Geoffrey G. Messier

Optimum receiver for molecule shift keying modulation in diffusion-based molecular communication channels

Abstract Designing an optimum receiver for diffusion-based molecular communication in nano-networks needs a well justified channel model. In this paper, we present a linear and time invariant signal propagation model and an additive noise model for the diffusion-based molecular communication channel. These models are based on Brownian motion molecular statistics. Using these models, we develop the first optimal receiver design for diffusion-based molecular communication scenarios with and without inter-symbol interference. We evaluate the performance of our proposed receiver by investigating the bit error rate for small and large transmission rates.

Using WLAN Infrastructure for Angle-of-Arrival Indoor User Location

This paper investigates the potential for future multiple antenna wireless local area network technologies such as 802.11n to perform indoor network-based positioning using angle of arrival (AOA) estimation. A multiple-input multiple-output (MIMO) channel measurement system is used to determine the statistical accuracy of the indoor AOA estimation when performed at an 802.11n wireless access point (AP). Two different channel parameter estimation algorithms are used to perform AOA estimation; a simple maximum-likelihood (ML) scheme and the space-alternating generalized expectation-maximization (SAGE) technique. Results indicate that general channel parameter estimation algorithms, such as SAGE, are ill suited to estimate AOA for positioning purposes. However, results show that with the use of a specialized channel parameter estimation algorithm, such as the simple ML algorithm, quality AOA estimates for positioning might be achieved with low computational complexity. A positioning simulation that incorporates the AOA estimates from the simple ML algorithm achieves a positioning accuracy of 1.7 m with the help of an extended Kalman filter.

Blind Synchronization in Diffusion-Based Molecular Communication Channels

Synchronization is an essential feature of any communication system. Due to the very low throughput of molecular communications systems, blind synchronization is preferred in order to reduce communications overhead. In this paper, we present the first blind synchronization algorithm for the diffusion-based molecular communication channel. Considering a diffusion-based physical channel model, we use the non-decision directed maximum likelihood criterion for estimating the channel delay. We then derive the Cramer-Rao lower bound and evaluate the performance of the proposed synchronization algorithm by investigating its mean square error.

Traffic models for medical wireless sensor networks

Stochastic data traffic models for medical wireless sensor networks (WSNs) are presented that represent the traffic generated by a single WSN node monitoring body temperature and electrocardiogram (ECG) data. The models are based on empirical data from public domain medical signal databases. In the interest of conserving energy, it is likely that some medical WSN nodes will employ source coding to reduce the amount of data that must be transmitted. As a result, traffic models are presented for nodes that use compression and nodes that do not.

Vehicle Routing Problems for Drone Delivery

Unmanned aerial vehicles, or drones, have the potential to significantly reduce the cost and time of making last-mile deliveries and responding to emergencies. Despite this potential, little work has gone into developing vehicle routing problems (VRPs) specifically for drone delivery scenarios. Existing VRPs are insufficient for planning drone deliveries: either multiple trips to the depot are not permitted, leading to solutions with excess drones, or the effect of battery and payload weight on energy consumption is not considered, leading to costly or infeasible routes. We propose two multitrip VRPs for drone delivery that address both issues. One minimizes costs subject to a delivery time limit, while the other minimizes the overall delivery time subject to a budget constraint. We mathematically derive and experimentally validate an energy consumption model for multirotor drones, demonstrating that energy consumption varies approximately linearly with payload and battery weight. We use this approximation to derive mixed integer linear programs for our VRPs. We propose a cost function that considers our energy consumption model and drone reuse, and apply it in a simulated annealing (SA) heuristic for finding suboptimal solutions to practical scenarios. To assist drone delivery practitioners with balancing cost and delivery time, the SA heuristic is used to show that the minimum cost has an inverse exponential relationship with the delivery time limit, and the minimum overall delivery time has an inverse exponential relationship with the budget. Numerical results confirm the importance of reusing drones and optimizing battery size in drone delivery VRPs.

A Sensor Network Cross-Layer Power Control Algorithm that Incorporates Multiple-Access Interference

This paper presents a wireless sensor network (WSN) transmit power control algorithm designed to minimize WSN node energy consumption. The algorithm determines transmit power levels using an optimization that accounts for energy consumed by the physical and link layers of the protocol stack. This cross-layer optimization incorporates a physical layer model that uses knowledge of the WSN medium access control (MAC) layer algorithm to accurately model multiple access interference (MAI). Analytical and simulation results show that accounting for MAI in this fashion results in a significant energy savings relative to comparable WSN power control algorithms.

Nano-machine molecular communication over a moving propagation medium

Abstract In this paper, we study a molecular communication system operating over a moving propagation medium. Using the convection–diffusion equation, we present the first separate models for the channel response and the corrupting noise. The flow-based molecular channel is shown to be linear but time-varying and the noise corrupting the signal is additive white Gaussian with a signal dependent magnitude. By modelling the ligand–receptor binding process, it is shown that the molecular communication reception process in this channel has a low-pass characteristic that colours the additive noise. A whitening filter is proposed to compensate for this low-pass characteristic. Simulation results demonstrate the benefit of the whitening filter and the effect of medium motion on bit error rate.

Using the Wireless and PLC Channels for Diversity

Performance of indoor home networks can be improved by simultaneous use of wireless and powerline communication (PLC) channels. A narrowband model representing an OFDM subcarrier is used to analyze the performance of several diversity combining schemes including optimum combining (OC), saturated metric combining (SMC) and maximal ratio combining (MRC). Results from BER analysis show that SMC achieves good performance in highly impulsive noise and is relatively insensitive to error in noise parameter estimates. Indoor measurements from 3 detached homes show that parallel wireless and PLC channels have a wide, but similar, signal-to-noise ratio (SNR) range. Measurement data is used with link throughput analysis to show that wireless/PLC diversity can be used to minimize the likelihood of low throughput links.

The Wireless/Power-Line Diversity Channel

Wireless devices are often connected to power outlets in residential data and smart-home networks. As a result, physical layer performance can be improved by using the power distribution tree as a diversity channel. This paper proposes a hardware-efficient, low intermediate-frequency (low-IF) transceiver architecture which allows existing wireless protocols to be used over both wireless and power-line communication (PLC) channels. A signal model for this form of hybrid transmission is presented assuming Rayleigh flat-fading and Middleton Class A impulsive noise in the wireless and PLC channels, respectively. Analysis of maximal-ratio combining (MRC) reveals that detector input noise is also Class A-distributed. Expressions for average bit-error rate (BER) of a BPSK subcarrier show that BER is a function of PLC impulsiveness and significant improvement can be achieved with diversity and PLC SNR > 10 dB. In regions of low and high wireless SNR, BER curves are approximately linear with slope of 0 and -1, respectively. The inflection point between these two regions can be used by transceivers to select between PLC-only and hybrid transmission modes.

Media Caching Support for Mobile Transit Clients

In this paper, we consider the design of caching infrastructure to enhance the client-perceived performance of mobile wireless clients retrieving multimedia objects from the Internet. We consider three primary issues: location of the cache, size of the cache, and management policy for the cache. We consider both infrastructure-oriented caching at the Access Point (AP), as well as peer-assisted caching at the mobile clients. Simulation is used as the methodology for evaluation and comparison of caching strategies. The simulation results show that AP caching is generally more effective than client-side caching, that adequate performance is achievable with a mix of rather modest AP and client-side caches, and that Least Frequently Used (LFU) is the most effective cache replacement policy. Additional simulation experiments show that our results are robust across different request generation rates and client turnover rates.