Presence Of Narrowband Interference Research Articles

Noise immunity of QAM-OFDM signal reception using soft-decision demodulation in the presence of narrowband interference

Noise immunity of QAM-OFDM signal reception using soft-decision demodulation in the presence of narrowband interference

Power Line Communication with Robust Timing and Carrier Recovery against Narrowband Interference for Smart Grid.

Power line communication (PLC) is an important interconnection technology for the smart grid, but the robustness of PLC transmission is faced with a great challenge due to strong non-Gaussian noise and interference. In this paper, a narrowband interference (NBI) resistant preamble is designed, and an effective timing and frequency synchronization method is proposed for OFDM-based PLC systems in the smart grid, which is capable of simultaneously conveying some bits of transmission parameter signaling (TPS) as well. In the time domain, the cyclic extension of the training OFDM symbol is scrambled, which makes it feasible to combat against NBI contamination. More accurate timing detection and sharper correlation peak can be implemented under the power line channel and the AWGN channel in the presence of NBI, compared with the conventional Schmidl’s and Minn’s methods with the same preamble length. Furthermore, the TPS transmitted using the proposed method is also immune from the NBI. The proposed method is capable of improving the synchronization performance of the PLC transmission significantly, which is verified by theoretical analysis and computer simulations.

ANALYSIS OF UWB BASED ANTENNA FOR WIRELESS COMMUNICATION

Ultra-wideband wireless communications techniques have many merits, including an extremely simple radio that inherently leads to low-cost design, large processing gain for robust operations in the presence of narrowband interference, covert operations, and fine time resolution for accurate position sensing. However, there are a number of challenges in UWB receiver design, such as capturing multipath energy, inter symbol interference especially in a non-line-of-sight environment, and the need for high-sampling-rate analog-to-digital converters. Microstrip Patch antenna (MPA) provides low profile and low volume, so it is use in a now a days communication devices. In this paper study of past few year shows that most of labour on MPA is targeted on planning compact sized microstrip antenna. A novel ultra-wideband printed monopole antenna can be used in wireless communication devices.

Computationally Efficient Algorithm for Estimating the Frequency of Signals at the Output of a Channel with White Gaussian Noise and Narrowband Interference

Abstract—A computationally efficient algorithm is proposed for estimating the frequency of a quasi-harmonic signal in the presence of narrowband interference based on iterative calculation of the autocorrelation sequence. A feature of the algorithm is the use of an additional filtering procedure that improves its stability. Simulation results have confirmed the proximity of the estimates obtained to the theoretical boundaries.

A New Enhanced Energy-Detector-Based FM-DCSK UWB System for Tactile Internet

Frequency-modulated differential chaos shift keying ultrawideband (FM-DCSK UWB) system has attracted more and more attention in recent years because of its low-complexity and low-power advantages. Nevertheless, its system performance is severely degraded in the presence of narrowband interference (NBI), which further limits its practical applications. In this paper, an enhanced energy-based detector (EED) is proposed for the FM-DCSK UWB system to tackle this problem. Compared with the conventional energy detector (ED), the proposed EED significantly enhances the anti-NBI capability while maintaining the low-power and low-complexity feature. As a further insight, the analytical bit-error-rate (BER) expression of the proposed EED-based FM-DCSK UWB system is derived over additive white Gaussian noise as well as IEEE 802.15.4a multipath fading channels. Moreover, simulation results are carried out to demonstrate the accuracy of the theoretical analysis and the merit of the proposed EED. It is illustrated that the proposed EED achieves better performance than the conventional ED in various transmission scenarios. Thanks to the above-mentioned advantages, the proposed EED-based FM-DCSK UWB system appears to be an excellent candidate for low-power and low-complexity tactile Internet-of-Things applications, e.g., wireless sensor networks and wireless body area networks.

Improving Soft Decoding by Spectral Leakage Reduction in Presence of Narrow Band Interference in PLC

Communications over power lines (PLC) is a promising technology for a variety of applications. The use of a single network for power and data transmission with PLC provides weight, space, and cost savings for vehicular communications. Current work focuses on broadband PLC (BPL) systems compliant with the IEEE 1901 standard. Given that transmissions occur on a physical medium not designed for data communication, the channel and noise characteristics are mostly unfavorable. To deal with these conditions, turbo codes have been widely employed due to their high performance. However, their performance strongly depends on the accuracy of the noise estimation. This work addresses the estimation of the noise power spectral density (PSD) to perform soft-decoding. A general background noise (GBN) model and a narrowband interference (NBI) model is considered. To the best of our knowledge, this is the first work that analyzes the effects of the NBI leakage on noise estimation when it is performed during the reception of the data frame. We propose the use of the frame control (FC) symbol to reduce interference leakage on noise estimation. In addition, we investigate the use of payload symbols to further reduce spectral leakage. Finally, we show that system performance considerably improves by using the FC-based estimation in soft-decoding procedures.

