1. M.V. RAGHUNADH
Assistant Professor, Dept. of ECE
NIT, Warangal – 506004.
raghu@nitw.ac.in

2. INTRODUCTION
TO
MOBILE & CELLULAR
COMMUNICATIONS

3. Wireless system
What is a wireless system?
 Provides communication without
the use of wire
 Computing and communication at
anytime and anyplace
 Small size, portable device
 Uses radio wave, to send voice,
data, internet and video signals
 Good energy management
 Access to resources

4. “ Mobile communications is
not Cellular communications
but
Cellular communications is
Mobile communications ” .

5. Mobile Com 
Ex :Public emergency services
Police, Fire, Ambulance
Single frequency communications
over entire area using one BS
and many mobile vehicular
transceiver sets
Cellular Com 
Public com services with frequency
reuse over multiple cells in entire
area using one BS and many
cellular phones in every cell.

6. “ Portable
communicators are not
mobile but
mobile communicators
are Portable ”

7. Communication devices exhibit following
Characteristics
a. Fixed & Wired:
Typical desktop PC, Telephone large, Data
Loggers  weight / high power
b. Mobile & Wired:
Today’s laptop PCs  mobile but connection to
company via wired line of PSTN & Modem
c. Fixed & Wireless:
WLL  last mile in PSTN, in house wireless
networks, local net in tradeshows.

8. d. Mobile & Wireless
Today’s Cell Phones, PDAs, Personal
Communicators
 Most interesting case, no cable restriction,
full mobility, roaming between cities
and even different networks
Ex: GSM , CDMA
> 900 million users worldwide

9. Applications:
1.Vehicles:
Cars with 
a) Digital Audio Broadcast (DAB) at 1.5 Mbps 
Music ,news, weather and GPS data
b) UMTS for Wireless Cell Telephony
– voice & Data at 384 kbps
c) Adhoc Networks with emergency services
Accidents, Maintenance Logistics.
d) Wireless Pico Nets PDA, Laptops, Mobile
Phones ,Bluetooth / Wi-Fi.
e) Rail / Air Traffic

10. 2.Emergencies 
Ambulance  high quality wireless adhoc nets
– accidents, natural disasters.
3.Business 
Sales  Database consistency,
wireless LAN hot spots at
supermarkets, gas stations,
laptop connections via
LAN,DSL…
4.Infotainment 
Up-to-date info over wireless net
i. Travel guide
ii. Cash payment
iii. Adhoc gaming networks

11. 5. Location Dependent Services 
Mobile computing and WLANs applications need to
know the mobile unit location.
a. Follow on Services  Call forwarding, e-mail,
multimedia conferencing.
b. Location aware Services  Printing service from a
hotel control room.
c. Privacy  Time dependent access/forwarding at
the will & wish of user
d. Info. Services Travel guide
e. Support services Caching of data on mobile
device via a wireless net access.

12. Wi-Fi
Stands for “Wireless Fidelity”
High-bandwidth category of wireless
communications
Short range (300-1600ft)
Used to connect laptops, PDAs, and
even workstations
Digital Cellular Telephony
CDMA, TDMA, GSM
Smart phones and some PDAs
Longer range than Wi-Fi

13. Mobile & Wireless Devices:
a. Sensors : Control state information sources
b. Embeded Controllers: Keyboards, mice, headset,
washing machine, TV set, …..
c. Pager : One or two line message service,
fast replaced by cell phone.
d. Mobile Phones : Vehicular Sets, Cell phones
e. PDA : Personal Communicators,
Pocket/Palm Computers
f. Notebook / Laptop : Portable PCs

14. MOBILE, CELLULAR
&
PERSONAL COMMUNICATIONS

15. Mobility : Mobility of Talker ( Transmitter )
Mobility of Listener ( Receiver )
Mobility of Both ( TX & RX )
Definition : Communication facility between
stationary and mobile or mobile and
mobile users ( units )
UserTypes : Walking Pedestrians
automobile computers
car, bus, train, plane, ship.

16. What is Mobility?
A device that moves
Between different geographical
locations
Between different networks
A person who moves
Between different geographical
locations
Between different networks
Between different communication
devices
Between different applications

17. Device mobility
Plug in laptop at home/work on Ethernet
Wired network access only
Network address changes
May want access to information
when no network is available: hoard
information locally
Cell phone with access to cellular network
Continuous connectivity
Phone # remains the same (high-
level network address)
Network performance may vary from
place to place
Can we achieve best of both worlds?
Continuous connectivity of wireless
access
Performance of better networks

18. People mobility
Phone available at home or at work
Multiple phone numbers to reach me
Breaks in my reachability when I’m not in
Cell phone
Only one number to reach me
Continuously reachable
Sometimes poor quality and expensive
connectivity
Cell phone, networked PDA, etc.
Multiple numbers/addresses for best quality
connection
Continuous reachability
Best choice of address may depend on
sender’s device or message content

19. Mobility means changes
How does it affect the following?
Hardware
Lighter More robust
Lower power
Wireless communication
Can’t tune for stationary access
Network protocols
Name changes ; Delay changes ;
Error rate changes
Fidelity
High fidelity may not be possible
Data consistency
Strong consistency no longer
possible
Location/transparency awareness
Transparency not always desirable
Names/addresses

20. Example changes
Addresses
Phone numbers, IP addresses
Network performance
Bandwidth, delay, bit error rates, cost,
connectivity
Network interfaces
PPP, eth0, strip
Between applications
Different interfaces over phone & laptop
Within applications
Loss of bandwidth triggers change from
color to B&W
Available resources
Files, printers, displays, power, even
routing

21. Enabling Technologies
Software Defined Radios
Advanced media access technology to connect
different cores to different access technologies
Variable spreading factor ( VSP )
All-IP networks and protocols
Ad-Hoc Networking algorithms
Ultra Wideband , variable power Hardware
Radio
Network-layer mobility protocols
Smart antennae
MIMO (Multi Input Multi Output) devices
Open platform architectures
Smart mediation devices for Handsets
Smart mediation devices for overlay network

22. Goal of emerging mobile & PCS systems To
enable communication with any person, at any
time, at any place (Home office in public in
Transit), in any form / device ( Home /normal
telephone, cellular/mobile phone , PC phone,
PDA, fax, Multimedia terminal).
On the basis of
“any time, any where, any one, any
service”
Information Services:
Voice, Video, Text, Fax ,Image, Data, Files

23. Technological Trends
• All Digital Optical Fiber or Satellite media ,
• Hyper media content
• Intelligent Networks
• Universal Reachability & Accessibility
• User specific & Interactive service
• Global Roaming & Interoperability
• Mobile ATM and Mobile Internet
• Mobile data and computing
• Guaranteed Quality of Service (QOS)
• Standardized Universal ID Numbers/
Addresses
• Personalization

24. The Electromagnetic Spectrum
Short Wave Radio FM Broadcast
AM Broadcast Television Infrared wireless LAN
Cellular
Microwave
Extremely Very Low Medium High Very Ultra Super Infrared Visible Ultra- X-Rays
Low Low High High High Light violet
2.4 – 2.4835 GHz
GSM: 5 GHz
802.11b (11 Mbps)
US ISM: 902-928 MHz 802.11a (54 Mbps)
802.11g (54 Mbps)

25. Wireless Network Area Definitions
GSM Courtesy of IEEE
802.15 Press Kit. Jan.
GPRS
2001
CDMA
IEEE802.11
WAN HyperLan Bluetooth
WAN-MAN
PAN
MAN
MAN-LAN
LAN-PAN
Pico-Cell
~50km ~2km 0km ~10m

26. Hierarchical Layers for 4G
IP-based backbone
Global layer Satellite
Regional layer DAB and DVB-T
National layer 2G, 3G Cellular
Local area layer Wireless LANs
Personal network layer Wireless PANs
Vertical Handover
Horizontal Handover

27. Inter-Working
Billing SIP Proxy Signalling WAP Accounting ISP
VHE Server Gateway
The
Interne
Satellite FES
Context-aware information
Centre
IP backbone
Broadcast Networks
(DAB, DVB-T)
GSM /
GPRS
UMTS
IP-based
micro-mobility Wireless
LANs

28. ENABLING CONCEPTS
FOR
MOBILE & PERSONAL
COMMUNICATIONS.

29. These concepts enable us to provide Universal
PCS with standardized systems & services at
local, regional, national and international levels.
They are :
Terminal Mobility  with wireless Access
Personal Mobility  with personal Number
Service Portability  with Intelligent Network
These are for location independent availability of
customized telecom services.

