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Time-varying channel causes intercarrier interference (ICI) and impairs the orthogonality among subcarriers in wireless mobile Orthogonal Frequency Division Multiplexing (OFDM) systems. The ICI and loss of carrier orthogonality degrade the bit error rate (BER), and thus results in intolerable loss of quality especially in applying multimedia data transmission. In this paper, we propose an unequal...
In this paper, three main code families for spectral amplitude coding optical code division multiple access (SAC-OCDMA) systems in terms of performance are compared when the system is affected by group velocity dispersion (GVD). The results show that m-sequence codes have the best performance compared to Walsh-Hadamard and modified quadratic congruence (MQC) codes. In addition, a SAC-OCDMA system...
In OFDMA, the subcarrier allocation process amongst the users has a significant role in governing the performance of the system. In this paper, we study the application of interleaver based subcarrier allocation schemes for ensuring uniform BER across all the active users. We show that for a slowly changing multipath channel, individual user's BER performance can vary from each other to a great extent,...
Power conservation for maximizing the lifetime of the limited battery powered ad hoc networks are one of the most important factors in a network design. Transmitting at high power may assure network connectivity but sacrifice network lifetime and increases the interference as well. Meanwhile transmitting at lower power reduces the interference on the expense on network robustness. We investigate the...
In this paper, the performance analysis for a dual-hop Amplify-and-Forward relaying network is extended to the context of impulse radio ultra-wideband. Due to multiple accesses,the interference distribution is not Gaussian. We propose a symmetric α-stable model compatible with the impulsive nature due to its heavy tailed distribution. Taking advantage of the stability property, we develop...
Researchers at The University of Iowa have encountered the need for an efficient 1-wire communication protocol for use in embedded systems and distributed wired sensors. One possible solution for this problem is the use of a Wired Code Division Multiple Access (CDMA). Although this approach has been investigated before, a key simplification can made with the use of a binary wired-OR channel. This...
Nonorthogonal Frequency Division Multiplexing (NOFDM) is a digital modulation technique that promises to provide extremely high spectral efficiencies. However, this modulation scheme is seldom used in practice due to the high computational complexity involved in decoding the received signal in the presence of noise. The basic aim of this paper is to reduce this decoding complexity. Here, we propose...
In this paper, a non coherent multiple access(MA) chaotic communication system using Orthogonal Chaotic Vectors (OCV) as spreading sequences with adaptive multi user receivers are tested and analysed. Here we consider two types of adaptive receivers 1) LMS based detector 2) CSE based detector. Theoretical equations for BER are also derived for both cases considering awgn channel. The simulation results...
In this paper we provide the details of a final project in digital communications, used in a signal processing first course taught to second year ECE students. Simple nulling filters are used to minimize a sinusoidal jamming signal. The students have already learned about an FIR nulling filter, the placement of zeros on the unit circle, and the frequency response. In the filter design the students...
For WPAN (Wireless Personal Area Network) applications, a low-power low-noise IF (Intermediate-Frequency) circuit is proposed for GFSK (Gauss Frequency Shift Keying) low-IF receivers. The proposed IF system is realized by an all-analog architecture, which is composed of a couple of LAs (Limiting Amplifiers) and RSSIs (Received Signal Strength Indicators), a couple of BPFs (Band-Pass Filters), a FD...
Mitigating non-stationary narrowband interference from a continuous phase modulation (CPM) signal is a challenge due to the correlation present in CPM signal samples. For such a scenario, use of a time-varying linear prediction error filter (TVLPEF) based on a decorrelating time-varying autoregressive (DTVAR) model was proposed earlier. TVLPEF based mitigation of the interference from a CPM signal...
We analyze the frequency diversity of intercarrier interference (ICI) reduction methods in the presence of phase noise over multipath fading channels. Based on analysis, we propose an enhanced symmetric data conjugate (ESDC) method to exploit the frequency diversity in multipath fading channel. We derive carrier-to-interference ratio (CIR) expression of proposed ICI reduction scheme. The BER performance...
In this paper, we propose the precoder with hidden pilots for orthogonal frequency-division multiple access (OFDMA) systems in order to enhance the transmission efficiency of the system and reduce peak-to-average power ratio (PAPR) which is the problem in OFDMA uplink. In wireless communication systems, the way to improve transmission efficiency is 1) to reduce bit error rate (BER) or 2) to increase...
In this paper, a candidate architecture for LTE-Advanced receiver is proposed. Based on the combination of MIMO techniques and flexible spectrum access, LTE-Advanced terminals will require the increasing of the analog front-end complexity. To reduce the complexity of the analog front-end, an innovative architecture based on the merge between the double IQ and the code multiplexing structures is proposed...
An upstream cable modem receiver is proposed, which is implemented in FPGAs, consists of a DDC, a pre-FEC and an FEC. It is found that when the BER of 64QAM is 10-5, the required Eb/N0 is 19.5 dB. Measured results show the maximum transmitted EVM of 1.54 % and maximum received EVM of 2.67%. The implemented receiver can receive 4 channels simultaneously supporting high data rate.
This paper presents a first order Takagi-Sugeno-Kang (TSK) type fuzzy equalizer to mitigate nonlinear power amplifier distortion effects from the received signal in orthogonal frequency division multiplexing (OFDM) systems. Here we propose a Comprehensive Learning Particle Swarm Optimizer (CLPSO) based structure identification of the TSK equalizer. CLPSO uses a new learning strategy that achieves...
Phase noise seriously affects performance in the OFDM-based wireless communication system. In order to reduce phase noise efficiency, phase noise suppression (PNS) algorithm was proposed. In this paper, OFDM system including PNS algorithm design is simulated by using Simulink. As simulation results, phase noise effect can be significantly compensated by PNS algorithm. Compared with the ordinary OFDM...
A virtual multiple-input multiple-output (MIMO) system based on cooperative communication is studied actively. This system is formed between base station and source node with using of two or more nodes around itself. These transmitters are equipped with a single antenna. This system is one of the solution methods for deterioration in communication quality from that the power supply of the node is...
An Ultra-Wideband hardware demonstrator based on Impulse Radio for Local Body Area Network applications is presented. The system includes an UWB transmitter, an UWB receiver and a microcontroller board. It operates in the frequency range from 3.1 - 5.0 GHz with a maximum data rate of 10 MBit/s. The performance of the system is shown in terms of BER. It was tested for different antennas and distances...
Transmitter equalization enables dramatic improvements in total link performance: >; 6 dB in sensitivity, 3X in timing margin, and 2X in power efficiency at 15 Gb/s, and a record 5.7 pJ/bit at 20 Gb/s.
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