Catálogo de publicaciones - libros

The increased use of ubiquitous computing devices is resulting in networks that are highly mobile, well connected and growing in processing and storage capabilities. The nature of these ubiquitous systems, however, also increases the risk of building systems that are undependable and potentially insecure. This paper investigates the use of autonomous agents combined with an intrusion tolerance technique for providing secure and dependable storage for ad hoc networks. The proposed approach is based on the fragmentation-redundancy-scattering (FRS) technique that is able to tolerate both accidental and intentional faults by fragmenting confidential information into insignificant fragments, and by scattering these fragments in a redundant fashion across a network. Two algorithms that are able to maintain a constant number of fragments replicas were developed for this study: one based on the game of life, and the other based on roaming ants. Both algorithms were simulated in NetLogo, and simulated further in a cluster of computers for evaluation of their scalability.

Sensor nodes have limited computation and battery power, and are not very reliable. A sensor network needs to be secure against eavesdrop when it is deployed in hostile environments. In order to provide security at low cost, symmetric key based approaches [11] have been proposed. In [9], an elliptic curve cryptography based approach has been implemented to facilitate the public-key cryptography. However, these schemes become ineffective in terms memory usage, communication time and energy required with the rapidly growing network size. We propose an Energy and Communication Efficient Group key management (ECEG) scheme which reduces the usage of memory, communication and energy in sensors. This scheme designed based on the idea that each node is pre-loaded with a key chain and an elliptic curve. In our scheme instead of computing the key by collaborating with other nodes a point of the elliptic curve broadcasted from the base station is used to compute the key. The simulations conducted using TinyOS [15] shows that ECEG scheme significantly improves the communication and energy usage in computing the key over EccM [9].

In this paper we present CCM-MAC, a cooperative CDMA-based multi-channel (MAC) protocol for multi-hop wireless networks. The protocol mitigates the multi-channel hidden and exposed terminal problems through cooperation from overhearing neighbours. By accounting for the multiple access interference obtained through cooperation, it also addresses the near-far problem of CDMA. We provide an analysis of the maximum throughput of CCM-MAC and validate it through simulation in Matlab. A significant improvement in network throughput is achieved over IEEE 802.11 and another multi-channel MAC protocol.

In this paper, we propose an efficient and practical routing scheme for MANETs based on a new routing metric called the free-degree of nodes. In the proposed routing scheme named FDAR (Free-Degree Adaptive Routing), it is intended to deliver data packets circumventing congested routes, so as to realize a short end-to-end delay and a moderate load balancing of the overall network. In addition, it tries to avoid frequent and unnecessary invocation of route discovery process which would significantly degrade the routing performance of the MANET. The effectiveness of the proposed scheme is evaluated by simulation. The result of simulations indicates that it certainly outperforms previous load-balanced routing schemes including DLAR and LBAR, in terms of the packet loss rate and the average end-to-end delay.

The multiple expected sources of traffic skewness in Next- Generation SensorNets (NGSN) will trigger the need for load-balanced point-to-point routing protocols. Driven by this fact, we present in this paper a load-balancing primitive, namely Traffic-Oblivious Load-Balancing (TOLB), to be used on top of any point-to-point routing protocol. TOLB obliviously load balances traffic by pushing the decision-making responsibility to the source of any packet without depending on the energy status of the network sensors or on previously taken decisions for similar packets. We present theoretical bounds on TOLB’s performance for special network types such as mesh networks. Additionally, we ran simulations to evaluate TOLB’s performance on general networks. Our experimental results show the high benefit (in terms of network lifetime and throughput) of applying TOLB on top of routing schemes to deal with various traffic skewness levels in different sensor deployment scenarios.

In this paper, we investigate the performance of multicast protocols for wireless mobile ad hoc networks (MANETs). Recently, there have been several proposals to reduce overhead and enable scalability in respect to the number of multicast members. Explicit multicast protocols, which differ from common approaches proposed for MANET multicast routing, are based on the Xcast scheme and intends to reduce energy consumption. These protocols are best suited for use with Small Multicast Groups operating in dynamic networks of any size. Classical multicast protocols which are tree based or mesh based are more appropriate for large scale multicast group. We evaluate the performance of EM2NET, an Explicit Multicast Protocol for MANET, with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation. The performance differentials are analyzed using varying network load, mobility and multicast group size in order to provide a qualitative assessment of the applicability of the protocols in different scenarios. Results indicate that EM2NET offers better energy conservation and also supports mobility better than existing explicit protocols.

Directed diffusion (DD), uses mechanisms such as data aggregation and in-network processing to suppress the additional data overhead however there is no guarantee that paths from nearby sources join after a few hops. In cases where sensed event is spread geographically, the probability of such combination is reduced. Another problem arises in presence of many source nodes near a single event. In DD for path construction, each source floods a distinct exploratory data (ED) packet through the network, thus a significant amount of network energy is dissipated. The ODCP protocol is proposed to address these two problems: late-aggregation and distinct ED-flooding. In our local on-demand clustering protocol, early aggregation and limited ED-flooding can be achieved by using a virtual sink (VS) near the sources. This node plays the role of sink node and broadcasts local interest messages. Therefore the data packets are sent initially to the VS node and then routed toward destination. Although in simulations we did not consider the improvements gained by early-aggregation, the results show that using this method, connection life-time between source and sink will be increased significantly (up to three times better than directed diffusion).

The primary concerns in ad hoc networks are bandwidth limitation and unpredictable dynamic topology. Therefore, efficient bandwidth utilization is crucial in routing protocols. The On-Demand Multicast Routing Protocol (ODMRP) was designed for multicast routing in ad hoc networks. It is very important to efficiently allocate and consume link bandwidth in this protocol, especially when many groups are working concurrently. In this paper, we propose a new method for estimating bandwidth in multicast protocols and also a new technique for supporting QoS routing in ODMRP by making an acceptable estimation of available and required bandwidth. Simulation results show that using QoS routing for ODMRP improves network performance in presence of mobility, by searching for suitable paths.

In some specific applications, sensors can be deployed in a deterministic way to form regular network. This paper firstly analyzes the relationship between the probability of coverage and that of the node failure in the network with triangular topology. Then the fault tolerance performance in triangular topology network is analyzed by using the -subnet. At last, the paper discusses the connectivity performance in triangular topology network and in grid topology network.

In the paper a performance evaluation model of mobile wireless sensor network is presented. The model is based on renewal theory. The hierarchical structure of the network holds a clusters composed of ordinary sensors. Afterwards, all clusterhead sensors belong to a backbone network which is needed for data transmission to the sink of the sensor network. Some sensors are mobile and can send their data to the clusterhead sensors. In this paper, we address one of the fundamental problems, namely performance modeling of mobile wireless sensor networks. Moreover, our model can also be used for ordinary wireless sensor networks which are static and geometrically constrained. Specific models are suggested and analysed for different communication needs.