30. TERMINAL MOBILITY
• The terminal mobility systems can locate and
identify a mobile terminal as it moves
• Allows a mobile terminal to access telecom
services from any location – even in
movements
• Uses wireless Access
• User must carry wireless terminal and be within
a radio coverage area
• Functional parts reside on portable IC / Smart
card
• Terminal and User have STATIC Relationship
• Terminal and Network have DYNAMIC Relation
• Call delivery and Billing are based on Terminal /

31. PERSONAL MOBILITY
• Terminal and user have DYNAMIC Relationship.
Call Delivery & Billing are based on Personal
Identity / Personal Number assigned to the
user.
• Locate and identify the end users as they move
• Allows end users to access subscribed telecom
services on any terminal, any location
• More broader access whether fixed or wireless

32. SERVICE PORTABILITY
• Network is capable to provide subscribed
services at a terminal or location designated by
the user.
• Depends on terminal capabilities
• Uses intelligent Network concepts
• Maintains User profile in a Database
• User can access, query, modify to manage &
control subscribed services.
• Intelligent services – seamless international
roaming

33. CELLULAR CONCEPT
&
INITIAL IMPLEMENTATION

34. Conventional Mobile Tele phone System
A Land mobile system in which available
frequency spectrum is divided into mobile radio
telephone channels using FDM without reuse
facility, serving an area with large size..
A dedicated channel is allocated for each user,
whether uses it or not.
Principle of operation is similar to cellular radio
telephony
As a result, It has several limitations that are
given below.

35. 1. Limited service capability
• Larger coverage area zones
• High Power Transmissions
• Re-initiation of call in every zone
(no auto handoff)
• One frequency per channel
• No. of active users is equal to No. of channels
allocated to zone
2. Poor Service Performance:
• Higher blocking probabilities due the smaller
number of radio channels.

36. 3. Inefficient frequency spectrum Utilization
• Smaller Frequency Utilization factor
Mo = max. no. of customers/channel at Busy
Hour.
• Each channel can serve only one customer at
a time in whole area.

37. SOLUTION
Cellular approach
• Reuse of frequencies
• Multiple Access
• Cell Splitting
• Smaller coverage area (cell)

38. Starting point :
AMPS by Bell Labs, 1983, USA
Cellular System :
A high capacity land mobile system in which
available spectrum is divided into discrete
channels, which are assigned in groups to
geographic cells covering an area and the
frequencies are reused, thus low power
transmissions.
Principle :
Divide large area into cells with 2 to 50 km
diameter, each cell allocated with a set of RF
channels

39. A cellular system: The tower represent base
station (BS) which provide radio access
between mobile users and the mobile switching
center (MSC).
BS MS BS BS

41. Cellular Advantages:
• Lower Power Transmissions
• Frequency Reusability
• Multiple Access capability
• Lower Antenna Heights
• Unlimited capacity and range
coverage
• Cell splitting & Micro cells
• Automatic hand off transparency
• Multi Level roaming

42. • Efficient Power control
• Handsets – Light weight, compact, Pocket held
• Digital Communication transceivers
• Value added & intelligent information services
• Mobile Multimedia broadband communication
• Minimal Blocking
• More than one license operator, Competition
• Better propagation models.

43. CELLULAR
SYSTEM
ARCHITECTURE

44. Basic Cellular system components :
1. Mobile Station / Unit / Site (MS)
2. Cell site / Base station (BS)
3. Mobile Telephone switching office/ Centre
4. Data Links

46. Mobile Station : (MS)
Mobile station/unit contains a Transceiver,
control unit and an Antenna.
Cell Site : (MSC)
Cell site contains a fixed Base station that has a
tower antenna, Transceivers (BS) for MS and
Fixed links to MTSO

47. MTSO or MSC
• This is the mobile switching exchange
• The central coordinating system for all the cells
• Contains cellular switch, control computer,
mobile management software, user
location mobile management software, user
location registers, Interfaces and links to BS &
PSTN.
• MTSO is the central administrator & Manager
• Cellular switch is Analog or Digital and switches
the calls to connect mobile – mobile or mobile –
fixed

48. • Coverage area is partitioned into nearly
hexagonal shaped areas called radio cells
• Each cell is served by one Base station for radio
coverage of all mobile units in that cell.
• Radio Link carries the VOICE and SIGNALLING
information (Channels) between the MS and BS
in that cell only.
• Base stations are connected to MSC through
fixed circuits (cables or fiber or microwave)
• MSC interacts with a database of subscriber
data and location information, to provide
dynamic terminal (MS) location to the switching
computer.

49. • MSC is connected to PSTN because majority of
calls originate from or terminate at fixed PSTN
phones.
• Every cellular system has some number of radio
channels for its use, depending on cellular
standard and RF band.
• The available radio channels are partitioned into
groups of channels, each group being allocated
to an individual cell.
• These individual group of channels can be
reused in distant cells without causing
interference.

50. Radio System Planning:
• Cell size design
• Cell location
identification/assignment
• Allocation of group of channels to
each cell
• Performance criteria
• Handoff mechanism
• Propagation modeling

51. • In each cell, one Radio Channel is set aside
permanently assigned to carry signaling
information between the cellular network (base
station) and all the mobile stations in that cell.
MS  BS Signaling Channel 
Location updating , call set up.
Paging response , user data
BS  MS Signaling Channel 
Operating parameters (identities)
Paging call, location updating, and control.

52. Location Updating
MS always monitors overhead information
broadcast by network on the signaling
channel
• MS updates the operating parameters as and
when necessary
• MS Checks Location information (area identity)
broadcast by new cell, if it is in new cell
location.
• MS advices the network about its new location
• Then network updates its location registers.
• This location information is used to route /
switch the incoming calls or determining paging

53. Mobile station initialization:
• Whenever a user activates the receiver of Mobile
unit, the receiver scans SETUP CHANNEL list
designated.
• It selects a strongest one and locks to it
• Each site has one set up channel only. Thus
strongest channel selection is the nearest BS
(Cell site) selection.
• This process is called SELF LOCATION

54. • This is done in Idle State also, transparently to
user.
• But, it can’t provide location information to
BS. Thus BS must search for idle mobile unit
by paging.
• In future, registration scheme will be used, in
which, the vehicles (MS) must register/update
location regularly, as shown above.

55. Mobile originated call set up:
• Exact procedure depends on particular cellular
standard.
• More or less similar in principle
• User places/keys in the called telephoned number
into an originating register and checks for
correctness in LCD display.
• Then user pushes ‘SEND’ button.
• This call request is sent on the already set up
channel on the uplink signaling channel
  there is no dial tone at all.

56. • The BS receives this call request signal and
sends a request to MTSO (MSC) via high speed
data link.
• BS selects an appropriate voice channel for the
call and sends a speech channel (number)
allocation message to mobile unit.
• MS now locks on to this allocated radio channel
• Network MSC proceeds now to set up the
connection to the called party.

57. NETWORK ORIGINATED CALL SETUP
(Mobile Terminated Call)
• A Landline phone dials a mobile unit number
• The PSTN exchange recognizes that the number is
a Mobile number
• PSTN exchange forwards this request to MTSO
(MSC)
• MTSO first establishes current location area for
the called mobile through signaling between
Home Location Register (HLR) and Visiting
Location Register (VLR).
• This process allows the call to be routed to the
current serving MTSO (MSC)

58. • The serving MTSO initiates a paging message
over the downlink-signaling channel toward the
cells contained in the paging area, through a cell
search algorithm
• Each cell site further transmits this paging
signal on its own set up channel.
• If mobile is in ON state, it receives paging
message, recognizes its own identification
number in it and locks to the strongest set up
channel (nearest BS).

