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From the course by Princeton University

Networks Illustrated: Principles without Calculus

43 ratings

Princeton University

Networks Illustrated: Principles without Calculus

43 ratings

What makes WiFi faster at home than at a coffee shop? How does Google order its search results from the trillions of webpages on the Internet? Why does Verizon charge $15 for every GB of data we use? Is it really true that we are connected in six social steps or less? These are just a few of the many intriguing questions we can ask about the social and technical networks that form integral parts of our daily lives. This course is about exploring the answers, using a language that anyone can understand. We will focus on fundamental principles like “sharing is hard”, “crowds are wise”, and “network of networks” that have guided the design and sustainability of today’s networks, and summarize the theories behind everything from the social connections we make on platforms like Facebook to the technology upon which these websites run. Unlike other networking courses, the mathematics included here are no more complicated than adding and multiplying numbers. While mathematical details are necessary to fully specify the algorithms and systems we investigate, they are not required to understand the main ideas. We use illustrations, analogies, and anecdotes about networks as pedagogical tools in lieu of detailed equations. All the features of this course are available for free. It does not offer a certificate upon completion.

From the lesson

Power Control in Cellular Networks

How is it possible that we can all communicate effectively without disrupting each other's calls, messages, or Internet usage? In this lesson, we will take a look at some of the methods that have been developed for letting us "share" the air over which our phones communicate.

Meet the Instructors

Christopher Brinton
Lecturer
Electrical Engineering
Mung Chiang
Professor
Electrical Engineering

So, the first place that we start to use FDMA in mobile wireless phone technology

was in what we call 0G, or zero generation.

And yes, that has evolved today to the 3G and 4G standards that we see.

But it had to all start somewhere. And while they probably didn't call it 0G

back then, we today refer to it as the 0th generation or the precursor to the

first generation. So, the first 0G system was called MTS,

or Mobile Telephone System, and that came about in 1946, by Bell Telephone.

And this was an FTMA system, and it basically linked the mobile and the

wireless communications to the telephone system, which was already established.

And that's how people would make their calls.

And you actually needed a physical operator.

If you were on one end, you would make a call.

And you would send a call to the operator, and you would tell the operator

who you wanted to dial, then the operator would connect you, or make the physical

connection here, between your cables so that you guys could speak.

And so, then in 1964, the improved mobile telephone system came about, and that

eliminated the need for an operator. That was much more convenient, because

then you didn't have to have an intermediate call, where you would have

to speak to the operator to have him physically connect your calls together.

And so, don't be deceived, though, because back then, these mobile phones,

we can't call them cellphones. You really can't call them mobile phones

either, because they were really car phones.

It not that you could carry around in your hands.

They were very expensive, reserved for successful lawyers, rich movie stars

people on those sorts and nothing that you could carry around by today's

standards. They would be sitting in your, in your

vehicles. And this is actually a 0G phone here that

would have plugged into the MTS or the IMTS back then and this isn't a car

phone, but you can see it's really large. It's basically land line phone, but not

really a land line, but it looks just like a land line phone that you would see

in your house. So, they didn't develop the technology to

make these things much smaller, and so we started to develop what was called the

transistor and very high-scale, high-speed small electronics that we'll

talk about soon. So, the first handheld phone came in 1973

from Motorola, they came up with the first ever hands held phone.

A guy by the name of Martin Cooper was convinced that mobile phones were the

wave of the future and though a lot of people didn't believe that he obviously

was right. And so, but if you look at a comparison

between an iPhone today, and what this first phone was called, or this DynaTAC

back in 1973. It's the DynaTAC, d, y, n, a, t, a, c.

You can see how much larger, and how much more inconvenient it would have been to

carry that phone around. But this is technically a hand-held

phone, and you can carry it around and walk around with it.

And while the iPhone today, in 2012, weighs less than a third of a pound, this

weighed close to two pounds. So, it would be very, very heavy.

And the iPhone you can buy, depending upon your cellular carrier and so on, for

$150 today. This DynaTAC costed close to $3000.

So, still, it was pretty expensive way back then, very, very hard to afford

phone. And this is in not even today's dollars

this is in 1973 dollars. And, well an iPhone can offer you hours

of uninterrupted service, and not only can you call, or text message, or go on

the internet on your smartphones. This only had the call function, and you

could only for a maximum of 30 minutes talk to someone before you'd have to go

back and recharge your phone. And so, for these reasons here, as well

as capacity issues, as we'll speak of in a second.

We didn't really start switching over to handheld phones that everybody could buy

or use and carry around with them until the mid-1990s.

So, they were just way too expensive and there were many capacity issues back

then, so we'd stayed largely with car phones up until then.

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