From GSM to LTE-Advanced: An Introduction to Mobile Networks and Mobile Broadband, Revised Second Edition

3.12 Radio and Core Network Enhancements: CPC and One Tunnel

While the evolution of wireless networks was mainly focused on increasing datarates for quite some time, other factors such as reducing power consumption and increasing efficiency of the core network architecture are also very important to keep the overall system viable. Starting with 3GPP Release 7, a number of enhancements were specified in that direction, CPC and One Tunnel.

CPC is a package of features to improve the handling of mobile subscribers while they have a packet connection established, that is, while they have an IP address assigned. Taken together, they have the following benefits:

• Reduction of power consumption;
• Reduction of the number of state changes;
• Minimization of delays between state changes;
• Reduction of signaling overhead;
• An increase in the number of mobile devices per cell that can be served simultaneously.

CPC does not introduce new revolutionary features. Instead, already existing features are modified to achieve the desired results. 3GPP TR 25.903 [22] gives an overview of the proposed changes and the following descriptions refer to the chapters in the document that have been selected for implementation.

3.12.1 A New Uplink Control Channel Slot Format

While a connection is established between the network and a mobile device, several channels are used simultaneously. This is because it is not only user data which is being sent but also control information to keep the link established, ...