Fariborz Entezami

Find the Weakest Link: Statistical Analysis on Wireless Sensor Network Link-Quality Metrics

Routing protocol plays an important role in data communication. A wireless sensor network (WSN) is usually deployed in scenarios where efficient and energy-aware routing protocols are desired. In wireless sensors, the radio-frequency (RF) modules consume most of the energy. Routing metrics are important in determining paths and maintaining the quality of service in routing protocols. The most efficient metrics need to send packets to maintain link-quality measurement using the RF module. In this article, two prominent link-quality metrics-received signal strength indication (RSSI) and link-quality indication (LQI)-are introduced; the symmetry of RSSI and LQI in two directions has been studied, and relations between the expected transmission count (ETX), RSSI, and LQI as link-quality metrics have been analyzed. The evaluation in this article is based on a series of WSN test beds in real scenarios. The collected data from the test beds show symmetry in the RSSI in both directions as well as a significant correlation between the RSSI and distance, making RSSI a suitable link-quality metric for use in routing protocols for devices that work in limited-resources scenarios.

An enhanced routing metric for ad hoc networks based on real time testbed

The deployment of wireless ad-hoc networks compared to traditional infrastructure based networks offers several advantages such as fully distributed mobile operation, easy discovery of joining wireless devices and quick cheap network setup. The design of an effective routing protocol is one of the main challenges in the ad-hoc networking paradigm and the utilisation of an adequate link cost metric is essential. In this paper, the validity of ETX (Expected Transmission Count) as a link cost metric is investigated by studying its behaviour in real-time testbeds. In our performance evaluation, the ETX performance was studied in different distance scenarios. Subsequently, the main observation was that ETX values was not steady over time and usually fluctuated for a fixed scenario. Fluctuation in the ETX values affects a routing protocol in wrongly identifying the best path based on current ETX link cost and therefore new methods for ETX calculation are proposed in this paper. These different methods for ETX link cost calculation are compared with each other and the best link cost formula has been proposed as a new method for ETX calculation towards the end of the paper. The new ETX calculation is called AETX that could be used as a link cost in routing protocols that reflects the balance required between the consistency of a link metric value over time for fixed scenarios and the flexibility required to detect actual changes in link metric values. We finally provide conclusions about our research and some avenues for future work.

Deploying parameters of Wireless Sensor Networks in test bed environment

IEEE 802.15.4 is a standard deification for networks with low data rate, low power consumption and also low characteristics of node resources. ZigBee is the emerging industrial standard for ad hoc network based on IEEE 802.15.4.Wireless Sensor Networks (WSNs) is expected to be used for remote monitoring, home automation and industrial control. One of the goals of WSNs is to minimize the running cost and therefore Star and Tree topologies have been designed to save energy as they do not require any routing table to send the packets to destination [1]. This paper includes the introduction to topologies supported by IEEE802.15.4, and also we have studied the deploying parameters of tree and star topologies in a test bed environment. In the end of this paper some techniques and measurements has been proposed for random deployment into the field.

3DPBARP: A three dimensions position based adaptive real-time routing protocol for wireless sensor networks

Devices for Wireless Sensor Networks (WSN) are limited by power and thus routing protocols should be designed with this constrain in mind. WSNs are used in three dimensions (3D) scenarios such as surface of sea or lands with different level of highs. This paper presents and evaluates Three Dimensions Position Based Adaptive Real-Time Routing Protocol (3DPBARP) as a novel, real-time, position based and energy efficient routing protocol for Wireless Sensor Networks (WSN)s. 3DPBARP is a lightweight protocol that reduces the number of nodes which receive the RF signal using a novel Parent Forwarding Region (PFR) algorithm. 3DPBARP as a Geographical Routing Protocol (GRP) reduces the number of forwarding nodes and thus the traffic and packet collision in the network. A series of performance evaluations through Matlab and Omnet++ simulations show significant improvements in network performance parameters and total energy consumption over 3D Position Based Routing Protocol (3DPBRP) and Directed Flooding Routing Protocol (DFRP).

RCTP: an enhanced routing protocol based on collection tree protocol

Due to implementation of routing protocols in limited power supply devices in wireless sensor networks (WSNs), this paper presents and evaluates Rainbow Collection Tree Protocol (RCTP) as an enhanced version of Collection Tree Protocol (CTP). CTP is a lightweight, efficient, robust, and also reliable routing protocol for WSNs. CTP as a cross layer routing protocol is also a platform-independent protocol. It uses Trickle Algorithm to optimize the overhead cost and also makes it quickly adaptable to changes in topology. The basic foundation of CTP is on link quality identification and it uses expected transmission count (ETX). ETX is not stable during the time in real environments and ETX fluctuations cause the routing protocols to not work in optimum level. RCTP uses average expected transmission count (AETX) as link quality metric that has shown it is more stable than ETX. It also uses a new mechanism in parent selection to make it more accurate. Rainbow mechanism is used in RCTP to detect and route around connectivity nodes and avoid route through dead end paths. The Omnet++ has been used as a simulator and the results show RCTP performs more efficiently than CTP in dynamic and crowded environments.