A Protocol Enhancement for IEEE 802.11 Distributed Power Saving Mechanisms No Data Acknowledgement

Mobile devices including wireless LAN functionality are becoming increasingly popular in society. The wide range of products available in the market target different customer needs but most of them should meet two main requirements: QoS support for differentiating real-time services from non real-time and power saving functionality to achieve an operating time according to users' expectations. The devices presenting the most challenging technical issues to meet these two requirements are dual-mode handsets (cellular/WLAN) because of their mandatory support of a strict QoS demanding application, VoIP, and their small device size which severely limits the battery capacity. The focus of our work in this paper is the design and evaluation of an enhancement of the distributed wireless LAN power saving mechanisms defined in the IEEE 802.11 and 802.11e standards, no data acknowledgment (NDACK). The objective of NDAck is to increase the battery lifetime of wireless LAN mobile devices while providing the required QoS. The protocol improvement designed has been implemented in OPNET to evaluate the performance enhancements obtained. Our results show that (i) NDAck significantly reduces the power consumption of stations running real-time applications, (ii) the larger the power consumption due to the congestion in the wireless channel the larger the power consumption reduction with NDAck and (iii) NDAck results in a considerable QoS improvement for real-time applications.