Timing Alignment in an LTE System

Abstract

A method for use in a user terminal in a cellular communications system. According to the method, the user terminal applies a first timing advance value to its transmissions to a controlling node, and the user terminal requests communication with the controlling node in a contention based procedure by transmitting an access request (MSG 1 ), in response to which the controlling node transmits an initiation message (MSG 2 ) along with a second timing advance value. According to the method, the user terminal uses the first timing advance value if the user terminal loses the contention based procedure, i.e. if the controlling node subsequently continues the initiated communication with said other user terminal.

What is claimed is: 
     
         1 . A method for use in a user terminal in a cellular communications system, according to which method the user terminal applies a first timing advance value to its transmissions to a controlling node, and according to which method the user terminal requests communication with the controlling node in a contention based procedure by transmitting an access request, and in response the user terminal receives from the controlling node an initiation message along with a second timing advance value, and wherein the method further includes the user terminal using the first timing advance value if the user terminal loses the contention based procedure, wherein the controlling node subsequently continues the initiated communication with another user terminal. 
     
     
         2 . The method of  claim 1 , according to which the user terminal uses the second timing advance value in a message which is subsequent to said initiation message. 
     
     
         3 . The method of  claim 2 , according to which the user terminal uses the second timing advance value if the user terminal wins the contention based procedure. 
     
     
         4 . The method of  claim 1 , according to which the user terminal uses the first timing advance value if the user terminal wins the contention based procedure. 
     
     
         5 . The method of  claim 1 , according to which the user terminal uses the first timing advance value if the first timing advance value is considered valid by the user terminal. 
     
     
         6 . The method of  claim 5 , according to which a given timing advance value in a user terminal is associated with a timer and is considered valid for the duration of said timer, the timer being started upon reception of a predefined message from the controlling node, so that each of the first and second timing advance values are associated with respective first and second timers that are started upon reception of respective messages. 
     
     
         7 . The method of  claim 6 , according to which the user terminal lets the timer associated with the first timing advance value continue running after receipt of the message which starts the second timer, and according to which method the user terminal uses the timer value associated with the timing advance value which is subsequently used. 
     
     
         8 . The method of  claim 6 , according to which the user terminal saves the value of the timer associated with the first timing advance value upon reception of the second timing advance value, and if the controlling node subsequently continues the initiated communication with said other user terminal, the user terminal uses a timer value which is the sum of the saved value and the current value of the timer of the second advance value. 
     
     
         9 . The method of  claim 1 , wherein the user terminal is an LTE UE and the controlling node is an LTE eNodeB. 
     
     
         10 . The method of  claim 9 , wherein the method is used in an LTE Random Access procedure. 
     
     
         11 . The method of  claim 1 , according to which, the user terminal which has a first timing advance value that is valid and uses this first timing advance value regardless of receipt of a second timing advance value. 
     
     
         12 . A transceiver for use as a user terminal in a cellular communications system, the transceiver comprising one or more control circuits configured to apply a first timing advance value to its transmissions to a controlling node, request communication with the controlling node in a contention based procedure by transmitting an access request, receive in response an initiation message from the controlling node along with a second timing advance value, and to use the first timing advance value if the user terminal loses the contention based procedure, wherein the controlling node subsequently continues the initiated communication with another user terminal. 
     
     
         13 . The transceiver of  claim 12 , wherein the one or more control circuits are configured to use the second timing advance value in a message which is subsequent to said initiation message. 
     
     
         14 . The transceiver of  claim 13 , wherein the one or more control circuits are configured to use the second timing advance value if the contention based procedure is won by the transceiver. 
     
     
         15 . The transceiver of  claim 12 , wherein the one or more control circuits are configured to use the first timing advance value if the contention based procedure is won by the transceiver. 
     
     
         16 . The transceiver of  claim 12 , wherein the one or more control circuits are configured to check if the first timing advance value is considered valid, and in that case, to apply the first timing advance value. 
     
     
         17 . The transceiver of  claim 16 , wherein the one or more control circuits are configured to associate a given timing advance value with a timer and to consider the timing advance value valid for the duration of said timer, and are further configured to start the timer upon reception of a predefined message from the controlling node, so that each of the first and second timing advance values are associated with respective first and second timers that are started upon reception of respective messages. 
     
     
         18 . The transceiver of  claim 17 , wherein the one or more control circuits are configured to let the timer which is associated with the first timing advance value continue running after receipt of the message which starts the second timer, and to use the timer value that is associated with the timing advance value which is subsequently used by the transceiver. 
     
     
         19 . The transceiver of  claim 17 , wherein the one or more control circuits are configured to save the value of the timer associated with the first timing advance value upon reception of the second timing advance value, and use a timer value which is the sum of the saved value and the current value of the timer of the second advance value, if the controlling node subsequently continues the initiated communication with said other user terminal. 
     
     
         20 . The transceiver of  claim 12 , wherein the transceiver is an LTE UE. 
     
     
         21 . The transceiver of  claim 12 , wherein the one or more control circuits are configured to use the first timing advance value, if the first timing advance value is valid, regardless of receipt of a second timing advance value. 
     
     
         22 . A method in a user terminal configured for use in a wireless communication network, said method comprising:
 maintaining a timing advance value at the user terminal, for use in transmitting to the network on the uplink;   performing a contention-based access procedure, in which the user terminal attempts to access the network and receives new timing advance information as part of said procedure; and   updating the timing advance value at the user terminal according to the new timing advance information, in dependence on whether the user terminal won the contention-based access procedure.