PSTN: The Traditional Phone

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Del curso dictado por University of California San Diego

Internet of Things: Communication Technologies

142 calificaciones

University of California San Diego

Internet of Things: Communication Technologies

142 calificaciones

Curso 4 de 6 en SpecializationInternet of Things

Have you wondered how “Things” talk to each other and the cloud? Do you understand the alternatives for conveying latency-sensitive real time data versus reliable signaling data? Building on the skills from the Sensing and Actuation course, we will explore protocols to exchange information between processors. In this course, you will learn how VoIP systems like Skype work and implement your own app for voice calls and text messages. You will start by using the Session Initiation Protocol (SIP) for session management. Next, you will learn how voice codecs such as Adaptive Multi Rate (AMR) are used in 3G networks and use them for voice traffic in your app. Learning Goals: After completing this course, you will be able to: 1. Implement session initiation, management and termination on your DragonBoard™ 410c using SIP. 2. Discover other users and exchange device capabilities. 3. Compare and contrast narrowband and wideband codecs and experience the voice quality differences between them. 4. Implement and demonstrate VoIP calls using the DragonBoard 410c.

De la lección

Terminology/Cheat Sheet (Beginner)

In this course, you will see a lot of new words and acronyms you might not be familiar with. If you feel comfortable with your knowledge of tech terminology, feel free to skip these lessons since they will not affect the overall integrity of the course. If you see something that you want to know a little more about, feel free to watch the video to gain insight on some basic concepts. We do expect you to know the majority of this material before going into the next module, we would recommend going through the lessons as a quick brush up.

Introduction to Lesson 32:06

PSTN: The Traditional Phone4:03

Linphone Source Code4:09

Codec Selection5:27

A look back at Lesson31:43

Conoce a los instructores

Ganz Chockalingam
Principal Engineer
Qualcomm Institute of Calit2, UC, San Diego
Harinath Garudadri
Associate Research Scientist
Qualcomm Institute of Calit2, UC, San Diego

Hey, everyone.

So, let's go ahead, and dive right into talking about the PSTN, or

the public switch telephone networks, which is just the traditional phone

sorta network, and how it relates to everything here.

>> Yeah, how it relates to VoIP.

>> Mm-hm.

So, first of all, it's just a circuit switch network, which basically means it's

a network that uses circuits to connect the nodes to send

the data instead of the packet switch network where it just uses the Internet.

So, that's just.

So, to get the circuit switch networks,

they would have to setup the physical telephone lines.

Sometimes you've seen them in movies where they have the long poles and

just runs across everywhere.

And then, sometimes you'll need to call someone in Europe,

you'll have to have an underwater giant cable, something like that.

>> And while traditional analog telephones still exist,

the public switched telephone network will as well.

Because even when using VoIP,

the VoIP signal eventually gets to a point where it needs to find the telephone.

>> Yeah, so all these were just the traditional landline phones, whatnot.

And since it's had so much time to grow, which is why the network is just

humongous right now, and that's why it's probably not gonna go away any time soon.

>> Yeah. >> So, here we're going look

at over some things about the original phone where it just has the microphone,

has the ear piece, or the speaker which is the receiver.

You have a ringer so you know when someone's calling you.

And you have some contacts or addresses so you know who to call.

And all of these are also encapsulated in VoIP.

Right?

But, it tends to be less efficient,

because it doesn't really use the bandwidth that well.

Because everything's just on analog.

>> Yeah, so when it comes to the old school telephones.

I don't know, maybe some of you remember because you still use the old school

telephones, the analog phones.

But you have to have all these other devices, you have your phone but

if you want a Caller ID, you have to hook up a Caller ID.

If you want a message machine, you have to hook up a message machine.

All of these things just come integrated- >> That adds up to have a overhead cost.

So, the old telephones didn't have more, but

often times with VoIP phones everything's already integrated, like software, or

just simply all in one package.

So, with that begs us to ask the question,

if VoIP is better then why is the PSTN still around?

And we just answered that earlier where it's humongous because there's been so

much time for the network to grow.

Because the analog phones came first,

Internet was not around until say two decades ago, right?

>> Yeah, so you have a huge network which means we still have to cater to that.

>> Right, so we have to find a way, if we're gonna slowly transition into VoIP,

we have to find a way to still be able to talk

to the old analog phones that are still on the PSTN network.

>> Mm-hm. >> Or PSTN.

And the way they do that, is, we would introduce a device that will just

basically convert the signal that the VoIP uses

into a signal that the traditional phone can understand.

And likewise, the traditional phone will be able to send a signal

that gets converted into a signal that VoIP can understand.

So, with that, and

here we have up on the slides where you can see how everything sort of connects.

Where there's the IP and then the PSTN and

they have to communicate through this gateway, basically.

>> Yeah, we're gonna actually talk about gateways a little bit later.

>> Mm-hm. Yeah, exactly.

But, that just wraps up our talk about the traditional phone,

and we'll see you next time.

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