A packet scheduling scheme for audio-video transmission over error-prone IEEE 802.11e HCCA wireless LANs

This paper proposes a packet scheduling scheme for QoS support in audio-video transmission with IEEE 802.11e HCCA. In the proposed scheme, the access point (AP) basically allocates transmission opportunity (TXOP) for each station like the reference scheduler of the IEEE 802.11e standard, which is referred to as the TGe scheme in this paper. However, the AP with the proposed scheme can allocate additional TXOP in a service interval (SI) if the AP has received corrupted MAC protocol data units (MPDUs) in the previous SI. In addition, the proposed scheme calculates the number of MAC service data units (MSDUs) arrived in an SI, considering the inter-arrival time of audio samples and that of video frames, which are referred to as media units (MUs), at the application-layer. We then compare the proposed scheme with the TGe scheme in terms of application-level QoS in the case where stations transmit audio and video flows to the AP in a noisy environment. Numerical results show that the proposed scheme improves the average MU delay and media synchronization quality even if channel transmission error occurs to some extent. Since the proposed scheme uses the surplus bandwidth for MPDU retransmission, we also discuss the number of admitted stations in the scheme.