A dynamic anchor-area (DAA) scheme is proposed to reduce the location management cost for PCS networks. Based on an Intra-LA location update (LU) scheme, the proposed DAA scheme utilizes a given timer value and a movement list. The DAA scheme considers a wider variety of mobile terminal's movement pattern than the previous intra-LA LU scheme. Simulations confirm that the proposed scheme offers a significant reduction in the location management cost.

In order to find paths guaranteed by Quality of Service (QoS), the link state database (LSDB), containing QoS constraint information, and residing in routers, needs to be well managed. However, there is a trade-off between the exact reflection of the current link status and the update cost to calculate and maintain this data. In order to perfectly reflect the current link state, each router immediately notifies its neighbors whenever link state information changes. However, this may degrade the performance of the router. On the other hand, if current link state information is not updated routinely, route setup requests may be rejected because of the discrepancy between the current link state information and the previously updated link state information in the LSDB. Therefore, we need link state update (LSU) algorithms making it possible to appropriately update the LSDB. In addition, to facilitate implementation, they also should have low-complexity and must be adaptive under the variation of network conditions. In this paper, we propose an enhanced simple-adaptive (ESA) LSU algorithm, to reduce the generation of LSU messages while maintaining simplicity and adaptivity. The performance of this algorithm is compared with five existing algorithms by rigorous simulations. The comparision shows that the ESU algorithm can adapt to changes in network conditions and its performance is superior to existing LSU algorithms.

Copyright protection is a major issue in distributing content on Internet or broadcasting service. One well-known method of protecting copyright is a traitor tracing scheme. With this scheme, if a pirate decoder is made, the content provider can check the secret key contained in it and trace the authorized user/subscriber (traitor). Furthermore, users require that they could obtain services anywhere they want (Anywhere TV). For this purpose, they would need to take along their secret keys and therefore key exposure has to be kept in mind. As one of countermeasures against key exposure, a forward secure public key cryptosystem has been developed. In this system, the user secret key remains valid for a limited period of time. It means that even if it is exposed, the user would be affected only for the limited time period. In this paper, we propose a traitor tracing scheme secure against adaptive key exposure (TTaKE) which contains the properties of both a traitor tracing scheme and a forward secure public key cryptosystem. It is constructed by using two polynomials with two variables to generate user secret keys. Its security proof is constructed from scratch. Moreover we confirmed its efficiency through comparisons. Finally, we show the way how its building blocks can be applied to anywhere TV service. Its structure fits current broadcasting systems.

Currently, Mobile IPv6 (MIPv6) working group of Internet Engineering Task Force (IETF) recommends to execute the Binding Update (BU) using Return Routability (RR) procedure. However, the RR procedure doesn't entirely satisfy the security requirements of MIPv6. The previous BU protocols are also likely to reduce the efficiency since they iterate entirely BU protocol courses in Pico/Micro cellular environment in which it occurs frequently handoff or handover and some protocols don't consider that the Correspondent Node (CN) is movable node and has the limited resources. In this paper we propose the ETBU protocol, which is based on Cryptographically Generated Address (CGA) to provide mutual authentication between nodes; it considers that the CN is a movable node. This protocol doesn't require a Mobile Node (MN) to create a signature each time it obtains a new Care-of Address (CoA) unlike the previous CGA-based BU protocol. An MN and its CN issue the ticket to minimize the computing costs that need to calculate CGA. Also, the ETBU protocol minimizes the loss of traffic using smooth handoff or handover. A performance analysis shows that the scheme provides the security as much as the previous BU protocols and more efficiency than them in case that each node obtains the ticket. Therefore, the proposed ETBU protocol can be applied easily to the mobile network environments.

Expressions are presented for the probability of target detection and the measurement accuracy of the detection, taking into account the effects of antenna beam-pointing error. Evaluation of these expressions requires numerical integration, which is computationally expensive. Approximate but analytic and efficient expressions are also presented. Numerical examples are given to present the relative accuracy of our analytic approximations.

There are two principal aspects of "mobility" in location-aware computing: (1) how to support mobility and (2) how to exploit it. This paper considers the latter, while many existing works only concentrate on the former. This work is trying to prove that the performance of location-aware systems will be greatly improved by understanding the user's movement. In this paper, we propose a novel location update protocol called state-based location update protocol (SLUP), which significantly minimizes the energy consumption of mobile client by exploiting a syntactic information of a user's movement. This concept is called mobility-awareness which is a kind of context-awareness. Moreover, there are three variations of the proposed protocol in terms of how to choose the optimal state: SLUP/BS, SLUP/UITR, and SLUP/IUT. Experimental results show that the proposed protocol outperforms the well-known existing protocols such as dead-reckoning and distance-based protocol, and that the SLUP/IUT approach can achieve different performance tradeoffs between energy efficiency and location accuracy by fine-tuning its algorithmic parameter Tiut.

