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MobileCommunication

MobileCommunication

Instructor: Swarup Sinha Ray

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Learning ObjectivesLearning ObjectivesLearning ObjectivesLearning Objectives

• To support you to refresh the basics of cellular To support you to refresh the basics of cellular technologiestechnologies

• To know the scope of functioning in cellular To know the scope of functioning in cellular environment environment

• To explain the technical aspects of cellular To explain the technical aspects of cellular telecommunicationstelecommunications

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Course AgendaCourse AgendaCourse AgendaCourse Agenda

– Access Method & Wireless AccessAccess Method & Wireless Access– Multiple AccessMultiple Access– Mobile Service Mobile Service – Evolution of Cellular CommunicationEvolution of Cellular Communication– GSM BasicsGSM Basics– Mobile NetworkMobile Network– Cellular Telephony in IndiaCellular Telephony in India– CDMA BasicsCDMA Basics– CDMA vs GSMCDMA vs GSM– Wireless in Local LoopWireless in Local Loop– Mobile Data (3G)Mobile Data (3G)

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Access MethodsAccess MethodsWIRELINEWIRELINE• CopperCopper

– Local Loop 2 Wire (analog) Local Loop 2 Wire (analog) e.g. Plain Old Telephone systeme.g. Plain Old Telephone system

– Local Loop 4 Wire (digital) Local Loop 4 Wire (digital) e.g. E1 line, E3 linee.g. E1 line, E3 line

• Optic FiberOptic Fiber• ModemModem

– OpticalOptical

– ISDN BRIISDN BRI

– Digital Subscriber Line (DSL - 2 wire) Digital Subscriber Line (DSL - 2 wire)

WIRELESSWIRELESS• MicrowaveMicrowave

– LMDS – Local Multichannel Distribution ServiceLMDS – Local Multichannel Distribution Service

– MMDS – Multipoint/Microwave Multichannel Distribution ServiceMMDS – Multipoint/Microwave Multichannel Distribution Service

– UBR – Unlicensed Band Radio LinkUBR – Unlicensed Band Radio Link

• VSAT = VSAT = Very Small Aperture TerminalVery Small Aperture Terminal

• CellularCellular– GSMGSM

– CDMA 2000 1xCDMA 2000 1x

• Wi-MAX, Wi-FiWi-MAX, Wi-Fi

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Electromagnetic WaveElectromagnetic WaveElectromagnetic WaveElectromagnetic Wave

• Light (Optic Fiber Cable)Light (Optic Fiber Cable)• Infrared for device to device data transferInfrared for device to device data transfer• Microwave Microwave

– VSAT (Very Small Aperture Terminal) + SatelliteVSAT (Very Small Aperture Terminal) + Satellite– LMDS (Local Multichannel Distribution system)LMDS (Local Multichannel Distribution system)– MMDS (Multipoint Multichannel Distribution system)MMDS (Multipoint Multichannel Distribution system)– WiMAX WiMAX (Worldwide Interoperability for Microwave Access)(Worldwide Interoperability for Microwave Access)

• RadioRadio– UBRS (Unlicensed Band Radio system) (2.4 GHz)UBRS (Unlicensed Band Radio system) (2.4 GHz)– WiFi (Wireless Fidelity) (2.4 GHz)WiFi (Wireless Fidelity) (2.4 GHz)– Cordless / Walkie TalkieCordless / Walkie Talkie– Cellular (450 MHz, 800MHz, 900 MHz, 1.8 GHz, 1.9 GHz)Cellular (450 MHz, 800MHz, 900 MHz, 1.8 GHz, 1.9 GHz)

2.5 GHz / 2.7 GHz3.3 GHz / 3.5 GHz5.2 GHz / 5.7 GHz10.5 GHz24.5 GHz / 26 GHz54 GHz / 66 GHz

2.5 GHz / 2.7 GHz3.3 GHz / 3.5 GHz5.2 GHz / 5.7 GHz10.5 GHz24.5 GHz / 26 GHz54 GHz / 66 GHz

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Multiple AccessMultiple AccessMultiple AccessMultiple Access

To share communication channels or physical communication mediums (air interface in case of wireless) between multiple usersMultiple access techniques developed due to Digital technology

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Frequency & Time Division Multiple AccessFrequency & Time Division Multiple Access

• User’s channel is specific RF channel • Multiple users access each channel w/o

interference• Each user is allocated unique time slots

within each channel• Current cellular standard divides signals into

6 time slots• Each signal uses 2 slots, hence allowing 3

signals per channel• Hence the channel belongs to the user

during the time slots in a repeating sequence• Problem of bandwidth wastage if no signal

