Kuen-Liang Sue

One-step pointer forwarding strategy for location tracking in distributed HLR environment

One of the main challenges in personal communication service (PCS) is to locate many mobiles that may move frequently from place to place. Such a system operation is called location tracking. Many network signals flow, and database queries are required to achieve such a task. In addition to the two-level hierarchical strategy in IS-41 and GSM, several strategies have been proposed to improve the efficiency of location tracking. Pointer forwarding was used to reduce the expensive home location register (HLR) accesses. Previously, the distributed HLR scheme was proposed to prevent the HLR from becoming a bottleneck in the signaling network. However, the length of a forwarding pointer chain may be lengthened in a distributed HLR environment. We propose a more efficient strategy to overcome this potential problem. This strategy attempts to migrate the locating chains in a distributed HLR system when a mobile issues a registration operation. As a consequence, the length of any forwarding pointer chain does not exceed one in our strategy. Simulation results indicate that our strategy significantly decreases the locating cost. In fact, this strategy provides an upper bound of location tracking time owing to the fact that the length of any locating path does not exceed one. Furthermore, obsolete entries in local databases visitor location registers can be reclaimed in this strategy.

FLEXOR: a flexible localization scheme based on RFID

There are many localization schemes used for the indoor or outdoor applications, such as the GPS, RADAR etc However, the accuracy of indoor localization scheme is easy to be influenced because of the obstacles and the environment interference LANDMARC which is proposed by Lionel et al uses the RFID tags to reduce the influence of the interference This paper proposes an improved localization scheme, FLEXOR, which divides the localization area into cells to reduce computational overhead and provide two localization modes: region mode and coordinate mode In the performance evaluations, FLEXOR has been proved to have the advantages of fast localization, flexibility, and it also provides the high localization accuracy as LANDMARC.

MAMBO: A Mobile Advertisement Mechanism Based on Obscure Customer's Location by RFID

The features of mobile advertisement include instantaneity, interaction, and personalization, which can enhance the efficiency and effectiveness of commercial advertisement. The study proposes a mobile advertisement mechanism for large supermarkets. The mechanism will provide both push and pull advertisement according the users location. In push mode, each customer can always receive the message of the promoted goods nearby. In pull mode, customer can request the information about the goods they need actively. The success of mobile advertisement depends on whether the system can send proper information to the potential consumer at the proper time based on his/her location and preference. The key issue is processed via an indoor localization scheme based on RFID in the investigation.

Second chance replacement policy for mobile database overflow

The visitor location register (VLR) is used to store temporary records for roaming users. Due to the limited capacity, the VLR may be full. This phenomenon is called VLR overflow. By replacing an existing record, the incoming user can still receive services. The most-idle replacement (MR) policy was proposed to improve the random replacement (RR) policy. The MR policy is almost the optimum method and outperforms RR policy significantly. However, the MR policy requires global information to find the most-idle user. It needs considerable extra cost and is unfeasible due to the separated VLR databases in the real mobile network. Therefore, we propose the second chance replacement (SCR) policy to overcome these drawbacks. The SCR policy needs only an additional bit in the record. Partial information is sufficient for our method, so it is feasible in the real mobile network. Moreover, the simulation results show that the SCR policy outperforms the MR policy in most scenarios investigated in our study.

Fast mode decision based on human noticeable luminance difference and rate distortion cost for H.264/AVC

This article proposes a fast mode decision algorithm based on the correlation of the just-noticeable-difference (JND) and the rate distortion cost (RD cost) to reduce the computational complexity of H.264/AVC. First, the relationship between the average RD cost and the number of JND pixels is established by Gaussian distributions. Thus, the RD cost of the Inter 16 × 16 mode is compared with the predicted thresholds from these models for fast mode selection. In addition, we use the image content, the residual data, and JND visual model for horizontal/vertical detection, and then utilize the result to predict the partition in a macroblock. From the experimental results, a greater time saving can be achieved while the proposed algorithm also maintains performance and quality effectively.

Centralized Mobile SensorGroup for Exploring Border of Target Area

A low-cost mobile sensor network structure with a sensing mechanism is presented to explore the border of unknown target areas effectively. At first, mobile sensors with GPS receivers are organized into groups called SensorGroup (SG) which works well for the detecting jobs. After that, an advanced structure called Centralized SensorGroup (CSG) is proposed to further reduce the device cost since only the center node of the group is equipped with a GPS receiver. To detect the target area, an S-shaped sensing mechanism is also presented to cooperate with SG and CSG. The operation processes and detection phases are provided and verified. The detection performance is evaluated by detection completeness and accuracy in different scenarios in a square area of 100m*100m sensing environment. The simulation results show that CSG has good detection accuracy and the same performance as that of SG.

AISMA: An Agent-based Intelligent System for Mobile Auction

An agent-based intelligent system for mobile auction (AISMA) is presented in this paper. AISMA includes the architecture of the auction platform, the smart agents bidding strategy, as well as the privacy and security protecting scheme. Compared to the online auction, the proposed system has an intelligent agent which can save much time for buyers and sellers. AISMA facilitates mobile auction process by software agents, provides buyers and sellers auto-auction services, also increases the efficiency and privacy of transaction.

A quality of relay-based routing scheme in multi-hop cellular networks

Discovering an available relaying path is a critical prerequisite for the success of the multi-hop cellular networks Since forwarding data for others utilizes the resources of the mobile nodes such as battery energy, link bandwidth, buffer space and processing time, the mobile nodes may accept only a certain number of relaying requests In this paper, we propose a Quality of Relay (QoR)-based routing scheme to select a routing path between a mobile node and the central base station based on the individual importance of each intermediate node contributing to hop-by-hop connections The proposed routing scheme can retain more valuable resource for later relaying requests, thereby supporting more connections successfully Simulation results indicate that the proposed routing scheme causes a lower new call blocking probability than the shortest-path routing scheme under a certain constraint on maximum relaying capacity of each mobile node.

Diminishing capacity requirement for mobility database in wireless ATM

In wireless ATM, Visitor Location Register (VLR) is the database that supports mobility management. In case the number of roaming users exceeds the VLR supports, the arriving users cannot receive any service. To solve the problem, the Random Replacement (RR) policy randomly selects a victim record in VLR to be replaced with the record of the arriving user. The quality of services for the victim user will certainly drop. Therefore, the proportion of affected users is not allowed to exceed a tolerable threshold. Apparently, VLR size is the key factor of the threshold. The cost for maintaining a VLR increases significantly as its size grows. So, how to utilize the capacity efficiently is an important issue in VLR planning. We propose a Second Chance Replacement (SCR) policy to reduce the requirements for VLR capacity. As compared with the RR policy, the discrete-event simulation results show that the SCR policy can save 2.5% to 28% VLR size under various QoS thresholds.

Diminishing signalling traffic for authentication in mobile communication system

In global system for mobile communication, the VLR requests the HLR for assistance in authenticating the visiting user. The authentication centre (AuC) in the home network generates 3-tuples and sends them back to the VLR for subsequent authentications during the users residence. If these 3-tuples are used up before the MSs leaving, another request is issued by the VLR. The request is expensive, because it needs to access the HLR/AuC. Traditionally, a fixed-K strategy is used. That is, K 3-tuples are sent to the VLR for each request. However, much waste of 3-tuples is observed, especially when an inactive user is considered. Hence, we propose a dynamic-K (DK) strategy to reduce the waste and diminish the signalling traffic for authentication. Simulation results show that the DK strategy can effectively determine the appropriate K value. Not only the waste but also the number of requests is diminished efficiently.