DEVELOPMENT TRENDS OF D2D COMMUNICATIONS IN THE LTE 魏存毅國 立台北 大學通訊系
The evolution A set of radio access technologies is required to satisfy future requirements Required Performance TRx Spectrum efficiency Traffic offloading TRx TRx TRx TRx WiFi TRx TRx TRx Non-orthogonal multiple access Controller 3D/Massive MIMO, Advanced receiver Study for new interference scenarios Tx-Rx cooperative access technologies Current performance Spectrum extension Existing cellular bands Higher/wider frequency bands Very wide Super wide Efficient use of higher spectrum bands Network density Cellular network assists local area radio access Frequency Hotspot Dense urban Shopping mall New cellular concept for cost/energyefficient dense deployments NTT DOCOMO, INC., Copyright 2012, All rights reserved. 12
The applications of D2D Proximity-based networking, gaming Advertisement for by-passers Public-Safety and more
The potential gains of D2D Capacity gain: due to the possibility of sharing spectrum resources between cellular and D2D users. Peak rate gain: due to the close proximity and potentially favorable propagation conditions high peak rates may be achieved. Latency gain: when devices communicate over a direct link, the end-to-end latency may be reduced. Coverage extension: the enb s coverage can be extended with the assistance of D2D UE located in celledge.
The illustration of D2D use cases IEEE Communications Magazine April 2014
The network control Device to Device and Cellular communications share the same radio resources. The network controls and optimizes the use of the resources for both Cellular communication and D2D, resulting in enhanced performance and quality of service.
The types of D2D
The scenarios of D2D communications IEEE Communications Magazine April 2014
D2D in R12 Objective: Coverage type: D2D discovery: in network coverage (intra-cell and inter-cell) D2D communication in network coverage (intra-cell and inter-cell), in partial network coverage and outside network coverage. Application: The communication part is targeted to apply only to public safety use. Scenarios UE1 UE2 1A: Out-of-Coverage Out-of-Coverage Out-of-Coverage 1B: Partial-Coverage In-Coverage Out-of-Coverage 1C: In-Coverage-Single-Cell In-Coverage In-Coverage 1D: In-Coverage-Multi-Cell In-Coverage In-Coverage
D2D operating bands
Channel bandwidths 10 MHz allocation for both UL and DL for FDD (20 MHz for TDD) for both the general and Public Safety scenarios 10 MHz channel bandwidth for D2D_communications, and all existing channel BWs per E-UTRA band be baseline for D2D_discovery.
Discovery - Types of Discovery Type 1: a discovery procedure where resources for discovery signal transmission are allocated on a non UE specific basis Type 2: a discovery procedure where resources for discovery signal transmission are allocated on a per UE specific basis: Type 2A: Resources are allocated for each specific transmission instance of discovery signals; Type 2B: Resources are semi-persistently allocated for discovery signal transmission.
Procedure: D2D discovery In case of Type 1, a UE autonomously selects radio resources from the indicated Type 1 transmission resource pool for discovery signal transmission. In case of Type 2B, only an RRC CONNECTED UE may request resources for transmission of D2D discovery messages from the enb via RRC. The enodeb assigns resource via RRC. As baseline, UE releases the transmission resources the latest when the UE enters RRC_IDLE or when the enb withdraws the resource by RRC signalling. In case of Type 2B as baseline radio resource are allocated by RRC. Use of activation/deactivation of radio resources using PDCCH is FFS. Receiving UEs monitor both Type 1 and Type 2B discovery resources as authorised.
Mode of D2D Communication From a transmitting UE s perspective, a UE can operate in two modes for resource allocation: Mode 1: enodeb or a relay node schedules the exact resources used by a UE to transmit direct data and direct control information Mode 2: a UE on its own selects resources from resource pools to transmit direct data and direct control information D2D communication capable UE shall support at least Mode 1 for in-coverage D2D communication capable UE shall support Mode 2 for at least edge-of-coverage and out-of-coverage
Procedure: D2D Communication Scheduling Assignment (SA) indicates the location of the resource(s) for reception of the associated physical channel that carries D2D data are transmitted by the UE and the transmission pattern for data transmission (T- RPT) The SA resource pool includes reception pool(s) for modes 1 and 2 and the transmission pool for mode 2. For Mode 1: The location of the resources for transmission of the SA by the broadcasting UE comes from the enodeb. For Mode 2: A resource pool for SA is pre-configured and/or semi-statically allocated. UE on its own selects the resource for SA from the resource pool and transmit its SA.
