Radio Frequency Interference (RFI) in Wireless Communications
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RFI is experienced in all radio communication systems, on the ground, in the air and on the sea, and in space. This three-day course will address all principal uses of radio and wireless and how RFI can be assessed and resolved. The approach is based on solid technical methodologies that have been applied over the years yet considers systems in use today and on the near-term horizon. The objective is to allow the widest variety of radiocommunication applications to operate and co-exist, providing for effective methods of identifying and resolving RFI before, during and after it appears.
Attendees will receive a copy of Mr. Elbert’s textbook Radio Frequency Interference in Communications Systems, Artech House, 2016.
What You Will Learn:
The objective of this three-day course is to increase knowledge in the area of RFI and EMI compatibility as well as the risk of potential interference among various wireless systems. The interference cases would result from the operation of one system as against others (e.g., radar affecting land mobile radio, and vice versa; satellite communications affecting terrestrial microwave, and vice versa). It is assumed that all operating equipment has been designed and tested to satisfy common technical requirements, such as FCC consumer certification and MIL STD 461F. As a consequence, RFI is that experienced primarily through the antennas used in communications. The instruction will be conducted in the classroom by Bruce Elbert using PowerPoint slides, Excel Spreadsheets, and link calculation tools such as HD Path and SatMaster. The overall context is spectrum and frequency management to enhance knowledge in identifying and mitigating potential interference threats among various systems. Attendees are expected to have a technical background with prior exposure to wireless systems and equipment.
- Key concepts of evaluating radio frequency interference:
- Elements of a wireless or radio communication system – land-based point-to-point and wireless/cellular, space-based systems
- Types of electromagnetic interference – natural and man-made (unintentional and intentional)
- Interference sources – conducted and radiated, radar signals, RF intermodulation (IM)
- Levels of RFI – permissible, accepted, harmful
- Signals, Bandwidth and Threshold Conditions
- Modulation – analog and digital
- Source encoding and error correcting codes
- Adaptation to link conditions
- Spread spectrum
- Eb/N0, protection ratio (C/I)
- Computing minimum acceptable signal (dBm at receiver input)
- Spectrum Allocations and Potential for Sharing with Acceptable Interference
- Current frequency allocations for government and non-government use (1 MHz through 100 GHz)
- ITU designated bands for sharing as Primary and Secondary services
- Sharing criteria – as mandated, as negotiated
- Link Budget equations
- Line-of-sight propagation, range equation, power flux density
- Evaluating antenna properties and coupling factors
- Calculating C/I from antenna characteristics – homogeneous and heterogeneous cases
- RFI on Obstructed Paths
- Path profiles and obstructions
- Diffraction and smooth earth losses
- Path analysis tools – HD Path
- Atmospheric losses and fading
- Constituents of the atmosphere
- Tropospheric losses
- Near-line-of-sight paths; Ricean fading model
- Obstructed paths (in building and concrete canyons); Rayleigh fading
- Interference analysis examples between various systems
- Service performance in the presence of interference, interference control through design and coordination
- Radars vs. land mobile and LTE systems
- WiFi and Bluetooth
- Satellite communications vs. terrestrial microwave systems
- Frequency reuse and signal propagation
- Cross polarization on the same path
- Angle separation through antenna beam selection
- Cellular pattern layout – seven and four color reuse patterns
- Non-steady state propagation – scatter, rain-induced interference, ionospheric conditions
- How to identify, prevent, and fix common RFI problems
- Identifying interference in the real world – detection, location, resolution
- Physical separation, orbit separation
- Site and terrain shielding
- Interference suppression – filtering, analog and digital processing techniques
Bruce R. Elbert, MS (EE), MBA, Adjunct Professor (ret), College of Engineering, University of Wisconsin, Madison. Mr. Elbert is a recognized satellite communications expert and has been involved in the satellite and telecommunications industries for over 40 years. He founded Application Technology Strategy, LLC, to assist major private and public sector organizations that develop and operate cutting-edge networks using satellite and other wireless technologies During 25 years with Hughes Electronics, he directed the design of several major satellite projects, including Palapa A, Indonesia’s original satellite system; the Galaxy follow-on; and the development of the first GEO mobile satellite system capable of serving handheld user terminals. Mr. Elbert was also ground segment manager for the Hughes system, which included eight teleports and 3 VSAT hubs. He served in the US Army Signal Corps as a radio communications officer and instructor. By considering the technical, business, and operational aspects of satellite systems, Mr. Elbert has contributed to the operational and economic success of leading organizations in the field. He has written nine books on telecommunications and IT.
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