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

QoS in LTE-Advanced

Most of the functionalities and specifications related to QoS and radio resource management deployed by LTE are supported by LTE-Advanced to guarantee backward compatibility, which is an essential requirement for the LTE-Advanced standardization. Specifically, QoS performance measures, classification, signaling bandwidth requests and grants are almost similar to LTE. Bandwidth allocation and traffic handling includes some enhancements required to support the new features included in LTE-Advanced to meet or exceed the IMT-Advanced requirements. In this section, we will discuss the major enhancements related to QoS and bandwidth reservation procedures.

Carrier Aggregation

LTE-Advanced provides support for a new feature called Carrier Aggregation, which entails aggregating two or more component carriers that are either contiguous or non-contiguous. The main objective of Carrier Aggregation is to provide larger bandwidth to meet the IMT-Advanced requirements of a spectrum up to 100 MHz.

Carrier Aggregation has an impact on both scheduling and HARQ. For HARQ, it is required in Carrier Aggregation, whether contiguous or non-contiguous, to have one independent HARQ entity per scheduled component carrier. Note that the maximum number of HARQ entities allowed by LTE-Advanced is eight entities for the FDD duplexing. For scheduling, and similar to Release 8, each UE may be simultaneously scheduled over multiple component carriers. However, at most one random access procedure ...