How does your mobile phone work? | ICT #1

Summary

This video script delves into the technology behind mobile communications, explaining how voice is converted into digital signals and transmitted via electromagnetic waves. It covers the role of cell towers and mobile switching centers in facilitating calls and the evolution of mobile generations from 1G to 5G, highlighting improvements in data transfer speeds and the introduction of new services like SMS and internet browsing. The script also touches on the importance of the frequency spectrum and the technologies used to efficiently allocate it among subscribers.

Takeaways

• 📞 Mobile phones convert voice into digital signals using a microphone and MEMS sensor with IC.
• 🌐 The digital signal is transmitted as electromagnetic waves, which can be altered in amplitude, frequency, phase, or a combination to represent data.
• 📡 Cell towers and cellular technology help overcome the limitations of electromagnetic wave transmission by dividing geographic areas into cells.
• 🌌 Optical fiber cables connect cell towers for national or international connectivity, showing that mobile communications also rely on wired mediums.
• 📶 Mobile switching centers (MSC) manage the location and activity status of subscribers, distinguishing between home and foreign MSCs.
• 📞 When making a call, the home MSC forwards the request to the recipient's MSC, which then locates the subscriber and establishes the call.
• 🔊 The frequency spectrum is crucial for mobile communications as it allocates frequency ranges to subscribers, with limited spectrum for billions of users.
• 📈 Frequency slot distribution and multiple access techniques efficiently manage the limited frequency spectrum for all active users.
• 📱 Each generation of mobile technology has improved upon its predecessor, with 1G being analog and suffering from poor voice quality and security.
• 🚀 2G introduced digital communication with TDMA or CDMA, SMS, and basic internet browsing, while 3G increased data transfer speeds for multimedia use.
• 🌐 4G further increased speeds with OFDMA and MIMO technology, enabling high-resolution content and setting the stage for 5G.
• 🚀 5G is expected to use enhanced MIMO and millimeter waves for seamless connectivity, supporting the Internet of Things including driverless cars and smart homes.

Q & A

How does a mobile phone convert voice into a digital signal?

A mobile phone's microphone picks up the voice and, with the help of a MEMS sensor and integrated circuit (IC), turns it into a digital signal represented by zeros and ones.

What is the role of electromagnetic waves in mobile phone communication?

Electromagnetic waves are used to transmit the digital signal, which contains voice data in the form of zeros and ones, by altering wave characteristics such as amplitude, frequency, or phase.

Why can't electromagnetic waves travel long distances without assistance?

Electromagnetic waves lose strength due to physical objects, electrical equipment, and environmental factors, and they cannot travel indefinitely due to the Earth's curved structure.

What is the purpose of cell towers in mobile communications?

Cell towers help overcome the limitations of electromagnetic wave transmission by dividing a geographic area into cells, each with its own tower and frequency slot, and relaying signals to other towers.

How are the signals from a mobile phone transmitted to another phone?

The signals from a phone are picked up by a cell tower, converted into high-frequency light pulses, processed, and then routed to the destination tower, which radiates them as electromagnetic waves for the recipient's phone to receive.

What is a mobile switching center (MSC) and why is it important?

A mobile switching center (MSC) is the central point of a group of cell towers that manages the transfer of signals between different cell towers and keeps track of a subscriber's location and service information.

How does a mobile phone network know the current location of a subscriber?

The MSC uses techniques such as periodic location updates, updates when the phone crosses a predefined number of towers, and updates when the phone is turned on to determine the subscriber's current cell location.

What is the significance of the frequency spectrum in mobile phone communications?

The frequency spectrum is important because it is limited, and each subscriber needs a frequency range for digital communication. Efficient allocation and multiple access techniques are used to accommodate billions of subscribers.

What are the main differences between the generations of mobile phone technologies?

1G was analog with poor voice quality and security; 2G introduced digital signals and services like SMS; 3G increased data transfer speeds for multimedia; 4G provided even higher speeds with OFDM and MIMO; and 5G aims to support the Internet of Things with enhanced MIMO and millimeter waves.

Why was the frequency division multiple access technique inefficient in 1G?

