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Code division multiple access (CDMA) utilizes spread spectrum techniques and has been widely deployed in wireless communications. Two major types of spread spectrum multiple access (SSMA) schemes are: i. direct sequence spread spectrum (DSSS) and ii. frequency hopped multiple access (FHMA). The benefits and technical advantages of CDMA could be translated in the optical-CDMA (OCDMA) for faster data...
Communication through intermediate relay node, splits the channel between source and destination into two possibly shorter links, which improves link quality as well as combat with harsh multi-path fading. Close form expressions of average received SNR, outage probability and average bit error rate (BER) have been derived, for the case when communication between source and multi-antenna destination...
The paper derives a more accurate upper bound for BER for M-QAM than is currently used in the literature. This allows a more thorough analysis of the power adaptation to fading conditions for optimization of spectral efficiency. By taking into account the effect of error coding gain on power adaptation, a 7-state FSMC model for the implementation of the adaptive modulation and coding scheme in WiMAX...
It is necessary that the satellite transponder has ability to suppress interferences for reliable communications in real applications, specially military areas. Adaptive interference suppression methods using transform domain approach are presented for an on-board filter bank in this paper. The three kinds of algorithms to compute the threshold level are jointly evaluated with the notch filter or...
We propose a transceiver structure that can effectively improve BER (bit error rate) performance for TR-UWB (transmitted reference-ultra wide band) systems based on impulse radios. Unlike coherent UWB systems that are too complex for practical implementation while having good BER performances, the complexity of the TR-UWB systems is quite low since they transmit data with the corresponding reference...
Bidirectional optical cross connects (BOXCs) using a fiber Bragg gratings (FBGs) and optical circulators (OCs) have been considered for bidirectional WDM ring networks. Theoretical analysis is carried out to evaluate the performance of a bidirectional optical cross connects (BOXCs) in a wave length division multiplexing (WDM) transmission system in the presence of homodyne crosstalk due to fiber Bragg...
The paper evaluates the performance of a CDMA based wireless sensor networks (WSN) in terms of outage probability and BER, considering correlation among interferers in shadowed environment. An appropriate model for the interference power, outage and BER are presented for a single hop communication. Detection probability is also evaluated in shadowed environment. The effects of node density, minimum...
Spread spectrum audio watermarking technique is developed by modifying the group of samples (GOS) in DCT domain. To check the robustness of the technique the watermarked signal is passed through different signal processing attacks and is observed that the watermark remains present after all signal processing attacks. The system is able to hide 1024 data bits in a clip of 6 sec MP3 song i. e. approximately...
In this paper, we propose a novel method of Cholesky factorization based on the minimum mean square error (MMSE) criterion for Tomlinson-Harashima precoding (THP), which is applied to the downlink of multiuser multiple-input multiple-output (MU-MIMO) system with single mobile antenna equipped for each user. The proposed scheme is also applicable to the MU-MIMO system with multiple mobile antennas...
OFDM is one of the most promising techniques for the high speed next generation mobile communication. However, it has a high peak to average power ratio. In this paper, we propose spread spectrum (SS)-OFDM for PAPR reduction. In this method, each subcarrier forms Nyquist pulse the same way to OSSR-OFDM which we proposed in. The results of computer simulation show that our proposal with a large roll-off...
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