A review of personal communications services

This article can be accessed from the link below - Copyright @ 2009 Nova Science Publishers, LtdPCS is an acronym for Personal Communications Service. PCS has two layers of meaning. At the low layer, from the technical perspective, PCS is a 2G mobile communication technology operating at the 1900 MHz frequency range. At the upper layer, PCS is often used as an umbrella term that includes various wireless access and personal mobility services with the ultimate goal of enabling users to freely communicate with anyone at anytime and anywhere according to their demand. Ubiquitous PCS can be implemented by integrating the wireless and wireline systems on the basis of intelligent network (IN), which provides network functions of terminal and personal mobility. In this chapter, we focus on various aspects of PCS except location management. First we describe the motivation and technological evolution for personal communications. Then we introduce three key issues related to PCS: spectrum allocation, mobility, and standardization efforts. Since PCS involves several different communication technologies, we introduce its heterogeneous and distributed system architecture. IN is also described in detail because it plays a critical role in the development of PCS. Finally, we introduce the application of PCS and its deployment status since the mid-term of 1990’s.This work was supported in part by the National Natural Science Foundation of China under Grant No. 60673159 and 70671020; the National High-Tech Research and Development Plan of China under Grant No. 2006AA01Z214, and the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant EP/E060722/1

New e-Learning system architecture based on knowledge engineering technology

The paper focuses on the field of research on next generational e-Learning facility, in which knowledge-enhanced systems are the most important candidates. In the paper, a reference architecture based on the technologies of knowledge engineering is proposed, which has following three intrinsic characteristics, first, education ontologies are used to facilitate the integration of static learning resource and dynamic learning resource, second, based on semantic-enriched relationships between Learning Objects (LOs), it provides more advanced features for sharing, reusing and repurposing of LOs, third, with the concept of knowledge object, which is extended from LO, an implementing mechanism for knowledge extraction and knowledge evolution in e-Learning facilities is provided. With this reference architecture, a prototype system called FekLoma (Flexible Extensive Knowledge Learning Object Management Architecture) has been realized, and testing on it is carrying out

An authentication scheme to defend against UDP DrDoS attacks in 5G networks

5th generation wireless systems are coming. While we are excited about the delay-free high speeds 5G will bring, security problems are becoming more and more serious. Increasingly rampant Distributed Denial of service (DDoS) attacks, particularly Distributed Reflection Denial of Service (DrDoS) attacks with User Datagram Protocols (UDPs) have developed into a global problem. This article presents a design, implementation, analysis, and experimental evaluation of an authentication scheme, a defense against UDP DrDoS attacks, by which attackers cleverly use rebound server farms to bounce a flood of packets to a target host. We call our solution IEWA because it combines the concepts of increasing expenses and weak authentication. In this paper, we apply IEWA to Network Time Protocol (NTP). First, we simulate and compare the original and improved protocols. Next, we verify the effectiveness of our proposed scheme. We show that our improved scheme is safer than the original scheme. Finally, we compare our solution with existing state-of-the-art schemes, using indicators such as communication overhead, server storage costs, client storage costs, computation costs of server and computation costs of client. We find that our scheme improves system stability and security, reduces communication overhead, server storage cost and computational costs. Our solution not only improves the NTP protocol to mitigate DrDoS attacks, but also strengthens other UDP protocols that are vulnerable to DrDoS attacks. Therefore, our solution can be used as a solution to UDP DrDoS attacks in 5G Network

QoS multicast routing protocol oriented to cognitive network using competitive coevolutionary algorithm

The human intervention in the network management and maintenance should be reduced to alleviate the ever-increasing spatial and temporal complexity. By mimicking the cognitive behaviors of human being, the cognitive network improves the scalability, self-adaptation, self-organization, and self-protection in the network. To implement the cognitive network, the cognitive behaviors for the network nodes need to be carefully designed. Quality of service (QoS) multicast is an important network problem. Therefore, it is appealing to develop an effective QoS multicast routing protocol oriented to cognitive network. In this paper, we design the cognitive behaviors summarized in the cognitive science for the network nodes. Based on the cognitive behaviors, we propose a QoS multicast routing protocol oriented to cognitive network, named as CogMRT. It is a distributed protocol where each node only maintains local information. The routing search is in a hop by hop way. Inspired by the small-world phenomenon, the cognitive behaviors help to accumulate the experiential route information. Since the QoS multicast routing is a typical combinatorial optimization problem and it is proved to be NP-Complete, we have applied the competitive coevolutionary algorithm (CCA) for the multicast tree construction. The CCA adopts novel encoding method and genetic operations which leverage the characteristics of the problem. We implement and evaluate CogMRT and other two promising alternative protocols in NS2 platform. The results show that CogMRT has remarkable advantages over the counterpart traditional protocols by exploiting the cognitive favors

