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  • As wireless technology is being refined more and more, it becomes a more affordable, reliable solution to applications that before would be unfeasible. Either physically or financially. We can now get useful data to and from places before would be unthinkable. From the bottom of a mine shaft, across a factory floor, around a mountain, even easily across a body of water without costly cables or fiber runs.
  • With 802.11 wireless ethernet, we can seamlessly, invisibly and reliably integrate data connectivity into new or existing networks. Wireless Lan’s generally provide one of two roles: Access Role – they provide wireless access to a wired resource or network Distribution Role – they are used to extend or join multiple wired networks to provide seamless connectivity
  • For this training, we will concentrate on the higher data rate DSSS wireless type, which is most widely used, readily available and most interoperable standard
  • When designing, building and configuring a wireless LAN or wireless link, it is important to think of the link in terms of the transmitter and receiver. When we discuss link planning and link budgets, the same gains and losses are not always the same on both and of the link. Therefore we will need to look at the links as 2 separate RF links.
  • CSMA/CA is not necessarily the best method of collision avoidance, but it is the fastest with less latency and overhead. Because of this, it is the default choice on a WLAN, unless problems are detected.
  • When designing and troubleshooting RF systems, there are a lot of terms, definitions and formulas to be aware of. This is just a sample of some of the terms and definitions we will discuss. Also note that most of these items have an associated mathematical formula as well.
  • Wavelength is the basis of all RF calculations and theory. With wavelength we can find the frequency of a waveform, choose proper equipment for an RF system such as cables, connectors, antennas… we can also calculate theoretical maximum distances and data rates that will be available in a certain application. With the formula here, we can also find the wavelength if we know the frequency, as waveform and frequency are inversely but proportionately related. Formula: λ = Lambda c = Speed of light (because RF signals travel at the speed of light) f = Frequency
  • Wavelength is directly used in the design of all RF antennas. Spatial placement is used in certain applications were there may be certain phenomenon such as reflections for example. Fresnel Zone is used to determine antenna height in a long distance point to point application as well as Free Space Path Loss.
  • In the first example (Top), we see a signal with a frequency of 1 Hertz. This means that the RF wave has a cycle period of 1 second or 1 cycle per second. In the second example (Bottom), we see a signal with a frequency of 2 Hertz. This mean that this RF wave has a cycle period of ½ a second or 2 cycles per second. By comparing the two waveforms, we can see the inverse relationship between waveform and frequency. The 1 Hertz (Top) waveform has a longer waveform than the 2 Hertz (Bottom) waveform.
  • Frequency is a measure of cycles per second. As an example, a 2.4GHz waveform (commonly used in 802.11 wireless networks) completes 2.4 Billion cycles per second.
  • If we compare RF waveforms to sound waves, Amplitude would be the “Loudness” of the waveform. Just like sound waves, the amplitude or “loudness” effects the distance the RF waveform can effectively travel.
  • As you can see in the above examples, all three waveforms have the same wavelength and frequency, but they all three have different amplitudes. Because of this they would all have different effective distances they could be transmitted.
  • In the above example, we have two waveforms of identical frequency and amplitude. The Inverted (lower) waveform is inverted or known as 180 degrees out of phase in relation to the original (Top) signal. Because of this Phase difference, if the two signals were both received by an RF device, the two would have cancelling effects on each other. In the right example of the two superimposed on top of one another, the effective combined waveform of the two would be no waveform at all. Just like adding a positive and negative of the same number. The sum would be zero.
  • In RF communications, there is a phenomenon known as reflection, which will be covered in greater detail later on in the course. Because of this phenomenon, in certain applications this can be a huge factor in effective RF communications. Especially in enclosed areas with highly reflective materials, such as metal walls or shelving of a warehouse.
  • Free Space Path loss can be compared to dropping an object into a standing pool of water. It causes ripples of water to go out in all directions away from the point where the object entered the water. As the waves travel outwards, they become smaller and smaller, losing amplitude (or height).
  • Active gain can be compared to sound waves going through a megaphone. The waves of sound from your voice get amplified and retransmitted through the air with a greater amplitude than the original waveform.
  • Passive gain is comparable to cupping you hands around your mouth. The sound is not louder and the amplitude is not greater, but appears to be because the sounds waves are concentrated in a desired direction. In RF communication this could be caused unintentionally by objects such as walls. If an antenna was inadvertently mounted too close to a metal studded wall, this could cause unintentional passive gain.
