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Multimedia Moeglich Machen...

Nach dem langen File der Kommunikationsverhinderer hier einer ueber
die Foerderung. Die Kommission war mal sehr stark im Bereich
von wireless, cordless etc. Vielleicht koennte sie auch mal eine
Empfehlung nach folgendem Muster machen, was die Freigabe bestimmter
Frequenzen betrifft. Eine Kompetenz wird sich schon finden lassen.
Ausserdem passts prima in die Initiativen zu "Kleine und mittlere
Unternehmen", das Thema hatten wir hier schon mal...

Was den deutschen Beitrag zu Rigos paper betrifft, stelle ich fest, dass
uns Schneider, Terra und Co schlicht belogen haben, was die angebliche
Befuerchtung von rechtlichen Schritten betrifft, oder waren sie wirklich 
so doof, wie sie sich dargestellt haben?? Ausserdem hat der Vertreter
der Bundesregierung die Durchsetzbarkeit des Konzeptes zu optimistisch 
dargestellt, wie wir an ULFs paper sehen konnten, namentlich der Reaktion
auf Nolte. Letzteres koennte Rigo ja mal auf jener Liste verbreiten, die
Nichtreaktion auf Nolte ist ja das gerade Gegenteil der Darstellung der
Bundesregierung. Oder ist Zundel mittlerweile geblockt??

Wie auch immer, was man mit ein paar freien Frequenzen anfangen koennte,
eines von vielen Szenarien, das Telephonnetz zu umgehen, und mehr:

Web page: HTTP://ksgwww.harvard.edu:80/iip/beyer.html
 The Rooftop Community Network:  

  Free, high-speed network access  

  for communities  

   Dave Beyer, Mark D. Vestrich and JJ Garcia-Luna-Aceves 



This chapter describes a dramatic departure from the conventional means of 
delivering high-performance end-user connections to Internet services. The 
Rooftop Community Network (or "Rooftop Network") offers not just a new 
technology, but a new economic model that relieves the current dependence on 
phone or cable companies to propagate local access infrastructure. The Rooftop 
Network uses innovative wireless technology to allow deployment of fast, 
robust, community networks, which are constructed entirely by the end-users, 
and which are free of monthly operating charges. 

A user joins a Rooftop Community Network by installing a Rooftop Connection Kit 
which couples a high-speed, digital radio with intelligent, packet-switching 
software. A Rooftop Community Network is a self-managing web of peer radios in 
which every Rooftop Connection can serve as a repeater in its Community 
Network. Thus the Rooftop Community Network approach carries the original, 
distributed Internet model to the next revolutionary generation by extending 
the switching infrastructure all the way out to the end-users. 

The Rooftop Community Network also enables its users to seamlessly connect to 
the rest of the Internet by conforming to the Internet protocol standards. Each 
user’s interconnect costs may be sharply reduced by sharing access to 
these Internet links among a number of users in the community. A Rooftop 
connection only uses network resources when there is actually data to transmit 
or receive due to its packet-switching technology. This delivers continuous 
connectivity for all users while still optimizing overall network performance. 
Continuous connectivity means email is delivered instantly and every user can 
publish information without tying up a dedicated line (with its associated 

Sample applications that a Rooftop Community Network enables include: 

     <*> Untariffed, high-speed access to corporate client/server applications 
         by telecommuting employees working from home. 
     <*> Shared access to databases by multiple sites in a metro area such as a 
         hospital with its affiliated clinics and doctors offices. 
     <*> High-speed "Public Access Networks" or "FreeNets" that have no monthly 
         charges for access to local content. 
     <*> Rich, networked, educational applications linked to local schools and 
         public libraries. 
     <*> For-profit service providers offering the Rooftop Network as an 
         alternative, high-speed access means for their subscribers while 
         bypassing the local phone or cable company loop. 

This chapter provides a brief introduction to the concept, technology, 
applications, and policy issues of concern for the Rooftop Community Network. 

