Accurate channel estimation is essential for reliable downlink synchronization (DLSync) in 5G and beyond wireless systems, especially during the initial access (IA) phase. This work focuses on synchronization signal blocks (SSBs), which play a crucial role in delivering system information from the base station (gNodeB) to user equipment (UE). We propose a deep learning-based approach using an inception-style neural network to estimate the channel across the SSB time-frequency grid. Our model outperforms traditional techniques such as demodulation reference signal (DMRS) interpolation and least squares (LS) estimation, especially under practical wireless conditions like multipath delay spread and Doppler shift. The proposed model achieves a bit error rate (BER) of 10−4at an SNR of 20 dB, significantly better than the 3 × 10−3BER of conventional methods. Moreover, we have observed 4-5 dB gain at high SNR with respect to LMMSE and LS estimators. These results demonstrate that our model offers more reliable and energy-efficient synchronization, even in challenging real-world environments.

Call muting-unexpected silences during voice calls due to extended RTP packet loss is a major challenge in high-mobility 5G environments, severely degrading Mean Opinion Score (MOS) and user experience. We propose DRLCQ, a Deep Reinforcement Learning-based framework that dynamically tunes Cell Individual Offset (CIO) in real time to reduce mute events and enhance voice quality. Integrated as an xApp within the O-RAN Near-RT RIC, DRLCQ leverages live network KPIs (e.g., SINR, jitter, packet loss) to learn optimal handover decisions. Evaluated against static and heuristic baselines, DRLCQ achieves over 20% fewer call mute incidents and up to 85% higher MOS, demonstrating a scalable and intelligent solution for AI-native RAN control.

In this paper, a reconfigurable intelligent surface (RIS)-assisted full duplex communication for quadrature channel modulation (QCM) is proposed. The proposed scheme exploits transmit antennas and radio frequency mirror selection to transmit the real and imaginary parts of a QCM symbol independently to improve spectral efficiency. A dual polarized RIS is also employed to extend the indexing of receive antennas at a dual polarized half duplex receiver to separate the real and imaginary parts of the QCM symbol transmitted during downlink communication. This setup facilitates quadrature spatial modulation at the half duplex receiver and further enhances spectral efficiency. After transmit antenna selection, the remaining silent antennas at the base station are further harnessed to receive the QCM modulated uplink symbol from the half duplex transmitter unit. A decision-making method is adopted at the base station to find these silent antennas that receive uplink signals. Each antenna functions as either a transmit or a receive antenna with the help of a duplexer switch which assists in full duplex communication with minimal self-interference. Finally, an enhanced greedy detector is proposed to detect the signal with lower computational complexity. The system performance is evaluated using measures like average bit error rate, throughput, ergodic capacity, and energy efficiency, and compared with that of the existing state-of-the-art techniques.

OFDM-IM NOMA is a newly created flexible scheme for future generation communication systems. For the downlink OFDM-IM NOMA system, a low-complexity “rotated constellation based log likelihood ratio (LLR) detector” has been proposed in this work. This detector is made by combining the Constellation rotation-based concept and the two-stage Log-Likelihood Ratio algorithm together. By using the rotated Constellation based concept, successive interference cancellation (SIC) process can be avoided, additionally the two-stage Log-Likelihood Ratio algorithm has a lesser complexity. As a result, the proposed detector is able to reduce the complexity significantly. Complexity analysis and simulation results show that the proposed detector achieves significantly lower computational complexity and much better error performance than the earlier introduced maximum likelihood (ML) based detector under different scenarios for the OFDM-IM NOMA scheme.

In this paper, we propose a mechanism, termed as Opti-Safe, such that the demand of end-users and supply of mobile sensor nodes is fulfilled in a Safety-as-a-Service (Safe-aaS) platform for Social Internet of Vehicles (SIoV) environment. The end-users/customers request for decision parameters and make payment to the Safe-aaS platform. Based on their request, safety-related customized decisions are provided to them. None of the existing mechanisms provide the equilibrium condition between the sensor and vehicle owners, customers, and SSPs. The customers' requests for safety services and the presence of active, mobile sensor nodes present within a particular geographical region fluctuates with time. These mobile sensor nodes attain mobility with the variation in the geographical location of the vehicles, to which they are attached. Moreover, the service region of the SSPs is bounded and may comprise various types of geographical regions such as hilly and plane. To quantify the quality of service provided by SSPs, we define the term satisfaction factor (SF) for the registered users. The demand of customers is computed depending on the SF value. In order to find the equilibrium point, we model the utility of SSPs as an optimization function. We apply Karush-Kuhn-Tucker (KKT) conditions to find the optimal price charged by the SSPs and the number of mobile sensor nodes necessary for decision generation. We extensively simulate our proposed mechanism and observe that the satisfaction factor of users and utility of SSPs fluctuates with time.

