Boon-Hee Soong

An Interference Minimization Game Theoretic Subcarrier Allocation Algorithm for OFDMA-Based Distributed Systems

In this paper, we consider a scenario where distributed users in an OFDM-based system share the spectrum for transmission. Each network user (player) comprises a pair of transmit and receive nodes and will be allocated a given number of subcarriers. We propose a utility function that aims at efficiently allocating subcarriers to all players by minimizing the amount of interference generated. We first show that for the utility function used in the subcarrier assignment problem, it is possible to find a network potential function for the game. This guarantees the existence of at least one pure Nash equilibrium if each player is assigned with a predetermined number of subcarriers for transmission. Hence, convergence to Nash equilibrium can be achieved by iteratively playing the best-response game (also known as myopic game) among the players. Our simulation results show that distributing power over a number of subcarriers can achieve better per user capacity compared to the case where transmission is made through only a single subcarrier.

PipeSense: A framework architecture for in-pipe water monitoring system

We present a framework for in-pipe water monitoring and feedback system. The goal is to monitor the potable water contaminations and leakages within pipes and share this information to conserve water and improve the current water distribution system through feedback. This is achieved through a seamless integration of RFID based wireless motes into the water distribution network while going beyond the traditional methods of ultrasonic water monitoring systems. Based on this framework, a prototype PipeSense system is being developed. We describe the framework architecture and design of this system and present details of the current system implementation. We also discuss some feasibility results along with directions for future research and implementation.

The effect of unreliable wireless channel on the call performance in mobile network

In this paper, we propose a model to study the call performance in mobile network taking into account the inherent time varying wireless channel. The performance metrics call complete probability and call complete ratio are introduced and further derived with the general call holding time. The impacts of the wireless channel error characteristics and the system parameters on the call performance are illustrated and discussed. The sensitivity problem with respect to the call holding time distribution is investigated. The result indicates that both call complete probability and call complete ratio exhibit a significantly different variation under different call holding time. The analytical model is verified by simulation result.

Framework of WSN based human centric cyber physical in-pipe water monitoring system

We present a human centric cyber physical framework architecture of our in-pipe water monitoring and feedback system. This system comprises of the physical water distribution infrastructure, together with the hardware and software supported intelligent agents for water allotment, leak detection and contamination spread control. An agent-based approach for connecting the cyber and physical layers is selected, where the agents get information from sensors monitoring the physical components and provide this information to the cyber system. The Hidden Markov Models (HMM) are briefly discussed to determine water consumption patterns and make decisions for cyber and physical systems.

Performance of mobile networks with wireless channel unreliability and resource insufficiency

New closed-form formulas for the call complete probability and the probability density function (pdf) of the completed call holding time (CCHT) are developed under the concurrent impacts of the resource insufficiency as well as the wireless link unreliability in the wireless mobile networks performance evaluation. The results are obtained with the general scenario, i.e. general call holding time, general cell residence time and the generalized wireless channel model. The analysis result is validated by the simulation model under typical call holding time and cell residence time distributions, Gilbert-Elliott or Fritchman wireless channel model. The comparison indicates that the wireless networks performance will be greatly overestimated without taking into account the unreliable wireless link effect.

Power Management of Intelligent Buildings Facilitated by Smart Grid: A Market Approach

The emergence of smart grid technology is offering a unique opportunity to improve power management in intelligent buildings through the integration and optimization of distributed energy resources and loads. In this paper, the interactions of multiple intelligent buildings in the context of energy market, as well as distributed energy generation and storage facilities, is considered. Within a time horizon divided into multiple periods in which generations and loads are forecasted, each building in a certain period may experience power surplus or deficit. While any deficit can be obtained from the market, buildings may consider selling their unused power back to the market. A dynamic pricing model based on differential game theory is set up in order to study the interactions of these players and how they maximize their profit. We also propose algorithms to implement and operate the system over the time horizon considered. Furthermore, numerical studies are performed to validate the model and algorithms.

Design of inductive coil for wireless power transfer

Recent advancements in the miniaturised electronics and embedded system are wide spread in the various fields of engineering applications. From bio-medical implants to actuating device for monitoring pressure and temperature for industrial applications have been developed in wide spread. Wireless power transfer application to such device may tap the full potential of such system and seems to be a viable option in many cases of low power devices. The study of power transfer including the performance of inductive link at radio frequency is dealt in the paper. Theoretical studies are backed up with a practical experiment of charging a cell phone which is dealt at the end of the paper.

Licensed-Assisted Access for LTE in Unlicensed Spectrum: A MAC Protocol Design

Licensed-assisted access (LAA), which conveys control signal via licensed anchor carrier and data information via both licensed and unlicensed bands, is a promising solution to enhance the throughput of wireless communications. In view of the potential impact on the incumbent services in the unlicensed band, how to design the medium access control (MAC) protocol for LAA system to make fair and friendly coexistence with its neighboring incumbent users is one of the most critical and challenging issues. In this paper, a LAA using LTE (LAA-LTE) system in the WiFi unlicensed spectrum is investigated. The listen-before-talk (LBT) protocol is designed for the LAA-LTE system. By quantifying the WiFi throughput in the coexisting system, allowable LTE transmission time is determined by considering different targets of WiFi service protection. Then, the LTE transmission time is optimized for maximizing the overall normalized channel rate contributed by both LAA-LTE and WiFi system, with the protection to the WiFi system. Our work offers guidelines of designing the LAA-LTE system, paving the way to a controllable, not only harmonious, coexistence of LAA-LTE and WiFi systems in the unlicensed spectrum.

Design of low power Rectenna for wireless power transfer

Current research trend in the RF wireless power transfer has a shift to new paradigm. Optimization of power transfer for wireless sensor networks has a new facelift due to the evolution of rectifier antenna (Rectenna). Wireless powering of sensors with Rectenna has kindled the interest of research society in the present trend. The research developed in the paper bounds within the wireless powering of miniaturized electronics with low power ratings. Wireless powering of sensors has a future potential to be tapped yet. The modelling and optimization that has been carried out have been backed up with simulations and practical experiments which are dealt later in the paper. The efficiency of Rectenna can have a significant improvement in working onto the each element of the Rectenna circuit as presented in the paper.

Spectrum Refarming: A New Paradigm of Spectrum Sharing for Cellular Networks

Spectrum refarming (SR) is a promising radio resource management technique which allows different generations of cellular networks to operate in the same radio spectrum. In this paper, an underlay SR model is proposed for an Orthogonal Frequency Division Multiple Access (OFDMA) system to refarm the spectrum assigned to a Code Division Multiple Access (CDMA) system through intelligently exploiting the interference margin provided by the CDMA system. We investigate the mutual effect of the two systems by evaluating the asymptotic signal-to-interference-plus-noise ratio (SINR) of CDMA users, based on which the interference margin tolerable by CDMA system is determined. With the interference margin together the transmit power constraints, the resource allocation problem of OFDMA system is formulated and solved through dual decomposition method. Simulation results have verified our theoretical analysis and validated the effectiveness of our proposed OFDMA resource allocation solution, as well as its protection to CDMA services.