Improving UDP and TCP performance in mobile ad hoc networks withINSIGNIA

There is a growing need to provide better service differentiation in mobile ad hoc networks; however, this is challenging. These networks are characterized as being multihop in nature where the wireless topology that interconnects mobile hosts/routers can change rapidly in unpredictable ways or remain relatively static over long periods of time. Power and bandwidth constrained, mobile ad hoc networks typically only support best effort communications where the transport protocol's “goodput” is often lower than the maximum radio transmission rate after encountering the effects of multiple access, fading, noise, and interference. We evaluate three routing protocols with INSIGNIA, an in-band signaling system that supports adaptive reservation-based services in mobile ad hoc networks. INSIGNIA represents a general-purpose approach to delivering quality of service in mobile ad hoc network supporting “operational transparency” between a number of IETF mobile ad hoc network routing protocols that include Ad Hoc On-Demand Distance Vector, Dynamic Source Routing, and the Temporally Ordered Routing Algorithm. We evaluate the performance gains delivered when using INSIGNIA with these MANET routing protocols in support of UDP and TCP traffic. The INSIGNIA ns-2 code used for the study reported in this article is available from the Web at comet.columbia.edu/insignia     

Virtual Surrounding Face Geocasting in Wireless Ad Hoc and Sensor Networks

Geocasting in wireless sensor and ad hoc networks means delivering a message from a source node to all the nodes in a given geographical region. The objectives of a geocasting protocol are two-fold: guaranteed message delivery and low transmission cost. Most of the existing protocols do not guarantee message delivery, and those that do, incur high transmission costs.      

Flooding-Based Geocasting Protocols for Mobile Ad Hoc Networks

Geocasting is a variation on the notion of multicasting. A geographical area is associated with each geocast, and the geocast is delivered to the nodes within the specified geographical area. Thus, geocasting may be used for sending a message that is likely to be of interest to everyone in a specified area. In this paper, we propose three geocasting protocols for ad hoc networks, obtained as variations of a multicast flooding algorithm, and then evaluate these approaches by means of simulations. Proposed geocasting algorithms attempt to utilize physical location information to decrease the overhead of geocast delivery.     

On-Demand Multicast Routing Protocol in Multihop Wireless Mobile Networks

An ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. Each host is mobile and must act as a router. Routing and multicasting protocols in ad hoc networks are faced with the challenge of delivering data to destinations through multihop routes in the presence of node movements and topology changes. This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile ad hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept; only a subset of nodes forwards the multicast packets via scoped flooding. It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP performance with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation.     

Improving Bandwidth Utilization of Intermittent Links in Highly Dynamic Ad Hoc Networks

Non-uniform node densities occur and intermittent links exist in highly dynamic ad hoc networks. To fit these networks, researchers usually combine delay tolerant network (DTN) routing protocols and mobile ad hoc network (MANET) routing protocols. The DTN protocol separates end-to-end links into multiple DTN links, which consist of multi-hop MANET links. Determining how to arrange DTN links and MANET links from source to end and dealing with intermittent links are performance issues, because node density ranges from sparse to dense and MANET protocols are much lighter than DTN protocols. This paper presents HMDTN, an application-network cross-layer framework, to solve the previously mentioned issues. The application layer in HMDTN supports disrupt tolerance with a large data buffer while adjusting the routing table on the basis of the connection state of links (link is disrupted or recovered), which are collected by the network layer. As a result, HMDTN increases the bandwidth utilization of intermittent links without compromising the efficiency of the MANET protocol in a reliable network. The HMDTN prototype was implemented based on Bytewalla (a Java version of DTN2) and Netfilter-based AODV. Experiments on Android devices show that unlike AODV and Epidemic, HMDTN increases the bandwidth utilization of intermittent links with a negligible increase of network overhead. In particular, HMDTN maintains the network throughput as high as regular network conditions even if the network undergoes relatively long-term (dozens of seconds or few minutes) data link disruptions.

     

Robust position-based routing for wireless ad hoc networks

We consider a wireless ad hoc network composed of a set of wireless nodes distributed in a two dimensional plane. Several routing protocols based on the positions of the mobile hosts have been proposed in the literature. A typical assumption in these protocols is that all wireless nodes have uniform transmission regions modeled by unit disk centered at each wireless node. However, all these protocols are likely to fail if the transmission ranges of the mobile hosts vary due to natural or man-made obstacles or weather conditions. These protocols may fail because either some connections that are used by routing protocols do not exist, which effectively results in disconnecting the network, or the use of some connections causes livelocks. In this paper, we describe a robust routing protocol that tolerates up to roughly 40% of variation in the transmission ranges of the mobile hosts. More precisely, our protocol guarantees message delivery in a connected ad hoc network whenever the ratio of the maximum transmission range to the minimum transmission range is at most .     

