) indicates to the MSS whether the acquisition messages were received correctly. In addition, it is assumed that the Top Layers will ensure that only valid discovery information is delivered to the access layer.

D2D sync

The main purpose of synchronization is to allow receivers to receive a time and frequency reference signal. Such a reference signal can be used for at least two purposes: 1) alignment of the receiver window and frequency equalization when detecting D2D channels and 2) aligning the timing and parameters of the transmitter when transmitting D2D channels. To date, the following channels have been defined for synchronization purposes in 3GPP:

- D2DSS - D2D sync signal

- PD2DSCH - D2D physical sync channel

- PD2DSS - D2D primary sync signal

- SD2DSS - D2D secondary sync signal

In addition, the following sync terminology has been agreed in 3GPP and will be used as an example throughout the rest of the application.

- D2D sync source: a node that at least transmits the D2D sync signal. The D2D timing source can typically be an eNB or a D2D UE.

- D2D sync signal: a signal from which the UE can obtain clock and frequency sync.

D2D synchronization can be thought of as a procedure similar to cell search in LTE. To allow both NW control and efficient synchronization for partial / over-coverage scenarios, the following receiver and transmitter synchronization procedures are currently under discussion within 3GPP.

Synchronizing the receiver

UE activated by ProSe regularly searches for LTE cells (in accordance with LTE mobility procedures) and D2DSS / PD2DSCH transmitted by different UEs by synchronization sources (SS).

If any suitable cell is found, the UE relies on it and follows the cell synchronization (in accordance with standard LTE procedures).

If any suitable D2DSS / PD2DSCH transmitted by different UE SS are found, the UE synchronizes its receiver with all incoming D2DSS / PD2DSCHs (depending on the UE capabilities) and monitors the incoming connections therein (scheduling assignments). It should be noted that the D2DSS transmitted by the D2D sync source, which is the eNodeB, must be PSS / SSS (Primary and Secondary Synchronization Signals) Ver. 8. D2D sync sources, which are eNodeBs, have higher priority than D2D sync sources, which are UEs.

Synchronizing transmitter

The UE activated by ProSe regularly searches for LTE cells (in accordance with LTE mobility procedures) and D2DSS / PD2DSCH transmitted by different UE SSs.

If any suitable cell is found, the UE relies on it and follows the cell synchronization for D2D signaling. In such a case, the network can configure the UE to transmit D2DSS / PD2DSCH after cell synchronization.

If a suitable cell is not found, the UE checks if any of the incoming D2DSS / PD2DSCHs can be transmitted further (i.e., the maximum number of hops is not reached), then (a) if the incoming D2DSS / PD2DSCH can be transmitted further is found, the UE adapts the timing of its transmitter to it and transmits D2DSS / PD2DSCH accordingly; or (b) if an incoming D2DSS / PD2DSCH that may be transmitted further is NOT found, the UE acts as an independent clock source and transmits D2DSS / PD2DSCH according to any internal clock reference.

Further details on the synchronization procedure for D2D can be found in TS 36.843 V12.0.1 clause 7, which is incorporated herein by reference.

Cell selection and RRC Connection establishment

FIG. 15 illustrates in a simplified and exemplary manner the exchange of prior art messages between a UE and an eNB for cell selection and RRC connection establishment. The cell selection in step 2 is based, for example, on 3GPP TS 36.304, for example section 5.2.3 of v12.1.0, incorporated herein by reference. A UE that is not based on any WAN (wide area network, eg LTE) cell is considered out of coverage. Cell referencing may be based on cell selection criteria / process as defined in Section 5.2.3 of 3GPP TS 36.304-v 12.1.0. Therefore, before completing step 2, the UE is generally considered to be out of coverage (OOC). Once the cell selection is successful and the UE is based (on a suitable cell or an acceptable cell), it is in the RRC idle state. The UE continues to be in the RRC idle state until step 7, i.e., until it receives an RRCConnectionSetup message from the network, after which it changes state to RRC connected.

DISCLOSURE OF THE INVENTION

In one non-limiting and illustrative embodiment, an improved method for allocating radio resources to a transmitting terminal for direct-link transmission over a direct link connection is provided, reducing the problems discussed above. The independent claims provide one non-limiting and illustrative embodiment. Preferred embodiments are to be included in the dependent claims.

In accordance with a first aspect, a network operator defines an additional (temporary) pool of radio transmission resources in addition to the pending pool of radio transmission resources already defined in the prior art in order to carry out the direct communication transmission by the network operator. Although the pending radio transmission resource pool of the prior art is limited to terminals in the idle state, the additional radio transmission resource pool in accordance with the first aspect, although independent of the pending or connected state of the terminal, is configured such that the amount of time in the duration of which the temporary pool of radio transmission resources can be used by the transmitting terminal is limited. Therefore, the base station broadcasts, in its cell, system information containing information about said radio transmission resource temporary pool and corresponding configuration information. As in the case of prior art radio resource pool idle transmission, the temporary radio transmission resource pool in accordance with the first aspect indicates radio resources that can be used by those transmitting terminals that receive the system information broadcast packet for direct communication to the receiving terminal on the direct communication line connection.

Different implementations of this first aspect differ in how the configuration information reaches the time limit for using this additional pool of resources, or include additional requirements that the terminal should (at least try) to establish a radio connection with the base station when the terminal must use such temporary radio transmission resource pool once.

By utilizing this additional pool of resources, it is possible to allow terminals in a cell to experience no interruption when establishing a radio connection with a base station.

Accordingly, in one general aspect, the techniques described herein provide a method for allocating radio resources to a transmitting terminal to perform a direct link transmission over a direct link connection to a receiving terminal in a communication system. The method comprises the following steps performed by a transmitting terminal: receiving from a base station a broadcast system information packet that contains information on a temporary transmission radio resource pool indicating radio resources that can be used by those transmitting terminals that receive a broadcast system information packet to effect a direct link transmission to the receiving terminal via a direct link connection, and which contains configuration information on the temporary radio transmission resource pool, the configuration information limiting the amount of time during which the temporary radio transmission resource pool can be used by the transmitting terminal. An appropriate terminal and base station are proposed to participate in this method.

In accordance with a second aspect, a pre-configured pool of radio transmission resources is made available to terminals that are within the coverage area of a cell of a base station. Such a preconfigured pool of radio transmission resources is already known in the prior art for use in out-of-coverage situations, a second aspect extends its use also to a situation in the coverage area of terminals. By “preconfigured” in this context, it should be understood that the preconfigured pool of radio transmission resources is known to the terminals even without receiving any system information from the radio access; for example, via information in the USIM card of a mobile phone or via high-level signaling from the core network.

Similar to the first aspect, various implementations of the second aspect include the option of limiting the amount of time such a pre-configured pool of radio transmission resources can be used for terminals while in a cell's coverage area, which can be done in various ways. Other implementations of the second aspect require the terminal to (at least try) to establish a radio connection with the base station when the terminal must use such resources of the preconfigured radio transmission resource pool once.

Accordingly, in one general aspect, the techniques described herein provide a transmitting terminal for performing a direct link transmission over a direct link connection to a receiving terminal in a communication system. The transmitting terminal is preconfigured using a preconfigured radio transmit resource pool indicating radio resources that can be used by the transmitting terminal to perform direct link transmission to the receiving terminal over a direct link connection, wherein the preconfigured radio transmit resource pool can be used when the transmitting terminal is in base station cell coverage area.

Additional benefits and advantages of the described embodiments will be apparent from the description and drawings. Benefits and / or advantages may individually be provided by various embodiments and features of the description and drawings, and need not all be provided to obtain one or more of them.

These general and specific aspects can be implemented using a system, method, and computer program, as well as any combination of systems, methods, and computer programs.

BRIEF DESCRIPTION OF DRAWINGS

Below, illustrative embodiments are described in more detail with reference to the accompanying drawings.

FIG. 1 shows an exemplary architecture of a 3GPP LTE system,

fig. 2 shows an illustrative overview of the general E-UTRAN architecture in 3GPP LTE,

fig. 3 shows exemplary downlink carrier subframe boundaries as defined for 3GPP LTE (Release 8/9),

fig. 4 shows an exemplary downlink resource grid of a downlink slot as defined for 3GPP LTE (Release 8/9).

fig. 5 and 6 show the structure of the LTE-A 3GPP Layer 2 (Release 10) with carrier aggregation activated for the downlink and uplink, respectively,

fig. 7 and 8 give an overview of the resource allocation mode (s) and transitions between resource allocation modes available to the terminal when in RRC_Idle, RRC_Connected, in and out of cell coverage,

fig. 9 illustrates the use of transmit / receive resources for upper layer (LTE) and lower layer (D2D) systems,

fig. 10 illustrates the transmission of scheduling assignment and D2D data for two UEs,

fig. 11 illustrates coverage for four different states with which a D2D UE can be associated,

fig. 12 schematically illustrates a PC 5 interface for direct discovery between devices,

fig. 13 illustrates a diagram showing an idle mode and a connected mode when receiving acquisition resources in D2D communication,

fig. 14 schematically illustrates the radio protocol stack for direct detection of ProSe,

fig. 15 illustrates an exemplary prior art messaging between a UE and an eNodeB for cell selection and RRC connection establishment,

fig. 16 illustrates the exchange of a D2D communication indication of interest message and a corresponding D2D communication response,

fig. 17 illustrates an exemplary UE movement at a cell boundary,

fig. 18 is a continuation of FIG. 15, illustrating by way of example the exchange of prior art messages for cell selection, RRC connection establishment, indication of UE-A interest in D2D communication, and request for allocated radio resources for D2D data transmission and additional indication of various time periods,

fig. 19 illustrates a message exchange for a failed RRC connection setup procedure,

fig. 20 illustrates those periods when D2D data transmission is not possible for the UE,

fig. 21, 22 illustrate how a UE can apply T-RPT patterns to subframes for mode 1 corresponding mode 2 resources.

