Is Our Model for Contention Resolution Wrong?

Randomized binary exponential backoff (BEB) is a popular algorithm for coordinating access to a shared channel. With an operational history exceeding four decades, BEB is currently an important component of several wireless standards. Despite this track record, prior theoretical results indicate that under bursty traffic (1) BEB yields poor makespan and (2) superior algorithms are possible. To date, the degree to which these findings manifest in practice has not been resolved. To address this issue, we examine one of the strongest cases against BEB: $n$ packets that simultaneously begin contending for the wireless channel. Using Network Simulator 3, we compare against more recent algorithms that are inspired by BEB, but whose makespan guarantees are superior. Surprisingly, we discover that these newer algorithms significantly underperform. Through further investigation, we identify as the culprit a flawed but common abstraction regarding the cost of collisions. Our experimental results are complemented by analytical arguments that the number of collisions -- and not solely makespan -- is an important metric to optimize. We believe that these findings have implications for the design of contention-resolution algorithms.Comment: Accepted to the 29th ACM Symposium on Parallelism in Algorithms and Architectures (SPAA 2017

ns-3 Implementation of the 3GPP MIMO Channel Model for Frequency Spectrum above 6 GHz

Communications at mmWave frequencies will be a key enabler of the next generation of cellular networks, due to the multi-Gbps rate that can be achieved. However, there are still several problems that must be solved before this technology can be widely adopted, primarily associated with the interplay between the variability of mmWave links and the complexity of mobile networks. An end-to-end network simulator represents a great tool to assess the performance of any proposed solution to meet the stringent 5G requirements. Given the criticality of channel propagation characteristics at higher frequencies, we present our implementation of the 3GPP channel model for the 6-100 GHz band for the ns-3 end-to-end 5G mmWave module, and detail its associated MIMO beamforming architecture

RoutesMobilityModel: easy realistic mobility simulation using external information services

Workshop on ns-3 (WNS '15). 13, May, 2015. Castelldefels, Spain.The current implementation of ns-3 provides only synthetic mobility models that disregard the map where the nodes are moving, however, the study of vehicular ad-hoc networks requires the usage of more realistic mobility models. The usage of mobility traces created by traffic simulators such as SUMO is feasible, however, these simulators possess a steep learning curve, which prevents their fruition for most researchers whose research focus and expertise are on the data communication layer. This paper presents a mobility model that generates realistic mobility traces that take into account the underlying maps, while maintaining the ease of usage that characterizes the synthetic mobility models. The module described herein is compared against SUMO and against the ns3::RandomWaypointMobilityModel of network simulator 3, to analyze the trade-off it implements in terms of realism and ease of usage

End-to-end networks vs named data network: A critical evaluation

Named data networking or information centric networking is the newest networking paradigm that gives foremost place to the contents in identification and dissemination.On the other hand, the end to end networking paradigm on which the Internet is currently built on places heavy emphasis on devices that make the architecture. The current Internet suffers from many shortcomings due to the misplaced emphasis. In order to overcome some of these deficiencies, researchers and developers have come up with patches and work around that have made the Internet more complex than it ought to be. Named data networking is a clean slate approach in building a network architecture overcoming all the current deficiencies and make it future safe. Several researchers have carried out comparative studies between named data networking and end to end networking. But these studies concentrate only on the features and capabilities of the networking paradigms. This is the first attempt at quantifying the performance the networking architectures experimentally. The authors in this paper present the results of the comparative study carried out experimentally in a simulated environment based on the final throughput. The results have been presented in a graphical form for easy visualization of results

A Detailed Analogy of Network Simulators � NS1, NS2, NS3 and NS4

Networking is a field of Computer Science where the researchers are dependent on simulators and simulation as the devices used in networking are very costly and complex. It is not easily possible to establish a computer network in real world easily, also direct installation of network devices and cables is not feasible. A simulator is a low cost mechanism which can be used to deploy a network and implement protocols and test the feasibility of the network. NS aka Network Simulator is one such low cost tool, which is available as open source software to network designers. With time simulators have evolved and now Network simulators can simulate wireless networks and advanced mobile networks. The Network Simulator evolution took place with the methodologies and coding technologies. Medium level language like C++ was used in NS1 and later in NS2 we started using easy modeling language like OTCL and C++. In NS3 we can now do coding with more powerful language Python, it also has support for OTCL and C++. High level and advanced language like P4 is the recent one to be used in NS4. The network simulators are now more powerful and fast, as compared to earlier generations of simulators. This paper talks about these advancements that have taken place in the history of Network Simulators and future scopes of NS

Modeling the processing delays of Internet of Things nodes in the ns3 network simulator

As arquiteturas de hardware dos dispositivos orientados para a Internet of Things (IoT), ou Internet das Coisas, pressupõem a existência de restrições energéticas. O hardware e o software destes dispositivos são, por isso, projetados por forma a minimizar o consumo energético e, frequentemente, a capacidade de processamento e memória destes dispositivos são bastante limitados. Como consequência os tempos de execução de processos ou funções de código podem ter valores médios e variações elevados. Estas restrições têm um impacto grande, e até agora pouco estudado, no desempenho das redes de comunicações de objetos. Torna-se por isso importante estudar e modelizar o desempenho das funções de comunicações destes dispositivos. Nesta tese pretende-se fazer este estudo e desenvolver um módulo de software para o simulador de redes ns-3 que simule os tempos de processamento das funções de comunicação de múltiplas combinações de plataforma hardware/sistemas operativos reais