计算MCS、调制阶数、编码速率、频谱效率关系表格
参考网址：http://4g-lte-world.blogspot.tw//12/transport-block-size-code-rate-protocol.html
参考网址：//10/22/1545/
（1）前提：
因此，efficiency可简化为下式：
TBS=传输块的大小（表7.1.7.2.1-1）
CRC=附加的用于检错的比特数量=24
RE=分给PDSCH或PUSCH信道的Resourceelaments数量（认为全部RE中，有90%用于共享信道）
BitsperRE=调制阶数
（2）举例
若eNB根据CQI分配该PUSCH传输的配置为：MCSindex=20，2个RB。则有：
1）表7.1.7.1-1，TBSindex=18
2）表7.1.7.2.1-1计算TBS（传输块大小，单位bits）
3）计算coderate
BitsperRE=调制阶数=(MCSindex=20)6阶=6
4）计算efficiency
（3）
计算RB数=12时，MCS
对应表
MCSindex
modulation
coderate×1024
efficiency
0
QPSK
99.329806
0.194003527
1
QPSK
126.4197531
0.24691358
2
QPSK
153.5097002
0.299823633
3
QPSK
198.659612
0.388007055
4
QPSK
243.8095238
0.476190476
5
QPSK
297.989418
0.58582
6
QPSK
352.1693122
0.687830688
7
QPSK
424.4091711
0.828924162
8
QPSK
478.5890653
0.934744268
9
QPSK
532.7689594
1.040564374
10
16QAM
266.3844797
1.040564374
11
16QAM
297.989418
1.164021164
12
16QAM
343.1393298
1.340388007
13
16QAM
388.2892416
1.51675485
14
16QAM
442.4691358
1.728395062
15
16QAM
496.64903
1.940035273
16
16QAM
514.7089947
2.01058
17
64QAM
343.1393298
2.01058
18
64QAM
367.2192828
2.151675485
19
64QAM
415.3791887
2.433862434
20
64QAM
451.4991182
2.645502646
21
64QAM
487.6190476
2.857142857
22
64QAM
523.7389771
3.068783069
23
64QAM
565.8788948
3.315696649
24
64QAM
609.5238095
3.571428571
25
64QAM
657.6837155
3.85361552
26
64QAM
681.7636684
3.994708995
27
64QAM
705.8436214
4.135802469
28
64QAM
826.2433862
4.841269841
参考文章附于此处
（1）CQI and MCS
LTE UE 會使用 CQI (Channel Quality Indicator) 動態調整 MCS 以降低傳輸錯誤率.
UE 測量 PRB (Physical Resource Block)的接收功率和干擾得到 SINR 值, 在 BLER 值不超過 10%. 將測量值轉換成 CQI. eNodeB 會根據 CQI 值選擇最合適的 MCS.
CQI 報告是由 eNodeB 主動發起, 可以是定時或是不定時.
不同的 CQI Index 有不同的 Code Rate.
如下表
CQI
Modulation
Bits/Symbol
REs/PRB
N_RB
MCS
TBS
Code Rate
1
QPSK
2
138
20
0
536
0.101449
2
QPSK
2
138
20
0
536
0.101449
3
QPSK
2
138
20
2
872
0.162319
4
QPSK
2
138
20
5
1736
0.318841
5
QPSK
2
138
20
7
2417
0.442210
6
QPSK
2
138
20
9
3112
0.568116
7
16QAM
4
138
20
12
4008
0.365217
8
16QAM
4
138
20
14
5160
0.469565
9
16QAM
4
138
20
16
6200
0.563768
10
64QAM
6
138
20
20
7992
0.484058
11
64QAM
6
138
20
23
9912
0.600000
12
64QAM
6
138
20
25
11448
0.692754
13
64QAM
6
138
20
27
12576
0.760870
14
64QAM
6
138
20
28
14688
0.888406
15
64QAM
6
138
20
28
14688
0.88840
MCS
Table 7.1.7.1-1: Modulation and TBS index table for PDSCH
MCS IndexModulation OrderTBS Index
020
121
222
323
424
525
626
727
828
929
1049
114
10
12411
13412
14413
15414
16415
17615
18616
19617
20618
21619
22620
23621
24622
25623
26624
27625
28626
292reserved
304
316
TBS Index (部份)
Table 7.1.7.2.1-1: Transport block size table (dimension 27×110)
12345678910
0
16
32
56
88
120
152
176
208
224
256
1
24
56
88
144
176
208
224
256
328
344
2
32
72
144
176
208
256
296
328
376
424
3
40
104
176
208
256
328
392
440
504
568
4
56
120
208
256
328
408
488
552
632
696
5
72
144
224
328
424
504
600
680
776
872
6
328
176
256
392
504
600
712
808
936
1032
7
104
224
328
472
584
712
840
968
1096
1224
8
120
256
392
536
680
808
968
1096
1256
1384
9
136
296
456
616
776
936
1096
1256
1416
1544
10
144
328
504
680
872
1032
1224
1384
1544
1736
11
176
376
584
776
1000
1192
1384
1608
1800
2024
12
208
440
680
904
1128
1352
1608
1800
2024
2280
13
224
488
744
1000
1256
1544
1800
2024
2280
2536
14
256
552
840
1128
1416
1736
1992
2280
2600
2856
15
280
600
904
1224
1544
1800
2152
2472
2728
3112
16
328
632
968
1288
1608
1928
2280
2600
2984
3240
17
336
696
1064
1416
1800
2152
2536
2856
3240
3624
18
376
776
1160
1544
1992
2344
2792
3112
3624
4008
19
408
840
1288
1736
2152
2600
2984
3496
3880
4264
20
