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Ben Wilson of Xirrus: Delivering WiFi For 10,000 Delegates

It’s time now for the second in the series of posts from our panel of industry experts discussing how to deliver brilliant WiFi services for 10,000 delegates at a conference/event.  (Do check the series introduction for the details).

Today’s industry expert is Ben Wilson, UK Country Manager for Xirrus, the leader in high performance WiFi equipment and services. (That’s Ben above).  He heads up the British operations for the company and kindly sent over these answers to my questions.

Right then, let’s get started! (My questions are in bold)

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What’s the best way of guaranteeing brilliant, seamless WiFi service at a PR launch for 100 users?

Ben Wilson: Very simple – Make sure that there are enough WiFi radios available on non-interfering channels to allow connectivity for that number of users – primarily use the 5GHz band as it offers far greater density to more available channels. Also make sure that the intelligence of the WiFi network (i.e. the data plane and processing power) is at the edge where the users are – just like in a switch. Many WiFi systems use a centralised controller with all of the intelligence at the centre of the network. This introduces a single point of failure and creates a bottleneck for the traffic. High Density, High Performance WiFi need in this type of environment needs multiple radio architecture with the intelligence at the edge of the network.  It’s very simple maths and physics. More Radios = more bandwidth. More bandwidth = more supported users.

Now, factor that up to 10,000 or 20,000 people at a huge exhibition?  What kind of technology is needed to support that?

Ben Wilson: Well consider how the Cell Phone industry conquered this. They had similar problems with needing to expand coverage and capacity form a system initially designed as an overlay to landlines. Once Mobile phones became prominent and they needed to ramp up the ability to connect more users, host more calls and deliver data services but only having a limited number of channels in the spectrum to play with, they moved to a multiple radio with directional antenna model. Just look at a modern mobile phone mast. Multiple radios using directional antennas to allow more non-interfering radios in the air to support more users. This is exactly what the WiFi industry has started to face for several years and the only people who solve this density issue is Xirrus with the WiFi Array. The unit contains 4, 8 12 or 16 radios combined with multiple directional antennas, a multi-gigabit switch with the intelligence at the edge of the network in each device. This is what allows us to deliver 1000’s of users simultaneously in conference facilities.

What kind of technical considerations are required when you’re dealing with multi-room or huge venues like Earls Court or big, big hotels that might need connectivity on multiple floors?

Ben Wilson: The big challenge to overcome with WiFi is the amount of available non-interfering channels. In 802.11bg (2.4GHZ) there are just 3. In 802.11a (5GHz) there are about 20 usable in the UK. Once a WiFi radio detects interference it shuts off, as WiFi (unlike wired networks) is a collision avoidance technology rather than collision detection. This means that interference immediately starts to halve the available bandwidth and double the latency. By using a directional antenna system it becomes a reality to be able to avoid interference and get more non-interfering radios in the air, allowing more users to connect.

Once you’ve managed to assign and log a user on to a WiFi network, what’s the best way to assure brilliant internet connectivity?  Is it just a matter of a big, big data pipe?  The bigger the better?

Ben Wilson: Let’s do the math – the bigger the data pipe, the more available bandwidth for the users. That simple.

Is there a functional limit for the amount of people that you can get connected to a single WiFi network?

BEN WILSON: If designed properly, and using the right equipment it is possible to scale to tens of thousands of users.  In theory, each radio can handle up to 64 users, though most would recommend around 20 power users per radio.  So it really becomes a matter of the number of people to determine the number of radios.  This again is where 5GHz comes into play – it offers 7X more channels of 2.4GHz.  More channels = more radios = more users supported.

Do you have any suggestions for a rule of thumb in terms of data consumption?  e.g. 1 user consumes 200mb WiFi internet data in a day, therefore 100 users would need 20gb bandwidth in total.  And what kind of backhaul pipe is needed for a decent service?  Does ‘fast broadband’ from the likes of BT cut it in this arena? Or should we be talking super-fast dedicated connectivity?

Ben Wilson: This is the wrong way to look at this. Total data over a day is irrelevant – it’s the amount of bandwidth per second per user is generally a good starting point as that is how your data pipe connectivity is measured. If you have 1000 concurrent users, stats and experience show that a max of 50% will be demanding bandwidth at any one time. Let’s say that for general email and internet use you decide to give them a solid 1mbps each. That’s 500 Mbps of bandwidth.  In most hotels and smaller conference centre, there are generally only about 50 users needing bandwidth at the same time, so dependent on the capacity and the venue depends on what kind of internet you need.

In reality, is it just too expensive to do this properly to serve, say, 5,000 or 10,000 delegates?

Ben Wilson: Quite simply – no. In the past with centralised architectures and lightweight AP’s then the cost of the cabling and the management and the ongoing interference problems and hassles made for an expensive layout for kit, installation and ongoing training and maintenance. With a fully distributed architecture and multiple directional antennas, with the intelligence at the edge, Xirrus requires 75% fewer cable runs, switch ports and devices to deliver this kind of solution. Selecting Xirrus makes this viable. Look at Microsoft – we served there roughly 3,000 concurrent users on just 12 devices with still plenty of head room – We could have had 2 to 3X more than that.

What are the main ‘gotchas’ that result in event organisers being harassed by frustrated users?

Ben Wilson: Poor design and implementation leading to lack of available bandwidth. Using products designed as an overlay rather than designed form the ground up for high density deployments and to replace wired switches a cause massive problems for users as they all try to log on.

Do you have any brief case studies or examples you could share where the technology has really worked?

We have several examples at http://www.xirrus.com/customerdeployments/hospitality.php
Microsoft Events: http://www.xirrus.com/customerdeployments/microsoftevents.php
Interop Las Vegas: http://www.xirrus.com/customerdeployments/interoplv09.php

What would your equipment/service shopping list look like to deliver WiFi to 500 or 10,000 delegates?

Ben Wilson: Let’s discuss what you want to do, how you want to perform, what devices you’ll be supporting, the existing RF environment and we can put something together. For a 500 user WiFi Network, you’re looking at around the 10k GBP mark.

Take a gaze into the future: What should we be looking for in the future to deliver this kind of connectivity?

Ben Wilson: No need to look at the future. As Microsoft and Interop prove, we can do this right now.

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Ben, that’s fantastic, thank you for taking the time to answer.  They will be really useful to many of the readers.

If you’d like to talk to Ben and his team at Xirrus, drop them a note — you can find all the details at http://www.xirrus.com/uk/.

By Ewan

Ewan is Founder and Editor of Mobile Industry Review. He writes about a wide variety of industry issues and is usually active on Twitter most days. You can read more about him or reach him with these details.

3 replies on “Ben Wilson of Xirrus: Delivering WiFi For 10,000 Delegates”

“primarily use the 5GHz band as it offers far greater density to more available channels”

I've just checked my six-month-old phone, and six-month-old laptop and neither support 5Ghz. If Ewan were organising a conference *today* then what proportion of delegates equipment do you think would have 5Ghz support?

[…] Néanmoins, et comme nous l’a démontré à plusieurs reprises l’organisateur du Mobile World Congress de Barcelone, c’est possible. J’invite d’ailleurs les anglophones à lire l’ excellent article publié par notre confrère de Mobile Industry Review sur l’enjeu crucial que cela représente  : Delivering WiFi For 10,000 Delegates […]

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