The frequency division multiple access technique used in 1G allocated a whole frequency channel for each call, leading to inefficient use of the limited frequency spectrum.

How does 5G technology plan to enhance mobile communications?

5G technology plans to enhance mobile communications by using enhanced MIMO technology and millimeter waves to provide seamless connectivity for applications like driverless cars and smart homes.

Outlines

00:00

📱 Understanding Mobile Communications

This paragraph introduces the fundamental concepts of mobile communications. It explains how a mobile phone converts voice into digital signals using a microphone, MEMS sensor, and IC. These signals are then transmitted as electromagnetic waves by the phone's antenna. The paragraph also discusses the limitations of electromagnetic waves, such as signal loss due to physical obstructions and the Earth's curvature. To address these limitations, cell towers were introduced, utilizing cellular technology to divide geographic areas into cells, each with its own tower and frequency. The towers are connected via optical fiber cables for national or international connectivity. The process of a phone call involves the conversion of digital signals into light pulses, which are then processed and routed to the destination tower, and finally received by the recipient's phone. The paragraph also touches on the role of the mobile switching center (MSC) in managing cell towers and subscriber information, including location updates and the process of call routing.

05:03

📡 The Evolution of Mobile Phone Technologies

This paragraph delves into the evolution of mobile phone technologies, starting with the first generation (1G) which introduced analog wireless transmission but suffered from poor voice quality and security. The second generation (2G) improved upon this with digital multiple access technologies like TDMA and CDMA, and introduced services like SMS and internet browsing. The third generation (3G) focused on higher data transfer speeds, using WCDMA and increased bandwidth to support services like GPS and video calls. The fourth generation (4G) achieved even higher speeds with OFDMA and MIMO technology, enabling high-resolution media streaming. The upcoming fifth generation (5G) is set to use enhanced MIMO and millimeter waves to support the Internet of Things, including applications like driverless cars and smart homes. The paragraph also discusses the importance of the frequency spectrum and the technologies used to efficiently allocate and distribute it among subscribers.

Keywords

💡Mobile Phone

A mobile phone is a portable electronic device that allows users to make telephone calls, send text messages, and access the internet. In the context of the video, mobile phones are the primary tools through which mobile communication is facilitated. The script discusses how mobile phones convert voice into digital signals and transmit them using electromagnetic waves.

💡Digital Signal

A digital signal is a type of signal that represents information as a series of discrete values, typically zeros and ones. The video explains that when you speak on your phone, your voice is converted into a digital signal by the microphone with the help of MEMS sensors and integrated circuits (ICs), which is essential for the transmission of voice data over mobile networks.

💡Electromagnetic Waves

Electromagnetic waves are waves of the electromagnetic field that propagate through space and carry electromagnetic energy. The video describes how these waves are used to transmit digital signals from one mobile phone to another, with the waves' characteristics such as amplitude, frequency, and phase being altered to represent the digital data.

💡Cellular Technology

Cellular technology refers to the use of small, low-power transmitters to create 'cells' that cover a geographic area for wireless communication. The video script explains that cell towers are used to overcome the limitations of electromagnetic waves' range and strength, dividing the area into hexagonal cells to ensure efficient signal coverage.

💡Optical Fiber Cables

Optical fiber cables are strands of glass or plastic that carry information as pulses of light across long distances. In the video, it is mentioned that these cables are used to connect cell towers, providing the necessary wired infrastructure for mobile communication networks to function.

💡Mobile Switching Center (MSC)

The Mobile Switching Center is a central office in the public land mobile network that performs call control and service delivery functions. The script highlights the role of the MSC in managing and routing calls, as well as tracking the location of mobile phones within its service area.

💡Frequency Spectrum

The frequency spectrum refers to the range of frequencies that can be used for electromagnetic wave propagation. The video discusses the importance of the frequency spectrum in mobile communications, noting that it is a limited resource that must be efficiently allocated to accommodate the vast number of mobile subscribers.

💡Multiple Access Technique

Multiple access techniques are methods used in telecommunications to allow multiple users to share the same transmission medium. The video explains that techniques like Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and Orthogonal Frequency Division Multiple Access (OFDMA) are used to efficiently distribute the frequency spectrum among users.

