Dynamic TXOP HCCA reclaiming scheduler with transmission time estimation for IEEE 802.11e real-time networks

Abstract

IEEE 802.11e HCCA reference scheduler guarantees Quality of\ud Service only for Constant Bit Rate traffic streams, whereas its as-\ud signment of scheduling parameters (transmission time TXOP and\ud polling period) is too rigid to serve Variable Bit Rate (VBR) traffic.\ud This paper presents a new scheduling algorithm, Dynamic TXOP\ud HCCA (DTH). Its scheduling scheme, integrated with the central-\ud ized scheduler, uses both a statistical estimation of needed trans-\ud mission duration and a bandwidth reclaiming mechanism with the\ud aim of improving the resource management and providing an in-\ud stantaneous dynamic Transmission Opportunity (TXOP), tailored\ud to multimedia applications with variable bit rate. Performance evaluation through simulation, confirmed by the scheduling analysis, shows that DTH is suitable to reduce the transmission queues length.\ud This positively impacts on the delay and on packets drop rate experienced by VBR traffic streams

Elastic QoS Scheduling with Step-by-Step Propagation in IEEE 802.11e Networks with Multimedia Traffic

“…DTH does not impact on the centralized scheduler, as mentioned before, nor on the admission control policy, as demonstrated in [38] and as will be deepened in the following.…”

“…This approach impacts only on the transmission time and does not involve the polling mechanism; this consideration is valid in general, since the algorithm does not operate on the polling engine and, in particular, since the period is not modified, the polling list is not changed in the case, for instance, when the polling order is set taking into account deadlines. Moreover, the shift of recovered resources to the next stations performed by DTH can imply only a polling advance, coherently to the reference scheduler and as shown in [38].…”

“…As when the price trend, growing, intercepts the trendline and a buying signal is triggered, so when the punctual value of the estimated transmission time at time exceeds its reference value , the recovery mechanism is activated and, if ̸ = 0, it is shifted to the next polled station. Finally, when the DTH recovery mechanism cannot be applied since there are no spare resources available, the centralized scheduler continues assigning for efficiency reasons and in order to avoid saturation effects, as theoretically demonstrated in [38]. As a result the new transmission time for the next polling of is computed as follows:…”

“…An approach alternative to proposing a further new scheduler is taking advantage of the existing schedulers and intervening on their policy by integrating a scheduling module focused on improving the offered QoS. Dynamic TXOP HCCA (DTH) [38] acts in this way, refining the behavior of a centralized HCCA scheduler with the ability of providing a dynamic . In this scope, an advanced version of DTH, Dynamic TXOP HCCA with threshold, is presented.…”

High performing multimedia transmission approach based on QoS support and admission control over IEEE 802.11e networks

“…This essentially causes the allocated time to be insufficient to empty the transmission queue of uplink traffics, resulting increased end‐to‐end delay. Some solutions to these problem involves the increased allocation of TXOP duration . These types of solutions, although feasible, result in the degradation of the overall bandwidth utilization when the data rate decreases.…”