Multi-dimensional radio frequency interference framework for characterizing radio astronomy observatories

Abstract. C-band weather radar data are commonly compromised by interference from external sources even though weather radars are the primary and therefore privileged user of this frequency band. This is also the case for the radar network of the German Meteorological Service (Deutscher Wetterdienst, DWD). Theoretically, dynamic frequency selection (DFS) by devices operating in the C band should prevent any disturbance of the primary user. In practice, this does not always work as intended under the current regulations. As it is not possible to separate a superimposed interference signal from measured weather radar data, the protection of the frequency band is of utmost importance. Currently, the only available option is to discard the compromised portions of the radar data. Therefore, the current best course of action is to shut down radio frequency interference (RFI) sources as quickly as possible. The automated RFI detection algorithm for the German C-band weather radar network, operational since July 2017, makes use of routinely measured radar moments. Built upon data gathered since 2017, an RFI classification with respect to the severity and duration of RFI sources was first implemented in 2019. An independent verification of the RFI detection algorithm was performed by using a commercially available Wi-Fi adapter, which is directly integrated into the radar receiver. Subsequently, a mitigation workflow was implemented to efficiently identify and shut down detected RFI sources by the German Federal Network Agency (Bundesnetzagentur, BNetzA). By following this workflow with great effort, the number of persistent RFI sources has been decreasing since October 2019, while a steady increase in short-lived RFI sources over the last 5 years also exists. In total, 11 889 RFI sources have been identified from July 2017 to May 2022. Most of these (94.8 %) are such short-lived sources that an unambiguous identification by the BNetzA is, in general, not feasible. However, as stated by the C-band regulations, any non-compliant transmitter compromising the operation of a weather radar has to be shut down. This is important, as even these short-lived RFI sources negatively affect meteorological product generation.

Radio frequency interference (RFI) sources pose threats to wideband synthetic aperture radar (SAR) systems and accurate SAR image interpretation. Since most of RFI sources are narrowband, notch filtering is a simple but effective method for RFI suppression. In this letter, a modified two-step notch filtering approach combined with linear prediction is proposed to improve the SAR image quality. The notch filtering is used to mitigate narrowband RFI energy, while the linear prediction is introduced to recover the missing range spectral component of the SAR raw data from the desired scene, which is removed together with RFI sources by the notch filter. Because of the Gibbs phenomenon in Fourier series, the small residual RFI energy after notch filtering is enough to cause image visual disturbances and affect the accuracy of the following missing range spectrum extrapolation. The two-step notch filtering with a limited bandwidth is applied for better RFI sources mitigation. Simulation results on both simulated targets and real SAR raw data validate the proposed approach.

We report the first measurements of radio frequency spectrum occupancy performed at sites aimed to host the future radio astronomy observatory in Indonesia. The survey is intended to obtain the radio frequency interference (RFI) environment in a spectral range from low frequency 10 MHz up to 8 GHz. The measurements permit the identification of the spectral occupancy over those selected sites in reference to the allocated radio spectrum in Indonesia. The sites are in close proximity to Australia, the future host of Square Kilometre Array (SKA) at low frequency. Therefore, the survey was deliberately made to approximately adhere the SKA protocol for RFI measurements, but with lower sensitivity. The RFI environment at Bosscha Observatory in Lembang was also measured for comparison. Within the sensitivity limit of the measurement equipment, it is found that a location called Fatumonas in the surrounding of Mount Timau in West Timor has very low level of RFI, with a total spectrum occupancy in this measured frequency range being about 1 %, mostly found at low frequency below 20 MHz. More detailed measurements as well as a strategy for a radio quiet zone must be implemented in the near future.

Mitigating in-band, continuous-wave (CW) radio frequency interference (RFI) is a common problem for radar systems which themselves may employ continuous-wave waveforms. The source of this RFI can be intentional or unintentional spectral artifacts of near-by narrowband communications systems. Radar signal modulations of just a few megahertz are frequently quite broad compared to the modulation bandwidths of the interferers. So, characterization of RFI by a simple tone can be sufficient to assess its impact. When the RFI sources are unanticipated or of uncertain characteristics, there is motivation to mitigate them in a responsive manner in receive processing. A computationally efficient RFI cancellation method for receive is described here. Salient properties of this method are the recovery of radar sensitivity in the presence of narrowband RFI and the preservation of pulse compression time sidelobe levels. In fact, the technique described here overcomes the disadvantages of isolating and removing an RFI source that is completely immersed in the radar waveform in both time and frequency. While removing each of possibly multiple RFI sources with surgical IIR filters, little secondary influences on pulse compression responses arise because the IIR filter is suitably designed with finite word influences and impulse-response time sidelobes in mind.

