Multicast video streaming over multirate wireless LANs imposes strong demands on video codecs and the underlying network. It is not sufficient that only the video codec or only the underlying protocols adapt to changes in the wireless link quality. Research efforts should be applied in both and in a synchronized way. Cross layer design is a new paradigm that addresses this challenge by optimizing communication network architectures across traditional layer boundaries. This paper presents cross-layer architecture for adaptive video multicast streaming over multirate wireless LANs where layer-specific information is passed in both directions, top-down and bottom-up. The authors jointly consider three layers of the protocol stack: the application, data link and physical layers. The authors analyze the performance of the proposed architecture and extensively evaluate it via simulations. The results show that the real-time video quality of the overall system can be greatly improved by cross-layer signaling.

During the past few years, the development of video services over wireless networks has been driven by Quality of Service (QoS) parameters and service level agreements. Even though QoS parameters, such as packet losses, jitter and delays are good indicators of the service provided by the underlying network services to the applications, they fall short on providing a better measure of the Quality of Experience (QoE) to the end-user. In order to gain a better understanding of the benefits in terms of the QoE guarantees, it is essential to evaluate the effectiveness of the enabling protocol mechanisms. In this paper, we introduce a novel multicast service for the IEEE 802.11 WLAN standard. The proposed service combines a novel MAC scheme and layered video, guaranteeing a minimum acceptable video quality to all the members of the multicast group through the base layer. To avoid penalizing the users capable of receiving data at higher rates and the performance of an IEEE 802.11 WLAN, the enhancement layers are transmitted using a higher transmission rate. We show that by properly coupling the video and multicast control mechanisms, the QoS as well as the QoE requirements of the end-user can be guaranteed. The performance of the proposed system architecture is extensively investigated by simulations and through numerical evaluation of relevant QoS and QoE metrics. Furthermore, our results show that the real-time video streaming quality of the total system can be greatly improved while keeping downward compatibility with the IEEE 802.11 multicast mechanism.

Current 802.11-based WLANs are asked to support an ever increasing number of services and applications, each of them characterized by a diverse set of requirements in terms of bitrate, latency, and reliability. Network virtualization and programmability are two emerging trends that can support the realization of such a vision in a cost-effective fashion. In this paper we introduce Lasagna, a novel end-to-end solution that enables flexible management of slices encompassing both the wired and the wireless segments of an Enterprise WLAN. Lasagna allows flexible management of network slices to meet their respective service requirements. An experimental evaluation carried out over a real-world testbed shows that Lasagna can ensure both functional and performance isolation between the different slices and efficient radio resource utilization. We release the entire implementation including the controller and the datapath under a permissive license for academic use.

The ever-increasing demand for mobile content delivery and multimedia services is bringing renewed interest in multicast communications in Wi-Fi based WLANs. Nevertheless, multicast over Wi-Fi raises several challenges including low data rates and coexistence issues with other unicast streams. Some amendments to the Wi-Fi standard, such as 802.11aa, have introduced new delivery schemes for multicast traffic as well as finer control on the low-level aspects of the 802.11 medium access scheme. However, the logic for using such features is left to the implementer of the standard. In this paper, we present SDN@Play Mobile, a novel SDN-based solution for joint mobility management and multicast rate-adaptation in Wi-Fi networks. The solution builds upon a new abstraction, named Transmission Policy, which allows the SDN controller to reconfigure a multicast transmission policy when its optimal operating conditions are not met. An experimental evaluation carried out over a real-world testbed shows that our approach can deliver significant improvements in terms of both throughput and channel utilization compared to the legacy 802.11 multicast scheme. Finally, we release the entire software implementation under a permissive APACHE 2.0 license for academic use.

With the deployment of Audio-Video (AV) services and the flexibility offered by wireless networks, there is more and more an increasing interest on defining more reliable multicast mechanisms. Towards this end, the IEEE Task Group aa (TGaa) is currently working on the definition of the IEEE802.11aa amendment. The standardization efforts in this area aim to develop efficient QoS mechanisms by keeping in mind that any new mechanism should: 1) properly interoperate with the already existing unicast mechanisms; and 2) provide the robustness required by AV applications. In order to meet the former, the efforts are focusing on amending the existing multicast standard while to meet the latter there is a need of better understanding the stringent requirements of AV streaming applications. In this work, after reviewing the amendments introduced by the IEEE 802.11aa, we carried out an evaluation of the proposed multicast mechanisms when supporting video streaming applications. The main contribution of this work focuses therefore on evaluating the QoS parameters that the TGaa has taken into account to define the proposed mechanisms.

The original version of the IEEE 802.11 standard is not able to provide the required Quality of Service (QoS) for real-time applications. The IEEE 802.11e amendment was developed to overcome this situation, introducing the Enhanced Distributed Channel Access (EDCA) as a new channel access method. This method makes it possible to prioritize the different types of traffic through a group of Medium Access Control (MAC) parameters. The most important role of these MAC parameters is played by the Arbitration Inter-Frame Space Number (AIFSN). Although the AIFSN can be modified during a transmission, the commercial Access Points (APs) only use the combination defined in the standard. Therefore, we propose a new adaptation scheme for network traffic priorities involving the construction of a J48 decision tree classifier with the main goal of enhancing the voice and video communications. This classifier calculates a new set of AIFSN values by taking into account the current network conditions, maintaining the interoperability with the legacy Distributed Coordination Function (DCF) applications. The results show that our proposal improves upon the voice+video performance results obtained by the AIFSN standard values by up to 20%. Furthermore, this scheme is fully compatible with the commercial network cards available on the market.