Disaggregated and open radio access network (O-RAN) architectures offer benefits such as enhanced interoperability, improved coordination between nodes, and cost reduction. However, they also introduce new security challenges related to open interfaces and distributed control mechanisms. This work focuses on analysing vulnerabilities of SCTP, one most widespread solutions in these interfaces, which facilitates communication with RAN Intelligent Controllers (RIC). The analysis addresses two specific attacks: denial of service and identity spoofing. Both have been implemented and experimentally validated on the FlexRIC platform within the O-RAN architecture framework, going beyond the predominantly theoretical approaches found in the literature. Based on these experiments, we critically evaluate various security solutions proposed for SCTP. While some of these solutions offer partial mitigation capabilities, they also present structural, operational, and compatibility limitations that affect their overall effectiveness. These findings underscore the need to adopt more efficient transport protocols, capable of natively integrating adequate security features for O-RAN environments.

Open Radio Access Network (O-RAN) fosters a new networking paradigm that supports flexible and open architectures, while enabling the functional disaggregation of traditional, monolithic, base stations. Specifically, the Lower-Layer Split (LLS) option 7.2x divides the PHY layer into Low-PHY at Open -Radio Unit (O-RU) and High-PHY at Open -Distributed Unit (O-DU), leveraging the so-called open fronthaul network, which imposes stringent latency requirements. In this work, we introduce and thoroughly examine the time window relationships that define the latency budget allocated to the open fronthaul network. Additionally, we propose a novel methodology to analyze the delay experienced by a realistic traffic pattern over a spine-leaf topology, accounting for various O-DU locations and site pools. To address the increased traffic load introduced by the fronthaul, we present a theoretical model to characterize the average delay across different priority levels when open fronthaul traffic coexists with flows from other Radio Access Technologies (RATs). This model is then validated and broadened through ns-3 simulations. Our findings show the applicability of the proposed methodology, which could be exploited by network operators in the planning phase, evincing its suitability to obtain benchmark delay values, offering a reliable tool for performance evaluation in open fronthaul networks.

5G and beyond technologies are designed to convey multiple QoS requirements coming from highly heterogeneous services. In this regard, 5G extends the QoS definition of previous technologies. In order to fulfill the requirements of new services, it is necessary to develop resource management solutions that effectively and efficiently translate them to usage of resources. Therefore, MAC schedulers are to be designed to accommodate the demands of emerging applications with stringent QoS requirements, such as XR. In this work, we introduce a Lyapunov-based MAC scheduler designed to appropriately tackle coexisting heterogeneous QoS flows. The proposed approach allows the implementation of policies that explicitly consider the QoS requirements, as well as an efficient use of allocated resources. The results obtained through extensive experiments over the ns-3 5G-LENA simulator demonstrate that our scheduler guarantees the required time-average bit rate for every QoS flow at every time window, while ensuring the stability of traffic queues for all users.

The Open-Fronthaul (O-FH) is a Time Sensitive Network (TSN) segment within the Open-RAN (O-RAN) architecture, where the legacy base station is disaggregated following the 7.2x functional split. One of the strategic objectives sought by network operators is to foster the centralization of the Open - Distributed Unit (O-DU), to serve multiple remote sites. Hence, ensuring an accurately modeling of the fronthaul performance becomes critical, due to its stringent timing requirements. In this work, we propose a novel modeling methodology, based on Generalized Jackson Networks (GJN), to derive key performance metrics such as waiting time and utilization. Additionally, we apply Kingman’s approximation to evaluate delay percentiles under high traffic load conditions. This analytical method allows for fast and scalable performance evaluation, avoiding the need for extensive packet-level simulations, which become computationally prohibitive as traffic load steadily increases. Our results evince that under sensible operating situations, the proposed approach yields rather precise results, providing an upper performance bound.

XR applications place increasing pressure on mobile networks to meet their stringent Quality of Service (QoS) demands. In particular, XR services require high throughput and low latency, with traffic patterns that differ greatly from traditional applications. To address these challenges, we propose a novel Medium Access Control (MAC) scheduling solution that takes into account the segmentation of XR media units into Packet Data Units (PDUs), referred to as PDU sets in 5G-Advanced networks. These PDU sets correspond to the core traffic unit for XR services and must be delivered according to their specific QoS requirements, which are dynamically established in real-time by the XR application. The proposed scheduling solution leverages Lyapunov drift-plus-penalty optimization to jointly optimize resource allocation and stabilize traffic queues while ensuring the timely delivery of PDU sets. Our solution is implemented within the ns-3 5G-LENA framework, and the paper features a comparative analysis through extensive simulations, evaluating the performance of our proposal against existing MAC scheduling algorithms. Results evince that the proposed scheduler enhances resource utilization, ensures QoS compliance, and improves network performance.

During the last years we have witnessed a growing trend towards the deployment of disaggregated Radio Access Network (RAN) networks. In this context, the Open-RAN (ORAN) architecture is one of the most relevant approaches for 5G/6G networks, and it is believed to be a key element of forthcoming deployments. The performance of the so called Open - Fronthaul ($\mathrm{O}-\text{FH}$) segment is of the utmost importance to ensure an appropriate overall system performance. In this sense, the overall delay of the communication between nodes within the O-RAN fronthaul needs to be kept at very low values, to fulfill the requirements of the corresponding technologies. In this paper we propose exploiting queuing theory to model the O-FH performance, including a realistic traffic characterization. In particular, we present a theoretical framework based on Open Jackson Networks to model the one-way end-to-end delay, and we compare it with a that obtained by a realistic simulation setup. The results show that the theoretical model provides a reasonably accurate behavior under certain conditions, setting in all cases a tight upper bound for the end-to-end delay, which we identify as a key performance indicator.

