Technology and Example
Standards
 The right technology/standard for the
problem/environment??
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Characteristics of selected wireless link
standards
Data rate (Mbps)
200
54
5-11
802.11n
802.11a,g
802.11b
4
1
802.11a,g point-to-point
data
802.16 (WiMAX)
UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO
3G cellular
enhanced
802.15
.384
UMTS/WCDMA, CDMA2000
.056
3G
2G
IS-95, CDMA, GSM
Indoor
Outdoor
10-30m
50-200m
Mid-range
outdoor
Long-range
outdoor
200m – 4 Km
5Km – 20 Km
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Differences in bandwidths
primarily from ...
 Physical layer
Spectrum allocation (wave length)
 Frequency; channel width; time multiplexing
 Signal-to-Noise; BER; Error correction; etc.

 MAC layer (sub-layer in data link layer)
 Multiple access techniques
 E.g., FDMA, TDMA, CDMA, SDMA, OFDMA
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Frequency band spectrum
 spectrum allocated by global and national agencies
(Less sensitive to obstacles)
Low frequency
(More sensitive to obstacles)
High frequency
ELF (30-300Hz) Telephone;
Visible light
(400-900THz)
AM broadcast
Cell phone;
Satellite
Microwave links
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IEEE 802.11 Wireless LAN
 802.11a
 802.11b
 5-6 GHz range
 2.4-5 GHz unlicensed spectrum
 up to 54 Mbps
 up to 11 Mbps
 802.11g
 direct sequence spread
spectrum (DSSS) in physical
 2.4-5 GHz range
layer
 up to 54 Mbps
• all hosts use same chipping
 802.11n: multiple antenna
code
 2.4-5 GHz range
 up to 200 Mbps
 all use CSMA/CA for multiple access
 all have base-station and ad-hoc network versions
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6
802.11 LAN architecture
 Wireless host communicates
Internet
AP
hub, switch
or router
BSS 1
with base station
 base station = access
point (AP)
 Basic Service Set (BSS) (aka
“cell”) in infrastructure
mode contains:
 wireless hosts
 access point (AP)
AP

BSS 2
ad hoc mode: hosts only
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802.11: Cells, channels, association
 802.11b has 11 channels
 Channels 1, 6, and 11 are
non-overlapping
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802.11: Cells, channels, association
Channel 1
Channel 11
Channel 1
 802.11b has 11 channels
 Channels 1, 6, and 11 are
AP
AP
Channel 6
AP
AP
Channel 1
AP
non-overlapping
 Each AP coverage area is
called a “cell”
 Wireless nodes can roam
between cells
AP
Channel 6
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802.11: Cells, channels, association
Channel 1
Channel 11
Channel 1
 802.11b has 11 channels
 Channels 1, 6, and 11 are
AP
AP
Channel 6
AP
AP
Channel 1
AP
non-overlapping
 Each AP coverage area is
called a “cell”
 Wireless nodes can roam
between cells
AP
Channel 6
 AP admin chooses frequency
for AP
 interference possible: channel
can be same as that chosen by
neighboring AP!
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802.11: Channels, association
 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
 typically run DHCP to get IP address in AP’s subnet
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802.11: passive/active scanning
BBS 1
AP 1
BBS 2
1
1
2
AP 2
BBS 1
BBS 2
AP 1
2
3
2
3
(1) Beacon frames sent from APs
(2) Association Request frame sent:
H1 to selected AP
(3) Association Response frame sent:
selected AP to H1
4
H1
H1
Passive Scanning:
AP 2
1
Active Scanning:
(1) Probe Request frame broadcast
from H1
(2) Probes response frame sent
from APs
(3) Association Request frame
sent: H1 to selected AP
(4) Association Response frame
sent: selected AP to H1
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802.11 frame: addressing
2
2
6
6
6
frame
address address address
duration
control
1
2
3
Address 1: MAC address
of wireless host or AP
to receive this frame
2
6
seq address
4
control
0 - 2312
4
payload
CRC
Address 4: used only
in ad hoc mode
Address 3: MAC address
of router interface to
which AP is attached
Address 2: MAC address
of wireless host or AP
transmitting this frame
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802.11: advanced capabilities
Rate Adaptation
10-1
 base station, mobile
10-2
QAM256 (8 Mbps)
QAM16 (4 Mbps)
BPSK (1 Mbps)
operating point
BER
dynamically change
transmission rate
(physical layer modulation
technique) as mobile
moves, SNR varies
10-3
10-4
10-5
10-6
10-7
10
20
30
SNR(dB)
40
1. SNR decreases, BER increase
as node moves away from base
station
2. When BER becomes too high,
switch to lower transmission
rate but with lower BER
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802.11: advanced capabilities
Power Management
 node-to-AP: “I am going to sleep until next beacon frame”
 AP
knows not to transmit frames to this node
 node wakes up before next beacon frame
 beacon frame: contains list of mobiles with AP-to-mobile
frames waiting to be sent
 Every 100ms (250s wakeup time)
 node will stay awake if AP-to-mobile frames to be sent;
otherwise sleep again until next beacon frame
 Explicit pull request
Note: Nodes with nothing to send/receive can save 99% of energy
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A typical Bluetooth data frame
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Bluetooth Networking
• Piconets and Scatternets:
– Bluetooth devices are organized in local networks called piconets
– up to eight devices can be part of a piconet
– devices are divided in master and slaves
– the master controls the utilization of the radio channel (e.g. frequencyhopping sequence and timing) in the communication with the slaves
– a slave may communicate only with the master and when allowed by the
master
– a device may belong to different piconets and may be both a master
and a slave in two different piconets
– a network formed by several connected piconets is called a scatternet
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802.15: personal area network (PAN)
 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


