presenter – keith r. parsons -...
TRANSCRIPT
802.11n Planning and Optimization Workshop
Outline
• Section I: 802.11 Fundamentals – Review of ‘Legacy’ 802.11a/b/g • Section II: 802.11n Concepts, Terms, Features • Section III: 802.11n Analysis • Section IV: 802.11n Design
Section I: 802.11 Fundamentals AirMagnet Product Family
Evolution of 802.11 Standards
Comparison of 2.4GHz and 5GHz Radio Waves
2.4GHz Channel Overlap
Want – Don’t Want – Don’t Care (Signal Strength)
RF Power and Distance
So, What *is* an Access Point Anyway?
Where 802.11 is in the OSI Model – Physical and Data Link
802.11 ‘classic’, b, a, g Available Data Rates
Protection ‘Penalty’ for b/g Mixed Mode
Effects of Multipath
More Subcarriers Available in 802.11n – with 40MHz Channels
Forward Error Correction (FEC)
40MHz Channels in the 2.4GHz Band 3 4 5 6 7 8 9
Channels defined for 2.4 GHz band, showing common 20 MHz channel plan and 40 MHz options
1Channel 2 3 4 5 6 7 8 9 10 11
1 6 11
12 132412Center Frequency 2417 2422 2427 2432 2437 2442 2447 2452 2457 2462 2467 2472
Legacy Protection Analysis
Modulation and Coding Schemes
Granulation and Additional Speeds with 802.11n
Affects of Channel Occupancy
New Start Columns to Support 802.11 n Fields
New 802.11n information in STA and AP detail
Section IV: 802.11n Design
Skills you’ll need for 802.11n Deployments
Migration Issues
New Features of AirMagnet Survey PRO
Throughput Simulator
802.11 n Heatmaps
– Color-coded by 'n'
– Channel Width
– Max MCS
– Operating Mode
– Measured PHY Data
– Predictive PHY Data
Updated AirWise
iPerf Survey
'n' Active Survey
'n' Passive Survey
Updated Heatmaps
Glossary 802.11 Groups PHY/MAC ‘Classic’1 & 2 Mbps, 2.4GHz FH, DS, and IR .a PHY up to 54 Mbps in the 5GHz band .b PHY up to 11 Mbps in the 2.4GHz band .c MAC MAC-layer Bridging .d PHY Additional Regulatory Domains for .11b .e MAC Quality of Service (QoS) Improvements .f MAC Inter-Access-Point Protocal IAPP .g PHY Up to 54 Mbps in the 2.4GHz band .h MAC Dynamic Frequency Selection/Transmit Power Control for .11a .i MAC Security Enhancements .j PHY 4.9GHz Regulatory Issues for Japan .k MAC Radio Resource Measurement .m PHY/MAC Maintenance and Technical Corrections .n PHY/MAC Performance and High Throughput - MIMO .p PHY/MAC Wireless Access in Vehicular Environment (WAVE) .r MAC Fast Roaming – reducing latency during handoffs .s MAC Mesh – for both AP and STA .t MAC Testing and Performance Prediction .u MAC Interworking with External Networks .v MAC Network Management .w MAC Management Frame Security .y PHY Operation in the 3650-3700 MHz Band
ACK Frame A short frame sent by the receiving station to the transmitting station to confirm the receipt of the frame.
A-MPDU Aggregate MAC Protocol Data Unit
A-MSDU Aggregate MAC Service Data Unit
AP Access Point
ASEL Antenna Selection
Block ACK Block Acknowledgement - a method of sending a single Acknowledgement frame to confirm receipt of multiple frames
BSA Basic Service Area
BSS Basic Service Set
CODEC Coder/Decoder – an algorithm implemented either in software or hardware to encode the digitized voice, video or image for optimum transmission over the network.
CSD Cyclic Shift Diversity
CSD Cyclic Shift Diversity – type of Transmit diversity used to spread spatial streams across multiple antennas.
ESS Extended Service Set
FEC Forward Error Correction – a method to help with transmit diversity.
Frame Aggregation
A protocol for combining several frames into a single frame, thereby eliminates some inter-frame gaps to improve efficiency on the RF link.
GI Guard Interval – a period at the end of each OFDM symbol allocated to letting the signal dissipate prior to transmitting the next symbol to prevent overlap. Legacy devices 802.11 abg use 800ns.
HT High Throughput
HT-GF-STF High Throughput – Greenfield – Short Training Field
HT-LTF High Throughput – Long Training Field
HT-SFT High Throughput – Short Training Field
HT-SIG High Throughput – Signal Field
Interframe Space
Is the quiet time between packets transmitted on media
LDPC Low Density Parity Check
L-LTF Non-HT - Long Training Field
L-SIG Non-HT - Signal Field
L-STF Non-HT - Short Training Field
LTF Long Training Field
MCS Modulation Coding Scheme
MIMO Multiple Input, Multiple Output “My Moe”
MPDU MAC Protocol Data Unit
MRC Maximum Ratio Combining – a technique used by a receiver that is working with two or more diversity antennas to optimally combine signals received taking into account the SNR of each of the received signals.
MSDU MAC Service Data Unit
NAV Network Allocation Vector – An indicator used by STA and AP to know time periods when the wireless medium will not be available. NAV information can be derived from announcements in packets concerning how long they intend to occupy the medium.
Non-HT Non-High Throughput – legacy devices not capable of 802.11 n communications contained in the HT Information.
Non-HT Duplicate Mode
A method to protect legacy networks from disruption caused by 802.11 n protocols. Two packets are sent on both halves of the 40MHz channel simultaneously announcing the NAV to tell legacy STA how long to stay off the medium.
OFDM Orthogonal Frequency Division Multiplexing
PCO Phased Coexistence Operation
PSMP Power Save Multi-Poll
RFS Reduced Interframe Spacing
RSSI Receive Signal Strength Indicator
SGI Short Guard Interval – an optional use of 400ns GI in the 802.11 n specifications.
SISO Single Input, Single Output
SM Spatial Multiplexing
STA Station – Client device
STBC Space-Time Block Coding – Transmitter diversity technique of spreading the signal over multiple antennas to improve reception. STBC also incorporates Forward Error Correction (FEC) coding.
STBC/SM Space-Time Block Code/Spatial Multiplexing
TPC Transmit Power Control
TxBF Transmit Beamforming
WMM Wireless Multi-Media – the WiFi Alliance QoS Protocol for defining different priority levels for Voice, Video, Background and Best Effort Traffic. Based on 802.11e and incorporated in the updated 802.11/2007 edition.