Browsing by Subject "Underwater communications"

Now showing 1 - 3 of 3

Open Access
Robust adaptive algorithms for underwater acoustic channel estimation and their performance analysis
(2017-09) Marivani, Iman
We introduce a novel family of adaptive robust channel estimators for highly chal- lenging underwater acoustic (UWA) channels. Since the underwater environment is highly non-stationary and subjected to impulsive noise, we use adaptive ltering techniques based on minimization of a logarithmic cost function, which results in a better trade-off between the convergence rate and the steady state performance of the algorithm. To improve the convergence performance of the conventional rst and second order linear estimation methods while mitigating the stability issues related to impulsive noise, we intrinsically combine different norms of the error in the cost function using a logarithmic term. Hence, we achieve a com- parable convergence rate to the faster algorithms, while signi cantly enhancing the stability against impulsive noise in such an adverse communication medium. Furthermore, we provide a thorough analysis for the tracking and steady-state performances of our proposed methods in the presence of impulsive noise. In our analysis, we not only consider the impulsive noise, but also take into account the frequency and phase offsets commonly experienced in real life experiments. We demonstrate the performance of our algorithms through highly realistic experi- ments performed on accurately simulated underwater acoustic channels.
Open Access
Robust adaptive algorithms for underwater acoustic channel estimation and their performance analysis
(Elsevier Inc., 2017) Kari, D.; Marivani, I.; Khan, F.; Sayin, M. O.; Kozat, S. S.
We introduce a novel family of adaptive robust channel estimators for highly challenging underwater acoustic (UWA) channels. Since the underwater environment is highly non-stationary and subjected to impulsive noise, we use adaptive filtering techniques based on minimization of a logarithmic cost function, which results in a better trade-off between the convergence rate and the steady state performance of the algorithm. To improve the convergence performance of the conventional first and second order linear estimation methods while mitigating the stability issues related to impulsive noise, we intrinsically combine different norms of the error in the cost function using a logarithmic term. Hence, we achieve a comparable convergence rate to the faster algorithms, while significantly enhancing the stability against impulsive noise in such an adverse communication medium. Furthermore, we provide a thorough analysis for the tracking and steady-state performances of our proposed methods in the presence of impulsive noise. In our analysis, we not only consider the impulsive noise, but also take into account the frequency and phase offsets commonly experienced in real life experiments. We demonstrate the performance of our algorithms through highly realistic experiments performed on accurately simulated underwater acoustic channels.
Open Access
A wideband and a Wide-Beamwidth acoustic transducer design for underwater acoustic communications
(IEEE, 2007-05) Elmaslı, I. Ceren; Köymen, Hayrettin
This paper is concerned with the design of an efficient, wideband and a wide-beamwidth resonant acoustic transducer for high frequency use. The general transducer structure which has two back-to-back quarter wave thick 1-3 composite ceramic elements at resonance frequency is introduced. The transducer is employed for both transmit and receive modes. Design of transmitting and receiving transducers are discussed. Several transfer functions are derived and their effective bandwidths are calculated. It is shown that the phase angle difference between two acoustic ports in receive mode can be processed at the electrical ports to maintain better throughput. The paper includes future works to be done. It is concluded that the proposed structure can be used for applications of spread spectrum schemes in underwater communications. ©2006 IEEE.