Seung Yeob Nam

Cognitive Radio Wireless Sensor Networks: Applications, Challenges and Research Trends

A cognitive radio wireless sensor network is one of the candidate areas where cognitive techniques can be used for opportunistic spectrum access. Research in this area is still in its infancy, but it is progressing rapidly. The aim of this study is to classify the existing literature of this fast emerging application area of cognitive radio wireless sensor networks, highlight the key research that has already been undertaken, and indicate open problems. This paper describes the advantages of cognitive radio wireless sensor networks, the difference between ad hoc cognitive radio networks, wireless sensor networks, and cognitive radio wireless sensor networks, potential application areas of cognitive radio wireless sensor networks, challenges and research trend in cognitive radio wireless sensor networks. The sensing schemes suited for cognitive radio wireless sensor networks scenarios are discussed with an emphasis on cooperation and spectrum access methods that ensure the availability of the required QoS. Finally, this paper lists several open research challenges aimed at drawing the attention of the readers toward the important issues that need to be addressed before the vision of completely autonomous cognitive radio wireless sensor networks can be realized.

Enhanced ARP: preventing ARP poisoning-based man-in-the-middle attacks

In this letter, an enhanced version of Address Resolution Protocol (ARP) is proposed to prevent ARP poisoning-based Man-in-the-Middle (MITM) attacks. The proposed mechanism is based on the following concept. When a node knows the correct Media Access Control (MAC) address for a given IP address, if it retains the IP/MAC address mapping while that machine is alive, then MITM attack is impossible for that IP address. In order to prevent MITM attacks even for a new IP address, a voting-based resolution mechanism is proposed. The proposed scheme is backward compatible with existing ARP and incrementally deployable.

Measurement-based admission control at edge routers

It is very important to allocate and manage resources for multimedia traffic flows with real-time performance requirements in order to guarantee quality of service (QoS). In this paper, we develop a scalable architecture and an algorithm for admission control of real-time flows. Since individual management of each traffic flow on each transit router can cause a fundamental scalability problem in both data and control planes, we consider that each flow is classified at the ingress router and data traffic is aggregated according to the class inside the core network as in a DiffServ framework. In our approach, admission decision is made for each flow at the edge (ingress) routers, but it is scalable because per-flow states are not maintained and the admission algorithm is simple. In the proposed admission control scheme, an admissible bandwidth, which is defined as the maximum rate of a flow that can be accommodated additionally while satisfying the delay performance requirements for both existing and new flows, is calculated based on the available bandwidth measured by edge routers. The admissible bandwidth is a threshold for admission control, and thus, it is very important to accurately estimate the admissible bandwidth. The performance of the proposed algorithm is evaluated by taking a set of simulation experiments using bursty traffic flows.

Decentralized Predictive MAC Protocol for Ad Hoc Cognitive Radio Networks

A new problem of spectrum scarcity has emerged due to the incredible technological advances in wireless communication. The spectrum scarcity issue is a bottleneck for the next generation of wireless communications. Therefore, efficient spectrum utilization has attracted considerable attention. This paper proposes a novel method of utilizing the white spaces in the licensed spectrum while ensuring the incumbent licensees’ rights. The protocol predicts the incumbents’ arrival using a historical prediction method and protects the incumbent users from the interference of opportunistic spectrum users. Distributed sensing is used to determine the network wide spectrum opportunity. The channel access delay in the proposed protocol is evaluated by simulation and mathematical analysis. The protocol has the advantages of a decentralized system, flexibility and low computing complexity. The simulations show that the protocol outperforms the existing opportunistic spectrum-sharing, media-access-control protocols in terms of the goodput and delay.

A Robust Trust Establishment Scheme for Wireless Sensor Networks

Trust establishment is an important tool to improve cooperation and enhance security in wireless sensor networks. The core of trust establishment is trust estimation. If a trust estimation method is not robust against attack and misbehavior, the trust values produced will be meaningless, and system performance will be degraded. We present a novel trust estimation method that is robust against on-off attacks and persistent malicious behavior. Moreover, in order to aggregate recommendations securely, we propose using a modified one-step M-estimator scheme. The novelty of the proposed scheme arises from combining past misbehavior with current status in a comprehensive way. Specifically, we introduce an aggregated misbehavior component in trust estimation, which assists in detecting an on-off attack and persistent malicious behavior. In order to determine the current status of the node, we employ previous trust values and current measured misbehavior components. These components are combined to obtain a robust trust value. Theoretical analyses and evaluation results show that our scheme performs better than other trust schemes in terms of detecting an on-off attack and persistent misbehavior.

