wireless and mobile communications by ugr
- 1. Evolution of Mobile Radio Communication • Wireless Communication isenjoyingits fastest growth period in history dueto enabling technologieswhich permit wide spreaddeployment. • Wireless Communication wasmadeavailable to the entire population when Bell laboratories conceivedthe Cellular conceptin the 1960sand1970s. • With the development of highly reliable, miniature, solid state radio frequency hardware in the 1970s,the wireless communications erawasborn. • Figure given illustrates how mobile telephony has penetrated our daily lives comparedwith other popular inventions of the 20thcentury. • With the boom in CB radio and cordless appliances , number of users of mobile and portable radio in 1995wasabout 100million or 37%of the U.S.population. • The number of cellular telephone users grew from 25000 in 1984 to about 16 million in 1994 and since then wireless services have experienced customer growth rateswell in excessof 50% peryear.
- 2. PagingSystems • Paging systems are communication systems that send brief messages to a subscriber. Depending on the type of service the messagemay be a numeric, alphanumeric or voice message. • Paging systems are used typically to notify a subscriber the need to call a particular telephone number or travel to known location to receive further instructions. • In modern paging systems, news headlines, stock quotations and faxes maybesent. • A message is sent to a paging subscriber via the paging system access number with telephone keypad or modem. The issued message is called a page. The paging system then transmits the page throughout the service area usingbasestations which broadcast the pageonaradio carrier.
- 3. • Pagingsystemsvary widely in their complexity and coveragearea. • Simple paging systems cover a limited range of 2 km to 5 km. They are confined to within individualbuildings. • Wide areapaging systemcanprovide worldwide coverage.They consistof a network of telephone lines, manybasestation transmitters and large radio towers that simultaneously broadcast apagefrom eachbasestation which is called simulcasting. Simulcasttransmitters maybelocated within the same serviceareaor in different countries or cities. • Paging systems require a large transmitter power and low data rates for maximum coveragefrom eachbase station. • The diagram of awide areapagingsystemisasshown.
- 6. • Cordless telephone systems are full duplex communication systemsthat use radio to connectaportable handsetto adedicated basestation, which isthen connectedto adedicated telephone line with aspecific telephone numberon the public switched telephonenetwork. • First generation cordless telephone systems in the 1980s had the portableunit communicating only to the dedicated base unit and only over distances of a few tens of meters. Early cordless telephones operated solely as extension telephones to a transceiver connected to a subscriber line on the PSTN and were primarily for in-homeuse. Secondgeneration cordlesstelephonesallow subscribersto usetheirhandsets at outdoor locations within urbancenters. • Modern cordless telephones are sometimes combined with paging receivers so that a subscriber may first be paged and then respond to the page using the cordless telephone. • Cordless telephone systems provide the user with limited range and mobility as it is usually not possible to maintain acall if the usertravels outside the rangeof the basestation. • Typical second generation base stations provide a coverage of up to a few hundredsof meters.
- 7. Comparison of commonmobile radio systems
- 8. Comparison of commonmobile radio systems
- 9. Introduction to cellular telephone systems • Cellular telephone began as a relatively simple concept. However, the increased demand for cellular services has caused cellular telephone systems to evolve into complicated networks and internetworks comprised of several types of cellular communications systems. • Cellular telephone beganasa relatively simple two-way analog communications system using frequency modulation (FM) for voice and frequency-shift keying (FSK) for transporting control and signaling information. • The most recent cellular telephone systems use higher-level digital modulation schemes for conveying both voice and control information. In addition, the Federal Communications Commission has recently assigned new frequency bandsfor cellular telephone.