Time

FrequencyChannel

FDMA

Time

FrequencyChannel

TDMA

User’s channel is private radio frequency (RF) channel during the duration of callWhen call is finished channel is released for another userLow radio capacity (no. of users)

Extended TDMA corrects the problem of wasted bandwidth by creating buffer queue for allocation of channel

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DuplexingDuplexing• Duplex communication system

– signal can flow in both directions between connected parties

• Half-duplex system – allows communications in both directions, but only one direction at a time

(not simultaneously)– Example: Radio, Walkie-Talkie, Push-to-Talk (PTT), Taxi Despatch

system, Police system

• Full-duplex system – allows communication in both directions, and allows this to happen

simultaneously– Example: Telephone, Mobile phone allows to talk & listen simultaneously

• Point-to-Multipoint Network– Frequency Division Duplexing (FDD) is the application of FDMA to

separate outward and return signals• Example: GSM combines the use of FDD to prevent interference between

outward and return signals, with TDMA to allow multiple handsets to work in a single cell.

– Time Division Duplexing (TDD) is the application of TDMA to separate outward and return signals

• Example: LMDS, MMDS, UBR, WiFi / Wi-MAX

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Elements of Mobile CommunicationElements of Mobile Communication

• Mobile Station (MS) (Mobile Subscriber Unit)– Mobile Telephone– Fixed Wireless Telephone

• Base station• Mobile station talks to many mobile stations at once, using

one channel per mobile• Each mobile station uses a separate, temporary RF based

channel to talk to base station• Channels use a pair of RF for communication

– Forward link (down link)– Reverse link (up link)

• Mobile Telephone Switching Office (MTSO)– Mobile Switching Center– Point of Interconnect (PoI) with Public Switch telephone Network

(PSTN)– PoI with other Mobile Service Provider

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Mobile Radio ServiceMobile Radio Service

Mobile radio service operates in a closed networkVery powerful transmitter located at the highest spot in an areaTransmission upto 50 km radius like television broadcast

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Mobile Radio Telephone SystemMobile Radio Telephone System

M TSOBase

Station

MTSO = Mobile Telephone Switching Office

PSTN

• 1946 – First car-based mobile system set-up in St. Lious• 1977 – First frequency modulation based cellular telephone system by

Bell Labs• 1981 – Nordic Mobile Telephone (NMT) was introduced as first

Commercial Cellular Services in the Nordic countries• 1983 - Advanced Mobile Phone System (AMPS) standard (Analogue)

was released in the US using 800 MHz to 900 MHz frequency and 30 kHz bandwidth for each channel

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Evolution of Cellular CommunicationEvolution of Cellular CommunicationEvolution of Cellular CommunicationEvolution of Cellular Communication

2G Cellular Technologies2G Cellular TechnologiesGSM (GSM (Global System for Mobile Communications)

CDMA (Code Division Multiple Access)CDMA (Code Division Multiple Access)

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Comparison ChartComparison Chart

Technology Theory

Calls / Omni Cell

Actual

Calls / Omni Cell

AMPS 6 6

D-AMPS (IS-54/136) 36 18

GSM 8 8

CDMA 22 / 14 22 / 14

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Evolution of GSMEvolution of GSM

- 1982: Groupe Speciale Mobile (GSM) was instituted by a group of European Committees. Later name was changed to Global System for Mobile Communication

- 1987: GSM design considered the following objectives - To enable greater capacity compared to 1G (analogue)- To offer good spectral efficiency - To support international roaming- To ensure inter-operability of network elements of different

vendors To offer good subjective speech quality- To keep phone or terminal cost low - To allow terminals to be handheld- To offer ISDN compatibility- To ensure privacy

- 1991: Commercial system start-upITU = International Telecommunications Union

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GSM DesignGSM Design- Digital technology, Cellular Architecture- Narrowband TDMA was chosen as the Access method- Defines Radio Frequency / Air Interface

- Deployed using radio frequency band of 900 MHz or 1800 MHz in Europe and 800 MHz or 1900 MHz in the US

- Difference between uplink and downlink frequencies is 80 MHz- eg. 933-960 MHz for uplink & 890-915 MHz for downlink

- Spectrum efficiency through usage of digital TDMA combined with 200 kHz RF channel separation

- GSM channels are time division multiplexed to enable upto 8 users to access each carrier

- Transmission rate over the air @ 270.833 kbps• Management Overhead causes data rate available to each time slot of 24.8 kbps

• Error correction to overcome problems of interference requires around 11-12 kbps

• Available data rate for transporting digitally encoded voice / data = 13 kbps

- Carrier modulation uses Gaussian Minimum Shift Key (GMSK) causing usage of narrow bandwidth and constant power level

- Defines Network Elements to fulfill objectivesITU = International Telecommunications Union