Wireless Ad Hoc Multicast Routing with Mobility Prediction

An ad hoc wireless network is an infrastructureless network composed of mobile hosts. The primary concerns in ad hoc networks are bandwidth limitations and unpredictable topology changes. Thus, efficient utilization of routing packets and immediate recovery of route breaks are critical in routing and multicasting protocols. A multicast scheme, On-Demand Multicast Routing Protocol (ODMRP), has been recently proposed for mobile ad hoc networks. ODMRP is a reactive (on-demand) protocol that delivers packets to destination(s) on a mesh topology using scoped flooding of data. We can apply a number of enhancements to improve the performance of ODMRP. In this paper, we propose a mobility prediction scheme to help select stable routes and to perform rerouting in anticipation of topology changes. We also introduce techniques to improve transmission reliability and eliminate route acquisition latency. The impact of our improvements is evaluated via simulation.     

An optimised resource aware approach to information collection in ad hoc networks

In ad hoc networks there is a need for all-to-one protocols that allow for information collection or “sensing” of the state of an ad hoc network and the nodes that comprise it. Such protocols may be used for service discovery, auto-configuration, network management, topology discovery or reliable flooding. There is a parallel between this type of sensing in ad hoc networks and that of sensor networks. However, ad hoc networks and sensor networks differ in their application, construction, characteristics and constraints. The main priority of sensor networks is for the flow of data from sensors back to a sink, but in an ad hoc network this may be of secondary importance. Hence, protocols suitable to sensor networks are not necessarily suitable to ad hoc networks and vice versa. We propose, Resource Aware Information Collection (RAIC), a distributed two phased resource aware approach to information collection in ad hoc networks. RAIC utilises a resource aware optimised flooding mechanism to both disseminate requests and initialise a backbone of resource suitable nodes responsible for relaying replies back to the node collecting information. RAIC in the process of collecting information from all nodes in an ad hoc network is shown to consume less energy and introduce less overhead compared with Directed Diffusion and a brute force approach. Importantly, over multiple successive queries (in an energy constrained environment), the use of resource awareness allows for the load of relaying to be distributed to those nodes most suitable, thereby extending the lifetime of the network.     

A Multi-Path QoS Routing Protocol in a Wireless Mobile Ad Hoc Network

A mobile ad hoc network (MANET) is one composed of a set of mobile hosts capable of communicating with each other without the assistance of base stations. This paper considers the QoS (quality-of-service) routing problem in a MANET, which is important for many real-time multimedia applications. We propose an on-demand protocol for searching for a multi-path QoS route from a source host to a destination host in a MANET, where a multi-path is a network with a source and a sink satisfying certain bandwidth requirement. Existing works all try to find a uni-path to the destination. The basic idea is to distribute a number of tickets from the source, which can be further partitioned into subtickets to search for a satisfactory multi-path. Through simulations, we justify that the value of our multi-path protocol is in its flexibility: (i) when the network bandwidth is very limited, it can offer a higher success rate to find a satisfactory QoS route than those protocols which try to find a uni-path, and (ii) when the network bandwidth is sufficient, it can perform almost the same as those protocols which try to find a uni-path (in both routing overhead and success rate).     

移动自组网络MANET路由策略综述

路由策略是网络技术研究的焦点问题之一。由于移动自组网络MANET中节点的动态性和节点资源的有限性,以及多媒体应用服务质量的需求,导致在MANET网络实现路由存在诸多困难。综述了目前文献中基于MANET网络的普通路由协议和满足服务质量需求的QoS路由协议/算法,详细说明了不同协议的实现过程和存在的优缺点,并指出了目前路由策略研究中存在的问题和将来的发展方向。     

