[MM S01 E06] Flexible Coverage Planing & Planning in NR - Part I

I have covered Massive MIMO in previous five articles step by step to understand easily. This will be the last article about MM and I will discuss one of the coolest application in MM (Massive MIMO) which used in 5G NR.

Three sector coverage pattern is something we all learn from first lesson of mobile communication technology (looks like a bee hive). This pattern was introduced mainly due to frequency reuse requirement in 2G and 120 degree radiation pattern per sector was used to patterned the cellular coverage close to this. UMTS and LTE also follow the same beam pattern per sector as one multi band 120 degree antenna per sector can cover all three technologies antenna requirement. CAPEX and OPEX wise it was a good move for operators. It was a perfect solution for high user density areas where coverage requirement is in 120, 240 or 360 degree per site. But not all the time we need 120 degree coverage. Coverage for a highway or a isolated high-rise building are easy examples where 120 degree coverage is not really required. So the most of radiated energy will not be focused to our desired area and we can say 'inefficient use of RF energy' .

The principle of 120 degree sector coverage pattern rule going to be invalid in 5G NR. It doesn't mean that there is no 120 degree option. But NR is providing you more options. In earlier generations were only focusing on horizontal beam area (2D coverage) and NR is focusing on vertical beams also (3D coverage). Below is an example use cases of scenario based coverage patterns :

Huawei current NR version is providing 16 difference coverage patterns and flexibility of coverage planing and energy efficiency is improved lot in these scenarios. These aspects can be taken into consideration for CAPEX saving. for example , a highway through a desert area need far distance coverage in a narrow angle. So the number of cell site requirement can be reduced.

Principles of coverage pattern in NR

Realization of different coverage patterns is a algorithm work, no requirement of any extra hardware components. BCH is the main channel which idle UEs should receive and coverage for the users will be defined. So above coverage patterns are basically controlling the SSBs of the cell which caring BCH of NR. As we learn earlier in my previous article , there are eight maximum SSBs per cell. So the algorithms are helping us to control the number of beams vertically and horizontally and eventually different coverage patterns forms. To understand it perfectly, lets look at some theories:

This picture is showing an example of SSBs in horizontal and vertical view. With the help of α and β in the picture, we can define HPBW (Half Power Beam Width). The green line is defining the 3dB level of the TX power (Beam No 3) , means half power level of the TX signal after travel through the free space air.

α = Horizontal HPBW

β= Vertical HPBW.

AAU with 64TRX can form 13.5 degree horizontal HPBW and 6.5 Vertical HPBW beams. By controlling the number of beams horizontally and vertically , Huawei has provided 16 coverage patterns. 110,90, 65,45,25 and 15 degree horizontal coverage options and vertically 6,12 and 25 degree options are available . These 16 patterns are from different combinations of these angles. The control is fully parameter based and no any physical adjustments required.

Ex: 110H25V, 110H6V, 15H25V, 65H12V, 25H25V, etc..

Let's look in to some patterns:

1. 110H25V

This option is almost equal to 120 degree earlier generation sector pattern. Number of SSBs are 8 in this scenario which will create a aggregated beam swamping range of 13.5*8=108 degree horizontally and 25 degree vertically wide coverage( 6.5*4=26). But Vertically, there is no beam swapping. So one single beam is 13.5 degree horizontally and 25 degree wide. If you are wondering about four in above calculation, please check my third article about 3D beam forming.

2. 25H25V

This option is good for a isolate highness building coverage.

See you in "Flexible Coverage Planing & Planning in NR - Part II" soon!

Thanks,

Hassan QADI