Daniele Domenicali

Performance Analysis for a Body Area Network composed of IEEE 802.15.4a devices

Body area networks (BANs) are wearable wireless sensor networks with a high potential for medical and sports applications. BANs appear to be a particularly appealing solution to provide information about the health status of a patient in medical environments such as hospitals or medical centres.This work analyzes the behaviour of a BAN composed of IEEE 802.15.4a ultra wideband (UWB) sensors. A body area network architecture is proposed and investigated by simulation. Performance evaluation takes into account bit error rate as a function of the number of nodes forming the BAN and of the asynchronism level between them.

UWB body area network coexistence by interference mitigation

This work analyzes the performance of a BAN composed of IEEE 802.15.4a Ultra Wide Band (UWB) sensors in terms of Bit Error Rate (BER), BAN throughput and network lifetime. The BAN performance is evaluated in presence of an external Low Data Rate (LDR) interfering network, that we suppose represented by a second BAN operating in the same hospital room. Coexistence between the two wireless networks is discussed and the reference BAN performance is improved by the adoption of an optimized time hopping code assignment strategy. A possible strategy to extend the lifetime of the network is also introduced.

Revisiting TH-IR-UWB performance limits dependency on essential system parameters using the Generalized Gaussian Approximation

The huge potential of Ultra Wide Band Impulse Radio (UWB IR) with Multiple Access was initially evaluated using the Standard Gaussian Approximation (SGA) which assumed Multi-User Interference to be representable as classical Gaussian noise. Thus, under the reference scenario of free space propagation and perfect power control, closed form expressions allowed to express performance in function of the essential system parameters (number of users, impulse waveform, and number of slots per frame). However the derivations of the closed form expressions were based on the Standard Gaussian Approximation which has been proven later to be not valid. We propose here to revisit performance using the more accurate Generalized Gaussian Approximation (GGA).

Clustered hybrid energy-aware cooperative spectrum sensing (CHESS)

This work proposes a novel algorithm for energyefficient and reliable spectrum sensing in a cognitive network. The algorithm relies on cooperation between secondary devices, that organize themselves in clusters defined according to both sensing reliability and energy efficiency. The proposed algorithm is compared by means of computer simulations with a simpler, non cluster-based cooperative sensing scheme. Simulation results highlight that the adoption of an energy-efficient, sensing-aware clustering algorithm in the sensing procedure can significantly improve both sensing reliability and network lifetime in secondary cognitive networks.

The non validity of the gaussian approximation for multi-user interference in ultra wide band impulse radio: from an inconvenience to an advantage - transactions papers

The huge potential of ultra wide band impulse radio (UWB IR) with multiple access was initially evaluated using the standard Gaussian approximation which assumed that multi user interference could be approximated as classical Gaussian noise. Later the standard Gaussian approximation has been proved to be invalid in several cases. Thus the performance of the classical UWB IR correlation receiver dramatically reduces. We show in this paper how the non Gaussianity of the multi user interference can be exploited, turning the non Gaussianity into an advantage, increasing the performance with respect to the Gaussian interference case which was supposed to be too optimistic until now.

Fluid coding and coexistence in ultra wide band networks

Time Hopping Ultra Wide Band (TH–UWB) commonly encodes the data symbols by shifting the position of the transmitted pulses by a quantity that is quantized over the inter-pulse interval range. In this paper, we relax the hypothesis of a discrete value for the time shift introduced by the TH code, by considering the possibility of generating real-valued codes that introduce time hopping in a “fluid” way. The effect on the power spectral density of generated signals is analyzed, and application of fluid coding to multiple access and to network coexistence is investigated by simulation.

Cognitive UWB: interference mitigation by spectral control

Introducing cognitive principles in the design of a wireless network appears as an attractive option when considering the emerging scenario of coexisting networks. In this paper we introduce cognitive features in a network of IEEE 802.15.4a devices, and show that significant improvements in terms of network lifetime can be achieved by allowing the devices to adapt their behavior to the unpredictable changes of the operating environment

Time-varying interference spectral analysis for Cognitive UWB networks

The potential interference from and to nearby wireless networks makes coexistence a crucial task in the design of ultra wide band (UWB) systems. UWB radio technology may surely benefit from the use of cognitive radio (CR) techniques, implementing collaborative coexistence schemes. In this work, we consider a network formed by self-organizing nodes that operate according to the UWB principle. A conscious node (CNode) acts as the coordinator of the network and implements cognitive rules. Spectrum sensing is necessary for the CNode to be aware of the RF context and of network state. We provide an analysis method for the internal UWB interference experienced at the CNode receiver, by making use of the short-term Fourier transform based on windowing. We show that by adopting particular windows, such as the blackmail window, specific characteristics of the sensed interference spectrum may be highlighted. This work provides a first step towards reliable models for network spectral evolution that may provide the basis for advanced predictive and cognitive mechanisms

Performance and energy efficiency of position-based routing in IEEE 802.15.4a low data rate Wireless Personal Data Networks

The IEEE 802.15.4a standard provides a framework for low data rate communications systems, typically sensor networks, with ranging and positioning capabilities. This work focuses on the analysis of the impact of position information on routing performance in a network of IEEE 802.15.4a-compliant devices. The well known Ad hoc On demand Distance Vector (AODV) routing protocol is compared with the position-based Greedy Perimeter Stateless Routing (GPSR) protocol, taking advantage of the position information provided by a distributed positioning protocol. The comparison is carried out in terms of throughput and consumed energy per bit, and by taking into account all transmitted and received packets, including the additional ones generated by the distributed positioning protocol. Simulation results show that the introduction of position information can lead to significant improvements in both throughput and energy efficiency. Results also show that the energy efficiency of the position based routing protocol is affected by the accuracy of the position information provided by the positioning protocol, in turn depending on the network density.

Ultra Wide Band radio in Distributed Wireless Networks

The material of this book chapter covers the topics presented within the corresponding IEEE ISCAS 2006 tutorial, and in particular it focuses on the following items: the UWB radio signal and its spectral characteristics, power issues and current standardization trends, multi user interference in impulse radio UWB networks, ranging and positioning with UWB, medium access control for UWB networks, location-aware UWB routing algorithms and metrics, and finally introducing cognitive principles in UWB networks