  • Losses introduced through connectors and cabling must be calculated into the overall link budget also. If using longer RF cabling, ultra low loss cable could be considered to help reduce unwanted losses. More about choosing the correct cables later on in this course.
  • Reflection is very easily explained in the analogy of looking into a mirror. If you look at the mirror at an angle, you do not see yourself, but whatever is located at the same angle in the opposite direction.
  • Diffraction can be analogized as dropping an object into a standing body of water with a stick or object that is placed some distance away from the point where the object contacts the water. The waves travels outward from the point of impact, as the waves near the stick, the waves start to concentrate near the side of the stick towards the point of impact, but the side of the stick away from the point of impact has a shadow area, or no waves on this side.
  • Absorption is most commonly used and seen in microwave ovens. When an object is heated in a microwave oven, the water particles present in the object absorb the RF radiation. Because of this absorption, the object becomes heated, thus allowing us to cook foods with RF waves. Because of the much lower power outputs used in RF communication, this phenomenon happens on a much smaller scale.
  • The Watt is named after an 18 th century Scottish inventor, James Watt. If either, or both the volts or amps increase, so does the watts. Most commonly used to measure the output of a light bulb. A typical household light bulb puts out 60 watts at 120vac. Knowing the Watts (60) and the Voltage (120v) we know that the light bulb draws .5 amps. Explain “PIE” Pyramid
  • The rule of 10’s and 3’s is a very quick an efficient method of finding the output power of an RF system. As you can see, a gain of 3db double’s the output power. A loss or reduction by 3db cuts the power output in half. For the rule of 10’s, a gain of 10db multiplies the output power by a factor of 10. A reduction of 10db would be 1/10 th of the output power.
  • By using these equations of 10’s and 3’s, we can find the output power of a system without using any complex physics equations. Give example…
  • Imagine having a conversation in a room full of people. If no one else is talking, your can converse very easily. As the people in the room begin talking, your conversation starts to drown out. Because of this, to have your conversation be as loud or effective, you must talk louder over the background noise.
  • Since the radius of the Fresnel Zone in this example is 7 meters, our antennas would need to be located at least 7 meters above the highest obstruction in the RF path. This ensures there will be no interference from reflections and diffractions. 5GHz Wavelength = .05 2.4GHz wavelength = .125
  • Before we begin a link budget calculation, we have to have an idea of how much cable will need to be used between the access point and antenna, attenuation factors of the cable, surge arrestors and other devices in the hard-wired link. As well as a data sheet for the access point listing the receive sensitivity for the various available data rates and the output powers available for the available channels/frequencies. It is recommended to do a link budget calculation before purchasing any equipment for the application, as there are quite a few variables that can effect the performance and reliability of the RF link.
  • One of the cheapest and most common RF cable types is RG-58. RG-58 cable is considered to be a “low-loss” cable. RG-58 cable typically has a loss of 60 to 100 db per 100 meters. This rating varies by manufacturer and also varies depending on the frequency being used. The lower the frequency, the lower the attenuation factor. In some RF applications, RG-58 cable adds too much attenuation due to the distance between the Access Point and the antenna. Because of this, typically more expensive “Ultra-low loss” cable must be used. Again, it is recommended to verify the attenuation factor by checking the manufacturers data sheet.
  • It is always recommended to use the highest level encryption possible. AES is best to use if all equipment supports its use
  • In the 2.4Ghz frequency band, there are 11 available channels allow in the U.S. The channels are 20MHz wide and are only spaced 5MHz apart. Because of this, there is quite a bit of overlap. As you can see in the chart above, you can have a maximum of 3 non-overlapping channels.
  • To make best use of the non-overlapping channels, and to minimize cross interference, channel selection must be carefully thought out. As shown here for coverage of an area, the use of staggered channels gives the best chance for no/minimal cross talk.
  • Orthogonal - intersecting or lying at right angles
  • This would be an example of a BSS
  • WDS or Point to Point
  • WDS again or Point – Multi Point
  • Wireless

    1. 1. Network Design V: Wireless Best Practices & Applications
    2. 2. Wireless Data Communications Standards and Uses
    3. 3. Wireless Ethernet PCI Cards USB Adapters PC Cards USB Sticks
    4. 4. Uses <ul><li>Untethered device/network access (roaming clients) </li></ul><ul><li>Replace standard cabling to reduce installation costs </li></ul><ul><li>Installations where standard cabling is not possible </li></ul><ul><li>Temporary Installations </li></ul>
    5. 5. Seamless Wired and Wireless By utilizing standards based wireless products, you have seamless integration between your devices.
