Michel Marot

Understanding topology challenges in the implementation of wireless sensor network for cold chain

This article presents the real difficulties and topological challenges while deploying the sensor networks for cold chain. At the highest level of deployment of a network, not only do we have to decide about the routing, but also have to come up with realistic scenarios. Link Quality based routing algorithms are used most of the time. In this context, routing parameters work well in simulation or in favorable conditions, but have limitations when we deploy them in the real network, especially when we have asymmetric links between the sensors. One of the answers is to add a few nodes with a high transmission power level which can act as the clusterhead and indeed these nodes really stabilize the system.

Modeling interactive real-time applications in VANETs with performance evaluation

Vehicular Ad-Hoc Network (VANET) is an emerging technology, which provides intelligent communication between mobile vehicles. Integrating VANET with Ubiquitous Sensor Networks (USN) has a great potential to improve road safety and traffic efficiency. Most VANET applications are applied in real time and they are sensitive to delay, especially those related to safety and health. Therefore, checking the applicability of any proposed application is very important. One way to achieve that is by calculating the Round Trip Time (RTT), which is the time taken by a VANET application starting from the initiator node (source vehicle) sending a message until receiving a response from the core network. In this paper, we present a new complete analytical model to calculate the RTT of VANET applications. Moreover, we introduce a novel detailed network architecture for VANET applications using the IP Multimedia Subsystem (IMS) as a service controller in the USN environment. To the best of our knowledge, there is no previous published work that either studied the RTT of VANET applications or developed a complete architecture to implement them by integrating VANETs with USNs and IMS. The RTT is calculated by combining two analytical models. Firstly, we developed an analytical model to calculate the time needed for the communication between two nodes on a road. Secondly, we developed a queuing model using Baskett Chandy Muntz Palacios (BCMP) queuing network for the IMS servers to calculate the applications execution time in the core network. These models are general enough to be applied to any VANET application. Finally, to assess the validity and the accuracy of the proposed architecture and models, we used three different tools: C++, MATLAB, and OPNET. The analytical results were compared to the simulation results to evaluate their consistency.

HybridLQI: Hybrid MultihopLQI for Improving Asymmetric Links in Wireless Sensor Networks

The article proposes HybridLQI to improve the performance of MultihopLQI in the asymmetrical wireless links sensor networks. Every node can maintain the number of messages it sends to each of its neighbours and how many of them are acknowledged, the packet loss percentage over the links can be calculated. Link Quality Indicator (LQI) is used to estimate the downlink channel. Therefore, without adding any extra cost to the network, the bi-directional channel quality can be calculated. Asymmetrical links are created by setting the Base Station transmitting at higher power than the other nodes. This approach in a dense network improves message received percentage by up to 20% for the whole network. For sparse asymmetrical links networks with nodes in straight line and having direct line of sight, this approach improves the packet reception percentage by up to 350% for the node which is 3 hops away from the Base Station. All the results are based on the experiments performed on the real platform.

Hybrid multi-channel multi-hop MAC in VANETs

In this paper, we propose a Hybrid Multi-Channel Multi-hop Medium Access Control (HMM-MAC) meeting the safety and non-safety requirements in Vehicular Ad-hoc Networks when no infrastructure is present (V2V communication) with only a single transceiver at each vehicle. The simulation results showed that our scheme could achieve a higher delivery ratio of road safety messages and a high probability to select a free transmission channel in a certain region and during a certain time.

Improving clustering techniques in wireless sensor networks using thinning process

We propose a rapid cluster formation algorithm using a thinning technique : rC-MHP(rapid Clustering inspired from Matern Hard-Core Process). In order to prove its performance, it is compared with a well known cluster formation heuristic: Max-Min. Experimental results show that rC-MHP outperforms Max-Min in terms of messages needed to choose the cluster head, cluster head maintenance and memory requirement, comprehensively in sparse as well as in dense networks. We show that rC-MHP has a scalable behavior and it is very easy to implement. rC-MHP can be used as an efficient clustering technique.

