Applying graph coloring in resource coordination for a high-density wireless environment

In a high density wireless environment, channel interference among users of many overlapped Basic Service Sets (OBSSs) is a serious problem. Our solution for the problem relies on a resource coordination scheme that utilizes the spatial distribution of the transceivers for channel reuse and time-slot division multiplexing for downlink transmission sharing among all participating BSSs. In this paper we show that an OBSS environment can be modeled by a planar graph and the OBSS group coordination assignment problem can be considered as a vertex coloring problem whose solution involves at most four colors. The graph coloring solution algorithm for the OBSS group coordination assignment is presented. The actual coloring is demonstrated, using a heuristics of Maximum Degree First. Performance simulation results of the coordination algorithm are also presented. © 2008 IEEE

Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View

Small satellite systems enable whole new class of missions for navigation, communications, remote sensing and scientific research for both civilian and military purposes. As individual spacecraft are limited by the size, mass and power constraints, mass-produced small satellites in large constellations or clusters could be useful in many science missions such as gravity mapping, tracking of forest fires, finding water resources, etc. Constellation of satellites provide improved spatial and temporal resolution of the target. Small satellite constellations contribute innovative applications by replacing a single asset with several very capable spacecraft which opens the door to new applications. With increasing levels of autonomy, there will be a need for remote communication networks to enable communication between spacecraft. These space based networks will need to configure and maintain dynamic routes, manage intermediate nodes, and reconfigure themselves to achieve mission objectives. Hence, inter-satellite communication is a key aspect when satellites fly in formation. In this paper, we present the various researches being conducted in the small satellite community for implementing inter-satellite communications based on the Open System Interconnection (OSI) model. This paper also reviews the various design parameters applicable to the first three layers of the OSI model, i.e., physical, data link and network layer. Based on the survey, we also present a comprehensive list of design parameters useful for achieving inter-satellite communications for multiple small satellite missions. Specific topics include proposed solutions for some of the challenges faced by small satellite systems, enabling operations using a network of small satellites, and some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications Surveys and Tutorial