8 1 Digital Cellular Telephony Chapter 8

8 2 Learning Objectives  Describe the applications that can be used on a digital cellular telephone  Explain how cellular telephony functions  List and describe the features of the generations of cellular telephony  List and describe the four types of client software used on a digital cellular telephone  Discuss the issues surrounding 3G implementation

8 3 Digital Cellular Telephony  Although commonplace, digital cellular telephony is most competitive and complex of all wireless telephony  Variety of competing technologies such as GSM and CDMA2000 1XEVDO rather than single standard  Competing carriers each push a specific technology  Governments have even auctioned off part of wireless spectrum to highest bidder

8 4 Applications  New and expanded features and applications are pushing wireless digital cellular networks beyond just voice communications  Digital cellular telephony can be used for Internet access, , video conferencing, and running a variety of programs

8 5 Short Message Services (SMS)  Short Message Services (SMS) delivers text-based messages up to 160 characters directly between wireless devices without using the Internet  SMS is popular in Europe and Japan with over 200 billion messages sent annually  SMS is slow in reaching the US because of profusion of other wireless digital alternatives

8 6 How Cellular Telephony Works  Two keys to cellular telephone networks  Coverage area is divided into cells, each with a cell transmitter connected to base station that, in turn, is connected to mobile telecommunications switching office (MTSO)  See Figure 8-1  All the transmitters and cell phones operate at low power level to prevent signals from interfering with other cells that may use same frequencies  See Figure 8-2

8 7 Cellular Network

8 8 Frequency Reuse

8 9 Cellular Telephone Codes  Special codes are associated with cell phones  Codes identify phone, phone’s owner, and carrier or service provider  Table 8-1 summarizes the codes

8 10 Cellular Telephone Codes

8 11 Cellular Telephone Handoffs and Roaming  When telephone user moves within same cell, base station handles transmissions  Handoff is when user moves to another cell and is automatically associated with base station of that cell  Roaming is when user moves beyond coverage area of entire cellular network into remote area, as seen in Figure 8-3  Network in remote area contacts home network to verify that user can make calls and is charged appropriately

8 12 Handoff and Roaming

8 13 How a Cellular Phone Receives a Call  Cell phone listens for SID transmitted by base station on control channel  If SID matches that programmed into phone, cell phone transmits registration request to base station that MTSO uses  If SID does not match, cell phone is roaming and MTSO of remote network contacts MTSO of home network to confirm SID is valid

8 14 How a Cellular Phone Receives a Call  MTSO locates phone and selects frequency which is sent to phone over control channel  As user moves to edge of cell, base stations coordinate through MTSO and instruct phone to change frequencies as it is handed off to another cell  See Figure 8-4

8 15 Receiving a Call

8 16 Digital Cellular Telephony  Existing since the early 1980s in the United States, cellular telephony is divided into several generations  First Generation  Second Generation  2.5 Generation  Third Generation

8 17 First Generation  1G uses analog signals and has 9.6 KHz maximum transmission speed  Based on Advanced Mobile Phone Service (AMPS), 1G uses MHz frequency  Each channel is 30 KHz wide with 45 KHz passband  832 frequencies are available, with 790 used for voice traffic and 42 for control channel  Two frequencies are required for conversation, so there are actually only 395 voice channels and 21 control channels

8 18 First Generation  AMPS uses Frequency Division Multiple Access (FDMA), as illustrated in Figure 8-5  User is allocated single channel at a time and is switched to another channel if original one deteriorates or has interference  1G networks use circuit-switching technology  Because analog signals are prone to interference, 1G is used basically for voice  It has been replaced with improved digital technology

8 19 FDMA

8 20 Second Generation  Started in early 1990s, 2G uses digital transmissions to transmits data between 9.5 Kbps and 14.4 Kbps in 800 MHz and 1.9 GHz frequencies  Offers several advantages over analog, including  More efficient uses of frequency spectrum  Quality of voice transmission does not degrade over distance  Better security; more difficult to decode  Requires less transmitter power  Uses smaller and less expensive individual receivers and transmitters