CARRYING OUT THE INVENTION

It should be noted that the embodiments may preferably be used, for example, in a mobile communication system such as the 3GPP LTE-A (Release 10/11/12) communication systems as described in the Technical Background section above, but the embodiments are not limited thereto. use in these specific illustrative communication networks.

A mobile station, or a mobile node , or a user terminal is a physical entity in a communication network. One node can have several functional objects. A functional entity refers to a software or hardware module that implements and / or offers a predefined set of functions to other functional entities of a node or network. Nodes can have one or more interfaces that connect the node to a communication medium or medium over which the nodes can communicate. Likewise, a network entity can have a logical interface that connects the functional entity to a communication facility or medium through which it can communicate with other functional entities or related nodes.

"Transmitting terminal" as used in the claims and the application refers to a user terminal in the role of a transmitter. In contrast, “receiving terminal” refers to a user terminal in the role of a receiver. The adjectives "transmitting" and "receiving" are intended only to explain the temporary action / role.

"Feed-forward" used in the claims and the application, by way of example, refers to inter-device communication (D2D) currently under discussion for LTE Release 12. The term "direct line connection" , accordingly, by way of example, refers to a connection or communication channel via a PC5 interface directly connecting two D2D user terminals, which allows data to be exchanged directly without involving a network. In other words, a communication channel is established between two user equipments in the communication system that are close enough to communicate directly, thereby bypassing the eNodeB (base station).

The term "radio connection establishment procedure" as used in the claims and the application may be understood to include or not to include a random access procedure. Accordingly, the initiation of the radio connection establishment procedure can be understood as equivalent to transmitting the random access procedure preamble or equivalent to transmitting the RRC connection request message. Accordingly, in the context of 3GPP LTE, the radio connection establishment procedure may be a random access procedure following the RRC connection establishment procedure.

The term “allocated radio resources” as used in the claims and the application refers to radio resources specifically assigned by a base station (eNode B) to a particular terminal. The allocated radio resources themselves can be either a Mode 1 or a Mode 2 resource as discussed in the prior art section. This term is considered as opposed to “common radio resources” , which can be widely used by terminals in a cell; for example, a pool of radio transmission resources defined by system information (eg, SIB18) is broadcasted in a cell, and therefore the same radio resources are available for use by terminals receiving the system information.

Under the expression “initiate the radio connection establishment procedure” and similar expressions it should be understood that the terminal is required to establish a radio connection with the base station, however, taking into account that the radio connection establishment procedure may not take place. In other words, although the terminal is required to try to establish a radio link, the terminal may only be able to initiate the appropriate radio link establishment procedure, but may not be able to continue the radio link establishment procedure to successfully establish a radio link. In this regard, this expression should be considered to make this requirement of initiating the radio connection establishment procedure independent of the outcome, i.e., success (eg, receipt of an RRC connection establishment message) or failure (eg, reception of an RRC connection rejection message) of the radio connection establishment.

By the expression "pool of radio transmission resources that can be used" (and similar expressions) used in the claims and the application, it should be understood in a broad sense that the resources should not, but can be selected from the pool of radio transmission resources and used by the terminal in the event that the terminal would like to perform a feedforward transmission (such as scheduling assignments or feedforward data). Accordingly, the expression about the used pool of radio transmission resources (and similar expressions) should be understood in a broad sense that the terminal actually intends to perform a feed-forward transmission and selects suitable resources from the pool of radio transmission resources and performs said feed-forward transmission on said selected resources.

The term “in coverage” as used in the claims and applications should be understood broadly to mean that a terminal is in coverage if it has successfully selected a cell, regardless of whether the terminal is idle or connected. Cell selection criteria are defined in TS 36.304. All UEs in the coverage area can receive signaling from the network either using broadcast messages (idle and connected) or using dedicated (ie, one-to-one between the UE and the network) messages in the connected state. For example, a UE is considered to be in coverage if it has a serving cell (ie, the UE is RRC_Connected or is cell-based at RRC_Idle). The expression "outside the coverage area" should be understood in reverse.

The term "preconfigured" as used in the claims and the application should be understood in a broad sense that the corresponding resources from the resource pool are known to the terminals even without receiving any information from the radio access; that is, the pre-configured pool of radio resources is available independently of the cells and the system information broadcast packets therein.

The term "radio resources" as used in the claims and the application should be understood broadly to refer to physical radio resources such as time-frequency resources.

As explained in the background section, a UE may use different resources for direct D2D communication with another UE depending on its state and the configuration being performed by the eNB. The inventors have identified many problems and disadvantages with the currently contemplated implementation of direct communication, ie, D2D 3GPP communication. The following various scenarios and problems are present and will be explained with reference to FIG. 18. FIG. 18, which is a continuation of FIG. 15 further illustrates a UE indicating an interest in D2D communication and a UE's request for dedicated radio resources for D2D data transmission, as well as various time periods 0, 1, 2, A, B, C, and D. While FIG. 18, not shown, the UE may have preconfigured Mode 2 resources when it is out of cell coverage for SA and D2D data transmission / reception as discussed in the background section.

The eNB may decide that Mode 2 resource allocation is not possible in its network when the UE is waiting for RRC. For purposes of explanation, networks of this type are denoted as Type A networks. In particular, in Type A networks, the UE sees in the SIB18 that D2D is allowed, but since there are no shared Mode 2 resources being broadcast for it (e.g. resource pool according to Mode 2) , it must first establish an RRC connection (see FIG. 15). Then, after it is properly configured for D2D (e.g., using an indication of interest in a D2D communication and a corresponding response to a D2D communication; see FIG. 16), it can access Mode 2 resources for transmission (depending on how the UE is configured by the eNB corresponding to the D2D communication response message). In the event that a D2D communication response no longer provides usable resources for D2D communication, for example, in the form of a dedicated Mode 2 resource pool, the UE may need to explicitly request D2D-related resources using dedicated signaling (scheduling request, report buffer state), as indicated in the prior art section above (see D2D communication in steps 1-5 in the Transfer Procedure section), which takes longer (see period C).

Moreover, the period D, as shown in FIG. 18 is the delay in sending the first D2D after receiving the corresponding D2D grant. While it may be considered negligible, it may not be as shown by the inventors' calculations; period D taken by itself can be around 300-400 ms depending on resource configuration such as the periodicity of the BITMAP resource pool for each SA and data, their offset (say, relative to SFN0), the exact allocated T-RPT (transmission pattern temporary resource), etc.

Therefore, the UE cannot perform D2D communications for the entire D period shown in FIG. 18, or even for periods C and D in the event that the response to D2D communication from the eNB, while providing D2D, does not provide Mode 2 resources allocated to the UE (in which case the UE must specifically request a resource grant for a specific D2D transmission).

Type A networks allow the network operator full control over resource usage since he will know how many UEs are performing D2D and can still split resources between using D2D and LTE. However, a UE in such a Type A network is unable to perform any D2D communication in the idle state. In addition, even after transitioning to the RRC connected state, the UE must send an indication of interest in D2D communication and at least wait for an explicit response from the network to receive D2D communication resources, and in addition, time before actual data transmission can take place. communication (period C and / or period D). This delay can easily add up to 2 seconds or more. Since in Ver. 12 D2D communications are mainly aimed at public safety applications, even a 2 second delay / interruption is unacceptable, especially for the VoIP / Speech / Dialogue class of service. This is especially true for UEs at the edge of a cell, which can move in and out between out-of-coverage and in-coverage positions; see fig. 17 is an illustration of a UE that is moving at a cell edge.

This problem is somewhat mitigated in another type of network in which eNB deployments provide for shared D2D Mode 2 communication resources to be used in the RRC idle state; such a network may be designated as a Type B network by way of example. In such Type B networks, the UE will initiate D2D communications using such Mode 2 idle resources upon receipt of SIB18 (containing the corresponding Mode 2 idle resource configuration, e.g. commIdleTxPool) and therefore before in type A networks; thus, these UEs can perform D2D data transmission for a short time before they encounter an interruption again in periods B, C and D. Therefore, although D2D communication is not possible in period 0, during period A, the UE can perform D2D communication ...

