WIS Research

Research Topics

Wireless Information Assurance

Interaction between Security and Survivability in Wireless Networks: Information assurance techniques employed in wired networks have limited direct applicability in wireless networks because of the unique aspects of wireless networks (e.g., user mobility, wireless communication channel, power conservation, limited computational power in mobile nodes, security at the link layer, etc.). The interaction between the components of information assurance, namely availability and security in a wireless network environment poses new challenges. We are investigating a framework for understanding survivability and security in wireless network and also evaluate the performance issues related to the interaction between survivability and security in hybrid wireless access networks.
Energy efficient Security Protocols for WLANs: Several security protocols designed for wired-line networks have been adopted for use in wireless networks. However, they may not be suitable for wireless networks and devices since scenarios and capabilities applicable to wired-line networks may not be valid in wireless networks. For example, wireless devices often have limited battery power, and performing several message exchanges used in typical wired-line security protocols may rapidly deplete the devices’ battery. Cryptographic primitives consume energy and could degrade the battery performance of wireless networks. In this paper, we classify energy saving mechanisms for security protocols in wireless networks. We apply these energy saving mechanisms to existing security protocols and demonstrate the reduction in energy consumption that is possible with the suggested approaches.

Wireless Network Design

An important issue in the widespread deployment of infrastructure based wireless local area networks (WLANs) is the network design. In this work, we proposed a new WLAN design approach that focuses on assuring sufficient data rate capacity to meet expected user demand in the coverage area, while still satisfying signal coverage and interference level requirements. Noting the low cost of WLAN access points, we formulated a novel mathematical network design model within the framework of constraint satisfaction problems. Our model is termed the capacity based WLAN constraint satisfaction problem (Cap-WLAN CSP). The solution of the Cap-WLAN CSP model yields a network design based on data rate demand by providing the access point locations, the frequency channel allocation, and power levels required for the WLAN to meet expected user demands. Our numerical results illustrate that the capacity based approach is more appropriate for the design of WLAN systems than those of traditional coverage based designs. We are extending the problem to wireless wide area networks.

Indoor Positioning using Wireless LANs

Indoor positioning systems that make use of received signal strength based location fingerprints and existing wireless local area network infrastructure have recently been the focus for supporting locationbased services in indoor and campus areas. A knowledge and understanding of the properties of the location fingerprint can assist in improving design of algorithms and deployment of position location systems. However, most existing research work ignores the radio signal properties.In this area, we are investigating the properties of the received signal strength reported by IEEE 802.11b wireless network interface cards. We are analysing the data to understand the underlying features of location fingerprints, model the indoor positioning system using the data, and determine the metrics that impact accuracy and precision.

Wireless Sensor and Ad Hoc Networks

We have proposed a novel energy saving scheme, termed the Gossip-based sleep protocol (GSP) for wireless ad hoc routing. With GSP, each node randomly goes to sleep for some time with gossip sleep probability p. When the value of p is small enough, the network stays connected. GSP does not require a wireless node to maintain the states of other nodes. It requires few operations and scales to large networks. Two versions of GSP, one for synchronous networks and one for asynchronous networks have been proposed by us. The advantages of the GSP approach has been demonstrated through both simulations and analysis. Our observation is that in a well connected ad hoc network there are usually many paths existing between a source and a destination, so a percentage (1 - p) of the nodes may be in an energy conserving sleep mode without losing network connectivity. We have extended the GSP to a non-uniform deployed network, where the node density is not a network-wide constant. The value of p for every node is determined by its local information without incurring much overhead.

QoS in Wireless Local Area Networks

It is well known that the distributed coordination function (DCF) of the IEEE 802.11 MAC protocol is not suitable for supporting multimedia and QoS-sensitive applications because of its inherent lack of QoS support and fairness. Recently, several distributed QoS mechanisms have been proposed which translate user QoS requirements into typically a single parameter of the DCF protocol. In this work, we have compared the pros and cons of the major distributed QoS mechanisms, and proposed a new mechanism that provides superior performance and supports two different QoS models. The proposed mechanism is based on deficit round robin scheduling and translates the user throughput requirements into the 802.11 MAC interframe space and backoff interval parameters. We have shown via simulations that the proposed mechanism provides low variability of throughput and delay and has the advantage of low complexity.