Disaggregated and open radio access network architectures offer benefits such as enhanced interoperability, improved coordination between nodes, and cost reduction; however, they also introduce new security challenges related to open interfaces and distributed control mechanisms. This work focuses on analyzing vulnerabilities in one of the protocols used in these interfaces—SCTP—which facilitates communication with Radio Intelligent Controllers (RIC). The analysis centers on two specific attacks: denial of service and identity spoofing. Both attacks have been implemented and experimentally validated on the FlexRIC platform within the O-RAN architecture framework, contrasting with the predominantly theoretical approaches found in the literature. Based on these experiments, a critical evaluation of various security solutions proposed for SCTP is conducted. While some of these solutions offer partial mitigation capabilities, they present structural, operational, and compatibility limitations that affect their overall effectiveness. These findings underscore the need to adopt more modern and efficient transport protocols capable of natively integrating adequate security functions for O-RAN environments.

In 5th Generation (5G) virtualized Radio Access Networks (vRAN), where the protocol stack is split across three different elements (Radio Unit (RU), Distributed Unit (DU), and Centralized Unit (CU)), and data is transmitted across the transport network (fronthaul (FH) and midhaul) between these units, the capacity of the fronthaul pipe can become a limiting factor for packet transmission. To address this challenge, state-of-the-art approaches have introduced several fronthaul control methods, designed to limit the sending rate, to ensure that it does not exceed the available capacity. However, it is important to avoid potential conflicts between the decisions of such fronthaul control methods and those of the Medium Access Control (MAC) scheduling schemes, as they might impact one another. In this context, we provide a thorough analysis of the trade-off between the fronthaul and the air interface limitations and we propose a new FH Control method to limit packet transmissions without altering the decisions made by the MAC scheduler. An extensive simulation campaign in a 3GPP defined scenario with Virtual Reality (VR) and Cloud Gaming (CG) services is conducted, for air-limited and air/fronthaul capacity-limited conditions. The results demonstrate that the proposed fronthaul control method efficiently coordinates the MAC scheduler decisions with the constraints imposed by the fronthaul capacity.

Robust and efficient communication frameworks have become essential for the advancement of manufacturing and industrial processes in the era of Industry 4.0. This paper presents a comprehensive performance analysis of Eclipse Zenoh, a promising solution for the Industrial Internet of Things (IIoT). The analysis is conducted using a real testbed built with Raspberry Pi devices, comparing Eclipse Zenoh’s performance against the widely used Message Queuing Telemetry Transport (MQTT) protocol. The study assesses Eclipse Zenoh’s capabilities in terms of latency, as well as its reliability and congestion control mechanisms over various network topologies, using both Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). The results indicate that Eclipse Zenoh offers significant advantages in specific scenarios, making it a compelling choice for IIoT applications. Additionally, this paper contributes to a deeper understanding of Eclipse Zenoh’s underlying principles and its communication capabilities, positioning it as a versatile and efficient solution for modern industrial environments. • Study of Eclipse Zenoh’s underlying principles. • Latency comparative analysis of Eclipse Zenoh and MQTT. • Evaluation of Eclipse Zenoh’s reliability and congestion control mechanisms over TCP and UDP.

We jointly consider network slicing and functional split for 5G/6G Radio Access Network (RAN). Exploiting virtu-alization techniques, virtual Radio Access Network (vRAN) is an architectural shift that moves some of the functions that were traditionally performed by the base station to centralized nodes, deployed at cloud-based resources. By appropriately selecting the location of these nodes, they can effectively coordinate a number of radio access elements, thus bringing potential gains, for instance, in terms of interference reduction. One pivotal decision for vRAN operation is how to split the functions between these central elements and the corresponding distributed units. Deploying more functions at the cloud could potentially bring more benefits, due to the tighter cooperation between access elements. On the other hand, higher centralization poses more requirements, in terms of computational resources at the nodes where these functions are deployed. Along with the virtualization, RAN slicing enables the deployment of independent service verticals over the same physical infrastructure, and this could greatly benefit from the coordination achieved by exploiting the vRAN features. In this paper we propose a vRAN model to jointly consider functional split and RAN slicing, and we establish the corresponding configuration, exploiting Lyapunov's Theory to tackle the underlying problem. The results show that, in highly heterogeneous networks, the dynamic configuration of the functional split can reach the same performance of fully centralized networks, with substantially fewer computation resources.

The advent of wireless technologies has led to the development of novel services for end-users, with stringent needs and requirements. High availability, very high throughput, low latency, and reliability are all of them crucial performance parameters. To address these demands, emerging technologies, such as non-terrestrial networks or millimeter wave (mmWave), are being included in 5G and Beyond 5G (B5G) specifications. mmWave enables massive data transmissions, at the expense of a more hostile propagation, typical for high frequency bands. Consequently, the inherent instability of the physical channel significantly affects the upper layers of the protocol stack, resulting in congestion and data losses, which might strongly hinder the overall communication performance. These challenges can be addressed not only at the link layer, but at any affected layer. QUIC is a new transport protocol designed to reduce communications latency in many ways. Among other features, it enables the use of multiple streams to effectively manage data flows sent through its underlying UDP socket. This paper introduces an implementation of priority-based stream schedulers along with the design of a flexible interface. Exploiting the proposed approach, applications are able to set the required scheduling scheme, as well as the stream priorities. The feasibility of the proposed approach is validated through an extensive experiment campaign, which combines Docker containers, the ns-3 simulator and the Mahimahi framework, which is exploited to introduce realistic mmWave channel traces. The results evince that an appropriate stream scheduler can indeed yield lower delays for time-sensitive applications by up to 36% under unreliable conditions.

