Progress of MB-OFDM UWB Baseband System Wen-Hua Wu May 26, 2006

Wen-Hua Wu 2 Outline Transmitter Architecture Channel Model Receiver Architecture Simulation Results Word Length Simulation Future Works Conclusions

Wen-Hua Wu 3 Transmitter Architecture

Wen-Hua Wu 4 System 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 ns Zero-padded Suffix 60.6 ns Guard Interval 9.5 ns Symbol Length ns Sampling Frequency 528 MHz

Wen-Hua Wu 5 Rate-dependent Parameters Data Rate (Mb/s) Modulation Coding Rate (R) Conjugate Symmetric Input to IFFT Time Spreading Factor Overall Spreading Gain Coded Bits per OFDM Symbol 53.3QPSK1/3Yes QPSK11/32Yes QPSK1/2Yes QPSK1/3No QPSK11/32No QPSK1/2No22200 QPSK5/8No DCM1/2No DCM5/8No DCM3/4No11200

Wen-Hua Wu 6 Transmitter Architecture Inner transmitter w/ frequency interleaving Scrambler/ Encoder Scrambler/ Encoder IFFT ZP DAC LPF BPF Pilot/Guard/Null Sub-carriers Puncturer/ Interleaver Puncturer/ Interleaver DCM Preamble Generation Preamble Generation Multi-Band Generation Multi-Band Generation Data Source Data Source

Wen-Hua Wu 7 Transmitted Signals 30 preambles, including… & data –21 packet synchronization sequences –3 frequency synchronization sequences –6 channel estimation sequences

Wen-Hua Wu 8 Channel Model

Wen-Hua Wu 9 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 modelLOS/NLOSTransmit DistanceAchievable data rate CM 1LOS0~4 m480 Mb/s CM 2NLOS0~4 m200 Mb/s CM 3NLOS4~10 m110 Mb/s CM 4NLOSextreme-

Wen-Hua Wu 10 Multipath Channel Model (2/2) CM1~CM4 Linear convolution –lost linearity in frequency domain Channel modelDelay Spread (ns)Number of Paths CM CM CM CM (> 70.1)48

Wen-Hua Wu 11 CFO & SFO Rx CFO Rx SFO Tx CFO CFO: carrier Frequency offset SFO: sampling frequency offset

Wen-Hua Wu 12 Channel Impairment 4 effects are added to simulate this system Multipath Channel Model Carrier Frequency Offset Sampling Frequency Offset AWGN Tx Rx

Wen-Hua Wu 13 Receiver Architecture

Wen-Hua Wu 14 Receiver Architecture Packet Detector Packet Detector Boundary Detector Boundary Detector CFO Compensator CFO Compensator ZP Remover ZP Remover FFT FEQ Phase Tracker Phase Tracker FFT Window Controller FFT Window Controller De-Mapper CFO Estimator CFO Estimator A/D RF Channel Estimator Channel Estimator

Wen-Hua Wu 15 Packet Detector D(495) ()* … … Shift Registers (128) ÷ Decision Var.>0.5? Rx Input () 2

Wen-Hua Wu 16 Boundary Detector KNOWN PREAMBLE Rx Input … Shift Registers (128) … *** … Shift Registers (?) Peak Detection * is MAC

Wen-Hua Wu 17 CFO Estimator D(495) ()* … Shift Registers (128) Rx Input tan -1 () Sampling Frequency ÷ -2*π*495 Estimated CFO

Wen-Hua Wu 18 CFO Compensator & ZP Remover exp( ) * j2π(estimated CFO)t Rx Input CFO Compensated Data D(1) Comparator 128 & 165 (++/--) flag 0 1 add-drop occurrence flag

Wen-Hua Wu 19 Channel Estimator (1/2) OUT 1OUT 2OUT 3OUT 4OUT 128 CE SEQUENCE 01CE SEQUENCE 02 …… Received CE Seq. Shift Registers (128) … ÷÷÷÷÷ … KNOWN CE SEQUENCE * 2 … Register Files (128)

Wen-Hua Wu 20 Channel Estimator (2/2) Magnitude Phase Magnitude Phase Actual Channel Estimated Channel Actual Channel Estimated Channel

Wen-Hua Wu 21 Phase Tracker KNOWN PILOTS POLARITY … ÷ … Register Files (127) Received Pilot Register Files (12) tan -1 () ( 正頻 ) Accumulator ( 負頻 ) ÷ 360 Estimated Slope ÷ 12 Estimated RCFO Extract pilots from FEQ

Wen-Hua Wu 22 FFT Window Controller (1/4) Register Files (12) KNOWN PILOTS POLARITY … ÷ … Register Files (127) Received Pilot tan -1 () >π? <-π? Comparator min index wanted index where add-drop occurs

Wen-Hua Wu 23 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 forward) Window Drift k: sub-carrier idx n: t-domain sample idx N: FFT size △ T: window drift amount

Wen-Hua Wu 24 FFT Window Controller (3/4) Observing phase drift –max_positive_freq_idx & min_negative_freq_idx

Wen-Hua Wu 25 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

Wen-Hua Wu 26 Simulation Results

Wen-Hua Wu 27 QPSK v.s. DCM Simulation environment: –under AWGN channels DCM is better than QPSK about 1~1.5 dB

