Henry C. B. Chan

Enabling technologies for wireless body area networks: A survey and outlook

A wireless body area network is a radio-frequency- based wireless networking technology that interconnects tiny nodes with sensor or actuator capabilities in, on, or around a human body. In a civilian networking environment, WBANs provide ubiquitous networking functionalities for applications varying from healthcare to safeguarding of uniformed personnel. This article surveys pioneer WBAN research projects and enabling technologies. It explores application scenarios, sensor/actuator devices, radio systems, and interconnection of WBANs to provide perspective on the trade-offs between data rate, power consumption, and network coverage. Finally, a number of open research issues are discussed.

Vita: A Crowdsensing-Oriented Mobile Cyber-Physical System

As a prominent subcategory of cyber-physical systems, mobile cyber-physical systems could take advantage of widely used mobile devices, such as smartphones, as a convenient and economical platform that facilitates sophisticated and ubiquitous mobile sensing applications between humans and the surrounding physical world. This paper presents Vita, a novel mobile cyber-physical system for crowdsensing applications, which enables mobile users to perform mobile crowdsensing tasks in an efficient manner through mobile devices. Vita provides a flexible and universal architecture across mobile devices and cloud computing platforms by integrating the service-oriented architecture with resource optimization mechanism for crowdsensing, with extensive supports to application developers and end users. The customized platform of Vita enables intelligent deployments of tasks between humans in the physical world, and dynamic collaborations of services between mobile devices and cloud computing platform during run-time of mobile devices with service failure handling support. Our practical experiments show that Vita performs its tasks efficiently with a low computation and communication overhead on mobile devices, and eases the development of multiple mobile crowdsensing applications and services. In addition, we present a mobile crowdsensing application, Smart City, developed on Vita to demonstrate the functionalities and practical usage of Vita.

A Survey on Mobile Social Networks: Applications, Platforms, System Architectures, and Future Research Directions

Mobile social networks (MSNs) have become increasingly popular in supporting many novel applications since emerging in the recent years. Their applications and services are of great interest to service providers, application developers, and users. This paper distinguishes MSNs from conventional social networks and provides a comprehensive survey of MSNs with regard to platforms, solutions, and designs of the overall system architecture. We review the popular MSN platforms and experimental solutions for existing MSN applications and services and present the dominant mobile operating systems on which MSNs are implemented. We then analyze and propose the overall architectural designs of conventional and future MSN systems. In particular, we present the architectural designs from two perspectives: from the client side to the server side, and from the wireless data transmission level to the terminal utilization level. We further introduce and compare the unique features, services, and key technologies of two generations of architectural designs of MSN systems. Then, we classify the existing MSN applications and propose one special form of MSN, i.e., vehicular social network, and demonstrate its unique features and challenges compared with common MSNs. Finally, we summarize the major challenges for on-going MSN research and outline possible future research directions.

A framework for optimizing the cost and performance of next-generation IP routers

The explosive growth of Internet users, the increased user demand for bandwidth, and the declining cost of technology have all resulted in the emergence of new classes of high-speed distributed IP-router architectures with packet-forwarding rates of the order of gigabits, or even terabits, per second. This paper develops an analytical framework for modeling and analyzing the impact of technological factors on the cost-performance tradeoffs in distributed-router architectures. The main tradeoff in a distributed router results naturally from moving the main packet-forwarding and processing power from a centralized forwarding engine to an ensemble of smaller forwarding engines, either dedicated to or shared among the line cards. Processing packets in these smaller engines can be much cheaper (by as much two to three orders of magnitude) than in a centralized forwarding engine. Therefore, the main goal of our modeling framework is to determine an optimal allocation of processing power to the forwarding engines (in a distributed router) to minimize overall router cost while achieving a given level of packet-forwarding performance. Two types of router models are analyzed using the proposed framework: a distributed-router architecture and parallel-router architecture.

Polling-based protocols for packet voice transport over IEEE 802.11 wireless local area networks

In this article we present a survey of different polling-based protocols for supporting voice over IEEE 802.11 wireless local area networks (WLANs). In particular, three key issues are discussed: managing a polling list, determining the polling sequence, and reducing polling overhead. These discussions motivate the proposal of an isochronous coordination function (ICF) for transporting voice packets over IEEE 802.11 WLANs, which combines the advantages of some of the previous protocols. Emulating a dynamic TDMA-like service, ICF can greatly reduce polling overhead and provide fair polling for both uplink and downlink voice traffic by means of a cyclic polling queue. Some simulation results are presented to illustrate the advantages of ICF.

