The reduction of the signaling load associated with IP mobility management is one of the significant challenges to IP mobility support protocols. Hierarchical Mobile IPv6 (HMIPv6) aims to reduce the number of the signaling messages in the backbone networks, and improve handoff performance by reducing handoff latency. However, this does not imply any change to the periodic binding update (BU) to the home agent (HA) and the correspondent node (CN), and now a mobile node (MN) additionally should send it to the mobility anchor point (MAP). Moreover, the MAP should tunnel the received packets to be routed to the MN. These facts mean that the reduction of the BU messages in the backbone networks can be achieved at the expense of the increase in the signaling bandwidth consumption within a MAP domain. On the other hand, it is observed that an MN may habitually stay for a relatively long time or spend on using much Internet in a specific cell (hereafter, home cell) covering its home, office or laboratory, etc. Thus, considering the preceding facts and observation, HMIPv6 may not be favorable especially during a home cell residence time in terms of signaling bandwidth consumption. To overcome these drawbacks of HMIPv6, we propose a history-based auxiliary mobility management strategy (H-HMIPv6) to enable an MN to selectively switch its mobility management protocols according to whether it is currently in its home cell or not in HMIPv6 networks. The operation of H-HMIPv6 is almost the same as that of HMIPv6 except either when an MN enters/leaves its home cell or while it stays in its home cell. Once an MN knows using its history that it enters its home cell, it behaves as if it operates in Mobile IPv6 (MIPv6), not in HMIPv6, until it leaves its home cell; No periodic BU messages to the MAP and no packet tunneling occur during the MN's home cell residence time. The numerical results indicate that compared with HMIPv6, H-HMIPv6 has apparent potential to reduce the signaling bandwidth consumption and the MAP blocking probability.

Mobile IP provides an efficient and scalable mechanism for host mobility within the Internet. Using Mobile IP, mobile nodes may change their point of attachment to the Internet without changing their IP address. In contrast to the advantages of Mobile IP, updating the location of a mobile node incurs high signaling costs if the mobile node moves frequently. Thus, IP paging schemes for Mobile IP have been proposed to avoid unnecessary registration signaling overhead when a mobile node is idle. However, they require the additional paging costs and delays associated with message delivery when a correspondent node sends packets to the idle mobile node. These delays greatly influence the quality of service (QoS) for multimedia services. Moreover, existing IP paging schemes do not consider a hierarchical mobility management scheme, which can reduce signaling costs by the significant geographic locality in user mobility pattern. Thus, we propose a novel IP paging protocol which can be used in hierarchical Mobile IPv6 networks. In addition, our proposal can reduce signaling costs for paging and delay using the concept of the anchor-cell. The cost analysis presented in this paper shows that our proposal has superior performance when the session-to-mobility ratio value of the mobile node is low.

In this letter, we propose PQ-MAC: a priority-based medium access control (MAC) protocol for providing quality of service (QoS) in wireless sensor networks (WSNs) which minimizes the energy consumption with traffic-based sleep-wakeup scheduling and supports QoS using differentiating channel access policy, packet scheduling, and queue management. The PQ-MAC utilizes the advantages of time division multiple access (TDMA) and slotted carrier-sense multiple access (CSMA). The proposed protocol is an energy-efficient, priority-based, and QoS compatible MAC protocol. It consists of multi-level queue management, sleep-wakeup scheduling, and an ordered contention period (CP) scheme. It also guarantees time-bounded delivery of QoS packets. Performance evaluation is conducted between PQ-MAC and S-MAC with respect to three performance metrics: energy consumption, throughput, and average latency. The simulation results show that the performance of PQ-MAC is better than that of S-MAC.

In this paper, we propose TB-MAC (Threshold-Based MAC), which has been designed to consider various network traffic conditions while providing energy efficiency in a wireless sensor networks. Existing MAC protocols for sensor networks attempt to solve the energy consumption problem caused by idle listening using an active/sleep duty cycle. Since there are various traffic conditions, however, they may not always provide improvements in energy consumption. Hence, we propose a MAC protocol algorithm that stores data in a buffer and transmits data when the buffer exceeds a threshold value so that energy efficiency is always guaranteed for any network traffic condition. The analytical results show that our proposed algorithm enables significant improvements in energy consumption compared to the existing MAC protocols for sensor networks.

This paper describes IP encapsulation technologies for the Mobile RSVP tunnel in next generation networks. Bandwidth is inherently a scarce network resource, and hence signaling overhead should be minimized as much as possible. However, because of duplicate RSVP messages, the existing RSVP tunnel-based mechanism suffers from bandwidth overhead and tunnel problems. The waste of network resources prevents low-cost network construction and the maximization of integrated network utility, which are the goals of next generation networks, and can lower the reliability of networks with the increase of service subscribers and resultant expansion of resource consumption. To solve these problems and to support end-to-end QoS efficiently, RSVP needs to be changed at a minimum degree. In this paper, a new IP encapsulation mechanism for saving of network resources in the Mobile RSVP tunnel (IPEnc-RSVP) is proposed. In order to compare the proposed mechanism and the existing RSVP tunnel-based mechanism in Mobile IP-based networks, we perform a comparative analysis of bandwidth consumption gain, throughput, mean packet delay, etc., and demonstrate the superiority of the proposed mechanism. In addition, we analyze several performance factors of RSVP protocols by applying the existing RSVP tunnel-based mechanism and the proposed mechanism, respectively.

