User Equipment, Network Node and Methods Therein for Handling Preamble Transmissions on a Random Access Channel in a Radio Communications Network

Abstract

The embodiments herein relate to a user equipment ( 121 ) and a method performed by the UE ( 121 ) for performing preamble transmissions, on a random access channel, to a network node ( 110 ). The method comprising: determining ( 801 ) a starting subframe for the preamble transmissions based on at least a system frame number (SFN), a number of times (R) the preamble transmissions is to be repeated and a random access channel configuration, and transmitting ( 802 ), to the network node ( 121 ) the preamble repeatedly starting in the determined starting subframe. The embodiments herein also relate to a network node ( 110 ) and a method performed by the network node ( 110 ).

1 . A method performed by a user equipment, UE, for performing preamble transmissions, on a random access channel, to a network node, the method comprising:
 determining a starting subframe for the preamble transmission(s) based on at least:
 a system frame number, SFN, received from the network node; 
 a number of times, R, the preamble transmission is to be repeated; 
 a random access channel configuration and transmitting, to the network node, the preamble repeatedly starting in the determined starting subframe. 
   
     
     
         2 . The method according to  claim 1  wherein determining the starting subframe based on the random access channel configuration comprises determining the starting subframe based on a first offset being dependent on the random access channel configuration. 
     
     
         3 . The method according to  claim 1  wherein determining further comprising determining the starting subframe based on a second offset being a cell identifier such as, a physical cell identity, PCI, received during synchronization with the network node, or the second offset is a cell identity received in a system information block from the network, or the second offset is determined by the UE based on a physical-layer cell identity. 
     
     
         4 . The method according to anyone of  claim 1  wherein determining further comprising determining the starting subframe based on a preamble sequence dependent offset; wherein the preamble sequence dependent offset is a function of a number of available preambles for the number of times the preamble transmission is to be repeated, or the preamble sequence dependent offset is a function of a physical random access channel sequence index. 
     
     
         5 . The method according to  claim 2  comprising determining the starting subframe for a frame with SFN as any subframe i fulfilling:
   0=(( SFN+T )· N+i ) mod  R  
 
 wherein, 
 i is a subframe comprising radio resources configured for the random access channel in frame SFN, wherein i=0, . . . ,NSFN−1; 
 T is the first offset dependent on the random access channel configuration and takes value T=1 if radio resources configured for the random access channel are available in only odd-number subframes, otherwise T=0; 
 NSFN is the number of subframes comprising at least one random access channel resource in frame with SFN; 
 N is the average number of subframes comprising at least one random access channel resource; 
 T, N and NSFN being derived from the random access channel configuration provided by the network; and 
 mod is a modulo operation. 
 
     
     
         6 . The method according to  claim 3  comprising determining the starting subframe for a frame with SFN as any subframe i fulfilling:
   0=(( SFN+T )· N+i+K ) mod  R  
 
 wherein, 
 i is a subframe comprising radio resources configured for the random access channel in a frame SFN, wherein i=0, . . . , NSFN−1; 
 T is a first offset dependent on the random access channel configuration and takes value T=1 if radio resources configured for the random access channel are available in only odd-number subframes, otherwise T=0; 
 NSFN is the number of subframes comprising at least one random access channel resource in frame with SFN; 
 N is the average number of subframes comprising at least one random access channel resource; 
 T, N and NSFN being derived from the random access channel configuration provided by the network; 
 K is the second offset, and 
 mod is a modulo operation. 
 
     
     
         7 . A user equipment, for performing preamble transmissions, on a random access channel, to a network node, the user equipment being configured to:
 determine a starting subframe for the preamble transmission(s) based on at least:   a system frame number, SFN, received from the network node;   a number of times, R, the preamble transmission is to be repeated;   a random access channel configuration and transmit, to the network node, the preamble repeatedly starting in the determined starting subframe.   
     
     
         8 . The user equipment according to  claim 7  is configured to determine the starting subframe based on a first offset being dependent on the random access channel configuration. 
     
     
         9 . The user equipment according to  claim 7  is configured to determine the starting subframe based on a second offset being a cell identifier such as, a physical cell identity, PCI, received during synchronization with the network node, or the second offset is a cell identity received in a system information block from the network node, or the second offset is determined by the user equipment based on a physical-layer cell identity. 
     
     
         10 . The user equipment according to  claim 7  is configured to determine the starting subframe based on a preamble sequence dependent offset; wherein the preamble sequence dependent offset is a function of a number of available preambles for the number of times the preamble transmission is to be repeated, or the preamble sequence dependent offset is a function of a physical random access channel sequence index. 
     
     
         11 . The user equipment according to  claim 8  is configured to determine the starting subframe for a frame with SFN as any subframe i fulfilling:
   0=(( SFN+T )· N+i )mod  R  
 
 wherein, 
 i is a subframe comprising radio resources configured for the random access channel in frame SFN, 
 wherein i=0, . . . ,NSFN−1; 
 T is the first offset dependent on the random access channel configuration and takes value T=1 if radio resources configured for the random access channel are available in only odd-number subframes, otherwise T=0; 
 NSFN is the number of subframes comprising at least one random access channel resource in frame with SFN; 
 N is the average number of subframes comprising at least one random access channel resource; 
 T, N and NSFN being derived from the random access channel configuration provided by the network; and 
 mod is a modulo operation. 
 
     
     
         12 . The user equipment according to  claim 9  is configured to determine the starting subframe for a frame with SFN as any subframe i fulfilling:
   0=(( SFN+T )· N+i+K )mod  R  
 
 wherein, 
 i is a subframe comprising radio resources configured for the random access channel in a frame SFN, wherein i=0, . . . , NSFN−1; 
 T is a first offset dependent on the random access channel configuration and takes value T=1 if radio resources configured for the random access channel are available in only odd-number subframes, otherwise T=0; 
 NSFN is the number of subframes comprising at least one random access channel resource in frame with SFN; 
 N is the average number of subframes comprising at least one random access channel resource; 
 T, N and NSFN being derived from the random access channel configuration provided by the network; 
 K is the second offset, and 
 mod is a modulo operation. 
 
