Analisa Kinerja Penerapan Standard Protokol Keamanan IEEE 802.11 Pada Layanan Wireless Fidelity

Jaringan komunikasi semakin bergantung pada WLAN, maka semakin tinggi tuntutan Quality of Service (QoS) WLAN seperti Throughput, delay, dan jitter Untuk menjaga keamanan media komunikasi data, maka digunakan mekanisme keamanan jaringan Wired Equivalent Privacy (WEP), WiFi Protected Access (WPA), dan WPA2 [14]. Mall Bali Galeria memiliki beberapa alternatif Free WiFi. Banyaknya Wi-Fi yang terpasang menimbulkan permasalahan interferensi yang mempengaruhi unjuk kerja jaringan WiFi, MBG sendiri memiliki area Indoor dan Outdoor, Alternatif untuk mengatasi interferensi adalah dengan melakukan automasi penkanalan dengan menerapkan Channel Fly, Background Scanning dan Static Channel. Dari mekanisme keamanan, Penkanalan dan frekuensi dibuat skenario dilakukan penelitian pada setiap askes point untuk mendapatkan skenario terbaik, dari skenario yang diajukan, nilai Paket loss terbaik lingkungan indoor AP 4 dengan skenario frekuensi 5Ghz, Statik Channel, WEP-64 paket loss 0,016 ms, lingkungan outdoor AP 5 Frekuensi 5Ghz, Channel Fly, WEP-64 paket loss 0.094 ms, nilai Jitter terbaik lingkungan indoor AP 2 5Ghz Background Scanning, WPA 2, Jitter 1.336 ms, lingkungan outdoor AP 8 5Ghz, Statik Channel, WPA2-Mixed Jitter 1,116 ms, nilai Throughput terbaik lingkungan indoor AP 1 5Ghz, Statik channel, WPA2-Mixed, Throughput 78,7Mbps, untuk Outdoor AP 8 5Ghz, Background Scanning, Disable Security, Throughput 80Mbps jika dibandingkan dengan skenario eksisting performa unjuk kerja meningkat sebesar 10-30%. WEP memiliki nilai packet loss baik tetapi memiliki nilai Throughput yang lebih kecil. Static channel disarankan pada lokasi yang memiliki interferensi tinggi.

Improving Performance of Bell Labs Layered Space-Time Systems by Multiframe Space-Time Interleavers

Turbo-BLAST (T-BLAST) is a multiple-input multiple-output (MIMO) wireless communication system. It is based on three main concepts: Bell laboratories layered space-time (BLAST) architecture, random space-time interleaving, and the turbo principle. T-BLAST system has many advantages including high data rate, excellent performance, and low complexity. These advantages make T-BLAST one the most important choices for future wireless communication systems. In this article, the authors study the effect of the space-time interleaver on the performance of T-BLAST system. This interleaver is split into two separated stages, time interleaving followed by space interleaving. They show that, in a quasi-static channel, the enhancement in performance provided by the time interleavers is very small compared to the gain provided by space interleavers. They also propose a new technique to improve the system performance, called multiframe space-time interleaving (MUSTI). Simulation results show an improvement in performance up to 6 dB at BER=10-4 for a (2,2) configuration.

