The 7.3 GHz (350 MHz bandwidth) Earth Observation Satellite (EOS) band, while not protected, is used for Passive Sea Surface Temperature (P-SST) measurements that provide important data for weather forecasts, coastal disaster prevention, climate modeling, and oceanographic research. The full 7 GHz band (7.125 to 8.4 GHz), which encompasses these EOS frequencies, is the largest contiguous block of potentially available mid-band spectrum and will play a significant role in meeting the anticipated demand for wireless services. A Real Time Geofenced Spectrum Sharing (RGSS) system is shown to be a practical and near term solution to spectrum sharing between P-SST measurements and 5G or 6G networks in the 7GHz band. RGSS enables IMT networks and EOS radiometers to share 350MHz of overlapping spectrum centered at 7.3 GHz. It prevents interference to P-SST measurements while simultaneously allowing IMT systems un-constrained access to the shared spectrum greater than 99.9% of the time. Subscriber impact during the less than 0.1 percent paused access time can be prevented by using 3GPP defined capabilities and O-RAN APIs to move subscribers to other frequencies. Paused access time data from a proof-of-concept RGSS system is available to academic, government, and industry researchers through a web or programmatic interface.

Real-time Geo-fencing for Spectrum Sharing (RGSS) is a dynamic, software driven spatiotemporal sharing mechanism which utilises the orbital motion of the EESS satellites relative to the ground, and the rotational motion of the instrument scan-head; in order to automatically schedule cessation of interfering transmissions by co-operative terrestrial 5G/6G networks, during “dark times”. Statistics of the “dark time” periods, for a chosen location within the contiguous US, incorporating - inter alia - duration, and period of recurrence - across all currently operational satellite radiometers; and a demonstration of the RGSS via a web-based API front-end are presented.

A team comprising the University of Colorado, Boulder (CUB), the Hat Creek Radio Observatory (HCRO) and UC Berkeley (UCB) is presently engaged in National Science Foundation (NSF) funded research and development of various tools to facilitate co-existence of active and passive users of the electromagnetic spectrum, within a prototype National Radio Dynamic Zone (NRDZ) - centred around the Allen Telescope Array (ATA) at HCRO.

A simple 'RF-flashlight' (or ground to satellite) interference testbed is proposed to experimentally verify real-time geofencing (RTG) for protecting passive Earth Exploration Satellite Services (EESS) radiometer measurements from 5G or 6G mm-wave transmissions, and ground to satellite propagation models used in the interference modeling of this spectrum coexistence scenario. RTG is a stronger EESS protection mechanism than the current methodology recommended by the ITU based on a worst-case interference threshold while simultaneously enabling dynamic spectrum sharing and coexistence with 5G or 6G wireless networks. Similarly, verifying more sophisticated RF propagation models that include ground topology, buildings, and non-line-of-sight paths will provide better estimates of interference than the current ITU line-of-sight model and, thus, a more reliable basis for establishing a consensus among the spectrum stakeholders.

The impact of 5G networks transmitting between 24.25- 27.5 GHz on Earth Exploration Satellite Services (EESS) microwave sounders used to measure atmospheric water vapor and temperature was widely discussed and modeled in preparation for setting emission recommendations by International Telecommunications Union (ITU) at the 2019 World Radio Congress (WRC-19). Since then, two new classes of network devices - 5G repeaters and high transmission power User Equipment (UE) for fixed wireless services - have been introduced and deployed in 28 GHz networks with expectations that they will also be deployed at 24 GHz. This paper discusses the (potentially significant) increase in interference from these new components along with open questions related to their regulatory status. While this paper discusses increases in interference to 23.8 GHz EESS measurements from 5G transmissions in the "24 GHz" band, it is important to recognize that repeaters and high power UEs need to be considered when modeling interference from 5G/6G networks in all bands. This paper also touches on whether the current ITU process and methodology to regulate interference with passive sensors (vendor applied hardware-based filtering based on long-term network forecasts and worst-case Monte Carlo modeling) can keep up with rapidly changing wireless technology and the increased competition for spectrum.

