Clock synchronization is particularly challenging in resource constrained networks. This paper presents an accurate, coherent and bandwidth efficient synchronization scheme called TurboSync. Unlike traditional solutions that synchronize pairs of nodes, TurboSync is able to synchronize entire node clusters. TurboSync relies on principal component analysis with missing data. Packets are broadcasted on the medium and their capture times at each node side are used to compute the clock conversion parameters. To have a complete and usable set of capture times for each broadcast, we propose to fill out the missing packet timestamps at the transmitters' side using an inference mechanism. TurboSync synchronizes all the clocks in the cluster at a time which leads to coherent clock conversion between nodes. Our performance results show better accuracy compared to the RBS protocol.

This paper presents an autonomic load balancing algorithm (ALBA) which enhances resource allocation in wireless local area networks (WLAN). ALBA offers autonomic management capabilities to access points that ensure the accommodation of more user traffic and an overall network capacity improvement compared to default signal strength based connectivity. Simulations with VoIP traffic over an agglomeration of WLANs show consistent behaviour among neighbouring access points and substantial performance gain in terms of call blocking rate.

With current network simulators, simulation results are obtained from flat trace files via sequential data access. To speed up simulation output analysis, we propose to store the simulation traces into data warehouse. Our proposed framework relies on a three-layer architecture, with the intermediary database layer serving the trace file post processing services. The trace files are accessed through SQL-like queries which greatly enhances the flexibility of the post processing tools. Furthermore, the database paradigm allows to separate the packets data from the nodes send and receive operations and thus to remove redundant information between simulation events. The global system relies on a new trace file format based on the popular XML language. XML pointers are used to create relationships between data so that post processing tools can navigate into simulation outputs. The tests are carried out under the MonetDB database. The obtained results show considerable response time improvement compared to traditional sequential access mode.

The widespread success of the WLAN technology raises the need for the efficient management of the different access points and the associated wireless devices, especially when multimedia and other QoS demanding applications are employed. In this paper we propose an autonomic load balancing mechanism for WLAN networks and test its applicability for a Voice over WLAN (VoWLAN) use case. The algorithm takes into account the channel utilization, the spatial distribution of wireless devices and the QoS requirements of user applications. The autonomic aspect of our algorithm is related to the use of a knowledge plane, which is a conceptual authority that entertains detailed runtime knowledge about the network state in terms of the load on each access point, as well as the connection speed and application QoS requirements of each wireless device. We use OPNET to evaluate the effectiveness of our management solution and load balancing algorithm. The paper presents the conducted simulations and ends by a critique of the general applicability of our algorithm and suggestions for future work.

The comparison and validation of MANET (mobile ad-hoc network) simulators is a difficult and little covered research area because the internal of these tools are complex. The lack of work and visibility in the domain often arouse users' negative feelings about simulation. In this article, we propose a framework dedicated to the validation, the comprehension and the analysis of MANET simulators. The system can process trace files generated by different versions of a simulator or different simulators. The solution is based on software instrumentation and the use of a standard trace format. It proposes three types of analysis: the representation of the network activity with timelines, the plotting of network metrics and the validation against the 802.11 standard specifications.