Routing and mobility approaches in IPv6 over LoWPAN mesh networks

It is foreseeable that any object in the near future will have an Internet connection—this is the Internet of Things vision. All these objects will be able to exchange and process information, most of them characterized by small size, power constrained, small computing and storage resources. In fact, connecting embedded low‐power devices to the Internet is considered the biggest challenge and opportunity for the Internet. There is a strong trend of convergence towards an Internet‐based solution and the 6LoWPAN may be the convergence solution to achieve the Internet of Things vision. Wireless mesh networks have attracted the interest of the scientific community in recent years. One of the key characteristics of wireless mesh networks is the ability to self‐organize and self‐configure. Mesh networking and mobility support are considered crucial to the Internet of Things success. This paper surveys the available solutions proposed to support routing and mobility over 6LoWPAN mesh networks. Copyright © 2011 John Wiley & Sons, Ltd.     

Cluster‐based mobility management algorithms for wireless mesh networks

Wireless mesh networks (WMNs) have been the recent advancements and attracting more academicians and industrialists for their seamless connectivity to the internet. Radio resource is one among the prime resources in wireless networks, which is expected to use in an efficient way especially when the mobile nodes are on move. However, providing guaranteed quality of service to the mobile nodes in the network is a challenging issue. To accomplish this, we propose 2 clustering algorithms, namely, static clustering algorithm for WMNs and dynamic clustering algorithm for WMNs. In these algorithms, we propose a new weight‐based cluster head and cluster member selection process for the formation of clusters. The weight of the nodes in WMN is computed considering the parameters include the bandwidth of the node, the degree of node connectivity, and node cooperation factor. Further, we also propose enhanced quality of service enabled routing protocol for WMNs considering the delay, bandwidth, hopcount, and expected transmission count are the routing metrics. The performance of the proposed clustering algorithms and routing protocol are analyzed, and results show high throughput, high packet delivery ratio, and low communication cost compared with the existing baseline mobility management algorithms and routing protocols.     

Metric anticipation to manage mobility in mobile mesh and ad hoc wireless networks

In mobile ad hoc networks (MANETs), node mobility management is performed by the routing protocol. It may use metrics to reflect link state/quality. But, the delay between measures of the link quality and its integration in the route computation is very detrimental to the mobility management. Consequently, routing protocols may use lossy links for a few seconds leading to a significant performance deterioration. In this paper, we propose a new routing metric technique calculation which aims at anticipating link quality. Basically, the idea is to predict metric values a few seconds in advance, in order to compensate the delay involved by the link quality measurement and their dissemination by the routing protocol. Our technique is based on measurements of signal strength and is integrated in two classical routing metrics: ETX (expected transmission count) and ETT (expected transmission time). Validations are performed through both simulations and a testbed experimentation with OLSR as routing protocol. NS-3 simulations show that our metric may lead to a perfect mobility management with a packet delivery ratio of 100%. Experiments on a testbed prove the feasibility of our approach and show that this technique reduces the packet error rate by a factor of 3 in an indoor environment compared to the classical metrics calculation.     

A unified mobility model for analysis and simulation of mobile wireless networks

We propose a novel mobility model, named Semi-Markov Smooth (SMS) model, to characterize the smooth movement of mobile users in accordance with the physical law of motion in order to eliminate sharp turns, abrupt speed change and sudden stops exhibited by existing models. We formulate the smooth mobility model by a semi-Markov process to analyze the steady state properties of this model because the transition time between consecutive phases (states) has a discrete uniform distribution, instead of an exponential distribution. Through stochastic analysis, we prove that this model unifies many good features for analysis and simulations of mobile networks. First, it is smooth and steady because there is no speed decay problem for arbitrary starting speed, while maintaining uniform spatial node distribution regardless of node placement. Second, it can be easily and flexibly applied for simulating node mobility in wireless networks. It can also adapt to different network environments such as group mobility and geographic constraints. To demonstrate the impact of this model, we evaluate the effect of this model on distribution of relative speed, link lifetime between neighboring nodes, and average node degree by ns-2 simulations.

