1. Use iPhone 4 as a 3G mobile hotspot for WiFi only iPad
Turn your WiFi iPad into iPad 3G with iPhone 4
Note: The 'iPhone Wi-Fi hotspot' feature is for the iPhone 4 only
Apple iPad Wi-Fi + 3G is expensive than Wi-Fi iPad. But if you already have an iPhone 4, then you
can save extra $130 and access 3G network with WiFi iPad by using iPhone as a 3G mobile Wi-Fi
hotspot. If iPhone is using 3G connection, then you can turn on “WiFi Tethering” on iPhone and
share Internet connection on other mobile devices like laptops, iPad, PSP or any other Wi-Fi
enabled devices. If you want to turn on hotspot on iPhone, then here is the tutorial.
How to turn your iPhone into a 3G mobile hotspot
1. Upgrade your iPhone 4 to 4.3 IOS:
Just plug your iPhone 4 into PC and open iTunes, click the "check for an update" button. (If
your iPhone 4 is already higher than 4.3 IOS, ignore this step)
2. How to set up your iPhone WiFi hotspot
Go to the settings menu, In “settings”, you'll see a new “personal hotspot” menu item. Tap
it.

2. In the personal hotspot menu, slide the "personal hotspot" option to "on".
You'll note that Apple has allocated the connection a default password which is shown on this
screen too. You can either use it (as each iPhone 4 gets a different random password) or change it
to something you can more easily remember by tapping on it.
Then, on your iPad's Wi-Fi menu, you should see your iPhone pop up in the list after a few
seconds. The network name is the name of your iPhone in iTunes.
iPhone 4 + Personal Hotspot + Wi-Fi iPad: Possible, but with drawbacks
"Awesome! So this means if I have an iPhone 4, there's no reason to get an iPad with built-in
3G, right?" Well, no, that's not necessarily true. I can think of 3 things you lose if you go

3. Wi-Fi-only with your iPad and use your iPhone 4 as a hotspot.
1. Locked phone makes locked tablet
In most countries the iPhone is locked to whatever carrier you buy it from; the iPad has no
carrier locks whatsoever, and you can roam between carriers (or between countries) at a
whim.
2. Additional fee
Many people think that use the iPhone wifi hotspot + WiFi iPad saves money, the truth is that
in several countries (most notably the US) you'll pay an extra monthly fee to enable Personal
Hotspot on your iPhone 4. In the States this comes to $20 per month, which gives you an
extra 2 GB of monthly data, for a total of 4 GB per month on your iPhone's plan.
3. Longevity
When using your iPhone 4 as a 3G mobile hotspot, you can expect the iPhone 4's battery to
last for only about five hours before it needs to be charged. But the iPad 3G supports 9 hours
surfing over 3G.
Turn your WiFi iPad into iPad 3G with a 3G WiFi hotspot
Recently I read an article which is about “How to turn Wi-Fi iPad into an iPad 3G with a 3G
hotspot?” It mentioned a tool named E583C WiFi Hotspot (Here is an article about how to use
E583C for an PSP), and actually it’s a kind of 3G Router which can be used as a 3G mobile hotspot
by just inserting a 3G SIM Card and not other settings needed. It can share the network with at
least 5 WiFi enabled devices without additional fee or longevity problem, and it is a unlocked 3G
Router cost about 140 dollars.