Layered RF Phantom Characterization for Wireless Medical Vital Sign Monitors

Wearable antenna performance measurements were used to characterize a synthetic variable layered phantom testbed, representative of human tissue for operation in the 868/915 MHz, and 2400 MHz industrial, scientific and medical frequency bands. Antenna radiation efficiency measurements on the phantom were compared with measurements on the thorax region of a human test subject. The results show that the phantom is representative of the human body for the application of wireless vital sign monitors, where conductive connections are made to the tissue.

Simple high sensitivity wireless transceiver

This article describes an extremely simple wireless transceiver, comprising of only a low Q VCO and a phase locked loop IC. It is experimentally shown to, simultaneously, transmit an 8-dBm CW interrogation signal, while concurrently demodulating a phase modulated received signal with sensitivity levels of -120 dBm. This makes the performance similar to conventional transceivers, which require complex superheterodyne type architectures and also require a means to provide a high isolation separate the transmit/receive signals (such as a circulator). 

BER Driven Synthesis for Directional Modulation Secured Wireless Communication

Directional modulation (DM) is a recently introduced technique for secure wireless transmission using direct physical layer wave-front manipulation. This paper provides a bit error rate (BER)-based DM array synthesis method. It is shown for the first time that the standard constellation mappings in In-phase and Quadrature (IQ) space to a pre-specified BER can be exactly achieved along a given specified spatial direction. Different receiver capabilities are investigated and different assessment metrics for each case are discussed. The approach is validated for a 1 × 4 element dipole array operating at 1 GHz.

Wireless Energy Harvesting and Spectrum Sharing in Cognitive Radio

A wireless energy harvesting protocol is proposed for a decode-and-forward relay- assisted secondary user (SU) network in a cognitive spectrum sharing paradigm. An expression for the outage probability of the relay-assisted cognitive network is derived subject to the following power constraints: 1) the maximum power that the source and the relay in the SU network can transmit from the harvested energy, 2) the peak interference power from the source and the relay in the SU network at the primary user (PU) network, and 3) the interference power of the PU network at the relay-assisted SU network. The results show that as the energy harvesting conversion efficiency improves, the relay- assisted network with the proposed wireless energy harvesting protocol can operate with outage probabilities below 20% for some practical applications.

Two-Way Relaying Networks with Wireless Power Transfer: Policies Design and Throughput Analysis

This paper exploits an amplify-and-forward (AF) two-way relaying network (TWRN), where an energy constrained relay node harvests energy with wireless power transfer. Two bidirectional protocols, multiple access broadcast (MABC) protocol and time division broadcast (TDBC) protocol, are considered. Three wireless power transfer policies, namely, 1) dual-source (DS) power transfer; 2) single-fixed-source (SFS) power transfer; and 3) single-best-source (SBS) power transfer are proposed and well-designed based on time switching receiver architecture. We derive analytical expressions to determine the throughput both for delay-limited transmission and delay-tolerant transmission. Numerical results corroborate our analysis and show that MABC protocol achieves a higher throughput than TDBC protocol. An important observation is that SBS policy offers a good tradeoff between throughput and power.

Investigation of secure wireless regions using configurable beamforming on WARP

In this paper, we examine a novel approach to network security against passive eavesdroppers in a ray-tracing model and implement it on a hardware platform. By configuring antenna array beam patterns to transmit the data to specific regions, it is possible to create defined regions of coverage for targeted users. By adapting the antenna configuration according to the intended user’s channel state information, this allows the vulnerability of the physical regions to eavesdropping to be reduced. We present the application of our concept to 802.11n networks where an antenna array is employed at the access point. A range of antenna array configurations are examined by simulation and then realized using the Wireless Open-Access Research Platform(WARP)

Creating secure wireless regions using configurable beamforming

We present a novel approach to network security against passive eavesdroppers by employing a configurable beam-forming technique to create tightly defined regions of coverage for targeted users. In contrast to conventional encryption methods, our security scheme is developed at the physical layer by configuring antenna array beam patterns to transmit the data to specific regions. It is shown that this technique can effectively reduce vulnerability of the physical regions to eavesdropping by adapting the antenna configuration according to the intended user's channel state information. In this paper we present the application of our concept to 802.11n networks where an antenna array is employed at the access point, and consider the issue of minimizing the coverage area of the region surrounding the targeted user. A metric termed the exposure region is formally defined and used to evaluate the level of security offered by this technique. A range of antenna array configurations are examined through analysis and simulation, and these are subsequently used to obtain the optimum array configuration for a user traversing a coverage area.

Green Media: The Future of Wireless Multimedia Networks:Guest Editorial

By 2015, with the proliferation of wireless multimedia applications and services (e.g., mobile TV, video on demand, online video repositories, immersive video interaction, peer to peer video streaming, and interactive video gaming), and any-time anywhere communication, the number of smartphones and tablets will exceed 6.5 billion as the most common web access devices. Data volumes in wireless multimedia data-intensive applications and mobile web services are projected to increase by a factor of 10 every five years, associated with a 20 percent increase in energy consumption, 80 percent of which is multimedia traffic related. In turn, multimedia energy consumption is rising at 16 percent per year, doubling every six years. It is estimated that energy costs alone account for as much as half of the annual operating expenditure. This has prompted concerted efforts by major operators to drastically reduce carbon emissions by up to 50 percent over the next 10 years. Clearly, there is an urgent need for new disruptive paradigms of green media to bridge the gap between wireless technologies and multimedia applications.

On the Exploitation of the Inherent Error Resilience of Wireless Systems under Unreliable Silicon

In this paper, we investigate the impact of circuit misbehavior due to parametric variations and voltage scaling on the performance of wireless communication systems. Our study reveals the inherent error resilience of such systems and argues that sufficiently reliable operation can be maintained even in the presence of unreliable circuits and manufacturing defects. We further show how selective application of more robust circuit design techniques is sufficient to deal with high defect rates at low overhead and improve energy efficiency with negligible system performance degradation.