Localization algorithm continues to be an important and challenging topic in today's wireless sensor networks (WSNs). In this paper, a novel range-free localization algorithm using expected hop progress (LAEP) to predict the location of any sensor in a WSN is proposed. This algorithm is based on an accurate analysis of hop progress in a WSN with randomly deployed sensors and arbitrary node density. By deriving the expected hop progress from a network model for WSNs in terms of network parameters, the distance between any pair of sensors can be accurately computed. Since the distance estimation is a key issue in localization systems for WSNs, the proposed range-free LAEP achieves better performance and less communication overhead as compared to some existent schemes like DV-Hop and RAW. In addition, we study the effect of anchor placement on the algorithm performance by deriving the corresponding mean position error range. Extensive simulations are performed and the results are observed to be in good agreement with the theoretical analysis.

Intrusion detection in Wireless Sensor Network (WSN) is of practical interest in many applications such as detecting an intruder in a battlefield. The intrusion detection is defined as a mechanism for a WSN to detect the existence of inappropriate, incorrect, or anomalous moving attackers. For this purpose, it is a fundamental issue to characterize the WSN parameters such as node density and sensing range in terms of a desirable detection probability. In this paper, we consider this issue according to two WSN models: homogeneous and heterogeneous WSN. Furthermore, we derive the detection probability by considering two sensing models: single-singing detection and multiple-sensing detection. In addition, we discuss the network connectivity and broadcast reachability, which are necessary conditions to ensure the corresponding detection probability in a WSN. Our simulation results validate the analytical values for both homogeneous and heterogeneous WSNs.

The problems of energy efficient sensor network configuration and local fusion of sensed data have been addressed separately in the previous works. In this paper, we propose to analyze the sensing accuracy with the consideration of the node distribution and fusion overhead in terms of the energy consumption. By extending existing sensing model in the literature, we quantify how the sensing ranges and node densities of sensor nodes impact the sensing accuracy, and how it affects the fusion overhead and the sensing lifetime of the network. We identify the tradeoff between sensing accuracy and energy consumption in an analytical framework. It can be used to choose optimal parameters of sensor networks to meet the specified sensing or lifetime requirements.

Assuming that all mobile nodes (MNs) have the same transmission range, the actual hop count between any two MNs is proportional to the distance between them. Based on the found relation between distance and hop count, the required hop count between two MNs can be accurately estimated, given the distance between them. Using the distribution of distance between MNs, this paper also suggests the optimal transmission range of MNs, which can guarantee delay constraints of a requested ratio of connections in an entire network.

While most existing research efforts in the area of wireless sensor networks have focused on networks with identical nodes, deploying sensors with different capabilities has become a feasible choice. In this paper, we focus on sensor networks with two types of nodes that differ in their capabilities, and discuss the effects of heterogeneity of sensing and transmission ranges on the network coverage and broadcast reachability. Our work characterizes how the introduction of a few sensor nodes with better capabilities can reduce the number of total required sensors without sacrificing the coverage and the broadcast reachability. Analytical results are validated via simulations. This work can serve as a guideline for designing large-scale sensor networks cost-effectively. It can also be extended to more complicated heterogeneous wireless sensor networks with more than two types of sensors.

Wireless sensor networks present a feasible and economic solution to some of the most challenging problems such as intrusion detection. In this paper, we establish relationship between node density, sensing range, and the possible intrusion distance before the intruder is detected by any of the sensors. We also extend our model to the multi-sensor joint detection case where an event can only be detected by k (k > 1) sensors simultaneously. Furthermore, we consider the effect of node heterogeneity on the intrusion detection in wireless sensor network, where two types of sensors with different sensing ranges are deployed. All the analytical results are validated via simulations. Our analysis can provide very useful insights in choosing network design parameters of sensor networks so that specified performance requirements can be met, thereby enhancing the acceptance of sensor networks.

In this paper, we propose a novel localization algorithm using expected hop progress (LAEP) to predict the positions of sensor nodes in WSNs. Our algorithm is based on a hop progress analytical model for a given network topology. By deriving relationship between node connectivity and expected-hop progress from the model, the distance between any two nodes can be accurately computed. As the distance estimation is a key issue in positioning system of WSNs, our expected-hop progress based localization algorithm also achieves reasonable performance in anchor-based WSNs with very few anchors. In addition, we considered the impact of deterministic anchor placement on the algorithm performance when the sensors are random deployed. Both grid and triangular placement of anchor nodes have been examined in this paper. Simulation results are seen to be in good agreement with the theoretical analysis and substantiate the validity of our proposed scheme LAEP

