The author begins by discussing the background, defining key terms and showing how wireless information systems can be viewed as a natural evolution of computing's relentless march toward greater distribution and ubiquity of access. Next, the research issues faced by designers of wireless information systems are detailed, and some large-scale engineering challenges for such designers are presented. The existing cellular system architecture, evolved from telephony, is compared with an alternative architecture more closely integrated with a computer networking view of wireless systems. Existing wireless systems are reviewed, and the final section presents the author's summary and conclusions, and charts the future of wireless information systems. >

Adaptation and mobility in wireless information systems

In recent years, power consumption has become a critical design concern for many VLSI systems Nowhere is this more true than for portable, battery-operated applications, where power consumption has perhaps superceded speed and area as the overriding implementation constraint This adds another degree of freedom--and complexity--to the design process and mandates the need for design techniques and CAD tools that address power, as well as area and speed This thesis presents a methodology and a set of tools that support low-power system design Low-power techniques at levels ranging from technology to architecture are presented and their relative merits are compared Several case studies demonstrate that architecture and system-level optimizations offer the greatest opportunities for power reduction A survey of existing power analysis tools, however, reveals a marked lack of power-conscious tools at these levels Addressing this issue, a collection of techniques for modeling power at the register-transfer (RT) level of abstraction is described These techniques model the impact of design complexity and signal activity on datapath, memory, control, and interconnect power consumption Several VLSI design examples are used to verify the proposed tools, which exhibit near switch-level accuracy at RT-level speeds Finally, an integrated design space exploration environment is described that spans several levels of abstraction and embodies many of the power optimization and analysis strategies presented in this thesis

Low-power architectural design methodologies

A new alternative is proposed for reducing the power consumption of the portable (battery-powered) units operating in a mobile packet-data network. First, a review of the current power-saving protocols is given. It is shown that the most common means for conserving power is the intermittent operation of the receivers (at the portable units) and a central administration authority that synchronizes the receivers. Some drawbacks of the synchronous operation lead us to the introduction of an asynchronous power-saving protocol, where no central synchronization is necessary and where each terminal may control its power consumption relative to its current needs. According to the proposed power-saving page-and-answer protocol, an acknowledgment paging procedure is preceding every packet transmission in order to alert mobile terminals with pending traffic. Steady-state performance is evaluated with the aid of simulation. The relationship between the achieved power-saving and the mean packet delay degradation is presented. Finally, we express some notable implementation issues and some considerations regarding the employment of this protocol as a supplementary power-saving service in microcellular mobile data networks and wireless local area networks.

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An in-band power-saving protocol for mobile data networks

We propose an intelligent clearinghouse, an electronic marketplace with computer-mediated negotiation that is supported with both data and textual information about the dynamic markets. Most existing electronic market systems support relatively stable markets: traders are not allowed to revise their bids and offers once they are entered to the system. The intelligent clearinghouse addresses dynamic markets where buyers and sellers are willing to change their utilities as the market evolves or when more information becomes available to them. Traders in dynamic markets may suffer significant losses if they fail to execute transactions promptly or cannot utilize all the available information. We developed a prototype Virtual Property Agency to study the usefulness of such an approach. The system was developed with agent technologies, where information, particularly the text files, about the market will be automatically collected by a search engine from the selected Web sites for users to design their negotiation strategies. This system also supports multi-criteria negotiation and allows the users to enter the ranking of attributes to create a utility function. The system aims to improve the transparency and efficiency of the real estate market. It enables traders to compromise their original utilities to avoid transaction failures. The paper also describes the foundation of the intelligent clearinghouse system and its trading mechanism, which includes a short discussion about its order matching method and negotiation support capabilities.

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John P. Mello

Papers

Wireless mobile communications