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Cellular ArchitectureCellular Architecture• CELL

– Basic geographic unit of cellular system– CGI = Cell Global Identity to identify each cell – FOOTPRINT = Coverage region around Base Stations are divided into

honeycomb shape (hexagon) or cell coverage area– Cell coverage area or size depends on landscape, natural terrain, man-

made structures and hence may not be perfect hexagons• CLUSTERS

– Interference problems are caused by mobile units using the same channel in adjacent areas led to cell wise channel allocation

– Interference effects are lowered by reducing the distance between cell areas (radius) to BTS

– Group of cells in which channels are not reused– FREQUENCY PLANNING through 7 cell frequency re-use pattern in a

cluster– CELL SPLITTING is used when a service area becomes full of users

• Urban centers are split into more cells to provide acceptable service in heavy-traffic regions

• Rural regions have larger, less expensive cells• Handoff of call for roaming user from one cell to another

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Cell RepresentationCell Representation

Actual Cell Coverage

Diagrammatic Cell Coverage

The cells are normally drawn as hexagonal, but in practice they are irregularly shaped, this is as a result of the influence of the surrounding terrain, or of design by the network planners

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Cell SizeCell Size

Small Cells

200 m+

Large Cells

Max 60-70 km

Number of cells in any geographic area is determined by the number of MS subscribers operating in the area, geographic layout of the area (hills, lakes, buildings etc), installation & maintenance cost.Large Cell size is dependent on the terrain the cell is covering and the power class of the MS. Terrain = cell site is on top of a hill, with no obstructions for miles. Power = In GSM, the MS can be transmitting anything up to 8 Watts; the higher the power output of the MS the larger the cell size.Small cells are used with a large number of MSs in a small geographic region, or where a low transmission power may be required to reduce the effects of interference.

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Frequency Re-use

Frequency 1

Frequency Re-use

Frequency 2

Frequency 1

Standard GSM has a small subset of 124 frequencies available for use in a network..

Frequency re–use pattern is planned to avoid co–channel and/or adjacent channel interference .

It depends on nature of the area to be covered - densely populated city (high frequency re–use, small cells, high capacity) or sparsely populated rural expanse (large omni cells, low re–use, low capacity).

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Frequency Planning in GSMFrequency Planning in GSM

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Cellular CoverageCellular Coverage

Many low-power transmitters placed throughout a coverage areaNumber of channels increase many-fold increasing system capacityRadio energy dissipates over distance, so the mobiles must be within the operating range of the base station

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Site Sectorization

Site

360 Degree cells

Omni-directional Cell Site Each site has a single cell and that cell has a single transmit antenna which radiates the radio waves to 360 degrees1 Transmit/Receive Antenna

Site

120 Degree Sectors/cells

Cell

Cell

Cell

3 Cell Site 3 Transmit/Receive Antenna

60 Degree Sectors/cells

Cell

Cell

Cell

Cell

Cell

Cell

6 Cell Site6 Transmit/Receive Antenna

Site

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Cellular CommunicationCellular CommunicationCellular CommunicationCellular Communication

Sector 2

Sector 3

Sector 1

Cell

BTS = Base Transceiver

Station

MS = Mobile Station

Forward Link

Reverse Link

Cellular Networkradio network made up of a number of cells each served by a fixed low-power wireless transceiver, known as a cell site or base station.

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Flexibility/Increased Capacity

• Digital air interface makes it more resilient to interference from users

on the same or nearby frequencies • Easily (RF) configured (software driven) making it flexible

– Network re–configurations can be made quickly and easily with a minimum of manual intervention

• Users per channel

– One carrier support eight users, hence expansion can be made with less equipment

– Half rate speech channel with 16 users per carrier requiring half data to be sent over the air interface

• International roaming (carry MS or SIM card)

• Better frequency re-use

• Multi-band operation (user can make use of both the 900 MHz network and the 1800/1900 networks)

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Compatibility

SWITZERLAND

DENMARK

SWEDEN

FINLAND

NETHERLANDS

FRANCE

GERMANY

TACS

NMTRADIOCOM 2000

C-450

RTMS

U.K

SPAINAUSTRIA NORWAY

ITALY

PORTUGAL

GSM

There is a large market for GSM equipment. This means that manufacturers can produce equipment in higher quantities and of better quality, and also, due to the number of manufacturers, a competitive and aggressive pricing structure exists. This results in lower costs for the MS subscriber and the network operators.

