1,721,246 research outputs found
On the Modeling of Inter-Sub-Symbol Interference in GFDM Transmission
Full text linkInter-sub-symbol interference (ISSI) refers to the interference that independently affects each group of sub-symbols transmitted on the same sub-carrier in generalized frequency division multiplexing (GFDM). In this letter, we derive a model to describe ISSI when transmission takes place over a frequency selective channel. The proposed model, which is derived by exploiting the discrete Gabor transform structure of GFDM, allows for the exact computation of the channel impulse response associated with each sub-carrier. Minimum mean-squared error and maximum likelihood receiver are considered as examples of the two different detection strategies based on the proposed modeling, together with the evaluation of their complexity. Simulation results demonstrate the improvement in the symbol error rate performance compared to another approach recently proposed in the literature that does not take into account the effect of ISSI
Improved Nyquist pulse shaping filters for generalized frequency division multiplexing
Full text linkGeneralized Frequency-Division Multiplexing (GFDM) is one of the multicarrier modulation schemes currently under study for next generation 5G cellular networks. One of the main characteristics of GFDM is the low out of band emission that is achieved by means of a flexible time-domain pulse shaping of individual subcarriers. In the paper, we propose to use improved Nyquist pulse shaping filters which have been originally introduced in the context of single-carrier modulation schemes for reducing the sensitivity to symbol timing error due to their higher eye opening and smaller maximum distortion. Here we consider their use in GFDM and evaluate their symbol error rate (SER) performance in case of 16-QAM transmission over an additive white Gaussian noise channel. Moreover, we also considered the concept of the wavelet for better time-frequency localization of the pulse shaping filters by using the Meyer auxiliary function. Numerical results are reported to demonstrate the superior SER performance achieved by the proposed improved Nyquist pulse shaping filters in comparison to that achieved with conventional Nyquist pulse shaping filters
Rapid prototyping and FPGA-in-the-loop verification of a DFrFT-based OFDM system
Full text linkOrthogonal frequency division multiplexing (OFDM) based on the use of discrete fractional Fourier transform (DFrFT) has recently gained interest due to its lower sensitivity to synchronization errors in comparison with conventional OFDM based on the use of the discrete Fourier transform (DFT). Although this higher robustness to synchronization errors is a well-recognized fact, only few works are available in the literature that concern with DFrFT hardware implementation. In this work, we consider its implementation in a Field Programmable Gate Array (FPGA). To verify the design of the DFrFT-based OFDM system, we use FPGA-in-the-Loop (FIL) co-simulation method to evaluate bit error rate (BER) in presence of carrier frequency offset (CFO) when transmission takes place over a frequency selective Rayleigh fading channel
An exact ser expression for QPSK OFDM system in presence of residual CFO and STO
No full textIn this paper exact closed form expressions of the symbol error rate (SER) are derived for a quadrature phase-shift keying (QPSK) orthogonal frequency-division multiplexing (OFDM) system in presence of both residual carrier frequency offset (CFO) and symbol timing offset (STO). Analytical expressions for SER computation are given for transmission over additive white Gaussian noise and frequency selective Rayleigh fading channels. Enumerative results for each SER expression are given and verified through a comparison with Monte Carlo simulations
Improving GFDM Symbol Error Rate Performance using Better than Nyquist Pulse Shaping Filters
Full text linkFourth generation (4G) cellular systems have been optimized to provide high data rates and reliable coverage to mobile users. New waveforms at the physical layer are needed. Generalized frequency division multiplexing (GFDM) is a candidate modulation for the fifth generation (5G) standard based on multi-branch multicarrier filter bank approach. A main characteristic of GFDM is its low out of band emission, achieved by means of a flexible time-domain pulse shaping of individual subcarriers. In this paper, the influence of the improved Better than Nyquist pulse shaping filters on symbol error rate (SER) performance of the GFDM system in the case of zero forcing (ZF) receiver is investigated. We considered their use in GFDM to evaluate the impact on SER performance in case of 16-QAM transmission over an additive white Gaussian noise channel. Moreover, we also considered the concept of the wavelet for better time-frequency localization of the pulse shaping filters by using the Meyer auxiliary function. Numerical results are reported to demonstrate the superior SER performance achieved
Exact ser Analysis of DFrFT-Based QPSK OFDM System over Frequency Selective Rayleigh Fading Channel with CFO
Full text linkWe present the exact symbol error rate (SER) expression for quadrature phase shift keying (QPSK) modulation in frequency selective Rayleigh fading channel for discrete fractional Fourier transform- (DFrFT-) based orthogonal frequency division multiplexing (OFDM) system in the presence of carrier frequency offset (CFO). The theoretical result is confirmed by means of Monte Carlo simulations. It is shown that the performance of the proposed system, at different values of the DFrFT angle parameter " α," is better than that of OFDM based on discrete Fourier transform
Fault Recovery in Time-Synchronized Mission Critical ZigBee-Based Wireless Sensor Networks
Full text linkPerformance comparison of blind and non-blind channel equalizers using artificial neural networks
Full text linkIn digital communication systems, multipath propagation induces Inter Symbol Interference (ISI). To reduce the effect of ISI different channel equalization algorithms are used. Complex equalization algorithms allow for achieving the best performance but they do not meet the requirements for implementation of real-time detection at low complexity, thus limiting their application. In this paper, we present different blind and non-blind equalization structures based on Artificial Neural Networks (ANNs) and, also, we analyze their complexity versus performance. Since the activation function at the output layer depends on the cost function with respect to the input, in the present work we use mean squared error as loss function for the output layer. The simulated network is based on multilayer feedforward perceptron ANN, which is trained by utilizing the error back-propagation algorithm. The weights of the network are updated in accordance with training of the network to improve the convergence speed. Simulation results demonstrate that the implementation of equalizers using ANN provides an upper hand over the performance and computational complexity with respect to conventional methods
A novel technique for ZigBee coordinator failure recovery and its impact on timing synchronization
No full textIn mission critical wireless sensor networks (WSNs) accurate timestamping of the occurrence of events measured by the sensor nodes is often required together with a high degree of reliability. While precise timestamping requires synchronization of the sensor nodes, reliability is obtained by adding redundancy in all potential single point of failure nodes. In this paper, we focus on a ZigBee-based WSN using two personal area network (PAN) coordinators with different PAN identifiers (IDs) and, for this configuration, we propose a solution where if the primary PAN coordinator goes down, connections are transferred to the other by changing the PAN ID of the nodes. Our proposed solution provides significant gains in terms of recovery speed and timing synchronization accuracy in comparison to a solution that is proposed in the literature
- …
