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2 3 4 5 6 7 8 9 10 11 12 13 14 15
0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 5 5 5 5 5 5 10 10 10 10 10 10 Inf reserved {1, 3} {1, 4} {1, 2, 3} {1, 2, 4} {1, 3, 4} {1, 2, 3, 4} {1, 2, 6} {1, 3, 6} {1, 6, 7} {1, 2, 6, 8} {1, 3, 6, 9} {1, 4, 6, 7} N/A reserved 5.6 SC-FDMA baseband signal generation
Table 5.6-1: SC-FDMA parameters.
Configuration Normal cyclic prefix Extended cyclic prefix Cyclic prefix length NCP,l 添加CP，表5.6-1给出了CP长度NCP,l
160 for l?0 Ts最小基本时间长度 144 for l?1,2,...,6 Ts 512 for l?0,1,...,5 Ts
5.7
5.7.1
物理随机接入信道PRACH
时频结构
The physical layer random access preamble, illustrated in Figure 5.7.1-1, consists of a cyclic prefix of lengthTCP and a sequence part of lengthTSEQ. The parameter values are listed in Table 5.7.1-1 and depend on the frame structure and the random access configuration. 高层控制导频结构
CPTCPSequenceTSEQ
图5.7.1-1: 随机接入导频格式
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表5.7.1-1: 随机接入导频参数
Preamble format 0 1 2 3 4 (仅用于帧类型2) TCP 3168?Ts TSEQ 24576?Ts 24576?Ts 2?24576?Ts 2?24576?Ts 4096?Ts 21024?Ts 6240?Ts 21024?Ts 448?Ts
The transmission of a random access preamble, if triggered by the MAC layer, is restricted to certain time and
frequency resources. These resources are enumerated in increasing order of the subframe number within the radio frame and the physical resource blocks in the frequency domain such that index 0 correspond to the lowest numbered physical resource block and subframe within the radio frame. PRACH resources within the radio frame are indicated by a PRACH Resource Index, where the indexing is in the order of appearance in Table 5.7.1-2 and Table 5.7.1-4. For frame structure type 1 with preamble format 0-3, there is at most one random access resource per subframe. Table 5.7.1-2 lists the preamble formats according to Table 5.7.1-1 and the subframes in which random access preamble transmission is allowed for a given configuration in frame structure type 1. PRACH-Configuration-Index is given by higher layers. The start of the random access preamble shall be aligned with the start of the corresponding uplink
subframe at the UE assuming NTA?0, where NTA is defined in section 8.1. For PRACH configuration 0, 1, 2, 15, 16, 17, 18, 31, 32, 33, 34, 47, 48, 49, 50 and 63 the UE may for handover purposes assume an absolute value of the relative
?Ts. The first physical time difference between radio frame i in the current cell and the target cell of less than 153600resource block nPRB allocated to the PRACH opportunity considered for preamble format 0, 1, 2 and 3 is defined as
RARARA, where the parameter prach-FrequencyOffset nPRB?nPRBn offsetPRBoffset is expressed as a physical resource block
RAnumber configured by higher layers and fulfilling 0?nPRBoffsetRAUL?NRB?6.
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Table 5.7.1-2: Frame structure type 1 random access configuration for preamble format 0-3.
