Browsing by Author "Freitas, Filipe"
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- Evaluating 5G coverage in 3D scenarios under configurable antenna beam patternsPublication . Jesus, Francisco; Sousa, Marco; Freitas, Filipe; Vieira, Pedro; Rodrigues, A.; Queluz, Maria PaulaActive Antenna Systems (AASs) play a key role in the performance of 5 th Generation (5G) networks as they enable the use of Massive Multiple-Input Multiple-Output (mMIMO) and directional beamforming. Besides, AASs can be configured with distinct broadcast beams configurations. In this work, the coverage provided by the broadcast beam configurations of a real AAS is evaluated. A 3-Dimensional (3D) configurable synthetic scenario was proposed to evaluate the resulting 5G coverage from all the possible antenna beam configurations. This analysis revealed that beam configurations with several horizontal beams and one vertical are recommended for urban macro deployments. Moreover, it was demonstrated that the percentage of covered area in a real scenario is approximated by an equivalent synthetic scenario with a Pearson correlation of 0.98. The synthetic scenario has the advantage of not requiring 3D building databases. Finally, an interference analysis in multi-site real scenarios was conducted, where it was verified that some antenna configurations introduce excessive interference for the level of coverage provided.
- Fine-grained consistency upgrades for online servicesPublication . Freitas, Filipe; Leitão, João; Preguica, Nuno; Rodrigues, RodrigoOnline services such as Facebook or Twitter have public APIs to enable an easy integration of these services with third party applications. However, the developers who design these applications have no information about the consistency provided by these services, which exacerbates the complexity of reasoning about the semantics of the applications they are developing. In this paper, we show that is possible to deploy a transparent middleware between the application and the service, which enables a fine-grained control over the session guarantees that comprise the consistency semantics provided by these APIs, without having to gain access to the implementation of the underlying services. We evaluated our middleware using the Facebook public API and the Redis datastore, and our results show that we are able to provide fine-grained control of the consistency semantics incurring in a small local storage and modest latency overhead.
- QuickFaaS: providing portability and interoperability between FaaS PlatformsPublication . Rodrigues, Pedro; Freitas, Filipe; Simão, JoséServerless computing hides infrastructure management from developers and runs code on-demand automatically scaled and billed during the code's execution time. One of the most popular serverless backend services is called Function-as-a-Service (FaaS), in which developers are often confronted with cloud-specific requirements. Function signature requirements, and the usage of custom libraries that are unique to cloud providers, were identified as the two main reasons for portability issues in FaaS applications, leading to various vendor lock-in problems. In this work, we define three cloud-agnostic models that compose FaaS platforms. Based on these models, we developed QuickFaaS, a multi-cloud interoperability desktop tool targeting cloud-agnostic functions and FaaS deployments. The proposed cloud-agnostic approach enables developers to reuse their serverless functions in different cloud providers with no need to change code or install extra software. We also provide an evaluation that validates the proposed solution by measuring the impact of a cloud-agnostic approach on the function's performance, when compared to a cloud-non-agnostic one. The study shows that a cloud-agnostic approach does not significantly impact the function's performance.