In this paper, relation between phase shifts due to chromatic dispersion with different subcarrier frequencies is investigated. To compensate the phase shift a method using pilot carriers is proposed in two different ways to minimize the BER. Using matlab simulation it is shown that dividing the subcarriers in groups and allocatingdifferent pilot for different groups gives better result than considering the pilot carriers over all subcarriers. SNR of 13dB is required to achieve 10-4 BER if conventional method of averaging is used where 11dB is enough to achieve the same BER by implementing our proposed method.
 

In this paper, a new approach of establishing database to estimate phase noise due to chromatic dispersion is proposed. The database can be used to compensate phase shift without using any pilot carriers, which results in high spectral efficiency and low BER. Time variability, temperature and aging effects of channel are introduced in order to ensure the suitability of the database for stable long termperformance. The proposal is confirmed by simulation using matlab.
 

In this paper, a new nonlinear companding technique, called “double companding” is proposed to reduce high Peak-to-Average Power ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) signals. In the double companding scheme, primarily companded signals are further companded by which the PAPR can be improved significantly. However, simulation shows that there is a trade-off between reduction of the PAPR and Bit Error Rate (BER).
 

In this paper, a new technique of BER minimization in a companding based PAPR reduction scheme is proposed. In this approach, the conventional companding scheme is only applied for those OFDM signals whose amplitude exceeds a predefined threshold level, which results in lower BER and lower computational time. Though for the proposed scheme, improvement of the PAPR is less than the conventional companding technique, however, BER performance is improved significantly.

In this paper, a new adaptive PAPR reduction scheme is proposed by which the PAPR of the OFDM signal can be reduced to keep the value lower than a predefined threshold level. A conventional companding is used as a technique to reduce the PAPR of the OFDM signal. If the PAPR of the OFDM signal is higher than any predefined level, one or more times companding operations are performed until the PAPR becomes lower than that level. On top of that, no companding is applied if the signal’s PAPR is lower than the predefined level. However, there is a trade-off between the improvement of the PAPR and BER which may be optimized based on any specific application requirements.

A compact capsule shaped multiband wearable antenna is presented in this paper. The antenna is composed of two nested C elements which operates at WMTS (1.43 GHz), GPS L1 (1.575 GHz), GPS L2 (1.227 GHz), DCS/GSM1800 and UWB (4.4-8.52 GHz) frequency bands. The designed antenna has a compact dimension of 27.11×19.92×0.4 mm³ and is employed on flexible Liquid Crystal Polymer (LCP) substrate. Considering -10dB reflection coefficient, the relative bandwidths for the lower and higher frequency bands are about 50.76% and 62.96% respectively. The performance of the antenna under structural deformation and on-body placement are also analyzed. The compact size, multiband operation, resilient to frequency detuning in on-body configuration with low specific absorption rate make the proposed antenna suitable for the wireless body area network (WBAN) applications.

A compact and broadband wearable antenna is presented in this paper. The coplanar waveguide (CPW) feed antenna is composed of a modified rectangle patch with truncated top and bevelled bottom corners which operates from 3.2 to 14 GHz frequency band. The proposed antenna is employed on flexible Liquid Crystal Polymer (LCP) substrate and has a compact dimension of 37.91×28.39×0.88 mm³. The fractional bandwidth of the antenna is about 125.58% by taking -10dB reflection coefficient into consideration. The performance of the antenna under structural deformation, humid condition and on-body placement are also evaluated. The wideband operation, compact size, resilient to frequency de-tuning in on-body configuration with low specific absorption rate make the proposed antenna suitable for the wireless body area network (WBAN) applications.

for achieving GPA 5 out of 5 in Higher Secondary Certificate Examination, 2006.

Achieved four times at IUB.

For maintaining a good CGPA in Undergraduate Study, Independent University Bangladesh (IUB) honored as "Magna Cum Laude"

Turkish Govt. Scholarship for M.Sc Program, 2012.

In Recognition of Outstanding Contribution in Research.