cell reference signal and mapping
DESCRIPTION
Cell Reference Signal and Mapping PT. Fusi Global Teknologi fusi.co.idTRANSCRIPT
Cell Reference Signal and Mapping
Yanuar T. Aditya N.
Cell Reference Signal are used for…
• Cell search and initial acquisition• Downlink channel estimation at the UE• Downlink channel quality measurements
Cell Search
Downlink RS (Reference Signals)
• Transmitted by each antenna (currently using single antenna)– Freq. domain spacing is 6 subcarrier– Time domain spacing is 4 OFDM symbols
Screenshot #1
CELL ID = 0 ; B/W = 10 MHz
Screenshot #2
CELL ID = 1 ; B/W = 10 MHz
Screenshot #3
CELL ID = 6 ; B/W = 10 MHz
Cell RS Equation
• Shall be transmitted in all downlink subframes• Shall be transmitted in one or several antennas
for number_of_slot=1:20 for ofdm_symbol=1:7 calculate rofdm_symbol,number_of_slot(m)
m = 0,1,…,2*N_RB - 1
Pseudo-Random Sequence Generator
• Initialized with
• Then, initialize the the Gold-Sequence m_seq1 and m_seq2. Each has 31-bit length.
for length=1:31 if length=1 m_seq1[length] = 1 else m_seq1[length] = 0
…more
• m_seq2 denoted by (need cinit)
for length=1:31 m_seq2[length] = c_init mod 2 c_init = c_init / 2
So far…
for length=1:31{ if length=1 m_seq1[length] = 1 else m_seq1[length] = 0}
for number_of_slot=1:20 for ofdm_symbol=1:7 { calc_c_init() for length=1:31 { m_seq2[length] = c_init mod 2 c_init = c_init / 2 } calc_pseudo_rand() calc_cell_RS() }
calc_pseudo_rand(){ for n=1:M_pn+Nc { m_seq1[n+31]=m_seq1[n+3]^m_seq1[n] m_seq2[n+31]=m_seq2[n+3]^m_seq2[n+2]^m_seq2[n+1]^m_seq2[n]
} for n=1:M_pn { pseudo_rand[n]=m_seq1[n+Nc]^m_seq2[n+Nc] }}
The cell RS value
…init m_seq1
for number_of_slot=1:20 for ofdm_symbol=1:7 { …init c_init …init m_seq2 …calc_pseudo_rand()
for m_index=1:N_RB*2 { out_signal[number_of_slot][ofdm_symbol][m_index].re = (1-2*pseudo_rand_seq[2*m_index])/SQRT_2; out_signal[number_of_slot][ofdm_symbol][m_index].im =
((1-2*pseudo_rand_seq[2*m_index+1])/SQRT_2); } }
Mapping
• We have to map the cell_RS which occupied m = 2 * N_RB on 12 * N_RB subcarriers per OFDM symbols.
• OFDM symbol wise, only selected symbol will be filled with cell_RS according to
…more
• v define the position in the freq domain (subcarrier) for the different RS
• vshift given by
Poured into code
for num_sub=1:2*N_RB /* 1 to 100 on 10 MHz */ for ofdm_sym=1:7 { if antenna_port == 0 || antenna_port == 1 { check_v01_value() slot[6 * num_sub + (v + v_shift)][ofdm_symb] = cell_RS[l][num_sub] } else if antenna_port == 2 || antenna_port == 3 { check_v23_value() slot[6 * num_sub + (v + v_shift)][ofdm_symb] = cell_RS[l][num_sub]] } }
Result
Q & A