We analyze the performance of QUIC over Non-Terrestrial-Networks (NTN). The presence of this transport protocol has strongly increased since it was originally proposed, but its behavior over wireless networks is still an open question. We focus on NTN, which will play a key role in forthcoming cellular systems, and whose underlying connectivity exhibits a highly variable behavior. We show that using multiple streams, which is one of the most relevant advantages of QUIC, yields performance improvements. We then propose a delay-based scheduler, based on dynamic queuing control, and we compare its behavior with that exhibited by legacy solutions. We carry out an extensive experiment campaign exploiting a novel methodology that combines virtualization techniques, real QUIC implementation, and ns-3 to model NTN links. The results show that the proposed scheduling policies fairly distribute the delay between streams, without jeopardizing the throughput, even under very high load situations.

We study the performance exhibited by the transport protocols, Transport Control Protocol (TCP) and QUIC, over realistic satellite networks. We propose a novel methodology, which combines real implementation (exploiting virtualization techniques) and simulation, to carry out systematic and repetitive experiments. We modify the default operation of the ns-3 framework and we integrate the dynamism that characterizes satellite communication links, particularly Low Earth Orbit (LEO). We carry out a thorough assessment over different setups, changing the operating frequency band and packet buffer lengths. In addition, we ascertain the impact of using the multi-streaming feature that QUIC integrates. The results show that QUIC yields lower delays than TCP, although it might suffer from higher jitter in particular setups. In addition, the results evince that using multiple streams in QUIC does not yield a relevant gain for the default Round-Robin (RR) scheduler. We propose more appropriate scheduling strategies, which are able to yield better performances with unbalanced traffic. Even if the behavior of transport protocols over non-terrestrial-networks might not be always appropriate, the obtained results evince that QUIC can definitively bring benefits when compared to TCP. Furthermore, we have shown that optimal scheduling policies yields a fairer performance when using multiple flows, having unbalanced traffic loads.

Low Earth Orbit (LEO) satellite constellations have been identified for new massive access networks, as a complement to traditional cellular ones, due to their native ubiquity. Despite being a feasible alternative, such networks still raise questions on their performance, in particular regarding the delay and queuing management under realistic channels. In this work, we study the queuing delay of a single satellite-to-ground link, considering a Land Mobile Satellite (LMS) channel in LEO with finite buffer lengths. We analyze the trade-off between delay and packet loss probability, using a novel model based on Markov chains, which we assess and extend with an extensive analysis carried out by means of system level simulation. The developed tools capture with accuracy the queuing delay statistical behavior in the S and Ka frequency bands, where LEO communications are planned to be deployed. Our results show that we can use short buffers to ensure less than 5-10% packet loss, with tolerable delays in such bands.

It is broadly accepted that network function virtualization will play a key role to meet the stringent and heterogeneous requirements of 5G networks. Although fully centralized approaches were initially proposed, they may impose unfeasible requirements over fronthaul links. Consequently, flexible functional split solutions are being fostered, where a central controller adapts the centralization level to current circumstances. In spite of the growing interest in this type of solutions, most of existing works focus on real implementation, while little attention has been paid so far to performance modeling. In this paper we propose a Markov Chain based controller model, which boils down to a Quasi-Birth-Death process. Under reasonable assumptions, this model provides expected values of buffer occupancy and the time frames would spend in the controller. In this sense, it aims to be a tool to support the allocation of computational resources of the virtualized entities. We validate the proposed model by comparing its results with those obtained by simulation, evincing an almost perfect match between both approaches.

We study Flexible Functional Split functionality of 5G vRAN controllers in 5G networks. We propose an innovative model, based on a Markov Chain, which can be used to characterize their performance. We consider both infinite and finite-buffer controllers. In the former, frames would not be lost (provided the system works in a stable regime), and we thus focus on the time frames stay at the controller. For the finite-buffer controller, there might be losses, and we analyze the trade-off between time at the controller (which might hinder the stringent delay requirements of 5G services), and loss probability. Matrix-geometric techniques are used to resolve the corresponding Quasi-Birth-Death process. The validity of the proposed model is assessed by means of an extensive experiment campaign carried out over an ad-hoc event-driven simulator, which is also used to broaden the analysis, considering different service rate distributions, as well as the variability of the studied performance indicators. The results show that the proposed model can be effectively exploited to tackle the dimensioning of these systems, as it sheds light on how their configuration impacts the expected delay and loss rate.

This work tackles the problem faced by network/infrastructure providers of jointly selecting routing and functional split level to satisfy requests from virtual mobile network operators (vMNOs). We build a novel system model that brings together all the involved elements and features, embracing split levels defined by the 3GPP and packet switch fronthaul network. To our best knowledge, this is the first work that provides a solution for multiple vMNO requests considering the two aforementioned sub-problems (i.e., split selection and routing). We use the model defined to formulate an optimization problem, which is characterized by the exponential size of its search space. We propose two heuristic approaches to address this problem: (1) a greedy scheme, and (2) an evolutionary algorithm, which is also improved with a specialized initialization. We conduct extensive experiments to assess the performance and behavior of the proposed methods, over varying network instances. When possible, we also perform comparisons with respect to the optimal solution and a well-known commercial solver. Our results indicate that the proposed techniques represent appropriate trade-offs between solution quality and execution time, and can serve complementary goals: the quality of the results yielded by our evolutionary method are better, but at the cost of longer execution times; in contrast, our greedy algorithm offers a reasonably appropriate performance, with an execution time that is notably lower. Our experiments show that it is possible to produce near-optimal results to the above complex problem through computationally efficient algorithmic solutions.

