Campus Best Practice (GN3+/NA3/T2) WLAN Network Planning

Transcription

1 Campus Best Practice (GN3+/NA3/T2) WLAN Network Planning Anders Nilsson, SUNET WLAN Network planning Sofia, 19 June 2014

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3 Agenda Background (how did we get here?) Wi-Fi standards (a/b/g/n/ac...) RF Basics (know your layer 1) Preparing for a site survey Cell planning (size matters) Practical issues in placing access points General guide lines Planning and verification tools (demo time) Further reading Q&A open discussion

4 Is this what you are experiencing at your university now?

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8 So how have WiFi evolved? A walk down memory lane..

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10 Note!! In theory n will reach 600Mbps with 4 spacial streams running on 5GHz but 450Mbps is the limit and for higher speeds go for ac

11 The IEEE standardization of n was a record long 6 year journey ac was much faster. ;)

12 802.11n? Yes, but what flavor? n? Yes but only on 2.4GHz

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15 802.11ac builds on ac and removes some of the limitations Note ac wave 2 MU-MIMO is not yet proven and reises a lot of question wether it will deliver a performance boost

16 Just because your brand new ac AP supports speeds above 1 Gb/s doesn t mean that all your devices will benefit from that.

17 Note in order for this to work you need to be able to use all your ac APs 80MHz mode which might not be possible in a HD environment.

18 New accesspoints should be at least n based, managed and operating on both 2.4 and 5 GHz band. Good features to look for are Transmit Beamforming and Bandselect (Bandstearing). Higher capacity means more room (Airtime) for clients and more throughput. The faster jour devices finish and can get off the air the more capacity is left to others. Now ac APs are coming out with just marginally higher price than n based

19 Comparing 2.4 and 5GHz

20 Effect of bonding 5GHz channels in ac In a real world campus deployment it s very unlikely the 160MHz (or even 80MHz) mode will be used. Note how we end up with the same issues as in 2.4GHz when bonding channels in 5GHz. ETSI is working on freeing up more channels for 5GHz.

21 2.4GHz is limited to only 3 non-overlapping channels (1-6-11) and is constantly filling up with other non-wi-fi devices competing for the spectrum. The future is 5GHz where you have a least 20 nonoverlapping channels (varies between countries). Also note that only 5GHz will get you 300Mbps (channel bonding) with n.

22 Interference: The usual suspects. 2.4GHz getting crowed Food for thoughts: Do rouge APs create interference and increase the channel utilization? (answer: YES! )

23 Always aim for the best fuel at the gas station. and in the future go ahead an fill your car with ac if possible.

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25 RF Basics (know your layer 1)

26 The dynamic nature of RF spectrum You are breathing the physical layer RF reflects off things RF is absorbed by things (walls, windows, furniture) It s a shared medium (as such, not all RF is always yours) Not all RF is traffic (especially true with 2.4GHz) In order to see what s really going on you might need more than a WiFi card. Things don t stay the same, the only constant in the RF spectrum is change.

27 And yes, other signals that the wifi chipset can t recognize (Bluetooth, Dect phones, Microwave Owens ) will be considered noise.

28 Cell size. Typical SNR versus speed values for 2.4GHz. Note how much more efficient g with ODFM is, you get 12Mbps versus 5.5Mbps with the same SNR

29 Basic antenna types

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31 Interference (problems and why MIMO might be your savior)

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34 An n accesspoint improves reception on older abg-client.

35 Interference mitigation Finding these evil polluters will need something better than an ordinary WiFi card. A higher resolution RF-spectrum analyzer device like Metageeks WiSpy ( ) are the right tools for this kind of job. Note that Ciscos latest APs with so called Clean Air capability include an spectrum analyzer chip. Most others are also doing spectrum analysis but in software. Even though the source of the interference is located you might end up having to keep the interferer. Removing Microwave Owens from the kitchen may be a problem. Depending on the type of interference you will end up with one or more channels ending up unusable.

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39 Preparing for a site survey

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41 Four basic types WLAN design focuses: What type of WLAN are you building? Coverage (as large area as possible) Where not capacity? ;) Capacity (density of user over a given area) High denisty ( requires carefull planning and special antennas) Location (the possibility to locate clients) Because the cell size dictates the capacity there s a tradeoff between Coverage and high Capacity. Location usually leads to even more APs required. Get rid of older legacy protocols? Disabling b will effectively almost double the capacity on 2.4GHz. WLAN NETWORK PLANNING Disable at least 1 & 2 Mbps and consider 5,5 or 11Mbps if b is left. What type of applications should run? Given the density of clients some demanding applications will not be possible without HD design (requires special antennas) Wireless Voice over IP (VoWLAN) demands certain attention (not covered in this presentation)

42 What type of clients do you have? Are you sitting with older client not supporting n. Make sure all newer clients support n on 5GHz also. Can we phase out old b ones? Also take into account that different clients have different RF-performace and hence you must find the Vorst client type and use that one as reference. (see next slide) How many SSIDs do we need? There should never be more than 4 SSIDs per AP even though the AP itself may support many more. (see separate Excel spreadsheet) u will hopefully solve this limitation in the future. What are the roaming requirements? WLAN NETWORK PLANNING Are we just building a single hotspot or do we need continuous coverage Do you have a monopoly on setting up APs? Finding yourself being the sole master is rare but if possible this definitly is an advantage. Investigate if you can divide up RF between you and others. Create a RF policy and get it signed.

