telecommunication basics

Telecommunication Basics

Brian (Yoohyun) KimProduct Marketing manager at CDNetworks

March, 2015

Contents • What is Telecommunication?

• Basic terms and concepts of Telecommunication

• Technical overview of the telephone service

• Cellular Telephony

• Residential internet access service

What is Telecommunication?

• Telecommunication Telecommunication occurs when the exchange of information between two entities

(communication) includes the use of technology. Communication technology uses channels to transmit information (as electrical signals), either over a physical medium (such as signal cables), or in the form of electromagnetic waves.

• Basic elements A transmitter that takes information (e.g. voice or text) and converts it to a signal. A transmission medium, also called the "physical channel" that carries the signal. An example of

this is the "free space channel, copper wire, coaxial cable or Fiber Optic cable, etc.". A receiver that takes the signal from the channel and converts it back into usable information. Transceiver: a single box of electronics working as both a transmitter and a receiver, or a

transceiver. For example, a cellular phone is a transceiver.

• Communication Channel The term "channel" has two different meanings. In one meaning, a channel is the physical

medium that carries a signal between the transmitter and the receiver. The other meaning of the term "channel" in telecommunications is seen in the phrase

communications channel, which is a subdivision of a transmission medium so that it can be used to send multiple streams of information simultaneously.

*Source: Wikipedia – “Telecommunication”, http://en.wikipedia.org/w/index.php?title=Telecommunication&redirect=no

http://en.wikipedia.org/w/index.php?title=Telecommunication&redirect=no

Basic Terms and Concepts

• Half duplex vs Full duplex A duplex communication system is a point-to-point system, usually in fixed-line telephone

network, composed of two connected parties or devices that can communicate with one another in both directions.

In a full duplex system, both parties can communicate to the other simultaneously. An example of a full-duplex device is a telephone

In a half-duplex system, there are still two clearly defined paths/channels, and each party can communicate to the other but not simultaneously; the communication is one direction at a time. An example of a half-duplex device is a walkie-talkie.

Full-duplex communication system

Half-duplex communication system

*Source: Wikipedia – “Duplex (Telecommunications), http://en.wikipedia.org/wiki/Duplex_(telecommunications) ”

http://en.wikipedia.org/wiki/Duplex_(telecommunications)


• Modulation The shaping of a signal to convey information is known as modulation. Modulation can be used

to represent a digital message as an analog waveform. This is commonly called “Keying”. Modem: “Modulator – Demodulator”, A to D and D to A because the voice network is analog.

• Analog Signaling vs Digital Signaling Analog signaling: Human friendly | AM, FM | Noise cancellation (Signal tuning is the core

technology) Digital signaling: Computer friendly | Error correction, Encryption enabled




• Switching (“The Cloud”) Switching makes better use of the “Cloud” Circuit switching, Packet switching (Internet), Broadcasting, Cellular

• Voice network vs Data network Voice network: PSTN (Public Switched Telephone Network)

Basically transmitting the voice

Data network: LAN, WAN (often (usually) use voice network transmission facilities) Anything goes (e.g. text, image, voice, video, etc.)

• Where do networks come from? Voice network: Telcos, Long distance carriers Data network: ISP (Internet Service Provider)


• Circuit vs Packet switching Circuit switching is old and expensive, and it is what PSTN uses Packet switching allows traffic to be routed around failures

*Source: IP Routing Tutorial, Stefan Fouant, Slideshare

• End-to-end circuit• Sequenced communication• PSTN• Traditional telephony• Not cost efficient• Less Delay• Highly reliable, but failures typically mean

the circuit must be rebuilt

• Packets represent piece of data• Unordered transmission• Internet• VoIP• Shared cost model• Highly Delay• Less reliable, but can reroute around

failures

Circuit Switching Packet Switching


• Multiplexing Multiplexing is the set of technique that allow the simultaneous transmission of multiple signals

across a single data link (transmission medium) Multiplexor is a mechanism that implements the concept

*Source: Introduction 1-1 Circuit Switching: FDM and TDM, Sandra4211, Slideshare


• Internet – computer networks that communicate with each other using Internet Protocol Any computer on the Internet can send a message to any other computer using its IP address. For the Internet, the physical medium and data link protocol can vary several times as packets

traverse the globe. This is because the Internet places no constraints on what physical medium or data link protocol is used.

At the network layer, things become standardized with the Internet Protocol (IP) being adopted for logical addressing.

At the transport layer, most communication adopts either the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP).

Above the transport layer, there are certain protocols that are sometimes used and loosely fit in the session and presentation layers, most notably the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols.