Popular Web sites form their Web servers into Web server clusters. The Web server cluster operates with a load-balancing algorithm to distribute Web requests evenly among Web servers. The load-balancing algorithms founded on conventional periodic load-information update mechanism are not scalable due to the synchronized update of load-information. We propose a load-balancing algorithm that the load-information update is not synchronized by exploiting variant execution times of executing scripts in dynamic Web pages. The load-information of each server is updated 'individually' by a new load-information update mechanism, and the proposed algorithm supports high scalability based on this individual update. Simulation results have proven the improvement in system performance through another aspect of high scalability. Furthermore, the proposed algorithm guarantees some level of QoS for Web clients by fairly distributing requests. A fundamental merit of the proposed algorithm is its simplicity, which supports higher throughput of the Web switch.

In mobile communication systems, mobility tracking operations are executed to maintain known the whereabouts of each mobile terminal (MT). In this article, we propose and analyse two new versions of the original time-based registration method, namely the Stop and Wait (S W) and the Reset and Wait (R W) time-based strategies. We also propose and study the modified S&W and R&W schemes as a result of combining the S&W and R&W policies with the enhanced time-based method in [3]. When the MT uses one of the four schemes proposed, it sends less location update (LU) messages. As a result of fewer LUs, which results in less contacts with the network, the uncertainty of the MT position increases in the proposed time-based schemes. Although the MT paging (PG) cost is lightly increased, a significant reduction in the LU cost is achieved. As it is shown, the net effect is a saving in the total location management cost per call arrival. In order to analyse the four strategies and compare them with the original and enhanced time-based schemes, a performance evaluation method based on Markovian standard tools is proposed here. The location management cost for all these time-based policies are evaluated analytically here by using this evaluation method.

This letter proposes an improved timer-based location management scheme for packet-switched (PS) mobile communication systems. Compared to the conventional timer-based scheme with a single timer threshold, a new timer-based scheme with two timer thresholds is proposed to accommodate the bursty data traffic characteristics of PS service. The location update and paging costs of the proposed scheme are analyzed and compared with those of the conventional scheme. We show that the proposed scheme outperforms the conventional scheme in terms of total cost of both location update and paging with an appropriate selection of timer thresholds.

We propose a method of controlling the view divergence of data freshness when copies of sites in a replicated database are updated asynchronously. The view divergence of the replicated data freshness is the difference in the recentness of the updates reflected in the data acquired by clients. Our method accesses multiple sites and provides a client with data that reflects all the updates received by the sites. First, we define the probabilistic recentness of updates reflected in acquired data as read data freshness (RDF). The degree of RDF of data acquired by clients is the range of view divergence. Second, we propose a way to select sites in a replicated database by using the probability distribution of the update delays so that the data acquired by a client satisfies its required RDF. This way calculates the minimum number of sites in order to reduce the overhead of read transactions. Our method continues to adaptively and reliably provide data that meets the client's requirements in an environment where the delay of update propagation varies and applications' requirements change depending on the situation. Finally, we evaluate by simulation the view divergence we can control using our method. The simulation showed that our method can control the view divergence to about 1/4 that of a normal read transaction for 100 replicas. In addition, the increase in the overhead of a read transaction imposed by our method is not as much as the increase in the total number of replicas.

This paper presents a novel decoding algorithm for turbo codes, in which the likelihood values for redundant parts are updated in order for those values to become more reliable. A criterion for updating the redundant likelihood values is proposed, which is based on the comparisons of the channel values with the re-generated values by the soft-input and soft-output encoders. It is shown that the proposed method can improve the error correcting capabilities, i.e., the improvement of BER/BLER performance and the achievable BER limit.

Future personal communication service (PCS) networks consider smaller cells to accommodate continuously growing population of subscribers. That results in frequent location update and consequently higher signaling cost. Among various schemes proposed for improving the efficiency of location management, the distance-based and the direction-based location update methods work well for just certain mobility patterns. In this paper, we propose a hybrid location update (HLU) scheme, which takes into account both the moving distance and the moving direction when deciding on updating the location. We analyze the performance of the HLU under different mobility patterns and call-to-mobility ratios based on a 2D Markov walk model. The numerical results demonstrate that the HLU scheme can achieve better performance than the distance-based or the direction-based methods applied individually.

