Lan Tien Nguyen

An energy efficient routing scheme for mobile wireless sensor networks

Research on wireless sensor networks has recently received much attention as they offer an advantage of monitoring various kinds of environment by sensing physical phenomenon. Among various issues, energy consumption is one of the most important criteria for routing protocol in wireless sensor networks (WSNs). This paper introduces an energy efficient clustering algorithm for mobile sensor network based on the LEACH protocol. The proposed protocol adds feature to LEACH to support for mobile nodes and also reduces the consumption of the network resource in each round. The proposed protocol is simulated and the results show a significant reduction in network energy consumption compared to LEACH.

A load-aware routing metric for wireless mesh networks

Routing metrics play a critical role in wireless mesh networks (WMNs). Several metrics have already been proposed but none of them can effectively capture both local traffic load and hidden node issues. This paper proposes a load and interference-aware routing metric for wireless mesh networks, named contention window based (CWB) metric. Our metric assigns weights to individual links based on both channel utilization and the average contention window used on these links. The individual link weights are combined into path metric that accounts for load balancing and interference between links that use the same channel. Thus the CWB metric helps the routing protocol to balance traffic and improve network capacity by avoiding routing traffic through congested areas. The preliminary quantitative experiments show significant improvement over hop-count based method when using the proposed metric.

A Multi-Purpose Wireless Network Emulator: QOMET

In this paper we present the design and usage of the multi-purpose wireless network emulator that we develop, QOMET. QOMET implements a two-stage scenario-driven approach to wireless network emulation. We give here the details of the improved model and additional functionality that make it currently possible to use QOMET to convert a real- world scenario to a sequence of network-condition descriptors for a wide range of experiments. QOMET was used on a real network testbed to perform experiments involving emulated 802.11 a/b/g WLAN technology over wired networks for several types of scenarios. We shall illustrate this in the final part of the paper, with emphasis on networked robot emulation.

QOMET: A Versatile WLAN Emulator

In this paper we present the design of QOMET, the wireless LAN (WLAN) emulator that we develop. Our approach to WLAN emulation is a versatile two-stage scenario-driven design. In the first stage a real-world scenario representation provided by the user is converted successively into physical, data link and network layer effects that correspond to the emulated WLAN scenario. The output of the first stage is a description of the network states at successive moments of time, which is used in the second stage to accurately reproduce the wireless environment conditions by means of a wired-network emulator. We give here the details of the overall model that makes it possible to accomplish this conversion in QOMET. We then present our test methodology and illustrate our approach by several experimental results.

QOMB: A Wireless Network Emulation Testbed

In this paper we present QOMB, a testbed we designed and implemented for the evaluation of wireless network systems, protocols and applications. The testbed uses the wireless network emulation set of tools QOMET so as to reproduce in a wired network, in real time, the wireless network conditions corresponding to a given scenario. In this context QOMET also provides support for features such as realistic virtual 3D environments, and node mobility generation. The infrastructure of QOMB is StarBED, the large-scale network experiment testbed at the National Institute of Information and Communications Technology, Hokuriku Research Center, in Ishikawa, Japan. The multi-hop wireless network emulation experimental results related to OLSR performance analysis in mesh networks and MANETs illustrate the main features and the usability of QOMB.

An interference and load aware routing metric for Wireless Mesh Networks

This paper proposes a load and interference-aware routing metric for wireless mesh networks, named Channel Utilisation and Contention Window Based (C2WB) metric. Our metric assigns weights to individual links which are proportional to the links service times estimated from both channel utilisation and the average contention window of the CSMA/CA mechanism. The path metric, combined from individual link weights, accounts for both load and interference of the links on the path. Thus the C2WB metric helps the routing protocol to balance the traffic and to improve the network capacity by avoiding routing the traffic through congested areas.

Performance analysis of IEEE 802.11 in multi-hop wireless networks

Multi-hop wireless networks provide a quick and easy way for networking when we need a temporary network or when cabling is difficult. The 802.11 Medium Access Control (MAC) plays an important role in the achievable system performance. There have been many studies on analytic modeling of single-hop 802.11 wireless networks but only a few on the analysis of multihop wireless networks. Furthermore, the object of these researches is an homogeneous ad-hoc wireless networks; therefore they are not appropriate for a network with structure such as wireless mesh networks. This paper introduces an analytic model of throughput performance for the IEEE 802.11 multi-hop networks, which allows us to compute the achievable throughput on a given path in multi-hop wireless networks. The model shows that there is an optimal point at which throughput is maximized. Using this model and a Markov model for modeling the operation of the IEEE 802.11 DCF we can determine the amount of data that each node should inject to the network to get the best throughput performance.

QOMB wireless network emulation testbed: evaluation and case study

This paper presents several evaluation tests, as well as a case study of large-scale wireless network emulation experiments performed using QOMB, the wireless network emulation testbed at the National Institute of Information and Communications Technology, Hokuriku Research Center in Ishikawa, Japan. The evaluation tests demonstrate the accuracy of wireless network emulation using QOMB in single and multi-hop settings, as well as in scenarios involving node mobility. The large-scale experiments illustrate the most important features of QOMB and its versatility by an OLSR protocol study in a MANET scenario including 50 emulated mobile nodes.

Multi-hop Wireless Network Emulation on StarBED

In this paper, we present an architecture to emulate multi-hop wireless networks on StarBED, a wired-network testbed at Hokuriku Research Center of NICT, Japan. The architecture uses a distributed approach, and it can effectively emulate in real time the properties of WLAN contention-based media access mechanism.

Application performance assessment on wireless ad hoc networks

Using ad hoc networks as alternative means of communication in disaster situations is a salutary solution. However, analysing application performance is mandatory for evaluating such a possibility. In this paper we present the two aspects of our approach to application performance assessment on wireless ad hoc networks. The first aspect refers to real-world tests in which we quantify objectively the relationship between network conditions and application performance. The second aspect is represented by the wireless network (WLAN) emulator that we design to run on StarBED, the large-scale network experiment environment of the Hokuriku Research Centre in Ishikawa, Japan. By combining these two aspects we perform experiments with real applications, while having full control of the network conditions in which the application is tested (when using emulation).