ISSN:0094-243X    

DOI:10.1063/1.47264

出版商:AIP    

年代:1995

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.47252

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Universities in the U.S. have a significant impact on business through the transfer of technology. This paper describes goals and philosophy of the Technology Licensing Office at the Massachusetts Institute of Technology. This paper also relates the critical factors for susscessful technology transfer, particularly relating to new business formation. These critical factors include the quality of the technology, the quality of the management, the quality of the investor, the passion for success, and the image of the company. Descriptions of three different levels of investment are also given and the most successful level of investment for starting a new company is reviewed. Licensing to large companies is also briefly reviewed, as this type of licensing requires some different strategies than that of licensing to start‐up companies. High quality critical factors and intelligent investment create rewards for the parties and successful ventures. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47258

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In this paper, we consider a large hybrid network which consists of a low‐delay terrestrial sub‐network and a high‐bandwidth satellite sub‐network. Both voice and data traffic are transmitted and routed through the same network. We show how to route both traffic via ground and/or satellite links. Two common voice/data integrated protocols such as fixed boundary and movable boundary schemes for the satellite channel are investigated, and the performance of both schemes is evaluated. The optimal splitting ratios for voice and data at the SIMPs (Satellite Interface Message Processors) are found using a powerful numerical optimization package (FSQP). We also develop dynamically optimal splitting ratios between satellite network and terrestrial network for data and voice traffic. We constantly monitor the traffic and measure the arrival rate and occupancy of every link. Based on these data, we optimize data traffic delay in a suitable time‐frame under the constraints of voice traffic blocking probabilities of voice transmission links being less than specified value, which is up to system’s design or users’ requirements. A dynamic routing algorithm is presented. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47267

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The public discussion on the National Information Infrastructure (NII) has been wide ranging and lacking in consensus as to the nature of the proposed NII itself. This paper in acknowledgement of the national policy origins of the NII debate begins with relevant remarks by President Clinton in his State of the Union Address. It defines an initial working definition of the NII based on the President’s challenge. It then provides some clarification to the discussion in terms of planning horizon, subscriber transport services and transport media. The working definition is further developed to incorporate the type of traffic the NII will be expected to support following a discussion of an emerging desktop computing imperative. From this implications are drawn as to the feasibility of the so called fiber solution and an argument made that in the evolution of the current infrastructure to the future NII satellites offer the best solution for a timely manifestation of the vision. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47283

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In mobile communications, new services are being launched that provide extended geographical coverage of cellular service via the satellite. The additional satellite capacity can be shared among all the cells, thereby augmenting the dedicated cellular capacity available within the cells. This additional shared capacity has the inherent potential for increasing efficiency, as the extra channels can be assigned wherever they are needed rather than pre‐allocating them. We considered the performance advantage the satellite offers in off‐loading congestion within the cellular covered area. We propose a model for the hybrid network based on the recently proposed Multiple Service Multiple Resource concept. This model has been used in performing a detailed analysis that demonstrates the marked improvement in performance obtained by augmenting cellular capacity via the satellite and quantifies the gains achieved therein. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47291

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Low Earth Orbit (LEO) communications satellite systems are emerging as attractive alternatives to the Geostationary Earth Orbit (GEO) systems. GEO satellites have largely dominated the commercial and government communications satellite systems for telecommunications services since the early 1960’s. A principal driver behind the move to LEO satellites is the competition to long propagation delay geostationary orbit satellite systems created by rapid expansion of short propagation delay terrestrial land and undersea fiber optic cable links for national and global connectivity. Communication paths over LEO satellites can have shorter propagation delay than terrestrial fiber. This is because the speed of electromagnetic wave propagation via LEO satellites is 50% greater than that of light in fiber optic cable. This fact eliminates the long propagation delay property that has become synonymous with GEO communications satellite systems. Other drivers are the use of small portable and hand‐held earth terminals and the promise of lower launch cost of small satellites to low earth orbits. The paper expands on the properties that promise to make LEO communications satellite systems the choice of the future. ©1995 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47249

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The Global Information Infrastructure of the future will include a great variety of heterogeneous, seamlessly interconnected networks. There are strong variety of heterogeneous, seamlessly interconnected networks. There are strong technical and economic reasons predicating the emergence of these hybrid networks which will include many diverse terrestrial (tethered or wireless) and satellite networks in an interoperating configuration. This paper critically analyzes the basis for these new architectures and examines the various possibilities that will emerge in various phases in the future. A summary view is presented for these emerging hybrid architectures, the alternative components and subsystems available and the trade‐offs that must be considered. The role of satellites is carefully analyzed and several conclusions are drawn. This paper will present a summary of the work and views of the Center for Satellite and Hybrid Communication Networks to date, in this important area. Specific design and performance evaluation tools being developed will also be described. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47250

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Under most system assumptions, closed form solutions of performance measures for input queueing crossbar switches are not available. In this paper, we present expressions and bounds for the derivatives of cell loss probabilities with respect to the arrival rate evaluated at a zero arrival rate. These bounds are used to give an approximation by Taylor expansion thereby providing an economical way to estimate cell loss probabilities in light traffic. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47251

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Efficient policies are derived for admitting voice and data traffic into networks of low‐earth‐orbit (LEO) satellites using code‐division multiple‐access (CDMA) with direct‐sequence spread‐spectrum (DS/SS) signaling. The satellites act as bent‐pipes; no on‐board processing or inter‐satellite links are present. Dual satellite diversity is used to mitigate the effects of shadowing. The policies assume a movable boundary form, allocate optimally the CDMA capacity (PN codes) to voice and data users, and can increase significantly the number of users served while satisfying their bit error rate (BER) requirements. A modified version of our policies can handle two classes of data users: one with high priority which requires real‐time delivery and another with low priority that can be queued; the BER requirements of the two data types may differ. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47293

出版商:AIP    

年代:1995

数据来源: AIP