The performance of query control schemes for the zone routingprotocol

We study the performance of route query control mechanisms for the zone routing protocol (ZRP) for ad hoc networks. The ZRP proactively maintains routing information for a local neighborhood (routing zone), while reactively acquiring routes to destinations beyond the routing zone. This hybrid routing approach can be more efficient than traditional routing schemes. However, without proper query control techniques, the ZRP cannot provide the expected reduction in the control traffic. Our proposed query control schemes exploit the structure of the routing zone to provide enhanced detection and prevention of overlapping queries. These techniques can be applied to single- or multiple-channel ad hoc networks to improve both the delay and control traffic performance of ZRP. Our query control mechanisms allow ZRP to provide routes to all accessible network nodes, with less control traffic than purely proactive link state or purely reactive route discovery, and with less delay than conventional flood searching     

Optimal cluster-based routing scheme using node mobility in ad hoc networks

Ad hoc networks have a scalability problem. When the nodes of an ad hoc network increase in number or mobility, the amount of control traffic for routing increases and could cause traffic congestion. Cluster-based routing schemes have been proposed as a solution to this problem. Typical cluster-based ad hoc networks use a proactive routing scheme for intra-cluster routes and a reactive routing scheme for inter-cluster routes. In this study, we propose a new cluster-based routing scheme for ad hoc networks which makes use of the mobility of nodes. Nodes are divided into two groups on the basis of their mobility. For a route search within a cluster, a proactive routing scheme is used for low-mobility nodes and a flooding-based reactive routing scheme is used for high-mobility nodes. The required control traffic of the proposed scheme is analyzed and optimal parameters of the proposed scheme are derived from the analysis. The numerical results show that the proposed scheme produces far less control traffic than a typical cluster-based routing scheme.     

A Distributed Virtual Backbone Development Scheme for Ad-Hoc Wireless Networks

The virtual backbone is an approach for solving routing problems in ad-hoc wireless networks. The virtual backbone approach features low latency, moderate routing overhead and is a hybrid scheme that uses the table-driven and on-demand routing protocols. This work presents a distributed virtual backbone development scheme for ad-hoc wireless networks. Using clustering, distributed labeling and heuristic Steiner tree techniques, our scheme outperforms other schemes in terms of the size and stability of the virtual backbone and the virtual backbone change rate. Experimental results demonstrate that our scheme has lower overhead than traditional table-driven and on-demand routing schemes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determining the optimal configuration for the zone routing protocol

The zone routing protocol (ZRP) is a hybrid routing protocol that proactively maintains routes within a local region of the network (which we refer to as the routing zone). Knowledge of this routing zone topology is leveraged by the ZRP to improve the efficiency of a reactive route query/reply mechanism. The ZRP can be configured for a particular network through adjustment of a single parameter, the routing zone radius. We address the issue of configuring the ZRP to provide the best performance for a particular network at any time. Previous work has demonstrated that an optimally configured ZRP operates at least as efficiently as traditional reactive flood-search or proactive distance vector/link state routing protocols (and in many cases, much more efficiently). Adaptation of the ZIP to changing network conditions requires both an understanding of how the ZRP reacts to changes in network behavior and a mechanism to allow individual nodes to identify these changes given only limited knowledge of the network behavior. We demonstrate the effects of relative node velocity, node density, network span, and user data activity on the performance of the ZRP. We then introduce two different schemes (“min searching” and “traffic adaptive”) that allow individual nodes to identify and appropriately react to changes in network configuration, based only on information derived from the amount of received ZRP traffic. Through test-bed simulation, we demonstrate that these radius estimation techniques can allow the ZRP to operate within 2% of the control traffic resulting from perfect radius estimation     

Optimal tradeoffs for location-based routing in large-scale ad hoc networks

Existing location-based routing protocols are not versatile enough for a large-scale ad hoc environment to simultaneously meet all of the requirements of scalability, bandwidth efficiency, energy efficiency, and quality-of-service routing. To remedy this deficiency, we propose an optimal tradeoff approach that: 1) constructs a hybrid routing protocol by combining well-known location-update schemes (i.e., proactive location updates within nodes' local regions and a distributed location service), and 2) derives its optimal configuration, in terms of location-update thresholds (both distance and time-based), to minimize the overall routing overhead. We also build a route-discovery scheme based on an Internet-like architecture, i.e., first querying the location of a destination, then applying a series of local-region routing until finding a complete route by aggregating the thus-found partial routes. To find the optimal thresholds for the hybrid protocol, we derive the costs associated with both location updates and route discovery as a function of location-update thresholds, assuming a random mobility model and a general distribution for route request arrivals. The problem of minimizing the total cost is then cast into a distributed optimization problem. We first prove that the total cost is a convex function of the thresholds, and then derive the optimal thresholds. Finally, we show, via simulation, that our analysis results indeed capture the real behavior.     

