Investigation of Wireless Channel Asymmetry in Indoor Environments

Asymmetry is unquestionably an important characteristic of the wireless propagation channel, which needs to be accurately modeled for wireless and mobile communications, 5G networks, and associated applications such as indoor/outdoor localization. This paper reports on the potential causes of propagation asymmetry. Practical channel measurements at Khalifa University premises proved that wireless channels are asymmetric in realistic scenarios. Some important conclusions and recommendation are also summarized.Comment: Accepted in IEEE International Symposium on Antennas and Propagation (APS17), San Diego, California, 9-14 Jul. 2017. arXiv admin note: substantial text overlap with arXiv:1704.0687

A Joint Model for IEEE 802.15.4 Physical and Medium Access Control Layers

Many studies have tried to evaluate wireless networks and especially the IEEE 802.15.4 standard. Hence, several papers have aimed to describe the functionalities of the physical (PHY) and medium access control (MAC) layers. They have highlighted some characteristics with experimental results and/or have attempted to reproduce them using theoretical models. In this paper, we use the first way to better understand IEEE 802.15.4 standard. Indeed, we provide a comprehensive model, able more faithfully to mimic the functionalities of this standard at the PHY and MAC layers. We propose a combination of two relevant models for the two layers. The PHY layer behavior is reproduced by a mathematical framework, which is based on radio and channel models, in order to quantify link reliability. On the other hand, the MAC layer is mimed by an enhanced Markov chain. The results show the pertinence of our approach compared to the model based on a Markov chain for IEEE 802.15.4 MAC layer. This contribution allows us fully and more precisely to estimate the network performance with different network sizes, as well as different metrics such as node reliability and delay. Our contribution enables us to catch possible failures at both layers.Comment: Published in the proceeding of the 7th International Wireless Communications and Mobile Computing Conference (IWCMC), Istanbul, Turkey, 201

Improving Resource Efficiency with Partial Resource Muting for Future Wireless Networks

We propose novel resource allocation algorithms that have the objective of finding a good tradeoff between resource reuse and interference avoidance in wireless networks. To this end, we first study properties of functions that relate the resource budget available to network elements to the optimal utility and to the optimal resource efficiency obtained by solving max-min utility optimization problems. From the asymptotic behavior of these functions, we obtain a transition point that indicates whether a network is operating in an efficient noise-limited regime or in an inefficient interference-limited regime for a given resource budget. For networks operating in the inefficient regime, we propose a novel partial resource muting scheme to improve the efficiency of the resource utilization. The framework is very general. It can be applied not only to the downlink of 4G networks, but also to 5G networks equipped with flexible duplex mechanisms. Numerical results show significant performance gains of the proposed scheme compared to the solution to the max-min utility optimization problem with full frequency reuse.Comment: 8 pages, 9 figures, to appear in WiMob 201

Practical service placement approach for microservices architecture

Community networks (CNs) have gained momentum in the last few years with the increasing number of spontaneously deployed WiFi hotspots and home networks. These networks, owned and managed by volunteers, offer various services to their members and to the public. To reduce the complexity of service deployment, community micro-clouds have recently emerged as a promising enabler for the delivery of cloud services to community users. By putting services closer to consumers, micro-clouds pursue not only a better service performance, but also a low entry barrier for the deployment of mainstream Internet services within the CN. Unfortunately, the provisioning of the services is not so simple. Due to the large and irregular topology, high software and hardware diversity of CNs, it requires of aPeer ReviewedPostprint (author's final draft

Exploring Symmetry in Wireless Propagation Channels

Wireless communications literature is very rich with empirical studies and measurement campaigns that study the nature of the wireless propagation channel. However, despite their undoubted usefulness, many of these studies have omitted a fundamental yet key feature of the physical signal propagation, that is, wireless propagation asymmetry. This feature does not agree with the electromagnetic reciprocity theorem, and the many research papers that adopt wireless channel symmetry, and hence rendering their modeling, unexpectedly, inaccurate. Besides, asymmetry is unquestionably an important characteristic of wireless channels, which needs to be accurately characterized for vehicular/mobile communications, 5G networks, and associated applications such as indoor/outdoor localization. This paper presents a modest and a preliminary study that reports potential causes of propagation asymmetry. Measurements conducted on Khalifa University campus in UAE show that wireless channels are symmetric in the absence of symmetry impairments. Therefore, care should be taken when considering some practical wireless propagation scenarios. Key conclusions and recommendation are summarized. We believe that this study will be inspiring for the academic community and will trigger further investigations within wireless propagation assumptions.Comment: Accepted in IEEE European Conference on Networks and Communications (EuCNC17), Oulu, Finland,12-15 Jun. 201

Not All Wireless Sensor Networks Are Created Equal: A Comparative Study On Tunnels

Wireless sensor networks (WSNs) are envisioned for a number of application scenarios. Nevertheless, the few in-the-field experiences typically focus on the features of a specific system, and rarely report about the characteristics of the target environment, especially w.r.t. the behavior and performance of low-power wireless communication. The TRITon project, funded by our local administration, aims to improve safety and reduce maintenance costs of road tunnels, using a WSN-based control infrastructure. The access to real tunnels within TRITon gives us the opportunity to experimentally assess the peculiarities of this environment, hitherto not investigated in the WSN field. We report about three deployments: i) an operational road tunnel, enabling us to assess the impact of vehicular traffic; ii) a non-operational tunnel, providing insights into analogous scenarios (e.g., underground mines) without vehicles; iii) a vineyard, serving as a baseline representative of the existing literature. Our setup, replicated in each deployment, uses mainstream WSN hardware, and popular MAC and routing protocols. We analyze and compare the deployments w.r.t. reliability, stability, and asymmetry of links, the accuracy of link quality estimators, and the impact of these aspects on MAC and routing layers. Our analysis shows that a number of criteria commonly used in the design of WSN protocols do not hold in tunnels. Therefore, our results are useful for designing networking solutions operating efficiently in similar environments