03 Radio Frequency Fundamentals for WLAN.pptx

Mobile and Wireless Technology CT090-3-2-MWT Version VD01 Radio Frequency (RF) Fundamentals for WLAN  Topic & Structure of The Lesson Radio Frequency (RF) Fundamentals for Wireless LAN Technology Fre...

Mobile and Wireless Technology CT090-3-2-MWT Version VD01 Radio Frequency (RF) Fundamentals for WLAN  Topic & Structure of The Lesson Radio Frequency (RF) Fundamentals for Wireless LAN Technology Frequencies Used for Wireless LANs Coverage and Capacity Basic Units of RF Measurement RF Range and Speed Environment: RF Behavior CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹2› of 9  Learning Outcomes At the end of this topic, You should be able to: Know the basic characteristics or properties of radio frequency. Be familiar with the frequencies used for wireless networks. Understand wireless network coverage and capacity. Know what RF factors will affect the range and speed of wireless networks. Identify basic RF units of measurement. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹3› of 9  Key Terms You Must Be Able To Use If you have mastered this topic, you should be able to use the following terms correctly in your assignments and exams: Radio Frequency (RF) Coverage Capacity Line of sight Interference Reflection Refraction Diffraction Scattering Absorption CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹4› of 9  Topic & Structure of The Lesson Radio Frequency (RF) Fundamentals for Wireless LAN Technology Frequencies Used for Wireless LANs Coverage and Capacity Basic Units of RF Measurement RF Range and Speed CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹5› of 9  Radio Frequency Fundamentals for Wireless LAN Radio frequency (RF) plays an essential role in wireless LAN technology. What is Radio Frequency? RF is a Radio Frequency, a electromagnetic wave. Radio waves/Radio Frequency waves/Electromagnetic waves are passed through the air (which is the medium) and are used to get information from one wireless device to another. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹6› of 9  Radio Frequency Fundamentals for Wireless LAN How these Radio waves/Radio Frequency waves/Electromagnetic waves are generated? High frequency alternating current (AC) signals passing over a copper cable connected to an antenna. The antenna then transforms the signal into radio waves that propagate through the air from a transmitter to a receiver. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Radio Frequency Fundamentals for Wireless LAN Radio frequency (RF) waves are used in a wide range of communications, including: Radio Television Cordless phones Wireless LANs, and Satellite communication. RF is around everyone and everything, and comes in many forms. Radio waves range from 3Khz to 300 Ghz. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9 CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Radio Frequency Fundamentals for Wireless LAN RF spectrum is governed by local regulatory bodies. Location Regulation Malaysia Malaysian Communications and Multimedia Commission(MCMC) Canada ISC RSS-210 China RRL/MIC Notice 2003-13 Europe (ETSI) ETS 300.328 ETS 301.893 Israel MOC Japan (MKK) TELEC 33B TELEC ARIB STD-T71 Singapore IDA/TS SSS Issue 1 Taiwan PDT USA FCC (47 CFR) Part 15C, Section 15.247 FCC FCC (47 CFR) Part 15C, Section 15.407 CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Topic & Structure of The Lesson Radio Frequency (RF) Fundamentals for Wireless LAN Technology Frequencies Used for Wireless LANs Coverage and Capacity Basic Units of RF Measurement RF Range and Speed CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹11› of 9  Frequencies used for Wireless LAN The Wireless LAN (IEEE 802.11) standard addresses the 2.4 GHz ISM band and the 5 GHz UNII bands. The 2.4 GHz ISM band allows for 11 of 14 channels to be used for wireless LAN communications. 2.4 GHz frequency band extend from 2.401 to 2.4835 GHz 1st channel occupies 22 MHz and the middle frequency is called centre frequency(2.412 GHz). 2nd channel starts with gap of 5MHz(2.406GHz) This band further divided in to sub-bands called channels. This channels are assigned to wi-fi devices and the Access point. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9 CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9 CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  2.4 GHz Vs 5 GHz Slower speed Faster speed Longer Range Low range More interference Low interference Under ideal conditions, 2.4 GHz will support anywhere between 450 Mbps and 600 Mbps. 5 GHz will support up to 1300 Mbps. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Topic & Structure of The Lesson Radio Frequency (RF) Fundamentals for Wireless LAN Technology Frequencies Used for Wireless LANs Coverage and Capacity Basic Units of RF Measurement RF Range and Speed CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹16› of 9  Coverage and Capacity Coverage and capacity are two key factors to take into consideration when designing and implementing an IEEE 802.11 wireless LAN. During the design phase of an IEEE 802.3 Ethernet wired network, the design engineer will take capacity into consideration, verifying and validating that there are enough capacity switches, ports, etc., for the user base of the network. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Coverage and Capacity The term coverage has different meanings depending on the context in which it used. For example, if you buy a gallon of paint, the label will specify the approximate coverage area in square feet. If one gallon of paint covers 300 square feet and the room you wish to paint is 900 square feet, simple math shows at least three gallons of paint would be needed to effectively cover the room. