Seeing the Unobservable: Channel Learning for Wireless Communication Networks

Wireless communication networks rely heavily on channel state information (CSI) to make informed decision for signal processing and network operations. However, the traditional CSI acquisition methods is facing many difficulties: pilot-aided channel training consumes a great deal of channel resources and reduces the opportunities for energy saving, while location-aided channel estimation suffers from inaccurate and insufficient location information. In this paper, we propose a novel channel learning framework, which can tackle these difficulties by inferring unobservable CSI from the observable one. We formulate this framework theoretically and illustrate a special case in which the learnability of the unobservable CSI can be guaranteed. Possible applications of channel learning are then described, including cell selection in multi-tier networks, device discovery for device-to-device (D2D) communications, as well as end-to-end user association for load balancing. We also propose a neuron-network-based algorithm for the cell selection problem in multi-tier networks. The performance of this algorithm is evaluated using geometry-based stochastic channel model (GSCM). In settings with 5 small cells, the average cell-selection accuracy is 73% - only a 3.9% loss compared with a location-aided algorithm which requires genuine location information.Comment: 6 pages, 4 figures, accepted by GlobeCom'1

Effects of Special Economic Zones on FDI in Emerging Economies: Does Institutional Quality Matter?

This study attempts to prove that emerging markets could partially improve institutional quality in a specific area and benefit the local economy despite the rest of the area having poor institutions. Interestingly, we observed that despite the presence of institutions of comparative disadvantage, emerging economies continue to constantly attract significant foreign direct investment. Hence, this study focuses on a type of place-based policy in China that provides a standard favorable institutional environment in a specific area. Using data from China’s Annual Survey of Industrial Firms and combining official lists of Chinese special economic zones (SEZs), we obtained a dataset of 2660 SEZs from 1998 to 2018, and a sample of 37,251 from 1998 to 2013. Then, we empirically examined the impact and mechanism of SEZs on foreign investment by using time-varying difference-in-difference specification. After a sequence of validity and robustness checks, we found that the establishment of SEZs significantly enhances foreign entry. We also found that partial institutional quality improvement of SEZs is a key mechanism in the location of foreign investment. We conclude that it is beneficial for the government to impose place-based policies such as SEZs that improve partial institutional quality efficiently and promote the local economy

Water Solubility Distribution of Organic Matter Accounts for the Discrepancy in Hygroscopicity among Sub- and Supersaturated Humidity Regimes

Water uptake properties of organic matter (OM) are critical for aerosol direct and indirect effects. OM contains various chemical species that have a wide range of water solubility. However, the role of water solubility on water uptake by OM has poorly been investigated. We experimentally retrieved water solubility distributions of water-soluble OM (WSOM) from combustion of mosquito coil and tropical peat using the 1-octanol–water partitioning method. In addition, hygroscopic growth and cloud condensation nuclei (CCN) activity of solubility-segregated WSOM were measured. The dominant fraction of WSOM from mosquito coil smoldering was highly soluble (water solubility (S) > 10–2 g cm–3), while that from peat combustion contained ∼40% of less-soluble species (S –3 g cm–3). The difference in water solubility distributions induced changes in the roles of less water-soluble fractions (S < 10–3 g cm–3) on CCN activity. Namely, the less water-soluble fraction from mosquito coil combustion fully dissolved at the point of critical supersaturation, while that for tropical peat smoldering was limited by water solubility. The present result suggests that water solubility distributions of OM, rather than its bulk chemical property, need to be quantified for understanding the water uptake process