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Noise Robustness

• Sources of Noise for MS

– Vehicle ignition systems

– Lightning bolt

– Co-channel interference (Another transmission on the same frequency)

– Adjacent channel interference (Another transmission “breaking through” from a nearby frequency)

– Background spurious noise intruding because the required signal is too weak to exclude it

• GSM Answers

– Digital interface instead of analog

• Allows data manipulation

• Interleaving

• Error detection

• Error correction

• GSM air interface in harsh RF environments can produce a usable signal

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Cell Handover GSMCell Handover GSM

f2

f1

Users roaming from one cell to another may get disconnected if time slot is occupied in next cell.Hard Handover in GSM = Break before make since adjacent cells use same radio channel.During a call, when a mobile unit moves out of coverage area of a given cell site, the reception becomes weak. The system switches the call to a stronger-frequency channel in a new site w/o interrupting the call or alerting the user.

ROAD

H/O

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Use of Standardized Open Interfaces

X.25 C7 LAP-B

V.35ISDN

G.703 IEEE 802.3

LAP-D

Network planners can select different manufacturers for different pieces of hardware and have a great deal of flexibility.Competition between manufacturers ensures latest developments at a competitive price.

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Improved Security and Confidentiality

BSS

“The Hacker”

GSM Offers:EncryptionME AuthenticationSubscriber Authentication (SIM)Frequency Hopping

Security with regards to call theft and equipment theft.Mobile Equipment (ME) has a unique number coded into it when it is manufactured.Subscriber is authenticated by use of a smart card known as a Subscriber Identity Module (SIM)Allows encryption and digital encoding of all signalling over the air interface.Supports frequency hopping; this entails each “burst” of information being transmitted to/from the MS/base site on a different frequency, again making it very difficult for an observer (hacker) to follow/listen to a specific call.

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Enhanced Range of Services

• Offered by Network Provider & Capabilities of Mobile Equipment

• Speech Services– Telephony

– Emergency Calls

– Short Message Services

– Dual Personal and Business Numbers

• Data Services– Raw Data (9.6 kbit/s or 4.8 kbit/s or 2.4 kbit/s)

– Fax

• Supplementary Services– Number Identification

– Call Barring

– Call Forwarding

– Call Completion

– Charging

– Multi-party

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GSM Network ComponentsGSM Network Components•Mobile Station (MS)

•Base Station System (BSS)

– BTS - Base Transceiver Station (cell site)

– BSC - Base Station Controller

•Switching System

– MSC - Mobile Switching Center

– HLR - Home Location Register

– VLR - Visitor Location Register

– AuC - Authentication Center

– EIR - Equipment Identity Register

– (PoI) Point of Interconnect with PSTN - Public Switched Telephone Network & other Cellular Service Provider

– IWF- Interworking Function

•Operation Support System

& Billing Support System (OSS / BSS)892AB_00

EIR

AUC

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GSM Network Components - MSGSM Network Components - MS•Mobile System (MS) or Mobile Equipment (ME)

– Hardware (display, case, battery)

– Power

• Low standard power level (800 mW) since mobiles transmit for 1/8 th of the time

• Power saving when person is listening, pausing during speech using Voice Activity Detector

– Electronics to generate signal, process data received and to be transmitted

– VOCODER / CODEC

• Digital encoding of Voice to reduce bandwidth requirement as well as to retain privacy

• Voice coding to analyse incoming speech data and reducing data rate, to re-constitute speech data at the receiving end

– Hard coded number known as International Mobile Equipment Identity (IMEI)

– Subscriber Identity Module (SIM) card

• Carries data of user identity,

• To store other information known as International Mobile Subscriber Identity (IMSI) to allow user to upgrade a phone while retaining the same identity on the network

• To store information such as “phone book”

• To increase demand for new phones with additional features

• To allow mobile operators to increase Average Revenue Per User (ARPU)

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GSM Network Components - BSSGSM Network Components - BSS

•BTS

– radio equipment (transceiver and antenna) that handles radio interface to the mobile station and to service a cell

– VOCODER / CODEC

•BSC

– provides control functions and physical links between BTS & MSC, high capacity switch that provides functions as handover, cell configuration data, RF power level control,

– usually co-located with one of the BTSs and controls a small group of BTSs

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GSM Network Components – Core NetworkGSM Network Components – Core Network•MSC – provides telephony switching function, registration, authentication, call location identification, call routing to mobile subscribers, performs toll ticketing, network interfacing and common channel signaling, interface to PSTN, controls calls to and from other telephone and data systems, manages inter-MSC handovers

•Databases to track location of mobiles and enables calls to be routed to them

– HLR – database that stores permanent data about subscribers, location information and activity status.

