Progress of MB-OFDM UWB Baseband System Wen-Hua Wu May 26, 2006.
-
date post
20-Dec-2015 -
Category
Documents
-
view
228 -
download
0
Transcript of Progress of MB-OFDM UWB Baseband System Wen-Hua Wu May 26, 2006.
Progress of MB-OFDM UWBProgress of MB-OFDM UWBBaseband SystemBaseband System
Wen-Hua Wu
May 26, 2006May 26, 2006
2Wen-Hua Wu
OutlineOutline
• Transmitter Architecture• Channel Model• Receiver Architecture• Simulation Results• Word Length Simulation• Future Works• Conclusions
4Wen-Hua Wu
System ParametersSystem Parameters
Info. Data Rate (MAC to PHY) 480 Mbps
Modulation/Constellation OFDM/DCM
IFFT/FFT Size 128
Spreading Rate 1
Information Tones 100
Data Tones 100
Information Length 242.4 ns
Zero-padded Suffix 60.6 ns
Guard Interval 9.5 ns
Symbol Length 312.5 ns
Sampling Frequency 528 MHz
5Wen-Hua Wu
Rate-dependent ParametersRate-dependent Parameters
DataRate
(Mb/s)Modulatio
n
Coding
Rate(R)
ConjugateSymmetric
Input to IFFT
TimeSpreadin
gFactor
OverallSpreadin
gGain
Coded Bits
per OFDM
Symbol
53.3 QPSK 1/3 Yes 2 4 100
55 QPSK 11/32 Yes 2 4 100
80 QPSK 1/2 Yes 2 4 100
106.7 QPSK 1/3 No 2 2 200
110 QPSK 11/32 No 2 2 200
160 QPSK 1/2 No 2 2 200
200 QPSK 5/8 No 2 2 200
320 DCM 1/2 No 1 1 200
400 DCM 5/8 No 1 1 200
480 DCM 3/4 No 1 1 200
6Wen-Hua Wu
Transmitter ArchitectureTransmitter Architecture
• Inner transmitter w/ frequency interleaving
Scrambler/Encoder
Scrambler/Encoder
IFFTIFFT ZPZP DAC LPF BPF
Pilot/Guard/NullSub-carriers
Puncturer/InterleaverPuncturer/Interleaver DCMDCM
PreambleGenerationPreamble
GenerationMulti-BandGenerationMulti-BandGeneration
DataSourceData
Source
7Wen-Hua Wu
Transmitted SignalsTransmitted Signals
• 30 preambles, including… & data– 21 packet synchronization sequences– 3 frequency synchronization sequences– 6 channel estimation sequences
9Wen-Hua Wu
Multipath Channel Model (1/2)Multipath Channel Model (1/2)
• 4 channel models are defined
• LOS: Line of sight– No obstacles between Tx and Rx
• NLOS: Non-line of sight
Channel model LOS/NLOS Transmit Distance
Achievable data rate
CM 1 LOS 0~4 m 480 Mb/s
CM 2 NLOS 0~4 m 200 Mb/s
CM 3 NLOS 4~10 m 110 Mb/s
CM 4 NLOS extreme -
10Wen-Hua Wu
Multipath Channel Model (2/2)Multipath Channel Model (2/2)
• CM1~CM4
• Linear convolution– lost linearity in frequency domain
Channel model Delay Spread (ns) Number of Paths
CM 1 28.5 15
CM 2 32.3 17
CM 3 55.1 29
CM 4 91.2 (> 70.1) 48
11Wen-Hua Wu
CFO & SFOCFO & SFO
Rx CFORx CFO Rx SFORx SFO
Tx CFOTx CFO
• CFO: carrier Frequency offset• SFO: sampling frequency offset
12Wen-Hua Wu
Channel ImpairmentChannel Impairment
• 4 effects are added to simulate this system
MultipathChannel Model
CarrierFrequency
Offset
SamplingFrequency
OffsetAWGNTxTx RxRx
14Wen-Hua Wu
Receiver ArchitectureReceiver Architecture
PacketDetectorPacket
DetectorBoundaryDetectorBoundaryDetector
CFOCompensator
CFOCompensator
ZPRemover
ZPRemover FFTFFT FEQFEQ
PhaseTrackerPhase
TrackerFFT WindowController
FFT WindowController
De-MapperDe-Mapper
CFOEstimator
CFOEstimator
A/DRFRF
ChannelEstimatorChannel
Estimator
15Wen-Hua Wu
Packet DetectorPacket Detector
D(495)
()*
…
…
Shift Registers (128)÷ DecisionVar.>0.5?
