Applications with deterministic quality of service (QoS) requirements are becoming widespread, driving the evolution of wireless networks to meet strict performance demands. Wi-Fi 7, the latest generation of IEEE 802.11 standard, introduces Restricted Target Wake Time (R-TWT). It serves latency-sensitive traffic by providing contention-free channel access for certain devices and reducing their energy consumption. This paper evaluates the performance of R-TWT across diverse service types and network sizes in terms of worst-case latency, energy efficiency, collision rate, and throughput. The results, generated using the ns-3 simulator, show that R-TWT achieves bounded latency for sensitive traffic types, such as Internet of Things (IoT) and real-time (RT) applications. Moreover, R-TWT outperforms legacy mechanisms, i.e., Power Saving Mode (PSM) and Distributed Coordination Function (DCF), by achieving higher energy efficiency and a lower collision rate. Furthermore, R-TWT maintains stable and scalable performance as network size increases. This makes it a robust solution for latency-sensitive and energy-efficient wireless applications.

The IEEE 802.11 working group is currently finalizing the 802.11be amendment, which defines the features that will be supported by Wi-Fi 7 devices. A prominent new feature, termed Multi-Link Operations (MLO), is the ability for a device to operate on multiplelinks, i.e., on multiple frequency channels. Among the various MLO modes defined, Enhanced Multi-Link Single Radio (EMLSR) is attracting the interest of many vendors due to its potential for exploiting operations on multiple links through reduced hardware capabilities. In this paper, we first provide an overview of the standard specifications for EMLSR and describe the model underlying its implementation that we have contributed to the ns-3 simulator. The implemented model is rather flexible and enables to simulate various architectures differing for implementation cost, power consumption and performance. Then, we thoroughly evaluate several EMLSR configurations with the goal of shedding light on the possible alternatives that are available. We consider both a scenario of saturated conditions without interfering traffic and a scenario of non-saturated conditions with interfering traffic. Our study shows that the main differences in performance among the various EMLSR configurations are observed in the uplink direction and that EMLSR operations enable to reduce latency with respect to single-link devices at the cost of a slight increase in power consumption.

Wi-Fi 7, based on the IEEE 802.11be amendment, is designed to increase the maximum achievable throughput, expand the range of operating frequencies, and improve latency and jitter in worst-case scenario. In the context of the discussions to shape what Wi-Fi 8 will be, the IEEE 802.11 WG is evaluating multi-AP coordination as a strategy to further improve network performance in several aspects. MAC-driven multi-AP coordination strategies include coordinated Orthogonal Frequency Division Multiple Access (c-OFDMA), coordinated Time Division Multiple Access (c-TDMA), and coordinated Spatial Reuse (c-SR). In c-OFDMA, a set of APs transmit during a Transmission Opportunity on different channels, whereas in c-TDMA, the APs take turns transmitting on the same channel during a Transmission Opportunity. Instead, in c-SR, a set of APs transmit simultaneously on the same channel and during the same Transmission Opportunity. In this paper, we focus on c-SR. We introduce a c-SR interference model and present a strategy based on the proposed model for estimating groups of APs that can transmit successfully simultaneously. We implemented the proposed approach in the multi-AP coordination framework of ns-3 that we developed to analyze c-TDMA. We then thoroughly evaluate the performance of the proposed c-SR scheme via ns-3 simulations. The proposed scheme allows increasing the system throughput of a dense deployment up to 2.3 times as well as substantially reducing the Head of Line delay.

With the introduction of Orthogonal Frequency Division Multiple Access (OFDMA) in 802.11ax, the role of the Access Point (AP) in Wi-Fi networks changes significantly, thanks to the opportunity of implementing more complex scheduling logic to handle Downlink (DL) traffic flows and simultaneously act as coordinator of Multi User (MU) Uplink (UL) transmissions. In this context, it becomes necessary to develop reliable network analysis and simulation tools that allow for an in-depth investigation of the trade-offs involved in the usage of OFDMA, especially considering that the standard leaves much of the actual scheduling algorithmic details to vendor-specific implementation. In this work we present a series of results highlighting how several network settings have an impact on throughput and Head-of-Line Delay, in a network that employs multiple 802.11ax features such as OFDMA and the MU Enhanced Distributed Channel Access (EDCA) Parameter Set, while also containing legacy devices. The results are obtained via both the newly re-designed ns-3wifimodule and an original analytical framework, based on the well-established Bianchi 802.11 model.

