Medium Access Control and Routing Protocols Design for 5G

In future wireless systems, such as 5G and beyond, the current dominating human-centric communication systems will be complemented by a tremendous increase in the number of smart devices, equipped with radio devices, possibly sensors, and uniquely addressable. This will result in explosion of wireless traffic volume, and consequently exponential growth in demand of radio spectrum. There are different engineering techniques for resolving the cost and scarcity of radio spectrum such as coexistence of diverse devices on the same pool of radio resources, spectrum aggregations, adoption of mmWave bands with huge spectrum, etc. The aim of this thesis is to investigate Medium Access Control (MAC) and routing protocols for 5G and beyond radio networks. Two scenarios are addressed: heterogeneous scenario where scheduled and uncoordinated users coexist, and a scenario where drones are used for monitoring a given area. In the heterogeneous scenario scheduled users are synchronised with the Base Station (BS) and rely on centralised resource scheduler for assignment of time slots, while the uncoordinated users are asynchronous with each other and the BS and rely unslotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) for channel access. First, we address a single-hop network with advanced scheduling algorithm design and packet length adaptation schemes design. Second, we address a multi-hop network with novel routing protocol for enhancing performance of the scheduled users in terms of throughput, and coexistence of all network users. In the drone-based scenario, new routing protocols are designed to address the problems of Wireless Mesh Networks with monitoring drones. In particular, a novel optimised Hybrid Wireless Mesh Protocol (O-HWMP) for a quick and efficient discovery of paths is designed, and a capacity achieving routing and scheduling algorithm, called backpressure, investigated. To improve on the long-end-to-end delays of classical backpressure, a modified backpressure algorithm is proposed and evaluated

Neighbors-Aware Proportional Fair scheduling for future wireless networks with mixed MAC protocols

Abstract In this paper, we consider a beyond-5G scenario, where two types of users, denoted as scheduled and uncoordinated nodes, coexist on the same set of radio resources for sending data to a base station. Scheduled nodes rely solely on a centralized scheduler within the base station for the assignment of resources, while uncoordinated nodes use an unslotted Carrier Sense Multiple Access (CSMA) protocol for channel access. We propose and evaluate through simulations: (a) a novel centralized resource scheduling algorithm, called Neighbors-Aware Proportional Fair (N-PF) and (b) a novel packet length adaptation algorithm, called Channel-Aware (CA) Packet Length Adaptation algorithm for the scheduled nodes. The N-PF algorithm considers the uplink channel state conditions and the number of uncoordinated nodes neighboring each scheduled node in the aggregate scheduling metric, in order to maximize packet transmission success probability. The CA algorithm provides an additional degree of freedom for improving the performance, thanks to the fact that scheduled nodes with lower number of hidden terminals, i.e., having higher packet capture probability, are assigned longer packet transmission opportunities. We consider two benchmark schemes: Proportional Fair (PF) algorithm, as a resource scheduling algorithm, and a discrete uniform distribution (DUD) scheme for packet lengths distribution. Simulation results show that the proposed schemes can result in significant gain in terms of network goodput, without compromising fairness, with respect to two benchmark solutions taken from the literature

Mac protocols for linear wireless (sensor) networks

Wireless sensor networks (WSNs) consist of a large number of sensor nodes, characterized by low power constraint, limited transmission range and limited computational capabilities [1][2].The cost of these devices is constantly decreasing, making it possible to use a large number of sensor devices in a wide array of commercial, environmental, military, and healthcare fields. Some of these applications involve placing the sensors evenly spaced on a straight line for example in roads, bridges, tunnels, water catchments and water pipelines, city drainages, oil and gas pipelines etc., making a special class of these networks which we define as a Linear Wireless Network (LWN). In LWNs, data transmission happens hop by hop from the source to the destination, through a route composed of multiple relays. The peculiarity of the topology of LWNs, motivates the design of specialized protocols, taking advantage of the linearity of such networks, in order to increase reliability, communication efficiency, energy savings, network lifetime and to minimize the end-to-end delay [3]. In this thesis a novel contention based Medium Access Control (MAC) protocol called L-CSMA, specifically devised for LWNs is presented. The basic idea of L-CSMA is to assign different priorities to nodes based on their position along the line. The priority is assigned in terms of sensing duration, whereby nodes closer to the destination are assigned shorter sensing time compared to the rest of the nodes and hence higher priority. This mechanism speeds up the transmission of packets which are already in the path, making transmission flow more efficient. Using NS-3 simulator, the performance of L-CSMA in terms of packets success rate, that is, the percentage of packets that reach destination, and throughput are compared with that of IEEE 802.15.4 MAC protocol, de-facto standard for wireless sensor networks. In general, L-CSMA outperforms the IEEE 802.15.4 MAC protocol

A Novel Routing and Scheduling Algorithm for Multi-Hop Heterogeneous Wireless Networks