Bit-per-joule performance of power saving ad hoc networks with a mobile backbone

Energy efficient MAC protocols have been developed for wireless sensor and mobile ad hoc networks so that inactive nodes can transition into sleep state to conserve energy. It has been recognized that maintaining a continuously awake connected dominating set (CDS) serves to reduce the route setup latency. Under the mobile backbone network (MBN) architecture introduced by Rubin et al., a mobile backbone (Bnet) is dynamically constructed to provide a topological covering of the network. The MBN employs a hybrid routing algorithm under which flows that travel a distance longer than a threshold are directed along routes across the Bnet. In turn, a limited span network-wide global route discovery process is applied for routing shorter distance flows. In this paper, we introduce and analyze an MBN based power saving protocol (MBN-PS) that employs this hybrid routing scheme. Under the MBN-PS scheme, dynamically elected backbone nodes are kept awake, while inactive non-backbone nodes can reside in sleep state. We analytically show that, when the number of network flows is above a minimal level, the throughput per watt efficiency attained in an ad hoc network under complete backbone coverage is better than that achieved by a corresponding network that does not form a backbone. We present a model for the calculation of the bit-per-joule performance of the network as a function of the distance threshold. We confirm the validity of our analytical approach through simulations. Using our method, a network designer is able to choose the optimal distance threshold to be used by this scheme, based on traffic loading conditions.     

A Hybrid Centralized Routing Protocol for 802.11s WMNs

Wireless mesh networks (WMNs) are being widely accepted as a critical wireless access solution for various applications. Due to minimal mobility in mesh nodes, a backbone topology can be effectively maintained in WMN using a proactive routing protocol. In IEEE 802.11s standard, a tree-based routing (TBR) protocol is adopted as a viable proactive routing protocol for a WMN with user traffic flowing to/from a wired network through a root (i.e., a mesh portal). However, the performance of the TBR protocol degrades rapidly as the user traffic becomes dominated by intra-mesh traffic. The reason is that the routing path through the root even for intra-mesh traffic unnecessarily overloads the root. Furthermore, the TBR performance becomes more severe when the network size of WMN is large, which could lead to the huge amount of intra-mesh traffic towards the root. To overcome these problems, we propose a new routing mechanism, root driven routing (RDR) protocol, for the root to quickly determine the best-metric route for any source-destination pair of intra-mesh traffic. For inter-mesh traffic, the original TBR protocol is employed. Thus, the hybrid centralized routing protocol that combines TBR and RDR and is adaptive to all traffic scenarios. Our simulation results reveal that the proposed RDR protocol outperforms the TBR protocol with much lower average end-to-end delay and much higher packet delivery ratio for intra-mesh traffic. The simulation results also provide some insight into the right tradeoff between the TBR protocol and the RDR protocol to achieve the best performance of the hybrid centralized routing protocol for WMNs.     

Discovering long lifetime routes in mobile ad hoc networks

In mobile ad hoc networks, node mobility causes frequent link failures, thus invalidating the routes containing those links. Once a link is detected broken, an alternate route has to be discovered, incurring extra route discovery overhead and packet latency. The traffic is also interrupted at the transport layer, and proper traffic recovery schemes have to be applied. To reduce the frequency of costly route re-discovery procedures and to maintain continuous traffic flow for reliable transport layer protocols, we suggest discovering long lifetime routes (LLR). In this paper, we first propose g-LLR, a global LLR discovery algorithm, that discovers LLRs of different route lengths for any given pair of nodes. We then propose a distributed LLR discovery scheme (d-LLR) that discovers two of the most desirable LLRs through one best-effort route discovery procedure. Simulations show that the lifetimes of the routes discovered by d-LLR are very close to those discovered by g-LLR. Simulations also show that the performance of different transport layer protocols is greatly improved by using LLRs. More importantly, traffic can remain continuous using the provided LLRs. D-LLR can be implemented as an extension to existing ad hoc routing protocols, and it improves the performance of transport layer protocols without modifications on them.     

Safari: A self-organizing, hierarchical architecture for scalable ad hoc networking

As wireless devices become more pervasive, mobile ad hoc networks are gaining importance, motivating the development of highly scalable ad hoc networking techniques. In this paper, we give an overview of the Safari architecture for highly scalable ad hoc network routing, and we present the design and evaluation of a specific realization of the Safari architecture, which we call Masai. We focus in this work on the scalability of learning and maintaining the routing state necessary for a large ad hoc network. The Safari architecture provides scalable ad hoc network routing, the seamless integration of infrastructure networks when and where they are available, and the support of self-organizing, decentralized network applications. Safari’s architecture is based on (1) a self-organizing network hierarchy that recursively groups participating nodes into an adaptive, locality-based hierarchy of cells; (2) a routing protocol that uses a hybrid of proactive and reactive routing information in the cells and scales to much larger numbers of nodes than previous ad hoc network routing protocols; and (3) a distributed hash table grounded in the network hierarchy, which supports decentralized network services on top of Safari. We evaluate the Masai realization of the Safari architecture through analysis and simulations, under varying network sizes, fraction of mobile nodes, and offered traffic loads. Compared to both the DSR and the L+ routing protocols, our results show that the Masai realization of the Safari architecture is significantly more scalable, with much higher packet delivery ratio and lower overhead.     

