在5G网络中,终端选择一个随机接入码进行接入及上行同步;这个随机接入码称为RAPID(随机接入ID);5G的随机接入码是根据ZC序列计算而得、传输中使用RA-RNTI进行加扰;整理:kangguoying20200702
RA-RNTI被用在随机接入过程中,gNB通过MAC层生成一个针对UE发送的接入请求发出的接入响应(RAR);接入响应(RAR)是映射于PDSCH,在DL-SCH信道上传递;gNB将PDCCH的CRC与RA-RNTI加扰,通过RAR消息通过在PDSCH下发;整理:kangguoying20200702
RA-RNTI可以携带多个UE的信息,多个UE可以用相同的扰码解调PDCCH;在PRACH信道上传输的随机接入码相关的RA-RNTI计算公式如下:整理:kangguoying20200702
RA-RNTI= 1 + s_id + 14 × t_id + 14 × 80 × f_id + 14 × 80 × 8 × ul_carrier_id整理:kangguoying20200702
Variable
Detail
字段释义
s_id
Index of the first OFDM symbol of the specified PRACH (0 ≤ s_id < 14)
PRACH首个OFDM符号指示(0-14)
t_id
Index of the first slot of the specified PRACH in a system frame (0 ≤ t_id < 80)
PRACH所在系统帧首个slot指示(0—80)
f_id
Index of the specified PRACH in the frequency domain (0 ≤ f_id < 8)
PRACH所在频域指示(0—8)
ul_carrier_id
Uplink carrier used for Msg1 transmission (0 for NUL carrier, and 1 for SUL carrier)
Msg1上传载波(0主载波,1为SUL载波)
RA-RNTI计算(Calculating RA-RNTI)
Calculating Min value – 0x0001整理:kangguoying20200702
s_id = 0 , t_id = 0, f_id = 0 , ul_carrier_id=0整理:kangguoying20200702
RA-RNTI= 1 + 0 + 14 × 0 + 14 × 80 × 0 + 14 × 80 × 8 × 0 = 1整理:kangguoying20200702
Calculating Max value整理:kangguoying20200702
s_id = 14 , t_id = 79, f_id = 7 , ul_carrier_id=1整理:kangguoying20200702
RA-RNTI= 1 + 13 + 14 × 79 + 14 × 80 × 7 + 14 × 80 × 8 × 1
RA-RNTI= 1 +13 +1106 + 7840 + 8960 = 17920整理:kangguoying20200702
Calculating Radnom value整理:kangguoying20200702
s_id = 3, t_id = 4, f_id = 2,ul_carrier_id=0整理:kangguoying20200702
RA-RNTI= 1 + 3 + 14 × 4 + 14 × 80 × 1 + 14 × 80 × 8 × 0
RA-RNTI = 4 + 56 + 1120 + 0 = 1180整理:kangguoying20200702
频域与时域位置(来自春天工作室)
原文来自:http://www.techplayon.com/ 整理:kangguoying20200702
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