IEEE 802.11be networks (aka Wi-Fi 7) will have to cope with new bandwidth-hungry and low-latency services such as eXtended Reality and multi-party cloud gaming. With this goal in mind, transmit opportunity (TXOP) sharing between coordinated access points (APs) may contribute to alleviating inter-AP contention, hence increasing the overall network throughput. This paper evaluates two coordinated TXOP sharing strategies: coordinated time division multiple access (c-TDMA) and coordinated-TDMA with spatial reuse (c-TDMA/SR). We show that, while c-TDMA alone does not result in any significant improvement in terms of the WLAN throughput, it lays the groundwork to implement coordinated SR (c-SR) techniques. To evaluate the performance of c-TDMA/SR, we propose a fair scheduler able to select the best subset of parallel transmissions in WLAN deployments, as well as the appropriate power levels to be used by APs and stations (STAs), leading to maximum performance. The results obtained for c-TDMA/SR show significant throughput gains compared with c-TDMA, with values higher than 140% in 90% of the considered scenarios.

The Next Generation Networks (NGN) set its standard to provide very high data rates, Ultra-Reliable Low Latency Communications (URLLC), increased network capacity and significantly improved Quality of Service (QoS). Thus, it provides an infrastructure for the Internet of Things (IoT) to power billions of connected devices. With this upsurge in IoT devices, the need for adopting IPv6 over exhausting IPv4 addresses becomes more unavoidable. Hence, Internet Service Providers (ISP's) are adopting IPv6 along with IPv4 addresses using an address transition method called dual-stack. However, the Dual-Stack network causes relatively more connectivity overhead than the single stack network. For example, DNS lookup and TCP connection time are comparatively high in dual-stack mobile devices. This affects the page loading time of the application, thereby impacting the user experience significantly. In this paper, we analyzed all these connectivity overheads and propose a novel solution called NexGen Connectivity optimizer (NexGenCO), which provides better connectivity for the applications using network-aware concurrency and intelligent DNS caching. NexGenCO is prototyped and evaluated in Samsung devices with Android Pie. It significantly reduces connectivity overhead and improves page loading time up to 18% consistently.

In this paper, we develop a novel throughput- maximizing OFDMA scheduler for the multi-user MAC framework for the IEEE 802.11ax networks. The scheduler works both in the downlink and uplink directions and assigns resource units to stations using a linear programming technique considering load of each client, possible resource unit configurations, modulation-coding scheme of each client, and ageing factor of each client's load. The performance of the proposed scheduler has been evaluated using the NS3 simulator and compared against the legacy MAC layer mechanism of IEEE 802.11 protocol (i.e., DCF/EDCA). Simulation results show that our proposed throughput-maximizing scheduler increases the total throughput in the network as well as decrease the average end-to-end delay regardless of the number of stations connected to the access point by prioritizing the traffic of clients connected via high modulation-coding schemes.

The Software Defined Network (SDN) paradigm represents a major breakthrough in the networking field, due to its unprecedented capabilities in terms of flexibility and programmability. SDNs have been successfully deployed in data centers and small to medium enterprises. However, adopting the SDN paradigm in the context of wide area networks is more challenging, due to a number of factors including the higher probability that node and link failures occur and the unavailability of a dedicated control channel. In this paper, we present a DAG (Directed Acyclic Graph) based forwarding paradigm addressing the challenges that arise when the SDN concept is applied to large scale networks. Specifically, the proposed paradigm aims to limit the number of entries required on the SDN switches, to provide a fast local restoration of single node/link failures without the intervention of the SDN controller and to prevent the possibility of having inconsistent forwarding tables during updates. The proposed paradigm does not require any extension to the OpenFlow protocol and we show how it can be implemented by only using standard features. The DAG-based forwarding paradigm requires to compute a DAG between every pair of ingress-egress switches and to design an index-based hashing scheme to balance the load across the paths in the DAG while avoiding TCP reordering issues. In this paper, we present heuristic algorithms providing a solution to such problems and report the results of a simulation study conducted to assess the performance of the proposed forwarding paradigm.