Traffic load metrics for multihomed mobile IP and global connectivity

Support for host mobility an essential and necessary feature for roaming users who connect to wireless networks via access points. Access points may have different capabilities, be connected to different networks and be installed by different providers. A mobile host will discover multiple access points in this environment. In such an environment, a mobile host should be able to use the best available connection to communicate with a correspondent host and perhaps use multiple connections for different hosts. In areas with wireless local area network access, pockets with limited or no coverage could exist. Such restricted connectivity could be compensated by neighbor hosts who form an ad hoc network and relay packets until they reach an access point. This paper describes and discusses a proposed solution towards enabling and supporting connectivity in wireless networks. In the proposed solution the network layer software will evaluate and decide which wireless network connections to use. A Running Variance Metric (RVM) and a Relative Network Load(RNL) are used to measure the traffic load of access points in wireless access networks. RVM and RNL can be efficiently used for both infrastructure networks and ad hoc networks. Multihomed Mobile IP (M-MIP) is an extension of Mobile IP that enables mobile hosts to use multiple care-of addresses simultaneously. The extension enhances network connectivity by enabling the mobile host, the home agent and correspondent hosts to evaluate and select the best connection. A proposed gateway architecture using M-MIP that integrates wired IP networks with ad hoc networks is described. The M-MIP and gateway architecture using the RVM and RNL metrics have been validated with simulation studies and results are presented.     

A survey of geocast routing protocols

Geocasting is the delivery of a message to nodes within a geographical region. With geocast, new services and applications are feasible, such as finding friends who are nearby, geographic advertising, and accident or wrong-way driver warning on a motorway. In this article we present a survey on geocast routing protocols. The protocols mainly differ in whether they are based on flooding, directed flooding, or on routing without flooding, and whether they are suitable for ad hoc networks or for infrastructure networks. Based on these criteria we propose a classification of geocast protocols. Our protocol comparison includes message and memory complexity, robustness, and the ability to deliver geocast packets in partially partitioned networks. Finally, we present simulations to compare the approaches based on flooding, directed flooding, and routing without flooding.     

Efficient geocasting with multi-target regions in mobile multi-hop wireless networks

Geocasting, a variation on the notion of multicasting, is a mechanism to deliver messages of interest to all nodes within a certain geographical target region. Although several geocasting protocols have already been proposed for multi-hop wireless networks, most of these algorithms consider a “single” target region only. Here, when more than one target regions need to receive the same geocast messages, multiple transmissions need to be initiated separately by the message source. This causes significant performance degradation due to redundant packet transmissions, and it becomes more severe as the number of target regions increase. To solve this problem, we propose a basic scheme and its variations which utilize the geometric concept of “Fermat point” to determine the optimal junction point among multiple geocast regions from the source node. Our simulation study using ns-2 shows that the proposed schemes can effectively reduce the overhead of message delivery while maintaining a high delivery ratio in mobile multi-hop wireless networks.     

Topology and mobility considerations in mobile ad hoc networks

A highly dynamic topology is a distinguishing feature and challenge of a mobile ad hoc network. Links between nodes are created and broken, as the nodes move within the network. This node mobility affects not only the source and/or destination, as in a conventional wireless network, but also intermediate nodes, due to the network’s multihop nature. The resulting routes can be extremely volatile, making successful ad hoc routing dependent on efficiently reacting to these topology changes.

In order to better understand this environment, a number of characteristics have been studied concerning the links and routes that make up an ad hoc network. Several network parameters are examined, including number of nodes, network dimensions, and radio transmission range, as well as mobility parameters for maximum speed and wait times. In addition to suggesting guidelines for the evaluation of ad hoc networks, the results reveal several properties that should be considered in the design and optimization of MANET protocols.     

A secure dynamic IP configuration scheme for mobile ad hoc networks

Secure dynamic IP addressing is a prime requirement for unicast communication between authorized hosts in mobile ad hoc networks (MANETs). Recently, several approaches have been proposed for dynamic addressing scheme. However, most of the approaches rely on broadcasting for address solicitation and/or duplicate address detection. As a result, several types of security threats in dynamic IP configuration can be observed. In this paper, we present an ID based dynamic IP configuration scheme that can securely allocate IP addresses to the authorized hosts for a mobile ad hoc network without broadcasting over the entire network. Each host in the MANET can generate an unique IP address from its own IP address for a new host. The proposed scheme provides authentication for address configuration without the help of a trusted third party while taking care of the security-threats associated with dynamic IP configuration. Performance analysis shows that even with added security mechanisms our proposed addressing scheme has fairly good addressing latency and control overhead compared to the similar existing schemes. Moreover, the proposed scheme is able to solve the problem of network partitions and mergers along with the arrival and departure of a host efficiently and securely.     