2.4-2.5 GHz radio band
up to 721 kbps
P
S
P
radius of
coverage
M
S
P
S
P
M Master device
S Slave device
P Parked device (inactive)
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802.16: WiMAX (MAN)
 like 802.11 & cellular:
point-to-point
base station model
transmissions to/from
base station by hosts with
omnidirectional antenna
 base station-to-base
station backhaul with
point-to-point antenna

point-to-multipoint
 unlike 802.11:
 range ~ 6 miles (“city
rather than coffee shop”)
 ~14 Mbps
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802.16: WiMAX: downlink, uplink scheduling
 transmission frame
down-link subframe: base station to node
 uplink subframe: node to base station

pream.
…
DL- ULMAP MAP
DL
burst 1
DL
burst 2
downlink subframe
…
…
DL
burst n
Initial request
SS #1 SS #2
maint. conn.
SS #k
…
uplink subframe
base station tells nodes who will get to receive (DL map)
and who will get to send (UL map), and when
 WiMAX standard provide mechanism for
scheduling, but not scheduling algorithm
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Components of cellular network architecture
MSC
cell
 connects cells to wide area net
 manages call setup (more later!)
 handles mobility (more later!)
 covers geographical
region

base station (BS)
analogous to 802.11 AP
 mobile users attach
to network through BS

Mobile
Switching
Center
air-interface:
physical and link layer
protocol between
mobile and BS
Public telephone
network, and
Internet
Mobile
Switching
Center
wired network
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Components of cellular networks, cont’d
• Frequency reuse: use the same
frequency spectrum in different
set of cells
• Cells that reuse the same
frequency must be distant enough
for avoiding interference
• Transmission power control
• Migration of a mobile station from
one cell to another with
continuance of communication ->
handoff
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Cellular standards: brief survey
2G systems: voice channels
 IS-136 TDMA: combined FDMA/TDMA (north
america)
 GSM (global system for mobile communications):
combined FDMA/TDMA

