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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
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