In this work, we propose an innovative approach to contrast the bufferbloat, one of the primary sources of queueing latency, in 3GPP mobile networks. Our purpose is to validate an all-software, in-node traffic-control infrastructure, similar to what the Linux operating system already employs for Ethernet and WiFi networks. We introduce the IPtraffic-control infrastructure in the RAN part of an LTE network, for both UE and eNB, that can perform packet scheduling on flows directed to the same Data Radio Bearer. The effectiveness of such strategy leverages on a reduced usable size of the in-node RLC buffer, thanks to the BQL algorithm, which we evaluate for the first time in the context of LTE. By using BQL, we can create a backlog of packets that stays in the Traffic Control layer, on which it is possible to perform packet scheduling without bloating the RLC buffer. We compare the performance of BQL to another algorithm, called DynRLC, proposed to dynamically size the RLC buffer eNB side. The preliminary evaluation of the proposed approach is done on the ns-3 network simulator and it shows that the proposed approach with BQL significantly improves the flow delay, by controlling the queueing latency, as well as enhancing the flow isolation.

The problem of bufferbloat arises due to the presence of large unmanaged buffers and leads to high queuing delays and significant degradation in the performance of time-sensitive and interactive Internet applications. Recently, a new smart queue management system called Common Applications Kept Enhanced (CAKE) has been introduced in Linux 4.19 to tackle the problem of bufferbloat in home Internet gateways. One of the integral parts of CAKE system is COBALT (CoDel and BLUE Alternate), a queue discipline which is a combination of Controlled Delay (CoDel) and BLUE algorithms. Although CAKE is a part of the Linux kernel, a detailed discussion on the design of COBALT is missing. In this paper, we discuss the design of COBALT and compare its performance with CoDel. Additionally, we propose a simulation model for COBALT in ns-3 and test its correctness by comparing the results obtained from it to those obtained from the Linux model. Our evaluation shows that COBALT offers substantial benefits in terms of curtailing queue delays when unresponsive flows exist.

Wireless mesh networks are being deployed all around the world both to provide ubiquitous connection to the Internet and to carry data generated by several services (video surveillance, smart grids, earthquake early warning systems, etc.). In those cases where fixed power connections are not available, mesh nodes operate by harvesting ambient energy (e.g., solar or wind power) and hence they can count on a limited and time-varying amount of power to accomplish their functions. Since we consider mesh nodes equipped with multiple radios, power savings and network performance can be maximized by properly routing flows, assigning channels to radios and identifying nodes/radios that can be turned off. Thus, the problem we address is a joint channel assignment and routing problem with additional constraints on the node power consumption, which is NP-complete. In this paper, we propose a heuristic, named minimum power channel assignment and routing algorithm (MP-CARA), which is guaranteed to return a local optimum for this problem. Based on a theoretical analysis that we present in the paper, which gives an upper bound on the outage probability as a function of the constraint on power consumption, we can guarantee that the probability that a node runs out of power with MP-CARA falls below a desired threshold. The performance of MP-CARA is assessed by means of an extensive simulation study aiming to compare the solutions returned by MP-CARA to those found by other heuristics proposed in the literature.

In the Cloud Computing paradigm there is an emerging Green Computing awareness, aimed at increasing the cost-efficiency of the underlying infrastructure. The pursued objective is to find the right compromise between the energy consumption and the perceived quality of service of the applications running in the cloud. Big data centers, along with the adoption of the virtualization technology, are increasingly experiencing the need to reduce consumption, because of both the environmental pollution and the economic concern. Among the novel techniques used to minimize the energy consumption wastefulness there is the Virtual Machines Consolidation, which leverages the VM live migration. The goal is to increase the overall cost-efficiency by reducing the number of active nodes. The main contributions of this paper are the proposal of a novel model for the consolidation problem and a Simulated Annealing based algorithm which solves it by evaluating the attractiveness of the possible VM migrations.

