Alessandra Giovanardi

Distributed power control for energy efficient routing in ad hoc networks

In this paper, distributed power control is proposed as a means to improve the energy efficiency of routing algorithms in ad hoc networks. Each node in the network estimates the power necessary to reach its own neighbors, and this power estimate is used both for tuning the transmit power (thereby reducing interference and energy consumption) and as the link cost for minimum energy routing. With reference to classic routing algorithms, such as Dijkstra and Link State, as well as more recently proposed ad hoc routing schemes, such as AODV, we demonstrate by extensive simulations that in many cases of interest our scheme provides substantial transmit energy savings while introducing limited degradation in terms of throughput and delay.

Statistical modeling and design of discrete-time chaotic processes: advanced finite-dimensional tools and applications

With the aim of explaining the formal development behind the chaos-based modeling of network traffic and other similar phenomena, we generalize the tools presented in the paper of Setti et al. (see ibid., vol.90, p.662-90, May 2002) to the case of piecewise-affine Markov maps with a possibly infinite, but countable number of Markov intervals. Since, in doing so, we keep the dimensionality of the space of the observables finite, we still obtain a finite tensor-based framework. Nevertheless, the increased complexity of the model forces the use of tensors of functions whose handling is greatly simplified by extensive z transformation. With this, a systematic procedure is devised to write analytical expressions for the tensors that take into account the joint probability assignments needed to compute any-order expectations. As an example of use, this machinery is finally applied to the study of self-similarity of quantized processes both in the analysis of higher order phenomena as well as in the analysis and design of second-order self-similar sources suitable for artificial network traffic generation.

Transparent mobile IP: an approach and implementation

The problem of Internet terminal mobility without reconfigurations and host software modifications (transparent) is presented. A solution based on the introduction of network agents, with proxy address resolution protocol and IP tunneling features, has been introduced, discussed and implemented. Some strategies for routing optimization, in order to avoid triangular paths, are investigated and tested. Implementation results demonstrate the value of this approach in terms of both functionality and performance and are of interest in indicating a simple way of supporting the increasing request for mobility.

Energy efficient unicast routing protocols over 802.11b

The paper compares the performance of the AODV, DSR, OESR classic routing protocols for ad hoc networks, when an IEEE 802.11b MAC protocol is used. The investigation, performed by means of simulations, evaluates the energy efficiency of these protocols and the effect of the 802.11b rate adaptation capability on the performance. The paper evaluates the effectiveness of a distributed power control (DPC) scheme (P. Bergamo et al., 2002) applied to the classic AODV, DSR and OESR routing algorithms. The DPC scheme, acting both at MAC and network layers, has the aim to reduce the overall power consumption of the network. In particular, DPC evaluates, hop-by-hop, the suitable transmit power level and then selects, end-to-end, for any destination, the path which minimizes the total transmit power required. A final comparison between classic and DPC routing protocols is also reported

Frequency domain chaotic watermarking

A watermarking procedure to be applied in the frequency domain to digital images has been proposed and investigated, with purpose of copyright protection. The selected digital signature is a chaotic sequence embedded by considering a shaping function to weight in different manner each sequence value, as a function of the image properties in the frequency domain. The shaping function proposed permits one to enhance the robustness of the watermarking to attacks like the JPEG one. Numerical results show the validity of the proposed approach and of the use of particular classes of chaotic maps.

An agent-based approach for multicast applications in mobile wireless networks

In this paper we propose a mobility support for multicast systems in a radio environment. This mobility support permits to a multicast mobile host (MMH) to maintain the connection to a multicast group, when it is moving from a network to another, with low connection loss occurrence or group joint delay. With this aim, an agent-based architecture has been designed and implemented. The mobility support acts in a transparent way, without any changes in MMH software, in network protocols and in multicast system applications. This architecture makes predictions about MMH movement and performs a reservation of resource in advance, by means of a re-creation in advance of the multicast tree. The effectiveness of our proposal has been tested with simulation test fields.

Energy Efficiency in OLSR Protocol

In this paper we study in details the optimized link state routing (OLSR) protocol for ad hoc networks. In particular, we investigate its performance by focusing the attention on its energy efficiency. To have some terms of comparison the performance are compared with those of other routing schemes. Furthermore, to improve the energy efficiency by increasing the network life time, we propose and discuss a power controlled version of OLSR. OLSR power controlled provides the optimal paths in terms of minimum power needed to reach the destination, and not in terms of number of hops as in the classic version. By means of extensive simulations, we show that, in many system conditions, OLSR power controlled is able to achieve good energy savings

Energy efficient forwarding strategies for wireless sensor networks in presence of fading and power control

In this paper we propose energy efficient forwarding techniques in a fading environment which exploit channel knowledge by means of nodes cooperation. Unlike forwarding strategies based on geographic information only, channel knowledge allows to take advantage from diversity by means of selection of the best node to forward the packet, and also to achieve higher energy savings thanks to power control. We also consider the case of multi-route diversity where redundancy packets are sent over different paths. We propose several adaptive strategies which explicitly address the energy issues and we compare them in terms of total consumed energy, mean packet error probability and delay. As a reference case we consider a forwarding strategy based on pure geographic routing (without channel knowledge). The results show that a considerable improvement can be obtained with respect to the pure geographic forwarding. Our algorithms are also in the direction of a cross layer view, since routing decisions are taken adaptively through physical layer information

TCP/IP header compression: proposal and performance investigation on a WCDMA air interface

Two TCP/IP header compression (HC) schemes for wireless networks are proposed and investigated on a WCDMA air interface. These novel schemes are compared with the classical ones by means of a TCP/IP New Reno simulator taking as input WCDMA channel traces. These channel traces are derived by using a simulator built according to the UMTS standard requirements. The RLC (radio link control) level operates in transparent mode, while overhead is added to simulate the presence of a MAC level. Some new performance metrics are introduced to evaluate the performance of HC schemes.

Optimization routing and security features for transparent mobile IP

By considering the problem of transparently linked mobile hosts (MH), i.e., without reconfigurations and host software modifications, this paper gives a possible solution and the relative details on the implementation. Even if the communications between MH to fixed hosts (FH) have just been investigated, the main topic of this work concerns those of MH versus MH (MH-to-MH). The transparent implementation is based on the introduction of network agents with proxy, tunneling and signaling functions that have been changing and improving in order to optimize MH-to-MH links by means of suitable notification procedures. In order to avoid intruders and unauthorized users, or those who should acquire privileges or perform dangerous procedures, security features based on an authentication strategy and a secure hash algorithm have been implemented. The system has been designed, realized and tested in an actual environment, by verifying that the average performance of MH-to-MH optimized links are closer to those of FH-to-FH.