Implementation and Experimental Evaluation of a Collision-Free MAC Protocol for WLANs

Collisions are a main cause of throughput degradation in Wireless LANs. The current contention mechanism for these networks is based on a random backoff strategy to avoid collisions with other transmitters. Even though it can reduce the probability of collisions, the random backoff prevents users from achieving Collision-Free schedules, where the channel would be used more efficiently. Modifying the contention mechanism by waiting for a deterministic timer after successful transmissions, users would be able to construct a Collision-Free schedule among successful contenders. This work shows the experimental results of a Collision-Free MAC (CF-MAC) protocol for WLANs using commercial hardware and open firmware for wireless network cards which is able to support many users. Testbed results show that the proposed CF-MAC protocol leads to a better distribution of the available bandwidth among users, higher throughput and lower losses than the unmodified WLANs clients using a legacy firmware.Comment: This paper was submitted to the IEEE International Conference on Communications 2015 and it is waiting for approva

μ\muNap: Practical Micro-Sleeps for 802.11 WLANs

In this paper, we revisit the idea of putting interfaces to sleep during 'packet overhearing' (i.e., when there are ongoing transmissions addressed to other stations) from a practical standpoint. To this aim, we perform a robust experimental characterisation of the timing and consumption behaviour of a commercial 802.11 card. We design $\mu$Nap, a local standard-compliant energy-saving mechanism that leverages micro-sleep opportunities inherent to the CSMA operation of 802.11 WLANs. This mechanism is backwards compatible and incrementally deployable, and takes into account the timing limitations of existing hardware, as well as practical CSMA-related issues (e.g., capture effect). According to the performance assessment carried out through trace-based simulation, the use of our scheme would result in a 57% reduction in the time spent in overhearing, thus leading to an energy saving of 15.8% of the activity time.Comment: 15 pages, 12 figure

Gaining insight on friendly jamming in a real-world IEEE 802.11 network

Frequency jamming is the fiercest attack tool to disrupt wireless communication and its malicious aspects have received much attention in the literature. Yet, several recent works propose to turn the table and employ so-called friendly jamming for the benefit of a wireless network. For example, recently proposed friendly jamming applications include hiding communication channels, injection attack defense, and access control. This work investigates the practical viability of friendly jamming by applying it in a real-world network. To that end, we implemented a reactive and frame-selective jammer on a consumer grade IEEE 802.11 access point. Equipped with this, we conducted a three weeks real-world study on the jammer's performance and side-effects on legitimate traffic (the cost of jamming) in a university office environment. Our results provide detailed insights on crucial factors governing the trade-off between the effectiveness of friendly jamming (we evaluated up to 13 jammers) and its cost. In particular, we observed - what we call the power amplification phenomenon - an effect that aggravates the known hidden station problem when the number of jammers increases. However, we also find evidence that this effect can be alleviated by collaboration between jammers, which again enables effective and minimally invasive friendly jamming

Gaining Insight on Friendly Jamming in a Real−world IEEE 802.11 Network

Frequency jamming is the fiercest attack tool to disrupt wireless communication and its malicious aspects have re-ceived much attention in the literature. Yet, several re-cent works propose to turn the table and employ so-called friendly jamming for the benefit of a wireless network. For example, recently proposed friendly jamming applications include hiding communication channels, injection attack de-fense, and access control. This work investigates the practical viability of friendly jamming by applying it in a real-world network. To that end, we implemented a reactive and frame-selective jammer on a consumer grade IEEE 802.11 access point. Equipped with this, we conducted a three weeks real-world study on the jammer’s performance and side-effects on legitimate traffic (the cost of jamming) in a university office environment. Our results provide detailed insights on crucial factors governing the trade-off between the effectiveness of friendly jamming (we evaluated up to 13 jammers) and its cost. In particular, we observed – what we call the power amplification phe-nomenon – an effect that aggravates the known hidden sta-tion problem when the number of jammers increases. How-ever, we also find evidence that this effect can be alleviated by collaboration between jammers, which again enables ef-fective and minimally invasive friendly jamming