Survivable WDM mesh networks

In a wavelength-division-multiplexing (WDM) optical network, the failure of network elements (e.g., fiber links and cross connects) may cause the failure of several optical channels, thereby leading to large data losses. This study examines different approaches to protect a mesh-based WDM optical network from such failures. These approaches are based on two survivability paradigms: 1) path protection/restoration and 2) link protection/restoration. The study examines the wavelength capacity requirements, and routing and wavelength assignment of primary and backup paths for path and link protection and proposes distributed protocols for path and link restoration. The study also examines the protection-switching time and the restoration time for each of these schemes, and the susceptibility of these schemes to multiple link failures. The numerical results obtained for a representative network topology with random traffic demands demonstrate that there is a tradeoff between the capacity utilization and the susceptibility to multiple link failures. We find that, on one hand, path protection provides significant capacity savings over link protection, and shared protection provides significant savings over dedicated protection; while on the other hand, path protection is more susceptible to multiple link failures than link protection, and shared protection is more susceptible to multiple link failures than dedicated protection. We formulate a model of protection-switching times for the different protection schemes based on a fully distributed control network. We propose distributed control protocols for path and link restoration. Numerical results obtained by simulating these protocols indicate that, for a representative network topology, path restoration has a better restoration efficiency than link restoration, and link restoration has a faster restoration time compared with path restoration.     

An IPv6‐based mobility framework for urban vehicular networks

This paper proposes an IPv6‐based mobility framework for urban vehicular networks. In this framework, the architecture for urban vehicular networks is presented, and based on this architecture, the IPv6 address structure for urban vehicular networks is proposed. In this framework, a vehicle is always identified by its home address and does not need to be configured with a care‐of address. Based on this architecture, the pre‐handover algorithm is presented. In this algorithm, the third‐layer (L3) mobility handover is performed before the second‐layer (L2) one. When a vehicle finishes the L3 handover but does not perform the L2 handover, the corresponding access router or border router reserves the messages destined for the vehicle. After the vehicle completes the L2 handover, the access router or border router transmits the reserved messages to the vehicle. The performance of this framework is evaluated, and the results show that this framework reduces the handover cost and delay and lowers the packet loss. Copyright © 2015 John Wiley & Sons, Ltd.     

Modeling 802.11 mesh networks

We introduce a tractable analytic model of throughput performance for general 802.11 multi-hop multi-radio networks subject to finite loads. The model's accuracy and utility is illustrated by comparison with simulation.     

Securing wireless mesh networks

Using wireless mesh networks to offer Internet connectivity is becoming a popular choice for wireless Internet service providers as it allows fast, easy, and inexpensive network deployment. However, security in WMNs is still in its infancy as very little attention has been devoted thus far to this topic by the research community. In this article we describe the specifics of WMNs and identify three fundamental network operations that need to be secured.     

Coaxial cable passive mesh networks

This paper presents a new type of fault-tolerant access network: an all-passive coaxial cable mesh network. The passive mesh network could have any topology, with cycles allowed. A technique for calculating the multipath response of the passive mesh network is presented. Both the delay and attenuation of a coaxial cable are represented by a single transform variable. The mesh network is modeled as a linear system with a state space that represents signal propagation. The channel responses of the individual sections of cable define the entries of a state-transition matrix. Using this theory, expressions are given for the overall mesh-network channel response. These expressions are manipulated to derive equalizer structures. The equalizers are zero-forcing and use decision feedback. It is shown that signals transmitted on any mesh network can be equalized. An example mesh topology, and equalizers for it, are presented. Signal and interference attenuation, and opposite-phase received carrier cancellation, are also discussed. The passive mesh network could be an inexpensive fault-tolerant architecture for residential access to telephony, cable TV, and future services     

A general framework to construct stationary mobility models for the simulation of mobile networks

Simulation has become an indispensable tool in the design and evaluation of mobile systems. By using mobility models that describe constituent movement, one can explore large systems, producing repeatable results for comparison between alternatives. In this paper, we show that a large class of mobility models - including all those in which nodal speed and distance or destination are chosen independently - have a transient period in which the average node speed decreases until converging to some long-term average. This speed decay provides an unsound basis for simulation studies that collect results averaged over time, complicating the experimental process. In this paper, we derive a general framework for describing this decay and apply it to a number of cases. Furthermore, this framework allows us to transform a given mobility model into a stationary one by initializing the simulation using the steady-state speed distribution and using the original speed distribution subsequently. This transformation completely eliminates the transient period and the decay in average node speed and, thus, provides sound models for the simulation of mobile systems.     