This paper studies how learning techniques can be used by the congestion control algorithms employed by transport protocols over 5G wireless channels, in particular millimeter waves. We show how metrics measured at the transport layer might be valuable to ascertain the congestion level. In situations characterized by a high correlation between such parameters and the actual congestion, it is observed that the performance of unsupervised learning methods is comparable to supervised learning approaches. Exploiting the ns-3 platform to perform an in-depth, realistic assessment, allows us to study the impact of various layers of the protocol stack. We also consider different scheduling policies to discriminate whether the allocation of radio resources impacts the performance of the proposed scheme.

We study the performance of the Message Queuing Telemetry Transport Protocol (MQTT) over QUIC. QUIC has been recently proposed as a new transport protocol, and it is gaining relevance at a very fast pace, favored by the support of key players, such as Google. It overcomes some of the limitations of the more widespread alternative, TCP, especially regarding the overhead of connection establishment. However, its use for Internet of Things (IoT) scenarios is still under consideration. In this paper we integrate a GO-based implementation of the QUIC protocol with MQTT, and we compare the performance of this combination with that exhibited by the more traditional MQTT/TLS/TCP approach. We use Linux Containers and we emulate various wireless network technologies by means of the ns3 simulator. The results of an extensive measurement campaign, show that QUIC protocol can indeed yield good performances for typical IoT use cases.

Network densification over space and spectrum is expected to be key to enabling the requirements of next generation mobile systems. The pitfall is that radio resource allocation becomes substantially more complex. In this paper, we propose LaSR, a practical multi-connectivity scheduler for OFDMA-based multi-RAT systems. LaSR makes optimal discrete control actions by solving a sequence of simple optimization problems that do not require prior information of traffic patterns. In marked contrast to previous work, the flexibility of our approach allows us to construct scheduling policies that achieve a good balance between system cost and utility satisfaction, while jointly operate across heterogeneous RATs, accommodate real-system requirements, and guarantee system stability. Examples of system requirements considered in this paper include (but are not limited to): constraints on how scheduling data can be encoded onto signaling protocols (e.g., LTE's DCI), delays when turning on/off radio units, or on/off cycles when using unlicensed spectrum. We evaluate our scheduler via a thorough simulation campaign in a variety of scenarios with e.g., mobile users, RATs using unlicensed spectrum (using a duty cycle access mechanism), imperfect queue state information, and constrained signaling protocol.

Network slicing has recently been proposed as one of the main enablers for 5G networks. The slicing concept consists of the partition of a physical network into several self-contained logical networks (slices) that can be tailored to offer different functional or performance requirements. In the context of 5G networks, we argue that existing ubiquitous WiFi technology can be exploited to cope with new requirements. Therefore, in this paper, we propose a novel mechanism to implement network slicing in WiFi Access Points. We formulate the resource allocation problem to the different slices as a stochastic optimization problem, where each slice can have bit rate, delay, and capacity requirements. We devise a solution to the problem above using the Lyapunov drift optimization theory, and we develop a novel queuing and scheduling algorithm. We have used MATLAB and Simulink to build a prototype of the proposed solution, whose performance has been evaluated in a typical slicing scenario.

QUIC, fostered by Google and under standardization in the IETF, integrates some of HTTP/s, TLS, and TCP functionalities over UDP. One of its main goals is to facilitate transport protocol design, with fast evolution and innovation. However, congestion control in QUIC is still severely jeopardized by packet losses, despite implemented loss recovery mechanisms, whose behavior strongly depends on the Round Trip Time. In this paper, we design and implement rQUIC, a framework that enables FEC within QUIC protocol to improve its performance over wireless networks. The main idea behind rQUIC is to reduce QUIC's loss recovery time by making it robust to erasures over wireless networks, as compared to traditional transport protocol loss detection and recovery mechanisms. We evaluate the performance of our solution by means of extensive simulations over different type of wireless networks and for different applications. For LTE and Wifi networks, our results illustrate significant gains of up to 60% and 25% savings in the completion time for bulk transfer and web browsing, respectively.

Quick UDP Internet Connections (QUIC) is an experimental transport protocol designed to primarily reduce connection establishment and transport latency, as well as to improve security standards with default end-to-end encryption in HTTPbased applications. QUIC is a multiplexed and secure transport protocol fostered by Google and its design emerged from the urgent need of innovation in the transport layer, mainly due to difficulties extending TCP and deploying new protocols. While still under standardisation, a non-negligble fraction of the Internet's traffic, more than 7% of a European Tier1-ISP, is already running over QUIC and it constitutes more than 30% of Google's egress traffic [1].

In this paper we propose a novel model for the uplink in heterogeneous cellular networks. Opposed to previous works, we accurately account for the mutual interference caused by other users' connections, and we pose an optimization problem that can be straightforwardly solved to establish the minimum required transmission power that satisfies the minimum Signal-to-Interference-plus-Noise Ratio (SINR) constraint. We assess the validity of the proposed approach by comparing the observed results with those obtained with a traditional closed-loop power control scheme. The main benefit of our solution is that it does not require any iteration to find the transmission power, while legacy approaches usually need a number of steps before finding it. Finally, we study the behavior of the uplink for different access selection strategies, and we compare the SINR and transmission power of open-loop and closed-loop power control solutions.

