Google Voice has been around for many years. The previous versions had several limitations that have now been addressed in the latest version.
Google voice is a telephone service from Google that provides a unique telephone number in the area code that you select. Voice calls are free in the US and Canada. International calls are deeply discounted, the UK for example is 1 cent per minute.
Incoming calls to the number can be setup routed to any number telephones whether it is a landline or cell phone. Incoming calls then ring on all the phones that have been setup. As an example, you have 3 phones that you normally use; a landline at home, a personal AT&T cell phone, and a business Verizon phone. Setting up the Google number to forward calls to all three of these numbers result all three numbers ringing if someone calls your Google number. A very convenient feature, if you are frequently at different places... a single number rings your mobile phone if you are in the car, or your home phone if you are home or your office.
Many of the limitations on the service have historically been with the outgoing service but those are now addressed. Calls and text messages from your google number are initiated from the Google voice app on your cell phone and by default, uses the minutes of your cellular service provider, which is fine if you have unlimited minutes but a problem if you don't. It's also a drag if you are in an area with bad cell coverage
The latest version of the service now has the option to use WiFi or Cellular data (VoIP) when available with fallback to carrier minutes when you don't (if you added your mobile number as a linked number). This opens up the possibilities. With WiFi calling, roaming charges while travelling internationally are eliminated or reduced. It allows you to place calls from almost any device, such as the browser based voice application, not just phones.
Per Google's support website, one minute of talk time consumes about .2MB of data, with the caveat that the exact amount is dependent on the Service Provider's quality and speed. However, there are other factors in play, such as the codec that being used, short for encoder decoder -- used to convert an analog voice signal to a digitally encoded version. The following table provides a quick and conservative estimate of consumption:
Type Duration/Number Consumption Voice 1 min .67MB Voice 60 mins 40.2MB Text 1 text .01MB Text 100 texts 1MB
The reported consumption rates of a codec can be confusing. The G.729 codec for example is shown as 8kbps on some documents and 32kpbs in others. The reason for the discrepancy is whether theoretical limit of the codec, 8kbps in this example, is being quoted, or the bandwidth of the codec including upper layer protocol payload such as IP headers etc, in the packet. The following are a list of codecs and their rate of consumption in kilobits per second, including payload and other factors:
G.729 : 32Kbps G.711 : 87Kbps G.723.1 : 22 Kbps G.723.1 : 21Kbps G.726 : 55 Kbps G.726 : 47 Kbps G.728 : 32 Kbps