QoS based scheduling in the downlink of multiuser wireless systems

With the new available frame aggregation technology in the 802.11n WLAN, the base station is able to transmit two or more data streams to different users in the system simultaneously. This fact enables us to design a more QoS aware scheduler from the MAC layer. In this paper, we first formulate the scheduling problem with frame aggregation into a knapsack problem that is shown NP hard. Then we propose a simple approximation algorithm (LUUF) based on the unit urgency concept. Our analysis shows that the complexity of LUUF is O(n log n) and it achieves an approximation ratio of F'/Fmax. We then show that in practice the complexity can be further reduced to O(n) and the approximation ratio can be made very near to 1, which make LUUF a promising candidate for wireless systems that support frame aggregation.

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