However, in Type B networks, the UE is also prevented from performing D2D communication at certain times, causing unwanted delays and / or interruptions. The UE may continue to use pending Mode 2 resources as long as it remains in the RRC idle state; pending prior art Mode 2 resources from SIB 18 can only be used in the RRC idle state. However, when the UE establishes an RRC connection (regardless of the reason; for example, based on the WAN, for example, for Internet access), and thus changes to the RCC connected state (see step 7 in FIG. 15), it can no longer use these resources of the Mode 2 resource pool defined by SIB18 to continue or initiate D2D communication, i.e., according to step 7 in FIG. 15. In such a case, in order to resume a previously started D2D communication or start a new D2D communication, the UE should at least send an indication of interest in D2D communication and wait for an explicit response from the network to obtain D2D Mode 2 communication resources (or even wait longer if necessary explicitly requesting a resource grant for a specific D2D transfer, as discussed above in relation to steps 1-5 of the transfer procedure for D2D communications). This leads to a delay and / or interruption in communication; The UE cannot perform D2D communication during periods B, C (and D).

FIG. 20 shows the various periods introduced in FIG. 18, in block form, depicts the difference between the periods when D2D communication is not possible for the UE, for Type A and Type B networks.

FIG. 19 is similar to FIG. 18, but illustrates a failed RRC connection setup. As is clear from this, once the RRC connection is initiated, it fails (eg, because the RRC connection is rejected by the eNB; other reasons are possible, such as cell reselection or T300 expiration). The UE remains in the RRC idle state anyway. In Type A networks, such situations are particularly unfavorable, since the UE will absolutely not be able to perform D2D communication while in the idle state. On the other hand, for Type B networks, D2D communication is possible upon receipt of SIB 18, which includes configuring a pending Mode 2 resource; that is, during A and beyond.

One explicit solution for Type B networks (which is also easy to implement) is to allow pending Mode 2 resources (commIdleTxPool) also by terminals in the RRC connected state; at least as long as the terminals are assigned by the eNodeB dedicated resources that can be used for feed-forward transmission (see period B + C (+ D) in FIG. 18).

The following first and second illustrative embodiments are conceived by the inventors to reduce the problems explained.

Several embodiments are explained in detail below. The implementation of some of them is assumed within the broad specification given in the 3GPP standards and partially explained in this section of the prior art, with specific key features explained below in relation to various embodiments. It should be noted that the embodiments may be preferably used, for example, in a mobile communication system such as the 3GPP LTE-A (Release 10/11/12) communication systems described in the BACKGROUND section above, but the embodiments are not limited thereto. use in these specific examples of communication networks.

The explanations are to be understood not as limiting the scope of the invention, but only as exemplary embodiments for a better understanding of the present invention. A person skilled in the art would appreciate that the general principles of the present invention set forth in the claims may be applied to various scenarios in ways that are not explicitly described herein. Accordingly, the following scenarios, intended for purposes of explaining various embodiments, do not limit the invention as such.

First embodiment

The first set of embodiments is explained below. To simplify the illustration of the principles of the first embodiment, several assumptions are made; however, it should be noted that these assumptions should not be interpreted as limiting the scope of the present application, as a whole, defined by the claims.

In accordance with a first aspect, an additional pool of transmission resources is determined by the network operator for performing direct-link transmission, this additional pool of resources differing in many respects from the pending pool of transmission resources already known in the prior art. As explained in the prior art section, at the discretion of the network operator, information on the radio transmission resource pool can be broadcast by the base station in its cell so that terminals receiving said broadcast system information packet can autonomously use resources from said radio transmission resource pool in the event that, if they want to communicate directly with another terminal. The prior art radio transmission resource pool (referred to as a pending radio transmission resource pool for ease of use) can be used by a terminal when it is idle, but not when it changes to connected, causing some of the problems mentioned above.

On the other hand, the additional pool of radio transmission resources introduced in accordance with this first aspect (and called for ease of use the temporary pool of radio transmission resources) is used only temporarily (i.e., for a limited amount of time), but regardless of whether whether the terminal is idle or connected. The network operator is able to control the amount of time that this temporary radio transmission resource pool can be used by appropriate additional indication (configuration information) in the system information broadcast packet. Limiting the use of said temporary pool of radio transmission resources in time can be implemented in several different ways, some of which will be explained below as examples, but are similar in that the time during which said temporary resources can be used is limited and can be controlled by the base station. (i.e., by the network operator).

Network operators may be reluctant to make the pending pool of radio transmission resources publicly available to terminals via a system information broadcast packet, but rather, would prefer to assign specific dedicated resource pools to specific terminals, or even only specific dedicated physical resources to each terminal in order to maintain full control. their radio resources (or at least as much control as possible). Consequently, a network operator may not want terminals in its cell to autonomously use a pending prior art radio transmission resource pool, for example, since a terminal can use resources from this pending radio transmission resource pool almost indefinitely (as long as the terminal remains in the idle state ) or because the network does not know how many UEs are actually using these D2D idle resources, since it does not know about the number of such UEs (idle UEs at the cell level are unknown, but are known only at the level of the tracking area, which is significantly larger than cell level); this prevents the network from concluding: the mentioned D2D resources of the idle mode are too few (i.e., many conflicts when using D2D resources) or too many (i.e., unnecessarily eating up other LTE resources). An additional temporary pool of radio transmission resources, on the other hand, allows the network operator to accurately determine the physical resources that can be used for a (more or less) configurable amount of time. Of course, there is a direct benefit here that terminals can access resources for direct-link transmission as soon as the terminals receive and process the corresponding system information broadcast packet with information about the temporary radio transmission resource pool, while the network operator can flexibly manage the time during which such resources are typically allocated to terminals in their cell. Since the number / number of UEs establishing an RRC connection will be significantly limited by the total number of idle UEs in the cell, the additional temporary radio transmission resource pool can be significantly more efficient / smaller in size compared to the pending prior art radio transmission resource pool (mode 2). broadcasted in SIB18. In addition, an additional temporary pool of radio transmission resources is especially useful for terminals located in cells that will not actually provide such a pending pool of radio transmission resources. But it is also useful for terminals in other types of cells that are actually broadcasting a pending pool of radio transmission resources, since in this case, resources for direct communication are also available when the terminal is already in a connected state, but the base station has not yet assigned it allocated resources to be used for feed-forward transmission, or it has not yet actually transferred the D2D communication data.

Thus, by providing a temporary radio transmission resource pool of the first aspect in the cell's system information broadcast packet instead of or in addition to the pending prior art radio transmission resource pool, the delay or interruption of direct communication for terminals is reduced or almost eliminated, while giving the network operator as much control as possible. resources. Depending on the specific implementation, in the cells of the type A network (i.e., in addition to the pending pool of radio transmission resources in the system information), the terminals can use resources from the temporary pool of radio transmission resources discussed above after they have been received, i.e., during the period A , period B, period C and period D as shown in FIG. 18. In cells of type B networks, terminals may use resources from the temporary radio transmission resource pool during periods B + C + D.

Additional implementations of the first aspect relate to how the configuration information can limit the amount of time that a temporary radio transmission resource pool can be used by transmitting terminals in a cell. For example, a system information broadcast packet may directly indicate the amount of time required, eg, 10 ms, 100 ms, 2000 ms for a temporary radio transmission resource pool. Then, depending on the specific implementation, this specified amount of time will be interpreted by the terminal in the sense that the temporary pool of radio transmission resources can be used for this specific time after, for example, receiving the broadcast packet of system information. Alternatively, instead of starting the timer when the terminal receives the system information broadcast packet, the timer may be started when the transmitting terminal starts using the temporary radio transmission resource pool (eg, by transmitting a scheduling assignment in a direct-link transmission to another terminal). In any case, there is a particular advantage here in that such a configuration is independent of the radio connection setup procedure and its outcome, and therefore is predictable for the base station.

Alternatively, or in addition, to directly indicate the amount of time, the time during which the temporary pool of radio transmission resources can be used can be limited "indirectly" by setting specific conditions / events that prevent the terminal from subsequently using said resources. For example, a system information broadcast packet may include an instruction associated with a temporary pool of radio transmission resources that a terminal wishing to use these resources should also try to establish a radio connection with a base station to avoid the terminal being in an idle state with infinite use of such resources. In this case, the terminal, for example, is only allowed to use resources from the said temporary pool of radio transmission resources until a connection is established and the base station assigns the allocated radio resources to the terminal, which is then used instead for possible direct-link transmission (see period A + B + C in Fig. 18); or, if the connection cannot be established or is rejected, until the terminal is informed of this setup failure (see period A in FIG. 19); or the base station at this moment, although establishing a connection with the terminal, may not allow the terminal to transmit with direct communication (see period A + B in Fig. 18). Moreover, taking into account the long time that the terminal may need to actually use the allocated radio resource assigned by the base station to the terminal, a further alternative can extend the time that the temporary radio resource pool can be used until the time when the terminal (after establishing a radio connection with the base station and receiving from the base station dedicated radio resources for direct-link transmission) will actually transmit SA or data using these dedicated radio resources assigned by the base station to the terminal (see Period A + B + C + D in FIG. 18 ).

