Methods and Apparatus for Fast Downlink Information of Uplink Out-of-Synchronization

Abstract

Information systems, detectors, and methods for a communication link, such as the downlink of a cellular telephone system, reduce the problem of uplink transmit power peaks when the uplink is out of synchronization (OoS). One method of indicating that a first link to a communication node is OoS includes the step of including an OoS signal in signals that are sent by the node on a second link. The OoS signal includes at least one data bit transmitted by the node that indicates that the first link is synchronized or OoS. A method of determining that a first link to a communication node is OoS includes the step of detecting an OoS signal in signals that are sent by the node on a second link. The OoS signal includes at least one data bit that indicates that the first link is synchronized or OoS.

1 .- 42 . (canceled) 
     
     
         43 . A method of indicating that a first communication link is out of synchronization (OoS), comprising the step of including an OoS signal in control signals that are sent on a second communication link, the OoS signal indicating that the first link is either synchronized or OoS and the first link having been synchronized at least at one time before the OoS signal is included, wherein the OoS signal comprises:
 a change-of-sign of at least one symbol transmitted on the second communication link, or   a power level offset between information elements included in a signal sent on the second communication link.   
     
     
         44 . The method of  claim 43 , wherein the at least one symbol is a pilot symbol transmitted on a dedicated physical channel (DPCH). 
     
     
         45 . The method of  claim 44 , wherein when the first communication link is synchronized, the signs of DPCH pilot symbols are the same as the signs of pilot symbols transmitted on a common pilot channel. 
     
     
         46 . The method of  claim 43 , wherein the information elements include pilot symbols transmitted on a dedicated physical channel and transmit power control commands. 
     
     
         47 . A method of determining that a first communication link is out of synchronization (OoS), comprising the step of detecting an OoS signal in signals that are sent on a second communication link, the OoS signal indicating that the first communication link is either synchronized or OoS, wherein the OoS signal comprises:
 a change-of-sign of at least one symbol transmitted on the second communication link, or   a power level offset between information elements included in a signal sent on the second communication link.   
     
     
         48 . The method of  claim 47 , wherein the at least one symbol is a pilot symbol transmitted on a dedicated physical channel (DPCH). 
     
     
         49 . The method of  claim 48 , wherein when the first communication link is synchronized, the signs of DPCH pilot symbols are the same as the signs of pilot symbols transmitted on a common pilot channel (CPICH), and the method further includes the step of comparing signs of such DPCH pilot symbols to signs of CPICH pilot symbols. 
     
     
         50 . The method of  claim 47 , wherein the information elements include pilot symbols transmitted on a dedicated physical channel and transmit power control commands. 
     
     
         51 . A communication node adapted to transmit and receive electromagnetic signals, comprising:
 a detector adapted to determine whether a first received link is synchronized; and   a device, responsive to the detector, adapted to include an out-of-synchronization (OoS) signal in signals transmitted on a second link, the OoS signal indicating that the first received link is synchronized or OoS, wherein the OoS signal comprises:
 a change-of-sign of at least one symbol transmitted on the second link, or 
 a power level offset between information elements included in a signal sent on the second link. 
   
     
     
         52 . The node of  claim 51 , wherein the at least one symbol is a pilot symbol transmitted by the node on a dedicated physical channel (DPCH). 
     
     
         53 . The node of  claim 52 , wherein when the first received link is synchronized, the signs of DPCH pilot symbols are the same as the signs of pilot symbols transmitted on a common pilot channel. 
     
     
         54 . The node of  claim 51 , wherein the node is a base station. 
     
     
         55 . The node of  claim 51 , wherein the information elements include pilot symbols transmitted on a dedicated physical channel and transmit power control commands. 
     
     
         56 . A communication terminal adapted to transmit and receive electromagnetic signals, comprising:
 a device adapted to recover information, including pilot symbols and transmit power control (TPC) commands, from electromagnetic signals received on a first link;   a control unit adapted to control a power level of electromagnetic signals transmitted by the terminal on a second link based on the TPC commands; and   a detector adapted to monitor recovered information for an out of synchronization (OoS) signal in signals received on the first link, the OoS signal indicating that the second link is synchronized or OoS, wherein the OoS signal comprises:
 a change-of-sign of at least one symbol transmitted on the second link, or 
 a power level offset between information elements included in a signal sent on the second link. 
   
     
     
         57 . The terminal of  claim 56 , wherein the at least one symbol is a pilot symbol transmitted on a dedicated physical channel (DPCH). 
     
     
         58 . The terminal of  claim 57 , wherein when the second link is synchronized, the signs of DPCH pilot symbols are the same as the signs of pilot symbols received on a common pilot channel (CPICH), and the terminal further includes a comparator adapted to compare signs of such DPCH pilot symbols to signs of CPICH pilot symbols. 
     
