Kartinah Zen

Performance evaluation of IEEE 802.15.4 for mobile sensor networks

The IEEE 802.15.4 standard medium access control (MAC) protocol for low rate wireless personal area networks (LRWPAN) is design mainly for static sensor networks and its capability to support mobile sensor networks has not yet been established. To the best knowledge of authors, this is the first paper that evaluates the suitability of IEEE 802.15.4 MAC in mobile sensor networks environment. We evaluate the performance based on nodes speed and beacon order, and observe the effect on energy usage, packet delivery ratio and time required to associate with its coordinator. From the experiment we observe that the moving nodes experienced serious problems in association and synchronization and show results on energy usage, throughput , association and reassociation rate with different speeds of moving node. We also identify some key research problems that need to be addressed for successful implementations of IEEE 802.15..4 in mobile sensor networks environment.

Performance evaluation of AODV routing protocol for mobile wireless sensor network

Topology change is the main factor that affects the network life time of Wireless Sensor Network (WSN) applications. In static WSN, the topology change is often caused by node failure which is due to energy depletion. However, in the Mobile WSN (MWSN), the main reason of the topology change is caused by the node movement. Since the mobile sensor nodes are limited in power supply and have a low radio frequency coverage, they are easily losing their connection with neighbours, and have difficulties updating their routing tables. The switching process from one coverage area to another consumes more energy that related to transmitting and receiving association packets. Using Ad hoc On-Demand Distance Vector (AODV) routing protocol in MWSN application shows degradation in network performance due to high density and speed of mobile nodes. In this paper, through extensive simulation we evaluated the capability of AODV on how far it can react to network topology change in MWSN. We investigated the performance metrics namely packet loss and energy consumption of mobile nodes with various speed, density and route update interval (RUI). Our performance study demonstrates that by applying the existing AODV in MWSN, the results show a high percentage of packet loss and the reduction in total network energy consumption of mobile nodes if RUI is getting longer due to serious broken link caused by nodes movement. We also identify some key research problems that need to be addressed for successful implementation of AODV in MWSN.

Transmission power control in mobile wireless sensor networks: Simulation-based approach

Saving energy is a very critical issue in wireless sensor networks (WSNs) because sensor nodes have a severe resource constraints such as lack of processing power and limited in power supply. Since the communication is the most energy consuming activities in WSNs, the power use for transmission or reception of packet should be managed properly. Transmission power control (TPC) technique is one of the techniques to reduce energy consumption which has been widely studied in mobile ad-hoc networks (MANETs). This technique is implemented by adjusting the transmission power in communication between nodes. However, as mobile wireless sensor networks (MWSNs) applications emerge, the unique characteristics of this network such as severe resource constraints and frequent topology change suggest that TPC might be useful to reduce energy consumption in MWSN. Therefore, we investigate the impact of TPC on Ad hoc On-Demand Distance Vector (AODV) routing protocol for MWSNs. AODV is used as a medium of communication to assist the investigation of the effects of TPC in multihop communication in MWSNs. The simulation results show that the implementation of TPC technique has some impact on MWSNs in respect to transmission energy consumption and transmission power level required at low node mobility.

MAC protocol to reduce packet collision in wireless sensor network

Wireless sensor network (WSN) consists of a large number of sensor nodes densely deployed closed to each other. Each sensor carries out task such as monitoring and collecting data, or detecting and identifying certain events. While nodes in operation, they will detect each other and form a communication network. The problem arises when two or more nodes send data at the same times over the same channel. Here, the task of Medium Access Control (MAC) is crucial to efficiently manage the transmission among nodes and reduce collision. However, most of the MAC protocols designed for WSN are for static environment. Applying the existing MAC protocol to application such as medical care and disaster response will raise few problems where the moving node will experience delay in sending and receiving data. Thus, there is a need to design a protocol which can tolerate the node moving without degrading network performance. The aim of this paper is to evaluate the capability of MAC protocol issues especially for the popular MAC protocol for sensor network, S-MAC and IEEE 802.15.4.

A new algorithm to improve mobile sensor node connectivity based on link quality indicator

In the standard protocol IEEE 802.15.4 for Wireless Sensor Network (WSN), the moving nodes experience difficulty in maintaining the connectivity within the network because of the low range and low power. The nodes easily lose their synchronization and connectivity in the beacon-enabled mode when they move from one coordinator to another. The connectivity maintenance introduced in the standard protocol does not satisfactorily maintain the smooth connectivity but it lengthens the inaccessibility time during the coordinator switching process. The mobile nodes consume more time and energy waiting for the lost beacon frames and performing the re-association process. This condition is becoming worse in the high speed nodes which operate within a long beacon interval mode. This paper presents a technique for the mobile sensor nodes to significantly improve their connectivity in wireless sensor networks without experiencing long inaccessibility times. We introduce a technique for the mobile nodes to predict the current link quality indicator (LQI) value of a beacon frame when they fail to receive any beacon frame from the coordinator. This LQI value is used to determine the mobile nodes position within the coordinator range. Based on this position, the mobile node decides either to straightaway start the association or wait for the next beacon frame. Simulation results indicate that our proposed protocol outperforms the standard protocol, increasing connectivity time and reducing inaccessibility time during the coordinator switching process.