Discrete fractional Fourier transform (DFRFT) based orthogonal frequency division multiplexing (OFDM) system significantly outperforms the conventional discrete Fourier transform (DFT) based OFDM system in the presence of carrier frequency offset (CFO). However, to achieve the interference‐free performance, the residual interference remaining after the channel equalisation in the fractional Fourier domain needs to be compensated. To enable this residual interference compensation with low complexity after DFRFT at the receiver, an accurate and generalized expression for inter‐carrier interference (ICI) coefficient from interfering to the desired subcarrier is derived over a multipath fading channel with CFO. The derived ICI coefficient is validated at the DFRFT angle equal to (i.e., for DFT‐OFDM system) and over AWGN and flat channel. Monte Carlo simulation of symbol error rate (SER) over the Rayleigh fading channel is also carried out to verify the derived theoretical closed‐form ICI coefficient for different values of the DFRFT angle. At the receiver, a low complexity residual interference cancellation stage is introduced by utilizing the banded matrix implementation of the derived closed‐form residual ICI matrix for the DFRFT‐OFDM system which only needs to perform operations for closely preserving the interference‐free performance.

In this study, the exact closed‐form signal‐to‐interference‐noise ratio (SINR) expression, for the impact of Doppler frequency shift on minimum mean square error receiver is derived for Walsh Hadamard (WH) and polyphase carrier interferometry (CI) code based multicarrier spread orthogonal frequency division multiplexing (SOFDM) transmission scheme over integrated satellite–terrestrial broadcast system. Additionally, bit error rate and spectral efficiency are analysed based on the obtained SINR expression. To examine that, three‐state Fontan land mobile satellite, and six‐path typical urban and rural area terrestrial channel models are employed. This analysis is performed to substantiate variable bit rate (VBR) quality of service at the physical layer of digital video broadcast satellite handheld (DVB‐SH)‐A architecture, the provision of which is absent in DVB‐SH standard. VBR is assumed for SOFDM. The results illustrate that WH‐SOFDM outperforms CI‐SOFDM under both performance measures in all the three channel environments. Further, pilot‐based channel estimation technique is performed and the estimated error variance is evaluated for VBR WH/CI‐SOFDM. Later, block‐wise system computational complexity of WH/CI‐SOFDM schemes is evaluated. It is shown that, CI‐SOFDM is a relatively more complex system than WH‐SOFDM. Thus, a trade‐off is present between the achieved performance gain and system complexity.

A cooperative cognitive radio network (CRN) with improved energy detection-based spectrum sensing is analyzed in various fading scenarios. Generalized multipath (Nakagami-m) fading and enriched multipath (Nakagami-q) fading models are considered along with two other general fading distributions, i.e., κ-μ and η-μ distributions. For spectrum sensing, instead of conventional power 2-based detection method, the arbitrary power p-based improved energy detector is used. The impact of the cognitive user mobility on the performance of the improved energy detector is investigated. Specifically, the statistics for the received signal are derived over various fading environments. The performance of the considered CRN system is evaluated in terms of probability of false alarm, probability of missed detection, and receiver operating characteristics (ROC) curves. Moreover, the area under the ROC curve is also obtained. Simulation results are provided to corroborate the theoretical results derived in this paper.

In this study, generalised expression of probability of error for binary phase shift keying (BPSK) and quadrature PSK (QPSK) modulated fractional Fourier transform (FRFT)‐based orthogonal frequency division multiplexing (OFDM) system has been derived over frequency selective Nakagami‐ m fading channel for any arbitrary Nakagami parameter m in the presence of carrier frequency offset (CFO). The symbol error rate (SER) performance of FRFT‐based OFDM system has been found to be better than fast FT‐based OFDM system at different values of FRFT angle for BPSK and QPSK. For different values of CFO, the optimum at which the error rate is minimum has been found and used for analysis and simulation. It has been observed that over Nakagami‐ m frequency selective channel, SER expression of BPSK and QPSK for FRFT‐OFDM system exactly follows the Monte Carlo simulation in MATLAB.