- 10. First-generation analog cellular telephone • First generation cellular and cordless telephone networks are based on analog circuit switching technology. The first 1Gmobile phone was introduced in the USA in 1980. FDMA was the multiple access technique used and worked mainly in the 800-900 MHz frequency bands. The 1Gmobile phone had only voice facility. • Examples of 1G systems are AMPS (Advanced mobile phone service) and TACS (total access communicationsystems) • The limitations of 1Gare: • SupportsSpeechonly • Low traffic capacity • Unreliable handover • Longcall setup time • Frequent call drops • Inefficient bandwidth usage • Poorbattery life • Poorvoice quality • Largesizeof handset • Allowed usersto makevoicecallswithin acountry only
- 11. • A typical example of a cellular telephone system is the Advance Mobile Phone Services (AMPS) system used in the United States. In 1971, Bell Telephone Laboratories in Murry Hill, New Jersey, proposed the cellular telephone concept as the Advanced Mobile Telephone System (AMPS). AMPS is a standard cellular telephone service (CTS) initially placed into operation on October 13, 1983, by Illinois Bell that incorporated severallargecell areasto coverapproximately 2100squaremilesin the Chicago area. • Basicallyall first generation systemsusethe transport architecture shownin thefigure
- 12. Blockdiagram of afirst- generation analogcellular telephonenetwork
- 13. • The block diagram of a first generation cellular telephone network is shown in the figure . • The system control for each market resides in the MSC which maintains all mobile related information and controls each mobile handoff. The MSC also performs the functions of network management, call handling and processing,billing and fraud detection within themarket. • The MSC is interconnected with the PSTN via the landline trunked lines and a tandem switch. MSCs are connected with other MSCs via dedicated signaling channelsfor exchangeof location, validation and call signaling information. • First generation wireless systems provide analog speech and inefficient low-rate data transmission between the base station and the mobile user. The speech signals are usually digitized using a standard TDM format for transmission between the base station and the MSC and are always digitized for distribution from the MSC to the PSTN.
- 14. Second-generationwireless telephone networks • First-generation cellular telephone systems were designed primarily for a limited customer base, such as business customers and a limited number of affluent residential customers. The problems inherent with these cellular telephones were poor battery performance and channel unavailability. Improved batteries were also needed to reduce the size and cost of mobile units, especially those that were designed to be handheld. Weak signal strengths resulted in poor performance and ahigh rate of falsely initiated handoffs (false handoffs). • It wasdetermined that improved battery performance and higher signalquality were possible only by employing digital technologies. • In the United States, the shortcomings of the first-generation cellular systems led to the development of several second-generation cellular telephone systems, such as narrowband AMPS (N-AMPS) and systemsemploying the IS-54, IS-136, and IS-95 standards. • A second-generation standard, known as Global System for Mobile Communications (GSM), emergedin Europe. The U.S Standards of TDMA and CDMA alsobelong to this generation. • Other second generation wireless standard include the British Cordless telephone standard CT2, Personal access Communication System (PACS) and the European standard for cordless and office telephony Digital EuropeanCordlesstelephone( DECT). • 2 G technology supports data, speech,fax, smsand WAP services.
- 15. • The architecture employed in secondgeneration networks havereduced the computational burden onthe MSC. • GSM for example uses a base station controller (BSC) which allowed the data interface between the BSC and MSC to be standardized. This allows carriers to use different manufacturers for MSC and BSCcomponents. • All Second generation systems use digital voice coding and digital modulation. The systems employ dedicated control channelswithin the air interface for simultaneously exchanging voiceand control information between the subscriber,the basestation and the MSC whilethe call isin progress. • Secondgeneration networks alsoprovide dedicated voiceand signaling trunks between MSCs and between eachMSC and the PSTN. • The first generation systems were designed primarily for voice whereas the second generation systemsarespecifically designed to provide paging, Fax and high data rate internet access. • The network controlling structure is more distributed in second generation networks since mobile stations assumegreater control functions. • The handoff process is more mobile controlled and is known as Mobile assisted handoff (MAHO). The mobile units perform additional functions of received power reporting, adjacent basestation scanning, data encodingandencryption.
