Inside A Mobile Device

Mobile phones are categorized by their capabilities. The initial ones provided just voice communication capabilities along with very limited data communication (SMS) capabilities. Mobile phones obviously use wireless radio frequency to enable any communication. The ubiquitous availability of such radio channels combined with the ability of technology to pack more data within those channels have always limited the data communication capabilities of cellphones till date. Fortunately, these two resources continue to evolve.

The difference between a desktop phone and the mobile phone is the simple fact that the mobile phone has a small computer built inside. This is required because cellphones need to be lot more intelligent compared to their tethered desktop counterparts.

The cellphone always communicates with the nearest radio tower unlike the desktop ones whose co-ordinates remain fixed and always have a permanent physical connection to the nearest telephone exchange (or the switch). The mobile phone first needs to communicate your phone number to the currently connected radio tower so that calls to you can be correctly routed to that tower by the network. Also when you make a call from anywhere, the nearest tower can correctly identify who you are, determine what services are to be provided to you as per your subscription, identify you correctly to the called party and charge you correctly for the services provided. In addition, as a user moves from the range of one radio tower to another, the mobile phone needs to recognize this transition and switch radio towers seamlessly without interrupting an ongoing call.  The cellphone therefore runs some complex communication protocols on its inbuilt computer when any communication is in progress.

However, the mobile phone computer is very different from the normal ones we see. The display has a small form factor and the exploratory creativity of the human mind initially just replicated the limited functionality desktop phone keypad as the keyboard on the cellphone. Being mobile, the power source to run the computer is its inbuilt battery. A computer means it has memory which is a power guzzler. The CPU also guzzles power whenever it does serious computing work. The radio transceiver consumes energy from the battery. The display consumes power. So does the audio circuit that drives the speaker and microphone for the voice call. It is evident that the stamina of the inbuilt battery determines the duration and intensity of computations that a cellphone can perform over and above the voice calls it supports. Now we understand why the initial cellphones looked and weighed like a brick.

Fortunately for us, human ingenuity and our insatiable desire to do things faster, better and cheaper eventually resulted in more powerful CPU, humongous amount of memory, and highly functional full color displays to be packed into a cellphone. This evolution is amazingly still in progress. As time travels, we see increasingly functional cellular phones at reducing prices. In parallel the cellular network is evolving to transfer increasing volumes of data at higher transfer speeds to and from your phone. Yet one needs to charge one's cellphone each night.