I agree with the previous answer. It is a daunting task to provide reliable wireless Internet access for 6000+ users.
For the past 5 years, I have worked for a company that is specialized in WiFi coverage for schools (some of them with over 1000 users). Big headache.
Firs of all you will need to define what type of service you would like to provide. For example browsing the web is not as demanding as watching Youtube.
Let's asume you want to give a good quality of service for each user while browsing webpages. This will set you at a data rate of 500Kbps per user. This number comes from ITU-T's recommendation for maximum time of non-realtime content load for a good MOS score (10 seconds). For example for a 480p youtube video this means = 1.5Mbps.
Also you need to consider the simultaneity coefficient of concurrent clients trying to access webpages. In a study me and my team conducted on over 10 facilities this proved to be close to 40%. This means that you could consider the simultaneous bandwidth you would need would be 0.4*500Kbps*6000 = 1.2Gbps. That is a big pipe!!
If you can afford to get such bandwidth from your ISP then your next concern is what type of WiFi will my users have (802.11n, b, g or, if you are lucky, 802.11ac). Let's assume you will have mostly new cellphones (802.11n dual-band and above), then you will have a total throughput per cell (per 802.11 5GHz radio, do not even try to turn 2.4GHz on) of 120Mbps (for 30 clients). Due to moderate interference this capacity will drop about 40%. These numbers come from a guide of high density WLAN network design by Cisco and from empirical data me and my team collected on real world cases.
So that leaves you, due to your capacity need of 1.2Gbps, with a need for 17 Access points, that need to be configured properly in order to get the least interference from adjacent cells (for an open environment this means almost every AP in sight). This config should:
- Be centrally administered
- Tx power auto-adjust for minimum cell size.
- Force station roaming, no sticky clients please!!
- Forbid slow clients (minimum PHY data-rate of 24Mbps).
- Configure MIMO technology for maximum cell isolation.
You also need to buy the correct AP for this type of scenario. Brands that have WiFi stadium coverage should suffice. Such brands are, among others:
- Ruckus Wireless
- Extreme Networks
To sum up, these brands cover stadiums with over 20000 people watching videos at half-time, so it is possible to cover 6000 on an open space. You just need to have the proper configuration and RF planning in order to squeeze the last drop of spectrum from 802.11.
Hope this helps!!