Do I need dual band?

You are correct,the 5 GHz band is horrible for distance and walls. You are much better off sticking with 2.4 GHz.

You can set the SSID just like a router. Just set the ssid on the 5g one to something you recognize. Some phones do this by default.

One caveat hotspot is not even close to standard on phones. Many have the basic ability as part of the OS but the provider may disable it. ATT for example if you have less than a 5m/month data plan they prevent tethering which includes turning on the hotspot feature.

There are a ton of hotspot apps for all models of phones if you do not like the ones that come as basic.

As to the phones themselves supporting 5g that you will need to look up. It mostly depends how new the phone is. The newest ones support even 802.11ac on the 5g band.

iPhone 5S will only give a hotspot on 2.4Ghz.

b and g are not supporting 5GHz
a, ac and n can do 5GHz

http://en.wikipedia.org/wiki/IEEE_802.11

there is some confusion in the name "dual-band".

It can stand for the data rate and for the frequency.
In your case dual-band is 2.4GHz and 5GHz. Some hotspots and clients can use both at a time, some only one or the other (like the iphone 5s).

but also it could mean 11Mbit and 54Mbit compatible, always the slowest client is dictating, which data rate (a, b, g, n, ac) is activated.

For you it´s important to know, the n standard has optional 5GHz, so manufactorers of these devices could choose, whether they support it or not, look into the data sheet of these devices.
The ac standard is designed for 5GHz, supporting 2.4GHz too.
dual-band means here, sending and receiving over the 2.4GHz and the 5GHz at the same time.


some more input:
http://en.wikipedia.org/wiki/Wi-Fi

Dual band is referring to wireless N. The 'dual' means it can use both 2.4GHz and 5GHz.

Many older devices can only use b/g, less old can use N 2.4GHz, and newer ones can use N 5GHz. A and AC are the devices that can use the wider bandwidth part of the 5GHz band, above 300mbps.

When you see routers advertised as 'dual band' but no mention of AC, they have 300mbps bandwidth on 2.4 and 5GHz. AC routers expand the 5Ghz to 450, 600, 750, and up. Some are at 3200 now! BUT most devices don't use the AC capability yet. Some adapters can, but that's going to be listed in their specs.

For example: iPhone 5S can use 2.4 and 5GHz wireless bands, but their hotspot function only gives the 2.4GHz band. Most newer phones can do the same. I don't know if any smartphones can provide a 5GHz hotspot as of yet.

So back to your original question, you should probably get dual band routers/access points, but don't kill yourself getting the bleeding edge. Plenty of Dual band/AC routers out there that give 600+ mbps that won't break the bank.

Generally the clue will be that the device supports "a" but almost all use the term dual band in the spec. You could get 5g only devices years ago but nobody really makes those anymore. So you can pretty much safely assume on any device that is fairly new that say it supports "a" it is a dual band device. For a phone I doubt they ever made ones that only support 5g. They are either 2.4g only or they are dual band.

You should be able to google the network adapters to find their exact specs.

AC routers aren't that much than plain dual band.

I think it's worth the investment to get some 'middle of the road' AC routers now.

To a point you are asking the wrong questions. Most commercial installations the most important feature is the manageability. You don't want to have to climb up and unmount devices to change configurations all the time.

The best...(almost unaffordable) systems have the ability to monitor the loads on the AP and dynamically change the radio transmission powers and other variable to try to keep the users balanced.

The best system that I have seen for smaller installs is made by ubiquiti. They give away the controller software. It is not as advanced as the cisco,aviya,HP etc but it doesn't cost $30,000 for the controller either. The AP are slightly higher than cheap netgear or linksys ones but they also have more features used in commercial installs. Some fancy AP from cisco that contain multiple 2.4g and 5g radios, in effect 3-4 AP in a single box, but cost well over $1000.

The key in a commercial install is not really so much the speed although that is important also. A wireless AP can really only handle a certain number of "active" users. What "active" means is a subject of much debate but in general you do not want more than say 10 device actually using the AP. So in a classroom if you had 30 students you would likely need 2 AP to really do the job right....but that assumes they are doing classwork type stuff not streaming video or something intensive.

The problem is there really is only so much radio bandwidth.

If we look at the 2.4g band there is only 60mhz total. This means you can really only put 3 AP in one area without them interfering using 20mhz channels. The catch here is all the fancy 802.11n router that claim 300m or 450m or what ever are assuming you are using 40mhz channels. So if you want to use 40mhz channels to get this you now can only have 1 AP that runs at that speed in any area. It is a trade off do you get lots of people using small connection for more total though put or a few users who can get the maximum speeds.

802.11ac is actually a worse offender in this area. There is much more radio bandwidth on the 5g band so you can put lots of 20mhz wide AP on it with no interference. I think it is 180mhz total but it depends on the country also. 802.11ac want to use 80mhz....this is why it can not run on 2.4g it won't fit in the 60mhz available there. So now 2 802.11ac devices can totally use all the bandwidth on 5g. Some of the newest devices coming out can actually use 160mhz so 1 device can hog all the bandwidth.

I would not worry about the top speeds on these devices other factors like the number of AP you will be required to use will make it so you can not use these options anyway.

Design of wireless system in a multi user building is a extremely complex subject. There are people who make this their whole career. There are many article on this subject.

In your case I suspect the hardest issue is going to be how many users you have in each area, how much bandwidth you see each users needing, and what type of end equipment mix you envision...ie how many 2.4g and 5g. Once you have a idea on this you can then decide which equipment is best.

You want to use different channels but what better AP can do is turn down the output power. Since you only want to talk to user close to the AP less power is actually a benefit. Combined with using different channels you can get more total AP in the same area. If a AP has multiple radios in the same band they are suppose to be used on different channels. It is purely done so you do not have to put 2 physical boxes at the same location. Those type of devices are used where you have extremely dense user concentrations. Lecture halls tend to be a example.

The really tricky part is finding a way to balance the users. This is where the high end commercial systems have the advantage. They will see too many users on a AP and start to decrease the power so other AP in the area will appear better to new users to connect to. You can do this manually also with the ubiquiti software.

Still the ubiquiti software they give for free is very powerful.

http://www.ubnt.com/unifi/unifi-ap/

These are the units that I helped someone install. I did not notice before that their non pro line was not actually PoE. I REALLY hate vendors that call things PoE that are not 802.3af. Power injectors just tend to be a pain because it is a extra thing you must deal with. It is so nice to get the PoE from a switch. I suspect even the switches Ubiquity make only supply power to standard 802.3af devices.

You can find Wireless planning and layout wiki things. They discuss the issues of overlapping AP and channel and power selection. It is hard to say were to really start this is a huge topic, it was much easier for me since I started you never even though every person would have a PC and and a phone and maybe a tablet all wireless. I know the last lan guy they hired they sent to a week long class just on wireless.