As a modulation scheme for optical wireless communication, there is MPolSK (multilevel polarization shift keying) that modulates a state of polarization of light. MPolSK has a problem that it is severely affected by mismatched polarization axes. Although MDPolSK (multilevel differential PolSK) can overcome the problem, it is susceptible to noise, and its SER (symbol error rate) degrades as compared to MPolSK. In this paper, we propose one kind of MDPolSK that estimates the mismatched polarization axes in the receiver. We analyzed SER of the proposed scheme by computer simulations. The result shows that the proposed scheme is not affected by the mismatched polarization axes, and it provides a good SER as compared to the conventional MDPolSK. In addition, we modified the constellation used in the proposed scheme to improve SER.

Recent localization methods for wireless networks cannot be applied to dynamic networks with unknown topology. To solve this problem, we propose a localization method based on partial correlation analysis in this paper. We evaluate our proposed localization method in terms of accuracy, which shows that our proposed method can achieve high accuracy localization for dynamic networks with unknown topology.

Cloud computing, which enables users to enjoy various Internet services provided by data centers (DCs) at anytime and anywhere, has attracted much attention. In cloud computing, however, service quality degrades with user distance from the DC, which is unfair. In this study, we propose a bandwidth allocation scheme based on collectable information to improve fairness and link utilization in DC networks. We have confirmed the effectiveness of this approach through simulation evaluations.

Content-centric networking (CCN) promises efficient content delivery services with in-network caching. However, it cannot utilize cached chunks near users if they are not on the shortest path to the server, and it tends to mostly cache highly popular chunks in a domain. This degrades cache efficiency in obtaining various contents in CCN. Therefore, we propose hash-based cache distribution and search schemes to obtain various contents from nearby nodes and evaluate the effectiveness of this approach through simulation.

Information-centric networking (ICN) provides low-latency content delivery with in-network caching, but delivery latency depends on cache distance from consumers. To reduce delivery latency, a scheme to cluster domains and retain the main popular content in each cluster with a cache distribution range has been proposed, which enables consumers to retrieve content from neighboring clusters/caches. However, when the distribution of content popularity changes, all content caches may not be distributed adequately in a cluster, so consumers cannot retrieve them from nearby caches. We therefore propose a dynamic clustering scheme to adjust the cache distribution range in accordance with the change in content popularity and evaluate the effectiveness of the proposed scheme through simulation.

Polarization-maintaining photonic crystal fiber couplers (PM-PCFCs) were fabricated using a CO2 laser irradiation technique. We could control the states of air holes in the tapered region of couplers by adjusting the laser power density in the fusion and the elongation processes. It was demonstrated that the air hole remaining PM-PCFC exhibited polarization-splitting characteristics and that the air hole collapsed PM-PCFC had polarization insensitive coupling characteristics.