- 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.