Jahangir H. Sarker

Urgency-Based MAC Protocol for Wireless Sensor Body Area Networks

In this paper, an Urgency-based MAC (U-MAC) protocol, in which sensor nodes reporting urgent health information are given higher priority by cutting-off the number of packet retransmission of sensor nodes with non urgent health information, is proposed. The main consideration of this work is providing Quality of Service (QoS) support in medical wireless sensor networks through differentiating nodal access to the medium. The proposed MAC protocol is mathematically analyzed considering a beacon-enabled star network configuration of the IEEE 802.15.4a standard at 2.4 GHz. The used wireless body area network (WBAN) consists of N sensor nodes controlled by a single network coordinator. The obtained performance results show the capability of the proposed UMAC protocol in providing service differentiation in medical WBAN. Also, the results show that the number of critical nodes that can be supported by WBAN and their packet arrival rates decrease as the number of packet retransmission of such nodes is increased.

Communication-based Plug-In Hybrid Electrical Vehicle load management in the smart grid

New services and applications that employ the advances in the Information and Communication Technologies (ICT) to the electrical power grid are rapidly emerging and consequently the traditional power grid is evolving into a smart grid. In the smart grid, communication among the supplier controlled generation units, utility administered transmission and distribution system and the consumer devices is providing new opportunities for improving the resilience and the efficiency of the grid. Resilience is a significant issue due to increasing demand, and in contrast, diminishing fossil fuels. Moreover, in the near future, resilience is expected to become a more significant concern especially due to the additional loads of the Plug-In Hybrid Electrical Vehicles (PHEVs). PHEVs are expected be widely adopted as passenger cars and as commercial vehicle fleets since they have low carbon emissions and low operating costs. On the other hand, their load on the power grid should be managed so that they do not cause failures. In this paper, we propose the Communication-based PHEV Load Management (Co-PLaM) scheme to control the load of the PHEVs. In our scheme, utilities provision a certain amount of energy for each distribution system based on the predicted supply level. The provisioned energy is communicated to the Substation Control Center (SCC) where each charging request is either accepted or rejected based on the utility set limits. Then, these decisions are sent to the smart charging stations through a Wireless Mesh Network (WMN) that uses IEEE 802.11s. In this paper, we simulate the Co-PLaM scheme and also mathematically analyze the blocking probability of the system. We show the performance of WMN in terms of delivery ratio, delay and jitter. Furthermore, we provide the blocking results and show the required additional capacity to supply all the PHEV loads without causing grid failures.

Quality of service in Plug-in Electric Vehicle charging infrastructure

Electrification of transportation is offering reduced vehicle emissions and operating costs in addition to increased energy-independence. Electric cars are anticipated to be adopted as passenger vehicles and in commercial fleets in the near future. Plug-in Hybrid Electric Vehicles (PHEVs) can drive on battery up to few hundred miles with the current battery technologies. Depleting PHEV batteries are charged from the power grid either with a Level 1 or Level 2 charger where the latter delivers more power than the former. Despite the advantages of PHEVs, charging several PHEVs simultaneously from the same distribution system may cause local outages due to transformer overloading. Thus, PHEV charging infrastructure calls for admission control schemes that operate on the smart grid. It is also essential to provide service differentiation to increase consumer satisfaction. In this paper, we propose a Quality of Service (QoS)-aware admission control scheme for the PHEV charging infrastructure. Our scheme operates on the Energy Management System (EMS) of the smart grid distribution system. The proposed approach relies on a wireless communication network that delivers the demands of PHEVs to the EMS and delivers the admission decisions of EMS to PHEVs. In our admission control scheme, PHEV owners who are willing to pay more can charge faster than the “best-effort” users similar to the Internet traffic service differentiation mechanisms. We provide mathematical analysis and simulation results for the proposed scheme. We show that high priority PHEVs are supplied with higher power rating, hence they are able to charge faster than low priority PHEVs.

Analysis of Plug-in Hybrid Electrical Vehicle admission control in the smart grid

In the power grid, efficient coordination among electricity generation, transmission, distribution and consumption processes call for integration of the advances in Information and Communication Technologies (ICT) to the physical components of the grid. The need for coordination and control becomes even more pronounced when the additional loads of the Plug-In Hybrid Electrical Vehicles (PHEVs) are considered. PHEVs are anticipated to be widely adopted in the following years, and this will increase the load on the power grid since the batteries of the PHEVs will be charged mostly from the grid supplied power. In this case, avoiding mismatch between generation and consumption is one aspect of the problem, whereas to avoid overloading the distribution system components, e.g. transformers, is another equally important challenge. In this paper, we consider an architecture where the status of the grid is monitored by the utility and translated into an amount of provisioned energy for each distribution system serviced by a substation. The substation employs an admission control mechanism for the PHEV charge demands based on the provisioned energy amount. We provide the theoretical analysis of this admission control scheme by calculating the blocking probability of the PHEV demands. We also propose a mechanism to reduce the load without increasing the blocking probability. We introduce an activity factor in the model and show that it can be used to reduce the load. We show by theoretical analysis and simulations that our PHEV admission control mechanism decreases the overall load in the system, and hence increases the resilience of the smart grid. Meanwhile, we show that load reduction can be implemented without increasing the blocking probability, thus customer satisfaction is not degraded.