无线Mesh网络综述

无线Mesh网络是无线局域网和移动自组织网络相结合的产物,是一种全新的网络架构,有着极大的应用前景。简要介绍了无线Mesh网络体系结构、特点和应用领域,总结了无线Mesh网络路由协议的研究状况,探讨了存在的问题和今后发展的方向。     

Availability analysis of span-restorable mesh networks

The most common aim in designing a survivable network is to achieve restorability against all single span failures, with a minimal investment in spare capacity. This leaves dual-failure situations as the main factor to consider in quantifying how the availability of services benefit from the investment in restorability. We approach the question in part with a theoretical framework and in part with a series of computational routing trials. The computational part of the analysis includes all details of graph topology, capacity distribution, and the details of the restoration process, effects that were generally subject to significant approximations in prior work. The main finding is that a span-restorable mesh network can be extremely robust under dual-failure events against which they are not specifically designed. In a modular-capacity environment, an adaptive restoration process was found to restore as much as 95% of failed capacity on average over all dual-failure scenarios, even though the network was designed with minimal spare capacity to assure only single-failure restorability. The results also imply that for a priority service class, mesh networks could provide even higher availability than dedicated 1+1 APS. This is because there are almost no dual-failure scenarios for which some partial restoration level is not possible, whereas with 1+1 APS (or rings) there are an assured number of dual-failure scenarios for which the path restorability is zero. Results suggest conservatively that 20% or more of the paths in a mesh network could enjoy this ultra-high availability service by assigning fractional recovery capacity preferentially to those paths upon a dual failure scenario     

网状WDM网络的抗毁设计

本文使用整数线性规划法对多光纤网状WDM网络进行抗毁设计,使用的保护策略为共享通道保护和共享链路保护,网络设计的优化目标是使全网铺设的光纤总长度最短。然后以类CERNET为例,求解出不同保护策略下网络需要的光纤总长度,并分析了它们各自的特点以及波长转换对目标函数值的影响。     

Lightpath Re-optimization in mesh optical networks

Intelligent mesh optical networks deployed today offer unparalleled capacity, flexibility, availability, and, inevitably, new challenges to master all these qualities in the most efficient and practical manner. More specifically, demands are routed according to the state of the network available at the moment. As the network and the traffic evolve, the lightpaths of the existing demands becomes sub-optimal. In this paper we study two algorithms to re-optimize lightpaths in resilient mesh optical networks. One is a complete re-optimization algorithm that re-routes both primary and backup paths, and the second is a partial re-optimization algorithm that re-routes the backup paths only. We show that on average, these algorithms allow bandwidth savings of 3% to 5% of the total capacity in scenarios where the backup path only is re-routed, and substantially larger bandwidth savings when both the working and backup paths are re-routed. We also prove that trying all possible demand permutations with an online algorithm does not guarantee optimality, and in certain cases does not achieve it, while for the same scenario optimality is achieved through re-optimization. This observation motivates the needs for a re-optimization approach that does not just simply look at different sequences, and we propose and experiment with such an approach. Re-optimization has actually been performed in a nationwide live optical mesh network and the resulting savings are reported in this paper, validating reality and the usefulness of re-optimization in real networks.     

