Energy efficiency and quality of service optimization for constant bit rate real-time applications in 802.11 networks

Abstract

In this paper, we propose a quality of service (QoS)-sensitive energy efficiency optimization mechanism for 802.11 networks on the basis of the dynamic and simultaneous adjustment of the content window (W ) and retry attempts limit (r) of the media access control (MAC) sublayer. The use of both operational variables let us not only find the optimum operational point regarding energy efficiency but also attain a positive impact on the QoS, which improves the results obtained with current single-variable optimization strategies. The model under consideration includes external noise and does not impose the saturation condition in stations and as such is well suited for real-time industrial applications under noisy channels. Results obtained from simulation confirm the advantages of adjusting simultaneously W and r versus adjusting either one separately, obtaining a slight improvement in energy efficiency and resulting in less loss and delay at the MAC sublayer.

Fast retry limit adaptation for video distortion/delay control in IEEE 802.11e distributed networks

“…which provides, for the VI AC, the approximated conditional collision probabil- (14) and (15). Observe that this simplification may be maintained even if the number of nodes is high.…”

“…Hence, the number of collisions grows rapidly with the increase of N , thus making difficult the support of many contending video flows of acceptable quality. By consequence, the selection of the maximum valueN = N − 1 in (14) and (15), which provides the highest accuracy, may be acceptable in practical scenarios, where, realistically, the number of contending video flows is limited.…”

“…In [16] the mean square error and the structural similarity are compared as video quality assessments for developing adaptive retransmission strategies. A tradeoff between energy efficiency and satisfaction of the QoS requirements for centralized operations is obtained in [15] by a joint dynamic adjustment of the contention window and of the retry limit.…”

“…Accordingly, several retry limit adaptation methods have been proposed in the research literature [5][6][7][8][9][10][11][12][13][14][15][16]. The QoS strategy presented in [5] adopts a priority queueing also at the network layer, in order to relate the adaptation to the tradeoff between drop probability and buffer overflow rate.…”