Chi-Hsiang Lo

Secure centralized spectrum sensing for cognitive radio networks

Spectrum utilization becomes more and more important while new communication techniques keep increasing and the spectrum bands remain finite. Cognitive radio is a revolutionary technology to make use of the spectrum more effectively. In order to avoid the interference to the primary user, spectrum sensing must be sensitive and reliable. Cooperative spectrum sensing (CSS) is one of the ways to increase the reliability of spectrum sensing. The information fusion technique is a key component of CSS. In this paper, we proposed a novel fusion scheme based on spatial correlation technique. We utilize geographical information with reputational weights to propose a two-level fusion scheme called secure centralized spectrum sensing (SCSS). The simulation results show that as the attackers present high density aggregation at some areas, the correct sensing ratio of SCSS is increasing as well even when the number of attackers is very large.

QoS/QoE Mapping and Adjustment Model in the Cloud-based Multimedia Infrastructure

The quality of service (QoS) requirement and multicast service support from IP networks are two important factors for providing cloud-based multimedia services. However, QoS lacks an important element in characterizing multimedia services, namely, user perception. In this paper, we propose a QoS to quality of experience (QoE) mapping and adjustment model to translate the network QoS parameters into the users QoE in the cloud-based multimedia infrastructure. The model is composed of three parts: QoE function, practical measurement and statistical analysis, and a simulated streaming video platform. We first discuss how to design the QoE function, and then use the practical measurement and statistical analysis to derive the optimum values of eight QoE parameters in the proposed QoE function. To map the network QoS parameters into the users QoE, a simulated streaming video platform is used to denote a cloud-based multimedia infrastructure. Each multicast member that has guaranteed bandwidth in the simulated streaming video platform uses the QoE function to calculate its QoE score after watching the streaming video. If the QoE score is less than a derived lower bound value, it means that one of the multicast members has a low QoE. In this situation, the genetic algorithm is enabled to adjust the constructed diffserv-aware multicast tree to respond quickly to the degradation of QoE. The simulation results show that the users QoE and network QoS are consistent with each other.

A network-based global mobility management architecture

This paper specifies a network-based global mobility management architecture, named NetGMM. NetGMM supports network-based mobility management and non-Mobile IP mobile environment. There are two design considerations. The first is that a future mobile network requires network-based mobility management, shifting the mobility management function from Mobile Nodes (MN) to Access Network (AN) nodes. The second is that future mobile networks will support IP multi-services, introducing a separation between network address and identity of a mobile node entity, allowing heterogeneous networks to work together without loss of functionality.

The disclosure of an Android smartphone's digital footprint respecting the Instant Messaging utilizing Skype and MSN

As Android Operating System (OS) for mobile computing devices become one of the major trends, the utilization of smartphones set the record for global users and they are taking advantages of the contemporary Instant Messaging (IM) as a convenient tool to communicate with global users in real time because of its competitive rate, high availability, robust reliability, and agile mobility. Undoubtedly, as IM has gradually become one of the channels to commit the cybercrime, the digital evidence collection, analysis, and preservation of the non-volatile data from the Random Access Memory (RAM) of the computing device in terms of cyber trails that were unknowingly left on the crime scene. Hence, this research conducts the design of the experiments to fulfill the essence of contribution of the paper. The SkypeChat and MSN are the popular IM tools, which are widely utilized in contemporary digital era. This paper provides a generic paradigm for the digital forensics specialists and law enforcement agencies to ponder if similar situations are faced.

Improvement of Channel Assignment Scheme for WiMax Mesh Networks

The IEEE 802.16 standard, also known as Worldwide Interoperability for Microwave Access (WiMax), provides a mechanism for deploying high-speed wireless mesh network in metropolitan areas, and Quality of Service (QoS) is thus very important for WiMax networks. While being scheduled at the same time, the multiple links may interfere with one another that makes it challenging to provide QoS in multi-hop WiMax mesh networks. In this paper, we propose the LMDFS (Layered Maximum Degree First Select) algorithm for channel assignment in multi-channel single-transceiver WiMax mesh network. The goal is to eliminate the interference, to allow multiple non-interfering links to be scheduled at the same time and to increase the throughput of traffic flows. The simulation results show that this proposed algorithm greatly reduces the length of scheduling and improves the throughput and the average delay from network nodes to the BS in insufficient channels.

