HICSS Distinguished Lecture

ALOHA TO THE WEB

Norman Abramson

ALOHA Networks, Inc.

 

Wireless access to the Web at the end of the 20th century is slow, unreliable, and expensive. ARDIS, Mobitex and CDPD each employ a variant of a conventional ALOHA channel to provide a nominal 10 kbs to 20kbs network. The useful data rate delivered to the end user is well below 10 kbs for the same reason that a 10 Mbs Ethernet delivers much less than 10 Mbs. In addition the symmetric channels employed by these data services are derived from a voice traffic model which seems ill suited to the highly asymmetric traffic generated by today's Web surfer.

Asymmetric broadcast data channels offered by DirecPC and DirecDuo provide a nominal 400 kbs to the user but require an awkward telephone connection for the reverse multiple access link from the user. Similar multiple access limitations arise in the use of wired cable modems for data.

In this talk we provide an overview of wireless Internet access, emphasizing four basic architectural features of networks which must be addressed before wireless data can achieve the levels of acceptability achieved by wireless voice.

The first of these architectural features is that of topology. Although some networks are based upon a peer-to-peer RF architecture, most networks are based upon a client-server architecture in order to obtain significant RF link advantages in both directions and in order to better match the logic of most user applications.

A second key architectural feature of wireless data networks, asymmetry, is related to the client-server decision but is more closely connected to the basic data rate asymmetry of most network applications. It is perhaps not surprising that surfing the Web and many data base applications provide highly asymmetric data rate requirements for the network. But it is often not appreciated that many other important applications such as Email and teleconferencing exhibit similar asymmetries.

The third architectural feature discussed in this talk deals with the advantages of putting aside the two way voice paradigm of a connection oriented service. In a connection oriented service a connection is established between the transmitter and the intended receiver before useful information is sent. The connection oriented service establishes a minimal value of latency for the transmission of packets in a packet network and dedicates a full time channel resource to a transmitter which may require only intermittent use of that resource. A connection free access architecture, such as used in Alohanet, Ethernet or the IP portion of the Internet TCP/IP protocols can provide zero latency and high efficiency in the use of shared channel resources for bursty data.

The last feature required a for truly pervasive wireless access to the Web is that of wideband operation. Conventional first generation ALOHA channels and their derivatives are all based upon a connection free, asymmetric client-server architecture, but in the wireless context they are condemned to narrowband operation for the same transmit power reasons which restrict TDMA architectures.

Spread ALOHA Multiple Access (SAMA) bypasses these restrictions. SAMA is a second generation version of the classical ALOHA protocols which can provide the wideband multiple access capabilities required for the applications of today. SAMA combines the proven simplicity and operational flexibility of an ALOHA multiple access channel with the high bandwidth and high throughput of a Spread Spectrum channel.


Norman Abramson

ALOHA Networks, Inc.

norm @ alohanet.com

Norman Abramson Is Vice President of ALOHA Networks, responsible for the development of multiple access technology for wireless and satellite applications. From 1966 to 1994 Dr. Abramson was Professor of Electrical Engineering, Professor of Computer Science and Director of The ALOHA System at the University of Hawaii. He directed the effort at the University of Hawaii which led to the construction and operation of the ALOHANET, which has been called the first modern data network. The ALOHANET, operating at 9600 bits per second throughout the state of Hawaii, went into operation in 1970, providing the first demonstration of the value of packet radio access in a data network. Among the innovations demonstrated in the ALOHANET were the first packet radio sensors, the first packet radio repeaters, the first satellite packet network and the first radio access to the Internet.

In 1995, Dr. Abramson was the recipient of the IEEE 1995 Koji Kobayashi Computers and Communications Award, with the citation.

"For development of the concept of the ALOHA System,

which led to modern local area networks."

 

Before moving to Hawaii Dr. Abramson was Associate Professor of Electrical Engineering at Stanford. He has also has taught communication theory, computer networks and satellite communication courses at Berkeley, Harvard and M.I.T. while on visiting appointments. He has served as a consultant in data networks and satellite communications to government and industrial laboratories in the United States. He has also served as an expert in computer networks for the ITU/Geneva and for the United Nations in Asia and in Europe.

Dr. Abramson has received several basic patents issued in the United States, Europe and in Japan in data communications. Among these are U.S. patent 3,114,130, and U.S. patent 3,163,848. The former is the first patent for the use of what are now known as CRC redundancy checks, the primary error control technique used today in data processing and data communication equipment. The latter is the first patent issued for the design of burst errors in digital systems. Both of these patents are assigned to IBM. He has been involved in communication theory, satellite communications and data network research for more than twenty years. In 1993 he edited Multiple Access Communications: Foundations for Emerging Technologies, for the IEEE Press. This work provides a view of multiple access technology for use in LAN's, packet radio networks, satellite networks and PCN's.

Dr. Abramson received an B.A. in Physics from Harvard, an M.A. in Physics from UCLA, and a Ph. D. in Electrical Engineering from Stanford University.

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