Null Subcarriers Assisted Impulsive Noise Mitigation for In-Vehicle Power Line Communication in the Presence of Narrowband Interference

Impulsive noise (IN) is one of the crucial affecting factors of in-vehicle power line communication (PLC) systems, and therefore an effective IN mitigation scheme is required to enhance the performance significantly. Narrowband interference (NBI) from various nearby radios often has great impact on the IN reconstruction and mitigation. In this paper, IN mitigation over uncoded orthogonal frequency division multiplexing (OFDM) PLC systems is investigated considering the impact of NBI. A null subcarriers assisted IN mitigation scheme is proposed to mitigate IN in the scenarios of NBI absence and NBI presence. The IN vector is reconstructed at the proposed receiver first, and then canceled out from the received signal. Theoretical analysis shows that the proposed scheme outperforms the blanking method. Also, the implementation of pre-joint NBI/IN mitigation with the aid of null subcarriers in the proposed scheme can combat the impact of intensive NBI, and achieve a near-optimal bit error rate performance with no iterations. The effectiveness of the proposed mitigation scheme is validated by simulation results, which is applicable to the vehicular environments under the disturbance of joint IN and NBI.

Sparsity-based narrowband interference mitigation in ultra wide-band communication for 5G and beyond

In real operating environments, the performance of low power large bandwidth ultra wide-band (UWB) communication systems suffers due to narrowband interference (NBI) from high power narrowband interferers. Since noise is not spectrally white in the presence of NBI in UWB systems, conventional matched filter based receivers are not optimum in such scenarios. Although NBI mitigation methods have been proposed using NBI subspace and/or limiters for UWB systems, subspace-based approaches are usually not feasible due to no apriori knowledge of the NBI subspace in a real scenario, and the limiter-based approach is also non-optimum. In this paper, we propose a sparsity-based NBI mitigation method that exploits distinct characteristics of UWB signals and NBI, and does not require a limiter. Improved performance of the proposed receiver has been validated via time hopping binary phase shift keying (TH-BPSK) UWB signal transmission in both additive white Gaussian noise and multipath fading channels.

The use of Synchronous Detection in Ultrasonic Flaw Detection of Large -Sized Products with Large Integral Attenuation of Signals

Background/Objectives: The use of simple radio-technical processing of signals – synchronous detection – in the ultrasonic testing of products with large frequency-dependent attenuation of ultrasound is considered. Methods: The use of radar in the ultrasonic flaw detection methods allows for control of objects with a high level of attenuation of ultrasonic vibrations in a material. Findings: It is demonstrated that synchronous detection increases the accuracy of echo signal temporal position measurement and increases the reliability of US testing in the presence of narrowband interference and the correlation with the probing signal of the electroacoustic pickup. Improvements: The use of synchronous detection will significantly increase the sensitivity and noise immunity of the ultrasound equipment used to control the complex structural materials with high attenuation of ultrasound, such as concrete, cast iron, plastic, etc.

Low Complex, Narrowband-Interference Robust Synchronization for NC-OFDM Cognitive Radio

This paper presents a new, low-complexity algorithm for time and frequency synchronization in a non-contiguous-orthogonal frequency division multiplexing (NC-OFDM) radio communication system in the presence of narrowband interference (NBI). This interference scenario is plausible for cognitive radio systems. The computational complexity of the proposed synchronization method is similar to the known Schmidl&Cox algorithm. The algorithm is partially blind, i.e., it does not require information on the NC-OFDM subcarriers used, nor on the center-frequency of the NBI. Moreover, it does not require filtering to remove the NBI. It performs best for the NBI of constant carrier frequency, but it also provides good results for the frequency-modulated interfering signal.

NBI Spectral Leakage Mitigation Based on Compressed Sensing in OFDM Systems

The performance of an orthogonal frequency division multiplexing system is degraded in the presence of narrowband interference (NBI). This degradation arises from spectral leakage of the interference power during demodulation, corrupting many subcarriers. There have been many attempts to mitigate the NBI, but most schemes need some prior information about the NBI or resources in frequency or time domain. Recently, compressive sensing (CS) theory has been introduced, and some researches show that CS theory can be applied to estimate the NBI effectively. However, they still need resources such as frequency domain known elements or time domain interference free region. Also, CS recovery algorithms require high computational complexity. In this paper, we propose an widely usable NBI estimation and mitigation scheme using CS theory without any requirement. We verified that the proposed scheme can sufficiently mitigate spectral leakage of the NBI. Then, we substantially reduce its computational complexity by introducing a neighborhood searching method by dominant samples based on sampling theory.