• When a user switches the mobile, it registers with the network / BTS it is communicating for incoming calls to be routed

• When phone is not active but switched on, it re-registers periodically to ensure that the network is aware is aware of its latest position

– VLR – database that contains temporary information about visiting subscriber. When a mobile unit roams into a new MSC area, the VLR connected to the MSC will request data about the mobile station from the HLR. Later, if the mobile station makes a roaming call, the VLR will have data w/o having to interrogate the HLR each time

•Systems to authenticate mobile unit to allow onto the network and for billing

– AUC – provides authentication and encryption parameters that verify the user’s identity & ensures confidentiality of each call. This is achieved by comparing AuC data with IMSI.

– EIR – database to identify mobile equipment to prevent calls from stolen, unauthorized or defective mobile stations. This is achieved by comparing EIR data with IMEI.

•Gateway MSC (GMSC) is where the call from visiting MS is initially routed. It obtains Mobile Station Roaming Number (MSRN) from HLR using Mobile Station-ISDN (MS-ISDN) & routes call to MSC

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Mobile ServicesMobile Services•Outgoing call

•Incoming call

•Roaming incoming (Domestic roaming, International roaming)

•Roaming outgoing (Domestic roaming, International roaming)

•Call forwarding to another number if the called mobile unit is not reachable (no reply)

•Call hold to interrupt an ongoing call and then subsequently reestablishing it

•Call waiting to be notified of an incoming call during a conversation (Subscriber can answer, reject or ignore the incoming call)

•Barring of incoming call

•Barring of outgoing call

•Multi-party calling or audio conference

•Closed user group (CUG) of a group of subscribers who are capable of calling themselves with specific facilities.

•Calling line identification to display number of calling party

•Calling line restriction to override the presentation

•Voice Mail

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Other ServicesOther Services

•GSM supports data rates up to 9.6 kbps & provides compatibility with ISDN

•Specifications incorporates short messaging service (SMS)-Modulation is achieved by Gaussian minimum shift keying (GMSK)-Supports Facsimile group III

•Short Messaging Service (SMS)– Allows bi-directional messaging using two SMS gateways

• SMS Gateway MSC (SMS-GMSC) for short messages to be sent to MS

• SMS Inter-Working MSC (SMS-IWMSC) for short messages originating from a mobile on the network

– Store and forward delivery

– Alphanumeric messages

•Cell broadcast

•Facsimile group III support using a special fax converter

•Advice of charge (AoC) to provide an estimate of call charges

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Cellular Telephony In IndiaCellular Telephony In India

• 1992: Resource gap in the 8th plan of Government of India = Rs. 23000 Cr.• 1994: Cellular licenses awarded to private sector for Delhi, Mumbai, Kolkota,

Chennai. (2 operators / circle with license for 10yrs)• 1995: Cellular licenses awarded to 19 circles.• 1998: Cellular operators were near bankruptcy (with less than 1 mn subscribers)• 1999: Government of India accorded highest priority to investment and

development of telecommunications sector.– National Telecom Policy introduced revenue sharing.

• 2000: TRAI Act amended. - Cellular tariffs dropped by 90% because role of independent regulator got clear - Cell phone costs dropped from Rs 25k to Rs 2k +

• 2001: 1400 cities and towns covered by GSM.– 89 Cellular Licenses released across the country

• 2003: CDMA introduced under WLL License• 2004: CDMA allowed under Unified Telecom License• 2006: More than 5000 cities / towns covered across the country

– 105 mn subscibers (74% GSM, 26% CDMA)

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CDMACDMA

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Advent of CDMAAdvent of CDMA

- 1995: CDMA as a digital wireless technology pioneered by Qualcomm-USA was commercially introduced

- 1999: CDMA was selected by ITU as the industry standard for 3G wireless systems

ITU = International Telecommunications Union

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Coded Messages in One AreaCoded Messages in One Area

“Guten Tag”

“Hello”

“Buenos Dias”“Bonjour”

“Shalom”

All Users on same Frequency at the same Time

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Code Division Multiple AccessCode Division Multiple Access

• CDMA is a scheme in which multiple users are assigned common radio resources

• CDMA uses direct sequence – spread spectrum techniques

• Each user has full time use of the entire spectral allocations

• Although all users are transmitting in the same RF band, all users are separated from each other via the use of Orthogonal codes (Walsh code).

• Each user’s signal energy is coded so as to appear like broadband noise to every other user.

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Spread Spectrum ConceptSpread Spectrum Concept

1800 MHz 1850 MHz 1910 MHz 1930 MHz 1990 MHz 2000 MHz

Mobile Tx Cell Tx

In GSM small time slots of the spectrum (200 kHz) are used by different users as channels.

In CDMA, Direct Sequence Spread spectrum uses much larger slice (1.25 MHz) of the available bandwidth.Same slice is used for all user with no time multiplexing but each user is assigned with a different code to uniquely identify them.

