Multivalued transmission system for UWB-CDMA using modified Hermite pulse shape

Abstract

Recently, a lot of attention has been paid to ultra wideband (UWB) wireless communications systems due to its potential to reach data rate in wireless communications. A UWB signal is defined as that whose bandwidth either surpasses 25% of its spectrum's center frequency or exceeds 1.5 GHz. The UWB communication systems is often referred to as impulse radio since such ultra wideband signal is composed of sub-nanosecond pulses. In addition to possibly enabling the implementation of high-speed wireless access with over 1 Gbit/s data-rules, UWB systems also have the potential to simplify the RF circuitry of the transceivers and lower the transmit power. Previous UWB-IR system proposals have used trains of Gaussian pulses at transmission, resulting, at the receiver. in waveforms known as the monocycle. In those schemes, a number of pulses are needed to transmit 1 bit of information. In this work, a system that transmits several bits per pulse, aimed at enhancing data rate, is studied. The pulse shape used on the UWB system is also studied. UWB pulses based on modified Hermite polynomials (MHP) have been proposed before. These pulses are orthogonal at the transmitter, but not at the receiver due to the differentiation effect of both transmit and receive antenna.