43 WLAN NETWORK PLANNING Pracical maximum speeds for different types of clients

44 Not all devices have the same radio sensitivity Don t forget your tablets and smartphones

45 Perform an onsite site pre-survey Try to get hold of the good drawings of the building. But after that it s very important to visit the location in person to understand if the drawing is still current or if walls have moved or reinforced or something similar. Really ambitious people classify walls and the manually input that info to their Wlan planning software (Ekahau and Airmagnet leads the market). Anyway to know where thick walls and elevator shafts are and maybe also look for modern high insulating windows (can reduce the signal more than 12dB) is very important.

46 Spot check design Rather than setting up all the APs at once simply select an area of you building and set up 3-4 APs according to your design and then verify. If your calculations seems to be right you can continue. Another method is to bring up the APs one by one (time consuming) but my experience is that you need to have 3-4 APs running and than after Cisco RRM has done it s magic se what the result became. RRM = Radio Resource Management

47 Setting up APs Make sure you read the instructions so that the accesspoint can work with full performance. To put it short the AP needs breathing space and to be mounted in the way the company manufacturing it intend.

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49 The AP1130 was designed for the office environment. Easy mount on a 3m ceiling and propagate the signal down and wide.

50 Even though MIMO based n APs are bit more forgiving try to avoid these type of installations a much as possible.

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57 Verify coverage Here there are many schools on how to proceed I personally prefer to use the Aircheck from Fluke (2000 euro) NEWS!! There s now a Aircheck for windows costing 1/3. A free alternative is to combine inssider and iperf to both test the channel allocation and throughput. Don t forget to read through the document titled. gn3-na3-t4-wlan-network-planning which can be found at

58 My own view and recommendation on WLAN Stop using b clients and disable it on you WLAN All new n clients should support 5GHz If possible no more than 20 active associated clients per AP (40 if ac) If you have more than 3 APs at one location you really need a managed WLAN If possible a 20% overlap of the cells is something to aim for (for good seamless roaming) You should never have less than -65dBm signal strength in your coverage zone Closest AP on the same channel should be less than -80dBm RF utilization should never go above 65%. If it does you have an issue. Get RF-spectrum analysis tools for better understanding of what s going on in your environment. Remember to turn on Bandstearing and Transmit beamforming if possible Don t forget to update your clients drivers (especially true on Windows with n cards) Remember that different devices have different RF-performance allways design and veriyfy with the vorst device in mind.

59 My own view and recommendation on WLAN Always focus on the optimal placement of the AP. If needed stand your grounds against architects and the estetics police. ;) CCI (Co-Channel Interference) is your enemy, Patch and directional antannas are your friends, use as much as possible Don t forget your wired infrastructure. Gigabit uplinks will be ok even with ac AP 802.3at PoE switches for newer AP 15.4W may not be enough CAT 6 or better cabling The world is 3d. Avoid if possible the long corridor multiple floor syndronme. Spread out APs and/or use directional antennas. And finally always install managed WLAN infrastructure where some sort of controller mechanism (RRM) manages channel and transmit level settings. Designing good work WLAN installations is a craft and requires skills and experience.

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61 Yes!!! We made it.

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63 Further reading links : Discovering_WLAN_802.11n_MIMO.pdf (Great blog) (another great blog) Free access after registration, great mobile network presentations. If you only have time for one link I highly recommend this one even if you don t have Cisco equipment.

64 DEMO TIME!!!

65 Bonus slides

66 Professional site survey on a shoestring budget? Of all the software I found I believe Wavedeploy from Veriwave (bought just recently by IXIA). is the best. Unfortunately the free version has been discontinued and the expert version is Of course this product is a bit expensive but if you want a product where you can put your laptops and tablets on a trolley or just carry it around and marking on your map and end up with a god coverage map. This could be a shared resource between the universities.

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69 Per-User Application Throughput examples

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72 If you want really good capacity in your cubicle landscape you may have to install one AP every 9 th meter but typically my experience is meters depending on walls etc.

73 Large highly populated auditoriums need a different approach.

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76 Typical settings on a Cisco WLAN controller with b disabled. This will decrease the cell size and increase the performance.

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79 Viewing neighbor APs frequency and signal strength on WLC

80 RF-Interferers show up on WLC with ver 7 software and Clean Air APs

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83 Bad channel planning lead to co-channel interference Actual measurements from my hotel yesterday

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87 RF terms

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