The actual instruction for establishing a connection may, for example, indicate a specific amount of time within which the terminal needs to (at least) initiate a connection establishment (starting, for example, immediately after receiving a system information broadcast packet or after starting to use the temporary radio transmission resource pool). Yet another option is that the terminal is even required to initiate a connection setup before it is allowed to use radio resources from the temporary radio transmission resource pool for point-to-point transmission. In this case, it can be understood, for example, that the terminal starts establishing a connection with the base station by transmitting a preamble of the random access procedure.

In addition, for the first aspect, just as with the prior art pending radio transmission resource pool, the temporary radio transmission resource pool can distinguish between the resources available for direct communication of the scheduling assignment and those available for direct communication of the immediate data to another terminal over a direct connection. Thus, the cell can provide various resources to be used for transmitting scheduling and data assignments.

Several different implementations of the first aspect have been discussed above. Below, the principles underlying the first aspect and their implementations are applied by way of example to an LTE system (such as the system described in the background section).

In particular, current 3GPP standardization suggests that the use of SIB18 contains some information related to forward communication and ProSe detection. Therefore, the temporary radio transmission resource pool information and its configuration information as described above may form part of this SIBType 18. Of course, it should be noted that for purposes of this aspect, any other type of system information block may be used to convey this information. In addition, in a specific selected example, a field in the system information block for transmitting information about the temporary radio transmission resource pool and configuration is called "commTxPoolTemp". Once again, it should be noted that for the purposes of this aspect, any other field name may be chosen, or the temporary radio transmission resource pool information may be inserted into another field from the corresponding configuration information. The same applies to the names and formats chosen for specific variables commSA-TxResourcePoolCommonTemp, commData-TxResourcePoolCommonTemp.

Accordingly, the following definition of System Information Block Type 18 is taken by way of example only.

SystemInformationBlockType18 Information Item

Field descriptions SystemInformationBlockType18 commIdleTxPool
Indicates the resources by which the UE is allowed to perform feedforward transmissions while in RRC_IDLE. discInterFreqList
Indicates adjacent frequencies on which direct detection notification is provided. discIdleTxPool
Indicates the resources by which the UE is allowed to send forward discovery notifications while in RRC_IDLE. commTxPoolTemp
Indicates the resources by which the UE is allowed to perform feedforward transmissions while in RRC_IDLE, but it can only use these resources up to allowedTime ...

Important changes made to this example of System Information Block Type 18 for the first aspect with respect to the prior art are in bold and underlined for ease of identification. As you can see from here, in this particular example, the configuration information is implemented as the variable “allowedTime” using the examples of times of 100ms, 200ms, etc., as shown above, thereby directly limiting the amount of time. Of course, the specific times, as well as the number of times that are configurable, should be considered as examples only; any other times and the number of configurable times can be selected as needed. By reading the value indicated by the variable ʺallowedTimeʺ, the terminal can determine how long the temporary radio transmission resource pool can be used after receiving the broadcast packet of system information (or after the terminal starts using resources from the temporary radio transmission resource pool for direct communication); the corresponding timer can be set, started and controlled by the UE.

As a further alternative, another example for defining SIB18 is provided below. As with the example definition above, any names given to variables, as well as specific meanings given to variables, should only be considered as examples.

Information element SystemInformationBlockType18

Field descriptions SystemInformationBlockType18 commIdleTxPool
Indicates the resources by which the UE is allowed to perform feedforward transmissions while in RRC_IDLE. discInterFreqList
Indicates adjacent frequencies on which direct detection notification is provided. discIdleTxPool
Indicates the resources by which the UE is allowed to send forward discovery notifications while in RRC_IDLE. commTxPoolTemp
Indicates the resources by which the UE is allowed to perform feed-forward transmissions while in RRC_IDLE, but should also subsequently or even earlier initiate the RRC connection setup procedure, ie, initiate access to the PRACH. timeToInitiateRRCConnEst
The time during which the UE should initiate the RRC connection establishment procedure, ie, initiate the PRACH access. ms01 means 1ms, ms05 means 5ms, etc. The value 'alreadyInitiated' indicates that the UE can use commTxPoolTemp only after the initiation of the RRC connection establishment procedure, for example, after the initiation of the PRACH access.

Important changes made to this example of System Information Block Type 18 for the first aspect with respect to the prior art are in bold and underlined for ease of identification. As you can see, the timeToInitiateRRCConnEst configuration variable was introduced to indirectly restrict the use of the temporary radio transmission resource pool (i.e., commTxPoolTemp) based on various exit conditions, as explained below. By using this timeToInitiateRRCConnEst configuration variable, the UE is instructed to try to establish an RRC connection with the eNB within an exemplary time of 1 or 5 ms, etc., as shown above. Depending on the different behavior of the UE, the UE may, for example, be allowed to use the resources of the temporary radio transmission resource pool until the RRC connection is established and the eNB assigns the allocated radio resources to the terminal; or until the UE realizes that the RRC connection setup has failed; or until the UE informs the eNB that it is not allowed to communicate directly in the cell; or before actually performing direct SA or data communication using dedicated resources assigned by the UE by the eNB.

It should also be noted that this new commTxPoolTemp field is made optional in SIB18, thereby giving control to the network operator to decide whether to broadcast the same as in said cell or not. As a result, since the commIdleTxPool field (already defined in the prior art) is also optional, the network operator (via the eNB) can optionally not configure the commIdleTxPool and commTxPoolTemp fields, or configure one or both of them.

Of course, a combination of the above SIB 18 definitions is also possible, allowing a configuration in which the commTxPoolTemp field contains the variables "allowedTime" and "timeToInitiateRRCConnEst".

Second embodiment

The second aspect of the invention also solves the aforementioned fundamental problem (s) of the prior art, but in a different way. Instead of defining an additional radio transmission resource pool in the system information broadcast burst, as is done for the first aspect, this second aspect is based on the concept of using a pre-configured radio transmission resource pool for possible direct-link transmission, not only when the terminal is out of the cell coverage area (like currently defined in the prior art), but also when the terminal is within a cell's coverage area. Preconfigured in this context is to be distinguished from those "configured" resources that are configured with a system information broadcast from the base station. In other words, the preconfigured resources, for example, are known to the terminals (and base stations) even without receiving any information from the radio access, that is, regardless of the cells and the system information broadcast therein. In this regard, the preconfigured radio resources in the prior art are already used by UEs that are outside the coverage area of the cell, ie, have not received any system information broadcast packet from the base station of any cell.

For example, a preconfigured pool of radio transmission resources can be defined by the network operator and hard-coded into a regular SIM / USIM card that can be inserted and used in most common mobile phones. Alternatively, higher layer signaling can be used to provide the terminal with the necessary information on such a pre-configured pool of radio transmission resources; for example, from a backbone over an Internet or no-access layer protocol.

By using resources from the preconfigured radio transmission resource pool, also when in the coverage area of the cell, the terminal can perform direct communication regardless of whether it receives a system information broadcast packet, whether the system information broadcast packet includes resource pool information , whether the radio connection is established, whether the terminal is in a state (waiting or connected), etc. Thus, the terminal is not blocked, delayed, or interrupted for feed-forward transmission. Therefore, and in contrast to the first embodiment, in accordance with the second aspect, terminals can also perform feed-forward transmission in period 0; in addition to periods A, B, C and D.

One option is to reconfigure a preconfigured pool of radio transmission resources already defined in the prior art for out-of-coverage terminals to be applied also to terminals that are in the coverage area of a base station cell.

On the other hand, an alternative would be to configure a new in-coverage pre-configured radio transmission resource pool, in addition to the pre-configured radio transmission resource pool already defined in the prior art for out-of-coverage terminals, the in-coverage pre-configured the radio transmission resource pool is applicable to terminals that are in the coverage area, but cannot be used by terminals still outside the coverage area of the base station cell. In this case, both the out-of-coverage pre-configured radio transmission resource pool of the prior art and the in-coverage pre-configured radio transmission resource pool in accordance with the second aspect can be stored on a SIM / USIM card, or alternatively can be determined by higher layer signaling. as mentioned above.

In yet another enhancement to the second aspect, the network operator should have some control over whether this pre-configured pool of radio transmission resources (even if pre-configured for a particular terminal) can actually be used in his cell. For example, the network operator may decide that in its cell these resources from the pre-configured pool of radio transmission resources will not be available to the terminals. For these purposes, the system information broadcast packet should properly indicate whether terminals that are within the cell's coverage area are allowed to use it or not.

One simple possibility for this indication is a one bit flag in the system information, a one bit value indicating validity, and another bit value indicating that the use of the preconfigured radio transmission resource pool is not allowed for terminals within the cell's coverage area.

Alternatively, the system information may optionally include configuration information for the preconfigured radio transmission resource pool such that, in the absence of the configuration information, the terminal realizes that the preconfigured radio transmission resource pool should not be used. On the other hand, when the configuration information for the preconfigured radio transmission resource pool is present in the system information and is therefore received by the terminal connected to the cell, the terminal realizes that it can continue to use the preconfigured radio transmission resource pool for direct link transmissions, but in the add-on applies the mentioned configuration information for its use.

