Sun Ok Yang

Maintaining mobile transactional consistency in hybrid broadcast environments

Abstract.Recently there have been attempts in several research areas at efficiently utilizing the resources of mobile computers. Considering the properties in mobile computing environments, push-based data dissemination systems have lately attracted considerable attention. However, skewed access patterns among mobile clients makes response time worse, and they prefer to send data requests to the server explicitly through an uplink channel. A broadcast supporting an uplink channel is called a hybrid broadcast. In this paper, we devise new transaction processing algorithms for hybrid broadcasts. It is assumed that data objects that the server maintains are divided into Push_Data for periodic broadcasting and Pull_Data for on-demand service. That is, clients have to explicitly request data objects in Pull_Data. Maintaining transactional consistency in this environment without much additional cost is our main concern. Finally, we evaluate performance behavior through simulation study.

Profile-Based Lifetime Determination Schemes for Mobility Management in HMIPv6 *

In Mobile IP, whether mobile nodes are moving or not, lots of messages have to be exchanged for various purposes. The frequent exchange of messages incurs overhead in several ways, especially in terms of energy use in mobile node. Of course, if fewer messages are delivered, issues related with authorization may become problematic. To deal with this situation properly, we propose new profile-based lifetime determination schemes. Our works are motivated by the observation that some people perform regular movements; thus, the related information can be useful for decreasing the number of messages forwarded. Therefore, each user can maintain a local profile based on movement logs. From the profile, the proper lifetime for a binding update message can be determined, which will also affect authorization for binding between mobile node and correspondent nodes. In extensive experiments, we mainly focused on bandwidth use for binding update messages. From the results, we found that our schemes can achieve considerable performance improvement by reducing the number of binding update messages at a small additional cost for the profile, which is an essential property in mobile computing environments.

Adaptive binding update schemes in NEMO

When a mobile network moves from one place to another, it changes the reachability of the mobile network in the Internet topology. Network Mobility (NEMO) is concerned with the management of this movement of the mobile network. It is necessary to exchange binding update messages frequently for seamless mobility. However, it incurs both the increase of network overhead and poor usage of mobile router energy efficiency. Our main concerns focus on binding update message management to support efficient network mobility. Thus, this paper proposes an adaptive binding lifetime according to the duration for which mobile router resides in each network under the condition that the mobility type of the mobile router is known in advance. By introducing this algorithm, the number of binding update messages for refreshing the binding could be reduced compared to the default behavior of NEMO, which is defined in RFC3963. Simulation results are shown to prove the effectiveness of the proposed schemes.

Network mobility in MIPv6 considering arrival time

Mobile IPv6 represents a global solution, providing mobility management for a wide variety of radio technologies, devices, and applications. In particular, Network Mobility basic support protocol is the one of fundamental solutions in MIPv6 which reduces the number of binding update messages issued from mobile network nodes except mobile routers. That is, it never reduces the number of binding update messages which mobile router issues. Significant research results relating to Network Mobility have been reported over last several years. However, practical and common issues exist within the technology; specification of Binding Update Lifetime has a substantial impact the system performance. The binding update message should be delivered periodically for the purpose of user location notification and binding authorization. If the lifetime is too short, the traffic load resulting from the messages may be significant. In addition, issues related to authorization can be problematic. In this paper, therefore, Network Mobility considering arrival time is devised to solve the binding update explosion of mobile routers without security problem in Network Mobility

Low-cost binding update schemes based on mobility type in HMIPv6

Mobile IP represents a global solution that provides mobility management for a wide variety of radio technologies, devices, and applications. Significant research results relating to extensions for Mobile IPv6 have been reported over the last several years. However, practical issues exist within the technology. In particular, specification of the binding update lifetime has a substantial impact on system performance. In Mobile IPv6, the binding update message should be delivered periodically for the purpose of user-location notification and binding authorization. If the lifetime is too short, the traffic load resulting from the messages may be significant. In addition, energy-efficiency problems may surface for mobile nodes in standby mode, and issues related to authorization can be problematic. In this paper, therefore, binding update schemes are devised to obtain high-energy-efficiency mobile nodes in hierarchical Mobile IPv6. These solutions also affect authorization for binding between the mobile node and correspondent nodes. Advance information about the mobility pattern of each mobile node can be very useful in decreasing the required frequency of binding update messages; that is, if each user maintains a locally based profile of moving history, this information can be very useful in fixing the lifetime in terms of current location. In addition, the resident time is occasionally affected by the daily arrival time as well as the subnet. Thus, an expanded scheme that considers the time region of the arrival time per subnet is also proposed. Through extensive experiments, the performance improvement achieved by the proposed schemes is presented.

Efficient binding lifetime determination schemes in HMIPv6

Mobile IP represents a global solution, providing mobility management for a wide variety of radio technologies, devices and applications. Significant research results relating to extensions for MIPv6 have been reported over the last several years. However practical and common issues exist within the technology, in particular, the specification of Binding Update Lifetime has a substantial impact on the system performance. In this paper, binding lifetime determination schemes are devised to obtain high energy-efficiency mobile nodes in HMIPv6. Some people may stay within some area for a long time and thus the related information can be very useful in decreasing the frequency of binding update messages. That is, if each user maintains a profile locally based on moving history; this can be very useful in fixing the lifetime in terms of current location. In addition, the resident time is occasionally affected by the daily arrival time as well as the subnet. Thus, we expand the scheme to consider the time region of arrival time per each subnet. We study the performance improvement of our schemes through extensive simulations.

Energy-Efficient Message Management Algorithms in HMIPv6

Mobile IPv6 enables nodes to move within the Internet topology while maintaining reachability and on-going connections between mobile node and correspondent nodes. Binding update and binding request messages are used for this purpose. However, highly frequent occurrence of those messages incurs high overhead in several ways. To solve the problem, we propose new binding update message management algorithms that consider each user’s mobility pattern. If each user maintains a profile locally based on mobility pattern logs, it helps to determine a proper lifetime for binding updates. In addition, we devise another lifetime determination scheme considering arrival time by expanding the first one. Through the extensive experiments, we focus and measure the bandwidth usage for binding update messages by comparing the proposed algorithms with that in Hierarchical MIPv6.