3GPP RAN1 Status:

LTE Licensed-Assisted Access (LAA) to

Unlicensed Spectrum

Richard Li

Mar. 4, 2016

1

Agenda

• Status Overview of RAN1 Working/Study Items

– Narrowband Internet of Things (NB-IoT) (Rel-13)

– Study on latency reduction techniques

– Study on LTE-based V2X services

– Support for V2V services based on LTE sidelink

– Study on channel model for frequency spectrum above 6 GHz

• LTE Licensed-Assisted Access (LAA)

to Unlicensed Spectrum

2

Narrowband Internet of Things (NB-IoT)

• A non-backward-compatible variant of E-UTRA

– Improved indoor coverage, massive number of low throughput devices, low

delay sensitivity, ultra low device cost, low device power consumption and

(optimised) network architecture

• Three modes of operation

– Stand-alone operation: a replacement of one or more GSM carriers

– Guard band operation: the unused RBs within a LTE carrier’s guard-band

– In-band operation: resource blocks (RBs) within a normal LTE carrier

• Basic Transmissions

– 180 kHz UE RF bandwidth for both DL/UL

– DL: 15 kHz sub-carrier spacing for all the modes of operation

– UL single tone transmissions: 3.75 kHz and 15 kHz, CP, freq. domain sinc

– UL multi-tone transmissions: SC-FDMA with 15 kHz subcarrier spacing

– NB-IoT UE: Only needs to support half duplex operations 3

Narrowband Internet of Things (NB-IoT)

• A resource unit, schedulable in NPUSCH transmission

– For single-tone transmission

• A single 3.75 kHz sub-carrier for 32 ms;

• A single 15 kHz sub-carrier for 8 ms;

– For multi-tone transmission

• 3 subcarriers for 4 ms / 6 subcarriers for 2 ms / 12 subcarriers for 1ms.

– A UL-SCH transport block can be scheduled over more than one resource

unit in time

• Synchronization signals

– NB-PSS: per 10 ms, at subframe 5, length-11 Zadoff-Chu Sequence

– NB-SSS: per 10 ms, at subframe 9, length-11, …

• ...

• NB-IoT vs. LTE Cat.1, Cat.0, LTE-M

4

Latency Reduction: Shortened TTI

5

• Latency reductions

– Protocol enhancements

– Shortened TTIs

• Delay per packet exchange

between UE & eNodeB

– Request, Grant, or Data

– 1 ms

• Shortened TTI candidates

– 1, 2, 3, 4, 7 symbols

MMEUE eNodeB S-GW PDN-GW

SR

Grant

BSR (+Data)

Data

Application Server

Data is created and packetized

Data

Data

Grant

Data

Data

Grant

Data

Data

Data

MMEUE eNodeB S-GW PDN-GW

Data packet

Data

Data

Data packet to

higher layers

Data

• Design assumptions

– No shortened TTI spans over subframe boundary

– At least for SIBs and paging, PDCCH and legacy PDSCH

are used for scheduling

– From eNB perspective, existing non-sTTI and sTTI can be

FDMed in the same subframe in the same carrier

– PSS/SSS, PBCH, PCFICH and PRACH, Random access,

SIB and Paging procedures are not modified 6

Shortened TTI(s)

LTE-based V2X Services

• Vehicle wireless communications

– V2V: Between vehicles.

– V2P: Between a vehicle and a device carried by an individual

• E.g. handheld terminal carried by a pedestrian, cyclist, driver or passenger

– V2I/N (vehicle-to-infrastructure/network): between a vehicle and a

roadside unit (RSU: eNB / stationary UE.) / network

7

V2V

V2P

V2I

Pedestrian

Vehicle

Vehicle

Network

8

LTE-based V2X Services RSU

Traffic-Safety

Server

Car accident Ahead

Pedestrian

Pedestrian

Vehicle

V2X Operation only based on PC5

9

E-UTRAN

SLE-UTRAN

SL

UE (RSU)

E-UTRAN

SL

UE (RSU)

E-UTRAN

SL

E-UTRAN

SL

V2X Operation only based on Uu

10

E-UTRAN

ULDL

E-UTRAN

(RSU)

UL

E-UTRAN

(RSU)

DL

E-UTRAN

ULDL

E-UTRAN

ULDL

V2V Services based on LTE Sidelink

• LTE sidelink enhancements for V2V services

– With and without LTE network coverage

• DM-RS enhancements

– Adopt DMRS location option 1 PSCCH/PSSCH for V2V

• Option 1: #2, #5, #8, #11 (i.e. the regular spacing)

– Working Assumption: 15 kHz subcarrier spacing with 1 msec TTI length

• Intel & ITRI proposed to support increased subcarrier spacing, e.g. 30 kHz.

