New-User Detection in Time Hopping Multi-User Environment for UWB Impulse Radio Systems

This paper addresses the problem of detecting a new user in time-hopping multiple access communication environment targeted for ultra wideband impulse radio (IR) systems. The proposed detector is based on exploiting the orthogonality between the new user and the other active user(s) in frequency domain. This is because the time-domain orthogonality is destroyed due to the long delay spread of a dense multipath channel experienced by IR transmission. This results in the presence of inter-frame, inter-path as well as inter-symbol interferences. To ensure the frequency-domain orthogonality, we propose a TH code design as a means of encoding a unique spectrum that is orthogonal to each user. Simulation results highlight the note-worthy improvement in frequency-domain detection performance that utilizes our proposed design algorithm. This gain is obtained without any significant increase in computational complexity or hardware costs. Unlike the rake detector, the frequency-domain detector does not require the time-of-arrival information of the multipath components.