Efficient flooding with passive clustering-an overhead-free selective forward mechanism for ad hoc/sensor networks

High capacity real-time data communications in sensor networks usually require multihop routing and ad hoc routing protocols. Unfortunately, ad hoc routing protocols usually do not scale well and cannot handle dense situations efficiently. These two issues-scalability and density-are the major limitations when we apply ad hoc routing schemes to sensor networks. Passive clustering (PC) classifies ad hoc/sensor nodes into critical and noncritical nodes without any extra transmission. By 2-b piggybacking and monitoring user traffic (e.g., data polling requests from a sink), PC deploys the clustering structure "for free". Moreover, PC makes even the first flooding as efficient as all subsequent floodings (i.e., no initialization overhead). PC introduces many benefits, including efficient flooding and density adaptation. As a result, PC reduces control overhead of ad hoc routing protocols significantly and, as a consequence, enables ad hoc routing in large, dense sensor networks. The resulting structure can be utilized in cluster-based ad hoc network/sensor networking as well as for active node selection.     

Regional Gossip Routing for Wireless Ad Hoc Networks

Many routing protocols have been proposed for wireless ad hoc networks, and most of them are based on some variants of flooding. Thus many routing messages are propagated through the network unnecessarily despite various optimizations. Gossip based routing method has been used and re-investigated to reduce the number of messages in both wired networks and wireless ad hoc networks. However, the global gossiping still generates many unnecessary messages in the area that could be far away from the line between sender node and receiver node. We propose a regional gossip approach, where only the nodes within some region forward a message with some probability, to reduce the overhead of the route discovery in the network. We show how to set the forwarding probability based on the region and the network density both by theoretical analysis and by extensive simulations. Our simulations show that the number of messages generated using this approach is much less than the simple global gossiping method, which already saves many messages compared with global flooding. We expect that the improvement should be even more significant in larger networks.     

An adaptive quorum-based energy conserving protocol for IEEE 802.11 ad hoc networks

The lifetime of a mobile ad hoc network (MANET) depends on the durability of the mobile hosts' battery resources. In the IEEE 802.11 Power Saving Mode, a host must wake up at every beacon interval, to check if it should remain awake. Such a scheme fails to adjust a host's sleep duration according to its traffic, thereby reducing its power efficiency. This paper presents new MAC protocols for power saving in a single hop MANET. The essence of these protocols is a quorum-based sleep/wake-up mechanism, which conserves energy by allowing the host to sleep for more than one beacon interval, if few transmissions are involved. The proposed protocols are simple and energy-efficiency. Simulation results showed that our protocols conserved more energy and extended the lifetime of a MANET.     

Unidirectional link-state advertisement based on power control for MANET

Link states are studied in ad hoc network. The characters of unidirectional links are discussed. Unidirectional link-state advertisement based on power control mechanism (ULAPC) for mobile ad hoc networks (MANET) is designed. ULAPC is able to advertise unidirectional link-state to relational nodes. And it may offer help for process of routing discovery in ad hoc network. Based on ULAPC, the routing method solving the problem of unidirectional link is described in ad hoc network. Simulation results show the performance of ULAPC is better than the traditional routing protocols in many aspects.     

The Effects of Physical Layer on the Routing Wireless Protocol

Mobile ad hoc networks (MANETs) are characterized by multiple entities, a frequently changing network topology and the need for efficient dynamic routing protocols. In MANETs, nodes are usually powered by batteries. Power control is tightly coupled with both the physical and medium access layers (MACs). However, if we increase the transmission power, at the same time we increase the interference to other nodes which diminish the transport capacity of wireless systems. Thus, the routing protocols based on hop count metric suffer from performance degradation when they operate over MANET. Routing in ad hoc wireless networks is not only a problem of finding a route with shortest length, but it is also a problem of finding a stable and good quality communication route in order to avoid any unnecessary packet loss. Cross-layer design of ad hoc wireless networks has been receiving increasing attention recently. Part of these researches suggests that routing should take into account physical layer characteristics. The goal of this paper is to improve the routing reliability in MANET and to reduce power consumption through cross-layer approach among physical, MAC and network layers. The proposed cross-layer approach is based on signal to interference plus noise ratio (SINR) and received signal strength indication (RSSI) coming from the physical layer. This solution performs in one hand the ad hoc on-demand distance vector routing protocol by choosing reliable routes with less interferences using SINR metric and in another hand; it permits to reduce the power transmission when sending the data packets by using RSSI metric.