10.1109/TCOMM.2006.876828

In this paper, the multiple access capacity of an Mary pulse position modulation (PPM) impulse radio (IR) system with antenna array is analyzed in dense multipath environments. An antenna array with Rake receivers is used to capture the signal energy from multipaths. Multiple access performance of the system is evaluated in terms of number of supported users for a given bit error rate and bit transmission rate with different number of antenna elements and selected paths. Numerical results show that the multiple access capacity of an M-ary IR system can be improved significantly by increasing the number of antenna elements and/or by adding more paths coherently at the receiver.

Ultra-wideband (UWB) technology is characterized by transmitting extremely short duration of radio impulses. To improve its multiple access capability, UWB technology can be combined with traditional spread-spectrum techniques. In this paper, we present the multiple access performance of direct-sequence (DS) UWB system with diversity reception. Numerical results show that the multiple access performance of a DS-UWB system can be improved significantly by increasing the number of antenna array elements and/or by adding more paths at the receiver

Impulse radio (IR) is based on the ultra-wideband (UWB) time-hopping spread spectrum technique in which subnanosecond pulses are modulated to convey information by precisely shifting the relative time position of the pulses. The influence of temporal and spatial diversities on the performance of ultra-wideband impulse radio systems is analyzed. We investigate how antenna diversity (uniform linear array and rectangular array) can be used to improve the bit error rate performance and to mitigate multiple user interference (MUI) of an IR system in multipath fading channels. Numerical results show that the bit error rate performance and multiple access capability of the IR system can be improved when the number of array elements and selected multipaths are increased.