An Improved FCME Algorithm Based on Differential Spectrum Envelope for Interference Detection in Satellite Communication Systems

Today, and especially in the future, there is an increasing need for complementary techniques to meet the growing capacity requirements of wireless communications. A high data rate connection with power line communication (PLC) is one attractive solution to achieve this need. One way to improve the data rates obtained in PLC networks is to increase the used bandwidth and operate at higher frequencies. At the same time, however, it should be kept in mind that the power lines, unfortunately, act as quite good antennas which can detect strong near-by FM and TV signals. In the future, the PLC frequency range can overlap with the broadcasting frequency bands resulting in interference for these transmissions and vice versa. With the static notching the whole FM-frequency band is notched during the PLC communication. This may result in inefficient spectrum utilization as in a given place and at a given time only a part of the FM-frequency band may be occupied. In this paper, a blind spectrum sensing algorithm based on forward consecutive mean excision (FCME) algorithm is proposed to locate the free frequency bands inside the broadcasting frequency range in PLC-network. The performance of this sensing algorithm is analyzed using spectrum analyzer measurement results and calculations in the broadcasting frequency range. The results verify that the proposed method performs well when detecting free frequency bands in broadcasting frequency band providing means for better spectrum utilization in PLC-network.

In dynamic spectrum access, a new wireless system (secondary user: SU) can utilize the spectrum licensed to an existing wireless system (primary user: PU) while the spectrum is vacant. For accomplishing effective and reliable spectrum utilization, statistics of the spectrum usage by the PU, such as

This paper investigates energy detection based wideband spectrum sensing for dynamic spectrum access (DSA) systems. The licensed frequency band of interest is resolved into a series of contiguous frequency bins via the FFT engine of the detector. By employing forward consecutive mean excision (FCME) algorithm and exploiting primary user (PU) signal's contiguity in frequency domain, computationally simple pre-processing of raw spectrum observation data and post-detection processing of decisions are proposed to perform frequency bin cluster based spectrum sensing. It is verified through simulations that these signal contiguity based sensing schemes can significantly increase the PU signal detection rate while at the same time maintaining the false-alarm rate sufficiently close to the desired constant one.

Orthogonal time frequency space (OTFS) modulation is a promising waveform for future wireless communication, offering robustness against time-varying channels and Doppler effects in high-mobility scenarios. However, the anti-jamming capabilities of OTFS systems remain underexplored, leaving gaps in understanding their potential in jamming-prone environments. In this work, we mainly focus on the jamming detection and suppression methods for OTFS systems in additive an white Gaussian noise (AWGN) channel. A frequency-domain anti-jamming technique is presented, employing a time-domain overlapping window approach to reduce jamming sidelobes while mitigating the signal-to-noise ratio (SNR) degradation caused by the window function. Additionally, a smoothing window method is introduced to provide stable samples for jamming detection, effectively reducing the false alarm rate. Furthermore, a low-complexity improved forward consecutive mean excision (FCME) algorithm is proposed, enhancing its practicality and making it more suitable for real-world applications. Finally, the effectiveness of the proposed anti-jamming methods is validated through simulation analyses under single-tone and partial-band jamming scenarios.

In this paper, we have developed a machine learning based adaptive predistorter for high power amplifier linearization approach under dynamically changing environment. In the “bent-pipe” transponder in satellite communication (SATCOM) system, the High Power Amplifiers (HPAs), which are similar to other amplifiers in the communication system, can cause nonlinear distortions to transmitted signals, deteriorating the system transmission performance. The traditional model based processing techniques such as the Extended Saleh's Model (ESM) based predistortion design can be applied to maximize transponder throughput along with HPA power efficiency but sensitive to dynamically changing environment. In this paper, the compensated HPA linearity characterized through Amplitude Modulation-to-Amplitude Modulation (AM-AM) and Amplitude Modulation-to-Phase Modulation (AM-PM) effects is used as the system reward, we leveraged reinforcement learning approach to dynamically optimize the parameter set for the ESM based PD to improve system performance in various environmental conditions. Finally, simulation results are provided to evaluate and verify Bit Error Rate (BER) improvement for the considered SATCOM system by applying our proposed PD technique.

