Ilyong Chung

Spectrum mobility in cognitive radio networks

Cognitive radio networks (CRNs) offer a promising solution for spectrum scarcity problem by means of dynamic spectrum access. So long as in highly dynamic environments, the secondary user (SU) communication is often interrupted, spectrum mobility is a key feature enabling continuous SU data transmission. Namely, SU performs spectrum handoff by transferring ongoing communication to a vacant channel. This article discusses some important features of spectrum mobility in CRNs. Qualitative comparison of various handoff strategies is considered with regard to handoff latency. Furthermore, essential design issues and associated research challenges are also addressed.

A multipath AODV routing protocol in mobile ad hoc networks with SINR-based route selection

This paper proposes a multipath routing protocol called cross-layered multipath AODV (CM-AODV), which selects multiple routes on demand based on the signal-to-interference plus noise ratio (SINR) measured at the physical layer. Note that AODV (ad hoc on-demand distance vector) is one of the most popular routing protocols for mobile ad hoc networks. Each time a route request (RREQ) message is forwarded hop by hop, each forwarding node updates the route quality which is defined as the minimum SINR of serialized links in a route and contained in the RREQ header. Compared to the conventional multipath version of AODV protocol (which is called AOMDV), CM-AODV assigns the construction of multiple paths to the destination node and makes it algorithmically simple, resulting in the improved performance of packet delivery and the less overhead incurred at intermediate nodes. Our performance study shows that CMAODV significantly outperforms AOMDV in terms of packet delivery ratio and average end-to-end delay, but results in up to 45 percent less routing overhead.

Vertex-Based Multihop Vehicle-to-Infrastructure Routing for Vehicular Ad Hoc Networks

Multihop data delivery in vehicular ad hoc networks (VANETs) suffers from the fact that vehicles are highly mobile and inter-vehicle links are frequently disconnected. In this paper, we propose a multihop vehicle-to-infrastructure routing protocol named Vertex-Based Predictive Greedy Routing (VPGR), which predicts a sequence of valid vertices (or junctions) from a source vehicle to fixed infrastructure (or a roadside unit) in the area of interest and, then, forwards data to the fixed infrastructure through the sequence of vertices in urban environments. The well known predictive directional greedy routing mechanism is used for data forwarding in VPGR. The proposed VPGR leverages the geographic position, velocity, direction and acceleration of vehicles for both the calculation of a sequence of valid vertices and the predictive directional greedy routing. Simulation results show significant performance improvement compared to conventional routing protocols in terms of packet delivery ratio, end-to-end delay and routing overhead.

ZigBee and The UPnP Expansion for Home Network Electrical Appliance Control on the Internet

Electrical appliances of the home network via the Internet can be controlled using the ZigBee system and the UPnP expansion like the ones in the same home network without the modification of the existing UPnP. In this paper, we propose an Internet gateway that consists of ZigBee and the UPnP IGD (Internet gateway device) DCP(device control protocol) and the UPnP bridge for the control of electrical appliances of the Internet home network with a low data rate and low power consumption. ZigBee technology is a low data rate, low power consumption, low cost, wireless networking protocol targeted towards automation and remote control applications. The UPnP IGD DCP is the configurable initiation and sharing of Internet connections, advanced connection-management, management of host configuration, and supports transparent Internet access by non-UPnP-certified devices. The UPnP bridge searches for local home network devices by sending control messages. Control points of the UPnP bridge searches for devices of interest on the Internet and can deliver the control devices on other home networks to devices within its home network. With our approach, devices can control home electrical appliances and ZigBee System via Internet through IGD DCP on other home network with control commands of the UPnP.

A Traffic Light Controlling FLC Considering the Traffic Congestion

The existing many fuzzy traffic controllers could not be applied to the traffic congestion situation because they have been developed and applied for a non-congestion traffic flow. In this paper, therefore, we propose a traffic light controlling FLC that is able to cope with traffic congestion appropriately. In order to consider such situation as missing the green signal because of spillback of upper crossroad, it uses as an input variable a degree of traffic congestion of upper roads, which vehicles on a crossroad are to proceed to. It uses the first-order Sugeno fuzzy model for modeling nonlinear traffic flow. In experiment, we compared and analyzed the fixed traffic signal controller and the proposed FLC. As a result of experiment, the proposed FLC showed more enhanced performance than the fixed traffic signal controller.