A novel and compact dual band planar antenna for 2.4/5.2/5.8-GHz wireless local area network(WLAN) applications is proposed and studied in this paper. The antenna comprises of a T-shaped and a F-shaped element to generate two resonant modes for dual band operation. The two elements can independently control the operating frequencies of the two excited resonant modes. The T-element which is fed directly by a 50 Ω microstrip line generates a frequency band at around 5.2 GHz and the antenna parameters can be adjusted to generate a frequency band at 5.8 GHz as well, thus covering the two higher bands of WLAN systems individually. By couple-feeding the F-element through the T-element, a frequency band can be generated at 2.4 GHz to cover the lower band of WLAN system. Hence, the two elements together are very compact with a total area of only 11×6.5 mm2. A thorough parametric study of key dimensions in the design has been performed and the results obtained have been used to present a generalized design approach. Plots of the return loss and radiation pattern have been given and discussed in detail to show that the design is a very promising candidate for WLAN applications.

In this work, we investigate the sensitivity to carrier phase jitter of a phase-locked local oscillator on the performance of variable rate CI/MC-CDMA system over non-dispersive channel. It is shown that for full load, the degradation depends on the jitter variance and non-orthogonality among the spreading codes of the users. When all the subcarriers have same power level and jitter spectrum, the degradation caused by the jitter variance and cross-correlation variance varies from user set to user set in variable rate transmission schemes.

This paper presents a comparative study of discrete cosine transform (DCT) spread orthogonal frequency division multiplexing (OFDM) with discrete Fourier transform (DFT) spread OFDM, applied to an underwater acoustic (UWA) channel. The UWA channel is characterized as a frequency selective multipath fading channel with long delay spread. Energy compaction property of DCT works well in reducing the peak to average power ratio (PAPR) in UWA channel. It is also shown that DCT spread OFDM has lower computational complexity compared to DFT spread OFDM. The bit error rate (BER) performance has been evaluated for both the schemes. Simulation results show that DCT spread OFDM has a better performance than DFT spread OFDM in UWA channel. A novel scheme of using the null subcarriers to implement complex field repetitive coding in case of DCT spread OFDM is proposed to further reduce the BER.

This paper introduces an improved iterative soft decision subcarrier parallel interference cancellation (SDSub-PIC) technique for the carrier interferometry/multicarrier code division multiple access (CI/MC-CDMA) system that significantly reduces the multiple access interference (MAI) for the desired user. Carrier interferometry (CI) codes are used to minimize the cross-correlation between different users. In this paper, the interference cancellation is done by taking the soft decision estimates of transmitted data bit at the subcarrier level. MAI estimates become more reliable with multistage iterative structure of the receiver, which ensures improved bit error rate (BER) performance. Simulation results show that SDSub-PIC provides average BER of 1e-04 at 10 dB SNR which is about 1.5 dB off from single user bound in an AWGN channel at 50% overloading. In slow frequency selective Rayleigh fading channel, SDSub-PIC ensures BER of 4e-05 at 25 dB SNR with four-fold diversity at 100% overloading. We have observed that the new scheme performs considerably better than Block-PIC [14] and Sub-PIC [15] proposed earlier for CI/MC-CDMA system. Complexity of SDSub-PIC is O(N) while for conventional PIC and Block-PIC, it is O(2N-1) and 2O(N) respectively.

A DS-CDMA system is said to be Overloaded if the number of users supported is more than the spreading factor N. Overloading is an attractive candidate for next generation cellular telephony that calls for a higher user capacity than that supported by conventional DS-CDMA systems. This work derives an accurate analytical model for Overloaded DS-CDMA system under imperfect synchronization. The Model also takes care of the degradation in signal energy due to the loss in Autocorrelation value at the matched filter receiver. BER expressions for Individual users are also derived for uniformly distributed synchronization errors that happen to be the case in practical scenario. Monte-Carlo simulations verify the presented analysis.

Overloading is a scheme to accommodate more users than the spreading factor N. This is a bandwidth efficient scheme to increase the number of users in a fixed bandwidth. One of the efficient schemes to overload a CDMA system is to use two sets of orthogonal signal waveforms (O/O). The first set is assigned to the N users and the second set is assigned to the additional users. An iterative multistage detection (IMSD) technique is used to cancel interference between the two sets of users. The interference cancellation receiver uses hard decisions (HDIC) or soft decisions (SDIC) to estimate the interference. In this paper, the BER performance of a new overloading scheme using orthogonal Gold code (OG/OG) sets is evaluated with SDIC receiver. It is observed that this scheme provides 25% (16 extra users) channel overloading for synchronous DS-CDMA system in an AWGN channel, with an SNR degradation of about 0.35 dB as compared to single user bound at a BER of 10-5. We have also evaluated the overloading performance, when the two set are scrambled with set specific complex scrambling sequence. It is shown that the amount of overloading increases significantly from 25% to 63% (40 extra users) by using complex scrambling for N=64.