Broadband and Personal Area Network

2110472 Computer Networks

Natawut Nupairoj, Ph.D.

Department of Computer Engineering

Chulalongkorn University

Outline

Overview. Broadband. Personal Area Network

Wi-Fi. Bluetooth.

Overview

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.

Frequency Hopping Scheme

Adhoc Configuration

Basic Service Set

Interconnection

Basic Service Set

Extended Service Set

Typical WLAN Configuration

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

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PO

Q

InquiryDiscovering Who’s Out There

D

A

Inquiry discovers what other devices are within range

10 meters

HM

N

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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

Summary

Broadband ASDL. Cable Modem.

Personal Area Network Wi-Fi. Bluetooth.

References J. Kurose and K. Ross, Computer Networking: A Top-Down

Approach Featuring the Internet, Addison Wesley, 2001. And many more.