Notice of RetractionAn improved admission control for HCCA in IEEE 802. 11 e WLANS

Notice of Retraction

After careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE´s Publication Principles.

We hereby retract the content of this paper. Reasonable effort should be made to remove all past references to this paper.

The presenting author of this paper has the option to appeal this decision by contacting TPII@ieee.org.

HCCA (hybrid coordination function controlled channel access) of IEEE802.11e provide QoS support and contention-free access for every QSTA (QoS station), while the reference admission control is somewhat inefficient due to adopting of the minimum physical rate which results in a low utilization of network resource when adapting modulation and coding is used and constructing on constant arrival rate which led to excess or lack of bandwidth by neglecting the characteristic of different service categories such as CBR (constant bit rate), VBR (variable bits rate) and so on and multiplexing gain for the same or different class. So the service categories in HCCA and the corresponding CBR and VBR time division multiplexing model describing the relation among the packet loss ratio, the request bandwidth, the length of queue and the serving rate is discussed at first. Bits allocation on subcarrier of OFDM adapting to channel characteristics by water-filling which maximize the utilization is suggested then. In order to make the admission control adapt to service class, the priority for different class is defined, furthermore the bandwidth allocation according to priority is proposed. Based on these, an improved flow-based and crossing-layer admission control is proposed, which consider the characteristic of different service and variable physical rate resulted by bits allocation simultaneously. Not only is the utilization of network resource increased, but also better guarantee of QoS by this algorithm. The numeric results- reveal that our proposal outperforms the reference algorithm.