nan Wirawan

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.

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.

Underwater sound propagation characteristics at mini underwater test tank with varied salinity and temperature

In this paper, we report the development of water tank for underwater acoustic communication. Compared to most of underwater test tank, the tank may be considered as mini in term of its size. However, the test tank is intended to serve as controlled environment to develop a theoretical model and its validation experimentally before full-scale test at sea. We present on how to analyze the physical characteristics of the test tank with respect to salinity and temperature affected to speed and pattern of propagation waves. We designed the test tank made of 12mm thick of glass with dimension 2 × 1 × 1 in meter, then we placed corrugated sponges inside the walls to reduce the echo from signal that we generated. The measurements were conducted by placing array of hydrophones and analyze the propagating waves in fresh water with variation temperature 15°C, 20°C, 25°C and 30°C to simulate depth. In term of salinity we fixed at room temperature 30°C and varied the salinity of 3.1%, 3.2% 3.3%, 3.4% and 3.5%, respectively. The results showed that the sound propagation characteristics are in agreement with previous studies. This may suggest that the test tank may serve as small scale underwater acoustic experiment with controlled environment.

Adaptive Combined Scalable Video Coding over MIMO-OFDM Systems using Partial Channel State Information

This paper proposes an adaptive combined scalable video coding (CSVC) system for video transmission over MIMO-OFDM (Multiple-Input Multiple-Output-Orthogonal Frequency Division Multiplexing) broadband wireless communication systems. The scalable combination method of CSVC adaptively combines the medium grain scalable (MGS), the coarse grain scalable (CGS) and the scalable spatial modes with the limited feedback partially from channel state information (CSI) of MIMO-OFDM systems. The objective is to improve the average of peak signal-to-noise ratio (PSNR) and bit error rate (BER) of the received video stream by exploiting partial CSI of video sources and channel condition. Experimental results show that the delivered quality using the proposed adaptive CSVC over MIMO-OFDM system performs better than those proposed previously in the literature.

Soft acoustic modem development for shallow water environment

Development of an underwater acoustic communication system is a necessity for the majority of the nation as a sea area of Indonesia. Most area s of the ocean in Indonesia is shallow, the environment has unique characteristics compared to other countries. It is a challenge in the research underwater acoustic communication system. This paper presented a preliminary study of the developing of soft acoustic modem testbed for underwater acoustic communication system with OFDM technique. Modem has been implemented on a PC with Matlab, with the objective to evaluate the algorithm development. Image file in JPEG format is encoded with a discrete cosine transform (DCT). To improve performance, information is encoded with a forward error correction, FEC-Hamming. The system uses BPSK modulation, OFDM transmission techniques, and using acoustic signal as carrier wave. In this system, the occupation bandwidth is 5.3 kHz, transmission rate of 3.7 k sps, and center frequency at 13.3 kHz. As an initial stage, the model presented in the form of simulator tesbed passband, and is treated with the propagation parameters that was obtained from measurements in a Towing Tank in previous experiment. The next stage is tesbed evaluation through experimental in a laboratory, such the effect of conversion process from electrical to audio signal at PC sound card and the capability of the receiver to recover the information.

Combined scalability technique for video transmission over wireless channel with MIMO-OFDM systems

The needs of efficient bandwidth utilization and how to handle fluctuation bandwidth condition of wireless channel have became fundamental problems in video transmission. This research uses Scalable Video Coding (SVC) that refers to Joint Scalable Video Model (JSVM), i.e. development of video coding H.264/AVC by exploiting scalable combination method on wireless channel of Multiple Input Multiple Output — Orthogonal Frequency Division Multiplexing (MIMO-OFDM). This research shows that the scalable combination method can implemented on the scenario of video transmission on multicast network. Experimental results are presented that the delivered quality is close to the alternative traditional simulcast delivery mechanism in MIMO-OFDM systems.

