Wireless networks are increasingly popular as the last-mile solution for a ubiquitous communication infrastructure. This trend in combination with the users? growing interest and falling cost in accessing vast amount of resources in Internet wirelessly has driven the developments of hybrid wireless network architecture such as Internet-based mobile ad hoc networks (IMANETs) and Internet-based vehicular ad hoc networks (IVANETs). However, it brings critical challenges in terms of limited storage space, frequent disconnections due to mobility, as well as unreliability of communication links. Caching a frequently accessed data in a local storage is shown to be an effective technique not only to relieve the network but also to improve data accessibility and availability in the presence of such challenges. The specific goal of this project is to develop algorithms and communication protocols that allow efficient and correct data caching in Internet-based wireless mobile networks. This project investigates cache management and invalidation strategies for IMANETs, and cache invalidation and consistency strategies for IVANETs. The project will make significant advances in understanding and designing an efficient data caching schemes for Internet-based wireless mobile networks. The success of this project will have a much broader impact on Internet-based wireless mobile network education and the corresponding industry, and provide versatile research opportunities to both undergraduate and graduate students. The algorithms and techniques developed in this research will be integrated with the education curricula
Project Number CNS-1004210 PI: Sunho Lim (Ph.D., Assistant Professor) Dept. of Computer Science Texas Tech University Lubbock, TX 79409 (Collaboration with Dr. Chansu Yu, Cleveland State University, CNS-0831853) This project outcomes report summarizes project findings associated with NSF Award CNS-1004210 (Collaborative Research: NEDG: Exploring Data Access in Internet-based Wireless Mobile Networks) at Texas Tech University, Lubbock, TX 79409 in collaboration with Dr. Chansu Yu, Cleveland State University, CNS-0831853. The original NSF Award CNS-0831673 was transferred and no-cost extended from South Dakota State University, Brookings, SD 57007, where the PI was affiliated as an Assistant Professor. Summary of Project Outcomes The specific goal of this project is to develop algorithms and communication protocols that allow efficient and correct data caching in Internet-based wireless mobile networks, such as Internet-based mobile ad hoc networks (IMANETs) and Internet-based vehicular ad hoc networks (IVANETs). The project will make significant advances in understanding and designing an efficient data caching schemes for Internet-based wireless mobile networks. Detail project outcomes are summarized below. Cache Invalidation Schemes: A key design optimization technique in IVANETs is to cache the frequently accessed data items in local storage of vehicles. Since vehicles are not critically limited by the storage/memory space and power consumption, selecting proper data items for caching is not very critical. Rather, an important design issue is how to keep the cached copies valid when the original data items are updated. This is essential to provide fast access to valid data items for fast moving vehicles. The proposed system model of IVANET is shown in Figure 1. The proposed cooperative cache invalidation(CCI) scheme and its enhancement (ECCI) were compared against two prior cache invalidation techniques such as a poll-each-read (PER) scheme and an extended asynchronous (EAS) scheme in terms of query interval, cache update interval, and data size. We found via simulation study that the proposed schemes can reduce the query delay up to 69% and increase the cache hit rate up to 57%, and had the lowest communication overhead compared to the prior cache invalidation schemes. Cache Scheme for Network Partition: Although IVANETs provide flexible information availability, its performance may be degraded by network partitions resulted from frequent changes of the network topology. According to our simulation study, the enhanced least recently used replacement policy proposed in this project significantly improves communication performance in varying network topologies, and relieves the network partition problem to a great extent. Clustered Mobility Model: Most of previous works on mobility models do not consider any explicit rationale behind the mobility behavior. In other words, a node does not make a move without referring to a certain demand for the move. In the context of random waypoint (RWP), the selection of a waypoint is random within a given terrain area and does not take a certain behavioral rule or rationale into consideration. This project developed a new mobility model called Clustered Mobility Model (CMM), where nodes tend to move towards a certain waypoint where more nodes are already present. It is not difficult to expect that CMM results in heterogeneous node densities across the terrain area. Some subareas are highly populated with nodes but others are sparse. It could also lead to the creation of highly connected nodes, called hubs, as well as clustering or gathering of nodes around the hubs. This is a clear contrast to the conventional random mobility models such as RWP, in which nodes are scattered almost uniformly in the network. Our intention in this research is to suggest that a mobility model can better represent real-life scenarios when the rationale behind the move is captured and incorporated in the mobility model. We believe this study opens up future development of mobility models based on more sophisticated node behavior. Finally, the project has been brought a much broader impact on Internet-based wireless mobile network education and the corresponding industry, and provided versatile research opportunities to both undergraduate and graduate students. The algorithms and techniques developed have been integrated with the education curricula. In addition, the results of this project reported in journal and conference papers.