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Coverage and Capacity The concept is similar in IEEE 802.11 wireless networks. However, unlike with paint, there is no simple rule that determines how much space an access point will cover with the RF energy it is transmitting. This coverage will depend on many factors, some of which include: Size of area Number of users Applications in use Obstacles, propagation and Radio Frequency Range WLAN Hardware and Output Power CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Coverage and Capacity 1. Size of area – The amount of area an access point will cover. Manufacturer (ASUS/TPLINK) of wireless LAN hardware will not commit to the amount of area an access point will cover. A site survey of the area will help determine the coverage area of an access point. 2. Number of users – The number of users in an area will also affect the RF coverage. Too many users using powerful applications will overload the access point, adding to the poor performance issues. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Coverage and Capacity 3. Applications in Use – The application types in use - either software or hardware - can affect the bandwidth of an access point. If the users connected to an access point use bandwidth- intensive applications such as the Computer Aided Design and Manufacturing (CAD/CAM) application, this could result in poor throughput for all users connected to that access point. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Coverage and Capacity 4. Obstacles, Propagation and Radio Frequency Range Obstacles in an area, such as walls, doors, windows, and furnishings, as well as the physical properties of these obstacles - thickness of the walls and doors, density of the windows, and type of furnishings - can also affect coverage. The radio frequency used - either 2.4 GHz or 5 GHz - will determine how well a signal will propagate and handle an obstacle. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Coverage and Capacity 5. WLAN Hardware and Output Power The wireless LAN hardware in use can also have an impact on the coverage area. Examples include the antenna type, antenna orientation, and gain of the antenna. Antenna Gain: Measurement of power that represent the efficiency in which the antenna converts electricity in to radio waves Gain+dB=dBi of an antenna The higher the gain of an antenna, the greater the coverage area; conversely, the lower the gain of an antenna, the smaller the coverage area. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  The polarization of an antenna (horizontal vs. vertical) will also have an effect on the coverage area because of the different shapes of the radiation patterns. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Coverage and Capacity 5. WLAN Hardware and Output Power The output power of the transmitter or access point will also have an effect on coverage. The higher the output power, the greater distance a signal will propagate. A higher power signal will provide more coverage. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Coverage and Capacity Just as an elevator or a restaurant has a limited number of people they can accommodate comfortably, wireless access points also have a capacity. The capacity of an access point is how many users the AP can service effectively, offering the best performance. This capacity depends on several factors, including: Software applications in use Number of users CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Topic & Structure of The Lesson Radio Frequency (RF) Fundamentals for Wireless LAN Technology Frequencies Used for Wireless LANs Coverage and Capacity Basic Units of RF Measurement RF Range and Speed CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹27› of 9  Basic Units of RF Measurement A wireless access point may be set to an output of 30 mW (milliwatts) of power. A milliwatt is 1/1000 of a watt. Watts and milliwatts are measurements of RF power. Other units of measurement for RF are dB, dBi, dBd, and dBm. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Decibel (dB) The decibel is a comparative measurement value. In other words, it is a measurement of the difference between two power levels. For example, it is common to say that a certain power level is 6 dB stronger than another power level or that it is 3 dB weaker. These statements mean that there has been 6 dB of gain and 3 dB of loss, respectively. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Decibel Relative to a Milliwatt (dBm) dBm represents an absolute measurement of power where the m stands for milliwatts. Effectively, dBm references decibels relative to 1 milliwatt such that 0 dBm equals 1 milliwatt. Once you establish that 0 dBm equals 1 milliwatt, you can reference any power strength in dBm. The formula to get dBm from milliwatts is: dBm = 10 × log10(Power mW) A dB is an example of a change in power or relative measurement of power where dBm is measured power referenced to 1 milliwatt or an absolute measure of power. dBm is output power measurement CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  The measurements are displayed as negative numbers on a scale from - 30 dBm to -90 dBm. A Wi-Fi signal strength of -30 dBm is considered a perfect signal. A Wi-Fi signal strength of -90 dBm is considered totally disconnected. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Topic & Structure of The Lesson Radio Frequency (RF) Fundamentals for Wireless LAN Technology Frequencies Used for Wireless LANs Coverage and Capacity Basic Units of RF Measurement RF Range and Speed CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹32› of 9  RF Range and Speed How far and fast an RF signal can travel depends on a variety of factors, including 1. line of sight, 2. interference, 3. Environment: RF Behavior RF communication between devices in 802.11 wireless networking requires a line of sight. There are two types of line of sight to take into consideration: visual and RF. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed – Line of Sight RF communication between devices in 802.11 wireless networking requires a line of sight. There are two types of line of sight to take into consideration: visual and RF. