Wireless Networking

By: Todd Deshane

And

Ashwin Venkatraman

Introduction

What is a wireless network? A technology that enables two or more entities to

communicate without network cabling

Different Wireless Networks

IrDA (Infrared Data Association) Uses beams in the infrared light spectrum

Bluetooth Uses 2.45 gigahertz radio waves, but emits weak

signals Limits distance to 10 feet, but travels through walls

HomeRF (SWAP) – developed by businesses 6 voice channels and 1 data channel Slow, and limited range, but cheap

Wireless Fidelity (Wi-Fi)

Essentially, this technology is a variation of the IEEE 802.11 specification known as 802.11b

Focuses on Direct-Sequence Spread Spectrum (DSSS)

High data rate (max of 11 Mbps) In the case of interference, speed drops in halves (11 Mbps

to 5.5 Mbps to 2 Mbps to 1 Mbps)

Wi-Fi

Advantages: Fast (11 Mbps) Reliable Long Range (up to 1000 ft outdoors, 400 ft indoors) Easy integration to wired networks Compatible with original 802.11 DSSS standard

Disadvantages: Speed may fluctuate

802.11a vs. 802.11b

Frequency 802.11b transfers at 2.4 gigahertz 802.11a transfers at 5 gigahertz

Coverage Distance 802.11b goes about 400 feet indoors 802.11a goes about 60 feet indoors

Need more access points to cover a location

Compatible to each other? Not yet.

ITL Wireless Equipment

2 Wireless Access Point Routers (with built in 4 port switch) Wired Equivalent Privacy (WEP) available

8 Wireless PCMCIA Cards4 ORiNOCO Gold 11 Mbps PC Cards4 3Com 11 Mbps PC Cards

Wireless Access Point

LINKSYS Model No. BEFW11S4 ver. 2 Supports

IEEE 802.3 (10BaseT) IEEE 802.3u (100BaseTX) IEEE 802.11b (Wireless)

Built-in router capability Obtains a Clarkson IP and uses DHCP

Built-in 4 port switch Fully-configurable through simple web interface

Wireless Cards

11Mbs 802.11b compatible 4 3Com Cards

Model No. 3CRWE62092A

4 ORiNOCO (Lucent) Cards Model No. 012352/G

Performance

Inside Range anywhere except in bathrooms Usually 11 Mbps connection

Outside Range To the SC lecture wing door (closest to ERC) Covers faculty lot next to ERC Half way to Rowley Connection slows as move away from access point

Summer Research

ProtocolMethod of Communication

Spoken Language Networked Programs (AIM) HTTP, Telnet, FTP

Two Main Protocols (Internet)

UDP (User Datagram Protocol) Fast, bare-bones, not reliable or friendly

Can lose data at any time

TCP (Transmission Control Protocol)Slower, many features, very reliable

All data will get to the other side

PCAttcp

Measuring tool for TCP and UDP Speed, Throughput, Time Amount of Data Sent vs. Amount Received

Our PCAttcp Controller

Enhanced UDP transfers Automated the entire process Created an easy way to compile results

and graphs using a spreadsheet for output Ran tests on various types of connections

The End!

Thoughts or questions?

References

http://www.howstuffworks.com/wireless-network.htm

http://www.80211-planet.com/columns/article/0,4000,1781_961181,00.html

http://www.80211-planet.com/columns/article/0,4000,1781_947661,00.html

http://www.pcausa.com

Different PCATTCP Trials

Same Host (same computer)

Same Switch (same lab)

LAN to LAN

(Clarkson to SUNY Potsdam)

LAN to Internet (Clarkson to a Roadrunner service)

Same LAN (inside Clarkson)

Note: LAN stands for “Local Area Network”

Bluetooth (cont)

spread-spectrum frequency hopping – a device will use 79 individual, randomly chosen frequencies within a designated range, changing from one to another on a regular basis

When two Bluetooth devices come in contact with each other, they automatically conversate and form a personal-area network (PAN)

Spread spectrum

Spread-spectrum – data is sent in small pieces over a number of discrete

frequencies available for use at any time in the specified range

Frequency-hopping spread spectrum send a short burst of data, shift frequencies

(hop) and then send another short burst Since the FHSS devices that are communicating

agree on which frequencies to hop to, and use each frequency for a brief period of time (less than 400 milliseconds) before moving on, several independent FHSS networks can exist in the same physical area without interfering with each other

Direct-sequence spread spectrum splitting each byte of data into several

parts and sending them concurrently on different frequencies

DSSS uses a lot of the available bandwidth, about 22 megahertz (MHz).

The Basics

4 different types of wireless networks IrDA (Infrared Data Association)BluetoothHomeRF (SWAP)

“Shared Wireless Access Protocol”

WECA (Wi-Fi) “Wireless Ethernet Compatibility Alliance”

IrDA (Infrared Data Association)

Uses beams of light in the infrared spectrumRemote controls

Fairly reliable and low-cost Drawback: It is a “line-of-sight” technology

less interference Drawback: “one-to-one” technology

You can send data only between two things at once (but increased security?)

Bluetooth

The magic number: 2.45 gigahertz Radio-frequency also used by baby monitors,

garage door openers, and cordless phones

How do you avoid interference?Bluetooth sends weak signals of 1 milliwatt

Powerful cell phones use 3 watts

Bluetooth devices limited to 10 meters But they can go through walls better than others

HomeRF (SWAP)

Shared Wireless Access Protocol (SWAP) Developed by an alliance of businesses

6 voice channels and one data channel The data channel is the 802.11 wireless-Ethernet

specification by the IEEE

One drawback: SWAP can only be used with computers Printers and such need to be attached to a

computer and used as a resource

HomeRF (SWAP)

Advantages: Cheap, easy-to-install Allows multiple-networks in the same location Can encrypt data

Drawbacks: Not very fast (typically limited to 1 Mbps) Limited Range (75 to 125 ft) Physical obstructions (walls, large metal objects) cause huge

interference issues Difficult to integrate into existing wired networks