Transcript wireless communication - Inplant Training in chennai

Wireless System
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WHAT IS 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.
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How communication takes place?
satellite
Transmitting signal
Transmitting
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antenna
Received signal
Receiving
antenna
TYPICAL FREQUENCIES
 FM RADIO
 TV BROADCAST
 GSM PHONES
 GPS
 PCS PHONES
 BLUETOOTH
 Wi-Fi
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88 MHZ
200 MHZ
900 MHZ
1.2 GHZ
1.8 GHZ
2.4 GHZ
2.4 GHZ
WHY WIRELESS COMMUNICATION?
 Freedom from wires.
 No bunch of wires running from here and there.
 “Auto Magical” instantaneous communication without
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physical connection setup e.g.- Bluetooth, Wi-Fi.
Global coverage
Communication can reach where wiring is infeasible or
costly
e.g.- rural areas,buildings,battlefield,outerspace.
Stay connected,flexiblity to connect multiple devices.
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TYPES OF 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.
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TYPES CONTINUED….
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.
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CURRENT WIRELESS SYSTEMS
 CELLULAR SYSTEM
 WIRELESS LANs
 SATELLITE SYSTEM
 PAGING SYSTEM
 PANs(BLUETOOTH)
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What is cellular system?
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.
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Practical
Cellular system basic concept?
 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.
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Cellular system basic concept
contd…
 By systematically spacing base stations and the channel
groups may be reuse as many number of times as necessary.
SUBSCRIBER
UNIT
Coverage
area
BASE
STATIONS
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CELLS
MSC
PSTN
Hand over ?
BSC
BS1
BS2
Out of BS1 coverage &
Connect to Bs1 & start
connect to BS2
callingWWW.KAASHIVINFOTECH.COM
BS3
Call
ended
Out of BS2 coverage &
connect to BS3
FREQUENCY REUSE THE NEED?
 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.
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Example of frequency reuse?
Co channel
cells
Co channel cells
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How to find co -channel cell?
 Co channels
u
v
60 degree
D
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The geometry of hexagon?
 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=1
 Or R = 1/√3. to find the distance of a point P(u , v) from the
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origin we use x-y to u-v coordinate transformation.
R² = x² + y²
x=ucos30˚
y=u+vsin30˚
r=√(v²+uv+u²)
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Geometry contd…
 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 by
 N = √(i²+ij+j²) where i and j are integers.
 Hence the possible values of N are 1 , 3 , 4 , 7 , 12……
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Co-channel location
 Formation of cluster for N=7
 Suppose i=2 and j=1 will give co channel cell
 Same color showing co-channel cells.
j-=1
i=2
Co channel cells
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What is GSM?
 Global system for mobile communication is a set of ETSI
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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)
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GSM system hierarchy?
GSM NETWORK
MSC REGION
MSC
REGION
LOCATION AREA (LA)
BS CONTROLLER
CELL
CELL
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BS
CONTROLLER
BS
CONTROLLER
LA
LA
MSC
REGION
OPENED VIEW OF GSM ARCHITECHTURE?
NSS
NMS
AUC
HLR
EIR
VLR
ISDN
MSC
PSTN
BSC
OTHER
NETWORKS
BSS
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Mobile station
Mobile
station?
 Consist of two main elements.
 1. The mobile equipment
 2. Subscriber identity module(SIM).
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The Base Station Subsystem?
 BSS =
1.
2.
RADIO PATH CONTROL
AIR INTERFACE
SIGNALLING
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BSC
+
BTS
1.
CENTRAL N/W
ELEMENT OF BSS
1.
SPEECH
PROCESSING
2.
CALL
ESTABLISHMENT
2.
MODULATION/DE
MODULATION
3.
MOBILITY MGMT
3.
TRANSCODER
4.
STATISTICAL RAW
DATA COLLECTION
4.
MINIMIZE
TRANSMISSION
PROBLEM
5.
AIR INTERFACE
MANAGEMENT
THE N/W SWITCHING SUBSYSTEM?
 NSS
= MSC +
MANAGE
COMMUNICATION
B/W USERS
INCLUDE
DATABASE TO STORE
INFORMATION
OF USER
HLR +
VLR + AUC + EIR
CALL
CONTROL
MOBILITY
MGMT
SUBSCRIBER
DATA
HANDLING
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CHECK
IDENTITY OF
USER
STORE A
COPY OF
HLR
PERMANENT
STORAGE OF
USER
INFORMATION
CHECK
ROAMIN
G
PROVIDE
AUTHENTI
CATION
SECURITY
CHECK
IMEI
NUMBER
OF
MOBILE
N/W MANAGEMENT SUBSYSTEM?
1. MONITORING
2. MANAGE
3. OPERATION
4. MAINTANENCE
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NMS
GSM TECHNOLOGY ?
USE TDMA + FDMA
MODULATION USED = GMSK(Gaussian minimum shift
keying)
UPLINK FREQUENCY = 890 – 915 MHZ
DOWNLINK FREQUENCY = 935 – 960 MHZ
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Wireless local area network(WLAN)
 WLAN connect local computers
 Range (100 m) confined region
 Break data into packets
 Channel access is shared
 Backbone internet provides best service
 Poor performance in some application like videos
 Low mobility
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Satellite system ?
 Global coverage
 Different orbit height
 Optimized for good transmission
 Expensive base stations.
 Voice and data transmission
 Telecommunication application
 GPS , global telephone connection
 TV broadcasting , military , whether broadcasting
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Paging
system ?
 Broad coverage for short messages
 Message broadcast from all base stations
 Simple terminals
 Optimized for one way transmission
 Answer back hard
 Overtaken by cellular
Pager system
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Wide area paging system ?
City 1
Terrestrial link
Paging
terminal
City 2
PSTN
Paging
control
center
Terrestrial link
Base
station
Paging
terminal
Base station
City N
Paging
terminal
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Base
station
Satellite link
Personal area network ?
 Bluetooth
 Cable replacement RF technology
 Short range(10m)
 2.4 GHz band
 TDD duplex scheme
 1 Mbps data rate shared b/w 7 devices
 Polling based multiple access
 Work on frequency hopping spread spectrum technology
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Ad-hoc network ?
 Peer to peer communication
 No backbone infrastructure
 Routing can be multihop
 Topology is dynamic
 Fully connected with different link SINRs.
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Ad-hoc network contd….
 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.
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Thank U
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