 The Concept  

With the emergence of the Internet and the current deregulation environment, 
communication infrastructures are becoming increasingly distributed. The 
Rooftop Community Network further extends this trend by bringing the 
communication infrastructure all the way down to the local community and 

To join a Rooftop Network, a user would purchase and install a Rooftop 
Connection Kit. The main components of the kit are: 

     <*> An "Internet Radio" consisting of a high-speed (256-kbps to 2-Mbps) 
         digital radio for an unlicensed band, and an embedded microcontroller 
         that runs intelligent wireless network and Internet routing software, 
     <*> An antenna, smaller and simpler than a typical TV antenna, to be 
         mounted on the user&#146;s roof, along with a cable (like that for 
         cable TV) to connect the antenna to the Internet Radio. 

After installing the antenna, the Internet Radio would be connected to the 
user&#146;s computer or local computer network in one of three ways: 1) over a 
simple serial connection to a single computer; 2) over a link to a local area 
network such as Ethernet; or 3) over a short-range wireless link to desktop or 
mobile laptop computers, an alternative that promises to become increasingly 
attractive as the price of radios continues to decline. 

Free Networking within the Community 

A Rooftop Community Network is a web of peer radios, all automatically 
participating in forwarding traffic for the network (see Figure 1). Each user 
with a Rooftop Connection is part of its local Rooftop Community Network and 
can send traffic to any other user in the network, for free. Unlike a cellular 
network, there are no base stations that need to be installed or maintained. 

Self-managing software protocols (discussed below) automatically control the 
routing of packets across multiple links between their source and 
destination(s). These protocols require no user configuration or intervention. 
They ensure fairness so that each user receives an adequate share of network 
bandwidth. The software also helps to ensure security so that traffic is safe 
from eavesdroppers and malicious users. By using RF bands that have been 
dedicated for unlicensed use by the Federal Communications Commission (FCC), 
there are no license fees to acquire spectrum or operate the radio. Equipment 
purchase is the only expense. Hence, there are no airtime charges to operate a 
Rooftop Network. 


 Figure 1 The Rooftop Community Network 


The Rooftop Community Network serves as an extension to the world-wide Internet 
or to any other private data network that uses the Internet protocols. Thus, 
users are free to use all of the same, familiar, well-supported, and rapidly 
growing base of network software applications that have become commonplace on 
the Internet including standard web browsers, email applications, and news 

Examples of applications enabled by the free community communication of a 
Rooftop Network include: 

     <*> Community education networks. These may support a wide range of 
         applications from rich networked, multi-user, educational role-playing 
         games linking homes, local schools, and public libraries, to simply 
         supporting free email between students doing their homework and 
         teachers or professional mentors in their home, 
     <*> High-speed "Public Access Networks" or "FreeNets". Rooftop Community 
         Networks can further stimulate the current explosion of local FreeNets 
         by eliminating the cost and limitations of the local-loop phone lines, 
         and by making it easy for all of its users to be publishers of 
         information, due to their continuous connectivity to the network. 
     <*> Business telecommuter networks. Businesses can reduce the cost of 
         telecommuters by eliminating monthly access charges. Good corporate 
         citizens can support their communities by sharing their infrastructure 
         to seed neighborhood networks. 
     <*> Shared access to community databases. These may include access to 
         local Government records such as the minutes to town assembly meetings 
         or building regulations, or shared access to medical information among 
         multiple hospital sites and their affiliated clinics and doctors 

The Rooftop Network also has a unique combination of characteristics which 
makes it ideal for disseminating community information:  
LocalityBroadcasts can be naturally limited to the geographic radius 
appropriate for the message,ImmediacyMessages are delivered immediately (unlike 
classified ads for instance),FreeThere are no fees or monthly charges for 
communication within the Rooftop Network. 

Examples of community information that can take advantage of these 
characteristics include: Neighborhood messaging(e.g., requests for assistance 
in locating a lost pet; invitations to upcoming garage sales); Community 
events(e.g., announcements of upcoming fairs; distributions of the Town Hall 
Meeting Minutes; emergency notifications); and Commercial events (e.g., 
"blue-light special" announcements at the local grocery store; solicitations of 
customers&#146; opinions concerning which items to stock). Virtual 
"subscriptions" can be used to help ensure that users only receive such 
messages from information types and sources to which they have "subscribed". 

