1. A position tracking apparatus, comprising:
a measured distance collector that collects distance information of adjacent nodes from a plurality of anchor nodes whose positions are known by being fixed and at least one sensor node whose positions are not known, respectively, in a sensor network;
a shortest distance calculator that calculates each of the shortest paths to the anchor nodes based on the distance information of the collected adjacent nodes and selects and manages a sensor node having the shortest path and shortest distance for the anchor node as a parent node;
a group separator that separates nodes in the sensor network into a first group whose positions are known and a second group whose positions are not known according to whether the positions of each node are known, the anchor node being included in the first group; and
a controller that selects a first sensor node nearest to the nodes of the first group from the second group to find its parent node and that corrects the distance information (measuring value) of the shortest path for the anchor node of the first sensor node by reflecting the estimated position of the parent node of the first sensor node and the distance information of the shortest path for the anchor node of the parent node,
the controller detecting the position of the first sensor node based on the distance information of the corrected shortest path.
2. The position tracking apparatus of claim 1, wherein
the controller
detects the positions by calculating the position of the n-th sensor node of the second group based on the corrected distance information.
3. The position tracking apparatus of claim 1, wherein
the controller,
when the position of the first sensor node is detected, removes the first sensor node from the second group and includes it in the first group.
4. The position tracking apparatus of claim 2, wherein
the shortest distance calculator
calculates the distance information of the shortest path by a sum of distances between nodes disposed on the shortest path from the sensor node to the anchor node.
5. The position tracking apparatus of claim 2, wherein
the group separator
classifies the first group and the second group into detailed groups based on each of the anchor nodes, and
the controller independently calculates positions of sensor nodes in the detailed group unit.
6. The position tracking apparatus of claim 5, wherein
the shortest path calculation for one anchor node has complexity of O(ElgV) where V means the number of nodes and E means the number of adjacent nodes.
7. A position tracking method for sensor nodes by a position tracking apparatus in a sensor network, comprising:
collecting distance information of adjacent nodes from a plurality of anchor nodes whose positions are known and at least one sensor node whose position is not known, respectively;
calculating each of shortest paths to the anchor nodes based on the distance information of the collected adjacent nodes and selecting and managing the sensor node having the shortest path and shortest distance for the anchor node as a parent node;
separating a first group whose positions are known and a second group whose positions are not known according to whether the positions of each node are detected, the anchor node being included in the first group;
selecting a first sensor node adjacent to the nodes of the first group from the second group to find its parent node and correcting the distance information (measuring value) of the shortest path for the anchor node of the first sensor nodes by reflecting the estimated position of the parent node of the first sensor node and the distance information of the shortest path for the anchor node of the parent node; and
detecting the position of the first sensor node based on the corrected distance information of the shortest path.
8. The position tracking method of claim 7, further comprising,
after the detecting the position of the first sensor node step,
detecting the positions by calculating the position of the n-th sensor node of the second group based on the corrected distance information.
9. The position tracking method of claim 7, wherein, the separating further
the first group and the second group are separated into at least three detailed groups which are respectively formed based on an anchor node in the case of tracking positions of sensor nodes in a two-dimensional plane, or
the first group and the second group are separated into at least four detailed groups which are respectively formed based on an anchor node in the case of tracking positions of sensor nodes in a three-dimensional plane.
10. The position tracking method of claim 9, wherein the detecting the position of the first sensor node, when the position of the first sensor node is detected, removes the first sensor node from the second group and includes it in the first group.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An optical device, comprising:
a first layer of mixed rare earth oxide on a silicon substrate, said mixed rare earth oxide being single crystal and lattice matched to said silicon substrate;
a first silicon layer formed on said layer of mixed rare earth oxide;
a second layer of mixed rare earth oxide formed on the first silicon layer; and
a second silicon layer formed on said second layer of mixed rare earth oxide.
2. The optical device of claim 1, wherein a lattice constant of said mixed rare earth oxide is substantially a multiple of a lattice constant of silicon.
3. A light-emitting device, comprising:
a first layer of mixed rare earth oxide on a silicon substrate, said mixed rare earth oxide being single crystal and lattice matched to said silicon substrate;
a quantum well comprising a first silicon layer formed on said layer of mixed rare earth oxide;
a second layer of mixed rare earth oxide formed on the first silicon layer; and
a second silicon layer formed on said second layer of mixed rare earth oxide.
4. The light-emitting device of claim 3, wherein said first silicon layer has a thickness of less than 20 nm.
5. The light-emitting device of claim 3, wherein said second silicon layer has a thickness of less than 20 nm.
6. The light-emitting device of claim 3, wherein a lattice constant of said first and second layers of mixed rare earth oxide is substantially a multiple of a lattice constant of said first and second silicon layers.
7. The light-emitting device of claim 3, wherein said first and second layers of mixed rare earth oxide and said first and second silicon layers have a thickness of less than 5 nm, and form a super lattice structure that acts as a luminescent material.