We consider indoor mobile access, a vital use case for current and future mobile networks. For this key use case, we outline a vision that combines a neutral-host-based shared small-cell infrastructure with a common pool of spectrum for dynamic sharing as a way forward to proliferate indoor small-cell deployments and open up the mobile operator ecosystem. Toward this vision, we focus on the challenges pertaining to managing access to shared spectrum [e.g., 3.5-GHz U.S. Citizen Broadband Radio Service (CBRS) spectrum]. We propose Iris, a practical shared spectrum access architecture for indoor neutral-host small-cells. At the core of Iris is a deep reinforcement learning-based dynamic pricing mechanism that efficiently mediates access to shared spectrum for diverse operators in a way that provides incentives for operators and the neutral-host alike. We then present the Iris system architecture that embeds this dynamic pricing mechanism alongside cloud-RAN and RAN slicing design principles in a practical neutral-host design tailored for the indoor small-cell environment. Using a prototype implementation of the Iris system, we present the extensive experimental evaluation results that not only offer insight into the Iris dynamic pricing process and its superiority over alternative approaches but also demonstrate its deployment feasibility.

The availability of multiple collocated wireless networks using heterogeneous technologies and the multiaccess support of contemporary mobile devices have allowed wireless connectivity optimization, enabled through vertical handover (VHO) operations. However, this comes at high energy consumption on the mobile device due to the inherently expensive nature of some of the involved operations. This work proposes exploiting short‐range cooperation among collocated mobile devices to improve the energy efficiency of vertical handover operations. The proactive exchange of handover‐related information through low‐energy short‐range communication technologies, like Bluetooth, can help in eliminating expensive signaling steps when the need for a VHO arises. A model is developed for capturing the mean energy expenditure of such an optimized VHO scheme in terms of relevant factors by means of closed‐form expressions. The descriptive power of the model is demonstrated by investigating various typical usage scenarios and is validated through simulations. It is shown that the proposed scheme has superior performance in several realistic usage scenarios considering important relevant factors, including network availability, the local density of mobile devices, and the range of the cooperation technology. Finally, the paper explores cost/benefit trade‐offs associated with the short‐range cooperation protocol. It is demonstrated that the protocol may be parametrized so that the trade‐off becomes nearly optimized and the cost is maintained affordable for a wide range of operational scenarios.

Emerging 5G mobile networks are envisioned to become multi-service environments, enabling the dynamic deployment of services with a diverse set of performance requirements, accommodating the needs of mobile network operators, verticals and over-the-top (OTT) service providers. Virtualizing the mobile network in a flexible way is of paramount importance for a cost-effective realization of this vision. While virtualization has been extensively studied in the case of the mobile core, virtualizing the radio access network (RAN) is still at its infancy. In this paper, we present Orion, a novel RAN slicing system that enables the dynamic on-the-fly virtualization of base stations, the flexible customization of slices to meet their respective service needs and which can be used in an end-to-end network slicing setting. Orion guarantees the functional and performance isolation of slices, while allowing for the efficient use of RAN resources among them. We present a concrete prototype implementation of Orion for LTE, with experimental results, considering alternative RAN slicing approaches, indicating its efficiency and highlighting its isolation capabilities. We also present an extension to Orion for accommodating the needs of OTT providers.

Emerging 5G mobile networks are envisioned to support the dynamic deployment of services with diverse performance requirements, accommodating the needs of mobile network operators and verticals. Virtualizing the mobile network components in a flexible and cost-effective way is therefore of paramount importance. In this work, we highlight the capabilities of Orion, a novel RAN slicing architecture that enables the dynamic virtualization of base stations and flexible customization of slices to meet their respective service needs. Our demonstration of Orion's capabilities is based on a prototype implementation employing a modified version of the OpenAirInterface software LTE platform. Using this prototype, we demonstrate the functional and performance isolation, and the efficient sharing of radio hardware and spectrum that can be achieved among Orion RAN slices. Moreover, we show how Orion can be used in an end-to-end network slicing setting and demonstrate the effects of the slices' configuration and placement of virtual functions in the overall quality of the deployed services.

Although SDN is considered as one of the key technologies behind the impending 5G evolution of mobile networks, the opportunity of reaping its benefits is largely still untapped on the Radio Access Network (RAN) side due to the lack of a software-defined RAN (SD-RAN) platform. In this work we demonstrate the capabilities of FlexRAN, an open-source SD-RAN platform developed to fill this void. FlexRAN separates the RAN control and data planes with a custom-tailored southbound API. Besides it features a hierarchical control plane architecture that enables programmability, flexible and dynamic control function placement (allowing different degrees of coordination within and among base stations) and real-time control. Virtualized control functions and control delegation are two key features in FlexRAN that makes these capabilities possible. This demo illustrates the capabilities and the performance of FlexRAN based on a prototype implementation, while its applicability is highlighted through a Mobile Edge Computing use case, where it acts as an enabler of a video bitrate adaptation application based on the radio conditions at the network edge.

