Mr. Zeeshan Ali, Asst. Professor Wireless Networking Mr. Zeeshan Ali, Asst. Professor Department: B.E. Electronic & Telecommunication Subject: Wireless Network Semester: VIII eCourseware@AIKTC Teaching Aids Service by KRRC Information Section

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: Disadvantages: 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 Coverage Distance 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 Cards 4 ORiNOCO Gold 11 Mbps PC Cards 4 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 Outside 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 Protocol Method 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 Switch (same lab) Same LAN (inside Clarkson) Note: LAN stands for “Local Area Network” Same Host (same computer) LAN to LAN (Clarkson to SUNY Potsdam) LAN to Internet (Clarkson to a Roadrunner service)

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) Bluetooth HomeRF (SWAP) “Shared Wireless Access Protocol” WECA (Wi-Fi) “Wireless Ethernet Compatibility Alliance”

IrDA (Infrared Data Association) Uses beams of light in the infrared spectrum Remote 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: Drawbacks: 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