说明：  This project aim was to build wireless software modem for data communication between two computers using an acoustic interface in the voice frequency range (20Hz– 20,000Hz). The transmitting antenna is a speaker (frequency response of: 90Hz – 20,000Hz) and the receiving antenna is a microphone (frequency response of: 100Hz – 16,000Hz). The test files used as information files were text files. This goal was attained both in an incoherent scheme and in a coherent scheme. Build under Matlab code, our modem uses OFDM (orthogonal frequency division multiplexing) modulation, synchronization by LMS sequence, channel estimation (no equalizer) via pilot tones. The symbols are either PSK or ASK for a constellation size of 2 or 4. To optimize the probability of error, these symbols were mapped using Gray mapping. Report
(This project aim was to build wireless software modem for data communicationbetween two computers using an acoustic interface in the voice frequency range (20Hz-20000Hz). The transmitting antenna is a speaker (frequency response of: 90Hz-20000Hz) and the receiving antenna is a microphone (frequency response of: 100Hz-16000Hz). The test files used as information files were text files.This goal was attained both in an incoherent scheme and in a coherent scheme.Build under Matlab code, our modem uses OFDM ( orthogonal frequency divisionmultiplexing) modulation, synchronization by LMS sequence, channel estimation (noequalizer) via pilot tones. The symbols are either PSK or ASK for a constellation size of2 or 4. To optimize the probability of error, these symbols were mapped using Graymapping.Report)