  IEEE 802.11e standard defines two Medium Access Control (MAC) functions to
support Quality of Service (QoS) for wireless local area networks: Enhanced
Distributed Channel Access (EDCA) and HCF Controlled Channel Access (HCCA).
EDCA provides fair prioritized QoS support while HCCA guarantees parameterized
QoS for the traffics with rigid QoS requirements. The latter shows higher QoS
provisioning with Constant Bit Rate (CBR) traffics. However, it does not
efficiently cope with the fluctuation of the Variable Bit Rate (VBR) video
streams since its reference scheduler generates a schedule based on the mean
characteristics of the traffic. Scheduling based on theses characteristics is
not always accurate as these tra_cs show high irregularity over the time. In
this paper, we propose an enhancement on the HCCA polling mechanism to address
the problem of scheduling pre-recorded VBR video streams. Our approach enhances
the polling mechanism by feed-backing the arrival time of the subsequent video
frame of the uplink traffic obtained through cross-layering approach.
Simulation experiments have been conducted on several publicly available video
traces in order to show the efficiency of our mechanism. The simulation results
reveal the efficiency of the proposed mechanism in providing less delay and
high throughput with conserving medium channel through minimizing the number of
Null-Frames caused by wasted polls