59. • Only the intended mobile now sends back a
response to its nearest cell site (BS) on the
signaling channel.
• Now the respective BS, sends a speech channel
allocation message to the mobile and informs
the network so that connection can be
established.
• The mobile unit tunes to the assigned voice
channel tend initiates user alert of an incoming
call

60. Call Termination:
• When mobile user turns OFF the transmitter, a
signaling tone is sent to the BS.
• Both the sides free up the voice channel.
• BS and MTSO recognize this and disconnect the
connections and refresh the switch.
• MS resumes monitoring the pages through the
strongest setup channel, i.e. expects a paging
message from nearest / strongest BS (current
cell)

61. Hand Off:
• During a call, serving BS monitors mobile signal
strength
• If signal strength falls below a threshold, Network
requests all the neighboring cell BS to measure
signal strength from this mobile.
• If any nearest BS indicates better quality and
strength than the current serving BS, the MSC
commands the current BS to send a signaling
message to the mobile, asking it to retune to a
free channel in neighboring cell.
• The MS retunes to new channel and network MSC
switches call to new BS

65. Data and Communications
Convergence
Media
Streaming video
Video on demand
Interactive video services
Telecommunication Internet
PSTN and cellular services
Video telephony
Wideband data services
Computer
Broadband Wireless
Internet access
Electronic mail
Mobile computing

66. Convergence of High Speed Internet & Mobility
A major driver of future wireless
The Wireless Industry has grown at enormous
pace over the past decade.
More than half a billion subscribers to cellular
services are enjoying the benefits of staying
connected while on the move.
With the growth in Internet , a wide range of
services are accessed by users through a
wired infrastructure.
The introduction of mobile Internet brought
about by the convergence of Mobile & Internet
technologies is the future objective.

67. Wireless Network Evolution
First generation (1G): Analog voice systems
No standardization
Second Generation (2G): Digital voice systems
Currently deployed systems
CDMA, GSM (Global System for Mobile communication)
PDC (Japan) D-AMPS (Digital Advanced Mobile Phone
System)
PCS Systems
Second Generation – advanced (2.5G): Combining voice
and data communications
Providing enhanced data rate
Two basic technologies:
GSM-based (high baud rate)
GPRS (General Packet Radio Service)
Utilizes voice time slots to send packet traffic
An overlay over the existing voice system
Should really be called 2.1G!!
Any standards?

68. Third Generation (3G)
Two basic proposals to handle voice and data
Ericsson: Universal Mobile Telecommunications systems
(UMTS)
Compatible with European GSM
Backed by ETSI and Japan
Qualcom: CDM2000
Not compatible with GSM
Compatible for IS-95 (supported by U.S)
3G Standards
1999 UMTS took over and an agreement was made over setting
some standards
Major competing technologies
Bluethood
Wireless LAN (IEEE 802.x standards) – also known as WiFi
Short range wireless communications
Highly utilized and very popular: offices, airports, coffee
shops, universities and schools
Two basic modes of operations:
• Ad-hoc networking: computers send data to one another
• Access point:: sending data to the base station

69. Fourth Generation (4G)
Supporting heterogeneous multitude of systems
Includes multiple networks:
Digital video broadband
Digital audio broadband
Wireless LAB, Bluethood-based networks
Open communication network: infrastructure independent which
can access to any services and applications
Complete compatibility between wireless and wired networks
through gateways
Supports statistical multiplexing of heterogeneous data over-the-air
Latency, noisy environment, unpredictable discontinuities and
loss, etc.
High-speed wireless transmission over the air
High performance physical layer
20Mbps (2G: 28Kbps, 3G: 2Mbps)
Scarce bandwidth availability
Efficient frequency spectrum utilization
Efficient hand off
Dynamic bandwidth allocation
Advanced digital transmission technology (modulation, low
power devices, etc.)

71. G-points in Mobile Comms History
2G 2.5G
1G digital
analog digital (analog)
- voice + data
- voice only - voice (data)
- flexible
- inflexible - inflexible
- optimised
- not optimised - optimised
- transparent
- very transparent - transparent
3G 3.5G 4G
digital digital digital/analog?
- data + voice - more data (IP) - even more
- very flexible - very flexible data
- ‘optimisable’ - ‘optimisable’ - very flexible
- not transparent - not transparent - ‘optimisable’
- transparent

72. GSM
 Global System for Mobile
Communications
 Digital cellular system for voice, fax, data
 >200 million customers
 >320 networks
 137 countries
 Annual growth rate of 100% - 200%
 4 new customers every second
Greater “presence” than MacDonalds!

73. Countries with GSM
with GSM
no GSM

74. Wireless Networks
Motivated by people-on-the-go
- PCs availability, Internet usage,
Mobile life
Aimed is to establish wide-area
voice data communications
Includes mobile systems (cellular
telecommunication systems)

76. Wireless Network Area Definitions
GSM Courtesy of IEEE
GPRS 802.15 Press Kit.
CDMA Jan. 2001
WAN IEEE802.11 Bluetooth
WAN-MAN HyperLan
PAN
MAN
MAN-LAN
LAN-PAN
Pico-Cell
~50km ~2km 0km ~10m

77. WLAN Network Architecture
Mobile
Agent
Laptop
Access
point
Fixed Fixed
Workstation Workstation
Mobile Mobile
Agent Agent
Wired Network
Workstation
PDA Access Access
point point
Printer
Fixed
Workstation
DBMS

78. WAN:
everywhere outside of the
hotspots, where wireless
GPRS, 3G – UMTS
Wide Area Internet connection are
provided
< 400 Kb/s – xx Mls, Kms
MAN:
Building to Building
Metropolitan Area connection
MMDS; LMDS; 802.16
10M > 155 Mb/s - Kms
LAN:
Local Area collection of secure “hot
spot” connections,
802.11b; 802.11a; 802.11g providing broadband
2M > 54Mb/s – > 300 ft, 100 m access to the Internet
Personal Area
Bluetooth; PAN:
collection of secure
< 800 Kb/s – < 30 ft, 10 m connections between
devices in a
“very” local area

79. Convergence
Convergence of Cellular Mobile Networks and WLANs
Benefits
For cellular mobile operators
 Higher bandwidths.
 Lower cost of networks and equipment.
 The use of licence-exempt spectrum.
 Higher capacity and QoS enhancement.
 Higher revenue.
For users
 Access to broadband multimedia services with lower
cost and where mostly needed (e.g. in Central Business
Districts and Business Customer Premises).
 Inter-network roaming.

80. These future networks will
have the following inherent
characteristics :
1. Broadband Internet access.
2. High (guaranteed) QoS.
3. Seamless access – fixed and mobile.
4. Intelligence.

81. The Internet is the driver
World Internet users (1999 – 2004)
Million 1999 2000 2001 2002 2003 2004
USA 97 118 135 145 148 152
Japan 23 32 38 43 47 50
Asia Pac 32 70 104 120 135 150
W.Europe 54 81 114 145 164 179
ROW 35 72 105 118 130 140
Total 241 373 496 571 624 671

82. Mobile Broadband Network
Categories
PAN Personal Area Networks
W-LAN Wireless Local Area Networks
W-WAN Wireless Wide Area Networks

83. Wireless Networking Standards
Overview
Market Name GPRS/GSM Wi-Fi Bluetooth ZigBee
IrDA UWB
Standard 1xRTT/CDMA 802.11b 802.15.1 802.15.4 802.15.3a
Application Wide Area Web, Email, Cable Monitoring &
Cable
Focus Voice & Data Video Replacement Control
replacement
System
16MB+ 1MB+ 250KB+ 4KB - 32KB ?
Resources
?
Battery Life
1-7 .5 - 5 1-7 100 - 1,000+
(days) ?
Network Size 1 32 7 255 / 65,000
1
Bandwidth
64 - 128+ 11,000+ 720 20 - 250
(KB/s) 9.6-115
Transmission
1,000+ 1 - 100 1 - 10+ 1 - 100+
Range (meters) 1-5
Success Reach Speed, Cost, Reliability,
Metrics quality Flexibility Convenience Power, Cost

84. Future PAN Technologies
Technology Max Introduction Advantages Dis- Bottomline
Speed advantages
Bluetooth 723.2Kbps 2001 Low cost Interference, Replace
security cables
Infrared 115Kbps In use Very low LOS Replaced by
cost Bluetooth
802.15.1 723.2Kbps 2002 Low cost Interference, Formalized
security Bluetooth
802.15.3 >20Mbps 2003 High data Expensive, Case not
High rate rates proven yet
Source: Gartner (2001)

