RF planning for high-densities of mobile devices and bandwidth-hungry mobile apps
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This document discusses integrating accurate capacity planning into WLAN design through an iterative methodology. It begins by covering network performance concepts like medium contention and defining WLAN capacity. It then presents the speaker's iterative design approach involving both RF and capacity planning. Finally, it provides a real-world example of applying this methodology to design a network for an advertising firm, and recaps the key points about measuring and optimizing WLAN capacity.
RF planning for high-densities of mobile devices and bandwidth-hungry mobile apps
- 1. Integrating Accurate Capacity Planning into WLAN Design Andrew von Nagy @revolutionwifi CWNE #84 CCIE #28298
- 2. Goal of this Presentation: To share my methodology for integrating capacity planning into WLAN design with the community ! What works for me might work for you! Agenda: ! 1. Network Performance Concepts 2. WLAN Design Methodology 3. Introduction to the Revolution Wi-Fi Capacity Planner Tool 4. Real-World Example
- 3. Network Performance Source: Martin Geddes
- 4. Link Speeds Reaching Limits Source: Martin Geddes
- 5. WLAN Capacity Single Client Multiple Client Coordinated APs All APs
- 6. Defining WLAN Capacity Net WLAN Capacity (-) (+) Spectral Inventory Spectral Efficiency Medium Contention RF Interference Goal: Increase spectral inventory and efficiency, decrease medium contention and RF interference
- 7. Medium Contention DFS Non-DFS 20 MHz 22 9 40 MHz 10 4 80 MHz 5 2 160 MHz 1-2* 0-1* United States Regulatory Domain * 80+80 MHz Channels 42 58 106 138 106 58 138 One cell ‘buffer’ before channel must be re-used 138 58 42 58 138 Co-channel Interference (CCI) •Typical WLAN (omni antennas, standard overlap for roaming) • Need ≥4 non-overlapping channels to effectively minimize co-channel interference at -85dBm 106
- 8. Medium Contention Airtime Demand within a Channel / Frequency
- 9. Airtime Utilization Where is the breaking point?
- 10. Airtime Utilization Airtime saturation varies by WMM Access Category 3% airtime demand per-client in this example Source: Comsis
- 11. Measuring Capacity Spatial Streams Channel Width Client Mix Signal Quality Protocol Version Frequency Bands Application Throughput Airtime Demand
- 12. Airtime Demand Y% airtime utilization (each) Z% airtime utilization (each) X Qty. X Qty. Total airtime utilization based on client mix Aggregate of individual client demands ! Dependent on application requirements, packet sizing & timing. (Remember that airtime saturation is dependent on WMM AC)
- 14. Iterative Approach RF Design Capacity Design Input AP / Radio Quantities; Revise RF Design to Provide Required Frequency Re-Use (e.g.Antennas, Power) 1.AP / Radio Quantities Required to Provide Coverage in All Areas 2. Channel Planning & Frequency Re-Use Revise Capacity Design if Frequency Re-Use Cannot be Obtained (e.g. per-device throughput, 5 GHz channel width, capacity distribution across bands vs. channel inventory) 1.AP / Radio Quantities Required for Capacity 2.Throughput Required for WAN / Backhaul
- 15. Hands-On
- 16. Real-World Example • Advertising Firm in Manhattan • Apple-centric computing environment • MacBook Air/Pro (3yr lifecycle) • BYOD (tablets, smartphones) • Some Windows (Finance Dept.) • Heavy graphics and media content • Open / Collaborative floorplan • Large Event Space (e.g.TED Events)
- 17. Floor Layout Open Office (~36k sq ft)! 350 Seats! 20 Conference Rooms! ! Graphic Designers! - 1 Apple Laptop ea.! - 1 BYOD ea.! ! Existing WLAN:! - 66% concurrent online! - 50% concurrent active Event Space (~15k sq ft)! 300 Seats (inside room)! 200 Seats (overflow area)! ! Large Events:! - 500 mobile devices! ! Internal Meetings:! - 300 laptops! Inflection! Point
- 18. Capacity Plans One for each unique use-case area (in this example 3)
- 19. Iteration between Capacity and RF Planning • Initial Capacity Plan - Select initial variables using informed idea of what you think can be achieved - Channel width, dual-band APs (no radios disabled) • RF planning - use capacity results as starting point - Can you fit the AP radios into the space without CCI? - Determine if adjustments are necessary (directional antennas, different channel widths, disable some 2.4 GHz radios, etc.) • Revise capacity plan, perform RF planning again (… iterate!)
- 20. 2.4 GHz RF Propagation
- 21. 5 GHz RF Propagation
- 22. 5 GHz AP Layout
- 23. 5 GHz CCI
- 24. 2.4 GHz AP Layout
- 25. 2.4 GHz CCI
- 26. Recap 1. Network performance is increasingly reliant on minimizing contention delay 2. Wi-Fi medium contention is dependent upon two causes: • Co-Channel Interference (CCI) • Airtime Demand (within a channel) 3. Airtime saturation occurs at different points based on WMM Access Category
- 27. Recap (cont.) 4. WLAN capacity is measured by airtime demand of clients within a channel 5. WLAN design should account for BOTH capacity and coverage • Don’t guess!!! • I recommend an iterative design approach 6. Revolution Wi-Fi Capacity Planner: http://www.revolutionwifi.net/capacity-planner