Improving Mobile Sensor Connectivity Time in the IEEE 802.15.4 Networks

In the IEEE 802.15.4 medium access control (MAC) protocol for wireless sensor networks, a sensor node needs to associate with a coordinator before it starts sending or receiving data. The sensor node will mostly choose the nearest coordinator to associate with. However, this method is not suitable for a constantly moving sensor node because it will end up switching coordinators too often due to short connectivity time. The IEEE 802.15.4 has a simplistic and inadequate method of choosing a coordinator in this context. In this paper, we introduce a method to increase the mobile sensor node connectivity time with its co-ordinator in IEEE 802.15.4 beacon-enabled mode. Our method is based on the timestamp of the beacons received from the nearby coordinators and filtering weak beacon signals. By choosing the coordinator which has sent the most recent received beacon with good signal quality, we increase the moving node connectivity time with the coordinator. Our technique results in significant improvement by reducing the number of times the moving node switches coordinators. This increases the throughput and reduces the wasted power in frequent associations.

Fast association process (FAP) of beacon enabled for IEEE 802.15.4 in strong mobility

In strong mobility the mobile node association with a coordinator (static or mobile) is an important part of IEEE802.15.4 protocol. This research analyzes the mobile node association attempt process flows in detail. This research also proposes an enhanced association procedure names Fast Association Process (FAP) in strong mobility. FAP is introduced with new Association_Data request MAC command that increases the association period and provides fast association process in strong mobility. It reduces the redundant service primitives, avoid collision and decrease association attempt process delay. Comparing FAP with the original IEEE802.15.4 protocol, the number of association service primitives in FAP is 67% less than the original protocol, and the simulation results show that the association attempt time decreases 75%. FAP will get fast association attempt as the number of mobile nodes increased and nodes having strong mobility. It can be widely used in mobile wireless sensor network application.

Simulation Tools for Mobile Ad-hoc Sensor Networks: A State-of-the-Art Survey

Mobile ad-hoc sensor networks (MASNETs) have recently become an important area of research for Mobile adhoc networks (MANETs) researchers. The increasing capabilities and the decreasing costs of sensors make MASNETs applications possible to be deployed in real world. However, before such application can be deployed, their performance need to be measured first. But, the use of real-world measurement is costly and time consuming. Therefore, it is more economical and practical to use simulation tools to simulate MASNETs applications. Although, there are many existing simulation tools for MANETs, most of them are not suitable for MASNETs due to resource-constraint of such networks. Therefore, it is essential to have a survey of the existing simulation tools for MASNETs. In this paper, the comparative study on different simulation tools is conducted to identify the most appropriate tool for MASNETs.

Forming a Social structure in mobile opportunistic networks

In mobile opportunistic networks, the network topology is unpredictable and very dynamic. Thus, broadcast or flooding is the best way to disseminate information. However, this approach consumes a lot of resources and introduces a duplication problem. One way to overcome this problem is to understand the relationship between the mobile nodes to guide the information dissemination flow. In this paper, we introduce three different approaches to form a node social relationship based on the node frequency interactions. The methods are Social structure based on average frequency interactions, Social Structure based on Periodicity Frequency Interactions and Social Structure based on Sliding Window. The results show that it is possible to form a social structure based on the nodes frequency interactions with other nodes. The most suitable approach to represent the nodes social relationship in opportunistic networks is the social structure based on Sliding Window approach.

Performance evaluation of ZigBee in indoor and outdoor environment

Wireless Sensor Network (WSN) comprises of many distributed independent tiny sensors that used to monitor statistical data of specific environmental conditions such as temperature, humidity, rain, pressure and many other. WSN use unlicensed 2.4 GHz Industrial, Scientific and Medical (ISM) radio frequency band for data transmission. WSN applications are being used in many industries and civilian areas, for various purposes such as environmental monitoring, habitat monitoring, traffic monitoring, precision agriculture monitoring, security monitoring, facility automation and traceability systems. Deployment of WSN in an outdoor or indoor environment always raised issue of signal loses and signal interference. In WSN, data is transmitted over wireless medium which is easily affected by external aspect such as walls, trees, heavy bushes, multiple signal interference and others. Currently, IEEE standard 802.15.4 MAC protocol and ZigBee are the most famous protocols which are been used in WSN industry. In this paper, we have performed several experiments under various conditions such as indoor, outdoor, co-existence of Bluetooth to observe the ZigBee performance and interference effects. The experiments were performed physically in real environments which showed ZigBee signal degradation under various indoor and outdoor conditions.