Transcript 4G and H.264 - University of Michigan

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The Next Generation Challenge for
Software Defined Radio
Mark Woh1, Sangwon Seo1, Hyunseok Lee1, Yuan Lin1,
Scott Mahlke1, Trevor Mudge1, Chaitali Chakrabarti2, Krisztian Flautner3
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Advanced Computer Architecture Lab, University of Michigan
Department of Electrical Engineering, Arizona State University
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ARM, Ltd.
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3G Wireless
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Large Coverage
Outdoor - High Mobility
Up to 14Mbps
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Expected Wireless Growth
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The growth of wireless will require more bandwidth
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4G Wireless
Macro Cells
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Pico Cells
Isolated HotSpots – 1Gbps Coverage
Large Coverage – 100Mbps Coverage
Indoor – Very Low Mobility
Outdoor - High Mobility
What we need
 Adaptive high performance transmission system
 Great candidate for SDR
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Next Generation Wireless – 4G
·
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IFFT
MIMO
encoder
Channel
Encoder
TX
...
...
DEMOD
(OFDM)
...
...
MOD
(OFDM)
MIMO
decoder
Channel
Decoder
RX
Antenna
·
FFT
·
·
STBC
VBLAST
·
·
Turbo code
LDPC code
 3 Major Components to 4G


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Modulation/Demodulation
Multiple-Input Multiple-Out (MIMO)
Channel Decoder/Encoders
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Modulation - OFDM
….
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Properties of OFDM
-High Spectral Efficiency
-Low Intersymbol Intereference
-Flat Fading Subcarriers
….
Can sustain high data rates with
multiple users
-Nfsc
-fsc
0
fsc
Nfsc
Can be implemented with IFFT/FFT
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Major Component of Modulation – FFT/IFFT
x[0]
x[1]
complex
mult
complex
add
X[0]
complex
sub
X[1]
eiw
Very wide data level parallelism
Requires complex operations
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MIMO (Multiple Input – Multiple Out)


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Previously we used single antenna systems
Now we use multiple antennas to increase the channel
capacity
 Diversity - High Reliability
 Space Time Block Codes (STBC)
 Multiplexing – High Throughput
 Vertical-BLAST (V-BLAST)
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Space Time Block Codes (STBC)
-x[2]*
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x[1]*
Time
x[1]
Transmit Antennas
x[2]
Tx1
Channel
Tx2
h11
h22
h21
Rx1
Receive Antennas
Noise
Received
Signal
h12
Rx2
n21
n22
n11
n12
y11 = h11x[1] + h12x[2] + n11
y21 = h21x[1] + h22x[2] + n21
y12 = -h11x[2]* + h12x[1]* + n12
y22 = -h21x[2]* + h22x[1]* + n22
Channel
Estimation
h11
h21
Combiner
h12
h22
Channel
Estimation
~x[1]
~x[2]
~x[1] = h11*y11 + h12y12* + h21*y21 + h22y22*
~x[2] = h12*y11 - h11y12* + h22*y21 - h21y22*
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STBC
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Receiver Antenna 1 and 2
y21 y11
y22* y12*
h22 h21 h12 h11
Complex
Multiply
Accumulate
~x[1] ~x[2]
Conjugate
+Negation
Channel
Estimation
Requires complex operations
Low Data Movement
Highly parallelizable
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Vertical-BLAST (V-BLAST)
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Mod
Demod
V-Blast
Detector
S/P
Mod
Demod
M Transmitters
R Receivers
Channel
Estimation
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2
3
4
1
2
3
4
1
2
3
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6
7
8
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6
7
8
5
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7
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Nulling
Vector
1
9
10
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12
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10
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12
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16
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Data Stream of 4 Tx
2
3
4
Strongest
Signal
Linear Combination
of Data
Subtract
Strong Signal
Repeat
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V-BLAST

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Implementation Based on Square Root Method for V-BLAST
 Original requires repeated pseudo-inverse calculation for finding the
strongest signal
This algorithm has reduces complexity


Complexity
 Requires matrix operations on complex numbers
 Many Matrix Transformations
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Channel Decoding


