Unified Packet Scheduling Method Considering Delay Requirement in OFCDM Forward Link Broadband Wireless Access

Abstract

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 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 = α Delay . P Delay + α Type . P Type + α SINR . P SINR (P Delay , P Type , and P SINR are the priority functions derived from the delay requirement, type of packet, and the received signal-to-interference plus noise power ratio (SINR), respectively, and α Delay , α Type , and α SINR are the corresponding weighting factors). The computer simulation results show that the weighting factor of each priority function as α Type /α Delay = 0.6, α SINR /α Delay = 0.4 assuming the linear-type function in P Delay and a constant-type function in P Type is optimized. Furthermore, we show that the outage probability for achieving the packet loss rate (PLR) of less than 10 -3 for non-real time (NRT) traffic users employing the proposed packet scheduling method is reduced by approximately two orders of magnitude compared to that using the Priority Queuing (PQ) method while maintaining the PLR of real-time (RT) traffic users at the same level as that using the PQ method.