User 1User 2User 3User 4

User n

Code 1Code 2Code 3Code 4

Code n

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CDMA System

PSTN

Encoder & Interleaver

@BTS

Spreader @BTS

Code generator

@BTS

Digital to Analog (RF) Converter

@BTS

Vocoder @MSC/BSC

Analog to Digital

converter @PCM/DLC

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CDMA System• VOCODER (voice coder) is used to compress the digital

signal from the Codec (code/decode). – CDMA systems can use either 8 kbps or 13 kbps vocoder. It is

located at the BSC / BTS and at the mobile station.– Variable Rate Vocoder - In CDMA, it compresses voice in one of

four rates (full, ½, ¼ or 1/8 rate) determined by user’s speech activity.

• CODES separate one encoded voice data from other encoded voice data.

– Orthogonal (Walsh) code is used on forward link to channelize users and

– Pseudorandon noise (PN) code is used on reverse link to channelize users.

– Channelization spreads encoded symbols across the entire bandwidth of the CDMA stream of data. RF signal transmits the channelized data.

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CDMA System• RECEIVER despreads / decodes signal & recovers

encoded data.

• ENCODER builds redundancy into the signal. Each bit of vocoded data is repeated thrice using encoded bits or symbols. Decoding at the receiver uses a majority logic rule (accept two out of three wins). If an error occurs, the redundancy can help recover the lost information.

• INTERLEAVING reduces the effects of burst errors during transmission & deinterleaving recovers bit burst error making it simpler to decode.

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Walsh Code 815-bit PN Code, Offset 0

42-bit PN Code (ESNnnn)Walsh Code10

Walsh Code 3515-bit PN Code, Offset 0

42-bit PN Code (ESNxxx)Walsh Code23

Walsh Code 3515-bit PN Code, Offset 1

42-bit PN Code (ESNyyy)Walsh Code15

Walsh Code 2115-bit PN Code, Offset 2

42-bit PN Code (ESNzzz)Walsh Code23

Unique Identification

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Signaling ServicesPilot channel is constantly transmitted to acquire system and after acquiring system for signal strength measurementSync channel is constantly transmitted to provide critical timing info to mobile and is used to sync mobile with base stationPaging channel is used to transmit overhead info like commands & forward traffic channel assignment to mobile when a call is being set upAccess channel is used by mobile when not assigned to traffic. It is used to register with network, originate calls, respond to commands from base station, send overheads to base station.Forward traffic channel is used when there is a callReverse traffic channel is used when there is a call

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Advantages of CDMA

• CDMA has 2-3 times more coverage than TDMA based service• CDMA offers more channel capacity• CDMA offers increased security & enhanced privacy because of the codes transmitted

with traffic• CDMA does not allow cross talks because of coding• CDMA transmits at lower power requirements, ensures precise power control, allows

increased talk time and standby time for portables• CDMA offers advanced features like over-the-air-activation, sleep mode and data/fax.• CDMA like GSM supports the mobile services

• Channel capacity in a TDMA system is fixed and indisputable. Each channel carries a finite number of "slots", and a new caller cannot be accommodated once each of those slots is filled.

• Capacity is one of CDMA's biggest assets, CDMA has a very high "spectral efficiency“. IT CAN ACCOMMODATE MORE USERS PER Mhz OF BANDWIDTH THAN ANY OTHER TECHNOLOGY. CDMA has what is known as "soft capacity". You can always add just one more caller to a CDMA channel at the cost of quality.

• CDMA system capacity is a compromise between the no. of users and call quality• CDMA allows extended reach & hence is beneficial to rural users situated far from cells.

Spectral Efficiency of CDMA

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f1

f1

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Universal Frequency Re-use in CDMA

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Cell Handover in CDMA

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‘Soft’ handover in CDMAMake before breakHigher voice qualityLess cell-to-cell coordination needed by operators

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Multipath

• GSM is subjected to multipath distortion. One way to avoid this is to put a time limit on the system. Affected by Multipath,there is signal loss at cell fringes where reflection and refraction may cancel or weaken signal

• Since CDMA is a wideband signal, multipaths can be used to increase the quality of the signal.

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Superior Voice Quality in CDMA • Variable rate vocoders compress speech, reduce bit rate, interference and

background noise. • It takes advantage of reduced speech activity and “silences”• CDMA takes advantage of various types of diversity to improve speech

quality: Frequency diversity (protection against frequency selective fading) Spatial diversity (two receive antennas) & soft hand-offs Path diversity (rake receiver improves reception of signal experiencing

multipath "interference," & actually enhances sound quality)

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Continuous Power Control in CDMA

• Signals from all mobiles are received at the Base Station with the same received power.