RxInput
()2
()2
16Wen-Hua Wu
Boundary DetectorBoundary Detector
KNOWN PREAMBLE
RxInput …
Shift Registers (128)
…
Shift Registers (128)
* * *…
Shift Registers (?)
PeakDetection
* is MAC
17Wen-Hua Wu
CFO EstimatorCFO Estimator
D(495)
()*
…
Shift Registers (128)
RxInput
tan-1()
SamplingFrequency
÷-2*π*495
EstimatedCFO
18Wen-Hua Wu
CFO Compensator & ZP CFO Compensator & ZP RemoverRemover
exp( )*
j2π(estimated CFO)t
RxInput
CFO Compensated
Data
D(1)
Comparator128 & 165 (++/--) flag
0
1
add-drop occurrence
flag
19Wen-Hua Wu
Channel Estimator (1/2)Channel Estimator (1/2)
OUT 1 OUT 2 OUT 3 OUT 4 OUT 128
CE SEQUENCE 01CE SEQUENCE 02… …ReceivedCE Seq.
Shift Registers (128) Shift Registers (128)
…
÷ ÷ ÷ ÷ ÷…
KNOWN CE SEQUENCE * 2…
Register Files (128)
20Wen-Hua Wu
Channel Estimator (2/2)Channel Estimator (2/2)
MagnitudeMagnitude
PhasePhase
MagnitudeMagnitude
PhasePhase
Actual ChannelActual Channel Estimated ChannelEstimated Channel
Actual ChannelActual Channel Estimated ChannelEstimated Channel
21Wen-Hua Wu
Phase TrackerPhase Tracker
KNOWN PILOTS
POLARITY
…
÷
…
Register Files (127)
ReceivedPilot
Register Files (12)
tan-1()
( 正頻 )
Accumulator ( 負頻 ) ÷360
EstimatedSlope
÷12
EstimatedRCFO
• Extract pilots from FEQ
22Wen-Hua Wu
FFT Window Controller (1/4)FFT Window Controller (1/4)
Register Files (12)
KNOWN PILOTS
POLARITY
…
÷
…
Register Files (127)
ReceivedPilot
tan-1()>π?
<-π?
