Smooth Handoff with Enhanced Packet Buffering-and-Forwarding in Wireless/Mobile Networks

As an alternative way of rendering novel views of real and/or virtual environments to geometry-based models, 3D image-based rendering is getting more attention. Taking the weak hardware acceleration support of mobile devices into consideration, image-based rendering is a good choice for interactive 3D applications for such devices. However, because of the small storage size of mobile devices, the large size of the data set used by most modern image-based rendering techniques often introduces difficulties in utilizing image-based rendering on mobile devices. Therefore, a reference image buffer management mechanism is critical to the success of image-based rendering techniques on mobile devices. Different buffer management policies may result in different quality-of-service. In this paper, we compare the performance of several buffer management policies based on customized QoS factors for image-based rendering techniques. In order to make our experiments general, we show that image-based rendering techniques are interpolations of the Plenoptic function and define the QoS factors based on the interpolation theory. The results of the experiments show the impacts of different buffer management policies on customized QoS factors. Because the QoS factors do not depend on any special algorithms, this result keeps true for all modern image-based rendering algorithms

Hybrid memory composed of DRAM and persistent memory (PM) offers a promising way to realize large-capacity main memory supporting in-memory data storage and computing. However, traditional buffer management schemes focus on improving the hit ratio but lack awareness of the limitations of PM, e.g., slower write time and lower write endurance than DRAM. Therefore, developing new buffer management policies that can reduce costly write-backs of PM blocks while maintaining high performance for the hybrid buffer, is of paramount importance. Existing approaches mainly use a page-grained buffering policy, which will cause unnecessary data migrations between DRAM and PM, leading to a high number of disk I/Os and PM writes. Aiming to reduce I/O costs and PM writes, we propose a new buffer manager named HiBuffer for DRAM/PM-based hybrid memory systems. HiBuffer presents several novel ideas. First, it adopts multi-grained data layouts to manage the hybrid buffer cooperatively. In addition to the page granularity, we introduce Lines for the DRAM buffer and Sectors to the PM buffer, forming a buffer with three granularities, including Line, Sector, and Page. We prove that the multi-grained cooperative buffer management can deliver higher performance than existing page-grained schemes. Second, we propose a sector-grained method to migrate data from DRAM to PM, which can avoid unnecessary data movements and reduce PM writes. Third, we use an out-of-place updating mechanism to absorb updates in DRAM, which can further reduce the writes to PM. We compare HiBuffer with three existing schemes, including LRU, CLOCK-DWF, and MiniPage, on five synthetic workloads and the YCSB benchmark using real Intel Optane DC Persistent Memory. The results in terms of various metrics, including running time, PM writes, hit ratio, and disk I/Os, suggest the efficiency of HiBuffer. In particular, HiBuffer reduces the running time by up to 37.8% and the writes to PM by up to 83% compared to the competitors when evaluated on the YCSB benchmark.

The buffer management policy used at an IP/ATM gateway can significantly impact end-to-end performance for IP traffic (particularly apparent when IP traffic is transported using the ATM ABR service class). The ABR service is designed to achieve near-loss free operation in the core of the ATM network by adaptively shaping traffic at the edge of the ATM network. This can cause buffer build-ups to occur at the IP/ATM gateway due to transient overloads. Since the buffering available at a IP/ATM gateway is small relative to the worst case buffer build up, the buffer management policy has a significant impact in determining the loss rate seen by individual connections. Moreover, for connections that use TCP as the transport protocol, throughput is directly proportional to the number of buffers available to a connection. Therefore, for this class of connections, the buffer management policy also affects the average throughput seen by a connection. Our results show that it is desirable for a buffer management policy at an IP/ATM gateway to incorporate first a mechanism to ensure that an individual connection receives a minimal buffer allocation that is proportional to the product of its bottleneck rate and round-trip delay, and second a mechanism to avoid synchronized losses among TCP connections passing through the same IP/ATM gateway. Rate proportional buffering enables a gateway to provide isolation between connections that have different (downstream) bottleneck links. Avoiding loss synchronization allows more effective use of the shared buffers. This improves the overall utilization of network links. We also show that using buffer management policies, developed in the context of IP routers, and ATM switches, at an IP/ATM gateway can often lead to under-utilization of link capacity and unfairness.

Supporting transmission of stream media over wireless mobile networks is often difficult because packets may be lost due to the rerouting of packets during handoff, and also because bursts of packet loss may occur during handoff due to the disparity in the amount of available bandwidth among different cells. In this paper, we propose an end-to-end multipath handoff scheme that provides smooth handoff for stream media in wireless networks with different amounts of available bandwidth from cell to cell. In the proposed scheme, multiple paths are established during handoff to reach a mobile destination node. The stream media sources are equipped with an adaptive multilayer encoder, and important layers in the encoded video stream are duplicated and transmitted over multiple paths during handoff. The effectiveness of the proposed multipath handoff scheme is verified and compared with existing schemes through extensive simulations. The simulation results show that the proposed scheme provides higher throughput and better quality for stream media.

