Wireless Networks
Wireless communications allow different new applications of computer networks, such as mobile ad hoc networks, wireless mesh networks, and sensor networks. Wireless networks come with the great advantage of user mobility. Where infrastrucure is used, wireless networks provide for lower cost.
Nevertheless, wireless communications are prone to much higher bit error probabilities than wired networks; depending on the application, energy consumption is a critical issue of wireless networks. Security is a very important research topic of wireless networks, given the decentralized architecture of different wireless applications and the very open nature of the wireless medium. In this research theme, different aspects of wireless networks are investigated.
Research Topics
Wireless Mesh Networks
Wireless mesh networks (WMNs) are a cost-effective solution for access networks. WMNs are characterized by the presence of a backbone composed of wireless routers. This backbone is typically stationary and provides backhaul access. Currently, we are investigating a new algorithm for link-state dissemination, which profits from the main WMN characteristics, which are stationary topology and traffic convergence towards the wired infrastructure. The proposed algorithm reduces the network routing overhead while keeping updated metrics for the frequently used links. Thus, we avoid latency in route discovery, and we also save network resources such as bandwidth. The proposed algorithm limits the range of routing updates towards the network gateway, since the common-case application in WMNs is Internet access.
Selected Publications
- Campista, M. E. M., Passos, D. G., Esposito, P. M., Moraes, I. M., de Albuquerque, C. V. N., Saade, D. C. M., Rubinstein, M. G., Costa, L. H. M. K., and Duarte, O. C. M. B. - "Routing Metrics and Protocols for Wireless Mesh Networks", in IEEE Network, ISSN 0890-8044, vol. 22, no. 1, pp. 6-12, January 2008 (GTA-07-19).
- Campista, M. E. M., Costa, L. H. M. K., and Duarte, O. C. M. B. - "WPR: A Proactive Routing Protocol Tailored to Wireless Mesh Networks", to appear in IEEE Globecom 2008 Ad Hoc, Sensor and Mesh Networking Symposium (GC'08 AHSN), New Orleans, LA, USA, December, 2008 (GTA-08-25).
Cooperative Communications
Wireless links are more error prone than wired links. Moreover, wireless links usually present a high quality variation. For instance, in Indoor and urban scenarios, even static nodes may be exposed to harsh fading. The use of spatial diversity has already proved to be efficient in combat fading and increasing the wireless channel capacity. Nevertheless, using this technology on single-antenna nodes is not a simple task. Cooperative communication is an evolving technique, which allows single-antenna nodes to benefit from spatial diversity. In order to make cooperation work on ad hoc networks, nodes must coordinate to share theirs antennas and relay other nodes communications. Many different approaches have been proposed at the Physical layer and dedicated MAC protocols are being developed. Our group focuses on the Network layer perspective and we are currently developing a cooperation-aware routing metric. The proposed metric takes into account the available relays and the statistics of the wireless links to choose routes where the benefits of the cooperation are maximized. It is expected that the proposed metric will enhance the network efficiency.
Selected Publications
- Cunha, D. O., Duarte, O. C. M. B., and Pujolle, G. - "An Enhanced Routing Metric for Fading Wireless Channels", to appear in IEEE Wireless Communications and Networking Conference - IEEE WCNC 2008, pp. 2723-2728, Las Vegas, USA, March/April 2008 (GTA-07-21).
- Cunha, D. O., Duarte, O. C. M. B., and Pujolle, G. - "A Cooperation-Aware Routing Scheme for Fast Varying Fading Wireless Channels", to appear in IEEE Communications Letters, ISSN 1089-7798 (GTA-08-29).
Security in Ad Hoc Networks
Network security is an important problem, mainly in wireless environments because the medium can be easily sniffed or jammed. Ad hoc networks are low-cost wireless networks, because they do not require fixed infrastructure and are based on wireless multihop communications to attain a large range. Despite of being less expensive, ad hoc networks have more vulnerabilities than infrastructured wireless networks because of the collaborative routing. In ad hoc routing, one single malicious node may prejudice all nodes. For this reason, many secure routing protocols were proposed, based mainly on cryptographic operations. Nevertheless, these protocols are not enough to provide security due to its dependency on key distribution and access control mechanisms. We are working to provide solutions to support secure ad hoc routing protocols. We have proposed a group key distribution protocol that works with Secure Optimized Link State Routing protocol (SOLSR) and that simplifies the detection and exclusion of non-authorized nodes in the network. Besides, we have proposed on address distribution and access control protocols controlled in a distributive way, avoiding the need of an infrastructure available all the time to all nodes. We aim to develop a complete solution for access control and secure communications in ad hoc networks.
Selected Publications
- Fernandes, N. C. and Duarte, O. C. M. B. - "Controle de Acesso Auto-Organizável e Robusto Baseado em Nós Delegados para Redes Ad Hoc", to appear in 8th Brazilian Symposium on Information and Computer System Security (SBSEG'08), Gramado, RS, Brazil, September, 2008 (GTA-08-23).
- Fernandes, N. C. and Duarte, O. C. M. B. - "An Efficient Group Key Management for Secure Routing in Ad Hoc Networks", to appear in IEEE Globecom 2008 Computer and Communications Network Security Symposium (GC'08 CCNS), New Orleans, LA, USA, December, 2008 (GTA-08-24).