85. W-WAN Categories
Analogue • AMPS • TACS
(1G) • N-AMPS • NMT
• GSM • CDMA/cdmaOne/IS-95A
Digital • CDPD • TDMA / IS-136
(2G) • PDC
• GPRS • EDGE Compact • PDC-P
2.5G • HSCSD • CDMA / IS-95B
• EDGE Classic • cdma2000 1xMC
• W-CDMA • CDMA 1 XTREME
3G • cdma2000 3xMC
• CDMA 1x EVDV
4G • Undefined

86. Technolog Max Introducti Advantage Dis- Bottomlin
y Speed on s advantag e
es
GPRS 171.2Kbp 2001 Packet data Data rates Will be
s for GSM may most
world disappoint successful
technology
through
2005
HSCSD 115Kbps In use Dedicated Low Will not be
channels deployment mainstrea
, expensive m
EDGE 384Kbps 2003 Higher data Expensive, Will not be
Classic rates for little able to
both packet terminal compete
& circuit support with W-
CDMA.
EDGE 250Kbps 2002 Higher data AT&T Unlikely to
Compact rates for (main be
both packet proponent) successful
& circuit has
TDMA changed
networks direction

87. Mobile Transactions
Transaction - Based
• Mobile Banking
• Mobile Stock Trading Technology Enabler:
• Travel Reservation & Payment
(Rail, LRT, Bus, Flights, Taxi, Dual – Slot Hand Phone
Hotel, Insurance)
• Entertainment Reservation & Payment
(Cinema, Theater, Concerts)
• Pre-Paid Voucher Recharge
• Vending Machine Purchases
• Electronic Cash Download
• Payment of Utility Bills
(Electricity, Water, Astro, etc)
• Other Payments
(Restaurant Bills, Takeaways, Parking)
• Online Auctions 2 nd
• Online Shopping (eg. CDs, Books) SIM Smart • Credit Card
• Music MP3 Downloads • Debit Card
Card Card
• eCash Card
• Customisable with SIM Toolkit • Pre-Paid Car
• Remote Upgrading • Loyalty Card

88. NEXT GENERATION MOBILE VISION &
CONCEPT
Ubiquitous connectivity for slow and fast moving
users, accessing high speed internet and related
multiple services at affordable cost and
reasonable QOS
Cooperation between content providers and
Wireless access providers- Virtual operators
Multi-Media, Multi-Environment, Multi-Operator
Environment
User Driven, User Controlled, Context Aware
Applications
Convergence of services, aggregation and inter-
working of existing and emerging technologies
and networks
Vertical and Horizontal Seamless Handover

89. Higher Data, Superior Radio Resource Management,
Seamless mobility, Aggregation of Generations
4G
Cost efficient, Higher Data
3G evolution
Multimedia messages, multiple services
3G
Packet Data, On
2G evolution
Digital Voice, data
2G
Analog Voice
1G
80’s 90’s 00’s 10’s

90. Evolution towards better Data rates
and higher mobility
Mobility
4G Research
V E-Mail 4.2 sec in 2G to 0.002s in 4G
Targets
Movie Download 926 hours in 2G to
1minute in 4G
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EV
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DO
0.1 1 10 100 1000

91. Convergence of High Speed Internet & Mobility
A major driver of future wireless
The Wireless Industry has grown at enormous
pace over the past decade.
More than half a billion subscribers to cellular
services are enjoying the benefits of staying
connected while on the move.
With the growth in Internet , a wide range of
services are accessed by users through a wired
infrastructure.
The introduction of mobile Internet brought
about by the convergence of Mobile & Internet
technologies is the future objective.

92. GENERAL REQUIREMENTS
 Handling multimedia Traffic
Data, Video, Voice
 Seamless Services on the move
User friendly smart devices
 Diversified wireless access
Under One Umbrella, Seamless
access
 Advanced Mobility Management
Independent of the IP version
Proactive, always-on
Intelligent integrated control

94. WIRELESS
TRANSMISSION

95. WIRELESS TRANSMISSION
Mobile Radio (Wireless) signals undergo many
impairments during transmission / propagation
through the radio channel (atmosphere / free space
/ any medium)
Frequencies
• Radio signals are modulated signals with carrier
frequency allotted in any of the frequency bonds.
• ITU Region
1. Europe, Middle East, Africa
2. Greenland, North & South America
3. Far East, Australia, New Zealand
• LAND / SATELLITE CELLULAR RADIO BANDS

96. SIGNALS: Mostly SINUSOIDAL(AM/FM)
or its variants (ASK, PSK)
spectrum has side bonds or
frequencies.
Fundamental + Harmonics
90° Ф = m sinФ
Phase
Zero phase
f
) Ф
I = m cosФ

97. ANTENNAS:
Energy Translators /Couplers from TX to CH.
Hence Radiation pattern.
Ideal Isotropic: Equal power in all directions
y
x
z
SMART ANTENNAS→ Use DSP

98. z
Real Directive: DIPOLE λ /2
omni directional uniform x
radiation in one plane
fig.of 8 in other two planes y y
DIRECTIONAL ANTENNA: x z
Main lobe in only y y z
one direction
x z x
SECTORIZED ANTENNA:
Several directed antennas z z
combined on a single pole x x
3 sector 8 sector

99. SIGNAL  Onlyone direction of
PROPAGATION transmission unlike wired
transmission
 Fixed error limited
transmission range
d
 Fixed error limited
detection range
 Interference range

100. SIGNAL IMPAIRMENTS
 Free space Loss or Los loss
Squared law  pr α 1/d2
- Due to equal distribution of
energy Over the surface of
energy sphere.
 Path Loss : Signal attenuation due to
rain,fog,dust,smog,air,snow
Signal penetration medium
attenuation frequency 

101. Blocking or Shadowing :
- due to large obstacles
Reflection : When λ < size of obstacle
- Mobile signal reflects from
sky scrapers, Walls,
Trucks,Mountains,Towers,
Birds.
Reflected signal is not as
strong as the original.
Reflection  Signal
strength 

102. Scattering : obstace size ≤ λ
Incoming signal is scattered in multiple directions
and become weak signals, due to many objects in
atmosphere or space .
Diffraction :
Similar to scattering Radio waves get deflected at
edges signals become weak

103. Multi Path Effects :
Delay Spread
POWER
ISI Fading –
Short term
t
Long term

104. MULTIPLE ACCESS OR MULTIPLEXING :
 Means of combining several user signals onto a
common channel
 Multiple users access and share a common channel
with no interference (Hope fully)
 Simple ex :1. Athletic tracks / Swimming lanes
2. Many cars/Buses/Trucks share a
multiple lane road due to separation
of lanes
Space Division Multiplexing
 However, needs a special identification and control
mechanism for proper MUX & DEMUX.
 For Wireless Communication,4 types of Multiplexing

105. SPACE DIVISION MULTIPLEXING :
 Assignment of space to each communication
channel i.e., actually a source signal, with minimum
interference and a maximum medium utilization
 Assume 3D space represented as shown
CH k1 k2 k3 k4 k5 k6
code c c
time t t
s1 frequency s2 s3 f
Κ
f
 Coverage Space is represented via circles
 Channels K1, K2, K3 can be mapped into three spaces S1,
S2, S3 with clear separation and no overlap
What about K4, K5, K6 ?

106.  Analogous to road traffic separate lanes
Analog fixed Telephone Network
separate wire pair
/ local loop
 For wireless, SDM implies , a separate sender for
each channel with wide space separations.
ex: FM radio stations.
• Problems arise if two or more channels occupy the
same space

107. FREQUENCY DIVISION MULTIPLEXING
(FDM / FDMA)
• Subdivision of frequency dimension into several
non-overlapping frequency bounds or slots.
c • Each channel Ki is allotted its
own (dedicated) band
f
• Sender uses this band
S1 S2 S3 continuously
• Guard spaces do exist for no
interferences.
t Ex:- Am radio stations
• Receivers must TUNE into the specific senders.
• Draw backs : Tremendous wasted frequency as user may
not transmit all the time (usually less than 1Hr per day).

108. TIME DIVISION MULTIPLEXING TDM(A)
• A channel Ki is given whole bandwidth, but only for
a fixed period of time
• Time dimension is partitioned into several Time
slots
• Each channel is allocated one Time slot.
c
t1
S1
t2 f
S2
t3 • Needs precise
S3
.
. synchronizatio
.
n in timings for
t TX or Rx.

