Ashutosh Bhatia

A cluster based minimum battery cost AODV routing using multipath route for zigbee

IEEE 802.15.4 standard is uniquely designed for low data rate wireless personal area networks (LR-WPANs). The IEEE 802.15.4 targets the applications such as industrial, agricultural, vehicular, residential, medical sensors and actuators which have more relaxed throughput requirements. ZigBee is a wireless technology based on IEEE 802.15.4. ZigBee routing uses ad hoc on-demand distance vector (AODV) routing protocol. In this paper we present an improved version of AODV called multipath energy aware AODV routing (ME-AODV), which utilizes the topology of network to divide it into one or more logical clusters and restricts the flooding of route request outside the cluster. The mesh links created at the time of cluster formation are used to decrease the routing path. ME-AODV uses nodes of the same cluster to share routing information, which significantly reduces the route path discovery. Since ZigBee routing is based on shortest-hop count, which causes overuse of a small set of nodes hence decreasing node as well as network lifetime. We also propose a mix of ad hoc on-demand multipath distance vector routing (AOMDV) and minimal-battery cost routing (MBCR) as an extension to AODV to increase the lifetime of network. The simulations have been performed using IEEE 802.15.4, ns-2 module.

RD-TDMA: A Randomized Distributed TDMA Scheduling for Correlated Contention in WSNs

In wireless sensor networks (WSNs), contention occurs when two or more nodes in a proximity simultaneously try to access the channel. The contention causes collisions, which are very likely to occur when traffic is correlated. The excessive collision not only affects the reliability and the QoS of the application, but also the lifetime of the network. It is well known that random access mechanisms do not efficiently handle correlated-contention, and therefore, suffer from high collision rate. Most of the existing TDMA scheduling techniques try to find an optimal or a sub-optimal schedule. Usually, the situation of correlated-contention persists only for a short duration, and therefore, it is not worthwhile to take a long time to generate an optimal or a sub-optimal schedule. We propose a randomized distributed TDMA scheduling (RD-TDMA) algorithm to quickly generate a feasible schedule (not necessarily optimal) to handle correlated-contention in WSNs. In RD-TDMA, a node in the network negotiates a slot with its neighbors using the message exchange mechanism. The proposed protocol has been simulated using the Castalia simulator to evaluate its runtime performance. Simulation results show that the RD-TDMA algorithm considerably reduces the time required to schedule.

A Design for Performance Improvement of Clock Synchronization in WSNs Using a TDMA-Based MAC Protocol

Clock synchronization in a wireless sensor network (WSN) is quite essential as it provides a consistent and a coherent time frame for all the nodes across the network. Typically, clock synchronization is achieved by message passing using a contention-based scheme for media access, like carrier sense multiple access (CSMA). The nodes try to synchronize with each other, by sending synchronization request messages. If many nodes try to send messages simultaneously, contention-based schemes cannot efficiently avoid collisions. In such a situation, there are chances of collisions, and hence, message losses, which, in turn, affects the convergence of the synchronization algorithms. However, the number of collisions can be reduced with a frame based approach like time division multiple access (TDMA) for message passing. In this paper, we propose a design to utilize TDMA-based media access and control (MAC) protocol for the performance improvement of clock synchronization protocols. The basic idea is to use TDMA-based transmissions when the degree of synchronization improves among the sensor nodes during the execution of the clock synchronization algorithm. The design significantly reduces the collisions among the synchronization protocol messages. We have simulated the proposed protocol in Castalia network simulator. The simulation results show that the proposed protocol significantly reduces the time required for synchronization and also improves the accuracy of the synchronization algorithm.

