IS605/606: Information Systems Instructor: Dr. Boris Jukic Voice Telephony: Technology and Industry Overview

Telecommunication Industry: Carriers Carriers – In the United States U.S. is divided into regions called local access and transport areas (LATAs) About 200 LATAs nationwide LATA

Intra-LATA (Local/Toll) Carriers – In the United States post 1996 Local exchange carriers (LECs) provide service within a LATA Incumbent LEC (ILEC) is the traditional monopoly carrier in the LATA Competitive LEC (CLEC) is a new competitor LATA LEC ILECCLEC

Inter-LATA (Long Distance) LATA IXC Carriers – In the United States Inter-exchange carriers (IXCs) provide service between LATAs – LEC versus IXC distinction is used by data carriers as well as voice carriers.

POPs – In the United States Point of Presence (POP) is a place in a LATA where all carriers interconnect to provide integrated service to all customers LATA POP ILEC CLECIXC IXCs carry traffic to POPs in other LATAs

Regulation of Land-Line Telephony Regulation – Why regulation? Two Main Reasons: An industry that supplies essential services where only one organization can operate efficiently in a given market is a "natural monopoly.“ Basic telephone service is considered a public utility whose efficient operation is in the public interest – the monopolistic aspect of the basic telephone service industry is debatable – First steps to regulation were taken by the states in the early 1900s; now all 50 states plus D.C. have commissions that regulate intrastate telecommunications. – State regulatory agencies are generally known as public utility commissions or public service commissions. – The Federal Communications Commission (FCC) was created by the Communications Act of Independent agency charged with regulating interstate and international communications originating in the United States

Regulation of Land-Line Telephony Common Carriers: carry signals between customer premises – Domestic Telephone Service provided by a single telephone carrier within many countries: PTT – Public Telephone and Telegraph Authority – Rights of Way: government permission to lay wire along roads, rails and in other public areas – Tariffs are the published rates, regulations, and descriptions governing the provision of communication services.

Regulation and Carriers International Service (Between Pairs of Countries) – Provided by international common carriers (ICCs) – Allowed carriers, prices, and conditions of service are settled through bilateral negotiation between each pair of countries Country 1Country 2 ICC

Basic Telephony Infrastructure: Public Switched Telephone Network (PSTN)

PSTN: Local Loop CO Thousands of Central Offices (COs) that house telecom equipment. Some serve as “end offices” and some just as tandem offices. COs are connected using high-speed, redundant circuits (e.g., ATM over OC-48) UTP, Coax, & Fiber are run into neighborhoods to serve businesses and homes “The Local Loop or Last Mile” Reg.De-Reg. Terminating Equipment “NID”

PSTN: Digital Trunks and Mostly Analog Local Loops Local Loop (Analog) Residential Telephone (Analog) Switch (Digital) Switch (Digital) Switch (Digital) Local Loop (Digital) PBX (Digital) Trunk Line (Digital) Circuit: End-to-End Connection Between Two Subscribers. Switches: Voice switches are Circuit-Switched.

Analog-to-Digital Conversion (ADC) Sampling of the Voice Signal – Each second is divided into 8,000 sampling periods (Nyquist’s Law) – Each sampling period is 1/8,000 of a second – Voice intensity in each sampling period is recorded as fraction of a maximum value (255). – The decimal value (210 in this example) is converted into an 8-bit binary value, Sample 1/8,000 sec Sampling Period Intensity Value 210/255 ( )

Transmission Rates Transmission Rate for a telephone line – 8,000 samples/second * 8 bits/sample = 64 kbps – This is why telephone channels are 64 kbps

Mobile (Cellular) Telephony: Analog vs. Digital Analog: broadcasts audio as a series of continuously changing, voltage levels representing the amplitude of the voice conversation. – Each call is sent through a channel separated by 30 kHz: Frequency Division Multiple Access (FDMA) Digital: quantizes the voltage levels into a number of bins (typically 28 or 256 representing 8-bit encoding). bins are encoded as a binary number and sent as a series of ones and zeros. Multiple conversations are possible over the same channel

Mobile (Cellular) Telephony: Digital Advantage It economizes on bandwidth. – More digitized conversations per frequency band Superior quality of voice transmission over long distances. More difficult to decode. It can use lower average transmitter power. It enables smaller and less expensive individual receivers and transmitters. It offers voice privacy.

Desirable Frequency Band for Wireless Providers: “Golden Zone” At lower frequencies, there is little total bandwidth. At very high frequencies, propagation is poor. Mobile devices tend to work in the “golden zone” from the high megahertz to the low gigahertz range. Frequencies in the golden zone are limited and in high demand. – Very expensive to obtain – EU wide auctions for 3G spectrum yielded > $100 Billion

Generations of Cellular Service GenerationFirst2nd2.5G3G TechnologyAnalogDigital Data Transfer Rate Data Transfer Is Difficult 10 kbps* 20 kbps to 144 kbps to 2 Mbps *Sufficient for Short Message Service (SMS) and wireless Web access using the Wireless Access Protocol (WAP) World Standardization (and therefore roaming) Poor Good (GSM) Based on 2G (W-CDMA, CDMA-2000, and other systems may compete ) U.S. Standardization Good (AMPS) Poor (GSM, CDMA, TDMA, & CDPD) Based on 2G ?

3G Speeds (Throughput Rates) ITU Speed Requirements for 3G – 2 Mbps for fixed devices – 384 kbps for walking people – 144 kbps for automotive users Anything Less is 2.5 G – Some 2.5G vendors call themselves 3G but are not

U.S. Cellular Telephony Usage Lag The U.S. lags many other countries in cellular telephone use. – Europe and Asia-Pacific have higher rates of usage The rest of the world also has very high usage rates when adjusted for per-capita income – U.S. wired telephone charges are low, and in the case of local loop not based on usage intensive usage of mobile telephony for local loop purposes is less attractive – The lack of a dominant U.S. standard for 2 nd generation cellular telephony – Pricing schemes in U.S. discourages intensive use (receiver-based charging) Recently, per-unit of usage prices have dropped significantly – 3G deployment may change the perception of the “Lag” (stay tuned)