109. HYBRID-FTDMA:
• A channel Ki use a certain frequency band fi for only a
certain amount of time ti
• More robust against frequency selective
interference / jamming.
• Better protection against Tapping / Intruder.
• But needs coordination between senders.
c
f
t

110. CODE DIVISION MULTIPLEXING : CDM(A)
 All channels use same
frequency at the same c
time.
 Separation through
coding each channel
with its own code.
 Guard space is the
distance in code space
t f
Ex:- ORTHOGONAL CODES

111.  Due to VITERBI.
Ex:- Different telephone calls use same band
width but different languages (Codes), at same
time.If language is same, then SDM is needed.
 Thus secret codes (Languages) provide security
 Code space is huge. Hence better protection
against interference and tapping .
 However, the intended receiver must know the
code and also must synchronize with Tx for
correct decoding .

112. AM
ANALOG
MODULATION FM
BINARY ASK, PSK, FSK
DIGITAL
M - ary MSK, QAM, GMSK,
QPSK, DQPSK
Analog
Base band
Digital signal
Data Digital Analog
Modulation Modulation
101101001
Radio
Carrier

113. SPREAD SPECTRUM MODULATION
 Developed for secured communication
 Means of transmitting a data sequence that
occupies larger bandwidth than the original base
hand
 Spreading of bandwidth is through the use of a
code that is independent of data
 Chief Advantages: 1. Resistance to narrow
band interference or
jamming
2. Multiple Access
Communication.

114.  Purposeful bandwidth spread to make the signal to
possess noise like appearance so as to blend into
the back ground noise.
Power P P P
f f f
i) ii ) iii )
P P
BPF
f f
iv ) v)

115. STEP i) Narrow band user input data
ii) Tx Spreads the signal into a wide band
signal. But energy is same as original.
iii) A Wide band interference and
Narrowband interference get added
to wide band signal during transmission
iv) Receiver dispreads the signal into
narrowband. Thus narrow band
interference gets spread and wide band
interference gets left as it is.
v) Receiver uses a BPF to band limit the
user signal to original bandwidth and yield
high SNR

116. MOBILE RADIO SIGNAL PROPAGATION &
ENVIRONMENT
Mobile radio signals propagating through a
communication medium are subjected to many
changes or modifications.
 Propagation path loss :-
- Due to beam Divergence (Free space Loss)
- Proportional to 1/d2
Terrestrial Losses :-
Terrain Dependent (Path Loss)
- Texture, roughness of terrain tends
to dissipate propagated energy.

117. • Scattering and Multipath effects :
- Signal gets scattered at ≤ λ obstacle points
and travel in multipaths.
- Result is different delay spreads of signal.
- Thus severe FADING of the received signal
(sum total of multipath signals).
- Because of low mobile antenna height and
near ground communication.

118. • Instantaneous Signal Strength :
S(t)
MS Stationary
avg Pr
m(t)
Local mean
MS moving r(t)
Time or
distance

119. • Depends on whether Mobile station (MS) is in
movement or stationary.
• Fading is always present due to multipath
effects due to multiple scattering points,
reflection points, dissipations.
• Delay spread is the smearing of received signal
due to lengthening of time period as a result of
different multipath signals arriving with
different phases.

120. • Short term fading is obtained by
r0(t) = r(t) - m(t) In db r0(t)
- multipath fading
Received Long term - Rayleigh fading
fading - due to multiple
reflections from
r(t) = r0(t) m(t) Model
buildings, structures.
m(t)
- Local mean long
term fading due to
terrain contour
• Signal fades about 40 dB
• Nulls around λ / 2
• Rate of fading α vehicle speed.

121. PROPAGATION PATH LOSS:
• Due to the presence of radio wave scatterers along
the path.
• No. of scatterers depend on the contour variations,
terrain roughness
T BS antenna MS antenna
▼ ▼
Snell’s law
▲
θ( )θ
Ф • Therefore changes in the
propagation as a result of
specular Reflection, Diffuse
T
Reflection and Diffraction.

122. Specular Reflection from smooth flat and
slopy terrains :
• Occurs when radio waves encounter a smooth
interface between two dissimilar media and linear
dimension of interface is larger than λ
Ex: Mirror reflection defined by Snell's law.
Elevation
 • Reflected wave at point θ
h1 due to reflection of incident
wave from BS antenna T
h1 can be thought of as
▼
originated from a fictitious
image antenna TI and
passed through the surface
Distance without refraction.

123. Diffuse Reflection:
• Occurs when radio waves encounter a rough
textured surface with roughness of order of λ
• Unlike specular reflection, this scatters energy and
focus a divergent radio path.
1
hp <
2 1 1
( + )
λ d1 d2
BS LOS
€ 
MS
LOS  ▼
h1 LOS h2
d1 d2

124. • Hygen’s principle explains this.
• In tensing of signals is smaller than that of
specular reflected wave
• Both these reflections correspond to LOS
propagation of reflected signals.

125. Diffraction:
• Occurs when the propagation path is obstructed by
the features of an intervening terrain between two
antennas.
•Thus out of sight propagation.
• Attenuation depends on
Elevation
whether obstruction extends
through the path or protrudes
into LOS path.
BS • Knife edge diffraction modals
€
h1 are used.
hp
▼
l h2
Distance

126. Path Loss : Propagation frequency distance
►
Path Loss
►
Ә1 (
100m ▼
► 3m
Ә2 (
> 2 km
Ә1 - incident angle / elevation angle
Ә2 - reflected angle
Propagation path loss is 40 dB / decade or 10 km.

127. Received carrier powered is inversely proportional to R 4.
-4 - For Mobile Radio Channel.
C αR
α R -2 - For Free space Radio Channel.
-γ - For Real Mobile radio model
αR 2<γ<5
FADING:
• Antenna height of Mobile unit is less than its
surroundings.
• Carrier signal wavelength is smaller than sizes of
surrounding structures.

128. Result : Multipath Fading due to net sum of multiple path
arriving signals with different phase.
Fading fluctuation range about 40 dB.
(10 dB above, 30 dB below avg / mean).
λ
• Nulls of fluctuation at the base band at about every
2
in space, but not with same levels.
• Rate of fluctuation α vehicle speed.

129. Multi path fading occurs in
Three situations :
1. Mobile unit and surrounding scatterers are still
/ stationary
2. Static Multipath Mobile unit standing still
scatterers moving
3. Mobile unit and scatterers moving.

130. Static Multipath Signal :
N
τ
s(t) = ∑ai s0(t − i )
i=1
{ i 2 Π f 0 ( t - τ ) + i Φ 0}
s(t) = x ( t - τ ) e
Envelope x(t) = a0 ∑ ai e - j 2 Π f 0 ∆ τi
ai → attenuation factor of ith path.
N signal paths,
τi → Propagation time
∆τi → additional relative delay on i th path.

131. Case 2 : MS still τi , a are
i uniquely different
scatterers along ith path at any instant.
moving cars
j Φ 0 - j 2 Π f0 t
∴ s(t) = x(t) e e
- j2 Πf0τ i(t)
x(t) = ∑ a0 ai(t) e
- jψ (t)
= A(t) e = a0 {R - js}
A(t) = a0 R + S 2 2
-1 S
ψ(t) = Tan
R

132. Case 3 : MS Moving – a) Scatters are absent
s0(t) b) only one scatterer present
▼ v c) Many scatterers present
θ near MS.
2π s(t) = a0 Exp [ j ( ω0t + φ0 − β vt cosθ ) ]
β=
λ
Doppler effect contributes additional frequency due
to movement of Mobile
v
Voltage fdoppler = fm cosθ = cosθ
λ
= ± depending on direction of travel
X(t)

133. Thus concept of standing waves is applied to radio
signals to understand the multipath effects.
A resultant signal due to an incident signal and a
perfect scatterer reflected signal, reaching a mobile
of speed V is
j [ ω0 t + φ0 - β vt] [ j ( ω0 t + φ0 + β vt - ω0 τ ) ]
s(t) = a0 e - a0 e
The envelope of S(t) looks like a standing wave pattern.
2
x2(t) = 4a02 sin2(β vt - )
ω0 τ
∴ Fading Frequency → 2V/λ

134. Scatterers (Houses)
As a mobile unit
proceeds in a
▼ street, it is passing
v through an avenue
of scatterers as
shown.
Highest Doppler Frequency fd is
v v
fm = max ( fd ) = max ( cosθ ) =
λ λ
W(f)
v
fd
2
λ

135. Why 800 MHz Band?
ITU - T and FCC chose 800 MHz initially because.
- Severe spectral limitations at lower frequency
Bands
- Maritime (ship) mobile service at 160 MHz
- Fixed station services from 30 to 100 MHz
- FM and VHF/UHF TV Bands from 80-600 MHz
- No Mobile radio transmission beyond 10 GHz
due to propagation path loss, multipath fading
and rain loss.
- 800 MHz allocated to educational TV Channels
was heavily under utilized.

