Vodafone has shown off a palm-size 5G base station, powered by a Raspberry Pi 4 single-board computer with Lime Microsystems software-defined radio technology inside – in an effort to make private cellular networking and edge computing more accessible.

“We looked at what Raspberry Pi did for computing, in terms of making it more accessible to people of all ages, and we wanted to do the same with 5G,” says Vodafone’s director of network architecture, Santiago Tenorio. “Whilst this is just a prototype, it has the potential to bring new cloud, AI [Artificial Intelligence], and big data technologies within reach of many of the small businesses we support across Europe.”

Eagle-eyed readers who have already watched Vodafone’s announcement video may have noticed that the compact self-contained 5G private cellular network base station system uses, in addition to a Raspberry Pi 4 single-board computer system, a LimeSDR XTRX software-defined radio system – and interested parties are advised to keep their ears to the ground for more news on this front in the near future.

In the meantime, Vodafone has confirmed it plans to continue working with Lime Micro on the effort, which it has made to Open Radio Access Network (Open RAN) standards for cross-network compatibility. “The next step is to take ideas like this to a place where they can be developed and eventually produced,” Santiago explains. “Our door is open to interested vendors.”

More details are available in Vodafone’s announcement video on YouTube and on the Vodafone website. The prototype will also be demonstrated live at Mobile World Congress in Barcelona, starting Monday the 27th of February.

Electrical engineer and ARK electronics owner Alex Kimaj is working on a Global Navigation Satellite System (GNSS) project, and has found the LimeSDR Mini a ideal companion – delivering simulated GPS signals for ease of testing.

“Best use case I’ve found for the LimeSDR Mini,” Alex writes of his project. “Using the GitHub project osqzss/gps-sdr-sim makes it trivial to simulate GPS for manufacturing testing of my ARK RTK GPS and ARK RTK Base. Using a 1dBm signal with 50dB of attenuation!”

Developed by Takuji Ebinuma, GPS-SDR-SIM allows a computer to generate Global Positioning System (GPS)-compliant baseband signal data streams and feed them to a range of software defined radio devices, including the LimeSDR family. Unlike real signals, the simulated data can be modified to describe a trajectory – allowing Alex and others working on GPS hardware to test out their creations in the lab, without having to take them out on the road.

GPS-SDR-SIM is available on GitHub under the permissive MIT licence, while Alex’s project progress can be followed on Twitter.

Radio-frequency and hardware security firm PentHertz has taken on the task of maintaining and updating the OpenBTS-UMTS project, releasing a version compatible with the LimeSDR family of software-defined radios: OpenBTS-UMTS Reloaded 2023.

“Still want to work in 3G/UMTS but your favourite project got obsolete,” the company asked, rhetorically, in introduction of its efforts. “Find our OpenBTS-UMTS backup (until it gets merged) for 2023 working [with] Ubuntu 22.04 and C++17. [And] OpenBTS-UMTS 1.1 now supports LimeSDR (experimental).”

OpenBTS-UMTS was originally developed by Range Networks as tool to allow Linux systems with compatible software-defined radio devices to host a private 3G UMTS network. Unfortunately, the company stopped all development three years ago – but the source code being published under the AGPL 3.0 licence allowed others, including PentHertz, to fork it and continue development themselves.

In the OpenBTS-UMTS Reloaded 2023 fork, the software has been updated for Ubuntu 22.04 and now includes a Docker image – “so,” PentHertz explains, “you will not [have] to follow the installations instructions and [can] run it straightforward even if system dependencies are broken in the future (in theory!)” The new release also adds support for LimeSDR hardware, though this is marked as “experimental.”

More information is available on the OpenBTS-UMTS Reloaded 2023 GitHub repository, along with full source code and instructions on using the Docker image.

The Osmocom project has announced the release of new Cellular Network Infrastructure (CNI) software, representing around seven months work.

“The Osmocom project has released new version 202302 of the CNI (Cellular Network Infrastructure) software, including OsmoTRX, OsmoBTS, OsmoPCU, OsmoBSC, OsmoMGW, OsmoMSC, OsmoHLR, OsmoSGSN, OsmoGGSN, OsmoSTP, OsmoSIPConnector, and others,” the organisation announced earlier this month. “Those new tagged/released versions contain 7 months of work since the previous versions released during end of June 2022.”

Among the changes and bug-fixes in the new releases are support for Ericsson RBS GPRS TRAU synchronisation frames in libosmotrau, “general fixes and improvements in code robustness,” the creation of an initial user manual and API documentation for the osmo-e1d project, “lots and lots” of improvements in osmux under the OsmoMGW project, osmux support in OsmoBTS, CPU optimisations to improve performance in OsmoBSC, and a fix for segmentation faults in OsmoHNBGW during an MGCP timeout condition.

