One of the things the original UMTS did not take into account were mechanisms to allow mobile devices to reduce their power consumption when they come to the conclusion that for the moment, physical connectivity to the network is no longer required. This has led to a significant reduction of battery autonomy with the rise of bursty applications such as push email. As a result, device manufacturers started to become creative with the 3GPP specs and used a mechanism referred to "Signaling Connection Release Indication" not quite as it was originally intended to cut the physical connection to the network. 3GPP then caught up and specified an enhancement of this procedure in 3GPP Release 8, which brings improvements for both mobile devices and networks over the initial non standardized solution.
So what are those enhancements and what are the benefits? I've discussed this topic at length over quite some time on this blog such as here, and I think that in combination with the Continuous Packet Connectivity features as described here, battery performance, network signaling and network capacity can be improved significantly today and in the future. As the topic is quite hotly discussed in the industry from various points of view, the GSM Association has set out to assemble a freely available technical white paper that contains a consolidated view of both network operators and manufacturers on the topic. In the 23 pages of the white paper that can be found on the GSMA website in the technical documents section, the technical background is explained in depth including the impact of other features and settings on mobile power consumption. An interesting read no matter whether you work on the mobile device side or the network side of things.
And a small disclaimer at the end: I was part of the team working on the paper and I am happy to recommend it as I in my opinion it contains a fair and balanced view in addition to all the technical details that can be found in it. Enjoy!