Wen-Hua Wu 28 Carrier Frequency Offset Simulation environment: –under AWGN channels CFO seems not degrade system performance a lot

Wen-Hua Wu 29 Data Payload Length Maximum data payload length is 4,095 octets –system performance degrades a little The following simulation use 2,500 octets SNR 10 -4

Wen-Hua Wu 30 Multipath CM1~CM4 (1/2)

Wen-Hua Wu 31 Multipath CM1~CM4 (2/2) good channels of each CM CM1~CM3 reach SNR 10 about 13, 14 dB Word length simulation 10, 14, 18 dB

Wen-Hua Wu 32 Word Length Simulation

Wen-Hua Wu 33 Introduction to WL sim. (1/2) 2 criteria for determining word length of each this circuit –Reduce hardware cost –Maintain the same system performance as in floating-point simulation According to system performance, … –10 dB should achieve BER –14 dB should achieve BER –18 dB should achieve BER 10 -4

Wen-Hua Wu 34 Introduction to WL sim. (2/2) Assume transmit from block A to block B, and quantized to 10 bits Preserve 1 bit for sign bit (LSB) A A B B *2 (10-1-2) = ( ) is transmitted +344 ( ) is received 344/2 (10-1-2) = sign bit integer bit

Wen-Hua Wu 35 Word length of each Tx DCMIFFT ZP MB Gen.

Wen-Hua Wu 36 Word length Rx WL simulation starts from AD’s output 14 AD

Wen-Hua Wu 37 Future Works Complete word-length simulation Fixed-point simulation (FPGA emulation)

Wen-Hua Wu 38 Conclusions 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

Wen-Hua Wu 39 Reference [1] working group, “IEEE Std TM -2003,” U.S. New York, NY , Sep. 29, [2] J. Foerster, Ed., “Channel modeling sub-committee report final,” IEEE /490.

Wen-Hua Wu 40 Appendix

Wen-Hua Wu 41 Multi-Band (1/3) Band allocation, 5 bands are defined frequency Band # MHz 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 # MHz 4488 MHz 5016 MHz 5544 MHz 6072 MHz 6600 MHz 7128 MHz 7656 MHz 8184 MHz 8712 MHz 9240 MHz 9768 MHz MHz Band Group #1Band Group #2Band Group #3Band Group #4Band Group #5

Wen-Hua Wu 42 Multi-Band (2/3) Time-frequency codes and preamble patterns for band group 1 TFC Number Base sequence / Preamble Mode 1 (mandatory): Length 6 Time-Frequency Code

Wen-Hua Wu 43 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) μsec (Preamble + Header) … Frequency

Wen-Hua Wu 44 Packet 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 PLCP Preamble PLCP Preamble PHY Header PHY Header Tail Bits Tail Bits MAC Header MAC Header HCS Tail Bits Tail Bits Pad Bits Pad Bits PLCP Header 53.3 Mb/s 53.3, 80,..., 480 Mb/s 528 Msamples/s Frame Payload: Variable Length Frame Payload: Variable Length FCS Tail Bits Tail Bits Pad Bits Pad Bits

Wen-Hua Wu 45 Preamble Generation There are 3 different kinds of preambles for UWB Packet Sync. Sequence 21 OFDM symbols Packet Sync. Sequence 21 OFDM symbols Frame Sync. Sequence 3 OFDM symbols Frame Sync. Sequence 3 OFDM symbols Channel Est. Sequence 6 OFDM symbols Channel Est. Sequence 6 OFDM symbols … PS 1 … CE 6 0…0 C 0 C 1 …C …0 -C 0 -C 1 …-C consecutive 0’s PS 2 PS 21 FS 1 FS 2 FS 3 CE 1 CE 2 32 consecutive 0’s 0 T 1 …T T -61 …T -1

Wen-Hua Wu 46 IFFT Pilot tones: #±5, #±15, #±25, #±35, #±45, #±55 Guard tones: #±57, #±58, #±59, #±60, #±61 IFFT NULL # 1 # 2 # 61 NULL # -61 # -2 # -1 Frequency-Domain Inputs Time-Domain Outputs M(n ) n - 56 n - 55 n - 54 n - 53 n - 52 n - 51 n - 50 n - 49 n - 48 n - 47 n - 46 n - 45 n - 44 n - 43 n = 0 1≦n≦91≦n≦9 10 ≦ n ≦ ≦ n ≦ ≦ n ≦ ≦ n ≦ ≦ n ≦ ≦ n ≦ ≦ n ≦ ≦ n ≦ ≦ n ≦ ≦ n ≦ ≦ n ≦ 98 n = 99

Wen-Hua Wu 47 Sampling Frequency Calculation The sampling frequency at the output end of the transmitter is 528 MHz Take info. data rate 480 Mb/s for example: DCM Pilot/Guard /Null tone Insertion Pilot/Guard /Null tone Insertion IFFT Add ZP/GI Add ZP/GI 480 Mb/s Outer Transmitter Outer Transmitter Data Source Data Source 640 Mb/s 320 Msample/s Msample/s 528 Msample/s