Abstract
Wireless Underground Networks (WUNs) include communications links between buried nodes and between buried and aboveground nodes. WUNs have many applications, such as border surveillance, agriculture monitoring, and infrastructure monitoring. Recent studies have shown that they are feasible and have deployment advantages over wired networks. Yet, so far WUNs evaluations have been done using testbeds only, and a tool enabling simulations on TCP/IP WUNs is lacking. We propose a simulator of TCP/IP wireless underground networks based on ns-3. The simulator was validated against experimental results for 433 MHz and 2.4 GHz frequency bands. The results show its accuracy for most of the communications scenarios. © 2014 IEEE.

Abstract
Interference is a fundamental issue in wireless mesh networks (WMNs) and it seriously affects the network performance. In this paper we characterize the power interference in IEEE 802.11 CSMA/CA based wireless mesh networks using directional antennas. A model based centralized call admission control (CAC) scheme is proposed which uses physical collision constraints, and transmitter-side, receiver-side and when-idle protocol collision prevention constraints. The CAC assists to manage requests from users depending on the available bandwidth in the network: when a new virtual link establishment request from a user is accepted into the network, resources such as interface, bandwidth, transmission power and channel are allocated in the participating nodes and released once the session is completed. The proposed CAC is also able to contain the interference in the WMN by managing the transmission power of nodes.

Abstract
Real-time monitoring applications may generate delay sensitive traffic that is expected to be delivered within a firm delay boundary in order to be useful. In this context, a previous work proposed an End-to-End Delay (EED) estimation mechanism for Wireless Sensor Networks (WSNs) to preview potential useless packets, and to early discard them in order to save processing and energy resources. Such estimation mechanism accounts delays using timers that make use of an Exponentially Weighted Moving Average (EWMA) function where the smoothing factor is a constant defined prior to the WSN deployment. Later experiments showed that, in order to enhance the estimation results, such smoothing factor should be defined as a function of the network load. The current work proposes an optimization of the previous estimation mechanism that works by evaluating the network load and by adapting the smoothing factor of the EWMA function accordingly. Results show that this optimization leads to a more accurate EED estimation for different network loads.

Abstract
This paper describes the evaluation of a multi-hop wireless networking solution for Smart Grid metering in an industrial environment. The solution relies on RPL, 6LoWPAN, and IEEE 802.15.4g protocols, and has been implemented using low-power and low-capacity devices. Also, it supports both TCP and UDP protocols to transport traffic from DLMS/COSEM Smart Grid metering applications. The experimental tests took place in an industrial environment during 20 days. The obtained results allowed the characterization and evaluation of the developed solution and can be used as a basis to evaluate other 6LoWPAN/IEEE 802.15.4g networking solutions.

Abstract
Wireless Underground Networks (WUN) have many applications, such as border surveillance, agriculture monitoring, and infrastructure monitoring. Recent studies have shown that they are feasible and have deployment advantages over wired networks, but only a few WUN evaluations in multiple access scenarios have been done. This paper presents a simulation study on medium access for a WUN with 4 nodes buried, and one node aboveground. The simulations were carried out using the ns-3 simulator and they evaluate both Wi-Fi, and Lr-Wpan networks for dry and wet soils. We verified that for the same number of concurrent nodes, the use of the RTS/CTS mechanism has a much higher influence than the soil water content. Furthermore, a study about the feasibility of using Wi-Fi fingerprinting for positioning above the ground based on the buried infrastructure revealed promising results.

Abstract
Radio Frequency (RF) communications su.er high attenuation underwater, limiting the range of standard IEEE 802.11 networks to a few centimeters underwater. The usage of custom RF solutions at lower frequencies to increase range entails high development costs, and proprietary hardware. This paper evaluates the performance of cost-e.ective, mass-market IEEE 802.11 networks underwater at di.erent frequencies in the sub-GHz bands using Software Defined Radio platforms. Optimizations to the gr-ieee802.11 implementation, together with custom designed antennas, allowed the testing of frequencies in the 70-700 MHz range, in a large-scale freshwater tank, and in real-world, seawater conditions in Tagus river estuary. Results show a frequency-dependent communications range up to 5 m in freshwater and 1.8 m in seawater, with bitrates up to 550 kbit/s and delay under 45 ms. This proves the feasibility of IEEE 802.11 networks in the sub-GHz bands for applications such as video streaming from an autonomous underwater vehicle and underwater sensors. Copyright 2015 ACM.