A Distributed TDMA Slot Scheduling Algorithm for Spatially Correlated Contention in WSNs

In wireless sensor networks (WSNs) the communication traffic is often time and space correlated, where multiple nodes in a proximity start transmitting at the same time. Such a situation is known as spatially correlated contention. The random access methods to resolve such contention suffers from high collision rate, whereas the traditional distributed TDMA scheduling techniques primarily try to improve the network capacity by reducing the schedule length. Usually, the situation of spatially correlated contention persists only for a short duration and therefore generating an optimal or sub-optimal schedule is not very useful. On the other hand, if the algorithm takes very large time to schedule, it will not only introduce additional delay in the data transfer but also consume more energy. To efficiently handle the spatially correlated contention in WSNs, we present a distributed TDMA slot scheduling algorithm, called DTSS algorithm. The DTSS algorithm is designed with the primary objective of reducing the time required to perform scheduling, while restricting the schedule length to maximum degree of interference graph. The algorithm uses randomized TDMA channel access as the mechanism to transmit protocol messages, which bounds the message delay and therefore reduces the time required to get a feasible schedule. The DTSS algorithm support sunicast, multicast and broadcast scheduling, simultaneously without any modification in the protocol. The protocol has been simulated using Castalia simulator to evaluate the runtime performance. Simulation results show that our protocol is able to considerably reduce the time required to schedule.

A DHCPv6 Based IPv6 Autoconfiguration Mechanism for Subordinate MANET

In order to communicate among themselves and with the devices on the Internet, a Mobile Ad-hoc NETwork (MANET) node needs to configure its interface(s) with IP address(es). MANET is a multi-hop network often consisting of mobile devices such as mobile phones, PDAs, laptops with wireless interface(s). Due to some of the MANET inherent characteristics such as mobility, multi-hop and ad hoc, manual configuration of IP address(es)/prefix(es) is not desirable and practical. The Dynamic Host Configuration Protocol version 6 (DHCPv6) is Internet Engineering Task Force defined standard mechanism to autoconfigure IPv6 address in a stateful manner. This paper discusses subordinate MANET scenario and applicability of DHCPv6 in such scenario. The paper then proposes a novel approach to dynamically configure DHCPv6 relay agents in order to make DHCPv6 message exchange possible between MANET nodes (DHCPv6 clients) and DHCPv6 server ensuring minimal control overhead. Proposed solution facilitates seamless integration of MANET with the Internet. Operation of the relay agent is kept transparent to the client and server as required by the DHCPv6 specification. The optimization helps to reduce configuration latency and signal overhead. The proposed mechanism is evaluated and analyzed using ns-2.31 over IEEE 802.11 MAC/PHY layer and Ad-hoc On-demand Distance Vector routing protocol.

A TDMA-Based Energy Aware MAC (TEA-MAC) Protocol for Reliable Multicast in WSNs

Multicast in wireless sensor networks (WSNs) is an efficient way to spread the same data to multiple sensor nodes. It becomes more effective due to the broadcast nature of wireless link, where a message transmitted from one source is inherently received by all one-hop receivers, and therefore, there is no need to transmit the message one by one. Reliable multicast in WSNs is desirable for critical tasks like code updation and query based data collection. The erroneous nature of wireless medium coupled with limited resource of sensor nodes, makes the design of reliable multicast protocol a challenging task. In this work, we propose a time division multiple access (TDMA) based energy aware media access and control (TEA-MAC) protocol for reliable multicast in WSNs. The TDMA eliminates collisions, overhearing and idle listening, which are the main sources of reliability degradation and energy consumption. Furthermore, the proposed protocol is parametric in the sense that it can be used to trade-off reliability with energy and delay as per the requirement of the underlying applications. The performance of TEA-MAC has been evaluated by simulating it using Castalia network simulator. Simulation results show that TEA-MAC is able to considerably improve the performance of multicast communication in WSNs.