It is well known that network function virtualization will be a key enabler to meet the stringent requirements of 5G networks. However, fully centralized approaches, such as Cloud Radio Access Network (C-RAN), might not be feasible, considering the particular needs of the fronthaul links and the large cost of implementing such architectural shift. In this sense, flexible functional split brings a practical solution, which trades off performance and practicability. In spite of the growing interest in flexible functional split, little attention has been paid to the interaction of split selection and scheduling. In this paper, we analyze joint strategies that minimize traffic delay. We compare the global optimum solution with partial optimizations, that can be more suitable in practical implementations, using different scenarios. According to our results, fixed scheduling behaves alike the global optimum in heterogeneous RAN scenarios. Furthermore, we observe that it is usually better to optimize the split degree for fixed scheduling setups, than deciding a scheduling policy for a particular split configuration.

In forthcoming 5G networks, slicing has been proposed as a means to partition a shared physical network infrastructure into different self-contained logical parts (slices), which are set up to satisfy certain requirements. Although the topic has been thoroughly investigated by the scientific community and the industry, there are not many works addressing the challenges that appear when trying to exploit slicing techniques over WiFi networks. In this paper, we propose a novel method of allocating resources for WiFi networks to satisfy minimum bit rate requirements. We formulate an optimization problem, and we propose a solution based on the theory of Lyapunov drift optimization. The validity of the proposed solution is assessed by means of a simulation-based evaluation in Matlab.

The presence of IoT in current networking scenarios is more relevant every day. IoT covers a wide range of applications, ranging from wearable devices to vehicular communications. With the consolidation of Industry 4.0, IIoT (Industrial IoT) environments are becoming more common. Communications in these scenarios are mostly wireless, and due to the lossy nature of wireless communications, the loss of information becomes an intrinsic problem. However, loss recovery schemes increase the delay that characterizes any communication. On the other hand, both reliability (robustness) and low delay are crucial requirements for some applications in IIoT. An interesting strategy to improve both of them is the use of Network Coding techniques, which have shown promising results, in terms of increasing reliability and performance. This work focuses on a possible new coding approach, based on systematic network coding scheme with overlapping generations. We perform a thorough analysis of its behavior. Based on the results, we draw out a number of conclusions for practical implementations in wireless networks, focusing our interest in IIoT environments.

We consider the transmission of packets across a lossy end-to-end network path so as to achieve low in-order delivery delay. This can be formulated as a decision problem, namely deciding whether the next packet to send should be an information packet or a coded packet. Importantly, this decision is made based on delayed feedback from the receiver. While an exact solution to this decision problem is challenging, we exploit ideas from queueing theory to derive scheduling policies based on prediction of a receiver queue length that, while suboptimal, can be efficiently implemented and offer substantially better performance than state of the art approaches. We obtain a number of useful analytic bounds that help characterise design trade-offs and our analysis highlights that the use of prediction plays a key role in achieving good performance in the presence of significant feedback delay. Our approach readily generalises to networks of paths and we illustrate this by application to multipath trans port scheduler design.

Multicast services are believed to play a relevant role in next wireless networking scenarios. In this paper we exploit Tunable Sparse Network Coding techniques to increase reliability of multicast communications. We show that the proposed network coding scheme yields a better performance than state-of-the-art solutions, which are traditionally based on retransmissions. We first use a model to analytically compare the two approaches. Then, we validate and broaden this analysis by means of an experimental campaign over a testbed deployed with Commercial Of-The-Shelf devices. This platform, comprising low cost devices (Raspberry-PI), allows us to assess the feasibility of the proposed solution, which offers a relevant gain in terms of performance.

Network slicing has recently appeared as one of the most important features that will be provided by 5G networks and is attracting considerable interest from industry and academia. At the wireless edge of these networks, most of the contributions in this area are related to cellular technologies leaving behind WiFi networks. In this work, we present a resource allocation mechanism based on airtime assignment to achieve infrastructure sharing and slicing in WiFi Access Points. The approach is simple and has the potential to be straightforwardly used within scenarios of wireless access infrastructure sharing.

Despite their high computational complexity, Random Linear Network Coding (RLNC) techniques have been shown to offer a good robustness against packet erasure wireless channels. Some approaches have been recently proposed to reduce such computational burden, for both encoder and decoder elements. One of those approaches are the so- called Tunable Sparse Network Coding (TSNC) techniques, which advocate limiting the number of packets that are combined to build a coded packet. They also propose dynamically adapting the corresponding sparsity level, as the transmission evolves, although an optimum tuning policy has not been yet found. In this paper we present a TSNC implementation that exploits a novel analytical model to estimate the probability of generating an innovative packet (linearly independent combination), given the current status at the decoder. Taking advantage of the model's accuracy, the proposed scheme offers a better trade-off between computational complexity and network performance. Furthermore, we broaden the analysis of TSNC techniques by thoroughly assessing their behavior over wireless networks using the ns-3 platform. The results yield a remarkable complexity reduction (approx. 3.33x less complexity), without jeopardizing network performance.

Random linear network coding has been shown to offer an efficient communication scheme, leveraging a remarkable robustness against packet losses. However, it suffers from a high-computational complexity, and some novel approaches, which follow the same idea, have been recently proposed. One of such solutions is sparse network coding (SNC), where only few packets are combined with each transmission. The amount of data packets to be combined can be set from a density parameter/distribution, which could be eventually adapted. In this paper, we present a semi-analytical model that captures the performance of SNC on an accurate way. We exploit an absorbing Markov process, where the states are defined by the number of useful packets received by the decoder, i.e., the decoding matrix rank, and the number of non-zero columns at such matrix. The model is validated by the means of a thorough simulation campaign, and the difference between model and simulation is negligible. We also include in the comparison of some more general bounds that have been recently used, showing that their accuracy is rather poor. The proposed model would enable a more precise assessment of the behavior of SNC techniques.

