101 Certified Wireless Network Professional :: CWNA-109 Fresnel Zones FZ1 FZ2 FZ3 View from Receiver looking at Transmitter View of first three Fresnel zones from the side Concentric ellipsoid-shaped volume between antennas Infinite number of Fresnel zones (theoretically) The first Fresnel zone (labeled FZ1) MUST be more than 60% clear of obstructions FZ1 FZ2 FZ3
102 Certified Wireless Network Professional :: CWNA-109 Fresnel Zone Calculations r D FZ1 r = radius (meters) f = frequency (GHz) D = distance (kilometers) = . = . r = radius (feet) f = frequency (GHz) D = distance (miles) Note that distance and frequency are the only two variables in this calculation Antenna beamwidth does not affect Fresnel zone size or obstruction clearance
103 Certified Wireless Network Professional :: CWNA-109 Free Space Path Loss (FSPL) f = frequency (MHz) D = distance (kilometers) 20log10(D) + 20log10(f) + 32.45 20log10(D) + 20log10(f) + 36.58 f = frequency (MHz) D = distance (miles) Free Space Path Loss (FSPL) is the power decrease with distance as the wavefront expands through space. FSPL is the single greatest loss factor in an RF system.
104 Certified Wireless Network Professional :: CWNA-109 Inverse Square Law I/4 Intensity at Source = I 2D Distance from Source = D 4D I D Inverse Square Law (geometric expansion) As the distance doubles, the energy is spread over four times the area, resulting in one quarter (1/4) of the original intensity. Power density decreases as the wavefront extends through space.
105 Certified Wireless Network Professional :: CWNA-109 Antenna Downtilt Antenna downtilt is a vertical alignment principle designed to point the antenna’s main lobe in the proper direction The downtilt angle is determined by the antenna height (at both locations, if bridging two radios) and distance 0° Angle of Downtilt
106 Certified Wireless Network Professional :: CWNA-109 Antenna Safety Basics Read factory manuals Use proper mounting equipment Consider professional installers Avoid power lines Use grounding rods and lightning protection
107 Certified Wireless Network Professional : CWNA-109 Common RF Connectors RP-TNC RP-SMA N-type
108 Certified Wireless Network Professional :: CWNA-109 RF Splitters RF Splitters are used to make additional physical connections from the transceiver to the antenna Anytime adapters, cables and connectors are added, loss is incurred including using splitters.
109 Certified Wireless Network Professional :: CWNA-109 Pigtail Cables Pigtails allow generic or third-party antennas to be connected to WLAN cards or APs. Pigtails are short RF cable adapters connecting to an antenna on one end and a WLAN transceiver on the other end.
110 Certified Wireless Network Professional :: CWNA-109 RF Cables RF cable loss is measured in dB /ft Carries electrical current between the antenna and WLAN transceiver Cabling causes loss, which is measured in dB (e.g. 3 dB per 100 ft.) Long RF cabling runs may cause enough loss to prevent radio communication
111 Certified Wireless Network Professional :: CWNA-109 Voltage Standing Wave Ratio 50 Ohms 50 Ohms 75 Ohms VSWR is a measurement of mismatch between the load and the transmission line 1:1 is perfect VSWR – no reflected power 1.1:1 up to 1.5:1 is considered to be good 2:1 is less desired and may cause problems Impedance (electrical resistance) must match Access Point connectors Cabling Connectors Antennas
112 Certified Wireless Network Professional :: CWNA-109 Lightning Arrestors Coaxial Gas Discharge Tube Surge Protectors Bi-metal conductors or gas discharge tubes Detect incoming over-voltages induced by nearby lightning strikes Shunt the current to earth ground Cannot fully protect against a direct lightning strike Gas discharge tube protectors feature easily replaced gas tube elements, multi-strike capability and bi-directional protection.