DSLR: A Distributed Schedule Length Reduction Algorithm for WSNs

Wireless sensor networks (WSNs) benefit from theMAC protocols that reduce power consumption by avoiding frame collisions. Time Division Multiple Access (TDMA) method provides collision free channel access by employing a pre-defined schedule so that the nodes can transmit at their allotted time slots. Most of the existing distributed TDMA-scheduling techniques for WSNs either try to improve the channel utilization by generating compact schedule which usually takes longer time, or generate schedule quickly, that may not be very efficient in terms of the schedule length. In this paper, we present a new approach to TDMA-scheduling for WSNs, that bridges the gap between these two extreme types of TDMA-scheduling techniques, by providing the flexibility to trade-off the schedule length with the time required to generate the schedule, as per the requirements of the underlying applications and channel conditions. The idea into generate a TDMA-schedule quickly using any of the existing algorithms, and then progressively reduce the TDMA-schedule length. In this context, we provide a distributed schedule length reduction (DSLR) algorithm which can be terminated after the execution of arbitrary number of iterations, and still bereft with a valid schedule. Additionally, unlike other TDMA-scheduling algorithms which use contention-based channel access, the DSLR algorithm uses TDMA-based channel access to perform the schedule reduction. The algorithm has been simulated using the Castalia simulator to compare its performance with those of others in terms of generated schedule length and the time required to generate the TDMA-schedule. Simulation results confirm the effectiveness of the approach, and show that the proposed algorithm generates a compact schedule in much less time in comparison to existing approaches.

Emergency handling in MICS based Body Area Network

Body Area Network, a new wireless networking paradigm, promises to revolutionize the healthcare applications. A number of tiny sensor nodes are strategically placed in and around the human body to obtain physiological information. The sensor nodes are connected to a coordinator or a data collector to form a Body Area Network. The tiny devices may sense physiological parameters of emergency in nature (e.g. abnormality in heart bit rate, increase of glucose level above the threshold etc.) that needs immediate attention of a physician. Due to ultra low power requirement of wireless body area network, most of the time, the coordinator and devices are expected to be in the dormant mode, categorically when network is not operational. This leads to an open question, how to handle and meet the QoS requirement of emergency data when network is not operational? Emergency handling becomes more challenging at the MAC layer, if the channel access related information is unknown to the device with emergency message. The aforementioned scenarios are very likely scenarios in a MICS (Medical Implant Communication Service, 402-405 MHz) based healthcare systems. This paper proposes a mechanism for timely and reliable transfer of emergency data in a MICS based Body Area Network. We validate our protocol design with simulation in a C++ framework. Our simulation results show that more than 99 percentage of the time emergency messages are reached at the coordinator with a delay of 400ms.

A Fast and Fault-Tolerant Distributed Algorithm for Near-Optimal TDMA Scheduling in WSNs

The time division multiple access (TDMA) based channel access mechanisms perform better than the contention based channel access mechanisms, in terms of channel utilization, reliability and power consumption, specially for high data rate applications in wireless sensor networks (WSNs). Most of the existing distributed TDMA scheduling techniques can be classified as either static or dynamic. The primary purpose of static TDMA scheduling algorithms is to improve the channel utilization by generating a schedule of smaller length. But, they usually take longer time to schedule, and hence, are not suitable for WSNs, in which the network topology changes dynamically. On the other hand, dynamic TDMA scheduling algorithms generate a schedule quickly, but they are not efficient in terms of generated schedule length. In this paper, we propose a novel scheme for TDMA scheduling in WSNs, which can generate a compact schedule similar to static scheduling algorithms, while its runtime performance can be matched with those of dynamic scheduling algorithms. Furthermore, the proposed distributed TDMA scheduling algorithm has the capability to trade-off schedule length with the time required to generate the schedule. This would allow the developers of WSNs, to tune the performance, as per the requirement of prevalent WSN applications, and the requirement to perform re-scheduling. Finally, the proposed TDMA scheduling is fault-tolerant to packet loss due to erroneous wireless channel. The algorithm has been simulated using the Castalia simulator to compare its performance with those of others in terms of generated schedule length and the time required to generate the TDMA schedule. Simulation results show that the proposed algorithm generates a compact schedule in a very less time.

A Media Access and Feedback Protocol for Reliable Multicast over Wireless Channel

A link level reliable multicast requires a channel access protocol to resolve the collision of feedback messages sent by multicast data receivers. In this paper, we propose a virtual token based channel access and feedback protocol (VTCAF), which can trade off between reliability and access delay. The protocol uses the virtual (implicit) token passing mechanism based on carrier sensing to avoid the collision of feedback messages. We have simulated our protocol using Castalia network simulator to evaluate the performance parameters. Simulation results show that our protocol is able to considerably reduce average access delay while ensuring very high reliability at the same time.