Wireless Networking b

Wireless Networking b Mbps Adopted June 1997

Wireless Networking b September b adopted 11Mbps Actual throughput under 5.5 Mbps Also called Wi-Fi Uses CSMA/CA

Wireless Networking b Here are some illustrations of how a wireless network is put together index.asphttp:// index.asp

Wireless Networking b CSMA/CA mostly copies 802.3’s CSMA/CD Wireless can’t use collision detect because it can’t sense and transmit at the same time Uses a backoff timer and active handshaking- RTS/CTS Addresses “hidden node” problem

Wireless Networking b

Uses direct sequence spread spectrum in the 2.4 GHz band Go to nets.com/articles/whitepaper_spread.htm for a clearer understanding of DSSS and a comparison with frequency hopping spread spectrumhttp:// nets.com/articles/whitepaper_spread.htm

Wireless Networking b Eleven 30Mhz overlapping channels available in the US. Europe uses channels 1-13 Japan uses channel 14 only Is compatible with Falls back to lower speed with distance and noise

Wireless Networking b 5 MHz between channels 30 MHz bandwidth channels Spread spectrum allows overlap, but causes problems Compare with usual guard band

Wireless Networking b Channel 1 starts at GHz and channels progress at 5MHz intervals. Ch2= 2.417GHz, Ch3=2.422GHz, etc. If you want no overlap, use Channels 1, 6, and 11

Wireless Networking b Channel Distribution

Wireless Networking b Mbps a54 Mbps at 5 GHz (not WiFi) b11 Mbps at 2.4 GHz (also WiFi) e adds QoS to a and b g54 Mps at 2.4 GHz (meets WiFi) h is a European standard like g i provides added security options

Wireless Networking b Hubs called Access Points They function as bridges, isolating the MAC layer functions NICs have radios and antennas APs are physically wired to the rest of the network

Wireless Networking b NIC

Wireless Networking b Range is 200 to 500 feet in an open office (claimed), 100 feet or less in closed offices Designed to be used with laptops Adapters for desktop computers were largely ineffective because of shielding problems Site surveys determine antenna placement fiplanet.com/tutorials/article.php/ fiplanet.com/tutorials/article.php/

Wireless Networking b Wireless networks are designed by doing a Site Survey to measure signal strength. There are built-in tools with every AP, but a Spectrum Analyzer does a much better job Spectrum Analyzers can display all of the frequencies within the range you are going to use, but they’re several thousand dollars.

Wireless Networking b Troubleshooting wireless networks can be difficult. Use network analyzers designed specifically for Wireless networks. Sniffer Wireless by Network Associates $10,000 Airopeek by Wildpackets, $3500

Wireless Networking b WEP is the security method (Wired Equivalent Privacy) Uses encryption. Weak, and causes a big impact on network speed Security is a major concern Biggest problem, most don’t implement any security at all

Wireless Networking b Here’s a little article about how to use WEP and the alternatives. planet.com/tutorials/article.php/ http:// planet.com/tutorials/article.php/ Here’s an article about the shortcomings of WEP. -faq.html -faq.html

Wireless Networking a runs at 5 GHz range Not compatible with b 54 Mbps, but very short range Requires lots of power Not often implemented

Wireless Networking a has not gained popularity because it’s expensive and incompatible with b. It also consumes a lot of power. However, at 54Mbps it’s fast.

Wireless Networking g runs at 54 Mbps 2.4 GHz band Became a standard June 2003, shipping since htmlhttp://zdnet.com.com/ html Compatible with b Also short range

Wireless Networking g is slower than b in some tests Adding an b device to an g network slows the entire network. For commercial applications, you may want to wait for the hardware to stabilize before adoption.

Wireless Networking Prices, as of Fall b bridges cost about $70, cards $ b+ (non standard, 22Mbps, TI) cost about $100, cards $ G bridges cost about $140, cards $90 Dual band a and g are ~$300

Wireless Networking b Personal Telco Communities of Portland andWirelessCommunitieshttp:// andWirelessCommunities Privately funded, all volunteer Here is a national list of wireless “hot spots”

Wireless Networking b Voice VoIP is moving ahead in the workplace, but the proliferation of may begin to cut into the cellular telephone market as well. e.php/10799_ http:// e.php/10799_

Wireless Networking b London is planning to use for their security cameras and for public workers like parking meter enforcers. Cisco is in this picture too htmlhttp:// 04.html

Wireless Networking b Commercial wireless hot spots are becoming more common, but profit seems to be elusive.

Directional Antenna 24 dB 8 degree

Directional Antenna 12dB Gain

Wireless Networking b Overlapping WLANs is becoming a problem. Service Set Identifiers, (SSID), are unique 32 character network identifiers that help make sure the proper network gets the data. The SSID is attached as a header to all packets. It is transmitted in the clear, so it doesn’t add to security. Also called the Network Name

Wireless Networking b To stay current in this emerging technology, go to the WiFi Networking News at Or Planet at Check out a tutorial on It has a range of 30 miles and a data rate of 70 Mbps http://networking.earthweb.com/netsp/article.php/

Wireless Networking Alternatives Check out a tutorial on as an alternative to last mile coverage. It has a range of 30 miles and a data rate of 70 Mbps. It operates in from GHz range. e.php/ http://networking.earthweb.com/netsp/articl e.php/

Wireless Networking b A great source for information about is

Wireless Networking Alternatives CDMA2000 is a 3G wireless phone alternative. It operates at 144Kbps and is backward compatible with standard CDMA cell phones. Operates in the 800 MHz band Qualcomm chipset dma2000.shtmlhttp:// dma2000.shtml

Wireless Networking Alternatives Bluetooth was designed as an inexpensive, point- to-point wireless connectivity solution designed for low speed, very short range (30’) communication. It uses frequency hopping spread spectrum at low power in the unlicensed 2.4 GHz range. A comparison of b and Bluetooth is at: fiplanet.com/tutorials/article.php/ http:// fiplanet.com/tutorials/article.php/