Random Linear Network Coding (RLNC) is a technique that provides several benefits. For instance, when applied over wireless mesh networks, it can be exploited to ease routing solutions as well as to increase the robustness against packet losses. Nevertheless, the complexity of the decoding process and the required overhead might jeopardize its performance. There is a trade-off when deciding the field and block sizes; larger values decrease the probability of transmitting linearly dependent packets, but they also increase both the required overhead and the decoding complexity. In order to overcome these limitations, we propose a sliding window enhancement; a fixed number of packets (fewer than the block size) is combined within every transmission, and the decoding process can therefore take advantage of the algebra with sparse matrices. The paper presents an analytical model, which is first validated and later broaden by means of an extensive simulation campaign carried out over the ns-3 simulator.

Random Linear Network Coding (RLNC) has been shown to be a technique with several benefits, in particular when applied over wireless mesh networks, since it provides robustness against packet losses. On the other hand, Tunable Sparse Network Coding (TSNC) is a promising concept, which leverages a trade-off between computational complexity and goodput. An optimal density tuning function has not been found yet, due to the lack of a closed-form expression that links density, performance and computational cost. In addition, it would be difficult to implement, due to the feedback delay. In this work we propose two novel tuning functions with a lower computational cost, which do not highly increase the overhead in terms of the transmission of linear dependent packets compared with RLNC and previous proposals. Furthermore, we also broaden previous studies of TSNC techniques, by means of an extensive simulation campaign carried out using the ns-3 simulator. This brings the possibility of assessing their performance over more realistic scenarios, e.g considering MAC effects and delays. We exploit this implementation to analyze the impact of the feedback sent by the decoder. The results, compared to RLNC, show a reduction of 3.5 times in the number of operations without jeopardizing the network performance, in terms of goodput, even when we consider the delay effect on the feedback sent by the decoder.

In this work we focus on the application of an intra-flow linear random coding scheme over wireless mesh networks. We propose a cross-layer technique to balance the load between relaying nodes, considering the quality of the wireless links. We assess the performance of our proposal by means of an extensive simulation campaign carried out over the ns-3 platform, exploiting a channel model based on a Hidden Markov Process, which accurately mimics the bursty behavior that is observed over real indoor channels. The results show the benefits of the proposed cross-layer technique. In addition, we also discuss the trade-off (between accuracy and overhead) that needs to be considered when obtaining the information that such scheme rely on. Our simulations yield a 10% performance gain when exploiting the link quality information, as it is already obtained by various routing protocols.

In this paper we propose a modification of the LTE Radio Link Control procedures so as to reduce the number of retransmissions that need to be carried out when a video streaming service is being transmitted from the end-user terminal to the base station. We exploit the fact that, in this case, some of the frames of the video flow might be lost without a strong impact on the perceived quality of experience. We carry out an extensive simulation study over the ns-3 framework, comparing the performance of the proposed scheme with that exhibited by the legacy operation of the RLC. The results yield that our proposal is able to significantly reduce the number of retransmissions, without a strong impact on the Mean Opinion Score.

This work presents a novel model for multi-hop networks which aims to include electro-magnetic exposure metrics within the routing paradigm. Given the need to include new metrics in the routing decision making, as a prelude to the protocols definition, it is deemed necessary the definition of novel network models and adequate algorithms so that they can be afterwards utilized to assess the performance of the routing protocols. In particular, this work proposes a network model to include the electro-magnetic exposure within the routing costs; besides, an algorithm (Cycle Canceling Algorithm) has been identified that is able to effectively solve the problem resulting from the model. Furthermore, the behavior of the proposed algorithm is compared with other which considers a different metric, so as to corroborate its operation and to provide information on how to tweak its configuration parameters.

It goes without saying that TCP is the de-facto transport protocol to ensure reliable communications (for instance, in file transfers). On the other hand, and despite the growing relevance of wireless networks, the behavior of TCP over such technologies is well-known to present clear limitations. Several approaches have been made so as to overcome these problems. In this work we propose a different approach to ensure reliable transmissions over wireless links, based on an Random Linear Coding (RLC) scheme, operating together with UDP. We provide a model of the expected performance of the new scheme. Furthermore, based on an extensive simulation campaign over the ns-3 simulation framework, we assess the validity of this model and we compare its performance with that exhibited by the legacy TCP. The results show that, in particular for lossy links, the proposed scheme clearly outperforms TCP.

This work proposes a solution to overcome the inherent degradation of TCP performance in multi- hop wireless networks. Based on a Network Coding entity integrated between the TCP and the IP layer, we propose a mechanism to encapsulate TCP acknowledgments, which are transmitted along with other segments, thus reducing the number of frames to be sent. We assess the performance of the combination of these two techniques by means of an extensive simulation campaign, carried out using the ns-3 framework. The results show that the addition of the encapsulation scheme brings about a performance enhancement (around 15%), compared to a standard Network Coding scheme. On the other hand, the performance deteriorates when transmission errors occur.

