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September2012

Symbolic Simulation by Nodal Method of Complementary Circuitry

Authors: I. I. Okonkwo, P. I. Obi, K. J. Offor, G. C Chidolue

Abstract

The initial values of transient response of the RLC circuit are mainly expressed in terms of branch state variables which may be of both the inductor current and capacitor voltage or either. When transient response is initiated from steady state, these state variables are direct consequence of steady state response. In this paper it is shown that when time domain nodal equation representing the transient response is translated to laplace domain, a guided substitution of the initialization quantities in terms of steady state nodal voltages would led to well-structured symbolic nodal equation which simplifies symbolic transient response simulation.

(pp. 599-605)                    Download PDF

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Cooperative OFDM Underwater Acoustic Communications with Limited Feedback: Part II

Authors: Qian Song, Mercedes Garcia

Abstract

Cooperative communications have been proved to be a promising technique in next generation wireless communication and network system. Limited feedback is a novel technique that employs several bit of channel state information (CSI) feedback and achieves almost the same performance as perfect feedback. However, literature on cooperative communications and limited feedback in underwater acoustic (UWA) environments is very scarce. Therefore, in this paper, we propose a novel UWA cooperative communication system with limited feedback. Minimum outage probability criterion-based optimization model (Part II) will be involved to analyze the performance of the adaptive power allocation based on the proposed system. Limited feedback general procedure and codebook design will be demonstrated. Simulation results will compare the performance of the full CSI feedback, a few bits of feedback and uniform power allocation.

(pp. 606-610)                    Download PDF

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OFDM Pilot-Aided Underwater Acoustic Channel Estimation

Authors: Thomas Pedersen, Alex Bloomberg

Abstract

Underwater Acoustic (UWA) communications have been regarded as the most challenging wireless communication systems due to their unique channel properties, such as severe multipath delay and large Doppler Shift. Orthogonal Frequency Division Multiplexing (OFDM)  is a promising technique has been widely adopted in the 4G wireless communication systems due to its unique merits, such as robust against multipath propagation. However, the literature on OFDM communications in UWA environments is scarce. In this paper, we investigate OFDM pilot-aided UWA channel estimation approaches, which involve in block-type pilot, comb-type pilot and grid-type pilot. Therein, comb-type pilot-aided channel estimation approach will combine some signal interpolation approaches. Simulation results will show the performance difference of UWA communication systems based on difference channel estimation pilots.

(pp. 611-613)                    Download PDF

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