Mohammad Rakibul Islam

Channel Estimated Cooperative MIMO in Wireless Sensor Network

Abstract Energy efficient data transfer is the key factor for the design of energy efficient wireless sensor network (WSN). In this paper, an energy efficient cooperative MIMO (C-MIMO) technique is proposed in the WSN where fixed constellation size is considered in transmitting both the local and long-haul communication. A selection criterion is used based on the channel conditions where a selected number of sensors in a cluster is used to form a multiple input multiple output (MIMO) structure wirelessly connected with multiple antennas of a data gathering node (DGN). The selected approach is tested on the correlated data scenario. Experimental results show that the selected C-MIMO structure outperforms the unselected C-MIMO in terms of total energy consumption and they show energy efficient performance over existing one when they are compared with SISO structure. Energy models are evaluated for this scenario while energy consumption and efficiency are compared for different combination of cluster sizes and selected number of sensors. Comparisons are shown for different fixed number of constellation sizes. The effect of correlation coefficient and intersensor distance are analyzed. Later, a delay analysis is shown considering optimal constellation size.

Porous core photonic crystal fibre for ultra-low material loss in THz regime

An extremely low-loss porous core circular photonic crystal fibre is presented for terahertz (THz) wave guidance. Much of attention is given to the geometries of the fibre to increase the fraction of power transmitted through core air holes. The finite-element method has been used to compute the modal characteristics of the fibre. Simulation results exhibit an ultra-low material loss of −0.05 cm−1 which is one-fourth of the bulk material loss and almost half of the useful power goes through core air holes at a frequency f = 1 THz. Besides, single-mode properties, confinement loss and dispersion of the fibre are rigorously discussed. The proposed fibre can be fabricated using capillary stacking or sol–gel technique and is useful for transmission applications in the THz frequency band.

PAPR in 3rd Generation Partnership Project Long Term Evolution: An Overview to Find the Impact

AbstractThird Generation Partnership Project Long Term Evolution (3GPP LTE) has adopted orthogonal frequency division multiple access (OFDMA) as the downlink and single-carrier frequency division multiple access (SC-FDMA) as the uplink for the multiple access scheme. SC-FDMA is adopted in the uplink due to its low peak-to-average-power ratio (PAPR). To reduce the PAPR in OFDMA, several techniques have been used in the literature. Many researches are still going on to find the impact of different parameters on PAPR in SC-FDMA. To further reduce the PAPR in SC-FDMA, techniques used to reduce the PAPR in OFDMA can be a potential choice. In this paper, we investigate some existing papers and find the opportunity to build a platform for further reduction in the PAPR in SC-FDMA environment.

Extremely low-loss, dispersion flattened porous-core photonic crystal fiber for terahertz regime

Abstract. A porous-core octagonal photonic crystal fiber (PC-OPCF) with ultralow effective material loss (EML), high core power fraction, and ultra flattened dispersion is proposed for terahertz (THz) wave propagation. At an operating frequency of 1 THz and core diameter of 345  μm, simulation results display an extremely low EML of 0.047  cm−1, 49.1% power transmission through core air holes, decreased confinement loss with the increase of frequency, and dispersion variation of 0.15  ps/THz/cm. In addition, the proposed PCF can successfully operate in single-mode condition. All the simulations are performed with finite-element modeling package, COMSOL v4.2. The design can be fabricated using a stacking and drilling method. Thus, the proposed fiber has the potential of being an effective transmission medium of broadband THz waves.

Optimized Min-Sum Decoding Algorithm for Low Density Parity Check Codes

Low Density Parity Check (LDPC) code approaches Shannon-limit performance for binary field and long code lengths. However, performance of binary LDPC code is degraded when the code word length is small. An optimized min- sum algorithm for LDPC code is proposed in this paper. In this algorithm unlike other decoding methods, an optimization factor has been introduced in both check node and bit node of the Min- sum algorithm. The optimization factor is obtained before decoding program, and the same factor is multiplied twice in one cycle. So the increased complexity is fairly low. Simulation results show that the proposed Optimized Min-Sum decoding algorithm performs very close to the Sum-Product decoding while preserving the main features of the Min-Sum decoding, that is low complexity and independence with respect to noise variance estimation errors.

