ECE 692 Special Topics:
Mobile Network Systems Design
Wireless Networking
Wei Gao
Spring 2013
Notes
 Mobile system research report
 Deadline for topic selection: Feb. 12
 Discuss with me about your selected topic
 Paper presenters to be determined this Thursday
ECE 692 Mobile Network Systems Design
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Wireless Technologies
WAN
(Wide Area Network)
MAN
(Metropolitan Area Network)
LAN
(Local Area Network)
PAN
(Personal Area
Network)
PAN
LAN
MAN
WAN
Bluetooth
802.11a,11b,11g
HiperLAN2
802.11
MMDS, LMDS
GSM, GPRS,
CDMA, 2.5-3G
Speed
< 1Mbps
2 to 54+ Mbps
22+ Mbps
10 to 384Kbps
Range
Short
Medium
Medium-Long
Long
Peer-to-Peer
Device-to-Device
Enterprise
networks
Fixed, last mile
access
PDAs, Mobile
Phones,
cellular access
Standards
Applications
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Contents
 Cellular network
 GPRS
 3G network architecture
 Wireless access
 Wireless radios
 Wireless MAC
 Wireless networking
 Wireless LAN
 Ad-hoc networks: routing
 Security
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Cellular Network
 UE: User Equipment
 USIM + ME
 USIM: Universal Subscriber Identity Module
 ME: Mobile Equipment
 RAN: Radio Access Network
 Base stations (node B) and radio network controllers (RNC)
 Controls the operation of multiple base stations
 CN: Core Network
 GSM
 GPRS
 3G/4G
UE
ECE 692 Mobile Network Systems Design
RAN
CN
5
3G Network Architecture
 MSC: Mobile-service Switching Controller
 HLR: Home Location Register
 SGSN: Serving GPRS Support Node
 GGSN: Gateway GPRS Support Node
 PSTN: public switched telephonic network
 Your home phone
USIM
B
B
RNC
MSC
GMSC
PLMN, PSTN
GGSN
Internet
HLR
B
Phone, PDA
B
RNC
SGSN
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GPRS: General Packet Radio Service
 Packet-switched network
 Delivers packets to mobile platforms
 Coexists with GSM network (voice, SMS)
 Packet-switched and circuit-switched services share
the same radio resources
 IP packets can be sent/received from the GPRS
network
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3G Network
 UMTS: Universal Mobile Telecommunication System
 Max rate: 42 Mb/s when HSPA is implemented
 EDGE: Enhanced Data rates for GSM Evolution
 Extending GSM/GPRS
 Complement UMTS when signal strength is low or 3G
coverage is limited
 Data rate: 1 Mb/s
 CDMA: Code Division Multiple Access
 Better reliability, lower energy consumption, and security
features
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Contents
 Cellular network
 GPRS
 3G network architecture
 Wireless access
 Wireless radios
 Wireless MAC
 Wireless networking
 Wireless LAN
 Ad-hoc networks: routing
 Security
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Wireless radios
 WiFi: 802.11
 Bluetooth: 802.15.1
 ZigBee: 802.15.4
 WiMAX: 802.16
 Near-Field Communication (NFC)
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RF Bands
Short Wave Radio
AM Broadcast
Audio
FM Broadcast
Infrared wireless LAN
Television
Cellular (840 MHz)
NPCS (1.9GHz)
Extremely Very Low Medium High Very Ultra Super Infrared Visible Ultra- X-Rays
Low
Low
High High High
Light violet
902-928 MHz
26 MHz
2.4 – 2.4835 GHz
83.5 MHz
(IEEE 802.11)
ECE 692 Mobile Network Systems Design
5 GHz
(IEEE 802.11)
HyperLAN
HyperLAN2
11
802.11 Family
 IEEE 802.11 became a standard in July 1997
 Infrared
 Two RF technologies defined:
•
•
Direct sequence spread spectrum - 1 Mbps and 2 Mbps
Frequency hopping spread spectrum - 1 Mbps and 2 Mbps
 IEEE 802.11b became a standard in September 1999
 Only one RF technology defined- DSSS at 5.5 Mbps & 11
Mbps
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Spread Spectrum Approaches
Direct Sequence
Frequency Hopping
100 Mw
Mhz
P
O
W
E
R
1 Mw
Mhz
2.402 GHz
1 Sec
1 Ms
22
FREQUENCY
2.483 GHz
Two-way communication: half duplex
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Channels – 802.11 DS
 (11) 22 MHz wide stationary
channels
 11 Mbps data rate
 3 non-overlapping channels
 3 Access Points can occupy
same area
Channel
10
5
4
9
3
8
2
1
2400
7
6
2437
11
2483
Frequency
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Frequency Hopping
 Avoid interference
 Security purposes
9
8
 A total of 79 channels,
Time
available
 Changes frequency
(hops) at least every 0.4
seconds
 Synchronized hopping
required
7
6
5
4
3
2
1
2.400 GHz
2.483 GHz
Frequency
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Access Point Coverage
1Mbps DSSS
2 Mbps DSSS
5.5 Mbps DSSS
11 Mbps DSSS
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802.11 MAC Layer
 CSMA/CA (Collision Avoidance)
 CSMA: sense before transmitting to ensure no collision
 Recall: CSMA/CD for Ethernet
• Exponential backoff if interference/collision is detected
 Avoiding collision: “reserve” the channel before sensing
• RTS/CTS mechanism
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802.11 MAC Layer
A
AP
B
reservation collision
DATA (A)
defer
time
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802.15 Family
 Bluetooth/ZigBee
 Low-range, low transmission rate,
but low power
 Bluetooth: ~10m, 3 Mb/s, ZigBee:
~100m, 250kbps
 Cable replacement: mouse,
keyboard, headphone
P
S
P
radius of
coverage
M
S
P
S
P
 Ad-hoc mode: no infrastructure
 Handshake: master/slave
 slaves request permission to send
M Master device
(to master)
 master grants requests
S Slave device
P Parked device (inactive)
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802.16 WiMAX
 Intermediate between
cellular and WiFi
point-to-point
 Base station model
 ~ 6 mile range, ~ 14Mbps
 Corporate broadband access
point-to-multipoint
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Near-Field Communication
 Easy-on connection
 Extending RFID/smartchip techniques
 Android-based smartphones
 Apple does not care…
 Usage
 Smart tags
 Building connection for Bluetooth/WiFi
 Digital commerce
 Social networking
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Comparison with Bluetooth
Aspect
NFC
Bluetooth
Bluetooth Low
Energy
RFID compatible
ISO 18000-3
active
active
Network Standard
ISO 13157 etc.
