Imdad Khan

A planar three-port annular-ring slot antenna has been described. The antenna has been designed to operate at 5.725-5.825 GHz (a IEEE 802.11a frequency band). Port 1 is associated with a dipole-like radiation pattern whose radiated field is perpendicular to the antenna plane. Port 2 and 3 both radiate a broadside radiation pattern, with two orthogonal linearly polarized electric fields. The

ABSTRACT On-body communication channels are affected by short term fading effects. In this paper, the effect of space diversity reception for on-body communications has been investigated at a frequency of 2.45 GHz using one transmitting and two receiving narrow-band monopole antennas. An annular-slot-monopole combination (pattern diversity antenna) was also used at the receiving end. Measurements were taken in different environments, i.e. in an anechoic chamber, an office environment, and a laboratory. The diversity gains were calculated and the cumulative distribution functions (CDF) were plotted for five body channels. Significant improvement is observed in terms of diversity gain for the non-line-of-sight channels and channels involving large movements. Also, the diversity gains of monopole antennas were compared with those of the pattern diversity annular-slot-monopole antenna.

The application of multiple-input multiple-output (MIMO) in body-area networks (BAN) is considered in the paper. The correlations between MIMO sub-channels and the MIMO channel capacity are investigated for three on-body channels when random movements are performed in an indoor environment. Some of the MIMO sub-channels were found to be correlated. Nevertheless, a significant capacity increase due to use of MIMO

Page 1. Wireless Channels and Antennas for Body-Area Networks Yuriy I Nechayev, Peter S Hall, Imdad Khan, and Costas C Constantinou School of Electronic, Electrical and Computer Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom ...

High diversity gains achieved for the on-body channels suggest that multipath due to the environment and the body both play a role in the propagation. The correlation of the diversity branches is low for most of the channels, which suggests that the diversity can provide very good improvement, if the power imbalance is carefully dealt with. The uplink and downlink

ABSTRACT In this paper, a wearable patch antenna is designed for Frequency Modulation radio applications. The resonant frequency of this designed antenna is 100 MHz. The main objective of this research work was to reduce the size of the designed antenna, so that it can be worn over human body. Shorting wall along the length of patch and U-slot in the patch are used to reduce the size of designed antenna. Parametric analysis on different parameters of designed antenna is done for achieving an optimal design with little compromise on antenna efficiency. Finally, the overall dimensions of patch, in terms of central frequency, are 0.0475 × 0.068 wavelengths. From the dimensions, it is shown that almost 84 % size of patch is reduced as compared to λ/2 patch antenna for 100 MHz. The designed antenna is flexible and conformal to the human body shape. Designed antenna is tested over human body and measurements of the return loss show that impedance bandwidth is 5 %.

ABSTRACT AC power lines not only provide electrical energy but can also be used as a communication medium for transmitting data. Besides having numerous advantages, there are certain issues which make the power line channel a hostile environment for communication. One major issue is the unpredictable variation in impedance of the network due to variable loads connected to or disconnected from the system, leading to poor transmission characteristics. These unpredictable variations need to be studied and characterized in order to obtain effective remedy of the problem. For this purpose, simulations were carried out in various scenarios to obtain the statistics/characteristics of impedance, so that useful statistical data are available for modem designers and matching circuit designers in power line communication.

ABSTRACT One way to combat channel fading and improve the wireless system performance is by using antenna diversity. Because of the presence of multiple multipath components, underground channels are prone to fading. In this paper, the performance enhancement provided by using a 1 2 space diversity system with the antennas designed at the LRCTS is investigated. The effect of the size of the demeaning window which allows to extract the fast fading signal component is also studied.

ABSTRACT This study reports on the measured polarisation diversity performance of on-body communication channels at 2.45 GHz. To perform the measurements, a new dual-polarised antenna was designed and fabricated. The antenna provides polarisations both normal and parallel to the body surface. Measurements were carried out with a subject wearing this antenna and moving in a laboratory environment. Diversity gains were then calculated for both the polarisation states based on the measured data. Reasonable gains of around 5 dB were achieved for the dynamic on-body channels, while static channels show little improvement.

Statistical analysis of the on-body diversity combined and branch signals are presented. The distribution of short-term fading envelopes of the branch and combined signals show that the fading environment for the on-body channels is Rician. The long-term fading best fits the log-normal distribution. The average best fit parameters are presented for short-term and long-term fading envelopes of the branch and combined signals. The Doppler spectra are also presented. Three different types of antennas were used and two on-body channels were characterized at 2.45, 5.8, and 10 GHz.

ABSTRACT The improvement in terms of channel capacity provided by using a MIMO antenna system in personal area networks is investigated. Two on-body channel models derived in the 2.45 GHz frequency band are also presented and applied to two on-body links. The first proposed model uses, for each spatial subchannel, the same average values for the Rician factor, received power, and shadowing deviation. The second model encompasses the polarization loss in the on-body channels by utilizing different values of these parameters per each spatial subchannel. Furthermore, the joint correlation matrix is used instead of the classical Kronecker product. It is shown that the second model results in a better agreement of the achievable capacity with the measured channel. Also, the equal power and waterfilling power allocation schemes are compared in such on-body channels and it is shown that, adopting waterfilling instead of the equal power provides a higher capacity in the low SNR range while yielding the same achievable capacity in high SNR.

Using multiple antennas at the transmitter and receiver has shown a remarkable scope for capacity increase for indoor wireless mobile and PAN communications and is here extended to on-body channels. The capacity and multiple-input multiple-output (MIMO) channel correlation analysis has been performed at 2.45 GHz frequency using planar inverted-F antennas (PIFA) for three on-body channels. The improvement offered by 2

Body-centric communications is an important part of fourth-generation personal communications systems. Like the mobile cellular communication channel, on-body communication channels are affected by fading. In this paper, the effect of diversity for on-body communication channels is investigated. Measurements were taken in both an anechoic and typical indoor environments, with random body movements. Three different types of antennas were used. The

ABSTRACT This paper describes an investigation into the polarization behavior of on-body wireless communication channels at 2.45 GHz. The effect of the polarization of an antenna on the channel path gain has been studied and the channel cross-polarization discrimination (XPD) has been quantified, using both simulation and measurement. In simulation, short dipole antennas, which significantly reduce the simulation time, were used to investigate path gain behavior in different channels for vertically and horizontally polarized antennas. Measurements were taken in an indoor environment using a novel dual-polarized antenna, producing normal and parallel polarizations to the body surface. The measured signals were also analyzed to extract the Rician K-factor which was defined as the ratio of the power in the line of sight (LOS) signal to the scattered power for various polarization combinations.

The Buriganga River is the main river in Dhaka city, capital of Bangladesh. The river not only surrounds Dhaka by two sides, but also it provides important services to the residents, including water supply, navigation, recreation, and sanitation and flood control. Due to the discharging and dumping of wastes in the river without treatment makes it almost look like an area which is lying under the blanket of pollution. This study focuses on the water pollution of Buriganga River and how it creates bad impacts on environment.

Transport is a key component and a crucial contributor to the social and economic development of any society. Depending upon how it is measured, transportation is responsible between 10-15 percent of Bangladesh's gross domestic product (GDP) and is accounting for nearly 15 percent of occupational employment. About 25 percent of government annual capital expenditure for development is put to transport development works. Transportation is thus a substantial part of the national economy and an important determinant of our lifestyle. Road transport in the carriage of freight and passenger traffic is by far the major mode of transportation in Bangladesh, accounting for more than 80 percent in tonne-km and more than 88 percent in passenger-km respectively.