Seamless transfer of electronic information/data between ship-to-shore and vice versa and between ship-to-ship and shore-to-shore is being developed in the IMO e-Navigation strategy implementation plan (SIP). We have been focused on wireless LAN for ship-to-ship radiocommunication. In a former field radiocommunication trial, omni-directional antennas were used and a few hundred kbps throughput between two ships was measured, which was not enough for our research target (over 1Mbps). In order to get faster throughput, a field radiocommunication trial was carried out again with a few types of directional antennas and RSSI (Received Signal Strength Indication) and the throughput between two ships was measured simultaneously. As a result, multi-path (2-path) model affected by the reflection of the sea surface was confirmed and also the characteristics of the directional antennas such as half-power angle were confirmed, but the measured throughput was fast enough to meet our expectation.

Abstract
I. Introduction
II. Trial Method
    2.1. Trial Ships
    2.2. Trial Sea Area
    2.3. Directional Antennas
    2.4. Encounter Situation for the Field Trial
    2.5. Measurement Items
III. Trial Results
IV. Conclusions
References

• Yasuyuki NIWA(National Maritime Research Institute (NMRI))
• Hisaya MOTOGI(National Institute of Technology, Oshima College)
• Chihiro NISHIZAKI(National Maritime Research Institute (NMRI))
• Misako URAKAMI(National Institute of Technology, Oshima College)
• Takahiro SETA(National Maritime Research Institute (NMRI))
• Mitsuru KOBAYASHI(National Maritime Research Institute (NMRI))
• Makiko MINAMI(National Maritime Research Institute (NMRI))