Dynamic bandwidth assignment system and dynamic bandwidth assignment method capable of reducing cell transmission delay

Abstract

A dynamic bandwidth assignment system includes a network unit for carrying out cell slot assignment, and a network termination for transmitting cells to the network unit by means of cell slots assigned by the network unit. When the number of consecutive valid cells the network unit receives from the network terminations exceeds a predetermined threshold value, the network unit increases the number of the cell slots to be assigned to the network termination. The system can solve a problem of a conventional system in that it is unavoidable that a cell transfer delay and a bursting tendency of cells are statistically increased.

1 - 14 . (canceled)  
   
   
       15 . A dynamic bandwidth assignment system including a network unit configured to control cell slot assignment, and a network termination unit configured to transmit cells to the network unit using cell slots assigned by the network unit, the transmitted cells including valid cells having a first cell header and idle cells having a second cell header, said network unit comprising: 
 a detection unit configured to detect valid cells and idle cells received from said network termination unit based on cell headers in the received cells;    a decision unit configured to output a decision result on a cell slot assignment to the network termination unit based on the valid cells and idle cells detected by said detection unit; and    a cell slot assignment unit configured to control the cell slot assignment to the network termination unit in response to the decision result of said decision unit.    
   
   
       16 . The dynamic bandwidth assignment system according to  claim 15 , wherein said decision unit is configured to supply the decision result to said cell slot assignment unit when a number of consecutive valid cells said network unit receives from said network termination unit exceeds a first predetermined threshold value, and wherein said cell slot assignment unit is configured to increase the number of the cell slots to be assigned to said network termination unit in response to the decision result.  
   
   
       17 . The dynamic bandwidth assignment system according to  claim 15 , wherein said decision unit is configured to supply the decision result to said cell slot assignment unit when a number of valid cells said network unit receives from said network termination unit in a decision period becomes less than a second predetermined threshold value, and wherein said cell slot assignment unit is configured to reduce a number of the cell slots to be assigned to said network termination unit in response to the decision result.  
   
   
       18 . The dynamic bandwidth assignment system according to  claim 15 , wherein said decision unit is configured to supply the decision result to said cell slot assignment unit when a number of valid cells said network unit receives from said network termination unit in a decision period exceeds a first predetermined threshold value, and wherein said cell slot assignment unit is configured to increase a number of the cell slots to be assigned to said network termination unit in response to the decision result.  
   
   
       19 . The dynamic bandwidth assignment system according to  claim 16 , wherein said decision unit is configured to determine the first threshold value in accordance with the total number of cells said network unit receives from said network termination unit in a decision period.  
   
   
       20 . The dynamic bandwidth assignment system according to  claim 17 , wherein said decision unit is configured to determine the second threshold value in accordance with the total number of cells said network unit receives from said network termination unit in the decision period.  
   
   
       21 . The dynamic bandwidth assignment system according to  claim 18 , wherein said decision unit is configured to determine the first threshold value in accordance with the total number of cells said network unit receives from said network termination unit in the decision period.  
   
   
       22 . A dynamic bandwidth assignment method in a network unit comprising: 
 receiving, from a network termination, cells including valid cells having a first cell header and idle cells having a second cell header;    detecting valid cells and idle cells based on cell headers in the received cells;    producing a decision result on a cell slot assignment to the network termination unit based on the detected valid cells and idle cells; and    controlling cell slot assignment to the network termination unit in response to the decision result.    
   
   
       23 . The dynamic bandwidth assignment method according to  claim 22 , wherein when a number of consecutive valid cells said network unit receives from said network termination unit exceeds a first predetermined threshold value, the step of controlling cell slot assignment increases the number of the cell slots to be assigned to said network termination unit in response to the decision result.  
   
   
       24 . The dynamic bandwidth assignment method according to  claim 22 , wherein when a number of the valid cells said network unit receives from said network termination unit becomes less than a second predetermined threshold value, the step of controlling cell slot assignment decreases the number of the cell slots to be assigned to said network termination unit in response to the decision result.  
   
   
       25 . The dynamic bandwidth assignment method according to  claim 22 , wherein when a number of the valid cells said network unit receives from said network termination unit exceeds a first predetermined threshold value, the step of controlling cell slot assignment increases the number of the cell slots to be assigned to said network termination unit in response to the decision result.  
   
   
       26 . The dynamic bandwidth assignment method according to  claim 23 , wherein the first threshold value is determined in accordance with the total number of cells said network unit receives from said network termination unit in the decision period.  
   
   
       27 . The dynamic bandwidth assignment method according to  claim 24 , wherein the second threshold value is determined in accordance with the total number of cells said network unit receives from said network termination unit in the decision period.  
   
   
       28 . The dynamic bandwidth assignment method according to  claim 25 , wherein the first threshold value is determined in accordance with the total number of cells said network unit receives from said network termination unit in the decision period.  
   
   
       29 . A dynamic bandwidth assignment system including a network unit configured to control cell slot assignment, and a network termination unit configured to transmit cells to the network unit via an Asynchronous Transfer Mode Passive Optical Network using cell slots assigned by the network unit, said network unit comprising: 
 a detection unit configured to detect valid cells and idle cells said network unit receives from said network termination unit;    a decision unit configured to output a decision result on a cell slot assignment to the network termination unit based on the valid cells and idle cells detected by said detection unit; and    a cell slot assignment unit configured to control the cell slot assignment to the network termination unit based on the decision result of said decision unit.