- 16. • DECT (Digital European Cordless telephone) is an example of a second generation cordless standard. It allows each cordless phone to communicate with any number of base stations. The base station with the greatest signal level is selected. The base stations havegreater control in terms of switching, signalingand controlling handoffs. • In general,secondgenerationsystemshavebeendesignedto reducethe computational and switching burden at the basestation or MSC. They alsoprovide moreflexibility in the channel allocation schemesothat systemsmaybedeployed rapidly and in a less coordinatedmanner. • The limitations of 2Gare • Low data rates ranging from 9.6 kbps to 28.8kbps • Circuit switchednetwork • End systemsarededicated for the entire callduration • Inefficient usageof bandwidth and resources
- 17. Interim 2.5 G -generation wireless telephonenetworks • The needfor increasedthroughput data rates in data transfer suchasweb browsing and email led to the evolution of 2.5 G which isbetween 2gand3G. • The mobile technologyusingGPRS(General Packet Radio Service) hasbeen termed as2.5G. • The 2.5 G wasstarted in 1998with added GPRSand enhanced data rates for GSM evolution (EDGE). In addition to the Hypertext transfer protocol (HTTP) it supports the Wireless Access Protocol (WAP) through which web pages can be viewd on the small screen of a mobile phone or a handheld device which led to the development of mobile commerce(m-commerce). • 2.5 G ispacket switched and canusesomeof the existing infrastructures of GSM and CDMA (Code division multiple access)networks.
- 18. Third-generation wireless telephonenetworks • The aim of third generation wireless networks is to provide a single set of standards that can meet a wide range of wireless applications and provide universal access throughout the world. • In 3 G networks the distinctions between cordless telephones and cellular telephones disappear and a universal personal communicator or personal handset provides access to avariety of voice,data and video communication services. • 3rd generation systems use the Broadband ISDN to provide access to information networks suchasthe internet and other private and publicdatabases. • 3G networks carry all types of information like voice,data andvideo. • They operate in denselypopulated and sparselypopulated areas. • They serveboth stationary usersand vehicular userstravelling at high speeds. • Packet radio communicationisusedin the 3G networks • Personal communication System (PCS) ,International Mobile Telecommunication (IMT-2000) and Universal Mobile telecommunication System(UMTS) are examples of 3G wirelessnetworks. UMTS isalsoknown asW-CDMA(WidebandCDMA)
- 19. • 3G technology hasadded multimedia facilities to 2.5 G phones. • 3G operatesin the 1710-2170MHz band • In short 3G is the next generation of wireless network technology that provides high speed bandwidth (high data transfer rates) to handheld devices. The high data transfer rates will allow 3G networks to offer multimedia services combining voice and data. • Main characteristics of 3G networks include • Always-on connectivity. 3G networks useIP connectivity, which ispacketbased. • Multi-media serviceswith streaming audio andvideo. • Email with full-fledged attachments suchasPowerPointfiles. • Instant messagingwith video/audioclips. • Fast downloads of largefiles suchasfaxesand PowerPoint files. • Accessto corporate applications. • Applications include Mobile TV, Video ondemand, Video conferencing, Telemedicine, Location based services.
- 20. Fourth-generation wireless telephone networks • 4th-generation networks emerged asa data-optimized technology with the promise of speedimprovements up to 10-fold overexisting 3G technologies. • It is basically the extension in the 3G technology with more bandwidth and services offers in the 3G. • The expectation for the 4G technology is basically the high quality audio/video streaming over end to end Internet Protocol. The transmission rates of 4G will be upto 20Mbps higher than that of3G. • The first two commercially available technologies billed as 4G were the WiMAX standard and the LTE standard. LTE – Advanced isthe newest versionof LTE. • One of the main ways in which 4G differed technologically from 3G was in its elimination of circuit switching, instead employing an all-IP network. 4G utilizes packet switching overinternet, LAN or WAN networks via VoIP. • 4G technology is meant to provide what is known as “ultra-broadband” access for mobile devices. It is set to deliver 100 Mbps to a roaming mobile device and up to 1 Gbpsto astationary device. • 4G will bring the perfect real world wireless inter networking called WWWW: World Wide WirelessWeb.
