計(jì)算MCS、調(diào)制階數(shù)、編碼速率、頻譜效率關(guān)系表格

參考網(wǎng)址：http://4g-lte-world./2012/12/transport-block-size-code-rate-protocol.html

參考網(wǎng)址：http://blog./2013/10/22/1545/

（1）前提：

因此，efficiency可簡(jiǎn)化為下式：

TBS=傳輸塊的大?。ū?span style="font-family:Calibri">7.1.7.2.1-1）

CRC=附加的用于檢錯(cuò)的比特?cái)?shù)量=24

RE=分給PDSCH或PUSCH信道的Resource elaments數(shù)量（認(rèn)為全部RE中，有90%用于共享信道）

Bits per RE=調(diào)制階數(shù)

（2）舉例

若eNB根據(jù)CQI分配該PUSCH傳輸?shù)呐渲脼椋?span style="font-family:Calibri">MCS index=20，2個(gè)RB。則有：

1）表7.1.7.1-1，TBS index=18

2）表7.1.7.2.1-1 計(jì)算TBS（傳輸塊大小，單位bits）

3）計(jì)算code rate

Bits per RE=調(diào)制階數(shù)=(MCS index=20)6階=6

4）計(jì)算efficiency

（3）

計(jì)算RB數(shù)=12時(shí)，MCS

對(duì)應(yīng)表

參考文章附于此處

（1）CQI and MCS

LTE UE 會(huì)使用 CQI (Channel Quality Indicator) 動(dòng)態(tài)調(diào)整 MCS 以降低傳輸錯(cuò)誤率.

UE 測(cè)量 PRB (Physical Resource Block)的接收功率和干擾得到 SINR 值, 在 BLER 值不超過(guò) 10%. 將測(cè)量值轉(zhuǎn)換成 CQI. eNodeB 會(huì)根據(jù) CQI 值選擇最合適的 MCS.
CQI 報(bào)告是由 eNodeB 主動(dòng)發(fā)起, 可以是定時(shí)或是不定時(shí).

不同的 CQI Index 有不同的 Code Rate.
如下表

MCS

Table 7.1.7.1-1: Modulation and TBS index table for PDSCH

TBS Index (部份)

Table 7.1.7.2.1-1: Transport block size table (dimension 27×110)

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(qǐng)見

http://4g-lte-world./2012/12/transport-block-size-code-rate-protocol.html

以下引用自書LTE 關(guān)鍵技術(shù)與無(wú)線性能
覺得整理的還不錯(cuò)

Ref.
3GPP 36.213 : 最主要的 Document.
http://www./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 first received by 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 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