NTU Confidential Baseband Transceiver Design for the DVB-Terrestrial Standard Baseband Transceiver Design for the DVB-Terrestrial Standard Advisor : Tzi-Dar Chiueh Student : Yi-Ju Chen Date : September 29 th, 2003

NTU Confidential 2 Outline Review of DVB-T SystemReview of DVB-T System Transmitter Block DiagramTransmitter Block Diagram Channel ModelChannel Model –Static Channel –Dynamic Channel Receiver ArchitectureReceiver Architecture –Coarse Boundary Detection –Integer CFO Estimation –WLS Fine CFO Estimation Future WorkFuture Work ReferenceReference

NTU Confidential 3 What is DVB-T ? DVB-T stands for Digital Video Broadcasting – Terrestrial –Wireless video DVB-T uses COFDM technique DVB-T Transmit Block Diagram

NTU Confidential 4 System Parameters Center frequency: 480MHz + ｉ *6MHz Region: 480MHz ~ 806MHz  Channel 14 ~ Channel 69 6MHz Channel Transmission mode8k mode2k mode Number of carriers K Duration T FFT us us Carrier spacing 1 / T FFT kHz kHz Bandwidth5.71 MHz ModulationQPSK, 16QAM, 64QAM Code rate 1 / 2, 2 / 3, 3 / 4, 5 / 6, 7/8 Guard interval ratio1 / 4, 1 / 8, 1 / 16, 1 / 32 Data Rate3.732 ~ Mbps

NTU Confidential Channel Model Static Channel Dynamic Channel

NTU Confidential 6 Channel Model (1/4) Static Channel Fixed Reception –where a directional receiving antenna mounted at roof level is used –A receiving antenna height of 10m above ground level is considered to be representative Portable Reception –Portable receiver with attached or built-in antenna –Absence of receiving antenna gain and directivity –Generally lower reception height Derived from the Spec. of DVB-T [1]

NTU Confidential 7 Channel Model (2/4) Static Channel Fixed ChannelPortable Reception

NTU Confidential 8 Channel Model (3/4) Dynamic Channel Typical Urban Reception(TU6) Typical Rural Area Reception ( RA6 ) Derived from COST 207 project (GSM transmission) [2] Tap number Delay (us)Power (dB) Doppler spectrum 10-3Rayleigh 20.20Rayleigh Rayleigh Rayleigh Rayleigh Rayleigh Tap number Delay (us)Power (dB) Doppler spectrum 100Rice Rayleigh Rayleigh Rayleigh Rayleigh Rayleigh [2]

NTU Confidential 9 Channel Model (4/4) Dynamic Channel SFN( Single Frequency Network) Channel [2] Tap numberDelay(us)PowerDoppler spectrumFrequency ratio 100Pure Doppler 21/2 Tg0Pure Doppler+1

NTU Confidential 10 BaseBand Channel Model

NTU Confidential Receiver Architecture

NTU Confidential 12 Receiver Block Diagram

NTU Confidential 13 Coarse Symbol Boundary Detection (1/5) DVB-T System doesn’t have preamble to do symbol boundary detection, but we can utilize the cyclic prefix to implement it.

NTU Confidential 14 Coarse Symbol Boundary Detection (2/5) For 1 tab Channel profile the result of Correlation Sum is as follows, The correlation sum appears triangle and changes slowly If we transmit the preamble to do auto correlation the correlation sum will be an ideal delta function The peak is interfered by noise seriously

NTU Confidential 15 Coarse Symbol Boundary Detection (3/5) As for multi-path channel profile, take a 2-path channel for example The correlation sum peak becomes ambiguous The peak might occur in the boundary which induces ISI

NTU Confidential 16 Coarse Symbol Boundary Detection (4/5) In the SFN Channel Model, there is no peak (extreme example) Add moving average to find the max. average power position

NTU Confidential 17 Coarse Symbol Boundary Detection (5/5) We can observe that the resulting boundary may induce ISI because of the delay spread of the channel Desired FFT window = Max Boundary Position – GI/2

NTU Confidential 18 Fractional CFO Estimation

NTU Confidential 19 Fractional CFO Estimation If we assume the normalized CFO is e Can’t use this formula to calculate Integer part of e If r(k) in the Guard Interval

NTU Confidential 20 Performance of Different Ns

NTU Confidential 21 Integer CFO Estimation

NTU Confidential 22 Integer CFO Estimation(1/2) Integer Frequency Offset (Normalized by Sub Carrier Spacing) will cause the sub-carrier index shift error Using Continual Pilots to find the shift of the index Y : Received Signal in Freq. Domain P m : [ p 1 +m, p 2 +m, ……, p L +m ] Continual Pilots Position shift m l : l ’ th Symbol [5]

NTU Confidential 23 Integer CFO Estimation(2/2) Block Diagram C++ Simulation Result

NTU Confidential Fine CFO Estimation Loop WLS Estimation

NTU Confidential 25 Fine CFO Estimation Joint WLS Estimation(1/2) [4] WLSE Block Diagram Assume the source of CFO and TFO is the same, by the result of joint WLS Estimation [3]

NTU Confidential 26 Fine CFO Estimation Joint WLS Estimation(2/2) Simulation Result Adding extra error=0.04 to see the convergence System Simulation result The result of fractional CFO is in the convergence region already

NTU Confidential 27 Conclusion and Future Work Conclusion –Although there is no preamble, the DVB-T can exchange time for good acquisition performance –It is the advantage of broadcast system Future Work –Design unfinished block –Add channel coding and outer decoding –Simulation the performance on mobile channel

NTU Confidential 28 Reference [1]ETSI EN V1.4.1( ) Framing structure, channel coding and modulation for digital terrestrial television [2]MOTIVATE report to the 36 th DVB-T Meeting ( ) Using DVB-T standard to deliver broadcast Services to mobile receiver [3]Joint weighted least squares estimation of frequency and timing offset for OFDM systems over fading channels Pei-Yun Tsai; Hsin-Yu Kang; Tzi-Dar Chiueh; Vehicular Technology Conference, VTC 2003-Spring. The 57th IEEE Semiannual, Volume: 4, April 22-25, 2003 [4]Design and Implementation of an MC-CDMA Baseband Transceiver Hsin-Yu Kang; July, 2003 [5] Frequency synchronization algorithms for OFDM systems suitable for communication over frequency selective fading channels Classen, F.; Meyr, H.; Vehicular Technology Conference, 1994 IEEE 44th, 8-10 June 1994 Page(s): vol.3