Comparatormin indexwanted
index whereadd-drop occurs
23Wen-Hua Wu
FFT Window Controller (2/4)FFT Window Controller (2/4)
• If sampling time is earlier 1 sample time than the original sampling time, …– drop 1 sample (fft window moves backward)– in contrast, add 1 sample (fft window moves forwar
d)
2 knN -1 -N
n=0
R'(k)= r(n - T)* e
2πk(n- T) 2πk TN -1 - -N N
n=0
= r(n - T)* e * e
2πk T-N= R(k)* e
Window DriftWindow Driftk: sub-carrier idxk: sub-carrier idx
n: t-domain sample idxn: t-domain sample idx
N: FFT sizeN: FFT size
△△T: window drift amountT: window drift amount
24Wen-Hua Wu
FFT Window Controller (3/4)FFT Window Controller (3/4)
• Observing phase drift amount @...– max_positive_freq_idx & min_negative_freq_idx
25Wen-Hua Wu
FFT Window Controller (4/4)FFT Window Controller (4/4)
AWGN, SNR = 10 dB
CFO/SFO = 40/40 ppm
With add-drop
data OFDM symbol # = 200
AWGN, SNR = 10 dB
CFO/SFO = 40/40 ppm
No add-drop
data OFDM symbol # = 200
27Wen-Hua Wu
QPSK v.s. DCMQPSK v.s. DCM
• Simulation environment:– under AWGN channels
• DCM is better than QPSK about 1~1.5 dB
28Wen-Hua Wu
Carrier Frequency OffsetCarrier Frequency Offset
• Simulation environment:– under AWGN channels
• CFO seems not degrade system performance a lot
29Wen-Hua Wu
Data Payload LengthData Payload Length
• Maximum data payload length is 4,095 octets– system performance degrades a little
• The following simulation use 2,500 octets
Saturate @ SNR 10Saturate @ SNR 10-4-4
31Wen-Hua Wu
Multipath CM1~CM4 (2/2)Multipath CM1~CM4 (2/2)
• Target @ good channels of each CM• CM1~CM3 reach SNR 10-3 @ about 13, 14 dB
• Word length simulation targets @ 10, 14, 18 dB
33Wen-Hua Wu
Introduction to WL sim. (1/2)Introduction to WL sim. (1/2)
• 2 criteria for determining word length of each signal @ this circuit– Reduce hardware cost– Maintain the same system performance
as in floating-point simulation
• According to system performance, …– 10 dB should achieve BER 10-2
– 14 dB should achieve BER 10-3
– 18 dB should achieve BER 10-4
34Wen-Hua Wu
Introduction to WL sim. (2/2)Introduction to WL sim. (2/2)
• Assume transmit 2.6921 from block A to block B, and quantized to 10 bits
• Preserve 1 bit for sign bit (LSB)
AA BB2.69212.6921
2.69212.6921*2*2(10-1-2)(10-1-2)==344.5888344.5888
+344 (+344 (01010110000101011000) is transmitted) is transmitted
+344 (+344 (01010110000101011000) is received) is received
344/2344/2(10-1-2)(10-1-2)==2.68752.6875
2.68752.6875
sign bitsign bit integer bitinteger bit
35Wen-Hua Wu
Word length of each block @ TxWord length of each block @ Tx
55 1010
99 99
DCMDCM IFFTIFFT
ZPZP MB Gen.MB Gen.
36Wen-Hua Wu
Word length Sim. @ RxWord length Sim. @ Rx
• WL simulation starts from AD’s output
1414
ADAD
37Wen-Hua Wu
Future WorksFuture Works
• Complete word-length simulation• Fixed-point simulation (FPGA emulation)
38Wen-Hua Wu
ConclusionsConclusions
• UWB’s fundamental receiver architecture is proposed
• Transmission data rate can be up to 480 Mbps
• RCFO will speed up the occurrence of add-drop
• ZP seems not better than CP• Word-length simulation takes time, but it is
necessary
39Wen-Hua Wu
ReferenceReference
[1] 802.15 working group, “IEEE Std 802.15.3TM-2003,” U.S. New York, NY 100 16-5997, Sep. 29, 2003.
[2] J. Foerster, Ed., “Channel modeling sub-committee report final,” IEEE802.15-02/490.
