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Wi-Fi
REFERENCE 802.11n Principles
SERIES
Data Rates MIMO Signal Processing
Expected 802.11n Data Rates MIMO (Multiple In Multiple Out) Signal Processing uses multiple antennas and takes advantage of multipath reflections to improve signal Expected First Generation Device Data Rates Expected Second Generation Device Data Rates coherence that greatly increases receiver sensitivity. This extra sensitivity can be used for greater range or highter data rates. One Spatial Stream Two Spatial Streams Three Spatial Streams Four Spatial Streams802.11a 802.11g 11n Mandatory With Channel With Short Two Spatial With Channel With Short Three Spatial With Channel With Short Four Spatial With Channel With ShortRates Data Rates Bonding (40MHz) Guard Interval Streams Bonding (40MHz) Guard Interval Streams Bonding (40MHz) Guard Interval Streams Bonding (40MHz) Guard Interval MIMO Digital Signal Processing6 6.5 13.5 15 13 27 30 19.5 40.5 45 26 54 60 The newly enhanced signal is the processed sum of individual antennas. Signal Processing eliminates nulls and fading that any one antenna would see. MIMO Signal Processing is sophisticated enough to discern multiple spatial streams (see Spatial Multiplexing).9 13 27 30 26 54 60 39 81 90 52 108 12012 19.5 40.5 45 39 81 90 58.5 121.5 135 78 162 18018 26 54 60 52 108 120 78 162 180 104 216 240 MIMO Processed Signal24 39 81 90 78 162 180 117 243 270 156 324 36036 52 108 120 104 216 240 156 324 360 208 432 480 Antenna 1 Signal A48 58.5 121.5 135 117 243 270 175.5 364.5 405 234 486 540 tte54 65 135 150 130 270 300 195 405 450 260 540 600 nuAntenna 2 Signal atiReceiver onObtaining 802.11n Choose New Base Encoding + Modulation Optionally Optionally OptionallyData Rates Multiply by 2, 3, 4 Multiply By 2.077 Multiply by 1.11 for BPSK (6.5) for the Number of to Bond Shorter Guard Interval New 11n Antenna 3 SignalQPSK (13, 19.5) x x x =Additional Two 20MHz to Increase Data RateQAM-16 (26, 39) Note: Wi-Fi Alliance 802.11n Certifica-Spatial Streams Channels Symbol Rate tion will require devices to support two QAM-64 (58.5, 65) spatial streams and channel bonding. Frequency Across Subcarriers
Improved MAC Throughput Client Shipments Relative Rate and Range Spatial Multiplexing Wi-Fi Certified Data Rates and Channels802.11a/b/gFrame Aggregation 802.11a/b/g/n100 Spatial Multiplexing transmits completely separate data streams on different antennas (in the same channel) that are recombined to produce MAC data frames are combined and given a single PHY header new 802.11n data rates. Higher data rates are achieved by splitting the original data stream into separate data streams. Each separate stream 802.11n Implicit Block ACK acknowledges all data frames within aggregate is transmitted on a different antenna (in the same channel). MIMO signal processing at the receiver can detect and recover each stream. 802.11b 802.11g 802.11a 802.11n (2.4GHz) 802.11n (5GHz)New 802.11n modes are 40% more efficient than legacy modes. Streams are then recombined which yielding higher data rates.Legacy Operation )s Wi-Fi Cert.noilData Frame ACK Frame Data Frame ACK Frame Data Frame ACK Frame 11Mbps 54Mbps 54Mbps 130Mbps 130Mbpsl50i Data RatesM(1 1 2 2 N N. . . Tx 1 Rx 1802.11a/g Channels 3 3 12 3 12PHY HeaderHigh Throughput Operation Data Frame Block ACK Frame MAC Header 0 802.11b2005 2006 2007 2008 2009 Capacity1 2 N 1 2 N Source: Dell'Oro Group 11/06Data Frame Payload. . . . . . Per Cell 33Mbps 162Mbps 648Mbps 390Mbps 1560MbpsACK Frame Payload Tx 2 Rx 2Transmitter ReceiverData Stream Data StreamRIFS Usage (Reduced Inter-Frame Spacing) M MStandardization TimelineLegacy OperationData Frame ACK Frame Data Frame ACK Frame Data Frame ACK Frame Wi-Fi Alliance Estimated Timeline UnPlug Fests Profiles and Final Certification New Applications1 1 2 2 N N Note: Wi-Fi Alliance 802.11n Certification will require . . . devices to support two spatial streams and channel bonding. Tx N Rx MBaseline SIFS SIFS Certification Enabling New ApplicationsHigh Throughput Operation Block ACK Block ACK CAD, Design EmployeeRequest Response Wireless Wireless Graphics On-Demand VideoData Frame Data Frame Data Frame Frame Frame 2003 2004 2005 2006 2007 2008 HDTV Backup Applications Training ConferencingQ1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 yti1 2 N 2 1 2 N ca. . . . . . RemoteWireless Video Remotep VideoaRIFS RIFS SIFS Channel Bonding SDTV On Demand Gaming LearningC SurveillanceComment IEEE Publishes Resoluti... [download for more]
