scusses the radio resource management (RRM) functions in LTE. This chapter gives an overview of the LTE RAN (radio access network) archi- tecture, including an overview of the OFDM-based radio interface. The notion of radio resource in LTE is defined, and the requirements that the 3GPP has set on the spectral efficient use of radio resources are presented. Section 4.2 gives an overview of the multiantenna solutions in general and then discusses the different MIMO variants in the context of LTE, also addressing the required resource management functions used for the antenna port configuration control. Section 4.3 discusses the most important measurements in LTE, grouping them into UE and eNode B © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology measurements and, when appropriate, draws an analogy with well-known wide- band code division multiple access (WCDMA) measurements. Chapter 4 shows that a number of advanced RRM functions are needed in today's wireless systems; these are being developed and standardized in particu- lar for the 3GPP LTE networks, in order to fulfill the ever-increasing capacity demands by utilizing the radio interface more efficiently. Considering the facts that the available radio spectrum is a limited resource and the capacity of a single radio channel between the UE and the network is also limited by the well-known theo- retical bounds of Shannon, the remaining possibility to increase the capacity is to increase the number of such "independent" radio channels in addition to trying to approach the theoretical channel capacity limits on each of these individual chan- nels. Advanced radio resource management techniques play a key role in achieving these goals. This chapter presents methods and examples of how advanced RRM functions are realized in LTE and how these functions together make LTE a high- performance, competitive system for many years to come. Multiple input, multiple output techniques have been integrated as one of the key approach