Mobile opportunistic networks are characterized by intermittent connectivity and practically no end-to-end connection. In these kinds of network, network capacity and throughput largely depends packet replication. As a result buffer space tends to quickly deplete which may result in severe data loss due to packet drop. To the best of our knowledge, the two important phenomenon of traffic management viz., jitter and packet loss have evaded the minds of researchers in this field and hence we study the problem of buffer management and packet scheduling in such networks. We propose a fair queue scheduling policy where packets are sorted based on total waiting time, i.e. sum of waiting times over all the previous hops, before being transferred over a network link. We analytically prove that scheduling packet transmission as above reduces overall waiting time which leads to lower delay. We also propose a source initiated congestion aware buffer management scheme which helps in reducing number of packet loss significantly. The proposed scheduling and buffer management policy is simulated using real world (Cambridge iMote traces) datasets and compared with other existing scheduling policies. Results show that that proposed scheme has lower delay and lower packet drop compared to other scheduling schemes.

The ultimate goal of this study is to reduce routing overhead and latency by using mobile agent to get the information about the mobile nodes. The mobile agent is a software program that able to migrate from one node to another node. The mobile agent is not executes under any controller. In this study, the mobile agent is used to get the information about link duration and the energy of the nodes. The source node accesses the information from the mobile agent by using Remote procedure call. When there exists a link between source and destination means it will directly transmit the data to the destination or otherwise transmit via relay node. The relay node is selected based on the link duration and energy of the node. So, the proposed technique reduces the link failure and routing overhead. The performance of the proposed scheme is analyzed by using the simulator NS2.

Due to the unstable network topology of Delay Tolerant Networks (DTNs), multi-copy routing is often used to increase the reliability of message delivery. However, this routing approach suffers from high buffer and bandwidth overhead. While much work has been done in the design of forwarding algorithms, little work has focused on studying forwarding under the presence of resource constraints such as short contact durations and small buffers. In this paper, we investigate a multi-copy routing strategy and a buffer management policy that maximize the delivery rate in DTNs. We consider a realistic DTN environment with resource constraints, heterogeneous node mobility, and varied message sizes. There are three key issues in DTN routing: (1) to which next hop relay node should messages be replicated, (2) in which order should messages be replicated, and (3) which messages should be dropped first when the buffer is full. We propose to forward a message to a neighboring node that has both a stronger social tie with the destination and a smaller or similar queue length. This aims to reduce traffic at highly connected network nodes, avoiding frequent message drops which compromise the delivery ratio. For the second and third issue, we develop a utility function using global network information to compute per-packet delivery rate utility. Messages are then scheduled and dropped according to their utility values. Extensive simulation results based on the real-world San Francisco cab trace show that our proposed scheme can achieve a delivery rate of up to 22% higher than existing schemes, while still maintaining a comparable average delivery delay. Furthermore, our scheme distributes the network loads more evenly, with the top 10% of network nodes handling only 24% of the forwardings.

In order to share the intelligence among all kinds of mobile nodes, this paper puts forward the intelligence sharing technology based on mobile agents in mobile peer-to-peer (MP2P) system. The MP2P system could build up a common applicable theoretical framework for mobile intelligence management such as mobile intelligence acquisition, query, synchronization, cache, and prefetching. In order to reduce the maintenance cost of intelligence index table for the mobile nodes in the MP2P network, use the edge intelligence of network enough, and parallel process the mobile task of network, we propose the intelligence management technology based on mobile agent (MA), which improves the execution efficiency of security authentication, intelligence distribution, cache prefetching, transaction processing, location service, and task cooperation among the mobile nodes.

The delay tolerant networks work in communication environments that are a subject to delays and distributions. Mobile nodes in DTN can communicate with each other even though there is no permanent link between the source and the destination. To have a better rate of delivery of messages in DTN, the long-term storage and message replication require an efficient buffer management. In this paper, we propose a partially observed Markov decision process framework to solve the problem of buffer management. The node uses messages' transmissions number to decide which message to drop. We look for an efficient strategy that a node can follow to maximise its average reward, while taking into account the energy penalties in different levels of cooperation. For this, we have analytically determined the optimal policy's interval of our proposal. Furthermore, we use ONE simulator to compare our findings to traditional buffer management policies under different mobility models.