In this work we describe and analyze a new Quality of Service (QoS) architecture for wireless mesh networks. Such architecture is mainly composed of two components, i.e. a new admission control criteria for flows and a new link metric. The first allows to only admit flows whose required QoS (specified in terms of bandwidth) can be guaranteed, while the latter allows to maximize the number of accepted flows. In particular, the admission control criteria is designed to precisely evaluate the available bandwidth of the WMN links, which depends not only on the transmission rate of the link but also on the number and the transmission rates of the links in the neighboorhood working on the same channel. The new link metric, instead, is designed to select paths for flows so as to reduce the usage of resources. The proposed architecture relies on the ability of explicitly routing flows. To this purpose, we chose to employ MPLS (Multi Protocol Label Switching), which is able to finely control the path of each single flow. Such possibility further allows to increase the number of accepted flows by exploiting bandwidth where available.

Cloud Computing has risen a great interest over the last years as it represents an enabling technology for flexible and ubiquitous access over the network to a set of shared computing resources. This work comes from an industrial experience aiming at exploiting the cloud potential for virtualizing complex infrastructures such as an entire Air Traffic Center (ATC), a clear example of complex SoS (System of Systems). The use of virtualization is convenient because industry can leverage in-house test-beds to perform distributed testing campaigns in pre-operational phases or to design new automatic fail-over mechanisms for fully distributed systems. In order to realize such mitigation and recovery techniques in the ATC field, indeed, a cloud platform is required to guarantee a low VM provisioning time with the objective of minimizing the service disruption. In this perspective, after having introduced the principal concepts and factors of the provisioning time, we propose a deep analysis and comparison for two different Infrastructure-as-a-Service (IaaS) platforms, namely Open Stack and Open Nebula (using KVM as hypervisor), that were selected through a preliminary scouting phase.

Network virtualization is gaining a lot of interest from the research community thanks to its ability to support new networking paradigms and experimental scenarios. Virtual network embedding (VNE) is a key step for enabling network virtualization and its efficiency allows to maximize the profits of the physical network (also called substrate network) provider. In this paper we focus on the cases where the substrate network consists of a multi-radio IEEE 802.11 wireless mesh network. In such kind of network, bandwidth of a wireless link depends on the rate used to transmit but also on the number of wireless links that use the same channel, because of interference. Exploiting such a property, we propose a heuristic for the online, i.e. requests are not known in advance, VNE problem that is able to increase the profit of the substrate network provider by fictitiously augmenting the network resources and then reconfiguring the channels to avoid congestion.

Welcome to HotMesh 2013: The Fifth IEEE International Workshop on Hot Topics in Mesh Networking. After the very successful editions in Europe (Lucca, Italy) two years ago and in the U.S. last year, we are happy to host this year the workshop in Europe again.

Channel assignment is among the most challenging issues for multiradio wireless mesh networks, given the variety of objectives that can be pursued and the computational complexity of the resulting problems. The channel assignment problem has been also shown to be interdependent with the routing problem, i.e., the problem to determine the amount of traffic flow to be routed on every link. Such a relationship raises the need to recompute the channel assignment every time the traffic pattern changes. However, channel assignment algorithms designed to assign channels from scratch will likely return a completely different configuration of radios, which would disrupt the network operation for the time required to switch to using the links established on the new channels. As shown by the experiments that we conducted, such a time may not be negligible, due to the resistance of routing protocols designed for wireless ad hoc and mesh networks to rapidly flagging a link as established/lost. Such a consideration, along with the observation that channel assignment algorithms may be suboptimal, led us to the design of a channel reassignment algorithm that takes the current channel assignment into account and attempts to cope with the new traffic pattern in the best manner possible while modifying the channel on a limited number of radios. In this paper, we illustrate such a channel reassignment algorithm and evaluate its performance by means of both simulations and experiments with real hardware.

Routing in multi-radio wireless mesh networks is a very challenging problem. In this paper, we propose a forwarding paradigm based on MPLS (Multi Protocol Label Switching) which makes use of a novel mechanism, denoted as MPLS splitting policy. Such mechanism allows to configure multiple next hops at an intermediate node, so that the incoming traffic is partitioned among the next hops according to predefined coefficients named split ratios. The MPLS splitting policy has been designed to allow for load balancing and fast local restoration. With such a mechanism, it is crucial to properly determine the set of split ratios, as they determine how the traffic is routed across the network. We present an approach to compute a set of split ratios that guarantee high performance under different traffic loads. To this end, we adopt the hose traffic model, according to which we only have knowledge of the maximum amount of traffic entering or leaving the network at each edge node. A thorough simulation study is conducted to show that our approach outperforms other routing protocols in terms of throughput and robustness against traffic load variations and single node failures.

