Equalization of packet delays in OFDMA scheduling of real-time video calls

This paper studies the scheduling of multiple real-time unicast videos (e.g. video calls) over the Orthogonal Frequency Division Multiple Access (OFDMA) air interface. Modified Largest Weighted Deadline First (M-LWDF) and Exponential Rule (EXP) were proposed to schedule traffic with quality-of-service constraints in shared-channel systems. Both have been proven to be throughput optimal and EXP also possesses delay optimality in a sense. This paper proposes several techniques that modify M-LWDF to further improve users´ 99% packet delays over M-LWDF and EXP. An interesting phenomenon of simultaneous reduction in latencies and bandwidth usages is demonstrated in various comparisons, which contradicts with the conventional observation that giving unequal weights to users sacrifices spectral efficiency. Our study shows that a better scheduling policy often improves both spectral efficiency and user latencies simultaneously in the scheduling of real-time traffic. Under the same user latency constraints, the proposed scheduler also improves the Peak-Signal-to-Noise-Ratio (PSNR) of received videos considerably under moderate system load.