Energy Detection based Blind Synchronization for Pulse Shape Modulated IR-UWB Systems

International audienceSynchronization is a key performance-limiting factor in any communication system and a challenging task to accomplish. In this paper, an energy detection based non dataaided (NDA) algorithm for orthogonal pulse shape modulated (PSM) impulse radio ultra wideband (IR-UWB) system is proposed. Relying on unique signal structure, simple overlap-add operation followed by energy detection enables synchronization. The algorithm remains functional under practical scenarios i.e. in the presence of inter-frame and inter-symbol interference (IFI & ISI) and with M-ary modulation. Simulation results are provided to demonstrate the performance of proposed algorithm

Waveform-independent frame-timing acquisition for UWB signals

In this paper, the problem of frame-level symbol timing acquisition for UWB signals is addressed. The main goal is the derivation of a frame-level timing estimator which does not require any prior knowledge of neither the transmitted symbols nor the received template waveform. The independence with respect to the received waveform is of special interest in UWB communication systems, where a fast and accurate estimation of the end-to-end channel response is a challenging and computationally demanding task. The proposed estimator is derived under the unconditional maximum likelihood criterion, and because of the low power of UWB signals, the low-SNR assumption is adopted. As a result, an optimal frame-level timing estimator is derived which outperforms existing acquisition methods in low-SNR scenarios.Peer Reviewe

Managing Impulsive Interference in Impulse Radio UWB Networks

Wireless sensor networks are ideally built on low-cost, low-complexity nodes that have a low power consumption to guarantee a long network lifetime. These are all properties that can potentially be achieved with impulse radio ultra-wide band (IR-UWB). In addition, IR-UWB has a fine timing resolution resulting in accurate ranging and localization possible. For all these reasons, IR-UWB is an extremely interesting physical layer technology for wireless sensor networks. In this article, we consider the management of impulsive interference in IR-UWB networks. Impulsive interference is due to uncoordinated concurrent transmissions. It occurs, for instance, when several independent piconets operate in close vicinity and is also present in some MAC layer proposals that allow concurrent transmissions. If not properly addressed, impulsive interference can severely affect the throughput and energy consumption of an IR-UWB network; as such, it already needs to be taken into account in the design phase. First, we show that impulsive interference is a serious concern for IR-UWB networks. Second, we present techniques at the physical layer and at the link layer to cope with and combat such interference efficiently. Finally, we present DCC-MAC as an example of an interference-aware design

A Robust Signal Detection Method for Ultra Wide Band (UWB) Networks with Uncontrolled Interference

We propose a novel detection method for non-coherent synchronization (signal acquisition) in multi-user UWB impulse radio (IR) networks. It is designed to solve the IUI (Inter-User Interference) that occurs in some ad-hoc networks where concurrent transmissions are allowed with heterogeneous power levels. In such scenarios, the conventional detection method, which is based on correlating the received IR signal with a Template Pulse Train (TPT), does not always perform well. The complexity of our proposal is similar to that of the conventional method. We evaluate its performance with the Line Of Sight (LOS) and the Non LOS (NLOS) office indoor channel models proposed by the IEEE P802.15.4a study group and find that the improvement is significant. We also investigate the particular case where the concurrent transmissions have the same time-hopping code, and we show that it does not result in collision, such scenarios appear in ad-hoc networks that employ common code for control or broadcast purposes

Cramer-Rao bounds in the estimation of time of arrival in fading channels

This paper computes the Cramer-Rao bounds for the time of arrival estimation in a multipath Rice and Rayleigh fading scenario, conditioned to the previous estimation of a set of propagation channels, since these channel estimates (correlation between received signal and the pilot sequence) are sufficient statistics in the estimation of delays. Furthermore, channel estimation is a constitutive block in receivers, so we can take advantage of this information to improve timing estimation by using time and space diversity. The received signal is modeled as coming from a scattering environment that disperses the signal both in space and time. Spatial scattering is modeled with a Gaussian distribution and temporal dispersion as an exponential random variable. The impact of the sampling rate, the roll-off factor, the spatial and temporal correlation among channel estimates, the number of channel estimates, and the use of multiple sensors in the antenna at the receiver is studied and related to the mobile subscriber positioning issue. To our knowledge, this model is the only one of its kind as a result of the relationship between the space-time diversity and the accuracy of the timing estimation.Peer ReviewedPostprint (published version