- 21. • 4 G allows for video conferencing, streaming picture perfect video for telemetric applications • OFDMA multi-carrier transmission methods ,frequency-domain equalization (FDE) methods, MIMO (Multiple Input Multiple Output) and Turbo Code techniques are usedin 4 Gnetworks. • Peakdata rates for 4G networks must becloseto 100megabit per secondfor auseron ahighly mobile network and 1gigabit per secondfor auserwith local wireless access or anomadic connection. • True 4G must alsobeable to offer smoothhandoversacrossdiffering networks without data lossand provide high quality of servicefor next-gen media. • One of the most important aspects of 4G technology is the elimination of parallel circuit-switched and packet-switched network nodes using Internet Protocol version 6 (IPv6). The currently used standard, IPv4, hasa finite limitation on the number of IP addressesthat canbeassignedto devices,
- 22. Comparisonof the different generations • A short history of the evolution from 1Gto 4G isshownbelow. • 4G is not a single defined standard but rather a collection of technologies and protocols aimed at creating fully packet-switched networks optimized fordata.
- 23. • Someexamplesof mobile communication systemscurrently in usein addition to the cellular radio networksare • Wireless LocalLoop(WLL) • Wireless Localareanetworks (WLAN) • PersonalArea Networks(PAN) • Bluetooth • Worldwide Interoperability for Microwave Access (WiMAX)
- 24. Wireless local Loop(WLL) • WLL is a cellular –like phone without mobility. These are designed for fixed communications where it is easier, cheaper or more advantageous than wire line connectionsand areoften basedoncellular or cordless technologies. • WLL employs a cellular-like technology where the subscriber unit is fixed like a wire line telephone. Thus the local loop between the exchange and the subscribers home is replaced with awirelesslink. The samebasicarchitecture and principles of radio communicationareused. • Fixed wirelessequipment isextremely well suited for rapidly deploying abroadband connection in homes and offices. These fixed wireless systems are able to take advantage of the very well-defined, time-invariant nature of the propagation channel between the fixed transmitter and fixedreceiver. • They are assigned microwave or millimeter frequencies in the 28 GHz band and hence the wavelengths are extremely small. Thus very high gain directional antennas are required. These high gain antennas reject multipath signals and in turn supports the transmission of very wide bandwidth signals.
- 25. • A WLL can be created asshown in the figure. The local loop is the last mile connection between the Central Office and individual homes and offices. Copper or fibre optic cables are installed to these destinations and canbeleasedfrom aservice provider onamonthly basis. • An advanced service that has beenproposedto make efficient use of the WLL technology is the Local Multipoint Distribution Service (LMDS) which provides broadband telecommunications access in the local exchange. The U.S LMDS band is in the 27-31 GHz range.
- 26. • A wireless local area network (WLAN) is a wireless distribution method for two or more devices that use high-frequency radio waves or spread spectrum and often include an accesspoint to the Internet. A WLAN allows usersto move around the coveragearea, often ahomeor small office, while maintaining anetwork connection. • The FCC hasallocated 300 MHz of unlicensedspectrum in the ISM bandsof 5.1GHz and 5.8 GHz rangefor supporting private computer connectionsby WLAN. TheIEEE 802.11 WLAN standard is the popular standard for the use of internet and wireless communication. • Types ofWLAN • Peerto peer–allows wirelessdevicesto directly communicatewith eachother. • Bridge-an Ethernet bridge actsasthe connection point to the wirelessLAN
- 27. Wireless LocalArea Network (WLAN) • Figure illustrates the evolution of the IEEE 802.11WLAN standards
- 28. • Both frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DS-SS) were used in the early IEEE 802.11 standard with 2MBps throughput. • Later only DS-SS was standardized for high rate 1 1 Mbps user data rates by the IEEE 802.11bstandard. This DS-SSIEEE 802.11bhasbeennamed Wi-fi. • The High performance Radio LocalArea Network (HiPERLAN) wasdeveloped to provide similar capability to IEEE 802.11.This was intended to provide individual wireless LANs for computer communications and usedthe 5.2 GHz and 17.1GHz frequency bands.
