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

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

Capacity and coverage of mmWave ad hoc networks

textAd hoc networks provide a flexible, infrastructure-free means to communicate between soldiers in war zones, aid workers in disaster areas, or consumers in device-to-device (D2D) applications. Ad hoc networks, however, are stilled plagued by interference. Communication with millimeter-wave (mmWave) devices offers hope to ad hoc networks through higher bandwidth, reduced interference due to directional antennas, and a lighter interference field due to blockage. This report uses a stochastic geometry approach to characterize the one-way and two-way coverage probability of a mmWave ad hoc network with directional antennas and random blockages. The coverage probability in the presence of noise and both line-of-sight and non-line-of-sight interference is analyzed and used to derive the transmission capacity. Several reasonable simplifications are used to derive the transmission capacity. Performance of mmWave is then analyzed in terms of area spectral efficiency and rate coverage. The results show that mmWave networks support larger densities, higher area spectral efficiencies, and better rate coverage compared to microwave ad hoc networks.Electrical and Computer Engineerin

Accuracy evaluation of probabilistic location methods in UWB-RFID systems

The present project is focused on investigating the achievable accuracy of classical location methods commonly used in wireless and proposing an alternative location method based on combining two of them. The first part of the project studies the advantages and disadvantages of extending Ultra Wideband and Radiofrequency Identification technologies on some classical location methods. As a result of the study and with the goal of improving accuracy in indoor radio propagation channels, the Received Strength Signal-based location method and the Time Difference Of Arrival-based location method are selected to be combined in the alternative location method, including the proper channel models. This combined location method takes advantage of the virtues of each location method and combines information in order to improve the estimation of one target's position when locating in indoor channel. The second part of the project is devoted to analyse and simulate the modified RSS, TDOA and Combined location methods, considering the randomness of a real multipath fading channel. Results show that the Combined location method performs always the best accuracy. Specifically in analytical study, the combined location method provides a deterministic error of 24 cm which represents an improvement of 54% and 15% of the RSS and TDOA accuracies respectively. In the simulated study, results show that it is able to improve the accuracy up to 46% and 85% of the RSS and TDOA respectively in specific evaluated points

Accuracy evaluation of probabilistic location methods in UWB-RFID systems

The present project is focused on investigating the achievable accuracy of classical location methods commonly used in wireless and proposing an alternative location method based on combining two of them. The first part of the project studies the advantages and disadvantages of extending Ultra Wideband and Radiofrequency Identification technologies on some classical location methods. As a result of the study and with the goal of improving accuracy in indoor radio propagation channels, the Received Strength Signal-based location method and the Time Difference Of Arrival-based location method are selected to be combined in the alternative location method, including the proper channel models. This combined location method takes advantage of the virtues of each location method and combines information in order to improve the estimation of one target's position when locating in indoor channel. The second part of the project is devoted to analyse and simulate the modified RSS, TDOA and Combined location methods, considering the randomness of a real multipath fading channel. Results show that the Combined location method performs always the best accuracy. Specifically in analytical study, the combined location method provides a deterministic error of 24 cm which represents an improvement of 54% and 15% of the RSS and TDOA accuracies respectively. In the simulated study, results show that it is able to improve the accuracy up to 46% and 85% of the RSS and TDOA respectively in specific evaluated points