LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

Wideband Transmissions

Another area where the flexible spectrum allocation of OFDMA and SC-FDMA systems is exploited is enabling wideband transmission. As has been discussed in the previous chapter, IMT-Advanced networks should support wideband transmissions of as high as 40 MHz, while LTE-Advanced promised supporting even wider transmissions up to 100 MHz. Achieving this while being compatible with 3G networks could be achieved through the so called carrier aggregation. Carrier aggregation refers to the possibility of concatenating several basic (legacy) carrier components into a larger one that can be viewed and managed as a single band. It involves multiple carriers being combined at the PHY layer to provide the user with the necessary bandwidth. The utilization of guard band is possible for the actual data transmission, and utilizing basic (legacy) carrier components achieves backward compatibility with LTE [5].

Figure 2.5 Sector-based frequency reuse.

Figure 2.6 Carrier aggregation. (a) Contiguous carrier aggregation and (b) noncontiguous carrier aggregation.

Figure 2.6 illustrates the two possible scenarios for carrier aggregation; namely, contiguous and noncontiguous. The introduction of the latter has been to support carrier aggregation in situations when sufficient contiguous ...