22 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 12, NO
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22 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 12, NO. 1, JANUARY 2013 UHF Propagation Along a Cargo Hold on Board a Merchant Ship Xiao Hong Mao, Student Member, IEEE, and Yee Hui Lee, Senior Member, IEEE Abstract—The characterization of a Line of Sight (LOS) and a Non-Line of Sight (NLOS) link is performed over the military Ultra High Frequency (UHF) band (225 to 450 MHz). This is done using experimental results collected inside the cargo hold of a merchant ship. By analyzing the guiding effect associated with the cargo hold and its sub-structures, the channel characteristics of the environment can be determined. This important propagation mechanism is analyzed using the 3-D ray tracing simulator. Path loss for both topologies is studied and linear path loss models are proposed. Small-scale channel characteristics, such as the number of multipath components, decay factor of the multipath components and Root-Mean-Square (RMS) delay spread are studied and compared for the LOS and NLOS scenarios. Due to the guiding effect and multiple reflections along the cargo hold, both the LOS and NLOS scenarios are found to exhibit similar channel characteristics. A linear decay function is proposed to model the average Power Delay Profiles (PDPs). It is concluded that the linear model provides a good representation for the shape of the impulse responses for a cluttered environment with reflec- tive substructures. This study is useful for the implementation of wireless sensor networks for status monitoring in maritime applications. Index Terms—3-D ray tracing, cargo hold, metallic structure, waveguide effect, wireless sensor network. I. I NTRODUCTION W Ireless propagation in shipboard environments is im- portant for both military and commercial applications. For military applications, in order to seize control of a ship, it is critical to establish a wireless communication link between the bridge and the engine control room. For commercial applications, wireless communication in and out of the cargo hold and within the cargo hold is important. For example, during the loading and unloading of hazardous goods, commu- nication between crew members in and out of the cargo hold is essential for safety reasons. Within the cargo hold, wireless sensor network can be used to monitor the transportation of perishable and hazardous items [1]. In [2]–[9], channel sounding on board different types of ships have been reported. Of these literatures, four of them are on propagation within naval ships (including warships) [2]– [5]. In [2], narrowband channel measurements were performed in the frequency band of 800 MHz to 2500 MHz in order to Manuscript received April 12, 2011; revised November 1, 2011 and May 10, 2012; accepted September 3, 2012. The associate editor coordinating the review of this paper and approving it for publication was D. Michelson. This work was supported in full by the Advanced Communications Re- search Program DSOCL06271, a research grant from the Directorate of Research and Technology (DRTech), Ministry of Defence, Singapore. The authors are with the School of Electrical and Electronic Engineer- ing, Nanyang Technological University, Singapore, 639798 (e-mail: xh- [email protected]; [email protected]). Digital Object Identifier 10.1109/TWC.2012.121112.110675 investigate the signal level of transmission from one compart- ment to another within a naval ship. They concluded that the rubber door gaskets and other non-conductive structures may be the source of bulkhead penetration. In [3], narrowband channel sounding was performed in the frequency range of 800 MHz to 3 GHz in order to model the opened/closed door effect and polarization effect on the received power level for different transmitter to receiver locations (with a maximum distance of 5 m) onboard a warship. It was found that a closed water tight door can result in a signal strength drop is large while the path loss exponent is small. These findings are independent on frequency over the band of interest. In these reported work, since the dimensions of the watertight compartments and the corridor within the naval ships and warships are small; the separation between the transmitter and receiver distance is therefore small. However, the dimensions within the cruise ship are generally larger and therefore, their channel characteristics are expected to be different. In [6] and [7], path loss in a restaurant hall and along a cabin corridor on board a cruise ship at 2.4 GHz was studied based on measurement results in the frequency domain. It was found that the path loss in the restaurant hall can be modeled as free space propagation. The path loss along the cabin corridor can better be modeled as dual-slope decay propagation. In [2]– [7], same deck propagation onboard ships were studied. In [8] and [9], inter-deck propagation onboard a merchant ship was investigated. In [8], the propagation mechanisms at 255.6 MHz associated with the channel along the lift shaft that connects the top deck and the bottom deck of the ship were discussed. Due to the guiding effect of the lift shaft and the rich multipath components from the complex metallic ship structure, the delay spread was found to be large. In [9], the feasibility of broadband communication in the military UHF band between two locations with large distance separation within the ship, 1536-1276/13$31.00 c 2013 IEEE
