Rank3 Rank4 Low Utilization

[ash98]

Our Rank3 and Rank4 utilization is very low on the 4x4 carriers, however rank 2 can go up to 75% to 85%. Would anyone share some of their experience for 4x4 deployment and how to bring up rank3/4 usage?

Thanks in advance.

[manu4ever]

Our Rank3 and Rank4 utilization is very low on the 4x4 carriers, however rank 2 can go up to 75% to 85%. Would anyone share some of their experience for 4x4 deployment and how to bring up rank3/4 usage?

Thanks in advance.

Check RF, Interference. In some cases, swapped antenna would make Rank3,4 utilization low.

[subway]

Our Rank3 and Rank4 utilization is very low on the 4x4 carriers

4x4 MIMO can benefit quite a lot from close loop (TM4) feedback, so if you are on TM3, I would advice to at least trial the TM4 possibility, even on TDD. In Huawei enodebs there is an option to enable open loop and closed loop in the same time, and the enodeb can switch adaptively, but no info about what is the switching criteria. So I would try TM4 only.

Another aspect of 4x4 MIMO is the very low UE penetration which actually supports 4x4 on the client side. Did you checked if there is high enough number of 4x4 capable devices in your network? Another issue might be CPE firmware, if you are operating a WTTx like network. I personally have bad experience with older Huawei CPEs in this regard.

The ultimate issue with MIMO (and high order MIMO even more so), is that you need very good SINR and 3-4 diverse enough signal path in the same time for 4x4 MIMO (rank3 and rank4) to work. Even with compatible UEs it is very unlikely, that the RF conditions are good enough for rank3 or rank4. There is a good reason why the industry turned towards beamforming instead of increasing the MIMO order.

[ash98]

Thanks Subway, what you said make sense but we do have TM4 configured on the site. UE penetration is one issue but based on the counter for UE CAT it seems we should have a good amount of UE supports 4x4, however rank 4 is very low (less than 2%), rank 2 is up to 75-80%.

[subway]

Thanks Subway, what you said make sense but we do have TM4 configured on the site. UE penetration is one issue but based on the counter for UE CAT it seems we should have a good amount of UE supports 4x4, however rank 4 is very low (less than 2%), rank 2 is up to 75-80%.

How many 4x4 capable UEs you have?

"based on the counter for UE CAT it seems we should have a good amount of UE supports 4x4"

I am not entirely sure what you mean here, but from the UE Category you cannot tell exactly the 4x4 capability, as the UE category defines the maximum capability. For example a CAT 6 UE can have a maximum number of 4 spatial layers, but most CAT 6 UEs do not have it. So I am not sure how you get the capable UE numbers, but if it is only based on UE category, you might made a mistake.

[faisaladeem]

Ofcourse, having very good SINR and multi-path environment is a given for higher Rank.

However, UE make and design has a lot to do with Rank 3 and Rank 4 usage as well. Some UEs have 8/4 passive antennas placed at different locations and they support dynamic antenna selection so only 4/2 best antennas can be used in DL/UL respectively at a given instant. Some UEs advertise themselves supporting antenna selection but in reality they don't (fake antenna selection UEs). Secondly, for UL Rank 2, UE power is divided and coverage is less.