Continuous, High-speed Internet Access at Low Cost 

Rooftop Community Network users will also benefit from high-speed, continuous 
(24-hours/day), low cost access to the rest of the Internet. With a local 
Rooftop Community Network amortizing the cost of a single fast link to the 
Internet, these Internet-access costs can be shared. The Rooftop Connection 
which serves as a relay (or "router") into the rest of the Internet is called an 
AirHead, short for Air-to-Internet-Router. 

Continuous Connectivity. Unlike dial-up connections, a Rooftop Connection only 
uses network resources when actually transmitting or receiving user data. This 
enables continuous connectivity for all users without bogging down the network. 
Continuous connectivity allows instant delivery of email rather than requiring 
the user to solicit for new email. Continuous connectivity also allows a user 
to become a provider of information without requiring a dedicated phone line 
for the purpose. For example, a home could post descriptions, pictures, the 
highest bid, and viewing hours for items in an on-line garage sale; the town 
weekly newspaper could consist largely of links to articles, editorials, and 
up-to-date classified ads located on the computers in people&#146;s homes; or, 
a family could post their family tree with web links to other family trees. 

Email is free. Electronic mail remains the most valuable application on the 
Internet. As an added incentive for new members, Rooftop Networks could promote 
that all email traffic from anywhere on the Internet will be delivered for free. 
For example, a traffic load of 150 kBytes of email, per member, per day, for 
free would equate to 50, 3-kByte messages per member each day. For a group of 
25 Rooftop Network users sharing an AirHead&#146;s 128-kbps link to the 
Internet, this would consume approximately 0.5% of the AirHead&#146;s link 

 Key Enabling Factors  

Four ongoing trends make Rooftop Community Networks feasible: 

       1 The exploding, wide-spread popularity of the Internet, and the 
         accompanying availability of, and familiarity with, a wide array of 
         network applications that facilitate communication and information 
       2 Recent development of high performance, low cost digital radios, which 
         have begun to bring these capabilities within reach of typical users. 
       3 The availability of unlicensed, wireless spectrum , enabling the 
         ad-hoc deployment and propagation of untariffed, high-speed Rooftop 
         Networks with no licensing costs or regulatory delays. 
       4 The advancement of software protocols for intelligent wireless 
         networks and the Internet, permitting the rapid and easy deployment of 
         self-managing, wireless Rooftop Networks, and the seamless integration 
         of these networks with the Internet. 

Below we discuss these last two trends of particular importance for Rooftop 
Community Networks. 

Availability of Unlicensed Wireless Spectrum 

In 1985, the FCC modified its regulations to permit unlicensed digital 
communications that meet certain "spread-spectrum" waveform requirements in the 
"ISM" (Industrial, Scientific, and Medical) RF bands of 902-928 MHz, 
2400-2.483.5 MHz, and 5725-5870 MHz. The maximum output power permitted by a 
transmitter was limited to 1 Watt, and the maximum antenna gain at the 
transmitter was also limited (to 6 dBi when transmitting at the maximum power). 

This ruling marked the FCC&#146;s first significant step towards allowing the 
introduction of new, unlicensed wireless networks such as the Rooftop Community 
Network, and was sufficient to support the development and deployment of the 
first of such networks to begin to test the general concepts [xx]. 

Intelligent Wireless Network Software 

The software in a Rooftop Community Network is based on a technology known as 
Distributed Packet Radio, or DPR. DPR protocols manage the self-organization, 
routing, and security within a Rooftop Community Network. Standard Internet 
protocols are used to handle the interface between Rooftop Networks and the 

The underlying concepts of DPR were largely developed during the 70&#146;s and 
80&#146;s in research and development programs funded by the U.S. Advanced 
Research Projects Agency (ARPA). These programs were given the task of 
demonstrating a robust, secure, self-organizing, and highly adaptable 
communication technology by capitalizing on the synergistic characteristics of 
two new technologies: 1) the flexibility and reliability of spread-spectrum, 
digital radios; and 2) the adaptivity and efficiency of packet-switching data 