• CDMA network independently controls the power of each mobile

• OPEN LOOP is an estimate of what power the mobile should use to transmit based on the strength of the mean signal power received by the mobile

• FAST CLOSED LOOP is when there is a call. Network sends command to mobile to increase or decrease power.

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Mobile Data

- GSM supports data rates up to 9.6 kbps & provides compatibility with ISDN

- CDMA Data Service superior compared to GSM.- CDMA supports data rates up to 144 kbps with cdma2000

1x technology from Qualcomm- CDMA supports upto 2 mbps with cdma 1xEV-DO

technology from Qualcomm- 3G mobile

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Disadvantages of CDMADisadvantages of CDMA

Limited Roaming - GSM is older technology and more wide-spread across the world while CDMA is proprietary and allows limited roaming

Poor Interoperability - CDMA is not interoperable between Service Providers while GSM is designed for interoperability

Near Far Problem – if all mobiles transmitted at the same power level, signals received by the base station from mobile further away would be weaker than those signals received from mobiles which were closer to the cell. This reduces capacity of a CDMA system.

Path Loss – With distance between cell and mobile, signal becomes weaker.

Fading – Due to two signals from same transmitter received due to multipath.

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3G Evolution Path ”

•CDMA

• GPRS/ UMTS/ WCDMA

•1996 1998 2000 2002 2004 2006

CDMAOne IS-95A

CDMAOne IS-95B(8 K ~ 13.3 Kbps) *13.3 Kbps

CDMA2000 1x IS-2000(64 Kbps)56 Kbps

•(307 Kbps)•144 Kbps

CDMA2000 1x Ev-DV

CDMA2000 3x

(more than 2.0 Mbps)

GPRS

GPRS

EDGE

(115 Kbps)28 ~ 40 Kbps

(115 Kbps)56 Kbps

(115 Kbps)112 Kbps

(384 Kbps)

UMTS

(1.920 Mbps)

•GPRS: General Packet Radio Service … 2.5G•EDGE(Enhanced Data rates for GSM Evolution),•UMTS: Universal Mobile Telecommunications System•WCDMA: Wideband Code Division Multiple Access WCDMA

W-CDMA is a type of 3G cellular network. W-CDMA is the technology behind the 3G UMTS standard and is allied with the 2G GSM standard with the International Telecommunication Union – ITU. (Developed by NTT – DoCoMo of Japan)

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Wireless in Local Loop Wireless in Local Loop (WLL)(WLL)

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Wireless Local LoopWireless Local Loop

Fixed Wireless Terminal on CDMAConnects to PSTN using radio signalsCan be linked to PBX for outward calling to CDMA mobiles at lower ratesUseful for voice / data access

Fixed Cellular Terminals with multiple GSM SIM cardsIt sits neatly along side your telephone exchange, diverting calls made from fixed lines to mobiles through the SIM cards, making them mobile to mobile calls.

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RJ45

Fixed Wireless Applications

RJ11

FAXPOTS

DATA

Console

Extension

PBX

WLL Service Provide

r

Other Service Provide

r

POI

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Mobile DataMobile Data

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Evolution of 3GEvolution of 3G

General Packet Radio Service (GPRS) is a 2.5G mobile data service for users of GSM mobile phones with data rates of 115 kbps. It uses packet-switching based on a tunneling protocol that delivers IP packers across the mobile network to a router.Enhanced Data rates for GSM Evolution (EDGE) improves GSM system data rates of between 160 and 236.8 kbit/s with modified 8PSK (phase shift key) modulation.3G allows data communication of 2 mbps with shift from circuit switching to packet switching technology

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3G - GSM3G - GSM

• Allows transmission of 384kbps for mobile systems and 2Mbps for stationary systems

• Entirely new networks need to be built and new frequencies need to be assigned to mobile operators to deploy 3G

• Uses 5 MHz channel carrier width to deliver significantly higher data rates and increased capacity

• Services applicable with 3G– Voice data (a telephone call) – Non-voice data (such as downloading information, exchanging email, and instant

messaging). – Music download – Videophone

• W-CDMA is a wideband spread-spectrum 3G mobile telecommunication air interface that utilizes code division multiple access and is allied with GSM

• Universal Mobile Telecommunications System (UMTS) is a 3G mobile technology that uses W-CDMA and supports upto1920 kbps

The first country which introduced 3G on a large commercial scale was Japan. In 2005, about 40% of subscribers used 3G networks only and upgrades to the next 3.5G stage with 3 Mbit/s data rates are underway.

