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Progress of MB-OFDM UWB Baseband System

Progress of MB-OFDM UWB Baseband System. Wen-Hua Wu. May 26, 2006. Outline. Transmitter Architecture Channel Model Receiver Architecture Simulation Results Word Length Simulation Future Works Conclusions. Transmitter Architecture. System Parameters. Rate-dependent Parameters.

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Progress of MB-OFDM UWB Baseband System

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  1. Progress of MB-OFDM UWBBaseband System Wen-Hua Wu May 26, 2006

  2. Outline • Transmitter Architecture • Channel Model • Receiver Architecture • Simulation Results • Word Length Simulation • Future Works • Conclusions

  3. Transmitter Architecture

  4. System Parameters

  5. Rate-dependent Parameters

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

  7. Transmitted Signals • 30 preambles, including… & data • 21 packet synchronization sequences • 3 frequency synchronization sequences • 6 channel estimation sequences

  8. Channel Model

  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

  10. Multipath Channel Model (2/2) • CM1~CM4 • Linear convolution • lost linearity in frequency domain

  11. CFO & SFO • CFO: carrier Frequency offset • SFO: sampling frequency offset Rx CFO Rx SFO Tx CFO

  12. Channel Impairment • 4 effects are added to simulate this system Tx Multipath Channel Model AWGN Carrier Frequency Offset Sampling Frequency Offset Rx

  13. Receiver Architecture

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

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

  16. Shift Registers (128) Rx Input … Shift Registers (?) … * * * KNOWN PREAMBLE … Peak Detection Shift Registers (128) is MAC * Boundary Detector

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

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

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

  20. Channel Estimator (2/2) Magnitude Actual Channel Estimated Channel Phase Magnitude Actual Channel Estimated Channel Phase

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

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

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

  24. FFT Window Controller (3/4) • Observing phase drift amount @... • max_positive_freq_idx & min_negative_freq_idx

  25. FFT Window Controller (4/4) AWGN, SNR = 10 dB CFO/SFO = 40/40 ppm No add-drop data OFDM symbol # = 200 AWGN, SNR = 10 dB CFO/SFO = 40/40 ppm With add-drop data OFDM symbol # = 200

  26. Simulation Results

  27. QPSK v.s. DCM • Simulation environment: • under AWGN channels • DCM is better than QPSK about 1~1.5 dB

  28. Carrier Frequency Offset • Simulation environment: • under AWGN channels • CFO seems not degrade system performance a lot

  29. Data Payload Length • Maximum data payload length is 4,095 octets • system performance degrades a little • The following simulation use 2,500 octets Saturate @ SNR 10-4

  30. Multipath CM1~CM4 (1/2)

  31. 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

  32. Word Length Simulation

  33. 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

  34. sign bit integer bit 2.6921*2(10-1-2)=344.5888 +344 (0101011000) is received +344 (0101011000) is transmitted 344/2(10-1-2)=2.6875 A B 2.6921 2.6875 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)

  35. Word length of each block @ Tx 10 5 DCM IFFT 9 9 ZP MB Gen.

  36. Word length Sim. @ Rx • WL simulation starts from AD’s output 14 AD

  37. Future Works • Complete word-length simulation • Fixed-point simulation (FPGA emulation)

  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

  39. Reference [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.

  40. Appendix

  41. Band Group #1 Band Group #2 Band Group #3 Band Group #4 Band Group #5 Band #1 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 3432 MHz 3960 MHz 4488 MHz 5016 MHz 5544 MHz 6072 MHz 6600 MHz 7128 MHz 7656 MHz 8184 MHz 8712 MHz 9240 MHz 9768 MHz 10296 MHz frequency Multi-Band (1/3) • Band allocation, 5 bands are defined

  42. Multi-Band (2/3) • Time-frequency codes and preamble patterns for band group 1

  43. Multi-Band (3/3) • OFDM symbols’ transmit orders: frequency jumps for each OFDM symbol Frequency Synchronization (24 symbols) Channel Estimation (6 symbols) Header (12 symbols) Payload (1~4096 bytes) Band #6 Band #5 Band #4 Band #3 Band #2 … … … Band #1 13.125 μsec (Preamble + Header) Time

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

  45. 32 consecutive 0’s 32 consecutive 0’s 32 consecutive 0’s 0…0 C0 C1…C127 0 0 0 0 0 0…0 -C0 -C1…-C127 0 0 0 0 0 0 T1…T610 0 0 0 0T-61…T-1 … CE6 PS1 PS2 … PS21 FS1 FS2 FS3 CE1 CE2 Packet Sync. Sequence 21 OFDM symbols Frame Sync. Sequence 3 OFDM symbols Channel Est. Sequence 6 OFDM symbols Preamble Generation • There are 3 different kinds of preambles for UWB

  46. IFFT n - 56 n = 0 NULL 0 0 n - 55 1≦n≦9 # 1 1 1 n - 54 10≦n≦18 # 2 2 2 ... ... ... ... n - 53 19≦n≦27 n - 52 28≦n≦36 # 61 61 61 n - 51 37≦n≦45 NULL 62 62 Frequency-Domain Inputs n - 50 46≦n≦49 M(n) NULL 63 Time-Domain Outputs 63 n - 49 50≦n≦53 NULL 64 64 n - 48 54≦n≦62 NULL 65 65 n - 47 63≦n≦71 NULL 66 66 # -61 67 67 n - 46 72≦n≦80 ... ... ... ... n - 45 81≦n≦89 n - 44 90≦n≦98 # -2 126 126 n - 43 n = 99 # -1 127 127 IFFT • Pilot tones: #±5, #±15, #±25, #±35, #±45, #±55 • Guard tones: #±57, #±58, #±59, #±60, #±61

  47. 480 Mb/s 640 Mb/s 320 Msample/s 409.6 Msample/s 528 Msample/s Data Source Outer Transmitter DCM Pilot/Guard /Null tone Insertion IFFT Add ZP/GI 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:

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