This paper presents the expected transmission count metric (ETX), which finds high-throughput paths on multi-hop wireless networks. ETX minimizes the expected total number of packet transmissions (including retransmissions) required to successfully deliver a packet to the ultimate destination. The ETX metric incorporates the effects of link loss ratios, asymmetry in the loss ratios between the two directions of each link, and interference among the successive links of a path. In contrast, the minimum hop-count metric chooses arbitrarily among the different paths of the same minimum length, regardless of the often large differences in throughput among those paths, and ignoring the possibility that a longer path might offer higher throughput. This

Existing wireless ad hoc routing protocols typically find routes with the minimum hop-count. This paper presents experimental evidence from two wireless test-beds which shows that there are usually multiple minimum hop-count paths, many of which have poor throughput. As a result, minimum-hop-count routing often chooses routes that have significantly less capacity than the best paths that exist in the network. Much of the reason for this is that many of the radio links between nodes have loss rates low enough that the routing protocol is willing to use them, but high enough that much of the capacity is consumed by retransmissions. These observations suggest that more attention be paid to link quality when choosing ad hoc routes; the paper presents measured link characteristics likely to be useful in devising a better path quality metric.

Mobile ad hoc networks (MANET) are becoming an integral part of the ubiquitous computing and communication environment, providing new infrastructure for multimedia applications such as video phone, multimedia-on-demand, and others. In order to access multimedia information in MANET, Quality of Service (QoS) needs to be considered, such as high success rate to access multimedia data, bounded end-to-end delay, and others. In this paper, we present a data accessibility service for a group of mobile users to access desired data with high success rate. This accessibility service is only possible if we utilize advanced data advertising, lookup and replication services, as well as a novel predictive location-based QoS routing protocol in an integrated fashion. Using cross-layer design, we illustrate how the QoS routing protocol assists data advertising, lookup and replication services to achieve high data access success rate. Simulation results have shown that our design is successful in a dynamic MANET.

Abstract- Geographic routing in mobile ad hoc networks has proved to provide drastic performance improvement over strictly address-centric routing schemes. While geographic routing has been shown to be correct and efficient when location information is accurate, its performance in the face of location errors is not well understood. In this paper, we study the effect of inaccurate location information caused by node mobility under a rich set of scenarios and mobility models. We identify two main problems, named LLNK and LOOP, that are caused by mobility-induced location errors. Based on analysis via ns-2 simulations, we propose two mobility prediction schemes--- neighbor location prediction (NLP) and destination location prediction (DLP) to mitigate these problems. Simulation results show noticeable improvement under all mobility models used in our study. Our schemes achieve up to 27 % improvement in packet delivery and 37 % reduction in network resource wastage on average without incurring any additional communication or intense computation. 1.

Location-Based Services (LBSs) utilize information about users’ locations through location-aware mobile devices to provide services, such as nearest features of interest, they request. This is a common strategy in LBSs and although it is needed and benefits the users, there are additional benefits when future locations (e.g., locations at later times) are predicted. One major advantage of location prediction is that it provides LBSs with extended resources, mainly time, to improve system reliability which in return increases the users ’ confidence and the demand for LBSs. However, much of the current location prediction research is focused on generalized location models, where the geographic extent is divided into regular-shape cells. These models are not suitable for certain LBSs whose objective is to compute and present on-road services, because a cell may contain several roads while the computation and delivery of a service may require the exact road on which the user is driving. We propose a new model, called Predictive Location Model (PLM), to predict locations in LBSs with road-level granularities. The premise of PLM is geometrical and topological techniques allowing users to receive timely and desired services.

Efficient resource provisioning that allows for cost-effective enforcement of application QoS relies on accurate system state information. However, maintaining accurate information about available system resources is complex and expensive especially in mobile environments where system conditions are highly dynamic. Resource provision-ing mechanisms for such dynamic environments must therefore be able to tolerate imprecision in system state while ensuring adequate QoS to the end-user. In this paper, we address the information collection problem for QoS-based services in mobile environments. Specifically, we propose a family of information collection policies that vary in the granularity at which system state information is represented and maintained. We empirically evaluate the impact of these policies on the performance of diverse resource provisioning strategies. We generally observe that resource provisioning benefits significantly from the customized information collection mechanisms that take advantage of user mobility information. Furthermore, our performance results indicate that effective utilization of coarse-grained user mobility information renders better system performance than using fine-grained user mobility information. Using results from our empirical studies, we derive a set of rules that supports seamless integration of information collection and resource provisioning mechanisms for mobile environments. These results have been incorporated into an integrated middleware framework AutoSeC (Automatic Service Composition) to provide support for dynamic service brokering that ensures effective utilization of system resources over wireless networks.

