Thomas Heide Clausen

Optimized link state routing protocol for ad hoc networks

In this paper we propose and discuss an optimized link state routing protocol, named OLSR, for mobile wireless networks. The protocol is based on the link state algorithm and it is proactive (or table-driven) in nature. It employs periodic exchange of messages to maintain topology information of the network at each node. OLSR is an optimization over a pure link state protocol as it compacts the size of information sent in the messages, and furthermore, reduces the number of retransmissions to flood these messages in an entire network. For this purpose, the protocol uses the multipoint relaying technique to efficiently and economically flood its control messages. It provides optimal routes in terms of number of hops, which are immediately available when needed. The proposed protocol is best suitable for large and dense ad hoc networks.

A Study of LoRa: Long Range & Low Power Networks for the Internet of Things

LoRa is a long-range, low-power, low-bitrate, wireless telecommunications system, promoted as an infrastructure solution for the Internet of Things: end-devices use LoRa across a single wireless hop to communicate to gateway(s), connected to the Internet and which act as transparent bridges and relay messages between these end-devices and a central network server. This paper provides an overview of LoRa and an in-depth analysis of its functional components. The physical and data link layer performance is evaluated by field tests and simulations. Based on the analysis and evaluations, some possible solutions for performance enhancements are proposed.

A critical evaluation of the IPv6 Routing Protocol for Low Power and Lossy Networks (RPL)

With RPL - the “IPv6 Routing Protocol for Low-power Lossy Networks” - emerging as a Proposed Standard “Request For Comment” (RFC) in the Internet Engineering Task Force (IETF) after a ∼2-year development cycle, this paper presents a critical evaluation of the resulting protocol and its applicability and limits. The paper presents a selection of observations of the protocol characteristics, exposes experiences acquired when producing a prototype implementation of RPL, and presents results obtained from testing this protocol - both in a network simulator, and in real-world experiments on a wireless sensor network testbed. The paper aims at providing a better understanding of possible weaknesses and limits of RPL, notably the possible directions that further protocol developments should explore, in order to address these.

Fish eye OLSR scaling properties

Scalability is one of the toughest challenges in ad hoc networking. Recent work outlines theoretical bounds on how well routing protocols could scale in this environment. However, none of the popular routing solutions really scales to large networks, by coming close enough to these bounds. In this paper, we study the case of link state routing and OLSR, one of the strongest candidates for standardization. We analyze how these bounds are not reached in this case, and we study how much the scalability is enhanced with the use of Fish eye techniques in addition to the link state routing framework. We show that with this enhancement, the theoretical scalability bounds are reached.

A comparative performance study of the routing protocols LOAD and RPL with bi-directional traffic in low-power and lossy networks (LLN)

Routing protocols for sensor networks are often designed with explicit assumptions, serving to simplify design and reduce the necessary energy, processing and communications requirements. Different protocols make different assumptions - and this paper considers those made by the designers of RPL - an IPv6 routing protocol for such networks, developed within the IETF. Specific attention is given to the predominance of bi-directional traffic flows in a large class of sensor networks, and this paper therefore studies the performance of RPL for such flows. As a point of comparison, a different protocol, called LOAD, is also studied. LOAD is derived from AODV and supports more general kinds of traffic flows. The results of this investigation reveal that for scenarios where bi-directional traffic flows are predominant, LOAD provides similar data delivery ratios as RPL, while incurring less overhead and being simultaneously less constrained in the types of topologies supported.

Comparative study of RPL-enabled optimized broadcast in Wireless Sensor Networks

Recent trends have suggested convergence to Wireless Sensor Networks (WSNs) becoming IPv6-based. To this effect, the Internet Engineering Task Force has chartered a Working Group to develop a routing protocol specification, enabling IPv6-based multi-hop WSNs. The current effort of this working group is development of a unicast routing protocol denoted RPL. RPL constructs a “DAG-like” logical structure with a single root, at which the majority of the traffic flows terminate, and assumes restrictions on network dynamics and traffic generality, in order to satisfy strict constraints on router state and processing. This paper investigates the efficient network-wide broadcast mechanisms in WSNs, using the logical structure already established by RPL. The aim hereof is to impose minimal additional state requirements on WSN routers, beyond that already maintained by RPL. This paper presents a selection of such broadcast mechanisms for RPL routed WSNs, and evaluates their performances. As part of this evaluation, the paper compares with MPR Flooding - an established efficient flooding optimization, widely used in MANETs.

Multipoint-to-Point and Broadcast in RPL

Recent trends in Wireless Sensor Networks (WSNs) have suggested converging to such being IPv6-based. To this effect, the Internet Engineering Task Force has chartered a Working Group to develop a routing protocol specification, enabling IPv6-based multi-hop Wireless Sensor Networks. This routing protocol, denoted RPL, has been under development for approximately a year, and this paper takes a critical look at the state of advancement hereof: it provides a brief algorithmic description of the protocol, and discusses areas where -- in the authors view -- further efforts are required in order for the protocol to become a viable candidate for general use in WSNs. Among these areas is the lack of a proper broadcast mechanism. This paper suggests two such broadcast mechanisms, both aiming at (i) exploiting the existing routing state of RPL, while (ii) requiring no additional state maintenance, and studies the performance of RPL and of these suggested mechanisms.

Evaluation of routing protocol for low power and Lossy Networks: LOADng and RPL

Routing protocol is a critical component of Low-power and Lossy Networks for Smart Grid. The protocols are used for data forwarding, which includes data acquisition, information dissemination, etc. This paper evaluates two main routing protocols used for Low-power and Lossy Networks: RPL and LOADng, to understand their strengths and limitations. Observations are provided based on analysis of specification and experimental experience, regarding the protocols routing overhead, traffic pattern, resource requirement, fragmentation, etc. Simulations are further launched to study the performance in different traffic patterns, which include sensor-to-sensor traffic, sensor-to-root traffic and root-to-sensor bidirectional traffic. By evaluating those protocols, the readers could have better understanding of the protocol applicability, and choose the appropriate protocol for desired applications.

Vulnerability analysis of the optimized link state routing protocol version 2 (OLSRv2)

Mobile Ad hoc NETworks (MANETs) are leaving the confines of research laboratories, to find place in real-world deployments. Outside specialized domains (military, vehicular, etc.), citywide community-networks are emerging, connecting regular Internet users with each other, and with the Internet, via MANETs. Growing to encompass more than a handful of “trusted participants”, the question of preserving the MANET network connectivity, even when faced with careless or malicious participants, arises, and must be addressed.

IPv6 operation for WAVE — Wireless Access in Vehicular Environments

The IEEE WAVE protocol suite is providing communications services to applications in vehicular networks, by way of promising support for two protocol stacks: the Wave Short Message Protocol (WSMP) and IPv6. While WSMP is developed within the IEEE 1609 family of standards, the authors of this paper assert, that considerations for IPv6 operation for WAVE are less developed, and several issues are left unaddressed by the current IEEE 1609 specifications. This paper reviews these issues and analyzes the main challenges in providing proper IPv6 operation for WAVE networks.