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed – Line of Sight Visual line of sight is the ability of the transmitter and receiver to see each other. In order for wireless networking direct link communication to be successful there should be a clear, unobstructed view between the transmitter and receiver. An unobstructed line of sight means few or no obstacles blocking the RF signal between these CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed – Line of Sight The RF line of sight, or the radio transmissions between a transmitter and receiver, could be affected if the total area of radio frequency transmissions(the Fresnel zone )is blocked by more than 40 percent. This blockage could be from a variety of sources such as trees, buildings, terrain, or other obstacles, including the curvature of the earth. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - Interference Interference from a radio frequency point of view occurs when a receiver hears two different signals on the same or similar frequencies. Interference causes distortion. In wireless LANs, this interference can have a severe impact on the quality of signal received by the wireless device. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - Interference IEEE 802.11 wireless network may use the unlicensed 2.4 GHz industrial, scientific, and medical (ISM) band. This band is also used for many other devices, including: Cordless phones Microwave ovens Medical devices Industrial devices Baby monitors CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed – Interference a) Co-channel and Adjacent Channel Interference Co-channel or adjacent channel interference occurs when two devices in the same physical area are tuned to a close or same radio frequency channel. For example, an access point on channel 1 and another access point on channel 2 in close or hearing range of each other will experience adjacent channel interference. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - Interference b) WLAN/WPAN Interference The performance of IEEE 802.11 wireless networks can be affected when they are co located with IEEE 802.15 wireless personal area networks or WPANs. Bluetooth is an example of a personal area network. Like 802.11, Bluetooth devices operate in the 2.4 GHz frequency range and use frequency hopping spread spectrum (FHSS). CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - Interference c) Bright Sunlight Interference Bright sunlight will not affect wireless LAN communications that use the 2.4 GHz ISM and 5 GHz UNII bands; CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - Environment Environment: RF Behavior RF behavior is the result of environmental conditions including: 1. Reflection 2. Refraction 3. Diffraction 4. Scattering 5. Absorption 6. Diffusion CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - Environment 1. Reflection – Reflection occurs when an RF signal bounces off a smooth, non absorptive surface such as a table top and changes direction. Reflections can affect indoor wireless LAN installations fairly significantly in certain cases. Depending on the interior of the building—such as the type of walls, floors, or furnishings —there could be a large number of reflected signals. If not properly handled, reflections could cause a decrease in throughput and poor network performance. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - Environment 2. Refraction When an RF signal passes between mediums of different densities, it may change speeds and also bend. This behavior of RF is called refraction. Glass is an example of material that may cause refraction. When an RF signal comes in contact with an obstacle such as glass, the signal is refracted (bent) as it passes through and some of the signal is lost. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - Environment 3. Diffraction When an RF signal passes an obstacle, the wave changes direction by bending around the obstacle. This RF behavior is called diffraction. A building or other tall structure could cause diffraction, as could a column in a large open area or conference hall. When the signal bends around a column, building, or other obstacle, the signal weakens, resulting in some level of loss. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - Environment 4.Scattering When an RF signal strikes an uneven surface, wave fronts of the signal will reflect off the uneven surface in several directions. This is known as scattering. Scattering is another form of loss that may severely degrade the RF signal. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  RF Range and Speed - 5.Absorption Environment When material absorbs an RF signal, no signal penetrates through the material. An example of absorption is the human body. The human body has a high water content and will absorb RF signals. This type of absorption can be a problem for wireless network deployments in certain environments. Densely populated areas such as airports and conference halls need to consider absorption when designing a wireless LAN deployment. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹#› of 9  Quick Review Question Coverage and capacity will depend on many factors. What are they? Explain each of them. How far and fast an RF signal can travel depends on a variety of factors. What are they? Explain each of them. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹48› of 9 Summary of Main Teaching Points This chapter looked at radio frequency basics and the essential role RF plays in the world of IEEE 802.11 wireless LANs. This chapter also looked at correct channel reuse to minimize interference from co-location of access points. Coverage and capacity are two important areas that should be closely looked at in order to ensure a wireless deployment will offer reliable connectivity and perform well for the user base. Finally, we discussed RF units of measure, including watt, milliwatt, dB, and dBi. We also looked at RF behaviors such as reflection, refraction, and absorption, and the impact of propagation on radio waves. CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹49› of 9  Question and Answer Session Q&A CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹50› of 9  What we will cover next WLAN Terminology and Technology CT090-3-2 and Mobile & Wireless Technology Radio Frequency Fundamentals for WLAN Slide ‹51› of 9