Yueh-Min Huang

Contention window optimization for ieee 802.11 DCF access control

According to the latest version of the IEEE 802.11 standard, the backoff parameters of its collision avoidance mechanism are far from optimal, especially in a heavy load or error-prone WLAN environment. This strategy has a high collision probability and channel utilization is degraded in bursty arrivals or congested scenarios. Besides, the standard backoff mechanism may treat noise corruption as packet collisions. In this paper, we identify the relationship between backoff parameters, contention level, and channel BER in order to propose a simple, but yet well-performing distributed algorithm that allows a station to dynamically adjust its contention window size based on turn-around-time measurement of channel status. In addition to theoretical analysis, simulations are conducted to evaluate its performance. The proposed scheme works very well in providing a substantial performance improvement in heavy loaded and error-prone WLAN environments.

A novel secure communication scheme in vehicular ad hoc networks

Vehicular networks are very likely to become the most pervasive and applicable of mobile ad hoc networks in this decade. Vehicular Ad hoc NETwork (VANET) has become a hot emerging research subject, but few academic publications describing its security infrastructure. In this paper, we review the secure infrastructure of VANET, some potential applications and interesting security challenges. To cope with these security challenges, we propose a novel secure scheme for vehicular communication on VANETs. The proposed scheme not only protects the privacy but also maintains the liability in the secure communications by using session keys. We also analyze the robustness of the proposed scheme.

Adaptive security design with malicious node detection in cluster-based sensor networks

Distributed wireless sensor networks have problems on detecting and preventing malicious nodes, which always bring destructive threats and compromise multiple sensor nodes. Therefore, sensor networks need to support an authentication service for sensor identity and message transmission. Furthermore, intrusion detection and prevention schemes are always integrated in sensor security appliances so that they can enhance network security by discovering malicious or compromised nodes. This study provides adaptive security modules to improve secure communication of cluster-based sensor networks. A dynamic authentication scheme in the proposed primary security module enables existing nodes to authenticate new incoming nodes, triggering the establishment of secure links and broadcast authentication between neighboring nodes. This primary security design prevents intrusion from external malicious nodes using the authentication scheme. For advanced security design, the proposed intrusion detection module can exclude internal compromised nodes, which contains alarm return, trust evaluation, and black/white lists schemes. This study adopts the two above mentioned modules to achieve secure communication in cluster-based sensor networks when the network lifetime is divided into multiple cluster rounds. Finally, the security analysis results indicate that the proposed design can prevent and detect malicious nodes with a high probability of success by cluster-based and neighbor monitor mechanisms. According to the performance evaluation results, the proposed security modules cause low storage, computation, and communication overhead to sensor nodes.

Genetic algorithm for delay- and degree-constrained multimedia broadcasting on overlay networks

Heterogeneous ISP router policies prevent QoS multimedia applications requiring IP layer multicasting, such as real-time media streaming, video conferencing and distance learning, from wide deployment on the Internet. Therefore recent studies have implemented such applications by application layer multicasting through organizing the multicast group in a peer-to-peer overlay network. QoS requirements limit the transmission time and the number of receivers to which each node can transmit. Such a communication scheme in an overlay network can be regarded as a degree- and delay-constrained minimum-cost broadcasting problem, and appears to be NP-complete. This study proposes a novel genetic algorithm for resolving this difficult broadcasting problem and, then, compares it with some state-of-the-art methods. Simulation results with a series of problems demonstrate the efficiency and effectiveness of the proposed algorithm.