113 Certified Wireless Network Professional :: CWNA-109 Lightning Protection
114 Certified Wireless Network Professional :: CWNA-109 Chapter 5: 802.11 PHYs and Network Types Objectives Covered: 2.3 Explain and apply the various Physical Layer (PHY) solutions of the IEEE 802.11-2016 standard as amended including supported channel widths, spatial streams, data rates and supported modulation types 2.4 Identify and apply 802.11 WLAN functional concepts 2.5 Describe the OSI model layers affected by the 802.11-2016 standard and amendments 2.6 Define the frequency bands used by the 802.11 PHYs 2.7 Identify and comply with regulatory domain requirements and explain how to determine constraints within a regulatory domain 2.8 Explain basic use case scenarios for 802.11 wireless networks 3.1 Describe the components that make up an 802.11 wireless service set
115 Certified Wireless Network Professional :: CWNA-109 802.11 Frequency Bands 2.4 GHz – 802.11b/g/n 5 GHz – 802.11a/n/ac 60 GHz – 802.11ad Sub-1 GHz – 802.11ah Traditional Wi-Fi (DSSS through VHT) Directional Multi-Gigabit (DMG) Low frequency wireless (S1G) Frequency Band Frequency Range Used by 802.11 Devices 2.4 GHz 2.400-2.500 GHz 2.401-2.495 GHz 5 GHz 5.150-5.925 GHz 5.160-5.835 GHz 60 GHz 57-66 GHz 57.24-65.88 GHz Sub-1 GHz 700-950 MHz Varies by regulatory domain
116 Certified Wireless Network Professional :: CWNA-109 802.11 Frequency Bands Compared Sub-1 GHz 2.4 GHz 5 GHz 60 GHz Wavelength 33+ cm 12 cm 5 cm 5 mm Typical Distance (non-bridging) Longer than 500 meters 30-200 meters 25-100 meters 1-10 meters Use Cases IoT, industrial, low throughput communications Standard Wi-Fi, IoT, Bluetooth, proprietary Standard Wi-Fi, video devices, proprietary High definition video Wi-Fi, short range backhaul, proprietary Industry Acceptance (2017) Low High High Moderate
117 Certified Wireless Network Professional :: CWNA-109 2.4 GHz Channels
118 Certified Wireless Network Professional :: CWNA-109 5 GHz Channels Channels 52-144 require DFS in many regulatory domains Channels 120-128 are allowed in North America as of April 1, 2014
119 Certified Wireless Network Professional :: CWNA-109 Channel Centers and Widths (2.4 GHz) Channel widths vary by PHY and 2.4 GHz channels overlap • DSSS and HR/DSSS (802.11/802.11b) – 22 MHz • ERP (802.11g) – 20 MHz • HT (802.11n) – 20/40 MHz Channel 1 is centered on 2.412 GHz and each channel increments by 5 MHz (causing overlap) • For example, channel 2 is 2.417 and channel 3 is 2.422
120 Certified Wireless Network Professional :: CWNA-109 Channel Centers and Widths (5 GHz) Channel widths vary by PHY and 5 GHz channels do not overlap • OFDM (802.11a) – 20 MHz • HT (802.11n) – 20/40 MHz • VHT (802.11ac) – 20/40/80/160 MHz Channels 36-64 are 20 MHz apart starting on center frequency 5.180 GHz Channels 100-144 are 20 MHz apart starting on center frequency 5.500 Channels 149-165 are 20 MHz apart starting on center frequency 5.745 GHz
121 Certified Wireless Network Professional :: CWNA-109 Adjacent Overlapping Channels 2412 MHz 2417 MHz 2422 MHz 2427 MHz 2432 MHz 2437 MHz 2442 MHz 1 2 3 4 5 6 7 2401 MHz 2452 MHz First seven channels of the 2.4 GHz band
122 Certified Wireless Network Professional :: CWNA-109 Non-Overlapping Channels 2412 MHz 2422 MHz 2427 MHz 2437 MHz 1 2401 MHz 2447 MHz Channels 1 and 6 of the 2.4 GHz band 5 MHz 6 In the 5 GHz band there is more separation between channels so no overlap occurs.