These R&D programs [xx], along with related efforts in the Amateur Packet Radio 
[xx], and Internet [xx] communities, have resulted in a mature technology that 
provides the self-managing, secure, efficient, and asynchronous packet-based 
characteristics needed for the successful introduction of Rooftop Community 

 Spurring the Internet Radio Industry  

Current unlicensed, digital radios are designed for local area networks and 
simple point-to-point or point-to-multipoint applications. In these topologies, 
the real-time processing capacity of the radio is typically limited to simple 
link reliability and channel-access protocols, with the more sophisticated 
routing and control functions left to wired routers. However, to support 
Rooftop Networks, these sophisticated functions are required of the Internet 
Radio including packet forwarding, distribution of routing information, 
security protocols, congestion avoidance, remote network management, as well as 
more intelligent link and channel access protocols to deal with the more 
complex, multihop radio environment of the Rooftop Network. In addition, to 
ensure efficient use of the available spectrum, Internet Radios must be 
designed to give the embedded protocol software finer control of the radio 
characteristics (e.g., transmit power, frequency, processing gain). 

Although current technology would permit the development of an integrated 
Internet Radio with a high-volume, end-user price of $500 to $750, the price of 
current Internet Radios, with board- or system-level integration of components, 
varies from around $3,000 to $5,000. Introduction of an integrated Internet 
Radio with an end-user price of under $1,000 is needed before large-scale 
adoption of Rooftop Community Networks by average home consumers can begin to 
be realized. 

In addition, a key missing ingredient needed to energize the Internet Radio 
industry, and help generate these lower cost Internet Radios, is a standard 
"Internet Radio API" (Application Programming Interface) between the radio 
platform hardware and the embedded network control software. The emergence of 
such an API would permit the independent, un-coupled development of the control 
software and radio hardware, allowing organizations to focus on what they do 
best, and providing multiple sources for these two key components of the 
Internet Radio system. 

 Scaling to Large Rooftop Networks  

There are three main technical issues concerning the scaling of Rooftop 
Networks to thousands or tens of thousands of users (or "nodes") in a regional 
area: routing within the Rooftop Network, routing between the Rooftop Network 
and the rest of the Internet, and RF spectrum congestion. These issues are 
briefly discussed in the following sections. 

Routing within Large Rooftop Networks 

As the number of nodes in a Rooftop Network increases, so does the size of the 
network routing tables and the number of control messages needed to update 
them. One way to cope with an increasing number of nodes is to assign addresses 
to them in a way that many routing table entries can be aggregated into a 
single entry. For example, fixed nodes can be assigned an address that has some 
correlation with their geographic location. By doing so, a node that is outside 
a given neighborhood may only have to store a single entry in its routing table 
corresponding to all of the nodes in an entire neighborhood, rather than an 
entry for each node in the neighborhood. Nodes in the neighborhood will have 
entries corresponding to all of the other nodes in their neighborhood. This 
form of hierarchical routing is an adaptation of the hierarchical routing 
scheme first proposed by McQuillan [xx] and recently extended to more efficient 
routing algorithms [xx]. Also, to avoid "traffic congestion" in a large Rooftop 
Network, traffic between distant nodes (e.g., greater than 6 hops apart) is 
routed to nearest AirHeads for forwarding over the wired Internet. 

Routing Between Large Rooftop Networks and the Internet 

To allow a Rooftop Network to connect with the rest of the Internet without 
forcing each node to maintain large routing tables to hold the many addresses 
known for the rest of the Internet, the AirHeads can mask the majority of the 
routing information from the rest of the Rooftop Network. The AirHeads can 
collaborate to decide who should advertise a route to an aggregate of address 
ranges in the Internet. Each AirHead then distributes routing information 
messages to a few large address ranges in the Internet, rather than a large 
number of information messages corresponding to very small address ranges. A 
Rooftop Network node chooses the best match between the Internet address it 
needs to contact and the address ranges advertised by AirHeads to select which 
AirHead to use. Therefore, AirHeads are the only members of the Rooftop Network 
that need to handle complex routing tables to connect to the Internet. A 
similar "route aggregation" strategy by the AirHeads will also help to limit 
the amount of routing information that the rest of the Internet must learn in 
order to route traffic to particular nodes within the Rooftop Network. 

