In cloud computing, the clients have to encrypt and store the data which contain critical information because cloud servers cannot be fully trusted in protecting them. A Searchable Encryption System enables the clients to search encrypted keywords without compromising the security of the original data. However, malicious users are able to take advantage of the Searchable Encryption Systems and impose overloads to the system using a Brute force attack. As a result, it may lead to retrieval of the critical information such as key or generation of false queries. Therefore, we propose a novel Searchable Encryption Scheme based on multi-indices by Bloomfilter to efficiently deal with such Brute force attack.
In order to build a new field domain network with low cost of installation, the research of an wireless sensor network technologies for an industrial factory has drawn much attention. This should be reflected in the research on an web for factory management. So, in this paper, we propose a management system for factory using CoAP that is a suitable web application for a constraint environment. In the proposed management system, a routing protocol is used for discovering a device. And the device registry server help to identify and verify a device and communicate a management server with devices. The management system make development cost low and scalability high, and minimizing a specialized function for the management server, a vendor of device can develop the devices easily and cheaply. It help to install a field network, quickly. We evaluate a performance of the proposed management system by the simulation. The result show that devices are discovered and installed properly without affecting the network.
Multimedia streaming services are rapidly deployed with the development of network technologies and smart devices. According to the increased multimedia traffic caused by the deployment of streaming services, various streaming schemes have been studied for improving the quality of video streaming service in the Internet. In order to guarantee the quality of service(QoS), the existing streaming schemes based on network characteristics improve both network stability and inter-protocol fairness. These schemes, however, do not always guarantee a quality of experience (QoE) for video streaming services due to frequent changes in the video quality. To improve the QoE for video streaming services by avoiding frequent changes in the video quality, we propose a new quality control mechanism, called smooth quality control(SQC). The SQC scheme estimates the network status by using TFRC throughput equation, and then operates the smooth quality control based on the network status and the client buffer status. Through the smooth quality control, our scheme provides the adaptive streaming service according to the varying network status and improves the QoE by avoiding frequent changes in the video quality. Simulation results demonstrate the effectiveness of the proposed scheme.
Geographic multipath routing is one of the most appropriate approaches which can improve the end-to-end reliability via multiple paths for the wireless sensor networks that have frequent network dynamics such as both node and link failures. It has been focused on how to construct a node-disjoint multipath that an intermediate node should be belonged by only a single path. It is because that if two or more paths share one intermediate node, the node may be congested by multiple traffics. Even it might bring multiple path failures if the shared node fails. However, if the node-disjoint multipath schemes are used, there might be another significant problem such as transmission failure or corrupted packet reception due to collisions between adjacent paths. Therefore, we propose a radio-disjoint geographic multipath scheme to avoid the collisions, which allow multiple paths to keep a certain distance between each other. Unfortunately, this simple idea still remains inevitable interference regions, i.e., both source side and destination side. So we eliminate the interferences in these regions by using local scheduling algorithms. We demonstrate that the proposed protocol shows better performance than the previous studies via extensive simulation in terms of end-to-end packet delivery ratio and the end-to-end delay.
In this paper, we propose a decision making mechanism to compare a device-to-base station communication with a device-to-device(D2D) communication. The proposed mechanism can estimate the distance between devices without using GPS and then make the comparison. The communication links between devices and the base station are considered as bi-directional communications between senders and receivers. The comparison mechanism is inspired by the proximity leveling method. In order to evaluate the proposed method's performance via simulation, we perform this decision making mechanism in various situations and identify the condition of device-to-device communications. As a result, when SNR of D2D communication is larger than some SNR, the D2D communication is performed.
Message In Message (MIM) is an emerging wireless technology to improve the capacity of wireless networks, which augments concurrent transmission opportunities of contending wireless nodes. In a MIM-capable communication system, however, the challenging problem is that the concurrent transmission opportunity is restricted by underlying network topologies. In this paper, we propose an MIM-aware association control scheme (MIMAC) that can greatly increase concurrent transmission opportunities by regulating the association among OpenFlow APs in NOX-based wireless systems. MIMAC exploits the distinctive features of NOX architectures, such as maintaining a global view of the network topology and controlling the association among OpenFlow APs in a centralized way. Using simulation-based evaluations, we demonstrate that MIMAC achieves high throughput enhancement by up to 200% compared to legacy WLAN systems.