Configuration information is subject to change. For example, in accordance with the improvements for the second aspect, it is also advisable to limit the use of the said pre-configured pool of radio transmission resources in time while in the coverage area of the cell. As described in the first aspect, there are several possibilities for how to limit the amount of time that a particular radio resource pool can be used by a terminal. The configuration information for the preconfigured radio transmission resource pool may be similar or identical to that discussed above for the temporary radio transmission resource pool.

Specifically, the system information broadcast packet may, for example, directly indicate the proper amount of time, for example, 10ms, 100ms, 1000ms, for a pre-configured radio transmission resource pool. Then - depending on the specific implementation - this specified amount of time must be interpreted by the terminal in the sense that the pre-configured pool of radio transmission resources can be used for that specific time after, for example, receiving the broadcast packet of system information. Alternatively, instead of starting the timer when the terminal receives the system information broadcast packet, the timer may be triggered when the transmitting terminal starts using the preconfigured transmission radio resource pool (eg, by transmitting the scheduling assignment in direct-link transmission to another terminal).

Alternatively, or in addition, to directly indicate the amount of time, the time during which a preconfigured pool of radio transmission resources can be used can be limited "indirectly" by setting specific conditions / events that stop the terminal from subsequently using said resources. For example, a system information broadcast packet may include an instruction associated with a preconfigured pool of radio transmission resources that a terminal wishing to use those resources should also attempt to establish a radio connection with a base station to avoid the terminal being in an idle state with infinite use of such resources. In this case, the terminal, for example, is only allowed to use resources from the said pre-configured pool of radio transmission resources until a connection is established and the base station does not assign the allocated radio resources to the terminal, which is then used instead for possible forward-link transmission (see period A + B + C in Fig. 18); or if the connection cannot be established or is rejected until the terminal is informed of this setup failure (see period 0 + A in FIG. 19); or the base station at this moment, although establishing a connection with the terminal, may not allow the terminal to transmit with direct communication (see period 0 + A + B in Fig. 18). Moreover, taking into account the long time that the terminal may need to actually use the allocated radio resource assigned by the base station to the terminal, a further alternative can extend the time that the preconfigured radio resource pool can be used until the time when the terminal (after establishing radio connection with the base station and receiving from the base station dedicated radio resources for direct-link transmission) will actually transmit SA or data using these dedicated radio resources assigned by the base station to the terminal (see period 0 + A + B + C + D on Fig. 18).

The actual instruction for establishing a connection may, for example, indicate a specific amount of time within which the terminal needs to (at least) begin to establish a connection (starting, for example, immediately after receiving a system information broadcast packet, or after starting to use a pre-configured radio transmission resource pool). Yet another option is that the terminal is even required to initiate a connection setup before it is allowed to use radio resources from a pre-configured radio transmission resource pool for point-to-point transmission. For this purpose, for example, this can be understood when the terminal starts establishing a connection with a base station by transmitting a preamble of a random access procedure.

The preconfigured pool of radio transmission resources can determine the actual physical radio resources (i.e., time and frequency) and can optionally also determine the specific transmission format or power associated with the physical radio resources. In addition, when the terminal is in the coverage area and uses a pre-configured pool of radio transmission resources for point-to-point transmission, the power for these transmissions can be controlled by the base station (normally).

Several different implementations of the second aspect have been described above. Below, the principles underlying the second aspect and their implementations are applied as an example to an LTE system (such as the system described in the background section).

In accordance with some implementations described above for the second aspect, the broadcast packet of system information from the base station is adapted to allow / disallow the use of a pre-configured pool of radio transmission resources while in the coverage area and / or to configure its use.

As mentioned for the first aspect, current 3GPP standardization suggests that the use of SIB18 contains some information related to forward communication and ProSe detection, and may contain the flag or configuration information mentioned above. Of course, it should be noted that for the purposes of this second aspect, any other type of system information block can be used to convey this information. Below is a very specific example where the config and config variables are given specific names (i.e., usePreconfigResInCoverage, allowedTime, timeToInitiateRRCConnEst) and the variables are specifically set (i.e. ms100, ms200, ms300, etc., ms01 , ms05, etc.). Once again, it should be noted that for the purposes of this second aspect, any other field name can be chosen, and, in addition, the actual values of the variables can be different.

Information element SystemInformationBlockType18

Field descriptions SystemInformationBlockType18 commIdleTxPool
Indicates the resources by which the UE is allowed to perform feedforward transmissions while in RRC_IDLE. discInterFreqList
Indicates adjacent frequencies on which direct detection notification is supported. discIdleTxPool
Indicates the resources by which the UE is allowed to send forward discovery notifications while in RRC_IDLE. usePreconfigResInCoverage
If included, indicates that the UE is allowed to use the pre-configured resources in the cell coverage area.
allowedTime
UE can use usePreconfigResInCoverage before allowedTime ... Ms100 means 100ms, ms200 means 200ms, etc.
timeToInitiateRRCConnEst
The time during which the UE should start the RRC connection setup procedure, ie, initiate the PRACH access. ms01 means 1ms, ms05 means 5ms, etc. The value 'alreadyInitiated' indicates that the UE can only use the pre-configured resources after initiating the RRC connection setup procedure, for example after initiating PRACH access.

Significant changes made to this illustrative system information block type 18 for the second aspect with respect to the prior art are in bold and underlined for ease of identification.

As can be seen from the above, the “usePreconfigResInCoverage” field of the configuration information is optional, so when this field is present in the system information broadcast packet, the UE can determine that the pre-configured radio transmission resource pool (Mode 2 resources) is available while in the coverage area; in the absence of this field, the UE determines that the corresponding pre-configured pool of radio transmission resources in the cell is not available.

The configuration variables ʺallowedTimeʺ and ʺtimeToInitiateRRCConnEstʺ are already known as such from the first aspect discussed above and are defined for this second aspect in the same way. As is clear from the above example, they may even be determined at the same time if so decided by the eNB, thereby allowing directly and / or indirectly limiting the amount of time that a pre-configured pool of radio transmission resources in the coverage area can be used. So, in this particular example, some of the configuration information is implemented as a variable “allowedTime” with exemplary times of 100ms, 200ms, etc., as shown above, thereby directly limiting the amount of time. By reading the value indicated by the variable "AllowedTime", the terminal can determine how long the pre-configured radio transmission resource pool can be used after receiving the system information broadcast packet (or after the terminal starts using resources from the temporary radio transmission resource pool for direct communication); the corresponding timer can be set, started and controlled by the UE.

Likewise, the "timeToInitiateRRCConnEst" configuration variable can be included to indirectly restrict the use of the temporary radio transmission resource pool (ie, commTxPoolTemp) based on various exit conditions, as explained below. By using this timeToInitiateRRCConnEst configuration variable, the UE is instructed to try to establish an RRC connection with the eNB within an exemplary time of 1 or 5 ms, etc., as shown above. Depending on the different behavior of the UE, the UE may, for example, be allowed to use the resources of the pre-configured radio transmission resource pool until the RRC connection is established and the eNB assigns the allocated radio resources to the terminal; or until the UE realizes that the RRC connection setup has failed; or until the UE informs the eNB that it is not allowed to communicate directly in the cell; or before actually performing direct SA or data communication using dedicated resources assigned by the UE by the eNB.

In addition, it should be noted that although this second embodiment has been explained as a separate solution different from the first embodiment, nevertheless, this second embodiment can be combined with the first embodiment as a whole.

Third embodiment

With regard to D2D communication and current development, the inventors have identified additional problems. More specifically, in addition to the above problem (s) with respect to the different periods in which the UE is prevented from performing D2D communication in different scenarios, another problem relates to state 3 and state 4 OOC UEs. In particular, it is not yet clear how a particular UE will know whether it is in state 3 (UE CP relay) or in state 4. This leads to the additional problem that the UE does not understand what resources and transmission power it should use to perform D2D communication.

FIG. 11 and the related description of the prior art section explain 4 basic states in which a UE can be, and which can be briefly characterized as follows:

State 1: In Cell Coverage (IC) - very close to the center of the cell

State 2: In Cell Coverage (IC) - At a Cell Boundary

State 3: Outside the cell coverage - slightly outside the cell; these UEs may cause some WAN interference "in case" of transmission over conflicting resources with high transmission power

State 4: "Really" outside the coverage area of the cell - cannot interfere with the WAN even in the case of transmission over conflicting resources with high transmission power

It is clear that in states 3 and 4, the UE is outside the coverage area of the cell, but it is not clear how the UE can distinguish between state 3 and state 4, since it only knows that it is not in the coverage area, i.e., it is not based on what or WAN cell.

Possibly (are) the following solution (s).

If the UE receives the PD2DSCH, it considers itself to be in State 3; otherwise, if the UE has not received the PD2DSCH for some predetermined (or configurable) time, it considers itself to be in State 4. As explained in the prior art, PD2DSCH is the physical layer information sent by the eNB in the OOS (Out of Area Coverage) of the UE by some UE IC (UE IC forwards PD2DSCH). PD2DSCH signals some resources for D2D communication. If they are received by the OBS UE, resources received at the PD2DSCH for D2D communication take precedence over any preconfigured Mode 2 resources available to the OBS UE. This is advantageous because in other cases the use of preconfigured Mode 2 resources may cause some interference to the WAN, because in other cases these UEs will consider themselves to be in state 4 and may transmit on conflicting resources at high transmit power.