Finally, at the application layer, are many of the protocols Internet users would be familiar with such as HTTP (web browsing), POP3 (e-mail), FTP (file transfer), IRC (Internet chat), BitTorrent(file sharing) and XMPP (instant messaging).



Technical elements of Voice network (PSTN)

*Source: Business Data networks and Telecommunications, Panko, University of Hawaii

• The Access System consists of the access line to the customer (called the Local Loop) and termination equipment at the end office (the nearest telephone office switch).

PSTN: Mostly Digital with Analog Local Loops

• Today, everything is digital except for the Local Loop access line and residential telephones.

• The actual Local Loop line can carry either analog or digital signals, but the equipment at both ends is analog.


SoundWave

Analog(Analogous)

Electrical Signal

Residential Telephone(Analog)

Local Loop(Analog)

PBX(Digital)

Local Loop(Digital)

Switch(Digital)

Switch(Digital)

Switch(Digital)

Trunk Line(Digital)

Example of today’s Telephone network

Codec at the End Office Switch


• A Codec at the end office translates between residential analog and PSTN digital signaling ADC = Analog to Digital conversion DAC = Digital to Analog conversion

• Analog-to-Digital Conversion (ADC): Bandpass Filtering and Pulse Code Modulation (PCM) Human voice bandwidth: 300Hz to 3,400Hz (3.1KHz bandwidth) – about 4KHz Nyquist sampling theory: Signals must be samples at twice their high frequency (1 / 8,000

second sampling, 8-bit sampling, 8,000 bytes/sec, 64Kbps)

Switch(Digital)

Telephone(Analog)

Codec

DAC

ADC

LocalLoop

Home End Office

Analog Signal

Digital Signal

Voice over IP (VoIP)


• Voice over Internet Protocol Voice over Internet Protocol (VoIP) allows data packets to be used for synchronous voice

communications. The data packets are marked as voice type packets and can be prioritized by the network administrators so that the real-time, synchronous conversation is less subject to contention with other types of data traffic which can be delayed (i.e. file transfer or email) or buffered in advance (i.e. audio and video) without detriment.

With IP, there is no wasted capacity as there is with circuit switching and this reduces cost. Stations can be special IP telephones with IP functionality or a PC with multimedia hardware and

VoIP software. IP phones need a Codec to convert voice analog signals form the microphone into digital IP signals.

PC w ith

Multimedia Hardw are

and VoIP Softw are

IP Telephone

w ith

Codec and

TCP/IP Functionality

Media

Gatew ay

PSTN

Internet

Cellular Telephony


• Microwave uses radio transmission for PSTN trunk lines Each circuit is sent in a separate channel and if each channel bandwidth is large, there will be

fewer channels. Frequency Division Multiplexing (FDM) used in AMPS (Advanced Mobile Phone System.) Voice uses 4 KHz-wide channels.

Cellular Telephony


• In Cellular technology, the region is divided into smaller cells. In each cell, a Cellsite (Base Station) serves cellphones in the cell. When a subscriber moves from one cell to another in a cellular system, this is called a handoff. When a subscriber moves from one city to another, this is roaming. The Mobile Telephone Switching Office (AKA Mobile Switching Center) coordinates the Cellsites

and implements signaling and handoffs.

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Channel47

Mobile Telephone Sw itching Office

Cellsite

PSTN

Handoff

GSM (Global Service for Mobile communication)


• GSM is the worldwide standard for cellular voice – especially Europe. Uses Time Division Multiplexing (TDM) Uses 200 kHz channels Divides each second into many frame periods Divides each frame into 8 slots Gives same slot in each frame to a conversation

Slot 1Conversation

A

Slot 2Conversation

B

Slot 8Conversation

H

……Slot 1

ConversationA

Time Frame 1 Frame 2

CDMA (Code Division Multiple Access)


• Code Division Multiple Access (CDMA) Used in the United States and Korea | A form of spread spectrum transmission Unlike traditional spread spectrum technology, multiple users can transmit simultaneously 1.25 MHz channels | Can support many users per channel

• Can use the same channel in adjacent cells So can only reuse a channel in every cell

3G Services

• 3G – Third generation of mobile telecommunication technology This is based on a set of standards used for mobile devices and mobile telecommunications use

services and networks that comply with the International Mobile Telecommunications-2000 (IMT-2000) specifications.

3G finds application in wireless voice telephony, mobile Internet access, fixed wireless Internet access, video calls (e.g. show) and mobile TV.

The original and most widespread radio interface is called WCDMA (Wideband CDMA).