    6. 6. Wireless Technologies <ul><li>Within the Wireless LAN Standards, there are a few different types of wireless technologies. </li></ul><ul><ul><li>FHSS: Frequency Hopping Spread Spectrum </li></ul></ul><ul><ul><ul><li>Utilizes very narrow RF channels </li></ul></ul></ul><ul><ul><ul><li>Transmits data while switching between different channels </li></ul></ul></ul><ul><ul><ul><li>Very Resilient to RF interference </li></ul></ul></ul><ul><ul><ul><li>Very Low Data rates </li></ul></ul></ul><ul><ul><ul><li>High Latency </li></ul></ul></ul><ul><ul><li>DSSS: Direct Sequence Spread Spectrum </li></ul></ul><ul><ul><ul><li>Utilizes Wide Band channels </li></ul></ul></ul><ul><ul><ul><li>Transmits data across multiple frequencies concurrently </li></ul></ul></ul><ul><ul><ul><li>Up to 300Mbps </li></ul></ul></ul><ul><ul><ul><li>Low Latency </li></ul></ul></ul>
    7. 7. CSMA/CA <ul><li>Duplex – Explained </li></ul><ul><ul><li>Half Duplex – A device can only send or receive at a given moment </li></ul></ul><ul><ul><li>Full Duplex – A device can send and receive at the same time </li></ul></ul><ul><ul><li>Think of Half Duplex as a two way radio – Only one person can talk at a time </li></ul></ul><ul><ul><li>Think of Full Duplex as a cell phone – each person can talk and listen at the same time </li></ul></ul>
    8. 8. The Wireless Link <ul><li>Transmitter </li></ul><ul><ul><li>Portion of the wireless device which transmits the RF signal </li></ul></ul><ul><li>Receiver </li></ul><ul><ul><li>Portion of the wireless device which receives the RF signal </li></ul></ul><ul><li>Standard </li></ul><ul><ul><li>The standard used between the transmitter and receiver which defines the way the 2 devices intercommunicate </li></ul></ul><ul><li>Channel </li></ul><ul><ul><li>Frequency of the RF waves used between the transmitter and receiver </li></ul></ul>
    9. 9. Access Methods <ul><li>In wireless networks, collisions are always possible. There are two methods used to help avoid collisions. </li></ul><ul><ul><li>CSMA/CA : Carrier Sense Multiple Access w/Collision Avoidance </li></ul></ul><ul><ul><ul><li>Devices check to see if the medium is in use before transmitting </li></ul></ul></ul><ul><ul><ul><li>2 internal timers present must both be counted down to 0 before transmission can take place (IFS, Random Back-off Times) </li></ul></ul></ul><ul><ul><li>RTS/CTS : Request to Send/Clear to Send </li></ul></ul><ul><ul><ul><li>Devices send a “Request to Send” message to the Access Point </li></ul></ul></ul><ul><ul><ul><li>When the Access Point is free to receive, it sends a “Clear to Send” message to the network so the device knows it is clear, and the other devices know to wait </li></ul></ul></ul>
    10. 10. Wireless Terms, Definitions and Acronyms
    11. 11. Terms, Definitions and Acronyms <ul><li>Access Point – an access point is a device which typically connects to a wired LAN or wired device and provides wireless connectivity to wireless devices. Also called “Wireless Bridge” or “BSS” </li></ul><ul><li>Access Client (Station) – A wireless device designed to connect to a wireless access point. Typically to gain access to resources connected to the access point. </li></ul><ul><li>WLAN – Wireless Local Area Network </li></ul><ul><li>802.11 – IEEE standard for wireless ethernet (contains many sub standards) </li></ul><ul><li>Repeater – Infrastructure devices used to extend the reach of a wireless LAN. </li></ul><ul><li>SSID – Service Set Identifier – Name used to identify a wireless network </li></ul>
