How to control hand-off drops is a very importantQualityof-Service (QoS) issue in cellular networks. In order to keep the hand-off dropping probability below a pre-specified target value (thus providing a probabilistic QoS guarantee), we design and evaluate predictive and adaptive schemes for the bandwidth reservation for the existing connections' handoffs and the admission control of new connections. We first develop a method to estimate user mobility based on an aggregate history of hand-offs observed in each cell. This method is then used to predict (probabilistically) mobiles' directions and hand-off times in a cell. For each cell, the bandwidth to be reserved for hand-offs is calculated by estimating the total sum of fractional bandwidths of the expected hand-offs within a mobility-estimation time window. We also develop an algorithm that controls this window for efficient use of bandwidth and effective response to (1) time-varying traffic/mobility and (2) inaccuracy of mobility estimation.Three different admission-control schemes for new connection requests using this bandwidth reservation are proposed.Finally, we evaluate the performance of the proposed schemes to show that they meet our design goal and outperform the static reservation scheme under various scenarios.

IEEE 802.11 Wireless Local Area Network (WLAN) physical layers (PHYs) support multiple transmission rates. The PHY rate to be used for a particular frame transmission is solely determined by the transmitting station. The transmission rate should be chosen in an adaptive manner since the wireless channel condition varies over time due to such factors as station mobility, time-varying interference, and location-dependent errors. In this paper, we present a novel link adaptation algorithm, which aims to improve the system throughput by adapting the transmission rate to the current link condition. Our algorithm is simply based on the received signal strength measured from the received frames, and hence it does not require any change in the current IEEE 802.11 WLAN Medium Access Control (MAC) protocol. Based on the simulation and its comparison with a numerical analysis, it is shown that the proposed algorithm closely approximates the ideal case with the perfect knowledge about the channel and receiver conditions.

Noninvasive intranasal drug administration has been noted to allow direct delivery of drugs to the brain. In the present study, the therapeutic efficacy of intranasal small interfering RNA (siRNA) delivery was investigated in the postischemic rat brain. Fluorescein isothiocyanate (FITC)-labeled control siRNA was delivered intranasally in normal adult rats using e-PAM-R, a biodegradable PAMAM dendrimer, as gene carrier. Florescence-tagged siRNA was found in the cytoplasm and processes of neurons and of glial cells in many brain regions, including the hypothalamus, amygdala, cerebral cortex, and striatum, in 1 hour after infusion, and the FITC-fluorescence was continuously detected for at least 12 hours. When siRNA for high mobility group box 1 (HMGB1), which functions as an endogenous danger molecule and aggravates inflammation, was delivered intranasally, the target gene was significantly depleted in many brain regions, including the prefrontal cortex and striatum. More importantly, intranasal delivery of HMGB1 siRNA markedly suppressed infarct volume in the postischemic rat brain (maximal reduction to 42.8 ± 5.6% at 48 hours after 60 minutes middle cerebral artery occlusion (MCAO)) and this protective effect was manifested by recoveries from neurological and behavioral deficits. These results indicate that the intranasal delivery of HMGB1 siRNA offers an efficient means of gene knockdown-mediated therapy in the ischemic brain.

IEEE 802.11ah is an emerging Wireless LAN (WLAN) standard that defines a WLAN system operating at sub 1 GHz license-exempt bands. Thanks to the favorable propagation characteristics of the low frequency spectra, 802.11ah can provide much improved transmission range compared with the conventional 802.11 WLANs operating at 2.4 GHz and 5 GHz bands. 802.11ah can be used for various purposes including large scale sensor networks, extended range hotspot, and outdoor Wi-Fi for cellular traffic offloading, whereas the available bandwidth is relatively narrow. In this paper, we give a technical overview of 802.11ah Physical (PHY) layer and Medium Access Control (MAC) layer. For the 802.11ah PHY, which is designed based on the down-clocked operation of IEEE 802.11ac's PHY layer, we describe its channelization and transmission modes. Besides, 802.11ah MAC layer has adopted some enhancements to fulfill the expected system requirements. These enhancements include the improvement of power saving features, support of large number of stations, efficient medium access mechanisms and throughput enhancements by greater compactness of various frame formats. Through the numerical analysis, we evaluate the transmission range for indoor and outdoor environments and the theoretical throughput with newly defined channel access mechanisms.

Smart devices such as smartphones and tablet/wearable PCs are equipped with voice user interface, i.e., speaker and microphone. Accordingly, various aerial acoustic communication techniques have been introduced to utilize the voice user interface as a communication interface. In this paper, we propose an aerial acoustic communication system using inaudible audio signal for low-rate communication in indoor environments. By adopting chirp signal, which is widely used for radar applications due to its capability of resolving multi-path propagation, the proposed acoustic modem supports long-range communication independent of device characteristics over severely frequency-selective acoustic channel. We also design a backend server architecture to compensate for the low data rate of chirp signal-based acoustic modem. Via extensive experiments, we evaluate various characteristics of the proposed modem including multi-path resolution and multiple chirp signal detection. We also verify that the proposed chirp signal can deliver data at 16 bps in typical indoor environments, where its maximum transmission range is drastically extended up to 25 m compared to the few meters of the previous research.