Format of Scheduling Assignment (SA) R1-142056
Format of Resource Pattern of Transmission The bitmap is mapped to the available D2D data subframes within a data scheduling period!
The source of interference to D2D reception D2D operates on the UL resource, i.e. UL spectrum for FDD bands and UL subframes for TDD bands. D2D reception is hence subject to interference from: a) D2D UEs operating on the same channel due to in-band emissions. b) LTE UEs operating on adjacent channel due to both Tx emissions from the LTE UEs and the receiver blocking of the D2D UE (LTE UE is the blocker). LTE$Cell (b) LTE$UE$to$D2D$UE$ interference D2D$Tx (desired$for$d2d$rx$ue) LTE$Tx D2D$Rx D2D$Tx (non/desired$for$d2d$rx$ue) (a)$ D2D$UE$to$D2D$UE$ in/band$interference
The impact of the interference to D2D Rx UE The minimum physical separation between the D2D Rx UE and the interference (co-channel D2D UE or LTE UE on adjacent channel Table 7.1.1-1: D2D Rx UE (handheld) desense due to (a) co-channel D2D UE, or (b) LTE UE on adjacent channel ProSe.Band./ ProSe.Operating.Channel Interfering.UE./ E(UTRA.Band./.UL.operating.channel Emissions Interference.calculations UE.dist.(m).@.UE.avg..tx.power Band FUL_low ( FUL_high FUL_low ( FUL_high Rx.freq Antenna.Gain Noise MCL LTE.UE.(dBm)./.D2D.UE.(23dBm) Interferer Band MHz MHz MHz MHz dbm/mhz MHz D2D.Tx D2D.Rx dbm/100khz db 23 15 8 14 20 788 832 / / 798 842 LTE$UE 13 777 / 787 /13 10 10 /43 72 120 48 21 (adj.$ul) 793 D2D$UE 14 788 / 798 /2.55 10 10 /33 82 399 (IBE) LTE$UE 20 843 / 853 /10 10 10 /40 75 160 64 28 (adj.$ul) 837 D2D$UE 20 832 / 842 /2.55 10 10 /33 82 378 (IBE) Table 7.1.1-2: D2D Rx UE (vehicle) desense due to (a) co-channel D2D UE, or (b) LTE UE on adjacent channel ProSe.Band./ ProSe.Operating.Channel Interfering.UE./ E(UTRA.Band./.UL.operating.channel Emissions Interference.calculations UE.dist.(m).@.UE.avg..tx.power Band FUL_low ( FUL_high FUL_low ( FUL_high Rx.freq Antenna.Gain Noise MCL LTE.UE.(dBm)./.D2D.UE.(23dBm) Interferer Band MHz MHz MHz MHz dbm/mhz MHz D2D.Tx D2D.Rx dbm/100khz db 23 15 8 14 788 / 798 LTE$UE 13 777 / 787 /13 10 1 /34 81 337 134 60 (adj.$ul) 793 D2D$UE 14 788 / 798 /2.55 10 1 /24 91 1124 (IBE) 20 832 / 842 LTE$UE 20 843 / 853 /10 10 1 /31 84 452 180 80 (adj.$ul) D2D$UE 20 832 / 842 /2.55 10 1 /24 91 1065 (IBE)
Priority of UE capabilities If UE transmission capabilities are limited at a given time: Cellular UL has highest priority Communication has higher priority than discovery both with in a carrier and across carriers If UE reception capabilities are limited at a given time: Cellular DL has highest priority Communication reception is the second priority D2D discovery is the third priority
D2D synchronization Signal design Synchronization signal (D2DSS) and synchronization channel (PD2DSCH) Timing of transmitting D2DSS Type of D2DSS/PD2DSCH to relay
PD2DSCH Format PD2DSCH contents: DFN: 14 bits = 10 bits counter + 4 bits offset TDD UL-DL config: 3 bits: In case of FDD, this field is set to 000, purely for the purpose of decoding of PD2DSCH and does not imply any other UE behaviour The UE is assumed to know a priori the duplex mode of the carrier In-coverage indicator: 1 bit Sidelink system bandwidth: 3 bits Reserved field: 20 bits set to a SIB-signalled or preconfigured value in Rel-12