A UE in state 3 will again consider itself a UE in state 4 when it stops receiving PD2DSCH or D2DSS (D2D sync signal) for a predetermined period of time.

By specifying how the UE distinguishes between state 3 and state 4, the resources and transmission power that it should use to perform D2D communication can be selected / calculated in an efficient manner so as not to cause any problems (interference) when using WAN communication.

It should be noted that the third embodiment explained above can be combined with the first and / or second embodiment explained above.

Fourth embodiment

Another problem identified in D2D communication is that it is not clear from the current standardization which UE should forward PD2DSCH to different UE OOCs.

The following alternative solutions are possible. Their combinations are also possible.

Typically, UEs that are reasonably within the cell's coverage area (eg, acceptable measured RSRP and RSRQ of the serving cell), but not near the center of the cell, may be a good option for PD2DSCH forwarding. In particular, UEs that are located between some predetermined radio reception threshold (eg, for which the RSRP / RSRQ measurements are between a specific threshold ʺxʺ and a threshold yʺ); RSRP (Received Reference Power); RSRQ (Received Reference Quality). In such a case, the threshold x and the threshold y are broadcast along with the PD2DSCH content.

Another possible option for PD2DSCH forwarding is UEs that transmit / forward D2DSS. The PD2DSCH content is broadcast.

Another possible solution is that the network explicitly requests specific UEs in dedicated signaling to forward PD2DSCH. The PD2DSCH content is broadcast or signaled to the UE using dedicated signaling.

One possible combination of the above solutions is a UE that already forwards D2DSS, but also has acceptable cell coverage, i.e. when RSRP or RSRQ is between the corresponding thresholds.

It should be noted that the fourth embodiment can be used with either one of the first, second and third embodiments, or any combination thereof.

Fifth embodiment

Another issue identified in D2D communication relates to the transmit / receive operation for D2D communication. As mentioned in the prior art section, depending on the resource allocation mode, the D2D transmission operation looks slightly different. For D2D Mode 1 communication, the eNB grants D2D permission, i.e. (E-PDCCH) with D2D-RNTI scrambling, to the transmitting D2D UE, which allocates resources for SA transmission and also for data (ProSe / D2D data). More specifically, the D2D grant contains at least an SA resource index (SA resource index) indicating time / frequency resources to be used by the transmitting D2D UE for SA transmission within the SA resource pool, as well as the T-RPT index and the field data RB allocations that mainly indicate time / frequency resources for D2D data transmissions. The T-RPT index field refers to a single entry in the table that lists all available T-RPT templates, for example, the table contains 128 entries. The Temporary Transfer Resource Template (T-RPT Template) defines the temporary resource template for D2D Data Transfers within a D2D resource pool.

Upon receipt of the D2D grant from the eNB, the transmitting D2D UE uses the SA resource index to determine subframes and frequency resources within the SA resource pool to be used to transmit the SA message accordingly. Next, the D2D transmitting UE uses at least the T-RPT index information received in the D2D grant to determine the subframes (and potentially also frequency resources based on some other information transmitted in the D2D grant) to be used for transmission. D2D data PDU. The function of how to obtain subframes for transmission of different D2D data PDUs differs for D2D mode 1 and mode 2 transmission. For D2D mode 2 transmission, the transmitting D2D UE will apply the T-RPT pattern to the subframes that are designated as subframes in the resource pool bitmap. As such, the D2D transmitting UE applies the T-RPT pattern to those subframes that are identified as potential D2D subframes for Mode 2 transmission according to the D2D Mode 2 transmission resource pool. Examples are shown in FIG. 22.

The 1s in the transmission resource pool bitmap denotes so-called D2D subframes, ie, subframes reserved for D2D Mode 2 transmission. The T-RPT template is applied to these D2D subframes. As seen in FIG. 22, these D2D subframes in which the corresponding T-RPT entry is 1 should be used for D2D data PDU transmissions (subframes in which both the resource pool bitmap entry and the T-RPT bitmap entry are 1). As mentioned in the prior art section, for Mode 2 resource allocation, the transmitting D2D UE autonomously selects the T-RPT template and signals it to the SA such that the receiving D2D UEs are able to determine (after correct SA decoding) based on the received T-RPT template, the timing / frequency resource of D2D data transmissions. There is no D2D clearance for D2D Mode 2 transmission.

For D2D Mode 1 transmission, the eNB allocates a T-RPT template to be used for D2D transmission and signals it to the D2D transmitting UE by granting D2D, as already explained above.

Given the lack of a pool of D2D transmission resources for mode 1, the parameters in the T-RPT should be directly applied to the physical uplink subframes, since the uplink subframes may be D2D subframes. In accordance with one exemplary embodiment, a D2D transmitting UE should apply the T-RPT pattern specified in the T-RPT pattern index at D2D resolution to all subframes in the resource pool bitmap, i.e., subframes in which the bitmap entry is 1 as well as 0. An example of D2D mode 1 data transmission is shown in FIG. 21.

As you can see, this is also the same T-RPT template used in the example script illustrating D2D Mode 2 transmission; however, for mode 1, it applies to all subframes (UL) in the resource pool. Since there is no data pool defined / configured for Mode 1, the transmitting UE D2D may apply the T-RPT template to either the Mode 2 data pool or alternatively to the receive data pool. The main difficulty is that some reference signal is needed corresponding to the initial subframe in which the T-RPT pattern is applied for Mode 1. Alternatively, there may be some timing relationship between the first D2D data transmission and the predefined SA. For example, the first D2D Mode 1 data transmission opportunity, i.e., this is the start subframe of the T-RPT pattern, occurs x ms after the last transmission of the SA message.

The T-RPT pattern is used differently depending on whether the transmitting D2D UE is using Mode 1 or Mode 2 D2D data transmission. Therefore, the D2D receiving UE must be able to distinguish between Mode 1 or Mode 2 D2D transmissions. More specifically, when receiving an SA in a pool SA resources, the receiving D2D UE must know whether the SA was transmitted using a Mode 1 or Mode 2 D2D transmission in order to accurately interpret the T-RPT pattern, i.e., to determine the exact time / frequency resources of the corresponding D2D data transmissions. In accordance with another exemplary embodiment, the SA message contains an explicit indicator of the resource allocation mode being used for D2D communication, i.e., a new field in the SA message indicates whether Mode 1 or Mode 2 was used for D2D data transmission.

Alternatively, the transfer / allocation mode is implicitly indicated by the T-RPT pattern signaled within the SA message. The available T-RPT templates, which are either preconfigured or listed in the table, are divided into two sets, one set of T-RPT templates is used for Mode 1 transmissions and the second set of T-RPT templates is used for Mode 2. For example, starting from 128 different T-RPT patterns, patterns 0-63 can be used for D2D Mode 1 transmissions, while T-RPT patterns with index 64-127 are reserved for Mode 2. Based on the received T-RPT index in the SA, the receiving D2D UE can understand whether the transmitting UE is using mode 1 or mode 2 resource allocation.

As a further alternative solution in accordance with yet another illustrative embodiment, the transfer / allocation of resources can be obtained from the value of the TA field contained in the SA. Since Mode 1 transmissions and Mode 2 transmissions use different transmission timing, the receiving UE can distinguish between Mode 1 and Mode 2 transmissions based on the value of this field. For example, the TA value for Mode 2 transmission is always zero, while for Mode 1 the TA value is set equal to the UE's NTA value, i.e., the UE uses the standard timed uplink transmission mode for D2D Mode 1 transmissions.

As a further alternative, the resource allocation / transmission mode may be indicated implicitly by the frequency resources used to transmit the SA message. For example, the SA messages sent by the transmitting Mode 2 UEs are different from the frequency resources used for the SA transmissions of the transmitting Mode 1 UEs. More specifically, the transmission resource pool for Mode 2 is different from the resources assigned by the eNB for the SAs (Mode 1) transmissions.

Yet another alternative solution in accordance with a further illustrative embodiment of the invention is to determine the length of the T-RPT pattern bitmap such that there is no ambiguity between Mode 1 and Mode 2 transmissions. More specifically, the length of the T-RPT pattern bitmap should be as follows: the same as the length of the resource pool bitmap to which the T-RPT template applies. Taking the examples depicted in FIGS. 21 and 22, the length of the T-RPT shall be 30 bits.

Since the T-RPT pattern for both Mode 1 and Mode 2 applies to the same start subframe, eg, the start subframe of a resource pool, the receiving D2D UE need not distinguish between Mode 2 and Mode 1 transmissions.

It should be noted that the fifth embodiment can be used in conjunction with either one of the first, second, third and fourth embodiments, or any combination thereof.

Hardware and software implementation of the present invention

Other illustrative embodiments relate to the implementation of the above-described various embodiments using hardware and software. In this regard, a user equipment (mobile terminal) and an eNodeB (base station) are proposed. The user equipment and the base station are configured to implement the methods described herein.

It is also understood that various embodiments may be implemented or performed using computing devices (processors). The computing device or processor may, for example, be general purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, etc. Various embodiments can also be performed or implemented using a combination of these devices.

