Factors affecting lte throughput

  • Monday, December 19 at 7:14PM
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In this blog I will explain about factors affecting downlink throughput in LTE

1. Radio Conditions –At radio level we have to check three major parameters i.e RSRP ,RSRQ , SINR.

  • RSRP-This is very important parameter which describe signal strength of radio , Good Value -65 to -85 dbm
  • RSRQ-This is also crucial because enode-b make many measurement on basis of this parameter ,Good Value – 10 to -19 db.
  • SINR-This is most Important radio parameter to achieve good throughput if SINR is good and above two parameters are bad than also we can achieve good throughput, Good Value 20 to 28 db.

2. PCI Planning-There should not any PCI confusion i.e no neighbor site having same PCI or mod collision , PCI collision also affects SINR , User will experience bad SINR and ultimately bad throughput.

3.Modulation and Coding Scheme-This also plays good role for throughput decision .Throughput depends upon coding scheme if UE gets 64-QAM that means it will get 6 bits per symbol and experience good throughput same as for 16-QAM UE will gets 4 bits per symbol. Table below shows relation between CQI, MCS index, MCS coding scheme , Transport block size.

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

0.888406

 

 

4.Rank Indicator- If UE do not experiencing good throughput we can check RI value as this parameter tells working of two antenna/MIMO. In simple words, RI is an indicator showing how well multiple Antenna work. What do you mean by "how well the multiple Antenna work ?". We usually say "Each of the multiple antenna (e.g, each antenna in MIMO configuration) works well if the signal from each antenna has NO correlation to each other". "No correlation" implies "no interference to each other".

Maximum RI value is very closely related to the number of Antenna. Maximum RI is same as number of antenna on each side if the number of Tx antenna and Rx antenna is same. If the number of Tx and Rx are different, the one with less antenna is the same as Max achievable RI.

 

Max RI means "No Correlation between the antenna", "No interference to each other", "Best Performance".

For example, in case of 2x2 MIMO, the RI value can be 1 or 2. When the value 2 in this case means "No Correlation between the antenna", "No interference to each other", "Best Performance". If the value is 1, it implies that the signal from the two Tx antenna is perceived by UE to be like single signal from single Antenna, which means the worst performance.

5.Number of resource blocks or resource block allocation.

6.Transmission Bandwidth or Backhaul-Sometimes transmission bandwidth is not as required suppose all above conditions are good and TX bandwidth is 4 Mbps then also user can experience bad throughput or equivalent to 5 Mbps.



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