Virtual base station election for wireless sensor networks

In a classical wireless sensor network, a base station is often present to ensure efficient data collection. Endowed with typical hardware feature, especially with high energy level and good stockpiling capabilities, the base station completes the architecture as a required component for a wide range of applications. However, there are some projects where base station deployment should be avoided without reducing network efficiency. Thus, in a cold chain supervision project, itŠs not necessary to add base station to a wireless sensors network deployed inside a food or a medical truck. In this manner, it is a low-budget sensors network deployment. Moreover, such applications have to replicate data across all nodes and to maintain same information as well. In this paper, we propose databases updating model for homogeneous wireless sensors network deployed in a food truck without any base station. In this model, Virtual Base Station (VBS) is the node which is elected to act as classical base station during a specific period of time. Virtual Base Station (VBS) electionŠs algorithm is based on the remaining energy for each node and latest Virtual Bases Station (VBS) to reduce overall energy spent by network. Simulation results (using MATLAB) show that VBS model introduces very low overhead with respect to the classical network with permanent Base Station (BS).

Network planning tool based on network classification and load prediction

Real Call Detail Records (CDR) are analyzed and classified based on Support Vector Machine (SVM) algorithm. The daily classification results in three traffic classes. We use two different algorithms, K-means and SVM to check the classification efficiency. A second support vector regression (SVR) based algorithm is built to make an online prediction of traffic load using the history of CDRs. Then, these algorithms will be integrated to a network planning tool which will help cellular operators on planning optimally their access network.

Cross-Layer Algorithm for VOIP Applications over Satellite

It is proved that the normal suite of the TCP/IP protocols works well when it is used in terrestrial networks transporting real time applications. The situation is quite different when wireless networks are used for the same services; their susceptibility to errors, losses as well as the existing delay cause a degradation in the overall performance. Due to the existing demand to interconnect terrestrial networks with satellite communications using DVB-S2/DVB-RCS standards, the satellite link poses a challenge which is to overcome the problems mentioned when applications as voice over IP (VOIP) are considered. In the same context, cross-layer mechanisms are being used successfully in ad-hoc networks. They propose interactions between layers different from the traditional ones in the protocol stack. These mechanisms provide a fast and better way to exchange parameters, drawing as a result a good option to improve the performance in wireless networks. This work proposes an innovative algorithm to adapt dynamically the coding for VOIP applications over satellite using a cross layer interaction between the application and network layers in order to improve the throughput and the perceived quality. This interaction with the network layer indirectly takes into account the state of the MAC and physical layers.

Dynamic link adaptation based on coexistence-fingerprint detection for WSN

Operating in the ISM band, the wireless sensor network (WSN) risks being interfered by other concurrent networks. Our concerns are the technologies that do not perform listening before transmission such as Bluetooth, and the ones that do not detect other technologies due to their channel sensing techniques like WiFi. To overcome this issue a WSN node should be able to identify the presence of such technologies. This will allow deducing the characteristics of the generated traffic of these technologies, and thus the behavior of the channel can be predicted. These predictions would help to trigger adequate reactions as to avoid or synchronize with the concurrent networks. Many works exist on link adaptation, but they concern blind adaptations which are unintelligent and solve momentarily the problem that may reappear over time. In this paper, we perform several experiments on a real testbed to categorize the model of the bit errors in corrupted received packets. These experiments are performed under different conditions of channel noise and interferences. This allows us to identify each corruption pattern as a fingerprint for the interfering technology. Then we propose the Fingerprint Identification Mechanism (FIM) to identify on the fly the source of the corruption. With an implementation on “Tmote Sky” motes using Tinyos1.x, We demonstrate the use of FIM for link adaptation in a coexistence environment. Our mechanism led to throughput improvements of 87%-100% depending on the transmission rate and channel quality.

Optimal and Cost Efficient Algorithm for Virtual CDN Orchestration

Virtual Content Delivery Network (vCDN) orchestration is necessary to optimize the use of resources and improve the performance of the overall SDN/NFV-based CDN function in terms of network operator cost reduction and high streaming quality. It requires intelligent and enticed joint SDN/NFV orchestration algorithm due to the evident huge amount of traffic to be delivered to end customers of the network. In this paper, a global vCDN architecture and an exact approach for finding the optimal path orchestration(s) and vCDN component instantiation(s) (OCPA) are proposed. Moreover, several scenarios are considered to quantify the OCPA behavior and to compare its efficiency in terms of caching and streaming cost, orchestration time, vCDN replication number, and other cost factors. Then, it is implemented and evaluated under different deployment flavors. Several scenarios are considered to study the algorithm’s behavior and to quantify the impact of both network and system parameters.