In addition, various embodiments can also be implemented with software modules that are executed by a processor or directly in hardware. In addition, it is possible to combine software modules and hardware implementation. The software modules can be stored on any kind of computer readable media such as RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROMs, DVDs, etc.

It should also be noted that individual features of different embodiments may, individually or in arbitrary combination, be the subject of another embodiment.

A person skilled in the art should understand that various variations and / or modifications are possible in the present invention, as shown in specific embodiments. The present embodiments are therefore to be considered in all respects illustrative and not restrictive.

Position 1. A method of allocating radio resources to a transmitting terminal for direct communication transmission over a direct connection of a communication line to a receiving terminal in a communication system, the method comprising the following steps performed by the transmitting terminal:

receiving from the base station a broadcast packet of system information containing information on

- a temporary pool of radio transmission resources indicating radio resources that can be used by those transmitting terminals that receive the broadcast packet of system information to perform a feed-forward transmission to the receiving terminal over a direct link connection, and

- configuration information on the temporary radio transmission resource pool, the configuration information limiting the amount of time during which the temporary radio transmission resource pool can be used by the transmitting terminal.

Position 2. The method according to Position 1, wherein the transmitting terminal selects radio resources from the temporary radio transmission resource pool and performs direct-link transmission of either scheduling assignments or data to the receiving terminal using the selected radio resources before the time for which can be used expires temporary pool of radio transmission resources.

Provision 3. A method according to Provision 1 or 2, wherein the configuration information on the temporary transmission radio resource pool comprises:

- an allowable time variable indicating the amount of time during which the temporary radio transmission resource pool can be used, either after receiving the broadcast packet of system information, or after the transmitting terminal starts using the temporary radio transmission resource pool, and / or

- a join instruction variable indicating either

- the amount of time after receiving a broadcast packet of system information or after the transmitting terminal starts using the temporary pool of radio transmission resources, during which the transmitting terminal must initiate the procedure for establishing a radio connection with the base station in case the transmitting terminal needs to use the temporary pool of radio resources for transmission to implement direct communication with a receiving terminal, or

- indicating that the transmitting terminal should initiate a radio link establishment procedure with the base station before using the temporary radio transmission resource pool.

Statement 4. The method according to Statement 3, wherein the transmitting terminal initiates a radio link establishment procedure with a base station by transmitting a random access procedure preamble.

Statement 5. A method according to one of Statement 1-4, wherein a temporary pool of radio transmission resources can be used by a transmitting terminal in an idle state and in a connected state.

Clause 6. A method according to one of Clauses 1-5, wherein the temporary pool of radio transmission resources may be used by the transmitting terminal only up to one of the following:

- the transmitting terminal is assigned dedicated radio resources by the base station, which can be used for direct communication,

- the transmitting terminal performs direct-link transmission for the first time using the allocated radio resources assigned by the base station to the transmitting terminal,

- the radio link establishment procedure initiated by the transmitting terminal fails,

- the transmitting terminal is informed by the base station that the transmitting terminal is not allowed to communicate directly in the cell of the base station;

in which, preferably, the allocated radio resources are radio resources selected from an assigned pool of radio transmission resources assigned to the transmitting terminal by the base station, or in which the allocated radio resources are radio resources assigned to the transmitting terminal by the base station in response to a resource request from the transmitting terminal for direct transmission communication.

Position 7. A method according to one of Positions 1-6, wherein the temporary radio transmission resource pool indicates a first radio resource set used for direct-link transmission of a scheduling assignment to a receiving terminal over a direct link connection, wherein the scheduling assignment indicates radio resources to be used the transmitting terminal for subsequent transmission with direct communication of data to the receiving terminal via a direct connection of the communication line, and / or

wherein the temporary radio transmission resource pool indicates a second set of radio resources used to effect direct data transmission to a receiving terminal over a direct link connection.

Statement 8. A method according to one of Statement 1-7, wherein the system information broadcast packet further comprises information on a pending radio transmission resource pool, or

wherein the system information further comprises information indicating that direct communication with the receiving terminal over a direct link connection is permitted in a cell of the base station, but does not contain information on the pending radio transmission resource pool,

in which the pending radio transmission resource pool indicates radio resources that can be used by those transmitting terminals that receive the broadcast packet of system information to perform direct-link transmission to the receiving terminal over a direct link connection, and the pending radio transmission resource pool can only be used when the transmitting terminal is in a waiting state.

Provision 9. A transmitting terminal for performing direct-link transmission over a direct connection of a communication line to a receiving terminal in a communication system, wherein the transmitting terminal comprises:

a receiving section configured to receive from the base station a broadcast packet of system information containing information about

- a temporary pool of radio transmission resources indicating radio resources that can be used by those transmitting terminals that receive the broadcast packet of system information to make a direct link transmission to the receiving terminal over a direct link connection, and

- configuration information on the temporary radio transmission resource pool, the configuration information limiting the amount of time during which the temporary radio transmission resource pool can be used by the transmitting terminal.

Clause 10. A transmitting terminal pursuant to Clause 9, containing:

a processing section configured to select radio resources from the temporary pool of radio transmission resources, and

a transmission section configured to effect feed-forward transmission of either scheduling assignments or data to the receiving terminal using the selected radio resources before the amount of time that the temporary radio transmission resource pool can be used has elapsed.

Clause 11. A transmitting terminal pursuant to Clause 9 or 10, wherein the configuration information on the temporary transmit radio resource pool contains:

- an allowable time variable indicating the amount of time during which the temporary radio transmission resource pool can be used, either after receiving the broadcast packet of system information, or after the transmitting terminal starts using the temporary radio transmission resource pool, and / or

- a join instruction variable indicating either

- the amount of time after receiving a broadcast packet of system information or after the transmitting terminal starts using the temporary pool of radio transmission resources, during which the transmitting terminal must initiate the procedure for establishing a radio connection with the base station in case the transmitting terminal needs to use the temporary pool of radio resources for transmission to implement direct communication with a receiving terminal, or

- indicating that the transmitting terminal should initiate a radio link establishment procedure with the base station before using the temporary radio transmission resource pool.

Provision 12. A transmitting terminal pursuant to one of Provisions 9-11, in which the temporary pool of radio transmission resources may be used by the transmitting terminal only up to one of the following:

- the transmitting terminal is assigned dedicated radio resources by the base station, which can be used for direct communication,

- the transmitting terminal performs direct-link transmission for the first time using the allocated radio resources assigned by the base station to the transmitting terminal,

- the radio link establishment procedure initiated by the transmitting terminal fails,

- the transmitting terminal is informed by the base station that the transmitting terminal is not allowed to communicate directly in the cell of the base station,

in which, preferably, the allocated radio resources are radio resources selected from an assigned pool of radio transmission resources assigned to the transmitting terminal by the base station, or in which the allocated radio resources are radio resources assigned to the transmitting terminal by the base station in response to a resource request from the transmitting terminal for direct transmission communication.

Clause 13. A transmitting terminal according to one of Clauses 9-12, wherein the system information broadcast packet further contains information on a pending radio transmission resource pool, or

wherein the system information further comprises information indicating that direct communication with the receiving terminal over a direct link connection is permitted in a cell of the base station, but does not contain information on the pending radio transmission resource pool,

in which the pending radio transmission resource pool indicates radio resources that can be used by those transmitting terminals that receive the broadcast packet of system information to perform direct-link transmission to the receiving terminal over a direct link connection, and the pending radio transmission resource pool can only be used when the transmitting terminal is in a waiting state.

Provision 14. Base station for allocating radio resources to a transmitting terminal for direct communication transmission over a direct connection of a communication line to a receiving terminal in a communication system, moreover, the base station contains:

a transmission section configured to transmit a system information broadcast packet containing information on

- a temporary pool of radio transmission resources indicating radio resources that can be used by those transmitting terminals that receive the broadcast packet of system information to perform a feed-forward transmission to the receiving terminal over a direct link connection, and

- configuration information on the temporary radio transmission resource pool, the configuration information limiting the amount of time during which the temporary radio transmission resource pool can be used by the transmitting terminal.

Provision 15. A transmitting terminal for making a direct link transmission over a direct connection of a communication line to a receiving terminal in a communication system,

wherein the transmitting terminal is preconfigured using a preconfigured radio transmit resource pool indicating radio resources that can be used by the transmitting terminal to perform a direct link transmission to the receiving terminal over a direct link connection, in which the preconfigured radio transmit resource pool can be used when the transmitting terminal is in the coverage area of the cell of the base station.

Clause 16. A transmitting terminal in accordance with Clause 15, in which the transmitting terminal contains:

a receiving section configured to receive, from the base station, a broadcast packet of system information indicating whether a pre-configured pool of radio transmission resources can be used while in the coverage area of a cell of the base station.

