[show abstract][hide abstract] ABSTRACT: Topology control protocols have been proposed to construct efficient network topologies with several design goals, e.g., network-wide connectivity, minimal energy cost, symmetry, lower nodal degree, and therefore higher spatial reuse or lower interferences. Neighbor-based topology control protocols are simple and assume that each node in the network is connected to its k least-distant neighbors. There have been several empirical and theoretical research efforts that recommend a network-wide optimal value of the local parameter k. However, since most of the design goals often run against each other the suggested lower and upper bounds on the values of k are not sufficient to provide a controllable trade-off among various design goals. In this article, an adaptive neighbor-based topology control protocol is presented where the neighboring nodes collaborate and provide feedback on the network connectivity to decide on their respective transmission ranges. Since every node adaptively adjusts its number of neighbors, the parameter k acts as a performance knob to choose a set of backbone nodes and to form a hierarchical topology structure consisting of symmetric links. Through extensive simulation-based study, it is shown that the value of k can be tuned to generate fully connected network topologies while offering an efficient trade-off among various design goals.
EURASIP Journal on Wireless Communications and Networking 08/2013; 2012(1). · 0.54 Impact Factor
[show abstract][hide abstract] ABSTRACT: In wireless sensor network applications for surveillance and reconnaissance, large amounts of redundant sensing data are frequently
generated. It is important to control these data with efficient data aggregation techniques to reduce energy consumption in
the network. Several clustering methods were utilized in previous works to aggregate large amounts of data produced from sensors
in target tracking applications (Park in A dissertation for Doctoral in North Carolina State University, 2006). However, such data aggregation algorithms show effectiveness only in restricted environments, while posing great problems
when adapting to other various situations. To alleviate these problems, we propose two hybrid clustering based data aggregation
mechanisms. The combined clustering-based data aggregation mechanism can apply multiple clustering techniques simultaneously
in a single network depending on the network environment. The adaptive clustering-based data aggregation mechanism can adaptively
choose a suitable clustering technique, depending on the status of the network. The proposed mechanisms can increase the data
aggregation efficiency as well as improve energy efficiency and other important issues compared to previous works. Performance
evaluation via mathematical analysis and simulation has been made to show the effectiveness of the proposed mechanisms.
KeywordsWireless sensor network–Data aggregation–Clustering–Adaptive
[show abstract][hide abstract] ABSTRACT: Smart grid environments require high standard of reliable transmission technologies to support various types of electrical services and applications. This paper recommends the utilization of IEEE 802.11s based Wireless LAN Mesh Networks as the high-speed backbone networks for smart grid infrastructure. 802.11s based mesh networks can provide high scalability and flexibility, along with low installation and management costs. We also describe some challenging issues of the IEEE 802.11s WLAN mesh based smart grid networks, and propose two novel methods for improving their routing reliability. A simulation study using the ns-3 was conducted to evaluate an important problem in the current mesh networks and prove the superiority of our proposed scheme.
Communications Workshops (ICC), 2011 IEEE International Conference on; 07/2011
[show abstract][hide abstract] ABSTRACT: In multi-interface multi-channel (MIMC) based tactical ad hoc networks, QoS support is one of the main challenging issues for multi-hop transmissions. To support QoS in such a harsh environment, we propose a novel MAC scheme to minimize multi-hop as well as per-hop delay. The current IEEE 802.11 MAC protocols should contend to reserve the channel resource at every hop by each sender. The every-hop channel contention results in a degradation of end-to-end delay for multi-hop transmissions. The basic idea of our scheme is to make a "multi-hop reservation" at the MAC layer by using the modified RTS frame. It contains additional information such as destination information, packet priority, and hop count, etc. Our scheme can minimize the multi-hop delay and support the QoS of the critical data in real time (i.e., VoIP, sensing video data, Video conference between commanders). Our simulation study and numerical analysis show that the proposed scheme outperforms the IEEE 802.11 MAC.
Advanced Information Networking and Applications (WAINA), 2011 IEEE Workshops of International Conference on; 04/2011
[show abstract][hide abstract] ABSTRACT: The IEEE 802.11s standard is designed to support multi-hop mesh networking between WLAN devices. It features the HWMP (Hybrid Wireless Mesh Protocol) as its default path selection protocol which combines the proactive tree building mode and the on-demand path selection mode. The proactive mode can periodically maintain the lowest link cost route to the root node, but poses the path instability problem, where the path is unnecessarily changed when the path is updated. As a result, the performance of the network is degraded. To alleviate this problem, we propose the Session-oriented Adaptive Routing (SOAR) protocol, which recognizes each data session and prevents path switching while the data session is in progress. To achieve this, we do not switch the existing path even though the link cost may be higher than the new path, unless the potential throughput gain of the new path is considered better than the pre-determined threshold. Moreover, the new path with lower link cost is also stored and used when a new data session is initiated. We have conducted preliminary simulation studies via the ns-3 to evaluate the performance of the proposed scheme.