     
     
         13 . A method performed by a network node for receiving preamble transmission(s) from a user equipment, UE, on a random access channel, the method comprising:
 transmitting a system frame number, SFN, to the UE and a random access channel configuration to the UE; and   receiving the preamble transmission repeatedly starting in a starting subframe wherein the starting subframe is determined by the UE and the network node based on at least the SFN, the random access channel configuration, and a number of times, R, the preamble transmission is to be repeated.   
     
     
         14 . The method according to  claim 13  wherein the starting subframe is determined based on a first offset being dependent on the random access channel configuration. 
     
     
         15 . The method according to  claim 13  wherein the starting subframe is determined based on a second offset being a cell identifier such as, a physical cell identity, PCI, transmitted to the UE during synchronization with the UE, or the second offset is a cell identity transmitted in a system information block to the UE. 
     
     
         16 . The method according to  claim 15  wherein the starting subframe is determined based on a preamble sequence dependent offset; wherein the preamble sequence dependent offset is a function of a number of available preambles for the number of times the preamble transmission is to be repeated, or the preamble sequence dependent offset is a function of a physical random access channel sequence index. 
     
     
         17 . The method according to  claim 14  wherein the starting subframe is determined for a frame with SFN as any subframe i fulfilling:
   0=(( SFN+T )· N+i ) mod R
 
 wherein, 
 i is a subframe comprising radio resources configured for the random access channel in frame SFN, 
 wherein i=0, . . . ,NSFN−1; 
 T is the first offset dependent on the random access channel configuration and takes value T=1 if radio resources configured for the random access channel are available in only odd-number subframes, otherwise T=0; 
 NSFN is the number of subframes comprising at least one random access channel resource in frame with SFN; 
 N is the average number of subframes comprising at least one random access channel resource; 
 T, N and NSFN being derived from the random access channel configuration provided by the network node to the UE; and 
 mod is a modulo operation. 
 
     
     
         18 . The method according to  claim 15  wherein the starting subframe is determined for a frame with SFN as any subframe i fulfilling:
   0=(( SFN+T )· N+i+K ) mod  R  
 
 wherein, 
 i is a subframe comprising radio resources configured for the random access channel in a frame SFN, 
 wherein i=0, . . . , N SFN −1; 
 T is a first offset dependent on the random access channel configuration and takes value T=1 if radio resources configured for the random access channel are available in only odd-number subframes, otherwise T=0; 
 NSFN is the number of subframes comprising at least one random access channel resource in frame with SFN; 
 N is the average number of subframes comprising at least one random access channel resource; 
 T, N and NSFN being derived from the random access channel configuration provided by the network node to the UE; 
 K is the second offset, and 
 mod is a modulo operation. 
 
     
     
         19 . A network node for receiving preamble transmission(s) from a user equipment, UE, on a random access channel, the network node being configured to:
 transmit a system frame number, SFN, to the UE and a random access channel configuration to the UE,   receive the preamble transmission repeatedly starting in a starting subframe wherein the starting subframe is determined by the UE and the network based on the SFN, the random access channel configuration, the offset value and a number of times, R, the preamble transmission is to be repeated.   
     
     
         20 . The network node according to  claim 19  wherein the starting subframe is determined based on a first offset being dependent on the random access channel configuration. 
     
     
         21 . The network node according to  claim 19  wherein the starting subframe is determined based on a second offset being a cell identifier such as, a physical cell identity, PCI, transmitted to the UE during synchronization with the UE, or the second offset is a cell identity transmitted in a system information block to the UE. 
     
     
         22 . The network node according to anyone of  claims 19   claim 19  wherein the starting subframe is determined based on a preamble sequence dependent offset; wherein the preamble sequence dependent offset is a function of a number of available preambles for the number of times the preamble transmission is to be repeated, or the preamble sequence dependent offset is a function of a physical random access channel sequence index. 
     
     
         23 . The network node according to  claim 20  wherein the starting subframe is determined for a frame with SFN as any subframe i fulfilling:
   0=(( SFN+T )· N+i ) mod R  
 
 wherein, 
 i is a subframe comprising radio resources configured for the random access channel in frame SFN, wherein i=0, . . . ,NSFN−1;  
 T is the first offset dependent on the random access channel configuration and takes value T=1 if radio resources configured for the random access channel are available in only odd-number subframes, otherwise T=0; 
 NSFN is the number of subframes comprising at least one random access channel resource in frame with SFN; 
 N is the average number of subframes comprising at least one random access channel resource; 
 T, N and NSFN being derived from the random access channel configuration provided by the network node to the UE; and 
 mod is a modulo operation. 
 
     
     
         24 . The network node according to  claim 21  wherein the starting subframe is determined for a frame with SFN as any subframe i
   0=(( SFN+T )· N+i+K )mod  R  
 
 wherein, 
 i is a subframe comprising radio resources configured for the random access channel in a frame SFN, wherein i=0, . . . , NSFN−1; 
 T is a first offset dependent on the random access channel configuration and takes value T=1 if radio resources configured for the random access channel are available in only odd-number subframes, otherwise T=0; 
 NSFN is the number of subframes comprising at least one random access channel resource in frame with SFN; 
 N is the average number of subframes comprising at least one random access channel resource; 
 T, N and NSFN being derived from the random access channel configuration provided by the network node to the UE; 
 K is the second offset, and 
 mod is a modulo operation.