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Author: search.filters.author.Bhatia, AshutoshSubject: search.filters.subject.Media Access Control

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    RD-TDMA: A Randomized Distributed TDMA Scheduling for Correlated Contention in WSNs
    (IEEE, 2014) Bhatia, Ashutosh
    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.
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    A TDMA-Based Energy Aware MAC (TEA-MAC) Protocol for Reliable Multicast in WSNs
    (IEEE, 2014) Bhatia, Ashutosh
    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.
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    A Fast and Fault-Tolerant Distributed Algorithm for Near-Optimal TDMA Scheduling in WSNs
    (IEEE, 2014) Bhatia, Ashutosh
    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.
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    DSLR: A Distributed Schedule Length Reduction Algorithm for WSNs
    (IEEE, 2015) Bhatia, Ashutosh
    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.
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    TRM-MAC: A TDMA-based reliable multicast MAC protocol for WSNs with flexibility to trade-off between latency and reliability
    (Elsevier, 2016-07) Bhatia, Ashutosh
    Multicast in wireless sensor networks (WSNs) is an efficient way to deliver the same data to multiple sensor nodes. Reliable multicast in WSNs is desirable for critical tasks like code updation and query based data collection. The erroneous nature of the wireless medium coupled with limited resources of sensor nodes, makes the design of reliable multicast protocol a challenging task. In this paper, we propose a framework for reliable multicast transmission in WSNs using TDMA-based channel access which works on top of a Multicast Spanning Tree (MST) rooted at the base station. The existing TDMA-based MAC protocols do not provide any mechanism to handle the collision and explosion of feedback messages, and therefore, they cannot be used in the proposed framework to support reliable multicast. To handle this issue, we propose a TDMA-based reliable multicast MAC (TRM-MAC) protocol for WSNs. The TRM-MAC protocol is parametric in the sense that it can be used to trade-off between reliability and delay performance, as per the requirement of the underlying applications. We have analyzed the TRM-MAC protocol to evaluate its delay and reliability performance at different packet loss rates, and have also compared its performance with those of others using simulation study. Both simulation and analytical results show that the TRM-MAC protocol considerably improves the performance of multicast communication in WSNs.
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    PMAC: A poll-based MAC protocol for wireless body area networks (WBANs)
    (IEEE, 2016) Bhatia, Ashutosh
    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 WBAN. WBAN consists of variety of medical and non-medical applications with aggregate data rate requirement ranging from few bytes per second to 10Mbps. These applications are having relatively different energy saving, reliability and quality of service (QoS) requirements. The existing MAC protocols present in various short and medium range wireless technologies such as 802.11 and 802.15.4 have been designed for specific purposes, and therefore, do not fulfill the diverse performance requirements across all WBAN applications. In this paper, we propose a poll-based MAC protocol (PMAC) for WBAN, which can meet such a diversified functional requirements of various WBAN applications. In particular, we introduce few concepts in polling based channel access mechanism to make an energy efficient and QoS aware MAC protocol. The design has been validated by obtaining the performance of proposed PMAC protocol through simulation