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Is Teaching Wireless Networking in your Future?

Is Teaching Wireless Networking in your Future?. Karl Dietrich – Lansing Community College Bill Saichek – Orange Coast College. Thanks to the book publishers. Cengage Sybex. Types of Wireless LANs. Since late 1990s, IEEE has approved five standards for wireless LANs: IEEE 802.11

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Is Teaching Wireless Networking in your Future?

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  1. Is Teaching Wireless Networkingin your Future? Karl Dietrich – Lansing Community College Bill Saichek – Orange Coast College

  2. Thanks to the book publishers • Cengage • Sybex

  3. Types of Wireless LANs • Since late 1990s, IEEE has approved five standards for wireless LANs: • IEEE 802.11 • IEEE 802.11b • IEEE 802.11a • IEEE 802.11g • IEEE 802.11n

  4. IEEE 802.11 • Specified that wireless transmission could take place via infrared (IR) or radio signals (RF) • Operated at 1 and 2 Mbps • WG formed in 1990

  5. IEEE 802.11b • 802.11 standard’s 2 Mbps bandwidth not sufficient for most network applications • 802.11b amendment added two higher speeds to original 802.11 standard • 5.5 Mbps and 11 Mbps • 2.4-GHz band • Uses ISM band • Separated into 22-MHz channels • DSSS • Direct Sequence Spread Spectrum signaling

  6. IEEE 802.11a • Released after 802.11b • 5-GHz frequency – UNII band • Not congested like 2.4-GHz band • Lower interference, requires more transmit power • Throughput • 54 Mbps theoretical • 11 and 18 Mbps effective • Attributable to higher frequencies and unique modulating data method • OFDM • Orthogonal Frequency Division Multiplexing

  7. 802.11g • Throughput • 54 Mbps theoretical • 20 to 25 Mbps effective • 2.4-GHz frequency band • Compatible with 802.11b networks • Operates in the ISM band • Data transfer range • 350 feet or 107 meters apart • Uses OFDM for transmission format • Same as 802.11a but different frequency

  8. IEEE 802.11n • Finally ratified in September 2009 • Speed of 802.11n standard will be anywhere from 100 Mbps to 600 Mbps • 600 Mbps is theoretical not there yet • Standard defines that all 802.11n devices must contain two radios

  9. 802.11n • 2.4-GHz or 5-GHz frequency range • Backward compatible with 802.11a, b, g standards • Compared with 802.11a, 802.11g • Same data modulation techniques • Compared with three 802.11 standards • Manages frames, channels, encoding differently • Allows high throughput (HT) • Greenfield mode

  10. 802.11n • MIMO (Multiple Input-Multiple Output) • Multiple access point antennas may issue signal to one or more receivers • Increases network’s throughput, access point’s range • Still a one-to-one communication between devices

  11. MIMO Signal Processing Techniques • Spatial Diversity: multiple redundant signals • Spatial Multiplexing creates separate data streams for each transmitting antenna • Maximal Ratio Combining can combine the signals of two antennas to increase the signal strength in a single stream • Transmit Beamforming(TxBF) allows a MIMO transmitter to focus the transmission and send in the direction of the receiving antenna

  12. IEEE 802.11ac • IEEE 802.ac is in now in development • Also called Gigabit Wireless (Gigabit Wifi) • IEEE 802.11ac will be a game changer

  13. IEEE 802.11ac • Some of the 802.11ac technologies include: • Spectrum: will operate in the less-crowded 5 GHz spectrum and not support 2.4 GHz • Roughly 8 times as many channels as 2.4 GHz • Increased channel bandwidth: uses channel bandwidths up to 80 MHz • Error correction coding: stronger processors can handle more internal instruction code • Beam forming: Transmit Beamforming (TxBF) is optional with 802.11n but will be standard for all ac devices

  14. IEEE 802.11ac • A MU-MIMO device can transmit to multiple sources at the same time and it can transmit different data to each end source From Tech Republic – Cheat sheet: What you need to know about 802.11ac By Michael Kassner June 18, 2013

  15. IEEE 802.11ac • Is there a downside to 802.11ac • There will be a significantly smaller coverage area • The 5 GHz range won’t go as far • Attenuation is directly proportional to the frequency • Will need multiple access points in large homes and buildings 802.11ac on the Horizon; Will You Be Ready? Posted on February 25, 2013 by Nick McLain

  16. Access Points • Autonomous Access Points • Also called fat access points • These are quickly becoming obsolete with very limited usage • Lightweight Access Points • Also called thin access points • Does not contain management and configuration functions • Management features are contained in a central device called wireless LAN controller

  17. Wireless LAN Controller • WLAN controller: used to manage devices from a central location • Devices are proprietary – all lightweight APs and WLCs must be from the same vendor • Cloud management: connecting wireless devices together using the Internet in order to remotely manage them • Because devices can be managed remotely there is no need for multiple support teams for each location