136. Even though not an ideal frequency for mobile
radio, the 800 MHz band demonstrated the
feasibility.
History of 800 MHz spectrum:
1958 -Bell lab proposal for 75 MHz system at 800
MHz.
1974 -FCC allocated 40 MHz spectrum for one
cellular operator licensed per market area.
1980 -FCC revised its policy and introduced
competition with two licensed carriers per
service area of course this resulted in trunk
efficiency degradation

137. FCC assigned frequencies in 20 MHz groups, as
Ban Mobile Base System
A 824-835,845-846.5 869-880, 890-891.5 non wire line.
B 835-845, 846.5-849 880-890, 891.5-894
Wire line
1986 – FCC added 5 MHz to each band.
old 333 + new 83 = 416 channels per band
with 30 KHz per channel.

138. TRUNKING EFFICIENCY:
No. of calls per hour per cell =
Φ = Offered traffic load / average calling time
Trunking efficiency degradation factor
η = {φOne carrier – φ Multi carrier} / φOne carrier
η%
30 5 ca
reer
/m arke
t
20
2 career/m
10 arket
0 1 2 5 Blocking30
10 probability %

140. UNIQUENESS OF MOBILE
RADIO ENVIRONMENT
Propagation path loss increases with
- Frequency
- distance θ1  elevation angle
θ2  incident angle
h
▼
Dire
ct path
Re
fle
30 – 100 m cte
d pa
θ1( ▼
th
θ2 (
2 km d

142. Cell antenna height: 30
-100 m
Mobile antenna height:
Received carrier Power C =α R3m -4
Difference in Powers C1 R2 - 4
=( )
C2 R1
R1
∆ C = C2 - C1 in dB = 40 log
R2
General Rule
=>40 dB/dec path loss
Δc = - 40dB

143. R1
Free Space- c α R -2 ∆C = 20 log = 20 dB/dec
R2
R1
∆C = 40 log = 40 dB/dec
Mobile radio CH- c α R-4 R2
Received signal fading levels:
10 dB above and 30 dB below mean.
- R2
CDF P(R) = R e
− (R) = βν × η
lcr Level crossing rate η R
2π
afd Average fading duration - 2π -
t (R) = × tR
βν

144. PATH LOSS MODEL
• Different, often complicated, models are used for different environments.
• A simple model for path loss, L, is
L= Pr =K 1
f dα
2
Pt
where Pr is the local mean received signal power
Pt is the transmitted power
d is the transmitter-receiver distance
f is frequency,
K is a transmission constant.
The path loss exponent α = 2 in free space;
2 ≤ α ≤ 4 in typical environments.

145. PATH LOSS LIMITATIONS
• The received signal-to-noise power ratio, SNR, is
Pr KP 1
SNR = = • αt
Pn d NoB
where No is the one-sided noise power spectral density
B is the signal bandwidth.
• Given the performance requirement SNR ≥ SNRo,
the path loss imposes limits on the bit rate and the signal coverage.
KPt KPt 1/α
B≤ or d ≤
( )
dα NoSNRo NoBSNRo

148. SHADOW FADING
• The received signal is shadowed by obstructions such as
hills and buildings.
• This results in variations in the local mean received
signal power,
Pr (dB) = Pr (dB) + Gs
where Gs ~ N(0, σ 2 ), 4 ≤ σ s ≤ 10 dB.
s
• Implications
– nonuniform coverage
– increases the required transmit power

149. First order statistics of Fading => Average power
CDF, BER
∴ independent of time
Second order statistics of Fading =>lcr, afd,
word Error Rate
∴time/velocity dependent
_
2
- A A2
Rayleigh Fading : CDF P(x ≤ A) = 1- e
_
P(y ≤ L) = 1− e −L L

150. NOISE LEVEL IN CELLULAR BANDS:
THERMAL NOISE  -129 dBm at B = 30 KHz, T=290K
IGNITION NOISE  -124 to –104 dBm at B=30 KHz,
T=290K
Ni + (Na G)
AMPLIFIER NOISE  NF =
KTB

151. DELAY SPREAD
• Base station sends an impulse signal to the mobile station.
error
s0(t) = a0 s(t)
BS a0
Antenna 1 3
▼
t
τ 1 τ2 τ3 τ4 t
4
▼
2
4 scatter case Delay spread N=4

152. • Because of multipath scattering, the impulse gets
reflected many times and thus many impulses
(echo's) arrive at mobile unit at different times.
a0
N>>4
t
∆
N-scatter case delay spread
• Received impulse signal is
s(t) = a0 ∑ aj δ(t - τ ) e jωt
jωt
= E(t) e

153. • As number of scatterers (N) increases, the received
impulse sequence becomes a continuous signal pulse,
with a pulse length Δ (called DELAY SPREAD).
• Delay envelopes contain multiple peaks.
• Shortest path signal need not necessarily produce
highest peak as the scatterer could be absorb in nature.
• Mean delay time d is the first moment or average.
∞
d =∫t E(t) dt
0
• Standard deviation or delay spread Δ is
t=0 → Leading edge of
∞
envelope E(t).
∆ = ∫ t E(t)dt - d
2 2 2
0

155. DELAY SPREAD
FREQUENCY DOMAIN INTERPRETATION
H(f)
Bs = signal bandwidth ≈ 1/T
Bs
1 f
2τ
• τ small flat fading
T
• τ large frequency-selective fading
T

157. Parameter Open Urban Suburban
Area Area Area
Mean Delay Time d, μs 0.2-0.5 1.5-2.5 0.1-2.0
Path Length, km 20–300 450-750 30-600
Max. Delay Time 0.5-2 5-12 0.3-7
(-30dB)
Path Length, Km 0.5-1 1.5-3.6 0.9-2.1
Range of delay spread 0.1-2.0 1-3 0.2-2
Δi, μs
Mean Delay Spread <0.2 3 0.5
Delay spread is assumed independent of frequency.

158. DOPPLER SPREAD
• A measure of the spectral broadening caused
by the channel time variation.
v
fD ≤
λ
Example: 900 MHz, 60 mph, fD = 80 Hz
5 GHz, 5 mph, fD = 37 Hz
• Implications
– signal amplitude and phase decorrelates after
a time period ~ 1/fD
8C32810.87-Cimini-7/98

159. COHERENCE BANDWIDTH:
• Bandwidth in which either the amplitudes or the phases
of two received signals have high degree of similarity or
correlated.
• Different delays in two fading signals that are closely
spaced in frequency can cause the two signals to become
correlated.
• The frequency spacing that allows this condition
depends on the delay spread Δ .
• This frequency interval is called coherence or correlation
Bandwidth Bc.