A Mobile ad hoc network is a collection of wireless nodes, all of which may be mobile, that dynamically create a wireless network amongst them without using any infrastructure. Ad hoc wireless networks come into being solely by peer-to-peer interactions among their constituent mobile nodes, and it is only such interactions that are used to provide the necessary control and administrative functions supporting such networks. Mobile hosts are no longer just end systems; each node must be able to function as a router as well to relay packets generated by other nodes. As the nodes move in and out of range with respect to other nodes, including those that are operating as routers, the resulting topology changes must somehow be communicated to all other nodes as appropriate. In accommodating the communication needs of the user applications, the limited bandwidth of wireless channels and their generally hostile transmission characteristics impose additional constraints on how much administrative and control information may be exchanged, and how often. Ensuring effective routing is one of the greatest challenges for ad hoc networking. As a practice, ad hoc routing protocols make routing decisions based on individual node mobility even for applications such as disaster recovery, battlefield combat, conference room interactions, and collaborative computing etc. that are shown to follow a pattern. In this thesis we propose an algorithm that performs routing based on underlying mobility patterns. A mobility pattern aware routing algorithm is shown to have several distinct advantages such as (a) A more precise view of the entire network topology as the nodes move (b) A more precise view of the location of the individual nodes (c) Ability to predict with reasonably accuracy the future locations of nodes (d) Ability to switch over to an alternate route before a link is disrupted due to node movements.

The expected transmission count (ETX) metric is a new route metric for finding high-throughput paths in multi-hop wireless networks. The ETX of a path is the expected total number of packet transmissions (including retransmissions) required to successfully deliver a packet along that path. For practical networks, paths with the minimum ETX have the highest throughput. The ETX metric incorporates the effects of link loss ratios, asymmetry in the loss ratios between the two directions of each link, and interference among the successive links of a path. Busy networks that use the ETX route metric will also maximize total network throughput. We describe the design and implementation of ETX as a metric for the DSDV and DSR routing protocols, as well as modifications to DSDV and DSR which make them work well with ETX. Measurements taken from a 29-node 802.11b test-bed show that using ETX improves performance significantly over the widelyused minimum hop-count metric. For long paths the throughput increase is often a factor of two or more, suggesting that ETX will become more useful as networks

Abstract — Many applications used in the Internet today benefit from using location information. To better handle location information in Internet telephony applications, we did a comprehensive application-layer analysis of location information and location-based communication services. We first summarize and categorize end-user-oriented location description and location detection approaches. We then summarize and categorize how to use location information to provide communication services and introduce several interesting location based communication services. Based on the analysis, we have incorporated location-based service handling in our Session Initiation Protocol (SIP) based Internet telephony infrastructure and our Language for End System Services (LESS). I.

The paper proposes several dynamic bandwidth allocation strategies for QoS routing on TDMA-based mobile ad hoc networks. Comprehensively, these strategies are called a distributed slots reservation protocol (DSRP). In DSRP, QoS routing only depends on one-hop neighboring information of each mobile host (MH). In addition, slot inhibited policies (SIPs) and slot decision policies (SDPs) are proposed to determine which slots are valid to use and which slots in the valid slots can be used actually, respectively. In SDPs, three heuristic policies, 3BDP, LCFP, and MRFP, are proposed to increase the success rate of a QoS route and alleviate the slot shortage problems. Moreover, a slot adjustment protocol (SAP) is proposed for a conflicting MH to coordinate the slot usage of its neighbors during the route reservation phase in order to accommodate more routes in the network. The slot adjustment algorithm (SAA) invoked in SAP is a branch-and-bound algorithm, which is an optimum algorithm in terms of the number of slots to be adjusted, on the premise that not to break down any existing route. QoS route maintenance and improvement are also provided. By the simulation results, the proposed protocol cannot only increase the success rate in search of a route with bandwidth requirement guaranteed but also raise the throughput and efficiency of the network.