Integrating Accurate Capacity Planning into WLAN Design. Andrew von CWNE #84 CCIE #28298

Transcription

1 Integrating Accurate Capacity Planning into WLAN Design Andrew von 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 All APs Single Client Multiple Client Coordinated APs

6 Defining WLAN Capacity Net WLAN Capacity (-) (+) Medium Contention RF Interference Spectral Inventory Spectral Efficiency Goal: Increase spectral inventory and efficiency, decrease medium contention and RF interference

7 Medium Contention 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 DFS Non-DFS MHz MHz MHz MHz 1-2* 0-1* United States Regulatory Domain! * MHz Channels One cell buffer before! channel must be re-used

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 Airtime Demand Client Mix Application! Throughput Channel! Width Frequency! Bands Spatial! Streams Protocol! Version Signal! Quality

12 Airtime Demand Aggregate of individual client demands Dependent on application requirements, packet sizing & timing. (Remember that airtime saturation is dependent on WMM AC)! Y% airtime utilization (each) Z% airtime utilization (each) X Qty. X Qty. Total airtime utilization based on client mix

13 Design Methodology

14 Iterative Approach Capacity! Design RF! Design Input AP / Radio Quantities;! Revise RF Design to Provide Required! Frequency Re-Use (e.g. Antennas, Power) 1. AP / Radio Quantities Required for Capacity! 1. AP / Radio Quantities Required to! 2. Throughput Required for WAN / Backhaul 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)

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 Inflection! Point Open Office (~36k sq ft)! 350 Seats! 20 Conference Rooms!! Graphic Designers! Event Space (~15k sq ft)! 300 Seats (inside room)! Apple Laptop ea.! 1 BYOD ea.! 200 Seats (overflow area)!! Large Events:! mobile devices!!! Existing WLAN:! % concurrent online! 50% concurrent active Internal Meetings:! laptops!

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:

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