123 Certified Wireless Network Professional :: CWNA-109 Dynamic Bandwidth Operation (DBO) 20 MHz 40 MHz 80 MHz One channel clear Two channels clear Four channels clear RTS/CTS used across multiple channels CTS response only on available channels Widest channel availability is used Allows sharing of channels Incurs some overhead that may not be required with use of narrower channels Not recommended for use beyond 80 MHz • Many organizations will not use it beyond 40 MHz
124 Certified Wireless Network Professional :: CWNA-109 2.4 GHz and 5 GHz Band Comparison 2.4 GHz ■ 100 MHz total spectrum ■ Heavily used by Wi-Fi and non-Wi-Fi ■ Longer range ■ 802.11b/g/n ■ Past ■ 600+ MHz total spectrum ■ Less traffic from Wi-Fi and non-Wi-Fi ■ Shorter range ■ 802.11a/n/ac ■ Future 5 GHz
125 Certified Wireless Network Professional :: CWNA-109 OSI Model Layers and Wi-Fi Layer 1 – Physical (PHY) Layer 2 – Data Link (MAC Sub-Layer) Layers 3-7 IP, TCP/UDP, and application data 802.11 Media Access Control (MAC) Operations 802.11 PHY Operations MSDU MPDU PSDU PPDU Datagrams & Packets
126 Certified Wireless Network Professional :: CWNA-109 802.11 Physical Layers (PHYs) Direct Sequence Spread Spectrum (DSSS) – 802.11 High Rate-DSSS (HR-DSSS) – 802.11b Orthogonal Frequency Division Multiplexing (OFDM) – 802.11a Extended Rate PHY (ERP) – 802.11g High Throughput (HT) – 802.11n Directional Multi-Gigabit (DMG) – 802.11ad Very High Throughput (HT) – 802.11ac TV Whitespace HT (TVHT) – 802.11af Sub-1 GHz (S1G) – 802.11ah
127 Certified Wireless Network Professional :: CWNA-109 DSSS and HR/DSSS Frequency Band Channels Bandwidth Modulation Data Rates Direct Sequence Spread Spectrum (DSSS) 802.11-Prime 2.4 GHz 1-14 Constrained by regulatory domains. 22 MHz DBPSK (1 Mbps) and DQPSK (2 Mbps); Barker code 1 and 2 Mbps High Rate/DSSS (HR/DSSS) 802.11b 2.4 GHz 1-14 Constrained by regulatory domains. 22 MHz DBPSK and DQPSK; complementary code keying (CCK) 1, 2, 5.5 and 11 Mbps Older PHYs, like DSSS and HR/DSSS, are often disabled on modern networks by disabling low data rates. When this action is taken, devices supporting only these PHYs cannot communicate with the network.
128 Certified Wireless Network Professional :: CWNA-109 OFDM and ERP Frequency Band Channels Bandwidth Modulation Data Rates Orthogonal Frequency Division Multiplexing (OFDM) 802.11a 5 GHz 5 GHz channels as previously defined. Constrained by regulatory domains. 20 MHz BPSK, QPSK, QAM-16 and QAM-64 6, 9, 12, 18, 24, 36, 48 and 54 Mbps Extended Rate PHY (ERP) 802.11g 2.4 GHz 1-14 Constrained by regulatory domains. 20 MHz DBPSK, DQPSK, QAM-16 and QAM-64 1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36, 48 and 54 Mbps The ERP PHY can operate in either ERP-OFDM-only or mixed ERP-OFDM and ERP-DSSS mode, the latter providing direct compatibility with DSSS and HR/DSSS.
