Public safety networks need to more effectively meet the increasing demands for images or videos to be shared among first responders and incident commanders. Long term evolution (LTE) networks are considered to be candidates to achieve such broadband services. Capital expenditures in deploying base stations need to be decreased to introduce LTE for public safety. However, out-of-coverage areas tend to occur in cell edge areas or inside buildings because the cell areas of base stations for public safety networks are larger than those for commercial networks. The 3rd Generation Partnership Program (3GPP) in Release 13 has investigated device-to-device (D2D) based relay communication as a means to fill out-of-coverage areas in public safety LTE (PS-LTE). This paper proposes a relay selection scheme based on effective path throughput from an out-of-coverage terminal to a base station via an in-coverage relay terminal, which enables the optimal relay terminal to be selected. System level simulation results assuming on radii of 20km or less revealed that the proposed scheme could provide better user ratios that satisfied the throughput requirements for video transmission than the scheme standardized in 3GPP. Additionally, an evaluation that replicates actual group of fire-fighters indicated that the proposed scheme enabled 90% of out-of-coverage users to achieve the required throughput, i.e., 1.0Mbps, to transmit video images.

In this paper, we propose to use graded-index multimode fibers (GI-MMFs) with Fabry-Perot laser diodes (FP-LDs) for short-span and low-cost feeders. The multimode fiber feeders can be applied to wireless personal communication systems where the required feeder length is within several hundred meters, such as distributed antenna networks for microcellular systems or wireless LANs. The use of multimode fibers makes fiber coupling and connection easier, and has the potential to greatly reduce total system cost. Three types of GI-MMFs are considered as transmission media, (1) silica-based glass optical fiber (GI-GOF),(2) silica-core plastic-clad fiber (GI-PCF), and (3) all-plastic optical fiber (GI-POF). It is shown that GI-GOF and GI-PCF are suitable for use as feeders in the microcells of CDMA cellular and wireless LAN systems within 300m in length. GI-POF is estimated to be suitable for use as feeders in wireless LANs within 100m in length. A multimode fiber feeder with FP-LDs and GI-PCF of 300 m is developed in order to demonstrate its applicability to a wireless LAN system operating in the 2.4 GHz ISM band.

Among the many fabrication methods for oxide superconductor films, metal organic chemical vapor deposition (MOCVD) is particularly suitable for industrial application because of its mass productivity and the low growth temperature. Therefore we have studied this technique using the horizontal cold wall furnace type MOCVD method to obtain high quality superconducting films. As the result, we have succeeded in fabricating YBa2Cu3Oy films which have high critical temperatures (over 80 K) under substrate temperatures as low as 700 without post-annealing. But, in the course of our experiments, it was found that the thicknesses of YBa2Cu3Oy films fabricated by MOCVD were not uniform. The cause of this non-uniformity is believed to be that the deposition rate exponentially falls off along the flow direction because of the decrease of the source gas concentration through the reaction. In this paper, this non-uniformity is analytically studied. It is shown that the deposition rate decrease can be controlled with a tapered inner tube, and that these theoretical results are in good agreement with the results of experiment. In addition, it is indicated that the superconducting property of the films has less dependence on substrate position as a result of the tapered inner tube.