• Sensing with semi-persistent transmission is supported

– Sets of resources among which a UE selects can be restricted based on

the geo information of the UE

• Mechanisms to report UE geographical information to the eNB

are supported

• … 11

E-UTRAN

SL

Channel Model for

Frequency Spectrum above 6 GHz

• A channel model from 6 GHz to 100 GHz

– Further evolution beyond LTE-Advanced / towards 5G

– Bandwidth: up to 1GHz (vs. LTE-A’s 100MHz by CA)

• Channel Modeling Scenarios

– 1st priority: UMi – street canyon, Indoor – office, and Uma

– 2nd priority: UMi – open square, Indoor – shopping mall

• Channel Modeling Requirements

– Blocking, atmosphere attenuation, etc.

– Large channel bandwidths (up to 10% of carrier frequency)

– Mobile speed up to [500] km/h

– Support large antenna arrays

• Channel Modeling Methodology

– Stochastic modeling methodology (3D spatial CM of TR 36.873)

12

1st Priority

UMi - Street Canyon

• O2O and O2I

• Cell radii: less than 100 m

• BS: below rooftops (e.g., 3-20 m)

UMa

• O2O and O2I

• Cell radii: above 200 m

• BS: Rooftops (e.g. 25-35 m)

13

1st Priority (cont’d)

• Indoor – office

– Sub scenario 1 – Open office: open office with cubicles, chairs, etc.

– Sub scenario 2 – Mixed office: open cubicle areas, meeting rooms,

walled offices, corridors, etc.

– APs: Ceilings or walls (e.g.2-3 m)

– AP density: depending on the frequency band and output power

• Range from one per floor to one per room

14

2nd Priority

UMi — Open Square

• O2O and O2I

• Cell radii: less than 100 m

• BS: below rooftops (e.g., 3-20 m)

Indoor - Shopping Malls

• BS: Ceilings

• Details FFS

15

LTE Licensed-Assisted Access

to Unlicensed Spectrum

• Access to unlicensed spectrum

– LAA deployment scenarios (vs. LWA, LTE-U, and MulteFire)

16

LAA in Rel-13

• DL-only LAA

• Cat. 4 LBT

– Random back-off

– Contention window

of variable sizes

– Four LBT priority

classes

• Transmissions

– PDSCH

– Discovery signal

• Multiple channel

access

– Type A (A1 & A2)

– Type B (B1 & B2) 17

LAA in Rel-14

• UL support for LAA SCell operation in unlicensed spectrum

• UL carrier aggregation for LAA SCell(s) using Frame

Structure type 3

– Channel access mechanism

• Use the decisions made in RAN1 during Rel-13 as a starting point

– PUSCH and SRS

– Self-scheduling and cross-carrier scheduling from licensed spectrum.

– If needed, specify support for PUCCH

– If needed, specify support for PRACH

• Complete support for 10 MHz system BW as an LAA SCell

18

Channel Access and PUSCH in LAA

• Channel access

– Support UL LBT based on a Cat-4 channel access procedure.

– Support UL LBT based on a CCA of at least 25 µs before the UL

transmission burst.

• PUSCH

– At least RB-level multi-cluster transmission (>2) is supported

– For eLAA, flexible timing between UL grant and UL transmission is

supported

– For UL transmission in eLAA Scells, flexible timing between the

subframe carrying the UL grant and subframe(s) of the corresponding

PUSCH(s) is supported

• Working assumption: The minimum latency is 4ms

– In Rel-14 LAA, UL grant(s) for a UE in a subframe can enable PUSCH

transmission for the UE in multiple subframes in LAA SCell for both

cross-cc scheduling case and self-scheduling case.

19

SRS, PUCCH, and PRACH in LAA

• SRS

– Aperiodic SRS transmission with PUSCH is supported in eLAA

• PUCCH

– Transmission of HARQ ACK for serving cells at licensed carriers on an

LAA SCell is NOT supported

– Transmission of HARQ ACK and CSI for serving cells at unlicensed

carriers on an LAA SCell is supported

• PRACH

– Contention based PRACH on LAA Scell is NOT supported in Rel-14

– Non-contention based PRACH on LAA Scell is supported in Rel-14

subject to LBT

• 10 MHz BW as an LAA Scell

– Shall not be used if the absence of Wi-Fi cannot be guaranteed

– Unless additional work on channel access is agreed 20