Outage Analysis of OFDM-Based Cognitive AF Relay Network in the presence of Narrowband Interference

Orthogonal frequency-division multiplexing (OFDM) is one of the most widely used technologies in current wireless communication systems and standards. Cognitive radio (CR) provides a robust solution to the problem of spectrum congestion as it offers opportunistic usage of frequency bands that are not occupied by primary users. Due to the underlying sensing, spectrum shaping, scaling, and interoperable capabilities of OFDM, it has been adapted as a best transmission technology for CR wireless systems. However, the performance of an OFDM-based CR wireless system is affected by the existence of narrowband interference (NBI) from other users. Further, due to carrier frequency offset in NBI sources, NBI energy may spread over all subcarriers of an OFDM signal. In this paper, a fixed Amplify-and-Forward (AF) relay that operates at a frequency band that is different from that of direct mode is introduced to suppress the effect of NBI. Analytical expressions are derived for outage probability in direct, AF-relay, and incremental relaying modes. The outage performance of the proposed AF relay–based CR network is proven to be better than that of direct mode.

웨이블릿 OFDM 시스템과 FD-OFDM 시스템 성능 비교 분석

본 논문에서는 웨이블릿 OFDM (Orthogonal Frequency Division Multiplexing) 및 FD-OFDM(Frequency Diversity OFDM) 시스템과 일반 OFDM 시스템의 성능을 비교 분석 한다. 푸리에 변환에 기반하는 일반 OFDM방식과는 달리 웨이블릿 OFDM 방식은 웨이블릿 변환을 사용하며, CDM (Code Division Multiplexing)과 OFDM의 중간적인 특성을 통해 심볼간 간섭을 효과적으로 제거할 수 있으며 채널간 간섭 역시 최소화 할 수 있다. FD-OFDM 방식의 경우, 각 병렬 브랜치에 입력된 심볼들이 직교 시퀀스로 곱해진 뒤 모든 부반송파에 분배되고, 각 부반송파는 주어진 프레임에서 각 병렬 브랜치의 심볼 조각들의 합의형태로 이루어진 정보를 전달한다. FD-OFDM의 한 부반송파 내에 포함된 모든 심볼들은 직교 시퀀스에 의해 구별되며, 간섭에 강하며 주파수 다이버시티 특성을 가진다는 장점을 지닌다. 협대역 간섭과 하모닉 잡음 환경에서 BER (Bit Error Rate) 성능을 통해 시스템 간 성능 비교 분석을 진행하였으며, 이를 통해 웨이블릿 OFDM과 FD-OFDM의 성능이 일반 OFDM보다 간섭에 대해 강건하고 특히 하모닉 노이즈 환경에서는 웨이블릿 OFDM이 가장 강건한 특성을 보이는 것을 알 수 있다.

Designing and Performance Evaluation of 64 QAM OFDM System

Bold) : — In this report, the performance analysis of 64 QAM-OFDM wireless communication systems affected by AWGN in terms of Symbol Error Rate and Throughput is addressed. 64 QAM (64 ary Quadrature Amplitude Modulation) is the one of the effective digital modulation technique as it is more power efficient for larger values of M(64). The MATLAB script based model of the 64 QAM-OFDM system with normal AWGN channel and Rayleigh fading channel has been made for study error performance and throughput under different channel conditions. This simulated model maximizes the system throughput in the presence of narrowband interference, while guaranteeing a SER below a predefined threshold. The SER calculation is accomplished by means of modelling the decision variable at the receiver as a particular case of quadratic form D in complex Gaussian random variables. Lastly comparative study of SER performance of 64 QAM-OFDM simulated & 64 QAM-OFDM theoretical under AWGN channel has been given. Also performance of the system is given in terms of throughput (received bits/ofm symbol) is given in a plot for different SNR. Keywords (11Bold) -64 QAM, BPSK, OFDM, PDF, SNR.

The Impact of Sub-Band Spreading Bandwidth on DS-MB-UWB System over Multipath and Narrowband Interference

In this paper, we investigate the impact of different sub-band spreading bandwidth (SSBW) on a direct sequence (DS) multiband (MB) ultra wideband (UWB) system in multipath and narrowband interference over realistic UWB channel models based on actual measurements. As an approach to effectively mitigate multipath and narrowband interference, the DS-MB-UWB system employs multiple sub-bands instead of a wide single band for data transmission. By using spreading chips with different duration settings, the SSBW can be manipulated. As a result, it is observed that increasing SSBW does not always improve system performance. Optimum SSBW values exist and are found to vary in accordance to different operating parameters such as the number of sub-bands and types of propagation channel model. Additionally, we have also found that system performance in the presence of narrowband interference is heavily dependent on the number of employed sub-bands.