PRACH Configuration Index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Preamble Format 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 N/A 1 System frame number Even Even Even Any Any Any Any Any Any Any Any Any Any Any Any Even Even Even Even Any Any Any Any Any Any Any Any Any Any Any N/A Even Subframe number 1 4 7 1 4 7 1, 6 2 ,7 3, 8 1, 4, 7 2, 5, 8 3, 6, 9 0, 2, 4, 6, 8 1, 3, 5, 7, 9 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 9 1 4 7 1 4 7 1, 6 2 ,7 3, 8 1, 4, 7 2, 5, 8 3, 6, 9 0, 2, 4, 6, 8 1, 3, 5, 7, 9 N/A 9 PRACH Preamble Configuration Format Index 32 2 33 2 34 2 35 2 36 2 37 2 38 2 39 2 40 2 41 2 42 2 43 2 44 2 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 2 N/A 2 3 3 3 3 3 3 3 3 3 3 3 3 N/A N/A N/A 3 System frame number Even Even Even Any Any Any Any Any Any Any Any Any Any Any N/A Even Even Even Even Any Any Any Any Any Any Any Any Any N/A N/A N/A Even Subframe number 1 4 7 1 4 7 1, 6 2 ,7 3, 8 1, 4, 7 2, 5, 8 3, 6, 9 0, 2, 4, 6, 8 1, 3, 5, 7, 9 N/A 9 1 4 7 1 4 7 1, 6 2 ,7 3, 8 1, 4, 7 2, 5, 8 3, 6, 9 N/A N/A N/A 9
For frame structure type 2 with preamble format 0-4, there might be multiple random access resources in an UL
subframe (or UpPTS for preamble format 4) depending on the UL/DL configuration [see table 4.2-2]. Table 5.7.1-3 lists PRACH configurations allowed for frame structure type 2 where the configuration index corresponds to a certain combination of preamble format, PRACH density value, DRA, and version index, rRA.
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Table 5.7.1-3: Frame structure type 2 random access configurations for preamble format 0-4
PRACH Preamble Density Version PRACH Preamble Density Version conf. Format Per 10 ms Format Per 10 ms rRA conf. rRA Index Index DRA DRA ????0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 0 1 2 0 1 0 0 0 0 0 0 1 ????2 0 1 0 0 0 0 0 0 1 2 0 1 0 0 0 0 1 2 0 1 0 0 0 0 0 N/A N/A N/A N/A N/A N/A 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 0.5 0.5 0.5 1 1 1 2 2 2 3 3 3 4 4 4 5 5 5 6 6 0.5 0.5 0.5 1 1 2 3 4 5 6 0.5 0.5 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 N/A N/A N/A N/A N/A N/A 0.5 1 1 2 3 4 5 6 0.5 0.5 0.5 1 1 2 3 4 0.5 0.5 0.5 1 1 2 3 4 5 6 N/A N/A N/A N/A N/A N/A
Table 5.7.1-4 lists the mapping to physical resources for the different random access opportunities needed for a certain PRACH density value, DRA. Each quadruple of the format (fRA,tRA,tRA,tRA) indicates the location of a specific random access resource, where
012fRA is a frequency resource index within the considered time instance,
0tRA?0,1,2indicates whether the resource is reoccurring in all radio frames, in even radio frames, or in odd radio
1frames, respectively, tRA?0,1 indicates whether the random access resource is located in first half frame or in second
2half frame, respectively, and where tRA is the uplink subframe number where the preamble starts, counting from 0 at
the first uplink subframe between 2 consecutive downlink-to-uplink switch points, with the exception of preamble format 4 which is always transmitted in UpPTS and tRA is denoted as (*). The start of the random access preamble formats 0-3 shall be aligned with the start of the corresponding uplink subframe at the UE assuming NTA?0 and the random access preamble format 4 shall start [5158?Ts] before the end of the UpPTS at the UE.
The random access opportunities for each PRACH configuration shall be allocated in time first and then in frequency if and only if time multiplexing is not sufficient to hold all opportunities of a PRACH configuration needed for a certain density value DRA without overlap in time. For preamble format 0-3, the frequency multiplexing shall be done according to
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RAnPRB?RA?fRA?n?6if fRAmod2?0??2?,?PRB offset?? ??f??ULRARA?NRB?6?nPRB offset?6??,otherwise2????RAwhere NRB is the number of uplink resource blocks, nPRBis the first physical resource block allocated to the PRACH opportunity considered and where the parameter prach-FrequencyOffset nPRB offset is the first physical resource block available for PRACH expressed as a physical resource block number configured by higher layers and fulfilling
RAUL0?nPRBoffset?NRB?6.
RAULFor preamble format 4, the frequency multiplexing shall be done according to
nRAPRB?6fRA,if (nfmod2)?(2?NSP)?t1RAmod2?0 ??UL?NRB?6(fRA?1),otherwise??wherenfis the system frame number and whereNSPis the number of DL to UL switch points within the radio frame. Each random access preamble occupies a bandwidth corresponding to 6 consecutive resource blocks for both frame structures.
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