José Núñez-Martínez

Validation of the IEEE 802.11 MAC model in the ns3 simulator using the EXTREME testbed

We validate the IEEE 802.11 MAC layer model in ns3 by means of measurements on the EXTREME testbed. We consider different scenarios: communications within a single pair of nodes, multi-user communications using either VoIP or saturated traffic, and communications in the presence of hidden nodes. For each scenario we describe in detail our testbed and simulation setup, and compare the results provided by the ns3 simulator with the performance measured on the testbed.

A Survey on Routing Protocols that really Exploit Wireless Mesh Network Features

The design of a routing protocol that really exploits the specific features of a Wireless Mesh Network (WMN) still remains a challenge. The expected additional benefit, with respect to those that do not or cannot exploit them, is an increase in overall throughput supported by the network. The static and non-power constrained nature of backbone nodes allow offering some exploitable features towards this goal, such as multi-radio and multi-channel support, stability, and increased CPU and storage capabilities. Such features have a strong impact on the design of the routing scheme, which makes inefficient to port existing solutions from wired and other wireless networks. As a consequence, in recent years, many alternative routing protocols have been proposed for WMNs. This survey paper presents the current stateof- the-art of routing protocols specifically designed for WMNs that try to maximize the throughput transferred by the network. First, a classification of routing protocols is provided. Second, the routing architecture is decomposed into three major building blocks. Open research issues related to each building block are also discussed. And finally, the main characteristics of the building blocks for each relevant routing protocol in the taxonomy are summarized.

The CTTC 5G End-to-End Experimental Platform : Integrating Heterogeneous Wireless\/Optical Networks, Distributed Cloud, and IoT Devices

The Internet of Things (IoT) will facilitate a wide variety of applications in different domains, such as smart cities, smart grids, industrial automation (Industry 4.0), smart driving, assistance of the elderly, and home automation. Billions of heterogeneous smart devices with different application requirements will be connected to the networks and will generate huge aggregated volumes of data that will be processed in distributed cloud infrastructures. On the other hand, there is also a general trend to deploy functions as software (SW) instances in cloud infrastructures [e.g., network function virtualization (NFV) or mobile edge computing (MEC)]. Thus, the next generation of mobile networks, the fifth-generation (5G), will need not only to develop new radio interfaces or waveforms to cope with the expected traffic growth but also to integrate heterogeneous networks from end to end (E2E) with distributed cloud resources to deliver E2E IoT and mobile services. This article presents the E2E 5G platform that is being developed by the Centre Tecnol?gic de Telecomunicacions de Catalunya (CTTC), the first known platform capable of reproducing such an ambitious scenario.

Traffic and Mobility Management in Networks of Femtocells

A deployment of femtocells that is harmonic with its environment is a challenging issue. In this respect, interference management has traditionally been in the spotlight. However, architectural improvements for efficient femtocell deployments, despite being equally relevant, have received less attention. This paper presents a system architecture conceived for efficiently deploying femtocells in the form of Networks of Femtocells (NoFs). In this scenario, a group of femtocells in the same administrative domain cooperate towards a global performance improvement. Key to this improvement is the introduction of a new entity called Local Femto Gateway (LFGW) and the modifications in the femtocells in the local network. This allows offloading a high volume of control and data traffic from the core network of the mobile operator to the functional entities in the NoF. In particular, this paper focuses on building blocks related to traffic and mobility management. A two-level routing approach is discussed. The highest level is carried out by the mobile network layer. It is in charge of (1) determining the communication endpoints in the form of GPRS Tunneling Protocol (GTP) tunnel endpoint IDs, and (2) forwarding packets between tunnels belonging to the same Evolved Packet System (EPS) bearer at the appropriate nodes. Solutions for efficient handoff, local breakout, and local location management are presented for this level of routing. On the other hand, the lowest-level routing is carried out by the transport network layer. This level is in charge of finding the path between the above endpoints by efficiently using the local transport network that interconnects the femtocells in the NoF. A distributed routing solution for a large-scale, all-wireless network of femtocells is also presented. Overall, these architectural improvements render NoFs a promising approach for efficient traffic management in large-scale femtocell deployments, hence making them a scalable solution.

Studying Practical Any-to-Any Backpressure Routing in Wi-Fi Mesh Networks from a Lyapunov Optimization Perspective

This paper studies practical backpressure routing strategies in WiFi-based Mesh Networks (WMN). It is practical in the sense that, unlike previous theoretical centralized algorithms, we present a distributed implementation of the algorithm with low queue complexity (i.e., one finite data queue at each node) to deal with any-to-any communications. To our knowledge, this is the first practical study based on Neelys Lyapunov optimization framework for WMNs. In fact, we propose a scalable and distributed routing policy that takes control actions based on Lyapunovs drift-plus-penalty minimization combinining local queue backlog and 1-hop geographic information. We characterize its strengths and weaknesses against network performance metrics such as throughput, delay, and fairness. By means of ns-3 simulations under different configuration setups, we study the impact of the weight of the penalty function on the network performance metrics. In addition, we show the influence of the location of the source-destination pairs in these configuration setups. Finally, we evaluate the objective function-backlog trade-off that characterizes Lyapunov optimization frameworks.