41Wen-Hua Wu
Multi-Band (1/3)Multi-Band (1/3)
• Band allocation, 5 bands are defined
frequency
Band#1
3432MHz
Band#2
Band#3
Band#4
Band#5
Band#6
Band#7
Band#8
Band#9
Band#10
Band#11
Band#12
Band#13
Band#14
3960MHz
4488MHz
5016MHz
5544MHz
6072MHz
6600MHz
7128MHz
7656MHz
8184MHz
8712MHz
9240MHz
9768MHz
10296MHz
Band Group #1 Band Group #2Band Group #3 Band Group #4Band Group #5
42Wen-Hua Wu
Multi-Band (2/3)Multi-Band (2/3)
• Time-frequency codes and preamble patterns for band group 1
TFC Numbe
r
Base sequence /
Preamble
Mode 1 (mandatory): Length 6 Time-Frequency Code
1 1 1 2 3 1 2 3
2 2 1 3 2 1 3 2
3 3 1 1 2 2 3 3
4 4 1 1 3 3 2 2
5 5 1 1 1 1 1 1
6 6 2 2 2 2 2 2
7 7 3 3 3 3 3 3
43Wen-Hua Wu
Multi-Band (3/3)Multi-Band (3/3)
• OFDM symbols’ transmit orders: frequency jumps for each OFDM symbol
…
Band #1
Band #2
Band #3
Band #4
Band #5
Band #6
…
Time
Synchronization(24 symbols)
Channel Estimation(6 symbols)
Header(12 symbols)
Payload(1~4096 bytes)
13.125 μsec (Preamble + Header)
…
Frequency
44Wen-Hua Wu
Packet FormatPacket Format
• 30 preambles must be transmitted during 9.375μs, with each preamble 165 samples
• The sampling frequency at the receiver must be faster than or equaled to 528 MHz
PLCPPreamble
PLCPPreamble
PHYHeader
PHYHeader
TailBitsTailBits
MACHeader
MACHeaderHCSHCSTail
BitsTailBits
PadBitsPadBits
PLCP Header53.3 Mb/s
53.3, 80, ..., 480Mb/s
528Msamples/s
Frame Payload:Variable LengthFrame Payload:Variable LengthFCSFCS Tail
BitsTailBits
PadBitsPadBits
45Wen-Hua Wu
Preamble GenerationPreamble Generation
• There are 3 different kinds of preambles for UWB
Packet Sync. Sequence21 OFDM symbols
Packet Sync. Sequence21 OFDM symbols
Frame Sync. Sequence3 OFDM symbols
Frame Sync. Sequence3 OFDM symbols
Channel Est. Sequence6 OFDM symbols
Channel Est. Sequence6 OFDM symbols
…PS1PS1 … CE6CE6
0…0 C0 C1…C127 0 0 0 0 00…0 C0 C1…C127 0 0 0 0 0 0…0 -C0 -C1…-C127 0 0 0 0 00…0 -C0 -C1…-C127 0 0 0 0 0
32 consecutive 0’s
PS2PS2 PS21PS21 FS1FS1 FS2FS2 FS3FS3 CE1CE1 CE2CE2
32 consecutive 0’s 32 consecutive 0’s
0 T1…T610 0 0 0 0T-61…T-10 T1…T610 0 0 0 0T-61…T-1
46Wen-Hua Wu
IFFTIFFT
• Pilot tones: #±5, #±15, #±25, #±35, #±45, #±55
• Guard tones: #±57, #±58, #±59, #±60, #±61
IFFT
012
61626364656667
126127
012
61626364656667
126127
...
...
...
...
...
...
...
...
NULL# 1# 2
# 61NULLNULLNULLNULLNULL# -61
# -2# -1F
req
uen
cy-D
om
ain
In
pu
ts
Tim
e-D
om
ain
Ou
tpu
tsM(n)
n - 56n - 55n - 54n - 53n - 52n - 51n - 50n - 49n - 48n - 47n - 46n - 45n - 44n - 43
n = 01≦n≦9
10≦n≦1819≦n≦2728≦n≦3637≦n≦4546≦n≦4950≦n≦5354≦n≦6263≦n≦7172≦n≦8081≦n≦8990≦n≦98
n = 99
47Wen-Hua Wu
Sampling Frequency Sampling Frequency CalculationCalculation
• The sampling frequency at the output end of the transmitter is 528 MHz
• Take info. data rate 480 Mb/s for example:
DCMDCMPilot/Guard/Null toneInsertion
Pilot/Guard/Null toneInsertion
IFFTIFFT AddZP/GIAdd
ZP/GI
480Mb/s
OuterTransmitter
OuterTransmitter
DataSourceData
Source
640Mb/s
320Msample/s
409.6Msample/s
528Msample/s