Software Defined Air Interface

- Air interface Design Paradigm Shift for 5G

Jianglei Ma

Dec. 8th, 2014

D2D

VerticalsMBB

Open OTT

SDN-RAN

IoT

Diverse QoE requirements (data rate; latency; reliability; packet size)

Diverse capabilities for both network transmit nodes and terminals

Diverse deployment environments & spectrum range

Challenges to 5G Air Interface

Single & unified air-interface for all spectrum and all use

cases

Latency（ms）

Links（Per/km2）

Speed（kbps/km2）

Software Defined Air Interface

A Flexible AI

Page 3

Candidate technologies for AI building blocks

Protocols Waveforms Frame

Structure

Multiple

Access

Scheme

Coding

Modulation

Air Interface

Configuration

(SoftAI)

Optimized

air Interface

Traffic type,

transmitting &

receiving condition

One size fits all -> AI Adaptation Optimized RAT for each application/use case

Dynamic or semi-static or static configurable

Across frequency carriers or within the same frequency carrier

Forward compatible : easy to add unforeseeable new service/use case

Backward compatible

SCMA

f-OFDM

FBMC

OFDM

Flexible TTI

Flexible duplex

Scheduled

Grant-free

LBT

Polar

Turbo

Network coding

Adaptive HARQ

AI Adaptation Example

Co-existence of Multiple AI configurations

Static Air Interface

Configurations

Spectrum dependent

WF , TTI

Spectrum

Range

Pre-defined

customized AI

Subset AI for low

cost node / device

Vertical

Applications

Tx and Rx

Capability

Support

Legacy RAT

Subset AI for legacy

UE

Traffic/QoE

classification

Selected AI options QoE/traffic characteristics

provisioning from network

Data

data

transmitted

with option 1

data

transmitted

with option 2

… data

transmitted

with option N

WF, MA, TTI,

Protocol selector

Content-aware

Dynamic configuration

4个RB

Flexible Waveform

Issues of Existing OFDM Waveform

Page 5

Frequency

OFDM

sub-carrier

spacing=

15 kHz

frame

10 ms

TTI-1 TTI-2 TTI-

10

1 ms

Slot-1 Slot-2

0.5 ms

Symbol-1 Symbol-2 Symbol-7

Cyclic prefix (4.7 s)

66.7 s

Cyclic prefix (5.2 s)

Normal CP

frame

10 ms

TTI-1 TTI-2 TTI-

10

1 ms

Slot-1 Slot-2

0.5 ms

Symbol-1 Symbol-2 Symbol-7

Cyclic prefix (16.7 s)

66.7 s

Cyclic prefix (16.2 s)

Extended CP

•OFDM waveform is not flexible

•OFDM waveform is not spectrum localized

•OFDM waveform cannot support asynchronous operation

time

Ch. 1

Ch. 2

Ch. 3

freq.

OFDM

UE #1

OFDM

UE #2

OFDM

UE #3

time

FFTdata of all

UEs

Page 6

Frequency Localized Waveforms

Subband Filtered OFDM (f-OFDM)

• f-OFDM: Sub-band digital filter is applied to shape the spectrum of subband

OFDM signal. • Good out-of-band leakage rejection

• Maintain all the benefits of OFDM

• M-MIMO friredly

• Fragmental spectrum utilization

-8 -6 -4 -2 0 2 4 6 8-90

-80

-70

-60

-50

-40

-30

-20

-10

0PSD Spectrum

Frequency(MHz)

PS

D

OFDM

Filtered-OFDM

Flexible Time-frequency Lattice

• Co-existence of

different time-

frequency

granularities

• Waveform

optimized for

different

transmission

condition and

applications

• Regional

broadcasting, high

speed train, fixed

devices,……

• Subband

spectrum filter to

control inter-block

interference

Spectrum filter

f

t

OFDM symbol

duration

Guard time

Sub-carrier spacing

f

t

OFDM symbol

duration

Guard time

Sub-carrier spacing

Frequency

Time

Enable Single Waveform for All Applications

UE1

UE2

UE3

UE4

UE5

UE6

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

FECEncoder 1

FECEncoder 2

FECEncoder 3

FECEncoder 4

FECEncoder 5

FECEncoder 6

b11b12…

b21b22…

b31b32…

b41b42…

b51b52…

b61b62…

f

SCMA block 1

Latency（ms）

Links（Per/km2）

Speed（kbps/km2）

Unified Air Interface to Support

Different Waveform / Multiple Access Schemes / Flexible TTI

FR

EQ

UE

NC

Y

TIME

f-OFDM Supports Asynchronous

OFDMA

time

Ch. 1

Ch. 2

Ch. 3

Freq.