In this paper we study the interactions between peer selection, routing and channel assignment while deploying Peer-to-Peer (P2P) systems over multi-channel multi-radio Wireless Mesh Networks (WMNs). In particular we propose Bestpeer, a novel peer selection algorithm for WMNs which incorporates a cross-layer path load metric and integrates multi-path load balancing capability throughout the P2P download process in order to achieve faster resource disseminations. By comparing Bestpeer with BitTorrent through extensive simulations, we show that we can reduce the time to disseminate a resource by up to 40 %. The key mechanism used by Bestpeer to increase performance in WMNs is the effective exploitation of cross-layer information made available from the routing and channel assignment during the peer selection process in order to balance the load along high capacity paths.

Welcome to HotMesh 2012: The Fourth IEEE International Workshop on Hot Topics in Mesh Networking. After the very successful edition in Europe (Lucca, Italy) last year we are happy to host this year workshop in the U.S.

In multi-radio wireless mesh networks, a network device simultaneously transmits packets over different channels by using multiple radios. Such frequency diversity not only in creases throughput but makes multi-path routing approaches extremely interesting. This is because the channel diversity reduces the risk for intra- and inter-flow interference. A fundamental problem to solve is the forwarding strategy which determines which packets to be sent over what multi-path segments at any given time. Ideally, the forwarding strategy should schedule flows according to the capacity constraints imposed by the channel assignment. However, the possibility to improve MAC layer efficiency by aggregating small packets into larger ones is reduced when packets are forwarded to different next-hops. In this paper, we develop a novel packet forwarding strategy for multi-radio mesh networks that combines the benefits of multi-path routing with packet aggregation. In our cross-layer approach, we effectively trade-off aggregation opportunities with channel diversity. Simulation results show that our approach can improve network throughput and delay by up to 15 percent and 25 percent, respectively, compared with aggregation unaware forwarding strategies.

Endowing mesh routers with multiple radios is a recent solution to improve the performance of wireless mesh networks (WMNs). The problem how to route flows and assign channels to radios in multi-radio WMNs has attracted a lot of attention in the recent years. However, the approaches proposed so far have mainly focused on reducing interference or maximizing the throughput. Little attention has been paid to the energy consumption of wireless mesh networks. However, with the rising concerns about the energy consumed by communication infrastructures, it makes sense to consider the minimization of the energy consumption as an objective of the channel assignment and routing problem. Our work stems from the observation that an idle radio simply overhearing a frame consumes nearly the same power as the radio actually receiving the frame. Hence, energy may be saved by turning off a number of radios, if the performance of the network is not impaired. In this paper, we define the energy-efficient channel assignment and routing problem, which is NP-complete, and propose a heuristic algorithm. We also present a Mixed Integer Linear Programs (MILP) to find an optimal solution to the energy-efficient channel assignment and routing problem. Finally, we show the results of extensive simulation studies we conducted to assess the effectiveness of the proposed algorithm. Such results show that our heuristic outperforms a previous proposal and that, on the average, it keeps 10% more radios turned on than the optimal solution.

The ultimate success of the Wireless Mesh Network paradigm (WMN) in large scale deployments depends on the ability to test it in real world scenarios. A typical application scenario which is worth to be investigated in such a context is peer-to-peer traffic management. The creation of large scale testbeds for evaluating wireless mesh technologies and protocols, and for testing their ability to support real world applications in realistic environments, is then a crucial step. OMF (cOntrol and Management Framework) is a well-established control, measurement, and management framework for wireless testbeds. In this paper we present how we integrated an OMF-based wireless testbed in the planetary-scale PlanetLab testbed, making it possible for PlanetLab users to run experiments spanning on both PlanetLab and an OMF-based wireless testbed. In order to demonstrate the usefulness of such an integrated scenario, we tested on it an innovative peer-to-peer traffic optimization technique for the BitTorrent file sharing application. The possibility of running this kind of experiments highlighted several real-world issues which could be investigated thanks to our hybrid experimental scenario.

