Anwar Khan

Soil and vegetables enrichment with heavy metals from geological sources in Gilgit, northern Pakistan.

This study was conducted to investigate the concentrations of heavy metals in soil and vegetables, and human health risks through ingestion of contaminated vegetables. Soil and vegetable samples were collected from different locations in Gilgit, northern Pakistan, and analyzed for Cd, Cu, Ni, Pb and Zn. Plant transfer factors (PTF), daily intake of metals (DIM) and health risk index (HRI) were also calculated. The concentrations of Cd, Cu and Zn exceeded their respective permissible limits in soil samples. The highest concentrations of Cu, Ni, Pb and Zn were observed in the edible parts of Malva neglecta, Brassica oleracea, Mintha sylvestris and Brassica campestris, respectively. PTF values were lower for all the selected heavy metals, except for Cd. Furthermore, the HRI values were within the safe limit (<1) except for Pb; therefore, the health risks of metals through ingestion of vegetables were of great concern in the study area.

EEIRA: An Energy Efficient Interference and Route Aware Protocol for Underwater WSNs

In this paper, an energy efficient, interference and route aware (EEIRA) protocol is proposed for underwater wireless sensor networks (UWSNs). The protocol combines the direct and relay forwarding mechanisms in transmitting the packets from source to destination. The relaying process involves selection of the best relay from a set of relay nodes. A relay node having the least distance from source to destination and the minimum number of neighbor nodes qualifies the criterion of the best relay. The direct transmission is used when the best relay is not within the transmission range of the source node. From top to bottom, the network is divided into three different zones, destination, relay and source zone, respectively. The relay zone has the greatest area to have maximum choices of selecting the best relay from the relay nodes residing in it. Nodes in all the three regions can sense the attribute and send the data to the sink. The destination nodes send data directly to sink. The relay nodes send the packets to the sink either directly or through the relaying process. The source nodes in the bottom send the data to sink via the best relay node or directly. Based on simulation results, the proposed protocol outperforms the depth based routing (DBR) scheme in terms of energy efficiency by selecting the best relay, reducing number of hops and following the shortest path to reduce channel losses.

A Localization-Free Interference and Energy Holes Minimization Routing for Underwater Wireless Sensor Networks

Interference and energy holes formation in underwater wireless sensor networks (UWSNs) threaten the reliable delivery of data packets from a source to a destination. Interference also causes inefficient utilization of the limited battery power of the sensor nodes in that more power is consumed in the retransmission of the lost packets. Energy holes are dead nodes close to the surface of water, and their early death interrupts data delivery even when the network has live nodes. This paper proposes a localization-free interference and energy holes minimization (LF-IEHM) routing protocol for UWSNs. The proposed algorithm overcomes interference during data packet forwarding by defining a unique packet holding time for every sensor node. The energy holes formation is mitigated by a variable transmission range of the sensor nodes. As compared to the conventional routing protocols, the proposed protocol does not require the localization information of the sensor nodes, which is cumbersome and difficult to obtain, as nodes change their positions with water currents. Simulation results show superior performance of the proposed scheme in terms of packets received at the final destination and end-to-end delay.

DNAR: Depth and Noise Aware Routing for Underwater Wireless Sensor Networks

Recently, the underwater wireless sensor networks (UWSNs) have been proposed for exploration of the underwater resources and to obtain information about the aquatic environment. The noise in UWSNs challenges the successful transmission of packets from a sender to a receiver. There are many protocols in literature that address noise reduction/avoidance during underwater communication. However, they require localization information of each sensor nodes that itself is a challenging issue. In this paper, the minimum channel noise is considered and the depth and noise aware routing (DNAR) protocol is proposed to send the packets reliably from a sender node to a surface sink. In the DNAR protocol, more energy is assigned to the sensor nodes that have depth level \(\le \)150 m. Therefore, the sensor nodes that deployed are nearby to the sink node have more capability of transmission and will not die quickly. Also, the proposed protocol selects the forwarder candidate that have lowest depth and minimum channel noise at the receiver. As compared to some existing schemes, the proposed scheme requires no geographical information of the nodes for data routing. The DNAR protocol is validated by Matlab simulation and compared it with the DBR scheme. The simulation results show that the DNAR has better results in-terms of packet delivery ratio (PDR), total energy consumption, and the network lifetime.