     
         59 . The terminal of  claim 57 , wherein the information elements include pilot symbols transmitted on a dedicated physical channel and transmit power control commands. 
     
     
         60 . A communication system, comprising:
 at least one base station adapted to propagate and receive electromagnetic signals, wherein the electromagnetic signals include at least one common pilot channel (CPICH) and at least one dedicated physical channel (DPCH); and   at least one user equipment adapted to propagate to and receive electromagnetic signals from the at least one base station, wherein the user equipment includes:
 a device adapted to recover information from the CPICH and the DPCH, including pilot symbols and transmit power control (TPC) commands; and 
 a control unit adapted to control a power level of a transmitter in the user equipment based on the TPC commands; 
   wherein the base station includes a detector adapted to determine whether an uplink (UL) from the user equipment is synchronized; and when the detector determines the UL is out of synchronization (OoS), the base station alters the DPCH pilot symbols propagated to the user equipment.   
     
     
         61 . The communication system of  claim 60 , wherein the DPCH pilot symbols are altered by a factor that depends on whether the UL is synchronized. 
     
     
         62 . The communication system of  claim 61 , wherein the user equipment is adapted to determine the factor of DPCH pilot symbols recovered by the device, and based on the factor determined, to base the power level of the transmitter on either the TPC commands or not. 
     
     
         63 . A method of indicating that a first link to a communication node is out of synchronization (OoS), comprising the steps of:
 checking, by the node, whether the first link is OoS;   if the first link is synchronized, transmitting pilot symbols having a first scale factor on a second link; and   if the first link is OoS, transmitting pilot symbols having a second scale factor on the second link.   
     
     
         64 . The method of  claim 63 , wherein the second link is a dedicated physical channel (DPCH), and the method further includes the steps of:
 transmitting, by the node as long as the first link is OoS, DPCH pilot symbols having the second scale factor; and   changing, by the node when the first link is synchronized, the scale factor of the DPCH pilot symbols to the first scale factor.   
     
     
         65 . The method of  claim 63 , further comprising the steps of fixing a transmit power level on the second link at a particular level and transmitting a sequence of transmit power control commands on the second link. 
     
     
         66 . The method of  claim 63 , further comprising the steps of transmitting the pilot symbols at a first power level and transmitting a second information element at a second power level different from the first power level, thereby indicating that the first link is OoS. 
     
     
         67 . The method of  claim 66 , wherein the second information element is a transmit power control command. 
     
     
         68 . A method of controlling transmit power on a first link to a communication node, comprising the steps of:
 detecting a scale factor of pilot symbols received on a second link; wherein if the first link is synchronized, pilot symbols having a first scale factor are detected, and if the first link is out of synchronization (OoS), pilot symbols having a second scale factor are detected;   if pilot symbols having the second scale factor are detected, limiting transmit power control (TPC) commands received on the second link in a TPC command combination; and   if pilot symbols having the first scale factor are detected, including TPC commands received on the second link in the TPC command combination.   
     
     
         69 . The method of  claim 68 , further including the step of including an information element in a message sent on the first link, wherein the information element indicates an ability to detect the scale factor of second link pilot symbols. 
     
     
         70 . The method of  claim 68 , wherein the method is carried out by a user equipment in a soft handover in a wideband code division multiple access communication system. 
     
     
         71 . The method of  claim 70 , wherein the scale factor is detected by examining channel estimates obtained from pilot symbols received on a dedicated physical channel (DPCH) and from pilot symbols received on a common pilot channel (CPICH) in at least one time slot. 
     
     
         72 . The method of  claim 71 , wherein the scale factor is detected by comparing signs of DPCH and CPICH channel estimates. 
     
     
         73 . The method of  claim 70 , wherein the step of detecting the scale factor includes comparing power levels of pilot symbols received on a dedicated physical channel with power levels of received transmit power control commands. 
     
     
         74 . A method in a user equipment of determining that an uplink (UL) to a communication node is out of synchronization (OoS), comprising the steps of:
 comparing newer transmit power control (TPC) commands to older TPC commands received from the node;   if an output signal generated from the comparing step exceeds a threshold, measuring a signal-to-interference ratio (SIR) for a downlink (DL) from the node; and   determining, based on the measured SIR, whether the node is following TPC commands sent to the node in the UL;   wherein if the node is not following the TPC commands, OoS is determined.   
     
     
         75 . The method of  claim 74 , wherein TPC commands are compared by calculating ratios between TPC commands during a latest and preceding time slots. 
     
     
         76 . The method of  claim 74 , wherein the determining step includes examining differences between SIRs of consecutive time slots and correlating the differences to the TPC commands sent to the node in the UL. 
     
     
         77 . The method of  claim 76 , wherein the differences are filtered, and filtered differences are compared to a threshold.