Population density and wireless networking: reexamining the world of wireless peer-to-peer networking

Japan, Inc., Sept, 2004 by Allen H. Kupetz

IN JUNE 2001 JI published Sam Joseph's article "When Population Density is a Plus." Now, three years later: What is the state of wireless peer-to-peer networking?

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MANY PEOPLE retain a perception of peer-to-peer networking based on the old Napster model of file sharing. While that model offers the advantage of lots of users, there is no benefit to having lots of users in close proximity (i.e., high population density).

But wireless peer-to-peer networking--networks using devices that serve as both transceivers and routers for other devices--is gaining broad acceptance in many different vertical markets, including public safety, mass transit and intelligent transportation-systems. And, not surprisingly, it is the more densely populated cities in north Asia like Beijing, Seoul and Tokyo that are among the earliest adopters of this technology. Increased bandwidth and decreased deployment costs are the reasons that north Asia is again at the leading edge of a new wireless technology.

  "... I began to notice people on the streets of Tokyo staring at their
mobile phones instead of talking to them. The sight of this strange
behavior, now commonplace in much of the world, triggered a sensation I
had experienced a few times before--the instant recognition that a
technology is going to change my life in ways I can scarcely imagine.
Since then, the practice of exchanging short text messages via mobile
telephones has led to the eruption of subcultures in Europe and Asia....
Adolescent mating rituals, political activism and corporate management
styles have mutated in unexpected ways."
--Howard Rheingold (Smart Mobs)

How it works

Wireless peer-to-peer networking, sometimes called "fourth generation" (4G) wireless, was originally conceived by the US Defense Advanced Research Projects Agency (DARPA), the same organization that developed the wired Internet. It is not surprising, then, that DARPA chose the same distribution architecture for the wireless Internet that had proven so successful in the wired Internet. Peer-to-peer networks eliminate the spoke-and-hub weakness of cellular architectures, because the elimination of a single node does not disable the network--just as the loss of a single router does not disable the wired Internet.

Because users carry much of the network with them, network capacity and coverage are dynamically shifted to accommodate changing user patterns. As people congregate and create pockets of high demand, they also create additional routes for each other, thus enabling additional access to network capacity. Users will automatically hop away from congested routes to less congested routes. This permits the network to dynamically and automatically self-balance capacity, increasing network utilization.

Furthering the economic argument is the 80/20 rule. With traditional wireless networks, about 80 percent of the cost is for site acquisition and installation, and just 20 percent is for the technology. Rising land and labor costs mean installation costs tend to rise over time. With wireless peer-to-peer networking, however, about 80 percent of the cost is the technology and only 20 percent is the installation. Because technology costs tend to decline over time, peer-to-peer networking will become less and less expensive to deploy.

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Back to the future

"When a distinguished and elderly scientist says something is possible,
he is almost certainly correct; when he says something is impossible he
is very probably wrong."
--Arthur C. Clarke

Sam Joseph was correct in several of his predictions, most importantly, the notion that "the population density of a city can suddenly become a blessing instead of a curse." In cellular networks, users compete for a finite number of channels.

Irrespective of the size of the cell, the n 1 user gets no coverage. In peer-to-peer networks, users cooperate instead of competing--they provide alternative paths to other users when the shortest (i.e., fewest number of hops) or fattest (i.e., highest throughput) path is not available at that moment.

Joseph also correctly noted that "centralized approaches ... are not likely to scale indefinitely." Dr. Keiji Tachikawa, CEO of NTT DoCoMo, said in January of this year that "by 2010, only 1/5 of DoCoMo's users will be human beings. The rest will be cars, bicycles, computers, ships, vending machines and home appliances."

While even experts still disagree as to what the final definition of "4G" will be, it is becoming increasingly obvious that the cellular architectures designed for 1G are not going to be able to provide an adequate number of users (human and non-human) with the amount of bandwidth they will demand in the future.

Other challenges Joseph identified now have solutions. The concern that "you might end up not being able to use your own phone because two of your friends are using it to talk to each other" has been solved. MeshNetworks, one of the two companies mentioned in the original article three years ago, uses four data channels. One channel is a common overhead channel shared by all users in the vicinity, which leaves three other channels available either for the user or for other users.