The effect of human shadowing on RF signal strengths of IEEE802.11a systems on board business jets

Wireless networks provide the technology that allows the service provisioning of a number of applications to mobile stations. In recent years, aircraft manufacturers have been evaluating the possibility of offering this technology on-board their aircrafts. This will help manufacturers to reduce cable complexity while offering new services to the passengers. This paper proposes a novel and efficient simulation technique that can be used to analyze the effect of a cabin attendant, or a passenger, walking down the aisle of a business jet on the signal strength received by the mobile users. The aircraft environment provides a particular radio propagation scenario with its tunnel shape and a high density clutter. The propagation is effected by obstacles inside the cabin, like furniture and seats, resulting in propagation that is mainly due to reflection, refraction and scattering. A further factor affecting the received signal field of a wireless system is human shadowing. Therefore, successful modeling of the wireless system requires that simulations include the effects introduced by people moving. This can result in signal fluctuations with fading depths that can exceed 40 dB. A 3D ray tracing technique, based on Geometric Optics (GO) was used to simulate the propagation characteristics inside a Falcon business jet. The internal of the aircraft was divided into a number of cells, with each cell having very small dimensions. The simulation was performed in two steps. Initially only a static channel was considered, where a large number of rays were launched from an antenna and the propagation path of each ray was followed. For each cell inside the cabin the index of the rays that passed through the cell were kept in conjunction to the power contribution of that ray. The starting angle of each ray launched was also stored. Secondly, the model of the human, consisting of different cylinders representing the legs, arms, torso and head, was superimposed on the cabin´s layou- - t. For each human position, only the rays passing through those cells were simulated, resulting in a significant reduction in simulation time. The human advanced 4 cells at a time, resulting in a walking speed of around 1.5 meters per second. Thus, the person will cover the length of the cabin´s aisle in a total of 67 steps. Different scenarios can thus be considered for the communication devices within the cabin. This work considers the scenario with four laptops, using an IEEE802.11a wireless connection, placed on top of the tables representing passengers working at their seats. Depending on the position of the moving person within the aisle, the received signal at particular laptop positions resulted in signal fluctuations between -6 dB to +67 dB from the nominal received signal strength.