Full details on the new software releases are available on the Osmocom website, along with links to their source code; binary builds are also available for a range of Debian and Ubuntu Linux distributions.

Researchers at the University of Washington have developed a radio transmitter with a difference: it uses “almost no power” to send messages, using an approach similar to Radio Frequency Identification (RFID) tags but without the need for there to be a pre-existing radio-frequency signal.

“[Our] new ultra-low-power method of communication at first glance seems to violate the laws of physics,” the researchers, writing for The Conversation, explain. “It is possible to wirelessly transmit information simply by opening and closing a switch that connects a resistor to an antenna. No need to send power to the antenna.

“Apart from the energy needed to flip the switch, no other energy is needed to transmit the information. In our case, the switch is a transistor, an electrically controlled switch with no moving parts that consumes a minuscule amount of power.”

The technique, which the team admits only appears to violate the laws of physics, is based on modulated Johnson noise: while every component in the transmitter is physically held at room temperature, it’s the difference in noise temperature between them that makes the transmission possible. In testing, a prototype proved capable of data rates of 26 bits per second over distances of up to 7.3 metres.

The team’s paper is available under closed-access terms in the Proceedings of the National Academy of Sciences (PNAS); a preprint is available under open-access terms on Cornell’s arXiv server.

A team of scientists from the Penn State College of Engineering have come up with a system for reconfigurable antennas, based on the same mechanics as a binder clip or a bow and arrow – in the hopes of dramatically reducing their power requirements while boosting service lifetime.

“Compliant mechanisms are engineering designs that incorporate elements of the materials themselves to create motion when force is applied, instead of traditional rigid body mechanisms that require hinges for motion,” explains corresponding author Galestan Mackertich-Sengerdy. “Compliant mechanism-enabled objects are engineered to bend repeatedly in a certain direction and to withstand harsh environments.”

That idea has now been applied to a reconfigurable antenna, creating an iris-shaped patch antenna which can physically shift its shape in order to tune into different frequencies – and the palm-size 3D-pritned prototype scales up or down to any size, the team claims, including being applicable at the integrated circuit level.

“The paper introduces compliant mechanisms as a new design paradigm for the entire electromagnetics community, and we anticipate it growing,” claims co-author Douglas Werner, the John L. and Genevieve H. McCain Chair Professor at the School of Electrical Engineering and Computer Science. “It could be the branching off point for an entirely new field of designs with exciting applications we haven’t dreamed of yet.”

The team’s work has been published under open-access terms in the journal Nature Communications.

Neil Smith, of the Machining and Microwaves YouTube channel, has teamed up with Rogers Corporation and Fortify to demonstrate “the future of antennas” – using a smart 3D-printable material to build antennas of almost any shape imaginable.

“Ever since 3D printers hit the mainstream, I dreamed of being able to print high-performance microwave antenna components,” Neil explains of his work with Rogers, which focuses on the company’s Radix dielectric UV resin. “The deal [with Rogers] was that if I created a design for a gradient index antenna lens they’d get it processed and print some examples for me.”

The company did just that, inviting Neil to their facilities to pick up the resulting lens in person. Designed on computer by Neil, the RF lens is printed using a resin-based 3D printer and the Radix resin – which is a ceramic-filled polymer designed for specifically for complex RF dielectric components, offering what its creators claim to be low-loss characteristics and low moisture absorption.

“I’m not an RF engineer, nor a designer. I’ve never worked professionally in those fields, but I’ve been experimenting with microwave engineering for almost fifty years,” Neil says. “If I can create a successful component using their services, then just imagine what a professional RF design engineer could achieve.”

The full video is available on the Machining and Microwaves YouTube channel now.

The United States Air Force (USAF), responding to a number of payload-carrying balloons at least one of which is said to have been sent and operated by the Chinese government, may have been responsible for a little collateral damage – seemingly shooting an experimental amateur radio balloon to the ground.

The Pentagon announced that a balloon seen in the skies of the US carried a multi-tonne payload was a device of the Chinese government sent to surveil US military facilities. After allowing it to leave populated areas, the US Air Force sent an F-22 to shoot it down – and apparently did the same for a number of other unidentified floating objects, seemingly including one launched with a far more benign purpose in mind.

According to detective work carried out by RTL-SDR, a USAF sortie over Canada’s Yukon territory may have downed a pico-balloon hosting an amateur radio payload – presumably after mistaking it for another spy balloon. “There is speculation that at least one of the objects shot down over Canada, Yukon by a US Air Force jet may have been amateur radio pico balloon K9YO-15,” the site explains, “which was launched from Illinois on October 10 2022. It was on it’s seventh circumnavigation of the globe after being aloft for 123 days.”

The USAF has not commented on the speculation, but the RTL-SDR blog has a range of supporting evidence suggesting that it has, indeed, been the victim of a fly-by.