Multipath TCP (MPTCP) has just been completed the standardization by IETF. MPTCP is designed to be backward compatible with regular TCP, and its performance is equivalent to that of a regular TCP flow on the best path for it. However, MITCP has performance degradation similar to that the regular TCP does, because MITCP is extended based on the regular TCP. Especially, the performance of TCP decreases in unreliable wireless network environment. TCP Westwood and SQRT TCP have been proposed for streaming transmission in wireless network. In this paper, we use the characteristics similar to those schemes. However, there are some problems that the TCP Westwood and SQRT TCP cannot fairly use the resources and properly distribute the load to multipath, because these schemes are designed for single-path transmission. Therefore, in this paper, we propose a multipath transmission scheme which improves TCP Westwood and SQRT TCP congestion control algorithms. The proposed scheme demonstrates that its performance is equivalent to that of a regular TCP flow on the best path for it, and is a well-suited method to solve the above mentioned problems. The results from extensive simulations show that the proposed SMITCP outperforms the existing TCP Westwood and SQRT TCP, and also achieves the goals of MITCP (i.e., improved throughput, fairness, load balancing).
Cellular network operators are seriously concerned with the ever increasing traffic demand from mobile users, which is overwhelming the wireless link capacity. The conventional pull-based communication model is not appropriate to deal with the data explosion problem. Instead, we propose to push the contents proactively. Also, we leverage the direct connectivity (e.g. Wi-Fi) among mobile users to reduce the traffic load on cellular links for content delivery. We analyze how fast content is disseminated by the push-based delivery via cellular links along with direct share-based delivery via ad hoc connectivity among users. We also formulate the optimization framework and design a split algorithm by which the tradeoff among dissemination cost, delivery delay, and dissemination portion is explored and evaluated.
With increasing use of internet services on mobile terminals, the importance of contents syndication technology is growing in order to provide services desired by users. In general, once multiple client access to resources, there'll be also multiple accesses at the next access time in client-initiated periodic update environment. In result, it may lower the efficiency of resource use because the network is overloaded by the simultaneous connection of multiple clients. In order to solve this problem, we propose a traffic dispersion algorithm that can disperse multiple accesses by providing each of multiple clients with a different next access time.
This paper proposes a new platform-independent security framework for smartphone environment. The proposed framework can be used on any platform and web-browser in order to support certificate operations, secret key management, and cryptographic operations such as digital signing. Based on PAKE, it can prevent URL spoofing attacks by making security association between the proposed framework and the external web servers or applications.
In wireless ad hoc networks, signal fading and interference have adverse effects on delivering signals. To alleviate this problem, MAC protocols for supporting cooperative communication have been introduced. One of the cooperative MAC protocols is using relay-based cooperative strategy. The performance of these MAC protocols depends on how to select relay nodes. We propose a novel cooperative MAC protocol with reactive relay selection that reduces collisions and overheads in relay selection. In our proposed protocol, using the overheard transmissions, each relay candidate node determines which group it belongs to, and estimates the number of nodes in the group. The source node transmits through the relay candidate node which belongs to best group in order to minimize the total transmission time. The reduction of the total transmission time leads to the increase in total network throughput.
In mobile ad-hoc networks, the network topology is changed due to environmental dynamics and node mobility. A routing protocol is a key element for performance of the mobile ad-hoc network and aims to minimize packet loss or delay by agilely adapting the changed topology. In the wireless channel, The Bit Error Rate (BER) increases with distance between the transmitter and the receiver. The periodic HELLO message indicates neighbor connectivity. When using the control message (HELLO, RREP) with small size to reduce the network overhead, it is difficult to find the reliable path for multimedia data transfer. Similarly, if the control traffic according to data traffic is generated, the serious network overhead can be increased. In this paper, we propose an efficient algorithm to select the path based on the size of data traffic and present an adaptive link estimation scheme to reduce the control overhead. Finally, we evaluate the effect of measured values on packet loss, delay, and routing overhead.
