HomePlug AV (HPAV) was designed to provide high speed in-home communication with 200Mbps PHY rate, with the goal to overcome various noises over power wires and to jump from one phase to a neighboring one. A HomePlug AV Logical Networks (AVLN) is defined by cryptographic means, i.e. stations that share the same key and hear each other are in the same AVLN; however, AVLNs which coexist in a neighborhood cannot communicate but share the same physical layer. These points imply that people using HomePlug AV may share system throughput with neighbors without being aware of it. In order to assess the reality of this potential problem, we performed measurements on an experimental testbed with several AVLNs and equipment from different manufacturers. Our results are: 1. we verified that HomePlug AV stations can communicate even over physically separated wires, and thus neighboring stations in the same AVLN or in different AVLNs may share the same throughput; 2. when stations are placed in two different AVLNs, system performance is noticeably less compared to having the same stations at the same locations but in one single AVLN; 3. HPAV stations from different manufacturers do interoperate but experience heavy per-pair throughput outages. Our findings suggest that HPAV does not perform satisfactorily in large deployments. A possible solution to the problem would be to make different AVLNs quasi-orthogonal at the physical layer, perhaps using the cryptographic key to seed an OFDM hopping sequence.

Recent analytical and experimental work demonstrate that IEEE 802.11-based wireless mesh networks are prone to turbulence. Manifestations of such turbulence take the form of large buffer build-up at relay nodes, end-to-end delay fluctuations, and traffic congestion. In this paper, we propose and evaluate a novel, distributed flow-control mechanism to address this problem, called EZ-flow. EZ-flow is fully compatible with the IEEE 802.11 standard (i.e., it does not modify headers in packets), can be implemented using off-the-shelf hardware, and does not entail any communication overhead. EZ-flow operates by adapting the minimum congestion window parameter at each relay node, based on an estimation of the buffer occupancy at its successor node in the mesh. We show how such an estimation can be conducted passively by taking advantage of the broadcast nature of the wireless channel. Real experiments, run on a 9-node testbed deployed over 4 different buildings, show that EZ-flow effectively smoothes traffic and improves delay, throughput, and fairness performance. We further corroborate these results with a mathematical stability analysis and extensive ns-2 simulations run for different traffic workloads and network topologies.

We identify vulnerabilities in epidemic forwarding. We address broadcast applications over wireless ad-hoc networks. Epidemic forwarding employes several mechanisms such as inhibition and spread control, and each of them can be implemented using alternative methods. Thus, the existence of vulnerabilities is highly dependent on the methods used. We examine the links between them. We classify vulnerabilities into two categories: maliccious and rational. We examine the effect of the attacks according to the number of attackers and the different network settings such as density, mobility and congestion. We show that malicious attacks are hard to achieve and their impacts are scenario dependent. In contrast, rational attackers always obtain a significant benefit. The evaluation is carried out using detailed realistic simulations over networks with up to 1000 nodes. We consider static scenarios, as well as vehicular networks.

We consider the design of the MAC layer for low power, low data-rate, and impulse-radio ultra-wide band (IR-UWB) networks. In such networks, the primary concern is energy consumption rather than rate efficiency. We explore several dimensions such as power control, rate adaptation, mutual exclusion, slotted versus non-slotted operation, power saving modes and interference mitigation. We analyze the effect of these design choices on the energy consumption and rate efficiency. We use a method of energy quanta for computing the energy consumption. We find that for both cases, the optimal operation is non-coordinated and with no power control. Sources should send at their maximum power and not pay attention to neighboring nodes. However, sources should constantly adapt their transmission rate to the level of interference

IEEE 802.11 works properly only if the stations respect the MAC protocol. We show in this paper that a greedy user can substantially increase his share of bandwidth, at the expense of the other users, by slightly modifying the driver of his network adapter. We explain how easily this can be performed, in particular, with the new generation of adapters. We then present DOMINO (detection of greedy behavior in the MAC layer of IEEE 802.11 public networks), a piece of software to be installed in or near the access point. DOMINO can detect and identify greedy stations without requiring any modification of the standard protocol. We illustrate these concepts by simulation results and by the description of a prototype that we have recently implemented