Routing Protocols for Underwater Wireless Sensor Networks: Taxonomy, Research Challenges, Routing Strategies and Future Directions

Recent research in underwater wireless sensor networks (UWSNs) has gained the attention of researchers in academia and industry for a number of applications. They include disaster and earthquake prediction, water quality and environment monitoring, leakage and mine detection, military surveillance and underwater navigation. However, the aquatic medium is associated with a number of limitations and challenges: long multipath delay, high interference and noise, harsh environment, low bandwidth and limited battery life of the sensor nodes. These challenges demand research techniques and strategies to be overcome in an efficient and effective fashion. The design of routing protocols for UWSNs is one of the promising solutions to cope with these challenges. This paper presents a survey of the routing protocols for UWSNs. For the ease of description, the addressed routing protocols are classified into two groups: localization-based and localization-free protocols. These groups are further subdivided according to the problems they address or the major parameters they consider during routing. Unlike the existing surveys, this survey considers only the latest and state-of-the-art routing protocols. In addition, every protocol is described in terms of its routing strategy and the problem it addresses and solves. The merit(s) of each protocol is (are) highlighted along with the cost. A description of the protocols in this fashion has a number of advantages for researchers, as compared to the existing surveys. Firstly, the description of the routing strategy of each protocol makes its routing operation easily understandable. Secondly, the demerit(s) of a protocol provides (provide) insight into overcoming its flaw(s) in future investigation. This, in turn, leads to the foundation of new protocols that are more intelligent, robust and efficient with respect to the desired parameters. Thirdly, a protocol can be selected for the appropriate application based on its described merit(s). Finally, open challenges and research directions are presented for future investigation.

Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions

Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal), long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node’s cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted.

A Localization Free Variable Transmit Power Routing Protocol for Underwater Wireless Sensor Networks

In underwater wireless sensor networks (UWSNs), adjusting the transmit power of a sensor node in response to the time-varying characteristics of the aquatic medium is one of the promising techniques to combat the hostile environment. It can be used to mitigate the unwanted effects of noise, fading and attenuation on data and reliably deliver it from source to destination utilizing more transmit power. For favorable channel conditions, data packets can be reached to destination at the expense of lower energy consumption. In this chapter, we propose a localization-free variable transmit power routing (LF-VTPR) protocol for UWSNs. The proposed protocol adjusts the transmit power level of the data to send in proportion to the latest link quality states of the routing trajectories. The proposed work is unique and never been done in that it does not involve calculation of position information of nodes. All the conventional and variable transmit power routing protocols that involve localization of nodes require that the three dimensional position coordinates of sensor nodes must be known. Localization is energy inefficient for the limited battery life of sensor nodes in underwater communications. Also, it is difficult to achieve when nodes change their positions with water currents. The LF-VTPR uses the depth and response time information of sensor nodes to forward data to final destination. Simulation results reveal that the scheme outperforms some of the existing schemes in terms of throughput and end-to-end delay.

EEORS: Energy Efficient Optimal Relay Selection Protocol for Underwater WSNs

In this paper, an energy efficient optimal relay selection protocol is proposed for underwater wireless sensor networks (UWSNs). Sensor nodes are randomly deployed in a three dimensional underwater network and is partitioned into three zones based on depth. The mid zone contains the relay nodes. Nodes in the relay zone are assigned values on the bases of location and depth. Nodes residing in the center of the relay zone are assigned highest location values. These values decrease as the nodes become farther from the center. Values are also assigned to the relay nodes based on depth. The optimal relay is the one having the highest (maximum) location and depth values. If the optimal relay is within the transmission range of the source nodes in the bottom zone, they send the data packets to the optimal relay that further forwards them to the sink. Direct transmission from source to sink at the expense of more energy is accomplished when the optimal relay lies outside the transmission range of the source nodes. Nodes in the top zone send data directly to sink. Relay nodes in the mid zone send the data to sink either directly or through the optimal relay node. When the most optimal relay node dies, the second optimal node becomes the most optimal relay node. Simulation results show that the proposed scheme outperforms the counterpart scheme in terms of energy efficiency due to the selection of the optimal relay.

Position Aware Mobility Pattern of AUVs for Avoiding Void Zone in Underwater WSNs

In this paper, we propose an optimization scheme for avoiding void zone and minimization of uncertainty in gliders position estimation. Gliders stay at sojourn positions for predefined time. At these stops, self-confidence (s-confidence) and neighbor-confidence (n-confidence) regions are estimated. On the basis of present state of glider, it estimates s-confidence region and share control information with neighbors. By using direction, present position, s-confidence region and distance from the neighboring glider, n-confidence region is estimated. Transmission power of glider is adjusted according to these confidence regions. Sojourn positions in the network minimize the uncertainty in position and confidence regions estimation.

A Transmit Power Efficient Non-Cooperative Game Design for Wireless Sensor Networks Based on the Utility and Cost Function.

A non-cooperative power control game (NCPCG) is designed for efficient power consumption in the wireless sensor and ad hoc networks by introducing a novel cost function. The proposed cost function in a game theoretic framework facilitates the nodes in increasing power efficiency by making independent decisions in a distributed environment. The Nash equilibrium is achieved among the nodes converging to the optimal value of the utility function for the entire network, beyond which even further increase in the power level reduces the signal-to-noise (SNR) ratio.