Comment: "Eenhanced novel access control protocol over wireless sensor networks"

In a recent paper in this journal, an enhanced novel access control protocol (ENACP) over wireless sensor networks was given for the problem of preventing malicious nodes from joining the sensor network based on elliptic curve cryptography (ECC) and hash chain. We show that the presented ENACP has a fatal weakness such that it is insecure to the active attack.

A concurrent access MAC protocol for cognitive radio ad hoc networks without common control channel

Cognitive radio ad hoc networks (CRAHNs) consist of autonomous nodes that operate in ad hoc mode and aim at efficient utilization of spectrum resources. Usually, the cognitive nodes in a CRAHN exploit a number of available channels, but these channels are not necessarily common to all nodes. Such a network environment poses the problem of establishing a common control channel (CCC) as there might be no channel common to all the network members at all. In designing protocols, therefore, it is highly desirable to consider the network environment with no CCC. In this article, we propose a MAC protocol called concurrent access MAC (CA-MAC) that operates in the network environment with no CCC. The two devices in a communication pair can communicate with each other even if they have only one common channel available. Therefore, the problems with CCC (such as channel saturation and denial of service attacks) can also be resolved. In CA-MAC, channel accesses are distributed over communication pairs, resulting in increased network connectivity. In addition, CA-MAC allows different communication pairs to access multiple channels concurrently. According to our performance study, CA-MAC provides higher network connectivity with shorter channel access delay compared to SYN-MAC, which is the conventional key MAC protocol for the network environment with no CCC, resulting in better network throughput.

An Efficient RFID Authentication Protocol Providing Strong Privacy and Security

As the radio frequency identification (RFID) technology continues to evolve and mature, RFID tags can be implemented in a wide range of applications. Due to the shared wireless medium between the RFID reader and the RFID tag, adversaries can launch various attacks on the RFID system. To thwart different types of attacks, we propose an Efficient RFID Authentication Protocol (ERAP), which can accomplish the authentication without disclosing real IDs of the participating tags and provide strong privacy and security protection of the RFID users. ERAP offers the anonymity of tags in addition to tag untraceability. It also provides forward security (forward privacy) which ensures that data transmitted today will still be secure even if secret tag information is revealed by tampering in the future. In this paper, we define a formal security model for authentication and privacy in RFID system. Under this model, we describe protocol that provably achieves the properties of authentication and privacy. In addition, the proposed ERAP requires only little resources to perform the authentication, which satisfies the requirement of highly resource-constrained low-cost RFID tags.

A Novel Anonymous RFID Authentication Protocol Providing Strong Privacy and Security

As the radio frequency identification (RFID) technology continues to evolve and mature, RFID tags can be implemented in a wide range of applications. Due to the shared wireless medium between the RFID reader and the RFID tag, however, adversaries can launch various attacks on the RFID system. The privacy and security issues of RFID are getting more and more important. To thwart different types of attacks, we propose a novel Anonymous RFID Authentication Protocol, termed ARAP, which can accomplish the authentication without disclosing real IDs of the participating tags and provide strong privacy and security protection of the RFID users. ARAP offers the anonymity of tags in addition to tag unlocatability and untrackability. It is also resistant to a wide range of attacks. Compared with the previous researches, the major advantages of ARAP are that ARAP can withstand physical attack, de-synchronization attack, disclosure attack and cloning attack, and also can provide anonymity and mutual authentication. We believe that our protocol is attractive to RFID applications.

The design and analysis of an efficient load balancing algorithm employing the symmetric balanced incomplete block design

In order to maintain load balancing in a distributed network, each node should obtain workload information from all the nodes in the network. To accomplish this, this processing requires O(v^2) communication complexity, where v is the number of nodes. First, we present a new synchronous dynamic distributed load balancing algorithm on a (v,k+1,1)-configured network applying a symmetric balanced incomplete block design, where v=k^2+k+1. Our algorithm designs a special adjacency matrix and then transforms it to (v,k+1,1)-configured network for an efficient communication. It requires only O(vv) communication complexity and each node receives workload information from all the nodes without redundancy since each link has the same amount of traffic for transferring workload information. Later, this algorithm is revised for distributed networks and is analyzed in terms of efficiency of load balancing.