Jiazi Yi

Multipath optimized link state routing for mobile ad hoc networks

Multipath routing protocols for Mobile Ad hoc NETwork (MANET) address the problem of scalability, security (confidentiality and integrity), lifetime of networks, instability of wireless transmissions, and their adaptation to applications. Our protocol, called MultiPath OLSR (MP-OLSR), is a multipath routing protocol based on OLSR [1]. The Multipath Dijkstra Algorithm is proposed to obtain multiple paths. The algorithm gains great flexibility and extensibility by employing different link metrics and cost functions. In addition, route recovery and loop detection are implemented in MP-OLSR in order to improve quality of service regarding OLSR. The backward compatibility with OLSR based on IP source routing is also studied. Simulation based on Qualnet simulator is performed in different scenarios. A testbed is also set up to validate the protocol in real world. The results reveal that MP-OLSR is suitable for mobile, large and dense networks with large traffic, and could satisfy critical multimedia applications with high on time constraints.

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.

Simulation and Performance Analysis of MP-OLSR for Mobile Ad Hoc Networks

Mobile ad hoc networks (MANETs) consist of a collection of wireless mobile nodes which dynamically exchange data without reliance on a fixed base station or a wired backbone network, which makes routing a crucial issue for the design of a ad hoc networks. In this paper we discussed a hybrid multipath routing protocol named MP-OLSR. It is based on the link state algorithm and employs periodic exchange of messages to maintain topology information of the networks. In the mean time, it updates the routing table in an on-demand scheme and forwards the packets in multiple paths which have been determined at the source. If a link failure is detected, the algorithm recovers the route automatically. Concerning the instability of the wireless networks, the redundancy coding is used to improve the delivery ratio. The simulation in NS2 shows that the new protocol can effectively improve the performance of the networks.

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.

Collection Tree Extension of Reactive Routing Protocol for Low-Power and Lossy Networks

This paper proposes an extension to reactive routing protocol, for efficient construction of a collection tree for data acquisition in sensor networks. The Lightweight On-Demand Ad hoc Distance Vector Routing Protocol-Next Generation (LOADng) is a reactive distance vector protocol which is intended for use in mobile ad hoc networks and low-power and lossy networks to build paths between source-destination pairs. In 2013, ITU-T has ratified the recommendation G.9903 Amendment 1, which includes LOADng in a specific normative annex for routing protocol in smart grids. The extension uses the mechanisms from LOADng, imposes minimal overhead and complexity, and enables a deployment to efficiently support “sensor-to-root” traffic, avoiding complications of unidirectional links in the collection tree. The protocol complexity, security, and interoperability are examined in detail. The simulation results show that the extension can effectively improve the efficiency of data acquisition in the network.

An Adaptive Jitter Mechanism for Reactive Route Discovery in Sensor Networks

This paper analyses the impact of jitter when applied to route discovery in reactive (on-demand) routing protocols. In multi-hop non-synchronized wireless networks, jitter—a small, random variation in the timing of message emission—is commonly employed, as a means to avoid collisions of simultaneous transmissions by adjacent routers over the same channel. In a reactive routing protocol for sensor and ad hoc networks, jitter is recommended during the route discovery process, specifically, during the network-wide flooding of route request messages, in order to avoid collisions. Commonly, a simple uniform jitter is recommended. Alas, this is not without drawbacks: when applying uniform jitter to the route discovery process, an effect called delay inversion is observed. This paper, first, studies and quantifies this delay inversion effect. Second, this paper proposes an adaptive jitter mechanism, designed to alleviate the delay inversion effect and thereby to reduce the route discovery overhead and (ultimately) allow the routing protocol to find more optimal paths, as compared to uniform jitter. This paper presents both analytical and simulation studies, showing that the proposed adaptive jitter can effectively decrease the cost of route discovery and increase the path quality.

Performance analysis of Trickle as a flooding mechanism

“The Trickle Algorithm” is conceived as an adaptive mechanism for allowing efficient and reliable information sharing among nodes, communicating across a lossy and shared medium. Its basic principle is, for each node, to monitor transmissions from its neighbours, compare what it receives with its current state, and schedule future transmissions accordingly: if an inconsistency of information is detected, or if few or no neighbours have transmitted consistent information “recently”, the next transmission is scheduled “soon” - and, in case consistent information from a sufficient number of neighbours is received, the next transmission is scheduled to be “later”. Developed originally as a means of distributing firmware updates among sensor devices, this algorithm has found use also for distribution of routing information in the routing protocol RPL, standardised within the IETF for maintaining a routing topology for low-power and lossy networks (LLNs). Its use is also proposed in a protocol for multicast in LLNs, denoted “Multicast Forwarding Using Trickle”. This paper studies the performance of the Trickle algorithm, as it is used in that multicast protocol.

Smart Route Request for on-demand route discovery in constrained environments

A derivative of AODV, denoted LOADng, is proposed for use in very constrained environment, sacrificing a number of features from AODV for the benefit of smaller control messages and simpler processing logic. Among these sacrifices is intermediate route replies. This paper presents an alternative to intermediate router replies, denoted Smart Route Request, which provides an optimization similar to that attainable by intermediate route requests, but without imposing additional processing complexity or additional signaling. A performance study is presented, showing that the use of Smart Route Requests can effectively reduce the control traffic overhead from Route Requests, while retaining the simplicity of LOADng. LOADng with Smart Route Requests effectively reduces control traffic overhead and on-link traffic collisions, and this especially for multipoint-to-point traffic.

Lightweight On-demand Ad hoc Distance-vector Routing - Next Generation (LOADng): Protocol, extension, and applicability

Abstract This paper studies the routing protocol “Lightweight On-demand Ad hoc Distance-vector Routing Protocol – Next Generation (LOADng)”, designed to enable efficient, scalable and secure routing in low power and lossy networks. As a reactive protocol, it does not maintain a routing table for all destinations in the network, but initiates a route discovery to a destination only when there is data to be sent to that destination to reduce routing overhead and memory consumption. Designed with a modular approach, LOADng can be extended with additional components for adapting the protocol to different topologies, traffic, and data-link layer characteristics. This paper studies several such additional components for extending LOADng: support for smart route requests and expanding ring search, an extension permitting maintaining collection trees, a fast rerouting extension. All those extensions are examined from the aspects of specification, interoperability with other mechanisms, security vulnerabilities, performance and applicability. A general framework is also proposed to secure the routing protocol.

Depth first forwarding for low power and lossy networks: Application and extension

Data delivery across a multi-hop low-power and lossy networks (LLNs) is a challenging task: devices participating in such a network have strictly limited computational power and storage, and the communication channels are of low capacity, time-varying and with high loss rates. Consequently, routing protocols finding paths through such a network must be frugal in their control traffic and state requirements, as well as in algorithmic complexity - and even once paths have been found, these may be usable only intermittently, or for a very short time due to changes on the channel. Routing protocols exist for such networks, balancing reactivity to topology and channel variation with frugality in resource requirements. Complementary component to routing protocols for such LLNs exist, intended not to manage global topology, but to react rapidly to local data delivery failures and (attempt to) successfully deliver data while giving a routing protocol time to recover globally from such a failure. Specifically, this paper studies the “Depth-First Forwarding (DFF) in Unreliable Networks” protocol, standardised within the IETF in June 2013. Moreover, this paper proposes optimisations to that protocol, denoted DFF++, for improved performance and reactivity whilst remaining fully interoperable with DFF as standardised, and incurring neither additional data sets nor protocol signals to be generated.