8 21 Second Generation  2G cellular networks use three different multiple access technologies summarized in Table 8-2  Time Division Multiple Access (TDMA), shown in Figure 8-6, allows 3 times as many calls over a single channel as FDMA  Code Division Multiple Access (CDMA) allocates entire spectrum all the time, as seen in Figure 8-7  Global Systems for Mobile Communications (GSM) divides a 25 MHz channel into 124 frequencies, each 200 KHz, and then uses 8 time slots to transmit up to 9.6 Kbps

8 22 TDMA

8 23 CDMA

8 24 2G Technologies

Generation  2.5G is regarded as an interim generation  Sparsely deployed 2.5G networks operate at 384 Kbps  Packet-switched 2.5G networks have two advantages over circuit switched networks  More efficient, increasing traffic from 3 to 5 times over that of circuit-switching  “Always on” with connection kept open all the time

Generation  2.5G networks use three technologies  General Packet Radio Service (GPRS) uses 8 time slots in a 200 KHz spectrum to transmit at speeds up to 114 Kbps  Enhanced Data Rates for Global Evolution (EDGE) uses new modulation technique to transmit up to 384 Kbps  CDMA2000 1XRTT supports 144 Kbps packet data transmissions

8 27 Third Generation  3G is intended to be a uniform global worldwide standard for cellular wireless communication  International Telecommunications Union (ITN) has outlined standard data rates for wireless digital networks  144 Kbps for a mobile user  386 Kbps for slowly moving user  2 Mbps for stationary user

8 28 Third Generation  Transition from CDMA2000 1XRTT is to CDMA200 1XEVDO with data transmission rates of 2.4 Mbps  Must be coupled with CDMA2000 1XRTT for both voice and data transmissions  CDMA2000 1XEVDV will send both voice and data  Transition from EDGE is Wideband CDMA (WCDMA)  Adds packet-switching data channel to circuit- switched voice channel to transmit at 2 Mbps in fixed position and at 300 Kbps when mobile

8 29 Third Generation  Several 3G technologies not yet tested  Actual technologies may be different from those currently proposed  Figure 8-8 shows digital wireless cellular migration paths  Table 8-3 summarizes digital cellular technologies

8 30 Digital Wireless Cellular Migration Path

8 31 Digital Cellular Technologies

8 32 Client Software  Client software that functions on wireless digital cellular devices provide function and user interface to display or manipulate data  Some client software is unique to cellular telephones  Other software may be used in a variety of different applications

8 33 Wireless Application Protocol (WAP)  WAP provides standard way to transmit, format, and display Internet data on cellular phones  Display only textual data because of slow transmission speed and smaller viewing area, as seen in Figure 8-9  Has a microbrowser that uses Wireless Markup Language (WML) instead of HTML, as seen in Figure 8-10  A WAP Gateway, also called a WAP Proxy, changes HTML into WML before forwarding it to cell phone, as seen in Figure 8-11

8 34 WAP Display

8 35 HTML Code

8 36 WAP

8 37 HTML and WML Differences  HTML controls layout, color, font, and styling, while WML controls only font size and basic font attributes, as seen in Figure 8-12  WML uses Extensible Markup Language (XML) and tags that specify how content should be formatted  WML document, called a deck, contains one or more blocks called cards that contain small parts of a text document and navigation controls  One card is displayed on the cell phone at a time as seen in Figure 8-13

8 38 WML Code

8 39 WML Deck

8 40 i-Mode  i-Mode, a Japanese-owned Internet access system, is based on compact HTML (cHTML)  Has its own set of tags and attributes  Users are charged for the service by amount of information downloaded plus a service charge  Expect i-Mode and WAP to merge into one technology in the future

8 41 Java  Developed by Sun Microsystems, Java is an object-oriented language that runs on almost any hardware platform  Java 2 Micro Edition (J2ME) was specifically developed for programming wireless devices  Allows cellular phone to access remote applications and  Can also run programs on cellular phone itself

8 42 Binary Runtime Environment for Wireless (BREW)  BREW, a runtime environment, is a thin software interface, that resides on wireless device  Users can download programs and run them on BREW-enabled devices  BREW uses memory efficiently, occupying only a small amount of flash memory and dynamically allocating RAM  Can be used in combination with other operating systems and any kind of browser