  18. Access Points - PoE • Power over Ethernet (PoE) • Power delivered to AP through unused wires in standard unshielded twisted pair (UTP) Ethernet cable • IEEE 802.3af – up to 15.4 watts • Only 12.95 watts of power is used • PoE+ or PoE Plus • IEEE 802.3at – up to 25.5 watts • Multiple radio APs need additional power

  19. Radio Signal Characteristics • Wavelength • Frequency • Amplitude • Phase • The higher the frequency the smaller the wavelength • Phase is measured in distance, time, or degrees

  20. Wavelength • Wavelength • Distance between the wave’s peaks • Can also be measured from anywhere in the wave as long as it is at the same point in each cycle

  21. Frequency • Frequency: Rate at which an event occurs • Number of times that a wave completes a cycle within a given amount of time • When wave completes trip and returns back to starting point it has finished one cycle

  22. Amplitude • Amplitude: the magnitude of change of the wave • Is measured by how high or how deep the wave is • Is essentially a measure of the strength of an electromagnetic wave’s signal

  23. Phase • Phase: the relationship between at least two signals that share the same frequency yet have different starting points

  24. Analog vs. Digital Transmissions • Analog signals are continuous • Digital signals are discrete • WLANs use digital transmissions Analog signal Digital signal

  25. RF Modulation • In order for an electromagnetic wave to transmit information it must be modified • Three types of modulations enable carrier signals to carry information • Amplitude modulation - Height of the signal • Frequency modulation – Frequency of the signal • Phase modulation – change the starting point of the signal

  26. Amplitude-Shift Keying (ASK)

  27. Frequency-Shift Keying (FSK)

  28. Phase-Shift Keying (PSK)

  29. Radio Frequency Behavior: Loss • Loss: Negative difference in amplitude between signals • Attenuation: loss of signal strength due to wave propagation and multipath • Propagation behaviors • FSPL - Natural loss of signal strength through space

  30. Wave Propagation Loss • Reflection • Refraction • Scattering • Diffraction • Absorption

  31. Amplification • Gain: Positive difference in amplitude between two signals • Technically, gain is measure of amplification • Power – a constant measured in mW (milliwatts) • Gain/Loss – a relative figure measured in dB • Combined to become dBm • Active Gain • Intentionally boosting the signal • Passive Gain • Using the antenna to strengthen the signal

  32. Types of Antennas • Three basic categories of antennas: • Omnidirectional • Semidirectional • Highly directional • Each category includes multiple types, each with different characteristics

  33. Omni-directional rod antenna Dipole Antenna

  34. How is the data prepared for transmission • Segments to Packets to Frames • Frames are dependent upon the standard being used to send the data • Wired vs. Wireless • Each wireless standard frames the data differently • Are they compatible?

  35. Our old friend the OSI Model

  36. IEEE 802.11Physical Layer Standards Data Link sublayers

  37. IEEE 802.11Physical Layer Standards PHY sublayers

  38. MAC Frame Formats SDUs and PDUs

  39. MAC Frame Formats – 802.11n A-MSDU and A-MPDU

  40. MAC Frame Types • Three categories of MAC frame types • Management Frames • Used to manage access to wireless networks and to move associations between APs • Control Frames • Used to assist with the delivery of data frames • Data Frames • The actual carriers of application level data

  41. WLAN Service Sets • Service set: all of the devices that are associated with an 802.11 WLAN • Three different WLAN service set configurations: • Basic service set • Extended service set • Independent basic service set

  42. Basic Service Set • Basic Service Set – BSS • One AP with one or more client stations • Infrastructure Mode • Service Set Identifier – SSID • A logical name used to identify an 802.11 wireless network • Comparable to a Windows Workgroup name • Up to 32 characters and is case sensitive

  43. Basic Service Set • Basic Service Area (BSA) • The physical area of coverage provided by an access point in a BSS • Power settings affect the coverage area

  44. Extended Service Set • Extended Service Set (ESS) • One or more BSSs connected by a distribution system medium • An overlap of 15 to 25% is needed to achieve seamless roaming between cells

  45. Independent Basic Service Set • Independent Basic Service Set (IBSS): Wireless network that does not use an AP • Peer-to-peer or ad hoc mode

  46. MAC Operations • MAC layer WLAN functions: • Discovering a WLAN • Joining the WLAN • Transmitting on a WLAN • Remaining connected to WLAN

  47. Discovering the WLAN: Scanning • Two types of scanning • Passive scanning - Wireless device simply listens for beacon frame. The station will determine the AP with the best signal (RSSI) • Active scanning - Wireless device first sends out a management probe request frame then waits for probe response frame • The difference between passive scanning and active scanning is which device initiates the discovery

  48. Joining the WLAN:Authentication and Association • Once a wireless device discovers the WLAN, it next requests to join the network • Authentication • Association • A client must authenticate before it can associate

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