This paper evaluates the energy efficiency of the IEEE 802.11 distributed coordinated function (DCF) over bursty error channel. Most existing works in the literature assume ideal channel or a simple uniform error model. These existing analysis can hardly capture the impact of fading on the energy efficiency accurately. In this paper, a Markov channel model is adopted, and the impact of bursty channel errors is characterized to obtain the energy efficiency of DCF. In our analysis, many factors that affect the energy efficiency of 802.11 DCF have been considered. Simulations in ns-2 are also performed to validate the analysis

The paper introduces an analytical model to investigate the energy efficiency of the IEEE 802.11 distributed coordinated function (DCF). Many factors, such as the number of contending nodes, packet size, contention window, packet transmission collision probability and channel condition, that affect the energy efficiency of 802.11 DCF have been considered. We determine the packet transmission probability by a method simpler than the existing Markov chain model. The paper identifies the tradeoff in choosing packet size to optimize the energy efficiency of DCF in error-prone environments. The effects of contention window and packet size on the energy efficiency are obtained for both DCF basic mode and DCF with four-way handshaking. It is shown that under error-prone environments, optimal packet size can improve more on the energy efficiency than optimal contention window. Combining both optimal contention window and optimal packet size can achieve the maximum optimization. To validate our analytical results, we have done extensive simulations, and they seem to match very well with the presented analytical results.

Due to the high node density and stringent constraints on the energy consumption in wireless sensor networks, designing an energy efficient flooding scheme with high reachability is critical for the operation and the lifetime of sensor networks. Many existing flooding approaches address the needs of general ad hoc networks. In contrast, this paper presents a cross-layer approach tailored specifically to the needs of sensor networks. Without assuming location awareness, a novel MAC layer access-deferring scheme, based on the received signal power, is proposed to reduce the collision possibility and broadcast redundancy. Local neighborhood information is piggybacked onto the broadcast packet, and exploited to enhance the reachability. Simulation results show that compared with probabilistic flooding, this scheme has good performance in terms of reachability, average delay and energy efficiency. Moreover, we examine how the range estimation error and neighborhood information inaccuracy introduced by the fading environment affects the performance of our flooding scheme.

Abstract In this paper, we evaluate the impact of transmission error rate on the contention and the system throughput in IEEE 802.11 DCF. We identify the trade‐off between the desire to reduce the ratio of overhead in the data packet by adopting larger packet size and the need to reduce the packet error rate by using smaller packet length. Meanwhile, we provide a novel approach to model the different channel conditions incurred by different nodes. This work has applications in performance optimization by establishing trade‐offs between transmission error rate and transmission power, modulation, coding scheme, packet size. Our results substantiate the intuition that in a contention‐based system like 802.11 DCF, the channel variation of any single node in the system not only impacts the throughput of itself, but also affects the throughput of other nodes and the system throughput. Our work shows that to achieve maximum optimization of the throughput, the channel conditions of all the nodes in the system have to be taken into account. Otherwise the optimization is suboptimal. Copyright © 2005 John Wiley & Sons, Ltd.

Energy efficiency has been a bottleneck in the wireless local area network (LAN) based communication of portable wireless devices. This paper introduces an analytical model to investigate the energy efficiency of 802.11 distributed coordinated function (DCF) under both ideal channel and error prone environment. The two major factors contributing to the extra energy consumption in 802.11 DCF: contention and transmission errors, are analyzed thoroughly. Based on the analysis, a scheme of choosing optimal minimum contention window size to optimize the energy consumption under both ideal and error prone environment is proposed. Our extensive simulation results are observed to match very well with the analytical results, which indicate that the analytical model is accurate.

With the popularity of the IEEE 802.11 based wireless network, it has become increasingly important to analyze the performance of the IEEE 802.11 protocol accurately. Throughput and delay are key measures, reflecting the performance of a wireless network. In this paper, we analyze the performance of the IEEE 802.11 distributed coordination function (DCF) in the saturated traffic condition, and consider the effects of packet size, the number of contention nodes, transmission collision probability and channel conditions. Under this analytical framework, we evaluate the impact of error-prone channel on unsuccessful transmission probability and its impact on the performance. A trade-off exists between the desire to reduce the ratio of overhead in the data packet by adopting larger packet size, and the need to reduce the packet error rate in the error-prone environment by using smaller packet length. An optimal packet size can be derived to maximize the throughput of the IEEE 802.11 DCF under various channel conditions and network configurations. To validate our analytical results, we have done extensive simulations, and the simulation results are observed to match very well with the analytical results.