RF Spectrum Congestion in Large Rooftop Networks 

Typically, all of the nodes in a Rooftop Network will share the same overall RF 
band for their transmissions. Thus, as the size of the Rooftop Network 
increases, the traffic demand within this shared band will increase. This 
raises the concerns of reduced network throughput per user, and of increased 
likelihood that simultaneous transmissions will "collide". To avoid these 
problems, a Rooftop Network can use a combination of methods including: 
reducing the power of each transmission to only that needed to reach the 
intended destination; scheduling transmissions within each local area to avoid 
collisions; and synchronizing the source and destination of each transmission to 
switch to a waveform that is less correlated with simultaneous transmissions 
outside this local area. Also, by combining the above methods with sufficient 
"spread-spectrum" techniques in the Internet Radio, and accounting for typical 
path loss characteristics, it can be shown that Rooftop Networks remain 
effective even with an infinite number of randomly distributed nodes [xx]. 

 Regulation and Policy  

Three specific areas of regulation and policy could have a significant impact 
on the rate of deployment of Rooftop Community Networks. Two of these are local 
issues, zoning and local taxation. The third is federal regulation of RF 

Local Antenna Regulations 

Local zoning would effect Rooftop specifically in the area of antenna 
installation. There is already an explosion of new antennas occurring in 
municipalities for a wide range of applications. Network operators will install 
tens of thousands of PCS antennas in the next few years. Institutions will 
install various microwave antennas of all shapes and sizes. Individuals will 
install millions of small satellite television receivers, too. Local 
governments are trying to cope with this flood, attempting to address citizen 
concerns about aesthetics, plus health and safety. 

For example, Medina, Washington, Bill Gates&#146; home town, recently obtained 
a federal injunction, preventing several wireless network operators from 
installing PCS antennas on a local commercial building. This location provides 
particularly critical radio coverage of the bridge which is the main commuter 
route between downtown Seattle and its eastern suburbs across a lake. The issue 
in this case is neighborhood aesthetics. An affluent residential area would 
prefer not to have an unsightly "antenna farm" populating its quaint downtown.  

In this type of case, and others around the country, these antennas are 
principally being installed and maintained by for-profit network operators. 
However, antennas for Rooftop Community Networks will be installed by 
individual citizens or local institutions such as schools and libraries. 
Nonetheless, there are closer examples. 

Direct Broadcast Satellite (DBS) antennas provide the closest parallel today, 
to deployment of Rooftop Community Networks by individual citizens. The number 
of these units in the US alone is over one million. These small DBS dishes are 
installed for personal use by their owners. Even so, some multiunit 
developments and certain subdivisions attempt to restrict or control their 
deployment, again on aesthetic grounds. 

The appearance of a Rooftop antenna is quite unobtrusive. A typical Rooftop 
antenna might be a dipole type antenna. This is a fiberglass rod one inch in 
diameter and three feet long mounted in a small bracket bolted to a roof. 
Another might be a directional antenna, which approximates the general 
appearance of the common TV antenna, but is significantly smaller. Either type 
would be far less obtrusive than either a DBS dish or a regular television 

Thus, to maximize rapid, widespread deployment of Rooftop Community Networks, 
we would strongly propose that any zoning regulations for its antennas be no 
more onerous than those applying to television antennas installed for personal 

Local Taxation 

Some municipalities around the country are attempting to impose sales taxes on 
wireless PCS or cellular network operators, and on Internet Service Providers 
(ISPs). Local efforts to tax Rooftop Community Networks would clearly have a 
chilling effect on their deployment, even though they pose a curious case.  

There are no access fees for traffic across the local Rooftop Community 
Network. That traffic is free of charge because it uses the shared, local, 
wireless infrastructure. Thus, the volume or revenue basis for any sort of 
traffic-based tax would be exceedingly elusive.  