Filtered

OFDM

UE #1

Filter #1Freq. Short FFT

processing

for UE #1

Short FFT

processing

for UE #2

Short FFT

processing

for UE #3

Filtered

OFDM

UE #2

Filtered

OFDM

UE #3

Filter #2

Filter #3

• Support

asynchronous

OFDMA/SC-

FDMA

transmission

• Robust to

frequency and

timing

mismatching

• No timing

advance

signal needed

OFDM tones

f-OFDM based SCMA (Sparse Code Multiple

Access)

UE1

UE2

UE3

UE4

UE5

UE6

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

SCMA MODULATION

CODEBOOK MAPPING

FEC

Encoder 1

FEC

Encoder 2

FEC

Encoder 3

FEC

Encoder 4

FEC

Encoder 5

FEC

Encoder 6

b11b12…

b21b22…

b31b32…

b41b42…

b51b52…

b61b62…

f

SCMA block 1

Spreading over

f-OFDM subcarriers

A new frequency domain non-

orthogonal waveform

SCMA codewords are carried by

f-OFDMA tones

SCMA Code Book

UE1 UE2 UE3 UE4 UE5 UE6

(1,0) (0,0) (1,1) (0,1) (b1,b2) (1,0) (1,1)

16-point orthogonal lattice

in 4 real dimensions

Unitary

lattice

rotation

Rotated 16-point lattice

in 4 real dimensions

Mother

constellation

Projections on first and

second complex dimensions

QPSK 1 QPSK 2

0000

0000

•SCMA codebook based on Multi-dimensional Lattice Constellation to exploit shaping gain and

coding gain

•Each UE/layer stores a unique codebook

•Binary input data is mapped to a codeword of the corresponding codebook

•Low PAPR and low projection codebooks possible

SCMA Benefits/Applications

Massive Connectivity, Spectrum Efficiency Enhancement, Ultra

Low Latency; Energy Saving

Page 12

Orthogonal multi-user multiplexing •Scheduling required to maintain the orthogonality •~100 ms delay due to state transition and request-grant procedure (UL) •Signaling overhead for small packet transmission

Non-orthogonal multi-user multiplexing •Support signal superposition •Better coverage •High multi-user detection complexity •Limited number of concurrent Users

Overloaded multi-user multiplexing •Less collision even with overloaded concurrent Users •Low multi-user detection complexity •Low latency (<1 ms) due to grant free access •0 dB PAPR for MTC •Long battery life •Better coverage with scalable SCMA codebook design

f

OFDM-CDMA OFDMA

f

SCMA

f

Non-active tone

M

SCMA Benefits/Applications

SCMA OL MU Transmission & CoMP

p

UEn

UE1

f

Sh

are

d C

H

CHn UEn

UL MU MA (SCMA

codeword

division

multiple

access)

with blind

detection

OL CoMP (Multi-TP SCMA layer & power based

coordination)

DL Open- Loop

MU MA (SCMA layer

& power allocation)

CH4 UE4

CH3 UE3

UE1 CH1

CH2 UE2

Conclusion

• Software configurable air interface

• Flexible air interface to meet 5G requirements

• Co-existence of different air interface configurations

• Optimized for different services and different applications

• Backward compatible & Forward compatible

• f-OFDM enables flexible waveform

• Basic waveform for 5G

• Co-existence of different waveforms, multiple access schemes and different

TTIs

• SCMA is a basic non-orthogonal multiple access scheme for 5G

• Massive connectivity

• Flexible multi-transmitter resource sharing to enable UE centric access