A vehicle tracking system is very useful for tracking the movement of a vehicle from any location at any time. An efficient vehicle tracking system is designed and implemented for tracking the movement of any equipped vehicle from any location at any time. The proposed system made good use of popular technology that combines a smartphone with an Arduino UNO. This easy to make and inexpensive compared to others. The designed in vehicle device works using Global Positioning System (GPS) and Global System for Mobile Communication(GSM) technology that is one of the most common ways for vehicle tracking. The device is embedded inside a vehicle those positions is to be determined and tracked in real time. A vehicle tracking system is an electronic device installed in a vehicle to enable the owner or a third party to track the vehicle's location. This paper proposed to design a vehicle tracking system that works using GPS and GSM technology, which would be the cheapest source of vehicle tracking and it would work as anti-theft system. It is an embedded system which is used for tracking and positioning of any vehicle by using Global Positioning System (GPS) and Global system for mobile communication (GSM). An Arduino UNO is used to control the GPS receiver and GSM module. The vehicle tracking system uses the GPS module to get geographic coordinates at regular time interval. The GSM module is used to transmit and update the vehicle location to a database. This paper gives minute by minute update about vehicle location by sending SMS through GSM modem. This SMS contain latitude and longitude of the location of vehicle. Arduino UNO gets the coordinates from GPS modem and then it sends this information to user in text SMS. GSM modem is used to send this information via SMS sent to the owner of the vehicle. Location is displayed on LCD. And then Google map displays location and name of the place on cell phone. Thus, user able to continuously monitor a moving vehicle on demand using smartphone and determine the estimated distance and time for the vehicle to arrive at a given destination.

A CNN and LSTM-based approach to classifying transient radio frequency interference

Modern infrastructure and a myriad of services rely on positioning and timing information provided by Global Navigation Satellite Systems (GNSS) and in particular the Global Positioning System (GPS). However, given their low received signal power levels, GNSS signals are vulnerable to Radio Frequency Interference (RFI), either from non-intentional or intentional (jamming), sources. Hence, GNSS itself has become a critical infrastructure which must be protected. Since RFI source is unknown a priori, passive localization systems consisting of spatially distributed Sensor Nodes (SNs) are needed to geo-locate the RFI. These systems typically use source Angle of Arrival (AOA), Time Difference of Arrival (TDOA) or a combination of AOA/TDOA measurements which are non-linear in nature, to estimate the RFI position. Also, dynamics associated with the RFI source(s) further complicates the geo-localization process. This paper explores and reports on the use of various Kalman Filters in combining AOA and TDOA measurements for efficient geo-localization and tracking of dynamic and stationary RFI sources based on real measurements from one such geo-localization system. We report on and contrast the geo-localization accuracies and computational complexities of the Extended, Unscented and Single Propagation Unscented Kalman Filters along with the traditional snap-shot approach.

The Giant Meterwave Radio Telescope (GMRT) observatory in India consists of 30 antennas in a Y-shaped array, spread out over a 14 km radius from the central processing center. This makes the protection of radio telescopes from increasing radio frequency interference (RFI) at meter wavelengths quite challenging. Radio telescopes are built with broadband receivers to observe beyond the narrow allocated radio astronomy bands, so protecting the receivers from out-ofband emission is a major task. With the rapid increase in mobile communication, TV and FM Radio transmitters, police wireless, industries and power line distribution networks, private and public transport, there is a significant increase in RFI at low frequencies. This paper presents the results of above studies of these external sources of RFI, their effect on the receiver system, and of various methods adopted to minimize the same to protect the GMRT. This paper also describes various control experiments carried out, with measurements made over the past 10 years, and methods adopted to co-exist with commercial communication operators and industries to control the RFI environment at the GMRT The GMRT RFI team has been able to detect and correct 1800 radiating domestic TV boosters spread over a 20 km radius with a simple low cost solution. Using RF and Ultrasonic detectors, dense electrical distribution networks with LT and HT power distribution lines and single phase, 3 phase transformer installations in the neighbor hood are monitored, and steps have been taken to control various power line sources of interference that have affected observations. The GMRT also faces challenges from many GSM and CDMA mobile operators in the region around the GMRT. We have been able to negotiate for a change in operating band and in the orientation of cell towers etc. to protect the GMRT. Efforts are also ongoing to monitor and control the interference from industries operating in nearby regions as well as from internally generated RFI at the GMRT.

