Indoor Arena Design Survey – Part 1: The Bowl

This post should be used as a quick reference for anyone needing to do a design and site survey for an indoor arena. This was written for WLAN engineers that already have experience in designing and implementing WiFi.

This is part 1 of 3 for performing a design focused site survey on an arena. The three parts will be broken out into:

1. Bowl
2. Concourse
3. Back of house

I highly recommend reading throughChuck Lukaszewski's Validated Reference Designson Very High-Density networks. He goes into much deeper detail than I could ever hope to with this. This is hoping to provide the tools to gather the information you will need. Most of the information in here is meant to be used in conjunction with those documents to develop your design.

现在…。碗…

The bowl is the most important part in an arena design. The bowl is where the majority of clients connect and spend most of their time and it is the one area pretty much guaranteed to break a poorly designed network. Here is my process for a survey of the bowl:

1. 找出您的安装选项
2. 找出您的容量要求
3. 找到您的“陷阱”
4. 建立您的调查套件
5. Setup your survey kit
6. Survey and analyze
7. 计划您的覆盖范围

The order of the first three doesn't really matter as you do all of them at pretty much the same time on your first initial walk-through.

找出您的安装选项

你的首要任务是找出你可以行动ually mount your Access Points (APs). Arenas normally have a few different options that you can mount your APs and antennas on. Common mounting options are:

• A catwalk or rigging structure suspended in the middle
• 外墙和悬垂
• 在座位下
• 在混凝土下beneath the seats

Now, one of these is a great option, one is OK, and the other two are just a bad idea. Let's take them one by one.

走秀或索具

A catwalk or rigging structure suspended in the middle is by far your best option. This gives the clients direct line-of-sight (LoS) to the antennas of the AP. It also gives you a chance on achieving spatial reuse in the bowl (which is extremely hard to do and the smaller the bowl, the harder it is) and gives free space between the AP and clients.

***Side note: Spatial reuse and channel reuse are two different things. If you want a really good explanation on this, then google "Chuck Lukaszewski" and click on any one of his talks because I am pretty sure he mentions this in all of them. A quick explanation is "channel reuse" means you are reusing a channel – that's it. "Spatial reuse" means you are actually reusing the spectrum and allowing two APs on the same channel to tx and rx at the same time by limiting how much the AP and clients that it is serving can hear the other AP.***

Every indoor arena I have ever been to has had a catwalk. However, there are some that have even better options – like this lighting grid:

The lighting grid ends up being better than a catwalk because it increases the mounting area for your APs. This means you can have better AP spacing and mount in places that a catwalk would not normally allow.

As long as it's a suspended structure in the middle of the arena that allows you to aim the antennas towards the outer walls instead of the middle – it is a decent option.

外墙和悬垂

外墙和悬垂are a bad idea in an indoor arena. You eliminate any chances you might have had at spatial reuse, while also drastically raising your CCI (Co-Channel Interference). Also, you are forcing clients to transmit behind the user which means it is no longer LoS.

您会看到一些具有这种设计的室外体育场，几乎总是由于缺乏选择。

在座位下

在座位下是室内竞技场的一个可以选择。由于身体衰减，它确实可以使您的细胞尺寸降低，从而增加了空间重复使用的机会。但是，它确实有一些缺点。一个是，您的客户不再有LOS到天线，这会增加数据包的重试。它的价格也不可避免地更昂贵，因为您很可能必须钻探混凝土，运行导管，安装安全的外壳等。

This is normally the best option for outdoor arenas since you usually won't have a permanent structure in the middle to mount to.

在混凝土下

在混凝土下is a bad idea. Concrete introduces a much larger amount of attenuation in the 5 GHz band than in 2.4 GHz. This was a popular design 5+ years ago. However, after seeing how the RF behaves and the increasing urgency to get as many clients on the 5 GHz band as possible, it just doesn't work out. Even with maxing the power on your 5 GHz radios and turning the 2.4 GHz radios down, it's next to impossible to get any sort of decent band split. You are also now asking your clients to also transmit through people and concrete, increasing your packet retires.

找出您的容量要求

Once again, Chuck's guides are fantastic at explaining how to size your network. For the sake of the survey, we just need to find out the minimum amount of APs we need in the bowl. Now, this will depend on which vendor you are deploying and you need to know the maximum clients their radio can handle. As a rule, you don't want to have more than 150 clients per radio in the worst (or best…depending on how you choose to look at it) case scenario. So, if I had an arena with a maximum seating capacity of 9,000 people, I would need a minimum of 30 APs if I am deploying dual-radio APs (9,000/300=30). This would mean the network would still work, albeit limping, if every single person in the bowl was connected at the same time.