In this paper we present an Open Connectivity Services architecture, which has been conceived such as to cope with the challenges posed by the Future Internet. By relying on currently working solutions and establishing a trustworthy migration strategy, the proposed architecture provides a flexible framework that supports both legacy and enhanced connectivity mechanisms. It is able to dynamically adapt the operation of the involved mechanisms according to the particular requirements of the services and applications. This open architecture is based on three main modules (information gathering, decision taking and decision enforcement) which mimic the basic functionalities of any connectivity mechanism. By having a common way of representing current and future mechanisms, the OConS operation eases the instantiation, launch and interconnection of mechanisms by the specified orchestration procedures. A challenging flash crowd scenario is presented for validation of the architecture, where enhanced connectivity mechanisms support both cloud networking and network of information use cases.

Modern mobile devices comprise multiple interfaces for heterogeneous network technologies. However, currently implemented mechanisms to decide which one(s) to use and distribute application flows accordingly (i.e., solving the multihomed flow management problem, MFM) are rather coarse and do not leverage the opportunities. A user-centric quality-aware (QA) MFM has been proposed which optimises network use based on user-perceivable metrics such as application quality as well as energy and monetary costs. This paper refines this approach by providing a single method for both real-time and elastic (i.e., TCP-based) traffic, and uses realistic available capacity estimation. We evaluate this method in OPNET-simulated LTE and WLAN mobile networks. We study the impact of methods used to trigger the decision algorithm, and investigate the influence of an increasing number of users employing the QA-MFM technique on both the user-perceivable metrics and the global network performance. We find that on-demand triggering performs better than a static periodic method. We also demonstrate that the proposed approach out-performs classical network selection techniques in terms of application quality. We also show that the QA-MFM is not too greedy as to not scale with a number of users, and has a positive effect on the network loads, by preemptively adapting applications parameters to match network conditions.

Since it was originally proposed by Ahlswede et al. (2000), network coding (NC) has been the focus of many research efforts and proposals. In particular, NC has been put forward as a means to increase the capacity of wireless mesh networks, by exploiting the broadcast nature of wireless links. However, in spite of the fairly large number of papers on the subject of network coding, the impact of NC on TCP performance in wireless mesh networks is still not fully understood. By means of a thorough simulation study, this paper aims thus at providing insights about the interaction between TCP's congestion control mechanisms and the underlying NC done by wireless relays. In particular, we focus on the influence of the main parameters related to the coding buffer used by such relays to encode packets. Our results suggest the feasibility of devising engineering rules for setting such parameters. Another main conclusion, in line with previous preliminary findings by the authors (Hassayoun et al., 2010) is that TCP performance can indeed be improved by the use of NC, but only as long as the wireless channel quality is above a certain level.

In this paper, we present a game theoretic approach to achieve load balancing within heterogeneous wireless environments. We deploy a number of access elements, which differ in terms of both coverage and capacity. We assume that access elements are able to limit the resources they provide to a certain area, leading to a number of different strategies. We also derive the expected benefits for each of them and we pose a discrete and finite game which is solved with the Gambit tool so as to obtain the Nash Equilibrium, which we consider as the optimum strategy. The paper shows that the use of such strategy brings about some benefit, in terms of the load carried by the network, and that it becomes more relevant for those technologies which have less capacity and coverage.

In this work we deal with the analysis of different channel models, which aim to replicate the bursty characteristic of real indoor wireless channels within a network simulation framework. In particular, we focus on the performance of Hidden Markov Processes, comparing it with other alternatives, such as the legacy models which the ns-3 network simulator implements by default and another one whose operation is based on the estimation of the received signal strength by means of an auto-regressive filter.

This paper analyzes the use of link quality, based on the signal to noise ratio, as a metric to improve routing in multi-hop wireless networks. We compare the behavior and performance with those of other approaches, namely a simple minimum-hop selection process, as well as the expected transmission count (ETX) metric, which has recently gathered relevant attention from the scientific community. We use a simulation based analysis, but we account for a realistic channel model, able to mimic the Gray Zones effect, which has been proven to have a great impact on wireless-based communications in general and over multi-hop topologies in particular. The results show that important improvements can be brought about by making use of the proposed metric to enhance route selection procedures.

This paper discusses a simulation based approach to evaluate legacy management frameworks over new personal networking architectures. After implementing a real demonstrator, gathering a broad range of devices, technologies, and services supported by this type of environments, we were able to assess the feasibility of a hierarchical management framework, validating its correct behavior. However, we realized that this demonstrator does not allow carrying out a thorough and systematic evaluation of more complex scenarios, mimicking potential real environments, especially in terms of network dimensions and mobility restrictions. Hence, we propose to extend the analysis performed over the real platform by means of the Network Simulator framework. Finally we obtain preliminary measurements to validate the approach, which aims at being the starting point to address management modeling and evaluation over multi-hop networks.

This paper discusses the benefits that mesh and multi-hop networking may bring about over traditional network deployments. An optimal distribution of access elements, following a grid structure is assumed, and the paper analyzes the coverage extension which could be achieved, by means of forwarding stations, assuming different number of hops per route, as well as different end user (and relaying nodes) densities. The paper follows a two-fold approach, since it presents both an analytical as well as a simulation-based analysis.

In this paper we show how traditional indoor channel models do not accurately reflect the real behavior exhibited by TCP when operated over error-prone wireless links, especially due to the large variability which is empirically observed. In contrast with them, we use a novel channel model, based on an auto-regressive filtering scheme, and which we have integrated into the Network Simulator framework, to better capture the real behavior of wireless links. We shall see that the memory characteristic of the channel, with a clear influence over retransmissions and inactivity times that the TCP transmitter suffers from, highlights as it most distinctive aspect. The idea is to provide a realistic modeling of wireless channels, so as to overcome the deficiencies which characterize other more traditional approaches.

