Performance of Downlink Schedulers with Superposed or Orthogonal Transmissions

This work looks into the extension of the proportional fair (PF) scheduler to the multi-user case, where the source is transmitting several messages under the superposition coding (SC) strategy in a Gaussian Broadcast channel. Jointly with the weighted sum-rate (WSR) scheduling criterion, we derive guidelines for 2-user pairing, based both on SNR and user priority. We compare superposition coding access with frequency division multiple access, while time division is obtained naturally as a result of the user pairing. Results elucidate that the 2-user SC PF always improves the single-user PF in terms of average throughput and delay reduction, and we compare its performance with the 3-user SC PF. Finally, the WSR shows throughput gains similar to the 2-user SC PF for certain configuration of the scheduler.