The question of who the taxed party ought to be also becomes highly ambiguous. 
The owner-operators of the local infrastructure are its users, who receive 
nocash remuneration for participating in the network. The supervisory 
institution for any given community network may be either a for-profit firm or 
a non-profit institution such as a school or library. Any revenue either might 
receive from network participants would most likely be for access to the rest 
of the worldwide Internet and as such would probably be interstate or even 
international traffic. It would be quite dubious for a local government to tax 
this traffic. 

We strongly suggest that the benefits in citizen participation and productivity 
to be gained from rapid, widespread deployment of Rooftop Networks in a 
community, far outweigh any slight revenue that could be generated from 
attempting to tax them locally. Forward-looking municipalities should in fact 
try to stimulate and possibly even subsidize their growth, rather than inhibit 
network growth through short-sighted, regressive taxes. 

Federal Radio Communication Regulations 

In the federal realm, the principal regulatory issue affecting successful 
deployment of Rooftop Community Networks is availability of suitable spectrum. 
As a technical issue, the core wireless network protocols can run on any 
intelligent packet-switch radio, operating at any frequency. From a practical 
point of view, however, users will make a utility decision to deploy a Rooftop 
Community Network by comparing the price and performance of Connection Kits 
against other alternatives, wired or wireless. Thus, the location and size of 
the frequency band available to operate Rooftop Networks, significantly gates 
their appeal. 

The selection of frequency has its biggest impact on the cost of Rooftop 
Connection Kits to the user. In general, the higher the frequency, the more 
expensive the components required to build Internet Radios. The size of the 
band available affects the maximum data rate, maximum range, and ability to 
effectively share the spectrum with other similar systems in the same area. 

Useful, affordable Rooftop Community Networks can be deployed today in the 
Industrial, Scientific and Medical, ISM bands, designated as unlicensed, shared 
frequencies by the FCC. Using these existing bands, Connection Kits can be 
highly competitive with ISDN adapters and even cable modems. However, all 
technologies improve at rapid rates. 

In the future, users will demand multimegabit speeds to access the Internet. To 
achieve these rates, a Rooftop Network would require two to three hundred 
megahertz of spectrum, with specifications similar to those that Apple Computer 
proposed in its original submission to the FCC&#146;s SUPERNet proceedings [xx]. 

The authors strongly endorse the general concept to create a new unlicensed 
data band that would support multimegabit data rates over ranges of several 
kilometers. We have repeatedly seen that spectrum auctions are dominated by 
either large corporations, sometimes foreign, or financial operators that have 
access to large pools of Wall Street capital. In the interests of economic 
diversity, it would seem extremely sensible to provide one segment of spectrum 
where communities and individual entrepreneurs could have the opportunity to 
experiment with more innovative or even radical ideas that could deliver 
significant economic and civic benefits to a broad array of citizens. It is 
ironic that as we approach the end of the 20th Century, we see the US 
Government using a 19th Century approach, namely auctions. We strongly suggest 
that other, innovative business models should also be tried to create 
breakthrough industries for the 21st Century .  


The writing of this chapter was supported, in part, by Small Business 
Innovative Research (SBIR) project number DAAB07-96-C-D010. 




Beyer, D., Vestrich M., and Nguyen B. (1996). Distributed Packet Radio: What is 
it? What good is it? How does it work? How can it help you today?" Rooftop 
Communications Corp. white paper. 

Beyer, D., Frankel M., et al (1989). Packet Radio Network Research, 
Development, and Application. Proceedings of the 1989 SHAPE Conference on 
Packet Radio, Amsterdam. Summary also published in MILCOM Conference, 1989. 

Beyer, D. (1990). Accomplishments of the DARPA SURAN Program. Proceedings of 
the 1990 MILCOM Conference. Monterey, California. 

McQuillan, J. (1974). Adaptive Routing Algorithms for Distributed Computer 
Networks, BBN Technical Report 2831. 

Murthy, S. and Garcia-Luna-Aceves J.J. (1997). Loop-Free Internet Routing Using 
Hierarchical Routing Trees, to appear Proc. IEEE INFOCOM 97, April 1997. 

Shepard, T (1995). Decentralized Channel Management in Scaleable Multihop 
Spread-Spectrum Packet Radio Networks, MIT Doctoral Thesis. 

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