most widely deployed
 IS-95 CDMA: code division multiple access
GSM
Don’t drown in a bowl
of alphabet soup: use this
for reference only
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Cellular standards: brief survey
2.5 G systems: voice and data channels
 for those who can’t wait for 3G service: 2G extensions
 general packet radio service (GPRS)
 evolved from GSM
 data sent on multiple channels (if available)
 enhanced data rates for global evolution (EDGE)
 also evolved from GSM, using enhanced modulation
 data rates up to 384K
 CDMA-2000 (phase 1)
 data rates up to 144K
 evolved from IS-95
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Cellular standards: brief survey
3G systems: voice/data
 Universal Mobile Telecommunications Service (UMTS)
 data service: High Speed Uplink/Downlink packet
Access (HSDPA/HSUPA): 3 Mbps
 CDMA-2000: CDMA in TDMA slots
 data service: 1xEvlution Data Optimized (1xEVDO)
up to 14 Mbps
4G systems: voice/data
….. more (and more interesting) cellular topics due to mobility (stay
tuned for details)
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More slides …
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IEEE 802.11 Architecture
• Station: a device containing 802.11
equipment
• Basic Service Set (BSS): set of
stations controlled by a coordination
function
• Coordination function: logical function
determining when a station can
receive and send data in a BSS
• Distribution System (DS): a system
connecting a set of BSS and
integrated LANs to create an
extended service set (ESS)
• Extended Service Set: a set of BSS
and LANs appearing as a single unit to
the LLC layer of the component
stations
• Access point (AP) : entity providing
access to the distribution system
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IEEE 802.11 Services
• IEEE 802.11 define 9 services:
– 6 services for supporting delivery of MAC service data units (MSDU)
between stations
– 3 services for LAN access and confidentiality
• Service provider type:
– station: services implemented in stations and access point stations
(APs)
– distribution system (DS): services between BSSs implemented in
access point stations or dedicated devices
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Bluetooth - Channel control in a piconet [1]
• Two major states of a Bluetooth device:
– Standby: low-power state
– Connection: the device is connected
• Seven states for adding new slaves to a piconet:
– Page – device issued a page (used by master)
– Page scan – device is listening for a page
– Master response – master receives a page response from slave
– Slave response – slave responds to a page from master
– Inquiry – device has issued an inquiry for identity of devices
within range
– Inquiry scan – device is listening for an inquiry
– Inquiry response – device receives an inquiry response
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Bluetooth - Channel control in a piconet [2]
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Bluetooth - Inquiry and Page Procedure [1]
Inquiry Procedure:
Potential master identifies devices in range that wish to
participate
– transmits an identification ID packet with inquiry
access code (IAC)
– occurs in Inquiry state
Devices receives inquiry
– enter Inquiry Response state
– return data with address and timing information (in an
FHS packet)
– slave moves to Page Scan state or returns to Inquiry
Scan
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Bluetooth - Inquiry and Page Procedure [2]
Page Procedure
• Master uses device address to calculate a page
frequency-hopping sequence
• Master pages with ID packet and device access code
(DAC) of specific slave
• Slave responds with ID DAC packet
• Master responds with a special FHS packet containing
its address and real-time Bluetooth clock value
• Slave confirms master’s FHS packet reception with a
ID DAC packet
• Slaves moves to Connection state
Connection state control for slaves
• Master send a Poll packet to verify that a slave has
switched on master timing and channel frequency
• Slave responds with any packet
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Bluetooth - Slave Connection State Modes
Active – slave participates in piconet
– listens, transmits and receives packets
– master sent regularly synchronization data
Sniff – slave listens only on specified slots
– master indicate a reduced number of slots
– slave can operate in reduced power mode when not listening
Hold – slave may participate partially in the piconet
– slave in reduced power status
– slave does not support ACL packets
– slave may participate in SCO exchanges
Park – slave does not participate currently in the piconet
– slave still retained as part of the piconet
– device receive a parking address and loses its active member
address
– piconet may then have more than 7 slaves, but only 7 are active
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Other PAN’s:
The ANT protocol stack
 Wireless sensor communications protocol stack
 2.4 GHz RF spectrum (i.e., the ISM band)
 Establishes rules for co-existence, data representation,
signaling, authentication, and error detection
 Low computational overhead and high efficiency
 Low power consumption by the radios
 Targeted at the sports sector, particularly fitness
and cycling performance monitoring.

Transceivers are embedded in equipment such as heart
rate belts, watches, cycle power and cadence meters, and
distance and speed monitors
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