Ambient Networks concentrates on the co-operation of heterogeneous networks over multiple domains and accesses. One of the main goals of the project is the integration of developed concepts for validation purposes. This paper presents a performance analysis on the integration of mobility triggering and Host Identity Protocol (HIP) based mobility on the Ambient Networks/FreeBSD platform. The scalability of triggering and handover latency has been focused on in terms of different mobility triggers and access technologies. The results enable identification of the largest delay components, which have been analyzed.

Due to the rapid growth of personal communications, it is now believed that multi-hop topologies will certainly play a key role in forthcoming wireless communications scenarios. Amongst other aspects, they will facilitate the appearance of new business models, allowing e.g. the possibility for operators to extend their services on a cost effective way. In this sense, an end-user may act as a relaying node, offering other end-users the possibility to connect to a base station (or access point) even if these were not able to do it directly (because e.g. they were not within the coverage area or they were not costumers of that operator). This paper analyzes one of the benefits brought about by multi-hop accesses, particularly the coverage extension that could be enabled by these approaches, by performing both an analytical and a simulation study. We analyze the outage probability over different network deployments, increasing the number of hops that a user might employ to reach an access point.

Wireless operators incorporate multiradio access technologies aiming at expanding their customer base and benefiting from synergies of existing and planned infrastructure. The result is areas with overlapping radio access technologies, enabling users to select from a large pool of available connections, based on several criteria. In these increasingly complex scenarios the importance of handover decisions cannot be underestimated. We study three different handover decision strategies, focusing on the tradeoff between continuous connectivity, network utilization and performance, and the associated costs, and compare them to the optimal strategy. We motivate the need for a distributed algorithm, especially when considering the deployment of multimedia applications, and reflect on the effective network capacity as a function of the handover strategy employed and the permitted offline time for the active mobile nodes in the network.

In this paper we propose a novel channel model for indoor wireless environments. Using a set of real measurements, we tune the parameters of an Auto-Regressive filter, which is the core of the proposed model; furthermore we assess that its behavior is much closer to real wireless links that those exhibited by some of the most currently used approaches. The novel channel model is integrated within the framework of the Network Simulator environment. Its goal is to mimic the "bursty" behavior that characterizes the aforementioned indoor wireless environments.

This paper describes the steps and the procedures involved to establish access flows for a user data session in multi-radio access networks. The description is evolved around the overall connectivity abstraction model defined in the ambient networks (AN) project. This model uses access flows as its fundamental objects which are the result of two main access selection procedures: network attachment and flow setup. All access abstractions and procedures have been developed to handle the requirements of efficient multi-access resource management through all stages of access connectivity. The paper discusses some design trade-off for the establishment of access flows concerning setup delays and resource efficiency.

Allowing a user to remain connected to the network whilst on the move is becoming a common requirement for any new communication system. The EU project Ambient Networks, therefore, considers mobility requirements and techniques in some depth. Two key ideas have been developed: the handover toolbox which contains and manages a variety of mobility protocols, handover techniques and, in particular, mobility optimisations; and the concept of routing groups, the establishment of which enables the mobility optimisations such as delegation of mobility management and aggregation of mobility signalling. In this paper we present these ideas and show how they are aligned with the ambient networks principles of being easily deployable, adaptable, and able to support heterogeneous network configurations.

This paper presents a hierarchical management architecture which has been designed to work over next generation WPAN environments. In this sense, it copes with e.g. ad hoc networks (likely to play a fundamental role within future wireless networks) as well as with low capacity devices, such as sensors and actuators (thus, highlighting the heterogeneity that also characterize these environments). The architecture uses both a traditional-management operation (based on SNMP) and a proprietary one. Furthermore, security concerns have also been considered. One of the main contributions of the paper is that it gives some insights about the implementation of the management architecture and on how the different pieces of information are managed. In particular, the paper discusses the following aspects: network topology, ad hoc routing mechanisms, sensors, and terminal status. The main goal of the implementation is to assess the feasibility of the proposed scheme over the high dynamic environments which have been targeted

Integration of heterogeneous access technologies to provide multi-radio access allows for dynamic access selection. The "always best connected" paradigm can increase system capacity and end user throughput, as well as, reduce the network deployment costs for multi-radio wireless networks. In this paper we present the functional entities generic link layer and multi-radio resource management, and describe their interactions for access selection. A focus of the paper is to show - with an example given for 3G and WLAN - how existing wireless networks can be migrated to provide multi-radio access functionality. This will be explained for a single operator integrating different radio access standards, as well as, for multiple cooperating network operators.

The aim of this paper is to characterize the behavior of the UDP transport protocol, mainly in terms of throughput and average delay, over an IEEE 802.11b compliant wireless local area network (WLAN) from an experimental approach. Although performance evaluation of these kinds of LAN is being extensively discussed in the current literature, most of these studies are analytical or simulation-based and they do not consider the influence of channel impairments or link quality over network throughput. After an exhaustive measurement campaign, different performance parameters such as throughput, goodput, effective goodput, frame error rate, IT loss rate, delay and jitter have been obtained. This could be a preliminary analysis of the behavior of real-time traffic over WLAN infrastructures, such as streaming audio and voice transmission, services that are expected to undergo substantial growth in the coming years. All these studies and results have been developed in the context of the WINE (Wireless Internet Networks) project belonging to the framework of the Information Society Technologies (IST) programme, addressed to enhancing the performance of TCP/IP protocol over WLAN such as IEEE 802.11, Bluetooth and HIPERLAN/2.