In this paper, we address the problem of scheduling and routing design in a multi-hop heterogeneous radio network. The scenario consists of two types of nodes: scheduled nodes, which depend upon a centralised resource scheduling scheme, and uncoordinated nodes, which employ an asynchronous Carrier Sense Multiple Access (CSMA) based medium access control protocol. Both types of nodes co-exist on the same spectrum and may interfere each other. In fact, scheduled nodes are synchronized to the Base Station (BS) and communicate to it in a multi-hop fashion, while uncoordinated users are asynchronous with respect to the BS and the other nodes. Our work focuses on the problem of routing and scheduling for the scheduled set of nodes, with the aim of avoiding interference caused by CSMA nodes. In particular, we propose a Coexistence-Aware (CA) routing scheme, based on the definition of a novel link cost metric accounting for the number of potential uncoordinated nodes interfering. The output of the CA routing scheme serves an input to a Multi-Link Proportional Fair (MLPF) scheme, where a new scheduling metric, accounting for the number of hops needed to reach the BS, is designed. The proposed algorithm is compared with a benchmark solution, where routing is based on the level of received power over the links and where the MLPF algorithm presented in the literature is applied. Results show the improvement achieved with the proposed solution

Neighbours-aware proportional fair scheduler for future wireless networks

n this paper, we present an uplink scenario where primary and secondary users coexist on the same set of radio resources. The primary users rely solely on a centralised scheduler within the base station for the assignment of resources, and the secondary users rely on an unslotted Carrier Sense Multiple Access (CSMA) protocol for channel access. We propose a novel centralised scheduling algorithm, Neighbours-Aware Proportional Fair (N-PF), which considers the uplink channel state conditions and the number of secondary users neighbouring each primary user in the aggregate scheduling metric. Through simulations we demonstrate that N-PF outperforms the chosen benchmark algorithm, Proportional Fair (PF), in terms of packet delivery rate while maintaining fairness. © ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2016

Routing protocols for video surveillance drones in IEEE 802.11s Wireless Mesh Networks

In this paper we consider a video surveillance application, using a camera mounted on a drone flying over the area to be monitored and sending the video to a control center (CC). In order to ensure connectivity between the drone and the CC some relays are deployed on the ground. The resulting network is composed of a static component (relays), and a moving component (the drone). All network devices are assumed to be equipped with IEEE 802.11s air interfaces. The goal of our work is to design and validate a routing protocol appropriate for this scenario. The IEEE 802.11s standard proposes Hybrid Wireless Mesh routing Protocol (HWMP) composed of a proactive tree-based routing and the reactive Radio Metric Ad-hoc On-Demand Distance Vector (RM-AODV) scheme to support mesh networks. To address the need for reliable connectivity, faster and resource-efficient path discovery, we envisage a mixed optimized scheme, called Optimized-Hybrid Wireless Mesh Protocol (O-HWMP), where both, RM-AODV and the proactive tree-based scheme, are used at the same time. In O-HWMP the output of the tree-based routing scheme provides input to the RM-AODV, in order to reduce flooding of control packets, and to minimize delays during path discovery. Through NS3-Evalvid simulations we demonstrate that, compared to RM-AODV scheme, our proposed protocol significantly improves network performance in terms of delays, packet success rate, overhead cost, and peak-signal-to-noise-ratio metric of the received video

Routing protocols for video surveillance drones in IEEE 802.11s Wireless Mesh Networks

In this paper we consider a video surveillance application, using a camera mounted on a drone flying over the area to be monitored and sending the video to a control center (CC). In order to ensure connectivity between the drone and the CC some relays are deployed on the ground. The resulting network is composed of a static component (relays), and a moving component (the drone). All network devices are assumed to be equipped with IEEE 802.11s air interfaces. The goal of our work is to design and validate a routing protocol appropriate for this scenario. The IEEE 802.11s standard proposes Hybrid Wireless Mesh routing Protocol (HWMP) composed of a proactive tree-based routing and the reactive Radio Metric Ad-hoc On-Demand Distance Vector (RM-AODV) scheme to support mesh networks. To address the need for reliable connectivity, faster and resource-efficient path discovery, we envisage a mixed optimized scheme, called Optimized-Hybrid Wireless Mesh Protocol (O-HWMP), where both, RM-AODV and the proactive tree-based scheme, are used at the same time. In O-HWMP the output of the tree-based routing scheme provides input to the RM-AODV, in order to reduce flooding of control packets, and to minimize delays during path discovery. Through NS3-Evalvid simulations we demonstrate that, compared to RM-AODV scheme, our proposed protocol significantly improves network performance in terms of delays, packet success rate, overhead cost, and peak-signal-to-noise-ratio metric of the received video

UAV-to-Ground Multi-Hop Communication Using Backpressure and FlashLinQ-Based Algorithms

The use of Unmanned Aerial Vehicles (UAVs) for remote sensing and surveillance applications has become increasingly popular in the last decades. This paper investigates the communication between a UAV and a final control center (CC), using static relays located on the ground, to overcome the intermittent connectivity between the two end points, due to the UAV flight. Backpressure and FlashLinQ routing and scheduling algorithms are jointly applied to this scenario. Backpressure has been shown to be able stabilize any input traffic within the network capacity region without requiring knowledge of traffic arrival rates and channel state probabilities. FlashLinQ is used in the scheduling phase to derive a maximal feasible subset of links which can coexist on a given slot without causing harmful interference to each other. Moreover, to overcome the limit on long end-to-end delays of backpressure, we propose a modified algorithm, where relays are selected depending on their proximity to the CC and on the UAV trajectory. Through extensive simulations, we demonstrate that, compared to the benchmark solution based on backpressure, the proposed algorithm is able to reduce delay significantly without any loss in throughput gain