Providing Efficient Secured Mobile IPv6 by SAG and Robust Header Compression

Abstract: By providing ubiquitous Internet connectivity, wireless networks offer more convenient ways for users to surf the Internet. However, wireless networks encounter more technological challenges than wired networks, such as bandwidth, security problems, and handoff latency. Thus, this paper proposes new technologies to solve these problems. First, a Security Access Gateway (SAG) is proposed to solve the security issue. Originally, mobile terminals were unable to process high security calculations because of their low calculating power. SAG not only offers high calculating power to encrypt the encryption demand of SAG’s domain, but also helps mobile terminals to establish a multiple safety tunnel to maintain a secure domain. Second, Robust Header Compression (RoHC) technology is adopted to increase the utilization of bandwidth. Instead of Access Point (AP), Access Gateway (AG) is used to deal with the packet header compression and de-compression from the wireless end. AG’s high calculating power is able to reduce the load on AP. In the original architecture, AP has to deal with a large number of demands by header compression/de-compression from mobile terminals. Eventually, wireless networks must offer users “Mobility” and “Roaming”. For wireless networks to achieve “Mobility” and “Roaming,” we can use Mobile IPv6 (MIPv6) technology. Nevertheless, such technology might cause latency. Furthermore, how the security tunnel and header compression established before the handoff can be used by mobile terminals handoff will be another great challenge. Thus, this paper proposes to solve the problem by using Early Binding Updates (EBU) and Security Access Gateway (SAG) to offer a complete mechanism with low latency, low handoff mechanism calculation, and high security.

Modelling and simulations for DDoS attacks mitigation in identifier–locator split network

With the increasingly prominent problems in the scalability, security, mobility and some other issues of Internet, identifier–locator split network has become a hot topic in the research of the next-generation network structure. In this network, split and mapping between identifier and locator make network security change accordingly compared with the current Internet. This paper makes a comparative analysis on distributed denial of service (DDoS) attacks between the current Internet and identifier–locator split network using the attack graph modelling approach based on the expected loss. It proves that the identifier–locator split network effectively alleviates DDoS attacks, and performs much better than the current Internet in security. Additionally, this paper verifies the correctness of the implementation of the attack graph as a model approach by simulations.

Early security key exchange for encryption in Mobile IPv6 handoff

Summary Wireless equipment has become ubiquitous. However, in facing various software attacks, wireless linked networks are more vulnerable than wire linked networks. The general problem with Mobile IPv6 (MIPv6) (Table I) is the long handover latency period. To reduce the security latency, we propose early security key exchange for encryption in MIPv6 handoff. In our approach, two issues are addressed in dealing with the latency within the encryption technology during the handover. First, we extend the Early Binding Update (EBU) method to deal with the long security exchange negotiation time for the MIPv6 handoff. Second, we adopt the Security Access Gateway (SAG) to solve the limited computing and memory in the Mobile Node (MN). Copyright # 2008 John Wiley & Sons, Ltd.

Neural Network Diagnosis System for 3-Dimensional Ultrasonography with Gabor Filter Aided Speckle Decorrelation

In this paper, a neural network diagnosis system for 3-dimensional ultrasonography using Gabor filters to eliminate the speckle noise is introduced. Since the importance of the relationship between surface features and internal architecture of the breast tumor, we applied our system using three dimensional (3D) inter-pixel correlation instead of 2D features. Furthermore, Gabor filters provide a multi-resolution representation of texture, which increasing the capabilities of ultrasound technology in the differential diagnosis of solid breast tumors. Our experiments show that the performance of the proposed diagnostic method is effective.

Advanced handover management framework for Mobile Router based on MCoA

In this paper, we design and implement a handover management framework which can integrate the multiple heterogeneous wireless networks (such as WLAN, GPRS and CDMA) with the support of Multiple Care-of-Address (MCoA) technology in the mobile network. The experimental results in a real network environment show that our proposed architecture can not only support the seamless handover, but also guarantee the scalability because of its modulised design. Besides, an adaptive handover trigger scheme and an access network selection scheme are proposed to initiate the handover and select the target access network intelligently.