Making free internet-based call using your Android phone

It's not a secret that you can make free calls using your Android phone and Google Voice, even without a SIM card in your phone. This is NOT a step-by-step guide, but instead a general description of how it works. Warning: setting this up is not a trivial process. You will need to fill in all the details for yourself. Google (Yahoo/Bing/your search engine of choice) will be your best friend.

DISCLAIMER: The information provided below comes with no guarentee of any sorts. Absolutely nothing. I do not encourage, endorse, or recommend the actions suggested below. Do them at your own risk, and don't blame me even if your phone stops working, your house burned, you lose your boyfriend/girlfriend, your candidate of choise loses the election, or the doomsday comes.

What you need

Let's first go over what you need:

• Google Voice Callback app
  
• A Google Voice account
  
• Internet connection for setup as well as every time you make a call
  
• A VOIP account that works with the SIP protocol
  
• A real phone number (DID) that can transfer call to your SIP account
  
• A SIP app for Android
  

In details:

Google Voice Callback

Duh! Get it now on Android Market. If you like it, be sure to buy the donate version, beer and coffee money is always welcome :)

Google Voice account

Duh, again! Sign up for one at www.google.com/voice . Google Voice is currently US/Canada only, so you will need a valid US/Canada number to sign up and verify a new Google Voice account. However, once the account is set up, you can make free VOIP calls anywhere in the world.

Internet Connection

Yes, this is aboslutely necessary. Wifi is probably best, but many people have success story with 3G connection. 2G is likely too slow for making voice call. If you phone can't check the latest news or the current weather forecast, it can't make an internet call either.
WARNING: Using data plan to make voice call might violate the term of service of your cellular service provider. Check with your cellular provider before doing anything. Of course, making internet call using wifi should not get you into trouble.

SIP account

VOIP stands for voice-over-IP, and SIP is one popular protocol that allows VOIP calls. You will want a SIP account that comes with free incoming calls. It does not matter how much your SIP provider charges for outgoing calls. Some of the popular providers are Sipgate, Nimbuzz, CallCentric, etc.
For your SIP provider, you will need to know your username, password, server name, and your SIP address (in the form of xxxxxxxx@some-sip-provider.com). Do your homework to find out those information if you don't know them already.

DID number

Your SIP account (see above) will give you a SIP address, which is almost like a phone number. But for our purpose, you need a real phone number (DID) such that when you call that number, it will redirect your call to your SIP address. IPKall gives out DID number for free; Sipgate also gives you one for free when you sign-up for your SIP account; and you can always buy a DID number from your SIP provider. If your DID number does not come from your SIP provider, make sure that it is set up to connect to your SIP account. For example, your SIP address is 123456@sip-account.com, but you can't really call that number from your phone. Instead, you need to a DID number, let's say, 123-456-7890. When someone calls 123-456-7890, your DID number provider will "call" 123456@sip-account.com and transfer the call to your SIP account.

SIP app

If your phone runs Android 2.3 (aka Gingerbread) or above, you don't even need this. A SIP client is included in Android 2.3 or above; you can set it up in Settings -> Call Settings. If you don't have Android 2.3 or above, there are many options, among them CSipSimple, Fring, and Sipdroid.

What you need to do

Once you have the above ingredients ready, you need to do a few things.

• Set up the SIP app with your SIP account. You gotta figure this one out yourself. At the end, make sure that you test whether you can receive an incoming call to your SIP account.
  
• Add your DID number to your Google Voice. Nothing complicated there, although the last step of this involves answering an automatic call from Google with your DID number, which means you need to be able to answer a call with your SIP account.
  
• Set up Google Voice Callback. Should be fairly straightforward, just make sure that you pick your DID number as the callback number.
  
• That's all! Start up your SIP app, and as long as Google Voice Callback is not disabled, just make a call the usual way with the Dialer app. You will be connected for a free call once you pick up the incoming call from your Google Voice number with your SIP app.
  

Caveats

• Internet call quality depends on 4 things. 1) Your internet speed. 2G will give you horrible call quality, guarenteed. 2) Your SIP provider. 3) Your SIP app and the codecs it supports. 4) Google Voice itself. Note!! Google Voice Callback has no control over call quality. I've experienced excellent, crystal clear, and no-delay call quality, as well as shitty, you-can't-hear-anything call quality. Your mileage will vary.
  
  
• SIP protocol usually uses a specific port, so if you are using public internet connection, or your cell phone's data plan, the port used by SIP may be blocked intentionally. In that case, it's likely that you are out of luck and you can't enjoy free internet calls while using such internet connection.