1. Computer networks
6: Wireless and Mobile Networks

2. Guided Transmission Data
Twisted Pair
Coaxial Cable
Fiber Optics
6: Wireless and Mobile Networks

3. Twisted Pair (a) Category 3 UTP. (b) Category 5 UTP.
6: Wireless and Mobile Networks

4. Coaxial Cable
A coaxial cable.
6: Wireless and Mobile Networks

5. Fiber Cables (a) Side view of a single fiber.
(b) End view of a sheath with three fibers.
6: Wireless and Mobile Networks

6. A comparison of semiconductor diodes and LEDs as light sources.
Fiber Cables (2)
A comparison of semiconductor diodes and LEDs as light sources.
6: Wireless and Mobile Networks

7. The Electromagnetic Spectrum
The electromagnetic spectrum and its uses for communication.
6: Wireless and Mobile Networks

8. Radio Transmission
(a) In the VLF, LF, and MF bands, radio waves follow the curvature of the earth.
(b) In the HF band, they bounce off the ionosphere.
6: Wireless and Mobile Networks

9. The Mobile Telephone System
First-Generation Mobile Phones: Analog Voice
Second-Generation Mobile Phones: Digital Voice
Third-Generation Mobile Phones: Digital Voice and Data
6: Wireless and Mobile Networks

10. Advanced Mobile Phone System
(a) Frequencies are not reused in adjacent cells.
(b) To add more users, smaller cells can be used.
6: Wireless and Mobile Networks

11. GSM Global System for Mobile Communications
GSM uses 124 frequency channels, each of which uses an eight-slot TDM system
6: Wireless and Mobile Networks

12. A portion of the GSM framing structure.
6: Wireless and Mobile Networks

13. Elements of a wireless network
wireless hosts
laptop, PDA, IP phone
run applications
may be stationary (non-mobile) or mobile
wireless does not always mean mobility
network
infrastructure
6: Wireless and Mobile Networks

14. Elements of a wireless network
base station
typically connected to wired network
relay - responsible for sending packets between wired network and wireless host(s) in its “area”
e.g., cell towers, access points
network
infrastructure
6: Wireless and Mobile Networks

15. Elements of a wireless network
wireless link
typically used to connect mobile(s) to base station
also used as backbone link
multiple access protocol coordinates link access
various data rates, transmission distance
network
infrastructure
6: Wireless and Mobile Networks

16. Characteristics of selected wireless link standards
200
802.11n 54
802.11a,g
data
5-11
802.11b
(WiMAX) 4
3G cellular
enhanced
UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO
Data rate (Mbps) 1
802.15
.384
UMTS/WCDMA, CDMA2000 3G
.056
IS-95, CDMA, GSM 2G
Indoor
10-30m
Outdoor
50-200m
Mid-range
outdoor
200m – 4 Km
Long-range
outdoor
5Km – 20 Km
6: Wireless and Mobile Networks

17. Elements of a wireless network
infrastructure mode
base station connects mobiles into wired network
handoff: mobile changes base station providing connection into wired network
network
infrastructure
6: Wireless and Mobile Networks

18. Elements of a wireless network
ad hoc mode
no base stations
nodes can only transmit to other nodes within link coverage
nodes organize themselves into a network: route among themselves
6: Wireless and Mobile Networks

19. IEEE Wireless LAN
802.11a
5-6 GHz range
up to 54 Mbps
802.11g
2.4-5 GHz range
802.11n: multiple antennae
up to 200 Mbps
802.11b
2.4-5 GHz unlicensed spectrum
up to 11 Mbps
6: Wireless and Mobile Networks

20. 802.11 LAN architecture wireless host communicates with base station
Internet
wireless host communicates with base station
base station = access point (AP)
Basic Service Set (BSS) (aka “cell”) in infrastructure mode contains:
wireless hosts
access point (AP): base station
ad hoc mode: hosts only AP
hub, switch
or router AP
BSS 1
BSS 2
6: Wireless and Mobile Networks

21. 802.11: Channels, association
802.11b: 2.4GHz-2.485GHz spectrum divided into 11 channels at different frequencies
AP admin chooses frequency for AP
interference possible: channel can be same as that chosen by neighboring AP!
host: must associate with an AP
scans channels, listening for beacon frames containing AP’s name (SSID) and MAC address
selects AP to associate with
may perform authentication [Chapter 8]
will typically run DHCP to get IP address in AP’s subnet
6: Wireless and Mobile Networks

22. 802.11: passive/active scanning
BBS 1
BBS 1
BBS 2
BBS 2
AP 1
AP 2
AP 1 1
AP 2 1 1 2 2 2 3 3 4 H1 H1
Passive Scanning:
beacon frames sent from APs
association Request frame sent: H1 to selected AP
association Response frame sent: H1 to selected AP
Active Scanning:
Probe Request frame broadcast from H1
Probes response frame sent from APs
Association Request frame sent: H1 to selected AP
Association Response frame sent: H1 to selected AP
6: Wireless and Mobile Networks

23. 802.15: personal area network
less than 10 m diameter
replacement for cables (mouse, keyboard, headphones)
ad hoc: no infrastructure
master/slaves:
slaves request permission to send (to master)
master grants requests
802.15: evolved from Bluetooth specification
GHz radio band
up to 721 kbps P S P
radius of
coverage M S S P P M S
Master device
Slave device
Parked device (inactive) P
6: Wireless and Mobile Networks

24. 802.16: WiMAX like 802.11 & cellular: base station model
point-to-point
like & cellular: base station model
transmissions to/from base station by hosts with omnidirectional antenna
base station-to-base station backhaul with point-to-point antenna
unlike :
range ~ 6 miles (“city rather than coffee shop”)
~14 Mbps
point-to-multipoint
6: Wireless and Mobile Networks