Cellular Mobile Communications-I An Introduction Dr. Nasir D. Gohar

Cellular Mobile Communications-I An Introduction Cell Phone Growth in Pakistan & Worldwide According to a Media Report (Goliath, May 25, 2005), Cell Phones in Pakistan to Touch 15M mark in December 2005 Another Media Report (Middle East Times, June 20, 2006) Predicts the number of Cell Phones will rise from 2.2 Billion to 3 Billion worldwide by the end of Year 2008 According to MOBILEDIA (Jan 20, 2006) U.S. offers more room for growth than Russia, and Japan offers greater future growth than South Africa The number of mobile subscribers worldwide reached over 2 billion by the end of 2005, and is predicted to rise to 3.96 billion by 2011 The Asia Pacific Region will account for 50% of the total number of subscribers worldwide by the end of this decade with a staggering 1.067 billion subscribers shared between China and India alone, the world's two biggest mobile markets

Cellular Mobile Communications-I An Introduction Several Types of Mobile Radio Systems Garage Door Controller [<100 MHz] Remote Controllers [TV/VCR/DISH][Infra-Red: 1-100 THz] Cordless Telephone [<100 MHz] Hand-Held Radio [Walki-Talki] [VHF-UHF:40-480 MHz] Pagers/Beepers [< 1 GHz] Cellular Mobile Telephone[<2 GHz] Classification Simplex System: Communication is possible in only one direction : Garage Door Controller, Remote Controllers [TV/VCR/DISH] Pagers/Beepers Semi-Duplex System: Communication is possible in two directions but one talks and other listens at any time[Push to Talk System]: Walki-Talki Duplex System: Communication is possible in both directions at any time: Cellular Telephone [FDD or TDD]

Cellular Mobile Communications-I An Introduction Paging System: For Transmission of Brief Numeric/Alpha-numeric/Voice Messages [Pages] to Subscriber To Notify/Alert the User Simplex Service Modern Paging Systems Can Send News Head-Lines, Stock Info, or Fax Application Dependent System Range [2 Km to World-wide]

Cellular Mobile Communications-I An Introduction Cordless Telephone System: To Connect a Fixed Base Station to a Portable Cordless Handset Early Systems (1980s) have very limited range of few tens of meters [within a House Premises] Modern Systems [PACS, DECT, PHS, PCS] can provide a limited range & mobility within Urban Centers

Cellular Mobile Communications-I An Introduction Limitations of Simple Mobile Radio Systems The Cellular Approach Divides the Entire Service Area into Several Small Cells Reuse the Frequency Basic Components of a Cellular Telephone System Cellular Mobile Phone: A light-weight hand-held set which is an outcome of the marriage of Graham Bell’s Plain Old Telephone Technology [1876] and Marconi’s Radio Technology [1894] [although a very late delivery but very cute] Base Station: A Low Power Transmitter, other Radio Equipment [Transceivers] plus a small Tower Mobile Switching Center [MSC] /Mobile Telephone Switching Office[MTSO] An Interface between Base Stations and the PSTN Controls all the Base Stations in the Region and Processes User ID and other Call Parameters A typical MSC can handle up to 100,000 Mobiles, and 5000 Simultaneous Calls Handles Handoff Requests, Call Initiation Requests, and all Billing & System Maintenance Functions

Cellular Mobile Communications-I An Introduction

Cellular Mobile Communications-I An Introduction The Cellular Concept RF spectrum is a valuable and scarce commodity RF signals attenuate over distance Cellular network divides coverage area into cells, each served by its own base station transceiver and antenna Low (er) power transmitters used by BSs; transmission range determines cell boundary RF spectrum divided into distinct groups of channels Adjacent cells are (usually) assigned different channel groups to avoid interference Cells separated by a sufficiently large distance to avoid mutual interference can be assigned the same channel group  frequency reuse among co-channel cells

Cellular Mobile Communications-I An Introduction An Example of Frequency Reuse Suppose we have spectrum for 100 voice channels Scenario 1: a high power base station covering entire area – system capacity = 100 channels Scenario 2: divide spectrum into 4 groups of 25 channels each; cells (1, 7), (2, 4), (3, 5), 6 are assigned distinct channel groups – system capacity = 175 channels

Cellular Mobile Communications-I An Introduction Frequency Reuse Factor Frequency Reuse Factor N = No. of Distinct Channel Groups = Maximum Cluster Size

Cellular Mobile Communications-I An Introduction Frequency Reuse Example-2 Suppose W = 25 MHz and B = 25 KHz/voice channel W/B = 1000 voice channels can be supported over the spectrum Scenario 1: a high power base station covering entire area (M = N = 1)  system capacity n = 1000 users Scenario 2: Coverage area divided into M = 20 cells with reuse factor N = 4 Each cluster accommodate 1000 active users 5 clusters in coverage area  system capacity n = 5000 users Scenario 3: M = 100 cells, N = 4  system capacity n = 25000 users Scenario 4: M = 100 cells, N = 1  system capacity n = 100000 users

Cellular Mobile Communications-I An Introduction Common Air Interface (CAI) Common Air Interface: A Standard that defines Communication between a Base Station and Mobile Specifies Four Channels [Voice Channels and Control / Setup Channels] FVC: Forward Voice Channel RVC: Reverse Voice Channel FCC: Forward Control Channel RCC: Reverse Control Channel Forward Channel Reverse Channel

