Multi-User Scheduling and Interference Coordination
The eNodeB in an LTE system is responsible, among other functions, for managing resource scheduling for both uplink and downlink channels. The ultimate aim of this function is typically to fulfil the expectations of as many users of the system as possible, taking into account the Quality of Service (QoS) requirements of their respective applications.
A typical single-cell cellular radio system is shown in Figure 12.1, comprising K User Equipments (UEs) communicating with one eNodeB over a fixed total bandwidth B. In the uplink, each UE has several data queues corresponding to different uplink logical channel groups, each with different delay and rate constraints. In the same way, in the downlink the eNodeB may maintain several buffers per UE containing dedicated data traffic, in addition to queues for broadcast services. The different traffic queues in the eNodeB would typically have different QoS constraints. We further assume for the purposes of this analysis that only one user is allocated a particular Resource Block (RB) in any subframe, although in practice multi-user MIMO schemes may result in more than one UE per RB, as discussed in Sections 11.2.3 and 16.6.2 for the downlink and uplink respectively.