Multi-carrier techniques

Increasing expectations of user experience and the need for providing increasing capacity have driven a continuous improvement in transmission efficiency. Improving efficiency alone cannot meet traffic and user demands and so operators typically acquire and deploy multiple carriers. It is advantageous to be able to allocate larger amounts of spectrum than 5 MHz to individual users. An attractive approach is to keep the concept of 5 MHz WCDMA carriers that can be accessed by all terminals but to enable new terminals to transmit and receive on multiple carriers simultaneously. This is the basis of dual-carrier and multi-carrier HSPA evolutions. The average amount of carriers scheduled to a user will usually be higher than one, and users will in effect experience larger bandwidth. From a network perspective, the freedom to schedule users on multiple carriers leads to significant trunking gains. This chapter outlines how multi-carrier support has evolved over several releases.