CELLULAR CONCEPTS AMIT SOROT EC-08007 ADVANCED GROUP OF INSTITUTION.

CELLULAR CONCEPTS

AMIT SOROT EC-08007

ADVANCED GROUP OF INSTITUTION

WIRELESS COMMUNICATION

Transmitting/receiving voice and data using electromagnetic waves in open space.

The information from sender to receiver is carried over a well defined frequency band(channel).

Each channel has a fixed frequency bandwidth & capacity(bit rate).

Different channels can be used to transmit information in parallel and independently.

WHAT IS WIRELESS COMMUNICATION?

How communication takes place?

Transmitting signalReceived signal

satellite

Transmitting antenna

Receivingantenna

FM RADIO 88 MHZTV BROADCAST 200 MHZGSM PHONES 900 MHZGPS 1.2 GHZPCS PHONES 1.8 GHZBLUETOOTH 2.4 GHZWi-Fi 2.4 GHZ

TYPICAL FREQUENCIES

Freedom from wires.No bunch of wires running from here and

there.“Auto Magical” instantaneous communication

without physical connection setup e.g.- Bluetooth, Wi-Fi.

Global coverageCommunication can reach where wiring is

infeasible or costly e.g.- rural

areas,buildings,battlefield,outerspace.Stay connected,flexiblity to connect multiple

devices.

WHY WIRELESS COMMUNICATION?

RADIO TRANSMISSION:- easily generated, Omni-directional , travel long distance , easily penetrates buildings.

PROBLEMS:- frequency dependent , relatively low bandwidth for data communication , tightly licensed by government.

MICROWAVE TRANSMISSION:- widely used for long distance communication , give high S/N ratio , relatively inexpensive.

PROBLEMS:- don’t pass through buildings , whether and frequency dependent.

TYPES OF WIRELESS COMMUNICATION?

INFRARED AND MILIMETER WAVES:- widely used for short range communication ,

unable to pass through solid objects , used for indoor wireless LANs , not for outdoors.

LIGHT WAVE TRANSMISSION:- unguided optical signal such as laser , unidirectional , easy to install , no license required.

PROBLEMS:- unable to penetrate rain or thick fog , laser beam can be easily diverted by air.

TYPES CONTINUED….

CELLULAR SYSTEM

WIRELESS LANs

SATELLITE SYSTEM

PAGING SYSTEM

PANs(BLUETOOTH)

CURRENT WIRELESS SYSTEMS

Definition Wireless communication

technology in which several small exchanges (called cells) equipped with low-power radio antennas (strategically located over a wide geographical area) are interconnected through a central exchange. As a receiver (cell phone) moves from one place to the next, its identity, location, and radio frequency is handed-over by one cell to another without interrupting a call.

What is cellular system?

Practical

High capacity is achieved by limiting the coverage of each base station to a small geographic region called a cell.

Same frequencies timeslots/codes are reused by spatially separated base stations.

A switching technique called handoff enables a call to proceed uninterrupted when one user moves from one cell to another.

Neighboring base stations are assigned different group of channels so as to minimize the interference.

Cellular system basic concept?

By systematically spacing base stations and the channel groups may be reuse as many number of times as necessary.

Cellular system basic concept contd…

MSC

CELLS

PSTN

SUBSCRIBER UNIT

BASE STATIONS

Coverage area

Hand over ?BSC

BS1

BS2

BS3

Connect to Bs1 & start calling

Out of BS1 coverage & connect to BS2

Out of BS2 coverage & connect to BS3

Call ended

Cellular radio systems rely on intelligent allocation and reuse of channels throughout the coverage area.

Each base station is allocated a group of radio channels to be used within the same geographical area of its cell.

Neighboring base stations are given different channel allocation from each other.

The design procedure of allocating channel groups for all of the cellular BS within a system is called frequency reuse or frequency planning.

FREQUENCY REUSE THE NEED?

Example of frequency reuse?

Co channel cells

Co channel cells

Co channels

How to find co -channel cell?

60 degree

u

v

D

Axes u and v intersect at 60 degree.Unit scale is the distance between center cells.If cell radius to point of hexagon is R then

2Rcos30=1Or R = 1/√3. to find the distance of a point P(u

, v) from the origin we use x-y to u-v coordinate transformation.

R² = x² + y²x=ucos30˚y=u+vsin30˚r=√(v²+uv+u²)

The geometry of hexagon?

Using this equation to locate co-channel cells we start from reference cell and moves i hexagon along u axis then j hexagon along the v axis.