In the late 70’s and early 80’s, Phase Shift Interferometry (PSI) was one of (if not the) hot topics in the Wyant lab. As my dissertation revolved around measuring the statistical properties of speckle patterns (using the newly invented CCD array), my work was somewhat out of the mainstream, and I developed a mild case of PSI envy. Two years after graduating, I finally had a chance to use PSI, although for a very different purpose. In the mid 1980s, there was a great deal of interest in being able to build heterodyne receivers for optical communications. An optical heterodyne receiver is exactly analogous to FM radio, where the input frequency modulated signal is beat against a cw semiconductor laser (the local oscillator) with a slightly different frequency. Heterodyne receivers can achieve shot noise limited performance by turning up the power of the local oscillator to the point where the shot noise becomes larger than the receiver thermal noise. Moreover, changing the frequency of the local oscillator enables decoding one of many channels in the signal). Among the many challenges facing the development of such systems was the problem that that semiconductor laser linewidths at the time were one or two orders of magnitude larger than the linewidth predicted by Schawlow-Townes for gas lasers, leading to unacceptable amounts of receiver phase noise. Moreover, the linewidth was not Lorentzian, but had structure - also contributing to excess phase noise with a resonance at the relaxation oscillation frequency of the laser. Two groups (Chuck Henry[1] at Bell Labs, and Vahala and Yariv at Caltech) were working to extend the Schawlow-Townes theory to account for the change in a semiconductor’s index of refraction due to spontaneous emission. At that time, measurements of linewidth were typically made in the frequency domain using a Fabry-Perot Interferometer. However, it is extremely difficult to deconvolve the effect of changes in the cavity index from the linewidth caused by simply adding spontaneous photons to the field in the frequency domain. In contrast, by measuring the coherence function (delayed time domain), these effects are multiplicative, and can be separated by simple curve fitting. Using Phase-Shifting Interferometry (PSI) it was possible to measure the coherence function of semiconductor lasers, enabling quantitative validation of the Henry/Vahala theory. Moreover, it was also possible separate out total impact of stochastic phase fluctuations, from the frequency modulation caused by direct current modulation of the signal laser, to show that the coherence properties of the signal laser do not change under modulation. I had the great fortune to work for Jim Wyant at the most pivotable point in my career. It led to the work described above, which in turn led to work on very high speed (>50 GHz) frequency modulation, receiver characterization, optical switching, and optical amplifiers. Perhaps more importantly (and something that took me many years following my graduate career to recognize), working for Jim provided a model for how to guide research groups, and how to mentor students. In this talk, I will discuss both the technical aspects of using PSI to measure the coherence properties of semiconductor lasers, as well as some of lessons learned (and a few of the humorous things that happened) during my apprenticeship in the Wyant lab.

A proof of concept system that enables real-time geospatial spectrum sharing between 5G/6G networks and Earth Exploration Satellite Services (EESS) has been developed. A simple algorithm that pauses network transmissions when there is potential interference from 5G/6G transmitters provides 99.6% network availability in the 24 GHz NR2 band while protecting all currently working EESS radiometers operating in the 23.8 GHz band. A more sophisticated algorithm that modifies transmission power levels and (if necessary) network traffic (similar to the methodologies used by Citizens Broadband Radio Service) can reduce interference so that there is no adverse impact on network availability. In addition to preventing interference, RGSS provides other significant benefits to both the wireless and the weather/climate communities, including improving network performance and coverage, the ability to support changes in network architectures, network elements, endpoints, and new or more sensitive radiometers, and a simple mechanism to test and police compliance with out-of-band emission requirements. RGSS is also compatible with existing spectrum management systems.

Out of band emissions from 5G transmissions in proposed mm-wave spectrum between 24 and 86 GHz (New Radio 2 or NR2 bands) has the potential to corrupt sensitive measurements of atmospheric water vapor and ice made in adjacent bands allocated to Earth Exploration Satellite Services (EESS). These measurements provide critical data for weather forecasting, and for understanding extreme weather events. A new mechanism - Real-Time Geographical Spectrum Sharing (RGSS) - that protects EESS measurements while adjacent NR2 spectrum is used for 5G communications, is proposed.

A new way to use an existing IMS feature - implicit registration - is discussed and demonstrated as a simple and practical mechanism to fully support multiple public identities (e.g., telephone numbers) on an IMS/VoLTE connected endpoint. Combining implicit registration with IMS functionality allowing multiple devices to share the same identity enables telephony services (voice/video/messaging/etc.) to support a many-to-many mapping between identities and endpoints. This breaks the traditional 1:1 mapping of identity to endpoint (phone number to device), and provides parity with conventional (IP connected) applications that support a many-to-many relationship between identities and endpoints or clients. Two new services that provide multiple telephone numbers simultaneously on native VoLTE smartphones and on other VoLTE clients (IMS desk-phones, voice activated telephony appliances, PC and OTT clients, etc.) have been prototyped and demonstrated on a commercial IMS mobile network: a Bring Your Own Device business communication service, and a consumer service that converges 5G residential endpoints with 4G mobile endpoints.