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As a critical technology of 5G air interface waveform, filtered orthogonal frequency division multiplexing (F-OFDM) not only inherits the technical advantages of OFDM, but also has outstanding advantages in system flexibility and spectrum efficiency. However, as a multi-carrier technology, it is still extremely sensitive to sample timing offset (STO) and carrier frequency offset (CFO). In this letter, an improved Park frequency domain training sequence (FS-Park) is proposed to complete STO and CFO estimation of F-OFDM system. Firstly, a real-value pseudorandom number (PN) sequence is sent to each subcarrier as training sequence in frequency domain, the corresponding time domain training symbol has a conjugate symmetry structure. Secondly, the training symbol is utilized for timing synchronization, then the fractional frequency offset is estimated based on the cyclic prefix in time domain. Finally, the integer frequency offset is estimated in frequency domain based on the auto-correlation of PN sequence. The simulation results illustrate that the FS-Park algorithm not only has a single pulse timing metric curve and great STO estimation accuracy, but also has better performance of CFO estimation than classical Park algorithm and Liang Xiao’s method.

In Vehicular Ad-Hoc Networks, a link failure may occur due to non-optimal channel conditions, congestion or node mobility which causes data loss. Common proposed approaches try to overcome this problem by anticipating link disruptions with MAC layer indicators. Such methods, particularly in urban environments (i.e. highly dynamic) are ineffective. Our aim is to setup an indicator that detects at the PHY level an upcoming link breakage before it causes packet loss at the NET layer. To this end, we use Orthogonal Frequency-Division Multiplexing decoding events that are combined thanks to the Dempster–Shafer Theory (DST). The proposed indicator, called Link Breakage Forecasting Indicator performs for a given link, an analysis based on decoding error density measurements, in order to maintain the link history. The adaptation of the DST to the analyzed phenomena relies on using mass functions controlled by the reception power, the relative speed and the error density. The link failure probability is obtained thanks to the fusion of these heterogeneous information using the cautious combination rule. The later allows to consider data even if it is dependent without providing biased results. Simulation results show that detection times are suitable and robust against mobility related characteristics, such as vehicle speeds and urban environment variability.

In recent years, there has been an increasing interest in the use of the discrete Hartley transform (DHT) for orthogonal frequency-division multiplexing (OFDM). Previous studies have not reported an improvement in bit error rate (BER) when using a DHT-based OFDM without substantial complexity increase due to the fact that the DHT cannot diagonalize a circulant channel matrix but rather produces a unique structured matrix that has only a main diagonal and anti-diagonal. In this paper, the coupling between symmetric carriers is exploited by introducing a frequency-domain subcarrier diversity receiver for DHT-based OFDM systems. The proposed simple receiver structure takes advantage of the coupling to enhance the BER performance of the DHT-OFDM system by increasing the diversity gain between subcarriers. A detailed statistical and performance analysis of the system is presented, in which closed-form expressions of the average BER were derived. The proposed system performance was compared to the conventional discrete Fourier transform OFDM (DFT-OFDM), the generalized DHT-OFDM, and the DHT-precoded OFDM systems in terms of average BER and peak-to-average power ratio (PAPR). The proposed DHT-OFDM system outperforms the generalized DHT-OFDM system by 12 dB and outperforms the conventional DFT-OFDM and the DHT-precoded OFDM systems by 17 dB at an average BER of 10−5. In terms of PAPR, the proposed DHT-OFDM system suffers from an approximately 5.5, 2, and 1 dB increase in PAPR when compared to the DHT-precoded OFDM, the conventional DFT-OFDM, and the generalized DHT-OFDM systems, respectively.

This study presents a comprehensive analysis to highlight advantages and disadvantages, in terms of channel capacity and computational complexity (CC), of a so-called clustered-orthogonal frequency division multiplexing (OFDM) scheme for power line communication (PLC) technologies for access networks. By taking into account filtering, decimation and upsampling techniques, the implementations of two transmitter schemes, named 𝒫(·)-I and 𝒫(·)-II, and three receivers ones, named 𝒬(·)-I, 𝒬(·)-II and 𝒬(·)-III, that can be easily derived from the hermitian symmetric OFDM (HS-OFDM) scheme are discussed. Numerical results show that the clustered-OFDM schemes based on HS-OFDM provide the same bit-error-rate performance as that of HS-OFDM, double sideband-OFDM and single sideband-OFDM. Also, clustered-OFDM based on the combination of 𝒬(·)-II and 𝒬(·)-III offers the lowest CC for both baseband and passband data communications. Further, it is demonstrated that the clustered-OFDM schemes can trade off channel capacity for CC, which can give rise to low-priced transceivers for PLC technologies. Finally, a comparative analysis of clustered-OFDM and orthogonal frequency division multiple access (OFDMA) points out the scenarios in which clustered-OFDM can be competitive if the complexity of the OFDM transceiver is a primary consideration.

With the increase in demand of bandwidth hungry applications, it is recommended to develop a high data rate system for long-haul coherent optical orthogonal frequency division multiplexing (CO-OFDM). At a very high data rate, CO-OFDM signal experiences deterioration. At 50 Gbps, the signal experiences ISI effect and in order to overcome this ISI effect, a prolonged system has been developed to reach optimal ISI compensation technique. One of the prominent and competent techniques to enhance system performance is (SDCM) symmetrical dispersion compensation module. In order to make system more bandwidth efficient 4-QAM (Quadrature Amplitude Modulation) with gray coding is applied and manual adjustments are done at receiver phase to decrease error vector magnitude (EVM). OFDM data stream is successfully transmitted over a distance of 4,000 km to compete the demand of long-haul CO-OFDM system. With different launch powers and laser linewidths, the performance of the system is enhanced in terms of -factor, SNR and EVM.

