Telecommunication basics
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The document provides an overview of telecommunications, detailing it as the exchange of information using technology through channels for transmission. It covers fundamental concepts such as modulation, types of communication (full duplex vs half duplex), and different network types including voice and data networks. The text also discusses modern advancements in cellular technology and internet access services, including various standards like 3G, LTE, and the impact of digital signaling and VoIP on telecommunications.
Telecommunication basics
- 1. Telecommunication Basics Brian (Yoohyun) Kim Product Marketing manager at CDNetworks March, 2015
- 2. Contents • What is Telecommunication? • Basic terms and concepts of Telecommunication • Technical overview of the telephone service • Cellular Telephony • Residential internet access service
- 3. 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
- 4. 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) ”
- 5. Basic Terms and Concepts • 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 *Source: Wikipedia – “Telecommunication”, http://en.wikipedia.org/w/index.php?title=Telecommunication&redirect=no
- 6. Basic Terms and Concepts • 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)
- 7. Basic Terms and Concepts • 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
- 8. Basic Terms and Concepts • 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
- 9. Basic Terms and Concepts • 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). *Source: Wikipedia – “Telecommunication”, http://en.wikipedia.org/w/index.php?title=Telecommunication&redirect=no
- 10. 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).
- 11. 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. *Source: Business Data networks and Telecommunications, Panko, University of Hawaii Sound Wave 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
- 12. Codec at the End Office Switch *Source: Business Data networks and Telecommunications, Panko, University of Hawaii • 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 Local Loop Home End Office Analog Signal Digital Signal
- 13. Voice over IP (VoIP) *Source: Business Data networks and Telecommunications, Panko, University of Hawaii • 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 with Multimedia Hardw are and VoIPSoftware IPTelephone w ith Codec and TCP/IPFunctionality Media Gatew ay PSTN Internet
- 14. Cellular Telephony *Source: Business Data networks and Telecommunications, Panko, University of Hawaii • 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.
- 15. Cellular Telephony *Source: Business Data networks and Telecommunications, Panko, University of Hawaii • 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 Channel 47 Mobile Telephone Sw itching Office Cellsite PSTN Handoff
- 16. GSM (Global Service for Mobile communication) *Source: Business Data networks and Telecommunications, Panko, University of Hawaii • 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 1 Conversation A Slot 2 Conversation B Slot 8 Conversation H …… Slot 1 Conversation A Time Frame 1 Frame 2
- 17. CDMA (Code Division Multiple Access) *Source: Business Data networks and Telecommunications, Panko, University of Hawaii • 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
- 18. 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
- 19. 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)
- 20. 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 Gen Late90’s- Early 2000 2nd Gen Early - Mid 2000 3rd Gen Late 2000 - Current 4th Gen 2013 - Beyond • ADSL: 8Mbps (DL), 1Mbps (UL) • VDSL: 52Mbps (DL), 6.4Mbps (UL) • FTTH: 100Mbps • Mobile Broadband • 4G / 5G (1Gbps) *Akamai acquires Netli in 2007
- 21. Telephone Modem Connection to an ISP *Source: Business Data networks and Telecommunications, Panko University of Hawaii & Wikipedia, “Modem” Client A Telephone Modem Telephone PSTN (Digital) 33.6 kbps Digital Analog Access 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.
- 22. 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. PC ADSL Modem Ordinary Telephone Service Single Pair of Voice-Grade UTPWires Dow nstreamData Up to 1.5 Mbps UpstreamData Up to 512 kbps Splitter DSLAM Telephone Telephone Company End Office Sw itch Subscriber Premises Data WAN PSTN *Source: Business Data networks and Telecommunications, Panko University of Hawaii & Wikipedia, “Asymmetrical digital subscriber line”
- 23. Thank you Brian (Yoohyun) Kim Product Marketing Manager| CDNetworks brian.Yoohyun.kim@gmail.com http://yoohyunkim.blogspot.com