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In this paper, a novel model of Gaussian pulse propagation in optical fiber is proposed to comprehensively analyze the impact of Group Velocity Dispersion (GVD) on the performance of two-dimensional wavelength hopping/time spreading optical code division multiple access (2-D WH/TS OCDMA) systems. In addition, many noise and interferences, including multiple access interference (MAI), optical beating...
This paper presents a new approach to equalization of communication channels using artificial neural networks (ANNs). A novel method of training the ANNs using Tabu based back propagation (TBBP) algorithm is described. The algorithm uses the Tabu search (TS) to improve the performance of the equalizer as it searches for global minima which is many a time escaped while back propagation (BP) algorithm...
Speech transmission are the most used form of communications in the personal communication systems and spectral efficiency is the very important aspect in wireless communication system and so low bit rate speech codecs play an important role in determining the systempsilas spectral efficiency. The AMR-WB+ (Extended Adaptive Multirate Wide Band) speech codec provides unique performance at very low...
We present bit error rate (BER) expressions of pi/4 shifted differential quadrature phase shift keying (pi/4-DQPSK) with single and multi-channel reception over generalized fading channels in presence of additive white Gaussian noise (AWGN). Slow flat small scale statistical fading models, namely Rayleigh, Rician, Nakagami-m and Hoyt fading has been assumed. Moreover, to improve the link quality receiver...
The main advantage of down stream power back off (DPBO) in VDSL2 is coexistence with ADSL. The ADSL link bit error rate (BER) will not get affected by introducing VDSL2 in the same binder. In this paper we present a new scheme that partitions the tones over the two latency paths based on signal-to-noise (SNR) with DPBO included in the computation. The bit loading is done from the obtained SNR profile...
In this work an iterative time domain least squares (LS) based channel estimation method using superimposed training (ST) for a multi input multi output(MIMO) orthogonal frequency division multiplexing (OFDM) system over frequency selective fading channels is proposed. The estimate of the channel is generalized to provide scope for exploiting the coherence time and the coherence bandwidth for an improved...
In modern wireless communication systems, forward error correcting codes are employed for efficient transmission of data in noisy environments. Achieving a very less bit error rate (BER) has been the major task in the field of error control coding. The recently developed Raptor codes, which are a class of Fountain codes and the extension of LT codes, tend to give better performance than the low density...
Broadcasting in ad hoc networks, widely utilized as a building block for many network layer protocols is prone to broadcast storm problem. This problem necessitates to carefully designate some nodes in the one-hop neighborhood of the sender as forwarding nodes and reduce broadcast redundancy. In this paper, we propose an algorithm called Dual Covered broadcast with Negative acknowledgements (DCN)...
This paper considers digital to analog conversion of OFDM signals which have been digitally upconverted to a digital IF (Intermediate Frequency). We examine the effect of clipping and quantization on the received constellations and the uncoded bit error rate (BER) and find that the clipping and quantization can be characterized as a gain and the addition of uncorrelated Gaussian noise. Extensive simulations...
This paper analyzes an adaptive processing gain based data transmission in cellular CDMA where processing gain is allocated depending on traffic intensity based on a constraint on bit error rate. Truncated automatic repeat request (T-ARQ) is used at link layer to satisfy a prescribed delay constraint. Effects of correlation among signal and interferers are included in the study. The impact of processing...
An adaptive data transmission scheme based on variable spreading gain (VSG) is studied in CDMA network in presence of soft handoff and space diversity. The processing gain is varied according to traffic intensity meeting a requirement on bit error rate (BER) at the output of a space diversity system provided by antenna array. Truncated automatic repeat request (T-ARQ) is used in link layer to further...
The challenges associated with the OFDM system are addressed. OFDM transmits redundancy in terms of Cyclic Prefix (CP), which decreases the spectral efficiency of the system. A pulse shaping filter for the OFDM systems is proposed to remove the constraint of CP. Also, transmit and receive filters in OFDM system suffer from poor frequency response because of the use of rectangular window function....
This paper proposes an analytical performance evaluation of an orthogonal frequency division multiplexing (OFDM) under the combined influence of carrier frequency offset (CFO), phase noise and timing jitter. An exact closed form expression for the signal-to-interference-noise ratio (SINR) is derived and the combined effects of these synchronization impairments are exhibited by expressing the OFDM...
Using dasiabetter thanpsila Nyquist pulse the average bit error rate performance of a time-hopping pulse position modulation and TH-binary phase shift keying ultra-wideband systems has been evaluated in the presence of multiple access interference and additive white Gaussian noise for different system and pulse parameters such as repetition code length, roll-off factor and the symbol repetition rate...
In recent years, steganography and steganalysis are two important areas of research that involve a number of applications. These two areas of research are important especially when reliable and secure information exchange is required. Steganography is an art of embedding information in a cover image without causing statistically significant variations to the cover image. Steganalysis is the technology...
In this paper, we address the estimation of carrier frequency offset (CFO) in orthogonal frequency division multiplexing (OFDM) based multiple input multiple output (MIMO) communication systems. One of the novelties of the proposed approach is the judicious combination of two methods so as to reduce the bandwidth overhead and computational complexity without compromising the CFO estimation range....
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