Puji Handayani

An autoregressive model for simulation of time-varying rain rate

An autoregressive (AR) model for computer generation of time-varying lognormally distributed rainfall rate is presented. The AR coefficients are derived from rain rate statistics and autocorrelation function obtained from measurement. Results from computer simulations are found to fit well with rain rate data from Barcelona.

A measurement system for space-time variation of rainfall rate and millimeter-wave specific attenuation in Indonesia

A system designed to measure the space-time variation of rainfall rate R (mm/h) and specific attenuation Y (dB/km) is presented. The design constraints include a limited budget and a desired capability of capturing realistic propagation conditions expected to occur in millimeter-wave wireless systems with short links operating in a tropical region. The system consists of a disdrometer, a network of rain gauges, and a 29 GHz transmitter-receiver set, all to operate in a small campus area. The rain gauges will measure the distribution and space-time variation of rain rate. The disdrometer will measure drop size distributions necessary to derive the power-law coefficients for R-to-Y conversion, to be verified against measurements of attenuation on the 29 GHz link.

Characterization of DOD and DOA correlation among converging indoor radio links by applying reciprocity principle

Many works on single link multi antenna channel characterization have been reported and adopted as parts of standardized channel model. In this paper we report the characterization of converging multi-antenna channels, particularly the correlations of direction of departure (DODs) and direction of arrivals (DOAs) of multipath component signals (MPCs) in two scenarios, first, multiple radio links between one transmitter and several receivers, and second, between several transmitters and one receiver, both in indoor non line of sight (NLOS) environment. We argue that DOD and DOA correlation of the second situation are identical to the first one according to the reciprocity principle of the channel. Through measurements we show that this channel reciprocity principle is well confirmed. We have conducted a set of measurement of the first situation described above to characterize the DOD and DOA correlation and propose curtailed Gaussian for statistical model of their distribution.

Pathloss and shadowing characteristics in indoor environment at 2.4 GHz band

This paper discusses the characteristics of attenuation and shadowing in indoor environment at 2,4 GHz. The characterization is done through measurements in the lab of Department of Electrical Engineering ITS using WARP (Wireless Open Access Reasearch Platform) equipment. This study is a beginning part of a further research about shadowing correlation in indoor cooperative link. The measurement results showed that the path loss exponent of the considered environment is 4, and the shadowing follows lognormal distribution with a standard deviation of 6.4 dB. These are relevant to the results found in the literatures.

A Model of Double-Directional Indoor Channels for Multiterminal Communications

We propose a model of double-directional indoor nonline of sight (NLOS) channels for multiterminal communications. We derive a simple channel matrix that describes input-output relationship for such channels. The multiterminal systems may consist of several terminals that act as amplify-and-forward (AF) relays, where source, relays, and destination have arbitrary numbers of antennas. We complete our model by characterizing the parameters of double-directional channel impulse response of such channels through measurements in indoor environment using 3D synthetic array antenna at 2.5 GHz band. To find out the relation between spatial characteristic of channels in each hop, we observe the direction of arrival (DOA) and direction of departure (DOD) of multipath component signals at the terminal that acts as relay. We find that there are several closely matched azimuths of DOAs and azimuths of DODs which follow uniform distribution in the range of −180° to 180° for elevation around the broadside direction of vertical omnidirectional elements of arrays.