129 Certified Wireless Network Professional :: CWNA-109 HT Frequency Band Channels Bandwidth Modulation Data Rates High Throughput (HT) 802.11n 5 GHz 5 GHz channels as previously defined. Constrained by regulatory domains. 20 or 40 MHz BPSK, QPSK, QAM-16 and QAM-64 Based on Modulation and Coding Scheme (MCS) tables High Throughput (HT) 802.11n 2.4 GHz 1-14 Constrained by regulatory domains. 20 MHz 40 MHz should not be used in 2.4 GHz DBPSK, DQPSK, QAM-16 and QAM-64 Based on MCS tables HT adds support for Multiple Input/Multiple Output (MIMO) communication, which uses multiple antenna chains to send and receive multiple streams of concurrent data.
130 Certified Wireless Network Professional :: CWNA-109 Frequency Band Channels Bandwidth Modulation Data Rates Very High Throughput (VHT) - required 802.11ac 5 GHz 5 GHz channels as previously defined. Constrained by regulatory domains. 20, 40 or 80 MHz BPSK, QPSK, QAM-16 and QAM-64, QAM256 Based on Modulation and Coding Scheme (MCS) tables Very High Throughput (VHT) - optional 802.11ac 5 GHz 5 GHz channels as previously defined. Constrained by regulatory domains. 20, 40, 80 or 160 MHz 160 MHz may be contiguous or 80+80 BPSK, QPSK, QAM-16 and QAM-64, QAM256 Based on MCS tables VHT VHT also introduced Multi-User MIMO (MU-MIMO), although production environments have not shown significant advantage in most deployments.
131 Certified Wireless Network Professional :: CWNA-109 S1G, DMG, and TVHT Frequency Band Channels Bandwidth Modulation Data Rates Sub-1 GHz (S1G) 802.11ah Under 1 GHz (varies by regulatory domain from 700 MHz to 900 MHz+) Number of channels depends on available bandwidth, some areas will have only 5 MHz total available. 1, 2, 4, 8 or 16 MHz BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM Defined by MCS tables. 346666.7 Kbps max (with 16 MHz channel and 4 spatial streams) Directional Multi-Gigabit (DMG) 802.11ad 60 GHz (57-64 GHz worldwide and 57-66 GHz in Europe) 1, 2, 3 and 4 (channel 2 is available in all regions and is the default) 2.16 GHz DBPSK (control PHY); SQPSK, QPSK, 16-QAM, 64-QAM (OFDM PHY); BPSK, QPSK, 16-QAM (SC PHY) Defined by MCS tables. 6756.75 Mbps max (with OFDM-64-QAM) TV White Space HT (TVHT) 802.11af Between 54 and 790 MHz varying by regulatory domain and available space Number of available channels depends on unused TV white space in the area 6, 7 or 8 MHz in a unit with up to 4 channel units aggregated BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM Defined by MCS tables. 568.9 Mbps max
132 Certified Wireless Network Professional :: CWNA-109 DMG Spectrum Mask DMG Details 58.32 GHz 60.48 GHz 62.64 GHz 64.80 GHz Channel 1 Channel 2 Channel 3 Channel 4 Europe and Japan (57 – 66 GHz) Australia (59.4 – 62.9 GHz) China (59 – 64 GHz) U.S. and Canada (57.05 – 64 GHz) Channel widths are 2160 MHz with 802.11ad. FSPL is -68 dB at one meter in the 60 GHz band.
133 Certified Wireless Network Professional :: CWNA-109 Throughput vs. Data Rate Data Rate BSS Operations 802.11 Data Frames Other Transmitting STAs Single STA Throughput Overhead Factors 6 Mbps 1733.3 Mbps 1 Mbps 130 Mbps
134 Certified Wireless Network Professional :: CWNA-109 RF Modulation Methods 802.11 networks use ASK and PSK modulation techniques. Commonly used PHYs today do not use FSK modulation in WLAN deployments. The baseband signal is the binary bits requiring transmission. Amplitude modulation alters the amplitude of the RF wave to indicate data. Frequency modulation alters the frequency of the RF wave to indicate data. Phase modulation alters the phase of the RF wave to indicate data.
