1,720,985 research outputs found
Symbol Error Probability of Hexagonal QAM
No full textThis letter studies the symbol error probability (SEP) of quadrature-amplitude modulation (QAM) signals constructed from the hexagonal lattice, known as hexagonal QAM or triangular QAM. In particular, we propose a simple and accurate approximation for the SEP of hexagonal QAM in additive white Gaussian noise. Simulation results show that the proposed approximation is very accurate for all the best-known QAM constellations constructed from the hexagonal lattice, including triangular QAM, for both high and low signal-to-noise ratio. In addition, the proposed approximation is suitable for the accurate estimation of the SEP of hexagonal QAM in slow-fading channels, such as Rayleigh fading channels
BER Performance Degradation of MC-DS-CDMA Systems Jointly Affected by Transmitter HPA and Receiver CFO in Frequency Selective Fading Channels
No full textMulticarrier systems are highly sensitive to the intermodulation distortion (IMD) introduced by high-power amplifiers (HPA) at the transmitter and to the intercarrier interference (ICI) due to a carrier frequency offset (CFO) at the receiver. We analyze the bit-error rate (BER) degradation induced by these impairments in the downlink of a multi-carrier direct-sequence code-division multiple-access (MC-DS-CDMA) systems in frequency-selective Rayleigh fading channels
BER of MC-DS-CDMA Systems with CFO and Nonlinear Distortions
No full textMulticarrier systems are highly sensitive to the intercarrier interference (ICI) caused by a carrier frequency offset (CFO) at the receiver and to the intermodulation distortion (IMD) introduced by the nonlinear amplifier (NLA) at the transmitter. We analyze how these impairments degrade the bit-error rate (BER) of multicarrier direct-sequence code-division multiple-access (MC-DS-CDMA) downlink systems in frequency-selective Rayleigh fading channels
Performance of nonorthogonal FSK for the Internet of Things
No full textIEEE 802.15.4 is a popular standard for low-rate wireless communications used for the Internet of Things (IoT). This IEEE standard contains a variety of physical layers (such as SUN, TVWS, RCC LMR, and LECIM) that make use of different modulations, such as nonorthogonal frequency-shift keying (FSK) and position-based FSK. This paper proposes simple closed-form expressions to evaluate the bit-error rate (BER) performance of nonorthogonal FSK schemes used for the IoT. Both coherent and noncoherent detection cases are investigated in additive white Gaussian noise (AWGN) and frequency-nonselective fading channels. In case of AWGN channels, the proposed BER expressions are obtained by selecting and modifying two terms of a union bound on the error probability. In case of fading channels, the proposed BER expressions are obtained by integration of the conditional BER over the fading statistics. Simulation results confirm the good accuracy of the proposed analytical BER expressions for different channel models (such as AWGN, Nakagami-m, Rice, lognormal) and for different detection techniques (such as noncoherent, coherent, and coherent with a residual phase error). Experimental results with wireless transmission and reception confirm the accuracy of the proposed approach. In addition, this paper also presents a BER expression for coherent detection of position-based FSK. Simulation results demonstrate that the presented BER expression for position-based FSK is more accurate than the BER expressions proposed in the literature
Joint Impact of Frequency Synchronization Errors and Intermodulation Distortion on the Performance of Multicarrier DS-CDMA Systems
No full text The performance of multicarrier systems is highly impaired by intercarrier interference (ICI) due to frequency synchronization errors at the receiver and by intermodulation distortion (IMD) introduced by a nonlinear amplifier (NLA) at the transmitter. In this paper, we evaluate the bit-error rate (BER) of multicarrier direct-sequence code-division multiple-access (MC-DS-CDMA) downlink systems subject to these impairments in frequency-selective Rayleigh fading channels, assuming quadrature amplitude modulation (QAM). The analytical findings allow to establish the sensitivity of MC-DS-CDMA systems to carrier frequency offset (CFO) and NLA distortions, to identify the maximum CFO that is tolerable at the receiver side in different scenarios, and to find out the optimum value of the NLA output power backoff for a given CFO. Simulation results show that the approximated analysis is quite accurate in several conditions.</p
Design and Validation of a Software Defined Radio Testbed for DVB-T Transmission
No full textThis paper describes the design and validation of a Software Defined Radio (SDR) testbed, which can be used for Digital Television transmission using the Digital Video Broadcasting - Terrestrial (DVB-T) standard. In order to generate a DVB-T-compliant signal with low computational complexity, we design an SDR architecture that uses the C/C++ language and exploits multithreading and vectorized instructions. Then, we transmit the generated DVB-T signal in real time, using a common PC equipped with multicore central processing units (CPUs) and a commercially available SDR modem board. The proposed SDR architecture has been validated using fixed TV sets, and portable receivers. Our results show that the proposed SDR architecture for DVB-T transmission is a low-cost low-complexity solution that, in the worst case, only requires less than 22% of CPU load and less than 170 MB of memory usage, on a 3.0 GHz Core i7 processor. In addition, using the same SDR modem board, we design an off-line software receiver that also performs time synchronization and carrier frequency offset estimation and compensation
Local Maximum-Likelihood Detection: Performance and Complexity in Multicarrier DS-CDMA
No full textUniversità degli Studi di Perugia, Dipartimento di Ingegneria Elettronica e dell'Informazione, Rapporto Tecnico RT-001-0
SVM-based CDMA receiver with incremental active learning
No full textRecently, the feasibility of using support vector machines (SVMs) for multiuser detection in code division multiple access (CDMA)
systems has been investigated. Previous results show that SVMs perform well with short training sequences but suffer from two
drawbacks that are highly undesirable in real-time applications: the run-time complexity and the block-based learning. To deal with these
problems, here we propose a sample-by-sample adaptive algorithm for CDMA systems based on incremental SVMs, incorporating an
active learning strategy aimed to reduce the complexity of both the training phase and the final classifier
Block DFE and Windowing for Doppler-Affected OFDM Systems
No full textRecently, a minimum mean-squared error (MMSE) block linear equalizer based on a band LDLH factorization has been proposed for equalization of orthogonal frequency-division multiplexing (OFDM) systems affected by Doppler spread. In this paper, we extend this approach towards two directions. First, we design an MMSE block decision-feedback equalizer (DFE) based on the band LDLH factorization. Both performance and complexity are analyzed. Second, we enhance the performance of the linear equalizer by means of receiver windows tailored to the band LDLH factorization approach. Simulation results show that the proposed techniques are effective in reducing the error floor caused by the intercarrier interference (ICI)
Basis expansion adaptive filters for time-varying system identification
No full textElectrical Engineering, Mathematics and Computer Scienc
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