David B. Smith

Enabling Interference-Aware and Energy-Efficient Coexistence of Multiple Wireless Body Area Networks With Unknown Dynamics

This paper presents an adaptive interference mitigation scheme for multiple coexisting wireless body area networks (WBANs) based on social interaction. The proposed scheme considers the mobility of nodes within each WBAN as well as the relative movement of WBANs with respect to each other. With respect to these mobile scenarios traffic load, signal strength, and the density of sensors in a WBAN are incorporated to optimize transmission time with synchronous and parallel transmissions to significantly reduce the radio interference and energy consumption of nodes. This approach leads to higher packet delivery ratio (PDR) and longer network lifetime even with nodes dynamically moving into and out of each others interference region. We make channel assignment more energy-efficient and further reduce power consumption using transmit power control with simple channel prediction. Simulation results show that our approach maintains optimum spatial reuse with a range of channel dynamics within, and between, coexisting BANs. This protocol based on social interaction is shown to mitigate interference and minimize power consumption, and increase the spatial reuse and PDR of each WBAN, while increasing network lifetime. In the context of the adaptive interference mitigation scheme proposed, this paper also reviews the state of the art in literature on mobility, MAC layer, and power control solutions for WBANs, as well as providing a summary of interference mitigation schemes previously applied for the coexistence of WBANs.

Competitive Energy Trading Framework for Demand-Side Management in Neighborhood Area Networks

This paper, by comparing three potential energy trading systems, studies the feasibility of integrating a community energy storage (CES) device with consumer-owned photovoltaic (PV) systems for demand-side management of a residential neighborhood area network. We consider a fully competitive CES operator in a non-cooperative Stackelberg game, a benevolent CES operator that has socially favorable regulations with competitive users, and a centralized cooperative CES operator that minimizes the total community energy cost. The former two game-theoretic systems consider that the CES operator first maximizes their revenue by setting a price signal and trading energy with the grid. Then the users with PV panels play a non-cooperative repeated game following the actions of the CES operator to trade energy with the CES device and the grid to minimize energy costs. The centralized CES operator cooperates with the users to minimize the total community energy cost without appropriate incentives. The non-cooperative Stackelberg game with the fully competitive CES operator has a unique Stackelberg equilibrium at which the CES operator maximizes revenue and users obtain unique Pareto-optimal Nash equilibrium CES energy trading strategies. Extensive simulations show that the fully competitive CES model gives the best tradeoff of operating environment between the CES operator and the users.

Receiver-transmitter pair selection in MIMO phased array radar

The increase in the number of degrees of freedoms (DoF) that is afforded by multiple-input-multiple-output (MIMO) phased arrays is accompanied by an increase in hardware and computational costs. We mitigate this problem in a collocated MIMO phased array system by employing a selection strategy where a subset of K transmitter-receiver (Tx-Rx) pairs is chosen from the availableN pairs. We formulate the selection task as an optimization problem using the spatial correlation coefficient (SCC). Minimizing the SCC leads to an increase in the orthogonality of the signal and interference subspaces. We formulate and solve both the joint Tx-Rx selection problem and factored selection where the Tx and Rx are decoupled and treated separately. We show that both approaches can achieve excellent trade-off between performance and cost. While the factored problem compromises performance with respect to the joint Tx-Rx selection, it allows for better transmit power efficiency, thus increasing the received signal-to-noise ratio.

Generalized space-time modelling of the MIMO channel applied to analysing and optimising transmit antenna configurations

For the purposes of macroscopic system design a space-time Rayleigh fading multiple-input multiple-output (MIMO) radio channel is modelled for an arbitrary transmit antenna configuration of three to six transmit antennas. A traditional ring of scatterers model is use to generate the space-time cross correlations and thence flat fading channel distortions. A general trend is demonstrated for a specific non-coherent modulation scheme where the optimality of different transmission frame lengths can be related to the well known autocorrelation functions; based on this trend two frame lengths are chosen for MIMO channel analysis. Several beneficial arbitrary transmit antenna configurations are obtained from this analysis using some typical arbitrary configurations, and some initial optimisation using a genetic algorithm, from which further possible optimisation is proposed.

