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Many of us take for granted the ability to roam when using our cell phones, thinking it a simple (and mostly nontechnical) matter of establishing agreements between Mobile Network Operators (MNOs). In reality, support for roaming in today’s cellular architecture involves operating an entirely separate private network that runs in parallel to the mainstream Internet. This network, called the IP Exchange Network (IPX), carries roaming cellular traffic but also provides MNOs with a mechanism to form roaming partnerships, resolve billing, and establish the appropriate QoS settings. In our CPX work, we examine the initial reasons for forming the IPX and then argue that, while its establishment made sense when it was created, it is now time to integrate roaming into today’s Internet. To that end, we developed a design which we call the CPX (Con- solidated IPX) that leverages existing edge providers (such as CDNs) to provide the support for the functions that the IPX currently provides. In addition to eliminating the need for a separate IPX network, the CPX architecture provides lower latency for roaming users; in our simulation of a global CPX deployment, we demonstrate an average of 322% improvement in roaming connection latency. 

Existing LEO satellite network simulators widely approximate satellite coverage using a cone-based model that assumes uniform capacity distribution within a satellite’s field of view. However, modern systems employ phased-array antennas that impose discrete beam constraints, fundamentally altering coverage characteristics. In this paper, we investigate the extent to which ignoring beam-level constraints biases network-level performance estimates. We introduce a simplified beam-aware model that captures beam count, capacity, and limited spatial reuse, and compare it against traditional cone-based approximations across a range of user distributions. Our results show that cone models can significantly overestimate service coverage, particularly under sparse or highly clustered demand, due to beam-count and beam-capacity exhaustion effects. We further analyze how beam-hopping and -stacking mitigate these limitations and quantify their impact on predicted coverage differences, demonstrating reductions in predicted coverage difference of 40% and 65% respectively. We position these results of our model as the first step towards higher-fidelity simulation to show the importance of modeling beams and we sketch directions for future work that further improves fidelity. 

Direct-to-Device (D2D) communication in satellite networks represents a significant advance in telecommunications, enabling seamless connectivity without relying on terrestrial infrastructure. This survey aims to provide a detailed overview of D2D communication technologies, protocols, applications, and recent advances based on the current state of D2D. We categorize the literature on D2D into a new taxonomy. This taxonomy covers technological foundations, protocols and algorithms, use cases, challenges, and future trends. We emphasize the key challenges and pinpoint research gaps within each category, offering a well-structured domain overview. 

Digibox is a prototyping environment for IoT applications. It enables a novel scene-centric prototyping where developers can program an ensemble of simulated devices to capture not only their individual but also their coordinated behaviors, making it possible to test, debug, and evaluate the behaviors of an IoT application. Using Digibox, developers can download and reuse existing scenes, customize, and repurpose them towards developing new applications; or replicate others' experiment results from scientific research. Digibox's Kubernetes-based runtime further allows developers to easily scale the prototyping environment from a single laptop to a cluster running simulated devices and scenes at a scale appropriate to the application.