Wireless & Mobile Communication

Wireless & Mobile CommunicationFreeha AzmatMobile Radio CommunicationIn last 10 years, this industry is fueled by:

Digital RF circuit FabricationNew Large Scale Circuit IntegrationMiniaturization Technologies which make portable radio equipment cheaper, smaller and more reliableElectronics boom :

Evolution of Mobile Communication1946:Mobile telephone services in 25 major American cities120KHz of RF bandwidth in half duplex mode1950 &1960:IMTS(Improved Mobile Telephone service) came which offered full duplex communicationIMTS became saturated due to availability of less channels1950 and 1960: AT &T labs and other telecom companies developed the theory and techniques for cellular radiotelephony : The concept of breaking a coverage zone into small cells, each of which reuse portions of spectrum to increase spectrum usage at the expense of greater system infrastructureAT &T proposed the concept of cellular mobile system to FCC in 1968,although the technology wasnt present to implement the concept.In 1983 FCC allocated 666 duplex channels (40MHz spectrum in 800MHz band) Additional 10MHz(166 channels) were allocated in 1989 which made the total spectrum of 50MHzJanuary, 2006 Frequency Allocation in the US for AMPS

EvolutionAMPS (Advance Mobile Phone Service) In 1970s,AT&T labs developed the first US cellular telephone system called the AMPS (Advance Mobile Phone Service) By mid 1960s,the FM bandwidth of voice transmission was cut to 30KHzETACS(European Total Access Communication System) Developed in 1980sIdentical to AMPS except the bandwidth was reduced to 25kHz

Evolution (Cont)USDC (US Digital Cellular System) :In 1991,the first digital cellular system hardware was installed in major US cities.Support 3 users in the same 30kHZ bandwidthCDMA (Code Division Multiple Access):Cellular system based on CDMA Can support variable users in 1.25MHz wide channelImprovement in capacity due to FM techniquesJanuary, 2006Major Mobile Radio Standards in North America

January, 2006Major Mobile Radio Standards in Europe

January, 2006Major Mobile Radio Standards in Japan

January, 2006Wireless Communications System Definitions:

Wireless Communication System Definitions:

Types of Mobile Radio Systems:1)SimplexRadio/TV broadcast2)Half-Duplex push to talk and release to listen3) Full Duplex:Cell Phone Full duplex requirement:FDDTDDFrequency Division Duplexing(FDD)Simultaneous Radio transmission channels for the subscriber and base station.To facilitate FDD, it is necessary to separate the transmit and receive frequencies by about 5% of the nominal frequency.

Time Division DuplexingShare a single radio channel in timePortion of the time consumed from base station to mobile and vice versaPreferred for indoor or small area wireless applicationsDo you know why?

Comparison of FDD and TDD:FDD is efficient in case of symmetric trafficIt makes radio planning easier because base stations do not hear each other. With TDD systems, guard bands between neighboring base stations is necessaryTDD has a strong advantage where asymmetry of the uplink and downlink data speed is variable.As the amount of uplink data increases, more bandwidth can dynamically allocated to that and vice versaPaging SystemsThose communication systems that send brief messages to subscriber. The message may either beA numeric messageAn alphanumeric messageA voice message The issued message is called Page. In modern Paging system, news headlines, stock quotations and faxes may be sentPaging systems vary on the basis of complexity and coverage area

A wide area Paging System

Simulcast transmitters can be located in the same service area or in different cities and countries A cordless Telephone system

1st generation Cordless Telephone systems2nd GenerationJanuary, 2006A Cellular System

January, 2006Definitions/AcronymsCAI: Common Air InterfaceFor communication between the base station and the mobileIt has 4 different channelsFVC: Forward Voice Channel (from base station to mobile)RVC: Reverse Voice ChannelFCC: Forward Control ChannelRCC: Reverse Control Channel** Control channels are often called setup channels because they are involved in setting up a call and moving to unused channel**Control channels contain handoff instructions** Control channels make up about 5% of the total channelsJanuary, 2006Definitions/Acronyms (contd.)MSC: Mobile Switching Center also called MTSO: Mobile Telephone Switching officePSTN: Public Switched Telephone Network

Call setup Procedure:1.ESN(Electronic Serial Number):

Is unique 32bit identification number embedded in a wireless phone by the manufacturer. Each time a call is placed, the ESN is automatically transmitted to the base station.ESN cannot easily be altered in the field.ESN can be checked electronically to prevent the fraud.2.MIN(Mobile Identification number)Is 24 bit number corresponding to the actual 7 digit telephone number assigned by the cellular carrier exclusively to a phone, used for billing and for receiving calls.The MIN is paired with ESN. Theoretically both numbers are verified, and in combination, every time a call is placed in order to verify the legitimacy of the call and device3.System Identification Number(SID)Is unique 5-digit number that has been assigned to identify the particular cellular carrier i.e. the service provider, from whom you are obtaining service. This number identifies your home systemJanuary, 2006How a Cellular Telephone Call is MadeFrom Land line to MobilePSTNMSCMIN: mobile identification numberMINFCC

MINRCCFree channelsJanuary, 2006Timing Diagram Illustration for Call from Land line to Mobile

29Fig. 1.6January, 2006How a Cellular Telephone Call is Made From Mobile to Land line PSTNMSCMIN: mobile identification number

Free channelsMIN/telephone #RCCMIN/telephoneJanuary, 2006Timing Diagram Illustration for Cal from Mobile to Land line

31Fig. 1.7Frequency ReuseThe problems with cellular concept was:Spectral congestionUser capacityLinear Cells as an Example of Frequency Reuse

f1f2f3f1f2f3PICell 1Cell 2Cell 3Cell 1Cell 2Cell 3Cluster 1Cluster 2Total Band width (BW) is divided into three adjacent bands f1, f2 and f3Such that BW = f1+f2+f3Cluster Size1231231231234123412343 Cell Cluster4 Cell Cluster