Evaluation of the fast handover implementation for mobile IPv6 in a real testbed

Fast Handovers is an enhancement to the Mobile IPv6 protocol, currently specified in an IETF draft, which reduces the handover latency. This can be beneficial to real-time applications. This paper presents a novel implementation of Fast Handovers and an analysis of the handover. Using a real testbed we study the handover latency and the provided QoS: analyzing the OWD, IPDV and Packet Loss before and after the handover. Finally we present a comparison between the Mobile IPv6 and the Fast Handovers handover.

A self-organized backpressure routing scheme for dynamic small cell deployments

The increase of demand for mobile data services requires a massive network densification. A cost-effective solution to this problem is to reduce cell size by deploying a low-cost all-wireless Network of Small Cells (NoS). These hyper-dense deployments create a wireless mesh backhaul among Small Cells (SCs) to transport control and data plane traffic. The semi-planned nature of SCs can often lead to dynamic wireless mesh backhaul topologies.This paper presents a self-organized backpressure routing scheme for dynamic SC deployments (BS) that combines queue backlog and geographic information to route traffic in dynamic NoS deployments. BS aims at relieving network congestion, while having a low routing stretch (i.e., the ratio of the hop count of the selected paths to that of the shortest path). Evaluation results show that, under uncongested conditions, BS shows similar performance to that of an Idealized Shortest PAth routing protocol (ISPA), while outperforming Greedy Perimeter Stateless Routing (GPSR), a state of the art geographic routing scheme. Under more severe traffic conditions, BS outperforms both GPSR and ISPA in terms of average latency by up to a 85% and 70%, respectively. We conducted ns-3 simulations in a wide range of sparse NoS deployments and workloads to support these performance claims.

Terrestrial-satellite integration in dynamic 5G backhaul networks

This paper presents a dynamic backhaul network in order to face some of the main 5G challenges such as 100% coverage, improved capacity or reduction in energy consumption. The proposed solution, elaborated within the SANSA H2020 project, is based on the seamless integration of the satellite component in a terrestrial network capable of reconfiguring its topology according to the traffic demands. The paper highlights the benefits of this hybrid network and describes the technology enablers to bring it to the reality. Finally, the SANSAs network simulation framework based on ns3 is presented, jointly with a preliminary analysis of the routing and load balancing needs for a hybrid and dynamic network.

A service-based model for the hybrid software defined wireless mesh backhaul of small cells

The backhaul of upcoming dense 5G Small Cell (SC) networks needs a full redesign, but there is no clear consensus on how to deploy such infrastructure. A low-cost backhaul solution is that provided by a wireless mesh network. Additionally, Software Defined Networking (SDN) is being considered as an alternative to distributed approaches to lower network infrastructure costs while enabling programmability and flexibility mostly for wired networks. This paper evolves the canonical SDN model by presenting a service-based hybrid SDN (hSDN) model that alleviates the problems caused by the unreliability of the in-band control channel formed by a wireless mesh backhaul between the SDN controller and the SCs. At the infrastructure level, we propose a wireless mesh backhaul combining sub-6GHz and millimeter wave links with long range microwave links. This architecture pursues the coexistence of network services located on top of a centralized SDN controller, with distributed network services, such as routing. To show the robustness of our proposed model, we compare a service-based hSDN model and a canonical SDN model under perfect control plane communication channel. In our service-based hSDN model, we further compare two distributed routing schemes used as fallback control plane mechanisms when the SDN controller is unreachable. Simulation results with ns-3 show improvements of up to 1.5x and 6x in terms of throughput and latency, respectively.

Distributed Lyapunov drift-plus-penalty routing for WiFi mesh networks with adaptive penalty weight

In our previous work on distributed backpressure routing for WiFi mesh networks (WMN), we showed that backpressure routing when combined with geographic information results in a (quasi-)stateless low-overhead (hence scalable) routing solution. Specifically, the Lyapunov drift-plus-penalty optimization framework allows trading off between 1) routing decisions for maintaining queue backlogs under control (and hence, the network stable) and 2) those that try to get close to the optimal value of an objective performance metric. Such framework offers a non-negative parameter (V) for weighting both components. However, fixed-V policies cannot efficiently handle WMN traffic dynamics in practical setups, as they will lead to queue overflows and degradation of the objective metrics. In this paper, we propose the first practical distributed variable-V algorithm that takes routing decisions aiming at achieving ideal objective metric values, yet not incurring into queue overflows. Furthermore, we compare variable- and fixed- V policies under several network setups. The simulation results obtained with ns-3 show that the variable-V policy is not only able to obtain the same throughput as that of the best fixed- V policy, but also to remarkably reduce the variability and maximum values of packet delay.