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Thread: LTE MIMO : RANK, LAYERS and Antenna ports

  1. #21
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    Default Re: LTE MIMO : RANK, LAYERS and Antenna ports

    Quote Originally Posted by firstmaxim View Post
    But is it required to have TX diversity in the 3rd layer, while using MIMO for the other two? TX diversity is used when CQI is poor.
    Its not required, but useful. If you have a 4T4R antenna and 4x4MIMO is not possible (due to radio conditions) - which is a likely scenario - the only way to benefit from your 4T4R system is Tx (and Rx) diversity. If you configure your cell to 4T4R, it will be Tx div on all non-MIMO channels. Of coarse you can configure your 4T4R antenna to 2T2R, but unless you save in terms of license, thats a waste of resources (you already payed for the 4T4R antenna, RRU and chains). In my view, you can benefit the most from a 4T4R system mainly with 4 way receive diversity (effectively doubles the uplink gain compared to 2 way, those improves the uplink imbalance), and beamforming. Switching on 4x4 MIMO is only realistic, if you have a large number of 4x4 MIMO capable UEs, and a reflective enough environment. In any other case turning on 4x4 MIMO will just increase the CRS overhead without much gains.
    Last edited by subway; 2019-01-13 at 11:50 PM

  2. #22
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    Default Re: LTE MIMO : RANK, LAYERS and Antenna ports

    Quote Originally Posted by mohsenJaz View Post
    according to algebra theory, maximum rank in a 4*2 MIMO is 2. to be specific, in a m*n MIMO, maximum rank is min(m,n)
    You are right, purpose of 4X2 is to improve Receive Diversity. In terminology used above, this will be like a,a,b,b or a,b,a,b

  3. #23
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    Default Re: LTE MIMO : RANK, LAYERS and Antenna ports

    I'm looking forward to get experience with 4x4 and 4x2 MIMO, so far I see that network penetration of UE's that support 4x4 MIMO in general is low and due to this KPI,s for Rank 3 and Rank 4 utilization compared to Rank 1 and Rank 2 is very low. I’m convinced that for some time it's more important to focus on drive testing.

    So here my questions:
    1) What percentage of rank 3 and rank 4 utilization do you observe in your network?
    See lot of cells that stay below 5% for rank 3 and that do only 0 to 1% for rank 4.
    2) Which Transmission Mode did you implement? TM-3 OLSM or TM-4 CLSM?
    3) What drive test solution do you use, in order to verify that 4x4 MIMO is properly working?
    please name model of UE (eg. Galaxy S8, Galaxy S9,...) and what tool you use to post process the log files (TEM-S, NEM-O, SWISSQUA-L)

    Last edited by pathloss; 2019-01-16 at 07:22 AM



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