Broadband and Personal Area Network
2110472 Computer Networks
Natawut Nupairoj, Ph.D.
Department of Computer Engineering
Chulalongkorn University
Broadband Speed
56k modem: 96sec - 1.5min
ISDN-data : 43 seconds
DSL: 2.5 -8.5 sec
Cable 2-way ( faster than or = to DSL )
DSL
Modem over PSTN Carry data over voice networks. Slow and difficult to handle.
Digital Subscriber Line (DSL) Dedicate line using special modems to transmit
digital information. Use the existing PSTN. ADSL: Asynchronous Digital Subscriber Line.
ADSL Speed
Unbalanced upstream/downstream bandwidth Allocate more for downstream traffic. Up to 10 to 1 ratio.
Max downstream bandwidth is varied based on the length from access point 6 Mbps – within 3 Kms. 1.5Mbps – more than 3 Kms.
Cable Modem
Broadband alternative. Comes with cable TV over
Coaxial cable: 2-way. Satellite dish (DSS): 1-way.
Coaxial cable Shared medium among neighbors. Send both downstream and upstream via the
cable.
Cable Modem
Satellite Dish – 1-way Can receive only the downstream. Use normal modem over PSTN for upstream.
Personal Area Network
Network within small spaces. Most of them are wireless
Wi-Fi (802.11b). HomeRF. Bluetooth.
Requirements Small. Low-power consumption.
Wireless LAN
Based on Ethernet Standard. 802.11a – up to 54 Mbps. 802.11b : WiFi – up to 11 Mbps.
Use CSMA/CA Similar to TDMA concept.
Characteristics 5 GHz (802.11a) and 2.4 GHz (802.11b). Frequency hopping scheme. Wired Equivalent Privacy (WEP)
Similar to SSL.
802.11 Comparison
802.11a Provide more bandwidth. Can cover shorter distance.
802.11b (WiFi) Low power consumption. Cheaper to produce. In market now.
Bluetooth
Wireless technology specifically for: Short range – up to 10 meters typically. 2.4 GHz, Frequency Hoping. Modest performance (721Kbps). Dynamic configurability
i.e. ad hoc networking/roaming. Low power, low cost, and small.
Well suited to handheld applications. Support for both voice and data.
History of Bluetooth
Ericsson, the principal inventor, borrowed the name from Harald Bluetooth (son of Gorm) The King of Denmark circa
900AD United Denmark and
Norway Seemed like a good name
for uniting many dissimilar devices from different manufacturers
What is Bluetooth Good For?
Short-range wireless connectivity within three areas: Data and voice access
points Cable replacement Ad-hoc networking
PDACell Phone
Bluetooth in the Home
Cordless PhoneBase Station
xDSLAccess Point
InkjetPrinter
Scanner
Home Audio System
Computer
Digital Camera
MP3Player
And On the Road
Car Audio System
Pay Phone& Access Point
Hotel Phone& Access Point
Headset
MP3Player
PDACell Phone
Laptop
How Does Bluetooth Work?
Master
Active Slave
Parked Slave*
Standby*
N
J
F
IC
D
M
OP
Q
Operational States
* Low power state
In the Beginning Initially Bluetooth devices only know about
themselves Everyone passively monitors in Standby mode No devices are synchronizedD
A
E
B
C
F
KJ
HG
I
MN
L
PO
Q
InquiryDiscovering Who’s Out There
D
A
Inquiry discovers what other devices are within range
10 meters
HM
N
L
PO
Q
B
C
F
KJ
G
I
E
H
Note that a device canbe “Undiscoverable”
D
E
FH
G
I
KJ
PagingCreating a Piconet
Paging creates a Master/Slave link called a Piconet
C
MN
L
PO
Q
BBAA
10 meters
D
Expanding a Piconet (1) Successive Pages can attach up to 7 Active Slaves to a Piconet at one time
H
B
C
MN
L
PO
Q
E
FG
I
J
F
J
I
E
G
KK
A
10 meters
BB
JJ
DH
K
F
I
E
G
Parking To save power and/or to connect to even more
devices Active Slaves can be Parked (up to 256 total!)
C
MN
L
PO
Q
A
10 meters
D
K
F
I
E
G
Expanding a Piconet (2) Masters can then attach additional Active Slaves using
Active Member Addresses freed up through Parking
B
J
MN
L
PO
Q
H
C
H
C
A
10 meters
J
F
I
E
A
G
Scatternets
D
M
O
Bluetooth devices can participate in multiple Piconets simultaneously creating a topologies called Scatternets
B
L
H
K
C
N
P
Q
NH
K
F
I
E
A
G
J
C
Advanced Scatternets
D
M
O
Scatternets can evolve into extremely complex structures creating a rich fabric of many, many, devices
P
Q
B
L