A personalized mobile IPTV system with seamless video reconstruction algorithm in cloud networks

Mobile Internet Protocol Television (IPTV) delivers omnipresent multimedia video services through mobile devices, and a cloud system provides services for content integration. This study presents a personalized mobile IPTV system based on a cloud network. The system allows users to browse their favorite multimedia videos in the cloud networks through mobile devices. Without the trouble of repeated and complex searches of multimedia files, the system can automatically search for nearby multimedia data that users are browsing, and reconstruct dispersed video contents through a seamless video reconstruction algorithm (SVRA) for integration into video data for continuous play, thus, becoming a user-friendly mobile IPTV system. The study focuses on the design and implementation of a SVRA, and validation of the accuracy of the theories and the algorithm through the proposed system are presented in this paper. This system was tested and validated with success. Copyright

UPnP IPv4/IPv6 bridge for home networking environment

The purposes of universal plug and play (UPnP) are to allow consumer electronics, intelligent appliances (IA) and mobile devices from different vendors to be Internet connected seamlessly and installed easily at home. Also, as the IPv6 environment becomes inevitable, IPv6 ready IA are more and more popular. However, the fact is that IPv4 UPnP control points cannot communicate with IPv6 UPnP devices or vice versa. In this paper, we proposed an UPnP IPv4/IPv6 bridge for control points and devices can interoperate between IPv4 and IPv6 protocols; that is, they can communicate with each other although some of them support only IPv4 and others support IPv6.

Reliable transmission of multimedia streaming using a connection prediction scheme in cluster-based ad hoc networks

Cluster-based routes help data transmission by acting as backbone paths in wireless ad hoc networks. Some mobile users form a cluster to obtain common multimedia services. However, node mobility does not guarantee multimedia transmission in a network with a dynamic topology. This study first presents a novel measure of cluster-based routes stability according to a prediction of connection probability at a specific time in future, helping transmit multimedia streams across many clusters in a network. The selected route is sufficiently stable to enable cluster-based mobile users to receive time-consuming multimedia streaming in future. Secondly, inter-cluster connectivity maintenance schemes, including forward and backward connectivity methods to protect nonstop multimedia streams, are developed to maintain inter-cluster links. Finally, analytical and evaluation results indicate that the cluster-based route chosen according to the connection probability scheme is more effective than routes chosen by other flat on-demand routing protocols for transmitting multimedia streaming in ad hoc networks.

Design and implementation of digital TV widget for Android on multi-core platform

With the rapid advancements in hand-held devices, traditional phone have also been developed into smart multifunctional mobile phones, which feature numerous functions and flexible operation. Such rapid advancement results from transformations of the embedded system architecture. In the mode of a multi-core cooperative work, the work requiring greater mathematical operations, such as video decoding, is assigned to a cooperative processor, which is specially designed for mathematical operations. In this way, the work load of a main processor can be reduced, and high operation loads can be realized. Based on the open source software model, Android may reduce time intervals in developing application programs, thus, hand-held manufacturers are paying increased attention to the system. Android has good network support capabilities, as well as a totally open software development environment, thus, there are many completed application programs available for download and use. However, until now, there was no digital TV player in Android. When a digital TV broadcast is combined with other application programs, other services will become available while TV programs are broadcast. This paper proposes how to add the mechanism for watching digital TV programs onto the multi-core platform, Texas Instrument TMS320DM6446, which is realized through cooperative works in order to use the processors of the multi-core system with Android.

Image encryption algorithm based on chaotic maps

In this paper, we proposed a new image encryption algorithm, that is based on Arnold cat map and logistic chaotic system to improve the security of the image transmission. An input image can be shuffled by iterative using Arnold cat map operations. But, after several iterations the shuffle image will return to the original image. It is obvious that we cannot using the Arnold cat map only to promise the system security. If we applied the logistic map algorithm to shuffled the original image. Then encrypted the shuffled results of the logistic map algorithm by the Arnold cat map. It will improve the system security largely.

Space-Time Complementary Coding MIMO with Joint Spatial Diversity and Multiplex Capability

This paper introduces a new space-time coding scheme, namely space-time complementary coding (STCC) scheme. With the help of pair-wise complementary codes, an STCC MIMO system can achieve both spatial diversity and multiplex transmission. The scheme requires neither bandwidth expansion nor feedback information from receiver, and it offers a nearly interference-free and multipath-resist performance due to a widely open interference-free window of the pair-wise complementary codes. The analytical results reveals that it provides a uniquely high diversity-multiplex gain product for its applications in flat or frequency-selective fading channel.