Introduction to Wireless Networks

1. Chapter 1:
Introduction to Wireless Networks
Student: Yusuf Farhan

2. Wireless Applications
• Wireless applications are found anywhere employees
need mobility, including in the
following industries:
– Education
– Military
– Business
– Entertainment
– Travel
– Construction
– Warehouse management
– Health care

3. Advantages of Wireless Networks
• No need to install and maintain wires
• Reduces cost –important in offices, hotels, …
• Simplifies deployment –important in homes, hotspots, …
• Supports mobile users:
– Move around office, campus, city, … -users get hooked
– Remote control devices (TV, garage door, ..)
– Cordless phones, cell phones, ..
– WiFi, GPRS, WiMax, …

4. Disadvantages of Wireless Networks
• Quality of transmission
• Interference and noise
• Capacity of the network
• Effects of mobility

5. Electronic Computing Devices & Technology
Trends
 Advances in Technology
 more computing power in smaller devices
 flat, lightweight displays with low power consumption
 user interfaces suitable for small dimensions
 higher bandwidths
 multiple wireless interfaces: wireless LANs, wireless WANs,
home RF, Bluetooth
 New Electronic Computing Devices
 small, cheap, portable, replaceable and most important of all
USABLE!
 Technology Trends
 devices are aware of their environment and adapt - “location
awareness”
 devices recognize the location of the user and react
appropriately (e.g., call forwarding, fax forwarding)

6. Wireless and Mobile Communications
 Definition of mobility:
 user mobility: users communicate anytime, anywhere, with anyone
 device portability: devices can be connected anytime, anywhere to the
network
 Definition of wireless:
 no physical wire attachment
 Wireless vs. Mobile Examples
  stationary computer
  notebook in a hotel
  wireless LANs in legacy buildings
  Personal Digital Assistant (PDA)
 The need for mobility creates the need for integration of wireless
networks into existing fixed network environments:
 local area networks: standardization of IEEE 802.11b/g/a
 Internet: Mobile IP extension of the internet protocol IP
 wide area networks: e.g., internetworking of 3G and IP
1.6

7. Applications I
 Vehicles
 transmission of news, road conditions, weather
 personal communication using cellular
 position identification via GPS
 inter vehicle communications for accident prevention
 vehicle and road inter communications for traffic control,
signaling, data gathering
 ambulances, police, etc.: early transmission of patient data to
the hospital, situation reporting
 entertainment: music, video
Spring 2003 1.7

8. Highway Scenario
c
GSM, 3G, WLAN, ho
Bluetooth, ... ad
PDA, laptop, cellular phones,
GPS, sensors
1.8

9. Applications II
 Mobile workers
 access to customer files and company documents stored in a
central location
 collaborative work environments
 access to email and voice messages
 Replacement of fixed networks
 remote sensors, e.g., weather, environment, road conditions
 flexible work spaces
 LANs in legacy buildings
 Entertainment, education, ...
 outdoor Internet access
 intelligent travel guide with up-to-date
Buil C
location dependent information
150
t
B
 ad-hoc networks for
multi user games
1.9

10. Mobile Devices
Pager PDA Laptop
• receive only • simple graphical displays • fully functional
• tiny displays • character recognition • standard applications
• simple text • simplified WWW
messages
Sensors,
embedded
controllers
Mobile phones Palmtop
• voice, data • tiny keyboard
• simple text displays • simple versions
of standard applications
performance
1.10

11. Impact of Portability on Device Design/Functionality
 Power consumption
 battery capacity - limited computing power, low quality/smaller
displays, smaller disks, fewer options (I/O, CD/DVD)
 Device vulnerability
 Required design
 withstand bumps, weather conditions, etc.
 theft
 Limited/Simpler User Interfaces
 display size
 compromise between comfort/usability and portability (keyboard size)
 Limited memory
 memory limited by size and power
 flash- or SD memory as alternatives.
ICS 243E - Ch. 1 Introduction Spring 2003 1.11