Although the radio access network (RAN) part of mobile networks offers a significant opportunity for benefiting from the use of SDN ideas, this opportunity is largely untapped due to the lack of a software-defined RAN (SD-RAN) platform. We fill this void with FlexRAN, a flexible and programmable SD-RAN platform that separates the RAN control and data planes through a new, custom-tailored southbound API. Aided by virtualized control functions and control delegation features, FlexRAN provides a flexible control plane designed with support for real-time RAN control applications, flexibility to realize various degrees of coordination among RAN infrastructure entities, and programmability to adapt control over time and easier evolution to the future following SDN/NFV principles. We implement FlexRAN as an extension to a modified version of the OpenAirInterface LTE platform, with evaluation results indicating the feasibility of using FlexRAN under the stringent time constraints posed by the RAN. To demonstrate the effectiveness of FlexRAN as an SD-RAN platform and highlight its applicability for a diverse set of use cases, we present three network services deployed over FlexRAN focusing on interference management, mobile edge computing and RAN sharing.

The availability of multiple collocated wireless networks using heterogeneous technologies and the multi-access support of contemporary mobile devices have allowed wireless connectivity optimization, enabled through vertical handover (VHO) operations. However, this comes at a high energy consumption on the mobile device, due to the inherently expensive nature of some of the involved operations. This work proposes exploiting short-range cooperation among collocated mobile devices to improve the energy efficiency of vertical handover operations. The proactive exchange of handover-related information through low-energy short-range communication technologies, like Bluetooth, can help in eliminating expensive signaling steps when the need for a VHO arises. A model is developed for capturing the mean energy expenditure of such an optimized VHO scheme in terms of relevant factors by means of closed-form expressions. This model is validated through simulations and results demonstrate that the proposed scheme has superior performance in several realistic usage scenarios considering important relevant factors, including network availability, the local density of mobile devices and the range of the cooperation technology.

The paper considers a two-way relay network with network coding capabilities and an additional mechanism based on timeouts, used to ensure stability and bound the mean delay experienced by packets through the relay. Modeling of this system leads to simple closed form expressions that illustrate clearly the impact of the timeout parameters on the performance and efficiency metrics associated with the network coding operation. These results are subsequently employed for optimally tuning the timeout parameters, towards achieving the greatest network coding efficiency (and the corresponding throughput and energy efficiency improvement) that is possible for the given traffic profile, subject to a delay-related QoS requirement. Again, simple closed form results are obtained that support intuition and provide additional insight on the involved tradeoffs.

The paper considers a two-tier wireless network structure, where the edge of a Macrocell is underlaid by a number of uniformly deployed femtocells, and studies the impact of interference to flow-level performance. A careful examination of the factors associated with interference and the use of appropriate modeling techniques from the theory of Processor Sharing systems give rise to a simple methodology for determining the values of important flow-level performance metrics. Two forms of interference are taken into account: cross-tier interference from the Macrocell to femtocells and co-tier interference between neighboring femtocells. The model developed by the paper is capable of capturing the combined impact of both these types. Numerical results investigate various tradeoffs between system parameters and indicate, among other findings, that in scenarios where the potential for cross-tier interference is more pronounced, increasing the number of femtocells above some threshold leads to performance degradation. The proposed methodology allows for a full quantification of such effects.

As networks and applications running on them become more complex, there is a need for an efficient framework supporting experimental performance evaluation based on real measurements. Towards this end, this paper presents: a) an advanced architecture for a traffic generation tool capable of producing complex traffic profiles, b) the architecture of a traffic analysis tool, and c) methods that allow for efficient monitoring and measurements of delay and loss-oriented metrics in packet networks. The effectiveness of these tools and the applicability of the measurement methodology are illustrated through experiments that evaluate the performance of vertical handovers between GPRS and WLAN networks.

Abstract This work addresses aspects relevant to the optimal joint exploitation of heterogeneous wireless networks in an ‘all‐IP’ integrated infrastructure, frequently called ‘Beyond 3G Systems’ (B3G) or composite radio networks. After briefly reviewing general architectural aspects pertaining to such systems, the paper focuses to the management functionality possessed by B3G systems and highlights the benefits that stem from sharing intelligence among the hybrid network (through a network management system) and the multimodal wireless terminals. In particular, the paper discusses an appropriate signaling protocol for the exchange of information between management modules at the network and the wireless terminal, investigates associated performance aspects and correlates the relevant findings with measurement results obtained from experiments over a prototype B3G network testbed. Copyright © 2005 John Wiley & Sons, Ltd.

This paper proves the existence of and explicitly determines effective bandwidths for a class of non Markovian fluid source models, featuring multiple data-transmission rates and arbitrary distributions for the times these rates are sustained. The investigated models cover considerably more traffic profiles than the usual Markovian counterparts and have reduced state-space requirements. The effective bandwidth, as a function of the asymptotic loss probability decay rate, is implicitly derivable by the requirement that the spectral radius of an appropriate nonnegative matrix be equal to unity. The effective bandwidth function is shown to be, either strictly increasing, or constant and equal to the mean rate. Sources of the second kind, which are characterized, generalize the notion of 'CBR' traffic. Furthermore, a study for the limiting effective bandwidth, towards a loss-less environment, is undertaken; it is shown that the limiting value may, under some fully identified restrictions on the source behavior, be less than the source's peak rate. Under those restrictions, a source may have reduced bandwidth requirements, even if it features a large peak rate.