The Evaluation of Probe Signals for Impulse Response Measurements in Shallow Water Environment

Understanding the characteristics of channel propagation plays an important role in designing communication systems. Underwater acoustic channel modeling is commonly done by the direct measurement result from a specific location and time. This paper presents an evaluation of channel impulse response (CIR) and power delay profile (PDP) measurements in shallow water environment using three types of probe signals, i.e., pseudonoise (PN)-sequence, exponentially sine swept (ESS), and amplitude-modulated ESS (AM-ESS). The measurements have been carried out in a laboratory-scale towing tank. The ESS signal has been found to produce CIR and PDP that are close to those of the ray tracing model. The multipath pattern of CIR obtained from ESS signal shows an 80% similarity; it was closer to the ray tracing model compared with other results, made using PN-sequence and AM-ESS signals. The estimated value of rms delay spread obtained by the ray tracing model is 1.023 ms and that obtained by the ESS signal is 1.502 ms. Meanwhile, the values obtained by the PN-sequence and AM-ESS signals are 0.769 and 1.410 ms, respectively. In the frequency domain, the spaced-frequency correlation function, obtained using the PN-sequence and ESS signals, is more similar to the ray tracing model compared with the AM-ESS signal.

Hop distances optimization for balancing the energy consumption of multi-hop clustered Wireless sensor Networks

Clustering has been proven by many researchers as the best solution for the need for energy efficiency and scalability on Wireless sensor Networks (WSN). To improve the scalability, especially for large scale networks, the most recent trend on WSN clustering utilizes the multi-hop communication,. However, there is one negative effect of multi-hop communication that commonly called hot-spot problem, where the closer to base-station cluster-heads (CHs) suffer more load because they must relay data from outer CHs. One solution for the problem is designing an unequal cluster model. Some algorithms have been proposed to realize it, but just a few that give a comprehensive energy model. In the paper, a new scheme for the optimum partitioning area is presented. The goal of the scheme is obtaining a load-balancing among region by arranging the width of the regions. The evaluation shows that the proposed scheme is more superior than the conventional uniform partitioning.

Localization of underwater moving sound source based on time delay estimation using hydrophone array

Signal and noise of an underwater moving sound source is used to track the azimuth of a target. Uniform linear array with four hydrophones is used to detect azimuth of target by obtain the time delay information to get azimuth information. Success rate of time delay estimation influenced by characteristics of sound propagation like reflection, reverberation, etc. Experiment in real environment was done to analyze performance of the cross correlation (CC) and generalized cross correlation with the phase transform (PHAT) weighting to estimate time delay between two signal. The simulation done by convolute two signal that has been given time delay and impulse response of the medium test. Then the time delay of two signal estimated by CC and PHAT algorithm in Matlab in the various SNR. Then the algorithm tested in a pool to detect stationary and moving position of sound source. Result of the simulation and experiment in real environment shown that PHAT better than CC. The best azimuth tracking achieved by using PHAT algorithm with error of 0 - 9.48 degree in stationary position. In moving sound experiments, tracking the bearing and azimuth of the mini vessel (sound source) can be done by time delay estimation using PHAT.

Time-Frequency Blind Source Separation at mini semi-anechoic underwater test tank

In this paper, we present a result from experiment about blind source separation at a mini underwater test tank. The test tank made of 12mm thick of glass with dimension 2 × 1 × 1 in meter, then we placed corrugated sponges inside the walls to reduce the echo from generated signal during experiments. The measurements were conducted by placing three hydrophones and two underwater speaker in variation water temperature and salinity. The temperature were set to 13°C, 17°C, 21°C, 25°C and 29°C respectively to simulate depth. In term of salinity we fixed at room temperature 29°C and varied the salinity of 3.1%, 3.2%, 3.3%, 3.4% and 3.5%, respectively. We used Time-Frequency Blind Source Separation (TFBSS) instantaneous based on joint diagonalization and convolutive method to obtain the performance. The obtained results based on MSE (Mean Squared Error) and SIR (Source to Interference Ratio) suggest that convolutive BSS outperformed the TFBSS indicating that the environment at the test tank is reverberant.