Kwanghun Han

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— In this paper, we analytically evaluate the sleep mode operation of the IEEE 802.16e, defined for the power saving. In the sleep mode, an Mobile Subscribe Station (MSS) sleeps for a sleep window and wakes up at the end of the sleep window in order to check pending download packet(s) destined to itself. If there is no such a packet, the MSS doubles the(More)
—Femto BS (Base Station) is emerging as a key technology to secure the coverage and capacity in indoor environments. However, since the existing macrocell network is overlaid on femtocell networks utilizing the same set of frequency channels, femtocell networks can originate severe co-channel interference to the macrocell network unless the femtocell(More)
Along with the wide acceptance of IEEE 802.11 Wireless Local Area Network (WLAN), new applications such as Internet Protocol (IP) telephony over WLAN are fast emerging today. For battery-powered IP phone devices, the life time extension is a key concern for the market acceptance while today's 802.11 is not optimized for such an operation. In this paper, we(More)
IEEE 802.11 Wireless Local Area Network (WLAN) became a prevailing technology for the broadband wireless Internet access, and new applications such as Voice over WLAN (VoWLAN) are fast emerging today. For the battery-powered VoWLAN devices, the standby time extension is a key concern for the market acceptance while today's 802.11 is not optimized for such(More)
— Cognitive radios are typically known to exploit vacant spectrum resources yet not interfering with primary communication systems. However, cognitive radios may not be able to secure a clear spectrum band, i.e., white hole, in certain environments. Underlay spectrum sharing provides a way to cope with such a spectrum sharing problem in a bustling spectrum(More)
The energy consumption in transmitting an information bit, i.e., energy-per-bit, has been known to decrease monotonically as the transmission time increases [1]. However, when considering the power amplifier (PA) characteristics, we learn that the energy-per-bit starts to increase as the transmission time becomes long over a certain threshold. This is(More)