An Unified Adaptive Software Defined Air Interface Dr. Peiying Zhu Huawei Fellow Sept 3rd, 2014, PIMRC
5G World Everything on Mobile
Everything Connected
Everything Virtualized
5G（Beyond Smartphone） Transform the Industry Verticals
400MHz
Auto-drive
Open OTT
D2D
Medicare
IoT
SDN-RAN 10GHz
MBB
Verticals
Meters Sensors
Robots
100GHz
Capacity
Speed
Latency
Links
Energy
1000X （Capacity/km2)
100X （10Gbps)
Less than 1ms
100x
1000X Reduce
5G（Beyond Internet Access and APPs） Unprecedented Performance Challenge Stretched in 3 Dimensions Speed Links Response Spectrum Efficiency All Spectrum Access
Links
（Per/km2）
Networks Re-Architect Challenge No-Cell Virtual RAN Software Defined &Simplicity Service Aware and Monetize
Latency （ms）
Speed （kbps/km2）
Single & Unified Air-Interface for All Spectrum Access
Complementary Band unlicensed
unlicensed
5 10
Macro 1Gbps~4Gbps
20
0.5-2km 0.5GHz
30
40
50
Micro 3Gbps~10Gbps
60
50-100m 2.5GHz
70
Visible Light
Cellular Bands
Primary Band
80
90
Local
GHz
50m
10Gbps~100Gbps 40GHz
Foundational Technologies Research Phase (2014-2018)
5G
Air Interface
Massive MIMO
5G
mmWave
Full/ 5G Flexible RAN&Core Duplex
5G UE
5G
Vertical
Standardization Phase Product Development Phase
Air Interface Characteristics
Sparse Code Multiple Access
(SCMA)
Orthogonalfree & Synchronous free
Spectral Localization
Variable sub-Carrier Tailored to Applications
F-OFDM Ultra-narrow Bands for Internet of Things Applications Ultra-wide-Bands for Virtual Reality Applications Ultra-low Latency for Vertical Applications Capacity X1000
Spectrum Efficiency
X30
Latency X1/10
Links X100
Reliability Coverage x1000 30dB
Virtualized & Software Defined RAN Primitives
Mobility 500km/h
SCMA (Sparse Code Multiple Access) LTE:
b11b12… SCMA MODULATION CODEBOOK MAPPING
FEC Encoder 1
K (4) symbols mapped to K (4) sub-carriers
SCMA: N (6) symbols mapped to K (4) sub-carriers (N > K, overloading)
b21b22… SCMA MODULATION CODEBOOK MAPPING
FEC Encoder 2
SCMA block 2
UE1
b31b32… SCMA MODULATION CODEBOOK MAPPING
FEC Encoder 3
SCMA block 1
UE2
UE3
b41b42…
UE4 SCMA MODULATION CODEBOOK MAPPING
FEC Encoder 4
UE5 UE6
b51b52…
b61b62… FEC Encoder 6
f
SCMA MODULATION CODEBOOK MAPPING
FEC Encoder 5
SCMA MODULATION CODEBOOK MAPPING
Non-orthogonal multiplexing of code layers Over-Dimension to increase overall rate and
connectivity
Sparsity to limit Rx complexity for detection Multi-dimensional codewords with shaping gain Spreading for robust link-adaptation, coverage
A new frequency domain non-orthogonal waveform
Input bits are directly mapped to codewords and spread over multiple sub-carriers Codewords can be assigned to same UE (SU-SCMA) or different UEs (MU-SCMA)
SCMA Code Book QPSK 1
Unitary lattice rotation
QPSK 2
Mother constellation 0000
0000
16-point orthogonal lattice in 4 real dimensions
UE1
(b1,b2)
(1,1)
UE4
UE3
UE2
(1,0)
(1,0)
Rotated 16-point lattice in 4 real dimensions
(0,0)
UE5
(0,1)
Projections on first and second complex dimensions
UE6
(1,1)
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
Scalable SCMA
with Adaptive System Parameters System requirements
SCMA
Network/UE
Configuration
SCMA Mode
capabilities Link-budget Coverage Connectivity Throughput Multiplexing gain Processing capabilities ……
SCMA OFDMA (fall back mode) NOMA (fall back mode) …… SCMA Parameters Number of codewords of an SCMA codebook: M Spreading factor: K Max number of layers (or codebooks/signatures) : J Number of nonzero elements of each codeword: N ……
Flexible and scalable SCMA based access scheme which can compromise among spectral efficiency, coverage, detection complexity, connectivity, and link budget to adapt to different application scenarios
Issues for OFDM Waveform Frequency
OFDM sub-carrier spacing=15 kHz
OFDM FBMC
Time Spectrum not localized, need guard band
Not flexible to change sub-carrier spacing in Frequency 10 ms
OFDM UE #1
OFDM UE #2
time
10 ms
frame
time
1 ms
Ch. 1 Ch. 2
frame
freq.
data of all FFT UEs
TTI-1
OFDM UE #3
TTI-2
TTI-1
Slot2
Slot1
66.7 s Symbol-1
Cyclic prefix (5.2 s)
TTI-2
TTI10
0.5 ms Slot2
66.7 s Symbol-2 Cyclic prefix (4.7 s) Normal CP
Synchronous Tx, large overhead for time alignment
TTI10
0.5 ms Slot1
Ch. 3
1 ms
Symbol-7
Symbol-1
Cyclic prefix (16.2 s)
Symbol-2
Cyclic prefix (16.7 s) Extended CP
Fixed symbol duration, not flexible to change CP
Symbol-7
Spectrum Filtered OFDM (f-OFDM)
1. Sub-band digital filter is applied to shape the spectrum of subband OFDM signal. 2. Orthogonal subcarriers within each subband 3. Allow co-existence of waveforms with different OFDM Primitives
Frequency
OFDM sub-carrier spacing=15 kHz
Time
OFDM sub-carrier spacing=3 kHz
OFDM sub-carrier spacing=30 kHz
Spectrum Filtered OFDM (f-OFDM)
1. Sub-band digital filter is applied to shape the spectrum of subband OFDM signal. 2. Orthogonal subcarriers within each subband 3. Allow different cyclic prefix for each specific sub-band
Frequency
Time
F-OFDM Supports Asynchronous OFDMA
1. Support asynchronous OFDMA transmission 2. Non timing advance signal needed
1. Good out-of-band leakage rejection 2. Similar spectrum localization performance compared to FBMC 3. Maintain all the benefits of OFDM 4. Easy for m-MIMO
-80
-100
-160
-120
-180 -8
-140
-6
-4
-2
2.2
2.25
0 2 Frequency(MHz)
2.3
2.35
2.4 2.45 2.5 Frequency(MHz)
4
2.55
6
2.6
2.65
2.7
8
Flexible Time-frequency Lattice 1. Co-existence of different timefrequency granularities 2. Waveform optimized for different transmission condition and applications 3. Regional broadcasting, high speed train, fixed devices,…… 4. Subband spectrum filter to control inter-block interference
Spectrum filter Sub-carrier spacing
t
Frequency OFDM symbol duration Guard time
f
Sub-carrier spacing
Time t OFDM symbol duration Guard time
f
An Unified Adaptive Software Defined Air Interface to Meet Diverse Services Demand
Unified air interface to support different waveform / multiple access schemes / flexible TTI