Multiple branch switched antenna diversity in Rayleigh and Rician fading channels

A new performance evaluation of switched antenna diversity, for the switch-and-examine strategy, is described. Expressions are derived for three-branch switched diversity with unequal branch statistics for independent Rayleigh and Rician fading channels. Comparisons are made using two and three-branch diversity with equal and unequal branch statistics. New expressions are also derived for an N-branch diversity system with equal branch statistics. The results of an analysis of various higher order diversity systems with equal statistics are compared to each other and to a no-diversity system. It is clearly demonstrated that, as the order of the diversity system increases, performance improves below and just above the switching threshold.

A Nash stable cross-layer coalition formation game for device-to-device communications

Device-to-Device (D2D) communications is a key aspect of future 5G cellular networks, as it can help improve spectral efficiency, system capacity, resource utilization, and quality-of-service (QoS), for the overall network. In this paper, a dynamic cross-layer leave-and-join based coalition formation game with non-transferable utility (NTU) is proposed. Our proposed game jointly optimizes mode selection (at the network layer), and resource allocation from the cell and cellular user/s, including power control (at the physical layer), in a distributed wireless network with D2D communications. Moreover, we aim to maximize channel rate and minimize transmit power for both cellular users and D2D pairs, while selecting optimal transmission mode for all D2D pairs. The coalition partition of the proposed game converges to a Nash stable outcome, which is socially efficient. The simulation results illustrate that once a Nash stable coalition partition is achieved, then optimal transmit power and channel rate are achieved for all D2D pairs and cellular users.

Management of Renewable Energy for a Shared Facility Controller in Smart Grid

This paper proposes an energy management scheme to maximize the use of solar energy in the smart grid. In this context, a shared facility controller (SFC) with a number of solar photovoltaic panels in a smart community is considered that has the capability to schedule the generated energy for consumption and trade to other entities. In particular, a mechanism is designed for the SFC to decide on the energy surplus, if there is any, that it can use to charge its battery and sell to the households and the grid based on the offered prices. In this regard, a hierarchical energy management scheme is proposed with a view to reduce the total operational cost to the SFC. The concept of a virtual cost is introduced that aids the SFC to estimate its future operational cost based on some available current information. The energy management is conducted for three different cases, and the optimal cost to the SFC is determined for each case by the theory of maxima and minima. A real-time algorithm is proposed to reach the optimal cost for all cases, and some numerical examples are provided to demonstrate the beneficial properties of the proposed scheme.

Channel Deviation-Based Power Control in Body Area Networks

Internet enabled body area networks (BANs) will form a core part of future remote health monitoring and ambient assisted living technology. In BAN applications, due to the dynamic nature of human activity, the off-body BAN channel can be prone to deep fading caused by body shadowing and multipath fading. Using this knowledge, we present some novel practical adaptive power control protocols based on the channel deviation to simultaneously prolong the lifetime of wearable devices and reduce outage probability. The proposed schemes are both flexible and relatively simple to implement on hardware platforms with constrained resources making them inherently suitable for BAN applications. We present the key algorithm parameters used to dynamically respond to the channel variation. This allows the algorithms to achieve a better energy efficiency and signal reliability in everyday usage scenarios such as those in which a person undertakes many different activities (e.g., sitting, walking, standing, etc.). We also profile their performance against traditional, optimal, and other existing schemes for which it is demonstrated that not only does the outage probability reduce significantly, but the proposed algorithms also save up to

Scalable MAC protocol for D2D communication for future 5G networks

{\text{35}}\%

Fast Differential Unitary Space-Time Modulation Decoding for a MIMO Radio Channel

average transmit power compared to the competing schemes.