Cellular Mobile Communications-I An Introduction Call Setup Procedure Cellular Phone Codes: Special Codes are associated with each Cell Phone to identify the phone, its owner, and service provider: Electronic Serial Number(ESN) -A Unique 32-bit Code Mobile Identification Number(MIN): A Subscriber’s Telephone Number Station Class mark (SCM): Indicates the Max Tx Power for the User When a Cellular Phone is turned on and Initiates a Call:[see next slide] Monitors the Control Channels and gets hold on to the strongest one Makes a Call Initiation Request[Dials the Called part Number, MIN , ESN and SCM automatically transmitted] Validation Procedure at MSC & Voice-Frequency pair Allocation Base Station Pages the Information for the Mobile MSC Connects the Mobile with the Called Party[Another Mobile/Landline Phone] Call is Established and Communication Starts

Cellular Mobile Communications-I An Introduction Call Setup Procedure (Cont’d)

Cellular Mobile Communications-I An Introduction Handoff and Roaming Handoff When a Mobile is on the edge of a Cell RSL of the Mobile in that Cell gets bellow a set Level Base Station of the Cell originates a Handoff request MSC gets RSL Info from all the Candidate Cells MSC asks the Originating Cell and the Strongest Candidate Cell to Coordinate In Case the Handoff is Successful, the Mobile is asked to switch to another VFP All this happens in a matter of seconds and you hear a little CLICK sound Roaming When SID of the Control Channel and that programmed in the Mobile does not match: The Mobile is in another Service Provider’s Area MSC of the Cell contacts the MSC of the Mobile’s Home System After Verification, if the Mobile is Allowed, the new MSC is ready to Serve.

Cellular Mobile Communications-I An Introduction Comparison of Common Wireless Communication Systems

Cellular Mobile Communications-I An Introduction Cellular Mobile Access Technologies FDMA Assigns each Call a Separate Frequency Works like Radio Stations Mainly Analogue Technology-used by AMPS, NAMPS, E-TACS, NMT-450, JTACS Not an Efficient Method for Digital Transmission 849 MHz 869 MHz

Cellular Mobile Communications-I An Introduction Cellular Mobile Access Technologies TDMA Assigns each Call a certain Time-Slot on a Designated Frequency Each Mobile/User gets one-third of a total Channel Time-Slot[6.7 ms] Courtesy of Compression Techniques: Speech Data in Digital Form takes considerably less time Optimal Frequency Usage: System Capacity improves by three times Operates both in 800 MHz[IS-54] and 1900 MHz[IS-136] Digital Access Technology use by GSM, USDC, IDEN, PDC and PCS

Cellular Mobile Communications-I An Introduction Cellular Mobile Access Technologies CDMA Assigns a Unique Code to each Call and Spreads it over the entire bandwidth available A form of Spread Spectrum Technology Speech Data is sent in small pieces over number of Discrete Frequencies available at any time in a specified range Receiver uses the same unique Code to Recover the Speech Data GPS used for Exact Time Stamp Can handle 8-10 Calls in the same Channel Space as one Analogue Channel An Access Technology for 3G Mobile Systems[IMT-2000] Supports both Bands [800 MHz and 1900 MHz]

Cellular Mobile Communications-I An Introduction Cellular System vs. Personal Communication System/Network (PCS/PCN) Personal Communication Services [PCS] is a system, very similar to Cellular Phone Service with great emphasis on personal services (such as Paging, Caller ID, and E-mail] and mobility Originated in UK, to improve its competitiveness in the field PCS has smaller Cell size, therefore, requires more infra-structure PCS works in 1.85-1.99 GHz band PCS uses TDMA Technology but with 200 KHz Channel Bandwidth with eight time-slots[as compared to 30 KHz and 3 time-slots used by Digital Cellular Phone System IS-54/IS-136] GSM and Cellular Digital Packet Data[CDPD] also use PCS Tech.

Cellular Mobile Communications-I An Introduction Dual Band/Dual Mode Cellular Phones Dual Band Phone: Supports both bands 800 MHz and 1900 MHz Dual Mode Phone: Supports both FDMA and TDMA Access Technologies Dual Band/Dual Mode Phone: Supports both Bands and Both Access Technologies Tri-Mode Phone: It can Support FDMA/TDMA/CDMA all Access Tech. A popular version of Tri-Mode Cellular Phone is the one which supports GSM [800 MHz as well as 1900 MHz (USA version)] as well as FDMA.

Cellular Mobile Communications-I An Introduction Trends in Cellular radio and Personal Communications PCS/PCN: PCS calls for more personalized services whereas PCN refers to Wireless Networking Concept-any person, anywhere, anytime can make a call using PC. PCS and PCN terms are sometime used interchangeably IEEE 802.11: A standard for computer communications using wireless links[inside building]. ETSI’s 20 Mbps HIPER LAN: Standard for indoor Wireless Networks IMT-2000 [International Mobile Telephone-2000 Standard]: A 3G universal, multi-function, globally compatible Digital Mobile Radio Standard is in making Satellite-based Cellular Phone Systems A very good Chance for Developing Nations to Improve their Communication Networks