D2DSS Format 40 ms of periodicity. Primary D2D Synchronization Signal (PD2DSS) PD2DSS is a Zadoff Chu sequence Secondary D2D Synchronization Signal (SD2DSS) SD2DSS is a M sequence D2DSS ID in D2DSSue_net has range {0-167} D2DSS ID in D2DSSue_oon has range {168-335} Note that the index in the agreement where the index of the D2DSS sequence in D2DSSue_oon is the same as the index of the D2DSS sequence in D2DSSue_net assumes that the index is relative to the start of the range of the respective set of sequences. A synchronization source has a physical layer identity known as Physical Layer Identity (PSSID) and PSSID is the same as D2DSS ID.
Timing of transmitting D2DSS -D2D communications For in-coverage UEs A UE transmitting SA or D2D data, in each subframe in the D2DSS resource, the UE shall transmit D2DSS the subframe does not conflict with cellular transmission from the UE perspective the subframe is within the SA or D2D data period in which SA or data is transmitted the UE is RRC_Connected and the enb has instructed it to start D2DSS transmission the RSRP value of the UE is less than the threshold For an in-coverage D2D communication-capable UE that is not transmitting SA or D2D data the UE shall transmit D2DSS if the UE is RRC_Connected and the enb has instructed it (by dedicated signalling) to start D2DSS transmission, AND the enb has not instructed the UE (by dedicated signalling) to stop D2DSS transmission
Timing of transmitting D2DSS -D2D communications For out-of-coverage UEs A UE transmitting SA or data A UE shall transmit D2DSS if the D2D measurement for selected transmission timing reference is below SynchSourceThresh
Timing of transmitting D2DSS -D2D discovery For a discovery UE, for each discovery pool, the UE shall transmit D2DSS in the first subframe of the discovery pool if this subframe is in the D2DSS resource, or otherwise in the latest subframe of the D2DSS resource before the start of the discovery pool
Type of D2DSS/PD2DSCH to relay In-coverage UE If the UE is camping/connected to an enb The D2DSS sequences and PD2DSCH contents are signalled by the enb Partial Coverage If the UE selects D2DSS/PD2DSCH from in-coverage UEs as its transmission timing reference and D2DSS belongs to D2DSSue_net The D2DSS sequences and PD2DSCH contents are the same as the received
Type of D2DSS/PD2DSCH to relay Out of coverage case 1 If the UE selects D2DSS/PD2DSCH from out-of-coverage UEs as its transmission timing reference and D2DSS belongs to D2DSSue_net The PD2DSCH contents are the same as the received PD2DSCH D2DSS is the sequence in D2DSSue_oon that has the same index as the received sequence in D2DSSue_net Out of coverage case 2 If the UE selects D2DSS/PD2DSCH from out-of-coverage UEs as its transmission timing reference and D2DSS belongs to D2DSSue_oon PD2DSCH contents are the same as the received PD2DSCH The D2DSS sequence is the same as the received D2DSS Out of coverage case 3 If the UE does not select any D2DSS/PD2DSCH as its transmission timing reference and it is not camping/connected to an enb The PD2DSCH contents are determined by the pre-configuration The D2DSS sequence is arbitrarily selected from D2DSSue_oon
Decision to become a synchronization source For in-coverage UE, it can become a D2D Synchronization Source at least if it is configured to do so by the enb For out-of-coverage UE, it may become a D2D Synchronization Source if received signal strength of all received D2DSS(s) by the UE are below a threshold.
