Article: Mobile Internet explained
There is a lot more than meets the eye in the two words "mobile Internet". The fact is that there are several levels of connectivity in mobile devices, and the level you have will decide what applications you can use, and what Internet services you can connect to. Generally speaking, there are 4 different levels, and the level of access you have depends on what your provider offers, which services you subscribed to, what your phone supports and how your phone is configured.
First, the most basic level would be being able to send SMS and MMS messages, and perhaps e-mails. Basically any cell phone today will be able to send and receive SMS messages, and if your cell phone has a camera you'll be able to do MMS. You may also be able to send e-mail messages, perhaps by sending a message to a specific SMS address called an e-mail gateway. These services are usually provided for free, with a per-use fee. With this limited access you won't be able to even start the built in browser, even less use a network application.
The second level would be the ability to browse WAP pages (text and image sites aimed at mobile devices) to connect to your provider and buy games and ringtones. Starting at this level, providers will start displaying the famous key words "mobile Internet" everywhere, with little details on what that means exactly. The most basic features of that key phrase would be to have a WAP browser, being able to connect to your provider's mobile portal, and that's about it. The key here is that providers want to sell you ringtones, games, wallpapers, screensavers, and everything they can possibly can. Of course if you were careful, you bought a device that allows you to upload your own files with a USB cable or bluetooth, so you don't need that crap. Unfortunatly, for many providers, "mobile Internet" stops there, unless you sell out cash. And even for this premium service of being able to buy more stuff from them, they will charge you an extra monthly fee, and you won't be able to access any real web page or use network applications.
The next level is where it starts being interesting. If you have access to the actual Internet, and not just the sub-set of WAP pages your provider decided, then you can browse any web site that has set a WAP portal. Even better, if your device is powerful enough, such as a smart phone, you can use a real mobile web browser to replace the built in WAP browser, such as mobile Internet Explorer or Opera. Even cell phones with Java support can use Java based browsers like Netfront or Opera Mini. This means you can also send and receive e-mail, and get any web based service that the Internet offers. Usually to have access to this kind of connectivity, you will need to pay a monthly fee, and you'll have a set download size limit that you need to be careful about. Be aware also that there can be limitations with this service, such as your provider blocking certain ports so that you can't use IM (instant messaging), chat or map programs, and also many will block streaming of audio and video content. This is where people may see that they are able to browse the web, but wonder why applications they download don't work, because they require a full Internet access, such as accessing a different port.
The last and best level of connectivity for a mobile device is really having full access to the Internet. This means not having to go through your provider's proxy server, not having any filtering applied and being able to use all protocols. This full access is what enables you to not only browse all web sites, but also use some popular programs such as Google Local for maps and directions, and Agile Messenger for IM. The level of access you have is dictated by your provider, and that's why there is more to ask than simply if your particular phone supports "mobile Internet".
Now that we definied the levels of access possible, let's see what can block you from having the prefered, full access. There are two components that come into play: your provider and your device. Your provider is the one that has the final word, and who decides what you can access. First of all you need what's called a data plan, which is something every provider will offer. There are usually several data plans offering different amounts of download sizes. The price will obviously vary a lot with the various sizes, but one important thing to note is some providers will offer unlimited plans, which may be a lot more cost effective for heavy users than having to pay extra for several MBytes of data, since some applications require a lot of bandwidth. Note that for prepaid it can vary: some providers will require that users subscribe to a data plan, while others will let all prepaid users have access to all their services, and only charge them on a download usage. Lastly, almost all providers will block all data access by default on new users, and you need to simply call in to have the data block removed. It's a way to prevent users from accidently using data services without knowing about the extra costs.
For the device itself, once you have your necessary access from your provider, you need to configure the phone to use it. There are 2 types of settings for network access on most phones: network permissions and access point configuration. A network permission is simply a setting you set for each application that say if it's allowed or not to use the network. It will usually ask you once you start the application, but if not you can change it by going into your application manager. This is one common cause of problems when an application refuses to connect when you know other applications are working, simply because the permission is denied. The access points configuration is a phone-wide setting that tell the phone which servers to use and can be more tricky to setup. This will usually come configured when you buy the phone from your provider. If it didn't, or if you bought the phone elsewhere, you need to call them up and ask for the settings and configure them yourself. Some modern phones will also accept special smart messages that your provider can send to configure your phone remotely. There's also often several access points configured in the phone, for different uses, and finding the right one to use is simply a matter of trying them. Lastly the names of those access points don't necessarily mean anything. For example, an access point called internet.com has no relation to the web address of the same name, since it uses a different naming scheme.
There's no real way to know what kind of access you have other than trying. Problems with network related issues is one of most common topic on forums, such as having an application being able to access the network and another not, or not being able to access some features or sending e-mails. Part of it is a configuration problem, part is providers doing some filtering, and part of it is a misunderstanding between being able to browse a WAP site not necessarily meaning that you will be able to run a full Internet application like Google Local.