• HSPA (High Speed Packet Access) HSPA is that extends and improves the performance of existing 3rd generation mobile

telecommunication networks utilizing the WCDMA protocols. HSDPA: The first step required to upgrade WCDMA to HSPA is to improve the downlink by

introducing HSDPA. The improved downlink provides up to 14 Mbit/s with significantly reduced latency.

HSPA+ (evolved High Speed Packet Access): Evolved HSPA provides data rates up to 84 Mbit/s in the downlink and 10.8 Mbit/s in the uplink (per 5 MHz carrier) with multiple input, multiple output (2x2 MIMO) technologies and higher order modulation (64 QAM). With Dual Cell technology, these can be doubled.

*Source: Wikipedia – “High Speed Packet Access”, http://en.wikipedia.org/wiki/High_Speed_Packet_Access

http://en.wikipedia.org/wiki/High_Speed_Packet_Access

LTE – Long Term Evolution

• LTE – Long Term Evolution LTE, commonly marketed as 4G LTE, is a standard for wireless communication of high-speed data

for mobile phones and data terminals. It is based on the GSM/EDGE and UMTS/HSPA network technologies, increasing the capacity and speed using a different radio interface together with core network improvements.

Peak download rates up to 299.6 Mbit/s and upload rates up to 75.4 Mbit/s depending on the user equipment category (with 4×4 antennas using 20 MHz of spectrum). Five different terminal classes have been defined from a voice centric class up to a high end terminal that supports the peak data rates. All terminals will be able to process 20 MHz bandwidth.

• Voice Calls Voice over LTE (VoLTE) vs VoIP Circuit-switched fallback (CSFB): TE just provides data services, and when a voice call is to be

initiated or received, it will fall back to the circuit-switched domain. Simultaneous voice and LTE (SVLTE): the handset works simultaneously in the LTE and circuit

switched modes, with the LTE mode providing data services and the circuit switched mode providing the voice service.

*Source: Wikipedia – “LTE (Telecommunications)”, http://en.wikipedia.org/wiki/LTE_(telecommunication)

http://en.wikipedia.org/wiki/LTE_(telecommunication)

Residential Internet Access Services

*Source: Business Data networks and Telecommunications, Panko University of Hawaii

• Telephone modems: 56Kbps (not 64Kbps since voice also should be delivered)• ISDN: 64Kbps-128Kbps

1st GenLate90’s-

Early 2000

2nd GenEarly -

Mid 2000

3rd GenLate 2000 -

Current

4th Gen2013 -

Beyond

• ADSL: 8Mbps (DL), 1Mbps (UL)• VDSL: 52Mbps (DL), 6.4Mbps (UL)

• FTTH: 100Mbps

• Mobile Broadband• 4G / 5G (1Gbps)

*Akamai acquires Netli in 2007

Telephone Modem Connection to an ISP

*Source: Business Data networks and Telecommunications, Panko University of Hawaii& Wikipedia, “Modem”

Client A

TelephoneModem

Telephone

PSTN (Digital)

33.6 kbps

DigitalAnalogAccess

Line

Analog

56 kbps

• Telephone modem Telephone modems convert digital computer signals to analog telephone signals. Very low transmission speeds. Long delays in downloading webpages. Subscriber cannot

simultaneously use the telephone line for voice calls. Modems are generally classified by the amount of data they can send in a given unit of time,

usually expressed in bits per second (symbol bit/s, sometimes abbreviated "bps"), or bytes per second (symbol B/s). Modems can also be classified by their symbol rate, measured in baud.

ADSL: Asymmetrical Digital Subscriber Line

• Asymmetric digital subscriber line Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a

data communications technology that enables faster data transmission over copper telephone lines than a conventional voice band modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call.

A splitter, or DSL filter, allows a single telephone connection to be used for both ADSL service and voice calls at the same time.

PCADSL

Modem

Ordinary TelephoneService

Single Pair ofVoice-GradeUTP Wires

Dow nstream DataUp to 1.5 Mbps

Upstream DataUp to 512 kbps

Splitter DSLAM

Telephone

Telephone CompanyEnd Office Sw itch

SubscriberPremises

DataWAN

PSTN

*Source: Business Data networks and Telecommunications, Panko University of Hawaii& Wikipedia, “Asymmetrical digital subscriber line”

Thank you

Brian (Yoohyun) KimProduct Marketing Manager| CDNetworks

[email protected]://yoohyunkim.blogspot.com

mailto:[email protected]

http://yoohyunkim.blogspot.com/

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