In mobile ad hoc networks (MANETs), nodes move freely and link/node failures are common, which leads to frequent network partitions. When a network partition occurs, mobile nodes in one partition are not able to access data hosted by nodes in other partitions, and hence significantly degrade the performance of data access. To deal with this problem, we apply data replication techniques. Existing data replication solutions in both wired or wireless networks aim at either reducing the query delay or improving the data availability, but not both. As both metrics are important for mobile nodes, we propose schemes to balance the trade-offs between data availability and query delay under different system settings and requirements. Extensive simulation results show that the proposed schemes can achieve a balance between these two metrics and provide satisfying system performance.

Most researches in ad hoc networks focus on routing and not much work has been done on data access. A common technique used to improve the performance of data access is caching. Cooperative caching, which allows the sharing and coordination of cached data among multiple nodes, can further explore the potential of the caching techniques. Due to mobility and resource constraints of ad hoc networks, cooperative caching techniques designed for wired networks may not be applicable to ad hoc networks. In this paper, we design and evaluate cooperative caching techniques to efficiently support data access in ad hoc networks. We first propose two schemes: CacheData, which caches the data, and CachePath, which caches the data path. After analyzing the performance of those two schemes, we propose a hybrid approach (HybridCache), which can further improve the performance by taking advantage of CacheData and CachePath while avoiding their weaknesses. Cache replacement policies are also studied to further improve the performance. Simulation results show that the proposed schemes can significantly reduce the query delay and message complexity when compared to other caching schemes.

In peer-to-peer networks, indices are used to map data id to nodes that host the data. The performance of data access can be improved by actively pushing indices to interested nodes. This paper proposes the Dynamic-tree based Update Propagation (DUP) scheme, which builds the update propagation tree to facilitate the propagation of indices. Because the update propagation tree only involves nodes that are essential for update propagation, the overhead of DUP is very small and the query latency is significantly reduced.

Most researches in ad hoc networks focus on routing, and not much work has been done on data access. A common technique used to improve the performance of data access is caching. Cooperative caching, which allows the sharing and coordination of cached data among multiple nodes, can further explore the potential of the caching techniques. Due to mobility and resource constraints of ad hoc networks, cooperative caching techniques designed for wired network may not be applicable to ad hoc networks. In this paper, we design and evaluate cooperative caching techniques to efficiently support data access in ad hoc networks. We first propose two schemes: cachedata which caches the data, and cachepath which caches the data path. After analyzing the performance of those two schemes, we propose a hybrid approach (hybridcache) which can further improve the performance by taking advantage of cachedata and cachepath while avoiding their weaknesses. Simulation results show that the proposed schemes can significantly reduce the query delay and message complexity when compared to other caching schemes.

In mobile ad hoc networks, nodes move freely and link/node failures are common. This leads to frequent network partitions, which may significantly degrade the performance of data access in ad hoc networks. When the network partition occurs, mobile nodes in one network are not able to access data hosted by nodes in other networks. In this paper, we deal with this problem by applying data replication techniques. Existing data replication solutions in both wired or wireless networks aim at either reducing the query delay or improving the data accessibility. As both metrics are important for mobile nodes, we propose schemes to balance the tradeoffs between data accessibility and query delay under different system settings and requirements. Simulation results show that the proposed schemes can achieve a balance between these two metrics and provide satisfying system performance.

Most of the prefetch techniques used in the current cache management schemes do not consider power constraints of the mobile clients and other factors such as the size of the data items, the data access rate, and the data update rate. In this paper, we address these issues by proposing a power-aware prefetch scheme, called adaptive value-based prefetch (AVP) scheme. The AVP scheme defines a value function which can optimize the prefetch cost to achieve better performance. Also, AVP dynamically adjusts the number of prefetches to get better tradeoff between performance and power. As stretch is widely adopted as a performance metric for variable-size data requests, we show by analysis that the proposed approach can indeed achieve the optimal performance in terms of stretch when power consumption is considered. Simulation results demonstrate that our algorithm significantly outperforms existing prefetching algorithms under various scenarios.

Most of the prefetch techniques used in the current cache management schemes do not consider the power constraints of the mobile clients and other factors such as the size of the data items, the data access rate, and the data update rate. We address these issues by proposing a power-aware prefetch scheme, called the value-based adaptive prefetch (VAP) scheme. The VAP scheme defines a value function which can optimize the prefetch cost to achieve better performance. Also, VAP dynamically adjusts the number of prefetches based on the current energy level to prolong the system running time. As stretch is widely adopted as a performance metric for variable-size data requests, we show by analysis that the proposed algorithm can indeed achieve the optimal performance in terms of stretch when power consumption is considered. Simulation results demonstrate that our algorithm significantly outperforms existing prefetching algorithms under various scenarios.