160. E(t)
Specular component
Scattered component
t
d dt Δ
Channel input response model
Correlation C(f)
function
Scattered component
f
Coherence bandwidth
1 1
Bc = or
Bc ≈
2Π Δ AM 8Δ
• A typical definition of Bc → 1 FM
= PM
4ΠΔ

161. NOISE IN MOBILE RADIO CHANNEL:
THERMAL NOISE
WIDEBRAND NARROWBAND
WHITE NOISE GAUSSIAN WHITE NOISE
n(t) = nc(t) + jns(t)

162. HUMAN MADE NOISE
URBAN SUBURBAN
EXTERNAL NOISE
SOLAR ATMOSPHERIC GALACTIC

163. NF
atmospheric
UR
SU BA
B N
UR
RU BA
RA N
L INTERNAL
RECEIVER
GA
0 RUR
AL Q
LA
CT
SOLA UITE IC
R
2 4 6 8 100 1000 105 109 f
-10 10
Mean Noise Figure Fa : 28 db / decade slopes for all.
Automotive Traffic Noise Power increases with traffic
density decreases with frequency

164. ELEMENTS OF CELLULAR MOBILE
RADIO SYSTEM DESIGN
GENERAL DESCRIPTION OF PROBLEM:
CONCEPT  efficient Spectrum Utilization
Major Elements of System Design 
1. Frequency Reuse Channels
2. Co channel Interference Reduction Factor
3. Carrier-Interference Ratio
4. Handoff Mechanism
5. Cell Splitting

165. Limitation / constraint In system design
 Frequency Resource
Challenge / goal  greatest no. of customers with
a specified system quality.
Ex :- Max. no. of calls/hour/cell Q
Max. No. of frequency Channels /cell - N
Q depends on
- cell size
- traffic conditions

166. Ex :- A BUSY Traffic area of 12 Km radius is divided into
seven 2 Km cells. Assume a traffic situation with the
busiest traffic cell cover 4 freeways and 10 heavy traffic
streets, with a total length of
• 64 Km of TWO 8 lane roads
• 48 Km of Two 6 lane freeways
• 588 Km of forty three 4 lane roads
average spacing of cars is 10m during busy periods. One
half cars have phones and eight tenths of them make a call
(ηc= 0.8) during the busy hour.
Total length of roads = 64 + 48 + 588 = 700km
700km
Total number of cars = = 70000
10m
70,000
No.of calls in busy hour = × 0.8 = 28,000
2

167. MAX. No. of Frequency Channels per cell (N)
• depends on average calling time T
• depends on maximum calls per hour per cell Qi
• Determined from a plot or Table that shows
N,B and A
• OFFERED TRAFFIC LOAD =
Q IT
A= Erlangs
60

169. Problems in wireless communication
• Available unlicensed spectrum allocation
(government regulation)
• Only low transmission power levels allowed
(No brute force possible: strong signal in
narrow band)
• Multi-path propagation echoes
• Interference
• Noise

179. RADIO ENVIRONMENT
• Path Loss
• Shadow Fading
• Multipath
• Interference
• Infrared Versus Radio
• Path Loss Limit the Bit Rate
• Shadow Fading and/or Coverage
• Multipath

180. FREQUENCY REUSE
BASE
STATION
• Frequencies (or time slots or codes) are reused at
spatially-separated locations.
• Introduces interference ⇒ system capacity is
interference-limited.
• Mainly designed for circuit-switched communications
• Base stations perform centralized control functions.
(call setup, handoff, routing, etc.)

181. DESIGN CONSIDERATIONS
• Reuse Distance (D)
– distance between cells using the same frequency,
time slot, or code
– smaller reuse distance packs more users into a given
area, but also increases their co-channel interference
• Cell Radius
– decreasing the cell size increases system capacity,
but complicates the network functions of handoff
and routing

196. History of Mobile Radio &Cellular Communication Systems
Year Telecom Event
1880 Initial radio demo by Hertz
1897 First radio transmission by Marconi
1921 Police car radio at 2 MHz in Detroit
1933 FCC permitted 4 channels in 30-40 MHz
1956 Simplex radio telephony system-450 MHz
1964 FCC – 152 MHz duplex radio telephony
1974
1979 FCC allots 40 MHz bandwidth in 800-900 MHz band
1981
First cellular system by NTT in Japan
First US cellular land mobile phone service in 800-
900 MHz band with 40 MHz bandwidth

197. 1984 AMPS cellular system introduced by AT&T in US
1986 FCC added 5 MHz extended band; two operators per
market
1988 TDMA digital cellular standard in North America (NA)
1992 GSM operable in Germany D2 cellular system
1993 CDMA chosen as digital cellular standard in NA
1994 American TDMA started in Seattle; PDC in Tokyo,
Japan
1995 CDMA in Hong Kong
1996 Six PCS licensed bands at 120 MHz given in US
1997 Broadband CDMA chosen as 3G Technology for
UMTS
1999 ITU decides nextG standards- W-CDMA, CDMA2000,
TD-SCDMA
2001 First commercial W-CDMA service in Japan
2002 FCC approves additional band for UWB

198. It is widely believed that the fixed landline telecom
network (Telephone, fax, etc) are the largest and
most complete integrated systems at present in the
world.
The cellular radio has rapidly evolved and had
already crossed the size of the fixed land telephone
network.
Let us consider the important differences between
the conventional landline telephone network and the
cellular radio telephone network.
Let us recall the basic features of the plain old land
telephone network (Public switched telephone
network – PSTN).

199. Plain old telephone:

200. DTMF Keypad for number dialing:

201. Features of land phone:
i) Telephone Number is registered solely in the local
exchange.
ii) Numbers are dialed from DTMF keypad as shown above.
iii)Central Battery supplies power to telephone handset.
iv)Subscriber loop is a 2 wire half duplex circuit.
v) Trunk circuits employ 4 wire circuits with Hybrid coil
doing 2/4 wire conversion.
vi)ON/OFF HOOK state of cradle switch is an indication to
the exchange about call REQ/ Disconnect signaling
information.
vii) subscriber can start dialing (entering telephone no.) only
after receiving the dial tone from the exchange.
viii) User must go to instrument to make a land phone call.

202. Features of mobile/cellular phone:
i) There is no dial tone and cradle switch (i.e. on/off Hook)
Hook
ii) User types in/ calls from memory and presses ‘SEND’
button to transmit telephone number of called party
iii)Power comes from the local Battery (LB), not from CB
iv)Local exchange is replaced by a base station (BS) and a
mobile switching centre (MSC)
v) Local 2 wire loop is replaced by 2 way HDX radio channel
vi)Cellular user talks on Reverse channel (MS to BS radio
link) and listens on forward channel (BS to MS radio link)
vii) signaling information is exchanged via separate set up
or control channels in each direction, user transparently

203. Fundamental principles of cellular
communications:
Cellular technology had evolved from the mobile radio
telephone technology.
Mobile radio telephone (R/T):
It is basically a transceiver handset with a 2 way duplex
link connecting to a base station and switching centre.
Mobile unit carries its own telephone number in a SIM /
smart card, which allows roaming using same number.
BS and MS always keep in touch by handshaking
protocols via control channels, transparent to the user.
The following figure depicts the components of a R/T.

204. Cellular radio phone and its components:

205. There are many ways of providing wireless and
mobile communications
For ex:- cordless phones used at homes employ
wireless technology, with a low power transmitter
and hence has small coverage area(<100 m)
Such phones used in adjacent homes do not
experience any interference, even by operating at
same frequency exactly
This is a perfect example for frequency reuse
The same principle of frequency interference
avoidance is used in cellular systems also, even
with much more transmission powers

206. Radio Cell Shape:

207. All users in a cell are served by central BS -gateway of cell !
Ideally all the cells are circular in shape for omnidirectional
coverage, with BS located at its centre as shown below.
Cell area and periphery are decided by minimum signal
strength, height of BS antenna, presence of hills, tall
trees/buildings and atmospheric conditions.
Thus actual shape of cell and coverage area is an irregular
zigzag circle, but modeled by a hexagonal building blocks.
Ex:- Bee hives are 3D hexagons
Multiple accessing is employed in cellular systems to allow
multiple cellular subscribers to access the same BS in a cell
They are FDMA, TDMA and CDMA

208. The limited bandwidth allocated to operator is divided into
number of radio channels, which are further grouped into
subsets, to assign one group of channels to a particular cell
This is the principle of FDMA employed in first
generation cellular systems.
Because of unique frequency sets allocated for each
cell, it is possible to use the same frequency set in a
distant cell, as long as the two transmissions do not
interfere with each other.
This is the principle of frequency reuse, a central theme
of cellular communications

209. Radio coverage in a single cell:
The fundamental radio cell and parameters that
dictate the radio coverage are shown below

210. Different cellular ranges for mobile radio communications
are indicated. The reverse path (MS to BS) limits the radio
range, due to limited TX. Power of mobile unit.
The no. of subscribers covered by a single cell depends on
the radius or area of the cell, as given in the table.
Cell area and number of subscribers covered
Cell radius Coverage Number of
km area km2 subscribers
covered
1 3.14 100
3 28.3 900
10 314 10,000
25 1960 60,000

211. Typical cellular system layout and signal power
distribution are shown below. One can see the
extensive signal processing required to meet this.

