Vol. 5, No. 3, Jun. 2009
Tin-Yu Wu, Han-Chieh Chao, Chi-Hsiang Lo
Vol. 5, No. 3, pp. 117-130, Jun. 2009
Keywords: SAG, RoHC, MIPv6, Handoff Latency, Early Binding Update
Show / Hide AbstractBy 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.
Guo Hao, Guo Tao
Vol. 5, No. 3, pp. 131-134, Jun. 2009
Keywords: Man-in-the-middle Attack, ARP Spoofing, Session Hijack
Show / Hide AbstractMan-in-the-middle attack is used wildly as a method of attacking the network. To discoverhow this type of attack works, this paper describes a method of man-in-the-middle attack based onARP spoofing, and proposes a method of preventing such attacks.
ZHAO Zhi-bin, GAO Fuxiang
Vol. 5, No. 3, pp. 135-144, Jun. 2009
Keywords: Real-time Schedule, Wireless Sensor Networks, Two-level Priority, TinyOS, Dynamic Schedule
Show / Hide AbstractMost of the tasks in wireless sensor networks (WSN) are requested to run in a real-timeway. Neither EDF nor FIFO can ensure real-time scheduling in WSN. A real-time scheduling strategy(RTS) is proposed in this paper. All tasks are divided into two layers and endued diverse priorities.RTS utilizes a preemptive way to ensure hard real-time scheduling. The experimental results indicatethat RTS has a good performance both in communication throughput and over-load.
Thanh Le Dinh
Vol. 5, No. 3, pp. 145-150, Jun. 2009
Keywords: Wireless Sensor Network, Hole, Boundary detection, 2-neighbor graph
Show / Hide AbstractThe awareness of boundaries in wireless sensor networks has many benefits. The identification of boundaries is especially challenging since typical wireless sensor networks consist of low-capability nodes that are unaware of their geographic location. In this paper, we propose a simple, efficient algorithm to detect nodes that are near the boundary of the sensor field as well as near the boundaries of holes. Our algorithm relies purely on the connectivity information of the underlying communication graph and does not require any information on the location of nodes. We introduce the 2-neighbor graph concept, and then make use of it to identify nodes near boundaries. The results of our experiment show that our algorithm carries out the task of topological boundary detection correctly and efficiently.
Shan Guo Quan, Jian Xu, Young Yong Kim
Vol. 5, No. 3, pp. 151-158, Jun. 2009
Keywords: utility, femtocell network, backhaul, cross-talk, Video Streaming
Show / Hide AbstractThis paper proposes a utility-based data rate allocation algorithm to provide high-quality mobile video streaming over femtocell networks. We first derive a utility function to calculate the optimal data rates for maximizing the aggregate utilities of all mobile users in the femtocell. The total sum of optimal data rates is limited by the link capacity of the backhaul connections. Furthermore, electromagnetic cross-talk poses a serious problem for the backhaul connections, and its influence passes on to mobile users, as well as causing data rate degradation in the femtocell networks. We also have studied a fixed margin iterative water-filling algorithm to achieve the target data rate of each backhaul connection as a counter-measure to the cross-talk problem. The results of our simulation show that the algorithm is capable of minimizing the transmission power of backhaul connections while guaranteeing a high overall quality of service for all users of the same binder. In particular, it can provide the target data rate required to maximize user satisfaction with the mobile video streaming service over the femtocell networks.
Jinsuk Kim, Du-Seok Jin, KwangYoung Kim, Ho-Seop Choe
Vol. 5, No. 3, pp. 159-166, Jun. 2009
Keywords: Automatic In-Text Keyword Tagging, Information Retrieval, pattern matching, Boyer-Moore-Horspool Algorithm, Keyword Dictionary, Cross-Referencing, in-text content link
Show / Hide AbstractAs shown in Wikipedia, tagging or cross-linking through major keywords in a document collection improves not only the readability of documents but also responsive and adaptive navigation among related documents. In recent years, the Semantic Web has increased the importance of social tagging as a key feature of the Web 2.0 and, as its crucial phenotype, Tag Cloud has emerged to the public. In this paper we provide an efficient method of automated in-text keyword tagging based on large-scale controlled term collection or keyword dictionary, where the computational complexity of O(mN) – if a pattern matching algorithm is used – can be reduced to O(mlogN) – if an Information Retrieval technique is adopted – while m is the length of target document and N is the total number of candidate terms to be tagged. The result shows that automatic in-text tagging with keywords filtered by Information Retrieval