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3G Technologies in 4G
 Viterbi
 Turbo Decoder
New to 4G
 LDPC
 Better performance characteristics compared to Turbo and Viterbi
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LDPC
L Node
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Original Value
L0
L1
L2
L3
L4
L5
L6
L7
1
1
0
1
0
1
0
0
1
H=
Message from Check Nodes Decision
E1 → 0
E0 → 0
E1 → 1
E0 → 0
E0 → 1
E1 → 0
E2 → 0
1
1
E0 → 1
E3 → 1
E1 → 0
E2 → 0
E3 → 1
E3 → 0
E2 → 1
E3 → 0
0
0
1
E2 → 1
1
0
1
1
1
0
0
1
0
0
0
0
1
0
0
1
1
1
1
0
0
1
1
0
1
0
1
0
0
1
0
1
0
1
E0
E1
E2
E3
0
L0
L1
L2
1
1
0
L 3 L4
1
0
L5
L6
L7
1
0
1
Message Sent = [ 1
0
0
1
0
1
0
1]
Message Recieved = [ 1
1
0
1
0
1
0
1]
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LDPC
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Min-Sum Decoding Used
Regular LDPC code
Can get benefit from Wide SIMD
 Can do the Bit Node and Check Node
Alignment of Check and Bit nodes is a problem
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SODA PE Architecture
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SODA
DSP
1. SIMD pipeline
Pred.
Regs
3. Local
memory
5. DMA
System Interconnect
Global
Memory
Local
SIMD
Memory
SIMD
ALU+
Mult
SIMD
Reg.
File
E
X
RF
S
T
V
DMA
ALU
Local
Scalar
Memory
AGU
RF
E
X
W
B
SIMD
Shuffle
Network
(SSN)
W
B
SIMD
to
Scalar
(VtoS)
V
T
S
2. Scalar pipeline
Scalar
RF
E
X
AGU
ALU
W
B
Scalar
ALU
W
B
4. AGU pipeline
SIMD – 32 Wide, 16-bit datapath, Predicate Execution
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4G Workload on SODA
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Key 4G
algorithms
100 Mbps
1 Gbps
MCycle/s
MCycle/s
FFT
2x360
4x360
IFFT
2x360
4x360
STBC
240
-
V-BLAST
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1900
LDPC
7700
4x18500
100 Mbps 4G requires 8Ghz SODA PE
1 Gbps 4G requires 20Ghz SODA PE
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4000
0.8
3500
0.7
3000
0.6
2500
0.5
2000
0.4
1500
0.3
1000
0.2
500
0.1
0
0
180nm 130nm
ITRS Scaled Frequency
Vdd (V)
Power (W)
Frequency (Mhz)
SODA With Technology Scaling
90nm
65nm
45nm
32nm
22nm
Fixed Scaled Frequency
Scaled Power
180nm
130nm
90nm
65nm
45nm
32nm
22nm
1.8
1.3
1.1
1.1
1
0.9
0.8
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SDR Challenges In 4G
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We can’t do any of 4G with technology scaling on one core
 Would 8GHz cores even be an energy efficient solution?
What about 1Gbps?
 Are we ever going to get a 20GHz core?
Cannot rely on technology scaling to give us 4G for free
 4G SDR will require algorithmic and architectural innovations
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4G Algorithm-Architectural Co-design

Architectural improvements (SODA II)
 Specialized functional units
 CISC-like complex arithmetic operations
 Specialized data movement hardware
 Less strain on the memory system
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 Wider SIMD
 How wide can we go?
 More PEs
 What does the interconnect look like?
Algorithmic optimization through parallelization
 Reduce intra-kernel communication
 Reduce memory accesses
 Arithmetic is much cheaper than data movement
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Thanks

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Questions?
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Successive Cancelling for V-BLAST
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V-BLAST successive interference cancelling (SIC)
The ith ZF-nulling vector wi is defined as the unique
minimum-norm vector satisfying
 Orthogonal to the subspace spanned by the contributions to yi due
to the symbols not yet estimated and cancelled and is given by the
~
ith row of H
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Alamouti Scheme
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Assumption: the channel remains unchanged over two consecutive symbols
 Rate = 1
 Diversity order = 2
Simple decoding
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Advantages of Software Defined Radio
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Multi-mode operations
Lower costs


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Faster time to market
Prototyping and bug fixes
Chip volumes
UWB
innovations
 Cognitive radio
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802.16a
SDR
Longevity of platforms
Enables future wireless communication
EDGE
Bluetooth
802.16a
802.11b
WCDMA
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802.11n