Effect of jamming and diversity on the performance of a wavelet packet based multicarrier multicode CDMA communication system

In this paper, the performance of multicarrier (MC), multicode (MCD), code division multiple access (CDMA) system employing wavelet packets (WPs) as subcarriers for modulation in the presence of narrowband interference is investigated. The performance analysis include the effects of diversity techniques such as selection, equal gain and maximal ratio combining. The system performance is evaluated by means of bit error rate (BER) and outage probability. The effects of system parameters such as channel intensity profile, diversity order and fading parameter on the system performances were investigated by means of analytical methods and numerical results. Also, the effect of jamming power is investigated. The performance of the system is compared to that of MC/MCD-CDMA based on sinusoidal carrier. Results reveal considerable performance improvement of the system that employ diversity techniques over the one without diversity and of our proposed system over the other system.

Performance of constrained blind adaptive DS-CDMA UWB multiuser detector in multipath channel with IEEE 802.11a interference

Ultra wideband wireless systems are supposed to coexist with other spectrally overlapping narrowband wireless systems especially IEEE 802.11a wireless LAN. Presence of narrowband interference degrades the performance of UWB. In this paper we study bit error probability performance of the constrained blind DS-CDMA UWB multi-user detection algorithms in the presence of IEEE 802.11a OFDM narrowband interference. The constrained blind adaptive algorithm is implemented using both least mean square and recursive least square algorithm and the bit error probability performance is compared with Rake matched filter receiver. The constrained blind receiver does not require spreading code knowledge of all users other than that of the user of interest. Simulation results show that the constrained blind detector cancels IEEE 802.11a interference significantly in comparison with that of the Rake matched filter in the UWB multipath channel.

An Ultra-Wideband Impulse-Radio Transceiver Chipset Using Synchronized-OOK Modulation

This work presents a low-complexity IR-UWB chipset which achieves synchronization and demodulation at the receiver relying only on a ring oscillator clock. The modulation scheme used, synchronized-OOK (S-OOK), permits low power timing acquisition and data reception with a static CMOS digital synchronizer and demodulator counting 61 logic elements. The receiver consists of a modified energy detector (ED) that allows to asynchronously receive UWB pulses in presence of narrowband interference (NBI) with power levels up to -5 and -16 dBm for 5.4 and 2.4 GHz continuous wave interfering signals respectively. The sensitivity is -60/ -66 dBm with an overall energy dissipation of 2.9/3.9 nJ/bit for a 1 Mbps S-OOK PRBS data stream and a 100% power duty cycle. The complete demodulation and synchronization digital back-end consumes only 0.2 mW (including on-chip output buffers) during normal operation. The IR-UWB transmitter is based on a gated LC oscillator and achieves pulse durations of ~2 ns for bandwidths of 500 MHz. It consumes 249 pJ/bit energy per bit at 1 Mbps OOK.

Effectiveness of ultra-wideband range and velocity estimation in presence of narrowband interference

Characteristics of two algorithms for estimating range and velocity are found. The influence of narrowband Gaussian interference on precision of the estimates is analyzed.

Zero padded suffix aided subspace-based narrowband interference detected adaptive channel estimation for MB-OFDM UWB systems

The ECMA-368 standard specifies multiband orthogonal frequency division multiplexing (MB-OFDM) as the definitive technology for high rate ultra-wideband (UWB) communications. Like other wireless systems, the performance of a correct data signals detection and decoding in MB-OFDM UWB is reduced by narrowband interference (NBI). A more specific problem of severity arises when interferences are present during the channel estimation process, since this eventually results to severe degradation in the performance of signal reconstruction in the whole packet layer convergence protocol (PLCP) and service data unit (PSDU). In this article, we propose an improved channel estimation technique for OFDM-based UWB systems in presence of NBI. Several steps have been carried out to achieve this purpose. First, the location of center frequency of NBI is found out through zero padded suffix (ZPS) aided subspace-based method. Secondly, we propose an adaptive band select and replace (ABSR) scheme to eliminate NBI based on frequency-domain redundancy (FR) property we introduce into preamble symbols during transmission. Thirdly, we perform least-square (LS) channel estimation on NBI-free received preamble symbols to get the estimated channel at each subcarrier. Fourthly, low rank least square minimum mean squared error (LMMSE) channel estimation is performed using this LS channel estimation. Lastly, Blackman windowing is applied on low rank LMMSE channel to reduce the spectral leakage and thus to increase the channel estimation accuracy. Link level simulation (LLS) urges that our proposed technique has improved performances. Key words: Ultra-wideband (UWB), channel estimation, multiband orthogonal frequency division multiplexing (MB-OFDM), narrowband interference (NBI), ECMA-368, wireless personal area network (WPAN).