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 IETF Mobile IPv6 enables any IPv6 node to both cache the Care-of Address associated with a mobile node's home address, and to directly send packets addressed to a mobile node at the Care-of Address using the IPv6 routing header. Support for optimizing the route is built in as a fundamental part of the protocol. Several hierarchical schemes have been presented recently on top of the Mobile IPv6. These schemes separate micro-mobility from macro-mobility and exploit a mobile node's locality. They can reduce the number of signaling messages sent to a home network and improve hand-off performance. However, existing hierarchical schemes do not achieve route optimization. When external correspondent nodes send packets to a mobile node, these packets are intercepted by an intermediate mobility agent encapsulated and routed to the mobile node. In this paper, we propose a new hierarchical scheme that enables any correspondent node to cache two Care-of Addresses; the mobile node's temporary address and the intermediate mobility agent's address. Also, we introduce two lifetimes managing the two Care-of Addresses. Until the lifetime associated with the mobile node's temporary address expires, a correspondent node can send packets directly to the mobile node. If the lifetime expires but the lifetime associated with the intermediate mobility agent's address has not expired, the correspondent node sends packets to the intermediate mobility agent. This proposal can reduce delay in packet delivery and optimize routing. Furthermore, based on the mobility of a mobile node, we introduce more reduced frequency of binding update and longer period of the lifetimes than the existing hierarchical schemes. Therefore, our proposal can reduce the binding update bandwidth as well as the packet delivery bandwidth lower than those of the IETF IPv6 and the existing hierarchical schemes.

This letter proposes a group-based distributed air index (called GDI) using two-leveled groups by partitioning the identifiers of data items to reduce the size of the index. GDI provides both global and local views of data items and multiple pointers to data items in a single access to an index. Simulation results show that GDI outperforms the existing index in terms of multiple data access, energy conservation and data waiting time.

This paper presents a novel analytical approach to evaluate the signaling load of Mobile IPv6 (MIPv6) and Hierarchical Mobile IPv6 (HMIPv6). Previous analytical approaches for IP mobility management have not provided a complete and general framework for the performance analysis; no consideration of either periodic binding refresh cost or extra packet tunneling cost from the viewpoint of IP mobility management, and no in-depth investigation with respect to various system parameters. In this paper, according to the proposed analytical approach, we derive the location update costs (i.e., the sum of binding update costs and binding refresh costs), packet tunneling costs, inside-domain signaling costs, outside-domain signaling costs, and total signaling costs, which are generated by a mobile node (MN) during its average domain residence time in case MIPv6 or HMIPv6 is deployed under the same network architecture, respectively. Moreover, based on these derived costs, we evaluate the impacts of various system parameters on the signaling costs generated by an MN in MIPv6 and HMIPv6. The aim of this paper is not to determine which protocol performs better, but evaluate the performance that can be expected for each protocol under the various conditions, broaden our deep understanding of the various parameters that may influence the performance, and provide insight for the deployment of the two protocols.

In wireless mobile environments, data requests based on the location of mobile clients (MCs) have increased. The requested data, called location-dependent data (LDD), may be uncertain if MCs use terms of general distance like "near". Fuzzy theory allows us to represent uncertainty without sharp boundaries. In this paper we quantify the fuzziness and propose a method for constructing the data region of LDD by the degree of the distance between LDDs' and MCs' locations. In simulation studies, we evaluate the LDD regions (LDRs) in various situations: MCs' extensive and intensive queried pattern in data regions of two "near" senses and civilized regions with regional features. Our performance evaluation shows that the number of database accesses in proposed LDRs can be reduced in each case.

In Optimistic Two-Phase Locking (O2PL), when a transaction requests a commit, the transaction can not be committed until all requested locks are obtained. By this reason, O2PL leads to unnecessary waits and operations even though it adopts an optimistic approach. This paper suggests an efficient optimistic cache consistency protocol that provides serializability of committed transactions. Our cache consistency scheme, called PCP (Preemptive Cache Protocol), decides whether to commit or abort without waiting when transactions request commits. In PCP, some transactions that read stale data items can not be aborted, because it adopts a re-ordering scheme to enhance the performance. In addition, for re-ordering, PCP stores only one version of each data item. This paper presents a simulation-based analysis on the performance of PCP with other protocols such as O2PL, Optimistic Concurrency Control and Caching Two-Phase Locking. The simulation experiments show that PCP performs as well as or better than other schemes with low overhead.