A block‐windowed burst orthogonal frequency division multiplexing (OFDM) technique which is a multicarrier technique with power spectral density similar to the filtered OFDM approach, since it also employs smoother, non‐rectangular windows, is presented. However, it does not need a cyclic prefix, which means the overall power and spectral efficiencies are higher. An appropriate receiver for typical time‐dispersive channels, allowing 2 dB of gain relatively conventional OFDM schemes is also presented.

Time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) enjoys the higher spectrum efficiency and faster synchronisation than the classical cyclic prefix OFDM (CP-OFDM). However, TDS-OFDM suffers from performance degradation especially under severely fading channels with long delays. To solve these problems, the authors propose an energy-efficient OFDM scheme called time–frequency-training orthogonal frequency division multiplexing (TFT-OFDM) based on the time–frequency joint channel estimation under the framework of compressive sensing (CS). The power of the guard interval (GI) in the proposed scheme can be reduced to achieve higher energy efficiency, which is infeasible for CP-OFDM. This method first utilises the time-domain pseudo noise sequence to acquire partial support information of the channel, and then some frequency-domain pilots are used for the exact channel estimation. Simulation results show that TFT-OFDM with CS can achieve much higher energy efficiency than the classical CP-OFDM, and outperforms the conventional OFDM schemes in both static and mobile environments. Moreover, for the channel with long delay spread, the TFT-OFDM scheme with CS can demonstrate robustness and much better performance than the conventional OFDM schemes. In this way, the TFT-OFDM scheme can use the same GI length for larger broadcasting coverage and hence further achieve higher energy efficiency.

Orthogonal frequency division multiplexing (OFDM) a multicarrier system [1, 2] provides base for all advanced wireless communication system. The performance of OFDM is degraded by peak-to-averagepower ratio (PAPR). High PAPR requires high power amplifiers (HPAs). The nonlinearity of the HPA exhibits amplitude and section distortions, that cause loss of orthogonality among the subcarriers, and hence, intercarrier interference (ICI) is introduced inside the transmitted signal. Not only that, high PAPR put together lands up in in-band distortion and out-of-band radiation. Rather than using HPA’s, the only way to improve performance of OFDM system is to reduce PAPR. The PAPR reduction of OFDM system gives fair reduction in PAPR under partial transmits sequence (PTS) and DCT-SLM techniques. Here in this paper we proposed a combination of PTS and DCT-SLM and an algorithm to cut back the PAPR. This hybrid combined technique reduces PAPR effectively and minimizes the complexity of PTS technique.

Cellular communication technology has been developed for over a hundred years and has reached its fifth generation in mobile. 5G, as a new generation of communication technology, has comprehensively changed the mobile network application model with its ability of high-speed transmission, low network latency, and large-scale connectivity. It has brought a new impetus to the development of various industries. Cellular communication uses cellular wireless networking to connect terminals and network devices through wireless channels so that users can communicate with each other during their activities, with the main feature being the mobility of the terminals and the automatic roaming process across local networks. The use of OFDM in 5G communications can significantly improve the efficiency and capacity of wireless signal transmission. This paper provides a detailed introduction to the use of OFDM in cellular communications through frequency division multiplexing and OFDM.

On the brink of sophisticated generations of mobile starting with the fifth-generation (5G) and moving on to the future mobile technologies, the necessity for developing the wireless telecommunications waveform is extremely required. The main reason beyond this is to support the future digital lifestyle that tends principally to maximize wireless channel capacity and number of connected users. In this paper, the upgraded design of the multi-carrier orthogonal generalized frequency division multiplexing (OGFDM) that aims to enlarge the number of mobile subscribers yet sustaining each one with a high transmission capacity is presented, explored, and evaluated. The expanded multi-carrier OGFDM can improve the performance of the future wireless network that targets equally the broad sharing operation (scalability) and elevated transmission rate. From a spectrum perspective, the upgraded OGFDM can manipulate the side effect of the increased number of network subscribers on the transmission bit-rate for each frequency subcarrier. This primarily can be achieved by utilizing the developed OGFDM features, like acceleration ability, filter orthogonality, interference avoidance, subcarrier scalability, and flexible bit loading. Consequently, the introduced OGFDM can supply lower latency, better BW efficiency, higher robustness, wider sharing, and more resilient bit loading than the current waveform. To highlight the main advantages of the proposed OGFDM, the system performance is compared with the initial design of the multicarrier OGFDM side by side with the 5G waveform generalized frequency division multiplexing (GFDM). The experimented results show that by moving from both the conventional OGFDM and GFDM with 4 GHz to the advanced OGFDM with 6 GHz, the gained channel capacity is improved. Because of the efficient use of Hilbert filters and improved rate of sampling acceleration, the upgraded system can gain about 3 dB and 1.5 dB increments in relative to the OGFDM and GFDM respectively. This, as a result, can maximize mainly the overall channel capacity of the enhanced OGFDM, which in turn can raise the bit-rate of each user in the mobile network. In addition, by employing the OGFDM with the dual oversampling, the achieved channel capacity in worst transmission condition is increased to around six and twelve times relative to the OGFDM and GFDM with the normal oversampling. Furthermore, applying the promoted OGFDM with the adaptive modulation comes up with maximizing the overall channel capacity up to around 1.66 dB and 3.32 dB compared to the initial OGFDM and GFDM respectively. A MATLAB simulation is applied to evaluate the transmission performance in terms of the channel capacity and the bit error rate (BER) in an electrical back-to-back wireless transmission system.