| CPC H04L 5/0051 (2013.01) | 20 Claims | 

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               1. An operation method of a first terminal in a communication system, the operation method comprising: 
              receiving a message including a first demodulation reference signal (DMRS) scrambling identifier NID for sidelink communication from a base station; 
                calculating a first pseudo-random sequence cinit by inputting the first DMRS scrambling identifier NID into Equation 1; 
                cinit=(217(Nsymbslotns,fμ+l+1)(2NID+1)+2NID) mod 231  (Equation 1) 
                calculating a first DMRS sequence rl(m) by inputting the first pseudo-random sequence cinit into Equation 2; and 
              ![]() transmitting sidelink control information (SCI) and a first DMRS generated based on the first DMRS sequence rl(m) to a second terminal through a physical sidelink control channel (PSCCH), 
                wherein Nsymbslot denotes a number of symbols in a slot, ns,fμ denotes a slot number in a frame, and l denotes a symbol number in the slot. 
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