Dense passive radio frequency identification (RFID) systems are particularly susceptible to reader collision problems, categorized by reader-to-tag and reader-to-reader collisions. Both may degrade the system performance decreasing the number of identified tags per time unit. Although many proposals have been suggested to avoid or handle these collisions, most of them are not compatible with current standards and regulations, require extra hardware and do not make an efficient use of the network resources. This paper proposes the Geometric Distribution Reader Anti-collision (GDRA), a new centralized scheduler that exploits the Sift geometric probability distribution function to minimize reader collision problems. GDRA provides higher throughput than the state-of-the-art proposals for dense reader environments and, unlike the majority of previous works, GDRA is compliant with the EPCglobal standard and ETSI EN 302 208 regulation, and can be implemented in real RFID systems without extra hardware.Note to Practitioners -UHF RFID systems with multiple readers are commonly installed in many scenarios, where readers are placed in strategic places for checking specific areas. In these scenarios, the reader interferences occur and they can degrade the performance of our system. An efficient anticollision scheduler is necessary for avoiding and minimizing these interferences, and the current standards and regulations do not propose any efficient solution. In this work, a new scheduler is proposed to get the best performance of a typical UHF RFID system with multiple readers. Our proposal is compatible with the global standard and the current European regulations and is designed to be implemented in any commercial UHF reader in the market without extra hardware cost.Index Terms-EPCglobal, ETSI EN 302 208, reader collision problems, radio frequency identification (RFID, sift geometric distribution function.

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Transport ecosystems that combine Software Defined Networking (SDN) and Network Function Virtualization (NFV) are characterized by an unprecedented network control and resource dynamicity. Manual optimization is unmanageable. In this context, open systems that manage and orchestrate SDN/NFV-enabled networks offer programming frameworks that abstract the low-level particularities in the data-plane forwarding devices and in the hardware appliances that provide the IT resources. Although these open systems present notable complexity, their programming abstractions promote a client layer where third-party applications can provide different functionalities thus enabling Optimization-as-a-Service (OaaS) business opportunities. In this paper, we cover open-source optimization software initiatives for offline planning and online provisioning and orchestration of SDN/NFV networks. With this goal in mind, we first focus on open software (and framework) initiatives through a set of realistic use cases that require optimization in multi-layer optical transport scenarios and ecosystems that combine transport with IT resources. The importance of a joint optimization of both network and IT domains is emphasized, a new paradigm triggered by SDN/NFV technologies. We discuss the theoretical limits to algorithm performances, and review available open-source frameworks for problem modelling that enable the interaction with solvers. Finally we focus on the Net2Plan open-source network planning tool, a Java-based software that suitably embraces the multiple features required in the optimization of joint transport network and IT resource SDN/NFV ecosystems. Recent works based on Net2Plan are reviewed to illustrate its suitability for rapid algorithm prototyping, and for interaction with SDN/NFV-enabled networks.

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