    12. 12. Terms, Definitions and Acronyms <ul><li>Channel – A specific frequency used for wireless communication </li></ul><ul><li>WEP – Wired Equivalent Protocol - Type of encryption used to make data more secure. WEP is an older encryption method and is easily broken. </li></ul><ul><li>WPA – WiFi Protected Access - Type of encryption used to make data more secure. Newer standard and much more secure than WEP. Not supported by some devices due to added hardware support. </li></ul><ul><li>Point to Point – Mode used by infrastructure devices (Access Points). In a Point to Point wireless network, access points are used to communicate to one another in order to extend a LAN from one location to another wirelessly. </li></ul>
    13. 13. WLAN Standards
    14. 14. Legacy <ul><li>IEEE 802.11 </li></ul><ul><ul><li>Wireless was first made standard in 1997 by the IEEE </li></ul></ul><ul><ul><li>2.4GHz Frequency </li></ul></ul><ul><ul><li>Very low data rates (1-2Mbps) </li></ul></ul><ul><ul><li>No encryption standards </li></ul></ul><ul><ul><li>Little to no interoperability between manufacturers </li></ul></ul><ul><ul><li>Not widely accepted/used </li></ul></ul>
    15. 15. Today's Standards <ul><li>802.11b/g </li></ul><ul><ul><li>2.4GHz operation </li></ul></ul><ul><ul><li>11 - 54Mbps </li></ul></ul><ul><ul><li>WEP/WPA and Radius authentication </li></ul></ul><ul><ul><li>Interoperability among various manufacturers </li></ul></ul><ul><li>802.11a </li></ul><ul><ul><li>5GHz operation </li></ul></ul><ul><ul><li>54Mbps </li></ul></ul><ul><ul><li>WEP/WPA and Radius authentication </li></ul></ul><ul><ul><li>Interoperability </li></ul></ul>
    16. 16. Today's Standards <ul><li>802.11n </li></ul><ul><ul><li>2.4 or 5GHz operation </li></ul></ul><ul><ul><li>MIMO (Multiple Input Multiple Output) </li></ul></ul><ul><ul><li>Up to 600Mbps </li></ul></ul><ul><ul><li>WPA2 and Radius authentication </li></ul></ul><ul><ul><li>Backwards Compatibility </li></ul></ul><ul><ul><li>Interoperability </li></ul></ul><ul><ul><li>RF Diversity built in </li></ul></ul>
    17. 17. Organizations
    18. 18. Organizations
    19. 19. Organizations - Regulatory <ul><li>FCC (Federal Communications Commission) </li></ul><ul><ul><li>Federal Government agency in charge of regulating communications by radio, wire, satellite… </li></ul></ul><ul><ul><li>Define usable frequencies (ISM, U-NII…) </li></ul></ul><ul><ul><li>Channel widths </li></ul></ul><ul><ul><li>Allowable output power levels </li></ul></ul><ul><ul><li>Certification Testing </li></ul></ul><ul><ul><li>Allowable noise emissions… </li></ul></ul>
    20. 20. Organizations - Regulatory <ul><li>ISM (Industrial, Scientific and Medical) Band </li></ul><ul><ul><li>Allocated by the FCC for unlicensed use </li></ul></ul><ul><ul><ul><li>6.78 MHz (+/- 15.0 kHz) </li></ul></ul></ul><ul><ul><ul><li>13.56 MHz (+/- 7.0 kHz) </li></ul></ul></ul><ul><ul><ul><li>27.12 MHz (+/- 163.0 kHz) </li></ul></ul></ul><ul><ul><ul><li>40.68 MHz (+/- 20.0 kHz) </li></ul></ul></ul><ul><ul><ul><li>915 MHz (+/- 13.0 MHz) </li></ul></ul></ul><ul><ul><ul><li>2,450 MHz (+/- 50.0 MHz) ->(used in 802.11b/g ) </li></ul></ul></ul>
    21. 21. Organizations - Regulatory <ul><li>U-NII (Unlicensed National Information Infrastructure) Band </li></ul><ul><ul><li>Allocated by the FCC for unlicensed use </li></ul></ul><ul><ul><ul><li>5.20 GHz (+/- 50 MHz) </li></ul></ul></ul><ul><ul><ul><li>5.30 GHz (+/- 50 MHz) </li></ul></ul></ul><ul><ul><ul><li>5.5975 GHz (+/- 127.5 MHz) </li></ul></ul></ul><ul><ul><ul><li>5.775 GHz (+/- 50 MHz) </li></ul></ul></ul>
    22. 22. Organizations - Regulatory <ul><li>Allowable Power Output </li></ul><ul><ul><li>To use the unlicensed ISM and U-NII bands without the need to obtain a license, the following are maximum allowable output power: </li></ul></ul>Allowable Power Output Indoor/Outdoor ISM/U-NII Total Bandwidth Frequency Band 800 mW Outdoor U-NII 100 MHz 5.725 – 5.825 GHz 200mW Indoor/Outdoor U-NII 255 MHz 5.470 - 5.725 GHz 200 mW Indoor/Outdoor U-NII 100 MHz 5.25 – 5.35 GHz 40 mW Indoor U-NII 100 MHz 5.15 – 5.25 GHz 1 Watt Indoor/Outdoor ISM 100 MHZ 2,400- 2,500 MHz
