PIANO: A power saving strategy for cellular/VoWLAN dual-mode mobiles

Shiao-Li Tsao*, E. Cheng Cheng

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


The integration of cellular and VoIP over WLAN (VoWLAN) systems recently has attracted considerable interest from both academia and industry. A cellular/VoWLAN dual-mode system enables users to access a low-cost VoIP service in a WLAN hotspot and switch to a wide-area cellular system without WLANs. Unfortunately, cellular/VoWLAN dual-mode mobiles suffer the power consumption problem that becomes one of the major concerns for commercial deployment of the dual-mode service. In this study, we present a novel power saving mechanism, called PIANO (paging via another radio), for the integration of heterogeneous wireless networks, and further apply the proposed methods to implement a cellular/VoWLAN dual-mode system. Based on the proposed mechanisms, a dual-mode mobile can completely switch off its WLAN interface, only leaving the cellular interface awake to listen to paging messages. When a mobile receives a paging message from its cellular interface, it wakes up the WLAN interface and responds to connection requests via WLAN networks. Therefore, a dual-mode mobile reduces the power consumption by turning off the WLAN interface during idle, and can also receive VoWLAN services. Measurement results based on the prototype system demonstrate that the proposed methods significantly extend the standby hours of a dual-mode mobile.

Original languageEnglish
Pages (from-to)683-698
Number of pages16
JournalWireless Networks
Issue number5
StatePublished - 1 Oct 2008


  • Cellular-WLAN interworking
  • Dual-mode mobile
  • Power saving technology
  • Voice over IP (VoIP)
  • VoIP over WLAN

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