12. Wireless Networks Compared to Fixed Networks
 Higher loss-rates due to interference
 other EM signals, objects in path (multi-path, scattering)
 Limited availability of useful spectrum
 frequencies have to be coordinated, useful frequencies are
almost all occupied
 Low transmission rates
 local area: 2 – 11 Mbit/s, wide area: 9.6 – 19.2 kbit/s
 Higher delays, higher jitter
 connection setup time for cellular in the second range, several
hundred milliseconds for wireless LAN systems
 Lower security, simpler active attacking
 radio interface accessible for everyone
 base station can be simulated, thus attracting calls from
mobile phones
 Always shared medium
 secure access mechanisms important

13. Location Dependent Services
 Location aware services
 what services, e.g., printer, fax, phone, server etc. exist in the
local environment that can be used by the user (security and
authentication)
 Follow-on services
 automatic call-forwarding, transmission of the actual
workspace to the current location
 Information services
 push: e.g., current special offers in the supermarket
 pull: e.g., where is the Sarah Lee New York Cheese Cake?
 Support services
 caches, intermediate results, state information, etc., follow the
mobile device through the fixed network
 Privacy
 who should gain knowledge about the location of the
user/device

14. Data Communication Terms
 Data - entities that convey meaning, or information
 Signals - electric or electromagnetic representations of
data
 Transmission - communication of data by the propagation
and processing of signals.
 Modulation is varying the properties of a career signal to
send information.
 The result of modulation is known as the carrier signal or
the baseband signal which we want to transmit to carry
information. The basic parameters used to describe the
carrier signal are (amplitude, frequency and phase).


15. Data Communication Terms
 Altering these parameters results in three types of
modulation; starting from amplitude modulation popularly
known as AM, frequency modulation (FM), QPSK, PCM,
GMSK, QAM etc.
 Multiplexing is a way of combining multiple signals
carrying information over a shared medium.

16. Analog Signals
 A continuously varying electromagnetic wave that may be
propagated over a variety of media, depending on frequency
 Examples of media:
 Copper wire media (twisted pair and coaxial cable)
 Fiber optic cable
 Atmosphere or space propagation
 Analog signals can propagate analog and digital data

17. Digital Signals
 A sequence of voltage pulses that may be transmitted over a
copper wire medium
 Generally cheaper than analog signaling
 Hardly affected by noise interference
 Suffer more from attenuation (reduction)
 Digital signals can propagate analog and digital data

20. Multiplexing

21. Multiplexing Techniques
 Frequency-division multiplexing (FDM)
 Takes advantage of the fact that the useful bandwidth of the
medium exceeds the required bandwidth of a given signal
 Time-division multiplexing (TDM)
 Takes advantage of the fact that the achievable bit rate of the
medium exceeds the required data rate of a digital signal

22. Frequency-division Multiplexing

23. Time-division Multiplexing

24. Areas of research in mobile communication
 Wireless Communication
 transmission quality (bandwidth, error rate, delay)
 modulation, coding, interference
 media access, regulations
 ...
 Mobility
 location dependent services
 location transparency
 quality of service support (delay, jitter, security)
 ...
 Portability
 power consumption
 limited computing power, sizes of display, ...
 usability
 ...

25. Mobile communications and the Reference Model
service location
Application layer 
 adaptive applications
 congestion and flow control
Transport layer  quality of service
 addressing, routing,
device location
Network layer  hand-over
 authentication
 media access
Data link layer  media access control
 multiplexing
 encryption
Physical layer  modulation
 interference
 attenuation
 frequency
ICS 243E - Ch. 0 Overview Spring 2003 0.25

26. The wireless space
WAN
(Wide Area Network)
MAN
(Metropolitan Area Network)
LAN
(Local Area Network)
PAN
(Personal Area
Network)
PAN LAN MAN WAN
802.11
Bluetooth
Standards 802.15.3
802.11 802.16 GSM, CDMA, Satellite
802.20
Speed < 1 Mbps 11 to 54 Mbps 10-100+ Mbps 10 Kbps–2 Mbps
Range Short Medium Medium-Long Long
Peer-to-Peer
Applications Device-to-Device
Enterprise Networks Last Mile Access Mobile Data Devices