Ajey Kumar

A weighted cache replacement policy for location dependent data in mobile environments

Developing widely useful mobile computing applications presents difficult challenges. On one hand, mobile users demand intuitive user interfaces, fast response times, and deep relevant content. On the other hand, mobile devices have limited processing, storage, power, display, and communication resources. Caching frequently accessed data items on the mobile client is an effective technique to improve the system performance in mobile environment. Due to cache size limitation, the choice of cache replacement technique to find a suitable subset of items for eviction from cache becomes important. In this paper, we propose a new cache replacement policy for location dependent data in mobile environment. The proposed policy selects the predicted region based on clients movement and uses it to calculate the weighted data distance of an item. This makes the policy adaptive to clients movement pattern and provides importance to the regions around clients position. This is unlike earlier policies that consider the directional/non-directional data distance only. We call our policy the Weighted Predicted Region based Cache Replacement Policy (WPRRP). Simulation results show that the proposed policy significantly improves the system performance in comparison to previous schemes in terms of cache hit ratio.

Prioritised Predicted Region based Cache Replacement Policy for location dependent data in mobile environment

Location Dependent Information Services (LDISs) provide information to mobile users depending on their current location. Data has to be transferred from the server to the mobile device, whenever required, due to mobile clients memory constraint. To improve system performance in mobile environment, frequently accessed data must be cached on the mobile client. In this paper, we propose a new cache replacement policy, the Prioritised Predicted Region based Cache Replacement Policy (PPRRP), which uses a cost function for data eviction based on the clients movement pattern. Earlier policies considered only the data distance. Simulation results show significant improvement in system performance with our policy.

A Predicted Region based Cache Replacement Policy for Location Dependent Data in Mobile Environment

Caching frequently accessed data items on the mobile client is an effective technique to improve the system performance in mobile environment. Due to cache size limitations, the choice of cache replacement technique to find a suitable subset of items for eviction from cache becomes important. In this paper, we propose a new cache replacement policy for location dependent data in mobile environment. The proposed policy uses a predicted region based cost function to select an item for eviction from cache. The policy selects the predicted region based on clients movement and uses it to calculate the data distance of an item. This makes the policy adaptive to the clients movement pattern unlike earlier policies that consider the directional/non-directional data distance only. We call our policy the prioritized predicted region based cache replacement policy (PPRRP). Simulation results show that the proposed policy significantly improves the system performance in comparison to previous schemes in terms of cache hit ratio

Scalability in an adaptive cooperative system for wireless sensor networks

The performance of wireless sensor networks (WSNs) can be significantly improved using adaptive cooperative diversity (SCA) technique, which is basically a cross-layer design that combines truncated ARQ at the link layer and cooperative diversity at the physical layer. LEACH is a protocol for wireless sensor networks that utilizes randomized rotation of local cluster heads to evenly distribute the energy load among the sensors in the network. This paper proposes and evaluates the performance of a selective cooperative scheme for wireless sensor networks based on scalability. The evaluation of the lifetime and packet loss rate is presented and results based on the maximum number of retransmissions, network size, packet length and initial energy by nodes are provided. Our scheme shows better performance as compared to others.

A survey of event detection techniques in online social networks

The online social networks (OSNs) have become an important platform for detecting real-world event in recent years. These real-world events are detected by analyzing huge social-stream data available on different OSN platforms. Event detection has become significant because it contains substantial information which describes different scenarios during events or crisis. This information further helps to enable contextual decision making, regarding the event location, content and the temporal specifications. Several studies exist, which offers plethora of frameworks and tools for detecting and analyzing events used for applications like crisis management, monitoring and predicting events in different OSN platforms. In this paper, a survey is done for event detection techniques in OSN based on social text streams—newswire, web forums, emails, blogs and microblogs, for natural disasters, trending or emerging topics and public opinion-based events. The work done and the open problems are explicitly mentioned for each social stream. Further, this paper elucidates the list of event detection tools available for the researchers.

