Processing of random access preamble sequences

Abstract

The present disclosure relates to random access in wireless communication systems, and in particular to a wireless device, a preamble receiver, and methods for processing random access preamble signals. A disclosed method in a wireless device comprises generating (S 11 ) one or more identical short sequences having a same time duration as an OFDM symbol used for carrying data traffic in a radio access network of the wireless device. The method also comprises generating (S 12 ) at least one offset indicator sequence different from each of the short sequences, and constructing (S 13 ) the preamble sequence by concatenating the at least one offset indicator sequence and the one or more identical short sequences in time, such that each of the at least one offset indicator sequence has a respective pre-determined location in the preamble sequence.

1 . A method in a wireless communication device (WCD) for processing a preamble sequence, the method comprising:
 generating, by the WCD, a plurality of identical short sequences, each of the short sequences having a same time duration as an orthogonal frequency division multiplexing (OFDM) symbol used for carrying data traffic in a radio access network of the WCD,   generating, by the WCD, a means for enabling a network node in the radio access network of the WCD that receives the preamble sequence to resolve an ambiguity in an estimate of the actual arrival time of the preamble sequence, said means being different from each of the short sequences,   constructing, by the WCD, the preamble sequence by concatenating said means and the plurality of identical short sequences in time, such that said means has a respective pre-determined location in the preamble sequence, and   wirelessly transmitting, by the WCD, the constructed preamble sequence for reception by a receiver of the network node in the radio access network of the WCD.   
     
     
         2 . The method according to  claim 1 , wherein said means for enabling the network node to resolve the ambiguity comprises at least one offset indicator sequence and said at least one offset indicator sequence has a zero amplitude. 
     
     
         3 . The method of  claim 2 , wherein the at least one offset indicator sequence has a time duration that is greater than or equal to T, wherein T is the time duration of each of the identical short sequences. 
     
     
         4 . The method of  claim 3 , wherein T is less than or equal to 1/15,000 seconds. 
     
     
         5 . The method according to  claim 1 , wherein said means for enabling the network node to resolve the ambiguity comprises a first offset indicator sequence having a respective first pre-determined location at an end of the preamble sequence. 
     
     
         6 . The method according to  claim 5 , wherein said means for enabling the network node to resolve the ambiguity comprises a second offset indicator sequence having a respective second pre-determined location in the preamble sequence such that there is at least one short sequence located before, and at least one other short sequence located after, the second offset indicator sequence in the preamble sequence. 
     
     
         7 . The method according to  claim 1 , wherein the constructed preamble sequence occupies two or more sub-frames of a radio access technology of the radio access network of the WCD. 
     
     
         8 . The method of  claim 1 , wherein
 the constructed preamble sequence consists of N number of said identical short sequences and M number of said offset indicator sequences,   N is greater than or equal to 2,   M is greater than or equal to 1, and   N is greater than M.   
     
     
         9 . The method of  claim 8 , wherein M is equal to 1. 
     
     
         10 . The method of  claim 8 , wherein M is equal to 2 and N is greater than 2. 
     
     
         11 . A computer program product comprising a non-transitory computer readable medium storing computer program code which, when executed in a WCD, causes the WCD to execute a method according to  claim 1 . 
     
     
         12 . A wireless communication device (WCD) arranged to process a preamble sequence, the WCD comprising:
 a transmitter for transmitting wireless signals; and   a processing system, comprising a processor, coupled to the transmitter, said processing system being configured to:   generate a plurality of identical short sequences, each of the short sequences having a same time duration as an orthogonal frequency-division multiplexing (OFDM) symbol used for carrying data traffic in a radio access network of the WCD,   generate a means for enabling a network node in the radio access network of the WCD that receives the preamble sequence to resolve an ambiguity in an estimate of the actual arrival time of the preamble sequence,   construct the preamble sequence by concatenating said generated means and the plurality of identical short sequences in time, such that said means has a respective pre-determined location in the preamble sequence, and   employ the transmitter to transmit the constructed preamble sequence for reception by a receiver of the network node in the radio access network of the WCD.   
     
     
         13 . The WCD according to  claim 12 , wherein said means for enabling the network node to resolve the ambiguity comprises at least one offset indicator sequence and said at least one offset indicator sequence has a zero amplitude. 
     
     
         14 . The WCD according to  claim 12 , wherein said respective first pre-determined location in the preamble sequence is at an end of the preamble sequence. 
     
     
         15 . The WCD according to  claim 12 , wherein the processing system is configured to generate a preamble sequence comprising a second offset indicator sequence having a respective second pre-determined location in the preamble sequence, and at least two short sequences, such that there is at least one short sequence located before, and at least one other short sequence located after the second offset indicator sequence in the preamble sequence. 
     
     
         16 . A preamble transmitter and receiver system, comprising at least one WCD according to  claim 12 , and at least one preamble receiver.