Gamantyo Hendrantoro

Effect of temperature and multiple scattering on rain attenuation of electromagnetic waves by a simple spherical model

Speciflc rain attenuation is discussed from the viewpoint of numerical solution for scattering and absorption of electromagnetic waves related to dielectric spheres. Special attention is paid to the quantitative evaluations considering the change of temperature and the existence of multiple scattering efiect. The analysis is based on the set of Strattons vector spherical wave functions and its addition theorem, which lead to the simultaneous linear equations for the expansion coe-cients with adaptively selected truncation numbers. Computed extinction cross sections lead directly to the speciflc rain attenuation, where the Weibull raindrop distribution model is used. It is discussed how the dependence of the permittivity of water on temperature and frequency afiects the attenuation property. Furthermore, the efiect of multiple scattering is evaluated in terms of the root mean square of attenuation deviation from the simple superposition of single scattering (Mies) coe-cients. Contrary to general belief, this deviation is the highest at around the boundary between microwave and millimeter wave bands.

A Multivariate Autoregressive Model of Rain Attenuation on Multiple Short Radio Links

A multivariate autoregressive (AR) model for rain attenuation on a network of radio links is presented. Underlying assumptions are discussed, including the stationarity of rainfall rate in space and time within the region enclosing the links. Formulation of the model is described, together with some considerations for its application in assessing performance of a network of radio links. An example of use of the model for simulation of rain attenuation on two short converging links operating at 30 GHz is given.

ARIMA Modeling of Tropical Rain Attenuation on a Short 28-GHz Terrestrial Link

This letter reports the result of modeling of the tropical rain attenuation at 28 GHz adopting the auto-regressive integrated moving average (ARIMA) model. The result obtained is useful for the evaluation of transmission system design in radio communications at millimeter-wave frequencies in tropical areas. In this research, radio power measurement on a 56.4-m link at 28 GHz was carried out in Surabaya, Indonesia, with a data acquisition system that recorded a sample once every second. Approximation of the data by ARIMA(p,d,q) models for every rain event was carried out in order to obtain a valid time series model. In the validation, comparisons were made of the distributions of attenuation from the models against those from direct measurement of attenuation and from estimation based on the synthetic storm method. Comparisons were also made of the attenuation slope distributions against that from the measurement. Each of rain attenuation time series obtained from events in February 2009 was found to be well approached by the ARIMA model with various sets of parameters (p,d,q). The best model was found to be ARIMA (0, 1, 1) , as indicated by the Akaike Information Criteria (AIC) and Schwarz Bayesian Criteria (SBC) test results. A procedure for generating rain events based on the model is presented.

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.

Image transmission with OFDM technique in underwater acoustic environment

Research developments and applications in the underwater acoustic communication fields have been a challenge for researchers. In this paper we present a study about image transmission over underwater acoustic channels. We present the 256 OFDM transmission technique with BPSK modulation, forward error correction (FEC)-Hamming (7,4), least square (LS) and minimum mean square error (MMSE) equalizations. The simulation results show that FEC-Hamming gives a good performance, e.g. 5 dB SNR results in 0.0017 BER and 20.84 dB SNR. The performance of LS equalization and MMSE equalization at the receiver are compared. MMSE equalization need approximately 12 dB SNR for the BER of 0.001, or 2 dB lower than the LS case.

Dynamic overlapping clustering algorithm for Wireless Sensor Networks

Clustering is believed to be the solution to the needs of energy efficiency as well as scalability in Wireless Sensor Network (WSN) application. In traditional clustering, each node belongs to only one cluster. However, some applications need some nodes to affiliate to more than one cluster. We propose a clustering algorithm that has capability to control the overlapping between clusters with still having ability to maintain the balance of energy consumption. Our proposed algorithm is a modification version of LEACH, so we call ours as Overlapping LEACH (O-LEACH). In the algorithm, we insert a mechanism so that it is able to control the overlap among clusters. In O-LEACH, as in original LEACH, a non-cluster-head (non-CH) will choose to join to a cluster-head (CH) that has largest received signal strength. Next, OLEACH will ask the node to affiliate to other CH that has received signal strength larger than X% from main CH. The X limit value is determined based on the expected overlapping degree. By simulation evaluation, O-LEACH has succeeded to control the overlapping among clusters. The proposed algorithm also still able to maintain the load balancing among node that be proven with the very little degradation compared to original LEACH on the performance of maintaining the balance of energy consumption.

A New Scheme for Evaluating Video Transmission over Broadband Wireless Network

Video streaming is a multimedia service that gains significant development in recent years. The main problem that arises within that service is bandwidth fluctuation utilization on wireless channel network. In this paper, we propose combined methods of scalability as an attractive solution for the aforementioned problem. Scalable method on wireless communication must be suited to processed input/video sequence. To create combined scalable video coding (CSVC) method that match the QoS (Quality of Service) of video streaming service on wireless channel, we use joint scalable video model (JSVM) amendment standard. The proposed scheme has implemented on Network Simulator II (NS2) for wireless broadband network application. This new scheme is an evaluation platform for the implementation CSVC on a more realistic simulation over wireless broadband networks based on open-source program. The results show that implementation of CSVC on mode of the medium grain scalable (MGS) outperforms coarse grain scalable (CGS) mode.

Improved range-free localization methods for wireless sensor networks

Localization in wireless sensor networks (WSNs) is an essential service, important as both a goal and a mean. It is a goal for WSNs in order to label reported data and a mean for most WSNs to implement networks management services. In distributed localization, there could be a small number of nodes, which have a priori knowledge about their position, called reference nodes and most of the other nodes which do not know their location. Range-free localization technique is the cost-effective technique because it does not require sensors to be equipped with any hardware, but use less information than range-based algorithm. Centroid algorithm is one of the range-free technique, where the references send out their position information to neighbor nodes at periodic intervals. The position of unknown node is then estimated to be centroid of the reference nodes. In this paper, we propose the improved centroid algorithm by selecting the neighbor references based on the connectivity of unknown node and them. Simulation results show that the localization error of unknown nodes is reduced by the proposed method.

Statistical of rain rates for wireless channel communication in Surabaya

This paper present an initial result of research on channel modeling of millimeter wave wireless channel in Indonesia considering the impact of rain rate of rainfall due to microwave attenuation, fading and wave polarization propagations millimeter in 30 GHz.. The channel model developed in time series (time domain) by assuming channel as a random variable. The rain data is based on retrieval result from Parsivel equipment with software ASDO recorded data in online manner. The statistical value of rain, i.e. mean, Varian, autocorrelation, and auto ovarian from rainfall is modeled. For goodness-of-fit test used Kolmogorov-Smirnov (K- S) test for continuous distributions and to generate long-term rain- rate model, the of Autoregressive (AR) method, Moving Average (MA), and Autoregressive Moving Average (ARMA) are applied on rainfall data measured in ITS Surabaya.

Measurement of Time-Varying Rainfall Rate in Surabaya and Estimation of Attenuation Statistics by Synthetic Storm Technique

Measurement of time-varying rain rate has been performed in Surabaya using an optical disdrometer. The results suggest that consecutive samples of rain rate in Surabaya possesses higher correlation than those measured in such non-tropical sites like Barcelona. Attenuation statistics obtained from a simulation study by means of the synthetic storm technique applied to the rain rate time series measurements agree with those predicted by ITU-R only for links of 1-2 km length at outage probabilities in the range of 0.01-0.1%. The simulation results also show that the use of daily and monthly averages of wind velocity does not yield significant differences in the attenuation statistics.