Controlling Inter-Cell Interference In Forward Access Channel (Cell_FACH) State

Abstract

Since common E-DCH resources may be assigned from a single Node B, uplink macro-diversity may not be possible between neighboring Node B's. In addition, a user equipment (UE) assigned a common E-DCH resource may not be allowed to perform cell reselection. Thus, maintaining the assignment of a common E-DCH resource to a given UE for more than a few hundred milliseconds may result in unacceptable inter-cell interference, for example, when the UE moves closer to a neighboring cell controlled by a non-serving Node B. To overcome inter-cell interference and allow a more extensive utilization of the Cell_FACH state, a method may be used to detect and/or control inter-cell interference.

What is claimed: 
     
         1 . A method for detecting inter-cell interference, the method comprising:
 obtaining, via a WTRU, a set of characteristics that identifies interference to a common enhanced dedicated cannel (E-DCH) resource;   determining a condition to apply an interference indication; and   receiving the interference indication using the set of characteristics of the interference.   
     
     
         2 . The method of  claim 1 , wherein receiving the interference indication using the set of characteristics occurs when the condition is met. 
     
     
         3 . The method of  claim 1 , further comprising applying the interference indication when the condition is met. 
     
     
         4 . The method of  claim 1 , wherein receiving the interference indication comprises receiving the interference indication from an enhanced relative grant channel (E-RGCH) using the set of characteristics. 
     
     
         5 . The method of  claim 1 , wherein obtaining a set of characteristics comprises receiving a mapping between the common E-DCH resource and the set of characteristics. 
     
     
         6 . The method of  claim 1 , wherein obtaining a set of characteristics comprises receiving characteristics for all common E-DCH resources. 
     
     
         7 . The method of  claim 1 , wherein obtaining a set of characteristics comprises receiving characteristics for a subset of common E-DCH resources. 
     
     
         8 . The method of  claim 1 , wherein the set of characteristics comprises a signature sequence and a channelization code. 
     
     
         9 . The method of  claim 1 , wherein determining a condition to apply the interference indication comprises determining a signal level or signal quality that should be met or exceeded. 
     
     
         10 . The method of  claim 1 , wherein determining a condition to apply the interference indication comprises determining a signal level or signal quality of a reference signal that is transmitted should meet or exceed. 
     
     
         11 . The method of  claim 1 , wherein determining a condition to apply the interference indication comprises determining a signal level or signal quality that a victim cell signal should meet or exceed. 
     
     
         12 . The method of  claim 1 , wherein the interference indication indicates that a victim cell is experiencing inter-cell interference. 
     
     
         13 . A method of controlling inter-cell interference, the method comprising:
 obtaining, via a WTRU, a set of characteristics that identifies interference to a common enhanced dedicated cannel (E-DCH) resource;   receiving an interference indication using the set of characteristics of the interference; and   applying the interference indication when a condition is met.   
     
     
         14 . The method of  claim 13 , wherein applying the interference indication comprises reducing a grant. 
     
     
         15 . The method of  claim 13 , wherein applying the interference indication comprises reducing a maximum enhanced dedicated physical data channel (E-DPDCH) power. 
     
     
         16 . The method of  claim 13 , wherein applying the interference indication comprises ceasing to transmit on E-DPDCH. 
     
     
         17 . The method of  claim 13 , wherein applying the interference indication comprises deactivating a hybrid automatic repeat request (HARQ) process that was used in a previous transmission. 
     
     
         18 . The method of  claim 13 , wherein receiving the interference indication using the set of characteristics occurs when the condition is met. 
     
     
         19 . A wireless transmit/receive unit (WTRU) for detecting inter-cell interference, the WTRU comprising:
 a receiver configured to obtain a set of characteristics for an interference applicable to a common enhanced dedicated cannel (E-DCH) resource; and   a processor configured to:
 determine a condition to apply an interference indication; and 
 receive the interference indication using the set of characteristics of the interference. 
   
     
     
         20 . The WTRU  claim 19 , wherein the processor determines a condition to apply the interference indication comprises determining a signal level or signal quality that should be met or exceeded.