Statement 17. The transmitting terminal of claim 16, wherein the system information broadcast packet contains configuration information on a pre-configured radio transmission resource pool for use in a coverage area of a base station cell to indicate that the pre-configured radio transmission resource pool can be used while in the area base station cell coverage,

wherein, preferably, the configuration information on the pre-configured radio transmission resource pool comprises:

- an allowable time variable indicating the amount of time that a preconfigured radio transmission resource pool can be used either after receiving a system information broadcast packet or after the transmitting terminal starts using a preconfigured transmission radio resource pool, and / or

- a join instruction variable indicating either

- the amount of time after receiving a broadcast packet of system information or after the transmitting terminal starts to use the pre-configured pool of radio transmission resources, during which the transmitting terminal must initiate the procedure for establishing a radio connection with the base station in case the transmitting terminal needs to use the pre-configured pool of radio transmission resources to carry out direct communication with the receiving terminal, or

- indicating that the transmitting terminal should initiate a radio link establishment procedure with the base station before using the pre-configured radio transmission resource pool.

Statement 18 A transmitting terminal according to one of Statements 15-17, wherein a preconfigured pool of radio transmit resources may be used by the transmitting terminal in the coverage area of a base station cell up to one of the following:

- the transmitting terminal is assigned dedicated radio resources by the base station, which can be used for direct communication,

- the transmitting terminal performs direct-link transmission for the first time using the allocated radio resources assigned by the base station to the transmitting terminal,

- the radio link establishment procedure initiated by the transmitting terminal fails,

- the transmitting terminal is informed by the base station that the transmitting terminal is not allowed to communicate directly in the cell of the base station,

in which, preferably, the allocated radio resources are radio resources selected from an assigned pool of radio transmission resources assigned to the transmitting terminal by the base station, or in which the allocated radio resources are radio resources assigned to the transmitting terminal by the base station in response to a resource request from the transmitting terminal for direct transmission communication.

Statement 19 A transmitting terminal according to one of Statements 15-18, wherein a pre-configured pool of radio transmission resources may also be used by the transmitting terminal when the transmitting terminal is outside the coverage area of a base station cell.

Statement 20. A transmitting terminal according to one of Statements 15-19, wherein a preconfigured transmit radio resource pool is preconfigured with a Universal Subscriber Identity Module (USIM) card inserted into the transmitting terminal, or

a configuration message received at the transmitting terminal from a layer higher than the access layer, preferably using the Internet protocol - IP - or the non-access layer protocol - NAS.

21. A transmitting terminal according to one of Provisions 15-20, wherein a pre-configured pool of radio transmission resources determines the physical radio resources and optionally controls the transmission format and / or power associated with the physical radio resources.

Statement 22: Base station for configuring radio resources for forward-link transmission on a forward link in a communication section in which the transmitting terminal is pre-configured using a pre-configured pool of radio transmit resources indicating radio resources that can be used by the transmitting terminal for forward-link transmission to a receiving terminal via a direct link connection, in which a pre-configured pool of radio transmission resources can be used when the transmitting terminal is in the coverage area of a cell of a base station, wherein the base station comprises:

a transmission section, configured to transmit a broadcast packet of system information indicating whether a pre-configured pool of radio transmission resources can be used while in the coverage area of a base station cell.

Statement 23. A method for allocating radio resources to a transmitting terminal for direct communication, transmission over a forward link connection to a receiving terminal in a communication system, the method comprising the following steps performed by the transmitting terminal, in which:

receiving from the base station a broadcast of the system information;

if the broadcast of the system information includes information about the radio transmission resource pool intended for the idle state, which information indicates the radio resources that can be used by the transmitting terminals in the idle state, direct communication to the receiving terminal over a forward link connection using a pool of radio transmission resources dedicated to the idle state; and

if the broadcast of the system information does not include information about the radio transmission resource pool intended for the idle state and includes information about the temporary transmission radio resource pool, which information about the temporary transmission radio resource pool indicates radio resources that can be used by the transmitting terminals in the state idle or connected state, direct communication is performed to a receiving terminal over a forward link connection using a temporary pool of radio transmission resources.

Statement 24 A method according to Statement 23 wherein a temporary pool of radio transmission resources may be used by a transmitting terminal only until one of the following occurs:

the transmitting terminal is assigned dedicated radio resources by the base station that can be used for direct transmission,

the transmitting terminal performs direct communication for the first time using the allocated radio resources assigned by the base station to the transmitting terminal,

the radio link establishment procedure initiated by the transmitting terminal fails,

the transmitting terminal is informed by the base station that the transmitting terminal is not allowed to communicate directly in the cell of the base station;

where the allocated radio resources are radio resources selected from the assigned pool of radio transmission resources assigned to the transmitting terminal by the base station, or the allocated radio resources are radio resources assigned to the transmitting terminal by the base station in response to a resource request from the transmitting terminal for direct communication.

Statement 25: The method of Statement 23, wherein the temporary radio transmission resource pool indicates a first set of radio resources that can be used for direct communication of transmitting a scheduling assignment to a receiving terminal over a forward link connection, the scheduling assignment indicating radio resources to be used by transmitters terminal for direct communication, subsequent data transmission to the receiving terminal over a forward link connection, or in which the temporary radio transmission resource pool indicates a second set of radio resources that can be used for direct communication, data transmission to the receiving terminal over a direct connection communication lines.

Statement 26 A method according to Statement 23, wherein the system information broadcast is a system information block (SIB) type 18.

Statement 27 The method of Statement 23, wherein the transmitting terminal uses a temporary radio transmission resource pool when a timer (T300) expires to establish a radio resource control (RRC) connection.

Statement 28 A method according to Statement 23, wherein the broadcast of the system information indicates whether a temporary pool of radio transmission resources can be used when the transmitting terminal is within the coverage area of a base station cell.

Position 29. The method according to Position 24, wherein the allocated radio resources begin with a subframe after the subframe in which the transmitting terminal transmits a scheduling assignment (SA) message.

Statement 30. A transmitting terminal for direct communication, transmission over a forward link connection to a receiving terminal in a communication system, the transmitting terminal comprising:

a receiver that, during its operation, receives a broadcast of the system information from the base station;

a circuit that is connected to the receiver and which, when it is working,

if the broadcast of the system information includes information about the radio transmission resource pool intended for the idle state, which information indicates radio resources that can be used by the transmitting terminals in the idle state, directly transmitting to the receiving terminal over a forward link connection using a pool of radio transmission resources dedicated to the idle state; and

if the broadcast of the system information does not include information about the radio transmission resource pool intended for the idle state and includes information about the temporary transmission radio resource pool, which information about the temporary transmission radio resource pool indicates radio resources that can be used by the transmitting terminals in the state idle or connected state, performs a direct link transmission to a receiving terminal over a forward link connection using a temporary radio transmission resource pool.

Statement 31 A transmitting terminal in accordance with Statement 30, whereby a temporary pool of radio transmit resources may be used by the transmitting terminal only until one of the following occurs:

the transmitting terminal is assigned dedicated radio resources by the base station that can be used for direct transmission,

the transmitting terminal performs direct communication for the first time using the allocated radio resources assigned by the base station to the transmitting terminal,

the radio link establishment procedure initiated by the transmitting terminal fails,

the transmitting terminal is informed by the base station that the transmitting terminal is not allowed to communicate directly in the cell of the base station;

where the allocated radio resources are radio resources selected from the assigned pool of radio transmission resources assigned to the transmitting terminal by the base station, or the allocated radio resources are radio resources assigned to the transmitting terminal by the base station in response to a resource request from the transmitting terminal for direct communication.

Statement 32 A transmitting terminal according to Statement 30 wherein the system information broadcast is a system information block (SIB) type 18.

Statement 33: A transmitting terminal according to Statement 30, which, when operating, uses a temporary radio transmission resource pool when a timer (T300) expires to establish a radio resource control (RRC) connection.

Position 34 A transmitting terminal according to Position 30, wherein the broadcast of the system information indicates whether a temporary pool of radio transmission resources can be used when the transmitting terminal is in the coverage area of a cell of a base station.

State 35. Transmitter according to State 31, where the allocated radio resources start from a subframe after the subframe in which the transmitting terminal transmits a scheduling assignment (SA) message.

Claims (8)

1. An integrated circuit that, when operating, controls the process of a communication device, which contains: receiving an index of the temporary resource pattern (T-RPT) in the control information; determining a data transmission mode based on the control information and determining, based on the received T-RPT index, the T-RPT in a predetermined set of T-RPTs to be used for forward link data transmission, wherein the T-RPT is a bitmap, which indicates subframes for forward link data transmission in the resource pool; and receiving data transmission on the forward link using said specific T-RPT for said specific data transmission mode. 2. The integrated circuit of claim 1, wherein in the case where the data transmission mode is Mode 1, said T-RPT in the predetermined set of T-RPTs is applied to resources allocated by the base station. 3. The integrated circuit of claim 1, wherein when the data transmission mode is Mode 2, said T-RPT is in a subset of a predetermined set of T-RPTs and is applied to resources autonomously selected by a user equipment (UE). 4. The integrated circuit of claim 1, wherein in the case where the data transmission mode is mode 1, the subframes for forward link data transmission start in the first uplink subframe after the last subframe of said control information including the index T- RPT. 5. The integrated circuit of claim 1, wherein said control information, which is received from the base station, is scrambled with a radio network temporary identifier (RNTI) for data transmission on a forward link.

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