    23. 23. Organizations - Standards <ul><li>IEEE (Institute of Electrical and Electronic Engineers) </li></ul><ul><ul><li>IEEE is the world's leading professional association for the advancement of technology. </li></ul></ul><ul><ul><li>Define standards for interoperability, reliable and compatibility </li></ul></ul><ul><ul><li>Most popular standards include IEEE 802 LAN/MAN standards and its sub-standards (802.3, 802.11…) </li></ul></ul>
    24. 24. Wireless Fundamentals
    25. 25. RF Fundamentals Gain Reflection Loss Refraction Attenuation db dbi dbm SNR Amplitude Fresnel Zone RSSI Free Space Path Loss Wavelength λ (Lambda) Frequency λ
    26. 26. RF Fundamentals - Wavelength <ul><li>Wavelength – The distance between two identical points in adjacent cycles of an RF waveform. </li></ul><ul><li>Wavelength is inversely related to frequency </li></ul>λ = c / ƒ λ = wavelength c = speed of light (299,792,458 m/s) ƒ = frequency Amplitude Time Wavelength (λ )
    27. 27. RF Fundamentals - Wavelength <ul><li>Wavelength </li></ul><ul><ul><li>Used to calculate: </li></ul></ul><ul><ul><ul><li>Antenna length </li></ul></ul></ul><ul><ul><ul><li>Spatial placement of antennas </li></ul></ul></ul><ul><ul><ul><li>Fresnel Zone </li></ul></ul></ul><ul><ul><ul><li>Free Space Path Loss… </li></ul></ul></ul>λ
    28. 28. RF Fundamentals - Wavelength Longer Wavelength Shorter Wavelength 0 seconds 1 second 0 seconds 1 second 1 cycle per second (1Hz) 2 cycles per second (2Hz)
    29. 29. RF Fundamentals - Frequency <ul><li>Frequency is how many cycles or waves per second </li></ul><ul><li>Frequency is inversely related to wavelength </li></ul>Time Amplitude ƒ = c / λ λ = wavelength c = speed of light (299,792,458 m/s) ƒ = frequency
    30. 30. RF Fundamentals - Amplitude <ul><li>Amplitude </li></ul><ul><ul><li>Independent of frequency and/or wavelength </li></ul></ul><ul><ul><li>Strength of an RF waveform </li></ul></ul><ul><ul><li>Greater or Higher amplitude means longer distances </li></ul></ul><ul><ul><li>Measured as Watts or decibels in RF communications </li></ul></ul>
    31. 31. RF Fundamentals - Amplitude P 1 P 2 Original Amplitude Lower Amplitude Higher Amplitude
    32. 32. RF Fundamentals - Phase Original Waveform Inverted Waveform <ul><li>Two waveforms 180° apart (Inverted) have cancelling effects. </li></ul>Average Signal -2+2=0
    33. 33. RF Fundamentals - Phase <ul><li>Because of RF reflections, we have to be </li></ul><ul><li>careful of Phase in a wireless system </li></ul>
    34. 34. RF Fundamentals - Free Space Path Loss <ul><li>Free Space Path Loss </li></ul><ul><ul><li>Reduction of power (amplitude) due to the natural expansion of the RF waveform through the air </li></ul></ul><ul><ul><li>As an RF waveform is transmitted through the air, the farther it gets from it’s point of origin, the wider the waveform becomes. </li></ul></ul><ul><ul><li>Because of this natural spreading, the waveforms amplitude becomes smaller and smaller </li></ul></ul>
    35. 35. RF Fundamentals - Gain <ul><li>RF Gain </li></ul><ul><ul><li>Increase in the signal level (Amplitude) or a concentration of a signal </li></ul></ul><ul><ul><li>Passive or Active </li></ul></ul><ul><ul><li>Intentional or Unintentional </li></ul></ul>
    36. 36. RF Fundamentals - Gain <ul><li>Active Gain </li></ul><ul><ul><li>Active gain is achieved by placing an amplifier in the RF line to increase the Amplitude of the original signal </li></ul></ul><ul><ul><li>Must be careful not to exceed FCC power requirements </li></ul></ul>Access Point RF Amplifier RF Antenna 1 Watt Signal 100mW Signal