Hybrid mobile backbone network routing with flow control and distance awareness (MBNR-FC/DA)

The mobile backbone network (MBN) architecture has been introduced to synthesize robust, scalable and efficient mobile ad hoc wireless networks that support multimedia flows. Backbone capable nodes are dynamically elected to construct a mobile backbone (Bnet). In this article, we present a hybrid routing mechanism for such networks, identified as MBN routing with flow control and distance awareness (MBNR-FC/DA) scheme. Flows that travel a distance longer than a threshold level are routed across the Bnet. This induces a significant reduction in the route discovery control overhead, yielding a highly scalable operation. In turn, a limited span global route discovery process is invoked for routing shorter distance flows. Discovered global routes use effectively the capacity of non-backbone wireless links. Such an operation serves to upgrade the network’s throughput capacity level when the backbone network does not provide global topological covering. The hybrid routing protocol introduced and studied in this paper, also employs combined nodal congestion control and flow admission control schemes to guide admitted flows across areas that are less congested, and to avoid overloading the network. We present a centralized procedure as well as a distributed adaptive scheme for the calculation of the distance threshold level under varying traffic loading and backbone coverage conditions. We show our schemes to make efficient use of network-wide capacity resources by dynamically selecting proper distance threshold levels, yielding outstanding delay–throughput performance.     

Resource Discovery in Activity-Based Sensor Networks

This paper proposes a service discovery protocol for sensor networks that is specifically tailored for human-centered pervasive environments and scales well to large sensor networks, such as those deployed for medical care in major incidents and hospitals. It uses the high-level concept of computational activities (logical bundles of data and resources) to give sensors in activity-based sensor networks (ABSNs) knowledge about their usage even at the network layer. ABSN redesigns classical service discovery protocols to include a logical structuring of the network for a more applicable discovery scheme. Noting that in practical settings activity-based sensor patches are localized, ABSN designs a fully distributed, hybrid discovery protocol based on extended zone routing protocol (EZRP), proactive in a neighbourhood zone and reactive outside, so that any query among the sensors of one activity is routed through the network with minimum overhead, guided by the bounds of that activity. Compared to EZRP, ABSN lowers the network overhead of the discovery process, while keeping discovery latency close to optimal.     

Independent zone routing: an adaptive hybrid routing framework for ad hoc wireless networks

To effectively support communication in such a dynamic networking environment as the ad hoc networks, the routing framework has to be adaptable to the spatial and temporal changes in the characteristics of the network, such as traffic and mobility patterns. Multiscoping, as is provided through the concept of the Zone Routing Protocol (ZRP) for example, can serve as a basis for such an adaptive behavior. The Zone Routing framework implements hybrid routing by every network node proactively maintaining routing information about its local neighborhood called the routing zone, while reactively acquiring routes to destinations beyond the routing zone. In this paper, we propose the Independent Zone Routing (IZR) framework, an enhancement of the Zone Routing framework, which allows adaptive and distributed configuration for the optimal size of each node's routing zone, on the per-node basis. We demonstrate that the performance of IZR is significantly improved by its ability to automatically and dynamically tune the network routing operation, so as to flexibly and robustly support changes in the network characteristics and operational conditions. As a point of reference, through this form of adaptation, we show that the volume of routing control traffic overhead in the network can be reduced by an order of magnitude, under some set of parameter values. Furthermore, the adaptive nature of IZR enhances the scalability of these networks as well.     

Link Dynamics and Protocol Design in a Multihop Mobile Environment

A multihop ad hoc network with mobile elements is considered. A model is created and analytic expressions derived to characterize the statistics for link lifetime, new link interarrival time, link breakage interarrival time, and link change interarrival time. Applications of these expressions to protocol design are discussed. As an example application, the link model is used to find an optimal balance between reactive and proactive routing strategies. It is shown that, when control traffic generated through proactive route updating is matched to link lifetimes, control traffic is significantly reduced while the goodput and delay benefits of the proactive approach are retained.     

