Manki Min

Wireless Sensor Networks with Energy Efficient Organization

A critical aspect of applications with wireless sensor networks is network lifetime. Battery-powered sensors are usable as long as they can communicate captured data to a processing node. Sensing and communications consume energy, therefore judicious power management and scheduling can effectively extend the operational time. One important class of wireless sensor applications of deployment of large number of sensors in an area for environmental monitoring. The data collected by the sensors is sent to a central node for processing. In this paper we propose an efficient method to achieve energy savings by organizing the sensor nodes into a maximum number of disjoint dominating sets (DDS) which are activated successively. Only the sensors from the active set are responsible for monitoring the target area and for disseminating the collected data. All other nodes are into a sleep mode, characterized by a low energy consumption. We define the maximum disjoint dominating sets problem and we design a heuristic that computes the sets. Theoretical analysis and performance evaluation results are presented to verify our approach.

Energy-efficient broadcast and multicast routing in ad hoc wireless networks

This paper considers the problem of broadcasting in large ad hoc wireless networks. We focus on the energy-efficient broadcast routing in stationary networks and consider the case where wireless nodes can dynamically control their transmission power for each broadcast session. The minimum spanning tree (MST) has the property that the longest edge in the tree is the shortest among all the spanning trees, We introduce a new algorithm called minimum longest edge (MLE) that constructs a broadcast tree using MST. This algorithm provides a scheme to balance the energy consumption among all nodes. The simulation results show that MLE improves the energy balance and network lifetime for a wide range of networks, and the improvement is more significant when the network size increases.

Resource Management for Ad-Hoc Wireless Networks with Cluster Organization

Boosted by technology advancements, government and commercial interest, ad-hoc wireless networks are emerging as a serious platform for distributed mission-critical applications. Guaranteeing QoS in this environment is a hard problem because several applications may share the same resources in the network, and mobile ad-hoc wireless networks (MANETs) typically exhibit high variability in network topology and communication quality. In this paper we introduce DYNAMIQUE, a resource management infrastructure for MANETs. We present a resource model for multi-application admission control that optimizes the application admission utility, defined as a combination of the QoS satisfaction ratio. A method based on external adaptation (shrinking QoS for existing applications and later QoS expansion) is introduced as a way to reduce computation complexity by reducing the search space. We designed an application admission protocol that uses a greedy heuristic to improve application utility. For this, the admission control considers network topology information from the routing layer. Specifically, the admission protocol takes benefit from a cluster network organization, as defined by ad-hoc routing protocols such as CBRP and LANMAR. Information on cluster membership and cluster head elections allows the admission protocol to minimize control signaling and to improve application quality by localizing task mapping.

A reliable virtual backbone scheme in mobile ad-hoc networks

In wireless ad-hoc networks, hosts communicate with each other without help of any physical infrastructure. Inevitably, the communication tends to be inefficient in terms of computational and network resources. Study on virtual infrastructures or backbones in wireless ad-hoc networks gets more attention in the hope of reducing the communication overhead. But the backbone structure is very vulnerable due to various factors like node mobility, unstable links, and so on. So a new scheme which is reliable and efficient both to construct and maintain the backbone structure is needed. We present our noble virtual backbone scheme which is reliable and efficient by considering stability and coverage of nodes.

Optimal solutions to minimum total energy broadcasting problem in wireless ad hoc networks

In this paper, we present three schemes to solve minimum total energy broadcasting problem in wireless ad hoc networks based on an efficient IP (integer programming) subproblem technique. Due to its NP-hardness, many heuristics have been studied. However, the heuristics in the literature suffer from coarse performance ratio. It is important to have knowledge of the optimal solution structure in order to develop more efficient heuristics and algorithms. We present one IP formulation and two iterative algorithms which make use of relaxed IPs to solve subproblems. The computational results show that our approaches outperform other techniques in the literature.

