If you have ever been confused about why your smart phone seems to work sometimes but not others, or some features seem to work but not others; you are not alone. Modern smart phones have more than just one communications mode; but could have as many as eight. For the purposes of this explanation I am going to call each receiver/transmitter/transceiver system in your phone a ‘radio,’ even though some have circuits in common and are not technically separate components.
All cell phones, of course, have a cellular radio for voice communications. Some of these are multi-band, meaning the phone can operate on digital frequencies or on older analog bands. This might be helpful in some countries that still use analog. Quad-band phones have four cellular radios.
Smartphones also have Wi-Fi capability to connect to the internet. There are two wireless frequency bands, 2.4 and 5.0 Gigahertz, and many modern phones have both. That can add two more radios to your phone.
For connecting to nearby peripherals such as headphones, there is the short-range radio technology known as Bluetooth. This has a range of only a few meters, but it is still a radio transmitter, so now we have up to seven radios.
Then too there is GPS (Global Positioning System). Smartphones only receive GPS signals and do not broadcast, but I am still going to count that as radio number eight.
With one little hand-held smartphone communicating with as many as eight different radios, is it no wonder they are so easily confused? Sometimes, when something is not working, it is hard to know which of the radios it might be.
Specifically, your voice calls do not use the cellular radio exclusively. Some cell phone providers support ‘Wi-Fi Calling,’ so that when a cell phone signal is weak or unavailable, but good Wi-Fi is, your phone might be able to switch to connecting your conversation via the internet radio rather than the normal cellular radio.
Similarly, when accessing the internet for web browsing or email, the phone will normally use one of the internet radios; but if there is no Wi-Fi available and cellular data is available, your phone can switch to using that instead. Be careful not to run up a large cell phone bill doing this.
The GPS radio receiver is used for location services and normally relies on receiving coordinates beamed down from the network of satellites orbiting the earth. Your phone cannot always receive those signals, so some phones have implemented a clever alternative that uses the Wi-Fi radios and/or the cellular radios, albeit with far less accuracy.
As you can see, your smartphone has several different communications systems. Understanding which is which is not always self-evident, so I hope the information above is some help.
Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981 and now practically a full-time resident. He may be contacted at 044 415 101 8528 or email FAQ8 (at) SMAguru.com.