Method and system for managing WTRU resources in wireless communication systems

Abstract

A method and apparatus for reducing the number of time slots allocated to a wireless transmit/receive unit (WTRU) by a serving cell in a time division duplex (TDD) wireless communication system that comprises a plurality of cells and a radio network controller (RNC) wherein each cell serves WTRUs in a coverage area of the cell and the RNC controls radio resource assignments in the cells comprises the RNC determining whether it is possible to reduce the number of time slots allocated to a target WTRU based on an interference level at each time slot in the serving cell. The RNC reduces the number of time slots allocated to the target WTRU where the determination is positive.

1 . A method for reducing the number of time slots allocated to a wireless transmit/receive unit (VVTRU) by a serving cell in a time division duplex (TDD) wireless communication system, the wireless communication system comprising a plurality of cells and a radio network controller (RNC) wherein each cell serves WTRUs in a coverage area of the cell and the RNC controls radio resource assignments in the cells, the method comprising: 
 (a) the RNC determining whether it is possible to reduce the number of time slots allocated to a target WTRU based on an interference level at each time slot in the serving cell; and    (b) the RNC reducing the number of time slots allocated to the target WTRU where the determination at step (a) is positive.    
   
   
       2 . The method of  claim 1  wherein the RNC performs the determination at step (a) by comparing a current level of interference at each time slot with a maximum allowable level of interference.  
   
   
       3 . The method of  claim 1  further comprising: 
 (c) if the determination at step (a) is negative, the RNC determining whether WTRUs in neighboring cells may be reallocated to different time slots to reduce interference perceived in the serving cell due to the neighboring cells;    (d) if the determination at step (c) is positive, the RNC reallocating WTRUs in neighboring cells to different time slots; and    (e) repeating steps (a)-(d) where WTRUs in at least one of the neighboring cells are reallocated.    
   
   
       4 . The method of  claim 3  wherein the RNC reallocates WTRUs in a time slot having a transmission power level exceeding a predetermined threshold to other time slots.  
   
   
       5 . The method of  claim 3  further comprising: 
 (f) if the determination at step (c) is negative, the RNC determining whether WTRUs in the serving cell may be reallocated to different time slots to reduce interference level at the time slots in the serving cell;    (g) if the determination at step (f) is positive, the RNC reallocates at least one WTRU in the serving cell to different time slots;    (h) repeating steps (a)-(g) if at least one WTRU in the serving cell is reallocated; and    (i) if the determination at step (f) is negative, the RNC terminates the process.    
   
   
       6 . The method of  claim 5  wherein at step (g) a WTRU with a highest transmission power is reallocated to a time slot with the lowest interference.  
   
   
       7 . The method of  claim 5  wherein the RNC waits for a predetermined time period before reallocating WTRUs in the serving cell at step (g).  
   
   
       8 . The method of  claim 1  wherein the RNC periodically repeats the process.  
   
   
       9 . A radio network controller (RNC) for reducing the number of time slots allocated to a wireless transmit/receive unit (WTRU) by a serving cell in a time division duplex (TDD) wireless communication system, the wireless communication system comprising a plurality of cells and an RNC wherein each cell serves WTRUs in a coverage area of the cell and the RNC controls radio resource assignments in the cells, the RNC comprising: 
 means capable of monitoring an interference level at time slots of the serving cell; and    means capable of reducing the number of time slots allocated to a target WTRU in the serving cell based on the interference level at each time slot.    
   
   
       10 . The RNC of  claim 9  wherein the RNC compares a current level of interference at each time slot with a maximum allowable level of interference in order to determine whether it is possible to reduce the number of time slots allocated to the target WTRU.  
   
   
       11 . The RNC of  claim 9  further comprising: 
 means capable of monitoring neighboring cells; and    means capable of reallocating WTRUs in neighboring cells to different time slots,    whereby the RNC reduces interference in the serving cell due to the neighboring cells and attempts to reduce the number of time slots allocated to the target WTRU in the serving cell.    
   
   
       12 . The RNC of  claim 11  wherein the RNC reallocates WTRUs in a time slot having a transmission power level exceeding a predetermined threshold to other time slots.  
   
   
       13 . The RNC of  claim 11  further comprising a means capable of reallocating at least one WTRU in the serving cell to different time slots based on an interference level of each time slot in the serving cell, whereby the RNC attempts to reduce the number of time slots for the WTRU in the serving cell.  
   
   
       14 . The RNC of  claim 13  wherein the RNC reallocates a WTRU with the highest transmission power to a time slot with the lowest interference.  
   
   
       15 . The RNC of  claim 13  wherein the RNC waits for a predetermined time period before reallocating WTRUs in the serving cell.  
   
   
       16 . The RNC of  claim 9  wherein the RNC periodically monitors the interference level at the serving cell and determines whether to reduce the number of time slots allocated to the WTRU.