135 Certified Wireless Network Professional :: CWNA-109 PSK Modulation Binary PSK – 1 Bit (0 or 1) Quadrature PSK – 2 Bits Two Phases Four Phases Phase° Q I Q=0 and I alternates between -1 and +1 Q and I alternate between -1 and +1 +1 -1 -1 +1 0 1 Q I +1 -1 -1 +1 00 Q I 01 11 10
136 Certified Wireless Network Professional :: CWNA-109 QAM Modulation Quadrature Amplitude Modulation (QAM) adds amplitude shifts to the equation.
137 Certified Wireless Network Professional :: CWNA-109 Coding Methods Coding is the conversion of data bits into a series of symbol bits Adds redundancy (communication resiliency) to the bit stream • Minimizes errors • Maximizes data recovery Coding rates are a ratio of data bits to coded bits (e.g. 1/2, 2/3, 3/4, 5/6) Output Data A Output Data B Input Data
138 Certified Wireless Network Professional :: CWNA-109 Modulation and Coding Schemes (MCS) PHYs that support multiple channel widths and spatial streams have an MCS table for each channel width/spatial stream combination.
139 Certified Wireless Network Professional :: CWNA-109 Co-Location/Co-Channel Interference Collocated interference is interference caused from another RF transmitter in the same device Co-location is the term often used to indicate that multiple BSS networks are in the same coverage area, but on different channels Co-channel interference (CCI) is interference caused by overlapping BSS signals BSS #1 Channel 1 BSS #2 Channel 1 Associated Associated CCI
140 Certified Wireless Network Professional :: CWNA-109 Transmit (Tx) Beamforming Beamformee Beamformer
141 Certified Wireless Network Professional :: CWNA-109 Multi-User (MU) MIMO Simultaneous beamformed transmissions
142 Certified Wireless Network Professional :: CWNA-109 Regulatory Domain Requirements Channel constraints Output power constraints Dynamic Frequency Selection (DFS) Transmit Power Control (TPC)
143 Certified Wireless Network Professional :: CWNA-109 Dynamic Frequency Selection (DFS) DFS is required in many regions for channels 52-144
144 Certified Wireless Network Professional :: CWNA-109 Transmit Power Control (TPC) TPC has two primary functions: Power Constraint – compliance with regulatory power requirements Dynamic power adaptation – improve battery life and/or cell performance by suggesting adjustments to the client transmit power
145 Certified Wireless Network Professional :: CWNA-109 802.11 Use Case Scenarios Wireless LAN (WLAN) Wireless Ad-Hoc (IBSS) Wireless PAN (WPAN) Wireless bridging Wireless Mesh Bridging WLAN Ad-Hoc
146 Certified Wireless Network Professional :: CWNA-109 BSA WLAN Operating Modes Independent Basic Service Set (IBSS) • Ad-hoc Basic Service Set (BSS) • Infrastructure Mode • Basic Service Area (BSA) Extended Service Set (ESS)
147 Certified Wireless Network Professional :: CWNA-109 BSS Components Access Point Clients Service Set ID (SSID) BSSID (AP MAC address or generated) Distribution System (DS) Distribution System Media (DSM)
148 Certified Wireless Network Professional :: CWNA-109 ESS and Roaming An Extended Service Set (ESS) is one or more BSSs interconnected by a shared distribution network Devices roam among APs in the same ESS, usually specified by a shared SSID Roaming can occur at Layer 1, Layer 2 or Layer 3 • Layer 1 – roaming from 2.4 GHz to 5 GHz and vice versa • Layer 2 – MAC sublayer • Layer 3 – IP layer
149 Certified Wireless Network Professional :: CWNA-109 Chapter 6: 802.11 Network Devices Objectives Covered: 3.6 Describe features of, select and install WLAN infrastructure devices 3.7 Identity the features, purpose, and use of the following WLAN client devices and adapters 4.2 Describe and implement Power over Ethernet (PoE)
150 Certified Wireless Network Professional :: CWNA-109 Access Point Features and Capabilities