Bangalore: One kilogram. That's what it weighed, the bulky prototype used for a wireless phone call by a Motorola engineer in 1973. For the real milestone 10 years later, a 790-gram Motorola DynaTAC made the first call from a commercial mobile phone, in a Mercedes in 1983. That makes the mobile 30 years old, and not the 40 that's being reported.

Since then, it's been a long road to today's smart, slim, all-colour 100-gram personal digital companion. The mobile helped India leapfrog past wireline telephony, to a personal phone for every other citizen. It's altered social behaviour. It's caused revolutions.

Mobile subscriptions grew from zero in 1983 to 12 million in 1990, and then to 6 billion in 2011. The world bought 1.75 billion mobiles in 2012. Of the 1.8 billion expected to sell in 2013, about half could be smartphones.

So how's the mobile changed in 30 years? Yes, it's now small and light, and has gone from one-line mono display to colour to high-definition. The bigger deal is that it's moved from voice to mostly data: email, browsing, apps. And from phone to personal companion. Yet the mobile is far from perfect. There are two big issues.

The first is the battery: The only reason why James Bond's wrist-watch mobiles are impractical. Ten years ago, my Nokia 6310i would last seven days on a charge. My 2013 BlackBerry Z10 struggles to last a day.

The battery hasn't kept up with the increase in data and apps use. In the voice-only era, the phone's radio (the part that sends and receives signals) would be in use for two hours in 24. In today's data age, those radios work continuously, draining batteries.

The second is congestion. Mobiles use radio spectrum, a scarce resource. The more phones fight for that spectrum, the worse our experience is: Failed and dropped calls, breaking voices.

Read: 11 Iconic Cell Phones In History

But with over 6 billion subscriptions already there for its 7 billion people, will our planet keep up the explosive mobile-telephony growth of the past 30 years? Oh, yes!

Let's look at those subscriptions. A half-billion are in multi-SIM phones or multiple phones owned by the same person. Or in other devices such as iPads, or laptop dongles.