Estimation of Rain Attenuation at EHF bands for Earth-to-Satellite Links in Bangladesh

Due to heavy congestion in lower frequency bands, engineers are looking for new frequency bands to support new services that require higher data rates, which in turn needs broader bandwidths. To meet this requirement, extremely high frequency (EHF), particularly Q (36 to 46 GHz) and V (46 to 56 GHz) bands, is the best viable solution because of its complete availability. The most serious challenge the EHF band poses is the attenuation caused by rain. This paper investigates the effect of the rain on Q and V bands' performances in Bangladeshi climatic conditions. The rain attenuations of the two bands are predicted for the four main regions of Bangladesh using ITU rain attenuation model. The measured rain statistics is used for this prediction. It is observed that the attenuation due to rain in the Q/V band reaches up to 150 dB which is much higher than that of the currently used Ka band. The variability of the rain attenuation is also investigated over different sessions of Bangladesh. The attenuation varies from 40 dB to 170 dB depending on the months. Finally, the amount of rain fade required to compensate the high rain attenuation is also predicted for different elevation angles.Comment: Int'l Conf. on Electrical, Computer and Communication Engineering (IEEE sponsored), Cox's Bazar, Bangladesh, February 2017, pp. 589-59

Sensing Models and Its Impact on Network Coverage in Wireless Sensor Network

Network coverage of wireless sensor network (WSN) means how well an area of interest is being monitored by the deployed network. It depends mainly on sensing model of nodes. In this paper, we present three types of sensing models viz. Boolean sensing model, shadow-fading sensing model and Elfes sensing model. We investigate the impact of sensing models on network coverage. We also investigate network coverage based on Poisson node distribution. A comparative study between regular and random node placement has also been presented in this paper. This study will be useful for coverage analysis of WSN.Comment: 5 pages, 5 figures, IEEE Region 10 Colloquium and the Third ICIIS, Kharagpur, INDIA December 8-10, 200

Strong enhancement of Jc in binary and alloyed in-situ MgB2 wires by a new approach: Cold high pressure densification

Cold high pressure densification (CHPD) is presented as a new way to substantially enhance the critical current density of in situ MgB2 wires at 4.2 and 20 K at fields between 5 and 14 T. The results on two binary MgB2 wires and an alloyed wire with 10 wt.% B4C are presented The strongest enhancement was measured at 20K, where cold densification at 1.85 GPa on a binary Fe/MgB2 wire raised both Jcpara and Jcperp by more than 300% at 5T, while Birr was enhanced by 0.7 T. At 4.2K, the enhancement of Jc was smaller, but still reached 53% at 10 T. After applying pressures up to 6.5 GPa, the mass density dm of the unreacted (B+Mg) mixture inside the filaments reached 96% of the theoretical density. After reaction under atmospheric pressure, this corresponds to a highest mass density df in the MgB2 filaments of 73%. After reaction, the electrical resistance of wires submitted to cold densification was found to decrease, reflecting an improved connectivity. A quantitative correlation between filament mass density and the physical properties was established. Monofilamentary rectangular wires with aspect ratios a/b < 1.25 based on low energy ball milled powders exhibited very low anisotropy ratios, Gamma = Jcpara/Jcperp being < 1.4 at 4.2 K and 10T. The present results can be generalized to alloyed MgB2 wires, as demonstrated on a wire with B4C additives. Based on the present data, it follows that cold densification has the potential of further improving the highest Jcpara and Jcperp values reported so far for in situ MgB2 tapes and wires with SiC and C additives. Investigations are under work in our laboratory to determine whether the densification method CHPD can be applied to longer wire or tape lengths.Comment: Submitted to Superconductors Science and Technolog

A study of the Haor areas of Sylhet-Mymensing districts with ERTS imageries (winter crop estimation)

There are no author-identified significant results in this report

Non-Fermi-liquid behavior at anti-ferromagnetic quantum critical point in heavy fermion system Ce(Cu1−x_{1-x}Cox_x)2_2Ge2_2

Polycrystalline samples of Ce(Cu$_{1-x}$Co$_x$)$_2$Ge$_2$ were investigated by means of electrical resistivity $\rho$($T$), magnetic susceptibility $\chi$($T$), specific heat $C$$_p$($T$) and thermo electric power $S$($T$) measurements. The long-range antiferromagnetic (AFM) order, which set in at $T$$_N$ = 4.1 K in CeCu$_2$Ge$_2$, is suppressed by non-iso-electronic cobalt (Co) doping at a critical value of the concentration $x$$_c$ = 0.6, accompanied by non-Fermi liquid (NFL) behavior inferred from the power law dependence of heat capacity and susceptibility i.e. $C$($T$)/$T$ and $\chi$($T$) $\propto$ $T$$^{-1+\lambda}$ down to 0.4 K, along with a clear deviation from $T$$^2$ behavior of the electrical resistivity. However, we have not seen any superconducting phase in the quantum critical regime down to 0.4 K.Comment: 8 pages, 11 figure

Throughput Maximization in Cloud Radio Access Networks using Network Coding

This paper is interested in maximizing the total throughput of cloud radio access networks (CRANs) in which multiple radio remote heads (RRHs) are connected to a central computing unit known as the cloud. The transmit frame of each RRH consists of multiple radio resources blocks (RRBs), and the cloud is responsible for synchronizing these RRBS and scheduling them to users. Unlike previous works that consider allocating each RRB to only a single user at each time instance, this paper proposes to mix the flows of multiple users in each RRB using instantly decodable network coding (IDNC). The proposed scheme is thus designed to jointly schedule the users to different RRBs, choose the encoded file sent in each of them, and the rate at which each of them is transmitted. Hence, the paper maximizes the throughput which is defined as the number of correctly received bits. To jointly fulfill this objective, we design a graph in which each vertex represents a possible user-RRB association, encoded file, and transmission rate. By appropriately choosing the weights of vertices, the scheduling problem is shown to be equivalent to a maximum weight clique problem over the newly introduced graph. Simulation results illustrate the significant gains of the proposed scheme compared to classical coding and uncoded solutions.Comment: 7 pages, 7 figure