Summary: Instability of the Proportional Fair Scheduling Algorithm for HDR
Matthew Andrews #
August 28, 2002
In this paper we study the Proportional Fair scheduler that has been proposed for
scheduling in the High Data Rate (HDR) wireless data system [4, 6]. We consider a
single basestation transmitting to a set of mobile users. In each time slot the scheduler
has to decide on a mobile to which it will transmit data. The decision is based on
information that the basestation receives about the timevarying channels between
itself and the mobiles.
We focus on deciding whether or not Proportional Fair is stable in a situation with
finite queues and a data arrival process. That is, we wish to decide if Proportional Fair
keeps all queues bounded whenever this is feasible.
There are in fact multiple versions of Proportional Fair, depending on how it treats
small queues. In this paper we consider six di#erent versions and show that all are
unstable for one simple example.
Index terms: Wireless scheduling. Proportional Fair. HDR. Instability.
We consider the Proportional Fair scheduling algorithm for the downlink of a High Data
Rate (HDR) wireless system [4, 6]. We assume a single basestation transmitting to a set of