8 43 Limitations and the Future  WAP and i-Mode allow remote access to the Internet  They do not support a rich set of graphics  J2ME and BREW are expected to become major platforms for variety of wireless devices

8 44 Digital Cellular Issues and Outlook  Several issues face digital cellular telephony that prevent its rapid acceptance  Competing technologies—no single road to 3G digital telephony; competing technologies are incompatible  Limited spectrum availability—No part of spectrum is designated exclusively for 3G; is enough spectrum available to meet needs

8 45 Digital Cellular Issues and Outlook  Several issues face digital cellular telephony that prevent its rapid acceptance  High infrastructure costs—3G telephones may cost as much as $300 with $90 monthly charge; carriers will spend billions for infrastructure necessary for 3G  Competition from other wireless options— Bluetooth, IrDA, and a WLANs are less- expensive choices

8 46 Chapter Summary  Two keys to cellular telephone networks are dividing coverage area into cells and using low power levels for transmission  At the center of each cell is a cell transmitter that sends and receives radio frequency (RF) signals  Low-power levels enable signals to stay confined to the cell and not interfere with other cells that use the same frequencies

8 47 Chapter Summary  All cell phones have special codes that identify the owner and carrier or service providers  Handoff is when user moves to another cell and is automatically associated with base station of new cell

8 48 Chapter Summary  Roaming occurs when a user moves beyond coverage area of entire cellular network and connects to network in remote area  Remote area network communicates with home area to verify that user can make calls and is charged appropriately

8 49 Chapter Summary  First generation of wireless cellular technology, known as 1G, uses analog signals and transmits at a maximum speed of 9.6 Kbps  1G uses Advanced Mobile Phone Service (AMPS) standard  Operates in MHz frequency  Uses Frequency Division Multiple Access (FDMA)  Is circuit-switching technology

8 50 Chapter Summary  Second generation, known as 2G, transmits data between 9.6 Kbps and 14.4 Kbps in 800 MHz and 1.9 GHz frequencies  Circuit-switched digital technology  Use three different multiple access technologies:  Time Division Multiple Access (TDMA)  Code Division Multiple Access (CDMA)  Global Systems for Mobile (GSM) communications

8 51 Chapter Summary  Currently, three variations in 2.5G interim generation of packet-switching network technologies:  General Packet Radio Service (GPRS) is for TDMA or GSM 2G networks  Enhanced Data Rates for Global Evolution (EDGE) is considered a “booster” for GPRS systems and can transmit up to 384 Kbps using a new modulation technique  CDMA2000 1XRTT supports 144 Kbps packet data transmission and doubles voice capability of current CDMA networks

8 52 Chapter Summary  3G digital networks transmit at higher speeds and provide new or expanded applications and features  Will require major changes to network infrastructures and a new generation of mobile cellular devices  Widely used in Europe and Japan, Short Message Services (SMS) allows delivery of text-based messages directly between wireless devices

8 53 Chapter Summary  Client software on cell phone is necessary for Internet surfing or videoconferencing  Wireless Application Protocol (WAP) provides a standard way to transmit, format, and display Internet data without requiring rich user interface  WAP cell phone runs microbrowser that uses Wireless Markup Language (WML) to display text- based Web content  A WAP Gateway must translate between WML and HTML

8 54 Chapter Summary  I-mode, another client technology, is based on compact HTML (cHTML)  It has its own set of tags and attributes  Expected I-mode and WAP to merge into one technology in the future  Java 2 Micro Edition (J2ME) is a Java subset for programming wireless devices  Allows cellular phones to access remote applications and programs as well as run programs

8 55 Chapter Summary  Binary Runtime Environment for Wireless (BREW), a thin software interface layer, resides on a wireless device  Allows users to download programs and run them on BREW-enabled devices  Competing cellular technologies, lack of standards, spectrum limitations, and high costs of implementing 3G technology have prevented rapid acceptance of advanced generations of digital cellular telephony

8 56 Chapter Summary  3G networks have competition from other wireless technologies  Top speed for 3G is 2 Mbps standing still, but a WLANs offer speeds over 100 Mbps while mobile  Some carriers install less-expensive stable WLANs in high-traffic “hot spots” in selected cities as alternative to 3G