Iterative ("Turbo") Multiuser Detectors for Impulse Radio Systems

Abstract

In recent years, there has been a growing interest in multiple access communication systems that spread their transmitted energy over very large bandwidths. These systems, which are referred to as ultra wide-band (UWB) systems, have various advantages over narrow-band and conventional wideband systems. The importance of multiuser detection for achieving high data or low bit error rates in these systems has already been established in several studies. This paper presents iterative ("turbo") multiuser detection for impulse radio (IR) UWB systems over multipath channels. While this approach is demonstrated for UWB signals, it can also be used in other systems that use similar types of signaling.When applied to the type of signals used by UWB systems, the complexity of the proposed detector can be quite low. Also, two very low complexity implementations of the iterative multiuser detection scheme are proposed based on Gaussian approximation and soft interference cancellation. The performance of these detectors is assessed using simulations that demonstrate their favorable properties.Index Terms-Ultra wide-band (UWB), impulse radio (IR), iterative multiuser detection, soft interference cancellation.

Interference mitigation and awareness for improved reliability

“…The OFC detector first combines the multipath components in each frame according to the maximal ratio combining (MRC) criterion, which is suboptimal in general, and then combines those combined samples in different frames according to the optimal linear MMSE criterion. Mathematically, the ith information symbol (bit) is estimated aŝ 39) whereθ i N f , . .…”

“…Although the iterative multiuser detectors for CDMA systems can be applied to IR-UWB systems [34][35][36][37][38], iterative algorithms that exploit the special structure of IR-UWB signaling can result in low-complexity receivers [14,39]. Specifically, iterative multiuser detectors can be designed for IR-UWB systems by regarding the IR-UWB signaling structure as a concatenated coding system, where the inner code is the modulation and the outer code is the repetition code.…”

“…Specifically, iterative multiuser detectors can be designed for IR-UWB systems by regarding the IR-UWB signaling structure as a concatenated coding system, where the inner code is the modulation and the outer code is the repetition code. In reference [39], a low-complexity iterative receiver, called the pulse-symbol iterative detector, is proposed for IR-UWB systems over frequency selective channels. In order to describe this detector in more detail, let…”

“…The general structure of the multiuser receiver in reference [39], where p rx (t) denotes the received UWB pulse.…”

Low-complexity iterative MUD algorithm for asynchronous UWB systems

“…Inspired by the iterative MUD for synchronous time hopping (TH) impulse radio systems proposed in [1], we present in this paper a low-complexity iterative MUD algorithm for asynchronous UWB communications. In order to figure out the multiple access interference (MAl) more precisely, a truncated detection window is used instead of the bit-by-bit detection.…”