Method of pre-computation of candidate handoff cell list for cellular communications
First Claim
1. A method of generating a candidate handoff cell list for controlling an individual subscriber unit in performing handoff determination in a cellular communication system, said method comprising:
- selecting an active current cell for which said candidate handoff cell list will be generated, said active current cell being a servicing cell from which said individual subscriber unit would desirably handoff communications;
adding a plurality of active neighboring cells to said candidate handoff cell list, said plurality of active neighboring cells being entries to said candidate handoff cell list;
generating a velocity vector for each of said entries of said candidate handoff cell list;
comparing an evaluation angle formed by each of said velocity vectors with said active current cell for each of said entries of said candidate handoff cell list; and
deleting said entries of said candidate handoff cell list wherein said evaluation angle exceeds a threshold value.
3 Assignments
0 Petitions
Accused Products
Abstract
A satellite cellular communication system includes satellites in motion that project cells upon the surface of the Earth. These cells are in motion and pass over individual subscriber units (26) engaged in communications, thus requiring individual subscriber units (26) to perform handoffs as an active current cell (300) currently servicing them advances. Selection of a subsequent servicing cell requires evaluation of active neighboring cells. A pre-computation of candidate cells is performed in advance according to a cell activation schedule. Active neighboring cells of an active current cell (300) are evaluated and prioritized in advance of individual subscriber unit'"'"'s need for them. A candidate handoff cell list is then delivered to a satellite (12). A candidate handoff cell list is broadcast to all individual subscriber units (26) located within active current cell (300) for use in handoff decisions.
-
Citations
17 Claims
-
1. A method of generating a candidate handoff cell list for controlling an individual subscriber unit in performing handoff determination in a cellular communication system, said method comprising:
-
selecting an active current cell for which said candidate handoff cell list will be generated, said active current cell being a servicing cell from which said individual subscriber unit would desirably handoff communications; adding a plurality of active neighboring cells to said candidate handoff cell list, said plurality of active neighboring cells being entries to said candidate handoff cell list; generating a velocity vector for each of said entries of said candidate handoff cell list; comparing an evaluation angle formed by each of said velocity vectors with said active current cell for each of said entries of said candidate handoff cell list; and deleting said entries of said candidate handoff cell list wherein said evaluation angle exceeds a threshold value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
-
-
12. A method of generating a candidate handoff cell list for use by an individual subscriber unit in a satellite cellular communication system wherein said satellite cellular communication system comprises a plurality of orbiting satellites wherein each of said plurality of orbiting satellites projects a plurality of cells upon the Earth, said plurality of cells being in motion with respect to the Earth, said plurality of cells being operative according to a cell activation schedule, said motion requiring said individual subscriber unit to perform a handoff from a first cell to a second cell, said method comprising the steps of:
-
retrieving said cell activation schedule; selecting an active current cell for which to generate a candidate handoff cell list, said active current cell corresponding to said first cell; adding a plurality of active neighboring cells to said candidate handoff cell list, said plurality of active neighboring cells being entries to said candidate handoff cell list, said active neighboring cells being adjacent or nearby said active current cell and said active neighboring cells being scheduled to be operative according to said cell activation schedule; generating a velocity vector for each of said entries of said candidate handoff cell list; comparing an evaluation angle formed by each of said velocity vectors with said active current cell for each of said entries of said candidate handoff cell list; and deleting said entries of said candidate handoff cell list wherein said evaluation angle exceeds a threshold value. - View Dependent Claims (13, 14, 15)
-
-
16. A method of managing a satellite cellular communication system comprising a plurality of orbiting satellites wherein each of said plurality of orbiting satellites projects a plurality of cells upon the Earth, as said plurality of orbiting satellites converge while orbiting, said plurality of cells of said plurality of orbiting satellites overlaps others of said plurality of cells, said method comprising the steps of:
-
generating at a gateway a cell activation schedule defining a plurality of active current cells, said plurality of active current cells being comprised of said plurality of cells of said plurality of orbiting satellites that are not overlapped by others of said plurality of cells and some of said plurality of cells that are overlapped by others of said plurality of cells; generating a velocity vector for each of said entries of said candidate handoff cell list; comparing an evaluation angle formed by each of said velocity vectors with said active current cell for each of said entries of said candidate handoff cell list; deleting said entries of said candidate handoff cell list wherein said evaluation angle exceeds a threshold value; delivering said cell activation schedule and said candidate handoff cell list to said plurality of orbiting satellites; activating, at said plurality of orbiting satellites, said plurality of active current cells according to said cell activation schedule; transmitting said candidate handoff cell list corresponding to each of said plurality of active current cells to a plurality of individual subscriber units located in each of said plurality of active current cells; receiving at said plurality of individual subscriber units, said candidate handoff cell list; and said plurality of individual subscriber units employing said candidate handoff cell list in handoff decisions as said plurality of active current cells continue in motion with respect to said plurality of individual subscriber units. - View Dependent Claims (17)
-
Specification