    37. 37. RF Fundamentals - Gain <ul><li>Passive Gain </li></ul><ul><ul><li>Passive gain is not an increase in signal Amplitude, but rather concentrating a signal in a desired direction </li></ul></ul><ul><ul><li>Intentional (Directional antennas); Unintentional (Reflections from objects such as metal walls) </li></ul></ul>Directional Antenna Omni-Directional Antenna
    38. 38. RF Fundamentals - Loss <ul><li>Unintentional loss cannot be avoided </li></ul><ul><li>By using properly planned and matching equipment it can and should be kept to a minimum (Using all 50ohm cables and connectors, low loss or ultra low loss cables…) </li></ul>Access Point RF Antenna 100mW Signal 50mW Signal attenuated by cable and connector loss
    39. 39. RF Fundamentals - Reflection <ul><li>Reflection </li></ul><ul><ul><li>The bouncing of an RF wave off of a smooth non-absorptive surface. </li></ul></ul><ul><ul><li>Changes the angle the RF wave travels </li></ul></ul><ul><ul><li>Can lead to other RF phenomena such as multipath or gain (unintentional) </li></ul></ul>Incoming RF Wave Reflected RF Wave
    40. 40. RF Fundamentals - Diffraction <ul><li>Diffraction </li></ul><ul><ul><li>Diffraction is when an object in the path of an RF waveform causes the waveforms to concentrate on the side of the object towards the transmitter and spread the waveform as it travels past the object. </li></ul></ul><ul><ul><li>Can cause RF shadows or dead spots </li></ul></ul>Building or Object
    41. 41. RF Fundamentals - Absorption <ul><li>Absorption </li></ul><ul><ul><li>Absorption happens when an object cannot reflect RF waveforms but rather turns the RF energy into some amount of heat energy </li></ul></ul><ul><ul><li>Mostly occurs with organic objects </li></ul></ul><ul><ul><li>An object can absorb some of the energy, while allowing the rest to pass through. </li></ul></ul><ul><ul><li>Results in a lower amplitude waveform than the original </li></ul></ul>
    42. 42. RF Units of Measure and Math
    43. 43. Units of Measure - Watt <ul><li>Watt </li></ul><ul><ul><li>Basic unit of power measurement </li></ul></ul><ul><ul><li>1 Watt = 1 volt at 1 amp </li></ul></ul><ul><ul><li>In RF is used to measure the strength of an RF waveform </li></ul></ul><ul><li>Milliwatt </li></ul><ul><ul><li>1/1000 of a Watt (.001watts) </li></ul></ul><ul><ul><li>Most common unit of measure for an RF radio system </li></ul></ul><ul><ul><li>Abbreviated as mW </li></ul></ul>
    44. 44. Units of Measure – Decibel (db) <ul><li>Decibel (db) </li></ul><ul><ul><li>1/10 of a Bel </li></ul></ul><ul><ul><li>A unit-less, logarithmic representation used to express the ratio between two measurements of the same unit </li></ul></ul><ul><ul><li>Usually written with a suffix to imply the reference measurement unit (dbm, dbi, dbv…) </li></ul></ul><ul><ul><li>Used to express very large ratios as a simple number </li></ul></ul>
    45. 45. Units of Measure – Decibel (db) <ul><li>Decibel </li></ul><ul><ul><li>Rule of 10’s and 3’s </li></ul></ul><ul><ul><ul><li>A gain of 3db doubles the output power </li></ul></ul></ul><ul><ul><ul><li>A loss of 3db halves the output power </li></ul></ul></ul><ul><ul><ul><li>A gain of 10db magnifies the output power by 10 </li></ul></ul></ul><ul><ul><ul><li>A loss of 10db is 1/10 th the output power </li></ul></ul></ul><ul><ul><ul><ul><li>Example: </li></ul></ul></ul></ul><ul><ul><ul><ul><li>100mW output power from an Access Point </li></ul></ul></ul></ul><ul><ul><ul><ul><li>3db cable loss </li></ul></ul></ul></ul><ul><ul><ul><ul><li>10db gain antenna </li></ul></ul></ul></ul><ul><ul><ul><ul><li>100mw - 3db + 10db = 500mW </li></ul></ul></ul></ul>