An Efficient Mailbox-Based Algorithm for Message Delivery in Mobile Agent Systems

Agent mobility presents challenges to the design of efficient message transport protocols for mobile agent communications. A practical mobile agent communication protocol should provide location transparency to the programmer and thus need to keep track of the movement of an agent. In addition, because of the asynchronous nature of message passing and agent migration, how to guarantee the delivery of messages to highly mobile agents is still an active research topic in mobile agent systems. In this paper we propose an efficient mailbox-based algorithm for inter-mobile agent communications. The algorithm decentralizes the role of the origin (home) host in locating an agent. Furthermore, by separating the mailbox from its owner agent, the algorithm can be made adaptive and is efficient in terms of location updating and message delivery. In the cases that mobile agents migrate frequently but seldom communicate, our algorithm turns out to be preferable.

Reliable message delivery for mobile agents: push or pull

Two of the fundamental issues in designing protocols for message passing between mobile agents (MAs) are tracking the migration of the target agent and forwarding messages to it. Even with an ideal fault-free network-transport mechanism, messages can be dropped during MA migration. Therefore, in order to provide reliable message delivery, protocols need to overcome message loss caused by asynchronous operations of agent migration and message forwarding. In this paper, two known message forwarding approaches, namely push and pull, are explored to design adaptive and reliable message delivery protocols. Based on a commonly used MA tracking model, the pros and cons of these two approaches are evaluated, both qualitatively and quantitatively. The comparative performance evaluation is presented in terms of network traffic and delay in message processing. We also propose improvements to the pull approach to reduce network traffic and the message delay. We conclude that with different message passing and migration patterns and varying requirements of real-time message processing, specific applications can select different message delivery approaches to achieve the desired level of performance and flexibility.

Business-to-Consumer Mobile Agent-Based Internet Commerce System (MAGICS)

We present MAGICS, a mobile agent-based system for supporting business-to-consumer electronic commerce (e-commerce) or mobile commerce (m-commerce) applications. To use the system, consumers first provide their buying requirements to a proxy/agent server through a Web browser or a wireless application protocol (WAP) terminal. Having obtained the requirements, mobile agents are generated to carry out tasks for the consumers including getting offers from merchants, evaluating offers, and even completing purchases. In the case of mobile commerce, consumers can generate a mobile agent to conduct a search and evaluation in the digital marketspace before making a purchase in the physical marketplace. To make it possible to choose an offer that best satisfies the consumers requirement(s), we present a mathematical model for evaluating multiple decision factors. To test the basic functions of the mobile agent-based Internet commerce system (MAGICS), we have built a prototype system. To minimize the average cost of a product (including the cost of sending agents), we have also developed an analytical model that can determine how many agents should be sent to compare prices. Four different price distributions and some real price information are analyzed based on the model. The analysis provides valuable insights into the design of mobile agent-based shopping applications for m-commerce, in particular, and for e-commerce, in general.

A Reliability Enhanced Address Mapping Strategy for Three-Dimensional (3-D) NAND Flash Memory

The linear scaling down of NAND flash memory is approaching its physical, electrical, and reliability limitations. To maintain the current trend of increasing bit density and reducing bit per cost, 3-D flash memory is emerging as a viable solution to fulfill the ever-increasing demands of storage capacity. In 3-D NAND flash memory, multiple layers are stacked to provide ultrahigh density storage devices. However, the physical architecture of 3-D flash memory leads to a higher probability of disturbance to adjacent physical pages and greatly increases bit error rates. This paper presents a novel physical-location-aware address mapping strategy for 3-D NAND flash memory. It permutes the physical mapping of pages and maximizes the distance between the consecutively logical pages, which can significantly reduce the disturbance to adjacent physical pages and effectively enhance the reliability. The proposed mapping strategy is applied to a representative flash storage system. Experimental results show that the proposed scheme can reduce uncorrectable page errors by 70.16% with less than 10.01% space overhead in comparison with the baseline scheme.

Performance evaluations of path optimization schemes for inter-switch handoffs in wireless ATM networks

One of the major design issues in wireless ATM is the support of inter‐switch handoff. An inter‐switch handoff occurs when a mobile terminal moves to a new base station connecting to a different switch. Recently, a two‐phase handoff protocol has been proposed to support inter‐switch handoff in wireless ATM networks. With the aim of shortening handoff delay while using the network resources efficiently, the two‐phase handoff protocol employs path extension for each inter‐switch handoff, followed by path optimization if necessary. To implement the two‐phase handoff protocol efficiently, we need to determine when to trigger path optimization. In this paper, we propose and analyze three path optimization schemes, namely: periodic, exponential, and Bernoulli, for the two‐phase handoff protocol. The design objective is to determine the time to invoke path optimization such that the average cost per connection is minimized. We develop a discrete time analytical model and a discrete‐event simulation model for comparing the performance of the three path optimization schemes. Results indicate that the Bernoulli path optimization scheme outperforms the other two schemes by providing a lower average cost per connection. The proposed models can also be adapted to analyze other path optimization schemes in general.