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With exponential growth in the number of wireless devices and limited available spectrum, the problem of spectrum sharing remains in forefront of the research community. Due to the large number of wireless sensing devices, even a small percentage of savings can translate into significant spectrum efficiencies. One of the main hurdles in efficient spectrum sharing in wireless sensor networks (WSN) is the problem of power management at the node level to promote longevity without polluting the spectrum, while promoting collaboration. This problem is even more challenging in extreme (harsh) environments where access to power and battery replacement and charging is limited, if not impossible. Passive sensor technology can be used to eliminate the need for batteries, but it suffers from short communication range. Recently, wireless energy transfer (WET) for powering remote sensor nodes in a WSN has drawn considerable research attention, since it can charge sensing circuits remotely and relieve the need for battery replacement. Modeling the charging and power utilization processes can help with smart transmission decisions, which can eliminate unnecessary transmissions and not only save limited battery power at the node level, but also efficiently utilize the shared spectrum. In this paper, we consider a general relay energy assisted scenario, where a transmitter is powered by an energy source through both direct and relay links. We model data and energy channels separately, transmit energy to power the transmitter battery and schedule data transmission based on stochastic models for data. We also consider various static, mobile and highly scattered channel models. We will set a threshold on required transmission energy and channel quality to decide whether the transmission can be successful (efficient use of spectrum) or the packet may not reach the destination (polluting the spectrum unnecessarily). An energy efficient scheduling method is proposed for the system model to determine whether to transmit data or stay silent based on the stored energy level and channel state. An analytical expression has been derived to approximate outage probability of the system in terms of energy and data thresholds. All theoretical results are validated by numerical simulations and verify the effectiveness of energy relaying and proposed energy efficient scheduling method in reducing the outage probability of the system [ABSTRACT FROM AUTHOR]

Grant-free media access is vital for applications in Industrial IoTs (IIoTs), where stringent delays are required. Recently, due to the capability of supporting parallel receptions, Non-Orthogonal Multiple Access (NOMA) has gained research interests in IIoTs. Obviously, combining them organically is beneficial for enhancing the delay performances. In this paper, for a typical convergecast wireless network where its data sink is NOMA-based, we propose a grant-free MAC (Media Access Contention) scheme based on Compressive Sensing in Busy Tone Channel (CSiBTC), by exploiting the transmission sparsity in IIoTs. First, a to-be transmitter acquires the identities of active transmitters with the proposed CSiBTC scheme completely by itself. Two construction methods for CSiBTC are proposed for two distinct application scenarios respectively. Then, given the locations of all wireless sensors and the data sink in the network, the to-be transmitter can find out if it is eligible for starting its transmission without impairing the on-going transmissions. The scheme is grant-free and makes the most use of the parallel reception capability of NOMA, and therefore both the delay performance and throughput performance can be improved with respect to the general CS-based MAC. Performance evaluations also strongly support the above conclusions. [ABSTRACT FROM AUTHOR]

Underwater acoustic channel, characterized by long propagation delay and low data rate, suffers from space time uncertainty which causes spatial unfairness in underwater sensor network. In this paper, we propose a spatially fair MAC protocol which divides all neighbor nodes of a receiving node into two groups based on their average propagation delay. The receiver then permits two different transmitters from each group by taking consideration of their earliest transmission time such that data packets sent from the two transmitters will never collide at the receiver end. A simulation model is developed to evaluate the performance of our proposed scheme. Simulation results show that the proposed scheme achieves better performance in terms of average RTS collision, network throughput and CTS success rate compared to the contemporary MAC protocols. [ABSTRACT FROM AUTHOR]

A novel distributed power allocation scheme for analog network coding (ANC) in high signal-to-noise ratio (SNR) is proposed by using statistical channel knowledge at the transmitters only. The scheme considers nonorthogonal amplified-and- forward (NAF) protocol. In the derivation, a general Rayleigh fading multiple hop network is accurately approximated by a simpler two hop network, and the closed-formed expression for the outage probability of the simplified two hop network is obtained and optimized with respect to the power allocation. Numerical results show that the derived power allocation scheme has significant performance gain over the equal power scheme. In some cases, it approaches the optimal scheme. [ABSTRACT FROM AUTHOR]

Human body communication (HBC) is a wireless transmission method that utilizes the human body as part of the transmission medium. A signal is transmitted by weak electric current through the human body and by capacitive coupling between transmitter, receiver, human body, and floor. Capacitive coupling with the floor is often included in the transmission models of HBC; however, its contribution is not well understood. This paper evaluated the contribution of the ground loop through the floor in HBC. The received signal strength was measured for two cases: two subjects shaking hands, and a subject touching an off-body receiver placed on a stand. The subjects each wore a transmitter or a receiver on their wrist. They stood on a carpet-covered metal floor, concrete floor, hardwood floor, and wooden chair to be above the floor. The variation of the signal attenuation was approximately 40 dB depending on which hand the subject used to shake hands or to touch the off-body receiver, while the variation caused by the different floor types was less than 5 dB. The attenuation obtained by numerical simulation showed similar results. These results show that the contribution of a ground loop through the floor was small. [ABSTRACT FROM AUTHOR]

In line-of-sight (LoS) conditions, the accuracy of time-of-arrival (ToA) based localization has proven to be superior to the received-signal-strength (RSS) and the angle-of-arrival (AoA) localization techniques. The accuracy of TOA ranging is limited to unexpected ranging errors caused by the human body obstructing the direct path (DP) between a transmitter and a receiver. Validated analysis of this effect is a challenging problem, and this paper proposes an analytical Uniform Geometrical Theory of Diffraction (UTD) approach, based on a hybrid applicability of conductor cylinder, wedge, and screen models, to analyze behavior of first path in proximity of human body that is in angular motion. The model introduced can cover for a variety of antenna positioning in respect to human body by addressing creeping waves for on-body, far-field and near-field waves for off-body propagations. Result of analytically calculated ToA and path-loss for shortest diffracted path is validated with UWB measurements conducted by a vector network analyzer sweeping 3-5 GHz of bandwidth. The analytical approach proposes an enhancement to existing RT algorithm to include the effect of human body. [ABSTRACT FROM AUTHOR]