Hadamard transforms for parallel digital communications. Applications to OFDM - DMT modulations on selective channels

摘要

Multicarrier modulations are often used to combate frequency selective channel . It is the case for digital broadcast with OFDMud(Orthogonal Frequency Division Multiplex), or for Digital Subscriber Line Services on the telephone twisted pair with DMTudmodulation (Discrete MultiTone) . This paper proposes to substitute Fast Fourier Transforms (ANSI and ETSI normalized), by digitaludreal transforms such as the Hadamard Transforms . As they only compute zeros and ones, their implementation is simple.udPerformances of this technique that we call HDM (Hadamard Division Multiplex) are presented for data transmission over theudradio mobile urban channel .udThe channel estimation is performed by interpolating techniques using digital Transforms (Fourier and Hadamard) . For identicaludperformances (in terms of bit error rate and spectral efficiency), the main advantage of the HDM system is a simpler implementation,udeventually ensuring cheap mass production.