Influence of frequency offset on the reception of OFDM/QPSK signal using MBDD algorithm

In this paper we present the basic characteristics of Orthogonal Frequency Division Multiplex (OFDM) systems with quadrature phase shift keying (QPSK) modulation and multi-bit differential detection (MBDD). In the simulation environment designed for this purpose, we analyze the effects of frequency offset on the performances of OFDM digital communications. We also analyze the influence of OFDM system parameters on system performances for various values of frequency offset, number of bits for multi-bit detection and the number of subcarriers. We have shown the advantages and disadvantages of using MBDD in the OFDM systems

Early identification of children with developmental delay and behavioural problems according to parents concerns in the Republic of Serbia

The main goal of this research was to describe the type and level of parents' concerns about child development and behaviour according to the PEDS test (Parents' Evaluation of Developmental Status). The sample included 289 parents of children from three to seven years of age, from two preschool institutions in Serbia. A significantly high correlation was determined between parents' general concerns and expressed concerns with regard to behaviour ((2)=17.86, df=2, p lt .001) and getting along with others ((2)=22.57, df=2, p lt .000). A marginally significant correlation was determined between parents' general concerns and manifested concerns with regard to fine motor skills ((2)=5.90, df=2, p=.052), as well as expressive language ((2)=5.858, df=2, p=.053). According to the criteria of PEDS test, this research identified 56.4% of children whose development needed to be monitored, 27.7% of children who needed to be referred for detailed diagnostic procedures, and 1.7% who needed to be included in treatment or special education support.This is the peer‐reviewed version of the article: Ilić, S. B.; Nikolić, S. J.; Ilić-Stošović, D. D.; Golubović, Š. S. Early Identification of Children with Developmental Delay and Behavioural Problems According to Parents Concerns in the Republic of Serbia. Early Child Development and Care 2020, 190 (16), 2605–2611. [https://doi.org/10.1080/03004430.2019.1595610

Improving OFDM/DQPSK System Performance in the Conditions of Frequency Offset Existence

The basic characteristics of Orthogonal Frequency Division Multiplex (OFDM) systems with DQPSK modulation and channel estimation with an adaptive transversal filter and LMS algorithm are analyzed and presented in this paper. In the simulation environment designed for this purpose, we analyzed the effects of frequency offset on the performance of OFDM digital communications and presented the method for improving system performance in the presence of frequency offset. We analyzed the influence of OFDM system parameters on system’s performance for various values of frequency offsets, filter lengths and the number of subcarriers. Finally, we compared the result with the one for a perfectly synchronized OFDM/DQPSK system with differential and coherent demodulation

Frequency Offset Influence on MDPSK Signal Reception in Fading Channel

The symbol error probability of M-ary differential phase shift keying (MDPSK) receiver, in the presence of carrier frequency offset, is analysed in this paper. The paper proposes a novel multiple symbol differential detection (MSDD) receiver. The influence of various receiver’s parameters on the error probability is analysed. The theoretical symbol error probability is derived and compared to the Monte-Carlo simulation results, for an AWGN channel. The analysis shows a good agreement between the theoretical and simulation results. The influence of the frequency offset in the Rician fading channel, using Monte-Carlo simulation, is also considered for the same receiver’s parameters as in the AWGN channel. Simulation results show good system performances in the case of Rician fading channel, also