💡Generations of Mobile Phone Technologies

The generations of mobile phone technologies refer to the evolution of mobile communication standards, from 1G to the upcoming 5G. The video script outlines the progression from analog to digital transmission, the introduction of data services like SMS and internet browsing, and the increasing focus on higher data transfer speeds and improved connectivity with each new generation.

💡MIMO Technology

MIMO (Multiple Input, Multiple Output) technology is a method for multiplying the capacity of a radio link using multiple transmitter and receiver antennas. The video mentions MIMO as a key technology that enables higher data rates in 4G networks by using multiple antennas to send and receive more data simultaneously.

💡Millimeter Waves

Millimeter waves are a band of frequencies in the microwave range of the electromagnetic spectrum. The video discusses how 5G technology will utilize millimeter waves to provide high data rates and support the Internet of Things (IoT), including applications like driverless cars and smart homes.

Highlights

A mobile phone's microphone converts voice into digital signals using MEMS sensors and ICs.

Digital signals are transmitted as electromagnetic waves with characteristics like amplitude, frequency, and phase.

Electromagnetic waves are limited by physical objects and environmental factors, necessitating cell towers.

Cellular technology divides geographic areas into hexagonal cells, each with its own tower and frequency slot.

Optical fiber cables connect cell towers for national or international connectivity.

Mobile communications use a combination of wireless and wired mediums.

Mobile switching centers (MSC) manage communication between cell towers and track subscriber locations.

Subscription information is registered in a home MSC, which updates when a user moves to a foreign MSC.

Location updates occur periodically or when a phone crosses a predefined number of towers.

The process of establishing a call involves the home MSC forwarding the request to the current MSC of the recipient.

Frequency spectrum allocation is crucial due to limited availability and high subscriber numbers.

Frequency slot distribution and multiple access techniques efficiently utilize the frequency spectrum.

1G introduced wireless phone communication but suffered from poor voice quality and security.

2G improved with digital transmission and introduced services like SMS and internet browsing.

3G increased data transfer speeds, enabling uses such as GPS and video calls.

4G provided even higher speeds suitable for high-resolution content with OFDMA and MIMO technologies.

5G will enhance connectivity with advanced MIMO and millimeter waves for the Internet of Things.

The evolution of mobile communications has transformed basic phones into smartphones and enabled advanced services.

Transcripts

- [Presenter] For most of us,

a mobile phone is a part of our lives.

But I'm sure you're curious minds

have always been struck by such questions

as how a mobile phone makes a call,

and why there are different generations

of mobile communications?

(upbeat music)

Let's explore the technology behind mobile communications.

When you speak on your phone,

your voice is picked up by your phone's microphone.

The microphone turns your voice into a digital signal

with the help of MEMS sensor and IC.

The digital signal contains your voice

in the form of zeros and ones.

An antenna inside the phone receives these zeros and ones

and transmits them in the form of electromagnetic waves.

Electromagnetic waves transmit the zeros and ones

by altering the wave characteristics,

such as the amplitude, frequency, phase,

or combinations of these.

For example, in the case of frequency,

zero and one are transmitted

by using low and high frequencies respectively.

So, if you could find a way

to transmit these electromagnetic waves

to your friend's phone,

you would be able to establish a call.

However, electromagnetic waves

are incapable of traveling long distances.

They lose their strength due to the presence

of physical objects, electrical equipment,

and some environmental factors.

In fact, if there were no such issues,

even then, electromagnetic waves would not carry on forever,

due to the Earth's curved structure.

To overcome these issues, cell towers were introduced,

using the concept of cellular technology.

In cellular technology,

a geographic area is divided into hexagonal cells

with each cell having its own tower and frequency slot.

Generally, these cell towers are connected through wires,

or more specifically, optical fiber cables.

These optical fiber cables are laid under the ground

or the ocean,

to provide national or international connectivity.

The electromagnetic waves produced by your phone

are picked up by the tower in your cell

and convert them into high frequency light pulses.

