Mohammad Monirujjaman Khan

Experimental investigation of ultra wideband diversity techniques for on-body radio communications

This paper presents an experimental investigations and analyses of ultra-wideband antenna diversity techniques and their efiect on the on-body radio propagation channels. Various diversity- combining techniques are applied to highlight; how the overall system performance may be enhanced. Diversity gain is calculated for flve difierent on-body channels and the impact of variation in the spacing between diversity branch antennas is discussed, with an emphasis on mutual coupling, correlation and power imbalance. Results demonstrate the repeatability and reliability of the analysis with error variations as low as 0.8dB. The study highlights the signiflcance of diversity techniques for non-line-of-sight propagation scenarios in body-centric wireless communications.

Off-Body Radio Channel Characterisation Using Ultra Wideband Wireless Tags

This paper presents an experimental investigation of off-body radio propagation channels based on commercially available UWB wireless tags. The tags operate at frequency band of 5.9~7.2 GHz. A measurement campaign was performed both in the chamber and in an indoor environment for comparison. The path loss for nine different channels is shown with parameters describing the radio channel derived through statistical analysis.

Characterization and modelling of Ultra Wideband radio links for optimum performance of body area network in health care applications

Ultra Wide band (UWB) is an appealing technology for health care applications. The paper aims to investigate the optimum location for putting sensors on the body for remote patient monitoring. The on-body measurements are performed in both anechoic chamber and in an indoor environment for more than 100 receiver locations for both line of sight (LOS) and non-line of sight (NLOS) scenarios. The on-body path loss model has been extracted from the measured data. Bit Error Rate (BER) for different receiver locations is calculated by incorporating channel impulse responses for each link in Multiband-OFDM based UWB system. The conducted system analysis shows that for LOS case best location for putting sensor are legs and for NLOS case both legs and arms perform equally well.

Ultra wideband off-body radio channel characterisation and modelling for healthcare applications

In this paper, the impact of different subject sleeping positions on the ultra wideband (UWB) off-body radio channel is experimentally investigated. Maximum of 15 dB path loss variation is noticed of a channel for different sleeping positions of the subject on the bed at the same location. Results and analysis show that the path loss value is dependent on the different sleeping modes and positions of the subject on the bed, body shadowing, multipath environment and also whether transmit antennas and receive antenna are in relative line of sight or non line of sight conditions.

Study of a small printed quasi-self-complementary ultra wideband antenna for on-body applications

In this paper, the performance parameters of a small printed quasi-self-complementary ultra wideband (UWB) antenna in close proximity to the human body is investigated. The return loss response, impedance, radiation pattern and gain are investigated. The antenna shows good on-body performance, and therefore it will be suitable for on-body applications in UWB wireless body area networks.

Performance of Ultrawideband Wireless Tags for On-Body Radio Channel Characterisation

Experimental characterisation of on-body radio channel for ultrawideband (UWB) wireless active tags is reported in this paper. The aim of this study is to investigate the performance of the commercially available wireless tags on the UWB on-body radio channel characterisation. Measurement campaigns are performed in the chamber and in an indoor environment. Statistical path loss parameters of nine different on-body radio channels for static and dynamic cases are shown and analyzed. Results demonstrated that lognormal distribution provides the best fits for on-body propagation channels path loss model. The path loss was modeled as a function of distance for 34 different receiver locations for propagation along the front part of the body. A reduction of 11.46% path loss exponent is noticed in case of indoor environment as compared to anechoic chamber. In addition, path loss exponent is also extracted for different body parts (trunk, arms, and legs). Second-order channel parameters as fade probability (FP), level crossing rate (LCR), and average fade duration (AFD) are also investigated.

Comparison of two measurement techniques for UWB off-body radio channel characterisation

This paper presents comparison of two measurement techniques for ultra wideband (UWB) off-body radio channel characterization. A measurement campaign was performed in indoor environment using UWB wireless active tags and reader installed with the tag antenna and same set of measurement was repeated in the frequency domain using Vector Network Analyser (VNA) and cable connecting two standalone tag antennas for comparison/with a view to finding out the cable effects. Nine different off-body radio channels were experimentally investigated. Comparison of path loss parameters and path loss model for nine different off-body radio channels for the propagation in indoor environment both measurement cases are shown and analyzed. Results show that measurement taken by VNA connecting two standalone antennas through cables experiences lower path loss value for all nine different off-body channels. Least square fit technique is obtained to extract the path loss exponent. Increase of 12.96% path loss exponent is noticed when measurements are made using UWB tags and reader, i.e., without cable measurement scenario.

Investigation of body shape variations effect on the Ultra-Wideband on-body radio propagation channel

In this paper Ultra Wideband (UWB) on-body radio propagation study is performed by characterizing the path loss for five different real human subjects of different sizes and gender in an indoor environment using UWB active tags provided by Time Domain PLUS™. The tags operate at the frequency band of 5.9∼7.2 GHz. Thirty four different transmitter locations on the front part of the body are considered for calculating path loss. Results showed that maximum of 29.83 % variation in path loss exponent is noticed for different body size and path loss exponent is generally increased with the body size.

Dual band and dual mode antenna for power efficient body-centric wireless communications

This paper presents a dual band and diverse radiation mode antenna for power efficient and reliable on-body and off-body communications. The antenna is dual band with omnidirectional radiation pattern over the body surface at 2.45 GHz (ISM band) to communicate power efficiently with other co-located body worn devices scattered on the body or body worn base station. At 1.9 GHz (PCS band), it has with directive radiation pattern towards off-the body to communicate power efficiently from on-body device to off-body units/access point or other wider e-health networks. Free space and on-body measured and simulated performances of the proposed antenna are shown and analyzed. The antenna shows very good on-body radiation efficiency as 58.23 % for 1.9 GHz and 50.41 % for 2.45 GHz. In addition, good measured on-body gain is noticed at both frequency bands. Increase of 17.39 % gain at 2.45 GHz is noticed when measured on the body.

Energy efficient transmission power estimation for WLAN VoIP

In this paper transmission signal power is optimized to increase the energy efficiency of Wireless Local Area Network (WLAN) Voice over IP (VoIP) application. We investigate how to optimize the transmission power without degrading the VoIP Quality of Service (QoS). A Transmission Power Optimization (TPO) algorithm is presented to adopt lowest possible transmission power that does not interrupt the VoIP service quality and increases energy efficiency as well. Extensive analysis is done in Network Simulator-2 (NS-2) [1] to estimate the optimal transmission power for various channel condition. According to our simulation results and analysis it is observed that the optimal transmission power increases the energy efficiency and improves the VoIP performance significantly.