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3G - CDMA3G - CDMA• CDMA 2000 1x allows data rates upto 144 kbps• Air Card in PCMCIA slot of Laptop / external PCMCIA port of

Desktop to access Internet • CDMA2000 1x-EV-DO (1x Evolution-Data Optimized) is a wireless

radio broadband data standard with air interface speeds of up to 2.4576 Mb/s with Rev. 0 and up to 3.1 Mb/s with Rev. A

4G will offer true high speed data services (2mbps to 156 mbps) based on IP switching, advanced signal processors, new modulation techniques like Orthogonal Frequency Division Multiplexing (OFDM), smart antennas.

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Wireless Application ProtocolWireless Application Protocol

• Wireless Application Protocol or WAP is an open international standard for applications that use wireless communication. Its principal application is to enable access to the internet from a mobile phone or PDA.

• WAP microbrowser software within the mobile device interprets the byte code and displays the interactive WAP content

• WAP sites, are websites written in, or dynamically converted to, WML (Wireless Markup Language) and accessed via the WAP browser

• Interactive data applications are required to support now commonplace activities such as:

– email by mobile phone – tracking of stock market prices – sports results – news headlines – music downloads

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Wi-MAXWi-MAX

• WiMAX = Worldwide Interoperability for Microwave Access• WiMAX (officially trademarked as WirelessMAN) promotes conformance with

IEEE 802.16 Working Group on Broadband Wireless Access Standards for its wireless metropolitan area network standard, which defines broadband Internet access from fixed or mobile devices via antennas.

• A standards-based technology enabling the delivery of last mile wireless broadband access over long range (many kilometers) that uses licensed spectrum to deliver a point-to-point connection to the Internet from an ISP to an end user.

– Can deliver upto 10 Mbps over 10 km with Line of Sight (LoS) and non-moving recipient, 2 km without LoS. For moving objects bandwidth falls significantly.

• The bandwidth and reach of WiMAX make it suitable for the following potential applications:

– Connecting Wi-Fi hotspots with each other and to other parts of the Internet. – Providing a wireless alternative to cable and DSL for last mile (last km) broadband

access. – Providing high-speed data and telecommunications services. – Providing a diverse source of Internet connectivity as part of a business continuity

plan. That is, if a business has a fixed and a wireless internet connection, especially from unrelated providers, they are unlikely to be affected by the same service outage.

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Wi-FiWi-Fi

• Wi-Fi is the underlying technology of wireless local area networks (WLAN) based on the IEEE 802.11 specifications.

• Wi-Fi is a short range (range is typically measured in hundreds of meters) system that uses unlicensed spectrum to provide access to a network, typically covering only the network operator's own property.

• Developed to be used for mobile computing devices, such as laptops, in LANs• Used for applications including Internet access to a computer or Personal

digital Assistant (PDA), VoIP phone access, gaming and basic connectivity of consumer electronics such as televisions and DVD players or digital cameras

• Wireless access point (WAP or AP) is a device that connects wireless communication devices together to form a wireless network.

• Hotspots are locations with public wireless access points where you can connect your mobile computers (such as a laptop or a PDA) to the Internet, using standard WLAN (Wi-Fi) technology.

• A typical Wi-Fi setup contains one or more Access Points (APs) and one or more clients. An AP broadcasts its identification packets called beacons every 100 ms. The beacons are transmitted at 1 Mbit/s and are of relatively short duration. Based on the identifier settings the client connects to an AP.

• Wi-Fi uses modulation technologies like single carrier direct-sequence spread spectrum radio and multi-carrier OFDM (Orthogonal Frequency Division Multiplexing) radio.

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BluetoothBluetooth

• Bluetooth is a radio standard and communications protocol primarily designed for low power consumption with a short range based around low-cost transceiver microchips in each device.

• Wireless Personal Area Network (PAN) specification developed by a Special Interest Group

• Named after Harald Blaatand “Bluetooth” II, King of Denmark 940-981, who controlled Denmark and Norway

• Replaces cables with radio system for linking devices

• Designed for notebooks, telephones, wireless headsets, handheld & wearable devices like scanners, bar-coders, data/voice access devices, peripheral connections for printers, PDAs, desktops, fax machines, keyboards, joysticks, mouse.

Class Maximum Permitted Power(mW)

Maximum Permitted Power(dBm)

Range(approximate)

Class 1 100 mW 20 dBm ~100 meters

Class 2 2.5 mW 4 dBm ~10 meters

Class 3 1 mW 0 dBm ~1 meter

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Future of Wireless Broadband Coverage – anytime, anywhere

•2006 – Bangalore has 200 private wireless hotspots in hotels, coffee shops, malls and airport lobby.•Taipei-Taiwan is the largest unwired metropolis with 90% of public spaces connected by 5000 access points mounted on facilities such as street lamps, traffic signals, subway stations, public buildings. Two Lakh subscribers already use wireless Internet phone in Taipei..•Municipal wireless network in 250 locations across the US