Unified packet scheduling method considering delay requirement in forward link broadband wireless access

This paper proposes a unified packet scheduling method that considers the delay requirement of each traffic data packet whether real time (RT) or non-real time (NRT), the channel conditions of each accessing user, and the packet type in the hybrid automatic repeat request (ARQ), i.e., either initially transmitted packet or retransmitted packet, in the forward link for orthogonal frequency and code division multiplexing (OFCDM) wireless access. In the proposed packet scheduling method, the overall priority function is decided based on P_total = a_Delay · P_delay + a_Type · P_Type + a_SIR · P_SIR (P_Delay, P_Type, and P_SIR are the priority function derived from the delay requirement, type of packet, and the received SIR, respectively, and α_Delay, α_Type, and α_SIR are the corresponding weighting factors). We optimize the weighting factors of three criteria as α_Delay = 1, α_Type = 0.5, and α_SIR = 0.5 by computer simulation. Simulation results also elucidate that the outage probability for achieving the packet loss rate (PLR) below 10^-4 for NRT traffic users employing the proposed packet scheduling method can be reduced by more than two orders of magnitude compared to that using the priority queuing (PQ) method, while maintaining the PLR of RT traffic users at the same level as that using the PQ method. We also clarify that by employing the optimized parameters including the weighting factors, the total sector throughput using the proposed packet scheduling method is increased by approximately 13% compared to that with the proportional fairness method.