Liangzhong Yin

Bio: Liangzhong Yin is an academic researcher from Pennsylvania State University. The author has contributed to research in topics: Cache & Ad hoc wireless distribution service. The author has an hindex of 10, co-authored 10 publications receiving 1402 citations.

Supporting cooperative caching in ad hoc networks

Abstract: 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.

Supporting cooperative caching in ad hoc networks

Abstract: 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.

Cooperative cache-based data access in ad hoc networks

Abstract: Cooperative caching, in which multiple nodes share and coordinate cached data, is widely used to improve Web performance in wired networks. However, resource constraints and node mobility have limited the application of these techniques in ad hoc networks. We propose caching techniques that use the underlying routing protocols to overcome these constraints and further improve performance.

A generalized target-driven cache replacement policy for mobile environments

Abstract: Caching frequently accessed data items on the client side is an effective technique to improve system performance in a mobile environment. Due to cache size limitations, cache replacement algorithms are used to find a suitable subset of items for eviction from the cache. In this paper, we propose a generalized cost function for cache replacement algorithms for mobile environment. The distinctive feature of our cost function is that it is general and it can be used for various performance metrics by making the necessary changes. To demonstrate the practical effectiveness of the general cost function, we derive two specific functions to be evaluated by setting two different targets: minimizing the query delay and minimizing the downlink traffic. Detailed experiments are carried out to evaluate the proposed methodology. Compared to previous schemes, our algorithm significantly improves the performance in terms of query delay or in terms of bandwidth utilization depending on the targets.

Adaptive power-aware prefetch in wireless networks

Abstract: 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.

VADD: Vehicle-Assisted Data Delivery in Vehicular Ad Hoc Networks

Abstract: Multihop data delivery through vehicular ad hoc networks is complicated by the fact that vehicular networks are highly mobile and frequently disconnected. To address this issue, we adopt the idea of carry and forward, where a moving vehicle carries a packet until a new vehicle moves into its vicinity and forwards the packet. Being different from existing carry and forward solutions, we make use of predictable vehicle mobility, which is limited by traffic pattern and road layout. Based on the existing traffic pattern, a vehicle can find the next road to forward the packet to reduce the delay. We propose several vehicle-assisted data delivery (VADD) protocols to forward the packet to the best road with the lowest data-delivery delay. Experimental results show that the proposed VADD protocols outperform existing solutions in terms of packet-delivery ratio, data packet delay, and protocol overhead. Among the proposed VADD protocols, the hybrid probe (H-VADD) protocol has a much better performance.

VADD: Vehicle-Assisted Data Delivery in Vehicular Ad Hoc Networks

Abstract: Multihop data delivery through vehicular ad hoc networks is complicated by the fact that vehicular networks are highly mobile and frequently disconnected. To address this issue, we adopt the idea of carry and forward, where a moving vehicle carries a packet until a new vehicle moves into its vicinity and forwards the packet. Being different from existing carry and forward solutions, we make use of predictable vehicle mobility, which is limited by traffic pattern and road layout. Based on the existing traffic pattern, a vehicle can find the next road to forward the packet to reduce the delay. We propose several vehicle-assisted data delivery (VADD) protocols to forward the packet to the best road with the lowest data-delivery delay. Experimental results show that the proposed VADD protocols outperform existing so- lutions in terms of packet-delivery ratio, data packet delay, and protocol overhead. Among the proposed VADD protocols, the Hybrid Probe (H-VADD) protocol has a much better performance.

Supporting cooperative caching in ad hoc networks

Abstract: 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.

Internet of vehicles in big data era

Abstract: As the rapid development of automotive telematics, modern vehicles are expected to be connected through heterogeneous radio access technologies and are able to exchange massive information with their surrounding environment. By significantly expanding the network scale and conducting both real time and long term information processing, the traditional Vehicular Ad- Hoc Networks U+0028 VANETs U+0029 are evolving to the Internet of Vehicles U+0028 IoV U+0029, which promises efficient and intelligent prospect for the future transportation system. On the other hand, vehicles are not only consuming but also generating a huge amount and enormous types of data, which are referred to as Big Data. In this article, we first investigate the relationship between IoV and big data in vehicular environment, mainly on how IoV supports the transmission, storage, computing of the big data, and in return how IoV benefits from big data in terms of IoV characterization, performance evaluation and big data assisted communication protocol design. We then investigate the application of IoV big data for autonomous vehicles. Finally the emerging issues of the big data enabled IoV are discussed.

Supporting cooperative caching in ad hoc networks

Abstract: 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.