440
904
1384
1864
2344
2792
3240
3752
4136
4584
21
488
1000
1480
1992
2472
2984
3496
4008
4584
4968
22
520
1064
1608
2152
2664
3240
3752
4264
4776
5352
23
552
1128
1736
2280
2856
3496
4008
4584
5160
5736
24
584
1192
1800
2408
2984
3624
4264
4968
5544
5992
25
616
1256
1864
2536
3112
3752
4392
5160
5736
6200
26
712
1480
2216
2984
3752
4392
5160
5992
6712
7480
依公式
Transport block size is 776 bits for ITBS = 18 and NPRB=2
code rate = (TBS + CRC) / (RE x Bits per RE)
code rate = (776 + 24) / (302 * 6 ) = 0.4
詳情請見
http://4g-lte-world.blogspot.tw//12/transport-block-size-code-rate-protocol.html
以下引用自書LTE 關鍵技術與無線性能
覺得整理的還不錯
Ref.
3GPP 36.213 : 最主要的 Document.
/html/Handbook_LTE_CQI.html
（2）Transport Block Size and Code rate
Since the size of transport block is not fixed, often a question comes to mind as to how transport block size is calculated in LTE.
Back Ground
If we only consider "Uplink direction" and we assume that the UE is already attached to the network, then data is firstreceivedby PDCP (Packet data compression protocol) layer. This layer performs compression and ciphering / integrity if applicable. This layer will pass on the data to the next layer i.e. RLC Layer which will concatenate it to one RLC PDU.
RLC layer will concatenate or segment the data coming from PDCP layer into correct block size and forward it to the MAC layer with its own header. Now MAC layer selects the modulation and coding scheme configures the physical layer. The data is now in the shape of transport block size and needed to be transmitted in 1ms subframe.
Transport Block size
Now how much bits are transferred in this 1ms transport block size?
It depends on the MCS (modulation and coding scheme) and the number of resource blocks assigned to the UE. We have to refer to the Table 7.1.7.1-1 and Table 7.1.7.2.1-1 from 3GPP 36.213
Lets assume that eNB assigns MCS index 20 and 2 resource blocks (RBs) on the basis of CQI and other information for downlink transmission on PDSCH. Now the value of TBS index is 18 as seen in Table 7.1.7.1-1
After knowing the value of TBS index we need to refer to the Table 7.1.7.2.1-1 to find the accurate size of transport block (Only portion of the table is shown here while for the complete range of values refer to 3gpp document 36.213http://www.quintillion.co.jp/3GPP/Specs/36213-920.pdf)
Now from the Table 7.1.7.2.1-1 the value of Transport block size is 776 bits for ITBS = 18 and NPRB=
Code Rate
In simple words, code rate can be defined as how effectively data can be transmitted in 1ms transport block or in other words, it is the ratio of actual amount of bits transmitted to the maximum amount of bits that could be transmitted in one transport block
code rate = (TBS + CRC) / (RE x Bits per RE)
where
TBS = Transport block size as we calculated from Table 7.1.7.2.1-1
CRC = Cyclic redundancy check i.e. Number of bits appended for error detection
RE = Resource elements assigned to PDSCH or PUSCH
Bits per RE = Modulation scheme used
While we know the values of TBS, CRC and bits per RE (modulation order), it is not easy to calculate the exact amount of RE used for PDSCH or PUSCH since some of the REs are also used by control channels like PDCCH, PHICH etc
In our case, lets assume that 10% of RE"s are assigned for control channels then
TBS = 776
CRC = 24
RE = 2 (RB) x 12 (subcarriers) x 7 (assuming 7 ofdm symbols) x 2 (slots per subframe) x 0.9 (10% assumption as above) = 302 REs
Bits per RE = 6 (Modulation order from table 7.1.7.1-1)
So
code rate = (776 + 24) / (302 * 6 ) = 0.4