Wireless Mesh Networks (WMNs) have recently gained wide attention as a way to provide Internet connectivity in hard-to-reach areas as well as in big cities. The main problem of such networks is their limited bandwidth availability compared to wired networks. Hence, efficient usage of available communication resources is of crucial importance for WMNs. Peer-to-peer applications, these days, produce a considerable amount of traffic over the Internet. Such applications build their own overlay network by not taking into account the topology and the status of the underlying infrastructure, so causing an inefficient utilization of physical communication resources. This problem is particularly severe for Wireless Mesh Networks. In this paper we propose a cross-layer solution for P2P Bittorrent traffic optimization in WMNs, based on the ALTO (Application Layer Traffic Optimization) Service recently defined by the IETF. Our solution is able to significantly optimize Bittorrent traffic and it does not require any modification to the Bittorrent application. The tests we performed show a reduction of about 27% of download time and a reduction of about 66% of traffic crossing the WMN borders.

Endowing mesh routers with multiple radios is a recent solution to improve the performance of wireless mesh networks. The approaches proposed in the literature to solve the problem how to assign channels to radio have mainly focused so far on reducing interference or maximizing the throughput. To the best of our knowledge, none of such approaches attempted to save network resources for the purpose of reducing energy consumption and RF emissions. In this paper, a channel assignment and routing algorithm is presented aiming to turn off as many radio interfaces as possible while providing a required level of performance. Simulation studies show that the proposed algorithm enables to achieve nearly the same performance of traditional algorithms while considerably reducing the number of radio interfaces turned on.

In this paper we address the impact of ACI on dynamic spectrum allocation in multi-radio systems. In particular, we present the benefits of dynamic spectrum allocation by adapting channel bandwidth and distance in order to mitigate ACI in multi-radio mesh networks. Based on our measurement campaign in an indoor mesh testbed, which we extended in order to use adaptive channel width, we evaluate the performance in terms of network throughput. We show that by using channel bandwidth adaptation and antenna separation, the impact of ACI can be significantly reduced. The performed experiments give important insights into ACI in multi-radio cognitive systems which help to develop e.g. better channel assignment algorithms or capacity estimation methods.

The focus of this paper is on wireless mesh networks. In particular, we study the multi-radio case, given the considerable improvement in network throughput that multiple radios allow to achieve and the availability of cost-effective wireless devices. Interesting research problems are still unsolved in this field. Due to the scarcity of non-overlapped frequency channels and available radios per node, interference is still present, which cuts the achievable throughput down. As interference depends on how channels are bound to radio interfaces, a proper channel assignment scheme is needed to reduce the interference. In this paper we identify some key requirements of a channel assignment scheme. Accordingly, a centralized channel assignment algorithm is developed for multi-radio wireless mesh networks in order to maximize the throughput and address the interference problems. Finally, a performance study is presented to assess the effectiveness of our proposed algorithm.

Different architectures have been proposed and standardized to provide the users with a certain level of quality of service (QoS). The traffic engineering (TE) concept was then introduced to account for resource optimization, as well as users' QoS requirements, and inspired new architectures. Routing has also been a flourishing research field. Proposed QoS routing algorithms seek a multi-constrained optimal path, while traffic engineering algorithms aim at maximizing throughput. However, architectures and routing algorithms have been developed rather independently of each other. This work presents a comprehensive framework which simultaneously pursues the objectives of resource optimization and QoS assurance while not requesting sophisticated queuing at individual routers. Our approach requires a QoS routing algorithm to compute a path subject to QoS constraints for each flow. We show that properly setting the QoS link weights is crucial to limit the burden imposed on the path selection process. We propose a simple yet effective strategy to set QoS link weights and present some considerations about how to set such weights in practice.

Different architectures have been proposed and standardized to support quality of service (QoS) in the Internet. The goal was to provide the users with a certain level of QoS guarantees. The traffic engineering (TE) concept was then introduced to account for resource optimization, as well as users' QoS requirements, and inspired new architectures. Routing has also been a flourishing research field. Proposed QoS routing algorithms seek a multi-constrained optimal path, while traffic engineering algorithms aim at maximizing throughput and the number of admitted requests. However, architectures and routing algorithms have been developed rather independently of each other. The aim of this work is to present a framework which provides predictable communication services to flows without requiring sophisticated queuing at individual routers. We show that the routing algorithm plays a key role to assure both QoS and resource optimization