As the number of mobile terminals (or users) keeps explosively increasing, the location management to track mobile terminals in cellular networks is becoming more important. However, the location management schemes presently adopted in cellular networks use static location information without considering the moving direction of a mobile terminal. This approach is insufficient in reflecting the different directional behaviors of mobile terminals. Thus, there is a need to develop a dynamic location management scheme more adaptive to the moving direction of a mobile terminal. This paper proposes a direction-based scheme (DBS) that can determine a location update and vary a paging area dynamically according to the moving direction. The direction vector was defined to represent the moving direction and to compute the distance from the cell where a location update occurs to the current cell. The offset operation of direction vectors represented the location of a mobile terminal in a paging area. This allowed the mobile terminal to determine whether a location update would be performed or not. In addition, simulations showed that DBS outperforms other location management schemes in most cases except in those with a low call-to-mobility ratio (CMR), particularly if a mobile terminal has directional behavior.

The most important function of a router is to perform IP lookup that determines the output ports of incoming IP packets by their destination addresses. Hence, IP lookup is one of the main issues in implementing high-speed routers. The IP lookup algorithm implemented in IQ2200 Chipset with two-level table architecture can efficiently use memory. However, it wastes processor resource for full re-construction of the forwarding tables whenever every route insertion/deletion is requested. In order to improve the utilization of processor resource, we propose an IP lookup algorithm with three-level table architecture for high-speed routers. We evaluate the performance of the proposed algorithm in terms of the memory size required for storing lookup information and the number of memory access in constructing forwarding tables. Being compared with the IQ2200 scheme, the proposed scheme can reduce the number of memory access up to 99% even though it needs about 16% more memory.

This paper proposes a learning classifier based on Support Vector Domain Description (SVDD) for two-class problem. First, by the description of the training samples from one class, a sphere boundary containing these samples is obtained; then, this boundary is used to classify the test samples. In addition, instead of the traditional quadratic programming, multiplicative updates is used to solve the Lagrange multiplier in optimizing the solution of the sphere boundary. The experiment on CBCL face database illustrates the effectiveness of this learning algorithm in comparison with Support Vector Machine (SVM) and Sequential Minimal Optimization (SMO).

Many algorithms have been introduced to obtain giga-bit routing performance by reducing searching time. As most of them, however, have not considered the importance of update time and memory requirement seriously, they couldn't work well in real networks. We propose a flexible and fast IP lookup algorithm, named FFILA, considering these factors and compare the performance of our scheme with that of the conventional scheme of Patricia trie.

In General Packet Radio Service (GPRS), combined mobility management is defined to efficiently perform both GSM and GPRS mobility management in a combined manner. In this letter, an enhanced scheme for combined mobility management based on a new mobile station (MS) state model is proposed. The steady state probabilities of the proposed MS state model are derived and the performance of the proposed scheme is analyzed. The results show that the proposed scheme outperforms the conventional scheme, especially for low mobility MSs.

Among several methods of storing XML documents, a straightforward yet efficient method is to store a string representation of the XML document. An XML node is usually represented by a region coordinate, which is a pair of integers expressing the start and end positions of the substring corresponding to the node. This approach, however, has the drawback that a change of a node's region coordinate causes change of the region coordinates of many other elements. This recomputation normally degrades the performance of XML applications, especially when content is updated frequently. In this paper, we propose the Relative Region Coordinate (RRC) technique to effectively reduce the cost of recomputation. The main idea is to express the coordinate of an XML element in the region of its parent element. We present a method to integrate the RRC information into XML systems and provide experimental results that demonstrate the effectiveness of the RRC in the content update.

The exciting goals of ubiquitous computing and communication services can only be achieved if we can increase the efficiency with which the location of mobile terminals can be managed; current mobile infrastructures are not efficient since they treat all mobile terminals uniformly despite that fact that many mobiles often move together (i.e. passengers on the same train or a group of cars on a road). This paper presents a hierarchical location management scheme that handles such grouped mobiles collectively and so reduces the overhead costs of location management. In our scheme, mobiles that move together for long enough form a mobile network and make a hierarchy in the wireless access network. The scheme also adjusts the number of mobile networks to keep communication overhead low. We apply the scheme to Mobile IPv6 and evaluate the resulting performance improvement. Simulation results confirm that our hierarchical approach can greatly reduce the overhead costs of location management, and that it is very practical since it can flexibly develop suitable mobile networks.

In this letter, we propose an enhanced time-based registration method and analyze the performance numerically. In the analysis, we assume Poisson call arrival distribution and exponential cell resident time. The performance of the enhanced time-based registration method is compared with the performance of the original time-based registration method. In the comparisons, we see that in a certain range of parameters, the enhanced time-based registration method has better performance.