Security is of critical importance for many potential applications of wireless sensor networks. In order to maintain
secure communication throughout the network, it is of vital importance to maintain encryption key freshness by
regularly distributing new keys to all nodes. Distribution of group keys used to encrypt broadcast communication
is expensive, as it is generally achieved via flooding, which taxes the limited battery life available to each node.
We propose LKDT, a lightweight encryption key distribution tree building mechanism with an optional Multi-
Coverage Reduction (MCR) stage to provide a framework by which to distribute keys while reducing power
consumption and broadcast coverage overlap. Additionally, LKDT can configure itself quickly, allowing the base
station to begin updating keys shortly after deployment.
Localization is an important challenge in wireless sensor networks (WSN). Localization usually refers to the process of dynamically determining the position(s) of one or more node(s) in a larger network. The challenge lies in efficiently providing "acceptable" accuracy while conforming to the many constraints of WSNs. We propose a Cluster-based Partial Localization (CPL) to provide efficient localization, where the focus is on providing scalable partial localization suitable to a large and high-density network. CPL utilizes both a computationallyintensive localization technique (non-metric MDS) and a less intensive triangulation to achieve balance between complexity and performance. Clustering is utilized to select a subset of nodes to perform the non-metric MDS localization and then extend to the rest of the network. We show, with simulation results, that CPL will provide a considerable reduction in both computation and communication, while still yielding an acceptable accuracy.
Disseminating data among sensors is a fundamental operation in
energy-constrained wireless sensor networks. We present a gossip-based adaptive protocol for data dissemination to improve energy efficiency of this operation. To overcome the data implosion problems associated with dissemination operation, our protocol uses meta-data to name the data using high-level data descriptors and negotiation to eliminate redundant transmissions of duplicate data in the network. Further, we adapt the gossiping with data aggregation possibilities in sensor networks. We simulated our data dissemination protocol, and compared it to the SPIN protocol. We find that our protocol improves on the energy consumption by about 20% over others, while improving significantly over the data dissemination rate of gossiping.
Bluetooth is a promising wireless technology that enables devices to form short-range multihop wireless ad-hoc networks, or personal area networks. However, the Bluetooth scatternet formation is one of the challenges that need to be resolved since the performance of a Bluetooth network depends largely on the scatternet topology used. We first present a height-balanced binary tree, termed ACB-tree for almost-complete-binary tree, that allows two such trees to be combined to create a larger ACB-tree retaining the height-balance requirements. And, then propose a distributed scatternet formation algorithm to create ACB-trees: the generated scatternet is shown to minimize the number of piconets and provide a logarithmic-diameter in the multihop interconnection network. We also present simulations, conducted using Blueware simulator, to provide experimental results to study and compare the performance of the resulting scatternets.
Multiple channel access interference is a major cause of throughput degradation in wireless networks because of the shared channel. IEEE 802.11 MAC protocol is a standard for medium access in wireless LANs, but suffers from contention and co-channel interference and thus performs poorly. We propose to use receiver-initiated MAC protocol, instead of the sender-oriented 802.11, to address these issues. The proposed protocol is based on carrier sensing and resolves collisions among senders based on a deterministic tree splitting algorithm to minimize the retransmissions of data packets due to hidden terminals. Further, subchannel assignment is used to exploit the parallel transmissions that are possible in multi-channel networks; thus, reducing the channel contention and improving the throughput. We also present simulation results, using ns-2 simulator, to evaluate our approach and compare it with 802.11. The simulation results indicate that collision resolution with multiple subchannel access is more effective in throughput and provides better packet delays than 802.11 MAC. We also observe that the maximum throughput is achieved when the channel is divided into three or four subchannels irrespective of the size and shape of the network and traffic load.