The reason for not overcompensating with APs is that there is a trade-off between AP capacity and CCI/ACI. Once you deploy over 24 APs in the bowl, each additional radio is potential CCI if you are unable to achieve your spatial reuse. So, I always try to deploy the minimum amount of APs that will still work if the max devices possible connected.

Now we know we need a minimum of 30 APs in the bowl.

找到你的“陷阱”

现在，是时候开始尝试寻找这个特定领域的普通事物了。这意味着要整个碗走。以下是一些“陷阱”的例子：

开放式会议 - 通常，每20-30一次都有一个狭窄的开口？在大厅和碗之间。这通常可以使大厅和碗中的RF之间进行良好的分离。有时，您会遇到竞技场，这些竞技场有他们的大厅或大厅的一部分。当试图使客户在碗中连接到​​APS时，这会引起挑战。

LOS障碍物 - 最好步行到碗的所有区域，因为您可能会发现它们与潜在的AP之间有障碍物的一些部分或行。一些例子…

Configurable seating – Be aware of what seating is permanent and what seating is configurable. I have been to some arenas that have 25+ seating configurations.

There are some that you can design plausible solutions for. However, there are some that simply will do more damage than good. If you can create a solution that doesn't degrade the system as a whole, then add it to the design. However, doing something like adding several APs and raising your CCI just to cover a single row isn't a good idea. If you can't design a solution that will benefit the overall system then note it as a potential problem area in the design.

建立您的调查套件

我通常在每个室内竞技场都有相同的过程。一旦找到一个可以在车行上安装的位置后，我便去了一家五金店并获得一些PVC。然后，我用Aruba IAP-224（即将为IAP-228）设置了一个“ T”，两个Diplexer（224具有双频段端口），ANT-5314，ANT-2314，RPSMA-M至NM和NM和NM至NM跳高，802.3AT POE喷油器，电源线和portable battery. I normally make it around 6? tall to make sure I have enough room to fasten it to the rails of the catwalk.

Now, this is another case of having to know your vendor. I use Aruba IAPs. There are a couple of things you have to do to configure the IAP as a survey AP. You have to configure it to function as a Standalone AP and configure the SSID to work without a wired uplink. I will make a separate blog post on this. Whatever type of AP you are using, make sure it is configured and tested prior to hanging it. The catwalk is not a fun place to troubleshoot an AP.

Setup your survey kit

Now that you have your survey kit built, it is time to hang it. To do this safely, it should be done with two people and during a time with no one on the arena floor. You lower the survey kit over the side where the antennas are ~2? below the catwalk and fasten it to the rails in at least two places. You also want some sort of secondary fall protection on it separate from the main mounts in case they fail. Also have the second person stay on the catwalk while you survey.

***Do not skimp on this part or take it lightly. Make sure it is 100% secure and everyone is alert while doing this. The catwalk is very high up and this equipment is heavy. If you are surveying and see someone walking below the mount, ask them to walk around.***

When you mount the antennas, make sure they are aimed at the middle of a large section. Also, make sure that section has sections on both sides.

当AP启动时，请确保您拥有静态分配的力量和频道。通常，除了一个5 GHz通道（64）和2.4 GHz通道（11）之外，我通常会删除所有通道。然后，我将TX功率设置为6 dBM（4 MW）。我很少最终在碗中部署了超过此功率水平的AP。

Survey

进行调查时，我调查了主要部分及其边界部分。我停下来保存每个部分的末尾。

Once you are finished with the survey, filter the results to show only the survey SSID. Then bring your cell size down to a -55 dBm cutoff. I recommend planning for -55 dBm cell sizes in the empty stadium because you can normally count on around 10 dBm of attenuation when the arena is full.

计划您的覆盖范围

现在我们有了单元的大小，我们可以计划覆盖范围。此步骤非常简单，您可以提取竞技场地图并创建一个与您的调查结果相同的覆盖范围匹配的单元格。然后复制，直到您将所有覆盖区域填满。

Make sure you account for scorer's/judge's tables and floor seats. Using the 9,000 seat arena example from earlier, I need a minimum of 30 APs. My coverage plan gives me a total of 44 to cover everything I need. If evenly distributed, then each AP will have roughly 200 clients if everyone in the bowl was connected at the same time.

Voila! Now we know what kind of APs and antennas we are using in the bowl, where we are mounting, and how many we need.

Stay tuned for Part 2: The Concourse

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