Wakeup Receiver for Radio-On-Demand Wireless LANs

Access points (APs) of wireless LANs (WLANs), always powered on and ready to serve mobile nodes, consume a large amount of power in total, but are idle during much of the time. Previous protocol-based sleep-wakeup scheduling schemes partially solve this problem, but the large wakeup delay remains a problem. Aiming at realizing Radio-On-Demand WLANs, in this paper, we suggest using an additional wakeup transceiver to convey wakeup signals from nodes to APs. APs in the sleep mode are activated by nodes when new data flows are initiated, where the wakeup delay is very low. The proposed wakeup transceiver works on the 2.4GHz ISM band and shares antenna with a co-located WLAN module to reduce hardware cost. The wakeup receiver is designed to be simple but very reliable, and consume a very low power. The contribution of this paper is two-fold: (i) Wakeup signals are designed to co-exist with WLAN signals by exploiting the carrier sense mechanism of WLAN devices, and, (ii), explicit signal recognition is used to achieve an extremely low false wakeup probability in an environment where the number of WLAN signals is overwhelming. Testbed experiments confirm that the proposed scheme, besides its simplicity, has good performance in both frame error rate and false wakeup probability.