The performance of a cross-frequency detector against pulsed sinusoidal Radio Frequency Interference (RFI) is analyzed theoretically. The effects of duty cycle and RFI strength are examined, and the detection performance of the cross-frequency algorithm is compared with that achieved by pulse and kurtosis detectors. The performance loss that occurs in the cross-frequency algorithm when an RFI source is not centered in a frequency channel is also quantified, and a computationally simple model for this loss is described.

Intentional electromagnetic interference is a potential issue for railway networks based on ground-to-train communications. Reported mitigation techniques usually rely on electromagnetic compatibility classical procedures, which are not always the best option for such an unpredictable event. In this work, offline adaptive filtering is used to recover global system for mobile communications - railway damaged data.

A simplified generalized radio frequency interference (RFI) detection method and principal component analysis (PCA) method are utilized to detect and attribute the sources of C-band RFI in AMSR2 L1 brightness temperature data over land during 1–16 July 2017. The results show that the consistency between the two methods provides confidence that RFI may be reliably detected using either of the methods, and the only difference is that the scope of the RFI-contaminated area identified by the former algorithm is larger in some areas than that using the latter method. Strong RFI signals at 6.925 GHz are mainly distributed in the United States, Japan, India, Brazil, and some parts of Europe; meanwhile, RFI signals at 7.3 GHz are mainly distributed in Latin America, Asia, Southern Europe, and Africa. However, no obvious 7.3 GHz RFI appears in the United States or India, indicating that the 7.3 GHz channels mitigate the effects of the C-band RFI in these regions. The RFI signals whose position does not vary with the Earth azimuth of the observations generally come from stable, continuous sources of active ground-based microwave radiation, while the RFI signals which are observed only in some directions on a kind of scanning orbit (ascending/descending) mostly arise from reflected geostationary satellite signals.

Short Message Service (SMS) has grown in popularity over the years and it has become a common way of communication. SMS is usually used to transport unclassified information, but with the rise of mobile commerce it has become a popular tool for transmitting sensitive information between the business and its clients. By default SMS does not guarantee confidentiality and integrity to the message content. Therefore SMS is not totally secure and reliable. The Short Messaging Service (SMS) is global wireless service that is used to send and receive the messages over Global System for Mobile Communication (GSM).There is no built –in procedure to authenticate and offer security for text transmitted over GSM network. The reason behind it is most of the applications for mobile devices are designed and developed without taking security into consideration. This paper describes all the existing security mechanisms in SMS and security shortfalls and various attacks on GSM networks which include Authentication, Encryption, Equipment Identification and Subscriber Identity Confidentiality, Denial of service Attacks, Brute force attack, Replay Attack as well as the manifestation of network vulnerabilities including SMS attacks, encryption attacks and security measures to prevent GSM network from these attacks. KeywordsShort message service security, mobile communication, Global System for Mobile Communication, Wireless Messaging API Short Message Service (SMS) can be defined as any text, voice, sound or image message sent over a public communications network, which can be stored in the network or in the recipient’s terminal equipment until it is collected by the recipient [1]. Although SMS was originally meant to notify users of their voicemail messages, it has now become a popular means of communication by individuals and businesses. Banks worldwide, including in South Africa, are using SMS to conduct some of their banking services [2]. For example, clients are able to query their bank balances via SMS. When sensitive information is exchanged using SMS, it is crucial to protect the content from eavesdroppers. By default, SMS content is sent over the Global System for Mobile communications (GSM) network in clear text form, or in a predictable format [3]. This allows an attacker with the right equipment to eavesdrop on the information that is being sent. Another problem with SMS is that the originating address (OA) field in the SMS header can be forged, thus allowing masquerading and replay attacks. Therefore SMS is not totally secure and cannot always be trusted. For example, there has been at least one case in the UK where SMS information has been abused by the operator employees [3]. SMS has become a popular wireless service throughout the world as it facilitates a user to be in touch with any mobile phone subscriber anywhere in the world, instantaneously and without any hassle [4].hence, it is important to prevent the SMS content from being illegally intercepted/interrupted by illegal sources as well as to ensure the origin of the message from the legitimate sender. Additionally, unencrypted SMS content during the transmission allows the mobile operator’s employee to read and modify the SMS content. Unfortunately, the SMS does not have any built in vetting procedure to authenticate the text or provide security for the data/text transmitted. All SMS facilities should incorporate some form of basic security mechanism in terms of confidentiality, integrity, authentication and non-repudiation of the messages before it can deemed suitable for use by the government, commercial and military services [5]. The Short Messaging Service, or SMS, is a bi-directional service to send text over wireless communication systems. It consists of a message that can be up to 160 alphanumeric characters in length. Though originally a GSM service, SMS messages are now a globally accepted service. The messages can be stored in that network until they are collected by the recipient’s terminal equipment II. SMS PACKET FORMAT An SMS packet contains a header and a payload (see Fig. 1). The header contains information that enables the cellular network to route the SMS message to the correct recipient. The originating address (the mobile phone number of the sender) is also included in the header. The payload is the message content that is displayed on the mobile handset. The size of the payload is 140 bytes, consisting of 160 seven-bit characters, or 140 eight-bit characters, depending on the Proc. of the Intl. Conf. on Advances in Computer Science and Electronics Engineering Editor In Chief Sahil Seth. Copyright © 2012 Universal Association of Computer and Electronics Engineers. All rights reserved. ISBN: 978-981-07-1403-1 doi:10.3850/978-981-07-1403-1 838