    46. 46. Units of Measure – Decibel (db) <ul><li>Rule of 10’s and 3’s </li></ul>+ 10 + 10 - 3 -3 - 3 – 3 8 + 3 + 3 + 3 9 + 3 3 + 3 + 3 + 3 + 3 - 10 2 + 3 + 3 + 3 + 3 + 3 – 10 5 + 10 - 3 - 3 4 + 10 – 3 7 + 10 10 + 3 + 3 6 + 10 - 3 - 3 - 3 1 Equation in 10’s and 3’s dB
    47. 47. Units of Measure – dbi <ul><li>dbi </li></ul><ul><ul><li>Decibels as compared to an isotropic radiator (antenna). </li></ul></ul><ul><ul><li>dbi is used to express the power gain of an antenna </li></ul></ul><ul><ul><li>Isotropic radiator is an ideal, theoretical antenna that radiates the same power in all directions equally. </li></ul></ul><ul><ul><li>(More on Isotropic in a later section) </li></ul></ul>
    48. 48. Units of Measure – SNR <ul><li>SNR </li></ul><ul><ul><li>Signal – to – Noise Ratio </li></ul></ul><ul><ul><li>Power level of the RF signal as measured against any RF “noise” that may be in the area </li></ul></ul><ul><ul><li>Used to determine the “usable” amount of RF signal in a given area </li></ul></ul><ul><ul><li>Also used to determine link budgets </li></ul></ul>
    49. 49. Units of Measure – Fresnel Zone <ul><li>Fresnel Zone </li></ul><ul><ul><li>A calculated zone of RF between 2 RF devices </li></ul></ul><ul><ul><li>Pointed Ellipsoid Shaped (Football-Shaped) </li></ul></ul><ul><ul><li>Used to determine area of interference and/or “RF Line of Site” </li></ul></ul><ul><ul><li>Help determine the required height of the antennas between 2 RF devices </li></ul></ul>
    50. 50. Units of Measure – Fresnel Zone <ul><ul><li>Formula: </li></ul></ul><ul><ul><ul><li>R = 0.5 x √(λ x d) </li></ul></ul></ul><ul><ul><ul><ul><li>R = Radius of Fresnel Zone </li></ul></ul></ul></ul><ul><ul><ul><ul><li>λ = Wavelength of signal in meters </li></ul></ul></ul></ul><ul><ul><ul><ul><li>d = Distance between RF transceivers in meters </li></ul></ul></ul></ul><ul><ul><ul><li>R = 0.5 x √ (.05 x 4000) </li></ul></ul></ul><ul><ul><ul><li>R = 7 meters </li></ul></ul></ul>Radius of Fresnel Zone 4km 5GHz
    51. 51. Units of Measure – Fresnel Zone <ul><li>Fresnel Zone </li></ul><ul><ul><li>Some RF links can go relatively long distances </li></ul></ul><ul><ul><li>Because of this, the curvature of the earth must also be considered in links greater than 2km. </li></ul></ul>Earth Curvature Radius of Fresnel Zone 4km 5GHz
    52. 52. Units of Measure – Fresnel Zone <ul><li>Mast Height </li></ul><ul><ul><li>Mast Height will now be calculated using the radius of the Fresnel Zone, Earth Curvature, safety factor and height of tallest obstruction </li></ul></ul><ul><ul><li>Mast Height = R+E+S+O </li></ul></ul><ul><ul><li>R = Fresnel Zone </li></ul></ul><ul><ul><li>E = Earth Curvature </li></ul></ul><ul><ul><li>S = safety Factor (typically 1 meter) </li></ul></ul><ul><ul><li>O = Height of obstruction (if any) </li></ul></ul>Earth Curvature 7 + .24 + 1 + 0 = 8.24 Radius of Fresnel Zone 4km 5GHz
    53. 53. Link Budget Calculations <ul><li>Link Budget </li></ul><ul><ul><li>To begin a link budget calculation for an application, several pieces of information are needed. </li></ul></ul><ul><ul><li>Distance of Point-to-Point link </li></ul></ul><ul><ul><li>Mounting criteria for access points and antennas </li></ul></ul><ul><ul><li>Cable type to be used </li></ul></ul><ul><ul><li>Attenuation factors of each piece of equipment between access point output and antenna input </li></ul></ul>
    54. 54. Choosing the Proper RF cable <ul><li>RF cable is a very important piece of the RF link </li></ul><ul><li>Effects power available at the antenna </li></ul><ul><li>Available in low-loss/ultra-low loss designs </li></ul><ul><li>As a rule of thumb, the thicker the RF cable, the less attenuation per meter it has. </li></ul><ul><li>Cable specs must be verified with the manufacturer’s data sheet for exact attenuation specs </li></ul>