Priority for Synchronisation source selection enb UEs within network coverage among which higher priority is given to D2DSS received with higher synchsourcethresh measurement UEs out of network coverage transmitting D2DSS from D2DSSue_net among which higher priority is given to D2DSS received with higher synchsourcethresh measurement UEs out of network coverage transmitting D2DSS from D2DSSue_oon among which higher priority is given to D2DSS received with higher synchsourcethresh measurement
Procedure of D2D synchronization R1-143978
Status of D2D in R12! Estimated level of completion of the work/study item overall (mandatory to be provided): Core part: 95% RAN4 Perf. part: 10% RAN5 Testing part: XXX % SI: XXX % per WG (mandatory to be provided) for Core part or SI: RAN WG1: 100% RAN WG2: 95% RAN WG3: 100% RAN WG4: 80% RAN WG5: XXX% Estimated completion date of the work/study item This SI is planned to be 100% complete in: XXXXXXX The Core part WI is planned to be 100% complete in: March 2015 The Performance part WI is planned to be 100% complete in: Sept. 2015 The Testing part WI is planned to be 100% complete in: XXXXXXX
D2D in R13 New WI: Enhanced Device to Device ProSe (RP-142311) Type 1 discovery for the partial and outside network coverage scenarios targeting public safety use Support the extension of network coverage using UE-to-Network Relays, including service continuity (if needed), based on Release 12 D2D communication, considering applicability to voice, video. Enhance D2D discovery support in the presence of multiple carriers and PLMNs Interference Issues
Service Continuity and UE-NW Relaying Traffic switch between infrastructure path, relay path and direct path EPC EPC UE3 enb1 Switch Switch enb2 enb1 Switch UE1 UE1-UE2 proximity border UE2 UE2 UE1-UE2 proximity border UE1
NEXT?
V2V (RP-142032 Ericsson) Cooperative Awareness Messages (CAM) for vehicular driving security are broadcasted using adapted D2D discovery channels and procedures CAM messages are typically 300-500 bytes in length and are delivered every 0.1-1s Support for occasionally out of coverage vehicles is required (the out of coverage discovery solutions for NSPS can be largely reused) The enb controls V2V resources Different RRM strategies are possible within the resources allocated by the enb LT E D2D
V2X (RP-141958 LG Electronics) Vehicle Pedestrian (UE, mobile device) Cellular network, Internet, application servers and so on V2P V2I* V2V V2I RSU (Road Side Unit for DSRC) Vehicle
Reference 3GPP TR 36.843 V1.2.0 (2014-02) 3GPP Radio Access Network : Rel-12 and beyond, Dino Flore, 3GPP RAN Chairman 3GPP TR 36.877 V1.0.0 (2014-12) RP-141894_Status_Report for D2D 3gpp.org
THANK YOU
3GPP structure
3GPP Documents on D2D SA1 Ø TR 22.803 Feasibility study for Proximity Services (ProSe) Ø TS 22.278 Service requirements for the Evolved Packet System (EPS) Ø TS 22.115 Service aspects; Charging and billing Ø TS 21.905 Vocabulary for 3GPP Specifications SA2 Ø TR 23.703 Study on architecture enhancements to support Proximity-based Services (ProSe) (Release 12) Ø TS 23.303 Proximity-based services (ProSe); Stage 2 (Release 12) SA3 Ø TR 33.833 Study on security issues to support Proximity Services RAN1 & RAN2 Ø TR 36.843 Study on LTE Device to Device Proximity Services - Radio Aspects RAN4 Ø TR 36.877 LTE Device to Device Proximity Services User Equipment (UE) radio transmission and reception. CT1 Ø TS 24.333 Proximity-services Management Object (MO) Ø TS 24.334 Proximity-services (Prose) User Equipment (UE) to Proximity-services (ProSe) Function aspects (PC3); Stage 3
Roadmap
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