Catálogo de publicaciones - libros

Real-life tests of ad hoc networks are invaluable in order to assess models used in simulation. However, the number of factors affecting the performance of an ad hoc network is high. There are, for example, system factors, such as routing protocols, MAC and physical layer protocols, as well as environment factors, such as the presence of walls, foliage and moving objects. In this regard, it is important to design repeatable experiments of the network, in order to identify the parameters which really affect the system behavior. Here, we leverage methods of statistical testing theory to identify these parameters in a compact manner. In particular, we use OLSR as a routing protocol. Results from real experiments confirm the horizon effect of ad hoc multi-hop networks and shown that there is a treatment effect caused by the window size of OLSR.

A wireless sensor-actuator network (WSAN) is composed of sensor and actuator nodes interconnected in a wireless channel. Sensor nodes can deliver messages to only nearer nodes due to weak radio and messages are forwarded by sensor nodes to an actuator node. Messages sent by nodes might be lost due to collision and noise. We discuss the redundant data transmission (RT) protocol to reduce the loss of sensed values sent to an actuator node even if messages are lost. In the RT protocol, a sensor node sends a message with not only its sensed value but also sensed values received from other sensor nodes. Even if a message with a sensed value from a sensor node is lost, an actuator node can take the value from other messages. We evaluate the RT protocol compared with the CSMA protocol in terms of how much sensed values an actuator node can receive in presence of message loss.

TCP, the transport protocol used to carry the major portion of the internet traffic, performs poorly in Mobile Ad Hoc Networks (MANETs) as broadly reported in the literature. This is mainly due to the interactions between TCP and lower layers protocols. Among these, routing protocols have perhaps the greatest impact on the performance of TCP. In this paper, by extensive simulation, we evaluate how TCP interacts with some of the IETF standardised reactive (AODV, DSR) and proactive (OLSR) routing protocols under varying network conditions such as load, size and mobility. In contrast to most of previously reported studies, which have relied solely on TCP traffic, we consider a more realistic traffic carrying a mixture of Constant Bit Rate (CBR) and TCP. We also show how appropriate tuning of route expiry parameters in reactive protocols can improves TCP performance considerably while still generating less routing overhead.

Ad hoc wireless networks are power constrained since nodes operate with limited battery. In this paper, it proposes the ad hoc network routing which considers both of power consumption and the amount of the battery remainder. To improve the availability of ad hoc networks, routing which considers both at the same time is needed though power consumption and the amount of the battery remainder have been separately examined in the research so far. We propose BPA-DSR (Battery and Power Aware enhancement to Dynamic Source Routing) which searches for the route by the flooding of two times. The path with large amount of the battery remainder is detected by the first flooding, and the location of the neighboring nodes of the route is computed from the received radio power at the same time. Each link of the route is divided into the power saving link and tuned up by the flooding of the second. Simulation results show that the amount of the battery remainder of the proposed method is better than other method (LP-DSR) which is aware of the power consumption. Power consumption of the proposed method is better than that of DSR though it is a little inferior to LP-DSR which detects the route of minimum power consumption. The number of hops of the detected route is suppressed to about 60% of LP-DSR.

In this paper, in order to quickly recover communication network where the communication facility was seriously damaged and to collect the information with evacuated residents and disaster areas, we propose a balloon wireless network which is realized by combining balloons and wireless LANs and organizing into an adhoc network in the air. Using this balloon network, the damaged communication line can be quickly recovered. By combining with balloon wireless network and wired Internet overlay network, more robust, flexible and large scale disaster information network system can be realized even though some of the network lines and nodes are damaged and destroyed. In order to verify the usefulness of the suggested balloon network, a prototype system was constructed and made performance evaluation.

Despite the dynamic growth of wireless network systems, their presence in business-support infrastructure has been limited. In the article we provide an overview of generic corporate network architecture and examine usefulness of available wireless network solutions in such systems. Following this overview we analyze new wireless network architecture which currently undergoes standardization process – wireless mesh. It can result in significant increase in both bandwidth and reliability of complex wireless systems, even to a level suitable for mission-critical business applications. In conclusion we point out research directions and topics which are critical for integration of wireless solutions into business-support network infrastructure as they differ from currently followed main line of standardization works on the subject.

Most of computer security systems use the signatures of well-known attacks to detect hackers’ attacks. For these systems, it is very important to get the accurate signatures of new attacks as soon as possible. For this reason, there have been several researches on honeypots. However, honeypots can not collect information about hackers attacking active computers except themselves. In this paper, we propose the DecoyPort system to redirect hackers toward honeypots. The DecoyPort system creates the DecoyPorts on active computers. All interactions with the DecoyPorts are considered as suspect because the ports are not those for real services. Accordingly, every request sent to the DecoyPorts is redirected to honeypots by the DecoyPort system. Consequently, our system enables honeypots to collect information about hackers attacking active computers except themselves.

In these years, many researchers proposed the way — to isolate the computers with sensitive information from outside attackers or unauthorized users. The Taiwan government has ruled the importance of network isolation in several policies, such as “The Handling Implementation Program of Information Security Emergency Incidents for government departments” and “The Responding Protocol of Notifying Information Security Events in Executive Yuan and its Departments.” However, there are few materials available for implementing network isolation. In ISO-17799, there is no implementation guidance for practicing network isolation but auditing network physical isolation. This paper provides the implementation guidance of network isolation with some logical isolation techniques and management polices.

In this paper we present a model that can prevent conflict situations caused by applying both positive and negative authorizations for access to a resource. Such conflict situations may occur if an organization has decentralized administration, and/or several collaborating organizations have access to one resource and some of them apply positive authorizations while others apply negative authorizations. The proposed solution involves Belnap’s logic.

The IEEE 802.16 Working Group on Broadband Wireless Access Standards released IEEE 802.16-2004 which is a standardized technology for supporting broadband and wireless communication with fixed and nomadic Access. The standard has a security sublayer in the MAC layer called, Privacy Key Management, which aims to provide authentication and confidentiality. However, several researches have been published to address the security vulnerabilities of 802.16-2004. After the IEEE 802.16-2004 standard, a new advanced and revised standard was released as the IEEE 802.16e-2005 amendment which is foundation of Mobile WiMAX network supporting handoffs and roaming capabilities. In the area of security aspects, Mobile WiMAX adopts improved security architecture, PKMv2, including Extensible Authentication Protocol (EAP) authentication, AES-CCM-based authenticated encryption, and CMAC or HMAC based message protection. However, there is no guarantee that PKMv2-based Mobile WiMAX network will not have security flaws. In this paper, we first describe an overview of security architecture of IEEE 802.16e-based Mobile WiMAX and its vulnerabilities. Based on the related background research, we focus on finding new security vulnerabilities such as a disclosure of security context in initial entry and a lack of secure communication in network domain. We propose possible solutions to prevent these security vulnerabilities.