These light pulses are carried to the base transceiver box,

located at the base of the tower

for further signal processing,

After processing, your voice signal is routed

towards the destination tower.

Upon receiving the pulses,

the destination tower radiates it outwards

in the form of electromagnetic waves,

and your friend's phone then receives the signal.

This signal undergoes a reverse process,

and your friend hears your voice.

So, it's true that mobile communications

are not entirely wireless,

they do use a wired medium too.

This is how mobile communications are carried out.

However, there was a big issue

that we intentionally left unanswered.

Mobile communication is only successful

when your tower transfers the signal to your friends tower.

But how does your tower know

in which cell tower area your friend is located?

Well, for this process, the cell tower gets help

from something called a mobile switching center.

The MSC is the central point of a group of cell towers.

Before moving further,

let's explain more information about the MSC.

When you purchase a SIM card,

all the subscription information

is registered in a specified MSC.

This MSC will be your home MSC.

The home MSC stores information such as service plans,

your current location, and your activity status.

If you move outside the range of your home MSC,

the new MSC, which serves you instead,

is known as a foreign MSC.

As you enter a foreign MSC region,

it communicates with your home MSC.

In short, your home MSC always knows

which MSC area you are in.

To understand in which cell location the subscriber is

within the MSE area,

the MSC uses a few techniques.

One way is to update the subscriber location

after a certain period.

When the phone crosses a predefined number of towers,

the location update is again done.

The last one of these is when the phone is turned on.

Let's try to understand all of these procedures

with an example.

Suppose, Emma wants to call John.

When Emma dials John's number,

the call request arrives at Emma's home MSC.

Upon receiving John's number,

the request will be forwarded to John's home MSC.

Now, John's MSC checks for his current MSC.

If John is in his home MSC,

the call requests will be immediately sent

to his current cell location,

and it checks whether John is engaged on another call,

or if his mobile is switched off.

If everything is positive, John's phone rings,

and the call will be connected.

However, if John is not in his home MSC,

John's home MSC simply forwards the call request

to the foreign MSC.

The foreign MSC

will follow the previously explained procedure

to locate John's phone,

and will then establish the call.

Now, let's discuss why the frequency spectrum

is quite important in mobile phone communications.

To transfer zeros and ones in digital communication,

each subscriber is allocated a frequency range.

However, the frequency spectrum available

for cellular communications is quite limited,

and there are billions of subscribers.

This issue is solved with the help of two technologies,

one frequency slot distribution,

and two, multiple access technique.

In the first technique,

different frequency slots are carefully allocated

to different cell towers.

In the multiple access technique,

this frequency slot is efficiently distributed

amongst all the active users in the cell area.

Now, the big question.

Why are there different generations

of mobile phone technologies?

1G originally allowed users, for the first time,

to carry a phone without a cable attached to it.

But 1G suffered from two major problems.

The first problem was that the wireless transmission

was in an analog format.

Analog signals that are easily altered by external sources.

So, it provided poor voice quality and poor security.

The second problem was that it used

the frequency division multiple access technique,

which used the available spectrum in an inefficient way.

These factors paved the way for the second generation

of mobile communications,

2G used digital multiple access technologies, namely TDMA,

or CDMA technology.

The second generation

also introduced a revolutionary data service, SMS,

and internet browsing.

3G technology was focused

on giving a higher data transfer speed.

It used a WCD multiple access technique,

along with an increase in bandwidth.

To achieve this, the 3G speed of two Mbps

allowed the transfer of data for uses

such as GPS, videos, voice calls, et cetera.

3G was a huge step in the transformation

of the basic phone to a smartphone.

Next came 4G, which achieved speeds of 20 to 100 Mbps.

This was suitable for high resolution movies and television.

This higher speed was made possible

due to the OFD multiple access technology,

and MIMO technology.

MIMO uses multiple transmitter receiver antennas

inside both the mobile phone and the towers.

The next generation of mobile communication, 5G,

to be rolled out soon,

will use enhanced MIMO technology and millimeter waves.

It will provide seamless connectivity

to support the internet of things,

such as driverless cars and smart homes.

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