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Aerial acoustic communication (AAC) has been developed for a variety of Internet-of-things (IoT) applications, thanks to the merit of embedding small amounts of data directly into audio contents and transmitting them through commercial off-the-shelf (COTS) devices without additional infrastructure. However, AAC has clear limitations due to ambient noise, severely frequency-selective acoustic channels, and high power consumption of COTS devices. We adopt chirp spread spectrum (CSS) modulation and design new quaternary symbols to overcome frequency selectivity of audio interfaces of COTS devices. We also develop a computation-efficient method to demodulate the proposed symbols, aiming to reduce the power consumption of COTS devices. We employ a frame combining technique without increasing computational complexity, to mitigate the effects of multipath fading and ambient noise in acoustic channels. To evaluate the proposed methods, we conduct extensive experiments with several smartphones in various environments. The experimental results and evaluation demonstrate that the proposed symbols and frame combining method contribute to improving the frame reception ratio by up to 59.8%p (267.9%) and 14%p (84.3%), respectively. The frame combining increases the possibility of receiving a frame within two attempts at extremely low SNR, by up to 107.9%, resulting in reduced excessive delay. The method to demodulate the proposed symbols lowers power consumption by tens to hundreds of milliwatts, depending on the device. Our proposal significantly helps to achieve high reliability and low power consumption of COTS devices in AAC.

Today, there exist two types of vehicular communication technology, namely, Long Term Evolution-based vehicle-to-vehicle (LTE-V2V) and dedicated short-range communications (DSRC). Although many studies dealing with vehicular communication have been conducted, the situation where separate groups of vehicles using different communication technologies coexist has never been studied. In the coexistence situation, the communication inability issue between the vehicles using different communication technologies is raised. To resolve the problem, we propose a relaying system, called Nearest-first, where hybrid user equipments (UEs), which are equipped with both DSRC and LTE-V2V modules, are considered. When a hybrid UE receives a cooperative awareness message (CAM), the UE relays the CAM using the other communication technology. We conduct simulations in various situations incorporating realistic mobility model and road topologies. We demonstrate that the Nearest-first outperforms existing relaying schemes with the performance gain of up to 91% in terms of effective communication distances.

In future cellular networks, performance target includes not only increasing data rate, but also reducing latency. The current LTE-Advanced systems require four message exchanges in the random access and uplink transmission procedure, thus inducing high latency. In this paper, we propose a 2-way random access scheme which effectively reduces the latency. The proposed 2-way random access requires only two messages to complete the procedure at the cost of increased number of preambles. We study how to generate such preambles and how to utilize them. According to extensive simulation results, the proposed random access scheme significantly outperforms conventional schemes by reducing latency by up to 43%. We also demonstrate that computational complexity slightly increases in the proposed scheme, while network load is reduced more than a half compared to the conventional schemes.

Damaging GATA6 variants cause cardiac outflow tract defects, sometimes with pancreatic and diaphragmic malformations. To define molecular mechanisms for these diverse developmental defects, we studied transcriptional and epigenetic responses to GATA6 loss of function (LoF) and missense variants during cardiomyocyte differentiation of isogenic human induced pluripotent stem cells. We show that GATA6 is a pioneer factor in cardiac development, regulating SMYD1 that activates HAND2, and KDR that with HAND2 orchestrates outflow tract formation. LoF variants perturbed cardiac genes and also endoderm lineage genes that direct PDX1 expression and pancreatic development. Remarkably, an exon 4 GATA6 missense variant, highly associated with extra-cardiac malformations, caused ectopic pioneer activities, profoundly diminishing GATA4, FOXA1/2, and PDX1 expression and increasing normal retinoic acid signaling that promotes diaphragm development. These aberrant epigenetic and transcriptional signatures illuminate the molecular mechanisms for cardiovascular malformations, pancreas and diaphragm dysgenesis that arise in patients with distinct GATA6 variants.

Along with the proliferation of mobile devices and applications, IEEE 802.11 wireless local area network (WLAN) has become one of the most popular Internet access technologies. This leads to dense deployment of WLAN devices, and the calls for better user experience in such high-density WLAN environments are mounting. To keep pace with this increasing demand for high efficiency WLAN, IEEE 802.11ax, whose key advance is adopting uplink multi-user transmission (UL MU), is currently entering the final phase of standardization. The UL MU in 802.11ax WLAN, however, has a difficulty that stems from the intrinsically distributed nature of WLAN. Specifically, concurrent frames from multiple stations are loosely synchronous in time, thus resulting in symbol timing misalignment which leads to poor decoding performance. In this paper, we dissect the performance degradation caused by symbol timing misalignment and examine the required symbol timing conditions in receiving UL MU. Based on the analysis, we present a new two-step synchronization method to accommodate asynchronously arriving UL MU. We develop an 802.11ax link-level simulator and comparatively evaluate the proposed synchronization method via extensive simulations. Simulation results demonstrate that the proposed method successfully stabilizes UL MU data delivery even with large UL MU arrival timing deviations and the use of short cyclic prefix.

Many researchers expect to see the efficiency of wireless local area networks (WLANs) increased by in-band simultaneous transmit and receive (STR). While insufficient suppression of self-interference has been a major obstacle to implementing the STR capability, an even bigger obstacle is the fact that enabling STR involves significant modification to the current IEEE 802.11 medium access control (MAC) protocol. In this paper, we propose MASTaR, a novel MAC protocol that enables STR in 802.11 WLAN using standard-compliant methods. The feasibility and performance of MASTaR are extensively evaluated via 3-D ray-tracing-based simulation. The simulation results demonstrate that significant performance enhancement, e.g., up to 2.58× higher throughput than the current 802.11 MAC protocol, can be achieved by an STR-capable access point.