Kasun M. S. Thotahewa

Power Efficient Ultra Wide Band Based Wireless Body Area Networks with Narrowband Feedback Path

The basic requirement of wireless healthcare monitoring systems is to send physiological signals acquired from implantable or on-body sensor nodes to a remote location. Low-power consumption is required for wireless healthcare monitoring systems since most medical sensor nodes are battery powered. The emergence of new technologies in measuring physiological signals has increased the demand for high data rate transmission systems. Ultra-wide band (UWB) is a suitable wireless technology to achieve high data rates while keeping power consumption and form factors small. Although UWB transmitters are designed based on simple techniques, UWB receivers require complex hardware and consume comparatively higher power. In order to achieve reliable low power two-way communication, a sensor node can be constructed using a UWB transmitter and a narrow band receiver. This paper proposes a new medium access control (MAC) protocol based on a dual-band physical layer technology. Co-simulation models based on MATLAB and OPNET have been developed to analyze the performance of the proposed MAC protocol. We analyzed the performance of the MAC protocol for a realistic scenario where both implantable and wearable sensor nodes are involved in the data transmission. Priority-based packet transmission techniques have been used in the MAC protocol to serve different sensors according to their QoS requirements. Analysis is done with regard to important network parameters, such as packet loss ratio, packet delay, percentage throughput, and power consumption.

SAR, SA, and Temperature Variation in the Human Head Caused by IR-UWB Implants Operating at 4 GHz

With the extensive use of wireless devices within or at close proximity to the human body, electromagnetic effects caused by the interaction between RF waves and human tissues need to be considered with paramount importance. The ultra-wideband (UWB) communication spectrum has recently been utilized in bio-telemetry applications, such as neural recording, brain-computer interfaces, and physiological data monitoring requiring high data rate and low power. This paper reports the electromagnetic effects of head-implantable transmitting devices operating based on impulse radio UWB wireless technology. Simulations illustrate the performance of an implantable UWB antenna tuned to operate at 4 GHz with an -10-dB bandwidth of approximately 1 GHz when it is implanted in a human head model. Specific absorption rate (SAR), specific absorption (SA), and temperature increase are analyzed to compare the compliance of the transmitting device with international safety regulations. The frequency- and age-dependent nature of the tissue properties, such as relative permittivity, is taken into account. The SAR/SA variation of the human head is presented with varying input power, different antenna orientations, and different signal bandwidths. We also present the percentage of SAR variation for each tissue type in the head model used for the simulations.

Transmit-Only Ultra Wide Band Body Sensors and Collision Analysis

Ultra wide band (UWB) stands out from other wireless technologies used for wireless physiological signal monitoring due to its low power transmitter, immunity from interference, small sized antenna, and high data rate. Although a UWB transmitter has low power consumption, the UWB receiver is generally complex and consumes more power. This paper investigates the use of a transmit-only mechanism for data transfer in wireless body area network (WBAN) applications. A transmit-only medium access control mechanism that can be used in low-power WBANs is developed. Detailed attention is given to the simulation-based analysis of collisions between data which occur in such a scheme. A performance enhancement scheme is suggested to achieve optimum data transmission. Results are validated using a hardware implementation of the proposed system.

Nanoscale displacement sensing using microfabricated variable-inductance planar coils

Microfabricated spiral inductors were employed for nanoscale displacement detection, suitable for use in implantable pressure sensor applications. We developed a variable inductor sensor consisting of two coaxially positioned planar coils connected in series to a measurement circuit. The devices were characterized by varying the air gap between the coils hence changing the inductance, while a Colpitts oscillator readout was used to obtain corresponding frequencies. Our approach shows significant advantages over existing methodologies combining a displacement resolution of 17 nm and low hysteresis (0.15%) in a 1 × 1 mm2 device. We show that resolution could be further improved by shrinking the devices lateral dimensions.

A low-power wearable dual-band wireless body area network system: Development and experimental evaluation

Wireless body area network (WBAN) applications benefit extensively from the advantages offered by unique features of ultra-wideband (UWB) wireless communication, such as high data rate, low power consumption, and simple transmitter design. A major disadvantage in using UWB for WBAN applications is the complexities introduced by UWB receivers, such as high power consumption, poor receiver performance due to low sensitivity, and complex hardware implementation. This paper presents hardware implementation of a new communication system, where UWB is used for high data-rate transmission from sensor nodes and a 433-MHz industrial, scientific, and medical (ISM) band receiver is used for receiving low data-rate control messages at the sensor nodes. A full network system for WBAN applications has been implemented including a unique medium access control protocol. The proposed WBAN system is designed to dynamically control the pulses per bit value used for the UWB data communication using control messages received via the narrowband feedback link (i.e., the 433-MHz ISM link). This leads to dynamic bit error rate (BER) and power control at the sensor nodes, which improves the reliability of communication and power efficiency of sensor nodes under dynamic channel conditions. The performance of the system is evaluated in terms of BER, sensor initialization delay, and power consumption. This novel dual-band architecture utilizes the unique advantages offered by UWB communication and narrowband technology to enable high data rate, low-complexity hardware design, low power consumption, and small form factor for WBAN sensor systems.

