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Network Coding (NC) is a technique that enhances the performance of wireless networks by increasing the throughput and decreasing the delay. The basic idea is to exploit the mixing of signals that occurs naturally when end nodes transmit at the same time. The main challenge stands for a medium access scheduling allowing synchronized coordination between the nodes involved in that coded transmission. Most of the proposed Medium Access Control (MAC) protocols are based either on the CSMA/CA or the TDMA scheduling. The CSMA/CA based protocols suffer from synchronization issues, while the TDMA based protocols suffer from the delay due to their static design. This paper introduces a new NC MAC protocol called Dynamic Slotted Network Coding Protocol (DSNCP) based on a time scheduling to avoid the synchronization issue and uses a new design that makes the data slot assignments dynamic in order to reduce the delay. Simulation results show a significant performance gain of the proposed DSNCP compared to CSMA/CA and static TDMA protocols in terms of throughput and delay. In some scenarios, the throughput gain of the DSNCP could reach 130% and 100% compared to TDMA and CSMA/CA, respectively, and the delay gain could reach 80% and 40% compared to TDMA and CSMA/CA, respectively.

International audience; In this paper, we address the problem of QoS support in an heterogeneous multi-rate wireless mesh network. We propose a new routing metric that provides information about link quality, based on PHY and MAC characteristics, including the link availability, the loss rate and the available bandwidth. This metric allows to apprehend inter-flow interferences and avoid bottleneck formation by balancing traffic load on the links. Based on the conflict graph model and calculation of maximal cliques, we define a method to estimate the available bandwidth of a path which considers, in addition, intra-flow interferences. Finally, we propose a routing protocol that supports this metric and we study by simulation its performances compared to different existing routing metrics and protocols. The results revealed the ability of our protocol (LARM) to support the network scalability as well as its ability to choose routes with high throughput and limited delay, thus, better delivery of data traffic.

International audience; In this paper we study through simulations the impact of PHY/MAC protocols on higher layers. In a comparative way, we investigate the effectiveness of some protocols when they coexist on a wireless mesh network environment. Results show that PHY/MAC parameters have an important impact on routing performances. Based on these results, we propose two tra c-aware routing metrics based on link availability. The information about the link availability/occupancy is picked up from lower layers using a cross-layer approach. The rst metric is load-sensitive and aims to balance the tra c load according to the availability of a link to support additional ows. The second metric reproduces better the capacity of a link since it is based on its residual bandwidth. Using several real experiments, we have shown that our proposals can accurately determine better paths in terms of throughput and delay. Our experiments are carried out into an heterogeneous IEEE 802.11n based network running with OLSR routing protocol.

International audience; Current routing mechanisms proposed for adhoc networks still feasibly applied in Wireless Mesh Networks given their similarities. Many researchers have conducted numerous simulations for comparing the performances of these routing protocols under various conditions and constraints. Most made comparisons are not aware of PHY/MAC layers and their impact on routing performances. In this paper we study through simulations the impact of PHY/MAC protocols on higher layers. The considered protocols include three propagation models, ie., FreeSpace, TwoRayGround and Shadowing, three different PHY/MAC protocols specified IEEE 802.11 standards namely, 802.11b, 802.11s and 802.11n, and finally three routing protocols, ie., AODV, OLSR and HWMP. In a comparative way, we investigate the effectiveness of these protocols when they coexist on a wireless mesh network environment. Our results show that the routing strategy can significantly impact the network performance only if it is strongly linked to the characteristics of the lower layers.