New Graph Model for Channel Assignment in Ad Hoc Wireless Networks

The channel assignment problem in ad hoc wireless networks is investigated. The problem is to assign channels to hosts in such a way that interference among hosts is eliminated and the total number of channels is minimised. Interference is caused by direct collisions from hosts that can hear each other or indirect collisions from hosts that cannot hear each other, but simultaneously transmit to the same destination. A new class of disk graphs (FDD: interFerence Double Disk graphs) is proposed that include both kinds of interference edges. Channel assignment in wireless networks is a vertex colouring problem in FDD graphs. It is shown that vertex colouring in FDD graphs is NP-complete and the chromatic number of an FDD graph is bounded by its clique number times a constant. A polynomial time approximation algorithm is presented for channel assignment and an upper bound 14 on its performance ratio is obtained. Results from a simulation study reveal that the new graph model can provide a more accurate estimation of the number of channels required for collision avoidance than previous models

DivORAM: Towards a practical oblivious RAM with variable block size

Oblivious RAM (ORAM) is important for applications that require hiding access patterns. Many ORAM schemes have been proposed but most of them support only storing blocks of the same size. For the variable length data blocks, they usually fill them upto the same length before uploading, which leads to an increase in storage space and network bandwidth usage. To develop the first practical ORAM with variable block size, we proposed the “DivORAM” by remodeling the tree-based ORAM structure. It employs an additively homomorphic encryption scheme (Damgård–Jurik cryptosystem) executing at the server side to save the client computing overhead and the network bandwidth cost. As a result, it saves network bandwidth 30% comparing with Ring ORAM and 40% comparing with HIRB ORAM. Experiment results show that the response time of DivORAM is 10 ×  improved over Ring ORAM for practical parameters

Medium optimization for acarbose production by Actinoplanes sp. A56 using the response surface methodology

In order to improve the production of acarbose, the fermentation medium of acarbose-producing strain Actinoplanes sp. A56 was optimized in this paper. Firstly, fractional factorial design was employed to investigate the influences of glucose, maltose, corn steep liquor, soy bean flour and monosodium glutamate on acarbose production, and the results revealed that maltose and corn steep liquor had significant and positive effects. Then, the two significant factors used the method of the steepest ascent to reach the yield plateau of acarbose. To explore the best condition obtained by the steepestmethod, the concentrations of maltose and corn steep liquor were further optimized with central composite design and response surface analysis. As a result, the acarbose production was increased from 837 to 1043 mg/L by using this optimization strategy

The Kinematic Evolution of Erupting Structures in Confined Solar Flares

In this Letter, we study the kinematic properties of ascending hot blobs associated with confined flares. Taking advantage of high-cadence extreme-ultraviolet images provided by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we find that for the 26 events selected here, the hot blobs are first impulsively accelerated outward, but then quickly slow down to motionlessness. Their velocity evolution is basically synchronous with the temporal variation of the Geostationary Operational Environmental Satellite soft X-ray flux of the associated flares, except that the velocity peak precedes the soft X-ray peak by minutes. Moreover, the duration of the acceleration phase of the erupting blobs is moderately correlated with that of the flare rise phase. For nine of the 26 cases, the erupting blobs even appear minutes prior to the onset of the associated flares. Our results show that a fraction of confined flares also involve the eruption of a magnetic flux rope, which sometimes is formed and heated prior to the flare onset. We suggest that the initiation and development of these confined flares are similar to that of eruptive ones, and the main difference may lie in the background field constraint, which is stronger for the former than for the latter.Comment: 13 pages,4 figure