Concepts for fast acquisition in optical communications systems

Abstract

As free-space laser communications systems proliferate due to improved technology and transmission techniques, optical communication networks comprised of ground stations, aircraft, high altitude platforms, and satellites become an attainable goal. An important consideration for optical networks is the ability of optical communication terminals (OCT) to quickly locate one another and align their laser beams to initiate the acquisition sequence. This paper investigates promising low-cost technologies and novel approaches that will facilitate the targeting and acquisition tasks between counter terminals. Specifically, two critical technology areas are investigated: position determination (which includes location and attitude determination) and inter-terminal communications. A feasibility study identified multipleantenna global navigation satellite system (GNSS) systems and GNSS-aided inertial systems as possible position determination solutions. Personal satellite communication systems (e.g. Iridium or Inmarsat), third generation cellular technology (IMT-2000/UMTS), and a relatively new air traffic surveillance technology called Autonomous Dependent Surveillance-Broadcast (ADS-B) were identified as possible inter-terminal communication solutions. A GNSS-aided inertial system and an ADS-B system were integrated into an OCT to demonstrate their utility in a typical optical communication scenario. Testing showed that these technologies have high potential in future OCTs, although improvements can be made to both to increase tracking accuracy.

Autonomous reconfiguration and control in directional mobile ad hoc networks

“…These two schemes are based on the use of GPS information and optical beacons, respectively. Much previous work on PAT systems has depended on optical devices [26][27][28][29][30] or Inertial Navigation Systems (INS) combined with GPS [28][29][30]; GPS or DGPS acts as a secondary device for providing position updates and correcting INS drift error, whose position accuracy is at the meter level.…”

“…Hence, it is essential to have complete information as to where nodes are (position coordinates) as well as where they are heading (pointing vectors) as shown in Figure 6. The use of various kinds of position and angular sensor devices is therefore natural in pointing techniques [26][27][28][29][30]. GPS (Global Positioning System) might be the alternative for providing such complete information in all weathers and global regions.…”

“…In previous work, low-cost and lightweight PAT systems for mobile nodes, such as aircraft or ground vehicles have been described [28,29]. These pointing systems used both Differential GPS (DGPS) and INS to measure a coarse pointing vector as well as a camera to provide a fine pointing vector.…”

Telecommunications Modeling, Policy, and Technology

“…Hence, it is essential to have complete information as to where nodes are (position coordinates) as well as where they are heading (pointing vectors) as shown in Figure 3. The use of various kinds of position and angular sensor devices is therefore natural in pointing techniques Ho et al, 2006;Wilkerson et al, 2006;Yee et al 1998). A GPS (Global Positioning System) might be the alternative for providing such complete information for all weathers and global regions.…”

Error Assessment Model for the Inverse Kinematics Problem for Stewart Parallel Mechanisms for Accurate Aerospace Optical Linkage

“…Typical pointing accuracies for laser satellite communications (LSC) systems vary from 1 to 200 rad; however most typical systems have a pointing accuracy within the range of 10 to 50 rad. In the tracking phase, the current values of accuracies typically reach 1 to 3 rad [4,5]. Lasercom links from low Earth orbit (LEO) to ground present several unique challenges for PAT.…”