- 29. PersonalArea Network (PAN) • PAN represents the interconnection of information technology devices within the rangeof anindividual persontypically within 10m, • This like a person while travelling with a laptop, Personal Digital Assistant (PDA) and a portable printer could interconnect them without having to plug in anything or by usingsomeform of wireless technology. • This kind of PAN alsocould beinterconnected without wires to theInternet. • The basicdifference between PAN and W AN isthat PAN iscentered around one personwhile the latter servesmultiple users. • The PANs canbeconstructed with cablesor wirelessUSB • Firewire technology links together awired PAN • Wireless PAN uses Bluetooth or Infrared connections. Bluetooth PANs are also called piconets. • A piconet schematic isshownin the figure.
- 30. • Piconet is formed by a composition of upto 8 devices in a master-slave relationship. The first Bluetooth device is called the master and all the others are slaves.These slaves communicate with the master within a range of 10m.Bluetooth is wireless PAN which uses the IEEE 802.15 standard.
- 31. Bluetooth Technology • Bluetooth is a short-range wireless communication technology that allows devices such as mobile phones, computers, and peripherals to transmit data or voice wirelessly over a short distance. The purpose of Bluetooth is to replace the cables that normally connect devices, while still keeping the communications between them secure. The devices can communicate within anominal rangeof 10m. • The "Bluetooth" name is taken from a 10th-century Danish king named Harald Bluetooth, who was said to unite disparate, warring regional factions. Like its namesake, Bluetooth technology brings together abroad rangeof devicesacrossmanydifferent industries through aunifying communication standard. • Bluetooth operates in the 2.4 GHz ISM band • It usesthe frequency hopping spreadspectrumtechnique. • The standard followed isIEEE 802.15. • The modulation usedisGaussianFSK (GFSK). • Data transfer rate of 1Mbps. • Useful for data transfer between two devices that are near to each other in low bandwidth situations. • Connection and exchangeof information between mobile phones,laptops, PCs,GPSreceivers, printers ,digital cameras,video gameconsolesetc ismade possible.
- 32. WiMAX Technology • WiMAX standsfor Worldwideinteroperability for Microwave Access. • This technology enables universal delivery of wireless broadband service for fixed mobileusers. • The technology isbasedonthe IEEE 802.16standard and uses OFDMA. • Alsoknown aswireless metropolitan areanetworks(WMANs) • This technology provides broadband wireless connectivity acrossalarge geographical areasuchasametro city. • Mobile WiMAX isbasedonthe IEEE 802.16estandard which provides mobilityand roaming access. The IEEE 802.16e standard uses OFDMA interface and gives better performance in non-line-of-sight(NLOS) environments. • WLANs and WPANs restrict the mobility of users to a few hundreds of metres from the source.LOSalsohasto be maintained. • IEEE 802.16 and WiMAX are designed as complimentary technology to WiFi and Blutetooth. The original 802.16a standard specified transmissions in the range 10 - 66 GHz. Different bands are available for WiMAX applications in different parts of the world. The frequencies commonly used are 3.5 and 5.8 GHz for 802.16d and 2.3, 2.5 and 3.5 GHz for 802.16e.
- 34. • WiMAX architecture comprisesof severalcomponents. • The basictwo components areBaseStation (BS) and Mobile Station(MS). • Mobile station isfor the end userto accessthe mobile network. It isaportable station that is ableto moveto wide areasand perform data and voicecommunication. It hasall the necessary userequipment suchastransmitter, receiver, antenna, amplifier and all the required software for communication. • The architecture isbasedonapacket-switched framework. • The mobile station usesGSM,CDMA,W-CDMA,TDMA,FDMA devices. • ASN isthe accessservicenetwork and createsradio accessalongwith ASN gateways. The gateway controls the accessin the network and coordinates between data and networking elements. • CSN is the connectivity service network which provides IP connectivity to the internet or other public or corporate networks. It also applies per user policy management, address management, location management between the ASNs and ensures quality of service, roaming and security.ASPisthe accessserviceprovider. • Home Agent, HA: The Home Agent within the WiMAX network is located within the CSN., the Home Agent works in conjunction with the ASN Gateway, to provide an efficient end-to- end Mobile IP (MIP) solution. • An Authentication, Authorisation andAccounting Server(AAA) isincluded within the CSN.