The advent of global system for mobile communication otherwise called GSM is no doubt a mixed blessing to humanity. Just as the relevant security agencies are appropriating the benefits offered by the global system for mobile communication in the policing, detecting and preventing acts of criminality in the society, so also the criminal elements are beneficially misusing the communication device for criminal purposes. It is a known fact that crime is continually evolving and adapting. Kidnapping as a form of crime in Nigeria is not novel as there were reported cases of kidnapping even before the advent of colonialism for either rape, ritual or hostage taking during tribal conflicts among other reasons which then certainly excluded ransom payment. The current spate of crime of kidnapping for ransom is however one of the misfortunes unleashed on the citizenry through the advent of mobile communication device. Kidnapping for ransom in Nigeria would have been a fruitless criminal indulgence but for the advent of global system for mobile communication through which kidnappers are able to establish contact with relatives or family members of their victims to demand, for ransom payment. The diametrically opposing usage of this communication device as a handy tool in the hands of law enforcement agents towards checkmating crimes in the society and as a tool of criminal engagement for committing crime of kidnapping for ransom in Nigeria constitutes the thrust of this paper. This study concluded that despite the efforts of government in curbing this menace, it has remained a thorn in the flesh of victims and their relatives.

This paper will discuss the operational impact of radio frequency interference on a space mission. Operations of unmanned spacecraft require reliable communications between controllers on the ground and the spacecraft they operate. Interference in the radio spectrum can affect not only the ability of operators to send commands to a spacecraft, but also the reliable return of information from the spacecraft payload. Unfortunately, it is not always easy to identify the source of radio frequency interference or to properly plan for service interruptions. The ESA Integral mission is used as a case study to demonstrate the impact of radio frequency interference. Several short duration service interruptions were impacting operations each week. Using the primary ground station located in Kiruna, Sweden, operational systems were developed to better monitor and characterize the source of radio signals. Statistics were derived from the data collected which were used to find ways of reducing the impact of radio frequency interference on operations. This paper will explore techniques which can be used to record radio frequency interference events, identify the source of interference, model future events, and ultimately to better plan mission operations.

To strengthen and improve the movement of cars in real-time location tracking to monitor in order to improve operational efficiency and ensure traffic safety of the vehicle is particularly urgent, global system for mobile communication system GSM (Global System of Mobile communication) has been developed to the 3G era and geographic information systems GIS (Geographic Information System) of rapid development, so that based on GPS / GSM tracking feasibility sports car positioning monitoring system design is growing. In this paper, GPS / GSM mobile vehicle as the monitoring terminal hardware platform combined with GIS positioning tracking and monitoring center software design in VC ++ environment, in order to reduce the GPS module positioning error, system application Kalman filter algorithm for GPS data filtering to increase GPS the positioning accuracy.