Analysis of a mobility management scheme considering battery power conservation in IP-based mobile networks

Mobile hosts (MHs) in all IP-based mobile networks must update their current location to receive incoming packets. The MHs are idle for most of time. Both registration of approximate location information and paging can facilitate efficient power management for the idle MHs. Furthermore, the MHs can be in switch-off state for battery power conservation. Mobile IP, the current standard for IP-based mobility management, needs to be enhanced for use in all IP-based mobile networks. Mobility management in all IP-based mobile networks should consider idle and detached MH states as well as active MH state. A mobility management scheme for all IP-based mobile networks is introduced in this paper. This scheme includes management of communicating, attentive, idle, and detached states. We model MH behavior in the networks when the binding-lifetime-based registrations are utilized as a means of identifying that an MH is switched off. The steady-state probabilities for MH state transitions are derived, and an optimal rate of binding-lifetime-based registrations that results in minimum network cost is derived.

Effective bandwidth for a single server queueing system with fractional Brownian input

The traffic patterns of todays IP networks exhibit two important properties: self-similarity and long-range dependence. The fractional Brownian motion is widely used for representing the traffic model with the properties. We consider a single server fluid queueing system with input process of a fractional Brownian motion type. Packet-loss probability and mean delay are considered as QoS. We show that there is a scaling property among the stationary queue-length distributions of different input parameters and service rates. We also evaluate the scaling factor. From the scaling property, we drive formulas for the effective bandwidth to guarantee the QoS in a single source and multiple sources cases. The formulas indicate that it is essential to evaluate the distribution functions of a type of random variables. For multiple sources the shape of an admissible region and multiplexing gain are analyzed. Finally, numerical examples are shown to validate the proposed scheme.

Probing-based estimation of end-to-end available bandwidth

A new mechanism to estimate available bandwidth for multiple hop routes is proposed based on a minimally backlogging concept. Since the proposed mechanism can estimate the available bandwidth quickly and track it adaptively, a reasonable range of available bandwidth for a short time interval can be obtained using the mean and variance of the estimated available bandwidth. The performance of the proposed mechanism is verified by simulation in a multiple hop network topology.

A spare bandwidth sharing scheme based on network reliability

Spare bandwidth is required for recovering the network service from network faults. However, it degrades the efficiency of network utilization. Spare bandwidth demand can be reduced significantly by letting spare bandwidth be shared among several network services. Spare bandwidth reserved on a network element can be shared by a set of network services for a network fault if they are not simultaneously affected by the network fault. A new, and more practical spare bandwidth sharing scheme, which is based on the network reliability, is proposed in this paper. In the proposed scheme, multiple link failures are allowed with a given link failure rate, and a reasonable restoration level of near 100%; while in the conventional scheme, only a single link failure, and 100% restoration level are considered. To develop the spare bandwidth sharing scheme, we first investigate the framework for evaluating the reliability of path-based network services, and then we explain the proposed spare bandwidth sharing scheme with decision parameters such as lifetime of the path, restoration level, and the maximum number of working paths which can be protected by a backup link. Simulation results show that the proposed spare bandwidth sharing scheme requires a smaller amount of spare bandwidth than the conventional scheme.

Collaborative approach to mitigating ARP poisoning-based Man-in-the-Middle attacks

In this paper, we propose a new mechanism for counteracting ARP (Address Resolution Protocol) poisoning-based Man-in-the-Middle (MITM) attacks in a subnet, where wired and wireless nodes can coexist. The key idea is that even a new node can be protected from an ARP cache poisoning attack if the mapping between an IP and the corresponding MAC addresses is resolved through fair voting among neighbor nodes under the condition that the number of good nodes is larger than that of malicious nodes. Providing fairness in voting among the nodes that are heterogeneous in terms of the processing capability and access medium is quite a challenge. We attempt to achieve fairness in voting using the uniform transmission capability of Ethernet LAN cards and smaller medium access delays of Ethernet than for wireless LAN. Although there is another scheme that resolves the same issue based on voting, i.e. MR-ARP, the voting fairness is improved further by filtering the voting reply messages from the too-early responding nodes, and the voting-related key parameters are determined analytically considering the fairness in voting. This paper shows that fairness in voting can be achieved using the proposed approach, overcoming the limitations of other voting-based schemes, and ARP poisoning-based MITM attacks can be mitigated in a more generalized environment through experiments.