Shared protection in mesh WDM networks

This article introduces the design principles and state-of-the-art progress in developing survivable routing schemes for shared protection in mesh WDM networks. This article first gives an overview of the diverse routing problem for both types of protection in mesh networks, path-base and segment shared protection; then the cost function and link state for performing diverse routing are defined by which the maximum extent of resource sharing can be explored in the complete routing information scenario. Review is conducted on the most recently reported survivable routing schemes along with state-of-the-art progress in diverse routing algorithms for segment shared protection. The following three reported algorithms are discussed in detail: iterative two-step-approach, potential backup cost, and maximum likelihood relaxation.     

Protection cycles in mesh WDM networks

A fault recovery system that is fast and reliable is essential to today's networks, as it can be used to minimize the impact of the fault on the operation of the network and the services it provides. This paper proposes a methodology for performing automatic protection switching (APS) in optical networks with arbitrary mesh topologies in order to protect the network from fiber link failures. All fiber links interconnecting the optical switches are assumed to be bidirectional. In the scenario considered, the layout of the protection fibers and the setup of the protection switches is implemented in nonreal time, during the setup of the network. When a fiber link fails, the connections that use that link are automatically restored and their signals are routed to their original destination using the protection fibers and protection switches. The protection process proposed is fast, distributed, and autonomous. It restores the network in real time, without relying on a central manager or a centralized database. It is also independent of the topology and the connection state of the network at the time of the failure.     

Multiaccess mesh (multimesh) networks

This paper introduces the multiaccess mesh (or multimesh) network. Stations are arranged in a two-dimensional (2-D) mesh in which each row and column functions as a conventional linear local-area network (LAN) or metropolitan-area network (MAN) subnetwork. Full connectivity is achieved by enabling stations to merge their row and column subnetworks, under the coordination of a merge control protocol. A two-dimensional token-passing protocol is considered, and a more complex protocol motivated by max-min fairness is also presented. Like conventional LANs and MANs, the multimesh requires no transit routing or store-and-forward buffering. The multimesh is a generalization of the token grid network. Using analysis and simulation, we study the capacity of multimeshes constructed of token rings and slotted rings, under uniform and nonuniform loads. A multimesh can support much higher throughput than conventional linear LAN and MAN networks with the same transmission hardware. Moreover, the multimesh capacity grows with the number of stations, We also present a healing mechanism that ensures full network connectivity regardless of the number of failed stations     

Diverse routing in optical mesh networks

We study the diverse routing problem in optical mesh networks. We use a general framework based on shared risk link groups to model the problem. We prove that the diverse routing problem is indeed NP-complete, a result that has been conjectured by several researchers previously. In fact, we show that even the fiber-span-disjoint paths problem, a special case of the diverse routing problem, is also NP-complete. We then develop an integer linear programming formulation and show through numerical results that it is a very viable method to solve the diverse routing problem for most optical networks found in many applications which typically have no more than a few hundred nodes and fiber spans.     

Multi-gateway association in wireless mesh networks

Most traditional models of wireless mesh networks involve a mobile device connecting to the backbone through one of the available gateways in a wireless mesh network. In this paper, we present an alternate model, in which mobile devices are allowed to connect through more than one of the available gateways. We call the model multi-gateway association (MGA). We present arguments for why such a model can result in better capacity, fairness, diversity and security when compared to the default single-association model. We also identify the primary challenges that need to be addressed when using multiple-gateway associations, and propose solutions to handle these challenges. Using simulations, we show that throughput benefits ranging from 10% to 125% can be obtained by the proposed model as compared to a default single association model with just two gateways and more importantly, benefits linear in the number of gateways are obtainable. Through simulations and analysis, we establish why only intelligent multi-gateway association and neither single or simple multi-gateway association strategies can yield significant benefits.     

A survey on wireless mesh networks

Wireless mesh networks (WMNs) have emerged as a key technology for next-generation wireless networking. Because of their advantages over other wireless networks, WMNs are undergoing rapid progress and inspiring numerous applications. However, many technical issues still exist in this field. In order to provide a better understanding of the research challenges of WMNs, this article presents a detailed investigation of current state-of-the-art protocols and algorithms for WMNs. Open research issues in all protocol layers are also discussed, with an objective to spark new research interests in this field.