This paper presents a mailbox-based scheme for designing flexible and adaptive message delivery protocols in mobile agent (MA) systems. The scheme associates each mobile agent with a mailbox while allowing the decoupling between them, i.e., a mobile agent can migrate to a new site without bringing its mailbox. By separating the concerns of locating the mailbox of a mobile agent and delivering a message to the agent, we obtain a large space of protocol design with flexibility. Using a three-dimensional model based on the scheme, we have developed a taxonomy of MA communication protocols, which not only covers, as special cases, several known MA message delivery protocols, but also allows for the design of new ones well suited for various application requirements. We describe such an efficient and adaptive protocol derived front the model. The protocol guarantees reliable delivery of messages to mobile agents. We analyze the design trade-offs and performance of the protocol, using an analytic model as well as extensive simulation experiments.

This book explores the implications of non-volatile memory (NVM) for database management systems (DBMSs). The advent of NVM will fundamentally change the dichotomy between volatile memory and durable storage in DBMSs. These new NVM devices are almost as fast as volatile memory, but all writes to them are persistent even after power loss. Existing DBMSs are unable to take full advantage of this technology because their internal architectures are predicated on the assumption that memory is volatile. With NVM, many of the components of legacy DBMSs are unnecessary and will degrade the performance of data-intensive applications. We present the design and implementation of DBMS architectures that are explicitly tailored for NVM. The book focuses on three aspects of a DBMS: (1) logging and recovery, (2) storage and buffer management, and (3) indexing. First, we present a logging and recovery protocol that enables the DBMS to support near-instantaneous recovery. Second, we propose a storage engine architecture and buffer management policy that leverages the durability and byte-addressability properties of NVM to reduce data duplication and data migration. Third, the book presents the design of a range index tailored for NVM that is latch-free yet simple to implement. All together, the work described in this book illustrates that rethinking the fundamental algorithms and data structures employed in a DBMS for NVM improves performance and availability, reduces operational cost, and simplifies software development.

Recently, there has been increasing interest in Mobile Wireless Sensor Networks MWSNs that are constructed by mobile sensor nodes held by ordinary people, and it has led to a new concept called urban sensing. In such MWSNs, mobile sensor nodes densely exist, and thus, there are basically many sensor nodes that can sense a geographical point in the entire sensing area. To reduce the communication cost for gathering sensor data, it is desirable to gather the sensor data from the minimum number of mobile sensor nodes which are necessary to guarantee the sensing coverage or the quality of services. In this paper, to achieve this, we propose a data gathering method using mobile agents in dense MWSNs. The proposed method guarantees the sensing coverage of the entire area using mobile agents that autonomously perform sensing operations, transmit sensor data, and move between sensor nodes. By gathering only sensor data generated by sensor nodes where mobile agents are running, our proposed method can achieve efficient gathering of sensor data.

Performance comparison of remote procedure calling and mobile agent approach to control and data transfer in distributed computing environment

Security has become important to mobile ad hoc networks (MANETs) due mainly to their use for many mission and life-critical applications. However, the broadcast nature of inter-node communications and node mobility in MANETs make it very challenging to secure MANETs. Moreover, their constantly changing topology causes network node density and neighbor relationships to change dynamically. This paper presents an intrusion detection system (IDS) for MANETs at the application layer. The IDS utilizes (1) both anomaly and misuse detection schemes to identify attacks in MANETs and (2) mobile agents (MAs) to augment each node's intrusion-detection capability. In particular, each node is equipped with a local IDS, and MAs will be dispatched periodically or on-demand to augment each node's IDS. We present the design of this IDS and the overall network structure, as well as the methods for authenticating and dispatching MAs. We also evaluate the trade-offs between different design parameters of MAs.

A Wireless Sensor network (WSN) consists of large number of low cost low power sensor nodes. The nature of wireless sensor networks makes them very attractive to attackers. One of the most popular and serious attacks in wireless sensor networks is sink hole attack and most existing protocols to defend against this attack used cryptographic methods with keys. In sink hole attack a sensor node will have a lot of false neighbors. Wireless Sensor Network has a dynamic topology, intermittent connectivity, and resource constrained device nodes. Researchers over the past years have encouraged the use of mobile agent to overcome these challenges. The proposed scheme is to defend against sink hole attacks using mobile agents. Mobile agent is a program segment which is self controlling. They navigate from node to node not only transmitting data but also doing computation. They are an effective paradigm for distributed applications, and especially attractive in a dynamic network environment. A routing algorithm with multiple constraints is proposed based on mobile agents. It uses mobile agents to collect information of all mobile sensor nodes to make every node aware of the entire network so that a valid node will not listen the cheating information from malicious or compromised node which leads to sink hole attack. The significant feature of the proposed mechanism is that it does not need any encryption or decryption mechanism to detect the sink hole attack. This mechanism does not require more energy than normal routing protocols like AODV. Here we implement a simulation-based model of our solution to recover from a Sinkhole attack in a Wireless Sensor Network. The mobile agents were developed using the Aglet.