Lucy J. Gudino

Performance analysis of rectangular, triangular and E-shaped microstrip patch antenna arrays for wireless sensor networks

Generally wireless sensor nodes have been using omni-directional antennas to broadcast data. But these antennas are not very efficient as they suffer from poor spatial reuse, high collisions, decreased throughput and are not energy efficient. Usage of directional antennas which radiate in a particular direction is more efficient as it can lead to significant energy savings. They reduce beamwidth by concentrating power in a certain direction. In this paper, the performance of conventional omni-directional quarter wave monopole antenna, rectangular patch antenna array, triangular patch antenna array and E-shaped patch antenna array are compared. The antenna arrays have been designed, simulated and tested. The antenna arrays designed are fabricated and then are mounted on a sensor node. The performance analysis in terms of power consumption, received signal strength and packet delivery ratio is performed for individual antenna arrays.

Implementation of multi-hop time synchronization on miniature test-bed setup of underwater acoustic sensor network

Time synchronization is an important part of any distributed networked embedded system. It is essentially the process of achieving and maintaining common time base among all network nodes of the system. This task is quite challenging for the systems or applications like sensor networks, since these systems are highly resource constrained, yet need to process time-sensitive data in collaborative manner. Though many protocols have been suggested for terrestrial sensor networks (RSB, TPSN, FTSP and LTS) and they perform reasonably well, very few protocols (THSL, Tri-message) have been suggested for the high-latency underwater acoustic networks, since achieving time-synchronization for high-latency networks is even more challenging issue. Here we describe a very simple extension and implementation of Tri-message time synchronization protocol for multi-hop Underwater Acoustic Sensor Network (UASN) on the miniature test-bed setup.

Cross Layer Best effort QoS aware routing protocol for Ad Hoc Network

Mobile Ad Hoc Networks (MANETs) are a self organizing and adaptive wireless networks. Currently MANETs possess an advanced challenge in providing Quality of Service( QoS) support for real time application data streaming through the network. These applications are delay sensitive and get affected due to congestion in the network. Thus, performance degrades due to high data loss, frequent link breakage and excessive retransmission. The strict layered network structure makes even more difficult to provide solutions for such issues. We propose a protocol which cooperates between adjacent layers and performs cross layer communication. We propose a novel QoS routing for MANET called Cross Layer Best effort QoS aware routing protocol (CLBQ) which considers the metric of link quality, data rates and MAC delay as the QoS parameters. The proposed protocol implements cross layer interaction between PHY, MAC and Network layer. The simulation results conducted shows best effort QoS service to the network in discovering the route and data transfer. Our analysis shows that the protocol has improved throughput and low network overhead.

Cross-layer protocol stack development for three-dimensional underwater Acoustic Sensor Network

Abstract There is a huge interest in the research community to explore the ocean using sensor networks. Various factors such as resource constraints of sensor networks, requirements of applications, properties of underwater acoustic communication and features of ocean environment have a big impact on the design and development of the network architecture as well as the protocol stack. For a long-term deployment of a network, energy efficiency is the most important design criteria. For achieving energy efficiency and overall improvement in network performance, a new approach of cross-layer protocol stack design is being explored by researchers. In this work, a cross-layer protocol stack has been developed for a three-dimensional Underwater Acoustic Sensor Network (UASN) that can be used for a long-term monitoring of ocean column. The proposed stack with cross-layer design combines physical layer, data link layer, network layer protocols along with time-synchronization, clustering and power level management. This protocol stack has been successfully implemented on the UnetSim which is an open source underwater network simulator. In this paper, the details of protocol stack, its implementation on UnetSim along with results and analysis of results have been provided.

Cross layered adaptive cooperative routing mode in mobile ad hoc networks

A Cooperative communication technique has gained considerable attention in the recent time to improve the quality of service (QoS) of ad hoc networks. Cooperative communication significantly improves link capacity through physical layer technique, and spatial diversity gain is achieved by using neighboring nodes to retransmit the overheard information to the intended destination node. However, upper layer protocols are not elegantly designed to adequately exploit the spatial diversity to improve overall network performance in ad hoc networks. Limiting the cooperation to one network layer may not be the best solution. Thus, in this paper, we intend to achieve multilayer functionality from physical layer to the routing layer to provide cooperative communication. An adaptive cross layered cooperative routing algorithm (ACCR) is proposed to analyze the channel state variations and selectively choose the cooperative MAC scheme on demand by exploiting spatial diversity. The algorithm dynamically selects best relay candidates based on QoS metric, contention delay and node energy fairness. Network layer, then chooses an optimized path from source to destination through the selected relay nodes. We validate the algorithm with extensive simulations. The results clearly show that cooperative cross-layer design approach effectively improves the average throughput and average delay for each packet transmission.

