Résumé:
This paper investigates the effects of power saving
strategies on the performance of wireless local area networks
(WLANs). More specifically, a power management model is
formulated as an integer linear program that the network
planner can use in order to achieve power savings while
maintaining an acceptable quality of service (QoS), measured by
the signal to interference ratio (SIR) for interference limited
WLAN. Furthermore, through a network simulation
implemented in NS-2, it is shown that the adaptive power saving
scheme can guarantee the same average throughput as the nonadaptive counterpart, while significantly reducing the total
transmitted power. Considering a realistic scenario, we show
that, using the proposed power management model, one can save
about 55% of the transmitted power while the SIR is increased
by 6 dB thus improving the QoS. Also, using a simple experiment
with two access points it is shown that, in the case of users within
the overlap of the two coverage areas, the throughput remains
constant when the transmit power is changed from a low value to
a high value although a minor degradation of the average delay
is noticed. As a conclusion, the commonly assumed fact that
increasing the transmit power results in better network
performance is not necessarily true and can result as shown in
this paper in energy waste.
