How to Investigate and Optimize LTE Throughput in 5 Steps ?

Let’s talk about Throughput Optimization.

 

 

 

If you are going to ask this question from an academic or researcher.

 

You would receive one of the two responses below.

 

1. Maximize SINR available
2. Reduce Network Load

 

Those are rationally and scientifically proven facts.

 

However, if you are performance engineer when you see Throughput Key Performance Indicators (KPIs) are getting degraded ?

What do you do ? 

In a live network. Do you always have a choice to perform either of the above two steps ?  If yes, you can start from scratch.

 

Otherwise,  below are the quick steps you can take note of  and start investigating when it comes to improving LTE Throughput

Optimization.

 

 Throughput Optimization

In LTE, end user quality of service is impacted by the cumulative effect of various nodes and interfaces. There is not one factor, but a number

of contributing factors which affect the end user throughput.

 

PREREQUISTE : General Guidelines Before diving into Throughput Investigation:

 

1. One of the first things to do is:  confirm parameter settings, system configuration and RF environment.
2. KPIs co-relate and depend on each other. Therefore knowledge of other KPIs such as Accessibility, Retainability , Mobility etc. is helpful to know , how they are performing . For example if Accessibility and Retainiabilty KPIs are bad, this will directly influence the throughput and end user QoS.
3. Do a site hardware audit (including jumpers, cables, connectors, antennas etc.)
4. Investigation of RF environment is a good idea to perform such as SINR, antenna types and planning.

 

Cumulative Effect on Throughput

 

The main factors which have a cumulative effect on throughput  are shown in the figure below.

 

 

 

 

The above diagram shows us, how various nodes and factors can affect the user throughput.

As an RF Performance engineer, you need to have knowledge of what counters do you need to take a look at in order to improve throughput?

Different vendors can have different names for the same counters.

 

Question:

What counters to look for when looking for Throughput improvement in LTE ?

Answer: It is better to understand the behavior of a certain part of the network. After that you can always figure out, where to go and look for counters. (Find the exact counter name in the documentation of the specific vendor)

 

 

What Sections and their Counters to Look for w.r.t Throughput?

As from the diagram above, you can look at the 7 sections to start with in order to improve throughput at RAN side.

 

 

 

 

 

 

In order to check the throughput being effected due to each of the section. One recommendation is to check the counters for each of the

section. The counters value, will tell you, how throughput is performing with respect to that specific section of the network. Based on the

value , you can take respective action to mitigate the negative influence (if that’s the case)

 

Channel Quality Indicator CQI :

Look for CQI counters. I am not going to list counters here specifically. For Samsung, it will have different counters compared to what Ericsson will have and same goes on for other vendors.

Throughput:

• Look for Throughput counters for a specific vendor in Downlink and Uplink.
• Counters such as which show , how much data is there in PDCP , or how much data volume was accumulated in the last Transmission Time Interval (TTI) .
• Also the counter which keeps track of how throughput is being estimated for the UE is important to know.

 

Interference :

In Downlink (DL) ,

There are no counters at the UE side.

But the way we measure DL RF conditions is based on the following which measure interference on the UE side.

For example, CQI distribution counters.

UE Rank Reporting distribution counters and Transmission rank distribution counters, will give you RF information,

which will translate to interference condition at the DL UE side. .

 

For Uplink (UL)

In this case check for Interference counters for Interference on :

• PUCCH
• PUSCH
• SINR Distribution on PUCCH
• SINR Distribution on PUSCH

 

For Block Error Rate (BLER)

 

In Downlink (DL):

For Downlink measure, you need to look for Hybrid Automatic Repeat Request (HARQ) Acknowledgements and Negative acknowledgements counters for each modulation type such as:

 

• QPSK
• 16-QAM
• 64-QAM

 

Having information of these counters, can help identify BLER.

 

In Uplink (UL) :

For Uplink. Measure HARQ UL success and Failure  for each modulation type in uplink such as:

•  16- QAM
•  QPSK

 

Using the above counters, you can identify BLER for UL case

 

 

Scheduling:

 

For Downlink 

In this case, look for counter which keeps track of UEs in Active mode at cell level. Also counters, which keep track of UEs which are being scheduled in the DL.

 

For Uplink :

In this case, look for counter which keeps track of UEs in Active mode at cell level in Uplink. Also counters, which keep track of UEs which are being scheduled in the UL.

 

 

Conclusion: 

The above list is not exhaustive. However it gives the starting pointers in order to investigate whenever you are faced with Throughput Optimization in LTE from Access Network perspective.

 

Still have Questions ? Speak Up your mind below in the comments.