212. MULTIPLE CEL LAYOUT:
The intracellular communication is duplex radio
communication between cell site (BS) and mobile unit (MS).
It needs a block allocation of frequencies for the control and
voice radio channels
Adjacent cells are not assigned the same frequency sets to
avoid the cochannel and adjacent channel interferences.
A handoff mechanism is required to automatically handover
an ongoing mobile call from one group to another frequency
group used in the next cell, as and when mobile unit is
crossing cell boundaries.
That means the cellular phone circuits must be frequency
agile to retune to a new frequency without call disconnects.

213. Basic cellular system architecture:
Cellular technology replaced a large coverage area
mobile radio system with many smaller cells, with a
single BS covering one particular cell only, as
depicted in the following figure.

214. The mobile and wireless devices used by subscribers are
cell phones, PDAs, palmtop/laptop PCs, web phone s, etc.
All devices are referred to as Mobile Stations/Units (MS)
An MS can communicate only with its nearest BS of a
cell in which it is located ( i.e., belongs to).
Hence a BS (with a base transceiver) acts as a gateway
switch/router to the rest of the world, to any MS.
Every BS is controlled by one base station controller
(BSC), which in turn is connected to a mobile switching
centre (MSC) as shown in the following figure.
Several MSCs are interconnected to PSTN and ATM
backbone networks.

215. Cellular system architecture:

216. Home location register (HLR) and visitor location
register (VLR) are two database pointers that support
mobility and enable the use of same telephone number
worldwide in cellular communications.
HLR is located at the home MSC where MS is registered
VLR stores all the visiting mobiles in that particular
area
Authentication centre (AUC) provides authentication for
an user attempting to make a cellular call.
This uses a 15 digit unique IMEI number programmed
into the MS at registration time and also stored in
Equipment identity register (EIR).
Network management and operations control are the
functions of the centers NMC and OMC.

217. BS and MS signaling and voice communication:
In any cellular system, four simplex radio channels are
needed to exchange synchronization and data between
BS and MS, as shown below.

218. The control channels are used to exchange control
messages like, authentication, subscriber identity, call
parameter negotiation, power control, etc.
Traffic (information) channels are used to transfer
actual data (voice/digital data)
Forward CH/ Downlink  BS to MS transmissions
Reverse CH/ Uplink  MS to BS transmissions
Control information shall be exchanged before the
actual data transfer can take place.
This necessitates the use of handshaking protocols for
cellular call setup, maintenance and disconnection.

219. Handshaking protocols in cellular call setup:
Simplified handshaking steps for a cellular call setup
are illustrated in following figure.
BS MS
1. Need to establish path
2. Frequency/time slot/code assigned
3. Control information acknowledgement
4. Start communication
fig. steps for a call set up from MS to BS

220. steps for a call set up from MS to BS:
MS BS
1. Call for MS # pending
2. Ready to establish a path
3. Use of frequency/timeslot/code
4. Ready for communication
5. Start communication

221. Wireless LANs and PANs:
Mobile wireless networks find extensive use in different
facets of human life.
Already we are accustomed to line orientd to Local Area
Networks (LAN) and Wide Area Networks (WAN).
Ex:- Internet access, a value added service offered
by landline telephone network PSTN
Wireless LANs (WLAN) are being developed to provide
mobile access to data users.
Personal access Networks (PAN) cover very small areas
referred to as Pico cells using low powers in ISM band.
WLANs and PANs are becoming popular choice and
influence the wholesome home and office automation.

222. It is predicted that the percentage of nonvoice
multimedia data traffic is increasing heavily.
Also the digital voice technology is permitting the
integration of voice and nonvoice traffic into unified
data stream.
Thus convergence of voice and nonvoice networks into
a single unified network supporting multimedia
communications is the order of the day.
Standards like IEEE 802.11, Bluetooth, HomeRF,
HiperLAN etc., are being developed and deployed
worldwide.
Adhoc networks are being devised for commercial and
military applications.

223. MOBILE ADHOC NETWORKS (MANNET):
Adhoc networks are basically peer to peer multihop
mobile networks for freely moving mobile users and
hosts interconnected by nodes (mobile transceivers).
Information packets are transmitted using a store and
forward protocol as shown in the fig.
Nodes are very small transceivers with antennas and
can be located inside airplanes, ships, trains, trucks,
cars, homes, offices, etc.
This adhoc network topology (multihop graph) may
change with time as the nodes move or adjust their
transmission or reception parameters.

224. Typical adhoc network is shown below.

225. Wireless Sensor Networks:
Sensor networks are the newest members of a special
class of wireless networks.
A large no. of tiny immobile sensors are planted on the
adhoc basis to sense and transmit some physical
characteristics of the environment.
An associated BS collects the information reported by
the sensors on a data centric basis.
Ex:- Battlefield surveillance of enemy territory/war front
by sensors dropped from a low flying aircraft.
Potential commercial uses include machinery
prognosis, biosensing and environment monitoring.

226. Typical wireless sensor network:

227. WLAN and PAN characteristics and features
Type of Range of Primary function Deployed
network node locations
IEEE 30 m Standard for Any peer-peer
802.11 wireless nodes connection
Hiper- 30 m High speed indoor Airports,
LAN connectivity warehouses
Adhoc ≥ 500m mobiles, wireless, Battlefields,
Networks similar to wired disaster networks
connectivity
Sensor 2 m Monitor Nuclear,
Networks inaccessible, chemical plants,
inhospitable terrain oceans
Home RF 30 m Resource sharing, Homes
device connections
Bluetooth 10 m Avoid wire clutter, offices, buildings
low mobility indoors

229. HANDOFF
Handoff is defined as a process used to allow
a call/data transfer to continue uninterrupted
as the mobile terminal moves between cells

230. Hard handoff vs. Soft handoff
Hard handoff- break before make
Soft handoff – Make before break
Vertical Handoff vs. Horizontal Handoff
Vertical Handoff- Between Different Networks
Horizontal Handoff- Between Same Networks
Decision to handoff is based on the received
signal strength or S/I ratio.

231. CHANNEL ASSIGNMENT
• Fixed Channel Assignment (FCA)
– each cell is assigned a fixed number
of channels
– channels used for both handoff and
new calls
• Reservation Channels with FCA
– each cell reserves some channels for
hand off calls
• Channel Borrowing
– a cell may borrow free channels from
neighboring cells
• Dynamic Channel Assignment

232. METHODS TO IMPROVE
SPECTRUM UTILIZATION
• Interference Averaging (CDMA)
• Interference Reduction
(power adaptation, sectorization)
• Interference Cancellation
(smart antennas, multi user detection)
• Interference Avoidance
(dynamic resource allocation)

233. PHYSICAL LAYER ISSUES
• Link Performance Measures
• Modulation Tradeoffs
• Flat Fading Countermeasures
• Delay Spread Countermeasures

234. LINK PERFORMANCE MEASURES
PROBABILITY OF BIT ERROR
• The probability of bit error, Pb, in a radio environment
is a random variable.
– average Pb, Pb
– Pr [Pb > Pbtarget] ∆ outage, Pout
=
• Typically only one of these measures is useful,
depending on the Doppler frequency and the bit rate.

235. HOW DO WE OVERCOME THE
LIMITATIONS IMPOSED BY THE
RADIO CHANNEL?
• Flat Fading Countermeasures
– Fade Margin
– Diversity
– Coding and Interleaving
– Adaptive Techniques
• Delay Spread Countermeasures
– Equalization
– Multicarrier
– Spread Spectrum
– Antenna Solutions

236. DIVERSITY
16
The chance that two deep fades
• Independent signal paths have a low probability
occur simultaneously is rare.
of experiencing deep fades simultaneously.
4 8 12
• The basic concept is to send the same
information over independently fading radio
• Independent fading paths can be achieved by
separating the signal in time, frequency, space, polarization, etc.
0
0
-20
-40
-80
-60
-100
(dBm)
Received Signal Power

237. DIVERSITY COMBINING TECHNIQUES
• • •
α1 α2 α3 αM
Combiner
Output
• Selection Combining: picks the branch with the highest SNR.
• Equal-Gain Combining: all branches are coherently combined
with equal weights.
• Maximal-Ratio Combining: all branches are coherently combined
with weights which depend on
the branch SNR.

248. THANK
YOU