Partition Discovery and Connectivity Restoration in WSN using Mobile Relays

Connectivity restoration in Wireless Sensor Network (WSN) is a common problem and several solutions has been proposed in the literature. Reasons for partition include initial random deployment, node failure due to low battery life, hardware malfunction etc. This paper focuses on partition discovery and hence restoring connectivity in a segmented network using Mobile Relay (MR) nodes. We propose a hybrid of frontier-based and random-direction exploration approaches for detecting partitions in a given area. An approximation algorithm for Steiner point based minimum spanning tree is adopted to determine the topology for connecting the discovered partition. Optimal assignment of mobile relays in this topology is visualized as a Bottleneck Assignment Problem (BAP). Our approach guarantees use of minimum number of MR nodes to be placed in minimum time. Experimental results indicate that the proposed approach can be effectively used for connectivity restoration in a partitioned network.

Cross layer approach for efficient dissemination of emergency messages in VANETs

This paper proposes a cross layer approach for efficient dissemination of emergency messages in VANETs (CL-DEM) by minimizing the message redundancy and maintaining low end-to-end communication delays. We propose a scheme to select a one-hop neighbor relay as a potential forwarder for relaying the broadcast messages to improve the transmission reliability in a platoon of vehicles. The relay selection metrics compose of vehicular density, vehicular velocity, and the geographical location. The selected relay controls the broadcast messages with minimum overhead and with minimum bandwidth consumption. To provide the service differentiation to different traffic classes, we adopt 802.11e MAC. The cross layer is further extended to the transport layer to dynamically adapt the data transmission rate based on the physical channel state. The extensive simulation analysis conducted reveals that the proposed cross-layer scheme effectively propagates the critical broadcast messages with minimum latency.

Cross layer adaptive congestion control for best-effort traffic of IEEE 802.11e in mobile ad hoc networks

The dominance of multimedia traffic over the Internet, coupled with the rising number of applications of MANETs, has made Quality of Service (QoS) a major concern. The IEEE 802.11e standard enhanced distributed channel access(EDCA) has been proposed as an enhancement of 802.11 standard, which provides QoS at MAC layer with a service differentiation scheme for high priority traffic. But IEEE 802.11e has not adequately addressed the issue of handling best effort traffic data flows through contention-based networks which in turn results in TCP performance degradation. To enhance the best effort traffic performance in 802.11e with high-quality of service to maximize the system throughput, we propose a novel scheme called, Adaptive Best Effort Traffic Scheduler for EDCA(ABET-EDCA). In this scheme, TCP packets get prioritized by dynamically adapting to contention window parameters. In addition to this, traffic class monitors the MAC queue and computes TXOP limits value at runtime. This results in reduced delay and loss factor. Additionally, we incorporate the cross layer approach by exploiting the physical and MAC layer information to initiate corrective measures at the Transport and Network layer to enhance best effort traffic performance. The simulation conducted shows the significant improvement in TCP performance in terms of goodput, delay and throughput even under high loads compared to EDCA.

DS-MMAC: dynamic schedule based MAC for mobile wireless sensor network

In this paper, we propose a medium access protocol for Mobile Wireless Sensor Network which uses dynamic scheduling of time slot for channel access. We have considered a mixed deployment of both mobile and static wireless sensor nodes. The static nodes, which act as cluster head, maintain a local schedule to service the mobile neighbors and also route data to the base station. The design goals of our MAC are energy efficiency, increased packet delivery and low control overhead. The request-reply mechanism for data transfer, used in our approach, plays a vital role in the handover process. Simulation results indicate that our approach performs better in terms of data rate, energy efficiency and control overhead when compared with Hybrid MAC protocol. Testbed results indicate that the proposed approach can be effectively used in WSN where topology change is frequent.

Simulation and testbed implementation of TDMA MAC on Underwater Acoustic Sensor Network

Three Dimensional (3-D) Underwater Acoustic Sensor Network (UASN) can be used to detect and observe ocean environment using co-operative and distributed sampling. We are proposing a multi-level clustering topology for ocean column monitoring application. A simple Cluster-Based TDMA MAC (CB-TDMA) protocol is simulated on this network using SUNSET platform developed by SENSES lab, Sapienza University, Rome. Analysis is provided in terms of packet delivery ratio, network delay and energy consumption. This CB-TDMA MAC along with multi-hop tri-message time synchronization is also implemented on a hardware test-bed in our laboratory. Brief description of this implementation is also provided in this paper.