ТЕПЛООБМЕН ВО ВРАЩАЮЩЕМСЯ ГЛАДКОМ КРУГЛОМ КАНАЛЕ И ВЛИЯНИЕ НА ЕГО ИНТЕНСИВНОСТЬ ВИХРЕВОГО ТЕЧЕНИЯ

The paper deals with the analysis of heat transfer intensity in a rotating smooth channel, which simulates a cooling channel of rotating blade of the gas turbine engine. A circle cross-section channel with a diameter of 6 mm and length of 80 mm was chosen as the base variant. The calculations of heat transfer in rotating and stationary channels were carried out, which allows estimating the influence of vortex flow on the intensity of heat transfer. Rotation of the channel was simulated by means of domain rotating. The rotation speed of the test channel is 7400 rev/min. Axis of rotation is at a distance of 0.49 m from the inlet section of the channel. Pressure and temperature were specified as inlet boundary conditions: 1040000 Pa and 733 K, respectively. The mass flow rate of 0.02 kg/s was specified as outlet boundary conditions. The computations were performed by solving the Reynolds-averaged Navier-Stokes equations (RANS method) using an SST (Shear Stress Transport) turbulence model. The air ideal gas was used as the working medium. The calculation was performed taking into consideration the Buoyancy effect. Verification of heat exchange calculation model in the rotary channel of the gas turbine engine rotor blade according to experimental data is carried out. The boundary conditions at the input and output of the channel were set in such a way that the flow parameters in the calculation corresponded to the experimental characteristics. The resulting numerical calculations of the temperature distribution and Nusselt Numbers are qualitatively and quantitatively consistent with the experiment. The distribution of Nusselt Numbers on the front and back walls for rotating and non-rotating channels, as well as the dependences of the relative tangential velocity on the relative channel length, were estimated. It has been shown that average Nusselt Number on the leading wall of the rotating channel is the same with the wall of the static channel, but detail Nu distribution over rotating leading wall undergoes considerable modification. Average Nusselt Number on the trailing wall of the rotating channel is higher than on the wall of the static channel, but the detail Nu distribution pattern on the rotating trailing wall generally follows the static result.

A Secure Transmission Scheme Based on Artificial Fading for Wireless CrowdSensing Networks

For secure transmission of low cost single antenna communication nodes in wireless crowdsensing networks under static channel, a physical layer communication scheme is proposed, where each digital modulated symbol is encrypted by a random key at the transmitter and decrypted with the same key at the receiver. The legal users exploit the synchronized chaotic sequence and the two-stage block interleaver to generate a complex random variable (random key), whereby its envelope obeys the Rayleigh distribution and its phase obeys the uniformly distribution. The modulated symbol is multiplied by the complex random variable (encryption) to imitate the Rayleigh fading of the channel at the transmitting end. The received symbol is divided by the identical complex random variable (decryption) to recover the transmitted message before the digital demodulation at the receiving end. Simulation results show that the bit error ratio (BER) performance of the legitimate users is consistent with the theoretical value of the Rayleigh fading channel, while the corresponding BER of the eavesdropper is too high (about 0.5) to intercept any information.

Influence of Rotating Directions on Hydro-Thermal Characteristics of a Two-Pass Parallelogram Channel With Detached Transverse Ribs

Two pairs of detailed Nusselt number (Nu) distributions on leading (LE) and trailing (TE) endwalls together with the Fanning friction factors (f) of a rotating two-pass parallelogram channel enhanced by the detached transverse ribs are simultaneously measured under forward and backward rotations. The tested Reynolds number, rotating number, density ratio, and buoyancy number are respectively in the ranges of 5,000 ≤ Re ≤ 15,000, 0 ≤ Ro ≤ 0.3, 0.044 ≤ Δρ/ρ ≤ 0.2, and 0 ≤ Bu ≤ 0.142. Due to the accelerating flows through the gaps between the detached ribs and channel endwalls, the transverse high Nu stripe emerges along the projection area of each detached rib on both static and rotating smooth endwalls. The disparities in the relative directions between Coriolis forces and channel periphery that restrains Coriolis flows at forward and backward rotations cause different heat transfer properties on the two pairs of rotating LE and TE. The area-averaged leading and trailing Nusselt numbers at forward rotations are 0.69–1.77 and 0.85–1.98 relative to the static-channel Nusselt number references (Nu0) respectively. With backward rotations, the ratios of regionally averaged Nusselt numbers between rotating and static channels for leading and trailing walls fall in the respective change to 0.86–2 and 0.91–1.76. At both forward and backward rotations, all the f factors over LE and TE are elevated from the static-channel levels (f0) and increased by increasing Ro. Channel averaged f/f0 ratios are respectively raised to 1.21–2.21 and 1.21–2.1 at forward and backward rotations. As the heat transfer enhancements attributed to the presence of detached transverse ribs taking precedence of the accompanying f augmentations, all the thermal performance factors (TPF) are above unity in the range of 1.26–2.94. Relative to the similar rotating two-pass parallelogram channel with attached 90° ribs, the detached ribs generate the higher degrees of heat transfer enhancements with the larger extents of f augmentations.

