Quiz Questions • What is Ad-Hoc? • What is an AP? • What is a MAN? • What is ESS? • Name two devices that can cause interference on a wireless network? • Name two non-routable IP address? • What is a free utility for doing site surveys? • What is a default gateway?
CH 4 Quiz And H.W. Lecture Lab NIC Set-up Out to WEB
RF In Wireless • An AP is a Transceiver • It operates at the 2.4Ghz band of the Radio Frequency Spectrum. • Low power, super high frequency (microwave) • Transceivers transmit and receive RF (Radio Frequency) energy
Radio Frequency • Refers to the electromagnetic field that is generated when an alternating current is input to an antenna. • Can be used for wireless broadcasting and communications over a significant portion of the electromagnetic radiation spectrum
Radio Frequency cont. • from about 9 kilohertz (kHz) to thousands of gigahertz (GHz)+ • This portion is referred to as the RF Spectrum • As the frequency is increased beyond the RF spectrum • electromagnetic energy takes the form of infrared (IR)
Radio Frequency cont. • visible light • ultraviolet (UV) • X rays • gamma rays • Many types of wireless devices make use of RF fields • radio, television, cordless and cellular telephones, satellite communication systems, and many measuring and instrumentation systems used in manufacturing.
IR • Visible light frequencies • Used by… • remote control boxes • cordless mice • Palm, and other PDA’s
This may help! • The RF spectrum is divided into several ranges, or bands. Each of these bands, other than the lowest frequency segment, represents an increase of frequency corresponding to an order of magnitude (power of ten).
8 Bands • This chart at the bottom of the page depicts the eight bands in the RF spectrum, showing frequency and bandwidth ranges. 802.11b&g
RF is Manipulated with Antennas • Antennas control signal pattern and power. • Done through… • Size • Shape • Power • Materials
Antenna Radiation Patterns Horizontal Plane Yagi Slice Horizonal Plane “Bread Slice” Pannel, Low backend
Antenna Radiation Patternscont Yagi Few Elements, More elements the cleaner it gets Not as Clean Yagi
AP Power • Typical AP transmits between 50 to 300 milliwatts • Wireless PC cards & USB adapters transmit 50 milliwatts or less • A 2400 MHz - 1/10 watt signal will travel up to 20 miles or less than 20 inches depending on antenna design, placement and terrain • Milliwatt= one thousandth of a watt
Cisco Aironet 350 • 100 mW Radio • Read Product Data Sheets!!
Linksys WAP 11 ver 2.6 • 100 mW Radio • You can push it up to almost 300mW • Enterprise AP????
Terrain Survey • Before choosing an antenna do a survey!!! • Trees, hills, mountains, buildings • Not always what you can see but where RF will go • Beware.. Trees grow! • Geographic Information Systems “GIS”
Terrain Survey cont. • Attenuation by rain, fog & smoke (limited effect, but important) • Remember conditions change, and things move! • City development plans. • Plan Ahead!!!
Line of Site???? From City Hall Roof
Local Codes & Ordinances • Regulate the placement of antennas. • Antennas higher than the roof line are regulated in most urban areas. • Antennas masts and towers have very strict regulations. • Some home owner associations and business associations have additional restrictions.
Local Codes & Ordinances cont. • Check before you install. • Maintain your customer base by following the rules. • RF causes interference in other electronic devices • You may be required resolve interference • Analog devices are more susceptible
Local Codes & Ordinances cont. • First come first serve. If you create the interference it’s your responsibility to solve it!!!!!
RF is potentially hazardous to humans and animals. • RF from an 802.11b device is more hazardous than RF produced by CB radio at the same wattage • Federal Band on 30 MHz and its harmonics’ (300, 3000). These frequencies resonate with human organs. These frequencies are used for weapons development.
RF is potentially hazardous to humans and animals.cont. • Avoid using damaged or modified equipment • Use of RF amplifiers requires special FCC approval
Parabolic dish • directional • narrow pattern • high gain- long distance point-to point)
Yagi antenna • Directional • Enclosed • narrow pattern • high gain • point-to-point
Panel antenna • semi-directional • Medium to low gain
Vertical antenna • omni directional • medium low gain
Connectors • Connector Conspiracy!!! • Nothing matches!!! • Antenna manufactures tend to use standardized connections • Pre-assemble systems before final installation to avoid connector conflicts
COAX • Coax antenna cables • Keep them short (line loss)
Coax cont. • Consume distances with CAT5 not coax antenna cable • Resolve some 120AC connection problems with devices that supply power-over-Ethernet • Getting CAT5 to exterior of a building can be difficult. Consult Universal Building Codes (UBC), and local building codes • Order pre-assembled cables carefully or learn how to build your own
Masts & Towers • Use buildings for elevation 1st • In many cases increasing antenna height will improve signal strength • Lighting protection (required by code) • Serviceability (what goes up must come down for repair and service) • Stay off the tower. Hire a State licensed contractor • Wind rating
FCC: Federal Communication Commission • *FCC Notice: Whenever changing, replacing or installing, amplifiers, antennas, cables or additional components not part of the OEM 802.11 product the installer must understand and follow the requirements of FCC part 15. Download a copy of Part15 from the FCC website for detailed information.