A printed quadrifilar-helical antenna for potential use in the mobile terminal of the satellite communication system is designed in this paper, the antenna combines the qualities of miniaturization, high gain, wide beam and wide angle circular polarization. The relative bandwidth is 8%, which enables the antenna to meet the requirements of multiple Ku-band satellite communication systems. The polarization purity is high, which restrains the ground clutter effectively. The radiation patterns show a regular hemisphere shape, making the antenna suitable for receiving satellite communication signals in a plurality of mobile platforms, such as the ship, the vehicle, the aircraft and the handset receivers. A compact designed Wilkinson power divider is employed as the feeding network of the antenna. The relations between the winding direction and the current phase stepping direction are given. Furthermore, the impacts of current amplitude error and phase error are comparatively analyzed. A good agreement is observed between simulated and measured results within the operating band. Through the integrated optimal design of the structure and material, the “three-proof” quality is achieved without any degradation to the radiation properties of the antenna.

Due to their smaller size and light weighted structures patch antennas are accustomed in modern communication Technology. With additional size in reduction, micro strip antennas are commonly used in handsets, GPS receivers etc. This paper presents a novel design of fractal shape patch antenna using U-slot on patch and defected ground structure. Due to slots on patch and ground, tri-band resonating response is attained with maximum gain and directivity of 4.22dB and 6.51dBi showing high impedance bandwidth and radiation efficiency. The antenna showed good VSWR of 1.63 to 1.02 thus, showing high efficiency. As evident in the simulation results, the proposed antenna has been found useful for W-LAN, GSM, Radio Satellite, Fixed Satellite Services (RSS) & (FSS) and satellite communication systems.

Signal detection and identification are critical in today's shared wireless communication environments with diverse devices. These processes are fundamental to wireless, satellite, cognitive radio, and military communication systems. Automatic and real-time identification of radio traffic enables efficient utilization of resources, such as transmission bandwidth and power. It also facilitates dynamic spectrum access by identifying unused spectrum bands and maintaining fair coexistence among the communication devices. Furthermore, it contributes to spectrum surveillance by detecting unknown or unauthorized transmissions, and, hence, enhancing the Quality of Service (QoS) and network performance through effective noise and interference detection and mitigation. In this work, a Deep Learning (DL) approach is proposed for feature extraction and classification of received signals. In particular, a Convolutional Neural Network (CNN) is employed to classify multiple modulation schemes in wireless fading channel conditions. Simulation results show that the CNN provides high classification accuracy, indicating the effectiveness of the proposed method in realistic wireless channels.

Continuous and precise code delay tracking is essential in challenging environments such as urban canyons where multipath and frequent signal blockage may lead to performance degradation and loss of lock of signals. The strobe correlator (SC) is an effective technique for baseband multipath mitigation and is commonly used for GNSS signal tracking enhancement. An SC has two pairs of early and late correlators, one with a wide and another with a narrow correlator spacing. This paper extends the conventional SC design by applying its correlator pairs on dual-band GNSS signals to realize an extended strobe correlator (ESC). An ESC takes advantage of the natural distinct bandwidth of narrow-band and wide-band signals, e.g., L1 C/A and L5Q signals, to form a dual-band combination at the correlator level in a deeply-coupled manner. Narrow-band L1 signal tracking ensures robustness, while the wide-band L5 signal improves the tracking precision. A moving average window filters the L1 measurement to prevent the noise impact on L5 tracking, providing necessary inter-band assistance to resolve challenges such as code delay misalignment and precision mismatch. Through both Monte Carlo simulation and real data collected in urban environments, this work demonstrates that an ESC can achieve improved overall robustness against loss-of-lock and multipath mitigation performance over standalone tracking. Compared with KF-based combined (KFC-based) tracking, ESC has higher tracking precision under weak signal environment and robustness during signal blockage, but larger residual multipath error.

As a powerful algorithm, fast spectral correlation (Fast-SC) is widely used in bearing fault diagnosis. However, the interference of strong background noise and the existence of multiple fault-related frequency bands make it difficult to diagnose bearing faults using enhanced envelope spectrum and improved envelope spectrum on the basis of Fast-SC. To alleviate the problem, fast kurtogram is imitated to divide the spectral frequency bands; then, the threshold-based diagnostic feature (TDF) of each integration band is calculated to guide the weighting function of the corresponding level; finally, weighted envelope spectrum with the largest TDF is determined as the output; this process is called the reselection mechanism. Simulation and experimental results indicate that the design of weighting function highlights the contribution of the fault-related frequency bands, and the reselection mechanism further improves its performance.

