HSUPA Scheduling

Scheduler at NodeB controls when and at what data rate the UE is allowed to transmit.

-High date rate ≈ High Power transmitted by Ues
-High Power ≈ Higher Interference (due to UL non
orthogonality)
Scheduler needs to manage the UL interference
-If Interference is too high, UL transmission may not received properly.
-If interference is too low, the full system capacity not exploited.

Since the scheduler and transmission buffer are not co-located, there is Request/Grant mechanism is defined. UE sends the Scheduling Request, indicating its buffer occupancy.

Scheduling Grant sent by the UEs to control the UE transmission activity. The Scheduling Grants control the maximum allowed E-DCH-to-pilot power ratio the terminal may use; a large grant means higher data rate but also contributes more to interference level in cell.

As the interference increases in the cell, it affects the neighbor cell also, so inter-cell interference needs to be controlled.

The scheduler has allowed a UE to transmit at a high data rate based on an acceptable intra-cell interference level, this may cause non-acceptable interference to the neighboring cell.

Therefore in soft handover, the serving cell has the main responsibility for the scheduling operation, but UE monitors scheduling information from all cells with which the UE is in soft handover.