Advanced Communication Technology (ICACT), 2011 13th International Conference on; 03/2011
[show abstract][hide abstract] ABSTRACT: Utilizing multi-interfaces and multi-channels (MIMC) is essential in increasing capacity and performance of emerging wireless mesh networks. However, the current IEEE 802.11s draft which is a standardization activity of the WLAN based mesh network does not sufficiently consider these capabilities. This may lead to poor performance of the network in terms of throughput and scalability. In this paper, first we analyze the misbehavior of the current standard especially in the path selection process. Then, we propose a new routing protocol that is suitable for the multi-interface and multi-channel environment. The proposed scheme selects high throughput paths based on channel diversity information and reduces the broadcast overhead of control messages. Moreover, it is fully compatible with Hybrid Wireless Mesh Protocol (HWMP) which is the default routing protocol proposed in the current standard. Interestingly, in the simulation study, we observe that the network performance increases even though only a partial number of nodes are equipped with the proposed scheme.
Information Networking (ICOIN), 2011 International Conference on; 02/2011
[show abstract][hide abstract] ABSTRACT: Flash memory is being rapidly deployed as data storage for embedded devices such as PDAs, MP3 players, mobile phones and digital
cameras due to its low electronic power, non-volatile storage, high performance, physical stability and portability. The most
prominent characteristic of flash memory is that prewritten data can only be dynamically updated via the time consuming erase
operation. Furthermore, every block in flash memory has a limited program/erase cycle. In order to manage these issues, the
flash memory controller can be integrated with a software module called the flash translation layer (FTL). This paper surveys
the state-of-art FTL algorithms. The FTL algorithms can be classified by the complexity of the algorithms: basic and advance.
Furthermore, they can be classified by their corresponding tasks: performance enhancement and durability enhancement. The
FTL algorithms corresponding to each classification are further broken down into various schemes depending on the methods
they adopt. This paper also provides the information of hardware features of flash memory for FTL programmers.
Design Automation for Embedded Systems 01/2011; 15:191-224. · 0.29 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this paper, we study the problem of how to design a medical-grade wireless local area network (WLAN) for healthcare facilities. First, unlike the IEEE 802.11e MAC, which categorizes traffic primarily by their delay constraints, we prioritize medical applications according to their medical urgency. Second, we propose a mechanism that can guarantee absolute priority to each traffic category, which is critical for medical-grade quality of service (QoS), while the conventional 802.11e MAC only provides relative priority to each traffic category. Based on absolute priority, we focus on the performance of real-time patient monitoring applications, and derive the optimal contention window size that can significantly improve the throughput performance. Finally, for proper performance evaluation from a medical viewpoint, we introduce the weighted diagnostic distortion (WDD) as a medical QoS metric to effectively measure the medical diagnosability by extracting the main diagnostic features of medical signal. Our simulation result shows that the proposed mechanism, together with medical categorization using absolute priority, can significantly improve the medical-grade QoS performance over the conventional IEEE 802.11e MAC.
Journal of Communications and Networks - JCN. 01/2011; 13(2):149-159.
[show abstract][hide abstract] ABSTRACT: Multicasting is a useful communication method in wireless mesh networks (WMNs). Many applications in WMNs require efficient and reliable multicast communications, i.e., high delivery ratio with low overhead among a group of recipients. In spite of its significance, little work has been done on providing such multicast service in multi-channel WMNs. Traditional multicast protocols for wireless and multi-hop networks tend to assume that all nodes, each of which is equipped with a single interface, collaborate on the same channel. This single-channel assumption is not always true, as WMNs often provide nodes with multiple interfaces to enhance performance. In multi-channel and multi-interface (MCMI) WMNs, the same multicast data must be sent multiple times by a sender node if its neighboring nodes operate on different channels. In this paper, we try to tackle the challenging issue of how to design a multicast protocol more suitable for MCMI WMNs. Our multicast protocol builds multicast paths while inviting multicast members, and tries to allocate the same channel to neighboring members in a bottom-up manner. By unifying fixed channels of one-hop multicast neighbors, the proposed algorithm can improve the performance such as reducing multicast data transmission overhead and delay, while managing a successful delivery ratio. In order to prove such expectation on the performance, we have implemented and evaluated the proposed solution on the real testbed having the maximum 24 nodes, each of which is equipped with two IEEE 802.11a Atheros WLAN cards.
[show abstract][hide abstract] ABSTRACT: Jamming attack by adversaries is the critical threat in Network Centric Warfare that uses tactical wireless networks. Thus research on developing new networking protocols that are resilient to such attacks are of high importance. Geocasting is a prominent routing mechanism in tactical networks to send critical messages such as alarm about chemical attack, guerrilla detection etc, to the nodes within a specific geographical region. To apply geocast protocols in the tactical environment, it should provide assurance that the packet delivery is reliable despite of jamming attacks. In this paper, we propose two jamming resilient geocasting schemes for tactical mobile ad hoc networks. Our first scheme called the “Failure-Based Learning” in which the sender nodes are not aware of the jamming attacks and try to send packets repeatedly. This method is enhanced by another scheme called “Detour by Anchor Point” with information about the jamming attack which sent to the source node, such that it can proactively avoid the jamming region for successful packet delivery. The simulation results show that our proposed schemes significantly outperform single and dual path geocasting protocols under jamming attack and mobile scenarios.
