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

Scheduling in LTE and LTE-Advanced

Scheduling the Uplink

LTE uplink scheduler acts as part of the LTE radio resource management functionalities to utilize the available radio resources within the physical uplink shared channel (PUSCH) as efficiently as possible, while satisfying the QoS requirements for active users within the network. Due to the configuration of the radio interface employed in LTE uplink, the uplink scheduler performs user multiplexing in both, time and frequency domains to the available resource blocks (RBs) within 1 TTI. The LTE uplink scheduler designs that have been proposed in literature so far perform scheduling per TTI according to the following phases:

1. UE Selection: The first phase of the scheduling operation is to select a subset of the UEs that await transmission to be scheduled for a current TTI. The selection process occurs either by a round robin fashion, a proportional fair criteria, or based on QoS attributes (bit rate, delay, etc.), buffer size, or a combination of these attributes. In a QoS-aware LTE uplink scheduler, the QoS attributes of each scheduler plays an important role in the UE selection process. Since the scheduling process is engaged once every TTI with no consideration for how the bandwidth is to be distributed among the selected UEs, the UE selection can be associated with the Time Domain (TD) scheduling, and be separated from the frequency allocation.
2. UE-Frequency Multiplexing: Once the set of UEs to be scheduled are selected, ...