Hence the distance between co-channel cells in adjacent cluster is given by D = √(i²+ij+j²)

The number of cells in a cluster N is given byN = √(i²+ij+j²) where i and j are integers.Hence the possible values of N are 1 , 3 , 4 , 7 ,

12……

Geometry contd…

Formation of cluster for N=7Suppose i=2 and j=1 will give co channel cellSame color showing co-channel cells.

Co-channel location

i=2

j-=1

Co channel cells

Global system for mobile communication is a set of ETSI standards specifying the infrastructure for a digital cellular services.

GSM networks are structured hierarchically it consist of one administrative region which is assigned to a MSC.

Each administrative region is made up of at least one location area (LA). LA is also called the visited area.

An LA consists of several cell groups.Each cell group is assigned to a base station

controller (BSC)

What is GSM?

GSM system hierarchy?GSM NETWORK

MSC REGIONLOCATION AREA (LA)

BS CONTROLLER

CELL

CELL

LA

LA

BS CONTROLLER

BS CONTR-OLLER

MSC REGION

MSC REGION

OPENED VIEW OF GSM ARCHITECHTURE?

BSC

MSCEIR

AUC

HLR VLRISDN

PSTN

OTHER NETWORKSBSS

NSS

NMS

Mobile station

Consist of two main elements.1. The mobile equipment 2. Subscriber identity module(SIM).

Mobile station?

BSS = BSC + BTS

The Base Station Subsystem?

1. RADIO PATH CONTROL

2. AIR INTERFACE SIGNALLING

1. CENTRAL N/W ELEMENT OF BSS

2. CALL ESTABLISHMENT

3. MOBILITY MGMT

4. STATISTICAL RAW DATA COLLECTION

1. SPEECH PROCESSING

2. MODULATION/DEMODULATION

3. TRANSCODER

4. MINIMIZE TRANSMISSION PROBLEM

5. AIR INTERFACE MANAGEMENT

NSS = MSC + HLR + VLR + AUC + EIR

THE N/W SWITCHING SUBSYSTEM?

MANAGECOMMUNICATI

ON B/W USERS

INCLUDE DATABASE TO

STORE INFORMATION OF USER

CALL CONTROL

MOBILITYMGMT

SUBSCRIBERDATA HANDLING

CHECK IDENTITY OF USER

PERMANENT STORAGE OF USER INFORMATION

STORE A COPY OF HLR

CHECK ROAMING

PROVIDE AUTHENTICATION

SECURITY

CHECK IMEI NUMBER OF MOBILE

N/W MANAGEMENT SUBSYSTEM?

1. MONITORING

2. MANAGE

3. OPERATION

4. MAINTANENCE

NMS

USE TDMA + FDMA

MODULATION USED = GMSK(Gaussian minimum shift keying)

UPLINK FREQUENCY = 890 – 915 MHZ

DOWNLINK FREQUENCY = 935 – 960 MHZ

GSM TECHNOLOGY ?

WLAN connect local computersRange (100 m) confined regionBreak data into packetsChannel access is sharedBackbone internet provides best servicePoor performance in some application like

videosLow mobility

Wireless local area network(WLAN)

Global coverageDifferent orbit height Optimized for good transmissionExpensive base stations.Voice and data transmissionTelecommunication applicationGPS , global telephone connectionTV broadcasting , military , whether

broadcasting

Satellite system ?

Paging system ?Broad coverage for short messagesMessage broadcast from all base stationsSimple terminalsOptimized for one way transmissionAnswer back hardOvertaken by cellular

Pager system

Wide area paging system ?

PSTN

Paging control center

Paging terminal

Paging terminal

Paging terminal

Terrestrial link

Terrestrial link

Satellite link

City 1

City 2

City N

Base station

Base station

Base station

Bluetooth Cable replacement RF technologyShort range(10m)2.4 GHz bandTDD duplex scheme1 Mbps data rate shared b/w 7 devicesPolling based multiple accessWork on frequency hopping spread spectrum

technology

Personal area network ?

Peer to peer communicationNo backbone infrastructureRouting can be multihopTopology is dynamicFully connected with different link SINRs.

Ad-hoc network ?

Ad-hoc network provides a flexible network infrastructure for many emerging applications.

The capacity of such networks is generally unknown.

Transmission , access and routing strategies for these networks are generally ad-hoc.

Cross layer design is very critical and challenging.

Energy constraints impose interesting design for trade offs communication and networking.

Ad-hoc network contd….