Information and Communication Technology Convergence (ICTC), 2010 International Conference on; 12/2010
[show abstract][hide abstract] ABSTRACT: To support reliable communication in tactical area networks, multi-path routing protocols can be utilized. Multipath routing protocol makes decisions to select primary route and alternative path by using routing metrics. Link quality routing metrics are popularly used for route selection but it may cause bottleneck and congestion problems. To overcome these problems, we can consider the traffic loads or congestion level into routing metric. In this paper we propose a load-aware routing metric which is based on Airtime link cost metric and combines traffic loads measured from MAC layer. To maximize load balancing effect, we utilize our proposed load-aware routing metric into a multipath routing protocol. The performance of the proposed metric is evaluated with the OPNET simulator and compared with other routing metrics.
Information and Communication Technology Convergence (ICTC), 2010 International Conference on; 12/2010
[show abstract][hide abstract] ABSTRACT: In this paper we propose a collaborative routing protocol (CORP) for wireless multi-hop network with directional antennas that utilizes the wireless broadcast advantage (WBA) properties. In CORP, the neighboring nodes collaborate with each other to directionally forward the packets when an intermediate relay node is unable to perform its task due to channel/node failure. The process of collaboration is supported by the RSS value obtained from the MAC layer to form the set of collaborating nodes. The temporary link formed by the collaborating node will maintain the ongoing transmission until the old route is recovered or a fresh route is generated. We performed simulation studies using QualNet to prove that our protocol is suitable for wireless multi-hop networks that are prone to frequent node/link failure.
Ubiquitous and Future Networks (ICUFN), 2010 Second International Conference on; 07/2010
[show abstract][hide abstract] ABSTRACT: Topology control and maintenance of network connectivity are two important issues that need to be addressed in wireless networks in tactical scenarios. Topology control is more prominent with multi-interface multi-channel (MIMC) tactical mobile ad hoc networks (MANETs) due to mobility of wireless nodes. The nodes in tactical mobile ad hoc networks within non-uniform transmission range require proper management, preservation and maintenance in terms of network connectivity. In this paper, we propose a K-Neigh Backbone Tree based topology control for MIMC Tactical MANETs that consists of K-Neigh Backbone Tree topology control algorithm, Backbone Tree Association algorithm, and Topology Maintenance algorithm in decentralized management mechanism. The performance and efficiency of the proposed scheme is evaluated with the QualNet simulator.
Information Science and Applications (ICISA), 2010 International Conference on; 05/2010
[show abstract][hide abstract] ABSTRACT: Although multi-path routing protocols are more complicated to design than single-path based ones, they can be more resilient to route failures. Also, they can achieve a load balancing and hence lower end-to-end delay of transmitted messages in between a source and destination. Such advantages of multi-path routing can be significant in tactical wireless networks, where the messages transmitted are often time-critical and the topology are very unpredictable due to node mobility and link instability. In this paper, we propose a simplified multi-path routing (i.e., dual path) protocol for tactical wireless networks with multiple interfaces. Our dual-path routing protocol has an on-demand routing feature with route request/reply message exchange. We performed a simulation study using the OPNET simulator.
Advanced Communication Technology (ICACT), 2010 The 12th International Conference on; 03/2010
[show abstract][hide abstract] ABSTRACT: Geocasting, a variation on the notion of multicasting, is a mechanism to deliver messages of interest to all nodes within
a certain geographical target region. Although several geocasting protocols have already been proposed for multi-hop wireless
networks, most of these algorithms consider a “single” target region only. Here, when more than one target regions need to
receive the same geocast messages, multiple transmissions need to be initiated separately by the message source. This causes
significant performance degradation due to redundant packet transmissions, and it becomes more severe as the number of target
regions increase. To solve this problem, we propose a basic scheme and its variations which utilize the geometric concept
of “Fermat point” to determine the optimal junction point among multiple geocast regions from the source node. Our simulation
study using ns-2 shows that the proposed schemes can effectively reduce the overhead of message delivery while maintaining
a high delivery ratio in mobile multi-hop wireless networks.
[show abstract][hide abstract] ABSTRACT: A link-state routing protocol tailored for multichannel mesh networks is proposed. One drawback of using multichannel communications is the high overhead involved in broadcast operations: a transmitter should transmit a broadcast packet to all channels that may be occupied by receivers. This makes certain broadcast-intensive mechanisms, such as link-state routing, difficult to implement. The link-state routing protocol proposed in this paper is tailored for multichannel mesh networks by minimizing the broadcast overheads. This is achieved by a special set of nodes, called cluster-heads. We have implemented our protocol on a multichannel mesh network test bed and compared its performance with an AODV-like reactive routing protocol, also tailored for multichannel mesh networks. The measurements show that the proposed link-state routing protocol provides transient communications with comparable or better performance. Ways to improve the performance of the proposed routing with infrastructure access is also discussed.