Analisa Teknik Dua Polinomial untuk Penekanan Sidelobe

Dalam radar, antena array sering digunakan karena memiliki nilai gain yang besar dan semakin banyaknya elemen yang digunakan nilai puncak sidelobe yang dihasilkan semakin rendah. Namun jumlah sidelobe akan semakin banyak dan sistem akan semakin kompleks. Untuk membatasi jumlah elemen, diperlukan metode yang menghasilkan nilai puncak sidelobe yang rendah. Metode sidelobe suppression (SLS) dengan teknik dua polinomial merupakan metode penekanan nilai sidelobe dengan cara mengalikan dua faktor array. Dengan jumlah elemen dan null yang ditentukan, pola radiasi yang didapat pada polinomial pertama digunakan untuk mencari posisi null kanan dan kiri yang berdekatan dengan mainlobe. Daerah diluar null tersebut dimanfaatkan untuk wilayah sidelobe serta digunakan untuk mencari bobot dari polinomial kedua yang ditujukan untuk penekanan sidelobe. Dalam penelitian ini, metode dibuat berdasarkan literatur penelitian Zafar-Ullah, Aqdas dan Fahad yang berjudul “Efficient Sidelobe Suppression by Matching Beam in Two Polynomial Technique”. Hasil simulasi kemudian dibandingkan dengan pola radiasi antena array uniform linier dengan 9 elemen dan jarak antar elemennya sebesar λ /2. Berdasarkan hasil simulasi, puncak sidelobe level (PSLL) yang dihasilkan pada antena array dengan metode dua polinomial sebesar -21,07 dB dan lebih rendah dibandingkan dengan PSLL pada antena array tanpa metode yaitu sebesar -11,92 dB.

Double-directional outdoor MIMO channel measurement at 2.4 GHz using SDR

Wireless communication offers greater mobility to users but also susceptible to disruption because of many scatterers result multipath fading. Proper knowledge about the conditions and characteristics of scatterers around communication channel is very important to evaluate the performance of communication systems. By measuring the double directional we could have knowledge about the direction of radio wave propagation. It could lead us to predict the scattering point which dissipating the radio wave. This paper reports the measurement system build on software defined radio (SDR) platforms at 2.4 GHz band and the preliminary measurement results of the MIMO channel at outdoor environment. Space Alternating Generalized Expectation-Maximization (SAGE) algorithm is used to estimate the parameters of the channel, i.e., delay, double directional (DOD and DOA), and complex amplitude of multipath component signals (MPCs) to observe scattering mechanism around MIMO communication link. The 2×2 MIMO channel measurements were performed at the courtyard of Robotics building at Institut Teknologi Sepuluh Nopember (ITS). Our measurement system use a sampling rate of 33.33 MHz, so it is only capable of separating two multipath component signals that have interval delay greater than or equal to its delay resolution which is 60 ns. Using SAGE we estimate the parameters of MPCs. Then we verify the obtained parameters value using simple ray tracing. The results show that there are three MPCs with different delay. They are a LOS component, a signal component scattered by the surface of the ground, and a signal component scattered by Robotics building. Therefore, for this measurement we conclude that there are two scattering objects which are ITS Robotics building and the land surface.

Performance analysis of the SAGE algorithm: Changing the update procedure

The extraction of multipath component signals from measured radiowave propagation channel can be carried out using some algorithms. One of these algorithms is Space Alternating Generalized Expectation-Maximization (SAGE). SAGE is based on two procedures, i.e., Expectation Step (E-Step) and Maximization Step (M-Step). In the E-Step, we decompose signal and noise while in the M-Step we update the parameters estimate, which are delay, DOA (direction of arrival), DOD (direction of departure), doppler shift, and complex amplitude consecutively. However, if the measurement systems used to sounding the channel have low delay resolution, we will have difficulty in separating multipath component signals (MPCs). In this paper we propose to change the update procedure to overcome this difficulty. The simulation results show that the performance of the proposed procedure does not change significantly compare to the original SAGE.

Simulation design of triple band metamaterial absorber for radar cross section reduction

The existence a problem of military vehicles at ship susceptible to noise propagation caused by a vibration of machine inside engine room. To solve interference problem that, it can be used by Radar Absorbing Material (RAM) such as metamaterial absorber in engine control room, so in this research will be proposed the design and simulation of metamaterial absorber at frequency in triple band that implemented at engine control room as reducer machine ship so it happen not interference to outside engine ship. Design of the metamaterial absorber will done with determine dimension and shape of metamaterial absorber and it will simulated with CST Microwave Studio 2012 software. The result of simulation at triple band metamaterial absorber brings S11 at frequency 2.079 GHz is −12.041 dB, so resulting the value of absorption is 99.6 %. For S11 at frequency of 2.895 GHz is −9.869 dB, so resulting the value of absorption is 98.93 % and frequency of 3.894 GHz is −15.544 dB, so resulting the value of absorption is 99.92 %. It show that the absorber has a good absorbing performance (absorption > 80 %) from three peaks frequency.