On the construction of stable virtual backbones in mobile ad-hoc networks

In mobile ad-hoc networks, hosts communicate with each other without the help of any physical infrastructure. Inevitably, the communication tends to be less efficient in terms of computational and communicational overhead. Recent studies have shown that virtual backbone can help reduce the communication overhead. However, the backbone structure is very vulnerable due to several reasons, e.g., node mobility and unstable links, etc. In this paper, we introduce a localized virtual backbone construction scheme, connected maximal independent set with multiple initiators (MCMIS), which takes node stability into consideration and can construct the backbone quickly. We design MCMIS aiming at three goals: small backbone size, fast construction, stable backbone. Through extensive simulations, we find that our scheme could obtain a better performance on stability and backbone size than other localized schemes.

Total energy optimal multicasting in wireless ad hoc networks

In this paper, we present our novel algorithm, SOR (Shrinking Overlapped Range), for the minimum energy multicasting in wireless ad hoc networks. The heuristics in the literature have not considered changing the intermediate tree structure and this may result in worse performance even after local improvements at the end. In SOR, we extensively change the intermediate tree structure to maintain tighter structure in terms of energy consumption. We do so by shrinking the overlapped transmission range following the idea of WMA (wireless multicast advantage) property and by allowing the selection of internal transmissions which further changes the tree structure. Both theoretical analysis and experimental results show SOR outperforms other heuristics in the literature.

OMEGa: an optimistic most energy gain method for minimum energy multicasting in wireless ad hoc networks

Abstract In wireless ad hoc networks where every device runs on its own battery, the energy consumption is critical to lengthen the network lifetime. The communication among devices in the network can be categorized as unicasting and multicasting (including broadcasting). For the case of unicasting, computing the energy optimal path between the two communicating nodes is polynomially solvable by computing the shortest path. But for the case of multicasting, shortest path or minimum spanning tree does not guarantee an energy optimal communication. In this paper, we present our novel approach, Optimistic Most Energy Gain (OMEGa) method, for the minimum energy multicasting in wireless ad hoc networks. OMEGa aims at maximum utilization of Wireless Multicast Advantage (WMA), which essentially means covering more nodes by using larger energy. Both theoretical and experimental analysis shows OMEGa method performs very well.

Lightweight Forwarding Protocols in Energy Harvesting Wireless Sensor Networks

Due to the unavoidable battery replacement or replenishment, diverse energy harvesting techniques have been integrated with Wireless Sensor Networks (WSNs) to overcome limited battery power and extend the network lifetime. However, variable transmission power levels based on non-uniform energy harvesting rates can incur asymmetric links. In this paper, we propose light-weight forwarding protocols to reliably deliver sensory data to a sink over time-varying asymmetric links in energy harvesting WSNs. A Weighted Confirmation (WCFM) scheme is proposed to differentiate multiple paths between a data source and a sink by assigning multiplicative weights on the paths. A Lazy Confirmation (LCFM) scheme is also proposed to assure a reverse path by waiting for extended communication range. In addition, an Asymmetric Link Aware Back off mechanism is proposed to avoid possible packet contentions and collisions. We evaluate the proposed techniques through extensive simulation experiments and their results indicate that the proposed forwarding protocols can be a viable approach in energy harvesting WSNs.

Improved PSOR algorithm for minimum power multicast tree problem in wireless ad hoc networks

In this paper, we introduce the application of partitioning-based SOR (PSOR) algorithm to the minimum energy multicast tree problem in wireless ad hoc networks. PSOR for broadcast was proposed in our previous work and it can be applied to the multicast tree problem with small modification. PSOR for multicast maintains the same theoretical bound for the approximation ratio and computational running time as PSOR for broadcast. The computational results show improvement in the solution quality (in terms of the sum of the transmission powers). PSOR outperforms the other algorithms and it shows better results compared to ISOR (iterated version of SOR). In this paper, we used the results of the corrected version of SOR for the comparisons. In addition, we present an improved version of PSOR based on simplified partition recovery method. The simulation results show significant reduction of computation time by the improved version.