Influence of Rotating Directions on Hydrothermal Characteristics of a Two-Pass Parallelogram Channel With Detached Transverse Ribs

The detailed Nusselt number distributions on leading and trailing endwalls together with the Fanning friction factors of a rotating two-pass parallelogram ribbed channel are simultaneously measured under forward and backward rotations. The tested Reynolds number, rotation number, density ratio, and buoyancy number are respectively in the ranges of 5000 < Re < 15,000, 0 < Ro < 0.3, 0.044<Δρ/ρ < 0.2, and 0 < Bu < 0.142. The area-averaged leading and trailing Nusselt numbers at forward rotations are 0.69–1.77 and 0.85–1.98 relative to the static-channel Nusselt number references, respectively. With backward rotations, the ratios of regionally averaged Nusselt numbers between rotating and static channels for leading and trailing endwalls fall in the respective range to 0.86–2 and 0.91–1.76. At both forward and backward rotations, all the f factors over leading endwall (LE) and trailing endwall (TE) are elevated from the static-channel levels and increased by increasing Ro. Channel averaged f/f0 ratios are respectively raised to 1.21–2.21 and 1.21–2.1 at forward and backward rotations. As the heat transfer enhancements (HTE) attributed to the presence of detached transverse ribs taking precedence of the accompanying f augmentations, all the thermal performance factors are above unity in the range of 1.26–2.94. Relative to the similar rotating two-pass parallelogram channel with attached 90 deg ribs, the detached ribs generate the higher degrees of heat transfer enhancements with the larger extents of f augmentations.

Translocation of structured biomolecule through a vibrating nanopore

ABSTRACTWe study the effect of fluctuating environment in protein transport dynamics. In particular, we investigate the translocation of a structured biomolecule (protein) across a temporally modulated nano-pore. We allow the radius of the cylindrical pore to oscillate harmonically with certain frequency and amplitude about an average radius. The protein is imported inside the pore whose dynamics is influences by the fluctuating nature of the pore. We investigate the dynamic and thermodynamical properties of the translocation process by revealing the statistics of translocation time as a function of the pulling inward force acting along the axis of the pore, and the frequency of the time dependent radius of the channel. We also examine the distribution of translocation time in the intermediate frequency regime. We observe that the shaking mechanism of pore leads to accelerate the translocation process as compared to the static channel that has a radius equal to the mean radius of oscillating pore. Moreover, the translocation time shows a global maximum as a function of frequency of the oscillating radius, hence revealing a resonant activation phenomenon in the dynamics of protein translocation.

Heredity and Evolutionary Theory

Heredity is a central concept in biology and one of the core principles needed for adaptive evolution. For most of the past 100 years, heredity has been defined and conceptualized in terms of transmission of genes. This is heuristically useful but imposes a certain structure on evolutionary theory and leaves out aspects of heredity that may be important to understand evolution. Emerging developmental perspectives on evolution suggests that alternative ways to represent heredity may prove useful. To this end, this chapter explains how evolutionary biologists treat heredity, conceptually and mathematically. It argues that treating heredity as an outcome of developmental processes not only makes it clearer how different mechanisms of inheritance contribute to evolution but also shows that inheritance cannot be treated as a static channel of transmission of information because it evolves as part of the process of adaptation.

On Carrier Sensing Accuracy and Range Scaling Laws in Nakagami Fading Channels

We make a detailed study on carrier sensing of 802.11 in Nakagami fading channels. We prove that to maximize sensing accuracy, the optimal channel accessing probability is solely determined by the path-loss SIR (Signal to Interference Ratio). We define pfail-interference range and pbusy-carrier sensing range for fading channels and prove that their scaling laws in Nakagami fading channels are similar to those in the static channel. The newly derived theoretical results show a unified property between the static and fading channels. By extensive simulations, we reveal that fading depresses the probability of a dominating transmission state, and therefore it can mitigate severe hidden and exposed terminal problems, but fading harms the average sensing accuracy for an optimally adjusted carrier sensing threshold.