Implementation of a dual band body sensor node

Ultra Wide Band (UWB) can be considered as a lucrative wireless technology for Wireless Body Area Network (WBAN) applications that demand for power stringent operation, high data rate and low form factor. The main drawback of the UWB technology is its receiver complexity. In order to overcome this barrier, this paper presents an implementation of a WBAN sensor node that uses UWB for data transmission and narrow band for data reception. This unique technique provides a means of achieving low power consuming sensor nodes with high data rate capability. The compact sensor platforms are implemented using off-the-shelf components; hence presents an economically viable solution for both commercial and research purposes.

Development of low-power UWB body sensors

Ultra-wide band (UWB) is gaining popularity as a physical layer technique for low power and high data rate wireless applications. Currently most wireless body area network (WBAN) platforms are based on narrowband wireless technology such as ZigBee and Bluetooth. This paper presents hardware implementation of impulse radio ultra-wide band (IR-UWB) based sensor nodes. Two major approaches for the development of an IR-UWB sensor node are discussed herein. A UWB receiver implementation using off-the-shelf components is also described. This communication system is used to evaluate the performance of the UWB sensor nodes in terms of bit error rate (BER). A technique for dynamically varying the pulse repetitive frequency (PRF) of the UWB pulses is also discussed in this paper as a further improvement for the suggested sensor designs.

A UWB wireless capsule endoscopy device

Wireless capsule endoscopy (WCE) presents many advantages over traditional wired endoscopic methods. The performance of WCE devices can be improved using high-frequency communication systems such as Impulse Radio-Ultra-Wideband (IR-UWB) to enable a high data rate transmission with low-power consumption. This paper presents the hardware implementation and experimental evaluation of a WCE device that uses IR-UWB signals in the frequency range of 3.5 GHz to 4.5 GHz to transmit image data from inside the body to a receiver placed outside the body. Key components of the IR-UWB transmitter, such as the narrow pulse generator and up-conversion based RF section are described in detail. This design employs a narrowband receiver in the WCE device to receive a control signal externally in order to control and improve the data transmission from the device in the body. The design and performance of a wideband implantable antenna that operates in the aforementioned frequency range is also described. The operation of the WCE device is demonstrated through a proof-of-concept experiment using meat.

Electromagnetic power absorption of the human abdomen from IR-UWB based wireless capsule endoscopy devices

Impulse Radio-Ultra Wide Band (IR-UWB) can be used to enhance the performance of Wireless Capsule Endoscopy (WCE) Devices due to its high data rate capability, low power consumption and small form factor. This paper reports simulation results regarding the electromagnetic effects on the human body caused by an IR-UWB based WCE operating inside the small intestine of the human abdomen. A complex human anatomical model consisting of human tissue simulating materials is used for the simulations. The performance of an implantable IR-UWB antenna operating at 4GHz with a -10dB bandwidth of 1GHz is shown in terms of the return loss, and antenna gain. Specific Absorption Rate (SAR), Specific Absorption (SA) and temperature increase are analyzed to compare the compliance of the WCE devices with international safety regulations. The frequency and age dependent nature of the tissue properties, such as relative permittivity, is taken into account for the simulations. The path loss variation of the electromagnetic signal emitted by a WCE device that is operating inside the small intestine is also analyzed in this paper.

Medium Access Control (MAC) Protocols for Ultra-Wideband (UWB)-Based Wireless Body Area Networks (WBAN)

A wireless body area network (WBAN) is a dedicated network developed to operate in, on or near the human body. In order to design a power-efficient WBAN, a cross-layer solution is required. The physical layer of a WBAN determines the choice of wireless scheme, modulation scheme, synchronization and data rate. The data-link layer provides medium access control (MAC), which ensures reliable and fair access to the communication channel. Ultra-wideband (UWB) is a suitable wireless technology to achieve high data rates while keeping power consumption and form factors small. Hence, it provides numerous advantages to WBAN applications. This chapter analyzes UWB-based MAC protocols available for WBAN systems in terms of their practicality in design, effectiveness in data delivery and power efficiency. In particular, the application of WBAN in healthcare monitoring environments is considered.