Cell phones have come a long way since they were first introduced. Remember when they were similar in size and weight to a mason's brick? I remember when you had to plug them into your car's cigarette lighter to get the juice to make a call. They were big (maybe 10 -12 inches long weighing a pound or more), bulky and expensive. Now, they have dimensions of a couple inches and weight in the ounces range. The prices are also dramatically less, especially if you get one on sale.
The newest models offer a camera, recording capability, Internet access, and even music. They also work hands-free with voice commands and with Bluetooth wireless connectivity. All these new features and functions cost, and not just money. They cost power and that means your phone needs to be close to a wall-wart charging unit. Of course, you and I don't want that, we want longer battery life even if we have all these goodies. You can be sure that the industry players in the cell phone market know this and are hard at work developing new techniques to keep power consumption to a minimum.
One of the places that I like to look for the hot research topics is in the sea of knowledge we call our universities. Recently I came upon some research from Georgia Institute of Technology and Professor Gabriel Rincon-Mora's students. They are researching energy-efficient, linear RF power amplifiers and ways to improve the power management of a WCDMA RF power amp by adjusting the supply voltage and current as a function of the transmitted power. And, they are doing it in standard CMOS. If you want to read more about this research take a look at: Georgia Tech research
I'm always looking for more links to university papers that deal with power management, so please drop me a line at firstname.lastname@example.org if you find any you want to share.