Multiplex communications – Communication over free space – Repeater
Reexamination Certificate
2001-08-07
2004-10-19
Pham, Chi (Department: 2663)
Multiplex communications
Communication over free space
Repeater
C370S331000, C370S338000, C455S013100
Reexamination Certificate
active
06807158
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to wireless networks and more particularly to performance optimization in hybrid, non-terrestrial-terrestrial multi-hop mobile wireless networks.
BACKGROUND
Existing wireless networks often fail to adequately perform in harsh terrestrial environments. Many performance shortcomings are related to inter-nodal terrestrial barriers. These barriers commonly result in one or more nodes becoming isolated from other nodes in the network. This is an undesirable situation, resulting in inefficient use of personnel, sensor arrays, or other aspects of the node based networking system. In an attempt overcome the problems associated with isolated nodes, artisans have suggested using nodes that have an airborne or satellite uplink. These nodes are often referred to as gateway nodes, in part because they serve as gateways to an airborne platform or a satellite. Thus, a determinable number of nodes are designated as gateway nodes, and these nodes provide bi-directional terristerial-non-terrestrial communication. In this way remote and isolated nodes are able to maintain contact with the main network.
Existing satellite-mobile ad hoc network hybrid systems generally assign static positions for gateways or define gateway trajectories using a heuristic approach. One of the main disadvantages of using heuristic, pre-defined trajectories or static placements of gateways has been sub-optimal performance in terms of performance metrics such as network throughput and end-to-end delay. Thus there is a need for a methodology that can achieve improved performance by optimizing network throughput, and minimizing end-to-end delay.
SUMMARY OF THE INVENTION
The present invention relates generally to wireless networks and more particularly to performance optimization in hybrid, non-terrestrial-terrestrial multi-hop mobile wireless networks.
One embodiment of the invention provides a method and apparatus for optimizing performance in a hybrid, non-terrestrial to terrestrial multi-hop mobile wireless network. As used herein, non-terrestrial connotes airborne or space based relative to the earth, a moon, or asteroid, whereas “terrestrial” connotes at or near the surface of the earth, the moon, an asteroid, a planet, or a satellite of a planet, moon or asteroid. More generically, “terrestrial” connotes a location having a gateway where a distributed process is located and monitored and “non-terrestrial” connotes a location remote from the terrestrial location, and which has a capability to connect two or more terrestrial locations or connect a terrestrial location with a central data management or processing point. The method includes providing a first cluster of wireless nodes that include a first plurality of mobile nodes, and a first gateway node. The gateway node interfaces with both the mobile nodes and a Low Earth Orbit satellite (LEO) or Geosynchronous Earth Orbit satellite (GEO). The invention also provides a communicatively isolated second cluster of wireless nodes and a second gateway node that is configured to operate in a manner similar to the first gateway node. The invention establishes a communications link between the first wireless cluster and the second wireless cluster by directing data through a first gateway node, a non-terrestrial and a second gateway node. The invention allows the first gateway node and the second gateway node to dynamically change positions to maximize data throughput, data transmission reliability, and minimize total power consumption, wireless node-level power consumption, gateway level power consumption, periodicity of updates and resulting signaling overhead and complexity of updates and resulting signaling overhead.
In another embodiment of the invention each mobile node in the wireless ad-hoc network includes elements configured to perform a local computation. This computation includes the steps of estimating the mobile nodes' positions and transmitting these positions to the gateway node at time interval T and computing and transmitting the mobile nodes' data load information at time interval t where t<T. The position estimation may be facilitated with the aid of a global positioning system, or a terrestrially based triangulation system, or any other positioning mechanism.
In another embodiment, especially useful in computationally complex environments, the wireless ad-hoc network is divided into a plurality of clusters of smaller wireless ad-hoc networks and additional gateways may be introduced to reduce the computational complexity of the optimization calculations.
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Ahmed Mohin
Kondylis George D.
Krishnamurthy Srikanth
George Keith M.
HRL Laboratories LLC
Pham Chi
Tope-McKay & Associates
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