IEEE 802.15.1
IEEE 802.15.1
Network Type
Point-to-point
WPAN
WPAN
Cryptography
not with RFID
available
available
Range
< 0.2 m
~100 m (class 1)
~50 m
Frequency
13.56 MHz
2.4–2.5 GHz
2.4–2.5 GHz
Bit rate
424 kbit/s
2.1 Mbit/s
~1.0 Mbit/s
Set-up time
< 0.1 s
<6s
< 0.006 s
varies with class
< 15 mA (transmit
or receive)
Power consumption < 15mA (read)
ECE 692 Mobile Network Systems Design
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Contents
 Cellular network
 GPRS
 3G network architecture
 Wireless access
 Wireless radios
 Wireless MAC
 Wireless networking
 Wireless LAN
 Ad-hoc networks: routing
 Security
ECE 692 Mobile Network Systems Design
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Wireless LAN
Ethernet
Hub/
Switch
10/100 Mbps
Shared
Bandwidth
(CSMA/CD)
Internet
Ethernet
11 Mbps Shared
Bandwidth
(CSMA/CA)
Access
Point
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Wireless LAN Topologies
Wireless “Cell”
Channel 1
Wireless “Cell”
Channel 6
LAN Backbone
Access Point
Wireless Clients
Access Point
Wireless Clients
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Wireless Ad-hoc Networks
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
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Basic Problem: Routing
 Proactive
 Continuously update reachability information in the network
 When a route is needed, it is immediately available
• DSDV by Perkins and Bhagwat (SIGCOMM 94)
• Destination Sequenced Distance vector
 Reactive
 Routing discovery is initiated only when needed
 Route maintenance is needed to provide information about invalid
routes
• DSR by Johnson and Maltz
• AODV by Perkins and Royer
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Opportunistic Mobile Networking
D
S
Carry-and-Forward
1
12
13
Relay
11
3
14
7
8
15
2 5
16
4
10
6
Contact
old link
current link
9
node movement
Opportunistic and intermittent network connectivity
Mobile Ad-hoc Networks (MANETs): end-to-end connectivity
Mobility
Functional failure
Battery depletion
ECE 692 Mobile Network Systems Design
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Contents
 Cellular network
 GPRS
 3G network architecture
 Wireless access
 Wireless radios
 Wireless MAC
 Wireless networking
 Wireless LAN
 Ad-hoc networks: routing
 Security
ECE 692 Mobile Network Systems Design
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802.11 Security
WEP (Wired Equivalency Privacy)
 40 bit keys
 128 bit keys
 Part of the association process
 WEP uses the RC4 stream cipher of RSA Data
Security, Inc. (RSADSI) for encryption.
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802.11 Open Authentication
Access
Point
A
Access
Point
B
Steps to
Authentication:
Client sends probe.
AP sends Probe Response.
Client evaluates AP
response, selects best AP.
Client sends authentication
request to selected AP (A).
AP A confirms authentication
and registers client.
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802.11 Shared Key Authentication
Access
Point
A
Access
Point
B
Steps to
Authentication:
Steps 1 - 3 are the same as Open
Authentication
AP A confirms authentication
and sends unencrypted test
packet.
Client encrypts packet and
returns to AP. AP checks encryption
against WEP key.
Correct WEP key is allowed on
the network. Incorrect WEP key
is not not allowed to associate.
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Enhanced Security Features
 802.1x
 IEEE standard in progress
 Port Based Network Access Control
 Extensible authentication support (EAP)
 Improved user authentication: username and password
 Dynamic, session-based encryption keys
 Centralized user administration
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Research Issues
 Cellular network
 3G is overloading! -> traffic offloading
 Are people using 3G resources efficiently?
 Wireless network
 Full duplex?
 Efficient utilization of radio spectrum -> cognitive radio
 Better MAC design?
 Ad-hoc network
 Argument between one-hop and multi-hop
 Non-commercial applications
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