    55. 55. Omni-Directional <ul><li>Omni-Directional </li></ul><ul><ul><li>360 degree RF coverage pattern </li></ul></ul><ul><ul><li>Used for area coverage or Point to Multi-Point Links </li></ul></ul>
    56. 56. Sectoral <ul><li>Sectoral </li></ul><ul><ul><li>Used to cover a distinct area </li></ul></ul><ul><ul><li>60 – 90 Degree vertical and Horizontal coverage pattern </li></ul></ul>
    57. 57. Semi-Directional <ul><li>Semi-Directional </li></ul><ul><ul><li>Used in medium range Point – Point Links </li></ul></ul><ul><ul><li>20 – 30 Degree vertical and horizontal coverage pattern </li></ul></ul>
    58. 58. Highly-Directional <ul><li>Highly-Directional </li></ul><ul><ul><li>Used in long Distance Point – Point Links </li></ul></ul><ul><ul><li>Approx 1- Degree vertical and horizontal coverage pattern </li></ul></ul>
    59. 59. WLAN Distance Calculator
    60. 60. Encryption/Security
    61. 61. Encryption <ul><li>WEP – Wired Equivalent Protocol </li></ul><ul><ul><li>WEP64, 128 or 152bit </li></ul></ul><ul><ul><li>Very weak security standard by today's standards </li></ul></ul><ul><ul><li>Can be cracked in minutes using freely available tools </li></ul></ul><ul><ul><li>Surprisingly still widely used </li></ul></ul><ul><li>TKIP – Temporal Key Integrity Protocol </li></ul><ul><ul><li>Supplemental encryption standard </li></ul></ul><ul><ul><li>Addressed major weaknesses found in WEP </li></ul></ul><ul><ul><li>Required little or no hardware modifications </li></ul></ul><ul><li>AES – Advanced Encryption Standard </li></ul><ul><ul><li>Requires additional hardware support </li></ul></ul><ul><ul><li>Addresses virtually all weaknesses associated with WEP and TKIP </li></ul></ul><ul><ul><li>Not as widely supported due to hardware requirements </li></ul></ul>
    62. 62. Channel Selection and Characteristics
    63. 63. DSSS Focussed Signal Spread Signal Noise limit 1 Bit 1 0 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 Data Chipping- Sequence XOR Exit Data + Chipping Sequence 0 1 0 0 1 0 0 0 1 1 1 1 0 1 1 0 1 1 1 0 0 0
    64. 64. 2.4GHz 2400 2483 2.412 2.417 2.422 2.427 2.432 2.437 2.442 2.447 2.452 2.457 2.462 2.467 2.472 1 2 3 4 5 6 7 8 11 10 9 13 12 7 1
    65. 65. Non-Overlapping Channels 11 1 6 11 1 11 1 6 11 1 1 6 11
    66. 66. Frequency Modulation (5GHz) OFDM - Orthogonal Frequency Division Multiplexing Frequency 5150 30 MHz 5180 5320 5300 5280 5260 5240 5220 5200 5350 30 MHz Frequency 52 Sub channels
    67. 67. WLAN Topologies and Solutions
    68. 68. <ul><li>Uses </li></ul><ul><li>And </li></ul><ul><li>Topologies </li></ul>
    69. 69. Topologies <ul><li>There are various topologies available with the BAT54-RAIL(F): </li></ul>BAT 54 Rail as a simple Access Point Access point LAN
    70. 70. Topologies LAN Client Access-Point Remote PLC Roaming Client BAT 54 Rail as an Access Point and an Access Client
    71. 71. Topologies LAN A Master Slave LAN B 2.4GHz 5GHz Dual Band radio connections using Spanning Tree for redundancy
    72. 72. Topologies Point to Multi-Point Topology Building 1 (Slave) Building 2 (Slave) Building 3 (Slave) Building 4 (Slave) MCC (Master)
    73. 73. Multiple SSID’s and VLAN’s Engineering VLAN 3 Accounting VLAN 2 Production VLAN 1 Public VLAN 4 Multiple SSID’s with VLAN tagging per SSID MCC (Master) HIRSCHMANN
    74. 74. Mesh Topology Master Slave Slave Slave Slave Slave Slave Master Master Redundant Wireless Link Redundant Wireless Link Redundant wireless links are placed into a standby state, blocking network traffic to eliminate network “loops” from being formed
    75. 75. Topologies LAN Remote PLC Remote PLC 2 Point to Point connections (WDS – Wireless Distribution System) 5GHz Backbone Topologies Wireless Repeater