A new cache replacement policy for location dependent data in mobile environment

Caching frequently accessed data items on the client side is an effective technique to improve the system performance in mobile environment. Due to cache size limitations, the choice of cache replacement techniques used to find a suitable subset of items for eviction from cache becomes important. In this paper, we propose a new cache replacement policy, predicted region based replacement policy (PRRP) for location dependent data in mobile environment. Unlike earlier cache replacement policies that consider only directional/non-directional data distance, PRRP takes into account data distance integrated with predicted region of clients movement that adapts to clients movement nature. It also considers the size of data item in cache. Simulation results show that our proposed policy significantly improves the system performance by more than 10 percent in terms of cache hit ratio, compared to previous schemes

Performance evaluation of a selective cooperative scheme for wireless sensor networks

Wireless sensor networks are becoming popular in many industrial and civilian application areas. The need is to improve the performance of such systems that can be significantly done by using adaptive cooperative diversity (SCA) technique, which is basically a cross-layer design that combines truncated ARQ at the link layer and cooperative diversity at the physical layer. In addition to it, LEACH protocol gives advantage of utilizing randomized rotation of local cluster-heads to evenly distribute the energy load among the sensors in the network. This paper proposes an integrated system, SCA with LEACH and evaluates its performance with LEACH with truncated ARQ system. Comparison is done based on network lifetime and packet loss rate of system under varying propagation scenarios, number of retransmissions, initial energy by node and network size. Simulation results show better performances with various achieved thresholds.

Cooperative Space-Time Block Codes for Wireless Video Sensor Networks

Wireless video sensor networks (WVSNs) are gaining popularity due to numerous potential applications such as video surveillance, environmental and habitat monitoring, and so on. Considering large-scale WVSNs, in which the sink node is not within the range of all other nodes, a multi-hop operation is desired. This paper proposes a novel cooperative system that uses space time-block codes to enhance the performance of multi-hop wireless video sensor networks. The proposed scheme is designed to deal with large-scale WVSNs, by adapting the cluster size and extending the cooperation between the cluster-heads. The performance comparison between the proposed system and a non-cooperative scheme is presented based on network lifetime for varying propagation scenarios, number of camera nodes, and on the quality of transmitted videos in a WVSN. Simulation results show an improvement in performance for the proposed system.

Challenges in the Analysis of Online Social Networks: A Data Collection Tool Perspective

The present era of internet has radically changed the way people communicate with each other. Online Social Network platforms have enhanced this to real-time communication where interactions vary from casual relationships to formal bonding. This real-time communication between the users over Online Social Network platforms generates data which directly or indirectly gives lot of information. But extracting this data and mining information out of it is a profound challenge. Researchers need appropriate tools to churn out this data and get valuable information by analyzing and visualizing it. This paper does a comprehensive survey of types of Online Social Network Analysis resulting in segregation of research challenges associated with each of the types. A detailed study of the existing data collection tools and analysis techniques was further carried out to understand the challenges a researcher faces while using it. Finally, mapping analysis was done using research challenges, data collection tools and the types of Online Social Network Analysis, to understand to what extent the existing data collection tools and analysis techniques can meet the research challenges. The mapping analysis shows an absolute requirement of new data collection tools and algorithms by the researchers/developers.

Cooperative STBC with fuzzy election applied to surveillance wireless video sensor networks

Wireless video sensor networks (WVSNs) have obtained popularity due to numerous potential applications such as video surveillance, environmental and habitat monitoring, etc. Transmitting video over WVSNs requires large bandwidth as well as lifetime of sensor nodes long enough to fulfill the application requirements. This paper proposes an integrated system for WVSNs (mainly used for surveillance) that combines the use of adaptive cooperative diversity and fuzzy logic. The cooperative space-time block codes (STBC) are used to achieve full diversity with a simple maximum-likelihood decoding algorithm in order to enhance the performance of the considered WVSN. The performance comparison between the proposed system and a non-cooperative scheme is presented based on network lifetime, quality of transmitted videos, and required number of retransmissions under varying propagation scenarios in a WVSN. Simulation results show better performance for the proposed system.