Step-by-Step Approach for Energy-Efficient Wireless Sensor Network

Abstract Energy minimization has become a key factor for efficient data transfer in wireless sensor network (WSN). IEEE 1451.5 standard explores the wireless communication schemes between multiple sensors and a data gathering node (DGN) emphasizing the multiple input single output (MISO) structure. In this paper, an energy-efficient cooperative technique which is done using distributed computing is proposed for a WSN. Selected numbers of sensors are used here to form a MISO structure wirelessly connected with a DGN. The selection of nodes is based on a step-by-step selection procedure where residual energy and channel gain parameter play the key role in selection. Data are sent by the sensors to a DGN using a multihop transmission. Energy models are evaluated for both correlated and uncorrelated scenarios while energy efficiencies are compared for different combination of cluster size and selected number of sensors. Delay difference is also derived.

Cooperative communication in wireless sensor network using low density parity check codes

Energy efficient data transmission is one of the key factors for energy constraint wireless sensor network (WSN). Cooperative communication explores the energy efficient wireless communication schemes between multiple sensors and data gathering node (DGN). In this paper, an energy efficient cooperative technique is proposed considering low density parity check (LDPC) codes. The result shows that the proposed cooperative communication outperforms SISO transmission when the error correction code is considered. Bit error rate (BER) analysis is also performed. In this work, it shows that the lower encoding rate offers better error characteristics for same signal to noise ratio (SNR)

A highly birefringent slotted-core THz fiber

We present a slotted porous-core microstructure polymer fiber for polarization maintaining (PM) guidance of terahertz (THz) waves. The numerical analysis is performed using a full vector finite element method (FEM). Our proposed structure contains a compact hexagonal lattice in the cladding and rectangular slotted air-holes inside the core. Geometries inside the core have been designed to introduce asymmetry which results in a high modal birefringence of ∼0.08. Moreover, majority of the mode power is propagated in air medium to exhibit a very low effective material loss of ∼0.08 cm−1. Some other modal characteristics of the fiber are also discussed rigorously, which include confinement loss, mode power fraction, dispersion properties etc.

Intensity Reflection Coefficient Based Min-Sum Decoding for Low Density Parity Check Codes

Abstract Low Density Parity Check Codes (LDPC) give groundbreaking performance which is known to approach Shannon’s limits for sufficiently large block length. Historically and recently, LDPC have been known to give superior performance than concatenated coding. In the following paper, a proposal to modify the standard Min-Sum (MS) algorithm for decoding LDPC codes is presented. This is done by introduction of a factor, intensity reflection coefficient (IRC),κ in the check to bit node updating process. Simulation results demonstrate that the proposed algorithms are effective in imparting a better performance in terms of a lower bit error rate (BER) at low to medium signal to noise ratio (SNR) when compared to the traditional MS or Belief Propagation (BP) algorithm while adding a minimum amount of complexity. The proposed algorithm results in a reduced hardware complexity when implemented in VLSI.

Secret data communication in a degraded practical multiple input multiple output multiple eavesdropper channel

In this paper, a Gaussian multiple input multiple output multiple eavesdropper (MIMOME) channel is considered where a transmitter communicates to a receiver in the presence of an eavesdropper. We present a technique for determining the secrecy capacity of the multiple input multiple output (MIMO) channel under Gaussian noise. We transform the degraded MIMOME channel into multiple single input multiple output (SIMO) Gaussian wire-tap channels and then use scalar approach to convert it into two equivalent multiple input single output (MISO) channels. The secrecy capacity model is then developed for the condition where the channel state information (CSI) for main channel only is known to the transmitter. The results show that the secret communication is possible when the eavesdropper channel noise is greater than a cutoff noise level. The outage probability is also analyzed of secrecy capacity is also analyzed. The effect of fading and outage probability is also analyzed.