e most suitable active carrier is used for transmitting the paging message. 11.5 3GPP LTE-ADVANCED MULTI-CARRIER OPERATION The 3GPP LTE-Advanced extends 3GPP LTE Rel-8 and 9 physical layer capabilities with the support of carrier aggregation, where two or more component carriers can be aggregated in order to support wider transmission bandwidths up to 100 MHz. It is possible to configure all component carriers which are required to be 3GPP LTE Rel-8 (backward) compatible when the number of component carriers in CHAPTER 11 Multi-Carrier Operation uplink and downlink are the same. Some of the component carriers may be non-backward compatible with 3GPP LTE Rel-8. A user terminal may simultaneously receive or transmit one or multiple component carriers depending on its capabilities. An LTE-Advanced terminal with reception and/or transmission capabilities for carrier aggregation can simultaneously receive and/or transmit on multiple component carriers. A 3GPP LTE user terminal can only receive and transmit on a single component carrier which is Rel-8 compatible. As shown in Figure 11-15, the spectrum aggregation scenarios can be generally classified into three categories: (1) intra-band contiguous; (2) intra-band non-contiguous; and (3) inter-band. Carrier aggregation is supported in both contiguous and non-contiguous scenarios with each component carrier limited to contain a maximum of 110 resource blocks in the frequency-domain, based on Rel-8 OFDMA/SC-FDMA numerology. It is possible to configure a UE to aggregate a different number of component carriers originating from the same eNB, and of possibly different bandwidths, in the downlink or uplink. Since OFDMA is utilized as the multiple access method in the downlink of 3GPP LTE, such carrier aggregation is a simple extension of the FFT sizes from the baseband perspective. In the uplink however, the 3GPP LTE Rel-8 single-carrier FDMA scheme does not allow such a simple extension of the bandwidth. Thus, a separate DFT module per component carrier is required prior to