信号与系统奥本海姆Project-OFDM.pptxVIP

Project: Ideal OFDM SystemWANG RuiAssociate ProfessorDepartment of Electrical Electronic Engineering2013-FallDiscrete-Time OFDM ModelThe discrete-time OFDM system model we have discussed is given below Detected Bit SequenceTransmission Bit SequenceDT OFDM TransmitterEquivalent Wireless ChannelDT OFDM ReceiverApproximated as DT LTI systemInclude RF front end of the transmitter and receiver + actual wireless channelDT OFDM TransmitterA sequence of transmission bitsSerial-to-ParallelConverterInverse DFT…?…?……Add CP?The length of CP is M?Parallel-to-SerialConverterTransmissionPage DT OFDM Receiver?Serial-to-ParallelConverter?Remove CP……??……??DFTDivided by Channel GainParallel-to-SerialConverter……Page Remove Cyclic Prefix?OFDM Symbol: CPDATA…CPDATAFunction of CP:Convert convolution to periodic convolutionAvoid inter-symbol interferenceChannel?Page Project IntroductionIn this project, we shall Design the RF front end of the receiverEvaluate the overall OFDM system analytically and numerically Detected Bit SequenceTransmission Bit SequenceOFDM TransmitterEquivalent DT Wireless ChannelOFDM TransmitterTransmitter Radio Frequency Front EndActual Wireless ChannelReceiver Radio Frequency Front EndDACDT SignalFromOFDM TransmitterDT Sequence to Impulse TrainLTI1TReal PartImaginary PartXX??to Antenna+Page Transmitter RF Front EndTime Domain Analysis?Suppose the input signal to the RF front end is Convert to impulse train: After DAC: c(t) is a rectangular wave Real part: imaginary part: After modulationAfter summation: How about frequency analysis?Page Wireless Channel?In this project, the wireless channel is approximated as a continuous-time LTI systemsThe impulse response is a causal finite-length continuous-time functionYou can assume the channel impulse response is How to determine the length of CP?Page Tips on Receiver Design?In order to demodulate the signal, receiver should Multiple the received signal with carrier: Use an ideal lowpass filterAfter demodulation, the receiv