An information system formed by high altitude platform (HAP) will be a new generation-system for the wireless communications and HAP station (HAPS) communication system combines the advantages of both terrestrial and satellite communication systems and avoids, to different extents, their disadvantages. The link simulation scenarios and results have been given for vehicular mobiles in 3.84 Mcps TDD systems in three different kinds of channels: case 3 in 3GPP. It is shown that the maximum performance degradation due to high mobility in 'case 3' and 'vehicular A' channel is about 3 dB while only less than 1 dB performance loss is observed in 'Rician' channel. Simulations show that no significant performance impact is introduced by high speed mobility. Even in the worst channel conditions, only extra 3 dB margin is required to deliver the high speed data service.

In order to provide high-precision satellite navigation services, continuous, high-precision and high-integrity signals should be provided. Non ideal property of each module will result in a certain degree of distortion to the navigation signals and affect. In this paper, channel simulation model based on the actual transmission channel is established firstly. Then, the analysis of independent simulation and that of combining simulation are applied to measure the impact of each module and the whole channel on signal quality. Finally, the corresponding pre-distortion method is put forward to compensate the distortion effects, simultaneously, simulations are compared to verify the performance. The research based on E1 signal is to assess the degree of distortion and the pre-distortion performance using constellation, power spectrum, SCB curve and correlation loss. Simulation results indicate that the program can Improve the constellation by inhibiting the band spectrum of the signal, optimize SCB curve, reduce correlation loss, eliminate the effect on the quality of signals caused by the transmission channel and increase the precision of positioning accuracy, which has great significances and prospects in satellite communication system.

Beam hopping (BH) has become one key technology for satellite communications due to its superior flexibility and efficient resource utilization. In order to balance the service latency of different users when BH is employed in low earth orbit (LEO) satellite communication systems, the objective of this paper is to minimize the maximum queuing delay among users by dynamically scheduling beams and allocating power among beams. The considered problem is a mixed-integer programming problem, and therefore is first transformed into two sub-problems, i.e., user selection and power allocation. Then, a two-stage low-delay algorithm is proposed in consideration of both the total transmit power constraint and traffic requirements. Simulation results indicate that the proposed algorithm can significantly reduce the maximum delay among users in each BH period compared to the existing algorithms.

Carrier Aggregation (CA) is an integral part of current cellular networks. Its ability to enhance the peak data rate, to efficiently utilize the limited available spectrum resources and to satisfy the demand for data-hungry applications has drawn large attention from different wireless network communities. Given the benefits of CA in the terrestrial wireless environment, it is of great interest to analyze and evaluate the potential impact of CA in the satellite domain. In this article, we provide a brief introduction to the possible CA configurations, their deployment scenarios/use cases as well as their advantages, disadvantages, and challenges. Next, the problem of multiuser aggregation and access control design for CA in multi-beam high throughput satellite systems under practical system constraints is presented. In particular, we propose an efficient CA design solution that gives the optimal carrier-user assignment along with the percentage that each user exploits each carrier assuming that multiple users can be multiplexed in each carrier. Both inter-transponder and intra-transponder CA at the satellite payload level of the communication stack are considered. We propose a flexible carrier allocation approach for a CA-enabled multi-beam satellite system targeting a proportionally fair user demand satisfaction. Simulation results and analysis shed some light on this rather unexplored scenario and demonstrate the feasibility of the CA in satellite communication systems.

Physical layer security has become popular in recent years. In satellite communication systems, wire-tap users are easy to obtain information from satellite side for the range of the beam is broad. In this work, we consider the multi user scenario, by adopting the dynamic beam forming in satellite networks, the beam could be restricted into the small range, where wire-tap users could not obtain information from the side band and the information security has been obtained by using the scheme. From the simulation result, we can conclude that, by using the proposed physical layer security method, the wiretap user could not retreat enough information.