HOPNET: A hybrid ant colony optimization routing algorithm for mobile ad hoc network

Mobile ad hoc network (MANET) is a group of mobile nodes which communicates with each other without any supporting infrastructure. Routing in MANET is extremely challenging because of MANETs dynamic features, its limited bandwidth and power energy. Nature-inspired algorithms (swarm intelligence) such as ant colony optimization (ACO) algorithms have shown to be a good technique for developing routing algorithms for MANETs. Swarm intelligence is a computational intelligence technique that involves collective behavior of autonomous agents that locally interact with each other in a distributed environment to solve a given problem in the hope of finding a global solution to the problem. In this paper, we propose a hybrid routing algorithm for MANETs based on ACO and zone routing framework of bordercasting. The algorithm, HOPNET, based on ants hopping from one zone to the next, consists of the local proactive route discovery within a node’s neighborhood and reactive communication between the neighborhoods. The algorithm has features extracted from ZRP and DSR protocols and is simulated on GlomoSim and is compared to AODV routing protocol. The algorithm is also compared to the well known hybrid routing algorithm, AntHocNet, which is not based on zone routing framework. Results indicate that HOPNET is highly scalable for large networks compared to AntHocNet. The results also indicate that the selection of the zone radius has considerable impact on the delivery packet ratio and HOPNET performs significantly better than AntHocNet for high and low mobility. The algorithm has been compared to random way point model and random drunken model and the results show the efficiency and inefficiency of bordercasting. Finally, HOPNET is compared to ZRP and the strength of nature-inspired algorithm is shown.     

Cover1

We propose and analyze an energy-aware traffic-adaptive routing strategy for large-scale mobile ad hoc networks (MANETs). Referred to as energy-aware geolocation-aided routing (EAGER), this protocol optimally blends proactive and reactive strategies for energy efficiency. Specifically, EAGER partitions the network into cells and performs intracell proactive routing and intercell reactive routing. The cell size and the transmission range are optimized analytically. By adjoining cells around hot spots and hot routes in the network, EAGER is capable of handling time-varying and spatially heterogeneous traffic conditions.     

Load-balancing in MANET shortest-path routing protocols

Mobile ad hoc networks (MANET) are infrastructure-less networks, dynamically formed by an independent system of mobile nodes that are connected via wireless links. Because routing is performed by nodes with limited resources, load should be efficiently distributed through the network. Otherwise, heavily-loaded nodes may make up a bottleneck that lowers the network performances by congestion and larger delays. Regrettably, load-balancing is a critical deficiency in MANET shortest-path routing protocols, as nodes at the center of the network are much heavily-loaded than the others. Thus, we propose, in this paper, load-balancing mechanisms that push the traffic further from the center of the network. Basically, we provide novel routing metrics that take into account nodes degree of centrality, for both proactive and reactive routing protocols. Simulations show that the proposed mechanisms improve the load distribution and significantly enhance the network performances in terms of average delay and reliability.     

Analysis of the joint use of the proactive and reactive methods of the topology information dissemination in ad-hoc wireless networks

A number of routing protocols for wireless ad-hoc (self-organizing) networks selects routes according to the topology information obtained by the station. Hence, the method of these protocols used to disseminate topology information strongly affects the network performance. An unsuccessful choice of the method can lead to a large amount of traffic and the information obsolescence. These factors diminish the network performance and make it impossible to meet quality of service requirements in transmitting realtime multimedia data, which is a topical problem. The routing protocol combining the proactive and reactive methods of the topology information dissemination has been proposed. It is demonstrated that this protocol is efficient in a wide range of scenarios applied to the exchange of real-time multimedia data.     

基于SDN的互联网域间路由研究

互联网流量的爆发式增长,叠加互联网流量固有的突发性特点,使得网络流量不均衡现象日益加剧。传统BGP协议由于缺乏全网拓扑和全局流量观,只能遵循标准BGP选路原则,在解决流量调度和负载均衡方面存在不足。针对BGP协议存在的局限性,研发了基于RR+的互联网骨干网流量调度系统,并应用于ChinaNet骨干网的网内中继、网间互联出口、IDC出口等多个流量优化场景。更进一步地,提出了一种基于SDN的互联网域间路由架构,通过在域间控制器之间交换BGP路由,无需在域内和域间运行BGP协议,极大地简化了网络协议,并能够实现灵活的流量调度和负载均衡。     

Energy-Aware Adaptive Routing for Large-Scale Ad Hoc Networks: Protocol and Performance Analysis

We propose and analyze an energy-aware traffic-adaptive routing strategy for large-scale mobile ad hoc networks. Referred to as Energy-Aware GEolocation-aided Routing (EAGER), this protocol optimally blends proactive and reactive strategies for energy efficiency. Specifically, EAGER partitions the network into cells and performs intra-cell proactive routing and inter-cell reactive routing. The cell size and transmission range are optimized analytically. By adjoining cells around hot spots and hot routes in the network, EAGER is capable of handling time-varying and spatially heterogeneous traffic conditions.