QoS-based MAC protocol for medical wireless body area sensor networks

In this paper, a random access protocol for quality of service (QoS) support targeted for medical wireless body area sensor networks (WBASNs) is proposed. In this proposal, the sensor nodes are classified into nodes of life-critical health information, and nodes of non-critical health information. The proposed QoS-based MAC protocol prioritizes the critical packets access to the transmission medium by cutting of the number of retransmissions of the collided non critical packets. Therefore, the critical traffic throughput is increased and its rejection rate is decreased while maintaining the non critical traffic QoS parameters above a minimum provisioned level. The proposed protocol is evaluated analytically and through simulation. The obtained results demonstrate a dramatic increase in the critical traffic throughput.

Stability of Multiple Receiving Nodes Slotted ALOHA for Wireless Ad Hoc Networks

In wireless ad hoc and sensor networks, communication may be achieved without a central entity (base station) and nodes communicate with each other in a half-duplex manner. In those kinds of networks each node either will be in a transmitting mode or in a receiving mode or in an idle mode. Stability of half-duplex slotted ALOHA is studied in terms of the node transmitting probability, the node receiving probability, capture ratio and the number of retransmission attempts. A close form equation is obtained for the stable operation of a distributed random access protocol with multiple receiving nodes. This equation provides the relationship between the new packet transmission probability from each mobile node, capture ratio and the number of retransmission attempts. The results of this study may be used for system design of half-duplex contention- based multiple access schemes with and without capture and retransmission cut-off.

An Efficient TDMA Scheme with Dynamic Slot Assignment in Clustered Wireless Sensor Networks

In this paper, we present an efficient MAC layer scheme using Dynamic Slot Assignment (DSA) in TDMA-based MAC protocols for cluster-based wireless sensor networks. The DSA scheme is presented to analyze the energy efficiency and channel utilization in a bursty traffic environment under low traffic conditions with a large number of sensor nodes in a single cluster. The DSA scheme will allow the network to adapt to the changing traffic load. Based on the network activity, the connection is established between the cluster-head node and those sensor nodes which have data to send, and a TDMA slot is assigned to each of them dynamically. We present the complete system model and model the data traffic by a correlated stochastic process (i.e. Markov chain) for a network where the second and subsequent connection arrival rate is dependent on the first arrival rate. We numerically compare our DSA with a traditionally proposed static TDMA model, the BMA model, and a variant of the BMA model (EA-TDMA), and prove substantial improvement in the energy consumption and channel utilization in low activity sensor networks. Results show that the efficiency of the MAC protocol can be increased significantly using the presented model.

Mitigating the effect of jamming signals in wireless ad hoc and sensor networks

In an infrastructure-less wireless ad hoc or sensor network, communication may be achieved between mobile nodes without a central entity (base station) using a half-duplex Slotted ALOHA protocol. The probability of success and the throughput per mobile node can be reduced significantly, if the network is attacked by jamming signals. Mitigating the effect of jamming signals using multi-packet transmission (MPT) and/or multi-packet reception (MPR) capabilities of each mobile node is studied. The effect of the probability of success reduction due to jamming signals can be mitigated by using the MPT and the MPR capabilities of each mobile node. Similarly, reduced throughput can be increased using the same techniques. The maximum throughput per mobile node can be obtained by the proper adjustment of the transmitting probability of each mobile node and the receiving probability of each mobile node. A lower mitigation of the maximum throughput reduction can be obtained by using only the MPT, if the jamming signal rate is very low. On the other hand, only the MPR capability can provide a lower mitigation of the maximum throughput reduction. The effect of jamming signals on the maximum throughput can be mitigated successfully at all traffic load conditions, if the MPT and the MPR capabilities work together.

Service reliability with enhanced failure recovery rate for multiple failures in survivable optical networks

In this paper, two basic parameters of service reliability, called service availability and service disruption rate against disjoint primary and backup paths failure in survivable optical networks are studied. The service availability and service disruption rate affected by dasiaenhanced failure recovery rate for multiple failurespsila is considered here. We consider enhanced failure recovery rate for multiple failures where a higher failure recovery rate is applied, if more than one path fail. Results of this paper can be divided into two parts. First, higher service availability can be achieved by dasiaenhanced failure recovery rate for multiple failurespsila. Secondly, reduction of the service disruption rate by increasing the dasiaenhanced failure recovery rate for multiple failurespsila is negligible. Therefore, this method is more applicable where connection availability is more important than that of the service disruption rate.

Mobile RFID System in the Presence of Denial-of-Service Attacking Signals

In a mobile radio-frequency identification (RFID) system, tagged items enter and leave the reader’s field at a constant speed. The possibility of tags leaving the reader’s interrogation zone without being identified is known as tag loss. Minimizing the tag loss ratio in the presence of random denial-of-service (DoS) attacking signals by optimizing the number of frames is investigated in this paper. The results show that the number of frame control is not needed to reduce the tag loss ratio if the tag entering rate is below a critical limit. The number of frames has to abruptly reduce to keep the tag loss ratio lower if the tag entering rate exceeds that critical limit. This critical limit of the tag entering rate is derived analytically. An analytical solution of the optimum number of frames in the presence of attacking signals that also minimize the tag loss ratio is devised. The technique for setting the optimum number of frames is also presented. The presented results in this paper with random DoS attacking signals is so general that those can be converted without DoS attacking signals by setting the DoS attacking signals equal to zero. The results of this paper can be used for mobile RFID system design with and without DoS attacking signals.